Determination of crack initiation direction from a bi-material notch based on the strain energy density concept

This work considers the numerical computation methods and procedures for the fatigue crack growth predicting of cracked notched structural components. Computation method is based on fatigue life prediction using the strain energy density approach. Based on the strain energy density (SED) theory, a fatigue crack growth model is developed to predict the lifetime of fatigue crack growth for single or mixed mode cracks. The model is based on an equation expressed in terms of low cycle fatigue parameters. Attention is focused on crack growth analysis of structural components under variable amplitude loads. Crack growth is largely influenced by the effect of the plastic zone at the front of the crack. To obtain efficient computation model plasticity-induced crack closure phenomenon is considered during fatigue crack growth. The use of the strain energy density method is efficient for fatigue crack growth prediction under cyclic loading in damaged structural components. Strain energy density method is easy for engineering applications since it does not require any additional determination of fatigue parameters (those would need to be separately determined for fatigue crack propagation phase), and low cyclic fatigue parameters are used instead. Accurate determination of fatigue crack closure has been a complex task for years. The influence of this phenomenon can be considered by means of experimental and numerical methods. Both of these models are considered. Finite element analysis (FEA) has been shown to be a powerful and useful tool1,6 to analyze crack growth and crack closure effects. Computation results are compared with available experimental results.

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Case Criterion of Crack Onset in Orthotropic Bi-Material Notches

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.465.157 ◽

2011 ◽

Vol 465 ◽

pp. 157-160 ◽

Cited By ~ 1

Author(s):

Tomáš Profant ◽

Jan Klusák ◽

Michal Kotoul

Keyword(s):

Energy Density ◽

Crack Initiation ◽

Strain Energy Density ◽

Strain Energy ◽

Local Minimum ◽

Plane Elasticity ◽

Mean Value ◽

Density Factor ◽

The Mean ◽

Energy Density Factor

A bi-material notch composed of two orthotropic parts is considered. The stresses and displacements are expressed using the Stroh-Eshelby-Lekhnitskii formalism for plane elasticity. The potential direction of crack initiation is determined from the maximum mean value of the tangential stress or the local minimum of the mean value of the generalized strain energy density factor in both materials [1, 2]. The matched asymptotic procedure is introduced to derive the change of potential energy for the debonding crack and the crack initiated in the determined direction [3].

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Probabilistic Fatigue Crack Initiation and Propagation Fields Using the Strain Energy Density

Strength of Materials ◽

10.1007/s11223-018-0007-5 ◽

2018 ◽

Vol 50 (4) ◽

pp. 620-635 ◽

Cited By ~ 9

Author(s):

J. A. F. O. Correia ◽

P. J. Huffman ◽

A. M. P. De Jesus ◽

G. Lesiuk ◽

J. M. Castro ◽

...

Keyword(s):

Fatigue Crack ◽

Energy Density ◽

Crack Initiation ◽

Strain Energy Density ◽

Strain Energy ◽

Fatigue Crack Initiation ◽

Crack Initiation And Propagation ◽

Initiation And Propagation

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Prediction of Crack Initiation Direction for Surface Flaws Under Biaxial Loading

Journal of Pressure Vessel Technology ◽

10.1115/1.1521712 ◽

2003 ◽

Vol 125 (1) ◽

pp. 65-70 ◽

Cited By ~ 1

Author(s):

Abdennour C. Seibi ◽

Sam Y. Zamrik

Keyword(s):

Energy Density ◽

Crack Initiation ◽

Strain Energy Density ◽

Strain Energy ◽

Biaxial Stress ◽

Crack Trajectory ◽

Fracture Crack ◽

Density Factor ◽

Crack Angle ◽

Energy Density Factor

This paper presents a simple method based on the strain energy density factor ΔS to study the fatigue characteristics of rhombic plates with induced angled flaws under biaxial stress field. The paper discusses in detail the procedures followed to predict the fracture crack initiation angle, θo, as a function of induced crack angle, β, the path of the crack trajectory at the initial stage of fracture and develop an expression for the crack growth rate. This method assumes that the crack extends in a radial direction and that the initial fracture crack angle, θo, is obtained by maximizing the hoop stress along a circumference of a radius r. Expressions for the stress-state near the crack tip were developed for computing the crack trajectory and the strain energy density factor. The crack trajectory path was estimated by computing the new values of the crack angle and a fictitious crack length. These computed values were in turn used to determine the strain energy density factor. The developed method revealed two important observations: i) The crack trajectory was in close agreement with the experimental data for the first 20% of the lifetime to failure, ii) the crack propagation rate is dependent on the crack angle using the stress intensity factor and exhibited no variation with respect to the crack angle when the strain energy density factor is used.

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