Academic literature on the topic 'Load-strain relationships'
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Journal articles on the topic "Load-strain relationships"
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Zheng, Guozhi, Naitian Zhang, and Songtao Lv. "The Application of Fractional Derivative Viscoelastic Models in the Finite Element Method: Taking Several Common Models as Examples." Fractal and Fractional 8, no. 2 (2024): 103. http://dx.doi.org/10.3390/fractalfract8020103.
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This paper aims to incorporate the fractional derivative viscoelastic model into a finite element analysis. Firstly, based on the constitutive equation of the fractional derivative three-parameter solid model (FTS), the constitutive equation is discretized by using the Grünwald–Letnikov definition of the fractional derivative, and the stress increment and strain increment relationship and Jacobian matrix are obtained by using the difference method. Subsequently, we degrade the model to establish stress increment and strain increment relationships and Jacobian matrices for the fractional derivative Kelvin model (FK) and fractional derivative Maxwell model (FM). Finally, we further degrade the fractional derivative viscoelastic model to derive stress increment and strain increment relationships and Jacobian matrices for a three-component solid model and Kelvin and Maxwell models. Based on these developments, a UMAT subroutine is implemented in ABAQUS 6.14 finite element software. Three different loading modes, including static load, dynamic load, and mobile load, are analyzed and calculated. The calculations primarily involve a convergence analysis, verification of numerical solutions, and comparative analysis of responses among different viscoelastic models.
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Sayed, Ahmed M. "Numerical Analysis of the Perforated Steel Sheets Under Uni-Axial Tensile Force." Metals 9, no. 6 (2019): 632. http://dx.doi.org/10.3390/met9060632.
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The perforated steel sheets have many uses, so they should be studied under the influence of the uniaxial tensile load. The presence of these holes in the steel sheets certainly affects the mechanical properties. This paper aims at studying the behavior of the stress-strain engineering relationships of the perforated steel sheets. To achieve this, the three-dimensional finite element (FE) model is mainly designed to investigate the effect of this condition. Experimental tests were carried out on solid specimens to be used in the test of model accuracy of the FE simulation. Simulation testing shows that the FE modeling revealed the ability to calculate the stress-strain engineering relationships of perforated steel sheets. It can be concluded that the effect of a perforated rhombus shape is greater than the others, and perforated square shape has no effect on the stress-strain engineering relationships. The efficiency of the perforated staggered or linearly distribution shapes with the actual net area on the applied loads has the opposite effect, as it reduces the load capacity for all types of perforated shapes. Despite the decrease in load capacity, it improves the properties of the steel sheets.
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Wang, Yunyang, Shengwei Sun, Liqing Zhang, and Yandong Jia. "Compressive Behaviors of Thin-Walled Steel Tube Stub Columns Filled with Self-Compacting Concrete Containing Recycled Aggregate." Materials 16, no. 18 (2023): 6088. http://dx.doi.org/10.3390/ma16186088.
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Natural resources have been excessively consumed, and large amounts of construction wastes have been generated, owing to the fast development of civil industry, causing crucial environmental issues. Therefore, reusable construction waste fabricated into recycled concrete offers a good strategy to solve this issue. Thus, this article first develops thin-walled steel tubes stub columns filled with self-compacting concrete containing recycled coarse aggregate. Afterwards, the compressive behaviors of the columns when undergoing axial compression loading to failure are explored. Subsequently, the effect of types of self-compacting concrete and wall thickness on failure modes and the relationships between load and displacement/strain is discussed comprehensively. Moreover, models of load–displacement/strain behaviors are proposed. The results show that columns with identical wall thicknesses containing both natural and recycled coarse aggregate display similar failure modes, mainly presenting as local buckling and rupture. The shape of the load–displacement/strain curves for identical wall thicknesses are almost the same. Nevertheless, the maximum load and stiffness of columns containing recycled coarse aggregate are lower than those of columns containing natural coarse aggregate. Additionally, the maximum loads corresponding to wall thickness of 1.2 mm and 3.0 mm are decreased by 18.4% and 5.8%, respectively. Moreover, the proposed models can reasonably evaluate the relationships between load and displacement/strain. This paper demonstrates that thin-walled steel tubular columns containing recycled coarse aggregate present positive compressive behaviors and thus exhibit great potential for developing environmentally friendly and sustainable civil infrastructures.
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Ding, Fa Xing, Zhi Wu Yu, and Jin Ping Ou. "Elasto-Plastic Analysis of Concrete-Filled Circular Steel Tubular Stub Columns after Exposed to High Temperatures." Key Engineering Materials 400-402 (October 2008): 763–68. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.763.
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Based on the research achievements of the mechanical properties of concrete at uniaxial compression and steel at uniaxial tension after exposed to high temperatures, the axisymmetric- triaxial-compressive stress-strain relationships of concrete and multiaxial stress-strain relationships of steel after exposed to high temperatures was suggested. Based on continuum mechanics, the mechanical model of concentric cylinders of circular steel tube with concrete core of entire section loaded after exposed to high temperature was determined. By applying Elasto-Plastic Analysis Method, theoretical calculation formulas for composite elastic modulus and composite stress-strain relationships of concrete-filled circular steel tubular (CFST) stub columns were proposed and a FORTRAN program was developed and the load-axial strain relationships of CFST stub columns after exposed to high temperatures were analyzed. The analysis results were in reasonable agreement with the experiment ones from references.
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Stich, Jean-Francois, Monideepa Tarafdar, Patrick Stacey, and Cary L. Cooper. "E-mail load, workload stress and desired e-mail load: a cybernetic approach." Information Technology & People 32, no. 2 (2019): 430–52. http://dx.doi.org/10.1108/itp-10-2017-0321.
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PurposeUsing e-mail is a time-consuming activity that can increase workload stress. The purpose of this paper is to investigate the relationship between the individual’s e-mail load, workload stress and desired e-mail load, drawing from the cybernetic theory of stress.Design/methodology/approachBased on prior theory, the authors first hypothesized relationships among e-mail load, workplace stress and desired e-mail load. The authors then tested these relationships on a sample of 504 full-time workers in the USA, using survey data and covariance-based structural equation modeling techniques.FindingsThe authors find that higher e-mail load is associated with higher workload stress; higher workload stress is associated with lower desired e-mail load; lower desired e-mail load is associated with lower e-mail load; and higher workload stress is associated with higher psychological strain, higher negative emotions and lower organizational commitment.Originality/valueThe study provides a novel understanding of workload stress due to e-mail load, through the lens of cybernetic theory. It contributes to the e-mail overload and technostress literatures by conceptualizing desired e-mail load as a potential outcome of workplace stress and as a regulator for e-mail load. For practitioners, the study highlights the importance of managing employees’ e-mail load to prevent the negative effects of workplace stress and associated strains.
