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1
Liu, Jifeng, and Huizhi Zhang. "Water Content Influence on Properties of Red-Layers in Guangzhou Metro Line, China." Advances in Materials Science and Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/4808909.
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In order to reveal water content influence on shear strength, swelling, and creep properties of red-layers in Guangzhou Metro, Southern China, the typical red-layers rock and soil specimens were experimentally studied by direct shear test, UU triaxial test, swelling test, and creep test, and the measured data were analyzed. The results showed that soil internal friction angle exponentially decreased with the water content increase and cohesion in accordance with the Gaussian function firstly increased and then decreased with the increase of water content. Expansion rate significantly decreased with the initial water content increase. The red sandstone had very strong isotropic expansion and disintegration properties. The mechanism of water content effect on red-layers properties was water induced microstructures and mineral compositions change which caused the macro physical and mechanical characteristics degradation. The results should provide the reference for further research for water induced damage mechanism or creep damage control of red-layers in engineering practice.
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Leng, Dingxin, Kai Xu, Liping Qin, Yong Ma, and Guijie Liu. "A Hyper-Elastic Creep Approach and Characterization Analysis for Rubber Vibration Systems." Polymers 11, no. 6 (June 4, 2019): 988. http://dx.doi.org/10.3390/polym11060988.
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Rubber materials are extensively utilized for vibration mitigation. Creep is one of the most important physical properties in rubber engineering applications, which may induce failure issues. The purpose of this paper is to provide an engineering approach to evaluate creep performance of rubber systems. Using a combination of hyper-elastic strain energy potential and time-dependent creep damage function, new creep constitutive models were developed. Three different time-decay creep functions were provided and compared. The developed constitutive model was incorporated with finite element analysis by user subroutine and its engineering potential for predicting the creep response of rubber vibration devices was validated. Quasi-static and creep experiments were conducted to verify numerical solutions. The time-dependent, temperature-related, and loading-induced creep behaviors (e.g., stress distribution, creep rate, and creep degree) were explored. Additionally, the time–temperature superposition principle was shown. The present work may enlighten the understanding of the creep mechanism of rubbers and provide a theoretical basis for engineering applications.
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Chan, K. S., N. S. Brodsky, A. F. Fossum, D. E. Munson, and S. R. Bodner. "Creep-Induced Cleavage Fracture in WIPP Salt Under Indirect Tension." Journal of Engineering Materials and Technology 119, no. 4 (October 1, 1997): 393–400. http://dx.doi.org/10.1115/1.2812275.
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The phenomenon of cleavage fracture initiation in rock salt undergoing concurrent creep was studied experimentally using the Brazilian indirect tension test technique. The tensile creep and cleavage fracture behaviors were characterized for rock salt from the Waste Isolation Pilot Plant (WIPP) site. The Brazilian test consists of a compressive line load applied diametrically on a disk specimen to produce a region of tensile stress in the center of the disk. The damage processes were documented using video photography. The experimental results were analyzed in terms of a wing-crack fracture model and an independently developed, coupled time-dependent, mechanism-based constitutive model whose parameters were obtained from triaxial compression creep tests. Analytical results indicate that coupling between creep and cleavage fracture in WIPP salt results in a fracture behavior that exhibits time-dependent characteristics and obeys a failure criterion involving a combination of stress difference and tensile stress. Implications of creep-induced cleavage fracture to the integrity of WIPP structures are discussed.
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Bao, Yi Wang, and Yan Chun Zhou. "Bending Creep and Stress Relaxation of Ti3AlC2 at High Temperature." Key Engineering Materials 280-283 (February 2007): 1373–78. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1373.
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Creep and stress relaxation of Ti3AlC2 were investigated using three-point bending tests at 800-1200°C under various load levels. The results show that the creep rate significantly increases with increasing temperature in the rang of 1000-1200°C. Subcritical crack growth during the creep process was found to be the main failure mechanism, i.e., the stress intensity factor increases with the creep-induced crack growth and results in the ultimate fracture. The lower limit of stress relaxation was considered as the threshold value of zero-creep stresses, and the ratio of the threshold stress to the applied stress was defined to be a parameter of creep resistance for estimating deformation behavior at high temperature. SEM examination confirmed that the creep failure in Ti3AlC2 was governed by such a damage evolution: cavitation ® crack initiation ® crack extension ® fracture.
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Wang, Yang-Yang, Chen Jia, Morteza Tayebi, and Bejan Hamawandi. "Microstructural Evolution during Accelerated Tensile Creep Test of ZK60/SiCp Composite after KoBo Extrusion." Materials 15, no. 18 (September 16, 2022): 6428. http://dx.doi.org/10.3390/ma15186428.
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In the current study, the creep properties of magnesium alloy reinforced with SiC particles were investigated. For this purpose, ZK60/SiCp composite was produced by the stir casting method following the KoBo extrusion and precipitation hardening processes. The creep tests were performed at 150 °C under 10–110 MPa. The results showed that the stress exponent (n) and the average true activation energy (Q) was changed at high stresses, was found with increasing stress, the creep mechanism changing from grain boundary sliding to dislocation climb. The results of microstructure characterization after the creep test showed that at low stresses, the dynamic recrystallization resulting from twinning induced the GBS mechanism. However, at high stresses, with increasing diffusion rates, conditions are provided for dynamic precipitation and the dislocation climb of the dominant creep mechanism. Examination of the fracture surfaces and the surrounding areas showed that the cavity nucleation in the ternary boundary and surrounding precipitation was the main cause of damage. The evaluation of the samples texture after creep showed that the unreinforced alloy showed a moderately strong fiber texture along the angle of ϕ1 = 0–90°, which was tilted about Φ = 10°. A new strong texture component was observed at (90°, 5°, 0°) for the composite sample, which crept due to minor splitting of the basal pole by ~5° toward RD.
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Khan, Talha H., Michael T. Myers, Lori Hathon, and Gabriel C. Unomah. "Time-Scaling Creep in Salt Rocks for Underground Storage." Petrophysics – The SPWLA Journal of Formation Evaluation and Reservoir Description 64, no. 6 (December 1, 2023): 954–69. http://dx.doi.org/10.30632/pjv64n6-2023a10.
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Salt is an elastoviscoplastic material that exhibits time-dependent deformation (creep). Experimental measurements of salt creep behavior help predict underground gas repositories’ long-term geomechanical behavior. Previous time-scaling creep experiments have focused on the axial strain of unconsolidated sands. i.e., time-scaling creep effects under zero lateral strain conditions without describing the creep behavior of the radial strain. In addition, the time-scaling creep of the radial and axial strain has not been investigated in salts. A comparative testing procedure and analysis method was conducted on Spindletop salt plugs using triaxial tests for multistage triaxial tests (MST) and different holding time durations and stress regimes, resulting in time-dependent strain responses (creep tests). The MST showed evolving deformational mechanisms under the mapped yield surface based on the irrecoverable to recoverable strain ratio beginning with crack closure or conformance, plasticity, and ending at early crystal surface failure. Unlike unconsolidated sands, salts showed both time and strain amplitude scaling. The axial and radial strain data show scaling behavior under low and high levels of deviatoric stress separated by a transitional period. The salt showed only an axial creep response at low deviatoric stress distally from the yield surface (one-dimesional (1D) response or zero lateral strain), which indicates negative dilatant deformation or uniaxial compaction. In contrast, the salts showed equal strain amplitude scaling factors both axially and radially at high deviatoric stress proximal to the yield surface (two-dimensional (2D) response or unconstrained boundary condition), which suggests positive dilatant deformation. Microstructural images showed accumulated creep damage under high deviatoric stress associated with parallel planes of dislocation-intergranular slip, microcracking, and compaction-induced dilational strains. The period of scaling is interpreted as regions where a single mechanism is dominating. Strain amplitude scaling for both low and high deviatoric creep stress tests provides inputs for a constitutive model of creep response in understanding the magnitude of mechanical damage associated with time-independent stress-strain curves in salts for the structural integrity of salt caverns during cyclic fluid injection and depletion.
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Jazaeri, Hedieh, P. Bouchard, Michael Hutchings, Mike Spindler, Abdullah Mamun, and Richard Heenan. "An Investigation into Creep Cavity Development in 316H Stainless Steel." Metals 9, no. 3 (March 12, 2019): 318. http://dx.doi.org/10.3390/met9030318.
