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 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.

scholarly journals Mixed-mode crack tip fields in a polycrystalline aluminum alloy

2019 ◽  
Vol 300 ◽  
pp. 11004 ◽  
Author(s):  
Marcel Wicke ◽  
Angelika Brueckner-Foit
Keyword(s):  
Mixed Mode ◽  
Crack Tip ◽  
Strain Partitioning ◽  
Crack Tip Field ◽  
Polycrystalline Aluminum ◽  
Digital Twin ◽  
Crack Tip Fields ◽  
Mixed Mode Crack ◽  
Threshold Regime ◽  
Near Threshold

Carefully performed experiments with long cracks in the near-threshold regime have shown that the crack tip field of these cracks significantly deviate from the expected mode-I butterfly-shaped ones and resemble strongly to mixed-mode crack tip fields. A simulation study using a crystal plasticity (CP) approach has been utilized in order to understand this phenomenon. To this end, a digital twin of an aluminum sample fatigued in the near-threshold regime was generated with the help of electron backscatter diffraction (EBSD) and X-ray tomography. Once set-up, the digital twin was loaded in uniaxial tension using the fast spectral solver implemented in the Düsseldorf Advanced Material Simulation Kit (DAMASK). The versatility of this experimental-computational approach for studying the strain partitioning at the crack tip is demonstrated in this work.

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.

Elastic-Viscoplastic Field at the Mixed-Mode Crack-Tip under Compression and Shear

2011 ◽  
Vol 488-489 ◽  
pp. 452-455
Author(s):  
Wen Yan Liang ◽  
Zhen Qing Wang ◽  
Fang Liu
Keyword(s):  
Interface Crack ◽  
Mixed Mode ◽  
Crack Tip ◽  
Viscosity Coefficient ◽  
Crack Tip Field ◽  
Displacement Potential ◽  
Dynamic Propagation ◽  
Singularity Exponent ◽  
Crack Interface ◽  
Main Factor

In the present paper, the mechanical model of dynamic propagation interface crack of the compression-shear mixed mode is proposed by using the elastic-viscoplastic constitutive model. Then the governing equations of propagation crack interface at crack tip are given. The numerical analysis is accomplished for the interface crack of compression-shear mixed mode by introducing a displacement potential function and some boundary conditions at interface crack tip. The distributed regularities of stress-strain fields of interface crack tip are discussed with several special parameters. The numerical results show that the viscosity effect is a main factor of interface propagating at crack-tip field, and the interface crack-tip is a viscoplastic field that is governed by viscosity coefficient、Mach number and singularity exponent.

The Elastic-Viscoplastic Field at the Mixed-Mode Crack-Tip under Compression and Shear

2008 ◽  
Vol 385-387 ◽  
pp. 321-324
Author(s):  
Wen Yan Liang ◽  
Zhen Qing Wang ◽  
Bo Zhou ◽  
Hong Qing Lv
Keyword(s):  
Numerical Solution ◽  
Mixed Mode ◽  
Equivalent Plastic Strain ◽  
Crack Tip ◽  
Viscosity Coefficient ◽  
Plastic Strain Rate ◽  
Crack Tip Field ◽  
Viscosity Effect ◽  
Mixed Mode Crack ◽  
Propagating Crack

Under the assumption that the viscosity coefficient is in inverse proportion to the power law of the equivalent plastic strain rate. The friction touch effect between viscosity and crack-tip surfaces is considered, the asymptotic solution is established for elastic-viscoplastic field at the mixed-mode quasi static crack-tip under compression and shear. The numerical solution at crack-tip without stress and stain gap is obtained. The variation of numerical solution is discussed for the mixed-mode under compression and shear according to each parameter. Through numerical results and analysis for the mixed-mode crack-tip field under compressing and shear, it is whole plastic without elastic unloaded section, viscosity effect is an important factor when propagating crack-tip field.

Asymptotic Self-Similar Solution of the Creep Crack Problems in Damaged Materials under Mixed Mode Loading

2015 ◽  
Vol 784 ◽  
pp. 145-152
Author(s):  
Larisa Stepanova ◽  
Ekaterina Yakovleva ◽  
Ekaterina Mironova
Keyword(s):  
Power Law ◽  
Mixed Mode ◽  
Eigenvalue Problems ◽  
Crack Tip ◽  
The Self ◽  
Mixed Mode Loading ◽  
Creep Crack ◽  
Crack Problems ◽  
Damaged Zone ◽  
Self Similar

The creep crack problem in damaged materials under mixed mode loading is considered. The class of the self-similar solutions to the plane creep crack problems in a damaged medium under mixed-mode loading is given. With the similarity variable and the self-similar representation of the solution for a power-law creeping material and the power-law damage evolution equation the near crack-tip stresses, creep strain rates and continuity distributions for plane stress conditions are obtained. The self-similar solutions are based on the hypothesis of the existence of the completely damaged zone near the crack tip. It is shown that the asymptotical analysis of the near crack-tip fields gives rise to the nonlinear eigenvalue problems. The technique permitting to find the eigenvalues numerically is proposed and numerical solutions of the nonlinear eigenvalue problems arising from the mixed-mode crack problems in a power-law medium under plane stress conditions are obtained. Using the approach the eigenvalues different from the eigenvalues corresponding to the Hutchinson-Rice-Rosengren (HRR) problem are found. Having obtained the eigenspectra and eigensolutions the geometry of the completely damaged zone in the vicinity of the crack tip can be found for all values of the mixity parameter.

Effect of stress triaxiality in crack tip field on validity of

1989 ◽  
Vol 34 (3) ◽  
pp. 637-643 ◽  
Author(s):  
Jun Sun ◽  
Zengjie Deng ◽  
Zhonghua Li ◽  
Mingjing Tu
Keyword(s):  
Stress Triaxiality ◽  
Crack Tip ◽  
Crack Tip Field

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.

Asymptotic Crack-Tip Fields for Perfectly Plastic Solids Under Plane-Stress and Mixed-Mode Loading Conditions

1990 ◽  
Vol 57 (3) ◽  
pp. 635-638 ◽  
Author(s):  
P. Dong ◽  
J. Pan
Keyword(s):  
Plane Stress ◽  
Mixed Mode ◽  
Crack Tip ◽  
Mode I ◽  
Mode Ii ◽  
Crack Tip Field ◽  
Crack Tip Fields ◽  
Perfectly Plastic ◽  
Mixed Mode Crack ◽  
Small Constant

In this paper, we first discuss some of the properties of the crack-tip sectors for perfectly plastic materials under plane-stress conditions. Then starting with the plane-stress mixed-mode crack-tip fields suggested by Shih (1973), we assemble these sectors in a slightly different manner from those in Shih (1973). The missing governing equations needed to completely specify the crack-tip fields for both near mode I and near mode II mixed-mode loadings are derived. The mode I crack-tip field, as the limit of the near mode I cases, differs from Hutchinson’s solution (1968) by the appearance of a small constant stress sector ahead of the crack tip. In addition, the relevance of the solutions of the near mode II cases to some interesting features of the mixed-mode crack-tip fields, as suggested by Budiansky and Rice (1973), is also discussed.

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