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1
Woo, Chang Su, Wan Doo Kim, Jae Do Kwon, and Wan Soo Kim. "Fatigue Life Prediction of the Vulcanized Natural Rubber." Key Engineering Materials 297-300 (November 2005): 16–21. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.16.
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Fatigue lifetime prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from fatigue test. Finite element analysis of 3D dumbbell specimen of natural rubber was performed based on a hyper-elastic material model determined from the tension, compression and shear tests. Stroke controlled fatigue tests were conducted using fatigue specimens at different levels of mean strain. The Green-Lagrange strain at the critical location determined from the FEM was used for evaluating the fatigue damaged parameter of the natural rubber. It was shown that the maximum Green-Lagrange strain was proper damage parameter, taking the mean strain effects into account. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at the critical location. Predicted fatigue lives of the natural rubber agreed fairly well the experimental fatigue lives a factor of two.
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Woo, Chang Su, Wan Doo Kim, and Jae Do Kwon. "Fatigue Life Evaluation of Rubber Components for Automobile Vehicles." Key Engineering Materials 324-325 (November 2006): 181–84. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.181.
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The interest of the fatigue life for rubber components was increasing according to the extension of warranty period of the automotive components. In this study, the fatigue lifetime prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from fatigue tests. Finite element analysis of 3D dumbbell specimen and rubber component was performed based on a hyper-elastic material model determined from the mechanical tests. The Green-Lagrange strain at the critical location determined from the finite element analysis was used for evaluating the fatigue damage parameter of the natural rubber. Fatigue tests were performed using the 3D dumbbell specimens and rubber component with different levels of maximum strain and various load. Fatigue life curves can be effectively represented by a following single function using the maximum Green-Lagrange strain. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at the critical location. Predicted fatigue lives of the rubber component for automobile vehicle agreed fairly with the experimental fatigue lives.
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de Sousa, José Renato M., Fernando J. M. de Sousa, Marcos Q. de Siqueira, Luís V. S. Sagrilo, and Carlos Alberto D. de Lemos. "A Theoretical Approach to Predict the Fatigue Life of Flexible Pipes." Journal of Applied Mathematics 2012 (2012): 1–29. http://dx.doi.org/10.1155/2012/983819.
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This paper focuses on a theoretical approach to access the fatigue life of flexible pipes. This methodology employs functions that convert forces and moments obtained in time-domain global analyses into stresses in their tensile armors. The stresses are then processed by well-known cycle counting methods, andS-Ncurves are used to evaluate the fatigue damage at several points in the pipe’s cross-section. Finally, Palmgren-Miner linear damage hypothesis is assumed in order to calculate the accumulated fatigue damage. A study on the fatigue life of a flexible pipe employing this methodology is presented. The main points addressed in the study are the influence of friction between layers, the effect of the annulus conditions, the importance of evaluating the fatigue life in various points of the pipe’s cross-section, and the effect of mean stresses. The results obtained suggest that the friction between layers and the annulus conditions strongly influences the fatigue life of flexible pipes. Moreover, mean stress effects are also significant, and at least half of the wires in each analyzed section of the pipe must be considered in a typical fatigue analysis.
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Guo, Min, Bo Zhu, Jianli Liu, and Weidong Gao. "Optimizing parameters of warp fatigue life tester by response surface methodology." Journal of Engineered Fibers and Fabrics 14 (January 2019): 155892501989380. http://dx.doi.org/10.1177/1558925019893808.
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The aim of this article was to provide an effective measurement method of the warp dynamic load capacity based on a warp fatigue life tester for sized yarns. Five parameters which affected the fatigue life of warp, respectively, namely, load frequency, warp speed, pre-tension weight, heald frame stroke, and static tension of the warp fatigue life tester, were studied. First, the influences of the five parameters on warp fatigue life were analyzed through single-factor experiments, and then, the Box–Behnken design based on the response surface methodology was adopted to optimize warp fatigue life tester parameters. The results showed that the optimum parameter conditions of the warp fatigue life tester for warp fatigue life were as follows: when heald frame stroke at 77.16 mm, load frequency of 205.49 times/min, and static tension as 6.96 cN, the optimal warp fatigue life was 1394.05 times. The theoretical and experimental values were in reasonable agreement, and the relative error was less than 1%. Verification and repeated trial results showed that the optimal parameters had good reproducibility, and the warp fatigue life tester with the optimal parameters provided an effective and reliable evaluation to the warp frictional, stretching, and buckling effects.
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Pettinà, Michele, Bahram Farahmand, Filippo Berto, and Frank Abdi. "Virtual Testing for Fracture Toughness, Fatigue Crack Growth and Fatigue Life Data Estimation of Metallic Components." Key Engineering Materials 577-578 (September 2013): 177–80. http://dx.doi.org/10.4028/www.scientific.net/kem.577-578.177.
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Evaluating fracture and fatigue life properties of structural components involves tests that are costly and time consuming. To estimate total life of engineering parts, high cycle fatigue data (S-N) for the material under study is needed. In many cases the S-N data is not available to the analyst and both the time and budget required for testing prevent engineers to meet the deadline imposed on the program. An analytical combined Progressive Damage and Fracture Mechanics based approach is proposed that estimates the S-N data for components that have stress concentrations. The proposed methodology starts from a full engineering tensile stress-strain curve of the material under study and ends up with the estimation of fracture toughness, fatigue crack growth and fatigue S-N curves.
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Woo, Chang Su, Wan Doo Kim, and Jae Do Kwon. "A Study on the Fatigue Life Prediction and Evaluation of the Natural Rubber Components for Automobile Vehicles." Key Engineering Materials 326-328 (December 2006): 589–92. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.589.
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The fatigue analysis and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. The interest of the fatigue life of rubber components such as the engine mount is increasing according to the extension of warranty period of the automotive components. In this study, the fatigue lifetime prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from fatigue tests. Finite element analysis of 3D dumbbell specimen of natural rubber was performed based on a hyper-elastic material model determined from the tension, compression and shear tests. The Green-Lagrange strain at the critical location determined from the finite element analysis was used for evaluating the fatigue damage parameter of the natural rubber. Fatigue tests were performed using the 3D dumbbell specimens with different levels of maximum strain and various load. The basic mechanical properties test and the fatigue test of rubber specimens under the normal and elevated temperature were conducted. Fatigue life curves can be effectively represented by a following single function using the maximum Green-Lagrange strain. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at the critical location. Predicted fatigue lives of the engine mount agreed fairly with the experimental fatigue lives a factor of two.
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Nahm, Seung Hoon, Chang Min Suh, Min Woo Jung, Jong Yup Kim, and Chang Hwan Yang. "Application of Damage Tolerance Approach for Turbine Disk Life Extension." International Journal of Modern Physics B 17, no. 08n09 (April 10, 2003): 1916–21. http://dx.doi.org/10.1142/s0217979203019873.
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For gas turbine engines, the safe life methodology has historically been used for fatigue life management of failure critical engine components. The safe retirement limit is necessarily determined by a conservative life evaluation procedure, thereby many components which have a long residual life are discarded. The objective of this study is to introduce the damage tolerant design concept into the life management for aircraft engine component instead of conservative fatigue life methodology which has been used for both design and maintenance. The residual lives of turbine disk component under various temperatures and conditions using creep-fatigue crack initiation and growth data were estimated. As the result of analysis, it was confirmed that retirement for cause concept was applicable to the evaluation of residual life of retired turbine disk which had been designed based on the conventional fatigue life methodology.
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Yeom, Jong Taek, Chong Soo Lee, Jeoung Han Kim, Dong Geun Lee, and Nho Kwang Park. "Continuum Damage Model of Creep-Fatigue Interaction in Ni-Base Superalloy." Key Engineering Materials 340-341 (June 2007): 235–40. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.235.
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A methodology for evaluating and predicting component lives in creep-fatigue interaction region was investigated for Waspaloy. A unified viscoplasticity constitutive equation including multi-back stresses was used to describe cyclic material behaviors. Also, a continuum damage model coupling with the creep-fatigue damage rules was established based on the analysis of creep and low cycle fatigue behavior. Multi-axial fatigue and creep equivalent stress concepts were employed to predict three dimensional component lives. Notched cyclic tests under various stress conditions in the creep-fatigue interaction region were carried out to validate the life prediction methodology with FEM simulation based on the continuum damage model. The comparison of experimental data and prediction results indicates that the continuum damage model is a powerful approach for the prediction of component lives.