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Creep-induced cavitation is an important failure mechanism in steel components operating at high temperature. Robust techniques are required to observe and quantify creep cavitation. In this paper, the use of two complementary analysis techniques: small-angle neutron scattering (SANS), and quantitative metallography, using scanning electron microscopy (SEM), is reported. The development of creep cavities that is accumulated under uniaxial load has been studied as a function of creep strain and life fraction, by carrying out interrupted tests on two sets of creep test specimens that are prepared from a Type-316H austenitic stainless steel reactor component. In order to examine the effects of pre-strain on creep damage formation, one set of specimens was subjected to a plastic pre-strain of 8%, and the other set had no pre-strain. Each set of specimens was subjected to different loading and temperature conditions, representative of those of current and future power plant operation. Cavities of up to 300 nm in size are quantified by using SANS, and their size distribution, as a function of determined creep strain. Cavitation increases significantly as creep strain increases throughout creep life. These results are confirmed by quantitative metallography analysis.
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Puzrin, Alexander M., Thierry Faug, and Itai Einav. "The mechanism of delayed release in earthquake-induced avalanches." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, no. 2227 (July 2019): 20190092. http://dx.doi.org/10.1098/rspa.2019.0092.
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Snow avalanches can be triggered by strong earthquakes. Most existing models assume that snow slab avalanches happen simultaneously during or immediately after their triggering. Therefore, they cannot explain the plausibility of delayed avalanches that are released minutes to hours after a quake. This paper establishes the basic mechanism of delays in earthquake-induced avalanche release using a novel analytical model that yields dynamics consistent with three documented cases, including two from Western Himalaya and one from central Italy. The mechanism arises from the interplay between creep, strain softening and strain-rate sensitivity of snow, which drive the growth of a basal shear fracture. Our model demonstrates that earthquake-triggered delayed avalanches are rare, yet possible, and could lead to significant damage, especially in long milder slopes. The generality of the model formulation opens a new approach for exploring many other problems related to natural slab avalanche release.
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Chen, Xingzhou, Quan Zhang, Xinchao Ding, Lili Chen, Wei Du, Hai Jiang, and Sheng Gong. "Study on the Creep Characteristics and Fractional Order Model of Granite Tunnel Excavation Unloading in a High Seepage Pressure Environment." Sustainability 15, no. 5 (March 3, 2023): 4558. http://dx.doi.org/10.3390/su15054558.
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The creep associated with unloading surrounding rock during the excavation of deep tunnels seriously affects the stability of the tunnel, and a high seepage pressure will aggravate the strength attenuation and structural deterioration of the surrounding rock. Based on the background of the excavation-induced unloading of the surrounding rock of a deeply buried granite tunnel with high seepage pressure, in this paper we carry out a triaxial unloading seepage creep test that considers the effects of both excavation disturbance and seepage pressure. We also analyze the mechanism of unloading and seepage pressure leading to sample failure and construct a fractional creep damage constitutive model that considers the unloading effect. The results include the following findings, firstly, seepage pressure will affect the creep deformation of rock for a long time, and the circumferential expansion of the granite creep process is more obvious than the axial expansion. Secondly, a high seepage pressure will reduce the rock bearing capacity. Under 0, 2 and 4 MPa seepage pressures, the long-term strength of the samples are 193.7 MPa, 177.5 MPa and 162.1 MPa, respectively. Thirdly, the rock damage factor increases with increasing seepage pressure, time and deviatoric stress. Finally, the rationality of a fractional-order model that considers the effect of unloading and seepage is verified by the test data. These research results may provide some reference for the stability analysis of surrounding rock during excavation in environments under high-stress and high-seepage-pressure.
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CHRZANOWSKI, MARCIN, and KRZYSZTOF NOWAK. "ON MULTISCALE MODELLING OF CREEP DAMAGE BY MEANS OF CELLULAR AUTOMATA." Journal of Multiscale Modelling 01, no. 03n04 (July 2009): 389–402. http://dx.doi.org/10.1142/s1756973709000153.
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Deterioration of the materials, particularly metals under environmental conditions such as high temperature, alternating loading and chemical aggression is an example of processes which happen on the microstructure levels but project themselves upon macroscopically observed behaviour of materials and structures. This connection between both levels of observation was obvious to many researches, even if they aimed at macroscopic description on the level of continuum mechanics. The wisdom of micro- and macro-coupling was induced by a very complex nature of microstructural processes which demonstrated themselves as transgranular or intergranular failures, just to mention two typical modes of creep failure. The gap between micro- and macro-world was a challenge to both material science and mechanics societies throughout the second half of 20th century. A proposed method to cover this gap for polycrystalline materials is based on Cellular Automata (CA) technique well suited to be used on the microscopic level and giving responses relevant to macroscopic observations. It allows for microstructure modelling to distinguish grains and grain boundaries. Once it is done, a cellular automaton can be attributed to the Representative Volume Element (RVE) and failure mechanism described on the basis of appropriate transition rules. Examples of transgranular and intergranular creep damage growth are demonstrated. This procedure can be extended over the feedback from micro-level to macro-level leading to the formation of so-called CAFE technique.
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Liu, Y., J. Lin, T. A. Dean, and D. C. J. Farrugia. "A Numerical and Experimental Study of Cavitation in a Hot Tensile Axisymmetric Testpiece." Journal of Strain Analysis for Engineering Design 40, no. 6 (August 1, 2005): 571–86. http://dx.doi.org/10.1243/030932405x30768.
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During axisymmetric hot tensile testing, necking normally takes place due to the thermal gradient and the accumulation of microdamage. This paper introduces an integrated technique to predict the damage and necking evolution behaviour. Firstly, a set of multiaxial mechanism-based unified viscoplastic-damage constitutive equations is presented. This equation set, which models the evolution of grain boundary (intragranular) and plasticity-induced (intergranular) damage, is determined for a free-cutting steel tested over a range of temperatures and strain rates on a Gleeble thermomechanical simulator. This model has been implemented using the CREEP subroutine of the commercial finite element (FE) solver ABAQUS. Numerical procedures to simulate axisymmetric hot tensile deformation are developed with consideration of the thermal gradient along the axis of the tensile testpiece. FE simulations are carried out to reproduce the necking phenomenon and the evolution of plasticity-induced and grain boundary damage. The simulated results have been validated with experimental tensile test results. The effects of necking and its associated stress state on flow stress and ductility are investigated. The flow stress and ductility data obtained from a Gleeble material simulator under various hot deformation conditions have also been numerically studied.
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Wang, Wentao, Kang Zhao, Tingting Xie, Huifang Liu, Guanyi Zhao, and Linbing Wang. "Rheological Behaviors and Damage Mechanism of Asphalt Binder under the Erosion of Dynamic Pore Water Pressure Environment." Polymers 14, no. 21 (November 4, 2022): 4731. http://dx.doi.org/10.3390/polym14214731.
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Asphalt binder plays an important role in the overall resistance of asphalt mixture to the moisture damage induced by a dynamic pore water pressure environment. This study evaluates the moisture sensitivity of asphalt binder from the perspective of rheological behaviors using the dynamic shear rheometer (DSR) and the bending beam rheometer (BBR) methods at high, medium, and low temperatures. The damage mechanism is further discussed quantitatively based on the Fourier transform infrared spectroscopy (FTIR) method. The results indicate that a longer conditioning duration is beneficial for asphalt binder to recover its adhesion at 60 °C in multiple stress creep recover (MSCR) tests, but the increasing pore water pressure magnitude of 60 psi held an opposite effect in this study. The asphalt binder’s fatigue life at 20 °C in linear amplitude sweep (LAS) tests decreased obviously with conditioning duration and environmental severity, but the reducing rate gradually slowed down, while the groups of 50 psi—4000 cycles and 60 psi—4000 cycles held a comparable erosion effect. Both the stiffness and relaxation moduli at −12 °C in the BBR tests exhibited an obvious decreasing trend with conditioning duration and environmental severity. The erosion effect on the asphalt binder was gradually enhanced, but it also exhibited a slightly more viscous performance. Water conditioning induced several obvious characteristic peaks in the FTIR absorbance spectra of the asphalt binder. The functional group indexes presented a trend of non-monotonic change with conditioning duration and environmental severity, which made the asphalt binder show complicated rheological behaviors, such as non-monotonic variations in performance and the abnormal improving effect induced by dynamic pore water pressure conditioning.
