Abstract:The basic methods and development process of traditional grinding simulation, as well as the research status of the abrasive model and the workpiece model are summarized. The research status of finite element method, smoothed particle hydrodynamics method, molecular dynamics method and comprehensive method are analyzed in detail, which is applied on the single abrasive grain grinding for the material removal mechanism, chip formation mechanism, workpiece surface quality and abrasive wear. Finally, the limitations of the simulation methods are expounded, and the development trend of single abrasive grinding simulation is put forward.

Abstract:With the development of space technology, the aircraft flight speed is much higher and the service environment is even worse. The effective thermal protection system is one of the key systems to ensure the safety of aircraft flight. In this paper, the application status of passive thermal protection system, active thermal protection system and semi-passive thermal protection system on the aerospace vehicles are reviewed. And the application and development of five kinds of thermal protection material in the aerospace field, including metal matrix composites, carbon based materials, ceramic matrix composites, resin matrix composites and aerogel materials are mainly introduced. Finally the future developments of the thermal protection for aerospace vehicles are prospected.

Abstract:Adhesively bonded scarf repairs are the preferred method for repairing laminated composite structures, limited mainly by the amount of material removal associated with scarfing. In addition to the high strength restoration, scarf repairs also enable recovery of the original external surface as required by aerodynamic and/or external mould line considerations. In this investigation, an optimization method has been developed for determining the optimum scarf repair angles, adhesive thickness and scarf patch material for a given biaxial loading condition. The scarf angle, adhesive thickness and scarf patch material was considered by adaptive response surface method (ASRM). The optimum and near-optimum scarf repair model are presented and discussed with respect to computational model using the finite element method. As a result, boron fiber scarf patch is the best with optimal matching modulus. When the scarf angle and adhesive thickness increased, the instability load also increased, then went into their matching zone, the instability load got its maximum value quickly. Once the value of scarf angle and adhesive thickness went out of their optimal matching zone, the instability load reduced soon. Meanwhile the matching between scarf repair patch material and the parent structure material is very important. It reveals that the ASRM method can realize the stability optimization of scarf repaired laminates with high efficiency.

Abstract:The characteritsic performances of two different bismaleimide based fiber reinforced composites were tested, and a finite element model for predicting the process induced distortion of hybrid fiber composite was built. The FEA results show that this finite element model can predict the distortion trend and the maximum distortion amount of hybrid fiber reinforced composites accurately. Compared the model output and the experiment result, the error is about 10%-15% considering the maximum distortion amount.

Abstract:During the cold roll forming process,a large elastic strain energy was stored in the deformation area when the rolling wheel hits and rolls the workpiece, resulting in emerging of springback. The springback had a great influence on the profile accuracy of workpiece. In order to control the precision of formed parts effectively, this paper studied the relation between rotational speed and springback. According to basic principle of cold roll-beating, a finite element dynamic simulation model is established. Through simulation, deformation law of the section of formed gullet in tangential direction, axial direction and radial direction under different rotational speed, and the springback law were obtained by static analysis. The results show that the workpiece profile obtained by cold roll-beating under the same process conditions is in agreement with the simulation results. The correctness of the simulation results is verified. The springback can be effectively controlled through the rational selection of process parameters, and the forming precision of the parts can be improved.

Abstract:The progressive damage analysis was used to explore the mechanical behavior of the fiber overwrapped aluminum liner cylinder. The plan of stiffness degradation was designed by the Hashin failure criteria, and the VUMAT subroutine was programmed. The generation and evolution of the damage for the composite laminates are simulated. According to the classical grid theory and the actual situation, the finite element model of the cylinder is established. The development and accumulation of progressive damage for composite layer is analyzed. The necessity of autofrettage technology to improve the bearing capacity of cylinder is verified, and the range of reasonable force of autofrettage is put forward. Results show that the order or possibility of damage is matrix tension damage > tensile delamination damage > fiber tension damage/matrix compression damage. Most of the damage starts from the spiral winding layer. In addition to the matrix tension damage from the head to the cylinder and the outside composite layer to the inside, most damages develop from the inner layer to the outer layer. The stress distribution and the carrying capacity of the cylinder structure are improved, when the force of autofrettage is 1.5~1.65 times of the maximum working pressure. The optimum force of autofrettage should be 1.5 times of the maximum working pressure from the standpoint of reducing the damage of composite material and minimizing the stress of lining.

Abstract:The mechanical performances of honeycomb sandwich structure and M5 inserts were tested. Results were discussed and the effects of panel thickness, areal density of adhesive and bonding strength on the mechanical performances were analyzed. It was found that properly increasing the panel thickness was effective to improve the mechanical performances of honeycomb sandwich structure and inserts. On conditions of the same bonding strength, mechanical performance was not affected by areal density of adhesive, therefore adhesive with lower areal density should be chosen to reduce weight. The in-plane shear carrying load capacity of inserts was better than the normal pull-out load carrying capacity. While under in-plane shear load, the failure mode of inserts was panel failure. While under normal pull-out load, the failure mode of inserts was honeycomb instability failure which finally caused panel deformed and destroyed at last. The conclusions can be used in product design.

Abstract:In this paper, the fiber Bragg grating sensor and carbon fiber composite materials were integratedly designed, by embedding the fiber Bragg grating sensor within the carbon fiber composite materials. The feasibility of the embedded technology was verified, the design was confirmed to real-time monitor the environment temperature. The structure strength change of the carbon fiber composite material after embedded fiber Bragg grating sensor as well as the fiber Bragg grating signal transmission rate was studied. The results show that the structure strength change rate of the carbon fiber composite materials before and after embedding fiber Bragg grating sensor is less than 10%, the strain signal transmission rate is above 90%. The fiber Bragg grating sensors can be used as an effective means of monitoring the whole life cycle structural strength of the carbon fiber composite materials from processing, using until failure.

