effect, magnetoacoustic emission, magnetic hysteresis, residual field and magnetically induced velocity change methods that have appeared to data.

39143 Anon. Introduction to flaw detection during production by magnetoelastic testing using Barkhausen noise (In French) Qua l i t e R e v u e Pra t ique de C o n t r o l e Indus t r i e l , No. 150, pp. 104-110 (Apr . 1988)

39142 Kaplan, B.Z.; Rabinovici, R. Nondestructive evaluation of ferromagnetic materials by a 'magnetometer like' experimental arrangement Jou rna l of N o n d e s t r u c t i v e E v a l u a t i o n , Vol. 6, No. 2, pp. 73-8/I (Jun. 1987)

The paper presents experimental results regarding the influence of mechanical stresses and thermal treatments on the Barkhausen noise and magnetization characteristic of MolyPermalloy and MuMetal ferromagnetic samples. The samples are different in stress magnitude and localization and in their thermal history. The level of Barkhausen noise and the changes in magnetization characteristic are estimated by measuring the sensitivity and transduction gain of 'magnetometer like' coils configurations which employ the studied ferromagnetic samples as their nonlinear ferromagnetic cores. The present method is unique in the sense that the two factors (one factor is related to the internal magnetic noise, and the other one is related to the form of the magnetic characteristic) arc obtained by employing a single relatively simple experimental arrangement. Various types of stresses, which arc different in magnitude and localization, become distinguishable one from the other, when considering their differential effects on the two factors. Several possible experimental arrangements are shown.

39(~)6 Pantermuehl, P.J.; Birring, A.S. Ultrasonic procedure for measuring bolt-up and long-term relaxation stress in steel studs Mate r i a l s E v a l u a t i o n , Vol. 46, No. 6, pp. 708-711 ( M a y 1988)

An ultrasonic procedure is described for measuring stresses in steels nondestructively with increased accuracy by incorporating a correction for temperature changes. It uses the acousto-clastic effect in calculating the stress from changes in ultrasonic transit time. This work has produced reference tables which will save time and effort in future investigations.

38958 Kameda. J. Characterization of tempered martensite microstructure and embrit- tlement by acoustic and magnetic Barkhausen signal measurement Scripta Me ta l lu rg i ca , Vol. 22, No. 9, pp. 1487-1492 (Sep. 1988)

It has bccn well recognized that ultrahigh strength alloy steels exhibit cmbrittlcmcnt when they arc tempered in the temperature range from 300 to 4(XX)'?C. This phenomenon is referred to as tempered martensite cmbrittlcmcnt and is attributed to the occurrence of intergranular and/or cleavage fracture. The fracture mode depends on the alloy composition and the impurity content of steels. The intergranular cmbrittlemcnt is caused by two events: segregation of impurities such as sulfur and phosphorus, and carbide precipitation at grain boundaries. The intergranular segregation of impurities during austcnitization weakens grain boundaries and the precipitation of carbides during tempering promotes the nucleation and propagation of cracks. The objective of this study is to evaluate nondestructivcly the characteristics of tempered martcnsite microstructurc and embrittlement in an ultrahigh strength steel by measuring the two types of Barkhausen signals.

38843 Kar]alainen, L.P.; Rautioaho. R.H. Detection of fabrication stresses by the Barkhausen noise method The Effects of Fabr i ca t ion R e l a t e d Stresses on Product Manufac tu r e and Pe r fo rmance , C a m b r i d g e ( U n i t e d K i n g d o m ) , 23-25 Sep. 1985. pp. 149-161. E d i t e d by J.F. A lde r . The Weld ing Ins t i tu te 11987)

The high efficiency of the magnetic Barkhausen noise method for qualitative detection of stress changes duc to welding, thermal and mechanical stress relief. machining and shot peening in structural steels is demonstrated. The importance of properly adjusting the strength of magnetization is pointed out. The steel composition, metallurgical structure, texture, dislocations and biaxiality of the stress field all affect the inherent Barkhausen noise level and its stress dependence, so that calibration for accurate determination of stress magnitudes does not generally sccm reasonable. Examples of the practical applications of the method are briefly outlined.