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Roberts, D. I., R. H. Ryder, and R. Viswanathan. "Performance of Dissimilar Welds in Service." Journal of Pressure Vessel Technology 107, no. 3 (August 1, 1985): 247–54. http://dx.doi.org/10.1115/1.3264443.
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Dissimilar metal welds (DMWs) between austenitic and ferritic steel tubing and piping are commonly employed in high-temperature applications in energy conversion systems. Differences in coefficient of thermal expansion between the two types of steel induce thermal stresses at the welds and local metallurgical changes near the low alloy steel/weld metal interface due to prolonged service at an elevated temperature. These phenomena, together with the differences in creep behavior of the materials joined, render the DMWs more prone to failure than welds between similar steels. This has been reflected in relatively high failure rates in DMWs in certain service applications (e.g., in utility power plant boiler tubing). Typically these welds fail by low ductility cracking in the low alloy steel at, or very close to, the fusion line. A project, sponsored by the Electric Power Research Institute (EPRI) and managed by the Metal Properties Council (MPC), has made significant headway over the last three years in understanding the failure modes and causes involved and in developing methods to assess residual life of DMWs. Welds from service in superheaters and reheater tubes and from laboratory simulation tests were examined to establish metallurgical characteristics and failure modes. Three failure modes were identified: (i) Prior austenite grain boundary cracking in the ferritic steel, one or two grains away from the fusion line; this mode was mainly observed in DMWs made with stainless steel filler metal. (ii) Cracking along the weld interface, which occurred in DMWs made with nickel-base filler metal. (iii) Propagation of cracks initiating from oxide notches formed at the weld outside surface; this mode occurred mainly in thin-walled tubes. Creep damage induced by steady and cyclic loading was found to be the predominant mechanism for damage and failure; therefore a dependence of damage on loading levels and service temperature was established. It was also determined that failure susceptibility in DMWs made with nickel-base filler was strongly influenced by the type of microstructure that formed at the low alloy steel/weld metal interface. The technique developed for estimating the condition and remaining life of DMWs in service involves detailed assessment of loading histories to which the welds are subjected, along with the use of empirical quantitative relationships established from both laboratory and service data. The methodology assumes that damage results from the combined effects of self damage (caused by thermal cycling of materials of different expansion coefficients) and service loadings, including both primary loads (e.g., pressure and deadweight) and secondary, or cyclic, loads due to the constrained thermal expansion of the system as a whole. The technique, Prediction Of Damage In Service (designated PODIS), has been found to adequately predict levels of damage in stainless-based DMWs in service. It is currently being developed further to embrace nickel-based DMWs.
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Xu, Tao, Gao Lin, Chun An Tang, and Zhi Qiang Hu. "Sustained Loading Fracture and Strength of Concrete Modelled by Creep-Damage Interaction." Key Engineering Materials 324-325 (November 2006): 51–54. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.51.
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The phenomenon creep fracture is well-known for concrete. In the present paper, the Material Failure Process Analysis (MFPA2D) model for concrete in the failure process is coupled in series with the time-dependence of the concrete damage and deformation. Further, the progressive creep failure of concrete specimens under constant tensile loading was numerically simulated and the typical time-dependent deformations: the transient creep, the steady-state creep and the accelerating creep were also represented. The numerical simulations indicate that the macroscopic creep failure is induced by clusters of micro-fractures on a mesocopic scale. The above numerical results offer us some theoretical indications and instructions to further investigate the instability failure mechanisms of engineering concrete structures in civil and hydraulic engineering.
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Ó Murchú, C., SB Leen, PE O’Donoghue, and RA Barrett. "A precipitate evolution-based continuum damage mechanics model of creep behaviour in welded 9Cr steel at high temperature." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 233, no. 1 (April 4, 2018): 39–51. http://dx.doi.org/10.1177/1464420718762607.
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A multiaxial, physically based, continuum damage mechanics methodology for creep of welded 9Cr steels is presented, incorporating a multiple precipitate-type state variable, which simulates the effects of strain- and temperature-induced coarsening kinematics. Precipitate volume fraction and initial diameter for carbide and carbo-nitride precipitate types are key microstructural variables controlling time to failure in the model. The heat-affected zone material is simulated explicitly utilising measured microstructural data, allowing detailed investigation of failure mechanisms. Failure is shown to be controlled by a combination of microstructural degradation and Kachanov-type damage for the formation and growth of creep cavities. Comparisons with experimental data demonstrate the accuracy of this model for P91 material.
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Seshadri, R. "Design and Life Prediction of Fired Heater Tubes in the Creep Range." Journal of Pressure Vessel Technology 110, no. 3 (August 1, 1988): 322–28. http://dx.doi.org/10.1115/1.3265606.
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Realistic fired heater tube-life predictions are essential to safe and economical design, proactive inspection strategy and meaningful tube retirement evaluations. The traditional method of heater tube design (API RP 530), that is based on the “mean-diameter equation,” sometimes implies tube-life in excess of actual operating experience. The main reason for this discrepancy is the interaction of cyclic radial thermal gradient, that exists across the tube wall, with the pressure-induced stresses resulting in enhanced creep damage. Upper-bound estimates for creep deformations and creep damage are obtained in this paper using a simple analytical procedure. Some broad guidelines relating to the assessment of remaining tube-life, tube retirement and inspection frequencies are presented.
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Stochioiu, Constantin, Horia-Miron Gheorghiu, and Flavia-Petruta-georgiana Artimon. "Visco-elastoplastic Characterization of a Flax-fiber Reinforced Biocomposite." Materiale Plastice 58, no. 1 (April 5, 2021): 78–84. http://dx.doi.org/10.37358/mp.21.1.5447.
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In the presented study, the load induced long-term behavior of a biocomposite material is analyzed. The studied material is a unidirectional flax fiber reinforced epoxy resin, material, whose quasi-static mechanical properties can compare with those of glass fiber composites. Samples with a fiber direction of 0� were subjected to two types of multi-level creep-recovery tests, one with a varying creep duration, and the other with a varying creep stress, with the purpose of discriminating the viscoplastic and viscoelastic behavior of the composite. Results show a significant viscous response in time, dependent on both creep duration and creep stress, up to 20% of the elastic one. Sample damage is absent, leading to the conclusion that the viscoplastic response is caused by the permanent reorganization of the fiber�s internal structure.
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Peloquin, Emilie. "Phase Coherence Imaging: Advantages of a New Ultrasonic Technique." AM&P Technical Articles 180, no. 6 (September 1, 2022): 27–29. http://dx.doi.org/10.31399/asm.amp.2022-06.p027.
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Abstract Phase coherence imaging is a new approach for processing ultrasonic signals generated during nondestructive testing. This article shows how it compares with amplitude-based focusing methods for detecting hydrogen-related microfissures, creep-induced damage, and stainless-steel weld voids.
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Miura, Hideo, Ken Suzuki, Hiroyuki Ito, and Tatsuya Inoue. "Creep and Fatigue Damages of Ni-Base-Superalloy Caused by Strain-Induced Anisotropic Diffusion of Component Elements." Key Engineering Materials 417-418 (October 2009): 261–64. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.261.
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The mechanism of the directional coarsening of ' phases (rafting) of Ni-base superalloy under an uni-axial strain was analyzed by molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the interface was observed clearly in a Ni(001)/Ni3Al(001) interface structure, The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Pd was one of the most effective elements which restrain Al atoms from moving around the interface.
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Barreira-Pinto, Rui, Rodrigo Carneiro, Mário Miranda, and Rui Miranda Guedes. "Polymer-Matrix Composites: Characterising the Impact of Environmental Factors on Their Lifetime." Materials 16, no. 11 (May 23, 2023): 3913. http://dx.doi.org/10.3390/ma16113913.
