Abstract:Materials and processing technologies for reusable liquid rocket engine are systematically reviewed in this paper.Some key components such as thrust chamber， turbopump，and nozzle， etc. used in hydrogen-oxygen rocket engine，liquid oxygen-kerosene rocket engine and liquid oxygen-methane engine are respectively expounded about the material selection and forming process. According to the performance requirement and structure character of different liquid rocket engine， the latest development trend of key material and processing is speculated.Compared with domestic research situation of material and processing on reusable liquid rocket engine， some development thought about subsequent material and processing technology is proposed.

Abstract:In response to the inadequacy of micro-textured tools for chip formation of Ti6Al4V titanium alloy and the analysis of the secondary cutting mechanism of microgroove， a thermo-mechanical coupled model was established to comparatively analyze the effects of different micro-textured tools， micro-textured geometric dimensions， and cutting speeds on chip formation. The simulation results show that micro-textured tools are more beneficial to the chip breakage， and the secondary cutting action makes the radius of chip bending larger. The micro-texture can reduce the actual contact area of tool-chip and the cutting temperature. Increasing the width of the micro-texture tool can enhance the secondary cutting effect of the micro-groove and facilitate chip breakage， but attention should be paid to its weakening effect on the tool strength. In contrast， increasing the adjacent microgroove spacing results in the opposite mechanism of the secondary cutting action. Increasing the cutting speed is beneficial to the chip breakage for all tools， and the curved micro-textured tool has the best cooling effect， followed by the V-shaped micro-textured tool， and the rectangular micro-textured tool has the worst cooling effect. The findings can provide some references for further understanding of the the secondary cutting action mechanism of micro-textured tools to titanium alloy chip.

Abstract:There were some problems in the ordinary cutting （OC） process of carbon fiber reinforced resin matrix composites， such as excessive cutting force， poor surface quality and serious under surface damage. In order to improve the above problems， this paper proposed to use ultrasonic vibration assisted cutting processed CFRP. The cutting force and subsurface damage depth were studied through simulation analysis. The results show that machining CFRP with UVC can reduce the cutting force by 13%~80%， and the fiber direction angle has little effect on the cutting force. Compared with OC， UVC processing CFRP with 0° and 45° fiber direction angle can reduce the depth of subsurface damage by appoximately 50%； When processing CFRP with 90° and 135° fiber direction angle， although the damage depth under the surface is not improved，a relatively flat machined surface and small damage area are obtained.

Abstract:In order to study the influence law of the inner sleeve material properties and geometric dimensions on the pre-tightening force，this paper firstly studied the influence law of different inner sleeve material and wall thickness on the pre-tightening force through experiments. Then， the numerical model of the joint pre-tightening force was established by the finite element software ANSYS， the simulation results were in good agreement with the experimental values， and the experimental phenomena were analyzed by the finite element. The results show that under the same extrusion amount，the higher the joint wall thickness， the higher pre-tightening force generated； for the inner sleeve joint of plastic material， when the external extrusion amount exceeds a certain value， the plastic material completely enters plasticity and deforms increase， but the stress value no longer increases significantly， and the pre-tightening force tends to be stable；for the inner sleeve joint of elastic material， the elastic material stress has been increasing linearly with the strain， so the pre-tightening force continues to increase with the increase of the extrusion amount.

Abstract:W-10Ti alloy was prepared，and the effects of cold isostatic pressing （CIP） pressure， hot isostatic pressing （HIP） temperature and high temperature treatment on the microstructure are studied.It is found that CIP can significantly increase the charge density，which is beneficial to HIP forming and element diffusion. The diffusion of W and Ti can be improved by increasing CIP pressure and HIP temperature.At HIP1 300 ℃， pure Ti phase is completely eliminated.When the high temperature treatment temperature is 1 300，1 400，1 500 and 1 700 ℃，the content of Ti-rich phase decreases first and then increases， and reaches the lowest at 1 400 ℃， which is 5.18%.When treated at more than 1 400 ℃，the Ti-rich phase underwent eutectoid transformation.

