Multiple Normal Loading-Unloading Cycles of a Spherical Contact Under Stick Contact Condition

2010 ◽  
Author(s):  
Y. Zait ◽  
V. Zolotarevsky ◽  
Y. Kligerman ◽  
I. Etsion
Keyword(s):  
Cyclic Loading ◽  
Contact Condition ◽  
Isotropic Hardening ◽  
Normal Loading ◽  
Hardening Model ◽  
Loading Cycle ◽  
Hardening Models ◽  
Plastic Sphere ◽  
Elastic Shakedown ◽  
Contact Parameters

The multiple normal loading-unloading process of an elastic-plastic sphere by a rigid flat is analyzed for stick contact condition and both kinematic and isotropic hardening models. The behavior of the global contact parameters as well as the stress field within the sphere tip is presented for several loading cycles. It was found that under stick contact condition secondary plastification occurs even after the second loading cycle and that the hardening model used has little effect on the loading-unloading process. The cyclic loading process gradually converges into elastic shakedown.

Multiple Normal Loading-Unloading Cycles of a Spherical Contact Under Stick Contact Condition

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Y. Zait ◽  
V. Zolotarevsky ◽  
Y. Kligerman ◽  
I. Etsion
Keyword(s):  
Finite Element Method ◽  
Contact Condition ◽  
Isotropic Hardening ◽  
Normal Loading ◽  
Hardening Model ◽  
Loading Cycle ◽  
Hardening Models ◽  
Plastic Sphere ◽  
Elastic Shakedown ◽  
Contact Parameters

The multiple normal loading-unloading process of an elastic-plastic sphere by a rigid flat is analyzed using finite element method for stick contact condition and both kinematic and isotropic hardening models. The behavior of the global contact parameters as well as the stress field within the sphere tip is presented for several loading cycles. It was found that under stick contact condition, secondary plastification occurs even after the second loading cycle and that the hardening model used has little effect on the loading-unloading process. The cyclic loading process gradually converges into elastic shakedown.

scholarly journals Effect of Strain Hardening on Elastic-Plastic Contact of a Deformable Sphere against a Rigid Flat under Full Stick Contact Condition

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Biplab Chatterjee ◽  
Prasanta Sahoo
Keyword(s):  
Strain Hardening ◽  
Kinematic Hardening ◽  
Contact Condition ◽  
Isotropic Hardening ◽  
Contact Conditions ◽  
Elastic Plastic ◽  
Finite Element Software ◽  
Hardening Models ◽  
Load Carrying ◽  
Contact Parameters

The present study considers the effect of strain hardening on elastic-plastic contact of a deformable sphere with a rigid flat under full stick contact condition using commercial finite element software ANSYS. Different values of tangent modulus are considered to study the effect of strain hardening. It is found that under a full stick contact condition, strain hardening greatly influences the contact parameters. Comparison has also been made between perfect slip and full stick contact conditions. It is observed that the contact conditions have negligible effect on contact parameters. Studies on isotropic and kinematic hardening models reveal that the material with isotropic hardening has the higher load carrying capacity than that of kinematic hardening particularly for higher strain hardening.

scholarly journals Finite-Element-Based Multiple Normal Loading-Unloading of an Elastic-Plastic Spherical Stick Contact

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Biplab Chatterjee ◽  
Prasanta Sahoo
Keyword(s):  
Finite Element ◽  
Strain Hardening ◽  
Tangent Modulus ◽  
Repeated Loading ◽  
Normal Loading ◽  
Elastic Plastic ◽  
Finite Element Software ◽  
Hardening Models ◽  
Hardening Rules ◽  
Contact Parameters

