Journal articles: 'Damage coefficient'

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Minhas, Zill-e. Hasnain, and Sun Qin. "Evolution of the Coefficient of Dynamic Viscosity with Growing Damage in Metals." Applied Mechanics and Materials 313-314 (March 2013): 72–76. http://dx.doi.org/10.4028/www.scientific.net/amm.313-314.72.

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Coefficient of dynamic viscosity (η) for uniaxial rectangular bar of steel is calculated using creep simulation in Ansys. Norton Secondary creep law with coefficients at 600 ᵒC is used. Steel bar is then inflicted with some damage elements in order to investigate the evolution of dynamic viscosity for varying degree of fatigued specimen at constant rate and temperature. Isotropic damage parameter (D) based on the volume fraction of damaged elements is used to formulate a linear relation between the coefficient of viscosity and D. It is found that with 0.001 increase is damage parameter (D), almost 0.6% decrease on the value of Coefficient of dynamic viscosity (η) is observed.

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Mei, Liu, Akira Mita, and Jin Zhou. "A Substructural Damage Identification Approach for Shear Structure Based on Changes in the First AR Model Coefficient Matrix." Journal of Structures 2015 (June 16, 2015): 1–16. http://dx.doi.org/10.1155/2015/976349.

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A substructural damage identification approach based on changes in the first AR model coefficient matrix is proposed in this paper to identify structural damage including its location and severity. Firstly, a substructure approach is adopted in the procedure to divide a complete structure into several substructures in order to significantly reduce the number of unknown parameters for each substructure so that damage identification processes can be independently conducted on each substructure. To establish a relation between changes in AR model coefficients and structural damage for each substructure, a theoretical derivation is presented. Thus the accelerations are fed into ARMAX models to determine the AR model coefficients for each substructure under undamaged and various damaged conditions, based on which changes in the first AR model coefficient matrix (CFAR) is obtained and adopted as the damage indicator for the proposed substructure damage identification approach. To better assess the performance of the proposed procedure, a numerical simulation and an experimental verification of the proposed approach are then carried out and the results show that the proposed procedure can successfully locate and quantify the damage in both simulation and laboratory experiment.

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Padzi, Mahfodzah M., S. Abdullah, and Mohd Zaki Nuawi. "Fatigue Damage Assessment Correlating with I-Kaz Coefficient." Applied Mechanics and Materials 471 (December 2013): 235–40. http://dx.doi.org/10.4028/www.scientific.net/amm.471.235.

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This paper describes the correlation between fatigue life with the I-kaz coefficients. Fatigue tests were performed according to the ASTM E466-96 standard with a strain gauge attached to the specimen being tested. AISI 1045 carbon steel was used as the material for this test due to its wide applications in the automotive and machinery industry. Fatigue tests were carried out at several constant loading stresses of 610 MPa, 650 MPa and 690 MPa at the sampling frequency of 8 Hz. A set of data acquisition system was used to collect the fatigue strain signals. The integrated Kurtosis-based algorithm for Z-filter (I-kaz) technique had been used to find the I-kaz coefficient. The I-kaz coefficient is found to have a good correlation with fatigue life, other than can represent fatigue damage.

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Bedrikovetsky, P., A. S. L. S. L. Vaz, C. Furtado, and A. L. S. L. S. de Souza. "Formation-Damage Evaluation From Nonlinear Skin Growth During Coreflooding." SPE Reservoir Evaluation & Engineering 14, no. 02 (March 24, 2011): 193–203. http://dx.doi.org/10.2118/112509-pa.

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Summary Injectivity decline of oilfield injection wells is a widespread phenomenon during seawater/produced-water injection. The decline may result in significant cost increase of the waterflooding project. Reliable modeling-based prediction of injectivity-index decrease is important for waterflood design as well as for the planning of preventive injected-water treatment. One of the reasons for well injectivity decline is permeability decrease caused by rock plugging by solid/liquid particles suspended in the injected water. The mathematical model for deep-bed filtration contains two empirical functions: the filtration coefficient and the formation-damage coefficient. These empirical coefficients must be determined from laboratory coreflood tests by forcing water with particles to flow through the core samples. A routine laboratory method determines the filtration coefficient from expensive and difficult particle-concentration measurements at the core effluent; then, the formation-damage coefficient is determined from inexpensive and simple pressure-drop measurements. An alternative three-point-pressure method uses pressure data at an intermediate point of the core, supplementing pressure measurements at the core inlet and outlet. The method provides unique and stable values for constant-filtration and formation-damage coefficients. In the current work, we consider a more complex case in which both coefficients are linear functions of retained-particle concentration. In this case, the model is fully determined by four constants. The three-point-pressure method furnishes unique values for the four model parameters. A new semianalytical model for axisymmetric suspension filtration was developed to predict well-injectivity decline from the linear coreflood data with pressure measurements in three core points.

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Qian, Yao, Ping Wang, Jiayin Chen, G. Bethel Lulu, Jingmang Xu, and Boyang An. "Numerical investigation of the influence of the creep curve on the wheel–rail contact damage in high-speed railway turnouts." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 233, no. 9 (December 26, 2018): 926–36. http://dx.doi.org/10.1177/0954409718819574.

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This paper studies the wheel–rail creep curve characteristics and dynamic behaviour in high-speed railway turnouts by considering different wheel–rail surfaces and simulating them using a dynamic functional vehicle–track model with different friction and Kalker’s weight coefficients. The dynamic performance and damage coefficient of CRH2 locomotive passing through the 18# turnout at a speed of 80 km/h are discussed under different friction and Kalker’s weight coefficients. The results show that the Kalker’s weight and friction coefficients have less influence on the wheel–rail dynamics and wear performance at low values. Vehicle operating stability is the highest when the high-speed wheels pass through the switching area and the Kalker’s weight coefficient is 0.1. In this case, both fatigue damage and wear are low. When the Kalker’s weight coefficient at the crossing area is 1 and the friction coefficient is 0.5, the dynamic wheel–rail performance is good, with reduced wear and good wheel–rail contact. When the Kalker’s weight coefficient is 0.1, the maximum wear number of the closure panel is closer to the lower limit of the second region of the damage function, and both fatigue damage and wear are very low. The results are useful for accurately describing the wheel–rail contact relationship in high-speed turnouts and for finding the most appropriate creep curve to decrease wear and to prolong the turnout service life.

