The defects of welding surface seriously affect the subsequent processing and service of welded structural parts. High-efficiency precision grinding is one of the key technologies to obtain high-quality weld surface. Therefore, the research on efficient precision grinding of weld beads is of great significance. This paper focuses on the intelligent technology of efficient and precise weld beads grinding, and summarizes the characteristics of welding beads grinding and polishing. The development status of welding seam grinding and polishing intelligent technology is elaborated from three aspects: Basic grinding and polishing principle and model, intelligent grinding equipment and force control algorithm and high-efficiency and precise weld beads grinding based on vision technology. Finally, the opportunities and challenges brought by intelligent technology to the efficient and precise grinding technology of welds are expounded, and the urgent problems to be solved in this field are put forward.

The extreme service parts represented by aerospace have harsh working environment, complex structure and integrated functions. Multi-material additive manufacturing (MMAM) can meet the macro performance customization and structure function integration in special areas, and has great application potential in nuclear, military, aviation and medical fields. The main factors that influence the interface bonding strength of MMAM technology and the methods to eliminate the defects are introduced. The different powder-feeding methods of MMAM technology and the advantages and disadvantages of each powder-feeding method are introduced. The influence of process parameters on MMAM technology is described. Finally, the current bottleneck problems of MMAM technology are summarized, and the main research directions in the future are prospected.

As an important part of aircraft manufacturing, final assembly line, how to improve and stabilize production capacity has always been a research hotspot. Based on the production capacity analysis of a transport airplane, the alarm problems in the final assembly have been normalized, and a pulsation closed-loop control model of the aircraft final assembly line has been proposed. The alarm type ratios have been used as the input variables of the control model, and the load rate and production capacity have been taken as the output parameters. The neural method has been used to construct the health status evaluation by analyzing the relationship between input variables and output parameters. According to the production capacity output of the above state evaluation model, the production capacity prediction model has been constructed using the Markov chain, which successfully evaluates the implementation of the production plan of the pulsation final assembly line and gives feedback to the pulsation controller to achieve production pulsation adjustment. Finally, the pulsation closed-loop controlling model is proved to be very effective through a practical design.

As a new joining technology, self-piercing riveting technology has excellent joining properties in the connection of thin sheet materials. The joint quality is affected by the feasibility of the connection and the connection parameters, and the joint quality is mainly characterized by the mechanical properties of the joint, so the joint quality and mechanical properties of self-piercing riveting have become the main research content. With the development of numerical simulation technology, the application of self-piercing riveting connection technology has become a research trend. With the development of numerical simulation technology, the application of self-piercing riveting connection technology has become a research trend. The development of self-piercing riveting numerical simulation technology in recent years is systematically elaborated, starting from the numerical simulation technology of the forming quality of self-piercing riveting joints, and the establishment of the numerical model of self-piercing riveting, the study of the influencing factors of selfpiercing riveting, the optimization of numerical model and the numerical prediction model are explained, and the feasibility of material connection and the influence of connection parameters on joint performance are summarized, the mechanical properties of joints are simulated, and the mechanical strength and fatiguelife of joints are predicted, which provides a new direction for the research and development of self-piercing riveting process.

To solve the problem of large dispersion of tightening force in the tightening process of aero-engine bolted connection based on the torque method, and to explore a more convenient and efficient optimization method of bolt tightening force loading process, a digital technology of bolt tightening load based on MATLAB–GUI was proposed based on torque method tests. A virtual bolt loading platform was built, and the virtual loading effect evaluation was carried out under different lubrication conditions with the torque angle method as an example. The tightening force under the two correction strategies has different improvement effects, which provides a new way to explore the optimization method of bolted connection tightening force loading process.

