Abstract:The grinding mechanism is very complicated, and single abrasive grinding is an important means to study the grinding mechanism. In this paper, the basic theory of grinding is expounded from the abrasive grain shape and the grinding process. It is stated that scholars form the removal of materials, and grinding force to research the progress of single-grain experiments.Nextly,On the basis of simulation discussed the influence of grinding parameters on grinding force, grinding temperature and surface quality of workpiece.This paper is of great significance for revealing the mechanism of grinding processing.Finally,the experiments and simulations of single abrasive particles are summarized and prospected.

Abstract:Research background, latest development direction, and present status of leakage performance of cryogenic composite tank are reviewed. Cryogenic microcracking, cryogenic permeability and their mechanism model are introduced. The methods of reducing microcracking and leakage rate are summarized.

Abstract:In this paper, to study the metal spring properties of high temperature sealing components, a parametric model of braided spring tube was established based on the characteristics of the Boeing’s braided spring and Streck cardiac stent, and the spring diameter formula are deduced. AUTODESK 3D-MAX was used to simulate braid spring, the effects of spring diameter, density, and method are studied. The results show that increasing the diameter of spring wire, reducing the density of woven springs in the axial direction，increasing the circumferential density of woven springs, and the way of the spring tube which is woven outside can improve the elasticity of spring tube.

Abstract:Based on the SPH method simulated process that the corrugation obliquity of stuffed corrugation-cored sandwiches is 30°,45°,56° and 60° impacted by space debris,and hypervelocity impact protection characteristics was compared,so,the corrugation obliquity of stuffed corrugation-cored sandwiches effect on hypervelocity impact protection characteristics was studied. The results show that expansion degree of debris cloud by impact is increscent by corrugation obliquity,and when the corrugation obliquity is 56°that the damage stuffed corrugation-cored sandwiches to space debris is the most bad; the difference of no-reversible work that four kinds structure translated is little,that show,corrugation obliquity effect on the no-reversible work transform is lesser；the damage in the spacecraft wall that be protect by different corrugation obliquity stuffed corrugation-cored sandwiches is different,when the corrugation obliquity is 56°that damage in the spacecraft wall is least,so,the protection characteristics is best in the four kinds corrugation obliquity structure.

Abstract:The pulsed laser ablates the material to form a surface micro-nano structure. In order to enhance the quality and efficiency of surface repair, the cold spray deposition process after pulse laser etching pretreatment was studied. Firstly, based on the pulsed laser action process and experimental observation results, simulation models between single/multiple particles and substrate were established. Secondly, thermal-structure coupling algorithm is used to carry out numerical simulation of the collision process between particle and substrate with surface micro-nano structures, and the effect of pulsed laser etching on the deposition process of cold sprayed materials is studied. Finally, the material deposition mechanism during the pulse laser assisted cold spray repair process was analyzed. The results show that the micro-nano structures formed by etching makes the temperature distribution in the collision area more uniform, and the deformation is more complicated, especially the deformation of the collision center area is significantly improved. When the collision position is the peak of the micro-nano structure, the strain and temperature rise are the largest, and the valley is the smallest. The deposition mechanism of pulse laser assisted cold spray is mechanical-physical bonding at plastic jet area and metallurgical welding in laser melting zone.smallest. The deposition mechanism of pulse laser assisted cold spray is mechanical-physical bonding at plastic jet area and metallurgical welding in laser melting zone.

Abstract:Mg-5Al-8Zn-xCa( x= 0, 1.75, 2.0, 2.25, 2.5, 2.75 and 3.0 wt%) Mg alloys were prepared by gravity casting. The effects of Ca content on microstructures and mechanical properties of the alloys were investigated by XRD, OM and SEM. The results show that the as-cast Mg-5Al-8Zn-xCa alloy is composed mainly of a-Mg matrix, b-Mg17Al12, Mg32(Al, Zn)49, MgZn2 and Al2Ca phases. With the increase of Ca content from 1.75% to 2.75%, the matrix grain is obvious refinement, the morphological change in b-Mg17Al12 phase occurs from coarse continuous network to fine intermittent network and distributed on the grain boundaries, the lamella-type phase Al2Ca is obvious refinement too, meanwhile the tensile strength of the alloy at room temperature reaches maximum, it is 138 MPa, increased by 27.8%, compared with the alloy with absence of Ca addition. When the Ca content reaches 3.0%, the grain is coarsened once more, meanwhile the tensile strength of the alloy decreased. The tensile fractures of the alloys are characterized by quasi-cleavage at room temperature.

