This paper reports the potential drop technique as an imaging tool for the clear identification and sensitive evaluation of very small surface cracks. The distributions of d-c potential drop around the surface cracks are obtained by scanning the closely coupled probes potential drop sensor, and a methodology for evaluating a 3-D crack from the potential drop profiles measured across and along t...

We developed a highly integrated, Field Programmable Gate Array (FPGA)-based digital multi-frequency eddy current platform which is capable of detecting surface breaking and subsurface cracks in non-magnetic plates. Excitation signal generation, receiving signal demodulation, and USB communication were all implemented inside a Xilinx FPGA (Spartan III). Multi-frequency test results provide rich...

This article presents statistical model parameter identification using Bayesian inference when parameters are correlated and observed data have noise and bias. The method is explained using the Paris model that describes crack growth in a plate under mode I loading. It is assumed that the observed data are obtained through structural health monitoring systems, which may have random noise and de...

This paper describes the crack sensing performance of a wireless and passive smart-skin sensor designed as a folded patch antenna. When strain/deformation occurs on the patch antenna, the antenna’s electrical length changes and its electromagnetic resonance frequency also changes accordingly. An inexpensive off-the-shelf radiofrequency identification (RFID) chip is adopted in the sensor design ...

In 2004, a team comprised of researchers and service providers launched the Safer Crack Use, Outreach, Research and Education (SCORE) project in the Downtown Eastside of Vancouver, British Columbia, Canada. The project was aimed at developing a better understanding of the harms associated with crack cocaine smoking and determining the feasibility of introducing specific harm reduction strategie...

Rotating machinery, such as steam turbo, compressor, and aeroengine etc., are widely used in many industrial fields. Among the important rotor faults, the fatigue crack fault, which can lead to catastrophic failure and cause injuries and severe damage to machinery if undetected in its early stages, is most difficult to detect efficiently with traditional methods. In the paper, based on the trut...

This paper presents a method to detect multiple cracks based on frequency information. When a structure is subjected to dynamic or static loads, cracks may develop and the modal frequencies of the cracked structure may change. To detect cracks in a structure, we construct a high precision wavelet finite element (EF) model of a certain structure using the B-spline wavelet on the interval (BSWI)....

This paper studies the application of an inverse methodology for problem solving in fracture mechanics using the finite element analysis. The method was applied to both detection of subsurface cracks and the study of propagating cracks. The procedure for detection of subsurface cracks uses a first order optimization analysis coupled with a penalty function to solve for the unknown geometric par...