Distribution Of Equivalent Plastic Strain Research Articles

Research on the Mechanism and Processability of Roll Forming.

Cold bending forming is a complex forming process, and its product quality is closely related to the forming process parameters. To mitigate issues such as bulging and waviness arising from the extension of the material at the edges during the forming process of thin-walled circular tubes, a comprehensive comparative analysis was conducted on four forming methods. This analysis determined that the combined bending method is the optimal forming technique for the equipment. For the impact of different parameters on the equivalent plastic strain distribution of the product and the force on the rollers, numerical simulations were carried out using the software COPRA (COPRA FEA RF 2023.1) after designing the pattern diagram based on the integrated bending method. The results showed that different processing speeds on the equivalent plastic strain distribution and work hardening of the plate have little effect. As the spacing between the upper and lower rollers increases, the equivalent plastic strain of the plate to a certain extent and the value of the moment of the rollers is significantly reduced. Analyzing the performance characteristics of high-strength steel materials from the aspects of the thickness strain and cross-sectional forming of the plate, this verifies the advantages of forming high-strength steel plates. The numerical simulation results of this study are in good agreement with actual production experimental results.

Investigating fretting wear mechanisms in Ti-6Al-4V: insights from residual stress and equivalent plastic strain analysis

Purpose The study delves into the influence of wear cycles on these parameters. The purpose of this paper is to identify characteristic patterns of σRS and εPEEQ that discern varying wear situations, thereby contributing to the enrichment of wear theory. Furthermore, the findings serve as a foundational basis for nondestructive and in situ wear detection methodologies, such as nonlinear ultrasonic detection, known for its sensitivity to σRS and εPEEQ. Design/methodology/approach This paper elucidates the wear mechanism through the lens of residual stress (σRS) and plastic deformation within distinct fretting regimes, using a two-dimensional cylindrical/flat contact model. It specifically explores the impact of the displacement amplitude and cycles on the distribution of residual stress and equivalent plastic strain (εPEEQ) in both gross slip regime and partial slip regimes. Findings Therefore, when surface observation of wear is challenging, detecting the σRS trend at the center/edge, region width and εPEEQ distribution, as well as the maximum σRS distribution along the depth, proves effective in distinguishing wear situations (partial or gross slip regimes). However, discerning wear situations based on εPEEQ along the depth direction remains challenging. Moreover, in the gross slip regime, using σRS distribution or εPEEQ along the width direction rather than the depth direction can effectively provide feedback on cycles and wear range. Originality/value This work introduces a novel perspective for investigating wear theory through the distribution of residual stress (σRS) and equivalent plastic strain (εPEEQ). It presents a feasible detection theory for wear situations using nondestructive and in situ methods, such as nonlinear ultrasonic detection, which is sensitive to σRS and εPEEQ. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0005/

Mathematical Formulation and Numerical Simulation of the Mechanical Behavior of Ceramic/Metal (TiB/Ti) FG Sheets Subjected to Spherical Indenter

The main motivation for the present work is to provide an improved description of the response of Functionally Graded (FG) structures under a spherical indenter, considering material nonlinearities. This is achieved through the implementation of elastoplastic material behavior using integration points to avoid the division of the structure into multiple layers. The current paper proposes a numerical investigation into the mechanical response of functionally graded materials (FGMs) in contact with a rigid hemispherical head indenter. The numerical model considers both the Mori–Tanaka model and self-consistent formulas of Suquet to accurately model the smooth variation of material properties through the thickness of the elastoplastic FG material. The model execution involves a UMAT user material subroutine to implement the material behavior into ABAQUS/Standard. The user material UMAT subroutine is employed to introduce material properties based on the integration points, allowing for an accurate representation and analysis of the material’s behavior within the simulation. The developed numerical model is validated through a comparison with experimental results from the literature, showing a good correlation that proves the efficiency of the proposed model. Then, a parametric study is conducted to analyze the effect of the indenter dimension, the indentation depth and the gradient index on the indentation force, the contact pressure evolution, von Mises equivalent stress and equivalent plastic strain distributions located on the vicinity of the contact zone. The results showed that the elastoplastic response of TiB/Ti FG plates is significantly influenced by the gradient index, which determines the properties of the FG composite through the thickness. These results may help development engineers choose the optimal gradation for each industrial application in order to avoid contact damage.

