In order to improve the quality and control precision of the end surface of the hole, the optimization of the processing parameters of the laser modified grinding hole of the hard material is tested and studied under the assistance of the ultrasonic vibration. By using the rotary ultrasonic method, the processing efficiency is significantly improved, and the difficulty of processing hard and brittle material holes is effectively overcome. In order to judge the quality level (Hd value) of the hole outlet, the range of the collapse area is analyzed, and the area ratio of the hole section is measured, and further discusses the influence of laser modified grinding process parameters on Hd value. Through the comprehensive test analysis, the best laser modified grinding process parameters are determined: the spindle speed is 14000–16000 r/min, the feed speed is 0.5–0.7 mm/min, and the amplitude is 7–8 μm. Compared with the traditional laser processing, the surface finish after ultrasound-assisted laser modification under the optimal parameters is significantly improved, and the scratches are greatly reduced, which significantly improves the processing quality. This study has important guiding significance for improving the quality of laser modified grinding of hard materials, and it can be easily applied in practical production.

The pulling core rivet is widely used in the field of aviation manufacturing and assembly. There is a quantitative standard for the protrusion of the core rod section relative to the surface of the nail sleeve head (flatness of core rod), but the influence of flatness of core rod on the mechanical properties of the connected structure is not clear. In order to solve this problem, the static and fatigue performance tests of the assembly structure induced by the flatness of the core rod were carried out. The assembly and static performance of the structure are simulated and verified. Through experimental research, it is found that the average shear failure strength of samples with qualified core rod flatness is 9570.535 N, and the standard deviation is 107.001 N; the average shear failure strength of samples with unqualified core rod flatness is 9532.14 N, and the standard deviation is 327.261 N. Compared with out-of-tolerance samples, the standard deviation of qualified samples is more stable. In the fatigue test, the average number of fatigue cycles of qualified core rod evenness samples is 456770, and the average number of fatigue cycles of unqualified core rod evenness samples is 456022.7, so the fatigue strength is less affected by this aspect. The simulation of riveting shows that there is almost no difference in the absolute interference of the core rod under the two conditions. This conclusion explains why there is not much difference in the shear force between the two groups of tests, and it is found that there is almost no difference in the force-displacement curves between the two groups during the simulation process, which further verifies the test conclusion.

On the premise of weak substitutability and being often used to manufacture key components of aeroengine, high-efficient and high-quality machining of difficult-to-cut materials such as titanium alloys is facing challenges. Aiming at the problems of poor surface integrity and service performance of titanium alloy Ti–6Al–4V, high-speed cutting tests of titanium alloy Ti–6Al–4V were carried out, and the improvement of high-speed ultrasonic vibration cutting technology on the surface integrity and the wear resistance of machined surface was analyzed, thus providing theoretical support for high-quality machining of titanium alloy Ti–6Al–4V. The results show that compared with conventional cutting, high-speed ultrasonic vibration cutting effectively reduces the surface roughness, and improves surface strength, surface residual compressive stress and wear resistance of titanium alloy Ti–6Al–4V.

The application prospects of titanium alloy in the manufacturing of microcomponents in aerospace, biomedical, and precision instruments are promising. The jet electrochemical micromilling (JEMM) technology, based on the principle of electrochemical anodic dissolution to remove material, holds advantages in the micromachining of titanium alloys. However, a dense passive film is easily formed on the surface of titanium alloys under the influence of electrochemical processes, making the material dissolution process difficult to sustain stably. To overcome this problem, the polarization curves of Ti–6Al–4V were measured in electrolytes with different compositions and concentrations. It was found that a 10% NaCl (mass fraction) solution exhibited a strong capability in breaking the passive film, and the passivation and dissolution process were relatively stable. Building upon this, the effect of the inner diameter of the metal nozzle, machining voltage, and scanning speed on the aspect ratio of microgrooves and the range of stray corrosion in JEMM was investigated. Finally, a square spiral microstructure was fabricated on the Ti–6Al–4V surface using optimal parameters with a metal nozzle inner diameter of 300 μm, machining voltage of 35 V, and scanning speed of 75 μm/s. The resulting groove had an average width of 823.1 μm (standard deviation of 10.42 μm), an average depth of 157.26 μm (standard deviation of 5.89 μm), and a surface roughness of 2.006 μm (standard deviation of 0.088 μm).

