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

The effect of aging temperature on mechanical properties of banana pseudostem fiber reinforced polymer composite

Polymer composites using natural fibers as the reinforcing agents have found their use in many applications. The initial development of polymer composite based on high density polyethylene (HDPE) with banana pseudostem fiber was studied based on the effect of non-aging and aging treatments. Tensile, flexural and impact tests were performed to investigate the mechanical properties of banana pseudostem fiber reinforced composite. Flexural and impact test results show that the specimen strength improved after aging treatment was applied. However, the tensile test results gave a reverse effect on the strength of the composite after aging. The specimen became more brittle when the composite was exposed to the aging temperature

Preparation and characterization of cassava starch / peel composite film

This work is focused on the use of cassava peel as a natural fiber for thermoplastic starch (TPS) based on the cassava starch. Starch was extracted from the cassava tuber and the peel was used as a film fiber in order to obtain fully biodegradable composites. The composite films were prepared using casting technique. The addition of peel results in an increase in the thickness, water content, and water absorption of the films while decreasing the density and water solubility. Moreover, no significant effect was noticed on the thermal properties of the composite films. Scanning electron microscopy showed that the films containing a small size of peel had a better compact structure and a homogeneous surface without pores. The addition of 6% peel increased the elastic modulus and tensile stress up to 449.74 and 9.62 MPa, respectively, this being the most efficient reinforcing agent. Also the temperature variation of the dynamic‐mechanical parameters of cassava starch/peel composites was investigated using DMA test. It was observed that the incorporation of peel increased the tensile strength and modulus. In conclusion, of all‐plant composites can be prepared using cassava as both the matrix and the reinforcement, adding value to the residue of starch extraction. Based on its excellent properties, cassava starch/peel composite films are suitable for various purposes such as packaging, automotive and agro‐industrial application, at lower cost

Interfacial reaction of Bi–Ag and Bi–Sb solders on copper substrate with multiple reflow number

Owing to the toxicity of lead, much effort has been put in studies on lead-free solders after environmental legislations prohibited the use of lead in these parts worldwide. Here, Bi–Ag and Bi–Sb alternative solder alloys containing 1·5–5 wt-% Ag and Sb were investigated. The effect of the reflow number and weight percentage of Ag and Sb on the surface properties of solders and interfacial reactions between the solder bulk and the Cu substrate were analysed by optical microscopy and scanning electron microscopy–energy dispersive X-ray. The results show that by increasing the reflow number and wt-% of Ag and Sb in the solder bulk, the thickness of the mechanical grain boundary grooving is increased. However, the thickness of the Cu3Sb intermetallic compound layer at the interface of Bi–5Sb decreased by increasing the reflow number. Moreover, our findings show that the amount of Ag and Sb in solder alloys and the reflow number have different behaviours on the wettability properties. By increasing the reflow number, the wetting angle decreased in Bi–Ag solder alloys, whereas it increased in Bi–Sb solder alloys

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

Design concept of a new bio-inspired tactile sensor based on main pulvinus motor organ cells distribution of Mimosa pudica plant

This paper proposed a novel concept for a new tactile sensor that is inspired by the seismonastic movement of plants. The movement of Mimosa Pudica leaf is due to the change of pressure between the upper and lower motor organ of main pulvinus. From an engineering point of view, the turgidity changes capable of reversible shape changes, thus bringing the idea of sensing and actuating concept of a new tactile sensor. The idea is to fusion the artificial cell of Mimosa Pudica as the sensing mechanism for the new bio-inspired tactile sensor. Experiments have been conducted in order to determine the volume of the upper n lower motor organ cells of main pulvinus. The aim is to view the cross section of the main pulvinus between before and after the stimulation applied which led to two experiment procedures. Experimental results show that area of upper motor organ cell is approximately 50% larger than lower part for all four samples when mechanical stimulation applied. The design concept of the bio-inspired tactile sensor is proposed

Transient and thermal contact analysis for the elastic behavior of functionally graded brake disks due to mechanical and thermal loads

In this paper, the transient and contact analysis of functionally graded (FG) brake disk is presented. The analysis was carried out using ANSYS parametric design language (APDL). The FG brake disk is made of metal–ceramic material. The material properties vary in radial direction with the values from full-metal at the inner radius to that of full-ceramic at the outer radius. In the analysis, FG brake disk is in contact with one pure pad disk and coulomb contact friction is considered as heat source. The non-dimensional results are obtained for specific value of grading index (n = 1) by considering different material property divisions of 25, 50, 100 and 200. The results presented are for the pressure distribution, total stress, pad penetration, friction stress, heat flux and temperature during contact, for different values of contact stiffness factor, Fkn, which depends on the property gradation of FG brake disk with 200 material property divisions. The results show that the contact pressure and contact total stress increase with increasing values of Fkn, and hence it can be concluded that gradation of the metal–ceramic has significant effect in the thermomechanical response of FG brake disks

Comparative study of physical properties based on different parts of sugar palm fiber reinforced unsaturated polyester composites.

This research was conducted to evaluate the potential of sugar palm residue as a raw material to produce the new green composites. The physical properties of sugar palm fibre reinforced unsaturated polyester composites from different part which are sugar palm frond (SPF/PE), sugar palm bunch (SPB/PE), sugar palm trunk (SPT/PE) and black sugar palm fibre (ijuk/PE) were studied. Samples were submerged in distilled water for 24 hours. The water absorption and thickness swelling were investigated in order to determine the dimensional stability of the composites. It is found that SPF/PE showed the higher value of water absorption and thickness swelling which are 1.57%, and 1.56% followed by SPB/PE (1.35%, 1.11%), ijuk/PE (0.65%, 0.76%) and SPT/PE (0.39%, 0.50%). Generally, this investigation is valuable for researchers in order to evaluate the potential and some possible application of sugar palm residues as a new natural composites product

Axial behavior of steel tube wrapped by composite as energy absorber under compressive load

Beside the mechanisms such as ABS and airbag, energy absorbers are one of the most important structures which can protect occupants during impact collisions. In this paper, the purpose concerns the crashworthiness of the widely used vehicle structure, circular metallic thin-walled tubes. For improving crashworthiness parameters and using benefits of metal and composite with together, metallic tube wrapped by composite. An experimental investigation was carried out to study the energy absorption characteristics of this structure subjected to quasi-static axial loading. Different number of composite layer and fiber orientation made of E-glass direct roving and polyester resin investigated to develop the optimum structural members

Finite element analysis of thermoelastic contact problem in functionally graded axisymmetric brake disks

An analysis of thermoelastic contact problem of functionally graded (FG) rotating brake disk with heat source due to contact friction is presented. Finite element method (FEM) is used. The material properties of disk are assumed to be represented by power-law distributions in the radial direction. The inner and outer surfaces considered are metal and ceramic, respectively. Pure material is considered for the brake pad. Coulomb contact friction is assumed as the heat source. It is divided into two equal parts between pad and brake disk which leads to thermal stresses. Mechanical response of FG disks are compared and verified with the known results from the literatures. The results show that the maximum value of radial displacement in mounted FG brake disk is not at outer surface. It is found that the all areas between pad and brake disk is in full-contact status when the ratio of pad thickness to brake disk thickness is 0.66. It is observed that the total strain due to thermomechanical load is negative for some parts of the disks, whereas, the thermal strains are always positive. It can be concluded that gradation index of the metal-ceramic has significant effect in the thermomechanical response of FG disks