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Luo, R. K., B. L. Gabbitas, and B. V. Brickle. "Fatigue Life Evaluation of a Railway Vehicle Bogie Using an Integrated Dynamic Simulation." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 208, no. 2 (July 1994): 123–32. http://dx.doi.org/10.1243/pime_proc_1994_208_242_02.
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An integrated design methodology has been developed for the fatigue life evaluation of railway vehicle bogies. In principle, there are five parts in the procedure: specification and measurement of track irregularities; modelling a railway vehicle and description of rail-wheel profiles; obtaining the railway vehicle suspension load histories; dynamic analysis and stress evaluation of the bogie frame; fatigue life evaluation of the bogie. The whole procedure has been applied to a typical London Underground railway vehicle. The theoretical results have been validated against field test data and fatigue calculations have indicated good agreement with operational data from the actual vehicles. It has been shown that a design methodology for railway vehicle bogies based on the track profiles on which they will run and on their own structural characteristics is possible and can be used at an appropriate stage in the design process.
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Song, Yongsheng, Youliang Ding, Fei Jiang, Zhiwen Wang, Jun Lu, and Huijuan Jia. "Multiaxial Fatigue Assessment for the Hanger Deck Connection of a High-Speed Steel-Truss-Arch Railway Bridge." Applied Sciences 11, no. 3 (January 26, 2021): 1142. http://dx.doi.org/10.3390/app11031142.
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Steel-truss-arch bridges have been applied in high-speed railway bridges due to their excellent dynamic and static structural performance. Under the action of high-speed trains, the steel connections between hangers and decks suffer from repeated stresses, inducing potential fatigue problems or even fatigue failure. In this study, a multiaxial fatigue evaluation method was first created and established based on critical damage-plane methodology, following which the fatigue evaluation procedure was also created and recommended. The methodology was applied to real-life strain data from a high-speed railway bridge from which an assessment of fatigue damage and predicted fatigue life was estimated. The connection between the shortest hanger and deck on the downstream side was selected as the target due to its relatively high stress. A multiscale finite-element model of this bridge was created according to the design profile and monitoring results of traffic flow, where the finite-element model was calibrated and validated by comparing the calculation results with the monitoring data. Influence analysis was then carried out to investigate two factors—i.e., the total traffic flow and compositions of freight trains—having effects on the fatigue life of the steel connection. The results indicate that the applied multiaxial fatigue method is suitable for online fatigue evaluation of actual bridges. In addition, by using the multiaxial fatigue method, the fatigue-damage accumulation rate can be nearly 60 times that obtained by the uniaxial fatigue method. If freighting is taken into consideration, the fatigue damage will increase rapidly, and for the case 10% of proportion traffic as freighting, the actual fatigue life is estimated to be shorter than the design life.
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Li, Shuangshuang, Xintian Liu, Xiaolan Wang, and Yansong Wang. "Fatigue life prediction for automobile stabilizer bar." International Journal of Structural Integrity 11, no. 2 (November 1, 2019): 303–23. http://dx.doi.org/10.1108/ijsi-07-2019-0063.
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Purpose During the running of automobile, the stabilizer bar is frequently subjected to the impact of complex random loads, which is prone to fatigue failure and accident. In regard to this, the purpose of this paper is to study and discuss fatigue life of automobile stabilizer bar. Design/methodology/approach Durability bench test shows that failure is located at the joint of sleeve and stabilizer bar body. Based on the collection and compilation of micro-strain load spectrum of the stabilizer bar, the strain-life model is studied considering the influence of average stress and maximum stress at failure area. Seven-grade strain-life curves of the stabilizer bar are established. According to the principle of linear damage accumulation, the relationship between fatigue life and damage is discussed, then the fatigue life of stabilizer bar is predicted. Fatigue life evaluation is carried out from three aspects: reliability analysis, static analysis and fatigue life simulation. Findings The results show that the reliability of the test sample is 99.9 percent when the confidence is 90 percent and the durability is 1,073 load spectrum cycles; the ratios of predicted and simulated life to design life are 2.77 and 2.30, respectively. Originality/value Based on the road load characteristics of automobile stabilizer bar, the method of fatigue life prediction and evaluation is discussed, which provides a basis for the design and development of automobile chassis components.
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Hu, Sheng, Fujie Zhou, and Tom Scullion. "Load Spectra–Incorporated Fatigue Cracking Model Implementation and Case Study." Transportation Research Record: Journal of the Transportation Research Board 2640, no. 1 (January 2017): 1–10. http://dx.doi.org/10.3141/2640-01.
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Traffic loading is one of the key factors that may cause asphalt concrete pavement fatigue cracking. Axle load spectra input provides an opportunity for evaluating the pavement response under real traffic loads throughout the pavement design life. This paper describes the methodology of incorporating axle load spectra into the mechanistic–empirical fatigue cracking model that uses a fracture mechanics method to determine crack propagation. The paper also presents the incorporation of the method into the Texas mechanistic–empirical flexible pavement design system. Several load spectra cases were studied, and the percentages of the corresponding fatigue cracking areas were predicted and compared. The comparison results confirmed the necessity of load spectra analysis. Overall, the implemented load spectra–incorporated asphalt concrete fatigue cracking model generated rational results. Further research is continuing on field validation and calibration.
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da Silva Gonçalves, Roberto, and Carlos E. Chaves. "Fatigue Life Estimation of Aeronautical Joints Based on Stress Severity Factor." Advanced Materials Research 1135 (January 2016): 128–39. http://dx.doi.org/10.4028/www.scientific.net/amr.1135.128.
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The goal of the present work is to investigate the validity limits and safe application range of Stress Severity Factor methodology in estimating fatigue life of aircraft fuselage joints. Fatigue tests were conducted and recorded data from aluminum alloys joints was subjected to analytical evaluation. FE models were created to obtain fasteners load distribution and determine normal stress due to secondary bending. Severity Factor method conservatively estimated fatigue life of 74% for the analyzed joints. Its robustness was verified for lap joints fatigue life estimative, but for almost all single strap joints, secondary bending effect were significant. Thus for this kind of joints, a term accounting for bending stress was added to the original severity factor formulation to increase level of safety in fatigue life estimates.
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Ma, Xiqiang, Fang Yang, Jishun Li, Yujun Xue, and Zhiqiang Guan. "Fatigue life assessment method of in-service mechanical structure." Advances in Mechanical Engineering 13, no. 2 (February 2021): 168781402199652. http://dx.doi.org/10.1177/1687814021996524.
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The most usual failure mode of any mechanical structure is fatigue, which is characterized by an important feature of the decrease of elastic modulus of the material. In this paper, a fatigue life evaluation model based on equivalent elastic modulus is proposed for in-service mechanical structure. In the proposed model, parameters that represent the operating conditions of the mechanical structure, such as load, vibration, and shaft torque, etc., are used as the generalized load. To replace the fatigue stress, the statistical method is used here, which is also used in the conventional fatigue analysis method. The structural strain is also measured simultaneously. Using the statistical theory, the equivalent modulus of elasticity is formulated based on the relationship of stress, strain, and modulus of elasticity. To validate the proposed model, an online fatigue damage experiment has been conducted. The experimental results have been compared with that of the fatigue life prediction model with good agreement. It is expected that the methodology proposed in this paper will be widely used.
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Depale, Bruno, and Mohamed Bennebach. "Residual life of steel structures and equipment: problems and application to cranes." Mechanics & Industry 20, no. 8 (2019): 802. http://dx.doi.org/10.1051/meca/2019047.
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The paper starts by considering, in general, the problem of evaluating residual life of structures and equipment that may have reached or exceeded the end of their design life. Whilst the problem is encountered in many industrial sectors, references available for dealing with it are often limited. Selected European references potentially suitable for this purpose for steel structures and cranes are presented and discussed in this paper together with some of the practical problems faced by the engineers responsible for evaluating the residual life of equipment and structures. This includes an overview of FEM Crane Codes and European EN standards for steel structures and cranes, their methods for assessing fatigue lives and their application to evaluating residual lives. A procedure developed in France and in use for such purpose since 2003, an approach developed in Italy and approach taken by ISO 12482 standard are all reviewed next. Finally, the paper presents a general methodology for the assessment and management of residual life of existing equipment and structures that has been developed by CETIM (Technical Institute for Mechanical Industry) and concludes with an example of its application to an AIRBUS load manipulating device.