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Polymer-matrix composites are widely used in engineering applications. Yet, environmental factors impact their macroscale fatigue and creep performances significantly, owing to several mechanisms acting at the microstructure level. Herein, we analyse the effects of water uptake that are responsible for swelling and, over time and in enough quantity, for hydrolysis. Seawater, due to a combination of high salinity and pressures, low temperature and biotic media present, also contributes to the acceleration of fatigue and creep damage. Similarly, other liquid corrosive agents penetrate into cracks induced by cyclic loading and cause dissolution of the resin and breakage of interfacial bonds. UV radiation either increases the crosslinking density or scissions chains, embrittling the surface layer of a given matrix. Temperature cycles close to the glass transition damage the fibre–matrix interface, promoting microcracking and hindering fatigue and creep performance. The microbial and enzymatic degradation of biopolymers is also studied, with the former responsible for metabolising specific matrices and changing their microstructure and/or chemical composition. The impact of these environmental factors is detailed for epoxy, vinyl ester and polyester (thermoset); polypropylene, polyamide and poly etheretherketone (thermoplastic); and for poly lactic acid, thermoplastic starch and polyhydroxyalkanoates (biopolymers). Overall, the environmental factors mentioned hamper the fatigue and creep performances, altering the mechanical properties of the composite or causing stress concentrations through microcracks, promoting earlier failure. Future studies should focus on other matrices beyond epoxy as well as on the development of standardised testing methods.
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Shevchenko, Yu N., R. G. Terekhov, N. S. Braikovskaya, and S. M. Zakharov. "Failure processes of a body element as a result of creep-induced material damage." International Applied Mechanics 30, no. 4 (April 1994): 264–71. http://dx.doi.org/10.1007/bf00847219.
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Fu, Y., C. Kwakernaak, W. G. Sloof, F. D. Tichelaar, E. Brück, S. van der Zwaag, and N. H. van Dijk. "Competitive Healing of Creep-Induced Damage in a Ternary Fe-3Au-4W Alloy." Metallurgical and Materials Transactions A 51, no. 9 (June 14, 2020): 4442–55. http://dx.doi.org/10.1007/s11661-020-05862-6.
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Gonçalves Filho, Orlando J. A. "Benchmark for finite element analysis of stress redistribution induced by creep damage." Computational Materials Science 33, no. 4 (June 2005): 419–28. http://dx.doi.org/10.1016/j.commatsci.2004.09.046.
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Ohtani, Toshihiro, Hirotsugu Ogi, and Masahiko Hirao. "Creep-Induced Microstructural Change in 304-Type Austenitic Stainless Steel." Journal of Engineering Materials and Technology 128, no. 2 (October 24, 2005): 234–42. http://dx.doi.org/10.1115/1.2172629.
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We studied microstructure changes of 304-type austenitic stainless steel subjected to a tensile stress at 973K. We monitored the shear-wave attenuation and velocity using electromagnetic acoustic resonance (EMAR). The attenuation peaks at 40% to 50% and a minimum value at 70% of the creep life, being independent of the applied stress. A drastic change in dislocation mobility and arrangement interrupted this novel attenuation phenomenon, as supported by SEM and TEM observations. The relationship between attenuation change and microstructure evolution can be explained with the string’s model. EMAR demonstrates a potential for assessing damage advance and predicting the remaining creep life of metals.
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Rui, Shao-Shi, Yi-Bo Shang, Ya-Nan Fan, Qi-Nan Han, Li-Sha Niu, Hui-Ji Shi, Keita Hashimoto, and Nobuyoshi Komai. "EBSD analysis of creep deformation induced grain lattice distortion: A new method for creep damage evaluation of austenitic stainless steels." Materials Science and Engineering: A 733 (August 2018): 329–37. http://dx.doi.org/10.1016/j.msea.2018.07.058.
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Polar, A., J. E. Indacochea, M. L. Wang, V. Singh, and G. Lloyd. "Measurement and Microstructural Evaluation of Creep-Induced Changes in Magnetic Properties of a 410 Stainless Steel." Journal of Engineering Materials and Technology 126, no. 4 (October 1, 2004): 392–97. http://dx.doi.org/10.1115/1.1790542.
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There is a compelling desire by power generating plants to continue running existing stations and components for several more years, despite many of them have surpassed their design service life. The idea is to avoid premature retirement, on the basis of the so-called design life, because actual useful life could often be well in excess of the design life. This can most readily be achieved by utilizing nondestructive monitoring methods to monitor the degradation of the microstructure, either when a station is down for maintenance or preferably when it is under operation. This study evaluates the use of quasi static hysteresis measurements as a possible procedure to evaluate creep in a 410 martensitic stainless steel, a material utilized in power plant components. The creep rupture tests were conducted at stresses of 100 and 200 MPa, temperatures of 500°C and 620°C, and the times varied between 48 and 120 hours. Following the creep tests all specimens were evaluated magnetically and then metallurgically by optical and scanning electron microscopy, x-ray diffraction (XRD) and by energy dispersive spectroscopy (EDS). The microstructural changes were compared with the magnetization changes. It was determined that the changes in the hysteresis curves were clearly detectable and correlated with the creep-induced damage.
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Wang, Xiaomeng, Yu Zhou, Jian Dong, Tianyou Wang, Zihua Zhao, and Zheng Zhang. "Microstructural Changes of a Creep-Damaged Nickel-Based K002 Superalloy Containing Hf Element under Different HIP Temperatures." High Temperature Materials and Processes 35, no. 2 (February 1, 2016): 153–59. http://dx.doi.org/10.1515/htmp-2014-0128.
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AbstractEffects of hot isostatic pressing (HIP) temperature on the microstructural evolution of a nickel-based K002 superalloy containing Hf element after long-term service were investigated using three different soaking temperatures during HIP. The degraded γ′ precipitates represented coarse and irregular morphology after long-term service. These γ′ precipitates still were of coarse and irregular shape, but the size and volume fraction of γ′ precipitates were markedly reduced under HIP condition of 1,190°C/200 MPa/4 h, indicating that the γ′ precipitates were experiencing a dissolution process. Meanwhile, the concentrically oriented N-type γ′ rafting structure around the cavities was formed. With HIP temperature increase to 1,220°C and 1,250°C, the small-sized, cubic and regular γ′ precipitates were re-precipitated, and the concentrically oriented γ′ structure vanished. The unstable morphology induced by the nucleation and growth of γ matrix was found near the creep cavities, indicating that the solute atoms diffused inward the creep-induced cavities during HIP. However, at HIP temperature of 1,220°C and 1,250°C, a large number of blocky MC(2)-type carbides containing amounts of Hf elements were precipitated, demonstrating that HIP treatment at higher temperatures can result in the formation of a large number of blocky MC(2)-type carbides.
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Hfaiedh, N., A. Roos, H. Badreddine, and K. Saanouni. "Interaction between ductile damage and texture evolution in finite polycrystalline elastoplasticity." International Journal of Damage Mechanics 28, no. 4 (May 21, 2018): 481–501. http://dx.doi.org/10.1177/1056789518775179.
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In this paper, a multiscale model of ductile damage and its effects on the inelastic behavior of face centered cubic polycrystalline metallic materials, such as the evolution of their crystallographic textures, are investigated. The constitutive equations are written in the framework of rate-dependent polycrystalline plasticity at the microscopic scale. Plasticity and damage are coupled through a ductile damage variable introduced at the scale of the crystallographic slip systems of each grain. When homogenized to the macro-scale, this becomes an approximate phenomenological measure of the macroscopic ductile damage which can describe the material degradation by initiation, growth, and coalescence of micro-defects. In this paper, thermally activated intergranular (or creep) damage is not taken into account. Both theoretical and numerical aspects of the model are presented. The model is implemented into a general-purpose finite element code in order to analyze the effects of texture evolution and ductile damage initiation in the grains with favorably oriented slip systems. The capability of the proposed model to predict the plastic strain localization and the induced textural evolution, as well as the effects of the ductile damage and its evolution up to the final macroscopic failure are studied for a classical tensile loading path, applied to a representative volume element and to a 3D tensile specimen on which a parametric study has been carried out.
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Yu, Tao, Masataka Yatomi, and Hui-Ji Shi. "Numerical investigation on the creep damage induced by void growth in heat affected zone of weldments." International Journal of Pressure Vessels and Piping 86, no. 9 (September 2009): 578–84. http://dx.doi.org/10.1016/j.ijpvp.2009.04.010.
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Ross, R. G., L. C. Wen, and G. R. Mon. "Solder Joint Creep and Stress Relaxation Dependence on Construction and Environmental-Stress Parameters." Journal of Electronic Packaging 115, no. 2 (June 1, 1993): 165–72. http://dx.doi.org/10.1115/1.2909313.
