scholarly journals Crystal plasticity model of residual stress in additive manufacturing using the element elimination and reactivation method

2021 ◽  
Author(s):  
Nicolò Grilli ◽  
Daijun Hu ◽  
Dewen Yushu ◽  
Fan Chen ◽  
Wentao Yan
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Crystal Plasticity ◽  
Grain Orientation ◽  
Large Temperature ◽  
Plasticity Model ◽  
Crystal Plasticity Model ◽  
Element Elimination

AbstractSelective laser melting is receiving increasing interest as an additive manufacturing technique. Residual stresses induced by the large temperature gradients and inhomogeneous cooling process can favour the generation of cracks. In this work, a crystal plasticity finite element model is developed to simulate the formation of residual stresses and to understand the correlation between plastic deformation, grain orientation and residual stresses in the additive manufacturing process. The temperature profile and grain structure from thermal-fluid flow and grain growth simulations are implemented into the crystal plasticity model. An element elimination and reactivation method is proposed to model the melting and solidification and to reinitialize state variables, such as the plastic deformation, in the reactivated elements. The accuracy of this method is judged against previous method based on the stiffness degradation of liquid regions by comparing the plastic deformation as a function of time induced by thermal stresses. The method is used to investigate residual stresses parallel and perpendicular to the laser scan direction, and the correlation with the maximum Schmid factor of the grains along those directions. The magnitude of the residual stress can be predicted as a function of the depth, grain orientation and position with respect to the molten pool. The simulation results are directly comparable to X-ray diffraction experiments and stress–strain curves.

Influence of Crystallographic Orientation on Energy Dissipation During Sliding

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Jeremy J. Dawkins ◽  
Richard W. Neu
Keyword(s):  
Finite Element Analysis ◽  
Plastic Deformation ◽  
Energy Dissipation ◽  
Crystal Plasticity ◽  
Crystallographic Orientation ◽  
Grain Orientation ◽  
Primary Energy ◽  
Plasticity Model ◽  
Element Analysis ◽  
Crystal Plasticity Model

The aim of this study is to evaluate a methodology for modeling the influence of crystallographic grain orientation in sliding contacts. The simulations of translating interfering cylindrical asperities, using finite element analysis, were conducted using two different plasticity models for copper: a conventional isotropic, homogeneous J2 plasticity model and a continuum crystal plasticity model. Using crystal plasticity, the dependence of crystallographic orientation on plastic deformation and energy dissipation can be determined. The relative trends predicted using crystal plasticity are consistent with experiments that show friction depends on crystallographic orientation when plastic deformation is one of the primary energy dissipation mechanisms.

A Method to Estimate Residual Stress in Metal Parts Made by Selective Laser Melting

2015 ◽  
Author(s):  
Xiaoqing Wang ◽  
Y. Kevin Chou
Keyword(s):  
Residual Stress ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Selective Laser Melting ◽  
Inconel 718 ◽  
Plane Surface ◽  
Texture Evolution ◽  
Large Temperature ◽  
Indentation Hardness ◽  
Laser Melting

Accurate evaluation of residual stresses in structures is very important because they play a crucial role in the mechanical performance of the components. As residual stresses can be introduced into mechanical components during various thermal or mechanical processes such as heat treatment, forming, welding and additive manufacturing. As an additive manufacturing method, selective laser melting (SLM) has become a powerful tool for the direct manufacturing of three dimensional nano-composite components with complex configurations directly from powders using 3D CAD data as a digital information source and energy in the form of a high-power laser beam. Therefore, the application of the SLM technology is necessary to manufacture Inconel 718 superalloy, which has been widely employed in industrial applications due to its remarkable properties. Hence, it is critical to measure and reduce the residual stress in the Inconel 718 parts formed by SLM due to rapid cooling and reheating. In this study, the process-induced residual stress in Inconel 718 parts produced by selective laser melting (SLM) has been investigated using the model established by Carlsson et al., which is an instrumented indentation technique based on the experimental correlation between the indentation characteristic and the residual stress. The samples were sectioned from an Inconel 718 block along its build direction, and subsequently prepared with general metallographic methods for Vickers indentation and measurements by optical microscopy. The residual stress on the scanning surface (Z-plane) and side surface (X-plane) at different build heights have been evaluated in micro-scale with the contact area, indentation hardness and the equai-biaxial residual stress and strain fields. The results show that the residual stress is unevenly distributed in the SLMed parts with some areas have an maximum absolute value around 350 MPa, about 30 percent of the yield strength of Inconel 718. The average residual stresses in the Z-plane and X-plane samples are tensile and compressive, respectively. Besides, the residual stress does not change significantly along the building direction of the part. Moreover, the Vickers hardness of the parts built with the SLM process is comparable to the literature, and the X-plane surface has a higher hardness than the Z-plane surface. The microstructures and texture evolution of the SLM processed Inconel 718 alloy are also investigated. The X-plane shows the columnar structure due to the large temperature gradient while the Z-plane presents the equiaxed structures. The random texture is shown in the SLM processed specimens.

