DEVELOPMENT OF DAMAGE MONITORING SENSORS FOR SHIP STRUCTURES

牺牲试样是一种小尺寸的疲劳试样，其设计使得当试样被固定在结构构件上时，试样中的疲劳损伤可能比结构构件中的疲劳损伤产生得更早。本研究开发了两种用胶粘剂固定在构件上的牺牲试件。第一种是具有普通灵敏度的牺牲试样，其目的是预测结构构件的疲劳寿命。第二种是高灵敏度的牺牲试样，其目的是估计作用在构件上的长期应力分布水平。将牺牲试样应用于光滑试样、缺口试样和焊接接头试样，并在恒应力幅和指数分布的块体加载下进行疲劳试验。结果表明，牺牲试样在疲劳载荷作用下表现出稳定的疲劳性能，对疲劳损伤具有较高的敏感性。疲劳裂纹在牺牲试样中产生的时间远远早于结构件。特别是对于高灵敏度牺牲试样，在2.5MPa的很小应力幅下产生疲劳裂纹。在此基础上，提出了一种基于牺牲试件疲劳损伤监测的构件疲劳寿命预测方法和长期应力分布水平估计方法。

Sacrificial specimen is a small sized fatigue specimen which is designed so that fatigue damage may be produced in the specimen sufficiently earlier than in a structural member when it is secured to the structural member. In this study, two types of sacrificial specimens which are secured onto the structural member by using adhesive agent are developed. First one is a sacrificial specimen with ordinary sensitivity, of which purpose is to predict fatigue life of structural members. Second one is a sacrificial specimen with high sensitivity, of which purpose is to estimate the level of long term stress distribution working on structural member.The sacrificial specimens are applied to smooth specimen, notched specimen, and welded joint specimen and fatigue tests are carried out under constant Stress amplitude and block loading with exponential distribution. It is found that the sacrificial specimens show stable fatigue properties under fatigue loading and have high sensitivity for fatigue damage. Fatigue cracks are produced in the sacrificial specimen sufficiently earlier than in the structural member. Especially, for the sacrificial specimen with high sensitivity type, fatigue crack is initiated under very small stress amplitude of 2.5MPa.Further, a method to predict fatigue life of structural member and a method to estimate the level of long term stress distribution are developed based on the fatigue damage condition monitored in the sacrificial specimen.