Prediction of Macroscopic Deformation Bands in Porous Metals with Unidirectional Through‐Pores

The formation of macroscopic deformation bands constitutes undesired stress fluctuations in the compression of porous metals. This research is aimed at revealing the predictability of the formation of deformation bands in porous metals with unidirectional through‐pores. Finite element analyses of compression tests of such porous metals are conducted with the commercial code Abaqus/Standard and Explicit 2018. Three cubic specimens with different L/d (specimen edge length L, pore diameter d) but with the almost same porosity are prepared, and quasi‐static compression is simulated. The results suggest that the formation of horizontally propagated deformation bands is suppressed as L/d increases. A path search is performed to predict the location of deformation bands on a graph that represents equivalent plastic strain (PEEQ) distribution in the specimens. It is revealed that horizontally propagated deformation bands at compressive strain e = 10.0 pct can be predicted as the path with the largest mean of PEEQ at e = 1.0 pct when the following two conditions are met; the minimum PEEQ in the path has to be larger than zero, and the standard deviation of the PEEQ mean in candidate paths has to be sufficiently large.

Seismic performance of bolted T-stub Beam-to-Box column connection

Using internal continuity plates in box columns due to accessibility problems and complicated detailing of connection was perceived as fraught with shortcomings and limitations. To overcome this deficiency, the effectiveness of external continuity plates in conjugation with T-stub connectors in I-beam to box-column connections under cyclic action is investigated in this study. Three damage control strategies based on the fuse action of T-stubs (T-F), strengthening the connections (T-S), and using reduced beam section (RBS) connections (T-R) are pursued and are compared to a corresponding end-plate connection (E). Nonlinear finite element analyses are conducted using the ABAQUS/STANDARD software on the connections under the qualification cyclic loading conditions to elucidate all the main seismic behavioral aspects, including the strength, initial stiffness, energy dissipation, ductility, von-Mises stress, and equivalent plastic strain distributions of models. First, the accuracy of numerical models is validated by a series of available experimental results. Then, a parametric study is performed on the effects of the moment ratio of the beam to column, the number of continuity plates, stiffeners embedded on the beam, and using high strength materials on the seismic performance of the connections. From the results, it is found that the T-S model was the most efficient among the different connections studied, supplying the stiffness, strength, energy absorption, and ductility increases by 2%, 21%, −17%, and 22%, respectively with respect to the E model, satisfying the requirements of AISC Seismic Provisions for SMF. Increasing the beam-to-column moment ratio and the number of continuity plates, had limited effects by less than 10% on the seismic performance of the connections. In the absence of continuity plates, the connections exhibited worse inelastic seismic performance with decreases in stiffness, strength, and energy dissipation up to 67%, 44%, and 74%, respectively. The T-F connection gained a 13% strength increase and satisfied the AISC requirements when high-strength T-stubs are used. Based on the numerical observations, design strength and rotational stiffness of the proposed connections on the component-based joint design strategies, are finally outlined.

A study on micro‐mechanical deformation behaviour of heat‐treated 20MnMoNi55 steel

AbstractSeveral heat treatment procedures are designed considering critical temperatures of phase transformation evaluated through dilatometric testing of 20MnMoNi55 steel to transform low carbon bainitic as‐received material into ferrite‐martensite dual‐phase steels consisting of varied martensite fractions. A thorough metallographic study correlated with the micro‐hardness of constituent phases ensures morphological characteristics along with its fractional variations in as‐received and dual‐phase steels. The impact of fractional variation in constituent phases on the uniaxial monotonic deformation characteristics of dual‐phase steels has been observed with a correlation study between experimental tensile and finite element simulated results. Therefore, a physical‐based model with a 2‐dimensional representative volume element has been established, addressing actual morphological characteristics obtained from metallographic studies. Moreover, the constitutive flow behaviours of ferrite and martensite are also derived from the dislocation‐based hardening model to address the actual deformation phenomenon. Finally, an inhomogeneous deformation behaviour among constituent phases and localization of plastic strain in ferrite matrix has been observed with von‐Mises stress, and equivalent plastic strain distribution through finite element simulated results. This phenomenon is again confirmed with kernel average misorientation mapping and geometrically necessary dislocation density evaluation through electron backscattered diffraction of tensile samples subjected to different degrees of plastic strain.

