Optimization of Tube Hydroforming Process Using Simulated Annealing Algorithm

AbstractIn this paper, forming parameters of tube hydroforming (THF) process are investigated and optimized using Simulated Annealing optimization algorithm linked with a finite element commercial code. The goal of this research is to obtain the maximum formability of two dimensional (2D) axisymmetric tubes under a failure criteria based on material's forming limit diagram (FLD). The initial approximated pressure loading path is determined by proved theoretical equations. Then the Simulated Annealing algorithm written in Matlab software is combined with a nonlinear structural finite element code ANSYS/ LS-DYNA in order to optimize internal hydraulic pressure. The results are compared by experimental observations and a good agreement was observed between them

Improving the fracture toughness and the strength of epoxy using nanomaterials : a review of the current status

The incorporation of nanomaterials in the polymer matrix is considered to be a highly effective technique to improve the mechanical properties of resins. In this paper the effects of the addition of different nanoparticles such as single-walled CNT (SWCNT), double-walled CNT (DWCNT), multi-walled CNT (MWCNT), graphene, nanoclay and nanosilica on fracture toughness, strength and stiffness of the epoxy matrix have been reviewed. The Young's modulus (E), ultimate tensile strength (UTS), mode I (GIC) and mode II (GIIC) fracture toughness of the various nanocomposites at different nanoparticle loadings are compared. The review shows that, depending on the type of nanoparticles, the integration of the nanoparticles has a substantial effect on mode I and mode II fracture toughness, strength and stiffness. The critical factors such as maintaining a homogeneous dispersion and good adhesion between the matrix and the nanoparticles are highlighted. The effect of surface functionalization, its relevancy and toughening mechanism are also scrutinized and discussed. A large variety of data comprised of the mechanical properties of nanomaterial toughened composites reported to date has thus been compiled to facilitate the evolution of this emerging field, and the results are presented in maps showing the effect of nanoparticle loading on mode I fracture toughness, stiffness and strength

An experimental study on damage intensity in composite plates subjected to low-velocity impacts

Today composite structures are widely used in different industries. Since these structures are sometimes experienced impacts of low-velocity objects, evaluating the intensity of the damage due to the impact in these structures seems important and necessary. In this article, the effectiveness of the thermography method with three different thermal excitation sources, including the ultrasonic vibrothermography, infrared thermography with the heating element, and infrared thermography with hot airflow, for damage evaluation in CFRP and GFRP composite plates subjected to low-velocity impacts are investigated. The ultrasonic vibrothermography method is introduced as the most promising technique for damage evaluation in CFRP and GFRP composite plates subjected to low-velocity impacts, and the effect of the excitation power and excitation frequency on the effectiveness of this method is studied. To find the damage location in the thermography images in which the damage is not clear enough to be identified, the wavelet transform is applied while it is not suitable for calculating the damaged area. Finally, finite element (FE) simulations are carried out for the case of an internal defect. The results show the acceptable accuracy of the FE simulation in comparison with the experimental results