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Cernescu, Anghel, Liviu Marsavina, and Ion Dumitru. "Structural integrity assessment for a component of the bucket-wheel excavator." International Journal of Structural Integrity 5, no. 2 (May 13, 2014): 129–40. http://dx.doi.org/10.1108/ijsi-08-2012-0019.
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Purpose – The purpose of this paper is to present a methodology for assessing the structural integrity of a tie member from a bucket-wheel excavator, ESRC 470 model, which was in operation for about 20 years. The tie member is made of S355J2N structural steel. Following the period of operation, the occurrence of microcracks which can propagate by fatigue is almost inevitable. It is therefore necessary to analyze the structural integrity and the remaining life of the component analyzed. Design/methodology/approach – In principle, the assessment methodology is based on three steps: first, the evaluation of mechanical properties of the material component; second, a BEM analysis using FRANC 3D software package to estimate the evolution of the stress intensity factor based on crack length and applied stress; third, risk factor estimation and remaining fatigue life predictions based on failure assessment diagram and fatigue damage tolerance concept. Findings – Following the evaluation procedure were made predictions of failure risk factor and remaining fatigue life function of crack length and variable stress range, for a high level of confidence. Originality/value – As results of this analysis was implemented a program for verification and inspection of the tie member for the loading state and development of small cracks during operation.
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Hu, Jimmy. "Life Prediction and Damage Acceleration Based on the Power Spectral Density of Random Vibration." Journal of the IEST 38, no. 1 (January 31, 1995): 34–40. http://dx.doi.org/10.17764/jiet.2.38.1.k463581ww2515u45.
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Fatigue life prediction and accelerated verification tests under a random vibration environment are important tasks for evaluating product reliability. This paper reviews the characteristics of random stress processes, discusses the methodology of life prediction and accelerated testing under various random loadings by using the stress power spectral density (PSD) function obtained from finite element analysis (FEA), and develops an engineering method to determine the acceleration level and test time in reliability verification tests. The discussions cover the narrow-band Gaussian processes, the wide-band Gaussian processes, and the nonGaussian processes. To illustrate the practical procedure of life prediction and accelerated testing based on the damage equivalent technique, the application example of an automotive component is presented.
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Leite, Regina C. G., Abilio M. P. de Jesus, José Correia, Patricia Raposo, Renato N. Jorge, Marco Paulo Parente, and Rui Calçada. "A methodology for a global-local fatigue analysis of ancient riveted metallic bridges." International Journal of Structural Integrity 9, no. 3 (June 11, 2018): 355–80. http://dx.doi.org/10.1108/ijsi-07-2017-0047.
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Purpose Recent studies have proposed the application of local fatigue approaches based on fracture mechanics or on strain-life material relations for the fatigue analysis of metallic structures. However, only few studies in the literature apply local approaches in the riveted bridges analysis; although these approaches can be applied to any type of connections, requiring a detailed stress analysis of joints and, consequently, considerable computational resources costs. The approach based on S-N curves, formulated in nominal or net stresses, is more usual in the fatigue analysis of riveted bridges. Due to economic factors, riveted bridges have had their operating life extended, while changes in the transport system over the years have subjected such structures to overloads different from those originally planned. These bridges, most of them centenary, were not originally designed accounting for fatigue damage; they represent an important group of structures that are very likely subjected to significant fatigue damage indexes. These factors make necessary detailed residual fatigue life studies to substantiate the decisions of extend (or not) the operational period of these bridges. The paper aims to discuss these issues. Design/methodology/approach The present paper presents a methodology aiming at applying the local approaches in the fatigue analysis of riveted joints of metallic bridges, through the use of sub-modeling techniques and procedures automation. The use of such techniques made such an application viable by keeping the computational costs involved at a moderate level. The proposed procedures were demonstrated using the Trezói Railway Bridge, located on the Beira Alta line, Portugal, built shortly after the Second World War. The proposed set of procedures allowed, through finite elements analysis, to obtain the relevant stresses to perform local fatigue damage analysis. A global structural model was constructed, using beam elements, and local models of a critical node were built with solid finite elements. The structure is analyzed under the passage of regulatory trains. The details of the modeling performed and the computation of the principal stresses in the vicinity of a node and the tangential/circumferential stresses at the holes of two critical riveted connections of that node are analyzed and a fatigue damage analysis is carried out. Findings In the proposed submodelling approach, disassembling the complex riveted nodes into riveted subassemblies allowed the evaluation of the local stresses at riveted holes at an affordable computational cost. Originality/value A methodology is proposed to allow the application of local fatigue analysis in real complex riveted joints, mitigating the computational costs that would result from a full model of the node with all rivets.
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Nemeth, N. N., L. M. Powers, L. A. Janosik, and J. P. Gyekenyesi. "Durability Evaluation of Ceramic Components Using CARES/LIFE." Journal of Engineering for Gas Turbines and Power 118, no. 1 (January 1, 1996): 150–58. http://dx.doi.org/10.1115/1.2816531.
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The computer program CARES/LIFE calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/or proof test loading. This program is an extension of the CARES (Ceramics Analysis and Reliability Evaluation of Structures) computer program. CARES/LIFE accounts for the phenomenon of subcritical crack growth (SCG) by utilizing the power law, Paris law, or Walker equation. The two-parameter Weibull cumulative distribution function is used to characterize the variation in component strength. The effects of multiaxial stresses are modeled using either the principle of independent action (PIA), the Weibull normal stress averaging method (NSA), or the Batdorf theory. Inert strength and fatigue parameters are estimated from rupture strength data of naturally flawed specimens loaded in static, dynamic, or cyclic fatigue. Application of this design methodology is demonstrated using experimental data from alumina bar and disk flexure specimens, which exhibit SCG when exposed to water.
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Wang, Haijie, Xintian Liu, Que Wu, Xiaolan Wang, and Yansong Wang. "An improved fatigue life prediction model for shock absorber cylinder with surface roughness correction." Engineering Computations 38, no. 6 (January 11, 2021): 2713–32. http://dx.doi.org/10.1108/ec-05-2020-0263.
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Purpose The purpose of this paper is to obtain a more accurate fatigue life of structures by introducing the surface roughness into fatigue life prediction model. Design/methodology/approach Based on the fatigue life prediction model with surface roughness correction, the shock absorber cylinder is taken as an example to verify the feasibility of the improved method. Based on the load of the shock absorber cylinder during driving, fatigue experiments are performed under longitudinal and lateral forces, respectively. Then, the fatigue life predicted by the modified model is compared with that predicted by the traditional model. Findings By comparing with the test results, considering the influence of mean stress, the Manson method is more accurate in life prediction. Then, the modified Manson-Coffin and Manson method with surface roughness is more accurate in life prediction under longitudinal force and lateral forces, respectively. This verifies the feasibility of the improved method with the surface roughness. Originality/value The research on the influence of surface roughness on fatigue life can lay the technical foundation for the life prediction of products and have great significance to the quality evaluation of products.
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Seo, Jung Won, Byeong Choon Goo, Heung Chai Chung, Jae Boong Choi, and Young Jin Kim. "The Effects of Residual Stress of Contact Fatigue Life for Railway Wheels." Key Engineering Materials 297-300 (November 2005): 115–21. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.115.
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Railway wheels and axles belong to the most critical components in railway vehicles. The service conditions of railway vehicles became more severe in recent years due to the increase of speed. Therefore, a more precise evaluation of railway wheel life and safety has been requested. Wheel/rail contact fatigue and thermal cracks due to braking are two major mechanisms of the railway wheel failure. One of the main sources of the contact zone failure is the residual stress. The residual stress on wheel is formed during the manufacturing process which includes a heat treatment, and then, is changed in the process of braking which results in wheel/rail contact stress and thermal stress. In this paper, an evaluation procedure for the contact fatigue life of railway wheel including residual stress is proposed. Also, the cyclic stress history for fatigue analysis is simulated by applying finite element analysis for the moving contact load. As a result, a fatigue life estimation methodology is proposed for railway wheels which includes the effects of residual stresses due to heat treatment, braking and repeated contact load, respectively.
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Krafft, R., and S. Mosset. "A Probabilistic Method for the Fatigue Life Assessment of Powder Metallurgy Parts of Aircraft Engines." Journal of Engineering for Gas Turbines and Power 118, no. 2 (April 1, 1996): 411–15. http://dx.doi.org/10.1115/1.2816605.
