信頼性工学的研究のための疲労き裂進展実験システムの開発 リアルタイム・マルチタスク処理の導入

Abstract

The variability of fatigue crack growth rate da/dN should be decomposed into two parts; the inter-specimen variability and the intra-specimen one. Recently, the inter-specimen variability is considered to be more important than the intra-specimen one from a reliability engineering point of view. In order to analyze the statistical prosperity of inter-specimen variability, fatigue crack growth tests must be conducted under the constant ΔK condition and the crack length must be measured at intervals of constant cycles, because the inter-specimen variability depends upon the intervals between measurements of crack length. Then an automated testing system is strongly needed for those statistical analysis. However, it is considered to be difficult to guarantee the measurements of crack length at regular intervals with single task processing, because the process of saving data in floppy disk or managing key-board may force the process of measuring crack length to wait. Thus an automated fatigue crack growth rate testing system using real-time multitask processing has been developed, which enables us to measure crack length at regular intervals. This paper describes in detail a personal computer-based testing system designed to be used with a standard servo-hydraulic test frame. A new algorithm is introduced to perform constant ΔP and constant ΔK fatigue crack growth tests effectively using a multi-tasking method. The system is designed to ease of operation and reduce the chance of operator error. The developed system was examined for the constant ΔK test and the satisfactory results were obtained. In this paper an error analysis was also performed to determine the crack length error. The analysis clarified the effect of an error in load and back face strain on determination of compliance-inferred crack length.