Abstract:In this work， the methods of laser machining， electrochemical machining， electrospark machining， chemical etching，photoetching and ultrasonic vibration-assisted machining were reviewed. The influence of surface texture shape on surface properties of material was analyzed. The influence of surface texture geometry parameters on surface properties such as lubricity， tribological properties and hydrophobicity was discussed. The results cancluded appropriate surface texture design parameters such as surface texture shape， area ratio and depth diameter ratio to improve the surface properties of mechanical parts. It was found that in order to obtain ideal surface properties， not only the texture shape and geometric parameters， but also operating conditions， material properties of workpiece and machining technology should be considered. Finally， the problems existed in surface texture processing technology were summarized and the influence of surface texture technology on material properties was prospected.

Abstract:This paper reviews the current research progress on the preparation and application of high-strength and high-modulus polyimide （PI） fiber-reinforced epoxy （EP） composites. It comprehensively introduces PI/EP composites properties including the molding process properties， interface properties， mechanical properties， failure mechanisms， electrical properties，damage resistance and ballistic resistance.The application direction of PI/EP composites is proposed.

Abstract:The patch curing behavior of fiber reinforced composite structures during scarf repair was studied via finite element simulation. A patch curing model of scarf repaired composite structures was established based on the temperature-dependent material parameters. The effect of heating rate and hold time on the temperature field in scarf repair was discussed. The results show that the influence of heating rate on the curing behavior of scarf repair is greater than that of hold time. When the heating rate increased one time， the curing temperature peak of the center increases by 1.1%. Moreover， the temperature change rate and curing reaction rate increase as the heating rate increases with an obvious temperature gradient generated in the curing area. In this work， the maximum temperature difference in the repaired area is up to 8℃.

Abstract:The influence of the outer skin assembly deviation， self-weight， forming and service temperature difference on the profile accuracy especially the R.M.S value of reflector working face is specially analyzed. The results show that through 0.5mm assembly offset of the outer skin， the reflector working face theoretical R.M.S value changes 0.47μm. Under the forming and placing condition， the 11kg self-weight has 0.55 μm deviation on the theoretical R.M.S value of the reflector working face. The temperature difference of it between the forming and service the reflector brings 17.79μm change of the theoretical R.M.S value.

Abstract:Unclear distribution of grinding traces in cross grinding leads to difficult control of grinding surface quality. To identify grinding traces distribution pattern in response to process parameters， the influence of main grinding parameters on surface quality was investigated. According to the grinding traces distribution formula of single abrasive diamond，the influence of the wheel speed，workpiece speed，feed rate，speed ratio and phase shift on the grinding traces distribution was analyzed and discussed. Based on the influence of grinding parameters on grinding traces distribution and scallop height，optimal grinding parameters combination was selected，and comparative grinding experiments were carried out. The results show that changes of grinding parameters would affect traces length，spacing， quantity，position and distribution in cross grinding therefore influence the ground surface quality of the workpiece. In particular，the extend of phase shift affects position relationship of grinding traces from end-to-end to staggered and directly determines how the grinding marks are formed. It is one of the key factors affecting the ground surface quality.In addition，small difference of workpiece speed in grinding experiment generates significant variation in grinding traces distribution with distinguished surface texture and cracks on workpiece and discrepancy in surface roughness Ra values between 59 to 125 nm. Therefore，based on the influence of grinding parameters on the grinding traces distribution，the surface quality of workpiece could be greatly improved with reasonable matching of grinding process parameters.

Abstract:In this paper， the typical hard-to-cut Cr12MoV die steel is taken as the research object. ABAQUS is used to conduct numerical simulation of the temperature field under electric spark discharge. Experimental results of the traditional milling and electric spark assisted milling are compared under different feed rates. By means of a high-speed camera， scanning electron microscope and dynamometer， the characteristics of cutting force， surface morphology and tool wear are analyzed and studied. The results show that the cutting force of EDM-assisted milling is 28.57%-51.47% lower than that of traditional milling， and the surface roughness is reduced by 2/3. Compared with traditional milling， EDM-assisted milling has significant advantages in reducing cutting force，improving surface quality and reducing tool wear.