Effects of Cold Expansion on Residual Stress of 7050 Aluminium Alloy Frame Forging

Regulation of residual stress in a component is the key to improving its service performance. A cold expansion method was proposed for reducing the residual stress in 7050 aluminium alloy curved frame forging after quenching. The effect of the cold expansion method on the residual stress and equivalent plastic strain distribution of the 7050 aluminium alloy curved frame forging was investigated. The results showed that the maximum residual stress at the center thickness was reduced from 153 MPa to 94 MPa after the cold expansion, while it decreased from 283 MPa to 120 MPa at the surface with the highest stress reduction rate of 86.2%. The stress uniformity in the final forming region of the forging was improved. The equivalent plastic strain of the forging gradually decreases from the center to each side along the diameter of the expanded hole in cold expansion. The stress reduction effect matched with the distribution of equivalent plastic strain. The surface stress of the forging measured by x-rays diffraction (XRD) method was in agreement with the simulation results, and the reliability of the numerical model was verified. The cold expansion method can effectively reduce the quenched residual stress in curved frame forging.

Study on hot deformation behavior of homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy using a combination of strain-compensated Arrhenius constitutive model and finite element simulation method

Isothermal hot compression experiments were conducted on homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy to investigate hot deformation behavior at the temperature range of 673–773 K and the strain rate range of 0.001–1 s − 1 by using a Gleeble-1500D thermo mechanical simulator. Metallographic characterization on samples deformed to true strain of 0.70 illustrates the occurrence of flow localization and/or microcrack at deformation conditions of 673 K/0.01 s − 1, 673 K/1 s − 1 and 698 K/1 s − 1, indicating that these three deformation conditions should be excluded during hot working of homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy. Based on the measured true stress-strain data, the strain-compensated Arrhenius constitutive model was constructed and then incorporated into UHARD subroutine of ABAQUS software to study hot deformation process of homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy. By comparison with measured force-displacement curves, the predicted results can describe well the rheological behavior of homogenized Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy, verifying the validity of finite element simulation of hot compression process with this complicated constitutive model. Numerical results demonstrate that the distribution of values of material parameters (α, n, Q and ln A) within deformed sample is inhomogeneous. This issue is directly correlated to the uneven distribution of equivalent plastic strain due to the friction effect. Moreover, at a given temperature the increase of strain rate would result in the decrease of equivalent plastic strain within the central region of deformed sample, which hinders the occurrence of dynamic recrystallization (DRX).

Microstructure based numerical simulation of the micromechanics and fracture in hypereutectic Al–Mg2Si composites

In the present study, both experimental and numerical examinations were performed to understand the hypereutectic Al–Mg2Si composite's microstructural morphology, mechanical properties and fracture correlation. The innovation of this research includes the micromechanics studies and failure initiation in hypereutectic Al–Mg2Si composite through the compiled induce stress, deformation plasticity and energy dissipation theory subjected to tension. Ultimate tensile strength (UTS), toughness and elongation have decreased, but the yield strength has increased up to 25% Mg2Si addition and then decreased at the composites with 30 wt% Mg2Si because the brittle fracture increases due to the presence of comparatively coarser and dendritic primary Mg2Si particles. Additionally, an increase in the microporosity with the increase in Mg2Si concentration also affects the same. Finite element analysis (FEA) was performed using the Ramberg-Osgood constitutive model and actual microstructure 2D representative volume elements model. The FEA and experimental results have a satisfactory agreement. The fractography unveils the presence of a mix-mode of fracture, i.e. the ductile and the brittle fracture of the composites. Mises and Tresca failure criteria reveal that the distribution of stress is non-homogeneous and stress is localized in the narrow eutectic and irregular Mg2Si phase region, which acts as a crack initiation site. Analysis of the stress triaxiality and equivalent plastic strain distribution shows that void initiation and growth take place during the deformation of the Al–Mg2Si composites. The plastic dissipated energy distribution in deformed RVEs interestingly consents to the von mises stress, plastic strain and stress triaxiality analysis findings.