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Jia, Hui Ji, Lian Fa Yang, and Jian Wei Liu. "Establishment of Stress-Strain Relationships of Tailor-Welded Tubes via DIC Method Based on Uniaxial Tensile Tests." Key Engineering Materials 611-612 (May 2014): 475–82. http://dx.doi.org/10.4028/www.scientific.net/kem.611-612.475.
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Tailor-welded tubes are widespread in aircraft and automotive industries due to their advantages of low cost, reduction in part weight and flexibility in mass production. It is necessary to obtain the stress-strain relationship of tailor-welded tubes to study deformation behaviors of tubes and simulate deformation tests of tubes. Then a method via digital image correlation (DIC) method based on uniaxial tensile test (UTT) is proposed in this paper to establish stress-strain relationship of tailor-welded tubes. Material parameters of tailor-welded tubes obtained from three methods, i.e. the method based on UTT, the iso-strain method based on a rule of mixtures and the proposed method, were compared in this paper. To assess the accuracy of material parameters obtained from these three methods, UTTs were simulated, and load-displacement curves and maximal loads obtained from simulations were compared with those obtained from UTTs. In simulations of UTTs, finite element models of specimens of sole parent metal and mixed specimens were established, respectively. The results show that: When HAZ included in the specimen has large proportion of the specimen, the proposed method is more reliable than the iso-strain method based on a rule of mixtures on determining the material parameters of the weld; load-displacement curve and maximal load obtained from the proposed method are more close to those obtained from UTT than those obtained from the method based on UTT.
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Cheng, Yang-Tse, and Che-Min Cheng. "Relationships between initial unloading slope, contact depth, and mechanical properties for conical indentation in linear viscoelastic solids." Journal of Materials Research 20, no. 4 (2005): 1046–53. http://dx.doi.org/10.1557/jmr.2005.0141.
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Using analytical and finite element modeling, we studied conical indentation in linear viscoelastic solids with either displacement or load as the independent variable. We examine the relationships between initial unloading slope, contact depth, and viscoelastic properties for various loading conditions such as constant displacement rate, constant loading rate, and constant indentation strain rate. We then discuss whether the Oliver–Pharr method for determining contact depth, originally proposed for indentation in elastic and elastic-plastic solids, is applicable to indentation in viscoelastic solids. We conclude with a few comments about two commonly used experimental procedures for indentation measurements in viscoelastic solids: the “hold-at-peak-load” technique and the constant indentation strain-rate method.
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Kim, Sung-Hu, Kyoung-Bong Han, Kwang-Soo Kim, and Sun-Kyu Park. "Stress–strain and deflection relationships of RC beam bonded with FRPs under sustained load." Composites Part B: Engineering 40, no. 4 (2009): 292–304. http://dx.doi.org/10.1016/j.compositesb.2008.12.003.
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Zhou, Ling Yuan, and Li Qiao. "Ultimate Load Analysis of Reinforced Concrete Beam with Finite Element." Advanced Materials Research 243-249 (May 2011): 1340–45. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.1340.
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A efficient 3D beam element based on the distributed nonlinearity theory is proposed for nonlinear analysis of reinforcement concrete structures. The sections consist of reinforcing steel and concrete in this formulation and the section stiffness matrices are calculated through the integration of stress-strain relations of concrete and the accumulation of reinforcing steel effect. The force-based formulation is adopted in the evaluation of the element stiffness matrix and the element state determination. The improved Kent-Park model is adopt for the stress-strain relation of concrete, and uniaxial stress–strain relationships proposed by Mander is introduced for reinforcing steel. Finally, the ultimate load of a cantilever reinforced concrete beam subjected to a lateral load was analyzed with the proposed formulation to illustrate its accuracy and computational efficiency.
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Alatshan, Faesal, Siti Aminah Osman, Roszilah A. Hamid, and Fidelis Mashiri. "Residual compressive strength of locally corroded circular CFST stub columns: An experimental study." IOP Conference Series: Earth and Environmental Science 1369, no. 1 (2024): 012036. http://dx.doi.org/10.1088/1755-1315/1369/1/012036.
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Abstract Circular concrete-filled steel tubular (CFST) columns are widely used in civil engineering structures due to their high strength, stiffness, and ductility. However, these columns are susceptible to local corrosion damage, which can reduce their load-carrying capacity and durability. This paper presents an experimental investigation of the impact of local corrosion on the residual compressive strength of CFST stub columns. The experimental program included 9 CFST columns, which were divided into two groups: G1 and G2. G1 specimens were subjected to actual electrochemical corrosion, while G2 specimens were subjected to mechanical damage to simulate the corrosion effect. The experimental results included the tested columns’ corrosion profiles, failure modes, load-strain relationships, and load-carrying capacities. The main findings of this paper show that: (1) Different heights and thicknesses of corrosion profile representing the non-uniform localized corrosion. (2) Failure modes were mainly affected by the localized damage conditions, where the buckling occurred in the affected area. (3) Load-strain relationships exhibited elastic behavior initially, followed by nonlinear plastic behavior until reaching their ultimate compressive capacity. (4) The mechanical damage method can reasonably approximate the corrosion damage in CFST columns. This paper provides useful insights into the structural behavior of locally damaged CFST short columns.
Dissertations / Theses on the topic "Load-strain relationships"
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Traser, Courtney Jo. ""Do I really have to complete another evaluation?" exploring relationships among physicians' evaluative load, evaluative strain, and the quality of clinical clerkship evaluations." Diss., 2017. http://hdl.handle.net/1805/13392.