Abstract:U3160 carbon fiber reinforced HT-350RTM polyimide composites (U3160/HT-350RTM) are fabricated by resin transform molding (RTM) process. The variation of weight loss rate of U-3160/HT-350RTM composites under different aging temperature and aging time were investigated, and the relationship between aging failure characteristics of polyimide composites and aging time/aging temperature was established. The failure mechanism during the process of thermal oxidation aging was discussed based on microstructure analysis. The results indicated that, at a certain temperature, the change of weight loss rate of the composites follows the variation law of three degree polynomial. The degradation of polyimide resin results in the increase of porosity of the composites, which especially occurrs on the surface of composites due to the oxidation.

Abstract:In order to solve the storage life of the fluoroelastomer seal in the hydraulic system, the accelerated aging test was carried out on two kinds of medium environment. The results show that the fluoroelastomer has good dielectric resistance and aging resistance. Accelerated aging 120 days under 90℃, compression rebond and mechanical properties to keep rates are above 80%.The storage life of fluoroelastomer is estimated to 20 years in the hydraulic system.

Abstract:In order to use the laser additivemanufacturing (LAM)techonology into the design and forming of the space vehicle structure more widely, based on the existing forming ability of the selective laser melting(SLM), the integrated design of the upper-stage cabin structure in the space vehicle was realized, the integrated model of the whole cabin structure was built, the scaling cabin structure was integrally formed, and in detail the design and forming integration was tested. The method of design and forming integration based on the laser additive manufacturing technology has been proven feasible, and the application of technology track in aviation and spaceflight field has been explored.

Abstract:Tension-compression fatigue test of LTX 1240 fiber/epoxy composite was studied in this paper. The fatigue life was predicted by plotting S-N curve, fracture surface were observed in SEM, and the failure mode was analyzed. The results show that the conditional fatigue limit of the composite laminates is 278MPa. The failure process is the first resin matrix failure, and then generate interface stratification and even the tensile and shear failure of the fiber, then the interactings form the dispersion damage zone lead to the material fracture occurred.

Abstract:The acoustoelastic relations in different fiber and loading directions were studied. With the aim of exciting LCR waves in the material, an incidence wedge was designed according to the snell's law. In addition, a system for measuring the time of fight (TOF) was set up. The system was used to measure the TOF variations along 0°

Abstract:By conducting uniaxial continuous loading on in-situ tensile machine, the validation of residual stress of Ti-6AL-4V alloy obtained by XRD method was studied. According to standard of JJF 1059.1-2012, the uncertainty of measurement of residual stress of high stress titanium alloy reference sample(-659±

Abstract:The drilling experiment of titanium alloy was carried out by using the self-grinding tool and compared with the ordinary twist drill. The drilling force, chip shape, pore size, pore wall surface roughness and burrs at entry and exit of hole were analyzed under different processing parameters. The experimental results show that the drilling force decreases with the increase of the spindle speed and increases with the increase of the feed rate. Compared with the ordinary twist drill, the drill force produced by the step drill is smaller, the chip is small and discharge from hole is smooth, the aperture value is close to the drill diameter, the surface roughness value of the hole wall is smaller and the burrs at entry and exit of hole are not obvious.

Abstract:The influence of different scratching speed of scratches on the critical state of brittle-plastic transition of single crystal germanium was studied based on the nano-scratch experiments, which were carried out on single crystal germanium (100) (110) (111) crystal surface by using a nano indentation instrument. Atomic force microscope was applied to observe the material surface. The results show that the plastic removal region of single crystal germanium will increase with the scratching speed raises. Nevertheless, the plastic removal region of single crystal germanium may decrease if the speed of scratches is too large. Furthermore, the influencing rules of cutting speed on the critical state of brittle to plastic transition of single crystal germanium in the ultra-precision machining process is predicted, which provides the data support for the ultra-precision machining of single-crystal germanium parts.

Abstract:Aiming at the air tightness ofSiCp/Al composites with high volume fraction, the influence of plating and orientation of raw materials on surface helium adsorption properties was systematically studied. It was found that after plating treatment on the high volume fraction of SiC_p/Al composite, the qualified rate of the helium adsorption capability increased 20%, and the qualified rate increased gradually with the increase of coating thickness. Difference in mechanical processing has little influence on the qualified rate of the helium adsorption capability. The raw material is anisotropic, the qualified rate of transverse cutting is 91%, and the longitudinal cutting is 68%.

Abstract:In order to solve the probrems such as the machining defects such as delamination, burrs, and chipping due to the poor stiffness and easily deformation of the launcher container, the technology on mechanical processing and optimize the process on a weapon composite launcher container are studied. Result of the test shows that the machining defects can be effectively controlled to ensure the quality of launcher container by designing a reasonable clamping method, optimizing the cutting tools and machining parameters. By optimizing the different processing steps and overall planning, the working time is shortened from 100 h to 46 h, the production efficiency is increased to 54%, significantly reduced the production costs.

Abstract:In order to eliminate the risk of inflammable and explosive, spraying ablation-resistant heat-insulating paint was realized by using non-inflammable and non-explosive solvent SK-410B as the diluents instead of gasoline. The shear strength,low temperature performance and hygrothermal property were tested. Arc heated wind tunnel test has shown that the coating has excellent thermal protection performance. The maximum temperature of the backside is 55℃. This method can satisfy the use requirement.