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Full-Text Articles in Mechanical Engineering

The Ultrasonic Measurement Of Stress On Ferrous Plate Using Pulsed Electromagnet Magnetostrictive Emat Probes, S. J. Wormley, R. Bruce Thompson, Yan Li Jan 1991

The Ultrasonic Measurement Of Stress On Ferrous Plate Using Pulsed Electromagnet Magnetostrictive Emat Probes, S. J. Wormley, R. Bruce Thompson, Yan Li

Review of Progress in Quantitative Nondestructive Evaluation

Last year we finished the design and assembly of a semi-automatic system for the measurement of stress in textured ferritic steel[2], Magneto- strictive EMATs, which have no contributions generated by Lorentz force, were used on ferrous alloys since the absence of the Lorentz force mechanism precludes any velocity errors that might be produced by interference of Lorentz force and magnetostrictively generated signals. Phase shifts due to lift-off were solved by driving the transmitter EMAT’s in series. To make reliable wave-speed measurements in an industrial environment with an economical sampling period of 100 nanoseconds, a Fourier Transform-Phase-Slope technique was ...


Ultrasonic Wave Propagation In Inhomogeneous, Anisotropic Cast Stainless Steel, Ali Minachi, R. Bruce Thompson Jan 1991

Ultrasonic Wave Propagation In Inhomogeneous, Anisotropic Cast Stainless Steel, Ali Minachi, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

The complex microstructures of the cast stainless steel found in nuclear reactors makes their ultrasonic nondestructive evaluation particularly difficult. Of concern in certain cast steels are the highly aligned grain structures that develop, creating significant elastic anisotropy and variation of wave speeds with direction. The dependence of wave speed on propagation direction, in turn, leads to such phenomena as beam skewing and excess beam divergence. Furthermore, when components of these materials are integrated into a structure by welding, additional inhomogeneities are introduced. In various components, there may be one or more layers with different anisotropy and grain morphology, separated by ...


Propagation Of Elastic Waves In Equiaxed Iron Polycrystals With Aligned [001] Axes, S. Ahmed, R. Bruce Thompson Jan 1991

Propagation Of Elastic Waves In Equiaxed Iron Polycrystals With Aligned [001] Axes, S. Ahmed, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

A polycrystalline material is composed of numerous discrete grains, each having a regular, crystalline atomic structure. The elastic properties of the grains are anisotropic and their crystallographic axes are differently oriented. Thus the anisotropic nature of elastic wave propagation in a number of structural materials, such as austenitic stainless steel welds and castings, used in nuclear power plants stems from the details of their grain structures. Columnar grain structure is seen in the austenitic stainless steel welds while the microstructure of cast stainless could vary from randomly oriented equiaxed grains to highly oriented columnar grains. An acoustic wave travelling through ...


Ultrasonic Detection Of Cracks Below Bolts In Aircraft Skins, Chien-Ping Chiou, Frank J. Margetan, James H. Rose Jan 1991

Ultrasonic Detection Of Cracks Below Bolts In Aircraft Skins, Chien-Ping Chiou, Frank J. Margetan, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

The detection of cracks below fasteners in aircraft skin has been a longstanding challenge for the aviation industry. Among conventional NDE inspection methods, radiography is more suited to the detection of relatively large cracks, while eddy current techniques can achieve good probability of detection for small cracks [1], but requires the removal of the fasteners. Consequently, considerable effort has been focussed on the development of ultrasonic inspection methods [2]. Aircraft skins are constructed in various ways, and the possibility of ultrasonic inspection depends critically on the manner of construction. For example, many commercial aircraft skins are constructed with a thin ...


Bond Strength Evaluation In Dissimilar Materials, G. C. Ojard, David K. Rehbein, Otto Buck, A. Bevolo Jan 1991

Bond Strength Evaluation In Dissimilar Materials, G. C. Ojard, David K. Rehbein, Otto Buck, A. Bevolo

Review of Progress in Quantitative Nondestructive Evaluation

Diffusion bonding is a useful joining technique that allows similar and dissimilar materials to be bonded together in near net shape. Although modelling of the diffusion bonding process has been done to predict the bonding parameters needed to achieve parent metal mechanical properties (1,2), the possibility still exists that defects will be present in the bonded plane. There are three classes of defects that can be formed, with voids being the most common and heavily studied ones (3–8). Contamination of the bond line is a serious defect and the effect on NDE interrogation has been discussed previously by ...


A Self-Calibrating Eddy-Current Instrument, M. W. Kubovich, J. C. Moulder, M. S. Hughes, Bert A. Auld Jan 1991

A Self-Calibrating Eddy-Current Instrument, M. W. Kubovich, J. C. Moulder, M. S. Hughes, Bert A. Auld

Review of Progress in Quantitative Nondestructive Evaluation

The calibration of eddy-current measurement systems is a long-standing problem in nondestructive evaluation. Calibration serves a number of purposes: for equipment setup and validation, for equalizing responses from different probes and instruments, for setting detection thresholds, and for quantitative flaw sizing. The most commonly used calibration method is to scan the probe to be calibrated over simulated defects such as electrical-discharge machined (EDM) slots, saw cuts, or laboratory-produced fatigue cracks. This method has the virtue of calibrating probe and instrument at the same time on the same material as that to be inspected. But it has a number of disadvantages ...