Advanced Materials Research Vols. 123-125

Abstract: The NiTi alloy can be trained by repetitive loading or heating cycles. As a result of the training, a two-way shape memory effect (TWSME) can be induced. Considerable research has been reported regarding the TWSME trained by tensile loading, however the TWSME trained by compressive loading has not been investigated nearly as much. In this research, six types of specimens (one solid cylindrical and five tubular) were used to obtain the two-way shape memory strain and two-way recovery stress and to evaluate the actuating capacity. The two-way actuating strain showed a saturated tendency after several training cycles for the same maximum deformation. A maximum value of the two-way strain was obtained for 7% of maximum deformation, independently of the geometry of the tubular specimens. The two-way strains obtained by the shape memory cycles and two-way recovery stress linearly increase as a function of the maximum deformation and the two-way strain, respectively, and the geometry of specimen affects the two-way recovery stress. Although the results show that sufficient recovery stress can be generated by either the two-way shape memory process or by the one-way shape memory process, the two-way shape memory process can be applied more conveniently to actuating applications.

Abstract: This paper demonstrates the feasibility of using piezoelectric actuators in controlling flow-induced vibration of a lightweight composite wing structure. Vibration characteristics of the composite wing model were predicted analytically against the air flow speed and the results were compared with experimental results from wind tunnel tests. Vibration control tests were successfully accomplished using positive position feedback (PPF) controller and the real-time operating deflection shapes of the composite wing were measured using 3D optical motion capture system.

Abstract: In order to obtain the favoured material properties for a particular application, it is important to know how the material performance changes with the filler content under given loading conditions. In this study, a series of bamboo fiber reinforced epoxy composites are fabricated using conventional filler (aluminium oxide (Al2O3) and silicon carbide (SiC) and industrial wastes (red mud and copper slag) particles as filler materials. By incorporating the chosen particulate fillers into the bamboo-fiber reinforced epoxy, synergistic effects, as expected are achieved in the form of modified mechanical properties. Inclusion of fiber in neat epoxy improved the load bearing capacity (tensile strength) and the ability to withstand bending (flexural strength) of the composites. But with the incorporation of particulate fillers, the tensile strengths of the composites are found to be decreasing in most of the cases. Among the particulate filled bamboo-epoxy composites, least value of void content are recorded for composites with silicon carbide filling and for the composites with glass fiber reinforcement minimum void fraction is noted for red mud filling. The effects of these four different ceramics on the mechanical properties of bamboo- epoxy composites are investigated and the conclusions drawn from the above investigation are discussed.

Abstract: 2021 series aluminum alloy is used as the matrix material for its wide application in engineering to make AlON coating layers by the electrolytic plasma processing (EPP) method. The experiments were carried out on 2021 Al alloys in alkaline electrolytes which are eco-friendly and low-cost. The experimental electrolyte composition includes: 2g/L NaOH as the electrolytic conductive agent, 6~14g/L Na3PO4 as alumina formative agent, 0.5g/L NaNO3 as a nitrogen inducing agent. The effects of phosphate content variation are evaluated by a combined composition and structure analysis of the coating layer using with Philips-X’Pert X-ray diffractometer, JSM 5610 scanning electron microscopy for the specimens EPP-treated at room temperature in 10 min under a hybrid voltage (260V DC + 200V AC-50Hz). In addition, microhardness of the ceramic coatings was measured to correlate the evolution of microstructure and resulting mechanical properties. The wear tests show that a composite of AlON-Al2O3 high anti-abrasive coating formed as a result of a reactive process between Al in the alloy itself and O-N supplied by the electrolyte.

Abstract: The effect of tungsten carbide (WC) particulate fillers incorporation on two-body abrasive wear behaviour of glass fabric reinforced-epoxy (GE) composites was investigated and findings are interpreted. The wear behaviour of the composites were performed using pin-on-disc tester at varying abrasive distances viz., 25,50,75 and 100 m at a constant load of 20 N. The experiment was conducted using two different water proof silicon carbide (SiC) abrasive papers and at two different velocity under multi-pass condition. The wear loss of the composites found increasing with increase in abrading distances. A significant reduction in wear loss and specific wear rates were noticed after incorporation of WC filler into GE composite. This result indicates a significant improvement in wear resistance after incorporation of WC filler. The WC loaded systems exhibit less wear of matrix during abrasion which in turn facilitates lower fiber damage, due to the presence of WC particles on the counter surface which act as a transfer layer and effective barrier to prevent large-scale fragmentation. The worn out surface features were examined through scanning electron microscopy (SEM) in order to probe the wear mechanism.

