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Development of Dynamic/Quasi-Static Fracture Toughness Testing Apparatus Using Miniaturized Specimens and Application to Evaluation of Local Toughness in Materials

小型化试样动/准静态断裂韧性测试仪的研制及其在材料局部韧性评价中的应用

基本信息

批准号：
10555224
负责人：
MISAWA Toshihei
金额：
$ 7.49万
依托单位：
Muroran Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

From the present research program the following conclusion can be drawn :1. We successfully developed the dynamic/quasi-static fracture toughness testing apparatus using miniaturized V-notch specimens where the fracture toughness can be evaluated under wide variety of deformation rate(4〜10^<-5>m/s).2. Small specimen impact tests using miniaturized specimens with 1.5, 1.0 and 0.7 mm square and 20 mm length were carried out to evaluate the toughness of a laser welded metal. The DBTTs and FATTs given by the miniaturized and standard specimens showed a simple linear correlation. The laser welded metal composed of an extremely fine acicular ferrite structure was estimated to have such an excellent toughness as 168K DBTT in conversion to the standard size specimen.3. Micro-structure, micro-hardness and micro-absorbed impact energy in the Japanese sword were investigated to clarify excellent mechanical properties of the Japanese sword. The HASAKI side had a lower value while the MUNE side showed a higher value in the micro-absorbed impact energies obtained with the 1.0 and 0.7 mm square miniaturized specimens. It was shown clearly that the TSUKURIKOMI and the TSUCHIOKI processes gave the excellent gradated balance of strength-toughness to the Japanese sword.4. In order to clarify influence of deformation rate on susceptibility to hydrogen assisted embrittlement(HAE)in low alloy steels, three points bend test using v-notched small specimen with a dimension of 1.5×1.5×20mm was applied high strength low alloy steels with cathodically hydrogen charged. The test was carried out at room temperature under a wide variety of deformation rates, i.e., from 2.0×10^0to 1.7×10^<-8>m・s^<-1>. The test results showed that there was a critical deformation rate for the HAE in the high stength low alloy steels, where the fracture energy suddenly drops off and the fracture mode also transits from ductile fracture to brittle one.

从目前的研究方案可以得出以下结论：1。我们成功地开发了动态/准静态断裂韧性测试装置，该装置使用小型化的v形缺口试样，可以在各种变形速率（4 ~ 10^<-5>m/s）下评估断裂韧性。采用尺寸分别为1.5、1.0和0.7 mm、长度分别为20 mm的微型化试样进行了激光焊接金属的韧性评价试验。小型化和标准试样的dbtt和fatt呈简单的线性相关。由极细针状铁素体组织组成的激光焊接金属在转换为标准尺寸样品时，估计具有168K DBTT的优异韧性。对日本刀的显微组织、显微硬度和微吸收冲击能进行了研究，阐明了日本刀的优异力学性能。1.0和0.7 mm方的微型化试样的微吸收冲击能中，HASAKI侧的数值较低，而MUNE侧的数值较高。这清楚地表明，“TSUKURIKOMI”和“TSUCHIOKI”工艺为日本刀提供了良好的强度-韧性的分级平衡。为研究变形速率对低合金钢氢辅助脆化（HAE）敏感性的影响，在高强度低合金钢阴极充氢条件下，采用尺寸为1.5×1.5×20mm的v形缺口小试样进行三点弯曲试验。试验在室温下进行，变形速率范围从2.0×10^0到1.7×10^<-8>m·s^<-1>。试验结果表明，在高强度低合金钢中，HAE存在一个临界变形速率，断裂能突然下降，断裂模式也从韧性断裂过渡到脆性断裂。