A finite element ductile failure simulation method using stress-modified fracture strain model

2011 ◽  
Vol 78 (1) ◽  
pp. 124-137 ◽  
Author(s):  
Chang-Sik Oh ◽  
Nak-Hyun Kim ◽  
Yun-Jae Kim ◽  
Jong-Hyun Baek ◽  
Young-Pyo Kim ◽  
...  
Keyword(s):  
Finite Element ◽  
Fracture Strain ◽  
Ductile Failure ◽  
Simulation Method ◽  
Failure Simulation ◽  
Strain Model

Ductile Failure Simulation of Tensile Plates With Multiple Through-Wall Cracks

2009 ◽  
Author(s):  
Nak-Hyun Kim ◽  
Yun-Jae Kim ◽  
Chang-Sik Oh
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Numerical Method ◽  
Ductile Failure ◽  
Crack Coalescence ◽  
Element Analysis ◽  
Failure Simulation ◽  
Damage Theory

This paper proposes a simple numerical method to simulate plastic behaviours of tensile plates with twin through-wall cracks. The method is based on finite element analysis with a simple damage theory. To validate the proposed method, simulated results are compared with experimental data performed by Japanese researchers. Despite its simplicity, the proposed method well predicts plastic behaviours of tensile plates with twin cracks, including crack coalescence. Predicted maximum loads are overall lower than experimentally-measured ones.

Applicability of Net-Section Collapse Load Approach to Multiple-Cracked Pipe Assessment: Numerical Study

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Myeong-Woo Lee ◽  
So-Dam Lee ◽  
Yun-Jae Kim
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Parametric Study ◽  
Fracture Strain ◽  
Numerical Study ◽  
Damage Analysis ◽  
Collapse Load ◽  
Fracture Test ◽  
Strain Model

In this paper, applicability of net-section collapse load approach to circumferential multiple-cracked pipe assessment is investigated using finite element (FE) damage analysis. The FE damage analysis based on the stress-modified fracture strain model is validated against limited fracture test data of two circumferential surface-cracked pipes. Then, the systematic parametric study is performed using the FE damage analysis for symmetrical and asymmetrical surface-cracked pipes. It is found that predictions using the net-section collapse load approach tend to be more accurate with increasing the distance between two symmetrical cracks. For asymmetrical cracks, it is found that the deeper crack plays a more important role and that the existing net-section collapse load expression can be potentially nonconservative. Idealization to symmetrical cracks based on the deeper crack is proposed.

Proposal of New Combination Criterion for Pipe With Circumferential Multiple Cracks Based on Ductile Failure Simulation

2018 ◽  
Author(s):  
Myeong-Woo Lee ◽  
Kunio Hasegawa ◽  
Yun-Jae Kim
Keyword(s):  
Ductile Failure ◽  
Numerical Data ◽  
New Combination ◽  
Multiple Cracks ◽  
Damage Analysis ◽  
Fracture Test ◽  
Combination Rule ◽  
Failure Simulation ◽  
Bending Stresses ◽  
Strain Model

In this paper, the combination rule for circumferential multiple-cracked pipe assessment is investigated using finite element damage analysis. The FE damage analysis based on the stress-modified fracture strain model is validated against limited fracture test data of two circumferential surface cracked pipes. Then systematic parametric study is performed using FE damage analysis for symmetrical surface cracked pipes. Failure bending stresses are calculated using the combination rule and the net-section collapse load approach for single crack provided in ASME BPV Code. It is found that predicted failure bending stress using the combination rule might be non-conservative when the distance between two cracks is short. To overcome the problem, a new combination criterion based on crack dimensions is proposed and compared with numerical data.

Ductile Fracture Simulation Considering Strain Rate Loading Effect

2015 ◽  
Author(s):  
Hyun-Suk Nam ◽  
Ji-Soo Kim ◽  
Yun-Jae Kim ◽  
Jin-Weon Kim ◽  
Chang-Young Oh
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Dynamic Loading ◽  
Fracture Strain ◽  
Fracture Toughness Test ◽  
Loading Conditions ◽  
Loading Effect ◽  
Fracture Simulation ◽  
Dynamic Loading Conditions ◽  
Strain Model

This paper is based on a ductile failure simulation under dynamic loading conditions using finite element (FE) analyses. Recently a simple finite element method in a quasi-static test has been proposed to implement fracture simulation based on the well-known stress modified fracture strain model. The stress-modified fracture strain model is determined to be incremental damage in terms of stress triaxiality and fracture strain for dimple fracture from tensile test result with FE analyses technique. Since dynamic loading effect is especially important to assess pipe with crack-like defect, this work propose the integrated model which combines quasi-static with dynamic loading effect. In order to validate stress-modified fracture strain model in dynamic loading conditions, this paper compares results of FE analysis using proposed method with strain dependent smooth bar tests and notch tensile tests using Johnson-Cook equation. In conclusion, the stress-modified fracture strain model criterion can be calibrated by FE analyses with strain rate dependent fracture toughness test results.

Comparison of fracture strain based ductile failure simulation with experimental results

2011 ◽  
Vol 88 (10) ◽  
pp. 434-447 ◽  
Author(s):  
Nak-Hyun Kim ◽  
Chang-Sik Oh ◽  
Yun-Jae Kim ◽  
Kee-Bong Yoon ◽  
Young-Hwa Ma
Keyword(s):  
Fracture Strain ◽  
Ductile Failure ◽  
Experimental Results ◽  
Failure Simulation

Application of Stress-Modified Fracture Strain Model to Full-Scale Pipes With a Circumferential Crack in the Center of Welds

2016 ◽  
Author(s):  
Ho-Wan Ryu ◽  
Hune-Tae Kim ◽  
Hyun-Woo Jung ◽  
Yun-Jae Kim
Keyword(s):  
Finite Element ◽  
Numerical Method ◽  
Fracture Strain ◽  
Damage Model ◽  
Full Scale ◽  
Piping System ◽  
Damage Analysis ◽  
Integrity Assessment ◽  
Material Discontinuities ◽  
Strain Model

A lot of welded joints are required to connect the junctions of components in the complex piping system. The structural integrity assessment on welded pipes is especially important, because the weldments are susceptible to material discontinuities, flaws and residual stresses. Finite element (FE) damage analysis can be useful and effective method for an accurate assessment on extensive structures. For the case of welded joint, the numerical method is necessarily required to assess complex features because of material discontinuities and flaws. This study provides a simple numerical method to simulate ductile tearing in welded full-scale pipes. Stress-modified fracture strain model is applied to finite element analysis with a stress reduction technique. An element-size-dependent critical damage model is also implemented in the full-scale pipe simulations. From the results of simulation, deformation response and characteristic loads are compared with experimentally measured values to verify the application of damage model on weld material. As a result, the predictions of finite element damage analysis are in good agreement with experiments.

Hot Compression Simulation of Ti75 Alloy Based on DEFORM-3D

2012 ◽  
Vol 229-231 ◽  
pp. 55-58
Author(s):  
Jun Fan
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Simulation Method ◽  
Hot Compression ◽  
Strain Rates ◽  
Know How ◽  
Numerical Simulation Method ◽  
Control Objective ◽  
Finite Element Numerical Simulation ◽  
Deform 3D

To obtain the know-how of the deficiency for the filling capability, taking Ti75 alloy as the research object, at the same height of reducing, strain rates during forming as the control objective, the finite element numerical simulation method was used to simulate the hot compression with DEFORM-3D, analyzing the effect of the strain rates on the distribution of strain and stress.

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