scholarly journals Failure Prediction for the Tearing of a Pin-Loaded Dual Phase Steel (DP980) Adjusting Guide

2019 ◽  
Vol 9 (24) ◽  
pp. 5460 ◽  
Author(s):  
Seokmoo Hong ◽  
Jinkyoo Kim ◽  
Taehwan Jun
Keyword(s):  
Large Strain ◽  
Damage Model ◽  
Failure Prediction ◽  
Strain Range ◽  
Complex Loading ◽  
Tensile Tests ◽  
Material Behavior ◽  
Image Correlation ◽  
Failure Behavior ◽  
Loading Mode

Owing to their outstanding strength, in recent years, there has been an increased use of advanced high-strength steel (AHSS) sheets in the automotive sector. Their low formability, however, poses a challenge to forming, and failure prediction requires accurate knowledge of its material behavior over a large strain range up to ultimate failure, in order to exploit their full capacity in forming, but also in crash events. For predicting the fracture of an adjusting guide loaded by a pin, first, the force–displacement data are extracted from tensile tests using DP980 specimens of diverse shapes, all of which represent a certain loading mode. Using digital image correlation (DIC), we determine the stress triaxialities corresponding to the diverse loading conditions and establish the triaxiality failure diagram (TFD), which serves as the basis for the generalized incremental stress state-dependent damage model (GISSMO). Then, the damage parameters (necking and failure strains) are determined for each loading mode by reverse engineering-based optimization. Finally, these damage parameters are applied to the adjusting guide, and the numerical results are compared with the experimental data. Comparisons of the external load–displacement curves and the local equivalent strain distributions show that using the damage model with the material parameters obtained in here allows for the accurate prediction of the guide’s failure behavior, and the applicability of GISSMO to complex loading cases.

scholarly journals White-light speckle image correlation applied to large-strain material characterization

2009 ◽  
pp. 377-392
Author(s):  
Giovanni B. Broggiato ◽  
Luca Cortese
Keyword(s):  
Material Characterization ◽  
Plastic Material ◽  
Large Strain ◽  
Equivalent Stress ◽  
Tensile Tests ◽  
Equivalent Strain ◽  
Image Correlation ◽  
Plastic Behavior ◽  
Full Field ◽  
Measurement Devices

In experimental mechanics, the possibility of tracking on component surfaces the full-field stress and strain states during deformation can be utilized for many purposes such as formability limits determination, quantification of stress intensification factors, material characterization and so on. Concerning the last topic, an interesting application could be a direct identification of the elasto-plastic material response up to large deformation. It is well known, in fact, that with traditional measurement devices it is possible to retrieve the true equivalent stress versus true equivalent strain data from tensile tests only up to the onset of necking, where localization starts to occur. This work aims to show how from the knowledge of a tensile test full-field strain and of load data it will be possible to obtain the full-stress field as well as the complete material elasto-plastic behavior.

Input Data Determination for Large Strain Simulations

2015 ◽  
Vol 751 ◽  
pp. 124-130
Author(s):  
Jan Džugan ◽  
Martina Maresova ◽  
Jan Nachazel
Keyword(s):  
Numerical Simulations ◽  
Input Data ◽  
Large Strain ◽  
Fem Simulation ◽  
Material Behavior ◽  
Production Costs ◽  
Image Correlation ◽  
Compression Tests ◽  
Material Models ◽  
Strain Measurements

Numerical simulations are widely used for forming processes optimizations nowadays. They significantly contribute to improvement of forgings quality and production costs reduction. The crucial points of the numerical simulations are material input data and implemented material models. The paper is dealing with overview of methods for the input data measurement. There are discussed tests with various options of strain measurements as well as modifications of compression tests. Part of the paper is dealing with 3D strain measurements by Digital Image Correlation (DIC) enabling local strains measurements. DIC enables direct comparison of strains experimentally measured and strains obtained by numerical simulations, which is going to be presented. Finally, possibilities of complex material description considering plastic damage are presented. The last approach is the most accurate providing the most information on material behavior for FEM simulation, the procedure includes measurements on samples of various geometries with various stress strain conditions. Examples of sample sets for these measurements are shown here together with material models describing multiaxial plastic flow and damage.