Rotor–blade parts are the core components of aero-engines, which have the characteristics of complex assembly structure and difficult assembly. Under high temperature and pressure conditions, the rotor-blade assembly error is catalytically amplified, resulting in fatigue cracks and other failures, which seriously affects the stability and reliability of the whole engine. For the rotor-blade structure, traditional variation analysis method cannot comprehensively consider the complex positioning structure and the partial parallel relation, as a result of that a branch chain in the multi-feature parallel structure is often used as a series relationship in a single direction. This paper proposed a variation analysis method of rotor-blade assembly based on the improved Jacobian–Torsor (J–T) model. Firstly, the multi-stage rotational structure, stop positioning structure and tenon tongue-groove structure were analyzed, and the assembly dimension chain considering partial parallel relationship of the rotor-blade with multi-feature was established. Then the assembly joint surface of rotorblade was expressed as the deviation torsor based on the points contact form by using the incomplete positioning strategy, and a united positioning reference scheme based on the positioning point system was established. Finally, the rotor–blade assembly precision index and the solution method based on the improved J–T model was proposed. Taking the assembly precision analysis for radial, axial and circumferential variation of the rotor-blades as an example, the calculation results of the traditional J–T model, Monte Carlo simulation model, and the improved J–T model were compared with the measured data. The results show that the proposed method has higher prediction accuracy than other methods. Compared with the measured results, the error rate is less than 9%. A more reasonable assembling and connecting mode of tenon tongue-groove structure was put forward

In order to investigate the influence of ultrasonic shot peening on the surface integrity of additive manufacturing γ–TiAl alloy, and verify the feasibility of the finite element simulation model, the samples of γ–TiAl alloy prepared by electron beam melting are studied, and a three-dimensional model of ultrasonic shot peening is established. The surface roughness and stress field distribution of ultrasonic shot peening samples under different shot peening parameters are simulated and analyzed. The ultrasonic shot peening tests with 0.15 A and 0.25 A shot peening intensities are carried out on the surface of samples by different shot peening parameters. The effects of shot peening process on the microstructure, residual stress distribution, surface roughness and microhardness of electron beam melted γ–TiAl alloy are revealed, and the validity of the simulation model is verified. The results show that the surface grain size of the samples are refined, the grain size gradient changes from surface to deep layer and the residual compressive stress layer about 150–250 μm depth is formed after ultrasonic shot peening. In addition, with the same projectile diameter, increasing shot peening intensity can significantly increase the distribution of sample surface roughness. Under the same shot peening intensity, the increase of projectile diameter can effectively reduce the sample surface roughness. The surface microhardness of ultrasonic shot peening samples are significantly higher than that of non-shot peening sample (305HV). The maximum microhardness occurs at the nearest measurement point from the surface, and the depth of the affected layer can reach 300–500 μm.

It is important to understand the damage and failure mechanism of unidirectional SiC/SiC composites during tensile process for mastering the mechanical behavior of SiC/SiC composites. In this paper, the tensile behavior of unidirectional SiC/SiC composite materials was investigated via a two-dimensional microscale finite element model. The random fracture process of fibers was simulated by strength judgment; The iterface debonding phenomenon was modeled using the cohesive zone model; A continuous medium damage model for the matrix was established through the uniform mass method and fracture energy release rate, specifically targeting the phenomenon of matrix cracks. The model  successfully simulated the microscale failure mechanism and macroscale mechanical behavior of unidirectional SiC/SiC composite materials in a tensile process. The three microscale damage mechanisms interact and eventually caused the final failure of the entire composite material. The results obtained in this paper might deepen the understanding on the tensile behavior of unidirectional SiC/SiC composite materials.