The repeated normal elastic plastic contact problem of a deformable sphere against a rigid flat under full stick contact condition is investigated with a commercial finite element software ANSYS. Emphasis is placed on the effect of strain hardening and hardening model with the maximum interference of load ranging from elastic to fully plastic, which has not yet been reported. Different values of tangent modulus coupled with isotropic and kinematic hardening models are considered to study their influence on contact parameters. Up to ten normal loading-unloading cycles are applied with a maximum interference of 200 times the interference required to initiate yielding. Results for the variation of mean contact pressure, contact load, residual interference, and contact area with the increasing number of loading unloading cycles at high hardening parameter as well as for low tangent modulus with two different hardening models are presented. Results are compared with available finite element simulations and in situ results reported in the literature. It is found that small variation of tangent modulus results in same shakedown behavior and similar interfacial parameters in repeated loading-unloading with both the hardening rules. However at high tangent modulus, the strain hardening and hardening rules have strong influence on contact parameters.

scholarly journals Effects of Hardening Model and Variation of Elastic Modulus on Springback Prediction in Roll Forming

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1005 ◽  
Author(s):  
Naofal ◽  
Naeini ◽  
Mazdak
Keyword(s):  
Elastic Modulus ◽  
Cyclic Loading ◽  
Kinematic Hardening ◽  
Roll Forming ◽  
Isotropic Hardening ◽  
Plastic Behavior ◽  
Forming Process ◽  
Hardening Models ◽  
Springback Prediction ◽  
Roll Forming Process

In this paper, the uniaxial loading–unloading–reloading (LUR) tensile test was conducted to determine the elastic modulus depending on the plastic pre-strain. To obtain the material parameters and parameter of Yoshida-Uemori’s kinematic hardening models, tension–compression experiments were carried out. The experimental results of the cyclic loading tests together with the numerically predicted response of the plastic behavior were utilized to determine the parameters using the Ls-opt optimization tool. The springback phenomenon is a critical issue in industrial sheet metal forming processes, which could affect the quality of the product. Therefore, it is necessary to represent a method to predict the springback. To achieve this aim, the calibrated plasticity models based on appropriate tests (cyclic loading) were implemented in commercial finite element (FE) code Ls-dyna to predict the springback in the roll forming process. Moreover, appropriate experimental tests were performed to validate the numerical results, which were obtained by the proposed model. The results showed that the hardening models and the variation of elastic modulus have significant impact on springback accuracy. The Yoshida-Uemori’s hardening represents more accurate prediction of the springback during the roll forming process when compared to isotropic hardening. Using the chord modulus to determine the reduction in elastic modulus gave more accurate results to predict springback when compared with the unloading and loading modulus to both hardening models.

Effects of Hardening Models on CUO Forming and Springback Simulation of High Strength Line Pipes

2015 ◽  
Vol 817 ◽  
pp. 8-13 ◽  
Author(s):  
Qiang Ren ◽  
Tian Xia Zou ◽  
Da Yong Li
Keyword(s):  
Bauschinger Effect ◽  
Oil And Gas ◽  
Kinematic Hardening ◽  
High Strength ◽  
Isotropic Hardening ◽  
Forming Process ◽  
Hardening Model ◽  
Hardening Models ◽  
Combined Hardening ◽  
Springback Prediction

The UOE process is an effective approach for manufacturing the line pipes used in oil and gas transportation. During the UOE process, a steel plate is crimped along its edges, pressed into a circular pipe with an open-seam by the successively U-O forming stages. Subsequently, the open-seam is closed and welded. Finally, the welded pipe is expanded to obtain a perfectly round shape. In particular, during the O-forming stage the plate is suffered from distinct strain reversal which leads to the Bauschinger effect, i.e., a reduced yield stress at the start of reverse loading following forward strain. In the finite element simulation of plate forming, the material hardening model plays an important role in the springback prediction. In this study, the mechanical properties of API X90 grade steel are obtained by a tension-compression test. Three popular hardening models (isotropic hardening, kinematic hardening and combined hardening) are employed to simulate the CUO forming process. A deep analysis on the deformation and springback behaviors of the plate in each forming stage is implemented. The formed configurations from C-forming to U-forming are almost identical with three hardening models due to the similar forward hardening behaviors. Since the isotropic hardening model cannot represent the Bauschinger effect, it evaluates the higher reverse stress and springback in the O-forming stage which leads to a failure prediction of a zero open-seam pipe. On the contrary, the kinematic hardening model overestimates the Bauschinger effect so that predicts the larger open-seam value. Specifically, the simulation results using the combined hardening model show good agreement in geometric configurations with the practical measurements.