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This paper will present a probabilistic approach developed in order to assess the fatigue life of aircraft engine parts (turbine disks) obtained by powder metallurgy technique. First of all, the main issues will be pointed out and the theoretical principles of the method will be described. Then the design implications and the experimental correlation will be emphasized. The scale effect is a major concern for the fatigue life assessment of a powder metallurgy part. It no longer allows the designer to evaluate the life of a massive part directly from experimental results based on small specimen fatigue tests as is done in the classical methodology. In order to describe this scale effect correctly, incubation sites (inhomogeneities like ceramic inclusions) must be characterized. The size of these inhomogeneities and their positions in the part appeared to be the most relevant parameters. Hence the methodology developed at SNECMA integrates the scale effect scatter through a binomial probability distribution as well as a temperature and stress-dependent life evaluation for each inhomogeneity size and position. The life calculation of a part implies an analysis of its whole volume and surface. An iterative process determines the number of cycles corresponding to a global reliability level requirement for the part. The complete methodology is then validated by comparing the calculated initiation distribution with experimental results on small specimens and test disks.
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Millwater, H. R., Y. T. Wu, J. W. Cardinal, and G. G. Chell. "Application of Advanced Probabilistic Fracture Mechanics to Life Evaluation of Turbine Rotor Blade Attachments." Journal of Engineering for Gas Turbines and Power 118, no. 2 (April 1, 1996): 394–98. http://dx.doi.org/10.1115/1.2816602.
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This paper describes the application of an advanced probabilistic fracture mechanics computational algorithm with inspection simulation to the probabilistic life assessment of a turbine blade attachment, sometimes referred to as a steeple or fir tree. The life of the steeple is limited by high cycle fatigue. The methodology utilized combines structural finite element analysis, stochastic fatigue crack growth, and crack inspection and repair. The resulting information provides the engineer with an assessment of the probability of failure of the structure as a function of operating time and the effect of the inspection procedure. This information can form the basis of inspection planning and retirement-for-cause decisions.
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Chiu, S. S., J. Eftis, and D. L. Jones. "Prediction of Fatigue Life With and Without Hold Times Using the Chaboche Viscoplastic Constitutive Theory." Journal of Engineering Materials and Technology 112, no. 2 (April 1, 1990): 188–97. http://dx.doi.org/10.1115/1.2903306.
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The titanium alloy Ti-6Al-4V is known to exhibit creep behavior at temperatures as low as room temperature. Consequently, for cyclic loading with hold times it is possible that the rate dependent behavior of Ti-6Al-4V can have negative bearing upon the low cycle fatigue life. If this effect is shown to be present at room temperatures, then it will certainly be magnified and, therefore, very important at elevated temperatures. In order to account for the effects of strain rate dependent deformation in fatigue life prediction methodology, it was considered necessary to incorporate a viscoplastic constitutive equation into the fatigue life calculational algorithm. After critical evaluation of a score of recently proposed viscoplastic constitutive theories, the Chaboche theory, which employs a yield condition, was considered to offer the most promise for description of a wide range of inelastic material behavior characteristics. The six viscoplastic material parameters that are required for nonelevated temperature applications were determined from data of uniaxial tests, conducted elsewhere and made avialable to this study. The fatigue life testing of smooth round bar specimens included load cycles with load hold times. Fatigue life predictions were performed using the equivalent fully reversed symmetric cycle, and the Smith-Watson-Topper parameter, for load cycles having varying stress amplitudes and varying hold times. The predicted fatigue life results indicate that: (i) For a given stress level above the initial yield stress, shorter load hold time periods result in longer fatigue lives. (ii) The higher the stress level (above the initial yield stress) the more pronounced becomes the effect of the load hold time on the fatigue life prediction. (iii) The rate of loading also has an effect on fatigue life. Analysis indicates that the slower the rate of loading, the higher the rate dependent (primary creep) deformation, and consequently, the lower the resulting fatigue life.
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Hartin, John R. "Evaluation of Prediction Methodology for Blade Loads on a Horizontal Axis Wind Turbine." Journal of Solar Energy Engineering 112, no. 4 (November 1, 1990): 315–19. http://dx.doi.org/10.1115/1.2929941.
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The accurate prediction of horizontal axis, wind turbine cyclic blade loads is critical in the design of a machine that is fatigue life limited. A rotor code called LOADS has been developed that analyzes blade loads for rigid-hub rotors of simple geometry but includes blade flap-wise flexing and unsteady aerodynamics. The code is described and the results of its application to the SERI Combined Experiment Tests using turbulent wind simulation are presented with some initial conclusions regarding the accuracy of the results.
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Loza, Brian, Josué Pacheco-Chérrez, Diego Cárdenas, Luis I. Minchala, and Oliver Probst. "Comparative Fatigue Life Assessment of Wind Turbine Blades Operating with Different Regulation Schemes." Applied Sciences 9, no. 21 (October 31, 2019): 4632. http://dx.doi.org/10.3390/app9214632.
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A comparative evaluation of the fatigue damage occurring in the blades of small wind turbines, with different power regulation schemes, has been conducted for the first time. Three representative test cases were built, one based on stall regulation and two using pitch regulation. The power curves were tuned to be identical in all cases, in order to allow for a direct comparison of fatigue damage. A methodology combining a dynamic simulation of a wind turbine forced by stochastic wind speed time series, with the application of the IEC 61400-2 standard, was designed and applied for two levels of turbulence intensity. The effect of the wind regime was studied by considering Weibull-distributed wind speeds with a variety of parameter sets. Not unexpectedly, in typical wind regimes, stall regulation led to a generally higher fatigue damage than pitch regulation, for similar structural blade design, but the practical implications were smaller than thought previously. Given the need for cost-effective designs for small wind turbines, stall regulation may be a viable alternative for off-grid applications.
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Fiorentin, Felipe, Bernardo Oliveira, João Pereira, José Correia, Abilio M. P. de Jesus, and Filippo Berto. "Fatigue Behavior of Metallic Components Obtained by Topology Optimization for Additive Manufacturing." Frattura ed Integrità Strutturale 15, no. 55 (December 28, 2020): 119–35. http://dx.doi.org/10.3221/igf-esis.55.09.
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The main goal of the present research is to propose an integrated methodology to address the fatigue performance of topology optimized components, produced by additive manufacturing. The main steps of the component design will be presented, specially the methods and parameters applied to the topology optimization and the post-smoothing process. The SIMP method was applied in order to obtain a lighter component and a suitable stiffness for the desired application. In addition, since residual stresses are intrinsic to every metallic additive manufacturing process, the influence of those stresses will be also analyzed. The Laser Powder Bed Fusion was numerically simulated aiming at evaluating the residual stresses the workpiece during the manufacturing process and to investigate how they could influence the fatigue behavior of the optimized component. The effect of the built orientation of the workpiece on the residual stresses at some selected potential critical points are evaluated. The final design solution presented a stiffness/volume ratio nearly 6 times higher when compared to the initial geometry. By choosing the built orientation, it is possible impact favorably in the fatigue life of the component.
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Ben Ahmed, Amal, Ahmad Bahloul, Mohamed Iben Houria, Anouar Nasr, and Raouf Fathallah. "Multiaxial fatigue life estimation of defective aluminum alloy considering the microstructural heterogeneities effect." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 233, no. 9 (August 16, 2018): 1830–42. http://dx.doi.org/10.1177/1464420718792024.
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The Al–Si–Mg high-cycle fatigue behavior is mainly affected by the microstructural heterogeneities and the presence of casting defects. This attempt aims to develop an analytical approach based on the evaluation of the highly stressed volume caused by local porosities and defined as the affected area methodology. The proposed approach is able to predict the aluminum alloy fatigue response by considering the effect of microstructure described by the secondary dendrite arm spacing and its correlation with the defect size effect. A representative elementary volume model is implemented to evaluate the stress distribution in the vicinity of the defect and to determine its impact on the high-cycle fatigue resistance. Work hardening due to cyclic loading is considered by applying the Lemaitre–Chaboche model. The Kitagawa–Takahashi diagrams corresponding to different microstructures and for two loading ratios: R σ = 0 and R σ = −1 were simulated based on the AA method. Simulations were compared to the experimental results carried out on cast aluminium alloy A356 with T6 post heat-treatment. The results show clearly that the proposed approach provides a good estimation of the A356-T6 fatigue limit and exhibits good ability in simulating the Kitagawa–Takahashi diagrams for fine and coarse microstructures.
