Examination of the Optimal Local Model Size in the Three-Dimensional Local Hybrid Method

2006 ◽  
Vol 326-328 ◽  
pp. 991-994
Author(s):  
Kenji Machida ◽  
Takanori Ueno ◽  
Hirohisa Oyama
Keyword(s):  
Aspect Ratio ◽  
Hybrid Method ◽  
Three Dimensional ◽  
Tensile Load ◽  
Local Model ◽  
Optimal Size ◽  
J Integral ◽  
Bending Load ◽  
Interior Stress ◽  
Model Size

The interior stress field of the surface crack specimen subjected to a uniform tensile load has been successfully analyzed by the 3-D local hybrid method. In this study, it was examined whether the 3-D local hybrid method was applicable to the specimen subjected to the bending load. It has been understood that the decision of the optimal size of the local model is indispensable in the improvement of accuracy from the previous research. Then, the width and thickness of the local model were changed widely, and analyses were carried out to find the optimal hybrid local model size. Moreover, it was examined how to decide the optimal size of the hybrid local model with various crack length and aspect ratio of the specimen. The optimal size of the hybrid local model was examined from the comparison with the J integral of the whole model.

Application of the Three-Dimensional Local Hybrid Method to the Structure with a Surface Crack Subjected to Bending Load

2007 ◽  
Vol 345-346 ◽  
pp. 469-472 ◽  
Author(s):  
Kenji Machida ◽  
Takanori Ueno
Keyword(s):  
Free Surface ◽  
Hybrid Method ◽  
Surface Crack ◽  
Three Dimensional ◽  
High Accuracy ◽  
Local Model ◽  
J Integral ◽  
Uniform Load ◽  
Bending Load ◽  
Model Size

We developed the 3-D local hybrid method to evaluate the 3-D stress field inside the specimen from displacement data on the free surface obtained from the 2-D intelligent hybrid method. When a uniform load was applied to the structure with a surface crack, high accuracy was already acquired in stress analyses. The 3-D local hybrid method was anew applied to a structure with a surface crack which is subjected to bending load. It is expected that the accuracy depends on local model size. In this study, the width, the thickness and the height of the local model were changed widely, and analyses were carried out. Then the size of the local model necessary for the analyses was examined. Assessment of analyses was performed by comparing J integral value of a whole model and a local model.

Examination of the Optimal Local Model Size of Structure with a Surface Crack in the 3-D Local Hybrid Method

2008 ◽  
Vol 33-37 ◽  
pp. 73-78
Author(s):  
Kenji Machida ◽  
Takanori Ueno
Keyword(s):  
Free Surface ◽  
Hybrid Method ◽  
Surface Crack ◽  
High Accuracy ◽  
Local Model ◽  
J Integral ◽  
Full Model ◽  
Uniform Load ◽  
Bending Load ◽  
Model Size

We developed the 3-D local hybrid method to evaluate the 3-D stress field inside the specimen from displacement data on the free surface obtained from the 2-D intelligent hybrid method. When a uniform load was applied to the structure with a surface crack, high accuracy was already acquired in stress analyses. The 3-D local hybrid method was newly applied to structure with a surface crack which is subjected to bending load. It is expected that the accuracy depends on local model size. In this study, the width, the thickness and the height of the local model were changed widely, and analyses were carried out. Then the size of the local model necessary for the analyses was examined. Assessment of analyses was performed by comparing J integral value of a full model and the local model.

Evaluation of the J Integral of a Surface Crack by the Three-dimensional Local Hybrid Method

2006 ◽  
Vol 321-323 ◽  
pp. 28-31
Author(s):  
Kenji Machida ◽  
Gaku Mizukami ◽  
Hirohisa Oyama
Keyword(s):  
Stress Field ◽  
Relative Error ◽  
Hybrid Method ◽  
Surface Crack ◽  
Three Dimensional ◽  
High Accuracy ◽  
Problem Analysis ◽  
J Integral ◽  
Uniform Load ◽  
Bending Load

To evaluate the 3-D stress field inside a specimen from displacement data on the free surface obtained from the 2-D intelligent hybrid method, we developed the 3-D local hybrid method based on inverse problem analysis. In a previous study, when a uniform load was applied to a structure with a surface crack, it was demonstrated that the stress field was analyzed with high accuracy. In this study, the 3-D local hybrid method was applied to a structure with a surface crack subjected to bending load. However, a suitable solution was not able to be obtained on a bending problem. Therefore, another method was applied. The relative error between the J integral value of the whole model and the local model was compared, and accuracy was investigated. First, the variation of accuracy with width and thickness was examined. If thickness is increased, the relative error decreases as found in the uniform load case. Moreover, as width increases, the relative error decreases. However, even if width and thickness become large, accuracy does not necessarily become better. Therefore, the relative error was compared and a suitable hybrid size was examined.

Fully-Plastic J and CTOD Solutions for Pipes With Circumferential Surface Cracks Subjected to Combined Bending and Tension

2011 ◽  
Author(s):  
Lui´s F. S. Parise ◽  
Claudio Ruggieri
Keyword(s):  
Material Properties ◽  
Tensile Load ◽  
Estimation Procedure ◽  
Large Set ◽  
J Integral ◽  
Surface Cracks ◽  
Defect Assessment ◽  
Wide Range ◽  
Bending Load ◽  
Assessment Procedures

This work provides an estimation procedure to determine the J-integral and CTOD for pipes with circumferential surface cracks subjected to combined bending and tensile load for a wide range of crack geometries and material (hardening) based upon fully-plastic solutions. A summary of the methodology upon which J and CTOD are derived sets the necessary framework to determine nondimensional functions h1 and h2 applicable to a wide range of crack geometries and material properties characteristic of structural, pressure vessel and pipeline steels. The extensive nonlinear, 3-D numerical analyses provide a large set of solutions for J and CTOD which enters directly into fitness-for-service (FFS) analyses and defect assessment procedures of cracked pipes and cylinders subjected to bending load.

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