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Mechanisms of the Transition in Static Fatigue of Pristine Silica Optical Fibers

原始石英光纤静态疲劳转变机制

基本信息

批准号：
12650069
负责人：
MURAOKA Mikio
金额：
$ 1.79万
依托单位：
Akita University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650069/
关键词：
Silica optical fibers Transition Aging Self-affined surface Stress concentration Stochastic differential equation Atomic force microscope Fluctuation of dissolution rate 複雑系モデル

项目摘要

The study aims to clarify a mechanism of"transitions" in static fatigue of pristine silica optical fibers under a stress and to present a method of predicting the phenomenon. The transition is a turning point where a trend in strength degradation of fibers changes abruptly. The research results are summarized as follows:1. Preliminarily we investigated an aging behavior of fibers in liquid water at 90 ℃, where the aging is a strength degradation under no stress and is recognized as a phenomena very close to the transitions. Atomic force microscopy (AFM) for aged surfaces of fibers showed that the surface roughness grows in proportion to a power of aging time but the profile keeps a self-affined fractal with a Hurst' index of 0.85. We also simulated aging of fiber based on a stochastic differential equation (SDE) taking account of a fluctuation of dissolution rate of silica. The simulations were able to explain the experimental results qualitatively. This insists that aging is caused by … More a fluctuation of dissolution rate. Stress analysis for aged surface profiles also showed that a stress concentration factor is a key parameter to predict aging of fibers.2. We simulated growth of surfaces roughness for fibers under a constant stress by using SDE It is found form the simulations that a main crack develops quickly and the crack growth controls lifetime of fibers at high stress conditions before transitions, but roughness developments dominates at low stress conditions after transitions.3. Observations of fiber surface profile are useful to predict a remained lifetime of fibers under a service use. To compensate a limited resolutions of AFM, we focused on an apparent contact stiffness between to AFM tip and sample surface. The stiffness must be affected local small roughness inside the contact area. Previously, we developed a special AFM cantilever with its mass concentrated as a way of enhancing the sensitivity in detection of a contact stiffness. In the present study, we produced a method of evaluating an elastic modulus of sample with a lateral resolution of about lOnm quantitatively. This method would be useful to detect a surface roughness of atomic levels. Less

本研究旨在阐明原始石英光纤在应力作用下的静态疲劳“转变”机制，并提出一种预测这一现象的方法。这一转变是纤维强度退化趋势突然改变的转折点。主要研究结果如下：1.初步研究了纤维在90℃的液态水中的老化行为，该老化是一种无应力下的强度退化，被认为是一种非常接近于相变的现象。原子力显微镜(AFM)对纤维老化表面的分析表明，纤维表面粗糙度与老化时间成正比，但表面轮廓保持自仿射分形，Hurst‘s指数为0.85。我们还考虑了二氧化硅溶解速率的波动，基于随机微分方程(SDE)模拟了纤维的老化。模拟结果能够定性地解释实验结果。这坚持认为衰老是由…引起的更多的是溶解速度的波动。对老化表面轮廓的应力分析还表明，应力集中系数是预测纤维老化的关键参数。利用SDE模拟了恒应力作用下纤维表面粗糙度的增长，发现在高应力条件下，转变前纤维表面的主裂纹扩展较快，裂纹扩展控制了纤维的寿命，而在低应力条件下，转变后，粗糙度的发展起主导作用。对纤维表面轮廓的观察有助于预测纤维在使用中的剩余寿命。为了补偿原子力显微镜有限的分辨率，我们重点研究了原子力显微镜针尖与样品表面之间的表观接触刚度。刚性必须受到接触区域内局部微小粗糙度的影响。在此之前，我们开发了一种特殊的原子力显微镜悬臂，其质量集中作为提高接触刚度检测的灵敏度的一种方式。在本研究中，我们提出了一种定量评估横向分辨率约为10 nm的样品弹性模量的方法。这种方法对于检测原子级的表面粗糙度是有用的。较少