Abstract: The sliding tensile and dry sliding wear behaviours of nylon 66/1 wt % carbon black composites with varying amounts viz., 0.5, 1, 2 and 3 wt % of molybdenum disulphide (MoS2) have been studied. The wear behaviour of nylon 66/carbon black/MoS2 composites has been investigated using pin-on-disc tester under dry condition. Wear characteristics have been measured at different sliding velocity, loads and sliding distances. The coefficient of friction of the composites increases with increase in normal load due to changes in the area of contact. Wear mechanisms were established using SEM.

Abstract: Laser surface melting (LSM) of aluminum alloy 6013 was conducted using a high power Nd-YAG laser under nitrogen gas with the aim of improving the stress corrosion cracking (SCC) resistance of the alloy. The SCC behavior was studied in a 3.5% NaCl solution using a slow strain rate test (SSRT). A laser-melted layer in the order of 500µm thick was produced, which consists of fine dendritic and cellular structures with some Al-Si-Cu-Fe-Mn phase particles formed at interdentritic boundaries. The results of the SSRT test showed that the susceptibility of the alloy to SCC, in terms of total elongation to failure, was decreased after the laser surface modification. This was considered to be attributed to the presence of the laser-formed AlN film, which acted as a barrier to the ingress of the corrosive Cl- into the material and enhanced the pitting resistance of the material. An examination of the fractured surface indicated that the crack propagation path, in the early stage of SCC, was along the tortuous dendrite and cell boundaries. This caused the crack path deviated from the growing direction and resulted in a longer crack length covered before failure thus increasing the overall crack propagation resistance.

Abstract: The effect of ultrahigh molecular weight polyethylene (UHMWPE) on solid particle erosion behaviour of aramid fabric reinforced-epoxy (A-E) hybrid composites was investigated. The aramid fabric reinforced-epoxy hybrid composites have been fabricated with and with out UHMWPE filler. The solid particle erosive wear was evaluated at different impingement angles from 300 to 90 0 at constant velocity and at constant standoff distance .The silica sand of size 30 -50 and 60 -80 μm was used as erodent. The results show erosive rate of UHMWPE filled aramid- epoxy composite shows lowest value. The presence of UHMWPE in epoxy matrix gives good bonding between filler and matrix. The morphologies of eroded surface were examined by the SEM in order to establish the erosion mechanism of the composites.

Abstract: In this study, wood surface was treated in metal processing using Cu/Ni electroplate methods. The bonding force and surface morphology between metal coatings and wood pores were measured by SEM. The non-lubricated friction was tested using the MMW-1 vertical universal friction and wear testing machine. Then the waterproof performance was measured by contact angle tester. The results show that the wood still remained original pore structure after treated by copper electroplate and nickel electroplate, but the surface had been completely covered by metal coating. The dense of coating was compact and uniformly distributed, the interfacial bonding was well. After the wood treated by Cu/Ni, the friction coefficient declined from 0.04-0.12 to 0.004 and 0.003, and the friction torque decreased from 10-30N.mm to 1N.mm, at the same time the average of hardness increased from 6.42HV to 93.18HV and 226.86HV. The treated metal-wood surface has higher wear-resisting property and hardness.

Abstract: Diameter of nanoparticles plays a vital role in tribological properties of lubricanting oil. Three kinds of nano-copper with different diameters (50nm, 65nm, 80nm) were produced using the electric explosion of metallic wire (EEW), and their diameters were characterized by Scanning Electron Microscope (SEM). The tribological properties of the lubricating oils containing nano-copper additives were investigated using friction wear testing machine, and the wear scar morphology photographs were observed by means of continuously multiple microscope. The results show that lubricanting oil with the large diameter of 80nm copper particles and the weight percentage of 1.0% ~ 1.2% has good characteristic of extreme pressure ; while the lubricanting oil with the small diameter of 50nm copper particles and the weight percentage of 1.2% provides good properties of anti-wear and friction reducing. This has a guiding role in selecting nanooil additives.