Dynamic Finite Element Analysis of an Elastic-Plastic Half-Space Indented by a Rigid Sphere

2010 ◽  
Author(s):  
A. Lee ◽  
K. Komvopoulos
Keyword(s):  
Finite Element ◽  
Half Space ◽  
Equivalent Plastic Strain ◽  
Dynamic Contact ◽  
Rigid Sphere ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Wide Range ◽  
Deformation Velocity ◽  
Elastic Plastic Materials

Dynamic indentation of an elastic-plastic half-space by a rigid sphere was studied with the finite element method. A parametric analysis was performed to examine the effects of indentation velocity and yield strength of the half-space material on dynamic contact deformation. Velocity effects are discussed in the context of simulation results of global and local contact parameters, such as mean contact pressure, contact area, and equivalent plastic strain. The evolution of deformation as the material response transitions from elastic to fully-plastic deformation during dynamic contact is interpreted in light of numerical results. This study elucidates the effect of dynamic contact loading on the deformation behavior of elastic-plastic materials for a wide range of length scales where a continuum mechanics description holds.

Finite Element Analysis of Repeated Indentation of an Elastic-Plastic Layered Medium by a Rigid Sphere, Part I: Surface Results

1995 ◽  
Vol 62 (1) ◽  
pp. 20-28 ◽  
Author(s):  
E. R. Kral ◽  
K. Komvopoulos ◽  
D. B. Bogy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Half Space ◽  
Contact Pressure ◽  
Peak Load ◽  
Rigid Sphere ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Surface Stresses ◽  
Residual Displacements

A comprehensive elastic-plastic finite element analysis is presented for the axisym-metric problem of a frictionless rigid sphere indenting a half-space with a harder and stiffer layer. The indenter is modeled by contact elements, thereby avoiding a priori assumptions for the pressure profile. Two layer thicknesses are examined, with layer elastic modulus and yield stress both two and four times greater than those of the substrate. Perfectly plastic and isotropic strain-hardening behavior of the layer and substrate media are investigated. At least three complete load-unload cycles are applied to a peak load of 300 times the load necessary to initiate yielding in a half-space of the substrate material. The effect of hardening properties on the loaded and residual stresses is presented and the consequences for crack initiation at the surface are discussed. Results for the contact pressure and surface stresses and deformations are presented, and the influence of residual displacements and load cycles on the contact pressure and the loaded and residual surface stresses is investigated.

Finite Element Analysis of Repeated Indentation of an Elastic-Plastic Layered Medium by a Rigid Sphere, Part II: Subsurface Results

1995 ◽  
Vol 62 (1) ◽  
pp. 29-42 ◽  
Author(s):  
E. R. Kral ◽  
K. Komvopoulos ◽  
D. B. Bogy
Keyword(s):  
Finite Element ◽  
Strain Hardening ◽  
Half Space ◽  
Peak Load ◽  
Interfacial Shear ◽  
Rigid Sphere ◽  
Shear Stresses ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Perfectly Plastic

Finite element solutions are presented for the subsurface stress and deformation fields in a layered elastic-plastic half-space subjected to repeated frictionless indentation by a rigid sphere. A perfectly adhering layer is modeled using two different thicknesses and elastic modulus and yield stress two and four times greater than those of the substrate. The significance of strain hardening during plastic deformation is investigated by assuming elastic-perfectly plastic and isotropically strain-hardening constitutive laws for both the layer and substrate materials. At least three load-unload cycles are applied to a peak load of 300 times the load necessary to initiate yielding in a homogeneous half-space with substrate properties. The effects of the layer thickness and material properties of the layer and substrate on the loaded and residual stresses are interpreted, and the consequences for subsurface crack initiation are discussed. The maximum principal and interfacial shear stresses are given as a function of a nondimensional strain parameter. The effect of subsequent load cycles on the loaded, residual, and maximum tensile and interfacial shear stresses and the protection provided by the harder and stiffer layer are analyzed. Reyielding during unloading and the possibility of elastic shakedown are discussed, and the accumulation of plastic strain in the yielding regions is tracked through subsequent load cycles.

