scholarly journals Determination of Directional Residual Stresses by the Contour Method

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1104 ◽  
Author(s):  
Josef Hodek ◽  
Antonín Prantl ◽  
Jan Džugan ◽  
Pavel Strunz
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Electrical Discharge Machine ◽  
Measurement Data ◽  
Coordinate Measuring Machine ◽  
Material Model ◽  
Element Model ◽  
Contour Method ◽  
Diffraction Measurement ◽  
Measuring Machine

This study evaluated residual stresses in heat-treated specimens made of 316L stainless steel using FE analysis and compared them with stresses determined by the contour method. Contour method is usually used just for evaluation of residual stresses that are normal to the cut plan. In the current study this approach is extended and both normal and tangential stresses are determined. The specimens were cut using wire electrical discharge machine and the contours of the cut were measured using a coordinate measuring machine. The prior treatment of the specimens was simulated using the finite-element method. An appropriate boundary condition and temperature-dependent material model were employed. The finite-element model was validated against neutron-diffraction measurement data. The results showed a good agreement in normal and tangential directions of stress.

Effect of Process Routing on Machining Deformation for Multi-Frame Double Sided Monolithic Components

2010 ◽  
Vol 97-101 ◽  
pp. 2894-2897 ◽  
Author(s):  
Zhi Tao Tang ◽  
Zhan Qiang Liu ◽  
Li Qiang Xu
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Coordinate Measuring Machine ◽  
Element Model ◽  
Fe Model ◽  
Clamping Force ◽  
Optimal Process ◽  
Machining Deformation ◽  
Measuring Machine ◽  
Monolithic Components

When machining aerospace monolithic components, a severe deformation can be observed due to the release and redistribution of the original residual stresses, together with the action of cutting loads and clamping force. In this paper, a finite element model predicting machining deformation was developed considering the above mentioned multi-factors coupling effects. Based on the model, the effect of process routing on machining deformation for multi-frame double sided monolithic components was studied. To validate the FE model, true frame components were machined and deformations were measured on a Coordinate Measuring Machine. The result revealed that the prediction model is credible. At last the paper puts forwards optimal process routing based on minimizing the machining deformation.

Validation of Residual Stresses of Finite Element Simulation of Multi Pass Butt-Welded Plates Using the Contour Method

2011 ◽  
Vol 681 ◽  
pp. 67-72
Author(s):  
Eduardo Rodríguez ◽  
Cristina Martín ◽  
José Luis Cortizo ◽  
Julio Guirao ◽  
José Manuel Sierra
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Finite Element Simulation ◽  
Fe Simulation ◽  
Coordinate Measuring Machine ◽  
Contour Method ◽  
Element Simulation ◽  
Measuring Machine ◽  
Number Of Passes ◽  
Good Agreement

In this paper a comparison between the results obtained using multi pass welding finite element (FE) simulation and the contour method was made to evaluate the accuracy in residual stresses simulated for plates with different thicknesses. The contour method has been used to measure the residual stresses in multi pass butt-welded plates. Two 316 austenitic stainless steel multi pass Metal Inert Gas (MIG) butt-welded plates of 10 mm thickness were cut using wire Electric Discharge Machining (EDM). The measurements of the cross-section were made with a coordinate measuring machine (CMM) and the points obtained were used to calculate the residual stresses by mean of static analysis of finite elements. A multi pass welding FE simulation of the two plates was made to obtain the residual stresses after time cooling. The simulated results are generally in good agreement with the experimental measurements. Other plates of 25 mm thickness and the same material were multi pass MIG butt-welded to evaluate the behavior with different thicknesses. In this case the number of passes was 11. The same method was applied to obtain the residual stresses. A comparison between different thicknesses was made. The residual stresses validation will allow the finite element simulation to be used for the later simulation of residual stresses relaxation.

Effect of the uncertainty of multi-cut contour method and friction coefficient on residual stresses of constrained groove pressing process

2020 ◽  
pp. 095440622094890
Author(s):  
F Nazari ◽  
M Honarpisheh ◽  
H Zhao
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Residual Stresses ◽  
Finite Element Model ◽  
Element Model ◽  
Contour Method ◽  
Ultrafine Grained ◽  
First Pass ◽  
Uncertainty Of Results ◽  
Ultrafine Grained Microstructure