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Creep strain is probably the most important time-dependent damage accrual factor affecting solder joint reliability. Under typical multi-hour loading conditions, creep-induced strain is a complex function of solder metallurgical structure, solder temperature, loading time per cycle, the applied stress, and the spring constant of the combined part/lead/board system. The complex system level creep-fatigue interactions involved in electronic part solder joints are shown to be a strong function of the relative stiffness ratio κ, which is the ratio of the stiffness of the combined solder-lead system to the stiffness of the solder element by itself. For a leadless chip package, κ is close to unity. For a compliant leaded package, κ is typically in the 0.01 to 0.0001 range. Important environmental stress dependencies, including the effects of operating temperature, displacement amplitude due to thermal and mechanical cycling, and cyclic frequency of loading are investigated for different levels of k. Understanding the sensitivity of solder strain range to relative stiffness and these key environmental parameters is important to understanding the behavior of alternative packaging concepts and to achieving robust electronic packaging designs and testiong approaches.
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Sato, Y., Y. Takeda, and T. Shoji. "Non-destructive evaluation of fatigue and creep-fatigue damage by means of the induced-current focused potential drop technique." Fatigue & Fracture of Engineering Materials & Structures 24, no. 12 (December 4, 2001): 885–93. http://dx.doi.org/10.1046/j.1460-2695.2001.00460.x.
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Pucha, Raghuram V., Krishna Tunga, James Pyland, and Suresh K. Sitaraman. "Accelerated Thermal Cycling Guidelines for Electronic Packages in Military Avionics Thermal Environment." Journal of Electronic Packaging 126, no. 2 (June 1, 2004): 256–64. http://dx.doi.org/10.1115/1.1756150.
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A field-use induced damage mapping methodology is presented that can take into consideration the field-use thermal environment profile to develop accelerated thermal cycling guidelines for packages intended to be used in military avionics thermal environment. The board-level assembly process mechanics and critical geometric features with appropriate material models are taken into consideration while developing the methodology. The models developed are validated against in-house and published accelerated thermal cycling experimental data. The developed mapping methodology is employed to design alternate accelerated thermal cycles by matching the creep and plastic strain contributions to total inelastic strain accumulation in solder under military field-use and accelerated thermal cycling environments, while reducing the time for accelerated thermal cycling and qualification.
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Petersen, RE, RE Link, M. Yamashita, S. Tada, Y. Sato, and T. Shoji. "Nondestructive Evaluation of Fatigue and Creep-Fatigue Damage in 12%Cr Stainless Steel by the Induced Current Focusing Potential Drop Technique." Journal of Testing and Evaluation 29, no. 6 (2001): 544. http://dx.doi.org/10.1520/jte12400j.
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Ladani, Leila Jannesari, and Abhijit Dasgupta. "Effect of Voids on Thermomechanical Durability of Pb-Free BGA Solder Joints: Modeling and Simulation." Journal of Electronic Packaging 129, no. 3 (September 8, 2006): 273–77. http://dx.doi.org/10.1115/1.2753911.
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The effect of process-induced voids on the durability of Sn–Pb and Pb-free solder interconnects in electronic products is not clearly understood. Experimental studies have provided conflicting ambiguous conclusions, showing that voids may sometimes be detrimental to reliability, but they may sometimes even increase the reliability of joints, depending on the size and location. Because of the higher level of process-induced voids in Pb-free solders, this debate is more intensified in Pb-free joints. This study presents finite element analysis (FEA) of the influence of void size, location, and spacing on the durability of Pb-free solders. A three-dimensional, global-local, viscoplastic FEA is conducted for a CTBAG132 assembly under thermal cycling. The displacement result of the global FEA at the top and bottom of the critical ball is used as the boundary condition in a local model, which focuses on the details of a single ball of the CTBGA package under temperature cycling. Parametric study is conducted to model a solder ball with voids of different sizes and locations. The maximum void area fraction modeled is from 1% to 49% of the ball area. An energy-partitioning model for cyclic creep-fatigue damage is used to estimate the damage and to monitor the trends as the size and location of voids are varied. Potential sites for maximum damage and crack initiation are identified. FEA results show that as void size increases up to about 15% of the area fraction of the ball, durability increases. For voids bigger than that, the durability starts to decrease. This study also confirms that as voids are located closer to the damage initiation site and the propagation path, their lifespan decreases.
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Utada, Satoshi, Jérémy Rame, Sarah Hamadi, Joël Delautre, Patrick Villechaise, and Jonathan Cormier. "Kinetics of creep damage accumulation induced by a room-temperature plastic deformation introduced during processing of AM1 Ni-based single crystal superalloy." Materials Science and Engineering: A 789 (July 2020): 139571. http://dx.doi.org/10.1016/j.msea.2020.139571.
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Arakere, Nagaraj K., and Gregory Swanson. "Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments." Journal of Tribology 123, no. 2 (June 27, 2000): 413–23. http://dx.doi.org/10.1115/1.1308032.
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Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. High cycle fatigue induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate advanced high pressure fuel turbo pump for the space shuttle main engine. Single crystal materials have highly anisotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale three-dimensional finite element model capable of accounting for contact friction, material anisotropy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation. Fretting stresses at the attachment region are seen to vary significantly as a function of crystal orientation. The stress variation as a function of crystal orientation is a direct consequence of the elastic anisotropy of the material. Fatigue life calculations and fatigue failures are discussed for the airfoil and the blade attachment regions.
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Qu, Feifei, Zhong Lu, Jin-Woo Kim, and Weiyu Zheng. "Identify and Monitor Growth Faulting Using InSAR over Northern Greater Houston, Texas, USA." Remote Sensing 11, no. 12 (June 25, 2019): 1498. http://dx.doi.org/10.3390/rs11121498.
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Growth faults are widely distributed in the Greater Houston (GH) region of Texas, USA, and the existence of faulting could interrupt groundwater flow and aggravate local deformation. Faulting-induced property damages have become more pronounced over the last few years, necessitating further investigation of these faults. Interferometric synthetic aperture radar (InSAR) has been proved to be an effective way for mapping deformations along and/or across fault traces. However, extracting short-wavelength small-amplitude creep signal (about 10–20 mm/yr) from long time span interferograms is extremely difficult, especially in agricultural or vegetated areas. This study aims to position, map and monitor the rate, extent, and temporal evolution of faulting over GH at the highest spatial density using Multi-temporal InSAR (MTI) technique. The MTI method, which maximizes usable signal and correlation, has the ability to identify and monitor faulting and provide accurate and detailed depiction of active faults. Two neighboring L-band Advanced Land Observing (ALOS) tracks (2007–2011) are utilized in this research. Numerous areas of sharp phase discontinuities have been discerned from MTI-derived velocity map. InSAR measurements allow us to position both previously known faults traces as well as nucleation of new fractures not previously revealed by other ground/space techniques. Faulting damages and surface scarps were evident at most InSAR-mapped fault locations through our site investigations. The newly discovered fault activation appears to be related to excessive groundwater exploitation from the Jasper aquifer in Montgomery County. The continuous mining of groundwater from the Jasper aquifer formed new water-level decline cones over Montgomery County, corroborating the intensity of new fractures. Finally, we elaborate the localized fault activities and evaluate the characteristics of faulting (locking depth and slip rate) through modeling MTI-derived deformation maps. The SW–NE-oriented faults pertain to normal faulting with an average slip rate of 7–13 mm/yr at a shallow locking depth of less than 4 km. Identifying and characterizing active faults through MTI and deformation modeling can provide insights into faulting, its causal mechanism and potential damages to infrastructure over the GH.
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Grottesi, Giulia, Guilherme B. A. Coelho, and Dimitrios Kraniotis. "Heat and Moisture Induced Stress and Strain in Wooden Artefacts and Elements in Heritage Buildings: A Review." Applied Sciences 13, no. 12 (June 17, 2023): 7251. http://dx.doi.org/10.3390/app13127251.
