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.

Numerical Study on Longitudinal Distance Effect on Failure Stress of Non-Aligned Twin Cracked Pipe

2018 ◽  
Author(s):  
Thanh-Long Nguyen ◽  
Myeong-Woo Lee ◽  
Kunio Hasegawa ◽  
Yun-Jae Kim
Keyword(s):  
Fracture Strain ◽  
Numerical Study ◽  
Distance Effect ◽  
Failure Stress ◽  
Axial Distance ◽  
Damage Analysis ◽  
Asme Code ◽  
Bending Stresses ◽  
Strain Model ◽  
Longitudinal Distance

In this study, the effect of longitudinal distance H between non-aligned twin cracks is investigated using finite element damage analysis. The FE damage analysis based on the stress-modified fracture strain model is used to calculate the failure stress of non-aligned twin cracked pipe. Parametric study on the axial distance H between non-aligned twin cracks with various crack depths and lengths were conducted and compared with predictions using the alignment rules and the net-section collapse load approach for single crack provided in ASME Code. It is shown that the trend of the predicted collapse bending stresses for the non-aligned twin cracked pipes using FE damage analysis are different from the ones using the alignment rule.

Effects of Side Groove on Fracture Toughness

2015 ◽  
Author(s):  
Ho-Wan Ryu ◽  
Hune-Tae Kim ◽  
Jae-Jun Han ◽  
Yun-Jae Kim ◽  
Jong-Sung Kim ◽  
...  
Keyword(s):  
Test Data ◽  
Fracture Strain ◽  
Failure Criteria ◽  
Compact Tension ◽  
Damage Analysis ◽  
Pipe Material ◽  
Ductile Tearing ◽  
Different Shapes ◽  
Strain Model ◽  
Good Agreement

This paper describes ductile tearing simulation for compact tension (C(T)) specimens using FE damage analysis based on the stress-modified fracture strain model. The side groove effect on J-resistance curve was estimated by experimental and analytical ways. In this paper, SA508 Grade 1A low alloy steel pipe material was considered. Tensile and C(T) specimens are simulated to determine the failure criteria with finite element method. Then, different shapes of C(T) specimens are analysed and the results from simulations are compared with test data for verification of proposed method. Overall, the predicted simulation results show good agreement with test data.

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.

Member distortional buckling behaviour of hybrid double-I-box beams

2018 ◽  
Vol 45 (8) ◽  
pp. 605-622 ◽  
Author(s):  
M.S. Deepak ◽  
V.M. Shanthi
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Parametric Study ◽  
Flexural Rigidity ◽  
Numerical Study ◽  
Plate Thickness ◽  
Distortional Buckling ◽  
Study Results ◽  
Box Beams ◽  
The Moment

This paper compiles the experimental and finite-element parametric study on member distortional buckling behaviour of new built-up metal hybrid double-I-box beams (HDIBBs). The cross-section of this built-up beam is unique and looks similar to the shape of a double-I-box fabricated using four channel sections. The flange plates were provided with an intermediate stiffener. In these built-up beams there is more material in the flange portions far away from the horizontal centroidal axis of their cross-section. Hence, there is an increase in the flexural rigidity that enhances the moment capacity of the beam, under major axis bending. The geometry consists of torsionally rigid closed-box web portion that provides high resistance to minor axis lateral-buckling. The varying parameters considered were the ratio of yield stresses of the flange to the web steel plates, the ratio of breadth to the depth of the section, and the flange plate thickness. In the experimental programme, all the HDIBB members failed due to kinds of distortional buckling which was identified by web buckling and flange twist along edges. The results revealed that when flange plate slenderness increases there is a drop in the moment resistance capacity of the beams. The numerical study was performed using ABAQUS software. In comparison, there was good agreement between experimental and numerical results. The validated finite element models were further extended to perform parametric studies on ideal HDIBB models. Both the experimental and parametric study results were compared with the predicted strengths using effective width method equations specified in the Euro code standards EN 3-1-3. It was found that the current Euro code design rules slightly over-estimate the distortional buckling resistance capacity of closed form built-up cold-formed steel members. A new design equation was formulated and recommended for estimating the reduction in distortional buckling moment resistance capacity for HDIBBs.