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Dubey, Anurag, Vivien Denis, and Roger Serra. "A Novel VBSHM Strategy to Identify Geometrical Damage Properties Using Only Frequency Changes and Damage Library." Applied Sciences 10, no. 23 (December 5, 2020): 8717. http://dx.doi.org/10.3390/app10238717.

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Vibration-based structural health monitoring is an efficient way to diagnose damage and structural integrity at the earliest stage. In this paper, a new strategy is developed for damage localization and estimation, as well as damage properties identification for a rectangular geometry damage using only eigenfrequencies of the healthy and damaged structure. This strategy is applied to a cantilever beam. In this framework, a damage library is built by correlating 2D and 3D finite element models. The correlation is done by minimizing a so-called frequency shift coefficient. The proposed strategy also uses the frequency shift coefficient to correlate a 2D damaged model with an unknown beam case. The 2D damage, represented by a bending stiffness reduction, is then associated to a 3D damage by employing the damage library. Numerical cases with single and double damage of varying position and severity are tested and used to validate the approach. Finally, experimental results are proposed that show the relevance of the strategy.

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Zhao, Xinze, Senming Xi, Meiyun Zhao, Wenyun PENG, Seng Tian, and Wei Li. "Fatigue Damage Analysis of Composite Insulator Cor Rod/sheath Interface." MATEC Web of Conferences 264 (2019): 01001. http://dx.doi.org/10.1051/matecconf/201926401001.

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A self-made fatigue testing machine was used to simulate the damage process of the insulator interface under working conditions and the damage degree is evaluated by the compressive shear test. The improved interface adhesion model reflects the interface debonding process under different fatigue loads by introducing the damage coefficient χ, migration coefficient α and the debonding coefficient μ. The relationship of fatigue loads and interface damage is established by the peeling force, the unit interface separation work and the peeling time. The test demonstrates that the interface damage near the bottom of the insulator is worse than that near the middle part. The result of this analysis will be beneficial in easily finding damaged places of the insulator, and so as to reduce the power breakdown.

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Le, Jie, Lingling Lu, Yabo Wang, Hongwei Song, Xiaodong Xing, and Chenguang Huang. "Damage identification of low-density material–filled sandwich panels with truss core based on vibration properties." Structural Health Monitoring 18, no. 5-6 (December 29, 2018): 1711–21. http://dx.doi.org/10.1177/1475921718820100.

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A damage-identification method based on flexibility matrix and Teager energy operator is proposed for low-density material–filled sandwich panels with truss core. In the proposed damage index, weight coefficient r is introduced to consider the effect of damages on both high-order and low-order modes. Numerical simulations and experiments are conducted to assess the performance of the proposed method. Effects of Young’s modulus of the filler material on the accuracy of the proposed method are also discussed. Results reveal that the method is reliable and effective for single-damage and multiple-damages identification of filled sandwich panels with truss core, and weight coefficient plays an important role, especially for cases with multiple damages or damages of small extent. Damage identification becomes more difficult as Young’s modulus of the filler increases, and there is a critical value, after which the damage could not be identified by the proposed method.

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Keyes, B. M., R. K. Ahrenkiel, G. J. Shaw, and G. P. Summers. "Minority-carrier lifetime damage coefficient of irradiated InP." Journal of Applied Physics 82, no. 5 (September 1997): 2156–63. http://dx.doi.org/10.1063/1.366023.

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Vellios, L., V. Kostopoulos, and S. A. Paipetis. "Fatigue Effect on the Dynamic Properties of Cfrp Composites." Advanced Composites Letters 3, no. 4 (July 1994): 096369359400300. http://dx.doi.org/10.1177/096369359400300405.

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Damage developing during fatigue of composite laminates affects both dynamic modulus of elasticity and damping coefficient of the material. It has been shown that the effect of fatigue on the damping coefficient is of particular importance. The damping variation could be used to characterise the damage state of the material, produced by fatigue. A model relating damage with damping was developed to correlate damage development to mechanical response. The damping coefficients of the composite of the fatigue test were measured at various stages, using the flexural free vibration of the test coupon hi cantilever configuration. The method was applied both in multidirectional and unidirectional laminates.

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Fadaei Kermani, E., G. A. Barani, and M. Ghaeini-Hessaroeyeh. "Prediction of cavitation damage on spillway using K-nearest neighbor modeling." Water Science and Technology 71, no. 3 (December 12, 2014): 347–52. http://dx.doi.org/10.2166/wst.2014.495.

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Cavitation is a common and destructive process on spillways that threatens the stability of the structure and causes damage. In this study, based on the nearest neighbor model, a method has been presented to predict cavitation damage on spillways. The model was tested using data from the Shahid Abbaspour dam spillway in Iran. The level of spillway cavitation damage was predicted for eight different flow rates, using the nearest neighbor model. Moreover, based on the cavitation index, five damage levels from no damage to major damage have been determined. Results showed that the present model predicted damage locations and levels close to observed damage during past floods. Finally, the efficiency and precision of the model was quantified by statistical coefficients. Appropriate values of the correlation coefficient, root mean square error, mean absolute error and coefficient of residual mass show the present model is suitable and efficient.

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Matsuoka, Masashi, and Fumio Yamazaki. "Use of Satellite SAR Intensity Imagery for Detecting Building Areas Damaged Due to Earthquakes." Earthquake Spectra 20, no. 3 (August 2004): 975–94. http://dx.doi.org/10.1193/1.1774182.

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Synthetic aperture radar (SAR) is remarkable for its capability to record the backscattering coefficient, the physical value of the earth's surface, regardless of weather condition or sun illumination. Therefore, SAR is a powerful tool that can be utilized to develop a universal method to comprehend damaged areas in disasters such as earthquakes, forest fires, and floods. We performed a feasibility study on backscattering characteristics of damaged areas in the 1995 Hyogoken-Nanbu (Kobe), Japan, earthquake using the pre- and post-event ERS images, revealing that the backscattering coefficient and intensity correlation between the two attained values were significantly lowered in hard-hit areas. The evaluation, however, was performed without speckle noise reduction. We also investigated the effects of speckle noise reduction and pixel-window size in evaluating building damage using the difference in the backscattering coefficient and correlation coefficient of the pre- and post-event ERS images. From the analysis, an optimum window size for the damage evaluation was obtained. It was also found that the accuracy of damage detection is not significantly improved for speckle-reduction filtering of window size larger than 21×21 pixels. We developed an automated method to detect hard-hit areas based on the discriminant analysis, and compared the detected distribution with a damage survey result.

