Effect of Flaw Dimensions on Ductile Fracture Behavior of Non-Aligned Multiple Flaws in a Plate

2011 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Kunio Hasegawa ◽  
Koichi Saito
Keyword(s):  
Ductile Fracture ◽  
Flat Plate ◽  
Fracture Behavior ◽  
Maximum Load ◽  
Surface Flaws ◽  
Fracture Tests ◽  
The Difference ◽  
Almost All ◽  
Maximum Minimum

The fitness-for-service codes require the characterization of non-aligned multiple flaws for flaw evaluation, which is performed using a flaw proximity rule. Worldwide, almost all such codes provide their own proximity rule, often with unclear technical bases of the application of proximity rule to ductile or fully plastic fracture. In particular, the effect of flaw dimensions of multiple surface flaws on fully plastic fracture of non-aligned multiple flaws had not been clear. To clarify the effect of the difference of part through-wall and through-wall flaws on the behavior of fully plastic fracture, the fracture tests of flat plate specimens with non-aligned multiple part through-wall flaws were conducted. When the flaw depth a was shallow with 0.4 in ratio of a to thickness t, the maximum load Pmax occurred at penetration of multiple flaws and the effect of vertical distance of non-aligned multiple flaws H on Pmax was not so significant. However, when flaw depth was deep with 0.8 in a/t, Pmax occurred after penetration of flaws and the effect of H on Pmax could be seen clearly. It was judged that the through-wall flaw tests were appropriate for discussion of the effect of H on Pmax and the alignment rule of multiple flaws. In addition, in order to clarify the appropriate length parameter to estimate Pmax of test specimens with dissimilar non-aligned through-wall multiple flaws, the fracture tests of plate specimens were also conducted. The effect of different flaw length on Pmax was discussed with maximum, minimum and averages of dissimilar non-aligned multiple flaw lengths. Experimental results showed that the maximum length lmax would be an appropriate length parameter to estimate Pmax, when the non-aligned multiple through-wall flaws were dissimilar.

Experimental Study of Ductile Fracture for Non-Aligned Multiple Flaws in a Plate

2009 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Kunio Hasegawa ◽  
Koichi Saito ◽  
Bostjan Bezensek
Keyword(s):  
Experimental Study ◽  
Ductile Fracture ◽  
Estimation Procedure ◽  
Maximum Load ◽  
Experimental Results ◽  
Collapse Load ◽  
Plate Specimen ◽  
Fracture Tests ◽  
Almost All

The fitness-for-service code requires the characterization of non-aligned multiple flaws for the flaw evaluation, which is performed using a flaw proximity rule. Worldwide almost all codes provide own proximity rule, often with unclear technical bases of the application of proximity rule to ductile fracture. To clarify the appropriate proximity rule for non-aligned multiple flaws in fully plastic fracture, fracture tests on flat plate specimen with non-aligned multiple through wall flaws were conducted at ambient temperature. The emphasis of this study was put on the flaw alignment rule, which determines whether non-aligned flaws are treated as independent or aligned onto the same plane for the purpose of flaw evaluations. The effects of the flaw separation and flaw size on the maximum load were investigated. The experimental results were compared with the estimations of the collapse load using the alignment rules in the ASME Section XI, BS7910 and API 579-1 codes. A new estimation procedure specific to the fully plastic fracture was proposed and compared with the comparison with the experimental results.

Ductile Fracture Strength of Ni-Based Alloy With an Inch Thickness

2010 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Koichi Saito
Keyword(s):  
Flat Plate ◽  
Limit Load ◽  
Maximum Load ◽  
Assessment Procedure ◽  
Element Analysis ◽  
Butt Weld ◽  
Metal Plates ◽  
Failure Assessment ◽  
Fracture Tests ◽  
The Difference

To develop the failure assessment procedure of Ni-based alloy, the fracture tests of flat plate specimens with a rectangular flaw were conducted at 302°C in temperature. The flat plate specimens were base metal plates, NCF600 and butt weld joints, whose weld metal was Alloy 182 with an inch (25 mm) in thickness. The maximum load at 302°C could be estimated by the limit load analysis (LLA) and twice elastic slope (TES) method with finite element analysis. In addition, the difference between maximum load obtained by the fracture tests and estimations by LLA and TES method became smaller with increasing the flaw area. The net stress at the maximum load depends on the flaw depth and this tendency in Ni-based alloy at 302°C is almost the same as the Hasegawa’s experimental proposal obtained by the fracture tests of austenitic stainless steel.

