A solution for SIFs of part-elliptical cracks based on approximate crack surface displacement and energy method

1992 ◽  
Vol 58 (2) ◽  
pp. 157-176 ◽  
Author(s):  
G. S. Wang
Keyword(s):  
Energy Method ◽  
Crack Surface ◽  
Surface Displacement ◽  
Elliptical Cracks ◽  
Crack Surface Displacement

A New Modified Crack Surface Displacement Extrapolation Method for Analysis of Package Delamination

2005 ◽  
Author(s):  
Guojun Hu ◽  
Andrew A. O. Tay
Keyword(s):  
Vapor Pressure ◽  
Crack Surface ◽  
Surface Displacement ◽  
Extrapolation Method ◽  
New Method ◽  
Bimaterial Interface ◽  
Solder Reflow ◽  
Displacement Extrapolation Method ◽  
Crack Surface Displacement ◽  
Displacement Extrapolation

Based on a new second-order analysis of the bimaterial interface crack, a modified crack surface displacement extrapolation method (MCSDEM) for evaluating the stress intensity factor (SIF) and mode mixity at a crack has been developed. Unlike existing methods which require extrapolation of values of SIFs with the concomitant uncertainties, the new method engenders a constant SIF over a considerable distance from the crack tip. The new method is also much less sensitive to mesh density than existing methods. The new MCSDEM is then used to investigate the effects of temperature, moisture diffusion and interface vapor pressure on the delamination of the interface between the leadframe pad and the encapsulant of a plastic quad flat pack (PQFP) during solder reflow for both eutectic solder and leadfree solder. Using a 160-leaded PQFP as a test vehicle, the effect of initial delamination size varying from 0.1 mm to 3.5 mm was studied. The results show that the relative contributions of temperature, moisture and interface vapor pressure is qualitatively different for solder reflow of leadfree soldered and eutectic soldered components.

The First-Order Variation of the Displacement Field Due to Geometrical Changes in an Elliptical Crack

1990 ◽  
Vol 57 (3) ◽  
pp. 639-646 ◽  
Author(s):  
T. Nishioka ◽  
S. N. Atluri
Keyword(s):  
Stress Intensity ◽  
Displacement Field ◽  
Crack Surface ◽  
Surface Displacement ◽  
Intensity Variation ◽  
Elastic Solid ◽  
Elliptical Crack ◽  
Weight Functions ◽  
Surface Flaws ◽  
Analytical Expressions

Analytical expressions are derived for the derivatives of the crack-surface displacement field, with respect to the lengths of the major and minor axes, respectively, of an elliptical crack embedded in an infinite isotropic elastic solid, when the crack faces are subjected to arbitrary tractions. These results are shown to lead, in turn, to analytical expressions for weight functions for the stress intensity factors along the fronts of elliptical-shaped embedded or part-elliptical shaped surface flaws, when a simple two-parameter characterization of the stress intensity variation along the flaw border is used. In the case of part-elliptical surface flaws, a finite-element alternating method, based on the Schwartz-Neumann superposition technique, is proposed to determine the coefficients in the analytical expressions for crack-surface displacements, and their gradients with respect to the crack dimensions.

scholarly journals The Crack Problem for a Nonhomogeneous Plane

1983 ◽  
Vol 50 (3) ◽  
pp. 609-614 ◽  
Author(s):  
F. Delale ◽  
F. Erdogan
Keyword(s):  
Integral Equation ◽  
Poisson’S Ratio ◽  
Crack Problem ◽  
Surface Displacement ◽  
Plane Elasticity ◽  
Poisson's Ratio ◽  
Cauchy Type ◽  
Crack Tips ◽  
Square Root Singularity ◽  
Crack Surface Displacement

In this paper the plane elasticity problem for a nonhomogeneous medium containing a crack is considered. It is assumed that the Poisson’s ratio of the medium is constant and the Young’s modulus E varies exponentially with the coordinate parallel to the crack. First the half plane problem is formulated and the solution is given for arbitrary tractions along the boundary. Then the integral equation for the crack problem is derived. It is shown that the integral equation having the derivative of the crack surface displacement as the density function has a simple Cauchy-type kernel. Hence, its solution and the stresses around the crack tips have the conventional square-root singularity. The solution is given for various loading conditions. The results show that the effect of the Poisson’s ratio and consequently that of the thickness constraint on the stress intensity factors are rather negligible. On the other hand, the results are highly affected by the parameter β describing the material nonhomogeneity in E (x) = E0exp(βx).

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