scholarly journals Combined hardening parameters of steel CK45 under cyclic strain-controlled loading: Calibration methodology and numerical validation

2020 ◽  
Vol 14 (2) ◽  
pp. 6848-6855
Author(s):  
Bahman Paygozar ◽  
S.A Dizaji ◽  
M.A Saeimi Sadigh
Keyword(s):  
Cyclic Loading ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Strain Curve ◽  
Experimental Tests ◽  
Isotropic Hardening ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Hardening Model ◽  
Combined Hardening

This study is to indicate the methodology of investigating the behavior of materials in the plastic domain while bearing cyclic loading i.e. low cycle fatigue. Materials under such loading, which experience huge amount of plastic deformation, are affected by the hardening or softening effects of loading which should be taken into account in all applications and numerical simulations as well. This work investigates the methodology of obtaining the nonlinear isotropic and kinematic hardening of steel CK45. To find the parameters of the above mentioned combined nonlinear isotropic/kinematic hardening one tensile test as well as three strain-controlled low cycle fatigue tests are carried out to extract the monotonic stress/strain curve and three diagrams of hysteresis curves, respectively. Then, four parameters necessary to simulate the nonlinear isotropic/ kinematic behavior of the material are extracted by means of curve fitting technique using MATLAB software. Afterwards, the accuracy of the data extracted from the experimental tests using the proposed methodology, are verified in a finite element package, ABAQUS, through implementing two user defined subroutines UMAT written in FORTRAN. It is indicated that the computed constants draw stress-strain curves much closer to experimental responses than isotropic hardening model does.  Eventually, the numerical results acquired by simulating the behavior of the sample under cyclic loading with importing the constants, calculated via combined hardening model, to ABAQUS reflects results highly close to the experimentally obtained response of the sample. It means that the procedure used to find the constants is accurate enough and consequently the constants computed are able to be used in both ABAQUS and subroutines.     

Comparison of Various Cyclic Hardening Models for Notched C(T) Specimen Simulation Under Cyclic Loading

2018 ◽  
Author(s):  
Jong-Min Lee ◽  
Hune-Tae Kim ◽  
Yun-Jae Kim ◽  
Jin-Weon Kim
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Plastic Strain ◽  
Tensile Test ◽  
Cyclic Hardening ◽  
Fe Analysis ◽  
Hardening Model ◽  
Hardening Models ◽  
Non Linear ◽  
Notch Tip

In this paper, simulations using various cyclic hardening models are performed to determine the effect of the hardening model that is used in a finite element analysis. Bi-linear, Armstrong-Frederick kinematic hardening model and Chaboche (third order non-linear) combined hardening model are used in finite element (FE) analysis to simulate material behavior under cyclic loading condition. Hardening parameters included in bilinear and non-linear hardening models are determined from monotonic stress-strain curve obtained from monotonic tensile test and parameters in Chaboche hardening model are determined from hysteresis loop obtained from cyclic tensile test. Simulation of notched C(T) test under cyclic loading is performed using three hardening models. Plastic strain, stress and plastic strain energy at notch tip of specimen are extracted from FE analysis results. Using energy based fatigue analysis, cycle to failure, the cycle at which crack initiation occurs at notch tip, are predicted and compared with experimental results. Through the comparisons, the effect of hardening model on the simulation result under cyclic load is confirmed.

