With bracket parts as the main research object, this paper mainly analyzed the various kinds of failures caused by the clamping damage of bolt holes, fretting wear of bolt holes, sudden change of bracket rigidity, the manufacturing defects (burrs, microcracks) and the failures of welded brackets, emphasizing on the research on structural characteristics of parts, the morphology of crack sources for proposed improvement recommendations.

The intermediate support is the bridge between the frame and the final assembly suspension system of a heavy truck that serves to connect the balance shaft, and keep the forces balanced between the rear axle and the middle/rear axle. This paper studied the common problems of intermediate support warpage, width and diagonal out-of-tolerance in the assembly process of the intermediate support for a heavy duty truck, analyzed the causes and developed effective solutions. By increasing the pressure type guide pin hole, repairing the wear mold, adjusting the width of the aircraft beam assembly, regulating the order of bolting at different positions, these solutions reduced the unqualified rate and production cost of the intermediate support assembly, improved the overall quality and production efficiency of the heavy duty truck frame.

Based on the frontal 25% offset collision condition, a mathematical model was established for simulation analysis. 2 000 MPa hot formed steel was used to replace 1 500 MPa hot formed steel, and the hot gas expansion method was used to replace the traditional hot forming method, thus realizing lightweight design on A-pillar structure of a vehicle model. Through the simulation analysis of small offset impact performance, it was concluded that the solution of 2 000 MPa hot formed steel meets the performance requirements. Through cost comparison and analysis, due to the reduction of the number of parts, the single vehicle cost and part mass of the overall scheme of 2 000 MPa hot gas expansion have decreased. The analysis results show that the lightweight design of A-pillar based on 2 000 MPa thermal expansion is feasible, which can reduce the cost of a single vehicle by 10.51 RMB and the weight of the designed A-pillar is 27.5% lower than the original one, which makes it have good economic benefits and lightweight effect. At the same time, the application of thermal expansion reduces the section of A-pillar cavity, reduces the obstacle angle of A-pillar by 22.2%, and effectively improves the blind area of A-pillar visual field.

With the vacuum formed and coated instrument panel of a vehicle as the research object, this article, through experimental analysis, indicated that the instrument panel blistered, and triggered the blistering condition after the vehicle was exposed to a high temperature of more than 100 ℃ for 30 minutes continuously. The research focused on enhancing the bonding strength of glue and skeleton as countermeasure. Through research, the bonding strength can be enhanced by adjusting the mold gap, enhancing the exhaust property of the skeleton, and increasing the roughness of the skeleton, so as to eliminate blistering. The article also pointed out that adding the oven with temperature of 100 ℃ for 30 min as a quality control procedure can effectively prevent the blistering and defective products from flowing out of the production line, and provide a reference for solving the problem of blistering in the vacuum forming coating process.

According to SEP1220-2 Standards, the resistance spot welding current process window of hot-dip galvanized DH600 steel plate with high formability was determined, and its welding process performance was comprehensively evaluated in combination with shear tensile test, cross tensile test, metallographic test, micro-hardness test and electrode life test. The results show that the new material shows better welding performance than traditional DP590. In the welding process window, with the increase of welding current, the nugget diameter increases, and the joint strength also increases. The microstructure of the weld nugget is lath Martensite, and no softening phenomenon is detected in heat affected zone. The electrode life test shows that the new material has good electrode wear resistance.

For the differences between BIW aluminum parts joining technology routes in Germany and Japan, the article adopted the research method of typical and benchmarking analysis to describe the principle, forming process and process characteristics of aluminum parts joining technologies of VW AG and Toyota Company, and compared the process technology routes of VW and Toyota from 4 aspects of lightweight, quality, efficiency and cost, and formed a comparative analysis table for the types of BIW aluminum parts and joining processes of VW and Toyota. It is concluded in this article that the types of BIW aluminum parts, joining processes and investment of VW are more than those of Toyota’s, which all meet their quality requirements. The article proposed that FAW should draw on the application experience of aluminum joining technologies of VW and Toyota.

2 test methods, i.e. neutral salt spray method and cyclic corrosion method are utilized to study the effects of different test environments on the corrosion morphology, typical corrosion depth, corrosion products and mechanical properties of A380, YL113 and YL104 alloys. The composition of corrosion products and its corrosion mechanism are explored. The results show that, after 504 h neutral salt spray and 60 days cyclic corrosion test, the corrosion resistance of A380 alloy is the worst among the 3 die-casting aluminum alloys. Under the 2 test environments, the tensile strength of A380 alloy is reduced by 31% and 38% respectively; followed by YL113 alloy, its tensile strength decreases by 13% and 25% respectively; the tensile strength of YL104 alloy decreases by 3.6% and 1% respectively. The root cause of corrosion of these die casting alloys is that, the potential difference between phases in the matrix and the humid environment on the sample surface constitute electrochemical corrosion, which leads to corrosion.

In order to achieve the goals of improving product performance index, technological innovation, reducing cost, shortening manufacturing cycle and personalized customization, this article made in-depth technical research on the metal 3D printing Selective Laser Melting (SLM) process to make aluminum alloy (AlSi10Mg) and stainless steel (316L) material parts. The article mainly studied the optimization of metal 3D printing support process, exploration of unsupported technology, mechanical properties of parts and its application in automotive products, and explored its practical application scenarios. According to the exploration results, the article summarized the process guidance specification of metal 3D printing supporting technology and the exploration rules of unsupported technology, and the specific values of mechanical properties of printed parts. Meanwhile, the application scenarios of automobile parts were developed, and the traditional parts with complex, long cycle and high cost were replaced by metal 3D printing laser selective melting (SLM) process. It provides theoretical basis and practical case reference for further application of metal 3D printing technology in automobile parts.

Automotive cooling hose with polyamid(PA66) as the host material was developed to replace the long chain nylon materials (including PA12, PA612, PA11 and so on), which solved many disadvantages of long chain nylon materials such as costliness, resource shortage and complex production processes. This article firstly introduced the development of hydrolysis resistant and flexible PA66 material. Adding toughening agent and hydrolytic resistant agent to PA66 material through blending modification effectively improved toughness and hydrolytic resistance, and the material performance index conformed to usage requirement. Then conventional hose extrusion process was applied to PA66 modified material for hose extrusion trial production. The test shows that burst strength of PA66 hose is greater than 2.6 MPa, which is still greater than 1.8 MPa after long-term use of coolant resistant fluid, proving it comply with the basic use condition of vehicle.

The factors affecting stamping parts in the production process are complex, and the correct use of grid test can effectively guide the optimization of necking and tearing of stamping parts qualitatively and quantitatively, can make stamping parts have a greater “Safety margin” in the stamping process, thus speeding up the speed of problem solving. Through Forming Limit Curve(FLC) analysis and Comsmart equipment measurement, the production guidance data can quantify and reflect the actual status of the mould, and then make specific mould margin adjustment and verify the adjusted mould margin.