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Indiana University-Purdue University Indianapolis (IUPUI)<br>Background. Despite widespread criticism of physician-performed evaluations of medical students’ clinical skills, clinical clerkship evaluations (CCEs) remain the foremost means by which to assess trainees’ clinical prowess. Efforts undertaken to improve the quality of feedback students receive have ostensibly led to higher assessment demands on physician faculty; the consequences of which remain unknown. Accordingly, this study investigated the extent to which physicians’ evaluative responsibilities influenced the quality of CCEs and qualitatively explored physicians’ perceptions of these evaluations. Methods. A questionnaire was delivered to physicians (n = 93) at Indiana University School of Medicine to gauge their perceived evaluative responsibilities. Evaluation records of each participant were obtained and were used to calculate one’s measurable quantity of CCEs, the timeliness of CCE submissions, and the quality of the Likert-scale and written feedback data included in each evaluation. A path analysis estimated the extent to which one’s evaluative responsibilities affected the timeliness of CCE submissions and CCE quality. Semi-structured interviews with a subset of participants (n = 8) gathered perceptions of the evaluations and the evaluative process. Results. One’s measurable quantity of evaluations did not influence one’s perceptions of the evaluative task, but did directly influence the quality of the Likert-scale items. Moreover, one’s perceptions of the evaluative task directly influenced the timeliness of CCE submissions and indirectly influenced the quality of the closed-ended CCE items. Tardiness in the submission of CCEs had a positive effect on the amount of score differentiation among the Likert-scale data. Neither evaluative responsibilities nor the timeliness of CCE submissions influenced the quality of written feedback. Qualitative analysis revealed mixed opinions on the utility of CCEs and highlighted the temporal burden and practical limitations of completing CCEs. Conclusions. These findings suggest physicians’ perceptions of CCEs are independent of their assigned evaluative quantity, yet influence both the timeliness of evaluation submissions and evaluative quality. Further elucidation of the mechanisms underlying the positive influence of evaluation quantity and timely CCE submissions on CCE quality are needed to fully rationalize these findings and improve the evaluative process. Continued research is needed to pinpoint which factors influence the quality of written feedback.
Book chapters on the topic "Load-strain relationships"
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Polienko, Wladislaw, and Klaus Holschemacher. "Influences of the Effectiveness of a Column Confinement with Textile Reinforced Concrete (TRC)." In Springer Proceedings in Materials. Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-72955-3_51.
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AbstractIn the present paper the results of uniaxial compression tests conducted on textile reinforced concrete (TRC)—confined reinforced concrete (RC) columns are reported. By confining the column with TRC, the lateral expansion of the concrete can be impeded. The resulting multiaxial compressive stress state allows to enhance the components axial capacity. Due to the corrosion-resistant textile, the usual concrete cover in reinforced concrete construction is reduced, which allows slender but at the same time highly load-bearing components to be created. Consequently TRC provides a sustainable, environmentally friendly and lighter option for column reinforcement due to the material savings. The aim of this study is the investigation of various influences on the achievable strengthening effect. The impact of ratio of textile reinforcement and the applied fine grain concrete jacket is evaluated. In addition, the influence of the concrete strength of the strengthened component on the overall increase in load-bearing capacity was investigated. With the help of experiments on TRC reinforced RC columns with a circular cross-section mechanical property and constraint mechanism under uniaxial compression were documented and analyzed. Based on the test results, stress distribution and failure mechanisms of the reinforced specimens is studied. Furthermore, stress-strain relationship of strengthened members is investigated. The results show an increasing in both strength and ductility related to the unstrengthened reference columns. The specimens with a lower compressive strength can achieve a higher degree of reinforcement. A high ductility of the reinforced columns could also be observed.
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Han J., Bhandari A., and Parsons R.L. "Influence of base course gradation on response of granular bases under cyclic loading: a micromechanical study." In Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering. IOS Press, 2009. https://doi.org/10.3233/978-1-60750-031-5-893.
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Performance of unpaved granular bases relies on the shear strength and stiffness of granular particles. These two mechanical properties depend on shape, size, and gradation of the particles. This paper presents a micromechanical study on the influence of particle gradation on the response of unreinforced and geogrid-reinforced granular bases under cyclic loading. Commercial software, Particle Flow Code (PFC) 2D based on the discrete element method (DEM), was used for this purpose. Different biaxial assemblies of uniform particles and well-graded particles were sheared at low confining stresses for their stress-strain relationships and friction angles. The geogrid was simulated using one layer of bonded particles with different sizes to mimic its grid structures. Two base courses consisting of uniform particles and well-graded particles, which were subjected to a 5kN cyclic ramp load at a frequency of 0.76 Hz using a wheel, were modeled. The DEM study showed that the assembly of well-graded particles had a higher angle of internal friction than the assembly of uniform particles. Further, the addition of the geogrid reduced the deformation after each load cycle.
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Sreng S., Ueno K., Mochizuki A., and Ma X. "Image analysis of shallow foundation tests on sand ground and their FE-analysis using a new elasto-plastic model." In Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering. IOS Press, 2005. https://doi.org/10.3233/978-1-61499-656-9-985.
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In this study a series of loading tests on dense sand under a centrifugal force field was carried out, and a newly developed image analysis method with an accuracy of 0.2 pixels was used to observe detailed deformation of sand models. Loading tests were also analyzed using a two-dimensional FE-analysis with a developed double yield surface model, referred as the MMX-model. The calculated bearing capacity factor, N&gamma;, compares well with other reported data and that obtained from classical theory. Load-settlement relationships, displacement and strain distributions at pre-peak, peak, and post-peak stages obtained from the FE-analysis agree well with those obtained from the loading tests. The FE-analysis using MMX-model is concluded to be applicable to practical design work with sufficient accuracy to permit prediction of bearing capacity and deformation behavior of ground.
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Kobayashi, Shiro, Soo-Ik Oh, and Taylan Altan. "Analysis and Technology in Metal Forming." In Metal Forming and the Finite-Element Method. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195044027.003.0006.
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The design, control, and optimization of forming processes require (1) analytical knowledge regarding metal flow, stresses, and heat transfer, as well as (2) technological information related to lubrication, heating and cooling techniques, material handling, die design and manufacture, and forming equipment. The purpose of using analysis in metal forming is to investigate the mechanics of plastic deformation processes, with the following major objectives. • Establishing the kinematic relationships (shape, velocities, strain-rates, and strains) between the undeformed part (billet, blank, or preform) and the deformed part (product); i.e., predicting metal flow during the forming operation. This objective includes the prediction of temperatures and heat transfer, since these variables greatly influence local metal-flow conditions. • Establishing the limits of formability or producibility; i.e., determining whether it is possible to perform the forming operation without causing any surface or internal defects (cracks or folds) in the deforming material. • Predicting the stresses, the forces, and the energy necessary to carry out the forming operation. This information is necessary for tool design and for selecting the appropriate equipment, with adequate force and energy capabilities, to perform the forming operation. Thus, the mechanics of deformation provides the means for determining how the metal flows, how the desired geometry can be obtained by plastic deformation, and what the expected mechanical properties of the produced part are. For understanding the variables of a metal-forming process, it is best to consider the process as a system, as illustrated in Fig. 2.1 in Chap. 2. The interaction of most significant variables in metal forming are shown, in a simplified manner, in Fig. 3.1. It is seen that for a given billet or blank material and part geometry, the speed of deformation influences strain-rate and flow stress. Deformation speed, part geometry, and die temperature influence the temperature distribution in the formed part. Finally, flow stress, friction, and part geometry determine metal flow, forming load, and forming energy. In steady-state flow (kinematically), the velocity field remains unchanged, as is the case in the extrusion process; in nonsteadystate flow, the velocity field changes continuously with time, as is the case in upset forging.