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13

Lu, Lingling, Hongwei Song, Wu Yuan, and Chenguang Huang. "Baseline-free damage identification of metallic sandwich panels with truss core based on vibration characteristics." Structural Health Monitoring 16, no. 1 (September 24, 2016): 24–38. http://dx.doi.org/10.1177/1475921716660055.

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A baseline-free damage identification method is proposed to identify damages in metallic sandwich panels with truss core in the article. The method is based on flexibility matrix and gapped smoothing method, with damage index defined DIm. The weight coefficient m is introduced to consider the effect of damages on both low-order modes and high-order modes. Numerical simulations and experiments are conducted to evaluate the present method. Besides, damage index [Formula: see text] is also defined by processing DIm with Teager energy operator, and comparisons between DIm and [Formula: see text] are also carried out. Results show that the proposed method is effective in detecting single damage and multiple damages of the same or different extent. The weight coefficient m plays a very important role in identification of multiple damages of different styles. When comparing with [Formula: see text], it is found that the present index DIm is better at suppressing the singularity caused by contact nodes and detecting of multiple damages which contain small or slight damages.

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Ota, Takao, Yoshiharu Matsumi, Nobuaki Kato, and Ken-ichi Ohno. "MODELING OF DAMAGE PROGRESSION OF RUBBLE MOUND REVETMENT AND APPLICATION TO PERFORMANCE EVALUATION." Coastal Engineering Proceedings 1, no. 33 (December 14, 2012): 50. http://dx.doi.org/10.9753/icce.v33.structures.50.

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In this study, the modeling of damage progression of rubble mound revetment and the performance evaluation based on laboratory experiments and numerical computations are performed. The model profiles for the damaged revetment are made on the basis of the experiments to measure the profile change. The model profiles corresponding to the degree of damage are determined by using some empirical equations that are related to the deformation quantity of the revetment. To examine the change of performance due to damage progression, the model profiles are also used in other experiments and numerical computations. The reflection coefficient and overtopping rate are taken as performance indices. The measured reflection coefficient shows a tendency to decrease, while the overtopping rate increases more than twice as much as that of the initial profile with damage progression of the revetment. The computed reflection coefficient and overtopping rate agree reasonably well with the experimental data.

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Schneider, Thomas, Katharina Voelkel, Hermann Pflaum, and Karsten Stahl. "Friction Behavior of Pre-Damaged Wet-Running Multi-Plate Clutches in an Endurance Test." Lubricants 8, no. 7 (June 30, 2020): 68. http://dx.doi.org/10.3390/lubricants8070068.

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Wet-running multi-plate clutches should be prevented from failing due to the often safety-relevant functions they fulfill in the drive train. In addition to long-term damage, spontaneous damage is of particular relevance for failures. This paper focuses on the influence of spontaneous damage on frictional behavior in the later life cycle. The aim of the experimental investigations is to initially cause spontaneous damage in wet-running multi-plate clutches with sintered friction linings. For this purpose, three clutches are first pre-damaged in stage tests with different intensities, so that the first spontaneous damage (local discoloration, sinter transfer) occurs. In the second step, an endurance test is carried out with the pre-damaged clutch packs and a non-pre-damaged reference clutch. The friction behavior of the clutches during the endurance test is compared and evaluated. It shows that local discoloration and sinter transfer are no longer visible after the endurance tests. At the beginning of the endurance test, the values of coefficient of friction are higher over the entire speed range of the heavily pre-damaged clutches than with the slightly pre-damaged clutch and the non-pre-damaged reference clutch. At the end of the endurance test, it can be observed that the greater the pre-damage to the clutches is, the greater the coefficient of friction increases with decreasing sliding speed.

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Jin, Guo Dong, Li Bin Lu, Liang Xian Gu, Juan Liang, and Xiao Fei Zhu. "Fatigue Life of UAV Airframe Based on Damage Coefficient." Advanced Materials Research 709 (June 2013): 358–62. http://dx.doi.org/10.4028/www.scientific.net/amr.709.358.

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Because of its advantage of zero casualties, Unmanned Aerial Vehicle (UAV) plays an important role in battlefield monitoring and information acquiring, thus caught great attention of the world. But with large quantities of UAVs equipped, uncertain life-span has become an important constraint of operating UAV safely and economically. So assessing the service life has important military and economic values. In the entire UAV system, the airframe life severely affects operation of UAV. According to method of damage coefficient, evaluation model on life of UAV airframe was established. In the case of security, its fatigue life was determined.

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Kim, Kyungmok, Jean Geringer, Julie Pellier, and Digby D. Macdonald. "Fretting corrosion damage of total hip prosthesis: Friction coefficient and damage rate constant approach." Tribology International 60 (April 2013): 10–18. http://dx.doi.org/10.1016/j.triboint.2012.10.008.

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Matsuoka, Masashi, and Fumio Yamazaki. "Building Damage Mapping of the 2003 Bam, Iran, Earthquake Using Envisat/ASAR Intensity Imagery." Earthquake Spectra 21, no. 1_suppl (December 2005): 285–94. http://dx.doi.org/10.1193/1.2101027.

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A strong earthquake occurred beneath the city of Bam, Iran, on 26 December 2003. High-resolution optical satellite images, such as Ikonos and QuickBird, obtained after the earthquake indicate that severely damaged areas were widely distributed in the city. A European radar satellite, Envisat, also captured the hard-hit areas on 07 January 2004. This paper introduces an automated damage detection technique that was developed based on the data set of the 1995 Kobe, Japan, earthquake and applied to Envisat/ASAR images of Bam. A detailed investigation of the characteristics of the areas damaged due to the Bam earthquake in terms of the differences in the backscattering coefficient and the correlation coefficient of the pre- and post-event Envisat/ASAR images was conducted in order to raise the precision of damage detection. Finally, the damage-mapping scheme was revised to present the distribution of damaged areas in Bam.

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Ghatrehsamani, Sahar, and Saleh Akbarzadeh. "Predicting the wear coefficient and friction coefficient in dry point contact using continuum damage mechanics." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 233, no. 3 (June 22, 2018): 447–55. http://dx.doi.org/10.1177/1350650118785045.

