Structural Aging Monitoring via Web-Based Nondestructive Evaluation (NDE) Technology

To assist owners and operators in real-time on-site monitoring and damage assessment of aging structures, we propose an “aging structure monitoring system” using direct measurements and web-based transmission technology. Such a system from field detection of surface or subsurface cracks to computer modeling/analysis/verification of simulated fatigue crack growth with ultimate delivery of remaining life prediction, is designed to have four major components: (1) The system is capable of transmitting from the field via internet to the office computer direct measurement data that are being collected in the field by personnel using handheld optical scanners to read bar-code-like strain gages either laser bonded (permanent marking) or adhesively bonded to selected critical high stress areas of the surface of a structure. (2) The office computer has a customized database that stores not only relevant geometric and material property data with variability information, but also a history of prior loadings, cumulated strain (plastic) measurements and fatigue crack length or crack tip opening displacement measurements. Such database is constantly being updated and enhanced with variability estimates subsequent to an event on a continouus or periodic inspection basis. (3) Using a minimum of four commercially-available finite-element method (FEM) packages, e.g., ABAQUS, ANSYS, LS-DYNA, and MPAVE, a numerical simulation experiment is conducted on real time using a fracture mechanics and fatigue damage theory-based deterministic model and the direct measurement data. This model is capable of predicting remaining lives for selected future loading scenarios. (4) The results of the FEM simulations are verified via a web-based statistically designed experiment using DATAPLOT where an uncertainty-bounded estimate of the remaining lives of the structure for selected loadings is delivered in real time to the field for decision making. Significance and limitations of this web-based direct-measurement approach to fatigue modeling are discussed.