In view of the characteristics of randomness, diversity and complexity of discrete manufacturing systems, efficiently and accurately identifying system quality risk factors and conducting quantitative assessment of quality risks are crucial to developing corresponding quality control activities and improving product quality. In this research, firstly a product quality risk assessment model for Fuzzy Colored Petri Nets was constructed. Then the fuzzy inference rules were determined, and the confidence of the intermediate library and the terminating library was calculated by fuzzy reasoning through the confidence empirical value obtained at the scene. Finally, the automotive top cover stamping process was analyzed as an example to verify the rationality of the model proposed in this paper, which can be applied to other similar discrete process manufacturing.

Based on the material consistency and mechanical properties, fracture morphology analysis, structure analysis, stress analysis, failure simulation, broken door handle shell material consistency and mechanical properties met the design requirements, it was found that the parts away from the tip of the modeling of gate structure was prone to stress fracture. Clearance between shell and skeleton was increased from 0.2 mm to 1.2 mm, handle tip comer with rectangular links was changed to bevel and circular arc transition, the position of mold feeding mouth was changed, temperature of the mold was fixed at 50~60 ℃, the drying time of baking material before injection was increased from 1 h to 2 h, the baking stress relief of 80 ℃ for an hour was increased after injection, and the pressure holding time was reduced from 7 s to 4 s, the stress could be reduced which eliminated handle fracture. After the rectification, the parts were verified and tracked, and no similar failure occurred again.

In order to solve the problem of microcracks in the ceramic chips causing failure of the sensor assembly, this article studied and analyzed a simple and non-destructive method for detecting the microcracks in the ceramic chips, which can be filled in the middle of the crack by using the good wettability of alcohol to the ceramic, and the difference between the conductivity of alcohol and air was used to quickly determine whether there were microcracks in the chips by detecting the change of the current of the ceramic chips. This method was applied to the case study of the failure of the front oxygen sensor of a vehicle model. The cause of microcracks was further proved by optical microscopy and high-precision CT. The results show that the alcohol detection method could accurately determine the occurrence of microcracks inside ceramic chips, and the cause of cracks is excessively high heater voltage, and the uneven internal thermal stress, which cause the heater electrode to detach from the chips’ body, which in turn leads to microcracks inside the chips.

Due to the variety of automotive interior materials, complex composition, and up to hundreds of kinds of odor substances inside each car, odor pollution easily occurs inside the car. In order to improve interior air quality, this study referred to the existing domestic and foreign research on the application of colorimetric technology, proposed an interior odor detection method based on colorimetric sensor array technology, and made colorimetric analysis on the interior materials widely used in the vehicle, accurately identified the odor intensity, odor type and odor pleasure of interior materials samples. In this study, colorimetric sensor array was applied for the first time in the objective characterization of vehicle odor, which can provide data support for odor control in the automobile industry.

In this research, the key properties of vacuum forming composite wheel house based on lightweight design including mechanical properties, stone impact resistance, vibration endurance, sound insulation performance, wind resistance deformation were studied and analyzed, those properties were compared and analyzed with mature injection molding and compression molding. Research result shows that comprehensive performance of the composite wheel house fender meets the technical requirements of passenger vehicle wheel house fender. Compared with injection molding products, the newly designed products have better stone impact resistance and sound absorption performance, with weight reduction of 22%. Compared with die pressing products, the new product has shorter development cycle and cost advantage.

With a car underbody protection panel as the research object, a solid model of the underbody protection panel was established using CATIA software. The finite element analysis software Hyperworks was used to simulate and analyze the static load and impact resistance performance of the car underbody protection panel, evaluate the effects of factors including fixed solutions, reinforcement structure, material selection and etc. The simulation results provide a theoretical basis for the design and material selection of the car underbody protection panel structure.

This paper introduced the process and performance of reaction injection molding polyurethane car trunk cover plate, and compared it with traditional car trunk cover plate. The results show that reaction injection molding polyurethane car trunk cover plate is easy to clean and daily maintain, it reduces the risk of sliding of items in the luggage compartment when the car is turning, improves the driving experience. At the same time, acetaldehyde is significantly reduced, and other properties also meet the requirements for trunk cover plate.

With the stress value, the maximum contact pressure and the compression force as evaluation basis, the influence of the straight line length of the return pipe joint and the return pipe on the assembly of the structure was studied by using the finite element simulation analysis method. With the increase of the length of the straight line, the stress value of the joint and the return pipe decreases gradually, and the maximum stress value of the joint and the return pipe is 650% and 295.2% larger than the minimum stress value, respectively. The maximum contact pressure of the inner liner and the outer liner also decreases gradually, and the maximum contact pressure of the inner liner and the outer liner is 384.9% and 290.2% greater than the minimum value. The pressing force gradually decreases, and the maximum value is 678.8% greater than the minimum value. The research results show that change of the length of the straight line has a significant impact on the assembly performance of the structure.

To solve the problem of performance degradation caused by abnormal rotor assembly, this paper analyzed the possible magnetic steel leakage and missing angle fault modes during the assembly process of the rotor assembly. The leakage mode can be prevented through surface magnetic detection, while the missing angle mode cannot be detected and recognized by surface magnetic detection equipment in the industry. Therefore, the paper proposed a method for error prevention and recognition through the analysis of the back electromotive force and vibration characteristic order of the motor, the method can identify the amplitude of higher characteristic order vibration of the motor that exceeding the standard value. In the actual production and manufacturing process, attention is paid to the collection of offline vibration signals of the motor for abnormal operation judgment. After practical verification, this method can effectively identify magnetic steel leakage and missing angle fault modes.

The application of post-treatment technology in the surface treatment of steel-aluminum mixture was studied by Scanning Electron Microscope (SEM), inductively coupled plasma emission spectrometer and cyclic alternating salt spray tester. The results show that the cold-rolled sheet and galvanized sheet on the car body form uniform and dense phosphating film after the new pretreatment process. After the new pretreatment process, a passive film was formed on the surface of aluminum plate. With the increase of aluminum in steel-aluminum mixture, the amount of slag in phosphating solution decreases gradually. When the treated material is only iron, the slag in phosphating solution is 2.5 g/m², and when all the treated materials are aluminum, the slag in phosphating solution is lower than 0.5 g/m². When the new pretreatment process is used to treat the steel-aluminum mixture, the concentration of all ions in the phosphating solution can be kept at a stable level. The adhesion test results of paint films of three aluminum plates meet the standard requirements. After 1 000 h salt spray test, the unilateral corrosion of cold-rolled plate is less than 2 mm, and there is no foaming and peeling of paint film. After 1 008 h cyclic alternating test of aluminum plate and galvanized plate, the width of unilateral corrosion expansion is less than 2 mm, and the paint film does not bubble or peel off.