Articoli di riviste: "Hardening-Softening"

1

Chen, Junchi, Weihua Wang e Longfeng Chen. "A Strain Hardening and Softening Constitutive Model for Hard Brittle Rocks". Applied Sciences 13, n. 5 (21 febbraio 2023): 2764. http://dx.doi.org/10.3390/app13052764.

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To study the strain hardening and softening mechanism for hard brittle rocks, a strain hardening and softening constitutive model for hard brittle rocks is developed. First, the normalised hardening and softening factors are defined, which characterise the yield state of rock at the stages of pre-peak hardening and post-peak softening, respectively. Then, a unified strength parameter evolution model is established that can describe the nonlinear characteristics of cohesion and the internal friction angle under different confining pressures. Based on the Mohr–Coulomb criterion, a strain hardening and softening constitutive model is proposed. Finally, the proposed model was implemented in FLAC3D, and triaxial compression numerical tests of granite and diabase were conducted. The results show that the constitutive model can characterise the nonlinear mechanical behaviour of the pre-peak hardening stage and post-peak softening stage of hard brittle rock. The model was also able to satisfactorily capture the transition from brittle failure to plastic failure for hard brittle rock under high confining pressures.

2

Needleman, A., S. B. Hutchens, N. Mohan e J. R. Greer. "Deformation of plastically compressible hardening-softening-hardening solids". Acta Mechanica Sinica 28, n. 4 (agosto 2012): 1115–24. http://dx.doi.org/10.1007/s10409-012-0117-4.

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3

Du, Changbo, e Fu Yi. "Analysis of the Elastic-Plastic Theoretical Model of the Pull-Out Interface between Geosynthetics and Tailings". Advances in Civil Engineering 2020 (13 giugno 2020): 1–22. http://dx.doi.org/10.1155/2020/5680521.

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Aiming at the strain-hardening and strain-softening phenomena between geosynthetics and tailings during pull-out tests, bilinear and trilinear shear stress-displacement softening models were proposed. The pull-out process of the hardening reinforcement was divided into the elastic stage, elastic-hardening transition stage, and pure hardening stage. The pull-out process of the softened reinforcement was divided into the elastic stage, elastic-softening transition stage, pure softening stage, softening-residual transition stage, and pure residual stage. The expressions of the interface tension, shear stress, and displacement at the different stages under a pull-out load were derived through the interface basic control equation. At the same time, the evolution law of the interface shear stress at different pull-out stages was analysed, and the predicted results of the two elastic-plastic models were compared with the experimental results. The results show that the predicted results are in good agreement with the experimental data, which verifies the validity of the proposed two elastic-plastic models for the progressive failure analysis of reinforcement at the pull-out interface. During the process of pull-out, the transition stage is not obvious. When the reinforcement is in the elastic stage, the nonlinearity and maximum value of the interface shear stress increase with an increase in the elastic shear stiffness, while the tensile stiffness shows the opposite trend. When the reinforcement is in the hardening or softening stage, the larger the hardening (softening) shear stiffness is, the larger the change range of shear stress is and the more obvious the hardening (softening) characteristics of the reinforcement are. The results comprehensively reflect the progressive failure of reinforcement-tailing interfaces with different strain types and provide theoretical support for the study of the interface characteristics of geosynthetic-reinforced tailings.

4

Xu, Zi-Han, Lin Zhan, Si-Yu Wang, Hui-Feng Xi e Heng Xiao. "Realistic hardening-to-softening transition effects of metals over the finite strain range up to failure". Multidiscipline Modeling in Materials and Structures 17, n. 3 (21 agosto 2020): 525–36. http://dx.doi.org/10.1108/mmms-05-2020-0099.

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PurposeA new approach is proposed toward accurately matching any given realistic hardening and softening data from uniaxial tensile test up to failure and moreover, toward bypassing usual tedious implicit trial-and-error iterative procedures in identifying numerous unknown parameters.Design/methodology/approachFinite strain response features of metals with realistic hardening-to-softening transition effects up to eventual failure are studied for the first time based on the self-consistent elastoplastic J2-flow model with the logarithmic stress rate. As contrasted with usual approximate and incomplete treatments merely considering certain particular types of hardening effects such as power type hardening, here a novel and explicit approach is proposed to obtain a complete form of the plastic-work-dependent yield strength over the whole hardening and softening range.FindingsA new multi-axial evolution equation for both hardening and softening effects is established in an explicit form. Complete results for the purpose of model validation and prediction are presented for the finite strain responses of monotonic uniaxial stretching up to failure.Originality/valueNew finite strain elastoplastic equations are established with a new history-dependent variable equivalently in place of the usual plastic work. With these equations, a unified and accurate simulation of both gardening and softening effects up to failure is achieved for the first time in an explicit sense without involving usual tedious implicit trial-and-error iterative procedures.

5

Huang, Kang, Wenbo Zhu, Xin Liu, Zhongyuan Yao, Yu Zhang, Shu Yan, Xiaojiang Guo e Guoliang Dai. "Study on Cyclic Bearing Capacity of Suction Pile Based on Equivalent Cyclic Creep Model". Sustainability 14, n. 22 (15 novembre 2022): 15152. http://dx.doi.org/10.3390/su142215152.