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Pender M.J., Kikkawa N., Orense R.P., and Ibrahim A. "Small-strain stiffness of Auckland residual clay." In Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering. IOS Press, 2009. https://doi.org/10.3233/978-1-60750-031-5-221.
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This paper presents the laboratory test results on the complete stress-strain curve for specimens of Auckland residual clay for axial strains ranging from less than 0.001% up to 1.0% using very sensitive LVDTs attached directly to the specimen. Three LVDTs were positioned around the periphery of the specimen to measure axial strains over a gauge length of 100mm. The axial load applied to the specimen was measured with a load transducer inside the triaxial cell. Use of a 16 bit A/D converter ensured accurate measurements of axial strains (resolution better than 1 micron over a gauge length of 100 mm) and load readings (resolution of 0.4N). The problem associated with the rotation of the end cap in conventional testing was resolved by fixing the cap against rotation, thus ensuring the same axial compression across the specimen. Moreover, to ensure excellent specimen end preparation, a thin layer of plaster was applied and the trimming mould was used to ensure the ends were parallel whilst the plaster sets. Using these measures, we were able to get very good quality axial strain data from less than 0.001%. Moreover, we applied the hyperbolic curve to the relationship between deviator stress and axial strain in order to estimate the small-strain stiffness of the soil.
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Liu, Fengxiao, and Hao Wu. "Soil Bin Test of Panel-Sand Interaction Under Wheel Load." In Advances in Transdisciplinary Engineering. IOS Press, 2024. http://dx.doi.org/10.3233/atde240284.
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Road equipment can ensure that the vehicle quickly through the soft muddy road section, has a very important application background. Pultruded aluminum truss-core sandwich panels are stiff and strong enough to construct lightweight deployable roadway. In this paper, vehicle-pavement-soil interaction was studied in a soil bin, and the deflection-load relationship, ground pressure-displacement relationship, strain-displacement relationship and soil parameters in the soil bin of two different types of aluminum alloy pavement slabs were determined under simulated wheel load. By comparing the mechanical results of AL 6061 and AL 6005A, it is concluded that AL6061 aluminum alloy sandwich plate is more suitable for making road equipment of wheeled vehicles.
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Khan Asad-ur-Rehman and Masood Fawwad. "Load-deflection curve prediction of RC beams strengthened by externally bonded CFRP wraps and strips." In Construction Materials and Structures. IOS Press, 2014. https://doi.org/10.3233/978-1-61499-466-4-1015.
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Increasing emphasis on serviceability and limit design has created a need for better understanding of the moment-curvature relationship of Reinforced Concrete (RC) beams cross-section. Non-linear characteristics of stress-strain curve of steel and concrete has been the major concern for many researchers, and accurate load versus deflection response can only be predicted by incorporating the same. In addition, Fibre Reinforced Polymers (FRP) has emerged as a viable solution to enhance the performance of RC beams both in terms of loads and deflection. An analytical tool has been developed in the present study to predict load-deflection and moment-curvature characteristics of RC beams (normal and strengthened by externally bonded FRP). The developed tool predicts complete load-deflection response of RC beams, with and without externally bonded CFRP system, using strain compatibility and force equilibrium technique with emphasis on cracked, yield and ultimate behaviour of such beams with shear span to depth (a/d) ratios varying from 2 to 6. Range of a/d ratios is selected to cover flexure and shear dominant loading regimes. Good agreement is found between predicted load-deflection curves with experimental data available in literature.
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Liu, Yun, Jie Lai, and Yuan Liu. "Research on the Tensile Properties of Ultra-High Toughness Cement-Based Composites." In Advances in Transdisciplinary Engineering. IOS Press, 2024. https://doi.org/10.3233/atde241025.
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To better guide engineering practice, this study investigated the mechanical properties of ultra-high toughness cement-based materials and conducts tensile mechanical experiments related to the materials. The experiments indicated that as the content of aramid fibers increased, the tensile strength initially increased and then decreased, reaching a maximum of 5.67 MPa at a fiber content of 0.1%. The ultimate tensile strain shown an initial decrease followed by an increase, but it did not exceed 3%. In terms of failure phenomena, at the initial loading stage, the stress-strain relationship of the specimen was linear due to the low load, and there was no noticeable change in the specimen. However, as the load increased, the first crack began to appear on the surface of the specimen, entering the elastoplastic phase, and the mode of failure transitions from single crack failure to stable failure with multiple cracks. According to data analysis, only four sets of experiments had ultimate tensile strains exceeding 3%. The failure mode shifts from a single crack to a stable failure with multiple cracks. As the load continues to increase, the width of the surface cracks enlarges
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Rodriguez Jorge Alberto. "Yielding and stress-strain relationships for Bogotá clays." In Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering. IOS Press, 2005. https://doi.org/10.3233/978-1-61499-656-9-587.
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Drained triaxial test results following load, unload and extension stress paths, as well as isotropic and Ko consolidation are used to identify the behavior of soft Bogot&aacute; clays. The intact drained strength and the critical state (CS) strength were obtained from the tests, as well as the volumetric compressibility, yielding and void ratio behavior at the critical state. The data is consistent with other natural clays reported in the literature, and provides the basis for a better understanding of the behavior of these soils for special projects in the city.
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Fu, Wei, Luo Shen, and Zhe Zhang. "Enhance the Understanding for the Permanent Deformation of Subgrade Clay: Considering the Characteristics of Traffic Load." In Advances in Transdisciplinary Engineering. IOS Press, 2024. https://doi.org/10.3233/atde241119.
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This study delves into the permanent deformation of subgrade soil by conducting triaxial shear tests and cyclic loading dynamic triaxial tests on compacted clay. These tests account for varying moisture content, stress levels, and loading characteristics, thereby revealing the evolution of permanent deformation in subgrade soil and enabling the construction of a predictive model. In a subgrade condition, the stress-strain relationship within the experimental clay exhibits a hardening tendency, with no evidence of strain softening. Moreover, an increase in moisture content and a decrease in confining pressure lead to reduced shear failure strength. The amplification of permanent deformation in the soil specimen can be attributed to the increase in cyclic deviatoric stress amplitude and the decrease in confining pressure, with the hygroscopic damage effect further exacerbating this deformation. Furthermore, both prolonged load durations and reduced intermittent times play a role in exacerbating the permanent deformation observed in the soil specimen. Notably, the impact of the intermittent time exhibits a critical threshold, beyond which the permanent deformation stabilizes. Utilizing the test findings, a comprehensive mechanical-empirical model has been developed. This model succinctly captures the influence of various factors on the permanent deformation of subgrade soil, including cyclic loading times, shear strain, constraint effect, hygroscopic damage effect, and the impact of both load duration and intermittent times. Verification indicated that this model possesses high predictive accuracy and broad applicability.