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In the world of cultural heritage, a wide range of artefacts and buildings are made of wood and, therefore, are subjected to moisture-induced stress and strain cycles, owing to environmental fluctuations. Simultaneous action of moisture and mechanical loads lead to a mechanosorptive effect on wood. Therefore, an increase in time-dependent creep, due to mechanical loads, is observed. The assessment of these complex phenomena entails the use of advance and interdisciplinary approaches. Consequently, this article reviews experimental and mathematical methods to study these degradation mechanisms in wooden artefacts and timber elements in heritage buildings. The paper presents the results of a six-step descriptive literature review, providing an overall picture of the ongoing research. Experimental techniques need to be improved so that they are in line with the conservation principles. The combination of experiments and simulations is a reliable predictive approach for better assessing the potential risk damages due to temperature, humidity cycles, and mechanical loads in complex structures. Thus, advanced numerical simulations and mathematical modelling include climate data and experimental measurements. This work also provides an overview of research performed on different categories of cultural heritage characterised by multi-layer structures. The mechanical response to wood–moisture relation is affected by the level of complexity of these structures. Finally, the use of realistic models is limited by knowledge about the material properties and the behaviour of complex structures over time. In addition, research gaps, limitations, and possible future research directions are also provided. This review may represent a starting point for future research on the thermo-hygro-mechanical behaviour of wood heritage.
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Ramani, Dilip, Yadvinder Singh, Robin T. White, Tylynn Haddow, Francesco P. Orfino, Monica Dutta, and Erik Kjeang. "4D Structural Characterization of Mechanical Degradation in Reinforced Fuel Cell Membranes Using in Situ Visualization." ECS Meeting Abstracts MA2018-01, no. 32 (April 13, 2018): 1962. http://dx.doi.org/10.1149/ma2018-01/32/1962.
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Perfluorosulfonic acid (PFSA) ionomer membranes in fuel cells are susceptible to operational mechanical stresses resulting in fatigue and/or creep failures that compromises their durability and lifetime. The fatigue based mechanical degradation is typically a result of repeated wet/dry humidity cycles that cause micro crack initiation and /propagation within the membrane [1]. Fatigue induced membrane failure in the form of cracks/tears/pinholes leads to a gradual increase in gas crossover and ultimately to fuel cell failure. Membranes with less conductive mechanical reinforcements have been developed to alleviate mechanical degradation yielding demonstrated improvements in lifetime and durability. Nevertheless, development of membrane damage remains a critical failure mode and the fundamental understanding of membrane mechanical degradation is a subject of ongoing research. Scanning electron microscopy (SEM) based studies have been used to characterize the degradation-induced structural changes in fuel cell membranes; however, SEM imaging is inherently destructive and inhibits any tracking of structural changes at a particular location over time. Hence, membrane degradation evolution studies are limited to ex situ analysis at various stages of degradation and with different samples. Recently, laboratory-based X-ray computed tomography (XCT) was introduced as an alternative imaging technique, which has enabled three-dimensional (3D) failure analysis of fuel cell membranes revealing novel insights on membrane failure [2,3]. In the present work, the XCT-based 3D failure analysis approach is extended to an in situ investigation of pure mechanical membrane degradation by utilizing a custom designed fixture. This X-ray transparent fixture houses a gas diffusion electrode (GDE) based MEA with a reinforced membrane, which is subjected to wet/dry cycling of N2 gas flowing through both anode and cathode sides, thereby producing a pure mechanical fatigue type degradation within the membrane. XCT-based 3D identical location tracking of membrane morphology as a function of degradation time facilitates a novel four-dimensional (4D) in situ workflow [4], which enables the characterization of the damage growth or evolution. Preliminary results show that no through- thickness membrane cracks developed until 3000 wet/dry cycles. However, minor crazes initiated on the cathode side membrane surface (Fig. 1) between 2000 and 2500 cycles. Crack initiation and growth within the reinforced membrane are comprehensively examined from various perspectives by simultaneously studying the two-dimensional (2D) planar and cross-sectional views. A clear interaction of membrane cracks with defect features, such as delamination and catalyst layer cracks is observed. Furthermore, the centrally located reinforcement layer is found to restrict the through-thickness growth of membrane cracks at several locations in the early stages of damage initiation. Overall, the size and density of membrane crack formation at a given number of cycles is found to be considerably reduced with the use of a reinforced membrane when compared to a non-reinforced membrane. A detailed study to understand the variation in degradation mechanisms between reinforced and non-reinforced membranes is carried out. Overall, the work summarized here is a unique study on the evolution of reinforced membrane degradation with a 4D perspective. The new findings from this work demonstrate the distinct advantage of XCT technology in gaining an improved fundamental understanding of membrane degradation by capturing critical failure modes and mechanisms at their different developmental stages. Acknowledgement This research was funded by the Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, and Ballard Power Systems through an Automotive Partnership Canada (APC) grant. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program. The authors thank Kevin Dahl and Alex Boswell for technical support. References [1] R.M.H. Khorasany, et al. J. Power Sources 274 (2015) 1208-1216 [2] Y. Singh et al. J. Power Sources 345 (2017) 1–11 [3] Y. Singh et al. J. Electrochem. Soc. 164 (2017) F1331-41 [4] R.T. White et al. J. Power Sources 350 (2017) 94-102 Figure 1
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Khan, Mohammed A., Miyuki Sakuma, Shingo Yasuhara, Li Ma, Jingyuan Chen, Nades Palaniyar, Jeevendra Martyn, and Yang Ren. "43 Activation of CCL2/CCR2 Signaling Axis Is Responsible for Spinal Cord Inflammation and Loss of Muscle Mass in Mice After Burn Injury." Journal of Burn Care & Research 41, Supplement_1 (March 2020): S28—S29. http://dx.doi.org/10.1093/jbcr/iraa024.047.
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Abstract Introduction Burn-induced systemic inflammation (BISI) can induce inflammatory responses in peripheral nervous system and also cause neuroinflammation in the central nervous system, leading to morbidity and mortality. The mechanisms of neuromotor impairment involving CCL2/CCR2 signaling axis are largely unknown. We hypothesized that BISI causes neuroinflammation in the spinal cord, and this inflammatory response can lead to motor neuronal damage, disintegration of nerve termini and eventually muscle wasting. Methods Cytokines/chemokines were estimated by Cytokine Antibody Array. Nerve termini and muscle fibers in abdominal muscle, and motor neuronal apoptosis in the spinal cord were analyzed by fluorescent microscopy and immunochemical analyses. Loss of muscle mass was assessed by wet weight of the muscles compared with control in mice after BISI. Results Our data showed that CCL2 was significantly increased in the serum (>2.4 fold) at day 1 and 3 after BISI in vivo. Iin the extracellular medium (>2.0 fold) of organotypic spinal cord explant after exposure to exogenous histones ex vivo at day1. Neuroinflammation in the spinal cord after BISI caused motor neuronal apoptosis, nerve termini disintegration, and loss of muscle mass of soleus (63.4 + 5.1%), tibialis (72.3 + 2.7%) and gastrocnemius (70.2 + 1.1%) compared to sham burn injured wild-type (WT) or YFP-neurons expressing transgenic mice. In contrast, GTS-21 reduced neuroinflammation and significantly prevented loss of muscle mass of soleus (86.8 + 0.2%), tibialis (85.4 + 4.5%) and gastrocnemius (89.0 + 4.0%). Depletion of macrophages by PBS-liposomes in burned mice showed transmigration of CCR2-containing monocytes-derived macrophages (CCR2-MDMΦ) in the ventral horn of the spinal cord, and led to the loss of all three muscles (soleus, 62.4 + 2.6%; tibialis, 86.3 + 3.5; gastrocnemius, 81.4 + 1.7%). Nevertheless, depletion of macrophages by Clophosomes in burned mice inhibited the transmigration of CCR2-MDMΦ, and protected muscle mass (soleus, 96.6 + 3.9%; tibialis, 101 + 3.9%; gastrocnemius, 98.3 + 1.2%) significantly. Subsequently, we demonstrated that the knocking out of CCR2 gene in mice protected motor neuronal apoptosis and inhibited loss of muscle mass of soleus, tibialis and gastrocnemius from 63.4 + 5.1%, 72.3 + 2.7% and 70.2 + 1.1% in WT mice to 82.1 + 4.7%, 85.4 + 4.5% and 95.8 + 3.2% in CCR2KO mice, respectively, after BISI. Conclusions Collectively, these results suggest activated macrophages creep to the spinal cord through CCL2/CCR2 signaling axis after BISI to cause neuroinflammation, leading to motor neuronal damage, nerve disintegration and muscle wasting. Applicability of Research to Practice These findings will be useful to understand the pathology occurring in burned patients and to develop the therapeutics measures to protect them from BISI.