Surface Microstructure Refinement and Mechanical Properties of GCr15 Steels Improved During Ultrasonic Surface Rolling Processing

In this paper, ultrasonic surface rolling processing (USRP) was used to strengthen GCr15-bearing steel. A finite element three-dimensional model of USRP was established to analyze the residual compressive stress and equivalent plastic strain distribution on the bearing steel surface. The microstructure, hardness, surface roughness, and corrosion resistance before and after USRP treatment were characterized by SEM, EBSD, X-ray diffraction (XRD), and electrochemical techniques. Results indicated that USRP treatment can significantly improve the material's surface microstructure and residual compressive stress distribution and obtain a plastic strain layer of about 60μm. After USRP treatment, the Kernel Average Misorientation (KAM) increased, and the dislocation activity was more intensive, resulting in aggregation near grain boundaries, and the percentage of LAGBs increased to 38.8%. Under the combined effect of surface grain refinement, residual compressive stress, and high glossy surface, the self-corrosion current density is reduced by two orders of magnitude, and the corrosion resistance is significantly improved. This investigation suggests a solution to the bearing failure problem and has implications for understanding the deformation mechanism of ultrasonic surface rolling processing.

Understanding the bending behavior and through-thickness strain distribution during asymmetrical rolling of high-strength aluminium alloy plates

The asymmetric rolling (ASR) process is highly desired to improve the through-thickness deformation/strain uniformity by introducing additional shear strains for uniform through-thickness microstructures and mechanical properties of metallic/alloy plates. In this study, the bending behavior and mechanism during the ASR processing of high-strength AA7050 aluminium alloy plates were simulated along with rolling trials. It shows that the plate will bend upward (toward slower roll) at larger speed ratios and smaller thickness reductions but downward (toward faster roll) at smaller speed ratios and larger thickness reductions. The ASR processing can increase the central equivalent plastic strains and decrease the surface-to-center strain gradient compared with that caused by the conventional symmetric rolling. The high strain rate bands (HSRBs) as key plastic strain accumulation regions are intimately connected with the post-rolling equivalent plastic strain distribution and the outgoing curvature. Especially, when the HSRB approaches the plate upper surface near the end of the deformation zone, normally at larger thickness reductions, a downward bending occurs despite that the lower roll rotates faster, and vice versa. The through-thickness HSRB induced by the ASR processing is considered to mainly enhancing the equivalent plastic strain homogeneity. The formation and interactive mechanisms of the HSRBs and their connection with the bending behavior during the ASR processing were discussed.

Preparation, microstructure, and mechanical behaviour of Ni3Al-based superalloy reinforced with carbide particles

The preparation, microstructure, and mechanical behaviour of Ni3Al-based superalloy have been studied. The superalloy reinforced with carbide particles forming in-situ in the melt was prepared by vacuum induction melting (VIM) followed by centrifugal casting. The as-cast alloy was subjected to heat treatment consisting of solid solution annealing, quenching, and ageing. The microstructure of the heat-treated superalloy consists of blocky MC carbides (6.9 vol%), which are uniformly distributed within the columnar grains containing cuboidal γ′(Ni3Al) precipitates (57.3 vol%) embedded in the γ (Ni-based solid solution) matrix and along γ′ grain boundaries. The equivalent plastic strain distribution in the plastic zone underneath Vickers macroindentation and within the compression specimens deformed to engineering strains ranging from 0.05 to 0.27 is calculated using finite element analysis (FEA). The correlation curve between experimentally measured Vickers microhardness values and calculated equivalent plastic strains has been proposed to quantify the level of local strain hardening state of the studied Ni3Al-based superalloy. The room temperature compressive strain hardening behaviour is evaluated and measured strain hardening exponent and strain hardening rate are discussed.

Investigating the Equivalent Plastic Strain in a Variable Ring Length and Strut Width Thin-Strut Bioresorbable Scaffold