Conference papers on the topic "Load-strain relationships"
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Chinthapally, Srinivas, Sidhardha Nuli, Arnab Das, and Akshay Hedaoo. "Method to Backout Load From Strain Gauges Using Machine Learning." In ASME 2023 Gas Turbine India Conference. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/gtindia2023-118279.
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Abstract During vibration tests, loads need to be measured for machine components such as bearings, mounts, lugs, etc. As load cells cannot be placed at certain locations in the interior, strain gauges are used instead to measure the strain. But we need a load strain relation for the components. Most of the real-life components experience axial, bending, and torsional loads. Hence a multi-dimensional force strain relationship needs to be established for each component. Hence, prior to the actual tests, calibration tests are performed, on each component separately. These calibration tests are most often static load tests, in which load is applied in one direction at a time in small increments of load. In addition to the unidirectional loads, combined loads are also applied to establish complete load strain surface. Multidimensional load strain data is compiled and pre-processed to develop a multivariable load-strain relationship. The load-strain relationship is later used to back out loads from the strain data. Currently methods such as Newton-Raphson, plate smoothing spline, surface fitting, etc. are used to develop this relationship. Newton-Raphson is an iterative technique which solves for the loads simultaneously at each strain points. This method iterates till the error is small to achieve convergence. Newton-Raphson and surface fitting methods require structured data for developing multivariable load-strain relationship. However, deriving load-strain relations for complex geometries exhibiting highly nonlinear relationships is mathematically complex and computationally expensive. Also, formulation of these methods limits the use of large number of variables (more than 3). In this paper, an ensemble of MARS (Multi variate adaptive regression spline) along with Adaboost boosting algorithm has been explored to predict loads from strain data by developing multivariable correlation between loads and strains. MARS is an improved multivariable spline regression technique that generates piecewise polynomial functions between the variables and automatically determines the number & size of segment to achieve high accuracy or best fit on nonlinear problems. With complex high dimensional and noisy non-linear problem, Adaboost helps to reduce overfitting and improve the performance of the MARS model. The proposed method is well suited for dealing with large number of variables and developing complex non-linear load-strain relationship as it doesn’t require any structured data or iterations like existing methods to backout loads. The proposed method reduces the run time by more than 90% as compared to the conventional methods without compromising on accuracy. The advantages of the proposed method over conventional techniques have been demonstrated in this paper.
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Hart, James D., Nasir Zulfiqar, and Joe Zhou. "Evaluation of Anisotropic Pipe Steel Stress-Strain Relationships Influence on Strain Demand." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90495.
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Buried pipelines can be exposed to displacement-controlled environmental loadings (such as landslides, earthquake fault movements, etc.) which impose deformation demands on the pipeline. When analyzing pipelines for these load scenarios, the deformation demands are typically characterized based on the curvature and/or the longitudinal tension and compression strain response of the pipe. The term “strain demand” is used herein to characterize the calculated longitudinal strain response of a pipeline subject to environmentally-induced deformation demands. The shape of the pipe steel stress-strain relationship can have a significant effect on the pipe strain demands computed using pipeline deformation analyses for displacement-controlled loading conditions. In general, with sufficient levels of imposed deformation demand, a pipe steel stress-strain curve with a relatively abrupt or “sharp” elastic-to-plastic transition will tend to lead to larger strain demands than a stress-strain curve with a relatively rounded elastic-to-plastic transition. Similarly, a stress-strain curve with relatively low strain hardening modulus characteristics will tend to lead to larger strain demands than a stress-strain curve with relatively high strain hardening modulus characteristics. High strength UOE pipe can exhibit significant levels of anisotropy (i.e., the shapes of the stress-strain relationships in the longitudinal tension/compression and hoop tension/compression directions can be significantly different). To the extent that the stress-strain curves in the different directions can have unfavorable shape characteristics, it follows that anisotropy can also play an important role in pipeline strain demand evaluations. This paper summarizes a pipeline industry research project aimed at evaluation of the effects of anisotropy and the shape of pipe steel stress-strain relationships on pipeline strain demand for X80 and X100 UOE pipe. The research included: a review of pipeline industry literature on the subject matter; a discussion of pipe steel plasticity concepts for UOE pipe; characterization of the anisotropy and stress-strain curve shapes for both conventional and high strain pipe steels; development of representative analytical X80 and X100 stress-strain relationships; and evaluation of a large matrix of ground-movement induced pipeline deformation scenarios to evaluate key pipe stress-strain relationship shape and anisotropy parameters. The main conclusion from this work is that pipe steel specifications for high strength UOE pipe for strain-based design applications should be supplemented to consider shape-characterizing parameters such as the plastic complementary energy.
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Lee, K., J. M. Tannenbaum, B. S. J. Kang, and M. A. Alvin. "A Load-Based Depth-Sensing Indentation Technique for Elastic-Plastic Material Mechanical Property Evaluation." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37698.
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A load-based depth-sensing micro-indentation technique has been developed for material mechanical properties evaluation including elastic modulus, yield stress, strain hardening exponent and stress-strain curve. Based on a Hertzian contact mechanics approach, this load-based depth-sensing micro-indentation technique does not require system compliance calibration or the use of high precision depth sensors. Furthermore a unique, material independent, indentation based load-depth algorithm has been developed accounting for both elastic and elastic-plastic deformation of the material beneath the indenter. This algorithm, found to be a function of material yield stress, strain hardening exponent and elastic modulus, is shown to be the basis for obtaining a stress-strain curve. Finite element analyses of multiple materials with various mechanical properties were employed to examine and develop the fundamental indention based relationships between these variables and the load/depth curve needed to extract the stress-strain diagram. In addition, experimental results obtained with this load-based micro-indentation technique were found to yield accurate material mechanical properties (elastic modulus, strain hardening, yield strength) at room and elevated temperatures (up to 1200°C).
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Machida, Hideo, Tetsuya Hamanaka, Yoshiaki Takahashi, et al. "Fracture Assessment of Pipes Having Multiple Flaws Based on Ramberg–Osgood-Type Stress–Strain Relationships." In ASME 2011 Pressure Vessels and Piping Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/pvp2011-57859.