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Kawada, Tatsuya. "(Invited) Chemo-Mechanical Coupling Phenomena in Solid Oxide Fuel Cells." ECS Meeting Abstracts MA2018-01, no. 32 (April 13, 2018): 1930. http://dx.doi.org/10.1149/ma2018-01/32/1930.
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The materials and the structure of solid oxide fuel cells are designed to avoid thermo-mechanical damages under various operation conditions. However, inherent risk of chemo-mechanical failures are still not fully understood. This paper aims to review the recent works related to this topic, and to address some issues which have not been widely recognized. The coupling of chemistry and mechanics are classified into four types, i.e. (1) chemically driven strain, (2) chemically modified mechanical properties, (3) mechanically driven chemical reactions, and (4) mechanically modified chemical (physical) properties. Since chemical energies are much larger than mechanical energy accommodated in SOFC, the former two types (type(1) and (2)) of chemo-mechanical coupling have been recognized as more important than the others, and have been studied intensively. An example of type-1 phenomena is chemical expansion of mixed conducting oxides with e.g. (La,Sr)(Co,Fe)O3 cathode, LaCrO3 based interconnect, and CeO2 based or (La,Sr)(Ga,Mg,Co)O3 electrolytes. Since the transient behavior as well as steady state distribution of oxygen potential inside the constituent solids is essential to know the effect of the chemical strain, Terada et al. developed a computer code “SIMUDEL” of an FEM-based calculation of oxygen potential. This code considers “chemical capacitance” due to nonstoichiometry of the materials to treat the transient responses, and the results of the calculation can be transported into some of major commercial programs for structure analysis. Volume change of a nickel cermet anode is also an important feature of type-1 coupling which must be considered in determining fabrication and operation processes. The electrode shrinks on reduction and expands on re-oxidation as expected from the lattice size of the metal and the oxide. However, under certain conditions, a porous cermet was found to “shrink” upon oxidation. It took place only during light re-oxidation around 400C. Under this condition the formation of NiO was not obvious from XRD, whereas weight gain was observed by thermo-gravimetry. Careful observation of the microstructure of a porous Ni revealed that, upon shrinkage, the particle-to-particle separation changed partly due to the neck growth between the particles and to the change of the connection angle of the particles. Further study is underway to elucidate the detailed mechanism of the oxidation-induced shrinkage. The change of mechanical properties such as elastic moduli and fracture strength are also dependent on defect concentration and its motion in the lattice (type-2 coupling). Young’s modulus of nonstoichiometric oxides show dependences not only on temperature but also on pO2 through the change of defect concentration. Also, domain boundary shift of ferroelastic phase of LSCF was found to be correlated with the defect concentration. As is discussed for the anomaly of Young’s modulus of YSZ around 400˚C, the motion of oxide ion vacancies may also have correlation with the ferroelastic strain observed with Sc and Ce doped ZrO2 electrolyte above 300˚C. Another interesting type-2 coupling is with the lightly oxidized Ni cermet electrode. It was found that the creep rate of Ni-YSZ cermet at 400˚C was dramatically increased when oxygen-containing gas was introduced. This may be by a correlated mechanism with the above mentioned oxidation induced shrinkage. Several reports, including those from our group, have been published on the effect of mechanical stress on defect formation (type-3 coupling) of nonstoichiometric oxides determined by experiments or by calculation. As is expected from thermodynamic consideration, the experimentally determined effect was not large, e.g. 1G Pa stress was equivalent to 1/5 order of magnitude shift of chemical potential of oxygen for nonstoichiometry of LSCF. Similarly, only minor effect on a practical system was reported for type-4 coupling. However, those phenomena can have significant effect on long-term stability if cation mobility and their driving force are modified at a strained interfaces or grain boundaries.
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Wu, Xijia, and Zhong Zhang. "A Mechanism-Based Approach From Low Cycle Fatigue to Thermomechanical Fatigue Life Prediction." Journal of Engineering for Gas Turbines and Power 138, no. 7 (December 4, 2015). http://dx.doi.org/10.1115/1.4031908.
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Deformation and damage accumulation occur by fundamental dislocation and diffusion mechanisms. An integrated creep–fatigue theory (ICFT) has been developed, based on the physical strain decomposition rule that recognizes the role of each deformation mechanism, and thus relate damage accumulation to its underlying physical mechanism(s). The ICFT formulates the overall damage accumulation as a holistic damage process consisting of nucleation and propagation of surface/subsurface cracks in coalescence with internally distributed damage/discontinuities. These guiding principles run through both isothermal low cycle fatigue (LCF) and thermomechanical fatigue (TMF) under general conditions. This paper presents a methodology using mechanism-based constitutive equations to describe the cyclic stress–strain curve and the nonlinear damage accumulation equation incorporating (i) rate-independent plasticity-induced fatigue, (ii) intergranular embrittlement (IE), (iii) creep, and (iv) oxidation to predict LCF and TMF lives of ductile cast iron (DCI). The complication of the mechanisms and their interactions in this material provide a good demonstration case for the model, which is in good agreement with the experimental observations.
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Xiao, Quanfeng, Yuanming Xu, Xinling Liu, Yibing Wang, and Weifang Zhang. "Oxidation-induced recrystallization and damage mechanism of a Ni-based single-crystal superalloy during creep." Materials Characterization, November 2022, 112465. http://dx.doi.org/10.1016/j.matchar.2022.112465.
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Huang, Wanpeng, Naser Golsanami, Chengguo Zhang, Ismet Canbulat, Guangming Xin, Gang Sun, and Lishuai Jiang. "Assessment of long-term large deformation in deep roadways due to roof fracturing impact loading." Scientific Reports 13, no. 1 (March 8, 2023). http://dx.doi.org/10.1038/s41598-023-30792-9.
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AbstractThe rock mass around deep roadways has obvious creep characteristics in high-stress environments. Meanwhile, the cyclic impact load induced by roof fracturing also causes dynamic damage to the surrounding rock, leading to long-term large deformation. This paper examined the rock mass deformation mechanism around deep roadways based on the theory of rock creep perturbation effect considering perturbation sensitive zone. This study proposed a long-term stability control guideline for deep roadways under dynamic load. An innovative support system was developed for deep roadways, with concrete-filled steel tubular support being recommended as the main supporting body. A case study was conducted to validate the proposed supporting system. Monitoring over one year in the case study mine showed that the overall convergence deformation of the roadway was 35 mm, indicating that the roadway’s long-term large deformation induced by creep perturbation was effectively controlled by using the proposed bearing circle support system.
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Najib, Najib, Dwikorita Karnawati, and Ignatius Sudarno. "INFLUENCE OF GEOLOGICAL CONDITION TOWARDS SLOPE STABILITY ON LANDSLIDE: CASE STUDY IN TENGKLIK VILLAGE, TAWANGMANGU DISTRICT, KARANGANYAR REGENCY, CENTRAL JAVA PROVINCE, INDONESIA." Journal of Applied Geology 2, no. 3 (September 5, 2015). http://dx.doi.org/10.22146/jag.7265.
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A rain-induced landslide has occured in Guyon Village, Tengklik Tawangmangu District Karanganyar Regency, Central Java Province, Indonesia on February 2009. The movement was initiated by crack occurrence, 30 cm in depth and 2 meter in length. Such crack continuously developed in depth, extention and numbers, until then it resulted in land subsidence up to 260 cm in depth. Accordingly, ten houses were damaged and ten of families must be evacuated. This subsidence is very potential to further grow and create more consequences for human life and houses / land damage. Therefore, this research is carried out to understand the influence of geological factors and rainfall to the landslide phenomena. This research conducted engineering geology investigation such as mapping, drilling, insitu test, XRD test, soil mechanic test and slope stability analysis by limit equilibrium method i.e. Seep/W and Slope/W. By those research activities, the cause and mechanism of landslide can be understood. Rainfall characteristics which triggered such landslide can also be identified.