Stainless steel is widely used in aerospace, energy development and other fields for its good mechanical properties, but its hardness and wear resistance is lower. In this study, 316L stainless steel is treated by electro-pulsing combining laser shock peening (EP-LSP) and laser shock peening (LSP), respectively. The effects of different processes on micro-hardness, surface morphology, friction and wear were investigated. The micro-hardness of the samples treated with LSP and EP-LSP was respectively increased by 26.1% and 38.3%, compared with the as-built samples. The wear rate of the samples treated with LSP and EP-LSP is reduced by 12.3% and 30.0% under the same friction conditions. The original samples mainly have adhesive and fatigue wear, the LSP and EP-LSP samples mainly have abrasive wear, and the furrow of EP-LSP samples is small and shallow. The current density of the EP-LSP sample increases gradually when the potential exceeds 1.1 V, which is larger than 0.4 V of the original sample and 0.7 V of the LSP sample, indicating that the passivated area of the EP-LSP sample is the largest and the corrosion resistance is the best.

Water cavitation peening is a material surface modification technology that uses the huge energy generated by the cavitation phenomenon to impact the material surface and intensify parts. It has a strengthening effect on numerous materials. Therefore, it is widely used to improve the surface state of parts, form residual compressive stress layer, and extend the fatigue life of parts. In this paper, basic principles, experimental setups, and research contents of water jet cavitation peening (WJCP), ultrasonic cavitation peening (UCP), and laser cavitation peening (LCP) are introduced. And the changes of residual compressive stress, roughness and fatigue life of different metal materials after water cavitation peening are summarized theoretically and experimentally. On the basis of the above research, combined with the advantages of water cavitation peening technology, the development direction and application prospect of the technology in the future are prospected. Research shows that water cavitation peening technology as a new surface strengthening technology has unique advantages and broad prospects for development.

During the additive manufacturing process of T-shaped structure, it is prone to the problems such as poor metallurgical bonding and remelting defects at the intersections, which restrict the improvement of the performance. In this paper, T-shaped structure of Al – Cu alloy was fabricated by the laser–arc hybrid additive manufacturing. The microstructure at the intersections were characterized, and the temperature field and flow characteristics in the molten pool were analyzed by numerical simulation. The results show that the curved stripes caused by remelting can be observed at the intersections of the structure, and the simulated morphology of this region showed great agreement with the actual. The isotherm distribution was denser at the edge of the molten pool. The internal Marangoni convection led to the formation of counterclockwise vortices with a maximum velocity of 0.16 m/s. According to the differences of the grain morphology, it can be divided into the remelting zone of intersection (RZI) and the heat-affected zone (HAZ). RZI was mainly composed of fine dendrites, and the average grain size was 20.8% lower than that in HAZ. The precipitates were mainly the largesize θ (Al2Cu) phases which were incoherent with the α-Al matrix. The average microhardness can reach (98.4 ± 6.4) HV_0.1, which was up to 14.0% higher than that in the unremelting zone.

Carbon fiber reinforced plastics (CFRP) and alloy stacked materials are used in the manufacturing process in the fields of aerospace. And the CFRP/Ti stacked material is widely used. The processing defects caused by heat are more significant in the drilling of CFRP/Ti stacked material, and mostly appear at the interface where two materials are in contact. Therefore, the main factors affecting the interface temperature in drilling of CFRP/Ti stacks are studied. The experiment of the interface temperature monitoring in the drilling of CFRP/Ti stacks with the help of thermocouples is designed. The processing parameters and ultrasonic assistance parameters were changed in the experiment. The primary object of this study is investigating the relationship between processing parameters and interface temperature in the variable parameters drilling of CFRP/Ti stacks, and the influence of the ultrasonic is also discussed.