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Wear coefficient and friction coefficient are two of the key parameters in the performance of any tribo-system. The main purpose of the present research is to use continuum damage mechanics to predict wear coefficient. Thus, a contact model is utilized that can be used to obtain the friction coefficient between the contacting surfaces. By applying this model to the continuum damage mechanics model, the wear coefficient between dry surfaces is predicted. One of the advantages of using this model is that the wear coefficient can be numerically predicted unlike other methods which highly rely on experimental data. In order to verify the results predicted by this model, tests were performed using pin-on-disk test rig for several ST37 samples. The results indicated that the wear coefficient increases with increasing the friction coefficient.

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Wang, Zhen, Fang Liu, Lian Qing Yu, and Shuang Hong Chen. "Structural Damage Detection Using Sensitivity-Enhanced Autoregressive Coefficients." International Journal of Structural Stability and Dynamics 16, no. 03 (March 3, 2016): 1550001. http://dx.doi.org/10.1142/s0219455415500017.

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This paper presents an innovative technique for structural damage detection based on time series analysis with feedback controllers incorporated into the structure. The sensitivity of autoregressive (AR) coefficients to element stiffness is first derived, and it is proposed that the sensitivity of the AR coefficients can be enhanced by intentionally assigning the poles of the detection system. Finally, an [Formula: see text] control chart is constructed based on the sensitivity-enhanced AR coefficient. Identification of the occurrence of damage is achieved by monitoring statistically significant changes in the control chart. The proposed methodology is validated by examples including a cantilever Euler beam and Phase I of the IASC-ASCE benchmark structure. The simulation results show that by utilizing the sensitivity-enhanced AR coefficients, the control charts are more sensitive to damage and are capable of detecting small levels of structural damage even in the presence of measurement noise.

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Uprety, Pralhad, Fumio Yamazaki, and Fabio Dell'Acqua. "Damage Detection Using High-Resolution SAR Imagery in the 2009 L'Aquila, Italy, Earthquake." Earthquake Spectra 29, no. 4 (November 2013): 1521–35. http://dx.doi.org/10.1193/060211eqs126m.

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Satellite remote sensing is being used to monitor disaster-affected areas for post-disaster reconnaissance and recovery. One of the special features of Synthetic Aperture Radar (SAR) is that it can operate day and night and penetrate the cloud cover because of which it is being widely used in emergency situations. Building damage detection for the 6 April 2009 L'Aquila, Italy, earthquake was conducted using high-resolution TerraSAR-X images obtained before and after the event. The correlation coefficient and the difference of backscatter coefficients of the pre- and post-event images were calculated in a similar way as Matsuoka and Yamazaki (2004) . The threshold value of the correlation coefficient was suggested and used in detecting building damage. The results were compared with ground truth data and a post-event optical image. Based on the study, building damage could be observed in an urban setting of L'Aquila with overall accuracy of 89.8% and Kappa coefficient of 0.45.

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Lu, Xiang, Liang Pei, Jiankang Chen, Zhenyu Wu, and Chen Chen. "Research and Application of a Seismic Damage Classification Method of Concrete Gravity Dams Using Displacement in the Crest." Applied Sciences 10, no. 12 (June 16, 2020): 4134. http://dx.doi.org/10.3390/app10124134.

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Concrete gravity dams are one of the most common water retention structures, some of which are located in seismically active regions. Determination of damage level after earthquakes plays an important role in assessing the safety behavior of concrete dams. Compared with the traditional performance parameters obtained from numerical simulations, such as the damage coefficient, energy dissipation, failure modes, and stress state, etc., the displacement of dams can be acquired from daily monitoring data conveniently and quickly. It is of great significance for the rapid and effective evaluation of dam properties after earthquakes. The residual displacement in the concrete gravity dam crest was adopted as the performance parameter in the paper, and the linear mapping function between the residual displacement and the damage coefficient was established based on the concrete damaged plasticity model (CDP). Based on the traditional classification method with damage coefficient, a residual displacement-based seismic damage classification method with corresponding level limits was proposed. The seismic fragility analysis of Guandi concrete gravity dam was conducted as an example to illustrate the presented methodology. The results indicate that the proposed method is reasonable, effective, and can be easily applied to different projects after slight modifications.

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Kells, J. A. "Hydraulic performance of damaged-end corrugated steel pipe culverts." Canadian Journal of Civil Engineering 35, no. 9 (September 2008): 918–24. http://dx.doi.org/10.1139/l08-055.

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Culverts are a common and physically simple type of hydraulic structure, which are often fabricated as circular, corrugated steel pipe (CSP) sections. Because of the relatively thin wall of CSP, the ends of such pipe are frequently in a damaged condition. It is hypothesized that the hydraulic impact of the damage is often quite significant, resulting in reduced discharge capacity and (or) increased headwater ponding. The study reported in this paper was focused on an evaluation of the hydraulic impact of various levels of damage to the end sections of a culvert operating under either inlet or outlet control. In general, it was found that, for end damage deformations up to 1/4 of the pipe diameter, the discharge coefficient is reduced by approximately 10%, while the loss coefficients are increased by about 48% and 35% for inlet and outlet control modes of operation, respectively. For greater degrees of damage, the hydraulic performance is considerably worse.

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Haddad, Rami H., and Ayat Hinawi. "Chloride intrusion into thermally damaged self-compacting concrete." Canadian Journal of Civil Engineering 42, no. 10 (October 2015): 720–27. http://dx.doi.org/10.1139/cjce-2014-0353.

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The post-heating resistance of limestone self-compacting concrete (SCC) against chloride intrusion is investigated considering key parameters such as water-to-cement ratio (0.4, 0.45, and 0.5), relative humidity, and elevated temperature (300 °C and 400 °C). The SCC mixtures were proportioned to conform to universal specification with regard to different workability requirements. Chloride profiles were determined for post-heated and companion prismatic (100 mm × 100 mm × 250 mm) specimens, kept at room temperature. Consequently, diffusion coefficients were determined based on Fick’s steady state formula. Post-heating damage was quantified, as well, using various techniques such as ultrasonic pulse velocity waves, resonant frequency, compression test measurements. The results indicated significant reductions in compressive strength and estimated dynamic modulus ranging from 20 to 60% and 10 to 40%, respectively, with a corresponding increase in chloride diffusion coefficient reaching 80%. Both temperature and relative humidity levels had tangible impact on post-heating damage of SCC, hence percentage increase in chloride diffusion coefficient. The empirical models developed in this work showed excellent correlation between various damage indices and the percentage increase in diffusion coefficient. Furthermore, the electrical charge passing through SCC compared very well with the percentage increase in diffusion coefficient.

