Development of a fatigue sensor for welded steel structures

TWI Industrial Member Report Summary 847/2006

By P J Tubby, Y-H Zhang and S Mason

Background

This report describes a fatigue damage sensor for welded joints in steel structures developed within a collaborative project managed by TWI. Known as the CrackFirst^TM sensor, it consists of a thin metallic coupon attached to the structure adjacent to a critical welded joint. Stress cycles in the structure cause a permanent change in the sensor, the magnitude of which is proportional to the cumulative fatigue damage for the target joint. Sensor readings therefore provide an estimate of the rate at which the structure's design life is being consumed, allowing the remaining safe life to be estimated and service inspection intervals to be defined. This report describes the sensor and its application, and presents results obtained from fatigue tests performed as part of its validation.

Objectives

Objectives of the present report are as follows.

• To describe the CrackFirst^TM sensor system and its application to welded structures.
• To present results obtained from validation tests.
• To review future plans for exploitation.