Abstract:The research and application of titanium alloys and its precision forming technologies,including precision casting, precision forging,superplastic forming,spinning forming and powder metallurgy,are reported systematically.Finally,based on the actual requirements of aerospace industry in china,the development trend of titanium alloys and relevant precision forming technologies are summarized and forecasted.

Abstract:In order to solve the problems of large cutting force,high cutting temperature and serious tool wear in the process of titanium alloy cutting,scholars have tried to use micro texture tools to solve these problems in recent years.In this paper,the application of micro textured tools in titanium alloy cutting is reviewed.The cutting mechanism of micro textured tools in improving surface quality,reducing cutting force,tool wear,friction coefficient and cutting temperature is analyzed,and the problems in micro texture cutting titanium alloy are pointed out.

Abstract:The cutting heat and cutting temperature in the drilling process of CFRP are studied. The formation mechanism,the influence and the factors relating to the cutting heat and the methods to control the cutting heat are systematically reviewed.The existing problems are comprehensively analyzed and the future research direction is prospected.

Abstract:To analyze the deformation and failure of composite unidirectional plate,an extended bond-based peridynamic constitutive model was proposed by PD theory.The macroscopic anisotropy of unidirectional plate was described through matrix bonds and fiber bonds,and a kernel function reflecting the internal length effect of long-range forces between material points was implemented into matrix bonds to improve the accuracy of quantitative calculation.Quasi-static numerical system in peridynamics was built correspondingly.Then,the presented model was verified through the quantitatively calculating of deformation in the unidirectional lamina under uniaxial tension with traditional peridynamic constitutive model,where the relative error of two models is 1.7% and 3.5%,respectively.There is a higher accuracy of quantitative calculation in the presented model.Numerical simulations and experiments were developed about composite unidirectional lamina with a central crack subjected to uniaxial tension，and numerical results agree well with experimental observations.The studies indicate the presented peridynamic constitutive model can successfully simulate the deformation and destruction of composite unidirectional lamina.Finally,this model is applied to analyze failure behaviors of unidirectional plates with the fiber angle of 0°.The results show that the matrix cracks mainly propagate in early stage,and when cracks extend to the clamping area, the fibers of structure are broken.In the last,a cross section through the whole structure is formed and lead to the failure of unidirectional lamina.

Abstract:In order to predict the changing trend of grinding force in ultrasonic grinding of alumina ceramics,a method based on the combination of fuzzy information granulation and support vector machine was proposed.Firstly,the ultrasonic grinding test of alumina ceramics was carried out.The grinding force obtained by the experiment was granulated by fuzzy information granulation method.The artificial immune system algorithm and the particle swarm algorithm were mixed in parallel to form the artificial immune system particle swarm algorithm (AISPSO).Secondly,a nonlinear regression support vector machine prediction model was established and fuzzy particles were predicted.The support vector machine prediction model was optimized through the AISPSO algorithm.Finally,the change trend and range of grinding force in ultrasonic grinding of alumina ceramics were obtained.The results show that this method can effectively realize the prediction of the change trend and range in ultrasonic grinding.And the error of prediction of the change range of the next 5 sets of data are less than 10%.A new idea for adjusting the process parameters by changing the grinding force to obtain a better-processed surface is provided.

Abstract:Some through hole pads of printed circuit board connected to ground layer. Large heat dissipation in ground layer would lead to low solder tin-permeability rate during the manual welding process. To solve the problem, temperature distribution of common and low tin-permeability rate pads was calculated by ABAQUS software. And the influence of whole board preheating on the peak temperature and permeability rate was analyzed. The results show that without preheating printed circuit board, the heat dissipation in ground layer is 4 times as that of the common through hole pads. The peak temperature of non-welded surface of low tin-permeability rate pads is 125~126 ℃, which was far lower than the melting point of the tin-lead eutectic solder (183 ℃). When printed circuit board is preheated to 85,100 and 115 ℃, the peak temperature of non-welded surface of low tin-permeability rate pads is increased to 171.5,179 and 187.5 ℃, respectively. Simulation and experimental results indicate that preheating Printed Circuit Board at 85~115 ℃ is beneficial to improve the permeability rate and solder-joint reliability of Sn-Pb eutectic solder.

