Modeling heat transfer during friction stir welding (FSW) process is crucial for understanding welding mechanism and optimizing process parameters. Since heat transfer is usually accompanied with the material flow in FSW, the meshless method, which can easily treat large deformation in a Lagrangian framework, is promising for FSW modeling. In this paper, we develop a meshless particle method for the analysis of transient heat transfer during FSW process. In the developed method, a heat source model based on sticking friction is implemented to describe the heat generation of FSW. A particle approximation with first-order consistency is employed to discretize the governing equation of heat transfer. A penalty method is proposed to impose different thermal boundary conditions, and a smoothing algorithm is introduced to enhance numerical stability. Two examples are firstly given to verify the accuracy and parametric effect of the meshless particle method. The method is then used to simulate heat transfer during FSW of 12.7mm-thick Al6061-T6 plates. The calculated temperature distributions are presented and compared with those computed by FEM. The obtained thermal cycles are found to be in good agreement with those obtained from experiments. The validated model of FSW of Al6061-T6 plates is then employed to predict the maximum temperature, heat generation rate and torque for various welding parameters and tool dimensions.

In order to consider corner configurations with straight corner fronts in three-dimensional (3D) solids, a super polygonal prismatic element containing a straight corner front is established by using the numerical eigensolutions of singular stress fields and the Hellinger–Reissner variational principle. Singular stresses near the corner front subject to far-field boundary conditions can be obtained by incorporating the super singular element with conventional 3D brick elements. The numerical studies are conducted to demonstrate the simplicity of the proposed technique in handling fracture problems of 3D corner configurations and cracks. The usage of the super singular element can avoid mesh refinement near the corner front domain that is necessary for conventional and enriched finite element methods, and lead to high accuracy and fast convergence. Compared with the conventional finite element methods and existing analytical methods, the present method is more suitable for dealing with complicated problems of stress singularity in elasticity including multiple defects.

An axisymmetric smoothed particle hydrodynamics (ASPH) with contact algorithm is presented to simulate the normal perforation of aluminum plates. Traditional ASPH considering contact implicitly by conservation equations has the problem of virtual tensile stresses and shear stresses for perforation simulation. To overcome the problem, a particle-to-particle contact algorithm is employed to treat contact interfaces explicitly in the present method. An artificial stress method is extended for the method to remove tensile instability. The present method is firstly validated by three test cases. Then, it is used to simulate the normal perforation of aluminum plates with ogive-nose steel projectiles. Numerical simulation results show that the method predicted residual velocities of projectiles in good agreement with the experimental data.

No abstract