Abstract:The grinding force， temperature and ground surface topography of the grinding process were studied by combination of simulation and grinding experiment with multi-abrasive grains.The differences in grinding characteristics between models of multi-abrasive-grain and traditional single-abrasive-grain were compared and analyzed. The simulation model of multi-abrasive-grain was verified by experiment. The results showed that by reducing grinding speed or increasing grinding depth， the grinding force in simulation and experiment of both models would increase. With increase of grinding speed or grinding depth， the grinding temperature in simulation and experiment of both models would rise. In simulation of the single-abrasive-grain model， the grinding force reduced with acceleration of feed rate， with the grinding temperature falling first before going up again. However， in simulation and experiment of the multi-abrasive-grain model， the grinding force increased with acceleration of feed rate， with grinding temperature going toward the opposite trend. The grinding force and grinding temperature in the multi-abrasive-grain model were higher than those of the single-abrasive-grain. The surface morphology of the workpiece after experiment using multiple abrasive grains was consistent with simulation result. The finite element simulation model using multiple abrasive grains to grind engineering ceramics gave closer to experiment result than using single abrasive grain.

Abstract:In order to improve the surface quality of single-crystal silicon by single-point diamond turning in the direction of surface roughness optimization， orthogonal cutting experiment are designed. The effects of spindle speed， feed speed and cutting depth on surface roughness are studied by variance analysis， response surface analysis and range analysis.The results show that the spindle speed has a significant effect on the surface roughness， and the larger the spindle speed is， the smaller the surface roughness value is. The regression model of surface roughness is established.The interaction of spindle speed and feed speed has the greatest influence on the surface roughness by response surface analysis.High-quality single-crystal silicon element with a surface roughness of Ra2.7 nm is obtained with the optimal combination of cutting parameters of 3300 r/min spindle speed，2 mm/min feed rate and 5µm depth of cut.Relatively smooth surface and the banded chip is observed.The material is removed in the ductile state.

Abstract:Offset paraboloid antenna reflectors （PSARs） made of carbon fiber prepregs are usually subject to thermal deformation， curing shrinkage deformation and mechanical deformation during the curing process.Excessive deformation will lead to the deviation of transmission signals. In order to effectively predict the deformation of the antenna reflector during the preparation process in a autoclave， a linear viscoelastic constitutive model is adopted to characterize the stress-strain relationship of the fiber reinforced composite material during the curing process. The temperature field， curing degree field and displacement field of the antenna reflector are modeled using the sequential thermal-force coupling analysis method， and the effects of the layup structure and the cooling rate on the deformation of the antenna reflector are analyzed. The analytical results show that the deformation in z-direction of PSARs with orthotropic or semi- isotropic layups is reduced by more than 51% compared with the zero-layup PSARs， and the reduced cooling rate could also help increase the shape accuracy of PSARs.

Abstract:In order to ensure the reliability of CLGA（Ceramic Land Grid Array）packaged devices，in this paper，secondary process design of the CLGA packaged devices were investigated by using Pb₉₀Sn₁₀ solder ball，Pb₉₀Sn₁₀ and Pb₈₀Sn₂₀ solder column，and Be-Cu/Sn₆₀Pb₄₀ Micro-Coil Spring（MCS）and Sn₆₃Pb₃₇ eutectic solder paste to assemble the devices on the printed circuit board through reflow soldering process. Through combination of finite element analysis and test，a high reliability assembly process suitable for such devices was explored. The finite element simulation models were established for the three components to simulate the stress and strain level.Mechanical and thermal experiments of the printed board assemblies were carried out. The simulation found minimum stress and strain in the micro-coil spring， lower stress and strain in the solder column，and maximum stress and strain in the solder ball.The research showed that the experimental verification was consistent with simulation results.The attaching Micro-Coil Spring devices had the highest reliability，whilst the attaching solder column devices had lower reliability，and the attaching solder ball devices had the worst. There were no cracks in the attaching micro-coil spring devices after 500 thermal cycles and vibration test.But some cracks appeared in the attaching solder column devices and the attaching solder ball devices. Solder joint metallographic microsection and SEM energy spectrum microstructure analysis met the requirements of aerospace standard. The fracture failure positions of the attaching solder ball and the attaching solder column devices all appeared in the touching position between the solder ball，the solder column and the printed circuit board.The thickness of the intermetallic compounds（IMC）layer and energy spectrum composition at the crack were normal.

