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.

Mismatch Effect on the Mixed Mode Type Creep Crack within Weldment

2016 ◽  
Vol 853 ◽  
pp. 281-285
Author(s):  
Jun Hui Zhang ◽  
Yan Wei Dai
Keyword(s):  
Mixed Mode ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Crack Tip Field ◽  
Creep Crack ◽  
Loading Mode ◽  
The Difference ◽  
Engineering Practices ◽  
Mismatch Effect ◽  
Transient And Steady State

Creep crack within weldments are very common in engineering practices, and the cracking location in these welding structures always appears at the HAZ location. The mismatch effect on the mixed mode creep crack is still not clear in these available literatures. The aim of this paper is to investigate the mismatch influence on the creep crack of mixed mode thoroughly. A mixed mode creep crack within HAZ is established in this paper. The leading factor that dominates the creep crack tip field under mixed loading mode is studied. The influences of mismatch effect on mode mixity, stress distribution and stress triaxiality are proposed. The difference of mixed mode creep crack and normal mode I or mode II creep crack are compared. The influence of mixity factor on the transient and steady state creep of crack tip are also analyzed.

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 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.

Theoretical Analysis and Engineering Implications for the High Order Term Solutions of the Mode II Type Creep Crack

2017 ◽  
Author(s):  
Yanwei Dai ◽  
Yinghua Liu ◽  
Yuh J. Chao
Keyword(s):  
Theoretical Analysis ◽  
Plane Strain ◽  
Order Term ◽  
Crack Tip ◽  
High Order ◽  
High Order Term ◽  
Mode I ◽  
Mode Ii ◽  
Mode I Crack ◽  
Creep Crack

The high order term (HOT) solutions of crack tip field should be taken into account in engineering applications due to their potential influences on the fracture toughness as well as the crack growth rate. Towards this end, the high order asymptotic analysis of mode II crack in a power-law creeping material under the plane strain condition is presented theoretically in this paper. By comparing among the three order term solution, HRR field and finite element calculations, it can be found that the proposed three order term solution is able to characterize the full field of mode II creep crack tip accurately. The high order term solution of mode II creep crack relies on the creep exponent, which is different from that of mode I crack case. There are two independent terms among these three terms of asymptotic solution for mode II creep crack, which indicates that there exists the constraint effect for the plane strain mode II creep crack though the effect of high order term may not be as significant as the mode I crack case. Based on the theoretical analysis, a modified time-dependent failure assessment diagram (TDFAD) for mode II creep crack is proposed by considering the high order term solution.

scholarly journals Numerical Investigations on the Effects of T-Stress in Mode I Creep Crack

2019 ◽  
Vol 16 (08) ◽  
pp. 1841002 ◽  
Author(s):  
Yanwei Dai ◽  
Yinghua Liu ◽  
Haofeng Chen
Keyword(s):  
Power Law ◽  
Large Scale ◽  
Crack Tip ◽  
Small Scale ◽  
Mode I ◽  
Stress Effect ◽  
Constraint Effect ◽  
Crack Tip Field ◽  
Creep Crack ◽  
Power Law Creep

The effects of [Formula: see text]-stress on the stress field, creep zone and constraint effect of the mode I crack tip in power-law creeping solids are presented based on finite element (FE) analysis in the paper. The characteristics of the crack tip field in power-law creep solids by considering low negative [Formula: see text]-stress and high positive [Formula: see text]-stress are studied in the paper. The differences of [Formula: see text]-stress effect on the crack tip field between power-law creeping solids and elastoplastic materials are also clarified. A modified parameter is proposed to characterize the influence of [Formula: see text]-stress on creep zone. The constraint parameter [Formula: see text] under both small-scale creep and large-scale creep with various [Formula: see text]-stresses for the modified boundary layer (MBL) model and various specimens with different crack depths are given. The applicability and the limitation of the MBL model for creep crack are also investigated. The inherent connection between [Formula: see text]-stress and [Formula: see text]-parameter is discussed. The investigations given in this paper can further promote the understanding of [Formula: see text]-stress effect and constraint effect on the mode I 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.

Study on Stress and Strain Field of Mode II Quasi-Static Growing Crack in Pressure-Sensitive Dilatant Material

2009 ◽  
Vol 417-418 ◽  
pp. 665-668
Author(s):  
Yong Yang ◽  
Ning Li ◽  
Li Qiang Tang
Keyword(s):  
Poisson Ratio ◽  
Crack Tip ◽  
Asymptotic Solutions ◽  
Mode Ii ◽  
Stress And Strain ◽  
Viscous Effect ◽  
Crack Tip Field ◽  
Pressure Sensitive ◽  
Stress Mode ◽  
Growing Crack

A mechanical model of the pressure-sensitive dilatant material is established in order to investigate the viscous effect in quasi-static growing crack-tip field. The constitutive equations on the pressure-sensitive dilatant material are deducted. Through asymptotic analysis, it is shown that in the stable creep growing stage, the elastic-deformation and the visco-deformation are equally dominant in the near-tip field, as . The asymptotic solutions of separative variable in the crack-tip field of plane stress mode II quasi-static are aslo obtained. According to numerical calculation, the curves of stress, strain and displacement in terms of various parameters are given. The asymptotic solutions of quasi-static growing crack-tip field gained here can conveniently degenerate the incompressible case, when the Poisson ratio , named as HR field. The conclusions can provide the references for further studying the dynamic growing crack-tip field in the pressure-sensitive dilatant material.

scholarly journals Oscillatory Singularity Behaviors Near Interface Crack Tip for Mode II of Orthotropic Bimaterial

2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Xiaomei Yang ◽  
Weiyang Yang ◽  
Junlin Li ◽  
Xuexia Zhang
Keyword(s):  
Interface Crack ◽  
Linear Independence ◽  
Linear Equations ◽  
Crack Tip ◽  
Analytic Solutions ◽  
Mode Ii ◽  
Crack Tip Field ◽  
Fracture Behaviors ◽  
Stress Functions ◽  
Singularity Exponent

The fracture behaviors near the interface crack tip for mode II of orthotropic bimaterial are discussed. The oscillatory singularity fields are researched. The stress functions are chosen which contain twelve undetermined coefficients and an unknown singularity exponent. Based on the boundary conditions and linear independence, the system of twelve nonhomogeneous linear equations is derived. According to the condition for the system of nonhomogeneous linear equations which has a solution, the singularity exponent is determined. Total coefficients are found by means of successive elimination of the unknowns. The theoretical formulae of stress intensity factors and analytic solutions of stress field near the interface crack tip are obtained. The crack tip field is shown by figures.

Crack-tip field on mode II interface crack of double dissimilar orthotropic composite materials

2009 ◽  
Vol 30 (12) ◽  
pp. 1489-1504 ◽  
Author(s):  
Xue-xia Zhang ◽  
Xiao-chao Cui ◽  
Wei-yang Yang ◽  
Jun-lin Li
Keyword(s):  
Composite Materials ◽  
Interface Crack ◽  
Crack Tip ◽  
Mode Ii ◽  
Crack Tip Field ◽  
Orthotropic Composite
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