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

Applicability of Net-Section Collapse Load Approach to Maximum Load Predictions of Multiple Circumferential Cracked Pipes: Numerical Study

2015 ◽  
Author(s):  
Myeong-Woo Lee ◽  
Seung-Jae Kim ◽  
So-Dam Lee ◽  
Jun-Young Jeon ◽  
Yun-Jae Kim
Keyword(s):  
Experimental Data ◽  
Numerical Method ◽  
Test Data ◽  
Numerical Study ◽  
Maximum Load ◽  
Load Carrying Capacity ◽  
Collapse Load ◽  
Crack Geometry ◽  
Large Sets ◽  
Load Carrying

To estimate maximum load-carrying capacity of pipes with multiple circumferential cracks, the net-section collapse load approach has been proposed. Although the proposed method has been validated against pipe test data, experimental data are quite limited due to large sets of variables to be considered. In this paper, a numerical method is proposed to generate virtual pipe test data with wide ranges of crack geometry and interspacing. To get confidence of the proposed numerical method, it is firstly applied to simulate existing 4-inch diameter schedule 80 pipes with two circumferential cracks. Predicted maximum loads agree well with experimental data. Then the proposed method is applied to generate maximum loads for wider ranges of crack geometry and loading conditions. It is found that the net-section collapse load approach works well for all cases considered.

Numerical study on racking behavior of light steel frames with K-shaped bracing

2019 ◽  
Vol 16 (2) ◽  
pp. 238-247
Author(s):  
Mohammad Javad Kazemi ◽  
Shahabeddin Hatami ◽  
Abdolreza Zare ◽  
Ali Parvaneh
Keyword(s):  
Finite Element ◽  
Parametric Study ◽  
Failure Modes ◽  
Numerical Study ◽  
Shear Walls ◽  
Element Analysis ◽  
Content Type ◽  
Lateral Strength ◽  
Cold Formed Steel ◽  
Lateral Behavior

Purpose This paper aims to study the lateral behavior of cold-formed steel walls with K-shaped bracing by finite element modeling. Design/methodology/approach The braces which have the same section as those for studs and tracks are connected to the frame by screw connections. By pushover analysis, lateral performance of two frame categories, with different dimensions and bracing arrangements, is examined, and the force-displacement diagram and the ultimate strength of walls are extracted. Probable failure modes during lateral loading including distortional buckling of studs, buckling in braces and failure of connections are simulated in the numerical model, and some strengthening suggestions would be offered to prevent brittle failures and, therefore, to increase the lateral strength of the walls. Findings The strengthened walls are examined, and their seismic behavior is compared with the original walls. Finally, a parametric study is carried out to evaluate the effect of factors such as thickness of frame members, frame height and yield tension of members on lateral behavior of the shear walls. Originality/value In the present research, lateral strength and failure modes of nine types of cold-formed steel shear walls with different arrangements of K-shaped bracing are examined by non-linear finite element analysis, and a parametric study is carried out to extract the effect of the wall frame characteristics on the lateral behavior. Shear walls are classified into two series.

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.

A Method to Quantify Thermal Aging Effect on Fracture Toughness of Cast Stainless Steels Using Small Punch Test

2014 ◽  
Author(s):  
Jun-Young Jeon ◽  
Dong-Il Ryu ◽  
Yun-Jae Kim ◽  
Mi-Yeon Lee ◽  
Jin-Weon Kim
Keyword(s):  
Fracture Toughness ◽  
Test Data ◽  
Stainless Steels ◽  
Fracture Strain ◽  
Fracture Toughness Test ◽  
Small Punch ◽  
Fracture Simulation ◽  
Toughness Test ◽  
Axial Fracture ◽  
Strain Model

In this study, a method to predict fracture toughness of aged cast austenitic stainless steels (CASSs) using small punch (SP) test and finite element (FE) analysis is proposed. Grade CF8M is considered and thermally aged up to 5,000 hours at 400°C. SP tests and fracture toughness test using compact tension (C(T)) specimen are conducted with virgin (unaged) and aged CF8M. FE analyses performed in this study use ductile fracture simulation technique with ‘the multi-axial fracture strain model’. The multi-axial fracture strain model for each aged CF8M are determined from SP test data and FE analyses. Fracture toughness of aged CF8M are predicted by conducting fracture toughness test simulations using FE damage analyses. Predicted fracture toughness results are compared with C(T) data to validate the method suggested in this study. The predicted initiation toughness values are predicted well and fracture toughness values are slightly conservative compared to test data.

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