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In the process of cyclic loading, strain development not only presents the strain softening phenomenon, but also a strain hardening phenomenon, depending on the different values of static deflection stress. The strain hardening and strain softening characteristics of soft clay are studied by cyclic triaxial tests. The test results show that when the static deflection stress is zero, the value of cyclic cumulative strain is small, and the strain development presents the softening phenomenon. When the static deflection stress is greater than zero, the accumulation strain increases with increasing cyclic deflection stress, and the strain development present strain hardening phenomenon. Therefore, a strain softening index and strain hardening index were proposed to describe the cyclic characteristics of soil. Moreover, an equivalent cyclic creep model was established by considering the strain hardening index to describe cyclic characteristics of suction pile. The results obtained using the proposed method are in reasonably good agreement with the measured results. This can provide a new method for analyzing the cyclic characteristics of soil and the suction pile.

6

Qin, Ji Sheng, Bjørn Holmedal e Oddsture Hopperstad. "Modelling of Strain-Path Transients in Commercially Pure Aluminium". Materials Science Forum 877 (novembre 2016): 662–67. http://dx.doi.org/10.4028/www.scientific.net/msf.877.662.

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In the current work, the recently proposed homogeneous anisotropic hardening (HAH) model, featuring a distorted yield surface, is applied to commercially pure aluminium. A dislocation-based hardening rule is incorporated into the HAH model to describe the transient stagnation of the hardening rate during strain reversal. A cast and homogenized material with random texture previously investigated by Mánik et al. [1] is selected. The material is prestrained either by compression or rolling, and then tested in uniaxial tension to acquire either reverse softening or orthogonal hardening. The Bauschinger effect, the permanent softening during reverse loading and the hardening in the course of orthogonal loading are captured by the model. However, the permanent softening during orthogonal loading cannot be predicted, and the transient variations of the R-value predicted by the HAH model are neither in qualitative nor quantitative agreement with the experimental data.

7

Cohen, Joanna E., Paul W. McDonald e Peter Selby. "Softening up on the hardening hypothesis". Tobacco Control 21, n. 2 (16 febbraio 2012): 265–66. http://dx.doi.org/10.1136/tobaccocontrol-2011-050381.

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8

Darinskaya, E. V., E. A. Petrzhik, Yu M. Ivanov, S. A. Erofeeva e M. R. Raukhman. "Magnetostimulated softening and hardening of semiconductors". physica status solidi (c) 2, n. 6 (aprile 2005): 1873–77. http://dx.doi.org/10.1002/pssc.200460553.

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9

Cheng, Jiwen, Gang Song, Xiaosheng Zhang, Chunbai Liu e Liming Liu. "Review of Techniques for Improvement of Softening Behavior of Age-Hardening Aluminum Alloy Welded Joints". Materials 14, n. 19 (4 ottobre 2021): 5804. http://dx.doi.org/10.3390/ma14195804.

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The softening phenomenon of age-hardening aluminum alloy-welded joints is severe during conventional fusion welding, which increases the likelihood of stress and strain concentration in the joint during the period of service, significantly reduces the mechanical properties compared to the base metal, and represents an obstacle to the exploration of the potential structural performance. This review paper focuses on an overview of the softening phenomenon. Firstly, the welding softening mechanism and the characteristics of age-hardening aluminum alloys are clarified. Secondly, the current main research methods that can effectively improve joint softening are summarized into three categories: low-heat-input welding, externally assisted cooling during welding, and post-weld treatment. The strengthening mechanism and performance change rule of age-hardening aluminum alloy joints are systematically analyzed. Finally, this paper considers the future development trends of further research on joint softening, and it is expected that interest in this topic will increase.

10

Han, Sang Mook, Yi Hong Guo, Xiang Guo Wu e Qing Yong Guo. "Numerical Simulation of Quasi-Brittle Fracture in UHPFRC I-Beam as a Linear Complementarity Problem". Key Engineering Materials 419-420 (ottobre 2009): 297–300. http://dx.doi.org/10.4028/www.scientific.net/kem.419-420.297.

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This paper presents a numerical simulation of quasi-brittle fracture in UHPFRC I-beam as a linear complementarity problem. Based on the investigation of Tin-Loi and Attard, the simulation of quasi-brittle fracture in concrete has been extended to model UHPFRC I-beam by including a tensile hardening. Fracture is simulated through a hardening-softening fracture constitutive law in tension and a softening fracture constitutive law in shear at the boundary nodes, with the material within the triangular unit remaining linear elastic. LCP is used to formulate the path-dependent hardening-softening behavior in non-holonomic rate form. The good matching of test results and numerical results indicates the effectivity of this method.

11

Ter-Martirosyan, Zaven, Armen Ter-Martirosyan e Aleksandr Akuleckiy. "INTERACTION OF LARGE PILES WITH A MULTILAYER SOIL MASS, TAKING INTO ACCOUNT HARDENING AND SOFTENING". International Journal for Computational Civil and Structural Engineering 17, n. 2 (24 giugno 2021): 67–75. http://dx.doi.org/10.22337/2587-9618-2021-17-2-67-75.

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This article discusses the formulation and solution of the problem of the interaction of a long pile with thesurrounding multilayer and underlying soils, taking into account the rheological properties of the surrounding soil mass. The creep process is considered taking into account hardening and softening. The problem was considered in a linear setting. The solution is presented by analytical method. To describe the creep process, the rheological parameters of hardening and softening were used. An expression is obtained for finding the reduced shear modulus for a multilayer soil mass. A dependence is obtained for determining the force on the pile heel on time, taking into account the rheological parameters of hardening and softening. Analytical solutions in the article are supported by a graphical part. The graphs of the dependence of the settlement of the pile, the force on the heel of the pile cutting through alternating layers, on time for various parameters of viscosity, as well as for variable parameters of hardening and softening are given. The solutions obtained can be used for preliminary determination of the movement of long piles with the surrounding multilayer and underlying soils.

