A Study on the Micro-mechanisms for the Crack Initiation and Growth Ductile Fracture.

裂纹萌生和扩展延性断裂的微观机制研究。

• 批准号: 15360458
• 负责人: KANEDA Shigehiro
• 金额: $ 6.91万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-15360458/
• 关键词: ductile fracture; stress triaxiality; SM490B; prestrain; AE; dimple; cleavage; 脆性破壊; 予ひずみ; 応力三軸度; 相当塑性ひずみ; 柱・梁部材; 予歪み; 結晶方位; 粒界; 相当塑性歪み

Relations between equivalent plastic strain and stress triaxiality were studied by fracture tests of round notched bar tensile specimens. The critical ductility curves represented by above-described relationship were constructed by fracture test results and FEM analyses.Base material used in the tests is as received SM490B steel. The yield and ultimate strength at room temperature were 353 and 543 MPa respectively. Compressive prestrain up to 30% plastic strain was given in some specimens. The effects of prestrain and notch radius on ductile fracture initiation behavior were investigated and observed the fractured surface by scanning electron microscope (SEM).Damage initiation behavior during the tests was detected by use of AE sensors attached to the specimens. It is shown that prestrain leads to cleavage micro-cracking and reduces ductility. From SEM-fractographs, it is found that fractured surface is 100% dimple in as-received material, in the meantime, tiny amounts of cleavage in 10% prestrain material, up to 100% cleavage in 30% prestrain material, respectively.

通过圆缺口拉伸试样的断裂试验，研究了等效塑性应变与应力三轴度的关系。根据断裂试验结果和有限元分析，建立了由上述关系表示的临界延性曲线，试验中使用的基体材料为SM 490 B钢。室温下的屈服强度和极限强度分别为353和543 MPa。某些样本的压缩预应变高达30%塑性应变。研究了预应变和缺口半径对材料韧性断裂起裂行为的影响，利用扫描电镜（SEM）观察了材料的断口形貌，并利用声发射（AE）传感器检测了材料在试验过程中的损伤起裂行为。结果表明，预应变导致解理微裂纹，降低塑性。断口扫描电镜分析表明，原始材料的断口为100%韧窝，而10%预应变材料的断口为少量解理，30%预应变材料的断口为100%解理。

项目成果

鋼材の延性破壊発生挙動に及ぼす予ひずみの影響

预应变对钢材延性断裂起裂行为的影响

• 发表时间: 2005
• 期刊: 材料 第54巻
• 作者: 吉成仁志;榎並啓太郎;菅 満春;金田重裕
• 通讯作者: 金田重裕

The Effect of Prestrain on ductile Fracture Initiation of Steel

预应变对钢延性断裂萌生的影响

• 发表时间: 2005
• 期刊: Journal of Materials Science JAPAN Vol.54, No3
• 作者: Hitoshi Yoshinari;Keitaro Enami;Mitsuharu Kan;Shigehiro Kaneda
• 通讯作者: Shigehiro Kaneda