Thermal Misfit and Thermal Fatigue Induced Damage in Brittle Composites

1994 ◽  
Vol 350 ◽  
Author(s):  
N. Sridhar ◽  
J. M. Rickman ◽  
D. J. Srolovitz
Keyword(s):  
Thermal Expansion ◽  
Crack Growth ◽  
Spherical Inclusion ◽  
Strain Energy Release ◽  
Misfit Strain ◽  
Crack Size ◽  
Critical Crack ◽  
Penny Shaped Crack ◽  
The Matrix ◽  
Shaped Crack

AbstractWe examine the conditions under which differences in thermal expansion between a particle and the matrix leads to crack growth within the matrix. Using linear elastic fracture mechanics, we obtain closed-form, analytical results for the case of a penny shaped crack present in the matrix interacting with a spherical inclusion which is misfitting with respect to the matrix. A simple and direct relationship is established between the strain energy release rate, the crack size, the crack orientation with respect to the inclusion, the crack/inclusion separation, the degree of thermal expansion mismatch and the elastic properties of the medium. We also analyze the size to which these cracks can grow and find that for a given misfit strain and material properties, crack growth is inhibited beyond a certain critical crack size. Finally, the preferred orientation of these cracks as a function of misfit strain is predicted. The implication of these results for thermal cycling are analyzed.

Numerical Analysis of the Crack Growth in a High Loaded Bolt Connection

2007 ◽  
Vol 348-349 ◽  
pp. 625-628
Author(s):  
Marko Knez ◽  
Srečko Glodež ◽  
Janez Kramberger
Keyword(s):  
Crack Growth ◽  
Crack Size ◽  
Initial Crack ◽  
Structural Elements ◽  
Element Analysis ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Final Failure ◽  
Heavy Loads ◽  
Bolt Connection

The present paper deals with the research on the crack growth in a bolt connection of a lug for crane counter weight bars. Counter weight bars are structural elements that are subjected to very heavy loads and therefore special attention must be paid. The main purpose of this research is to determine the number of the load cycles required for a crack to propagate from initial to critical crack length, when the final failure can be expected to occur. All required material parameters and the experimental results were determined in our previous research. The influence of the initial crack size upon the remaining life of the lug is researched numerically by means of finite element analysis and analytically by use of the corrected analytical model.

scholarly journals Experimental and Numerical Investigations on Crack Propagation in Titanium Alloys

2018 ◽  
Vol 8 (04) ◽  
Author(s):  
Varimadugu Sandhya ◽  
Jyothirmayi Narne ◽  
Nagini Yerramsetty ◽  
V. Jaipal Reddy
Keyword(s):  
Titanium Alloys ◽  
Energy Release ◽  
Crack Growth ◽  
Cleavage Fracture ◽  
Tensile Load ◽  
Strain Energy Release ◽  
Tensile Tests ◽  
Tensile Specimen ◽  
Crack Size ◽  
Element Analysis

The titanium alloys are the objects of wide experimental analysis in the terms of crack growth characteristics and mechanism of fracture due to their applications. The Ti-6.4%Al-2.6%Mo-1.7%Cr-0.5%Fe-0.5%Si (wt %) alloy was used in the investigation. The tensile tests were conducted on plate specimens. The test variables considered are width of tensile specimen, crack size and tensile loading. The mechanism of fracture that appeared in the specimens was established from the TEM micrographs of the replicas taken from different zones of the fracture surfaces. The mechanism of fracture was also studied using finite element analysis. The results obtained from the FEA were verified with experimental results. It can be concluded that there is a general trend of increasing stress intensity factor with increasing applied tensile load, crack size and width of the flat specimen. The strain energy release increases with increasing applied tensile load. Crack extension can occur when crack-driving force is equal to the energy required for crack growth. For a particular stress the energy release rate is proportional to the crack size. As the tensile load and the size of the initial crack increase, there is an increased crack growth in the Ti alloy. In the crack initiation zone evidence of quasi-cleavage fracture with limited plastic striations symptoms was found in the specimen tested under  =1000MPa. Micro fracture analysis of the specimens (tested under =1100MPa) has revealed quasi-cleavage fracture with small symptoms of plastic shearing in the early part of cracking.

