Papers by Author: Aidy Ali

Abstract: Ultrasonic method for the investigation of multi-layered laminates such as glass fiber reinforced plastics (GFRP) has been a challenging task in industry due to their inherent nature as a combination of constituents and the respective fabrication process. The coarse-grain structure of the material, fiber orientation and stacking sequence of laminated composites generate undesirable echoes for the ultrasonic signals during the testing. These echoes distributed randomly in time affects the measurements of ultrasonic parameters. In this paper, the utilization of attenuation and time-of-flight (TOF) of ultrasound signals to reconstruct the internal structure of GFRP subsurface region were investigated. Comparisons of these two methods were conducted on two sets of GFRP with different structure condition. Analysis of C-scan images constructed by amplitude and TOF were conducted in a two dimensional region map of the scanning profile. Experimental results showed that attenuation of amplitude gave a better indication of damage and successfully improved the defect region detection in multi-layered reinforced composite materials.

Abstract: Towards green material, fatigue life of unidirectional kenaf fibre reinforced epoxy composites was investigated made from the hand-layout technique. The composites were subjected to tension-tension fatigue loading at stress ratio of 0.5 and 5 Hz of frequency. Fibre content ratios were found to affect fatigue life on the low cycle fatigue regime strongly as illustrated with stress level versus cycles to failure. It is found that kenaf fibre reinforced epoxy composites with higher fibre content posses higher load carrying capacity and degradation rates.

Abstract: This paper presents the performance of Aluminium Alloy side door subjected to side pole impact test. Aluminium Alloy is used in order to reduce the overall car weight. Therefore further improvements of the Aluminium Alloy side door system were carried out to obtain similar crash performance with the conventional steel side door system. The main crash performance properties are the internal energy, bending displacement, and mass. These properties were used to simulate the pole impact test using LS-DYNA Finite Element software. The improvements techniques used involved parameters such as thickness variation of the parts, ribs addition, beam shape variations, and combination of the factors. From the tests, three designs which include combination of parameters have met the target requirements. Thus, the use of Aluminium Alloy in side door system is acceptable provided there are improvements regarding the crash performance.

Abstract: In this study, a computer program for calculating fatigue life of component is developed and introduced in LS-PrePost software. The program is written in Fortran programming language and the fatigue life equations used is taken from well-published literature. The materials covered are steel and aluminum. The developed program is able to read stress, strain and element values from d3plot and the keyword file. Having extracted the output from d3plot and keyword file, the fatigue life is then calculated and presented into a separate file called FATIGUE. The integration of output from FATIGUE will is displayed in LS-PrePost. Finally, the results of fatigue life contour are successfully displayed through LS-PrePost.

Abstract: The aim of this study is to analyze the effect of steel and composite material on pedestrian head injury criteria of hood system. The hood is made of mild steel and aluminum, e-glass/epoxy composite and carbon epoxy composite are studied and characterized by impact modeling using LS-DYNA V971 in accordance with United States New Car Assessment Program (US-NCAP) frontal impact velocity and based on European Enhanced Vehicle-safety Committee. The most important variable of this structure are mass, material, internal energy, and Head Injury Criterion (HIC). The results are compared with hood made of mild steel. Three types of materials are used which consists of mild steel as reference materials, Aluminum AA5182, E-glass/epoxy composite and carbon fiber/epoxy composite with four different fiber configurations. The in-plane failure behaviors of the composites were evaluated by using Tsai Wu failure criterion. The results for the composite materials are compared to that of steel to find the best material with lowest HIC values. In order to evaluate the protective performance of the baseline hood, the Finite Element models of 50th percentile an adult pedestrian dummy is used in parallel to impact the hood. It was found that aluminum AA5182 hood can reduce the Head Injury Criterion (HIC) by comparing with the baseline hood. For pedestrian crash, it is observed that Aluminum AA5182 hood gave the lowest HIC value with 549.70 for HIC15 and 883.00 for HIC36 followed by steel hood with 657.40 for HIC15 and 980.90 for HIC36, e-glass/epoxy composite hood with 639.60 for HIC15 and 921.70 for HIC36 and carbon/epoxy composite hood with 1197.00 for HIC15 and 1424.00 for HIC36.

Abstract: The leg injury criteria subjected to frontal impact is presented and discussed. The aim is to analyze the effect of steel material of bumper shell on pedestrian leg injury criteria of front bumper system. The front bumper beam is made of mild steel and characterized by impact modeling using LS-DYNA V971, according to United States New Car Assessment Program (US-NCAP) frontal impact velocity and based on European Enhanced Vehicle-safety Committee. The most important variable of this structure are mass, material, internal energy, and Leg Injury Criterion (LIC). In order to evaluate the protective performance of the baseline hood, the Finite Element Models (FEM) of legform of an adult pedestrian is used. The result shows that the acceleration of 91.5 g, shear displacement of 4.2 mm and bending angle of 12.0˚ graphs are performing below the danger limit. The reason found to be there were no contact between the front bumper beam and the legform, so that the injury is less. This is shows that the clearance between the bumper shell and front bumper beam are sufficient.

Abstract: In this study an aluminium alloy is introduced as an alternative lightweight material in automotive industry. In order to achieve lightweight design, the study was undertaken on a side member of automotive parts. Crashworthiness performance of AA5182 side member is compared to the automotive steel side member. By designing 16 experiments based on full factorial design, the effect of thickness with four levels on the crash performance of the AA5182 side member was investigated for each loading conditions, axial and oblique loading. Mass, energy absorbed and maximum force is set as the evaluation criterion and the full factorial design has presented several designs to serve the evaluated criterion.

Abstract: The thin-web structure component is widely used in aviation and aerospace industries with the reason of light weight and high performance. However, the thin-web components are tending to deflect because of their poor rigidity and the effect of cutting force during cutting process. It is required to perform of high-speed machining that can remove the large number of material in a shorter time in order to allow machining of such structure. The performance of high-speed machining operation is restricted by the static and dynamic stiffness of the tool and part that can cause some problems such as regenerative chatter and ‘push-off’. The tool path plays an important function to avoid the problem occurs as it assists to reduce the workpiece vibration during machining. The optimization of tool path is done by determining the element removal sequences and the materials removal are implemented using milling cutter. The maximum deflection for each element removed is recorded in order to define the optimum solution of element removal sequences. The analysis shows that there are significant effects of workpiece stiffness with relation to the cutting parameters setting.

Abstract: 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.

Abstract: It is important to account for residual stress relaxation phenomenon in the design of the component. Specimens of 2024-T351 aluminium alloy were used in this study. The specimens were shot peened under three different shot peening intensities. Cyclic tests for two load magnitudes were performed for 1, 2, 10, 1000 and 10000 cycles. Residual stresses, microhardness and the cold work percentage were measured at initial state and after each loading cycle for the three shot peening intensities and for the two loads. The study revealed that most of the drop in the residual stress, microhardness and cold work happened in the first cycle are dependent on the applied load.