A Finite Element Analysis of the Effect of Hardening Rules on the Indentation Test

1998 ◽  
Vol 120 (2) ◽  
pp. 143-148 ◽  
Author(s):  
N. Huber ◽  
Ch. Tsakmakis
Keyword(s):  
Finite Element Method ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Half Space ◽  
Kinematic Hardening ◽  
Indentation Test ◽  
Rigid Sphere ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Hardening Rules

Using the Finite Element Method, an analysis is given of the indentation of an elasticplastic half-space by a rigid sphere. In particular, attention is focused on the effect of hardening rules on the material response. The materials considered are supposed to exhibit isotropic and kinematic hardening. Moreover, it is shown that the possibility of similar behavior due to effects of friction can be ruled out.

Effects of Local Peak Stress Distribution on the Ratchet Limit

2002 ◽  
Author(s):  
Nobuyoshi Yanagida ◽  
Masaaki Tanaka ◽  
Norimichi Yamashita ◽  
Yukinori Yamamoto
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Plastic Strain ◽  
Equivalent Stress ◽  
Equivalent Plastic Strain ◽  
Peak Stress ◽  
Element Analysis ◽  
Stress Evaluation ◽  
Elastic Plastic ◽  
Plastic Analysis

Alternative stress evaluation criteria suitable for Finite Element Analysis (FEA) proposed by Okamoto et al. [1],[2] have been studied by the Committee on Three Dimensional Finite Element Stress Evaluation (C-TDF) in Japan. Thermal stress ratchet criteria in plastic FEA are now under consideration. Two criteria are proposed: (1) Evaluating variations in plastic strain increments, and (2) Evaluating the width of the area in which Mises equivalent stress exceeds 3Sm. To verify of these criteria, we selected notched cylindrical vessel models as prime elements. To evaluate the effect of the local peak stress distribution on these criteria, cylindrical vessels with a semicircular notch on the outer surface were selected for this analysis. We used two notch configurations for our analysis, and the stress concentration factor for the notches was set to 1.5 and 2.0. We conducted elastic-plastic analysis to evaluate the ratchet limit. Sustained pressure and alternating enforced longitudinal displacements which causes secondary stress were used as parameters for the elastic-plastic analysis. We found that when no ratchet was observed, the equivalent plastic strain increments decreased and the area in which Mises equivalent stress exceeds 3Sm are below the certain range.

Elastic-Plastic Finite Element Analysis of Repeated Indentation of a Half-Space by a Rigid Sphere

1993 ◽  
Vol 60 (4) ◽  
pp. 829-841 ◽  
Author(s):  
E. R. Kral ◽  
K. Komvopoulos ◽  
D. B. Bogy
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Strain Hardening ◽  
Half Space ◽  
Contact Pressure ◽  
Peak Load ◽  
Rigid Sphere ◽  
Load Range ◽  
Elastic Plastic ◽  
Residual Displacements

The elastic-plastic contact problem of a rigid sphere indenting a homogeneous halfspace is analyzed with the finite element method. Emphasis is placed on the load range between elastic and fully plastic deformation, which has not yet been fully investigated. The rigid sphere is modeled by contact elements, thus eliminating the need to assume a particular pressure profile. Different elastic properties, with both elastic-perfectly plastic and isotropic strain hardening behaviors, are considered. Up to four complete frictionless load-unload cycles are applied to a peak load of 300 times the load necessary for the initiation of yielding. Results for the contact pressure, surf ace and subsurface stresses, initiation and growth of the plastic zone, and yielding of the half-space during unloading are presented. The effect of residual displacements on the contact pressure during subsequent load cycles is examined. The influence of strain hardening on the loading and residual stresses is analyzed and the consequences for crack initiation are discussed in light of these results. The accumulation of plastic strain in the yielding regions is tracked through the subsequent load cycles as the material approaches a steady-state elastic cycle, and the significance of the loading and residual stresses on the deformation characteristics is interpreted in the context of finite element results.

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