Simulated Load Fatigue Tests for Reliability Assessment of Marine Structure

为了提供结构在随机载荷作用下的合理疲劳设计所需的数据，必须有一些适当的试验方法，这些方法能够再现随机变量（如载荷、应力、应变和应力强度因子）的指定时间历史，并且必须是廉价的。由于试验系统的动态特性随试件疲劳损伤的累积而变化，单靠小型微机系统很难进行精确的试验。在本报告中，使用两个微处理器进行FFT响应补偿或不进行响应补偿的实验。平稳高斯随机过程由一台大型计算机生成，数据被打包成特殊的形式，在合理的时间内通过TSS发送。本文还编写了一个生成平稳高斯随机过程的微机程序。所开发的软、硬件均令人满意，在平稳随机应力强度因子下的疲劳裂纹扩展试验表明了补偿的效果，并指出了一种无需响应补偿的简化、省时的试验方法的可能性。

To supply data needed for a rational fatigue design of structures subject to random load there must be some approp riate testing methods which are able to reproduce a specified time history of the random variable such as load, stress, strain and stress intensity factor and also must be inexpensive to be popular ones.With a small micro conmputer system alone, it is very difficult to perform exact experiments considering the dynamic characters of the test system varying as the fatigue damage accumulates in the specimen.In this report, two Micro Processing Units are used to perform experiments with or without resposnse compensation by FFT. Stationary Gaussian random processes are generated with a large computer and data are packed into special forms to be sent through TSS within a reasonable time. A micorcomputer program which generates stationary Gaussian Random Process is also developed.The developed soft and hardware are satisfactory and fatigue crack growth tests under a stationary random stress intensity factor showed the effect of the compensation and indicated the possiblility of a simplified and less time consuming test method without resposnse compensation.