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Yu, H. Y., Zhen Bing Cai, Zhong Rong Zhou, and Min Hao Zhu. "Fretting Damage of Human Cortical Bone in Transverse Orientation against Titanium." Key Engineering Materials 288-289 (June 2005): 607–10. http://dx.doi.org/10.4028/www.scientific.net/kem.288-289.607.

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Under simulated human physiological solution, the fretting behaviors of flat cortical bone specimen from fresh human femur in the transverse orientation were investigated by sliding against pure titanium ball counterpart (tangential fretting technique). The friction coefficients and logs were calculated automatically. The worn surfaces of the cortical bone were analyzed by means of laser confocal scanning microscopy. The results show that the fricion coefficient of cortical bone directly relate with the magnitudes of displacement. The friction logs for cortical bone change with the magnitudes of displacement (Fn=90N) from elastic partial slip (D≤5 µm), plastoelastic partial slip (D=10 µm) to slip (D ≥20 µm) respectively. The fretting damages of cortical bone in the elastic partial slip were slight. But ploughs and delaminations were observed in the plastoelastic partial slip and gross sliding with loss of contact stiffness of cortical bone. The wear depth increased with cycles and well related to the friction coefficient of cortical bone in each fretting regime. Controlling the displacement amplitude and friction coefficients of bone-implant interface, it might be helpful to increase the anti-fretting capacities of human cortical bone.

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Cosic, Mladen, and Radomir Folic. "Performance analysis of damaged buildings applying scenario of related non-linear analyses and damage coefficient." Gradjevinski materijali i konstrukcije 58, no. 3 (2015): 3–27. http://dx.doi.org/10.5937/grmk1503003c.

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Ma, Shilong, Zhaoming Yao, Shuang Liu, and Xuan Pan. "Analysis of Three-Dimensional Damage Constitutive Model of Frozen Sand Based on the Influence of Intermediate Principal Stress and Temperature." Advances in Civil Engineering 2020 (September 26, 2020): 1–15. http://dx.doi.org/10.1155/2020/8860333.

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To study the mechanical properties of frozen soil, it is necessary to understand the damage characteristics of frozen soil. Four types of three-dimensional indoor tests of frozen sand were carried out at −5°C, −10°C, and −15°C to study the mechanical damage properties. These include different stress path tests with the principal stress coefficients of 0, 0.25, 0.5, and 0.75 while analyzing the entire failure process. First, the three-dimensional compression test of frozen sand was studied to analyze the influence of temperature and intermediate principal stress coefficient on the large principal stress of frozen soil. The damage cost of frozen sand under the influence of different temperatures and intermediate principal stress coefficients was also established. Second, using the characteristics of discreteness and randomness of the distribution of the microelements inside the frozen soil and assuming that the failure of the microelement of the frozen soil obeys the Weibull distribution, the Drucker–Prager strength criterion was used as the statistical distribution variable of the microelement of the frozen soil based on the strain equivalence hypothesis, statistical theory, and continuous damage mechanics. This allows for a constitutive model of frozen sand damage under the three-dimensional stress state to be established. Finally, the model parameter values through low-temperature three-dimensional test data were able to be determined. This model allows for the physical meaning of Weibull distribution parameters F0 and m to be analyzed, and the distribution parameters with temperature and intermediate principal stress coefficient can be modified to obtain a modified frozen sand damage constitutive model. The results show that the modified damage constitutive model can simulate the entire process curve of the large principal stress-strain of frozen sand. It shows that the large principal stress of frozen sand increases with the increase of temperature and intermediate principal stress coefficient. Concurrently, the frozen sand damage constitutive model proposed in this paper can describe the deformation behavior of frozen soil under different temperature and stress paths and can be adapted to various other sediment types.

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Law, S. S., X. Y. Li, and Z. R. Lu. "Structural Damage Detection from Wavelet Coefficient Sensitivity with Model Errors." Journal of Engineering Mechanics 132, no. 10 (October 2006): 1077–87. http://dx.doi.org/10.1061/(asce)0733-9399(2006)132:10(1077).

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Liu, Jun, Xiang Wang, Xue Rong Zhang, and Xiao Dong Cheng. "Booster Seat Dynamic Parameter and Damage Analysis." Advanced Materials Research 718-720 (July 2013): 1579–84. http://dx.doi.org/10.4028/www.scientific.net/amr.718-720.1579.

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In order to reduce the rate that child passengers injury their chest and head in a collision, parameter analysis of child restraint system is performed. Based on multi-body dynamics software MADYMO, child occupant crash simulation model is built. In accordance with the laws and regulations, the validity of the model is verified. Damage criterions, such as head the centroid synthesis of acceleration, HIC36 and resultant chest acceleration, are used to analyze the influence of different coefficients on childs injury, including friction between booster seat and vehicle seat, safety belt stiffness and friction between the dummy and safety belt. Results show that increasing the coefficient of friction of boost seat bottom and seat belt by coating them with friction material can reduce childs head and chest injuries significantly during the collision.

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Kaloop, Mosbeh R., and Jong Wan Hu. "Damage Identification and Performance Assessment of Regular and Irregular Buildings Using Wavelet Transform Energy." Advances in Materials Science and Engineering 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/6027812.

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This study investigates a novelty wavelet application for damage detection of regular and irregular building structures under seismic load effects. The energy of wavelet transform and correlation coefficient are used to detect the performance of the damaged building. The simple 3D regular and irregular simulation (finite element model) models of a building are designed to verify the methods’ uses and optimum applications. The obtained results reveal that the energy of Discrete Wavelet Transform (DWT) shows significantly higher performance than the energy of Continuous Wavelet Transform (CWT) in detecting the damage of the building, and the performance of irregular buildings appeared suitable for use in the seismically active areas. In addition, it can be concluded that the correlation coefficient can be applied to study the effects of damage and the safety of structures.

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Ding, Hui, Jian Ping Wang, and Cheng Fan. "Application of Damaged Plasticity Model on Slab-Column Joints." Applied Mechanics and Materials 777 (July 2015): 13–17. http://dx.doi.org/10.4028/www.scientific.net/amm.777.13.

