Fatigue Crack Growth on Heterogeneous Stress Fields: Best Analytical Approach

ABSTRACTA way of estimating Stress Intensity Factors is proposed by extending available solutions (solid and crack configurations) to stress fields not considered in available formulations. The accuracy of the proposed estimation is considered with respect to fatigue life assessment and crack shape tracing. It is aimed as very fast initial estimation, in comparison with the use of Finite Elements, in those cases were a high stress gradient is observed: stress concentrations (holes, notches, grooves) or due to surface residual stresses produced by machining techniques or induced –on purpose- to improve fatigue life (for example, by shot-peening), where no SIF solutions are available.

Accounting for High Stress Gradient by a Modified Weibull Failure Theory

A high stress gradient occurs in a component when the stress, due to external loading, rises asymptotically. The Weibull failure theory overestimates the probability of failure for components with high stress gradients generated due to the geometric irregularities, material mismatch, thermal mismatch, and contact loading. A modified Weibull failure theory is proposed in this paper. The method is based on the weight function method. The modified Weibull failure theory was applied to two specimens, and the results showed the ability of the proposed theory to handle high stress gradients. The theory considers variable equivalent stress intensity factors along the faces of cracks; hence, it considers the strength of a specimen to be dependent on the stress field.

Nonrectilinear Light Propagation in Integrated Photoelasticity of Axisymmetric Bodies

The general character as well as the order of magnitude of deflection of light in axisymmetric photoelastic specimens has been investigated. Experimental studies of deflection of light in case of a particular axisymmetric state of stress with high stress gradient has been carried out. It has been shown that the integral fringe patterns depend strongly on the parameters of the recording system. Fringes of a different origin have been observed together with the integral fringe pattern.