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Chung, Hsin-Yang, Lance Manuel, and Karl H. Frank. "Reliability-Based Optimal Inspection for Fracture-Critical Steel Bridge Members." Transportation Research Record: Journal of the Transportation Research Board 1845, no. 1 (January 2003): 39–47. http://dx.doi.org/10.3141/1845-05.
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To prevent fatigue failure of members in steel bridges, one usually needs to perform frequent periodic bridge inspections and employ detailed inspection methods. This is especially true for fracture-critical members or details. Carrying out these inspections puts a large burden on a transportation agency’s bridge maintenance budget. A systematic reliabilitybased method for inspection scheduling is proposed to yield the most economical inspection strategy for steel bridges that, at the same time, guarantees an acceptable safety level through the planned service life. A methodology is presented for evaluating the fatigue reliability of a specified detail classified according to AASHTO fatigue categories. A Miner’s rule approach is used to evaluate the fatigue reliability. The inspection scheduling problem is modeled as an optimization problem with a welldefined objective function that includes the total expected cost of inspection, repair, and failure formulated on the basis of an event tree framework and appropriate constraints in inspection intervals and minimum (target) structural reliability. An optimal inspection-scheduling plan can thus be obtained for any specified fatigue details (fracture-critical details) in steel bridges. Examples presented demonstrate the advantage of the reliabilitybased optimal inspection scheduling in cost saving and structural reliability control over alternative periodic inspection plans. Two numerical examples for a steel bridge in Texas are presented to demonstrate the proposed reliability-based optimal inspection scheduling.
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Stoschka, Michael, Hermann Maderbacher, and Martin Stockinger. "Microstructural Assessment of IN718: A Closed-Loop Fatigue Approach." Materials Science Forum 706-709 (January 2012): 2468–73. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2468.
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The goal of relating a local fatigue life approach with different microstructures requires the consideration of the main forging process dependent influence factors and their effect on grain size, grain shape, grain contiguity and others. The presented methodology shows the generation and use of a microstructural based evaluation method to link the grain-shape based texture and morphology to the low-cycle-fatigue behavior of superalloy 718. The developed microstructural based energy approach supports an alternative description of the microstructure and grain shape texture. Both, the morphology and the statistical distribution, although covering as-large-as grains, are assessed by two independent numerical parameters. A parametric link to local fatigue parameters was established using this alternative microstructural characterization technique. A prediction of the microstructural evolution during the forging process is already available at design stage for hot-forging of this nickel-base superalloy. In this regard the value of the first parameterecorrelates with the mean grain size; the value of the second parameterbis affected by the local forging process history. This enables the lifetime assessment of local forging process at design stage using advanced forging simulation tools. This holistic approach of establishment an experimental based methodology from specimen tests, extensive companying metallographic evaluations, linking them with local forging parameters, implementing the supported microstructural parameters to forging simulation codes and calculating the local component lifetime closes the simulation chain for superalloy 718.
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Jeong, Youn-Ju, Min-Su Park, Sung-Hoon Song, and Jeongsoo Kim. "Numerical Evaluation of Structural Safety for Aged Onshore Wind Foundation to Extend Service Life." Applied Sciences 10, no. 13 (June 30, 2020): 4561. http://dx.doi.org/10.3390/app10134561.
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In this paper, for the case of “service life extension” with the same capacity for wind turbines, a structural safety evaluation was carried out to determine whether to extend the service life of the aged foundation. As a result of this study, it was found that the aged foundation satisfies the structural safety of material strength, ultimate strength, fatigue life, and serviceability up to the present. Although the in-service period has been over 16 years, it has been shown that the material properties of concrete have exceeded the design strength, and no significant material deterioration has occurred. Also, structural safety could be evaluated more realistically based on actual concrete properties. In particular, it has been shown that it has a fatigue life of 40 years or more, so service life can be extended. It is expected that the methodology used in this paper will be useful not only for structural safety evaluation of the foundation in service, but also for decision-making for extending the service life. Furthermore, a more technical approach should be explored by many researchers in the future.
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Branco, Ricardo, P. A. Prates, J. D. Costa, Filippo Berto, and Andrei Kotousov. "New methodology of fatigue life evaluation for multiaxially loaded notched components based on two uniaxial strain-controlled tests." International Journal of Fatigue 111 (June 2018): 308–20. http://dx.doi.org/10.1016/j.ijfatigue.2018.02.027.
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Yang, Lin, Yan Jin, Pei Cai, Fu Xing Yin, Qiang Li, and T. Zhai. "Quantification of Fatigue Weaklinks in High Strength Al Alloys." Materials Science Forum 877 (November 2016): 427–34. http://dx.doi.org/10.4028/www.scientific.net/msf.877.427.
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Fatigue weak-link density and strength distribution are materials fatigue properties which are useful in evaluation of alloy quality in terms of the fatigue crack nucleation behavior. This paper reports: 1) an experimental methodology developed to measure fatigue weak-link density and strength distribution by measuring surface crack population as a function of the maximum applied stress, and 2) a quantitative model to quantify fatigue weak-links, based on the 3-D effects of pores in cast alloys. The experimental method could be employed to characterize the fatigue crack initiation behaviors and their anisotropy in wrought and cast Al alloys such as AA8090 Al-Li, AA2026, AA7075 and A713 alloys. It was found that the crack populations were a Weibull function of the applied maximum stress. By fitting this measured curve, fatigue weak-link density could be quantified in these alloys. The derivative of the measured Weibull function resulted in the strength distribution of the fatigue weak-links. The fatigue weak-links could also be quantified from the reconstructed microstructure of a cast Al alloy by analyzing the stress/strain fields around a micro-pore (an elasto-plastic media) under cyclic loading as a function of pore position in depth on surface using a 3-D finite element method. The incubation life for the fatigue crack initiated from a surface pore could be estimated using a microscopic scale Manson-Coffin equation. The results obtained using the 3-D pore-sensitive model were consistent with the experimental results, i.e., the crack population was a Weibull function of the applied stress. The percentage of crack initiation life was found to increase with decrease in cyclic load, i.e., at the stress just above the fatigue limit, it was over 95% the total fatigue life, compared to just 62.5% at the maximum stress of 110% yield strength.
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Zuluaga-Ramírez, Pablo, Malte Frövel, Álvaro Arconada, Tomás Belenguer, and Félix Salazar. "Evaluation of the Fatigue Linear Damage Accumulation Rule for Aeronautical CFRP Using Artificial Neural Networks." Advanced Materials Research 1016 (August 2014): 8–13. http://dx.doi.org/10.4028/www.scientific.net/amr.1016.8.
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New optimized aerospace structures use composite materials for critical components and subsystems which make essential the knowledge of their fatigue properties. In the present work, the conventional methodology based on linear damage accumulation rules, applied to determine the fatigue life of structures subjected to spectral loads was evaluated for an aeronautical Carbon Fiber Reinforced Epoxy composite material. A test program has been performed to obtain the classical S-N curves at different stress ratios. Constant life diagrams, CLDs, where determined by means of Artificial Neural Networks due to the absence of consistent models for composites. A series of coupons have been tested until failure with a modified version of the standard FALSTAFF load sequence and were compared to the theoretical damage index calculated based on the conventional linear damage accumulation rule. The obtained results show non-conservative predictions.
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Cunha, F. J., M. T. Dahmer, and M. K. Chyu. "Thermal-Mechanical Life Prediction System for Anisotropic Turbine Components." Journal of Turbomachinery 128, no. 2 (February 1, 2005): 240–50. http://dx.doi.org/10.1115/1.2137740.