Numerical analysis of damage and failure behavior of concrete

2019 ◽  
Vol 29 (4) ◽  
pp. 570-590 ◽  
Author(s):  
Michael Brünig ◽  
Alexander Michalski
Keyword(s):  
Failure Modes ◽  
Damage Model ◽  
Numerical Procedure ◽  
Image Correlation ◽  
Failure Behavior ◽  
Correlation Technique ◽  
Strain Rate Tensor ◽  
Continuum Damage ◽  
Finite Element Program ◽  
Continuum Damage Model

The paper discusses an anisotropic continuum damage model for concrete and its numerical implementation into a finite element program to provide an efficient approach suitable for boundary-value problems analyzing nonlinear concrete behavior. The phenomenological continuum approach is based on kinematic description of damage. Irreversible deformation behavior as well as volume increase of material samples even under compression loading are simulated by a damage strain rate tensor. The elastic constitutive equations are affected by damage strain tensors modeling decrease of elastic material parameters. The numerical procedure is based on the damage predictor–elastic corrector technique and the corresponding consistent tangent modulus is presented. Different experiments have been performed and deformation fields are analyzed by digital image correlation technique. Numerical simulations of the experiments show good agreement of the results and elucidate stress and damage states in the specimens. They allow prediction of failure modes of the tested specimens agreeing well with photographs of fractured cylinders and cubes. They also demonstrate the efficiency and the applicability of the proposed continuum damage model.

A Cumulative Fatigue Damage Model for Gas Turbine Engine Disks Subjected to Complex Mission Loading

1979 ◽  
Vol 101 (4) ◽  
pp. 563-571 ◽  
Author(s):  
T. A. Cruse ◽  
T. G. Meyer
Keyword(s):  
Gas Turbine ◽  
Low Cycle Fatigue ◽  
Damage Model ◽  
Complex Loading ◽  
Gas Turbine Engine ◽  
Initial Crack ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Turbine Engine ◽  
Surface Residual Stresses

The objective of a continuing research program is to develop a low cycle fatigue (LCF) damage model which accurately evaluates the life exhaustion of military gas turbine engine disks subjected to complex loading spectra. This paper reports the results of the first phase of the effort and specifically concerns “cold region” disk bolt holes. A simple cycle LCF model is developed which accounts for nonlinear material behavior and the presence of local surface residual stresses due to machining. Nonlinear cumulative damage is clearly observed in specimen and component testing and is successfully modeled by a “double damage” principle in which an initial crack length need not be known explicitly. Testing of full-scale components under complex loading is used to verify the models.

Full-strain range characteristics of the Poisson’s ratio for coated biaxial warp-knitted fabrics under bias tensile loading

2018 ◽  
Vol 89 (10) ◽  
pp. 1997-2009 ◽  
Author(s):  
Jianwen Chen ◽  
Han Zhou ◽  
Wujun Chen ◽  
Mingyang Wang ◽  
Bing Zhao ◽  
...  
Keyword(s):  
Poisson’S Ratio ◽  
Interaction Mechanism ◽  
Strain Range ◽  
Tensile Tests ◽  
Image Correlation ◽  
Poisson's Ratio ◽  
Correlation Technique ◽  
Poisson Effect ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

It is undeniable that full-strain range characteristics of Poisson’s ratios on the behaviors of a fabric composite are crucial. However, there have been relatively few papers devoted to this subject. In this study, tensile tests of seven bias angles with a 15° increment are conducted on a typical coated biaxial warp-knitted fabric (BWKF) to estimate the Poisson’s ratios in full-strain range. By utilizing the digital image correlation technique, experimental results are processed, and detailed responses of strain contours and Poisson’s ratios are determined for specific strain states. Then, two typical types, that is recession and peak types, of the Poisson’s ratio strain curves are proposed and their characteristics evolving with the strain, bias angle and stress state are discussed. Results show that characteristics of Poisson’s ratios and strain contours vary noticeably with the yarn orientations, strain and stress levels. As the strain increases, the Poisson’s ratio of peak type first ascends markedly, and then descends moderately after arriving at a peak, generating three distinct stages: the ascending, peak and post-peak stages; in contrast, the recession type only experiences a downward trend, resulting in two characteristic stages: the recession and stable stages. In addition, there is an M-shaped relationship between the Poisson’s ratio and bias angle, with a local valley at 45°, which is not consistent with results in previous works. This investigation could provide new insights into the orientation dependence, Poisson effect and warp–weft interaction mechanism of BWKFs.

Low-Cost Flexible Strain Sensor Based on Thick CVD Graphene

NANO ◽  
2018 ◽  
Vol 13 (11) ◽  
pp. 1850126 ◽  
Author(s):  
Bailiang Chen ◽  
Ying Liu ◽  
Guishan Wang ◽  
Xianzhe Cheng ◽  
Guanjun Liu ◽  
...  
Keyword(s):  
Large Strain ◽  
Low Cost ◽  
Flexible Substrate ◽  
Graphene Film ◽  
Strain Sensor ◽  
Strain Range ◽  
Tensile Tests ◽  
Adhesive Tape ◽  
Cvd Graphene ◽  
Flexible Strain Sensor