Abstract:Blending different kinds of rubber was one of the effective ways to improve the properties of products. By blending part of chloroprene rubber （CR） into EPDM rubber， the influence law of blending insulation properties was studied. The results show that， properties can be improved by blending CR with EPDM rubber. When the content of CR is no more than 30 parts by weight， the vulcanization properties，heat resistance and tensile properties of the blended rubber can be improved obviously. And the glass transition temperature， preparation technology and other basic characteristics of rubber blends do not change substantially.In addition， the ablation test results show that the addition of CR increases the deposition amount on the surface of aramid fiber after ablative substrate， which is beneficial to improve the ablative resistance of insulation.The application results show that the tensile strength and ablation performance of EPDM/CR blending insulation is better than that of the single EPDM rubber insulation.

Abstract:Based on the high strength of flake Al₂O₃ ceramic interlocking structure，Al₂O₃ porous ceramics with high porosity and graphite were prepared， and Ni particles were prepared by in-situ reduction in the porous skeleton to form a lightweight double-loss ceramic-based absorbing material. The effects of reduction temperature on the composition， microstructure，element distribution and microwave absorption properties of porous absorbing materials were studied by XRD，FE-SEM and EDS. Results concluded the following.The results show that Ni on the framework can be completely reduced when the temperatures is up to 700 ℃. The composite with a double loss function is composed of an interlocking Al₂O₃ matrix with graphite flakes embedded in it and Ni particles on the surface of pores. As the thickness of the composite is 6.5 mm，the reflection loss （RLmin） value is 35.01 dB and the effective bandwidth （RL ≤10 dB） is 1.75 GHz.Microwave absorption can be attributed to the conductive network formed by graphite flakes between flaky Al₂O₃ grains，as well as to the good impedance matching and polarization effect caused by the Ni particle-matrix interface.

Abstract:Poor mechanical properties was the major factor restricting the development of room temperature vulcanized silicone rubber application， the structure of crosslinking agent on the mechanical properties had important influence. In order to improve the mechanical properties of room temperature vulcanized silicone rubber， a kind of modified crosslinking agent （E44-APS） was synthesized by epoxy resin E-44 and ammonia propyl three alkoxy silane as raw material through ring opening reaction. The structure of E44-APS was determined by the infrared spectrum， nuclear magnetic hydrogen spectrum.The tensile properties， curing properties，contact angle， surface morphology，thermal stability of the room temperature vulcanized silicone rubber was studied. The experimental data show that with E44-APS content increases， the tensile strength of room temperature vulcanized silicone rubber increase first and then decrease.When E44-APS content is 10%， the tensile strength and elongation at break can be up to 0.47 MPa and 306%. Curing time increases with the increase of E44-APS content，5% heat temperature loss decreases with increasing content of E44-APS.With the increase of E44-APS content， contact angle reduces first and then increases. The results show that the E44-APS can effectively improve the mechanical properties of room temperature vulcanized silicone rubber， will also bring some negative impacts， such as curing time prolong and thermal stability and hydrophobic descent.

Abstract:Silicon nitride porous ceramics possessed excellent mechanical， dielectrical， thermal properties and chemical stability. It was very suitable for broadband wave transparent materials using in high temperature， large load and strong corrosion circumstance. Reaction bonded silicon nitride porous ceramics had advantages of excellent properties， convenient process and low cost. The characteristics of Si powders remarkably controlled the phase component， microstructure， mechanical and dielectric properties. In this study， Si powders with different particle size and purity were used to prepare gelcasting and reaction bonded silicon nitride porous ceramics. The results show that dual granularity produces close packing effect in the green body， which is inherited and further evolves into a reinforcing and toughening mechanisms of two-tier microscopic tissue in the sintered body. Dual granularity of 5 μm and 45 μm obtains the largest bending strength of 109.94 MPa and work of fracture of 990.74 J/m². The values are 111.42% and 25.97% higher than that of single granularity of 5 μm as well as 46.55% and 20.46% higher than that of single granularity of 45 μm . The dielectric constant and dielectric loss are about 4.20 and 0.007 respectively. Gelcasting and reaction bonded silicon nitride porous ceramics can possess both good mechanical and dielectric properties， which are suitable for special-shaped and large scale component such as radome.