12

Pan, Yan Feng, Pi Zhi Zhao, Yi Fu Shen, Xiang Jun Shi e Tao Jiang. "A Study on the Deformation Dehaviours of Al-1.4Fe-0.2Mn Alloy Sheets". Materials Science Forum 877 (novembre 2016): 380–86. http://dx.doi.org/10.4028/www.scientific.net/msf.877.380.

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The deformation behaviours and microstructure transformations during the cold rolling process of Al-1.4Fe-0.2Mn alloy sheets prepared from 99.7% pure aluminium were investigated by means of hardness-testing, transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS). The phenomena of work hardening and work softening were observed. The hardness of Al-1.4Fe-0.2Mn alloy sheets increased with the increasing of cold rolling reduction firstly, and reached to a peak at 80% cold rolling reduction, meaning work hardening. However, with further increasing of cold rolling reduction, the hardness decreased, which indicates work softening. During the initial deformation stage, the dislocation density and the number of sub-grain structures increased gradually, and many dislocations formed tangles, resulting in work hardening. When the cold rolling reduction exceeded 80%, the dislocation density decreased and sub-grain structures polygonized, leading to work softening. The forming of Mn, Fe and Si bearing compounds is an important reason for the work softening due to lowering solid solution content.

13

Fang, N. "A New Quantitative Sensitivity Analysis of the Flow Stress of 18 Engineering Materials in Machining". Journal of Engineering Materials and Technology 127, n. 2 (1 aprile 2005): 192–96. http://dx.doi.org/10.1115/1.1857935.

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It has long been argued about which effect, among the effects of strain hardening, strain-rate hardening, and temperature softening, is predominant in governing the material flow stress in machining. This paper presents a new quantitative sensitivity analysis of the flow stress of 18 engineering materials based on the well-known Johnson-Cook model. It is demonstrated that the first predominant factor governing the material flow stress is either strain hardening or thermal softening, depending on the specific material employed and the varying range of temperatures. Strain-rate hardening is the least important factor governing the material flow stress, especially when machining aluminum alloys.

14

Wang, X. B. "Effects of Constitutive Parameters on Thickness of Phase Transformed Adiabatic Shear Band for Ductile Metal Based on Johnson-Cook and Gradient Plasticity Models". Advanced Materials Research 15-17 (febbraio 2006): 609–14. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.609.

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Gradient-dependent plasticity where a characteristic length is involved to consider the microstructural effect (interactions and interplaying among microstructures due to the heterogeneous texture) is introduced into Johnson-Cook model considering the effects of strain-hardening, thermal softening and strain rate sensitivity. Effects of initial static yield stress, strain-hardening coefficient and exponent, strain-rate and thermal-softening parameters on the occurrence of phase transformation and the thickness of phase transformed adiabatic shear band (ASB) in deformed ASB are numerically investigated. Higher initial static yield stress, strain-hardening coefficient, strain-rate parameter and lower strain-hardening exponent lead to earlier occurrence of phase transformation (lower plastic shear strain). Effect of thermal-softening parameter on plastic shear strain corresponding to the onset of phase transformation is not monotonous. Transformed ASB is located at the center of deformed ASB since the position has higher temperature exceeding the temperature of phase transformation. The thickness of transformed ASB increases with decreasing flow shear stress and the increasing tendency becomes slow. For the same flow shear stress, the thickness of transformed ASB is wider for higher initial static yield stress, strain-hardening coefficient and exponent, strain-rate and thermal-softening parameters. Compared with classical elastoplastic theory applicable to completely homogenous material, gradient-dependent plasticity considering the microstructural effect predicts that phase transformation occurs earlier and that the thickness of transformed ASB changes with flow shear stress.

15

Choi, Shi Hoon, Y. S. Song, Jong Kweon Kim, B. J. Jung e Yong Bum Park. "Implementation of Twin Reorientation and Softening Schemes in a Polycrystal Plasticity Model for Mg Alloys". Materials Science Forum 558-559 (ottobre 2007): 1063–68. http://dx.doi.org/10.4028/www.scientific.net/msf.558-559.1063.

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Uniaxial compression tests on hot-rolled AZ31 Mg alloy were carried out at a temperature of 300°C. In order to investigate work hardening and texture evolution during plastic deformation, cylindrical specimens were compressed to the rolling direction. Experimental investigation reveals that flow curves are strongly dependent on microstructure evolution such as deformation twinning and softening phenomenon. The occurrence of deformation twinning and softening phenomenon was revealed by the observation of microtexture using electron backscatter diffraction (EBSD). A visco-plastic self-consistent (VPSC) polycrystal model was used to simulate the work hardening, softening and texture evolution during the uniaxial compression. In order to calculate orientation of deformation twins, predominant twin reorientation (PTR) scheme was implemented into the polycrystal model. A softening scheme was also implemented in the polycrystal model to predict softening phenomenon and texture evolution after a peak stress.

16

Liu, Shuaiyang, Aiqin Wang e Jingpei Xie. "Effect of Deformation Temperature, Strain Rate and Strain on the Strain Hardening Exponent of Copper/Aluminum Laminated Composites". Advanced Composites Letters 27, n. 4 (luglio 2018): 096369351802700. http://dx.doi.org/10.1177/096369351802700401.

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In order to investigate the strain hardening behaviour of Cu/Al laminated composites, isothermal compression tests were conducted in the temperature range of 300–450 °C and stain rate range of 0.01–1 s−1. Based on the experimental data, stain hardening exponent n was calculated to evaluate the strain hardening ability of Cu/Al laminated composites during the deformation process. The results show that deformation temperature, strain rate, strain and laminated structure are all responsible for the evolution of flow stress during the isothermal compression. The highly non-linear character of Ln σ - Ln ε curves shows the dynamic competition between work hardening and dynamic softening, and dynamic softening gradually plays a dominant role with the increase of strain. Furthermore, strain hardening exponent n is more sensitive to deformation temperature than strain rate. Lower deformation temperature and higher strain rate contribute to the enhancement of strain hardening exponent n.

