Mismatch Constraint Effect of Creep Crack With Modified Boundary Layer Model

2015 ◽  
Vol 83 (3) ◽  
Author(s):  
Yanwei Dai ◽  
Donghuan Liu ◽  
Yinghua Liu
Keyword(s):  
Boundary Layer ◽  
Creep Crack Growth ◽  
Stress Fields ◽  
Constraint Effect ◽  
Creep Crack ◽  
Match Condition ◽  
Maximum Value ◽  
Creep Crack Growth Rate ◽  
Material Mismatch ◽  
Mismatch Effect

Mismatch effect plays a crucial role in weldments, and an independent mismatch constraint parameter M* is proposed to characterize the material mismatch constraint effect in this paper. A mismatched modified boundary layer (MBL) model for creeping solids is developed to simulate the stress field of creep cracks in mismatched weldments. It can be found that there still exists the similarity between creep crack tip stress fields under different mismatch factors. Numerical results show that M* obtains the minimum value on the under match condition and the maximum value on the over match condition. Comparisons between M* and other geometric constraint parameters (A2(t) and Q22) are carried out and the applicability of M* is verified. A modified assessment formula for creep crack growth rate ratio is proposed based on the parameter M*. It is found that M* is a reasonable and remarkable parameter to characterize the mismatch constraint effect of creeping cracks.

Mismatch Constraint Effect for Bimaterial Interfacial Creep Crack

2016 ◽  
Vol 853 ◽  
pp. 286-290
Author(s):  
Yan Wei Dai ◽  
Ying Hua Liu ◽  
Hao Feng Chen
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Stress Field ◽  
Structural Integrity ◽  
Creep Crack Growth ◽  
Constraint Effect ◽  
Creep Crack ◽  
Engineering Practices ◽  
Material Mismatch ◽  
Mismatch Effect

Mismatch effect of weldments is important for the assessment of structural integrity at elevated temperature. The interfacial creep crack is a common model which can be found in lots of engineering practices. Recently, the constraint effect is also considered to be significant for the evaluation of creep crack growth under high temperature. In this paper, a model for bimaterial interfacial creep crack is introduced to study the mismatch constraint effect. The stress field for bimaterial interfacial creep crack is investigated. An M*-parameter is proposed to characterize the constraint effect caused by material mismatch for bimaterial creep crack. A comparison is made between the geometry constraint caused by specimen loading and mismatch constraint caused by inhomogeneous material.

Mismatch Effect on the Mode II Type Crack Tip Field in Power-Law Creeping Materials

2018 ◽  
Author(s):  
Yanwei Dai ◽  
Yinghua Liu ◽  
Yuh J. Chao
Keyword(s):  
Order Term ◽  
Crack Tip ◽  
Mode Ii ◽  
Constraint Effect ◽  
Crack Tip Field ◽  
Creep Crack ◽  
Engineering Practices ◽  
Haz Width ◽  
Material Mismatch ◽  
Mismatch Effect

The mismatch effect in weldments are widely to be seen in engineering practices. In this paper, the material mismatch effect on the mode II creep crack tip field is investigated and discussed. The effects of material mismatch and heat affected zone (HAZ) width on the C(t)-integral are presented. Both the local mismatch effect and the general mismatch effect are found to play important roles in the variations of C(t)-integral. The mismatch effect on the stress field of the mode II creep crack is also studied. The two-order term solutions are presented to characterize the material mismatch constraint effect on the mode II type creep crack. Some typical cases by considering general mismatch effect and local mismatch effect are given so as to make comparisons between the HRR field, FE solutions and the two-order term solutions. It can be seen that the two-order term solutions can coincide with the FE solutions quite reasonably regardless of creep extent, creep exponent, mismatch factor and HAZ width. This research also reveals the significant effect of the material mismatch on the high order term solutions under various conditions for mode II creep crack.