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By the analysis of reinforced concrete slab, combined with experiment tests the feasibility of damaged plasticity model for concrete. Using parametric analyses, further the plastic damage model of related parameters set methods were discussed, concrete dilatation Angle, viscous coefficient, tensile stiffness, tensile damage on the results, in order to the design of slab-column connections engineering personnel to provide the reference.

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Jun, J. H., J. L. Harris, J. D. Humphrey, and S. Rastegar. "Effect of Thermal Damage and Biaxial Loading on the Optical Properties of a Collagenous Tissue." Journal of Biomechanical Engineering 125, no. 4 (August 1, 2003): 540–48. http://dx.doi.org/10.1115/1.1591202.

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Thermal denaturation can induce marked changes in the optical and mechanical properties of collagenous tissues. The optical properties are important in both therapeutic and diagnostic applications of lasers in medicine. Although mechanical stress can be caused by collagen shrinkage in laser-based therapies, how the mechanical loading state affects the optical properties is not well understood. We used a new computer-controlled biaxial testing system to subject bovine epicardium to various loading conditions both before and after multiple levels of thermal damage. An integrating sphere technique was used to measure transmittance and diffuse reflectance, from which absorption and scattering coefficients were calculated using a Monte Carlo method. Results showed that the scattering coefficient increased with increasing mechanical load but decreased as the degree of thermal damage increased. There was no significant change in the absorption coefficient due to thermal damage over the ranges studied.

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Hameed, M. Saqib, Zheng Li, and Kaihong Zheng. "Damage Detection Method Based on Continuous Wavelet Transformation of Lamb Wave Signals." Applied Sciences 10, no. 23 (December 1, 2020): 8610. http://dx.doi.org/10.3390/app10238610.

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A damage estimation method based on continuous wavelet transformation (CWT) of the normalized Lamb wave signals is proposed here. Lamb waves are actuated and sensed using piezoelectric (lead zirconate titanate, PZT) transducers arranged in the form of square detection cells on a plate-like structure. Excitation sequences based on pitch–catch and pulse–echo configurations are tested for the same arrangement of the transducers. The possibilities of the existence of damage for each actuator–senor pair are formed by using the normalized coefficient of CWT. The size of the possible damage region is directly controlled through envelopes defined by the coefficients of CWT, and no additional parameter is required to define its size. The aggregate damage image is constructed by the fusion of damage possibilities from all actuator–sensor pairs using damage indices based on conjunctive and compromised fusion schemes. The results indicate that the proposed method can estimate the location and severity of multiple damage with signals directly from the damaged plate, without the need of baseline signals from the undamaged plate, and the time-compensated signals provide better damage imaging than the raw signals. The most accurate and computationally inexpensive combination is the pulse–echo configuration with damage index based on conjunctive image fusion scheme. The method is computationally inexpensive and can be applied for multiple damage estimations in large structures to reduce the evaluation cost and inspection time during on-line structural health monitoring.

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Jiang, Fu Xiang, Lei Xin, Tie Jun Zhao, and Xiao Mei Wan. "Inner Damage and Anti-Chloride Penetration of High-Performance Concrete under Axial Tensile Load." Advanced Materials Research 261-263 (May 2011): 1210–14. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1210.

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The total porosity of high performance concrete specimens after different level uniaxial tensile loading were measured to reflect the damage degree of mechanical load to the microstructure of the concrete. Meanwhile, considering the environmental characteristics of the ocean tidal zone, chloride penetration tests of the concrete were carried out with salt solution capillary absorption method. Based on the profile of chloride measured from specimens, chloride diffusion coefficients of the concrete under uniaxial tensile load with different levels are determined further by Fick’s second law. Results show that both of total porosity and chloride diffusion coefficient of the concrete are increased significantly after short-term tensile loading. And the evolutions of the porosity and chloride diffusion coefficient are similar with the development of micro-cracks under uniaxial tensile load.

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Fan, Hao, Lianguo Wang, and Kai Wang. "Stability Analysis of Surrounding Rock in Circular Tunnels Based on Critical Support Pressure." Advances in Civil Engineering 2020 (October 16, 2020): 1–9. http://dx.doi.org/10.1155/2020/8870928.

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Accurate calculation for the critical support pressure of tunnels plays an important role in tunnel stability evaluation and support design. In this study, a mechanical model for circular tunnels is developed. Considering the intermediate principal stress and strain-softening characteristic of rock mass, the critical support pressure when the plastic zone and damage zone begin to occur is determined based on the unified strength criterion and strain-softening model. Through the example study, the critical support pressure under different intermediate principal stress coefficient is solved. Furthermore, the effect of initial field stress, softening coefficient, and maximum damage variable on the critical support pressure are also discussed. The results show that the critical support pressure and radii of plastic and damage zones all decrease with the increase of the intermediate principal stress coefficient. The larger the initial field stress, the larger the critical support pressure. The softening coefficient and maximum damage variable of rock mass has no influence on the critical support pressure when the plastic zone begins to form, but has a significant effect on the critical support pressure when the damage zone begins to form. As softening coefficient increases and maximum damage variable decreases, the critical support pressure when the damage zone which begins to form increases. Data presented in this contribution provide significant theoretical insights into evaluating tunnel stability and support system reliability.

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Zahra, Basati, Rasekh Mansour, and Abbaspour-Gilandeh Yousef. "Mechanical test suitable for detection of bug-damage wheat grains abstract." Research in Agricultural Engineering 64, No. 2 (June 28, 2018): 77–84. http://dx.doi.org/10.17221/45/2017-rae.

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Considering the fact that the presence of bug-damaged wheat in the bulk results in a decrease of the flour quality and its final product, which is bread, it is necessary to differentiate the bug-damaged wheat grains from the healthy ones. Therefore, the present study investigated the mechanical properties of bug-damaged and healthy wheat grains of the Azar cultivar. By making use of these mechanical properties, it would be possible to provide a more precise texture identification of the bug-damaged wheat grains compared to the healthy ones. In this study, the mechanical properties (rupture energy, toughness and apparent elastic coefficient) were determined under compressive loading, with four levels of loading velocity (5, 15, 25 and 35 mm.min<sup>–1</sup>) and four levels of moisture content (9, 11.5, 14 and 16.5% wet basis) in both bug-damaged and healthy wheat grains. Due to the significant difference in the mean value of apparent elastic coefficient between the bug-damaged grains (74.779 MPa) and the healthy ones (289.071 MPa), this parameter can be employed as the most appropriate factor to distinguish the bug-damaged wheat grains from the healthy ones.