The effects of solution aging heat treatment on the microstructure and mechanical properties of a new kind of Ti–Al–Mo–V–Cr–Zr series ultra-high strength titanium alloy were investigated. The results indicate that the microstructure of the raw material consists of equiaxed or short rod-shaped primary α phase and matrix β phase. After solution and aging treatment, the microstructure is composed of primary α phase and transformed β phase with a large number of secondary α phases dispersedly distributed. Otherwise, the aging temperature has a significant effect on its mechanical properties. With the increasing of aging time, the tensile strength and yield strength of the alloy decrease and the plasticity increases. Under the condition of aging treatment at 520 ℃ , the tensile strength is 1508 MPa, the yield strength is 1439 MPa, and the elongation is 7.6%, showing a relatively good match of strength and plasticity. At the same time, the room temperature smooth （Kt=1） axial high-cycle fatigue performance is good, and the median fatigue strength is 868 MPa, which can provide data support for promoting its engineering application.

Aiming at the DZ125 and DZ406 superalloys used in aero-engine turbine blades, a thermal barrier coating system (TBCs) consisting of the rare earth oxide modified zirconia topcoat and platinum modified aluminide (PtAl) bondcoat was applied, and the preparation process and high temperature performance were studied. The PtAl bondcoat was prepared by electroplating platimum followed by vapor aluminizing treatment. Effects of key process parameters such as plating pretreatment, thicknesses of Pt, and aluminizing temperature on the microstructure and high-temperature oxidation resistance of the PtAl coating were studied. The results shows that the PtAl bonadcoat prepared by optimized process has excellent oxidation resistance at 1150 ℃. On the surface of the PtAl bondcoat, rare earth oxide modified zirconia (GYb–YSZ) ceramic topcoat were prepared by electron beam physical vapor deposition (EB–PVD). The thermal cycling lifetime of the GYb–YSZ/PtAl TBCs at 1050 ℃ is beyond 720 h (4320 times thermal cycling), indicating that the GYb–YSZ/PtAl TBCs have good performance.

As a key process for spiral bevel gears, shot peening process induces residual compressive stress field on parts surface and improve their fatigue strength. In order to accurately calculate the residual stress field of the tooth surface after shot peening, we established a simulation model for the shot peening process of spiral bevel gears, which based on the coupling of discrete element method and finite element method. The errors between the simulated results and the experimental results are within 10%, which means the model can predict the residual stress distribution well. The correlation law between the shot peening process parameters and the residual stress distribution of AISI 9310 spiral bevel gear is investigated. The results show that under the processing parameters used in this paper, shot peening mainly affects the residual stress field from the surface of the target to a depth of 50 μm. When the coverage is 200%, the increase of shot diameter and velocity works little on the surface residual compressive stress. The maximum residual compressive stress will increase to –1251.5 MPa and the depth of maximum residual compressive stress increases to 40 μm with the increase of shot velocity and diameter. The residual stress calculation model established in this paper provides a tool for the optimization of shot peening parameters of spiral bevel gears, and makes the process calculable and predictable instead of the trial-and-error method.

In order to expand the market application range of friction stir lap welding in magnesium alloy dissimilar materials, AZ31 magnesium alloy and LA141 magnesium lithium alloy were welded by friction stir lap welding. The microstructure, microhardness and shear tensile of friction stir lap welded joints were analyzed and tested by means of optical microscope, Vickers hardness tester and universal testing machine. The results show that when the rotation speed is 1800 r/min and the welding speed is between 80 mm/min and 120 mm/min, the friction stir lap welding of AZ31/LA141 had sound joints without obvious defects. Under the same welding process parameters, the grain size of the upper layer AZ31 and the lower layer LA141 in the thermo-mechanically affected zone on the advancing side are both smaller than those of the thermo-mechanically affected zone on the retreating side, while the grain size of the heat affected zone on the advancing side are larger than the grain size of the heat affected zone on the retreating side. When the welding speed increases, the grain size of the thermo-mechanically affected zone on the advancing side of the upper layer AZ31 and the lower layer LA141 decreases accordingly. The microhardness values of the upper AZ31 and lower LA141 weld nuggets have different trends. The former increases first and then decreases, while the latter tends to increase. With the increase of welding speed, the tensile shear force of AZ31/LA141 lap joint increases first and then decreases.