Abstract:A novel polymeric precursor for SiC-ZrC composite ceramics was synthesized by methyl trichlorosilane, dimethyl dichlorosilane, zirconocene dichloride and sodium in one-pot synthesis. The pyrolysis behavior and structural evolution of the precursor, the microstructure and composition of the synthesized ceramics were fully investigated by TG, FTIR, XRD and SEM. The results show that the precursor can completely be transformed into SiC-ZrC composite ceramic after heat treatment in argon at temperatures above 900 ℃ with ceramic yields above 60%. The obtained ceramic consists mainly of amorphous matrix phase SiC, in which ZrC nanocrystallites are distributed uniformly with 10 to 45 nm in size. This new precursor is suitable for production of ultra-high temperature ceramic fiber and ceramic matrix composite.

Abstract:Aim at the urgent requirements of alumina-based continuous ceramic fibers,boron-containing alumina-based continuous fibers were prepared through a sol-gel combined dry spinning technique.The effect of the content of spinning additive on the spinnability of the sol and the evolution of the phase composition and microstructure of the fibers during the ceramization were investigated.The results indicate that the gel fibers is lengthen up to 1.8 km with the PVA content of 1.5%.After ceramization, the ceramic fibers with the uniform diameter of 12 to 14 μm can be formed.The fibers obtained at 1 000 ℃ are composed of the crystalline γ-Al₂O₃ and amorphous phase.These fibers exhibit high tensile strength and modulus up to 2.0 GPa and 149 GPa, respectively.After calcined at 1 100 ℃ for 1 h,the fiber still can retain the 93% of original tensile strength. The as-prepared fibers show great potential in the area of aerospace and advanced manufacturing industry.

Abstract:Nanocrystalline cellulose (NCC) had been widely used in polymers due to its unique properties, but the surface hydroxyl limitd its application in hydrophobic polymers.In this paper,NCC was modified by 3-aminopropyltriethoxysilane (KH550) to improve its compatibility with ethylene propylene diene monomer (EPDM). Fourier Transforminfrared spectroscopy (FTIR) and XRD test results show that NCC successfully modified by KH550 and keep the original crystal structure intact.The vulcanization and mechanical properties test results of EPDM compound show that the addition of modified NCC promotes the vulcanization and when the addition amount of modified NCC is 6phr,the comprehensive mechanical property of EPDM vulcanizate is the best.

Abstract:In order to investgate the mechanical properties of silicone rubber based coatings at high temperatures,two types of silicone rubber based thermal protective coatings were investigated by high temperature compression tests.The macroscopic morphology and microstructure of the compression sections after high temperature compression were observed.Combined with the analysis of thermal weight loss at high temperature, the mechanism of thermo-mechanical property change was discussed.The results show that the thermal pyrolysis temperature range of methyl phenyl silicone rubber based coating is mainly about 500 to 650 ℃,and the final mass residual rate is 67.61%.The compressive strength increases with the temperature from 25 to 800 ℃.The strength has a decrease from 400 to 700 ℃ beacuse of the softening of the glass microsphere and the thermal pyrolysis reaction of the silicone rubber.At 800 ℃,the compression strength reaches significant increase as a result of the co-melting of glass microsphere,reinforcing fillers and the ablation products. The thermal pyrolysis reaction temperature range of methyl vinyl silicone rubber based coating is 450 to 800 ℃, and the final mass residual rate is 89.95%.After thermal pyrolysis reaction, methyl vinyl silicone rubber transforms from organic to new ceramic phase,which prevents the decrease of the strength caused by resin pyrolysis.Thus the thermo-mechanical properties of methyl vinyl silicone rubber based thermal protective coatings stay steady from 25 to 800 ℃.The mechanism analysis indicates that the main influencing factors of thermo-mechanical properties are pyrolysis of resin matrix and physicochemical changes of fillers under high temperature conditions.