Abstract:The notch in the middle of the original friction stir welding （FSW） joint was patched to simulate the weld defects. The weld defects in the middle position of the FSW joint were repaired by Tungsten Inert Gas （TIG）. The influence of the repair welding process on the microstructure and mechanical properties of the joint was studied to provide technical support and follow-up engineering guidance for the performance evaluation of the FSW weld of the tank. The results show that the TIG weld zone of the repaired joint is mainly composed of coarse equiaxed dendrites as compared to FSW joint.At the interface between the FSW joint and repaired joint coarse equiaxed grains and refined equiaxed grains are intermingled. The solid- solution zone of the repaired joint is greatly affected by the thermal cycle with coarsened grain， while the overaging zone is less affected by the thermal cycle with the occurance of over-aging phenomenon and the presence of a softening zone. The tensile strength and elongation of the repaired joint are decreased as compared to the original FSW joint. The hardness distribution is substantially "W" shape with the lowest hardness in the WNZ. Crack initiation of the repaired joint occurs at the weld toe displaying a large number of dimples on the fracture surface. Meanwhile， second phase particles are detected in the dimples showing a typical ductile fracture mechanism.

Abstract:Based on wear measurement of brush seals in existing tests， grey prediction model of wear amount of brush seal is established using the grey prediction theory. The service life of the brush seal is estimated， and the test verification is carried out. The results between prediction and test show that the grey model prediction is feasible with good prediction accuracy. Comparison of the wear amount of brush seals under three conditions for 500 min shows maximum relative residual error of 1.57% and maximum absolute residual error of 0.16 mm³.The result can be used as reference for determining operation time and repair and replacement demand of future brush seal devices.

Abstract:In the rolling process of thick plates， it is easy to have problems of uneven distribution of material structure and coarse grains due to improper process control. In this paper， ultrasonic testing signal on the internal structure of TC4 rolled plate is studied. The results show that the sound attenuation distribution is uniform when the sound wave is incident perpendicular to the plate streamline direction. However， the distribution of sound attenuation is very uneven and stripped in stripe shapes when the incident wave is parallel. For this reason， the section structure with different acoustic attenuation is analyze. It is found that the ultrasonic attenuation is related to the distribution and morphology of α phase in the material：in the area where the sound attenuation is reduced， there are more equiaxed α phases in the material， and the grains are fine and evenly distributed； in the area with large acoustic attenuation， α phase is obviously elongated， the tissue distribution is not uniform， and there is stripe structure.

Abstract:The large thin-wall curved surface composite parts are mostly formed by autoclave process，which will cause deformation in the curing process and demoulding process，resulting in deformation out-of-tolerance and assembly difficulty. In order to solve this problem， this paper firstly used the path-dependent constitutive model to analyze the curing process， then carried on the autoclave molding test to verify the theoretical analysis results， and finally used the reverse compensation method to correct the mold surface according to the theoretical analysis results. The simulation results show that the maximum displacement and minimum displacement of a large thin-wall surface composite parts after forming are 11.121mm and 0.171mm， respectively， which occur at the corner points of the short side and the corner points near the short side of the symmetry axis.The residual stress of the parts is larger on the two sides and the short side of the larger deformation， which is about 7MPa different from the long side of the smaller deformation. The simulation results are in good agreement with the experimental results， and the average curing deformation error is 8.6%. The maximum curing deformation of the part was reduced by 70.8% when the compensated mold was used for curing deformation simulation again.

Abstract:Due to the complexity and non-quantitative process of installation procedure of electric heater for propellant-line，test matrix method according to engineering experience was implemented to determine the influence of the status of insulation flim，glue thickness and embedded air bubble on pipeline heating. This study indicates that by choosing non-overlap wrapping for inner/outer insulation flim and 0.2 mm glue thickness using special rubber scraper， it is useful to reduce air bubble formation and improve the heating quality. The test results may serve as a reference for future installation of similar pipelines with electric heater.