scholarly journals ON THE PROBLEM OF STRAIN LOCALIZATION AND FRACTURE SITE PREDICTION IN MATERIALS WITH IRREGULAR GEOMETRY OF INTERFACES

2019 ◽  
Vol 17 (2) ◽  
pp. 169 ◽  
Author(s):  
Ruslan Balokhonov ◽  
Varvara Romanova
Keyword(s):  
Stress Concentration ◽  
Strain Localization ◽  
Steel Substrate ◽  
Constitutive Relations ◽  
Fracture Site ◽  
Boride Coating ◽  
Third Stage ◽  
Strain Formulation ◽  
Irregular Interface ◽  
Interface Geometry

The interfacial mechanisms of the stress-strain localization in non-homogeneous media are investigated, using a steel substrate - iron boride coating composition subjected to tension as an example. A dynamic boundary-value problem in a plane-strain formulation is solved numerically by the finite-difference method. The curvilinear substrate-coating interface geometry is assigned explicitly in calculations and is in agreement with experiment. Constitutive relations accounting for an elastic-plastic response of the isotropically-hardened substrate and for a brittle fracture of the coating are employed. Three stages of the plastic strain localization in the steel substrate are found to occur due to the irregular interface geometry. Distributions of the stress concentration regions in the coating are shown to be different at different stages. The stress concentration in the coating is demonstrated to increase nonlinearly during the third stage. The location of fracture is found to depend on the strength of the coating.

scholarly journals A mesoscopic analysis of a localized shear band propagation effect on the deformation and fracture of coated materials

2021 ◽  
Vol 2 (1) ◽  
pp. 6-22
Author(s):  
Ruslan Balokhonov ◽  
◽  
Varvara Romanova ◽  
Aleksandr Zemlianov ◽  
◽  
...  
Keyword(s):  
Shear Band ◽  
Complex Geometry ◽  
Steel Substrate ◽  
Front Propagation ◽  
Front Velocity ◽  
Boride Coating ◽  
Iron Boride ◽  
Coated Materials ◽  
Deformation And Fracture ◽  
Cracking Pattern

The numerical simulations of the deformation and fracture in an iron boride coating – steel substrate composition are presented. The dynamic boundary-value problem is solved numerically by the finite-difference method. A complex geometry of the borided coating – steel substrate interface is taken into account explicitly. To simulate the mechanical behavior of the steel substrate, use is made of an isotropic strain hardening model including a relation for shear band propagation. Local regions of bulk tension are shown to arise near the interface even under simple uniaxial compression of the composition and in so doing they determine the mesoscale mechanisms of fracture. The interrelation between plastic deformation in the steel substrate and cracking of the borided coating is studied. Stages of shear band front propagation attributable to the interface complex geometry have been revealed. The coating cracking pattern, location of the fracture onset regions and the total crack length are found to depend on the front velocity in the steel substrate.

Localized metal forming simulation by r-s-adapted arbitrary Lagrangian-Eulerian finite element method

1997 ◽  
Vol 32 (4) ◽  
pp. 237-252 ◽  
Author(s):  
S Ghosh ◽  
S Raju
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Strain Localization ◽  
Metal Forming ◽  
Constitutive Relations ◽  
Arbitrary Lagrangian Eulerian ◽  
Localized Deformation ◽  
Forming Simulation ◽  
Ductile Materials ◽  
Element Method

In this paper, an adaptive arbitrary Lagrangian—Eulerian (ALE) large deformation finite element method (FEM) is developed for solving metal forming problems with strain localization. The ALE mesh movement is coupled with r-adaptation of automatic node relocation to minimize mesh distortion during the process of deformation. A strain localization phenomenon is incorporated through constitutive relations for porous ductile materials. Prediction of localized deformation is achieved through a multilevel mesh superimposition method, called s-adaptation. A few metal forming problems are simulated to test the effectiveness of this model.

scholarly journals The Effect on the Fracture Healing following Femoral Neck Shortening after Osteoporotic Femoral Neck Fracture Treated with Internal Fixation: Finite Element Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Xiao Yu ◽  
Peng-ze Rong ◽  
Qing-jiang Pang ◽  
Xian-jun Chen ◽  
Lin Shi ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Femoral Neck ◽  
Femoral Neck Fracture ◽  
Maximum Stress ◽  
Fracture Site ◽  
Cannulated Screws ◽  
Element Analysis ◽  
Neck Fracture

Objective. To evaluate the stress status of fracture site caused by femoral neck shortening and to analyze the stress of fracture site and the implants from the finite element point of view. Methods. CT scan data of hip of a normal adult female were collected. Three-dimensional reconstruction MICs and related module function simulation was used to establish the postoperative shortening model of femoral neck fracture with Pauwels   angle > 50 ° , which was treated with cannulated screws. The models were divided into four groups: normal femoral neck, shortening in 2.5 mm, shortening in 7.5 mm, and shortening in 12.5 mm. The finite element analysis software msc.nastran2012 was used, and the data of maximum stress and stress nephogram of fracture site and implants were carried out. Results. From normal femoral neck to shortening in 12.5 mm of the femoral neck, the maximum tensile stress increased gradually in the fracture site above the cannulated screws while compressive stress decreased gradually in the fracture site below the cannulated screws, and the maximum stress of the cannulated screws increased gradually with obvious stress concentration at the screw holes in the fracture site, and the peak value of stress concentration was about 179 MPa. Conclusion. The biomechanical environment of the fracture site changed by femoral neck shortening. With the increasing of femoral neck shortening, the stress of the fracture site and implants would be uneven; then, the stability of fracture site would become worse, and the possibility of implant sliding or even breakage would be increased.

Finite Deformation Constitutive Relations for Elastic-Plastic Fibrous Metal Matrix Composites

1993 ◽  
Vol 60 (3) ◽  
pp. 619-625 ◽  
Author(s):  
N. Fares ◽  
G. J. Dvorak
Keyword(s):  
Finite Deformation ◽  
Large Deformations ◽  
Fibrous Composite ◽  
Constitutive Relations ◽  
Shear Stiffness ◽  
Fiber Direction ◽  
Matrix Composites ◽  
Axial Loads ◽  
Strain Formulation ◽  
Fibrous Metal

This paper presents a finite strain formulation of a plasticity theory of fibrous composite materials. An additive decomposition is adopted to describe the kinematics of large deformations; a lattice is defined by the current fiber direction. Elastic and plastic constitutive relations are developed from the proposition that distortions take place relative to the fiber direction. A numerical method is proposed for integrating the constitutive equations. Finally, an illustrative example of the formulation indicates that when axial loads along the fiber direction are comparable to the instantaneous shear stiffness, the finite deformation formulation is needed even with small strains.

IMPLICATIONS OF A CONSTITUTIVE MODEL FOR STRAIN LOCALIZATION

1988 ◽  
Vol 49 (C3) ◽  
pp. C3-489-C3-496
Author(s):  
B. D. COLEMAN ◽  
M. L. HODGDON
Keyword(s):  
Constitutive Model ◽  
Strain Localization
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