Abstract:The integral forming technology of a polyhedral composite support was introduced.Machining scheme,mould design,the optimistic design of overlay processing,pressured curing technique were researched.The results show that integrated forming process can achieve the forming of large-scale polyhedral composite support. The process is based on combined mould，including core and external mold. Through the method of symmetrical,step transition laying,vacuum assisted pressurization of silicone rubber curing is 0.7 MPa. The product possesses high molding quality,dimensional accuracy and mechanical properties.The surface of the composite parts which have no lamination,porosity,voids and other defects are flat without wrinkle.The fiber volume fraction can be controlled at (60±3)%,and the voids are all lower than 1.0%. The flatness of the product installation plane is better than 0.3 mm,and the angle tolerance is within ±0.1°.The mechanical properties of the samples in the furnace are all higher than the design indexes which can meet the user"s requirements.

Abstract:During the drilling of carbon fiber reinforced polymer (CFRP), the defects, such as burrs and delamination, are prone to occur. The drill structure is a key factor influencing the formation of the defects. Two new drills are designed according to the existing novel drill bit. The thrust forces and the performances of these drills are investigated. The results show that the thrust force degradation rate of the existing novel drill bit in the trimming stage of the “V-shaped” cutting edges is the biggest, and that of the newly designed swallowtail-grooved drill is smallest. These change rules of the thrust force degradation rates are basically the same as that of the defects. Then, the changes of the thrust force degradation rates have good mapping relations with the regularities of the defects. The burrs can be effectively reduced by using these three drills. Compared with the existing novel drill, the burrs and the delamination can be more effectively reduced by the two newly designed drills. The main defects form of the existing novel drill is the tearing, but the main defects forms of the two newly designed drills are the delamination. This paper provided a new design idea for the tool structure design of CFRP drilling.

Abstract:Al₂O₃/Al-10Si composites solidified with different pressures were prepared by hot pressing and high pressure solidification.The effects of high pressure on the microstructure evolution and mechanical properties of Al₂O₃/Al-10Si composites were investigated.The results show that the high pressure solidified Al₂O₃/Al-10Si composite consists of α phase,β phase and Al₂O₃ strengthening phase, and α phase is cell-like.There is a small amount of fine granular β phase with a particle size of about 0.1 μm at α phase grain boundary.The solid solubility of Si in α phase and the microhardness increases with the increasing solidification pressure.The microhardness of the hot pressed sintered material is 55.3 HV.When solidification pressure is 5 GPa,the microhardness is 128 HV and has increased by 133%.The compressive strength has increased from 126 MPa to 702 MPa at 5 GPa.This is due to the high pressure causing an increase in the solid solubility of Si in α phase to form a solid solution strengthening.

Abstract:Aiming at the product with variable cross-section structure, a friction stir welding method for variable cross-section lap joint was proposed.By adding an auxiliary plate, the entire weld was compensated to equal thickness in the welding direction.Welding adopts frist-position welding + second-position welding + formal welding process,frist-position welding was pre-positioned, second-position welding ensured an effective connection between the auxiliary plate and the main structure of the test piece,and the formal welding ensured the formation of a complete weld. The surface of the weld is well formed,and the ultrasonic phased array detection has no defects beyond the standard.Through analysis of mechanical properties, the mechanical properties of the weld at the variable cross-section and the non-variable cross-section are basically the same,the average tensile strength reaches more than 70% of that of the base material,and the average elongation is above 5.8%.The morphology of the grains at the weld nugget of the variable cross-section weld is fine equiaxed grains. The grain size near the shoulder impact zone is larger than that near the weld root. The lap interface of the auxiliary plate at the heat engine affected area on both sides of the weld disappears because of recrystallization influence.