Constrained groove pressing (CGP) process is a severe plastic deformation (SPD) method that can create ultrafine-grained microstructure in the sheet metals. In this study, residual stresses of the CGP process and the effect of the friction coefficient on the residual stresses were investigated. The residual stresses were measured in two directions using a multi-cut contour method and a mathematical-finite element model was developed to estimate the uncertainty of results of the multi-cut contour method. In order to study the effect of the friction coefficient on the residual stresses, a 3D finite element model was employed and the results of it were validated with the experimental results of the CGP process. According to the results, residual stresses in the first pass of CGP are compressive on the surface and gradually change to tension at the center of the thickness. Investigation of the effect of the first cut on the residual stresses and uncertainty of the second cutting plane showed that the effect of the first cut is only confined to regions near the intersection of the two cuts. Distancing from the intersection of two cuts causes the effect of the first cut to be ineffective on the second cut. Also, evaluation of the effect of friction coefficient on the residual stress illustrated that friction has a direct relationship with the residual stresses.

scholarly journals Residual Stress From Cold Expansion of Fastener Holes: Measurement, Eigenstrain, and Process Finite Element Modeling

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Renan L. Ribeiro ◽  
Michael R. Hill
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Slow Crack Growth ◽  
Measurement Data ◽  
Equivalent Plastic Strain ◽  
Contour Method ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Cold Expansion

Cold expansion (CX) is a material processing technique that has been widely used in the aircraft industry to enhance fatigue life of structural components containing holes. CX introduces compressive hoop residual stresses that slow crack growth near the hole edge. The objective of this paper is to predict residual stresses arising from cold expansion using two different finite element (FE) approaches, and compare the results to measurement data obtained by the contour method. The paper considers single-hole, double-hole, and triple-hole configurations with three different edge margins. The first FE approach considers process modeling, and includes elastic–plastic behavior, while the second approach is based on the eigenstrain method, and includes only elastic behavior. The results obtained from the FE models are in good agreement with one another, and with measurement data, especially close to the holes, and with respect to the effect of edge margin on the residual stress distributions. The distribution of the residual stress and equivalent plastic strain around the holes is also explored, and the results are discussed in detail. The eigenstrain method was found to be very useful, providing generally accurate predictions of residual stress.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

A Finite Element Model of Orthogonal Metal Cutting

1985 ◽  
Vol 107 (4) ◽  
pp. 349-354 ◽  
Author(s):  
J. S. Strenkowski ◽  
J. T. Carroll
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Residual Stresses ◽  
Finite Element Model ◽  
Metal Cutting ◽  
Element Model ◽  
Effective Plastic Strain ◽  
Orthogonal Metal Cutting ◽  
Chip Separation ◽  
Chip Geometry

A finite element model of orthogonal metal cutting is described. The paper introduces a new chip separation criterion based on the effective plastic strain in the workpiece. Several cutting parameters that are often neglected in simplified metal-cutting models are included, such as elastic-plastic material properties of both the workpiece and tool, friction along the tool rake face, and geometry of the cutting edge and workpiece. The model predicts chip geometry, residual stresses in the workpiece, and tool stresses and forces, without any reliance on empirical metal cutting data. The paper demonstrates that use of a chip separation criterion based on effective plastic strain is essential in predicting chip geometry and residual stresses with the finite element method.

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

2000 ◽  
Vol 123 (1) ◽  
pp. 150-154
Author(s):  
John H. Underwood ◽  
Michael J. Glennon
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Yield Strength ◽  
Residual Stresses ◽  
Solid Mechanics ◽  
Element Model ◽  
Pressure Vessels ◽  
Material Strength ◽  
Element Analysis

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.

scholarly journals Numerical investigation of plastic flow and residual stresses generated in hydroformed tubes

2021 ◽  
pp. 146442072198974
Author(s):  
A Ktari ◽  
A Abdelkefi ◽  
N Guermazi ◽  
P Malecot ◽  
N Boudeau
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Finite Element Model ◽  
Plastic Flow ◽  
Tube Hydroforming ◽  
Three Dimensional ◽  
Element Model ◽  
Tube Cross Section ◽  
Straight Wall ◽  
Hydroforming Process

During tube hydroforming process, the friction conditions between the tube and the die have a great importance on the material plastic flow and the distribution of residual stresses of the final component. Indeed, a three-dimensional finite element model of a tube hydroforming process in the case of square section die has been performed, using dynamic and static approaches, to study the effect of the friction conditions on both plastic flow and residual stresses induced by the process. First, a comparative study between numerical and experimental results has been carried out to validate the finite element model. After that, various coefficients of friction were considered to study their effect on the thinning phenomenon and the residual stresses distribution. Different points have been retained from this study. The thinning is located in the transition zone cited between the straight wall and the corner zones of hydroformed tube due to the die–tube contact conditions changes during the process. In addition, it is clear that both die–tube friction conditions and the tube bending effects, which occurs respectively in the tube straight wall and corner zones, are the principal causes of the obtained residual stresses distribution along the tube cross-section.

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