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This paper describes a fracture assessment method for a pipe having multiple circumferential flaws. According to Fitness-for-Service (FFS) codes for nuclear facilities published by the Japanese Society of Mechanical Engineers (JSME), the fracture strength of a high-ductility pipe having a circumferential flaw is evaluated using the limit load assessment method assuming the elastic–perfectly-plastic stress–strain relationship. In this assessment, flow stress is used as a proportional stress. However, previous experimental results [1, 2, 3] show that a crack penetrates before the entire flawed pipe section reaches the flow stress. Therefore, stress concentration at a flaw was evaluated on the basis of the Dugdale model [4], and the fracture strength of the crack-ligament was evaluated. This model can predict test results with high accuracy when the ligament fracture strength is assumed to be tensile strength. Based on this examination, a fracture assessment method for pipes having multiple flaws was developed considering the stress concentration in the crack-ligament by using the realistic stress–strain relationship (Ramberg–Osgood-type stress–strain curve). The fracture strength of a multiple-flawed pipe estimated by the developed method was compared with previous experimental results. When the stress concentration in the crack-ligament was taken into consideration, the fracture strength estimated using the Ramberg–Osgood-type stress–strain curve was in good agreement with experimental results, confirming the validity of the proposed method.
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Wu, Tsu-te. "An Analytical Method of Determining Damage Initiation for Potential Use in Establishing Strain-Based Failure Criteria." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77435.
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This paper proposes a methodology for analytically determining the initiation of ductile fracture due to the nucleation, growth, and coalescence of voids. Since structural damages in the shipping packages of radioactive materials are judged to be mainly caused by ductile fracture rather than shear fracture due to shear band localization, the proposed methodology has potential use in establishing strain-based failure criteria. The proposed methodology is based on the concept that, to ensure its structural integrity, a package should be designed within the maximum load-carrying capability. The load-carrying capabilities for various states of stress can be determined from the load-displacement relationships obtained from the numerical simulations of various specimen tests. As a result, the maximum equivalent plastic strain corresponding to the maximum load-carrying capability can be expressed in terms of stress triaxiality. This paper demonstrates that it is possible to analytically determine the effective plastic strains at the damage initiation in the state of multiple stresses where the load-carrying capacity is at maximum. By considering both material and geometrical nonlinearity in the mathematical representations of structures, the maximum load-carrying capabilities can be calculated as long as the stress-strain data is given.
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Cai, Wayne W., John E. Carsley, Daniel B. Hayden, Louis G. Hector, and Thomas B. Stoughton. "Estimation of Metal Hardening Models at Large Strains." In ASME 2007 International Manufacturing Science and Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/msec2007-31137.
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Simulation accuracy of large strain deformation of sheet metals, such as that which occurs during hemming and vehicle crash situations, is limited because existing hardening laws (true stress vs. true strain relationships) are extrapolated from uniform elongation data and applied for post-uniform deformation. In this paper, a reverse-engineering method was developed to predict metal hardening laws at large strains beyond uniform elongation for sheet metals. The method required a standard uniaxial tensile test and finite element analyses (FEA), and was implemented as a custom computer code called GMSS (General Motors Stress-Strain). The true stress vs. true strain data pairs are determined when the load and displacement history of a tensile test specimen matches the FEA results using GMSS. Test cases showed that the true stress vs. true strain relationships at very large strains (75% for AA6111 aluminum, and 85% for DP600 steel) could be automatically generated using GMSS. This reverse-engineering method will provide General Motors with an easy-to-use tool for generating very accurate metal hardening laws for post-uniform deformation that can greatly improve the accuracy of FEA for formability (including hemming), and crashworthiness simulations.
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Hu, Yifeng, Gang Chen, and Weizhe Wang. "Investigation of Stress-Strain Behavior of a Component Under Variable Frequency Non-Proportional Loading." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76768.
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With the flexibility operation demand of the plants, the load change becomes more and more often. The torsion loading due to load change becomes larger and more frequent. The influence of torsion loading frequency (the number of repeating cycles in a unit time) on the stress-strain behavior of component was numerically investigated under non-proportional loadings. A hollow cylinder specimen was chosen in this study. And three conditions of non-proportional loadings (Case1, Case2 and Case3) were chosen. The relationships between cyclic stress response and cyclic strain response were obtained for Case1, Case2 and Case3. The numerical results revealed that the distortion of stress-strain response curve was intensified with the increase of torsion loading frequency. The cyclic softening behaved in the first 2 cycles for the tension and torsion stress responses; however, the characterizations of the cyclic hardening and the cyclic softening for the material appeared after the starting 2 cycles. Furthermore, with the increase of cycle number and torsion loading frequency, there is a significant difference between the tension stress response and the torsion stress response.
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Knippel, E. P., A. P. Villaquiran Vargas, Q. Xiong, and J. C. Hampton. "Capturing Elastic Properties and Their Dependencies as a Precursor to Understanding Damage." In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0764.
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ABSTRACT Experimental rock mechanics testing provides an effective method for measuring physical properties, their dependencies, and their evolution due to the addition of localized microcracks in a controlled laboratory environment. In order to understand the contributions of microcrack parameters to first order changes in compliance, the behavior of initial undamaged properties of a material must be thoroughly understood as a function of stress, load path, and load history. To that end, we perform a comprehensive study of elastic properties and their dependence on testing parameters for a variety of materials exhibiting linear, nonlinear, and varying levels of anisotropic elastic stiffnesses. We utilize a programmatically controlled triaxial testing apparatus to perturb specimens instrumented with strain gauges and ultrasonic transducers. Elastic moduli are then measured along multiple discrete loading paths as a function of stress, with the upper limit calculated through an experimental derived failure envelope. Once the experimental results of those effects are isolated, we will then be able to assess the accuracy of limiting the modeled damage related changes in compliance to solely crack density, length, and orientation in a homogenized medium. INTRODUCTION The relationship between stress and strain is a constitutive law governed by properties intrinsic to a material. This is often assumed to be linearly elastic, where strain increases constantly with stress and deformation fully recovers once the applied stress is released. This is not always the case and is readily observed in experimental data, however the relationship is close enough for undamaged materials that the assumption is still valid in a variety of applications (Jaeger et al. (2007)). As stress and strain are both second order tensors, a fourth order tensor is required to relate these properties. This compliance tensor contains 81 components, however due to symmetry this can be reduced to 36 similarly to how both stress and strain contain six independent coefficients out of the total nine. For layered and isotropic materials, the number of independent coefficients can further be reduced. The compliance tensor for layered or vertically transversely isotropic (VTI) materials contain eight independent coefficients. Materials that are isotropic in all directions contain three independent coefficients. These coefficients can be calculated through experimental testing, where applied stress is manipulated along various load paths and resulting strain measured. There exists dynamic elastic moduli as well, measured through the use of ultrasonic transducers, where high frequency and low strain amplitude ultrasonic waves propagate through the material. The differences between static (low frequency and higher strain amplitude) and dynamic (high frequency and low strain amplitude) stress-strain perturbations often result in subtle differences between the moduli, though typical relationships between dynamic and static elastic moduli have been studied extensively and is out of the scope of this paper. VTI samples with non-uniform static elastic moduli are expected to have similar differences in velocity and dynamic moduli.