Abstract:In order to study the influence of Fe content on the microstructure,properties and electrochemical corrosion properties of 2219 aluminum alloy and its welded joints,mechanical tensile test,welding test, metallographic and scanning electron microscope were used to conduct experimental research and analysis on 2219 aluminum alloy forgings with different Fe contents from 0.15%(w) to 0.01%(w).The results show that there are Al₇Cu₂(Fe,Mn) phases in 2219 aluminum alloy which are transformed into granular and fibrous Al₇Cu₂(Fe,Mn) phase after thermal deformation processing.With the decrease of Fe content from 0.15%(w) to 0.01%(w),the Al₇Cu₂(Fe,Mn) phase after solid solution aging of the alloy is significantly reduced, and the strength and plasticity of the forging are significantly increased.The fracture of the alloy welded joint is transformed from brittle fracture to ductile fracture with small dimple size.The strength and plasticity are significantly increased,and elongation is increased to nearly 1.4 times especially.The corrosion current of the alloy decreases gradually and the linear polarization resistance per unit area increases,so the corrosion resistance of alloy welded joints is improved significantly.

Abstract:Due to the lack of industry standards of CT detection for solid rocket motors, a standard sample motor was made by using positive density material blocks to simulate the debonding defects and alloy blocks to simulate the defects inside grain. The CT comparison tests were carried out between a standard sample motor and an actual motor, and the actual motor was dissection and sampled for verification. It is shown that results of motor CT detection are consistent with that of radiographic and dissection tests, and design of the standard sample motor meets the requirements of research. The minimum detection ability of industrial CT system is determined: debonding area is 20mm×20mm, width is 0.4mm, diameter of voids and inclusions is 5mm, and width of cracks is 0.4mm. The CT detection standard is established and the CT detection process for solid rocket motors is normalized accordingly.

Abstract:In order to solve the problem that the structure welding and composite nozzle of 5 kN engine could not be detected,the industrial CT detection technology was studied.Based on the analysis of the difficulties in the conventional methods of detecting complex structure weldings and composite nozzles,and taken the advantages of industrial CT detection technology,such as strong penetration ability and not affected by the complex structure of the workpiece, the structures of electron beam weldings,argon arc weldings and composite nozzles in 5 kN engine products were tested,and good detection results were obtained.The test results show that the industrial CT detection technology can solve the inspection problems of structural welding and composite nozzle in 5 kN engine products,realize the identification,location and measurement of defects such as porosity, incomplete penetration, delamination and crack,and provide the basis for welding quality evaluation.

Abstract:The friction properties of friction pair C/C-40Cr were analyzed and characterized by MMUD-10B friction and wear tester under dry friction and water lubrication conditions with fixed rotation speed of 100 r/min and three different loads（70,150 and 230 N）.The wear marks on the surface of the samples were observed by Olympus GX51 metallographic microscope, the wear amount of each experiment was characterized by J324BC electronic balance, and the morphology of wear debris and atomic ratio of each element were observed by JSM-6510A scanning electron microscope (with EDS energy spectrometer).The experimental results show that in dry friction,the friction coefficient fluctuates at 0.046 to 0.070, and the friction coefficient and wear amount increase with the increase of load, while in water lubrication,the variation range of friction coefficient is small from 0.037 to 0.052, but the wear amount is more.Under dry friction and water lubrication, the friction coefficient and wear amount are positively correlated with the load. Carbon fiber and laminated 40Cr structure exist stably in the wear debris.The wear mechanism is adhesive wear and abrasive wear

Abstract:The intersection joint weld on 6 mm 2A14 aluminum alloy sheets was obtained by fusion welding (TIG) and friction stir welding (FSW).The macrostructure and microstructure were analyzed, and the fusion area was on the left side of the joint with the porosity defects on the upper of the area.The FSW area was on the right of the joint and displayed a “bowl” shape and the weld is well-formed.Microhardness test results reveal that the microhardness in the TIG weld is obviously lower than that in FSW weld,and the microhardness distribution in the right side of NZ presents “U” type.The tensile test is conducted in fusion welding direction and the joint fails in the base metal with M temper,and apperance of fracture is the toughness fracture modes.