Alloying is one of the key approaches to improve the mechanical properties and thermal resistance of SiMo ductile iron. This paper reviews the effects of alloying elements on the microstructure and properties of SiMo ductile iron. A systematic study on multi-element alloyed SiMo ductile iron was carried out targeting exhaust manifolds of high peak-pressure diesel engines and gas engines. The results show that when the mass fraction of Mo increases from 0.9% to 1.46%, the volume fraction of carbides in the microstructure rises, leading to increases in the tensile strength, yield strength and hardness of SiMo ductile iron, while the elongation decreases by 50%. Vanadium alloying elevates the tensile strength but reduces the elongation of SiMo ductile iron; the material achieves satisfactory room-temperature mechanical properties at a V mass fraction of 0.4%. The short-term tensile strength at 800 ℃ increases with the rise of V content, yet no significant change is observed when the V mass fraction exceeds 0.4%. Among the multi-element alloyed SiMo ductile irons, the V-Nb alloyed SiMo ductile iron reaches a high-temperature tensile strength of 59 MPa, while the V-Cr and V-Nb-Cr alloyed variants exhibit high-temperature strengths of 61~64 MPa. These values meet the high-temperature tensile strength requirements for SiMo ductile iron applied in exhaust manifolds of high peak-pressure diesel engines and gas engines.

The differences in humidity resistance between synthetic fiber filter materials and traditional wood pulp fiber filter materials are systematically evaluated through static and dynamic moisture absorption tests, and the intrinsic mechanism underlying the variation in intake resistance of filter materials under high-humidity conditions is investigated. The results show that synthetic fiber filter materials are significantly superior to traditional wood pulp fiber filter materials in terms of dust holding capacity, initial filtration accuracy and full-life filtration performance, while exhibiting lower intake resistance and more stable structural characteristics. In bench tests under humid environments, synthetic fiber filter elements demonstrate excellent humidity resistance without obvious structural deformation or intake resistance rise. Further drum bench test results indicate that synthetic fiber filter elements can reduce the intake resistance by approximately 20% under high-humidity conditions, improving fuel economy by 1%. In addition, the 60,000 km on-vehicle test verified that synthetic fiber filter elements achieve a remarkable fuel-saving effect, which confirms their performance advantages in practical applications.

To solve the defects of the engine cylinder bore thermal spray materials, namely the brittle fracture of welding wire, the peeling of copper plate layer, and the coating holes, the defect mechanism is clarified through microstructure analysis and full-process process optimization, and corresponding countermeasures are formulated. The results show that the brittle fracture of the imported material is caused by the large amount of hard bainite resulting from composition segregation, which causes cracks during drawing. The electromagnetic stirring, light pressure reduction and "air cooling + slow cooling" process can effectively inhibit bainite and avoid brittle fracture. The peeling of the copper plating layer is mainly due to insufficient bonding force and low mold surface finish. The "alkaline pre-plating + acidic main plating" and diamond coating drawing die can significantly improve it. The coating holes are related to process fluctuations, nozzle slagging and cleanliness. Through real-time monitoring of key parameters, nozzle maintenance and cleanliness system control, the defect rate of holes is reduced by about 70%. This provides a systematic technical path for the development and quality control of high-performance cylinder bore thermal spray materials.

To investigate the effect of automotive millimeter-wave radar radome matenvls on millimeter-wave transmittance performance, this paper inelaborates the intrinsic relationship between material transmission loss and electromagnetic parameters, and tests the electromagnetic parameters and transmission loss of several commonly used radar cover plastics, as well as the transmission loss of different Polypropylene (PP) material thicknesses. The results indicate that low polarity materials generally have lower dielectric constants and dielectric losses. The transmission loss of millimeter waves in bumpers exhibits a periodic relationship with wall thickness, and the transmission loss is minimal when the thickness is an integer multiple of half a wavelength. Furthermore, through analysis of the transmission loss of materials with different paint coatings and metal coatings, it is found that aluminum powder and pearlescent powder in paint components have a significant negative impact on the transmission performance of millimeter waves. Physical Vapor Deposition (PVD) aluminum plating is not suitable for Adaptive Cruise Control(ACC) vehicle logos, while appropriate film thickness PVD indium plating has minimal interference with millimeter waves and meets the transmission requirements.

In response to the problem of insufficient fatigue strength of the shear edge of the 700 MPa level frame longitudinal beam, optical microscopy, scanning electron microscopy and fatigue testing machine are used to evaluate the properties of the shear edge under existing process conditions in this paper. The research results indicate that the burrs on the shear edge of the 700 MPa level frame longitudinal beam are effectively removed by rolling deburring process. However, due to the folding caused by burr lodging, the fatigue strength of the shear edge is only 206 MPa, and the fatigue failure originates from the folding root at the rolling edge of the tear band side. To improve the fatigue strength of the shear edge in further, the parameters of the shear edge rolling process are analyzed and optimized combined with CAE analysis. The results show that in order to form a large residual compressive stress on the shear edge, the optimal angle between the roller working surface and the hot-rolled plate surface is 30°~45°, with a rolling depth of 0.5~1.0 mm. The chamfered surface formed by rolling the upper and lower edges of the shear edge is smooth and flat by using optimized rolling process. The hot-rolled surface of the original plate has no obvious protrusions, and there is no outward protrusion in the middle of the cross-sectional profile of the shear edge. Finally, the fatigue strength of the shear edge reaches 263~270 MPa.

