To enhance both the crashworthiness and lightweight design of an all-aluminium frame, a multidisciplinary, performance-oriented development strategy was formulated. The methodology integrates functional zoning with material matching, enabling a region-specific development process that achieves an optimal trade-off between structural performance and mass efficiency. During the structural design phase, a topology optimisation approach based on the variable density method is implemented, with particular attention paid to energy-absorbing components and critical cast regions. This facilitated the resolution of conflicting performance requirements and the establishment of an optimal structural architecture. In the subsequent lightweight design phase, a parametric thickness optimisation technique is adopted to determine the most favourable distribution of material gauge across all functional zones. Under the precondition of satisfying requirements for strength, durability, Noise, Vibration and Harshness(NVH), as well as crash safety, the mass of the all-aluminium frame was reduced by 16.7%, corresponding to 7.5% of the total vehicle mass. The final design was subsequently validated through a comprehensive series of physical tests, and all performance indicators were confirmed to meet the predefined development targets.

To address the significant anisotropy and complex failure behaviors exhibited by high-strength extruded aluminum alloys in vehicle crash structures, the prediction accuracy of the traditional Barlat89 criterion and the Yld2000-2d criterion based on dual linear tensor transformations is systematically investigated in crash simulation. Static and dynamic mechanical tests covering multiple stress states (pure shear, tension-shear, notched, and central-hole specimens, etc.) are conducted based on actual components, and the full-field local strain evolution responses and fracture limits of 6082-T6 aluminum profiles are obtained. To address the difficulty in direct calibration caused by measurement errors and the lack of biaxial tensile data, an inverse identification scheme based on Digital Image Correlation (DIC) and multi-load-case global optimization is proposed, by which the anisotropic parameters and the Modified Mohr-Coulomb (MMC) criterion coupled with the GISSMO damage boundary are efficiently calibrated. It is demonstrated by the verification results that the anisotropic response of the material under complex loading paths is precisely captured by the Yld2000-2d criterion. In the load cases of bumper beam drop-weight impact and full-vehicle low-speed crash, the macroscopic tearing morphology is accurately reproduced by the model, and the prediction error of critical intrusion is significantly reduced from 16.1% (with the Barlat89 criterion) to 3.9%.

To address the issues of insufficient simulation accuracy for nonlinear large deformation and fracture induced by premature necking in numerical simulations of high-elongation metals, as well as prediction deviations in the failure behavior of the spot weld heat-affected zone, an SHS & linear extrapolation necking control strategy is proposed based on Considère instability theory. The modified Mohr-Coulomb (MMC) failure surface for DC03 base metal is established via mechanical tests under multiple stress states. Combined with parameter inversion technology, the failure parameters of the generalized incremental stress-state-dependent damage model for the spot weld heat-affected zone are calibrated, and verification is conducted through full-vehicle crash simulations. The results show that the numerical necking strain of DC03 material is delayed by 0.103 with a substantial efficiency improvement; the average peak error of spot weld failure simulation reaches 3.3%; the full-vehicle simulation can accurately reproduce the deformation and failure behaviors of both the base metal and the spot weld heat-affected zone. This scheme enables intelligent control of necking points, and significantly improves the accuracy of full-vehicle crash simulation and the prediction precision of structural performance boundaries.

To meet the requirements for vehicle lightweighting, resistance element welding (REW) is performed on a die-cast magnesium alloy and a steel plate using steel rivets. Under constant heat input, different magnesium/steel REW joints are produced by adjusting the welding current and welding time. The macrostructure, microstructure, mechanical properties, and fracture morphologies of the joints are observed and analyzed. The results show that, under constant heat input, heat is transferred from the surface of the electrode cap toward its interior; as the welding time decreases, the through-thickness integral nugget transforms into two fan-shaped nuggets in the upper and lower regions. With increasing welding current, the length of the gap extending along the interface and the distribution length of the eutectic phase at the nugget edge between the steel rivet and the lower steel sheet decrease. Under constant heat input, as the welding current increases and the welding time decreases, the shear resistance initially decreases and then increases, reaching a maximum shear resistance of 6.37 kN; the effective shear displacement increases with increasing welding current, reaching a maximum effective shear displacement of 4.56 mm.

To address the difficulty in accurately assessing the fatigue life of welded structures, a multi-fatigue-parameter coupled equivalent structural stress evaluation method is adopted. Based on material constitutive relations, mechanical principles, and numerical analysis, an original algorithm for the fatigue life assessment of welded structures is developed, and a quantitative mapping relationship between equivalent structural stress and fatigue damage under multiaxial stress states is established. By combining multi-channel quasi-static superposition technology and integrating rainflow counting and the Miner cumulative damage model, fatigue simulation analysis software suitable for engineering applications is developed through independent programming. A welding simulation case validates the good mesh insensitivity of the software, effectively solving the technical problem of mesh-size sensitivity in traditional industry simulation methods. Through systematic simulation benchmarking of fatigue failure cases, it is demonstrated that the proposed analysis method can accurately predict the fatigue failure risk of welded structures, and the fatigue life prediction accuracy is substantially improved compared with traditional industry simulation methods.

To achieve accurate and efficient prediction of mechanical response and crash failure of steel‑aluminum hybrid self‑piercing riveted joints, and support the lightweight and crashworthiness design of steel‑aluminum hybrid vehicle bodies, adaptive mesh technology is adopted to establish an SPR forming simulation model for high‑strength steel and cast aluminum, and the influence law of process parameters on joint forming quality is analyzed. A refined solid model incorporating process history is constructed through residual stress‑strain field mapping, and the joint failure mechanism is revealed combined with mechanical tests. An efficient numerical simulation model for self‑piercing riveting (SPR) is developed and calibrated, and applied to the analysis of vehicle small‑overlap crash conditions. The results show that the error of characteristic cross‑sectional dimensions from forming simulation is no more than 10%; the peak load prediction error of the model considering process history is less than 6%, and that of the efficient SPR model is below 2%. Vehicle‑level simulation can accurately reproduce joint failure and structural deformation behaviors.

Polypropylene (PP) resin automotive bumpers tend to accumulate static electricity due to their high insulation, which causes particles to firmly adsorb on the surface through Coulomb force, and also leads to safety hazards and reduced coating efficiency when grounding performance is poor during electrostatic spraying. Taking the full bumper coating process as the research object, this paper systematically analyzes the static electricity accumulation mechanism and particle force characteristics of bumper materials, proposes a collaborative destaticization and dust removal process scheme that combines ionized-air pre-treatment with ionized-air purgingThe working principle, calibration method, and process implementation procedure of a non-contact electrostatic grounding detection system are also described in detail. Practical results show that the integrated ionized air application scheme can significantly reduce the number of particles after baking, and the grounding detection system can effectively eliminate the safety hazards of electrostatic spraying. The organic combination of the 2 comprehensively improves both the quality and safety of bumper coating, achieving the production goal of cost reduction and efficiency improvement.