Evaluation of Mechanical Properties of Microelements and Environmental Strength under Dynamic Loading

动态载荷下微元力学性能和环境强度评价

基本信息

批准号：
09450048
负责人：
KOMAI Kenjiro
金额：
$ 8.96万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09450048/
关键词：
Microelement Micromachine Environmental Strength under Dynamic Loading Small Notch Effects Fatigue Vacuum Effects Water Environment Atomic Force Microscopy 曲げ強度引張強度疲労強度高強度・高弾性繊維

项目摘要

The fracture and fatigue behavior of micromaterials including single-crystal Si microelements and an advanced fiber reinforcement of aramid fiber have been performed. The specially designed testing machines are developed, which are capable of performing quasi-static and fatigue tests in mum sized microelements. Single crystal Si microelements deform elastically until final failure, giving a brittle nature. The fracture strength increases with a decrease in specimen size, and the maximum fracture strength is about 7.7 GPa. However, Si microelements are sensitive to notch, and sub-mum deep notch introduced by focused ion beam decreases the fracture strength. As for fatigue loading, no fatigue damage is observed even though the surface is nanoscopically examined by an atomic force microscope. However, in water, the fatigue lives are decreased : crack formation is promoted by a synergistic effect of dynamic loading and water environment. Atomic force microscopy is capable of imaging a nanoscopic crack, which causes the failure in water. The fiber strength of aramid fiber, Kevlar 49, is strongly influenced by an environment : water absorption and vacuum conditioning decrease the fracture strength. As for fatigue, aramid fibers have excellent fatigue properties, compared with metallic materials, showing gentle slope in s-N curves, although they have large scatter band. As for vacuum effects, the fatigue strength in vacuum is higher than that conducted in air. The fiber breaks with fiber splitting, and the fiber surface damage induced by fatigue loading in air and in vacuum was examined by using an atomic force microscope, and the influence of environment on fatigue and damage mechanisms are discussed.

已经进行了微材料的断裂和疲劳行为，包括单晶Si微元素和芳香纤维的先进纤维增强。开发了专门设计的测试机，能够在妈妈大小的微元素中进行准静态和疲劳测试。单晶Si微元素弹性变形直至最终失败，具有脆弱的性质。裂缝强度随标本尺寸降低而增加，最大断裂强度约为7.7 GPa。但是，Si微元素对缺口很敏感，并且由聚焦离子束引入的子撞击凹口降低了断裂强度。至于疲劳负荷，即使表面通过原子力显微镜检查表面检查，也没有观察到疲劳损伤。然而，在水中，疲劳寿命减少了：动态载荷和水环境的协同作用促进了裂纹的形成。原子力显微镜能够成像纳米骨裂纹，从而导致水失败。 Aramid纤维的纤维强度，Kevlar 49，受到环境的强烈影响：吸水和真空调节降低了断裂强度。至于疲劳，与金属材料相比，Aramid纤维具有出色的疲劳性能，尽管它们的散射带很大，但在S-N曲线中显示了柔和的斜率。至于真空效应，真空中的疲劳强度高于空气中的疲劳强度。通过使用原子力显微镜检查了纤维分裂的纤维断裂，并通过使用原子力显微镜检查了由空气和真空中疲劳载荷引起的纤维表面损伤，并讨论了环境对疲劳和损害机制的影响。