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Modern gas turbine engines provide large amounts of thrust and withstand severe thermal-mechanical conditions during the load and mission operations characterized by cyclic transients and long dwell times. All these operational factors can be detrimental to the service life of turbine components and need careful consideration. Engine components subject to the harshest environments are turbine high-pressure vanes and rotating blades. Therefore, it is necessary to develop a turbine component three-dimensional life prediction system, which accounts for mission transients, anisotropic material properties, and multi-axial, thermal-mechanical, strain, and stress fields. This paper presents a complete life prediction approach for either commercial missions or more complex military missions, which includes evaluation of component transient metal temperatures, resolved maximum shear stresses and strains, and subsequent component life capability for fatigue and creep damage. The procedure is based on considering all of the time steps in the mission profile by developing a series of extreme points that envelop every point in the mission. Creep damage is factored into the component capability by debiting thermal-mechanical accumulated cycles using the traditional Miner’s rule for accumulated fatigue and creep damage. Application of this methodology is illustrated to the design of the NASA Energy Efficient Engine (E3) high pressure turbine blade with operational load shakedown leading to stress relaxation on the external hot surfaces and potential state of overstress in the inner cold rib regions of the airfoil.
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Kim, Jong Choon, Sung Wook Jung, Jae Boong Choi, Yoon Suk Chang, Young Jin Kim, and In-Ju Hwang. "Development of a Neural Network-Based Real-Time Fatigue Monitoring System for the Heavy Load Carrying Facility." Solid State Phenomena 110 (March 2006): 201–12. http://dx.doi.org/10.4028/www.scientific.net/ssp.110.201.
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The heavy load carrying facility, such as ladle crane, is operating under severe working environment. It usually carries melted iron to the furnace, and thus, the accident due to crane failure may cause detrimental damage to the entire steel making factory. While the ladle crane is designed for 20 years of safe operation in a steel making company, several critical cracks due to fatigue loading have been reported during the maintenance process. In order to prevent fatal failure due to crack growth, ladle crane has been periodically inspected and maintained. However, the inspection and maintenance including repair and replacement cause the whole manufacturing line to stop, it is critical to set the appropriate inspection interval and replacement criteria. For this reason, the importance of plant maintenance (PM) has been highly raised to provide efficient plant operation. Recently, a number of engineering methodologies, such as fitness for service guidelines (FFS) and plant lifecycle management (PLM) system, have been applied to improve the plant operation efficiency. Also, a network-based business operation system, which is called ERP (Enterprise Resource Planning), has been introduced in the field of plant maintenance. However, there hasn’t been any attempt to connect engineering methodologies to the ERP PM(Plant Maintenance) system. In this paper, an engineering methodology which provides life time evaluation under fatigue loading has been implemented to the web-based ERP PM system along with real-time fatigue monitoring system. In order to monitor the real time loading, a web-based fatigue monitoring system for ladle crane has been developed and installed inside the ladle crane. For the estimation of fatigue life, 3-dimensional finite element (FE) analyses were conducted for actual transients. Finally, the fatigue life time estimation program is developed by integrating FE analysis results and real-time monitoring data. For the direct calculation of remained fatigue life, an artificial neural network (ANN) algorithm has been applied. The proposed system is expected to play a great role in determining appropriate inspection and maintenance schedule which has become critical issue for the efficient plant maintenance.
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Tomaru, Shuji, and Akiyuki Takahashi. "Three-dimensional fatigue crack growth simulation of embedded cracks using s-version FEM." International Journal of Structural Integrity 11, no. 4 (December 19, 2019): 547–55. http://dx.doi.org/10.1108/ijsi-10-2019-0107.
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Purpose Since the most of structures and structural components suffers from cyclic loadings, the study on the fatigue failure due to the crack growth has a great importance. The purpose of this paper is to present a three-dimensional fatigue crack growth simulation of embedded cracks using s-version finite element method (SFEM). Using the numerical results, the validity of the fitness-for-service (FFS) code evaluation method is verified. Design/methodology/approach In this paper, three-dimensional fatigue crack propagation analysis of embedded cracks is performed using the SFEM. SFEM is a numerical analysis method in which the shape of the structure is represented by a global mesh, and cracks are modeled by local meshes independently. The independent global and local meshes are superimposed to obtain the displacement solution of the problem simultaneously. Findings The fatigue crack growth of arbitrary shape of cracks is slow compared to that of the simplified circular crack and the crack approximated based on the FFS code of the Japan Society of Mechanical Engineers (JSME). The results tell us that the FFS code of JSME can provide a conservative evaluation of the fatigue crack growth and the residual life time. Originality/value This paper presents a three-dimensional fatigue crack growth simulation of embedded cracks using SFEM. Using this method, it is possible to apply mixed mode loads to complex shaped cracks that are closer to realistic conditions.
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Pelegatti, Marco, Alex Lanzutti, Enrico Salvati, Jelena Srnec Novak, Francesco De Bona, and Denis Benasciutti. "Cyclic Plasticity and Low Cycle Fatigue of an AISI 316L Stainless Steel: Experimental Evaluation of Material Parameters for Durability Design." Materials 14, no. 13 (June 27, 2021): 3588. http://dx.doi.org/10.3390/ma14133588.
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AISI 316L stainless steels are widely employed in applications where durability is crucial. For this reason, an accurate prediction of its behaviour is of paramount importance. In this work, the spotlight is on the cyclic response and low-cycle fatigue performance of this material, at room temperature. Particularly, the first aim of this work is to experimentally test this material and use the results as input to calibrate the parameters involved in a kinematic and isotropic nonlinear plasticity model (Chaboche and Voce). This procedure is conducted through a newly developed calibration procedure to minimise the parameter estimates errors. Experimental data are eventually used also to estimate the strain–life curve, namely the Manson–Coffin curve representing the 50% failure probability and, afterwards, the design strain–life curves (at 5% failure probability) obtained by four statistical methods (i.e., deterministic, “Equivalent Prediction Interval”, univariate tolerance interval, Owen’s tolerance interval for regression). Besides the characterisation of the AISI 316L stainless steel, the statistical methodology presented in this work appears to be an efficient tool for engineers dealing with durability problems as it allows one to select fatigue strength curves at various failure probabilities depending on the sought safety level.
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Babu, S., and P. K. Iyer. "Inelastic Analysis of Components Using a Modulus Adjustment Scheme." Journal of Pressure Vessel Technology 120, no. 1 (February 1, 1998): 1–5. http://dx.doi.org/10.1115/1.2841879.
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Mechanical components and structures loaded into inelastic region can fail by low cycle fatigue (LCF). Evaluation of inelastic strain is an important stage in the LCF life prediction methodology. Different techniques, viz., experimental methods, elastic-plastic finite element analysis (FEA), and robust methods, can be used to predict inelastic strains. The state predicted by available robust methods does not correspond to equilibrium state of the component. A method called MARS (modulus adjustment and redistribution of stress) based on linear elastic FEA has been developed to obtain equilibrium and kinematic distributions close to the actual one. The proposed method uses an iterative strategy combined with a modulus reduction technique.
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CHEBBI, EL, A. JARRAYA, and F. DAMMAK. "A COMPARATIVE STUDY FOR TWO-DAMAGE MODELLING MODELS USING COMPOSITE MATERIAL." International Journal of Computational Materials Science and Engineering 01, no. 02 (June 2012): 1250014. http://dx.doi.org/10.1142/s2047684112500145.
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Purpose- This paper describes finite element fatigue damage modeling. Design/Methodology/Approach- Fatigue life prediction and damage progressive evaluation are analytically studied. We present a numerical implementation of the studied models into the home made finite element code MPEF. Numerical simulations are performed on composite and metallic material. We carried out a parametric study to investigate the influence of model's parameters on the damage accumulation and their sensitivity on its kinetics. Simulations are conducted for two different loading levels to characterize cumulative damage and to study loading sequence effect. A comparative study is performed to characterize the efficiency of the two models to describe the damage evolution for the two different materials. Findings- Numerical examples are presented to illustrate its performance. Originality/value- This paper intends to present a comparative study of the damage evolution for metallic and composite material under uniaxial loading. The effect of the loading sequence will be investigated.
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Johansson, Jonas, Ilja Belov, Erland Johnson, and Peter Leisner. "A computational method for evaluating the damage in a solder joint of an electronic package subjected to thermal loads." Engineering Computations 31, no. 3 (April 28, 2014): 467–89. http://dx.doi.org/10.1108/ec-07-2012-0163.
