DEVELOPMENT OF DAMAGE MONITORING SENSORS FOR SHIP STRUCTURES

牺牲试件是一种小尺寸疲劳试件，其设计使得当将试件固定到结构构件上时，在试件中产生的疲劳损伤比在结构构件中产生的疲劳损伤早得多。在本研究中，开发了两种类型的牺牲试件，通过使用粘合剂固定到结构构件上。第一种是普通灵敏度的牺牲试件，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件，其目的是评估作用在结构构件上的长期应力分布水平，将牺牲试件应用于光滑试件、缺口试件和焊接接头试件，在等应力幅和指数分布的块体载荷下进行疲劳试验。结果表明，牺牲试件在疲劳载荷作用下具有稳定的疲劳性能，对疲劳损伤具有较高的敏感性。疲劳裂纹在牺牲试样中比在结构构件中产生得早得多。特别是对于高灵敏度的牺牲试件，疲劳裂纹在2.5MPa的应力幅下就开始萌生。进一步，基于对牺牲试件疲劳损伤的监测，提出了一种预测构件疲劳寿命的方法和一种估算长期应力分布水平的方法。

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.