The effect of the microstructure heterogeneity on the tensile plastic deformation characteristic of friction-stir-welded (FSW) dual-phase (DP) steel was investigated for the potential applications on the lightweight design of vehicles. Friction-stir-welded specimens with a butt joint configuration were prepared, and quasi-static tensile tests were conducted, to evaluate the tensile properties of DP980 dual-phase steels. The friction-stir welding led to the formation of martensite and a significant hardness rise in the stir zone (SZ), but the presence of a soft zone in the heat-affected zone (HAZ) was caused by tempering of the pre-existing martensite. Owing to the appearance of severe soft zone, DP980 FSW joint showed almost 93% joint efficiency with the view-point of ultimate tensile strength and relatively low ductility than the base metal (BM). The local tensile deformation characteristic of the FSW joints was also examined using the digital image correlation (DIC) methodology by mapping the global and local strain distribution, and was subsequently analyzed by mechanics calculation. It is found that the tensile deformation of the FSW joints is highly heterogeneous, leading to a significant decrease in global ductility. The HAZ of the joints is the weakest region where the strain localizes early, and this localization extends until fracture with a strain near 30%, while the strain in the SZ and BM is only 1% and 4%, respectively. Local constitutive properties in different heterogeneous regions through the friction-stir-welded joint was also briefly evaluated by assuming iso-stress conditions. The local stress-strain curves of individual weld zones provide a clear indication of the heterogeneity of the local mechanical properties.

The stiffness in various directions of air springs have a great influence on the stability of high-speed trains. Due to the change in the bogie structure, the required functions of the air springs have also diversified, and the damping of various loading modes such as vertical, lateral, and torsional movements is emerging as important. The stiffnesses are affected by the shape of the air bag, the material, and the ply angles. In this paper, the relationship between the ply angle and the radial position is proposed by equations from deformation modes. The variable angles in the plies were compared and demonstrated in air-spring analysis using the rebar elements. The vertical, lateral, and torsional stiffness of air springs without auxiliary springs were compared between constant ply angles and variable ply angles with respect to the positions. When mainly dealing with the vertical stiffness, the effect of the angle variation was small; however, it was found that it had a large effect of more than 24% and 30% on the stiffness in the lateral direction and torsional direction, respectively.

Despite the growing importance of autonomous driving (AD) education, educators face substantial challenges in providing undergraduate students with accessible, hands-on learning experiences that connect theory and practice. AD education requires students to master complex, interdisciplinary systems, yet traditional teaching methods often fail to fully integrate theory and practice. Various strategies, such as simulation environments and small-scale autonomous vehicle platforms, have been explored to address these challenges. However, these approaches often lack the realism or scalability required to provide students with a comprehensive understanding of AD systems. To address these challenges, we developed and evaluated a competition-based learning framework designed to teach AD software technology. In a three-year iterative design study, we implemented a framework combining a cost-effective 1/5-scaled autonomous vehicle platform with team-based competitions. This framework was progressively improved through a mixed-methods analysis of data from 445 students across five competitions and two capstone design courses. The quantitative results showed statistically significant improvements in the students’ self-assessed skills with large effect sizes, demonstrating that the framework significantly boosted students’ technical abilities and motivation. The qualitative feedback confirmed the educational value of the platform’s realism and peer-based observations of the competitions. This article presents the complete educational framework, outlines the iterative design process and key design decisions, and discusses the lessons learned. It also provides a validated model and practical guidelines for educators seeking to incorporate effective, competition-based AD education into their curricula.