Flaw Testing Research Articles

The Role Of Grain Noise In Eddy Current Inspection Of Titanium Alloys

ABSTRACTThis paper discusses the role electrical anisotropy plays in the structural integrity assessment of polycrystalline titanium alloys from the standpoint of fatigue crack detection and the related issue of microstructural noise. In eddy current inspection of noncubic crystallographic classes of polycrystalline metals the electric anisotropy of individual grains produces an inherent microstructural variation or noise that is very similar to the well-known acoustic noise produced by the elastic anisotropy of both cubic and noncubic materials in ultrasonic characterization. The presented results demonstrate that although the electrical grain noise is detrimental in eddy current nondestructive testing for small flaws, it can be also exploited for characterization of the microstructure in noncubic polycrystalline materials such as titanium alloys in the same way acoustic grain noise is used for ultrasonic characterization of the microstructure in different materials.

Are good virus simulators still a bad idea?

The term virus simulator is likely to conjure up different visions to different people. To some, virus simulators represent a way to test anti-virus programs without having to use real, potentially dangerous, viruses. To others, they can mean a way to demonstrate the effects of viruses without the time and trouble of configuring and cleaning a demonstration machine. Finally, to many, they can bring to mind flawed tests based on inaccurate assumptions or ways to perpetuate faulty ways of thinking. This article will examine the positive and negative connotations of virus simulators; by its conclusion, it is hoped that the reader will be able to make a well-informed decision concerning the use of simulators in both test and teaching environments.

Aspects of a Common Missed Diagnosis: Thyroid Dysfunction and Management

The all too common misdiagnosis of hypothyroidism is the result of poor clinical appraisal and undue reliance on flawed blood tests. The condition is simply and satisfactorily treated by replacement therapy and a plea is made for greater awareness among clinicians.

乱れ磁束検出型渦電流探傷法の基礎実験

A method of eddy current flaw test that detects disturbed magnetic flux was proposed, to improve the crack direction dependency of the detectability of bobbin-coil-type probes. These are conventionally used for eddy-current nondestructive examination of steam generator tubes in pressurized- water-type nuclear plants. The principle of this method is based on the fact that the symmetrical spatial distribution of the magnetic field induced by the exciting coils is disturbed by a flaw and that the pick-up coils effectively detect only the magnetic flux component disturbed by a flaw. The feasibility of this method was examined by using a sample probe in the test conditions in which the direction and location of an artificial flaw were varied.

Fluvial facies models: a review of Canadian research

Canadian river scientists made significant contributions to the early development (1960-80) of fluvial facies models, particularly to those for braided rivers. More recent Canadian studies (1980-92) have centred on understanding the facies sedimentology of anastomosed and wandering gravel-bed rivers. River planform facies models are distinctly limited as indicators of fluvial style because of: (1) spurious environmental correlations; (2) the difficulty of river planform definition; (3) differential preservation potential of facies; (4) inadequate and unsystematic field sampling; (5) flawed statistical testing; and (6) the inappropriate space scale adopted for analysis. The scale problems of facies analysis may be overcome by employing architectural element analysis in conjunction with modem geophysical methods such as shallow reflection seismology and ground-penetrating radar. Future research should focus on devising specific tests of element-scale sedimentological relationships based on the contemporary fluvial enrivonment.

Transversal flaw testing of seamless tubes-a new test system

Transversal flaw testing of seamless tubes-a new test system

High sensitive nondestructive flaw testing of wires, bars and tubes : Proceedings of the 12th World Conference on Non-Destructive Testing, Amsterdam (Netherlands) 23–28 Apr. 1989, Vol. 2, pp. 1328–1330. Edited by J. Boogaard and G.M. van Dijk, Elsevier, 1989

High sensitive nondestructive flaw testing of wires, bars and tubes : Proceedings of the 12th World Conference on Non-Destructive Testing, Amsterdam (Netherlands) 23–28 Apr. 1989, Vol. 2, pp. 1328–1330. Edited by J. Boogaard and G.M. van Dijk, Elsevier, 1989

Microhardness indentation application and limitation in fracture-toughness evaluation of ceramics

The use of a microhardness indentation as a controlled flaw in a flexural specimen for measuring fracture toughness in advanced ceramics is critically evaluated. From a review of fracture-toughness testing methodologies for ceramics it is shown that currently there are not any standardized or widely agreed uponKIc test procedures. The problems associated with the controlled flaw test are discussed and analyzed. An experimental program is used to investigate the effects of residual stress on the measurement of fracture toughness in a wide variety of sintered and hot-pressed advanced ceramics including TiB2, Al2O3, SiC, ZrO2, Si3N4. The validity of the test procedure for evaluatingKIc of advanced ceramics in general is put forth.

Application of a phenomenological fatigue model to optical fibers

A phenomenological formulation of Si-O bond dissociation is utilized to interpret stable crack velocity and static and dynamic fatigue phenomena. The resulting model has an exponential form and is applicable to a wide range of flaw sizes, service stresses, and test environments. Furthermore, it is readily reduced to the power law by retaining the first term of the series expansion of the exponential function. The model provides a sound physical basis for comparing different fiber compositions, service environments, and stress-time histories (static versus dynamic) from the fatigue point of view. The application of the model to silica and titania-doped silica optical fibers provides valuable insight into their relative fatigue behaviors and sheds further light on the fundamental mechanisms controlling such behavior.