Quantification of Stress Field for Mixed Mode Creep Crack Considering Mismatch Effect

2016 ◽  
Vol 853 ◽  
pp. 291-295
Author(s):  
Jun Hui Zhang ◽  
Yan Wei Dai
Keyword(s):  
Stress Field ◽  
Mixed Mode ◽  
Creep Crack Growth ◽  
Mode Mixity ◽  
Integrity Assessment ◽  
Creep Crack ◽  
Practical Engineering ◽  
Definition Of ◽  
Engineering Practices ◽  
Mismatch Effect

Accurate description of creep crack stress field is very important to characterize the creep crack growth of the structures at elevated temperature. In general, the crack mode in practical engineering practices is not mere the mode I or mode II, and it is the mixed mode. The mismatch effect in weldment is also concerned by many researchers, however, there is no available literatures to discuss the stress field of mixed mode creep crack yet. The overall aim of this paper is to investigate and qualify the distribution of stress field for the mixed mode creep crack. In this paper, a mixed mode creep crack within the mismatched plate is discussed. The stress distribution of mixed mode creep crack are given in this article. With the definition of mode mixity for creep crack, the influence of mode mixity on the stress field is presented. The influence of mismatch effect on the principal stress, open stress and shear stress for mixed mode creep crack is also figured out. The main factor leads to the variation of creep crack tip stress field for mixed creep crack is analyzed. Some useful guidelines are proposed for the engineering purpose of integrity assessment for the structure at high temperature.

The Variation of Crack Energy Density (CED) on Creep Crack Growth

2007 ◽  
Vol 353-358 ◽  
pp. 106-109
Author(s):  
C.S. Jeong ◽  
Byeung Gun Nam ◽  
Katsuhiko Watanabe
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Energy Density ◽  
Crack Growth ◽  
Early Stage ◽  
Creep Crack Growth ◽  
Creep Crack ◽  
Crack Behavior ◽  
Creep Crack Growth Rate ◽  
Unified Description

Creep crack growth (CCG) rate has been organized frequently by C* or Ct parameter However, crack behavior of early stage under unsteady state condition has not been explained. Crack energy density (CED), which has been proposed as a parameter that can provide a unified description of crack behavior with no restriction on constitutive equation, can give the general expression about creep crack growth rate. By applying Ct and the concept of CED to the results, we showed that creep crack growth rate for all ranges of creep can be explained in a unified way by CED and its derivatives. Moreover, the physical meaning of the Ct is clarified in the discussion.

The Linkage Between Microscopic Cavitation Damage and Macroscopic Crack Growth

2000 ◽  
Vol 122 (3) ◽  
pp. 279-282 ◽  
Author(s):  
P. R. Onck ◽  
B.-N. Nguyen ◽  
E. van der Giessen
Keyword(s):  
Crack Growth ◽  
Power Law ◽  
Scale Up ◽  
Creep Crack Growth ◽  
Stress Fields ◽  
Process Window ◽  
Macroscopic Scale ◽  
Cavitation Damage ◽  
Creep Crack ◽  
Random Nucleation

This paper is concerned with a recent microstructural approach to model creep crack growth. The model spans three different length scales, from the scale of individual cavities, through the grain scale up to the macroscopic scale of cracks in components and test specimens. In order to study the initial stages of creep crack growth, we consider a near-tip process window in which a large number of grains are represented discretely. This window is surrounded by a standard continuum. Macroscopic specimen dimensions and loading configuration are communicated to this near-tip region by applying boundary conditions in accordance with the asymptotic stress fields for power-law creeping materials. The paper presents some novel results of this type of modeling obtained using remote higher-order crack-tip fields. Specific attention is focused on the effect of random nucleation and grain deformation on nonsymmetric crack growth from either initially sharp or blunt cracks. [S0094-4289(00)00703-9]

Application of Creep Ductility Model for Evaluation Creep Crack Growth Rate of Type 316SS Series

2005 ◽  
Vol 475-479 ◽  
pp. 1433-1436 ◽  
Author(s):  
Woo Gon Kim ◽  
Hyun Hie Kim ◽  
Kee Bong Yoon ◽  
Woo Seog Ryu
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Creep Ductility ◽  
Creep Crack ◽  
Creep Crack Growth Rate ◽  
Applied Stresses

This paper is to evaluate the creep crack growth rate (CCGR) of the type 316SS series: 316SS, 316FR and 316LN, and to apply a creep ductility model. A number of the data are collected through wide literature surveys and experiment, and evaluated by the C* parameter. The results of the CCGR data were nearly matched with a small scattering band regardless of the different applied stresses, temperatures and test specimens configuration. In the CCGR, type 316FR and 316LN steels were slower than type 316SS. Type 316SS showed a better agreement in the application of the creep ductility model than the type 316FR and 316LN steels.

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