In order to determine the fracture mechanism and cause of the trunk lid torsion bar spring, the fracture morphology, composition, size, material strength, microstructure and residual stress were tested, and a comprehensive analysis was conducted in combination with background information. The results indicate that the torsion bar spring of the trunk lid experienced high-strength steel delayed cracking at the concentrated bending stress caused by high material strength, insufficient tempering, and high residual stress. Based on the cause of cracking, improvements were made from two aspects: controlling the strength of raw materials and optimizing the stress relief tempering process to reduce residual stress, and ultimately the delayed cracking failure of the luggage torsion bar spring was effectively solved.

In order to address the issue of low automation and digitalization of the automotive body wax filling process, this paper discussed feasibility of total process automation from production, inspection to repair in automobile wax filling, and proposed an automatic solution of automobile wax filling. In the production process, the body wax filling was realized through technological transformation by the application of low cost automation. In the inspection process, visual identification technology was used instead of manual inspection to capture and identify the wax mist on the vehicle body and reduce the body defect outflow rate. In the repair process, through the analysis of the wax defects, the auto body bottom plate purge device was designed to eliminate the wax overflow on the premise of meeting the performance requirements of the vehicle. In addition, the paper also proposed the data interconnectivity scheme. The results show that the production efficiency and cost have been greatly improved through the application of automation.

To address the interference of Liquid Apply Sound Deadener (LASD) robot nozzle block on parts installation in the assembly shop, this article analyzed LASD robot nozzle block. Through studying the LASD robot nozzle block times and equipment downtime of paint shop, the root cause of nozzle block was the high robot inlet gluing pressure and short material surface drying time. The LASD robot nozzle block time was reduced effectively by reducing robot inlet gluing pressure and adding gasket to material package, which reduced the risk of faulty car body going to assembly shop to the maximum, and reduced equipment and personnel manpower cost, which effectively reduced the cost from paint shop equipment downtime caused by abnormal gluing status. Meanwhile, it can also shorten the time of production line downtime and car body offline rework that caused by LASD interference in assembly shop.

Carbon Fiber Reinforced Polymer (CFRP) is a material with excellent mechanical properties. The application of bonding CFRP parts with body has not been realized in mass automobile production in China. The article described the performance test on CFRP parts bonding with aluminum material and the optimization of process flow. The bonding process flow and process parameters of each process of CFRP on ES6 were ultimately determined based on the test of the curing strength of adhesive under different conditions and the influence of external factors on the adhesive bonding strength, Thus, for the first time, CFRP was applied to the body structure of new energy vehicle on a large scale (production capacity 20 job/hour) in China.

The effects of alkyl acid surfactants with different carbon chain lengths (decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid) on the properties of CeO₂-ZrO₂-Y₂O₃-La₂O₃ (CZ) materials were studied and analyzed, and the underlying mechanism of surfactants in building high performance CZ materials has also been revealed. The results of N₂-adsorption/desorption, OSC, H₂-TPR, and catalyst activity show that the addition of all surfactants with different carbon chain lengths during the nucleation stage of nanocrystals can increase the initial grain size of nanocrystals, thereby reducing the driving force of sintering. At the same time, the introduction of surfactants produces more oxygen vacancies in the material, thereby improving its redox performance. Among them, dodecanoic acid plays the most prominent effects improving the thermal stability and redox performance of CZ materials, the resultant CZ exhibits the lowest loss rate of specific surface area of 46.3%, the lowest reduction peak temperature of 497℃, the highest utilization rate of Ce of 39%, and consequently the best catalytic activity of its supported Pd-only TWC.

In order to shorten the cycle of product, design and developent, procurement and production, construction of a flexible, efficient, low-cost and high-quality manufacturing operation system, digital twin technology is crucial. This article used an automotive welding production line as an example to elaborate the process of setting up a digital twin factory in Tecnomatix software. Using Tecnomatix series software, the digital model and process information were imported in the pre-planning process, the 3D process layout was carried out in advance, the accessibility of connection processes such as solder joints and gluing was simulated, the spatial static and dynamic interference as well as offline program output were analyzed and solved. Utilizing digital twin technology, the mapping and correlation of real factories in the simulation environment was realized. As a result, the on-site installation and commissioning was accelerated, the project cycle was reduced, the efficiency and quality of production line planning and design were improved.

In order to address the issue of failure fracture of balance suspension leaf spring seat of engineering vehicle, this paper analyzed the balance suspension leaf spring seat by process analysis, fracture analysis, metallographic examination, strength test, hardness test and material fatigue limit testing. The results show that the material used in the balance suspension leaf spring seat meets the standard requirements, and the failure modes include multi-source high stress and low cycle bending fatigue cracking, the crack originates from the rounded root between the balance suspension leaf spring seat and the U-bolt, which is thick and easy to produce defects like shrinkage and porosity in the production process. In the structure, this position is the balance suspension leaf spring seat under the greatest stress position and a dangerous section of the part.

When the exhaust pipe is welded with the flange, the welding deformation of the flange affects the tightness of the exhaust pipe assembly. In order to avoid excessive welding deformation of flange during manufacturing, the FEA model was established with the moving Gaussian heat source to simulate flange welding process. After analyzing and comparing the temperature field, stress and strain results of flanges under different constraint conditions and different welding parameters, the solution that can effectively reduce the welding deformation of flanges in the production and manufacturing of exhaust pipes was determined. This paper proposed suggestions of welding electric current, welding speed and heat source radius, which provided theoretical basis for the optimization of welding process of exhaust pipe flange.

In order to eliminate abnormal sound of the knuckle cone ball stud of a passenger car on proving ground test, this paper proposed a new method based on virtual simulation. Firstly, the ball stud contact area variation tendency was simulated and the contact area critical preload was identified according to limit value of the road load data; then the residual preload under alternate working condition was simulated, and the residual preload was controlled larger than critical preload to avoid large contact area separation which will cause abnormal sound; finally, the tightening process was determined through joint test. The results show that this method can redefine the tightening torque, and the abnormal sound problem was eliminated successfully.

In order to improve the service life of spot welding electrodes, TiB2-reinforced copper matrix composites were prepared using a multi-step method. The physical phase and microscopic morphology of the TiB2-reinforced copper matrix composites prepared by the multi-step method were analyzed using X-ray diffraction (XRD), metallographic microscopy and scanning electron microscopy (SEM) characterization. By measuring the mechanical property indexes of the composites, it was found that the copper matrix composites prepared by the multi-step preparation had better comprehensive mechanical properties. The copper matrix composites prepared by the multi-step method were processed into spot welding electrodes, its life test results were the highest compared with other comparison samples, with a life time of 1 500 solder joints, which was 2.6 times longer than the life time of common chromium zirconium copper spot welding electrodes.