The surface modificative layer microstructure, residual stress and microhardness of carbonitriding M50NiL steel after different grinding parameters were studied. The results show that grinding surface modificative layer is very small deformation martensite and some austenite which is nanometer grain zone. The grain turning phenomenon is apparent. The content of austenite is affected by grinding heat of different grinding parameters. The grinding surface modificative layer may be divided into three parts, the outermost grinding heat affected layer about 0–20 μm, the middle high hardness surface modificative layer about 20–70 μm and the internal diffusion surface modificative layer about 70–200 μm. In order to reduce the impact of different grinding parameters and improve the structure property of surface modificative layer, some grinding surface modificative layer may be removed but keep the maximum depth of not more than grinding heat affected layer and then the high mechanical properties of M50NiL steel are obtained.

In the blanking layout problem of special-shaped parts, the most difficult thing is to determine the position of special-shaped parts for high material utilization rate, and the complexity of the algorithm increases rapidly with the increase of the quantity and boundary complexity of special-shaped parts. The critical polygon algorithm is a basic geometric tool for calculating the position and overlap between special-shaped parts, and the performance of the critical polygon algorithm is closely related to the efficiency of the blanking algorithm. In this paper, an improved and more efficient algorithm to calculate no-fit polygon (NFP) is proposed and it is based on the trace line presented. The algorithm effectively combines the mobile collision algorithm and the trajectory algorithm, and gives full play to the respective advantages of the two algorithms, thus improving the speed of calculating no-fit polygon.

Suspension wire pendulum accelerometer is widely used in aviation, aerospace, inertial navigation and other fields, and its assembly quality has a great influence on the accuracy of acceleration measurement. The assembly of its key components involves the adjustment of position and posture, and the suspension wire needs to control the tension force and complete welding during assembly. Aiming at the precision assembly of suspension wire pendulum accelerometer components, a precision assembly and welding system integrating force, temperature sensors and machine vision has been developed. The camera is used with the turntable to realize the visual measurement of the parts to be assembled and complete the identification and positioning of the feature points of the parts; The position and posture of the parts to be assembled are adjusted by the precision sliding table and the turntable; The linear motor motion combined with force feedback realizes the gap adjustment and tension control of the parts during assembly; Develop a special welding unit to realize automatic temperature control welding of micro devices in compact space. The experimental results show that the system can complete the automatic assembly and welding of accelerometer components. The assembly results meet the requirements of technical indicators and the solder joints without virtual welding. The gap deviation between the inner edge of the pendulum assembly and the edge of the magnetic steel is less than 10 μm, the position accuracy of the center of the suspension wire relative to the ground of the accelerometer base is better than 20 μm, and the tension deviation of suspension wire is controlled within ±5 mN. It can meet the product assembly quality requirements.

Based on the fatigue testing machine，this study independently designed bolt loosening test devices under complex loads. The loosening process of bolted joints under complex load had been investigated under many different experimental parameters, and the loosening behavior of bolted joints of different load amplitude and load type under complex load were systematically investigated. Combining the microscopic analysis using optical microscope and obtaining the real-time residual clamping force of bolt connection and the relative rotation angle of bolt and nut, this paper revealed loose mechanism of composite bolt connection. The main conclusions obtained in this study are as follows: When the load amplitude is larger, the residual clamping force of bolt connection decreases more, and the connection structure is more prone to relaxation. The increase of axial amplitude leads to the aggravation of the damage around the hole of the composite plate; The increase of transverse amplitude leads to the increase of wear of composite board surface; The load type of complex load obviously affects the relaxation behavior of the connection structure; Compared with static tension load, vibration load has greater influence on the residual clamping force of bolt connection.