17

Touzé, Cyril, Cédric Camier, Gaël Favraud e Olivier Thomas. "Effect of Imperfections and Damping on the Type of Nonlinearity of Circular Plates and Shallow Spherical Shells". Mathematical Problems in Engineering 2008 (2008): 1–19. http://dx.doi.org/10.1155/2008/678307.

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The effect of geometric imperfections and viscous damping on the type of nonlinearity (i.e., the hardening or softening behaviour) of circular plates and shallow spherical shells with free edge is here investigated. The Von Kármán large-deflection theory is used to derive the continuous models. Then, nonlinear normal modes (NNMs) are used for predicting with accuracy the coefficient, the sign of which determines the hardening or softening behaviour of the structure. The effect of geometric imperfections, unavoidable in real systems, is studied by adding a static initial component in the deflection of a circular plate. Axisymmetric as well as asymmetric imperfections are investigated, and their effect on the type of nonlinearity of the modes of an imperfect plate is documented. Transitions from hardening to softening behaviour are predicted quantitatively for imperfections having the shapes of eigenmodes of a perfect plate. The role of 2:1 internal resonance in this process is underlined. When damping is included in the calculation, it is found that the softening behaviour is generally favoured, but its effect remains limited.

18

Mirsayapov, Ilizar T., e Irina V. Koroleva. "Softening and hardening clay soil under loading". IOP Conference Series: Materials Science and Engineering 890 (13 agosto 2020): 012070. http://dx.doi.org/10.1088/1757-899x/890/1/012070.

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19

Mermet-Guyennet, M. R. B., J. Gianfelice de Castro, M. Habibi, N. Martzel, M. M. Denn e D. Bonn. "LAOS: The strain softening/strain hardening paradox". Journal of Rheology 59, n. 1 (gennaio 2015): 21–32. http://dx.doi.org/10.1122/1.4902000.

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Lukáč, P., e Z. Trojanová. "Hardening and softening in selected magnesium alloys". Materials Science and Engineering: A 462, n. 1-2 (luglio 2007): 23–28. http://dx.doi.org/10.1016/j.msea.2006.01.170.

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Niu, Rongmei, e Ke Han. "Strain hardening and softening in nanotwinned Cu". Scripta Materialia 68, n. 12 (giugno 2013): 960–63. http://dx.doi.org/10.1016/j.scriptamat.2013.02.051.

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22

Ottosen, Niels Saabye, e Karl‐Gunnar Olsson. "Hardening/Softening Plastic Analysis of Adhesive Joint". Journal of Engineering Mechanics 114, n. 1 (gennaio 1988): 97–116. http://dx.doi.org/10.1061/(asce)0733-9399(1988)114:1(97).

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Máthis, K., Z. Trojanová e P. Lukáč. "Hardening and softening in deformed magnesium alloys". Materials Science and Engineering: A 324, n. 1-2 (febbraio 2002): 141–44. http://dx.doi.org/10.1016/s0921-5093(01)01296-5.

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24

Rusinko, A. "Analytical description of ultrasonic hardening and softening". Ultrasonics 51, n. 6 (agosto 2011): 709–14. http://dx.doi.org/10.1016/j.ultras.2011.02.003.

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25

Yu, T. X., S. R. Reid e B. Wang. "Hardening-softening behaviour of tubular cantilever beams". International Journal of Mechanical Sciences 35, n. 12 (dicembre 1993): 1021–33. http://dx.doi.org/10.1016/0020-7403(93)90053-w.

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26

Wang, Lei, Kun Cai, Siyu Wei e Yi Min Xie. "Softening to hardening of stretched diamondene nanotubes". Physical Chemistry Chemical Physics 20, n. 32 (2018): 21136–43. http://dx.doi.org/10.1039/c8cp03243b.

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Trojanová, Z., P. Lukáč e A. Dlouhý. "Hardening and softening in ZrSn polycrystals". Materials Science and Engineering: A 164, n. 1-2 (maggio 1993): 246–51. http://dx.doi.org/10.1016/0921-5093(93)90671-z.

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Field, D. P., e B. L. Adams. "Unrecoverable Strain Hardening in Torsionally Strained OFHC Copper". Journal of Engineering Materials and Technology 112, n. 3 (1 luglio 1990): 315–20. http://dx.doi.org/10.1115/1.2903330.

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This paper investigates the recoverable and unrecoverable components of strain hardening in OFHC copper tubing subjected to torsional strain. Individual hardening components are classified and the magnitude of each is experimentally determined. Recoverable strain hardening is defined to be the difference between the final shear stress and the yield stress measured after recovery annealing. The recoverable hardening, due primarily to dislocation pileups, accounts for about 95.5 percent of the measured strain hardening at a shear strain of 1.9. Crystal lattice rotation during shear strain accounts for a portion of the unrecoverable hardening at shear strains less than .25, but becomes a strain softening effect at shear strains above .5. The evolution of the texture is measured experimentally and analyzed using both Taylor’s and Kochendorfer’s models. Texture evolution is also simulated up to a shear strain of 2.0 using Taylor’s model. This simulation yields similar results to the measured texture in determining strain hardening caused by rotation of the crystal lattice. The softening effect of crystalline reorientation accounts for a decrease in the observable hardening of 1.5 percent at a shear strain of 1.9.