Adhesion Failure in Bonded Rubber Cylinders Part 1: Internal Penny-Shaped Cracks

2003 ◽  
Vol 76 (1) ◽  
pp. 160-173 ◽  
Author(s):  
D. C. Leicht ◽  
O. H. Yeoh ◽  
A. N. Gent ◽  
J. Padovan ◽  
R. L. Mullen
Keyword(s):  
Crack Length ◽  
Strain Energy Release ◽  
Element Analysis ◽  
Shape Factors ◽  
Metal Plates ◽  
Adhesion Failure ◽  
Penny Shaped Crack ◽  
Shaped Crack ◽  
Small Cracks ◽  
Tearing Energy

Abstract Rubber disks bonded between flat parallel metal plates are often used as adhesion test specimens such as ASTMD 429 1999, Method A. However, the mechanics of adhesion failure (debonding) for this geometry have not been fully analyzed previously. Therefore, a study has been conducted of the strain energy release rate (tearing energy) for bonded rubber disks having cracks at the rubber-to-metal bond. In this paper, we consider internal penny-shaped cracks. A future paper will discuss external ring cracks. Finite element analysis was used to determine the tearing energy as a function of crack length for disks of various dimensions (shape factors). The crack configurations considered were an internal penny shaped crack located at the center of either one or both rubber-to-metal bonds. The rubber was assumed to be linearly elastic and nearly incompressible. For any bonded disk held in constant tension, the tearing energy was found to be a non-linear function of crack length. For small cracks, the tearing energy was linearly related to the crack length. As the crack grew, the tearing energy increased until it passed through a maximum value. The peak tearing energy was found to depend on the height of the disk. Finally, for large cracks, the tearing energy decreased as the crack grew. Analytical and empirical models were developed and shown to be in good agreement for both small and large cracks in disks of different dimensions.

An Axisymmetric Crack in Bonded Materials With a Nonhomogeneous Interfacial Zone Under Torsion

1995 ◽  
Vol 62 (1) ◽  
pp. 116-125 ◽  
Author(s):  
M. Ozturk ◽  
F. Erdogan
Keyword(s):  
Crack Opening ◽  
Crack Problem ◽  
Strain Energy Release ◽  
Interfacial Region ◽  
Interfacial Zone ◽  
Mode Iii ◽  
Shear Moduli ◽  
Penny Shaped Crack ◽  
Energy Release Rates ◽  
Shaped Crack

In this study the mode III axisymmetric crack problem for two dissimilar homogeneous materials bonded through a thin layer of nonhomogeneous interfacial region is considered. The shear modulus of the interfacial layer is assumed to be μ2(z) = μ1 exp (αz). It is also assumed that μ3 = μ1 exp (αh), h being the thickness of the layer and μ1 and μ3 the shear moduli of the adherents. The main results of the study are the stress intensity factors, the strain energy release rates and, to a limited extent, the crack-opening displacements obtained as functions of the two primary variables h/a and μ3/μ1 under various loading conditions, where a is the radius of the crack. Some results are also presented for a penny-shaped crack in an unbounded nonhomogeneous medium.

Comparison of Leak-Before-Break Assessment of Main Loop Piping Lines Fabricated of Different Materials

2016 ◽  
Author(s):  
Linwei Ma ◽  
Xiaotao Zheng ◽  
Yan Wang ◽  
Jiasheng He ◽  
Anqing Shu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Material Properties ◽  
Plastic Instability ◽  
Crack Size ◽  
Critical Crack ◽  
Main Loop ◽  
Critical Crack Size ◽  
Leak Before Break

Leak-Before-Break (LBB) assessment is used for the design of nuclear reactor coolant system main loop piping to lower the cost of construction and operation in China. In these applications, the materials of main loop piping lines are cast austenitic stainless steel (CASS) or wrought stainless steel (WSS) due to the different type of reactor design. According to US.NRC SRP3.6.3, LBB assessment includes two major calculations, such as critical crack size calculation and leakage flaw size calculation. The elastic-plastic instability analysis or plastic instability analysis is chosen to perform critical size calculation depending on material properties, especially fracture toughness. In this paper, LBB assessment in the guidance of SRP 3.6.3 was performed to evaluate main loop piping lines of CASS and WSS. The JR curve tests and the adjustment due to thermal aging are performed to achieve reasonable material properties. J integral/tearing modulus approach is used to determine critical crack size of CASS pipe and net section collapse (NSC) approach is used to determine critical crack size of WSS pipe. Leakage flaw size under 1gpm leakage detection capability is determined based on Henry’s homogeneous nonequilibrium critical flow model. In order to demonstrate that fatigue crack growth is not a potential source of pipe rupture for the evaluated piping lines, the fatigue crack growth of a postulated circumferential part-through-wall crack under nuclear power plant full life time operating transients and the fatigue crack growth of a circumferential through-wall crack under one time safe shutdown seismic are analyzed. And the LBB assessment procedure and results of CASS pipe and WSS pipe are compared.

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