Flexible strain sensors, as the core member of the family of smart electronic devices, along with reasonable sensing range and sensitivity plus low cost, have rose a huge consumer market and also immense interests in fundamental studies and technological applications, especially in the field of biomimetic robots movement detection and human health condition monitoring. In this paper, we propose a new flexible strain sensor based on thick CVD graphene film and its low-cost fabrication strategy by using the commercial adhesive tape as flexible substrate. The tensile tests in a strain range of [Formula: see text]30% were implemented, and a gage factor of 30 was achieved under high strain condition. The optical microscopic observation with different strains showed the evolution of cracks in graphene film. Together with commonly used platelet overlap theory and percolation network theory for sensor resistance modeling, we established an overlap destructive resistance model to analyze the sensing mechanism of our devices, which fitted the experimental data very well. The finding of difference of fitting parameters in small and large strain ranges revealed the multiple stage feature of graphene crack evolution. The resistance fallback phenomenon due to the viscoelasticity of flexible substrate was analyzed. Our flexible strain sensor with low cost and simple fabrication process exhibits great potential for commercial applications.

scholarly journals Manufacturing of Titanium Components with 3DPMD

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 562 ◽  
Author(s):  
Kevin Hoefer ◽  
Alexander Nitsche ◽  
André Haelsig ◽  
Peter Mayr
Keyword(s):  
Tensile Tests ◽  
Material Behavior ◽  
Failure Behavior ◽  
Metal Powders ◽  
Structure Property ◽  
Fracture Elongation ◽  
Structure Property Relationships ◽  
Critical Issues ◽  
Near Net Shape ◽  
Process Structure

Within this work, the 3D plasma metal deposition (3DPMD) process is introduced as an additive manufacturing process for titanium components. For this purpose, demonstrators were designed, manufactured and subsequently analyzed. Process-structure-property relationships are discussed. By analyzing the microstructure, the chemical composition and the mechanical-technological properties, it is shown that the production of titanium parts with 3DPMD is possible. The micro tensile tests showed that a load parallel to the build direction is the most critical case for the component. Furthermore, a brittle material behavior could be determined due to enhanced oxygen content in the component. By subsequent heat treatment, the brittle failure behavior could be increased to a fracture elongation of 4.6%. In sum, the 3DPMD process has the potential to manufacture near-net-shape titanium parts out of metal powders. Critical issues are the protection of the weldment and the lack of ductility of the titanium component.

Structural Integrity Assessment of Defected Gas Pipelines Using a Simplified Ductile Damage Model

2021 ◽  
Author(s):  
Ik-Joong Kim ◽  
Cheol-Man Kim ◽  
Jong-Hyun Baek ◽  
Young-Pyo Kim ◽  
Youngseog Lee ◽  
...  
Keyword(s):  
Void Growth ◽  
Structural Integrity ◽  
Fracture Strain ◽  
Damage Model ◽  
Damage Index ◽  
Stress Triaxiality ◽  
Tensile Tests ◽  
Image Correlation ◽  
Integrity Assessment ◽  
Failure Simulation

Abstract The finite element method using the damage model has been increasingly used to predict the failure of various structures. Thus, various damage models were presented, and recently, a phenomenological model called the local fracture strain model was presented, making it easy and accurate to predict the damage of the structure. This model has the advantage of defining fracture strain as a function of stress triaxiality with only a few notched tensile tests but has a limitation because it does not consider the damage evolution because of the void growth. This study presents an enhanced damage model that improves the accuracy of the failure simulation of defected structures by adding a parameter that considers stiffness degradation according to void growth to the damage model based on the fracture strain. Therefore, loading-unloading tests were conducted and the damage index of fracture was identified using a three-dimensional digital image correlation system. The failure simulation results using the proposed damage model were compared with experimental, such as notched tensile, SENT, and full-scale burst tests.

A viscoelastic in-plane damage model for fibrous composite materials

2021 ◽  
pp. 146442072110650
Author(s):  
Matheus Urzedo Quirino ◽  
Volnei Tita ◽  
Marcelo Leite Ribeiro
Keyword(s):  
Fibrous Composite ◽  
Damage Model ◽  
Strain Curve ◽  
Tensile Tests ◽  
Calibration Procedure ◽  
Material Behavior ◽  
Evaluation Procedure ◽  
Nonlinear Phenomena ◽  
Stress Strain ◽  
Plane Shear

This work presents a viscoelastic in-plane damage model for fibrous composites. The material behavior is modeled as linear viscoelastic, with brittle failure in the fiber-dominated direction, and progressive degradation of the matrix-dominated properties, when the composite is loaded perpendicularly to the fibers or in in-plane shear. An evaluation procedure has been performed by comparing computational stress-strain curves against tensile tests curves under three different displacement rates. In addition, a calibration of the viscoelastic properties, by means of the response surface methodology, is also presented. The proposed material model has shown reasonable performance up to the material reaching an experimentally-verified modulus transition zone. Besides, the viscoelastic calibration procedure has produced a good agreement with the experimental results, concerning maximum stresses. It was observed that the computational stress-strain curve has deviated from the experimental one for higher stress values, indicating that it is necessary to improve the assessment of the nonlinear phenomena, which occur within the material.

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