摘要
通过冲压弯曲试验研究800MPa级DP钢的极限拉伸,采用扫描电子显微镜观察分析钢板的微观组织及动态拉伸过程,探讨其微观组织与其稳机理的关系。结果表明,DP800钢断口为剪切型断裂。凸模圆角半径较小时,拉深弯曲断裂是由于折弯角过小而在凸模圆角处折弯断裂;凸模圆角半径较大时,冲压弯曲断裂由于受到板料延伸率的限制,在材料流动受限的凹模圆角附近断裂。DP800的断口均分布着大量韧窝的韧性断裂,其裂纹扩展机理是微裂纹,主要产生于铁素体或马氏体/铁素体相界面,主裂纹沿两相界面或贯穿铁素体而继续扩展。
The ultimate tensile of DP800 steel have been studied and their instability and failure mechanisms have also been discussed from the standpoints of the microstructure and the dynamic tensile process.Results showed that the final failure mode of DP800 mainly was the typical shear fracture.When the punch fillet radius was small,the fracture of the bending stamping was due to small bending angle and cracked near the punch radius.But the fracture of the stretch bending was subject to the restrictions on elongation of the sheet under the large punch radius and cracked near the die radius where the material was restricted.From the SEM observation on the fracture surfaces,and the crack initiation and propagation paths of the dynamic tensile process,a large number of dimples on the fracture surfaces were observed,which testified the ductile fracture mode.The crack propagation mechanism of DP800 was that the micro-cracks were mainly produced in ferrites or in the ferrite/martensite interfaces.The main crack propagated along the interface of two phases or through ferrite and continued to expand.
出处
《塑性工程学报》
CAS
CSCD
北大核心
2013年第1期121-125,共5页
Journal of Plasticity Engineering
基金
国家自然科学基金资助项目(51005144)
上海汽车工业科技发展基金资助项目(1009)
上海市数字化汽车车身工程重点实验室开放基金资助项目(201202)
上海大学研究生创新基金资助项目(SHUCX120062)
关键词
双相钢
R
t值
冲压成形
扩展机理
dual phase
R/t value
formability
propagation mechanism