PurposeThe ArterioSorb^{rm{{TM}}} bioresorbable scaffold (BRS) developed by Arterius Ltd is about to enter first in man clinical trials. Previous generations of BRS have been vulnerable to brittle fracture, when expanded via balloon inflation in-vivo, which can be extremely detrimental to patient outcome. Therefore, this study explores the effect of variable ring length and strut width (as facilitated by the ArterioSorb^{rm{{TM}}} design) on fracture resistance via analysis of the distribution of equivalent plastic strain in the scaffold struts post expansion. Scaffold performance is also assessed with respect to side branch access, radial strength, final deployed diameter and percentage recoil.MethodsFinite element analysis was conducted of the crimping, expansion and radial crushing of five scaffold designs comprising different variations in ring length and strut width. The Abaqus/Explicit (DS SIMULIA) solution method was used for all simulations. Direct comparison between in-silico predictions and in-vitro measurements of the performance of the open cell variant of the ArterioSorb^{rm{{TM}}} were made. Paths across the width of the crown apex and around the scaffold rings were defined along which the plastic strain distribution was analysed.ResultsThe in-silico results demonstrated good predictions of final shape for the baseline scaffold design. Percentage recoil and radial strength were predicted to be, respectively, 2.8 and 1.7 times higher than the experimentally measured values, predominantly due to the limitations of the anisotropic elasto-plastic material property model used for the scaffold. Average maximum values of equivalent plastic strain were up to 2.4 times higher in the wide strut designs relative to the narrow strut scaffolds. As well as the concomitant risk of strut fracture, the wide strut designs also exhibited twisting and splaying behaviour at the crowns located on the scaffold end rings. Not only are these phenomena detrimental to the radial strength and risk of strut fracture but they also increase the likelihood of damage to the vessel wall. However, the baseline scaffold design was observed to tolerate significant over expansion without inducing excessive plastic strains, a result which is particularly encouraging, due to post-dilatation being commonplace in clinical practice.ConclusionTherefore, the narrow strut designs investigated herein, are likely to offer optimal performance and potentially better patient outcomes. Further work should address the material modelling of next generation polymeric BRS to more accurately capture their mechanical behaviour. Observation of the in-vitro testing indicates that the ArterioSorb^{rm{{TM}}} BRS can tolerate greater levels of over expansion than anticipated.

Investigation by numerical modeling of the mechano-electrochemical interaction at a dent-corrosion defect on pipelines

Dent-corrosion combination defect causes the curvature change and wall thickness thinning on the pipeline simultaneously, which poses a higher threat to pipeline integrity than a single type of defect. In this work, a finite element (FE) based multi-physical field coupling model was developed to investigate the mechano-electrochemical (M-E) interaction at the dent-corrosion defect on an operating X80 pipeline. Parameter effects, including internal pressure, the diameter-to-thickness ratio of the pipe, and the geometries of the defect, were determined. Results demonstrate that the local equivalent plastic strain and anodic current density are insensitive to practical operating pressure but highly dependent on the diameter-to-thickness ratio and the geometries. A critical dent depth of 4% of the pipe diameter existed, exceeding which the increase of dent depth hardly affects the maximum equivalent plastic strain of the pipeline. The size of the indenter is negatively correlated with the equivalent plastic strain and the anodic current density at the defect center. There is also a critical threshold of 10% pipe diameter, below which the distribution of equivalent plastic strain and anodic current density at the defect is significantly affected. The effect of the circumferential dent is significant, while that of the axial dent is marginal.

Compressive Behavior of a Fully Prefabricated Liftable Connection for Modular Steel Construction

Modular steel construction (MSC) consists of the off-site prefabrication of a fully finished module and the on-site assembling of the module unit. The popularity of MSC is on the rise, attributable to its technical advantages of speed and quality of buildings with repetitive units. Inter-module connection is critical for the overall stability and load-bearing capacity of MSC. An innovative, fully prefabricated liftable connection (FPLC) using standard corner fittings and long stay bolts is proposed in this paper. This paper focuses on the axial compressive behavior and design of FPLC. Five full-scale specimens were tested under axial compression. Local buckling of the column and shear of the long stay bolts were observed during the test. It can be concluded from the test results that the load-bearing capacity may decrease as the number and diameter of the stay bolts increase. A three-dimensional nonlinear finite element model (FEM) was developed and validated against the test results by general purpose finite element software ABAQUS. Furthermore, a parametric study was conducted using the verified FEM to provide a better understanding of the axial compressive behavior of the FPLC. The results of the parametric study indicated that the corner fitting can be up to 15% lighter for columns with thicknesses of 6 mm and 8 mm without substantial reduction of the axial load-bearing capacity of the FPLC. Moreover, the location of the column can be adjusted to achieve a uniform Von Mises stress and equivalent plastic strain (PEEQ) distribution of the connection. The presented research work provides an engineering-practical inter-module connection on its axial compressive behavior, which will provide helpful references for further application of MSC.