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Warren, A. W., and Y. B. Guo. "An Experimental Study on Subsurface Mechanical Behavior, Residual Stress, and Microstructure Induced by Process Dynamics in Machining." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60021.
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Surface integrity of machined components is critical for product performance in service. Process dynamic parameters, such as cutting speed and the changing contact condition between the tool flank face and machined surface, have a significant influence on surface integrity of a machined surface. Due to the very small scale of surface integrity factors on a machined surface, nanoindentation can be used to determine the surface/subsurface mechanical properties. However, the test data may be significantly influenced by machining induced residual stresses, strain hardening, and microstructure changes. The fundamental relationships between residual stress, microstructure, and nanohardness in the machined surface are yet to be understood. Further, it is not clear how to determine residual stress, at least its nature of tensile or compressive, from the nanoindentation data with the presence of complex residual stress state, strain hardening, and microstructure changes. This study focuses on the effects of cutting speed and machining system damping or rigidity (through varying tool flank wear) on subsurface mechanical state and the basic relationships between residual stress, white layer, and nanohardness. A series of nanoindentation tests were conducted to machined samples with distinct surface integrity by hard turning, grinding, and honing. It was found that white layer increases nanohardness and dark layer decreases nanohardness in subsurface, while strain hardening only slightly increases subsurface hardness. The research results indicate that subsurface residual stress can be qualitatively characterized by the load-displacement curve pattern and its parameters such as slope at initial loading, total depth, residual depth, and the ratio of residual depth to total depth. Residual stress would affect a load-displacement curve shape only at onset of yielding. Microstructure changes would make a significant difference on the characteristics of a load-displacement curve, while strain hardening exerts slight influence on the curve characteristics. In addition, the mechanism of residual stress on indentation depth was explained using a Mohr’s circle.
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Zhao, Ruogang, Krista Lynn Sider, and Craig A. Simmons. "Comparison of Analytical and Finite Element Implementation of Exponential Constitutive Models for Valve Tissue Under Micropipette Aspiration." In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19245.
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Micropipette aspiration (MA) has been widely used to measure the biomechanical properties of cells and biomaterials [1]. Typically a linear elastic half-space model is used to fit the experimental load-deformation data [1]. However, load-deformation relationships for most biological tissues are highly nonlinear, suggesting alternative constitutive models are necessary. In the case of aortic heart valve tissue, exponential-type constitutive models have been found to fit the biaxial stress-strain behavior well [2]. Based on these studies, Butcher et al. used an exponential constitutive model to characterize the response of chicken embryonic valve (atrioventricular cushion) under MA [3]. To do so, they implemented an analytical exponential constitutive model [2] and directly related the stress and strain to the experimentally measured pressure and aspiration length. This allowed the authors to fit the tissue MA data without accounting for the complexities of the boundary conditions and multicomponent strain field inherent in MA. However, it is unclear whether the material parameters estimated using this approach are different from those estimated by solving the more complex boundary value problem, which presumably more faithfully simulates the physical process of tissue aspiration.
Reports on the topic "Load-strain relationships"
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Dinovitzer, Aaron. PR-214-144500-R05 Weld Hydrogen Cracking Susceptibility Characterization. Pipeline Research Council International, Inc. (PRCI), 2018. http://dx.doi.org/10.55274/r0011495.
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Hydrogen cracking has been and continues to be observed in both heat-affected zones and weld metals. High carbon equivalent weldment heat-affected zones (HAZ) combined with rapid cooling have been related to the development of hydrogen cracking susceptible microstructures. Weld metal cracking is observed in both high and low strength weldments and is a particular concern for root passes due to the use of cellulosic electrodes, parent metal dilution, applied load, and weld fault stress riser effects promoting cracking. The risk of HAZ and weld cracking are increased for repair and in-service welds and/or welds deposited on older generation materials (e.g., pipe or fittings) and this can pose a significant risk to the integrity of welded connections. This report presents the result of research in the application and extension of the "Slow Bend" testing technique used to quantify the hydrogen cracking susceptibility of a weldment. This testing is being used to quantify the susceptibility of a microstructure to hydrogen cracking by defining the critical combinations of strain and hydrogen concentration (i.e. hydrogen embrittlement curves) that result in cracking in a given material. The testing and modelling results have been used to define relationships between the hydrogen embrittlement curve parameters (i.e. ductility and hydrogen embrittlement indices) and the properties of the deposited weld metal. These preliminary relationships were defined separately for cellulosic and basic SMAW electrodes providing insight to the factors that make a weld material susceptible to hydrogen cracking.
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Diwakar, Vidya, and Richard Bwalya. Poverty and Wellbeing in Zambia: Pandemic Update. Institute of Development Studies, 2024. http://dx.doi.org/10.19088/cpan.2024.001.
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This study attempts to provide a descriptive assessment of the reasons behind the increase in poverty witnessed in Zambia between 2015 and 2022. Although poverty in Zambia is more pronounced in rural than urban areas, the increase in poverty was much higher in urban areas. This increase may be at least partly explained by a confluence of factors, including load shedding, the Covid-19 pandemic, which considerably negatively affected businesses and employment, and the effect of rising prices, which also put pressure on households’ purchasing power. There were also dramatic increases in certain provinces (Lusaka, Southern, and Copperbelt) in the share of household heads who were not working due to pandemic-induced business closures in 2020, which is likely to have put a strain on pathways out of poverty, given the positive relationship between non-farm enterprises and resilience before the pandemic.
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Brosh, Arieh, David Robertshaw, Yoav Aharoni, Zvi Holzer, Mario Gutman, and Amichai Arieli. Estimation of Energy Expenditure of Free Living and Growing Domesticated Ruminants by Heart Rate Measurement. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7580685.bard.