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Xu, Chunguang, Lei He, Shiyuan Zhou, Dingguo Xiao, and Pengzhi Ma. "Evaluation of Damage Process of a Coating by Using Nonlinear Ultrasonic Method." Coatings 11, no. 4 (April 11, 2021): 440. http://dx.doi.org/10.3390/coatings11040440.

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During the service or external loading of the surface coating, the damage accumulation may develop in the coating or at the interface between the substrate and the coating, but it is difficult to measure directly in the early stage, so the acoustic nonlinear parameters are used as the early damage index of the coating. In this paper, the nonlinear wave motion equation is solved by the perturbation method and the new relationship between the relative ratio of second-order parameter and third-order parameter was derived. The nonlinear ultrasonic testing system is used to detect received signals during tensile testing of for the specimen with Al2O3 coatings. It is found that when the stress is less than 260 MPa, the appearance of the coating has no obvious change, but the nonlinear coefficients measured by the experiment increase with the increase of the tensile stress. By comparing the curves of nonlinear coefficients and stress respectively, the fluctuation of curves the second-order nonlinear coefficient A2 and the relative nonlinear coefficient β′ to stress is relatively small, and close to the linear relationship with the tensile stress, which indicates that the two parameters of the specimen with Al2O3 coatings are more sensitive to the bonding conditions, and can be used as an evaluation method to track the coating damage.

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Hoshyar, Azadeh Noori, Bijan Samali, Ranjith Liyanapathirana, Afsaneh Nouri Houshyar, and Yang Yu. "Structural damage detection and localization using a hybrid method and artificial intelligence techniques." Structural Health Monitoring 19, no. 5 (November 22, 2019): 1507–23. http://dx.doi.org/10.1177/1475921719887768.

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In this article, an intelligent scheme for structural damage detection and localization is introduced by implementing a hybrid method using the Hilbert–Huang transform and the wavelet transform. First, the second derivatives of the Discrete Laplacian are computed on Hilbert spectrum parameters at each frequency coordinate, and then, in order to highlight the influence of damage on signals, the data are rescaled and weighted with respect to the variance to adjust the differences in amplitude at different scales. Afterwards, the anti-symmetric extension is applied to deal with the boundary distortion phenomenon. A two-dimensional map is created using the multi two-dimensional discrete wavelet transform. This generates the coefficient matrices of level 2 approximation and horizontal, vertical and diagonal details. Horizontal detail coefficients are used to localize damages due to its sensitiveness to any perturbation. Finally, the validity of the algorithm corresponding to various damage states, the single state damage and multiple state damage, is examined through experimental analysis. The results indicate that the proposed framework can effectively localize cracks on concrete and reinforced concrete beams and can provide reliable crack localization in the presence of noise up to 5% more than the expected noise. In addition, the detection problem is mapped to machine learning tasks (support vector machine, k-nearest neighbours and ensemble methods) to automate the damage detection process. The quality of the models is evaluated and validated using the features extracted from the horizontal detail coefficients. The numerical results show that the ensemble models outperform the other models with respect to accuracy, prediction speed and training time.

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Xie, Fan, Weibin Li, and Yuxiang Zhang. "Monitoring of environmental loading effect on the steel with different plastic deformation by diffuse ultrasound." Structural Health Monitoring 18, no. 2 (March 27, 2018): 602–9. http://dx.doi.org/10.1177/1475921718762323.

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Diffuse ultrasound is highly sensitive to changes in mechanical properties. Based on the coda wave interferometry analysis, we investigate the environmental temperature-induced wave velocity variations in high-manganese steels with plastic deformations by diffuse ultrasound. We observe the velocity changes in the materials at test with [Formula: see text] relative resolution. We propose the temperature-dependent coefficient as the key parameter for damage assessment in the specimens with different plastic deformations. The results show that the early-stage damage caused by plastic deformation in the specimens at test varying from 6% to 14% are successfully characterized by temperature-dependent coefficients in the absence of external mechanical load. The theoretical analysis on the sensitivity of the temperature-dependent coefficient to plastic deformation as well as the potential on-site application is discussed in this article.

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Peterson, Brandon W., Prashant K. Sharma, Henny C. van der Mei, and Henk J. Busscher. "Bacterial Cell Surface Damage Due to Centrifugal Compaction." Applied and Environmental Microbiology 78, no. 1 (October 28, 2011): 120–25. http://dx.doi.org/10.1128/aem.06780-11.

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ABSTRACTCentrifugal damage has been known to alter bacterial cell surface properties and interior structures, including DNA. Very few studies exist on bacterial damage caused by centrifugation because of the difficulty in relating centrifugation speed and container geometry to the damage caused. Here, we provide a simple, versatile method of analysis for describing the compaction of bacteria during centrifugation based on a proposed centrifugation coefficient,C. Values ofCcan be related to different bacterial cell surface properties. Changing the geometry of the centrifugation container or centrifugation speeds changed the value ofCsignificantly. Initial deposition rates ofStaphylococcus aureusATCC 12600 to a glass surface decayed exponentially from 4,217 to 1,478 cm−2s−1with increasingC, while the proportion of staphylococci with a zeta potential of around −15 mV decreased from 97 to 58%. These surface-sensitive parameters were used independently to derive a critical centrifugation coefficient (0.040), above which centrifugation was considered to impact the outcome of surface-sensitive experiments due to cell surface damage. The critical centrifugation coefficient could successfully predict staphylococcal cell surface damage, i.e., a significant change in initial deposition rate or zeta potential distribution, in 84% of all cases included here, whereas the centrifugation speed could predict damage in only 58% of all cases. Moreover, controlling the centrifugation coefficient within narrow limits over a series of experiments yielded 43% smaller standard deviations in initial staphylococcal deposition rates than with centrifugation at fixed speeds for replicate experiments.

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Zhang, Xin Zhong, Ai Hong Han, and Zong Liang Wu. "Research on Pipe-Soil Displacement Transfer Coefficient for Buried Pipeline." Advanced Materials Research 201-203 (February 2011): 2891–95. http://dx.doi.org/10.4028/www.scientific.net/amr.201-203.2891.