Abstract:This artical carried out a comparative study between helical milling and drilling of C/SiC composite ma- terials. The cutting force,cutting temperature and hole quality of helical milling and drilling were measured under the same working efficiency. The results indicate that the axial force of PCD helical milling is less than PCD drilling and ocuppies nearly 56.9% of PCD drilling. The hole roughness and tolerance of helical milling are less than drilling. The cutting temperature of PCD drilling is less than helical milling and ccupies 58.7% of helical milling. In addition, the cutting heat of helical milling has a small influence on C/SiC composite materials and PCD tools.

Abstract:Based on the solid rocket motors of different diameters spliced, a set of automatic spraying device for solid rocket motor interface adhesive had been developed , adhesives property, spraying process parameters,quality control parameters research was carried out. Through the related experiments,it confirm that the equipment worked steadily and bonding Characteristics fulfilled the requirement of product by selecting reasonable parameter to sparying . High quality of the products obtained and work efficiency greatly improved, it provide the basis for related equipment studies

Abstract:To improve the surface integrity of nickel-based superalloy GH4169 after grinding, this paper uses a magnetorheological elastomer grinding wheel to perform a polishing test on the nickel-based superalloy GH4169. Firstly, a magnetorheological elastomer grinding wheel was prepared by compression molding, the surface micromorphology and hardness under different magnetic field strengths were characterized. Secondly, the prepared magnetorheological elastomer grinding wheel is used in the polishing process test of nickel-based superalloy GH4169, and the influence of magnetic field strength on the surface integrity of nickel-based superalloys in polishing process parameters is also discussed. The experiment results show that within a certain range of magnetic field strength, the surface roughness and microhardness of the part after polishing decrease with increasing magnetic field strength, and increasing the magnetic field strength is also beneficial to improve the surface morphology of the part reduce the amount of grinding wheel wear, reduce the thickness of the subsurface damage layer after the part is ground.

Abstract:Some CCGA Packages using on aerospace products should be assembled after PCB assembling for Space Applications by using infrared-hot flow hybrid SMT rework platform. This paper studied the temperature-control procedure, welded CCGA chips, and tested the assembling reliability. It confirmed the temperature control position should be located at 1-2mm from the edge of CCGA chips. The results proposed a simple and effective method to control the high thermal area(＞183 ℃). The results indicate that temperature curve range is feasible and there is no crack by dyeing experiment. The microstructure analysis by SEM and EDS indicates the thickness of IMC layer is uniform. There is no any crack inside the solder joint after reliability tests. This study standardized the soldering procedure of CCGA Packages after PCB assembling for Space Applications, the results indicate temperature-control method in this paper is reasonable and feasible. This method improved the reliability of CCGA solder point. It can be used on chips’ reworking and welding on aerospace products.

Abstract:The AuSn alloy was grown by magnetron sputtering as the solder layer and the Al/Ni energetic multilayer film was used as the heat supply layer to realize the heterogeneous soldering between stainless steel and Al2O3.The morphology and basic properties of the AuSn alloy and Al/Ni energetic multilayer films were investigated by SEM, XRD and DSC. The mechanical properties of the welded joints were tested by a universal testing machine. The result shows, the mass ratio of AuSn alloy is basically 80:20, and the layered structure of the multilayer film is clear, the heat of reaction reaches 1239 J/g. Studies have shown that only AuSn solder has a shear strength of 46 MPa. After increasing the Al/Ni energetic multilayer film, the shear strength can reach 90 MPa and the strength is increased by about one time. The microstructure and phase structure of the welded joints show that the increase of shear strength is mainly due to the additional energy provided by the Al/Ni multilayer film, which makes the reaction at the interface intense, and the reaction between the ceramic metallization layer and the intermediate layer is intensified,and new reaction products formed.

