The Coherent Gradient Sensor (CGS) is extended to the optical differentiation of specular, diffracted wave fronts leading to the combined measurement of inand outof-plane displacement field gradients. A derivation of the underlying optical interference principles is presented along with an analysis of the effective instrument sensitivity. In order to demonstrate the capabilities of the techniqu...

This paper describes a method for determining the depth of machined slots simulating cracks by the use of Rayleigh waves. Six slots varying in depth from 0.5 mm to 3.0 mm fabricated in medium carbon steel have been sized using a commercially available 1.5 MHz Rayleigh wave transducer. One measurement using the pulse-echo method is made for determining the depth of the crack. Minima in the decon...

In some applications such as quality control of metal components or inspection of large metal structures, inspection systems with rapid scanning capability are required. Of particular interest are systems capable of real-time detection and sizing of surface breaking cracks in metals. Since such systems have to perform the data processing in the course of scanning, they should be based on NDE te...

This paper first examines the problems of using impact methods to achieve fast fracture of polymers. On-specimen gauges are employed to obtain the distribution of transient and other stresses in different parts of the specimen. A new method is then introduced that avoids transient forces and achieves crack velocities in small specimens of tough polymers of over 300 m s-l. It provides for the me...

Fracture and failure characterization of materials have been a crucial issue regarding reliable structural design. Stress Intensity Factor (SIF) is one of the most commonly used material parameters for more purpose. This study utilized Compact Tension (CT) Specimen test to determine mode-I SIF of polycarbonate material. Force, displacement and images of the near crack tip region were simultaneo...

A B S T R A C T Pump shafts used for power generation are susceptible to fatigue cracking while often in near-continuous operation. Technology based on torsional vibration is under development for condition-based assessment of shaft health. The focus of this paper is on the relationship between a crack, which propagated due to bending loads, and the torsional stiffness of the shaft. An analytic...

Neutron diffraction measurements have been performed to determine the full residual stress tensor along the expected crack path in an austenitic stainless steel (Esshete 1250) compact tension weld specimen. A destructive slitting method was then implemented on the same specimen to measure the stress intensity factor profile associated with the residual stress field as a function of crack length...

As one of Full Field Optical Measurement (FFOM) technologies, Smart 3-D Laser Scanner measurement technique enables to monitor the shape and dimension measured-objects in non-contact, remotely and globally. By taking its capability in capturing 3-D spatial information, 3-D Laser Scanner has been utilized effectively in numerous field application, such as, landscaping simulation during structura...

A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) ...