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Singh, Sushant, e Debashis Khan. "Quasi-statically growing crack tip fields in plastically compressible hardening-softening-hardening solid". International Journal of Structural Integrity 9, n. 4 (13 agosto 2018): 532–47. http://dx.doi.org/10.1108/ijsi-11-2017-0063.

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Purpose As the normality concept for frictional dilatant material has a serious drawback, the key feature in this numerical study is that the material here is characterized by elastic-viscoplastic constitutive relation with plastic non-normality effect for two different hardness functions. The paper aims to discuss this issue. Design/methodology/approach Quasi-static, mode I plane strain crack tip fields have been investigated for a plastically compressible isotropic hardening–softening–hardening material under small-scale yielding conditions. Finite deformation, finite element calculations are carried out in front of the crack with a blunt notch. For comparison purpose a few results of a hardening material are also provided. Findings The present numerical calculations show that crack tip deformation and the field quantities near the tip significantly depend on the combination of plastic compressibility and slope of the hardness function. Furthermore, the consideration of plastic non-normality flow rule makes the crack tip deformation as well as the field quantities significantly different as compared to those results when the constitutive equation exhibits plastic normality. Originality/value To the best of the authors’ knowledge, analyses, related to the constitutive relation exhibiting plastic non-normality in the context of plastic compressibility and softening (or softening hardening) on the near tip fields, are not explored in the literature.

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Khudiakova, A. D., A. N. Servetnik, M. E. Volkov e S. B. Polianskii. "Cyclic behavior of heat resistant nickel-base alloys EP741NP and EI698VD under strain-control loading". Industrial laboratory. Diagnostics of materials 89, n. 4 (22 aprile 2023): 50–62. http://dx.doi.org/10.26896/1028-6861-2023-89-4-50-62.

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Low cycle fatigue behavior of nickel-base alloys EP741NP and EI698VD under strain-control loading with zero strain ratio was studied for a wide range of strain amplitudes and temperatures. Dependences of the stress amplitude, mean stress and plastic strain range on the number of cycles were analyzed. Three stages of the cyclic behavior were marked out: the first stage of non-steady behavior with hardening, or softening, or transition from hardening to softening; the second stage of steady hardening, softening or stability; and the third stage associated with a crack development. Qualitative and quantitative parameters are proposed that make it possible to determine a share of the first stage of cyclic instability in the total cyclic durability and the nature of the material behavior in the first and second stages proceeding from the analysis of the dependence of the range of plastic deformations on the cycle number. The absence of cyclic stability was demonstrated for both alloys almost in the whole range of testing. It was shown, that the contribution of the first stage to the fatigue life (total durability) can be up to 30% and the greater the strain range, the greater the contribution. The temperature dependence of the character of cyclic behavior of materials is revealed. Alloy EP741NP is softened at the first and second stages at room temperature and is liable to hardening at elevated temperatures 300, 450, and 600°C, whereas alloy EI698VD is hardened at the first stage at 20 and 400°C, but inclines to softening at 650°C. At the second stage alloy EI698VD inclines to softening at 20 and 650°C and is liable to hardening at 400°C. With strain ranges 0.6 and 0.7%, both alloys can be considered cyclic stable at the second stage over the entire temperature range

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Jiang, Hua, Jian Qiu Zhou e Rong Tao Zhu. "Constitutive Model for Large Plastic Deformation of Nanocrystalline Materials". Materials Science Forum 682 (marzo 2011): 139–44. http://dx.doi.org/10.4028/www.scientific.net/msf.682.139.

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A constitutive model was presented for nanocrystalline metallic materials that can experience large plastic deformation with shear band. The model was composed of two parts for different deformation stage: hardening stage and softening stage. In the hardening stage, the phase mixture model was used, and in the softening stage, a shear band deformation mechanism was proposed. Based on the model presented, numerical simulations were carried out to prove that the predications kept in good agreement with experimental data.

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Wang, Qiang Song, Dong Mei Liu, Guo Liang Xie, Wei Bin Xie, Yang Li e Xue Cheng Gao. "High Temperature High Strain-Rate Tensile and Compressive Deformation Behaviors of Cu-Zn-Sn-Al Alloy". Materials Science Forum 817 (aprile 2015): 55–62. http://dx.doi.org/10.4028/www.scientific.net/msf.817.55.

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The present work gives a systematic study on the high temperature and high strain-rate deformation behaviors of a two-phase α/β Cu-Zn-Sn-Al alloy, by combining the split Hopkinson bar experiments and microstructural investigations. The results show that under high strain-rate, both the dislocation slip and deformation twins within the α phase contribute to the plastic strengthening of Cu-Zn-An-Al alloy, resulting in the strain-rate-hardening effect. As the deformation temperature increases, the shapes of the stress-strain curves are mainly influenced by the temperature-softening effect and the dynamic recrystallization of the α phase. Finally, material constants regarding the strain-rate-hardening and temperature-softening effects are determined, based on the Johnson-Cook constitutive model. The results show that compared with other metallic materials, the present Cu-Zn-Sn-Al alloy has a relatively stronger strain-rate-hardening effect and weaker temperature-softening effect.

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Fronk, Matthew D., Stephanie G. Konarski, Caleb F. Sieck, Alec K. Ikei e Matthew D. Guild. "Dispersion in lattices with patterns of hardening and softening stiffness nonlinearity". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A40. http://dx.doi.org/10.1121/10.0010588.

