Application of the local approach to the fatigue assessment for welded joints

The fatigue behavior of welded structures is currently determined by means of recommendations defined in terms of S-N curve corresponding to the detail classes of welded joints without taking account of the actual geometry of the weld. A new fatigue strength assessment method based on Dang Van multiaxial fatigue limit criterion was introduced, which is named the local approach and presented by Institut de Soudure recently. The local approach has advantages in taking welding residual stresses and the geometry of the weld toe and weld root into consideration. The application of the local approach to the fatigue strength assessment of low carbon steel Q235B welded joints was studied. The fatigue tests and finite element analysis results show that the local approach parameters recommended by Institut de Soudure were incorrectly for low carbon steel Q235B welded joints. With aluminum alloy welded joints being used widely, the parameters of the local approach used for aluminum alloy welded joints were obtained and verified on bases of the fatigue tests and finite element analysis.

Weakly-Singular Traction and Displacement Boundary Integral Equations and Their Meshless Local Petrov-Galerkin Approaches

The general meshless local Petrov-Galerkin (MLPG) weak forms of the displacement and trac- tion boundary integral equations (BIEs) are presented for solids undergoing small deformations. Using the directly derived non-hyper-singular integral equations for displacement gradients, simple and straight- forward derivations of weakly singular traction BIEs for solids undergoing small deformations are also pre- sented. As a framework for meshless approaches, the MLPG weak forms provide the most general basis for the numerical solution of the non-hyper-singular displacement and traction BIEs. By employing the various types of test functions, several types of MLPG/BIEs are formulated. Numerical examples show that the pre- sent methods are very promising, especially for solving the elastic problems in which the singularities in dis- placements, strains, and stresses are of primary concern.

Enhancing performance of oppositional BBO using the current optimum(COOBBO)for TSP problems

Purpose-The purpose of this paper is to examine and compare the entire impact of various execution skills of oppositional biogeography-based optimization using the current optimum(COOBBO)algorithm.Design/methodology/approach-The improvement measures tested in this paper include different initialization approaches,crossover approaches,local optimization approaches,and greedy approaches.Eight well-known traveling salesman problems(TSP)are employed for performance verification.Four comparison criteria are recoded and compared to analyze the contribution of each modified method.Findings-Experiment results illustrate that the combination model of“25 nearest-neighbor algorithm initialization+inver-over crossover+2-opt+all greedy”may be the best choice of all when considering both the overall algorithm performance and computation overhead.Originality/value-When solving TSP with varying scales,these modified methods can enhance the performance and efficiency of COOBBO algorithm in different degrees.And an appropriate combination model may make the fullest possible contribution.