Time‐Dependent Strength of Siliconized Silicon Carbide under Stress at 1000° and 1100°C

The time‐dependent strength of a fine‐grained siliconized silicon carbide under stress at 1000° and 1100°C was investigated. Both macroscopic stress redistribution and localized flaw blunting were found to contribute to the strengthening of siliconized silicon carbide in bending tests. Strengthening through macroscopic stress redistribution involved nonlinear creep behavior which decreased the maximum outer fiber stress in the bending beam. Localized flaw blunting processes were determined to be operative in this material through artificial flaw tests using a prestress to prevent flaw healing. The sharp artificial cracks were blunted during static load tests by localized deformation processes at the crack tip.

A review of the literature evaluating the defensive driving course

The Defensive Driving Course (DDC), like other post-licensure driver training programs, is intended to reduce the rate of motor vehicle crashes among those who take the course. A review of the literature revealed 14 controlled studies of the effects of DDC. About a third of these studies provided methodologically strong tests of DDC, but the remainder had design flaws that made their findings questionable or inadequate as tests of DDC. Only among the flawed tests were there large, positive effects of DDC. In the methodologically strong tests, DDC had no consistent effect on crashes but did decrease the frequency of traffic violations by about 10%. The failure of violation reductions to be translated into crash reductions may indicate that the violation reduction is an artifact of traffic record procedures or that the changes in driver behavior, if real, were insufficient to modify individual crash likelihoods. In either event, the best available evidence does not support the hypothesis that DDC decreases the likelihood of motor vehicle crashes.

Thermographic nondestructive evaluation of steel-polypropylene laminates

The efficacy of passive thermography as a nondestructive evaluation technique for detection of voids and interlaminar flaws in steel-polypropylene laminates was investigated. Both analytical and experimental studies were conducted to assess the flaw resolution characteristics of the technique and to determine the effects of pertinent geometric and thermal parameters on resolution. The implications of the analytical and experimental results from the parametric studies are discussed in terms of their effects on flaw resolution and test technique optimization for development of on-line NDE for quality control monitoring.

High-speed measurement of the internal diameter of tubes: a comparison of methods

The authors have compared various methods of tube measurement and have made the striking conclusion that the continuous measurement of the internal diameter of precision tubes with an air gauge is often useless in practice. The methods selected for experiment were all contactless and so included only air-gauging techniques and the capacitive measurement system. The authors propose an improved air-gauging technique where the pressure transducer is close to the air nozzles thus increasing the measurement speed by 12 times. However, the capacitive method was found to be even faster as well as stable and accurate. The disadvantage with the capacitive method is the need to introduce a probe into the tube. This difficulty is avoided by an indirect method where both external diameter and wall thickness were found instead and the difference taken. The perfected system has now been combined with ultrasonic immersion testing for flaws to make a complete tube testing facility.

Non-destructive testing of silicon carbide tubes

The development of three non-destructive methods for testing silicon carbide fuel-sheathing is described. The ultrasonic method provides a sensitive flaw test for tubes, the eddy-current method shows promise as a simpler flaw test for tubes, and radiography provides a complementary test for suspect tubes and a means of examining sealing welds.

Transducerless method for ultrasonic flaw testing in metals: Wallace, W.D. et al, Review of Scientific Instruments, Vol 39, No 12 (December 1968) p 1863 (1308)

Transducerless method for ultrasonic flaw testing in metals: Wallace, W.D. et al, Review of Scientific Instruments, Vol 39, No 12 (December 1968) p 1863 (1308)

Transducerless Method for Ultrasonic Flaw Testing in Metals

An ultrasonic method for detecting flaws in metals has been developed which does not require physical contact with the metal in order to excite or detect the ultrasonic signal. The method of direct electromagnetic generation of ultrasound in the presence of magnetic fields has been used to detect both artificial flaws and naturally occuring inhomogeneities in aluminum bars and rods. Results are presented which demonstrate that this technique may offer some advantage over conventional transducer methods.

Electromagnetic testing for mechanical flaws in steel wire ropes

This paper contains an account of an electromagnetic method of testing for mechanical flaws in wire ropes such as colliery winding ropes, the method comprising the use of a band of in combination with a search-coil system. In the introduction are detailed the advantages of the use of alternating as compared with direct current for the excitation of the magnet system. Section 1 describes the results of an experimental investigation of the penetration of magnetic flux in locked coil wire ropes, for a supply frequency of 50 and 20 cycles per second respectively. In Section 2 the effect of mechanical strain on magnetic permeability is considered, with special reference to a.c. excitation. In Section 3 the change in reluctance of the air space due to eccentricity of the rope in the magnet system is examined. Section 4 contains an account of the construction of the rope-testing magnet system, and the method of utilizing the search band of flux is explained. Section 5 contains the results of tests on a length of wire rope which was specially constructed for the purpose by Messrs. Latch and Batchelor, and in which a series of hidden flaws were incorporated. A complete rope-testing equipment constructed in accordance with the principles explained in this paper has been installed in one of the Carlton Main Co.'s collieries in south Yorkshire.