Experimental Study on the Flaw Characterization of Multiple Flaws for Ductile Fracture

2011 ◽  
Author(s):  
Fuminori Iwamatsu ◽  
Katsumasa Miyazaki ◽  
Koichi Saito ◽  
Tetsuya Hamanaka ◽  
Yoshiaki Takahashi
Keyword(s):  
Ductile Fracture ◽  
Flat Plate ◽  
Testing Machine ◽  
The United States ◽  
Flat Plates ◽  
Combination Rules ◽  
Ductile Fractures ◽  
Fracture Tests ◽  
Flaw Characterization

Flaw characterization of multiple flaws for ductile fractures was verified by comparing results of flat plate fracture tests and flaw combination rules in typical fitness-for-service codes. Single or double coplanar surface flaws were introduced into flat plate specimens made of Type 304 stainless steel using an electric discharge machine. Fracture tests of sixteen flat plates with flaws were conducted using a tensile testing machine. According in results of the fracture tests, collapse behavior for flat plates with double coplanar flaws was divided into two broad categories. One was coalescence behavior, in which the double flaws combined before the wall was penetrated. The other was penetration behavior, in which the wall was penetrated before coalescence. Rules for characterizing multiple flaws in fitness-for-service codes in Japan, the United States, and Europe were surveyed in order to compare them with test results. When the multiple flaws satisfy the criteria of rules in fitness-for service codes, a single combined flaw is assumed to conservatively estimate the limit load analysis for a ductile fracture. Flaw combination rules in typical fitness-for-service codes were found to conservatively estimate ductile fractures.

Experimental Study for Proximity Rule of Multiple Flaws for Ductile Fracture

2004 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Kunio Hasegawa ◽  
Takeshi Shimamura
Keyword(s):  
Aspect Ratio ◽  
Ductile Fracture ◽  
Fracture Behavior ◽  
Maximum Load ◽  
Tensile Tests ◽  
Fracture Pattern ◽  
The Other ◽  
Plastic Collapse ◽  
Intensity Factors ◽  
Class 1

The proximity rule of multiple flaws in ASME B&PV Code Section XI 2003 addenda was mainly determined by the evaluation of stress intensity factors from the viewpoint of brittle fracture. Since the austenitic steel and carbon steel for class 1 piping shows a ductile manner in fracture, a new proximity rule for ductile fracture is required. To understand the fracture behavior of multiple flaws, tensile tests, using flat plate specimens made of Type 304SS with twin flaws, were conducted. When the shapes of twin flaws were semi-circular with aspect ratio, a/l = 0.5, the effect of the space of multiple flaws on maximum load is clear. On the other hand, the effect of flaw spacing on maximum load was insignificant for flat multiple flaws with 0.167 in a/l. The effect of space of multiple flaws, aspect ratio of multiple flaws on ductile fracture pattern was discussed. Finally, the proximity rule for plastic collapse was proposed in this paper.

Improvement of an Ellipsoidal Void Model for Simulating Ductile Fracture Behavior

2013 ◽  
Vol 577-578 ◽  
pp. 93-96
Author(s):  
Kazutake Komori
Keyword(s):  
Finite Element ◽  
Ductile Fracture ◽  
Fracture Behavior ◽  
Fracture Strain ◽  
Volume Fraction ◽  
Deformation Gradient ◽  
Simple Relationship ◽  
The Matrix ◽  
The Difference ◽  
Deformation Gradients

An ellipsoidal void model for simulating ductile fracture behavior was proposed by the author [K. Komori: Mech. Mater., Vol. 60 (2013), p. 36]. The nominal fracture strain calculated from this model is slightly larger than that calculated from the finite-element void cell when the initial void volume fraction is specified. To decrease the difference, an assumption must be made that the deformation gradient of the void does not coincide with that of the matrix. This study proposes a simple relationship between the two deformation gradients that produces agreement between the nominal fracture strain calculated using the ellipsoidal void model and that using the finite-element void cell.

