A novel ultrasonic non-destructive testing methodology to monitor fatigue crack growth in compact tension specimens.

Detection and evaluation of fatigue cracks in structural materials are extremely important for life prediction analysis as part of the structural integrity procedure. In this article, we present a novel ultrasonic measurement methodology, based on the diffraction of elastic waves at the crack tips, to monitor the fatigue crack growth near the threshold regime in compact tension specimens at different load ratios. The diffraction phenomenon of ultrasonic waves from the crack tip is demonstrated using a finite element 2D wave propagation simulation.

An experimental investigation on the combined effect of plastic deformation and grain size variation on the acoustic nonlinearity parameter.

The combined effect of grain size variation and plastic deformation on the acoustic nonlinearity parameter has been investigated in an austenitic stainless-steel material of grade 304. The nonlinear behavior of this parameter with grain growth has deviated to linear fit with deformation. This is due to the interaction of elastic waves with the strain-induced dislocation substructure in the grains.

Signal quality enhancement using higher order wavelets for ultrasonic TOFD signals from austenitic stainless steel welds.

Time of flight diffraction (TOFD) technique is a well-developed ultrasonic non-destructive testing (NDT) method and has been applied successfully for accurate sizing of defects in metallic materials. This technique was developed in early 1970s as a means for accurate sizing and positioning of cracks in nuclear components became very popular in the late 1990s and is today being widely used in various industries for weld inspection. One of the main advantages of TOFD is that, apart from fast technique, it provides higher probability of detection for linear defects.

Inhibition of Ras-GTPase signaling by FPTIII ameliorates development of cardiovascular dysfunction in diabetic-hypertensive rats.

We studied the effect an inhibitor of Ras-GTPase (FPTIII, 1.5 mg/kg alt diem for 4 weeks) on mean arterial pressure (MAP), urine protein, vascular reactivity and cardiac function in streptozotocin (STZ)-induced diabetes in control normotensive (WKY) and spontaneously hypertensive rats (SHR). The increased urinary protein in STZ-treated WKY (D-WKY) and STZ-treated SHR (D-SHR) were significantly lower in FPTIII treated D-WKY and D-SHR.

Inhibition of Ras-GTPase improves diabetes-induced abnormal vascular reactivity in the rat perfused mesenteric vascular bed.

Objective: The signalling mechanisms involved in regulating altered vascular reactivity in diabetes are not fully understood. The aim of this study was to investigate the role of Ras-GTPase in the development of abnormal vascular reactivity in diabetes.

Materials And Methods: We investigated the ability of chronic administration of FPTIII (1.