Numerical Simulation of Dimensional Variations for Roller Hemming

2010 ◽  
Vol 160-162 ◽  
pp. 1601-1605
Author(s):  
Xing Hu ◽  
Yi Xi Zhao ◽  
Shu Hui Li ◽  
Cheng Liu
Keyword(s):  
Numerical Simulation ◽  
Aluminum Alloy ◽  
Uniaxial Tension ◽  
Kinematic Hardening ◽  
Isotropic Hardening ◽  
Hardening Model ◽  
Tension Tests ◽  
Hardening Models ◽  
Width Direction ◽  
Combined Hardening

A study to investigate the effect of hardening models on roller hemming in the case of aluminum alloy sheets is described in this approach. The most popular hardening models including isotropic hardening, kinematic hardening and combined hardening are studied using the uniaxial tension tests. Then the roll-in/out values over the hemline along width direction after pre-hemming with different hardening models are compared with the experimental results. It is verified that combined hardening model is most efficient to predict roll-in/out.

Local vs. Global Ratcheting in Cracked Structures

2014 ◽  
Author(s):  
R. Adibi-Asl ◽  
Wolf Reinhardt
Keyword(s):  
Cyclic Loading ◽  
Component Structure ◽  
Elastic Range ◽  
Cracked Structures ◽  
Elastic Shakedown ◽  
Plastic Shakedown ◽  
Time Invariant ◽  
Global And Local ◽  
Mean Time ◽  
Cracked Structure

The classical approaches in shakedown analysis are based on the assumption that the stresses are eventually within the elastic range of the material everywhere in a component (elastic shakedown). Therefore, these approaches are not very useful to predict the ratcheting limit (ratchet limit) of a cracked component/structure in which the magnitude of stress locally exceeds the elastic range at any load, although in reality the configuration will certainly permit plastic shakedown. The Non-Cyclic Method (NCM) has been proposed recently to determine both the elastic and the plastic ratchet boundary of a component or structure under cyclic loading by generalizing the static shakedown theorem (Melan’s theorem). The proposed method is based on decomposing the loading into mean (time invariant) and fully reversed components. When a cracked structure is subjected to cyclic loading, the crack and its vicinity behave differently (local) than the rest of the structure (global). The crack may propagate during the application of cyclic loading. This will affect both local and global behavior of the cracked structure. This paper investigates global and local ratcheting of the cracked structures using the NCM and fracture mechanic parameters.

scholarly journals Simulation of Cyclic Loading on Pipe Elbows Using Advanced Plane-Stress Elastoplasticity Models1

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Konstantinos Chatziioannou ◽  
Yuner Huang ◽  
Spyros A. Karamanos
Keyword(s):  
Cyclic Loading ◽  
Large Scale ◽  
Mechanical Response ◽  
Low Cycle Fatigue ◽  
Constitutive Relations ◽  
Cyclic Plasticity ◽  
Integration Scheme ◽  
Repeated Loading ◽  
Finite Element Software ◽  
Hardening Models

Abstract This work investigates the response of industrial steel pipe elbows subjected to severe cyclic loading (e.g., seismic or shutdown/startup conditions), associated with the development of significant inelastic strain amplitudes of alternate sign, which may lead to low-cycle fatigue. To model this response, three cyclic-plasticity hardening models are employed for the numerical analysis of large-scale experiments on elbows reported elsewhere. The constitutive relations of the material model follow the context of von Mises cyclic elasto-plasticity, and the hardening models are implemented in a user subroutine, developed by the authors, which employs a robust numerical integration scheme, and is inserted in a general-purpose finite element software. The three hardening models are evaluated in terms of their ability to predict the strain range at critical locations, and in particular, strain accumulation over the load cycles, a phenomenon called “ratcheting.” The overall good comparison between numerical and experimental results demonstrates that the proposed numerical methodology can be used for simulating accurately the mechanical response of pipe elbows under severe inelastic repeated loading. Finally, this paper highlights some limitations of conventional hardening rules in simulating multi-axial material ratcheting.

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