Influence of Crystallographic Orientation on Energy Dissipation During Sliding

2007 ◽  
Author(s):  
Jeremy J. Dawkins ◽  
Richard W. Neu
Keyword(s):  
Plastic Deformation ◽  
Energy Dissipation ◽  
Crystal Plasticity ◽  
Crystallographic Orientation ◽  
Crystal Orientation ◽  
Primary Energy ◽  
Homogeneous Material ◽  
Plasticity Model ◽  
Deformation Response ◽  
Crystal Plasticity Model

This work presents the results of a finite element study of the sliding contact of interfering cylindrical asperities. One asperity is modeled as elastic with steel properties, while the other asperity is modeled as elastic-plastic copper. The simulations were run using two different plasticity models for copper, conventional J2 plasticity describing an initially homogeneous material and a continuum crystal plasticity model that can capture the influence of crystallographic orientation on the deformation response. The use of the crystal plasticity model and frictionless contact enables us to study the dependence of plastic deformation and energy dissipation as a function of crystal orientation and vertical interference. The relative trends predicted using crystal plasticity are consistent with classical experiments showing the dependence of friction with crystal orientation when plastic deformation is the primary energy dissipation mechanism.

Multi-level direct crystal plasticity model of polycrystalline specimen: Grains generation

2021 ◽  
Author(s):  
Artyom A. Tokarev ◽  
Anton Yu. Yants ◽  
Alexey I. Shveykin ◽  
Nikita S. Kondratiev
Keyword(s):  
Crystal Plasticity ◽  
Plasticity Model ◽  
Polycrystalline Specimen ◽  
Crystal Plasticity Model ◽  
Multi Level

Effect of Residual Stress or Plastic Deformation History on Fatigue Life Simulation of Pipeline Dents

2018 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Rick Wang
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Strain History ◽  
Deformation History ◽  
Stress Strain ◽  
Element Analysis ◽  
Fea Model

Mechanical dents often occur in transmission pipelines, and are recognized as one of major threats to pipeline integrity because of the potential fatigue failure due to cyclic pressures. With matured in-line-inspection (ILI) technology, mechanical dents can be identified from the ILI runs. Based on ILI measured dent profiles, finite element analysis (FEA) is commonly used to simulate stresses and strains in a dent, and to predict fatigue life of the dented pipeline. However, the dent profile defined by ILI data is a purely geometric shape without residual stresses nor plastic deformation history, and is different from its actual dent that contains residual stresses/strains due to dent creation and re-rounding. As a result, the FEA results of an ILI dent may not represent those of the actual dent, and may lead to inaccurate or incorrect results. To investigate the effect of residual stress or plastic deformation history on mechanics responses and fatigue life of an actual dent, three dent models are considered in this paper: (a) a true dent with residual stresses and dent formation history, (b) a purely geometric dent having the true dent profile with all stress/strain history removed from it, and (c) a purely geometric dent having an ILI defined dent profile with all stress/strain history removed from it. Using a three-dimensional FEA model, those three dents are simulated in the elastic-plastic conditions. The FEA results showed that the two geometric dents determine significantly different stresses and strains in comparison to those in the true dent, and overpredict the fatigue life or burst pressure of the true dent. On this basis, suggestions are made on how to use the ILI data to predict the dent fatigue life.

Sign in / Sign up

Export Citation Format

Share Document