A diesel engine failed during running, its mileage was only more than 2 743 kilometers. After disassembling, it was found that the needle valve body of high pressure common rail injector of cylinder 6 cracked in axial direction, failure analysis was performed. By means of macroscopic trace analysis, scanning electron microscope fracture analysis, energy spectrum analysis, metallographic analysis and microhardness test, it is pointed out that the main cause for the cracking of needle valve body is the existence of fusiform defect in the matrix of needle valve body head, which is the raw material slag containing Zr, O and other elements. The material of needle valve body is ASP steel, in its production process, when the liquid steel flows through the atomizing nozzle (high density zirconia material), a small part of the nozzle material falls into the liquid steel, forming the slag inclusion. The crack initiates and spreads from the slag inclusion, leading to early fatigue fracture of needle valve body.

In this paper, the influence of defects on mechanical properties of high-pressure die-cast aluminum alloy was studied by means of greenhouse stretching, scanning electron microscopy and automatic defect identification and statistics program based on deep learning and threshold segmentation. The results show that the mechanical properties of high-pressure die-cast aluminum alloy castings fluctuate at different positions. The accuracy of the image recognition program was verified by comparing the results of the image recognition program and the manual statistics of the defect area of the fracture. The relationship between the fracture defect area and mechanical properties shows that the porosity and maximum defect size are correlated with the elongation. When the porosity or maximum defect size increases, the elongation of high-pressure cast aluminum alloy shows a downward trend.

In order to improve the simulation prediction accuracy of failure behavior of AHSS in vehicle crash, this paper studied the principle of 6 typical failure models such as GISSMO in mainstream LS-DYNA solver, it also studied the calibration methods of material fracture limit strain and mesh size regularization, the most crucial parameters affecting the failure behavior prediction accuracy of ultra-high strength steel during vehicle crash simulation. During the calibration process of fracture limit strain, average stress triaxiality should be used in order to describe the non-linearity loading paths. To overcome the limitations of default mesh size regularization method, the paper proposed a customized mesh size regularization method, which can effectively improve the consistency of simulation results for different mesh size models under typical stress states.

This paper discussed the determination of hexavalent chromium content in automobile materials and its uncertainty evaluation process based on colorimetric method. Hexavalent chromium in automobile materials was determined by UV spectrophotometry with a pretreatment method of lye digestion, and the uncertainty of measurement results was evaluated. A mathematical model is established to analyze and discuss the source of uncertainty measurement, calculation and result representation. The results show that the preparation process of standard solutions, measurement repeatability and calibration curve fitting quantification are the main contributors to the uncertainty of measurement results, which should be paid attention to in the testing process.

This paper discussed the product process design and welding defects debugging method of the laser brazing for the roof of Body In White (BIW) based on the industrial practice and application of the laser brazing of the BIW roof in Dongfeng Honda Automobile Co., Ltd., and focused on product structural design of the laser brazing of roof, component dimension accuracy control, production line process planning and plane layout of roof laser brazing, welding defects debugging method, manual inspection and repair process. By comprehensive introduction of process design and defect debugging method of laser brazing for BIW roof, the paper provided technical reference of laser brazing product design and process planning for subsequent new vehicle roof.

In order to eliminate surface defects around the roof antenna mounting boss, this paper used Autoform simulation and experimental verification to analyze 2 causes of defects, cause 1: stroke during the forming process is small, and the plastic deformation of the material is insufficient; cause 2: the pressing force of the pressing plate is insufficient, resulting in the deformation in the deformation area affecting the non-deformed area. Through the simulation analysis of the 2 process methods of the antenna mounting boss drawing forming and upper forming, it is confirmed that the upper forming process can effectively solve the defect around the antenna mounting boss, and the real effect is completely consistent with the theoretical simulation, which solves the problem of the surface defect of the antenna boss.

To meet the development needs of commercial vehicle light weight, from the perspective of materials light weight, the original glass fiber composite deflectors were replaced by Carbon Fiber Reinforced Plastics (CFRP) deflectors, It is achieved that the weight is reduced by 30% and the performance index is consistent, and even better. Based on the composite material failure criterion of 3D-Hashin and Cohesive layered failure criterion, a simulation model of basic mechanical properties of CFRP was established, and the effectiveness of the model was verified by comparing with experimental results. through the design of CFRP layer angle, finite element modeling was founded, the modal performance and stiffness of the 2 materials deflectors were compared and analyzed, the results show that the theoretical quality of carbon fiber reinforced plastics (CFRP) deflectors model is reduced, at the same time, compared with the original glass fiber composites deflectors, the modal performance and the average stiffness increase, and meet the fracture strength requirements.

The dissimilar galvanized steel sheets with thickness of 0.7 mm St17E and FC180/340HD for car door were tested and studied for laser welding process. The effects of key process parameters (laser power and welding speed) on the weld surface morphology and weld cross section were investigated. The microstructure and mechanical properties of welded joints were analyzed and evaluated. The results indicate that when the laser power and welding speed are 1 300 W and 2.0 m/min respectively, there are less welding spatters and the weld surface is smooth. As the laser power increases and the welding speed decreases, the weld penetration depth and weld area increase. For the dissimilar galvanized steel sheets welded joint, the hardness of the St17E base metal is the lowest, and the hardness of the weld zone is much higher than that of the base metal zone. The tensile specimen of the welded joint obtained with optimized parameters fractures in the St17E base metal.

Due to the poor wettability and thermal stability of electrolyte, the application of traditional lithium ion battery separator in the field of high-performance and high safety battery is limited. The surface modification of the separator to realize its surface functionalization has become a feasible strategy to solve the inherent problems of lithium-ion battery separators. From perspective of surface physical modification and surface chemical modification, this paper elaborated respectively the features and cutting-edge dynamics of various surface modification methods, such as spray coating, dip coating, solution casting, electrospinning, chemical grafting, plasma, radiation grafting and UV grafting. The paper also indicated that developing multifunctional separators, intelligent response separators, and reducing modification costs would be the research directions for surface modification of lithium-ion battery separators in the future.

The current cleaning solvent has the problem of endless cleaning for the long used automobile base coat pipeline. In this paper, the principle of paint remover was applied to the cleaning of automobile paint pipelines. A cleaning solvent and its corresponding cleaning program with benzyl alcohol and lye as the main agents and ethylene glycol butyl ether, isopropyl alcohol and ethyl acetate as auxiliary agents were developed to realize efficient cleaning of paint transfer pipelines. The results show that, compared with traditional cleaning solvents, this formula is not only suitable for water-based paint topcoat systems, but also for solvent-based topcoat systems, and the cleaning effect of long-term used pipes is greatly improved, the cleaning time is shortened by more than 50%, the cost of cleaning materials and VOC emissions are reduced by 50%, and the cleaning efficiency of the paint transfer system is effectively improved.