A novel process for manufacturing large-diameter thin-walled metal ring: Double-roll pendulum hot rotary forging technology

Large-scale thin-walled metal ring parts are the key main structural parts in new energy sources and aerospace equipment. How to form reliable large-diameter thin-walled metal rings has become the focus of attention of researchers. This paper proposes a double-roll pendulum hot rotary forging (DRPHRF) process for forming such components and demonstrates the feasibility of forming rings with a diameter of 4 m and a thickness of 0.1 m (axial) using this process. The forming process of DRPHRF is analyzed and designed, and the critical instability and forming conditions are obtained. The finite element model of the ring DRPHRF was established in the DEFORM-3D software using the scale-down process with a ratio of 10:1, and the accuracy of the model was verified through experiments. Based on the reliable finite element model, the deformation behavior of the ring DRPHRF is analyzed. The results show that each part of the ring is subjected to periodic stress, which reduces the residual stress. The uniform circumferential equivalent plastic strain (PEEQ) distribution and the characteristics that the axial PEEQ becomes uniform as the thickness decreases are conducive to forming a thin-walled ring with uniform performance. There is less heat loss during the forming process, which is beneficial to reduce the stress during forming.

Analysis of Strain Inhomogeneity in Extruded Al 6061-T6 Processed by ECAE

This paper presents an analysis of the test and simulation of the equal channel angular extrusion (ECAE) of a commercial Al 6061-T6 alloy previously extruded. Special emphasis is given to the analysis and comparison of the simulated values and distribution of equivalent plastic strain with those calculated with analytical models across the height of the middle section of the deformed billet. The results reveal the limitations of the analytical models when the effects of the inner die corner and curvature of the outer wall on the material response during the test are considered for the ECAE device used in this work. Specifically, in the simulations performed in this work, the plastic deformation zone, far from being uniform, extends along with the height of the billet where, in particular, near the inner wall over the inlet and outlet channels, even in the central region of the billet, the equivalent plastic strain is not homogeneous or discontinuous, varying mainly due to the effect of the curvature of the outer channel.

Friction Coefficient Effect on Stress-Strain Distribution of Ceramic Coated Aeroengine Substrate Using Finite Element Analysis

This study presents the investigation of friction coefficient effect on stress-strain distribution of ceramic coated aeroengine specific material substrate using explicit finite element method. Half-cylinder-on-flat contact configuration subjected to normal and tangential loading is examined. Elastic ceramic coated elastic-plastic Ti-6Al-4V and Super CMV substrates are assigned to study the influence of different friction coefficient on contact pressure, von Mises stress, tangential stress and equivalent plastic strain distribution. The outcome of present research is quite revealing that stress-strain distribution response is remarkable for sliding step which experiencing significant traction compared to normal loading step. Higher possibilities of coated substrate equivalent plastic strain (plastic deformation) are registered under higher friction coefficient cases due to substantial resistance to overcome relative to tangential motion of contacting bodies.

A new model of critical resolved shear stress with the effect of geometrical relationship between slip plane and microstructure interface

A new model of critical resolved shear stress with the effect of geometrical relationship between slip plane and microstructure interface, was investigated using a crystal plasticity analysis with Cu polycrystals. The extended expression of the Bailey-Hirsch type model was used for the critical resolved shear stress. The effect of geometrical relationship between slip plane and microstructure interface was incorporated into the values for microstructural size parameter that express size effects in the extended expression of the Bailey-Hirsch type model l. The distribution of equivalent plastic strain and plastic shear strain on slip systems were investigated. At a nominal strain of 0.03, almost the same distributions of equivalent plastic strain were obtained with the simple grain size model and the new model where the effect of geometrical relationship between slip plane and microstructure interface were taken into account. On the other hand, the distributions of plastic shear strain on slip systems were different in the two models.

降伏曲面上に形成される尖り点を考慮した弾粘塑性モデルによるモードIき裂進展解析

It has been confirmed by experiments and crystal plasticity analysis that a vertex is formed at the loading point of the yield surface in the stress space during plastic deformation. However, most past deformation analyses for crack tip behavior have used plasticity models with a classical normality flow rule. In this study, we introduce a non-normality flow rule, which considers the formation of a vertex on the yield surface. We investigate the effect of vertex formation on Mode I crack growth behavior for cyclic loading. Numerical results show that both crack tip opening displacement and crack growth are greater for the model with the non-normality flow rule than for the standard normality flow rule. The distribution of equivalent plastic strain near the crack tip indicates that the model with the non-normality rule leads to localized plastic deformation, which is not seen in the case where the standard normality flow rule is adopted.