NiTi shape memory alloys(SMAs) was developed using the spark-plasma sintering(SPS) process with different average particle size(45 μm and 10 μm) under various temperature. The influence of particle size and temperat...NiTi shape memory alloys(SMAs) was developed using the spark-plasma sintering(SPS) process with different average particle size(45 μm and 10 μm) under various temperature. The influence of particle size and temperature on the density, microstructure, and corrosion behavior of the NiTi in simulated body fluid was examined. The porosity decreased with increasing sintering temperature and decreasing particle size, which resulted in an increase in density of the alloy. Increasing the sintering temperature led to the formation of Ni-and Ti-rich intermetallic such as Ni3Ti and NiTi2. The formation of these secondary phases influenced the corrosion behavior of NiTi by changing its chemical composition. The planar structure of NiTi was transformed into a dendritic structure at 900℃, which resulted in the formation of uniform oxide and phosphate layers on the entire surface. A high corrosion potential and low corrosion current density were achieved with NiTi prepared with 10 μm particles at 900℃, which exhibited superior corrosion resistance.展开更多
The formulation of nanocrystallinc NiTi shape memory alloys has potential effects in mechanical stimulation and medical im- plantology. The present work elucidates the effect of milling time on the product＇s structur...The formulation of nanocrystallinc NiTi shape memory alloys has potential effects in mechanical stimulation and medical im- plantology. The present work elucidates the effect of milling time on the product＇s structural characteristics, chemical composition, and mi- crohardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fractur- ing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninter- rupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to -93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline in- termetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.展开更多
The correlation between the wear behavior of a heavy commercial vehicle (HCV) brake liner tested under controlled laboratory conditions and that in actual field conditions is investigated.A brake liner study for frict...The correlation between the wear behavior of a heavy commercial vehicle (HCV) brake liner tested under controlled laboratory conditions and that in actual field conditions is investigated.A brake liner study for friction and wear is performed on an inertia brake dynamometer (IBD) at different temperatures (200 ℃,250 ℃,and 300 ℃) using 6000 brake actuations in a laboratory.The total wear loss of the brake liner at three different temperatures for 6000 brake actuations in IBD is found to be 1.12 mm.The actual field test is conducted on four different HCVs,namely,a city bus (CB),a high speed bus (HSB),a highway truck (HWT),and a tipper lorry (TL).These HCVs run at different terrain/traffic conditions and load conditions.When comparing the predicted life of the brake liner through the IBD test with the actual life of the brake liner in different HCVs,a vast difference is observed.Due to the large variation of liner life observed between the actual and predicted tests,an extensive field test is conducted.In the field test,the liner with identical formulation is fitted in the four types of HCVs.The predicted life of the liner using IBD is then correlated with the field test observation and a correlation factor is determined.Based on this correlation factor,the predicted life of the liner and the achieved life on the HCV are found to be fairly close.This study will be useful to design the friction material formulation and to predict the actual life of the brake liner for various HCVs.展开更多
文摘NiTi shape memory alloys(SMAs) was developed using the spark-plasma sintering(SPS) process with different average particle size(45 μm and 10 μm) under various temperature. The influence of particle size and temperature on the density, microstructure, and corrosion behavior of the NiTi in simulated body fluid was examined. The porosity decreased with increasing sintering temperature and decreasing particle size, which resulted in an increase in density of the alloy. Increasing the sintering temperature led to the formation of Ni-and Ti-rich intermetallic such as Ni3Ti and NiTi2. The formation of these secondary phases influenced the corrosion behavior of NiTi by changing its chemical composition. The planar structure of NiTi was transformed into a dendritic structure at 900℃, which resulted in the formation of uniform oxide and phosphate layers on the entire surface. A high corrosion potential and low corrosion current density were achieved with NiTi prepared with 10 μm particles at 900℃, which exhibited superior corrosion resistance.
文摘The formulation of nanocrystallinc NiTi shape memory alloys has potential effects in mechanical stimulation and medical im- plantology. The present work elucidates the effect of milling time on the product＇s structural characteristics, chemical composition, and mi- crohardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fractur- ing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninter- rupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to -93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline in- termetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.
文摘The correlation between the wear behavior of a heavy commercial vehicle (HCV) brake liner tested under controlled laboratory conditions and that in actual field conditions is investigated.A brake liner study for friction and wear is performed on an inertia brake dynamometer (IBD) at different temperatures (200 ℃,250 ℃,and 300 ℃) using 6000 brake actuations in a laboratory.The total wear loss of the brake liner at three different temperatures for 6000 brake actuations in IBD is found to be 1.12 mm.The actual field test is conducted on four different HCVs,namely,a city bus (CB),a high speed bus (HSB),a highway truck (HWT),and a tipper lorry (TL).These HCVs run at different terrain/traffic conditions and load conditions.When comparing the predicted life of the brake liner through the IBD test with the actual life of the brake liner in different HCVs,a vast difference is observed.Due to the large variation of liner life observed between the actual and predicted tests,an extensive field test is conducted.In the field test,the liner with identical formulation is fitted in the four types of HCVs.The predicted life of the liner using IBD is then correlated with the field test observation and a correlation factor is determined.Based on this correlation factor,the predicted life of the liner and the achieved life on the HCV are found to be fairly close.This study will be useful to design the friction material formulation and to predict the actual life of the brake liner for various HCVs.