Based on those investigations, it is found that the landslide occurred in slow rate sliding (creep) due to the control of slope stratigraphy conditions and gentle slope inclination, which is induced by rainfall. Stratigraphy condition that plays important role in landslide mechanism are the permeable layers consisted of sandy silt (shear strength 12 kPa) and silty sandstone (shear strength 18 kPa) overlaid above impermeable andesite breccia (shear strength 104 kPa). Undulating slope may induce landslide in creep rotational type. Based on slope stability simulation, it is known that rainfall triggered landslide is rainfall 20 mm/ day average precipitation in 55 days and rainfall 20 mm/ day average precipitation in 49 days followed by one day with 178 mm/ day average precipitation.
Keywords: Landslides, slope stability
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Yu, Yongjiang, Yuntao Yang, Jingjing Liu, Pengbo Wang, Shipeng Zhang, Zhenmeng Wang, and Shangqing Zhao. "Experimental and constitutive model study on the mechanical properties of a structural plane of a rock mass under dynamic disturbance." Scientific Reports 12, no. 1 (December 8, 2022). http://dx.doi.org/10.1038/s41598-022-25544-0.
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AbstractAn accurate description of the mechanical properties and deformation characteristics of a structural plane of a rock mass with a large chamber or slope under the ultimate stress with periodic stress disturbances is of great significance to ensure the stability and safety of underground rock engineering. By theoretically analysing the strength effect of a structural plane of a rock mass under dynamic disturbance, a criterion for the occurrence of shear damage on a structural plane of a compressed rock mass under dynamic disturbance is proposed. The results of the cyclic disturbance kinetic test show that there is a disturbance threshold for the shear failure of the structural plane under different disturbance stresses. When the disturbance stress is lower than the disturbance threshold, the cumulative plastic strain stabilizes with an increasing number of cycles; when the disturbance stress is higher than the disturbance threshold, an S-shaped curve of cumulative plastic strain versus the number of cycles is observed, revealing the progressive damage process and mechanism of such a rock structure plane under periodic dynamic disturbance. Based on perturbation concept theory, the relationship between the accumulated plastic strain and the number of cyclic loadings is similar to the relationship between strain and time, the creep curve. A new nonlinear viscous element is proposed, and the nonlinear element and the deformation element considering structural plane closure and sliding are combined with the Burgers model to form an 8-element nonlinear viscoelastic‒plastic creep constitutive model. Using the global optimization algorithm of 1stOpt, model validation and parameter identification are performed on the experimental data, and the results show that the model curve has a very good agreement with the experimental data. The model can accurately reflect the deformation characteristics of a structural plane of a rock mass under periodic dynamic disturbance. These research results provide a new idea for analysing disturbance-induced geohazards.
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Yang, Yuting, Chenyang Zhang, Yushi Lu, and Zhenwei Dai. "Mechanism of large-scale reservoir landslides with double-sliding zones: insights from long-term field monitoring." Frontiers in Ecology and Evolution 11 (January 10, 2024). http://dx.doi.org/10.3389/fevo.2023.1301261.
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A significant number of ancient landslides with double or multi-sliding zones exist in reservoir areas. However, understanding large-scale reservoir landslides with double-sliding zones remains limited due to the challenges of studying deformation along the sliding zone independently from surface deformation. In this study, the seepage and deformation characteristics of the Taping landslide were obtained through field investigations and long-term in-situ monitoring. For the first time, hydrological factors influencing double-sliding zones were revealed using an attribute reduction algorithm based on long-term field data. The results indicate that the Taping landslide undergoes significant step-like consistent creep deformation, exhibiting failure along double-sliding zones. For the toe part, reservoir water level (RWL) and precipitation are two critical hydrological factors triggering deformation. Shallow sliding is more susceptible to rainfall, while the deep sliding zone is more affected by RWL variations. In the rear part, precipitation has a greater impact than RWL. Daily precipitation is the primary hydrological factor affecting slope movement along the shallow sliding zone. However, accumulated precipitation over the previous seven days is the most crucial factor influencing slope movement along the deep sliding zone. During the RWL drawdown period, shallow sliding initially occurs at the toe, induced by the de-buttressing effect, while deep sliding occurs after the RWL reaches 145 m, induced by the downslope seepage force. Local damage and failure at the toe provide space for the instability of the rear part, reducing the anti-sliding force. Consequently, failure extends to the rear part. The findings of this study hold significant implications for gaining a deeper understanding of the deformation mechanisms of large-scale reservoir landslides with double-sliding zones and improving landslide management and mitigation strategies in reservoir area.
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Evans, A. G., and C. H. Hsueh. "Residual Stresses and Damage in Multilayer Ceramic/Metal Packages." MRS Proceedings 72 (1986). http://dx.doi.org/10.1557/proc-72-91.
Full textAbstract:
AbstractMultilayer ceramic/metal modules are subject to stresses that develop both upon co-sintering and upon cooling. The sources and magnitudes of these stresses are described and discussed. The co-sintering induced stresses derive from densification-rate mismatch and can be analyzed in terms of constitutive laws that describe the densification and creep of partially dense ceramic and metal bodies. Cooling induced stresses are associated with thermal contraction mismatch and are strongly influenced by the plastic flow laws for porous metals. Typical stresses produced during co-sintering and cooling are calculated and techniques for minimizing such stresses are discussed and analyzed. Mechanical damage, manifest as brittle cracks and creep cracks, are also described and analyzed. Critical values of material parameters that exclude extensive crack damage are then emphasized, based on models of crack propagation.
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Yokobori, A. Toshimitsu, Haruki Ishikawa, Ryuji Sugiura, Toshihito Ohmi, and Masaaki Tabuchi. "Correlation of deformation with damage progression behavior around a notch tip under creep and fatigue conditions for W-added 9Cr steel including weld joint." Strength, Fracture and Complexity, May 4, 2022, 1–25. http://dx.doi.org/10.3233/sfc-228010.
Full textAbstract:
Research concerning heat-resistant steels for the application in fossil-fired power plants has progressed remarkably during the past 60 years. This has resulted in improvements in the electrical efficiency of fossil-fired power plants. Currently, there are plans and programs to develop ultra-supercritical plants designed to operate at steam temperature and pressure conditions of 600/650 °C and 32 MPa. The W-added 9%Cr ferritic heat-resistant steel, that is, ASME grade P92, has been developed as a boiler material for this ultra-supercritical plant. Boiler materials, whose performance is critical for ultra-supercritical plant, are required to possess high creep resistant properties. In addition, these materials are exposed to fatigue induced by thermal stresses, that is, they are operated under creep-fatigue interacting conditions. In this study, mechanical tests under the condition of high temperature creep-fatigue interaction were conducted for P92 steel under stress-controlled and various load frequency conditions using the in-situ observational creep-fatigue testing machine to observe the damage formation behavior around a notch tip composed of voids in mesoscale. On the basis of these results, the effects of damage formation behavior on crack growth life were clarified. Furthermore, for the case of creep deformation, the numerical analyses of vacancy diffusion and concentration around a notch tip were conducted using our proposed numerical method of local stress-induced vacancy diffusion behavior, which is a nanoscale phenomenon to relate these behaviors to the damage formation behavior in mesoscale (μm scale).
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Guo, Yuhao, Gang Liu, Huaqing Liu, and Yi Huang. "Creep damage model considering unilateral effect based on bimodulus theory." International Journal of Damage Mechanics, June 16, 2021, 105678952110173. http://dx.doi.org/10.1177/10567895211017319.
Full textAbstract:
Based on the continuous damage mechanics (CDM) theory, Ambartsumyan bimodulus theory and creep damage theory, a bimodulus creep damage constitutive model is proposed in this paper. The model is able to describe the damage-induced unilateral behaviour related to the microdefect closure effect. The unilateral behaviour is considered a special bimodulus property. By judging the tension or compression state in bimodulus theory, different elasticity properties matrixes are selected according to signs of principal stresses. Then, an elasticity properties matrix is linearly converted to a general stress space. The model effectively solves the difficulty of determining tension or compression in complex stress states when the unilateral effect of damage is considered in the analysis of actual structures. The tangent elasticity matrix is used to improve the convergence of the proposed algorithm. In this study, a numerical simulation of the proposed model is achieved by writing subroutines in the FORTRAN language. A numerical example of a hole-in-plate structure under uniaxial stress is analysed. By comparing the results with those obtained by the traditional model, which does not consider the unilateral effect of damage, it is demonstrated that the proposed model is capable of describing the damage-induced unilateral behaviour related to microcracked closure effects. The numerical example validates the effectiveness and realizability of the proposed model.