Application of numerical method to investigation of fatigue crack behavior through the friction stir welding

Fatigue crack propagation through a friction stir welded (FSW) joint of 2024-T351 Al alloy is investigated numerically. The governing relationships for predicting the crack behavior including incremental crack length, crack growth rate, and crack growth direction are presented. Stress intensity is calculated based on displacement correlation technique, and fatigue crack growth through the FSW joint is investigated under linear elastic fracture mechanics (LEFM) using the Paris model. The concepts of crack closure, residual stress, and stress relaxation are incorporated into the Paris model to support the final results. Maximum circumferential tensile stress method is applied to predict the crack growth direction. Finally, the numerical approaches are employed to the high number of elements in the framework of Fracture Analysis Code (FRANC2D/L) to simulate the fatigue crack propagation through the FSW joint including various zones with different material properties. Fatigue lifetime of the welded joint is predicted by implementing the same procedure for various loading values. The obtained numerical results are validated with the experimental work (Ali et al., Int J Fatigue 30:2030–2043, 2008)

Fracture toughness of kenaf mat reinforced polyester composite

The fracture behaviour represents the most critical issue in the automotive and aerospace engine fields. Thus, the objective of this study was to estimate and analyze the crack criteria by using the Mathematical laws that were limited in E 1820 standard and the results affirmed by applying the numerical solutions of ANSYS to estimate the fracture toughness value KIC, besides the energy release rate of biomass composite. The specimens were prepared from different percentage of kenaf mat (KM) and unsaturated polyester resin (UP) 20% KM – 80% UP and 40% KM – 60% UP, respectively, as well the other composite properties which were calculated using the stress-strain data. The fracture characterizations of this composite were carried out using the compact tension (CT) specimen that was commonly used to determine Mode-I fracture properties. The fracture toughness has been found to be independent of pre-crack length. Meanwhile, the tests were performed at room temperature. The numerical simulations of the ANSYS model results demonstrated a good agreement between the experiments computed results of the fracture toughness. The fracture toughness KIC of 20% KM – 80% UP and 40% KM – 60% UP was equivalent to 0.76 MPa√m and 2.0 MPa√m, respectively. Thus, the fracture propagation is dependent on the fibre percentage of the composite. On the other hand, there are unlimited mechanisms of crack paths derived from randomly kenaf mat packs, particularly in the frontal process zone of crack tip

A review of non-destructive thermography techniques toward structural integrity of bio-composites

It is well known those two popular methods of testing; destructive testing based on fracture mechanics and non-destructive testing (NDT) which does not make any damage in the specimen. NDT was first used for military purpose but nowadays it is used widely in many fields such as composite materials, medical purposes, fire safety, laser welding, food safety and quality and characterization of materials. The aim of this paper is to review the recent advancement of thermography non-destructive methods especially in testing a quality of bio-composites materials. The review reveals the advantages and disadvantages of pursuing any of the available methods in NDT on bio composite materials

Characterisation and fatigue of friction stir welding

Previous attempts on the characterisation of Friction Stir Welding (FSW) based on microstructures, hardness, and residual stress distribution have been reviewed. The role of these parameters on fatigue damage of FSW is then discussed. Relevant conclusions have been drawn to demonstrate the current issues and the future research potential of these joints

Fatigue strength improvement of MIG-welded joint by shot peening

In this study, the effect of controlled shot peening (CSP) treatment on the fatigue strength of an ASTM A516 grade 70 carbon steel MIG-welded joint has been studied quantitatively. Metallurgical modifications, hardness, elemental compositions, and internal discontinuities, such as porosity and inclusions found in treated and untreated fusion welded joints, were characterized. The fatigue results of as-welded and peened skimmed joints were compared. It was observed that the effect of the CSP and skimming processes improved the fatigue life of the fusion weld by 63% on MIG-welded samples

Development of a green combat armour from rame-Kevlar-polyester composite

This study was conducted for the development of the green protection garments. For this purpose, laminate composite material was developed from Kevlar 29-ramie-unsaturated polyester resin. The aim of this study was to develop a solid body armour that meets the specific requirements of ballistic resistance. This composite is subjected to high impact loading. The target was shot using gas gun machine that is supported by camera hardware to capture the projectile speed. In order to achieve the goal of the research, several experiments were conducted with the aim to estimate the ballistic limit, maximum energy absorption, composite failure mode, life time rupture, target geometry, and environmental effect. The results of these experiments indicated that the maximum ballistic limit validated at impact speed is in the range of 250 m/s to 656.8 m/s for the second protection level. The targets are improved in term of the impact response with the increase in the relative humidity, i.e. the range of 50% ± 20%, whereas, reduction of resistance results in the increase of temperature. The range of temperatures was between 20°C and 70°C. A limited delamination was generated under multiple shots. Targets geometry plays a major role in increasing the impact response. Hence, the results present a high resistant impact for pairs from the panels with total thickness arrived to 15 mm ± 3 mm. This body armour is one of the most economical armour products, in which common materials are used in its production, particularly to reduce the amount of Kevlar, and this could further lead to a decrease in its production cost. On the other hand, this armour meets the ballistic threats under 623 m/s of 15 mm ± 3 mm target thickness and 837.5 m/s of 25 mm ± 2.mm. Thus, the armour is equivalent to the third level of protective ballistic limits in the National Institute of Justice (NIJ) standards

Evaluation the Effect of Laminated Layer Sequence of Plain-Woven Bamboo on Tensile and Impact Performance of E-glass Woven / Epoxy Hybrid Composites

Bamboo reinforced hybrid composites are needed in claim to progress use of polymer composite technology. This paper describes a hand lay-up laminate process using plain-woven bamboo/E-glass woven/epoxy hybrid composite with the Design of experiment (DOE) 2 factor with 3- level and analysis of variance (ANOVA) was implemented for an evaluation against how the bamboo and e-glass woven affect the mechanical properties of hybrid composite in various sequence. The present study considers influence of plain-woven bamboo and e-glass woven laminated hybrid composite towards its tensile and charpy impact test performance. The results show that the 2-layer composites withstood better tensile strengths 185.372 MPa for EG/BW/EG while charpy impact 158.224 KJ/m2 for EG/BW sequence respectively. Experiments results show that concentrate on both lay-up sequence and layers are important effect factors for tensile and charpy performance. It had been proven that both the layers and also the lay-up sequence demonstrated significantly different leads to terms of the mechanical performance

A review and comparison on some rubber elasticity models

This study reviews several classical continuum mechanics models for incompressible and isotropic materials based onstrain energy potential and then compares ability of neo-Hookean, Yeoh, Mooney-Rivlin and Ogden models in predicting uniaxialdeformation states based on experimental data from dumb-bell test specimen under uniaxial loading

Characterization of shot peened 2024-T351 aluminum alloy

Specimens of 2024-T351 aluminium alloy under different three shot peening intensities were studied. The modifications of the surface layers of the shot peened specimens were investigated through microhardness, surface microstructure and residual stress relaxation after the first and second load cycles under two cyclic loads. No significant changes in microstructure after the three shot peeing intensities were observed with respect to untreated specimens. Rapid residual stress relaxation was observed in specimens after the first cycle. Relaxation of residual stresses occurred within first loading cycles were increased with increasing loading stress amplitude and due to quasi-static relaxation effects