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In anti-seismic design of buried pipeline, selection of pipe-soil displacement transfer coefficient is the decisive factor for reasonable and stable analysis on seismic damage. This paper discusses calculation and selection of pipe-soil displacement transfer coefficient and related parameters, gives more definite, reasonable, simple, and reliable method of determination incorporating with existing achievements for analysis on seismic damage to buried pipelines. The results of analysis provide for anti-seismic design of buried pipelines with basis of reference.

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Nezu, Atsuo, Seiji Kimura, Takuya Kobayashi, Hitoshi Osaka, and Saori Uehara. "Coefficient of variation of R-R intervals in severe brain damage." Brain and Development 18, no. 6 (November 1996): 453–55. http://dx.doi.org/10.1016/s0387-7604(96)00048-4.

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Zhang, Yuling, Xuezhong Xin, and Xin Cui. "Updating Fatigue Damage Coefficient in Railway Bridge Design Code in China." Journal of Bridge Engineering 17, no. 5 (September 2012): 788–93. http://dx.doi.org/10.1061/(asce)be.1943-5592.0000310.

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Hua, Jiadong, Jing Lin, and Liang Zeng. "High-resolution damage detection based on local signal difference coefficient model." Structural Health Monitoring: An International Journal 14, no. 1 (December 17, 2014): 20–34. http://dx.doi.org/10.1177/1475921714546060.

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Bibik, V., and A. Galeeva. "Estimation of Temperature Conductivity Coefficient Impact upon Fatigue Damage of Material." IOP Conference Series: Materials Science and Engineering 91 (September 14, 2015): 012033. http://dx.doi.org/10.1088/1757-899x/91/1/012033.

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Pines, Darryll J. "Detection of utility pole rot damage by measuring the reflection coefficient." Journal of Nondestructive Evaluation 16, no. 1 (January 1996): 43–54. http://dx.doi.org/10.1007/bf03323653.

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Pines, Darryll J. "Detection of utility pole rot damage by measuring the reflection coefficient." Journal of Nondestructive Evaluation 16, no. 1 (March 1997): 43–56. http://dx.doi.org/10.1007/bf03325384.

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Skrzyszewski, Jerzy, and Maciej Pach. "The use of the slenderness coefficient in diagnosing wind damage risks." Acta Silvestria LVII (2020): 7–24. http://dx.doi.org/10.15576/actasilvestria/2020.lvii.7.

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Xinhua, Xue, Zhang Wohua, and Xingguo Yang. "Study on constitutive model of coupled damage-permeability of porous media." International Journal of Numerical Methods for Heat & Fluid Flow 24, no. 2 (February 25, 2014): 359–75. http://dx.doi.org/10.1108/hff-04-2012-0086.

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Purpose – The paper aims to clarify the relationship between the micro-structures of porous media and the coefficient of permeability. Most materials involve different types of defects like caves, pores and cracks, which are important characters of porous media and have a great influence on the physical properties of materials. To study the seepage mechanical characteristics of damaged porous media, the constitutive model of porous media dealing with coupled modeling of pores damage and its impact on permeability property of a deforming media was studied in this paper. Design/methodology/approach – The paper opted for an exploratory study using the approach of continuum damage mechanics (CDM). Findings – The paper provides some new insights on the fluid dynamics of porous media. The dynamic evolution model of permeability coefficient established in this paper can be used to model the fluid flow problems in damaged porous media. Moreover, the modified Darcy's law developed in this paper is considered to be an extension of the Darcy's law for fluid flow and seepage in a porous medium. Research limitations/implications – Owing to the limitations of time, conditions, funds, etc., the research results should be subject to multifaceted experiments before their innovative significance can be fully verified. Practical implications – The paper includes implications for the development of fluid dynamics of porous media. Originality/value – This paper fulfils an identified need to study the relationship between the micro-structures of porous media and the coefficient of permeability.

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Hagoort, Jacques. "An Improved Model for Estimating Flow Impairment by Perforation Damage." SPE Journal 12, no. 02 (June 1, 2007): 235–44. http://dx.doi.org/10.2118/98137-pa.

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Summary In this work, we present two simple formulas for the skin of a perforated well caused by perforation damage: one for the reduction in permeability, and one for the increase in non-Darcy flow coefficient (beta factor). They are based on the inflow performance of a single perforation obtained by means of a prolate-spheroidal flow model. This model rigorously accounts for the flow convergence toward a perforation, especially near the tip of the perforation. It provides a more realistic description of the inflow than a radial flow model, the basis for the existing skin formulas proposed by McLeod (1983). In the case of perforations with a large aspect ratio and a thin damaged zone, the formula for the skin due to permeability reduction reduces to McLeod's formula. The formula for the non-Darcy skin yields a significantly larger skin than predicted by the radial flow model, up to a factor 1.4 for large aspect ratios. Finally, we demonstrate that perforated wells are much more liable to non-Darcy flow than openhole wells, in particular if the perforations are severely damaged. Introduction Oil and gas wells are commonly completed with production casing cemented in place and perforated to enable fluids to enter the wellbore. The perforations are created by perforating guns and have the form of straight elongated and circular holes that stick into the formation perpendicular to the wall of the wellbore. The perforation holes are surrounded by a damaged zone of crushed and compacted rock. Typically, a perforation has a diameter of approximately a quarter-in., a length of a few up to more than a dozen inches and a crushed zone thickness of up to 1 in. It has been long recognized that perforation damage may drastically impair the flow efficiency of a perforated well. Not only is this caused by a lower permeability in the crushed zone, but also by a higher inertial resistance coefficient (non-Darcy flow coefficient), which is particularly important for prolific, high-rate gas wells. Customarily, the inflow performance of a perforated well is described by the radial openhole inflow formula, in which the effect of the perforations (e.g. geometry, shot density, phasing, and perforation damage) is included as a pseudo skin (Bell et al. 1995). The current model for estimating the Darcy and non-Darcy skins due to perforation damage was proposed by McLeod(1983). In this model the perforation is represented by an open circular cylinder surrounded by a concentric crushed zone of reduced permeability and enhanced non-Darcy flow coefficient, and the inflow into this cylinder is assumed to be radial, perpendicular to its axis.

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Journal articles on the topic 'Damage coefficient'

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