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Recent focus has been given to analytically predicting amplitude-dependent dispersion in periodic structures with weak stiffness nonlinearity. These dispersion relationships may inform devices such as amplitude-dependent filters, waveguides, and diodes. However, attention is generally restricted to either spatially uniform nonlinearity or mutually exclusive distributions of hardening or softening stiffness. This study investigates dispersion in lattices with spatial modulations in stiffness nonlinearity. Special attention is given to modulations consisting of both hardening and softening nonlinear terms. A multiple scales perturbation analysis reveals that patterns of hardening and softening stiffness enable both lifting and lowering of a passband’s frequencies. In such cases, passbands contain discrete frequency and wavenumber pairs that prevent amplitude-dependent dispersion shifting. Numerical integration of the lattice equations of motion are carried out to confirm the analytically predicted dispersion behavior. A design of experiment is proposed in which strength and sign of nonlinearity can be tuned with the initial angle of additively manufactured grounding springs. [Work supported by the Office of Naval Research.]

34

Michelis, Paul, e E. T. Brown. "A yield equation for rock". Canadian Geotechnical Journal 23, n. 1 (1 febbraio 1986): 9–17. http://dx.doi.org/10.1139/t86-002.

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A yield equation for isotropic, homogeneous, geotechnical materials has been developed and applied to the work-softening and work-hardening behaviour of granular rocks. The development of this yield equation was based on a comparison of the work done and the energy dissipated within a sample undergoing yield in triaxial compression. The formulation takes into account friction and dilatancy and also an experimental observation leading to the derivation of a nonassociated flow rule. The analysis of extensive experimental data indicates that the flow rule is consistent for work-softening and -hardening behaviour, and validates the application of the incremental theory of plasticity to the irrecoverable strain behaviour of rocks in which the predominant mode of deformation is cataclastic. The yield equation, which is expressed in terms of readily indentifiable material parameters, predicts yield strength or strength at a given value of plastic strain invariant, and relates stress and strain increments at yield. Key words: rocks, yield, plastic strain, work softening, work hardening, energy, dilatancy, nonassociated flow.

35

Cui, Liuliang, Xihong Zhang e Hong Hao. "Improved analysis method for structural members subjected to blast loads considering strain hardening and softening effects". Advances in Structural Engineering 24, n. 12 (12 aprile 2021): 2622–36. http://dx.doi.org/10.1177/13694332211007382.

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In analysis and design of structures subjected to blast loading, equivalent Single-Degree-of-Freedom (SDOF) method is commonly recommended in design guides. In this paper, improved analysis method based on SDOF models is proposed. Both flexural and direct shear behaviors of structures subjected to blast load are studied using equivalent SDOF systems. Methods of deriving flexural and direct shear resistance functions are introduced, of which strain hardening and softening effects are considered. To collocate with the improved SDOF models, the improved design charts accounting for strain hardening and softening are developed through systematical analysis of SDOF systems. To demonstrate the effectiveness of the proposed analysis method, a model validation is made through comparing the predictions with laboratory shock tube testing results on reinforced concrete (RC) columns. It is found that compared to the conventional approach with elastic and elastic-perfectly-plastic model, the elastic-plastic-hardening model provides more accurate predictions. Additional non-dimensional design charts considering various levels of elastic-plastic-hardening/softening resistance functions are developed to supplement those available in the design guides with elastic-perfectly-plastic resistance function only, which provide engineers with options to choose more appropriate resistance functions in design analysis.

36

Taleb, Lakhdar, e Crescent Kpodekon. "Effect of Pre-Deformation on the Cyclic Behavior and Fatigue of 304L SS". Key Engineering Materials 703 (agosto 2016): 125–31. http://dx.doi.org/10.4028/www.scientific.net/kem.703.125.

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This study deals with the effect of the loading history on the cyclic behavior and the fatigue life of a 304L stainless steel at room temperature. The experiments have been performed using two specimens’ categories. The first one (virgin) has been submitted to only classical fatigue tests while in the second category, prior to the fatigue test; the specimen was subjected to a pre-hardening process under either monotonic or cyclic strain control. Cyclic softening followed by cyclic hardening are observed for the virgin specimens while only cyclic softening is exhibited by the pre-hardened specimens. The obtained results show that fatigue life is strongly influenced by the pre-hardening: the latter seems beneficial under stress control but detrimental under strain control, even in the presence of a compressive mean stress. The results are discussed regarding the cyclic evolution of the elastic modulus as well as the isotropic and kinematic parts of the strain hardening in different configurations: with or without pre-hardening, stress or strain control.

37

Petrenec, Martin, Karel Obrtlík, Jaroslav Polák e Jiří Man. "Effect of Temperature on the Low Cycle Fatigue of Cast Inconel 792-5A". Key Engineering Materials 345-346 (agosto 2007): 383–86. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.383.

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Cyclic strain control tests have been performed on cylindrical specimens of cast polycrystalline Inconel 792-5A superalloy at 23, 500, 700 and 800 °C in laboratory atmosphere to study the effect of temperature on the fatigue behavior. Cyclic hardening-softening curves and fatigue life curves were measured. Scanning electron microscopy was used to investigate the surface relief. Low amplitude straining was characterized by saturation of the stress amplitude. In room temperature high amplitude straining cyclic hardening was followed by marked saturation. Pronounced continuous hardening until failure was observed at 500 °C. Initial cyclic hardening was followed by softening at 800 °C. A systematic shift of the Manson-Coffin and of the Basquin curves to lower fatigue lives was found when temperature was increased. Fatigue cracks were observed to initiate from surface slip markings at all temperatures.

38

Nikulin, Ilya, Takahiro Sawaguchi, Kazuyuki Ogawa e Kaneaki Tsuzaki. "Low-Cycle Fatigue Behavior and Microstructural Evolution of the Fe–30Mn–4Si–2Al Alloy". Materials Science Forum 783-786 (maggio 2014): 944–49. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.944.

