Early HAC Warning System Using Model-Based Sensors

A system is proposed for early detection of hydrogen ingress and hydrogen-assisted cracking (HAC) in ship structures, using the unique capabilities of model-based sensor arrays. These MWM-Array sensors were used earlier in a preliminary demonstration to detect magnetic permeability changes during preloading and subsequent cathodic charging of an aircraft steel specimen having ultimate tensile strength of 1700 MPa (250 ksi). This capability to monitor hydrogen embrittlement effects and stresses will now be extended to detection of excessive hydrogen ingress and/or detection of hydrogen-induced microcrack clusters in high-strength ship steels. In Phase I, the focus will be on feasibility investigation and preliminary demonstration of HAC detection in ship steel test coupons instrumented with MWM-Arrays. This capability would ultimately provide an HAC-FUSE for timely detection of excessive hydrogen uptake effects under conditions of cathodic overprotection. In Phase I, JENTEK will adapt the procedures for magnetic permeability measurements on the coupons and identify coupon/test parameters best suited for development of an HAC-FUSE in Phase II as well as requirements for device implementation. In Phase II, JENTEK intends to develop fieldable HAC detection systems with in-situ monitoring.