Z.N. Ismarrubie

Effect of length on crashworthiness parameters and failure modes of steel and hybrid tube made by steel and GFRP under low velocity impact

The use of tubes as energy absorption structures has been prevalent for many decades and numerous studies have been done on metal and composite tubes of varying thickness, length and section geometry. This paper extends the work to hybrid tubes and presents the results of experimental work pertaining to the collapse modes and crashworthiness characteristics of hybrid tubes that were subjected to quasi-static axial compressive loading. The hybrid specimens were featured by inner mild steel tube wrapped by a material combination of glass fibres in the form of reinforcing direct roving fabric in thermosetting polyester resin. Tubes were cut at different lengths of the same circular cross-section that encompassed both classical progressive buckling and the global bending modes of failure. Particular attention was paid to the investigate effect of tube length on crashworthiness parameters and critical length to avoid global bending during quasi-static crushing of thin-walled tubes. At first, similar work was done on steel tubes to compare results obtained by hybrid tubes with plain counterparts.

Optimization of Cold Rolling and Subsequent Annealing Treatment on Mechanical Properties of TWIP Steel

This research work studied the effect of cold rolling reduction and subsequent annealing temperature on the microstructural evolution and the mechanical properties of Fe-32Mn-4Si-2Al twinning-induced plasticity steelxa0plates. For this, uniaxial tensile tests were carried out for three cold rolling reductions (50, 65 and 80%) and subsequent annealing treatment at 550-750xa0°C for 1.8 ks. The results were discussed in terms of the yield strength, ultimate tensile strength and total elongation and its dependence on the introduced microstructure. Regression analysis was used to develop the mathematical models of the mechanical properties. Moreover, analysis of variance was employed to verify the precision of the mathematical models. Finally, desirability function was used as an effective optimization approach for multi-objective optimization of the cold rolling reduction and annealing temperature. It is considerable that there is no research attempting to find optimum mechanical properties of the steels using this approach. The results indicated that applying large cold rolling reduction (upper than 75%) and subsequent annealing treatment in the recovery region and also the application of large cold rolling reduction and the subsequent annealing treatment in the lower limit of partial recrystallization region were effective methods to obtain an excellent combination of mechanical properties.

Effect of Fiber Loading on the Mechanical Properties of Millet Husk Filled High Density Polyethylene Composites

The aim of this study is to determine the effect of fiber loading on the mechanical properties of millet husk (MH) filled high density polyethylene (HDPE) thermoplastic composites. Three different fiber sizes; 250 μm, 500 μm and 750 μm were pulverized and the fiber loading was 10 %, 20 %, 30 % and 40% by weight. The MH-HDPE composites were prepared by application of internal mixer, accompanied by compression molding process. Tensile properties were tested using universal testing machine (UTM). The tensile strength increase from 0 % to 10 % by weight fiber loadings. But this strength decrease as the fiber loading increase, while the modulus increase as the loadings increases. At 30 % fiber loadings, the strength of the composites decrease for high fiber sizes of 500 μm and 750 μm and increases for small fiber sizes of 250 μm for both the composites strength and modulus . This is presume the maximum loading for MHHDPE composites.

Microstructural Evaluation of Bi-Ag and Bi-Sb Lead-Free High-Temperature Solder Candidates on Copper Substrate with Multiple Reflow Number

An impetus has been provided towards the development of lead-free solders by worldwide environmental legislation that banned the use of lead in solders due to the lead toxicity.This study focus on Bi-Ag and Bi-Sb solder alloys, in compositions from 1.5 to 5 wt % Ag and Sb. The effects of Ag and Sb amount, and reflow number on the microstructure and morphology of solder bulk were analysed by optical microscope and scanning electron microscope-energy dispersive X-ray. Based on the results, the grain boundary grooving was observed in all samples except Bi-5Sb in all three reflows. Metallurgical and chemical reaction between interface and solders were found in Bi-5Sb solder alloys in different reflow numbers which lead to appearance of Cu3Sb intermetallic compound layer at the interface. Reflow numbers had a significant effect on the size of Cu-rich phase. Also it was observed that, with increasing reflow number Bi-Cu phase found in Bi-2.5Sb solder dissolves into the solder bulk.

Tactile Slippage Analysis in Optical Three-Axis Tactile Sensor for Robotic Hand

This paper presents experimental results of object handling motions to evaluate tactile slippage sensation in a multi fingered robot arm with optical three-axis tactile sensors installed on its two hands. The optical three-axis tactile sensor is a type of tactile sensor capable of defining normal and shear forces simultaneously. Shear force distribution is used to define slippage sensation in the robot hand system. Based on tactile slippage analysis, a new control algorithm was proposed. To improve performance during object handling motions, analysis of slippage direction is conducted. The control algorithm is classified into two phases: grasp-move-release and grasp-twist motions. Detailed explanations of the control algorithm based on the existing robot arm control system are presented. The experiment is conducted using a bottle cap, and the results reveal good performance of the proposed control algorithm to accomplish the proposed object handling motions.

Effect of Heat Treatment on Mechanical Properties and Susceptibility to Stress Corrosion Cracking of Aluminium Alloy

The effect of the retrogression and reaging (RRA) heat treatment on the correlation between microstructure, mechanical properties and susceptibility to stress corrosion cracking (SCC) of the 6061-T6 aluminium alloy in dry air and sprayed in 3.5% NaCl solution has been studied. The as-received T6 alloy was subjected to retrogression at temperature 200°C for 10 minutes, quenching for 30 seconds and reaging at temperature 180°C for 24 h. In this study, the effect of RRA on mechanical properties of the as-received 6061-T6 alloy was investigated by tensile test in air and sprayed in 3.5% NaCl solution. Alternate immersion preparation was conducted to expose the as-received 6061-T6 alloys and RRA heat treated alloys into the corrosive environment, 3.5% NaCl solution for 20 days. The susceptibility to SCC was investigated by direct tension stress-corrosion (DTSC) tests sprayed in a 3.5% NaCl solution at crosshead speed of 0.2 mm/min; the loss of elongation (ELloss) was taken into account for the susceptibility to SCC. Generally, the RRA heat treatment improves the mechanical properties including yield strength, ultimate tensile strength and ductility. On the other hand, the RRA heat treatment decreases the susceptibility to SCC.

Energy Absorption Capability of Hybrid Tube Made by Mild Steel and GFRP under Quasi-Static Loading

Hybrid tubes made by metal and composite combine the benefits of the high strength to weight ratio of the fiber/resin composite and the stable, ductile plastic collapse mechanism of the metal, to form a composite tube with high strength and energy absorption capability. The improvement of energy absorption parameters of circular steel tube as crash energy absorber that usually is used in automobile and train structures is studied in this paper. In order to improving energy absorption characteristics, circular steel tube wrapped by glass fiber reinforced polyester with different fiber orientation and various number of layers tested under axial quasi-static loading to achieve the optimum structure.