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Superior fatigue life of 8000 cycles at low-cycle fatigue with a total strain Δε=2% was found in the Fe–30Mn–4Si–2Al high-Mn alloy, as compared to Fe–30Mn–6Si–0Al and Fe–30Mn–3Si–3Al alloys with fatigue life of 2×103 cycles. Examination of microstructural evolution and cyclic hardening/softening behavior was shown that high fatigue resistance of Fe–30Mn–4Si–2Al alloy associated with delayed development of the deformation induced martensite and inhibited dislocation slip as compared to Fe–30Mn–6Si–0Al and Fe–30Mn–3Si–3Al alloys, respectively. Cyclic strain softening followed by secondary strain hardening was observed in the Fe–30Mn–4Si–2Al alloy after primary hardening. Primary hardening to about 40 cycles was associated with continuous increase in density of planar dislocations and the development of slip bands. The cyclic softening manifesting as the drop of the stress amplitude in the range of the cycles from 40 to 400 was accompanied by development of deformation induced ε-martensite in place of the slip bands. At the N>400 cycles further increase in the volume fraction of deformation ε-martensite leads to continuous hardening up to the failure. In the presentation we will discuss the details of microstructural evolution during LCF of the Fe–30Mn–4Si–2Al alloy.

39

Zhu, Jun, e Yin Zhong Shen. "The Effect of Fe-Ion Irradiation on Hardness Changes in P92 Ferritic/Martensitic Steel". Applied Mechanics and Materials 446-447 (novembre 2013): 418–21. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.418.

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The irradiation-induced hardness change in a commercial P92 ferritic/martensitic steel has been investigated through 3.5MeV Fe-ions irradiations to a dose of 0.29dpa at room temperature, 673K and 973K combined with nanoindentation techniques. The results show that irradiation-induced hardening was observed at the room temperature, and softening occurred at 673K and 973K. The hardening at room temperature is ascribed to the crystal defects in the steel generated by Fe-ions irradiations. The softening at 673K and 973K may be caused by the recovery of the defects.

40

Lan, Bo, Shenghong Liu e Xingyu Ma. "Microstructure and Macroscopic Characteristics of Powder Superalloy under Different Plastic Deformation Process Parameters". Journal of Physics: Conference Series 2468, n. 1 (1 aprile 2023): 012088. http://dx.doi.org/10.1088/1742-6596/2468/1/012088.

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Abstract Through the uniaxial compression deformation test, this work focuses on analyzing the microstructure evolution of the alloy in the two stages of dynamic softening and strain hardening in the true stress-true strain curve during hot deformation, including grain size, local misorientation and The interaction of its relative mobility, and through the grain boundary orientation difference and grain orientation, explained the dynamic softening mechanism and strain hardening phenomenon, so as to find the microstructure-determining characteristic parameters of the dynamic recrystallization nucleation and core growth of the alloy and its evolution.

41

Singh, S., e D. Khan. "Crack Tip Radius Effect on Fatigue Crack Growth and Near Tip Fields in Plastically Compressible Materials". Defence Science Journal 71, n. 2 (10 marzo 2021): 248–55. http://dx.doi.org/10.14429/dsj.71.15983.

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Motivated by the prospective uses of plastically compressible materials such as, metallic and polymeric foams, transformation toughened ceramics, toughened structural polymers etc., the present authors investigate the crack-tip radius effect on fatigue crack growth (FCG) of a mode I crack and near-tip stress-strain fields in such plastically compressible solids. These plastically compressible materials have been characterised by elastic-viscoplastic constitutive equations. Simulations are conducted for plane strain geometry with two different hardness functions: one is bilinear hardening and the other one is hardening-softening-hardening. It has been observed that plastic compressibility as well as strain softening lead to significant deviation in the amount of crack growth. It has further been revealed that the nature of FCG is appreciably affected by initial crack-tip radius. Even though it may look from outside that the increase in tip radius will lead to decrease in FCG, but the nature of FCG variation with respect to tip radius is found to be a combined effect of tip radius, plastic compressibility and work or strain softening etc.

42

Obrtlík, Karel, Alice Chlupová, Martin Petrenec e Jaroslav Polák. "Low Cycle Fatigue of Cast Superalloy Inconel 738LC at High Temperature". Key Engineering Materials 385-387 (luglio 2008): 581–84. http://dx.doi.org/10.4028/www.scientific.net/kem.385-387.581.

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Cylindrical specimens of cast polycrystalline nickel base superalloy Inconel 738LC were cyclically strained under total strain control at 23 and 800 °C to fracture. Cyclic hardening/softening curves, cyclic stress-strain curves, and fatigue life curves were obtained at both temperatures. Surface relief was studied in specimens fatigued to failure using scanning electron microscopy. Cyclic hardening/softening behaviour depends both on temperature and strain amplitude. Low amplitude straining was characterized by saturation of the stress amplitude. In high amplitude straining a pronounced hardening was found which was followed by saturation at room temperature and by cyclic softening at 800 °C. The cyclic stress-strain curves can be fitted by power law. They are shifted to lower stresses with increasing temperature. Fatigue life curves can be approximated by the Manson- Coffin and Basquin laws. The Manson-Coffin and Basquin curves are shifted to lower lives with increasing temperature. Slip markings were detected on specimen surface at all test temperatures. When temperature grows the density of slip markings is reduced.

43

Nguyen, Duc-Toan. "A New Constitutive Model for AZ31B Magnesium Alloy Sheet Deformed at Elevated Temperatures and Various Strain Rates". High Temperature Materials and Processes 33, n. 6 (1 dicembre 2014): 499–508. http://dx.doi.org/10.1515/htmp-2013-0109.