Ductile Fracture Simulation of Mulitple Surface Flaws

2011 ◽  
Author(s):  
Kazuhiro Suga ◽  
Katsumasa Miyazaki ◽  
Ryotaro Senda ◽  
Masanori Kikuchi
Keyword(s):  
Ductile Fracture ◽  
Fracture Behavior ◽  
Tensile Load ◽  
Crack Interaction ◽  
Cracked Plates ◽  
Fracture Simulation ◽  
Crack Problems ◽  
Surface Flaws ◽  
Fracture Processes ◽  
Effect Of Surface

Effect of surface flaw on ductile fracture behavior of non-aligned multiple flaws in plate is studied numerically using Gurson’s constitutive equation. Based on experiments, 2 parallel crack problems are simulated. In experiments and simulation crack coalescence, crack non coalescence and crack interaction was observed. In all cases, ductile fracture processes are obtained and results are compared with experimental ones. In this study, a new alignment rule for the prediction of maximum tensile load or rupture load for multiple cracked plates is compared with the simulation result.

Macroscopic fracture behavior of nickel foam under tension

2016 ◽  
Vol 12 (1) ◽  
pp. 110-118 ◽  
Author(s):  
Q.C. Yang ◽  
M.J. Zhang ◽  
P. S. Liu
Keyword(s):  
Fracture Behavior ◽  
Dense Body ◽  
Nickel Foam ◽  
Maximum Load ◽  
Metallic Nickel ◽  
Tensile Fracture ◽  
Displacement Curve ◽  
Content Type ◽  
Apparent Strain ◽  
The Difference

Purpose – The samples of nickel foam with porosity of about 88 percent were uniaxially tensioned at room temperature, and the phenomena of tensile fracture were compared with that from the fully dense plate of metal nickel. The purpose of this paper is to investigate the differences between their behaviors of tensile fracture. Design/methodology/approach – The tensile test was carried out by using the tester of CMT-series microcomputer-controlled electronic universal testing machine. The difference of tensile fracture behavior between the nickel foam and the dense metal nickel was discussed by analyzing the load-displacement curve and the microscopical fracture. Findings – The results indicated that, nickel foam also displayed the feature of macroscopic plastic-deformation during tension, but it showed a macroscopic brittleness much more than that of the fully dense body. The axial apparent strain at the maximum load for the foamed sample was markedly less than that for the dense one. In addition, an obviously gradual course exhibited for the foamed body during tensile failure and a rapidly instant course for the dense body correspondingly. Originality/value – There have been some studies on the tensile behavior for metal foams, but much less than on the compression, and the relevant works are mostly for aluminum foam. The present work provides the investigations on the difference of tensile fracture behavior between the nickel foam and the dense metal nickel, as well as that of the corresponding samples in various cases with different tensile velocities. It is found that the porosity can make a remarkable decrease of the apparent strain at the maximum load and a significant increase of the macroscopical brittleness for the metallic nickel under tension.

Fracture Tests of Flat Plate and Pipe With Non-Aligned Multiple Flaws

2017 ◽  
Author(s):  
Fuminori Iwamatsu ◽  
Katsumasa Miyazaki ◽  
Koichi Saito
Keyword(s):  
Experimental Data ◽  
Ductile Fracture ◽  
Flat Plate ◽  
Evaluation Method ◽  
Tensile Load ◽  
Pressure Vessels ◽  
Flat Plates ◽  
Bending Load ◽  
Fracture Tests ◽  
Flaw Characterization