Abstract:In tap test on the honeycomb sandwich structures, the contact time of the tapping head changes with the flow sizes and the plates. To quantitively show these relationships, a mechanical model describing the tapping head movement was given. The equation of the contact time varying with the flow diameter and the plate tension was derived. The contact time variations under different tension parameters were given and compared with the experiment data. The result shows, by using suitable tension parameters, the contact time given by the mechanical model agrees with the experiment data. The model can be used to calculate the contact time and analysis its variation. For flows on a same plate, the contact time increases with the flow diameters. For flows with same diameter and on plates with same material, the contact time decreases with the plate thicknesses. For flows with same diameter and on plates with same thickness, the contact time on a FRP plate is shorter than that on an Al plate.

Abstract:The influencing spatial resolution, SNR and factors of contrast of images were researched. The digital radiography experiments were carried out on carbon filament-wound motor case with different technological parameters. The results show that when other parameters are consistent, focus size and magnifications have great effects on spatial resolution, the SNR of the images are affected by the tube voltage, tube current and single frame integration, both tube voltage and tube current have effects on image contrast.

Abstract:In view of the quality deviations that often occur in the process of manufacturing and inspection of titanium alloy tanks, a comprehensive analysis of the acoustic emission amplitude, time history and positioning results of two cases of abnormal spherical titanium alloy tanks was carried out. The results show that the acoustic emission detection technology has a strong sensitivity to the deviation of the tank manufacturing process state. The acoustic emission detection results can not only faithfully reflect the strength and quality of the tank product, but also reflect the stability and deviation of the tank manufacturing process state.

Abstract:In order to meet the application requirements of high-precision and high-resolution inspection of aerospace thin-wall aluminum alloy stir welding welds, ultrasonic array testing using total focusing method was studied. The array ultrasonic testing system was built based on the multi-reflection full focus optimization algorithm of shear wave coupled with oblique wedges. The comparative test of phased array ultrasonic testing by sector scanning and array ultrasonic testing by total focusing method for the Φ0.35 mm transverse holes at different positions of the 6mm friction stir welding seam were carried out by using the developed array ultrasonic testing system. The test results show that both methods can effectively detect the transverse holes in the weld center or heat affected zone, but array ultrasonic testing by total focusing method has more advantages in signal-to-noise ratio and longitudinal resolution, which can more effectively distinguish the three holes which are 1 mm、3 mm and 5 mm from the surface in the center of the weld, and the measured signal-to-noise ratio of three holes are higher than 20dB.The development of this technology provides a new way to solve the problems of high precision, high score rate and high reliability detection of complex components in aerospace field.

Abstract:The tungsten inert gas welding (VPTIG) and metal inert gas welding (MIG) welding tests were carried out on the 15mm-thick 2219 aluminum plates. The shape, internal quality, microstructure and tensile properties of the joints were compared and analyzed. The results show that the surface of TIG weld is bright and clean while the MIG welds are rough. There are a few tiny pores in MIG weld while the inside of the TIG weld is very clean. The grain size in weld seam of TIG joint is finer and more uniformly distributed than that of MIG joints. The grain size in heat affected zone (HAZ) of MIG joints is coarser than that of TIG joints. The grain size in fusion zone of both joints is quite uneven. Two kinds of joints cracked along the fusion zone in the tensile test at room temperature. The strength and plasticity of TIG joint is better than that of MIG joint.

Abstract:The heatshield of ShenZhou spacecraft is mainly composed of FRP honeycomb sandwich structure. Aiming at the problem that the hole position accuracy is difficult to guarantee due to the clamping deformation, the process optimization and improvement are carried out. The tooling structure, clamping method, process flow and drilling equipment are improved. The test results show that the drilling accuracy can be effectively improved by adopting the low stress clamping method, reducing the turnover times and using the numerical control processing equipment.