大阪大学 · Engineering
Yunwu Ma 교수의 연구실은 고강도 철강 및 경량 합금(알루미늄 합금, 마그네슘 합금 등)의 접합 기술에 중점을 두고 있으며, 특히 저항점-welding, 자가피어싱 라이브릿팅(F-SPR)을 포함한 고성능 기계적 접합 공정의 개발과 기계적 거동 분석을 핵심 연구 분야로 다룹니다. 재료의 미세구조, 열영향부, 균열 거동 및 인장/피로 거동에 대한 정밀한 실험 및 유한요소 해석을 융합한 다각적 접근을 통해 접합 품질과 수명을 향상시키는 데 기여하고 있습니다. 특히, 액체 금속 취성 연화, 열가소성 거동, 라이브릿팅 공정 최적화 등 복잡한 물리현상을 정량적으로 분석하는 데 뛰어난 전문성을 보유하고 있습니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
Safety evaluation of resistance spot welds necessitates the accurate measurement of local constitutive properties. This study employed miniature mechanical tests to investigate the deformation and failure behaviors of nugget, heat affected zone (HAZ), and corona bond of resistance spot welded JSC980YL steel. A novel mini-peel test was developed to enable local fracture in HAZ for numerical inverse calibration of constitutive parameters. The fracture constants of weld zones calibrated using Cockc
In this paper, self-piercing riveting (SPR) and friction self-piercing riveting (F-SPR) processes were employed to join aluminum alloy AA5182-O sheets. Parallel studies were carried out to compare the two processes in terms of joint macrogeometry, tooling force, microhardness, quasi-static mechanical performance, and fatigue behavior. The results indicate that the F-SPR process formed both rivet–sheet interlocking and sheet–sheet solid-state bonding, whereas the SPR process only contained rivet–
Zinc-coated ultra-high-strength steel (UHSS) sheets are highly susceptible to liquid metal embrittlement (LME) during resistance spot welding. However, systematic understanding on LME cracks in the pullout fracture of UHSS welds is still lacking. This study employs artificially created pre-cracks on bare DP980 steel welds to simulate the LME cracks, allowing accurate control of the crack shape and location. To investigate the fracture initiation and propagation behavior of welds with various pre
Friction self-piercing riveting (F-SPR) process based on a pip die has been invented to solve the cracking problems in riveting high-strength and low-ductility light metals, such as magnesium alloys, cast aluminum, and 7 series aluminum alloys. In this paper, in order to solve quality issues caused by the misalignment between rivet and pip-die in F-SPR, a flat-die based F-SPR process was proposed and employed to join 1.27 mm-thick AA6061-T6 to 3 mm-thick AZ31B. The results indicate that a 1.0 mm
