Aluminum and magnesium were joined through diffusion bonding using Ni interlayer. The micro- structure and mechanical performance of the A1/Ni/Mg joints at different temperatures was investigated by means of scanning electron microscope （SEM）, electro-probe microanalyzer （EPMA）, X-ray diffraction （XRD）, Vickers hardness testing, and shear testing. The results show that the addition of Ni interlayer eliminates the formation of Mg-A1 intermetallic compounds and improves the bonding strength of the A1/Mg joints. The AI/Ni/Mg joints are formed by the diffusion of A1, Ni and Mg, Ni. The microstructure at the joint interface from A1 side to Mg side is A1 substrate/A1-Ni reaction layer/Ni interlayer/Mg-Ni reaction layer/Mg substrate multilayer structure. The mi- crohardness of the Mg-Ni reaction layer has the largest value of HV 255.0 owing to the existence of Mg2Ni phase. With the increase of bonding temperature, the shear strength of the joints increases firstly and then decreases. The A1/Ni/Mg joint bonds at 713 K for 90 min, exhibiting the maximum shear strength of 20.5 MPa, which is greater than that of bonding joint bonded directly or with Ag interlayer. The fracture of the joints takes place at the Mg- Ni interface rather than the A1-Ni interface, and the frac- ture way of the joints is brittle fracture.
This paper presents a segmented trajectory planning strategy for active collision avoidance system.Considering the longitudinal and lateral movement of the obstacle vehicle,as well as the ego vehicle and obstacle outer contour limitations,the collision avoidance trajectory is divided into three segments:lane changing,overtaking and back to original lane.The starting point and end point of lane-change are decided based on longitudinal and lateral safety distance model according to the relative speed and distance as well as the outer contour of the two vehicles.Based on system objective function and lane-change trajectory cluster,vehicle states,dynamic constraints and vehicle body kinematics constraints,the optimal trajectory can be selected,which can monitor the relative location of the obstacle vehicle constantly and then ensure the vehicle can accomplish the collision avoidance safely and smoothly.Simulation and experiment results demonstrate the effectiveness and feasibility of proposed trajectory planning strategy for the active collision avoidance.
Using high aluminum refractory material as substrate at 1400℃, we studied the connections between several oxides such as Fe203, MnOv CuO, and the formation of defects such as coating crack, exfoliation, blistering, erosion, and fading away appeared in the application of high temperature infrared radiation coating. Analyses showed that thermal stress formed during the heating process due to the thermal expansion coefficient differential between the coating and the substrate, and volume effect caused by the crystal transferred when the temperature changed, which resulted in the coating crack and exfoliation. The gas produced by the reactions between components and binder or the components themselves during the heating process caused the coating blistering. The EMPA and XRD analyses show that oxides with low melting point in the penetrating area of the substrate may form eutectic with low melting point and produced thermal defects, which leads to the erosion by penetrating to the substrate. The valent changes of Fe2O3 and MnO2 during the heating process cause the volatilization of the oxides or the pulverization of the coatings, resulting in the coating fades away easily at high temperature for a long time.
YE JingLAN HelongWANG ChuanbinLUO GuoqiangZHANG Lianmeng