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AbstractIn this study, a new constitutive model is established for AZ31B magnesium alloy sheet at elevated temperatures and strain rates in order to describe two competing mechanisms for deformation, i.e. both work-hardening and softening stage of AZ31B magnesium alloy sheet. Stress-strain curves obtained by conducting uni-axial tensile tests at elevated and strain rates were first separated at the maximum stress and corresponding strain values. Voce's law [25] was then employed to fit separated hardening and softening stage. A MATLAB tool is used to determine material parameters by using least square fitting method at various temperatures and strain rate. The mergence of separated work-hardening and softening equations is in good agreement with experimental data. The parameters of fitting curves are utilized to determine them as a function of temperature and strain rate using a surface fitting method. The final equation is then implemented to predict stress-strain curves at various temperatures and strain rates. The proposed equation showed the good comparability between the simulation results and the corresponding experiments.

44

Feng, Jingjing, Cheng Liu, Wei Zhang, Jianxin Han e Shuying Hao. "Mechanical Behaviors Research and the Structural Design of a Bipolar Electrostatic Actuation Microbeam Resonator". Sensors 19, n. 6 (18 marzo 2019): 1348. http://dx.doi.org/10.3390/s19061348.

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A class of bipolar electrostatically actuated micro-resonators is presented in this paper. Two parametric equations are proposed for changing the microbeam shape of the upper and lower sections. The mechanical properties of a micro-resonator can be enhanced by optimizing the two section parameters. The electrostatic force nonlinearity, neutral surface tension, and neutral surface bending are considered in the model. First, the theoretical results are verified with finite element results from COMSOL Multiphysics simulations. The influence of section variation on the electrostatic force, pull-in behaviors and safe working area of the micro-resonator are studied. Moreover, the impact of residual stress on pull-in voltage is discussed. The multi-scale method (MMS) is used to further study the vibration of the microbeam near equilibrium, and the relationship between the two section parameters of the microbeam under linear vibration was determined. The vibration amplitude and resonance frequency are investigated when the two section parameters satisfy the linear vibration. In order to research dynamic analysis under the case of large amplitude. The Simulink dynamics simulation was used to study the influence of section variation on the response frequency. It is found that electrostatic softening increases as the vibration amplitude increases. If the nonlinearity initially shows hardening behavior, the frequency response will shift from hardening to softening as the amplitude increases. The position of softening-hardening transition point decreases with the increase of residual stress. The relationship between DC voltage, section parameters, and softening-hardening transition points is presented. The accuracy of the results is verified using theoretical, numerical, and finite element methods.

45

Hwang, Joong-Ki. "Hardening and Softening Behavior of Caliber-Rolled Wire". Materials 15, n. 8 (18 aprile 2022): 2939. http://dx.doi.org/10.3390/ma15082939.

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The different behaviors of the mechanical properties of drawn and caliber-rolled wires with applied strain were investigated to determine the appropriate process between wire drawing and caliber rolling with consideration of materials and process conditions. Ferritic, pearlitic, and TWIP steels were drawn and caliber-rolled under the same process conditions. Caliber-rolled wires exhibited a hardening behavior in the early deformation stage and softening behavior in the later deformation stage compared with the drawn wires, regardless of the steel. The hardening behavior of the caliber-rolled wires was explained by the higher strain induced by caliber rolling compared with wire drawing, especially the higher amount of redundant work in caliber-rolled wire. The caliber-rolled wire had approximately 36% higher strain than the drawn wire and approximately 85% higher strain than nominal strain. The softening behavior of the caliber-rolled wire in later deformation stages was related to the Bauschinger effect or low-cycle fatigue effect caused by the roll geometries and loading conditions during caliber rolling. The different intersection points of the tensile strength between drawn and caliber-rolled wires with the steels were attributed to the different strain hardening rates of each steel. Between the options of the caliber rolling and wire drawing processes, the appropriate process should be selected according to the strain hardening rate of the material and the amount of plastic deformation. For instance, when the wires need to deform at high levels, wire drawing is the better process because of the appearance of the Bauschinger effect in caliber-rolled wire.

46

OBATAYA, Yoichi, e Shinobu KOHNO. "Cyclic strain hardening and softening of carbon steel." Transactions of the Japan Society of Mechanical Engineers Series A 54, n. 499 (1988): 583–91. http://dx.doi.org/10.1299/kikaia.54.583.

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47

KATZ, JOSHUA T., e KATHARINA VOLK. "EROTIC HARDENING AND SOFTENING IN VERGIL'S EIGHTH ECLOGUE". Classical Quarterly 56, n. 1 (maggio 2006): 169–74. http://dx.doi.org/10.1017/s0009838806000139.

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48

Harada, Y., Y. Murata e M. Morinaga. "Solid solution softening and hardening in alloyed MoSi2". Intermetallics 6, n. 6 (gennaio 1998): 529–35. http://dx.doi.org/10.1016/s0966-9795(97)00103-9.

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49

Sharif, A. A., A. Misra, J. J. Petrovic e T. E. Mitchell. "Solid solution hardening and softening in MoSi2 alloys". Scripta Materialia 44, n. 6 (aprile 2001): 879–84. http://dx.doi.org/10.1016/s1359-6462(00)00698-9.

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Fougere, G. E., J. R. Weertman e R. W. Siegel. "On the hardening and softening of nanocrystalline materials". Nanostructured Materials 3, n. 1-6 (gennaio 1993): 379–84. http://dx.doi.org/10.1016/0965-9773(93)90102-h.

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