Search

Wrinkling is increasingly becoming one of the most common and troublesome modes of unacceptable deformation in sheet metal-forming prediction that is very important on the design of die geometry and processing parameters. In an effort to provide a reliable and efficient tool to predict the critical blank holding force for prevention of wrinkling, an analytical model for flange wrinkling in high-velocity forming processes, such as explosive forming, is presented here. With consideration of constant blank holder force and using a combination of energy method and plastic bending theory, the critical radial displacement and number of wrinkling waves are obtained. For validation, some experimental tests have been performed that their results have adequate agreements with the analytical ones. Moreover, the effects of process parameters such as blank holding force, radii ratio, and material mechanical properties on wrinkling behavior has been discussed. [ABSTRACT FROM AUTHOR]

The paper deals with the minimum value of a fracture load, with respect to the notch root radius, in plates weakened by U-notches under Mode I loading. It has been found that the fracture load has a minimum value at a critical value of the notch root radius ( ρ ), using four criteria, namely, Mean Stress (MS), maximum tangent stress or Point Stress (PS), Critical Strain-Energy (CSE) and Averaged Strain-Energy Density (ASED). Using a characteristic length ( l c h ), which is a function of material properties, the results showed that the dimensionless critical notch root radius ( ρ / l c h ) c r depended on w / a ratio (the specimen width to the notch depth), Poisson ratio, and loading condition (tensile or bending loading) under Mode I loading. In other words, according to these criteria, a notch root radius different from zero exists, providing a minimum fracture load. Therefore, a crack is not more dangerous rather than a U-notch under Mode I loading. This critical notch root radius is important for a quasi-brittle material, but may not be significant for brittle ones in practical engineering situations. Good agreement was found between theoretical predictions and experimental results on Al356-T6. [ABSTRACT FROM AUTHOR]

ABSTRACT The main purpose of the paper is to propose a numerical method for evaluation of J-integral in plates made of functionally graded materials (FGM) with sharp and blunt V-notches under Mode I loading. The material properties have been assumed to be varied exponentially along the specimen width (notch direction). Using the proposed method, the effect of material gradient on the J-integral for two cases of sharp and blunt V-notches has been studied. The results have shown that in FGMs with sharp V-notches, the J-integral is not proportional to . So, the parameter JL is path dependent. It has been observed that the material gradient has larger effect on the J-integral in sharp V-notch compared with that in blunt V-notch. [ABSTRACT FROM AUTHOR]

Abstract: The paper deals with calculations of the J-integral for a plate weakened by U-notches under Mode I bending loading in the case of a material obeying a linear elastic law. The main aim of the study is to suggest some new equations suitable for calculations of the J-integral under bending loading. Although some closed-form solutions exist in the literature based on elliptic integrals, some expressions, simple to be implemented, are useful as a rapid engineering tool. The semi-circular arc of the notch, which is traction-free, is assumed as the integration path and the J-integral is given as a function of the strain-energy density. For a numerical investigation of the strain-energy density distribution on the notch edge, the equation W(θ)= W max cos δ (θ) has been assumed, where the exponent δ has been determined from finite element analyses. The influence on δ of the notch acuity of the specimen width to the notch depth ratio w/a has been investigated by means of several parametric finite element analyses. In particular, the following values of the notch acuity (a/ρ) and notch depth ratio (w/a) have been analyzed: and . [Copyright &y& Elsevier]

Abstract: The present paper deals with the effect of notch depth on J-integral and critical fracture load in a plate made of functionally graded aluminum–silicone carbide composite (Al–SiC) with U-notch under bending. The weight fraction of SiC particles varies from 0% to 20% through the specimen width. Using three criteria namely mean stress (MS), point stress (PS), and averaged strain-energy density (ASED), the critical fracture load has been predicted and its variation with respect to the notch depth has been studied. A comparison of the J-integral between functionally graded and homogeneous Al–SiC composite were made, where the notch tip in the functionally graded material is situated in a layer with same mechanical properties as the homogeneous composite. The results indicated that in the case where the notch scene is toward brittleness increment the critical J-integral in functionally graded material (FGM) is larger than that of in homogeneous material with the same mechanical properties at the notch tip. Therefore, FGM is more convenient than homogeneous material against fracture. [Copyright &y& Elsevier]