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Purpose – The purpose of this paper is to introduce a novel computational method to evaluate damage accumulation in a solder joint of an electronic package, when exposed to operating temperature environment. A procedure to implement the method is suggested, and a discussion of the method and its possible applications is provided in the paper. Design/methodology/approach – Methodologically, interpolated response surfaces based on specially designed finite element (FE) simulation runs, are employed to compute a damage metric at regular time intervals of an operating temperature profile. The developed method has been evaluated on a finite-element model of a lead-free PBGA256 package, and accumulated creep strain energy density has been chosen as damage metric. Findings – The method has proven to be two orders of magnitude more computationally efficient compared to FE simulation. A general agreement within 3 percent has been found between the results predicted with the new method, and FE simulations when tested on a number of temperature profiles from an avionic application. The solder joint temperature ranges between +25 and +75°C. Practical implications – The method can be implemented as part of reliability assessment of electronic packages in the design phase. Originality/value – The method enables increased accuracy in thermal fatigue life prediction of solder joints. Combined with other failure mechanisms, it may contribute to the accuracy of reliability assessment of electronic packages.
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Chen, B. L., X. Q. Shi, G. Y. Li, K. H. Ang, and Jason P. Pickering. "Rapid Temperature Cycling (RTC) Methodology for Reliability Assessment of Solder Interconnection in Tape Ball Grid Array (TBGA) Assembly." Journal of Electronic Packaging 127, no. 4 (February 24, 2005): 466–73. http://dx.doi.org/10.1115/1.2056574.
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In this study, a thermoelectric cooler-based rapid temperature cycling (RTC) testing method was established and applied to assess the long term reliability of solder joints in tape ball grid array (TBGA) assembly. This RTC testing methodology can significantly reduce the time required to determine the reliability of electronic packaging components. A three-parameter Weibull analysis characterized with a parameter of failure free time was used for assembly reliability assessment. It was found that the RTC not only speedily assesses the long-term reliability of solder joints within days, but also has the similar failure location and failure mode observed in accelerated temperature cycling (ATC) test. Based on the RTC and ATC reliability experiments and the modified Coffin-Manson equation, the solder joint fatigue predictive life can be obtained. The simulation results were found to be in good agreement with the test results from the RTC. As a result, a new reliability assessment methodology was established as an alternative to ATC for the evaluation of long-term reliability of electronic packages.
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Kwak, Jae B., and Soonwan Chung. "Thermal fatigue reliability for Cu-Pillar bump interconnection in flip chip on module and underfill effects." Soldering & Surface Mount Technology 27, no. 1 (February 2, 2015): 1–6. http://dx.doi.org/10.1108/ssmt-03-2014-0008.
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Purpose – The purpose of this paper is to assess the thermo-mechanical reliability of a solder bump with different underfills, with the evaluation of different underfill materials. As there is more demand in higher input/output, smaller package size and lower cost, a flip chip mounted at the module level of a board is considered. However, bonding large chips (die) to organic module means a larger differential thermal expansion mismatch between the module and the chip. To reduce the thermal stresses and strains at solder joints, a polymer underfill is added to fill the cavity between the chip and the module. This procedure has typically, at least, resulted in an increase of the thermal fatigue life by a factor of ten, as compared to the non-underfilled case. Yet, this particular case is to deal with a flip chip mounted on both sides of a printed circuit board (PCB) module symmetrically (solder bump interconnection with Cu-Pillar). Note that Cu-Pillar bumping is known to possess good electrical properties and better electromigration performance. The drawback is that the Cu-Pillar bump can introduce high stress due to the higher stiffness of Cu compared to the solder material. Design/methodology/approach – As a reliability assessment, thermal cyclic loading condition was considered in this case. Thermal life prediction was conducted by using finite element analysis (FEA) and modified Darveaux’s model, considering microsize of the solder bump. In addition, thermo-mechanical properties of four different underfill materials were characterized, such as Young’s modulus at various temperatures, coefficient of temperature expansion and glass transition temperature. By implementing these properties into FEA, life prediction was accurately achieved and verified with experimental results. Findings – The modified life prediction method was successfully adopted for the case of Cu-Pillar bump interconnection in flip chip on the module package. Using this method, four different underfill materials were evaluated in terms of material property and affection to the fatigue life. Both predicted life and experimental results are obtained. Originality/value – This study introduces the technique to accurately predict thermal fatigue life for such a small scale of solder interconnection in a newly designed flip chip package. In addition, a guideline of underfill material selection was established by understanding its affection to thermo-mechanical reliability of this particular flip chip package structure.
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Nafees, B., M. Stafford, S. Bhalla, and J. Watkins. "Health state utility and toxicities in metastatic lung cancer: A qualitative study." Journal of Clinical Oncology 24, no. 18_suppl (June 20, 2006): 16017. http://dx.doi.org/10.1200/jco.2006.24.18_suppl.16017.
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16017 Background: In metastatic lung cancer, it is expected that quality of life is impacted both by the efficacy and toxicity of therapy. Previous research has reported health states either based on response to therapy or on toxicity, but not in combination. Using methodology applied in breast cancer (Narewska 2005), we developed health state descriptions for advanced non-small cell lung cancer (NSCLC) for use in cost-utility analyses. Methods: An interview discussion and content validation guide was produced based on literature review and clinical input. Response to therapy was described as responding disease, stable disease, or progressive disease. The most common toxicities were selected based on randomized clinical trials. Descriptions of health states were reviewed by clinical specialists. Final health states will be piloted and then used in a societal-based valuation study using standard gamble technique. The contributory effect of disease state and toxicity will be estimated using a mixed model analysis and compared with the data from the previous breast cancer utility study. Results: Eight toxicities were identified: alopecia and grade 3/4 neutropenia, febrile neutropenia, hand-foot syndrome, gastrointestinal (diarrhea/vomiting), rash, stomatitis and fatigue. These were combined with response to therapy to yield 19 health states: 9 responding disease (one with each toxicity plus one with no toxicity), 9 stable disease (one with each toxicity plus one with no toxicity) and one progressive disease (toxicity not included). These health states were reviewed by 6 pulmonary oncologists and 3 specialist nurses. Conclusions: Development of health states that combine both efficacy and toxicity will be useful in evaluating the relative value of therapies for advanced NSCLC and comparison with other diseases. Input by clinical experts has provided validation for the proposed health states. Evaluation of these health states by members of society will provide appropriate perspective for economic evaluations. [Table: see text]
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Bhalla, S., B. Nafees, M. Stafford, and J. Watkins. "Health state utility and toxicities in metastatic lung and breast cancer: A qualitative study." Journal of Clinical Oncology 24, no. 18_suppl (June 20, 2006): 16021. http://dx.doi.org/10.1200/jco.2006.24.18_suppl.16021.
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16021 Background: In metastatic lung cancer, it is expected that quality of life is impacted both by the efficacy and toxicity. Previous research has reported health states either based on response to therapy or on toxicity, but not in combination. Using methodology applied in breast cancer (Narewska 2005), we developed health state descriptions for advanced non-small cell lung cancer (NSCLC) for use in cost-utility analyses. Methods: An interview discussion and content validation guide was produced based on literature review and clinical input. Response to therapy was described as responding disease, stable disease, or progressive disease. The most common toxicities were selected based on randomized clinical trials. Descriptions of health states were reviewed by clinical specialists. Final health states will be piloted and then used in a societal-based valuation study using standard gamble technique. The contributory effect of disease state and toxicity will be estimated using a mixed model analysis and compared with the data from the previous breast cancer utility study. Results: Eight toxicities were identified: alopecia and grade 3/4 neutropenia, febrile neutropenia, hand-foot syndrome, gastrointestinal (diarrhea/vomiting), rash, stomatitis and fatigue. These were combined with response to therapy to yield 19 health states: 9 responding disease (one with each toxicity plus one with no toxicity), 9 stable disease (one with each toxicity plus one with no toxicity) and one progressive disease (toxicity not included). These health states were reviewed by 6 pulmonary oncologists and 3 specialist nurses. Conclusion: Development of health states that combine both efficacy and toxicity will be useful in evaluating the relative value of therapies for advanced NSCLC and comparison with other diseases. Input by clinical experts has provided validation for the proposed health states. Evaluation of these health states by members of society will provide appropriate perspective for economic evaluations. [Table: see text]
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Aigner, Roman, Martin Leitner, and Michael Stoschka. "Fatigue strength characterization of Al-Si cast material incorporating statistical size effect." MATEC Web of Conferences 165 (2018): 14002. http://dx.doi.org/10.1051/matecconf/201816514002.