Fracture tests of flat plates and pipes with non-aligned multiple flaws were conducted to investigate an appropriate flaw characterization rule for ductile fracture evaluation. Worldwide fitness-for-service codes, such as the JSME Code and the ASME Boiler and Pressure Vessels Code provide flaw characterization rules for flaws detected by in-service inspection. Since the flaw characterization rules seems to be determined based on linear-elastic fracture mechanics, developing appropriate rules remains a ductile fracture evaluation issue. Although experimental approaches have been attempted to establish an evaluation method for ductile fractures of non-aligned multiple flaws, further efforts are required. Hence, this study deals with expanding the experimental data of a flat plate subjected to tensile load and a pipe subjected to bending load. Each specimen was given one, two, or three through-wall flaws by electrical discharge machining. The tensile tests of flat plate specimens and the 4-point bending tests of pipe specimens were conducted to observe the collapse behavior and obtain load-displacement relationships. Flaw interactions, which depend on the distances between two flaws, were observed from the test results. The experimental data to investigate an evaluation method were expanded by performing fracture tests on the flat plate and pipe specimens.

Evaluation Procedure of Limit Load for Non-Aligned Multiple Flaws

2013 ◽  
Author(s):  
Fuminori Iwamatsu ◽  
Katsumasa Miyazaki ◽  
Hidekazu Takazawa ◽  
Koichi Saito
Keyword(s):  
Correlation Coefficients ◽  
Limit Load ◽  
Evaluation Procedure ◽  
Collapse Load ◽  
Evaluation Procedures ◽  
Direct Distance ◽  
Fracture Tests ◽  
Almost All ◽  
Technical Basis

The fitness-for-service codes such as the ASME Boiler and Pressure Vessel Code Section XI require the characterization of non-aligned multiple flaws for flaw evaluation, which is performed using a flaw alignment rule. Worldwide, almost all such codes provide their own alignment rule, often with an unclear technical basis regarding the application of the rule to plastic collapse due to ductile fracture as prescribed by limit load analysis based on a net-section approach. Therefore, evaluation procedures to calculate collapse load for non-aligned multiple flaws have been proposed in various experimental and analytical studies. In these proposals, a collapse load for non-aligned multiple flaws is evaluated using the net-section stress approach in consideration of the ratio of a distance between flaws to a flaw length parameter. However, because each study proposes its own appropriate length and distance parameters, which are based on a few experimental results limited to that study, the applicability of the proposed parameters to evaluation of collapse load for arbitrary flaw sizes and locations is unclear. In this study, we performed fracture test result on a flat plate with two through-wall flaws in order to determine appropriate parameters for the evaluation procedure of the collapse load for non-aligned multiple flaws. Appropriate parameters were determined by correlation coefficients obtained by comparison of maximum loads of fracture tests and collapse loads of evaluation with various parameters. We found that the appropriate parameters to apply the alignment rule with equations to evaluate collapse load for non-aligned flaws were the ratio of the vertical or direct distance between flaws to the maximum or average flaw length.

Evaluation of Ductile Fracture Behavior Using GTN Model

2014 ◽  
Author(s):  
Hidekazu Takazawa ◽  
Fuminori Iwamatsu ◽  
Katsumasa Miyazaki
Keyword(s):  
Tensile Test ◽  
Ductile Fracture ◽  
Flat Plate ◽  
Material Properties ◽  
Fracture Behavior ◽  
Monotonic Loading ◽  
Gtn Model ◽  
Plate Specimen ◽  
Safe Side ◽  
Load Displacement

Ductile fracture behavior using GTN (Gurson-Tvergaard-Needleman) model in commercial FEA code was evaluated. The material properties of the GTN model for Type 304 SS were experimentally identified. Smooth-bar and notched-bar specimens were subjected to monotonic loading by tensile test, and load-displacement curves were measured. Then, the tensile test was simulated. Material properties of the GTN model were calculated from measured and simulated load-displacement curves with inverse analysis based on Bayes’ theorem. Simulated load-displacement curves using the GTN model of different curvature notched-specimens agreed well with the measured results. To verify the evaluation of ductile fracture behavior using the GTN model, flat-plate specimen with a single surface flaw and specimen with multiple through flaws were subjected to monotonic loading. Ductile fracture of the flat-plate specimen was simulated by FEA using the GTN model using the calculated material properties. The simulated load was less than the measured load at the same displacement. The analysis using the GTN model can estimate the load on the safe side and the GTN model can conservatively simulate ductile fracture behavior.

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