Abstract:For the problems such as fiber burrs and ablation in the processing of aramid fiber reinforced composites （AFRP）， a laser-milling combined processing method was proposed to conduct experimental research on AFRP. The parameters of AFRP laser-milling combined processing were optimized. The results show that compared with the milling processing， the temperature of laser-milling combined processing is lower， the milling force and the burr factor are smaller， the milling force fluctuation is smaller， the milling is more stable. The optimal laser processing parameters of AFRP laser-milling are as follows： laser power P=20 W， scanning speed v=3 mm/s， pulse width L_f=60 ns， repetition frequency f=50 kHz. The optimal milling process parameters are as follows： spindle speed n=2 000 r/min， feed speed v_f=105 mm/min， cutting depth a_p =0.5 mm.

Abstract:In order to study the effect of the cylindrical centerless grinding without dressing and grinding on the outer ring of bearing ring，the outer ring of 6202 deep groove ball bearing ring was used as the research object. Cylindrical centerless grinding tests were conducted to analyze the effect of the new cylindrical centerless grinding process without dressing on the roundness and diameter of the bearing ring. The harmonic control principle was utilized to investigate the control of harmonic on the roundness during grinding. The results show that the new process achieves the dimensional accuracy requirements of 6062 bearing ring. The method of increasing the machining allowance first and then decreasing it during cylindrical centerless grinding is helpful to improve the roundness of bearing ring， shorten the process flow， reduce the production time and improve the production efficiency. Centerless grinding effectively reduces low-order harmonics， while cylindrical superfinishing efficiently reduces high-order harmonics on the ring surface to control roundness. In conclusion， the novel cylindrical grinding process without dressing can improve product quality and production efficiency..

Abstract:In order to improve the milling of carbon fibre reinforced polyether ether ketone （CF/PEEK） composites with defects such as burrs， delamination and surface pits， the processing method of ultrasound-assisted milling with CF/PEEK at four fibre orientation angles of 0°，45°，90° and 135° was carried out and compared with conventional milling.The results show that ultrasonic-assisted milling has lower cutting forces and better machining quality than conventional milling. The most significant reductions in cutting forces， surface roughness and burr height are achieved by ultrasound-assisted milling of specimens along a 90° fibre orientation angle， with reductions of 16.79%，28.9% and 71.9% respectively.Furthermore， ultrasonic-assisted milling is effective in improving surface defects such as surface pits and delamination， compared to conventional milling under the same machining parameters.

Abstract:Aiming at the problem of delamination defect monitoring at hole outlet during CFRP drilling and hole making process，the delamination damage identification at hole outlet during CFRP drilling and hole making process was studied based on acoustic emission detection technology. The time and frequency characteristics of acoustic emission and axial force signals related to delamination damage were extracted by destructive delamination test， which were used as the signal basis for judging delamination damage in drilling. Then， drilling tests were carried out，and delamination damage at hole outlet of CFRP laminates was identified based on the actual damage morphology. The results show that the instantaneous drilling axial force is higher than the critical axial force when the delamination damage occurs at the drilling outlet.The amplitude of acoustic emission signal in time domain will change dramatically，and the intensity of signal in middle and high frequency band will also increase significantly. Due to the significant time and frequency characteristics of the signal， the delamination damage at the hole outlet can be effectively identified， which provides an idea for on-line monitoring and control of delamination damage in drilling of CFRP laminates.

Abstract:Due to the great difference of physical properties between CFRP and TC4 materials， the cutting performance matching of CFRP/TC4 stack components was poor. There were some problems such as interface damage and CFRP hole wall damage that were difficult to control during drilling. In view of the above problems， the drilling experiments of CFRP/TC4 stacks were carried out by using variable parameter pecking drilling technology， variable parameter drilling technology and constant parameter drilling technology. The thrust force， interface quality， chip morphology of TC4 and hole wall quality of CFRP under different process conditions were compared and analyzed. The results show that the thrust force of TC4 obtained by variable parameter pecking drilling process is significantly higher than that under the other two processes， and short ribbon and short spiral chips are produced. The diameter at the exit and entrance of the CFRP stack are closer to the nominal diameter， and the hole wall defects are less， and the surface roughness is relatively low.