New strain measurement technology for material damage assessment

摘要

A new strain sensing methodology for the measurement of peak strain in engineering materials has been developed. The approach involves the correlation of change in the magnetic susceptibility attendant with the strain-dependent, solid-state phase transformation in a sensing element. The sensing materials are metastable steel alloys that irreversibly transform from nonferromagnetic to ferromagnetic behavior as a function of the peak, applied normal strain. The technology makes available a reliable method for passive, semi-active, or active monitoring of strains or deflections and is applicable as either embedded sensors or attached strain gages, i.e., monitors. Strain assessment devices of various types have been conceptualized to meet a variety of needs. The history, principles, and test data on the development are presented. Discussion and results of a prototype system installed on the I-95 Savannah River bridge are presented. Examples of current projects and future applications of the technology are presented and discussed. A range of applications is discussed that illustrates the versatility of the approach and the value of such systems in materials and structural safety assessment.