To address the issue of excessive engine exhaust smoke and insufficient power occurring after 275 km of operation in a certain engine turbocharger, a systematic analysis of the failed turbine shaft is conducted using methods such as macroscopic inspection, scanning electron microscopy analysis, metallographic observation, and hardness testing. The results indicate that the turbine shaft fracture is a low-stress, high-cycle fatigue failure under significant stress concentration. The fracture originated from a severely scratched area at the fillet caused by poor grinding processing. The root cause is identified as poor lubrication leading to dry friction between the shaft and bearing, subjecting the bearing to abnormal alternating stress. The study concludes that although the machining defect created a stress concentration source, the abnormal operating condition (dry friction caused by oil shortage) is the primary factor triggering this premature fracture.

To study the testing methods and issue diagnosis of high-voltage systems in new energy vehicles, this paper examines high-voltage electrical safety from two levels: equipment-level and vehicle-level and analyzes existing the high-voltage electrical safety regulations, standards, and the current technological status of new energy vehicles. The study also investigates the high-voltage insulation condition of new energy vehicles and corresponding protective measures, including the principles and testing methods of high-voltage insulation systems and monitoring systems. Finally, comprehensive solution for high-voltage electrical safety analysis, protection, design, and testing has been developed. This solution can perform exhaustive verification across various operating scenarios of new energy vehicles, enabling precise identification of system safety threshold violations and validation of operational safety, thereby simplifying the difficulty of issue diagnosis.

To improve the reliability of hemming processes for automotive closure panels and prevent appearance defects, the hemming processes of the hood, front door, and rear door assemblies are analyzed during the process design phase using AutoForm software and CAE numerical simulation technology. 2 rounds of hemming simulation and 1 round of simulation validation are conducted, yielding the following results: The first simulation identifies the location, extent, and severity of wrinkling in the 3 assemblies. The second simulation addresses the wrinkling defects by adjusting roller parameters and flange lengths, achieving a 100% qualification rate for both gap and flushness simulations across all 3 assemblies, with the rear door gap qualification rate increasing by 27.78 percentage points. Validation results show strong correspondence between the measured data and the first simulation: the hood gap control qualification rate is 86.21%, while the front and rear door assemblies achieved 100% gap control qualification. The overall consistency between measured and simulation results exceed 95%. The flushness qualification rates for the hood, front door, and rear door are 67.24%, 67.86%, and 97.22%, respectively. However, the consistency between measured and simulation results for the hood and front door is below 81%, primarily due to the absence of chain analysis and the inability of ideal numerical simulations to account for stamping stress and forming tolerances.

To quantitatively analyze the impact of electrode tip diameter on nugget diameter, resistance spot welding experiments and finite element analysis are conducted on hot-stamped steel using electrode tips with diameters of 6 mm and 8 mm. The welding currents required to obtain the same nugget diameter with electrode tips of 6 mm and 8 mm diameter are investigated. The results show that with the increase of welding current, the influence of electrode tip on the nugget diameter of resistance spot welding is gradually reduced without splash; When splash occurs, the electrode tip of 8mm diameter will obtain a larger nugget diameter. For 1.6 mm HQAS1500H+1.6 mm HQAS1500H plate group lapping form, the resistance spot welding process parameters can be set as 3.43 kN/420 ms/7 kA~3.43 kN/420 ms/8 kA. Within the common production welding current range, the deviation between the actual nugget diameter and the finite element simulation nugget diameter is less than 10%.

To study the applicability and advantages and disadvantages of recycled plastics in the automotive field, bumpers skins are made from recycled and virgin polypropylene plastics (RPP and VPP), and the low-speed collision performance of the 2 materials'bumpers is compared and analyzed using a pendulum impact system. The results show that no fracture occurred after the test of the 2 material bumpers under different impact strengths, but the width of the RPP bumper abrasion is larger than that of the VPP, and the visual performance is not excellent. The impact force generated by the collision under the same load was less than that of the VPP, but the impact time is reversed, indicating that the impact acceleration of the RPP bumper is more modest, which is more advantageous in pedestrian protection. In addition, the mechanical properties of materials are analyzed in order to investigate the reasons for the variation in test. The yield elongation of the VPP material is lower than that of the RPP (35%) and the impact strength and energy absorption are slightly great. This allows the RPP bumper skin to generate the same deformation with less force (less impact acceleration). The performance of RPP bumpers is close VPP due to the advantage of additives of RPP and the greater melt fluidity.