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Research objectives were: 1) To study the effect of diet energy density, level of exercise, thermal conditions and reproductive state on cardiovascular function as it relates to oxygen (O2) mobilization. 2) To validate the use of heart rate (HR) to predict energy expenditure (EE) of ruminants, by measuring and calculating the energy balance components at different productive and reproductive states. 3) To validate the use of HR to identify changes in the metabolizable energy (ME) and ME intake (MEI) of grazing ruminants. Background: The development of an effective method for the measurement of EE is essential for understanding the management of both grazing and confined feedlot animals. The use of HR as a method of estimating EE in free-ranging large ruminants has been limited by the availability of suitable field monitoring equipment and by the absence of empirical understanding of the relationship between cardiac function and metabolic rate. Recent developments in microelectronics provide a good opportunity to use small HR devices to monitor free-range animals. The estimation of O2 uptake (VO2) of animals from their HR has to be based upon a consistent relationship between HR and VO2. The question as to whether, or to what extent, feeding level, environmental conditions and reproductive state affect such a relationship is still unanswered. Studies on the basic physiology of O2 mobilization (in USA) and field and feedlot-based investigations (in Israel) covered a , variety of conditions in order to investigate the possibilities of using HR to estimate EE. In USA the physiological studies conducted using animals with implanted flow probes, show that: I) although stroke volume decreases during intense exercise, VO2 per one heart beat per kgBW0.75 (O2 Pulse, O2P) actually increases and measurement of EE by HR and constant O2P may underestimate VO2unless the slope of the regression relating to heart rate and VO2 is also determined, 2) alterations in VO2 associated with the level of feeding and the effects of feeding itself have no effect on O2P, 3) both pregnancy and lactation may increase blood volume, especially lactation; but they have no effect on O2P, 4) ambient temperature in the range of 15 to 25°C in the resting animal has no effect on O2P, and 5) severe heat stress, induced by exercise, elevates body temperature to a sufficient extent that 14% of cardiac output may be required to dissipate the heat generated by exercise rather than for O2 transport. However, this is an unusual situation and its affect on EE estimation in a freely grazing animal, especially when heart rate is monitored over several days, is minor. In Israel three experiments were carried out in the hot summer to define changes in O2P attributable to changes in the time of day or In the heat load. The animals used were lambs and young calves in the growing phase and highly yielding dairy cows. In the growing animals the time of day, or the heat load, affected HR and VO2, but had no effect on O2P. On the other hand, the O2P measured in lactating cows was affected by the heat load; this is similar to the finding in the USA study of sheep. Energy balance trials were conducted to compare MEI recovery by the retained energy (RE) and by EE as measured by HR and O2P. The trial hypothesis was that if HR reliably estimated EE, the MEI proportion to (EE+RE) would not be significantly different from 1.0. Beef cows along a year of their reproductive cycle and growing lambs were used. The MEI recoveries of both trials were not significantly different from 1.0, 1.062+0.026 and 0.957+0.024 respectively. The cows' reproductive state did not affect the O2P, which is similar to the finding in the USA study. Pasture ME content and animal variables such as HR, VO2, O2P and EE of cows on grazing and in confinement were measured throughout three years under twenty-nine combinations of herbage quality and cows' reproductive state. In twelve grazing states, individual faecal output (FO) was measured and MEI was calculated. Regression analyses of the EE and RE dependent on MEI were highly significant (P<0.001). The predicted values of EE at zero intake (78 kcal/kgBW0.75), were similar to those estimated by NRC (1984). The EE at maintenance condition of the grazing cows (EE=MEI, 125 kcal/kgBW0.75) which are in the range of 96.1 to 125.5 as presented by NRC (1996 pp 6-7) for beef cows. Average daily HR and EE were significantly increased by lactation, P<0.001 and P<0.02 respectively. Grazing ME significantly increased HR and EE, P<0.001 and P<0.00l respectively. In contradiction to the finding in confined ewes and cows, the O2P of the grazing cows was significantly affected by the combined treatments (P<0.00l ); this effect was significantly related to the diet ME (P<0.00l ) and consequently to the MEI (P<0.03). Grazing significantly increased O2P compared to confinement. So, when EE of grazing animals during a certain season of the year is estimated using the HR method, the O2P must be re measured whenever grazing ME changes. A high correlation (R2>0.96) of group average EE and of HR dependency on MEI was also found in confined cows, which were fed six different diets and in growing lambs on three diets. In conclusion, the studies conducted in USA and in Israel investigated in depth the physiological mechanisms of cardiovascular and O2 mobilization, and went on to investigate a wide variety of ruminant species, ages, reproductive states, diets ME, time of intake and time of day, and compared these variables under grazing and confinement conditions. From these combined studies we can conclude that EE can be determined from HR measurements during several days, multiplied by O2P measured over a short period of time (10-15 min). The study showed that RE could be determined during the growing phase without slaughtering. In the near future the development microelectronic devices will enable wide use of the HR method to determine EE and energy balance. It will open new scopes of physiological and agricultural research with minimizes strain on animals. The method also has a high potential as a tool for herd management.
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LOW-CYCLE FATIGUE PROPERTIES OF AUSTENITIC STAINLESS STEEL S30408 UNDER LARGE PLASTIC STRAIN AMPLITUDE. The Hong Kong Institute of Steel Construction, 2022. http://dx.doi.org/10.18057/ijasc.2022.18.1.10.
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The application of stainless steel materials in civil structures for seismic protection lies in its low-cycle fatigue characteristic. However, the data of existing research are mainly based on the low-cycle fatigue in small strain amplitudes. To this end, we perform low-cycle fatigue testing of Austenitic stainless steel S30408, which has low yield point and good elongation performance, under the cyclic load with a maximum strain amplitude reaching up to 5%, to fill the gap. The stress-strain response characteristics of the stainless steel material under the cyclic load are analyzed; then, the parameters of the strain-fatigue life relationship and the cyclic-plastic constitutive model used for FEA simulation are extracted. Results show that the stainless steel’s stress-strain curve is nonlinear without a yield plateau, thus presenting a high strength yield ratio and ductility. The hysteresis loops of the material are plump with a shuttle shape and are symmetric to the origin, indicating a fine energy dissipation capacity. The skeleton curve under cyclic loading with cyclic hardening can be significantly reflected by the Ramberg Osgood model, which is affected by the strain amplitude and loading history; it is also different from the monotonic tensile skeleton curve. The strain-fatigue life curve fitted by the Baqusin Manson Coffin model can predict the materials’ fatigue life under different strain amplitudes. The mixed hardening model, including isotropic and kinematic hardening, based on the Chaboche model, is able to simulate the cyclic stress-strain relationship. Further, its parameters can provide basic data information for the seismic design of civil structures when Austenitic stainless steel S30408 is used.