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Cast aluminium components may exhibit material imperfections such as shrinkage and gas pores, or oxide inclusions. Therefore, the fatigue resistance is significantly influenced by the size and location of these inhomogenities. In this work, two different specimen geometries are manufactured from varying positions of an Al-Si-Cu alloy casting. The specimen geometries are designed by means of shape optimization based on a finite element analysis and exhibit different highly-stressed volumes. The numerically optimized specimen curvature enforces a notch factor of only two percent. To enable the evaluation of a statistical size effect, the length of the constant testing region and hence, the size of the highly-stressed volume varies by a ratio of one to ten between the two specimen geometries. Furthermore, the location of the crack initiation is dominated by the comparably greatest defects in this highly-stressed volume, which is also known as Weibull’s weakest link model. The crack initiating defect sizes are evaluated by means of light microscopy and modern scanning electron microscope methods. Finally, the statistical size effect is analysed based on the extreme value distribution of the occurring defects, whereby the size and location of the pores is non-destructively obtained by computed tomography (CT) scanning. This elaborated procedure facilitates a size-effect based methodology to study the defect distribution and the associated local fatigue life of CPS casted Al-Si lightweight components.
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Michailidis, Nikolaos, Konstantinos D. Bouzakis, Fritz Klocke, Martin Witty, Eleftheria Lili, Stefanos Gerardis, and Maria Pappa. "Evaluation of PVD Coated Tools’ Life in Milling Ti6Al4V, Based on Impact Tests at Ambient and Elevated Temperatures." Key Engineering Materials 438 (May 2010): 187–94. http://dx.doi.org/10.4028/www.scientific.net/kem.438.187.
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A methodology based on FEM-calculations and experimental tests for predicting coated tool efficiency in milling Ti6Al4V by coated cemented carbide inserts is introduced. The used coatings were: (Ti,Al,Si)N and (Ti,Al)N films. The stress-strain curves and the fatigue critical loads of the coatings were determined by nanoindentations and impact tests respectively at various temperatures, employing FEM-supported procedures developed for results evaluation. The milling investigations were conducted at various cutting speeds. The stress and temperature fields in the cutting edge region were obtained by FEM calculations of the milling process. These results facilitated the explanation of the coated inserts’ cutting performance versus the cutting speed. The cutting tests at various cutting speeds and the impact tests at ambient and elevated temperatures revealed that the tool life and the film impact resistance versus the temperature are not linear. Moreover, a sufficient correlation of the coatings’ impact resistance at various temperatures with their cutting performance at corresponding cutting speeds was revealed. In this way, an adaption of the cutting conditions to the films’ temperature-dependent strength can lead to a considerable cutting performance improvement.
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Poberezhny, L., S. Tregubenko, L. Poberezhna, A. Hrytsanchuk, and A. Stanetsky. "Influence of loads in the process of laying on the resource of sea pipelines." Archives of Materials Science and Engineering 2, no. 96 (April 1, 2019): 63–72. http://dx.doi.org/10.5604/01.3001.0013.2385.
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Purpose: In the process of laying on the bottom of the sea material of the pipeline undergoes single-cycle alternating load. The purpose of the work is to determine the effect of pre-operational loads on the resource of marine pipelines. Design/methodology/approach: The influence of the method of construction of pipelines on their stress-strain state is analysed. According to the real modes of packing of sea pipelines, the loading regime is programmed and the laboratory modelling of the pipe- laying process by the S-method has been programmed. Findings: According to the results of one-cycle shift load were obtained characteristics of the hysteresis loop. It is proposed to simplify the mathematical description of the hysteresis loop of the pipeline laying cycle in the given form. It was shown that the preload during the construction process negatively affects the durability of the pipeline material due to the exhaustion of its plasticity resource, reducing it to 70%. Research limitations/implications: In the future, investigations into the effect of overloading and overloading during the repair of pipeline sections on their durability and on the safe exploitation of resources should be continued. Practical implications: The developed method of estimation of influence of pre- operational loads in the process of pipeline laying on its safe exploitation resource is used in gas-extraction enterprises. Originality/value: To forecast the deformation behaviour of the pipeline material in the laying cycle, it is efficient to use diagrams of a sign-changing single-cycle bend, which were built considering the creep. The fatigue life capability of a steel pipeline depends on the history of the pipeline load in the laying cycle. Ratio σ*0.2c / σ*0.2t and ε yc / ε yt can use as power and deformation criteria for evaluating Bauschinger effect. It is suggested that fatigue damage is determined by the width of the hysteresis loop.
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Knott, Jayne F., Mohamed Elshaer, Jo Sias Daniel, Jennifer M. Jacobs, and Paul Kirshen. "Assessing the Effects of Rising Groundwater from Sea Level Rise on the Service Life of Pavements in Coastal Road Infrastructure." Transportation Research Record: Journal of the Transportation Research Board 2639, no. 1 (January 2017): 1–10. http://dx.doi.org/10.3141/2639-01.
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Coastal communities with road infrastructure close to the shoreline are vulnerable to the effects of sea level rise caused by climate change. The sea level in coastal New Hampshire is projected to rise by 3.9 to 6.6 ft (1.2 to 2.0 m) by 2100. Climate change vulnerability and adaptation studies have focused on surface water flooding caused by sea level rise; however, little attention has been given to the effects of climate change on groundwater. Groundwater is expected to rise with sea level rise and will intersect the unbound layers of coastal road infrastructure, thus reducing the service life of pavement. Vulnerability studies are an essential part of adaptation planning, and pavement engineers are looking for methods to identify roads that may experience premature failure. In this study, a regional groundwater flow model of coastal New Hampshire was used to identify road infrastructure for which rising groundwater will move into the unbound materials during the design life of the pavement. Multilayer elastic theory was used to analyze typical pavement profiles in several functional classifications of roadway to determine the magnitude of fatigue and rutting life reduction expected from four scenarios of sea level rise. All the evaluation sites experienced service life reduction, the magnitude and timing of which depended on the current depth to groundwater, the pavement structure, and the subgrade. The use of this methodology will enable pavement engineers to target coastal road adaptation projects effectively and will result in significant cost savings compared with implementation of broad adaptation projects or the costs of no action.
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Rencken, Camerin A., Silvanys L. Rodríguez-Mercedes, Khushbu F. Patel, Gabrielle G. Grant, Erin M. Kinney, Robert L. Sheridan, Keri J. Brady, et al. "1 Development of the School-Aged Life Impact Burn Recovery Evaluation (SA-LIBRE: 5–12) Profile: A Conceptual Model Framework." Journal of Burn Care & Research 42, Supplement_1 (April 1, 2021): S6—S7. http://dx.doi.org/10.1093/jbcr/irab032.006.
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Abstract Introduction Pediatric burn injuries can alter the trajectory of the survivor’s entire life. Patient-centered outcome measures are helpful to capture and assess their unique physical and psychosocial needs and long-term recovery. This study aimed to develop a conceptual model framework to measure outcomes most important to pediatric burn survivors aged 5 to 12 years as a part of the SA-LIBRE5-12 Computer Adaptive Test (CAT) development. Methods This study used a systematic literature review guided by the WHO International Classification of Functioning – Child and Youth. Previously established domains in the American Burn Association/Shriners Hospitals for Children Burn Outcomes Questionnaire5-18 further guided framework development. Individual interviews with parents and clinicians were conducted to obtain perspectives on domains most important to assess following a burn injury in children aged 5 to 12 years. One clinician focus group was completed to identify gaps in the preliminary framework, and semi-weekly expert consensus meetings were conducted to solidify the framework. Qualitative data were analyzed by grounded theory methodology in NVivo 12 software. Results The literature review identified 82 articles. Eight parents and seven clinicians participated in individual interviews, four clinicians participated in one focus group, and three consultants were included in the expert consensus meetings. The consultants included a burn surgeon, psychiatrist, and health services researcher. Three major domains emerged from the grounded theory approach, including: 1) Physical Functioning: fine motor and upper extremity, gross motor and lower extremity, pain, skin sensitivity, sleep and fatigue, and physical resilience; 2) Psychological Functioning: cognitive, behavioral, emotional, resilience, and body image; and 3) Family and Social Functioning: school, peer relations, community participation, family relationships, and parental satisfaction. Conclusions The comprehensive literature review, clinician and parent individual interviews, clinician focus group, and expert consensus meetings resulted in a conceptual model framework for parent-reported health outcomes after a burn injury in school-aged children aged 5 to 12 years. The framework will be used to develop item banks for a CAT-based assessment of school-aged children’s health and developmental outcomes.