38835 Jiles, D.C. Integrated on-line instrumentation for simultaneous automated measurement of magnetic field, induction, Barkhausen effect, magnetoaeonstic emission, and magnetostriction Jou rna l of A p p l i e d Physics , Vol. 63, No. 8, pp. 3946-3948 (15 Apr . 1988)

A microcomputer-controlled instrument for simultaneous measurement of magnetic hysteresis, magnetostriction, Barkhausen effect, and magnetoacoustic emission is described. It incorporates custom designed software for control of the magnetic field during operations such as demagnetization, field sweeping, and anhysteretic magnetization, and for data logging and analysis. Results are recorded using a 12-bit analog to digital converter and are then stored on floppy disk. The magnetic hysteresis data are converted into six important magnetic parameters: coercivity, remanence, hysteresis loss. initial permeability, maximum differential permeability, and anhysteretic permeability. These, together with the magnetostriction, Barkhausen. and magnetoacoustic emission, are then related to the microstructure of the material.

38629 Musikhin, S.A.; Novikov, V.F.; Borsenko, V.N. Use of coercive force as an indicator parameter in nondestructive measurement of mechanical stresses Soviet Jou rna l of N o n d e s t r u c t i v e Tes t ing , Vol. 23, No. 9, pp. 633-635 ( M a y 1988)

The results of using the KIFM-1 coercive force meter for measurement of uniaxial mechanical stresses are presented, utilising the correlation relationship with the anisotropy of the coercive force. The operation of a magnetoelastie tester developed on the basis of the KIFM-1 is described.

38474 Kaczkowski, Z. Piezomagnetic ultrasound alcofer 44 kHz transducers Ult rason ics I n t e r n a t i o n a l 87, C o n f e r e n c e P roceed ings , L o n d o n ( U n i t e d K i n g d o m ) , 6-9 Jul . 1987. pp. 856-859. B u t t e r w o r t h and Co. (Publ i shers ) L td . , Gu i ld fo rd , Sur rey (1987)

Some mechanical, magnetic, acoustical and piczomagnetic properties of the alcofcr transducers for the frequency range of 44 kHz are discussed. The cores of the 44 kHz transducers were prepared from the 0.2 mm sheets of the iron-aluminium-cobalt alloy containing 12 wt. % AI and 2 wt. % Co. The sheets after cutting were annealed at the temperature of 1000 C for 2 hours in hydrogen atmosphere and slowly cooled with the furnace. Maximum of magnetom- echanical coupling coefficient was equal to 0.31 at the polarization of 200 A/re. Magnetic permeability at the optimum bias was equal to 300.

38306 Gorkunov, E.S.; Khamitov, V.A.; Bartenev, O.A.; Somova, V.M.; Volkov, V.A. Magnetoelastic acoustic emission in heat-treated constructional steels Soviet Jou rna l of N o n d e s t r u c t i v e Tes t ing , Vol. 23, No. 3, pp. 147-152 (Nov. 1987)

The influence of heat treatment on magnetoelastic acoustic emission in medium- and high-carbon low-alloy constructional steels for the inspection of their structural condition and strength characteristics was investigated. It was shown that the magnetoelastie acoustic- emission signals depend upon the internal stresses and also upon the structural changes and phase transformations occuring in the steels in heat treatment.

38249 Ran jan, R. Microstructural characterization of ferromagnetic materials using magnetic NDE techniques A m e s Labo ra to ry , A m e s , Iowa ( U n i t e d S ta tes ) , IS-T-1231, DE87- 010918, 117 pp. (Jun. 1987)

Magnetic NDE techniques, namely, the acoustic Barkhausen noise, the magnetic Barkhausen noise and the magnetic hysteresis curves, were simultaneously used for microstructural characterization of nickel and steels. Results showed that, in nickel, the non-f80 deg domain walls interact more strongly with dislocations than the 180 deg domain walls. A study of the grain size effect on the magnetic and acoustic Barkhausen noises showed a great potential as a NDE grain size measurement tool. Moreover, the Barkhausen signals indicate that the 180 deg domain walls in nickel seem to have a stronger interaction with grain boundaries than the non-f80 deg domain walls, as indicated by the acoustic Barkhausen signal. Based on the experimental observations, a theoretical model is being proposed to explain the grain size effect on the Barkhausen signals. The model takes into account the density of magnetic domain walls and their initial velocity, with both quantities being strongly dependent on microstructure. The acoustic and magnetic Barkhausen noises were also found to be very sensitive to the change in carbide morphology.

38246 Kim, H.C. : Hwang, D.G.; Choi, B.K. Barkhausen noise in 5% Mo-78.5% Ni permalloy with rolling texture Journa l of Physics D, Vol. 21, No. 1, pp. 168-174 (Jan. 1988)

Measurements of the Barkhausen noise have been made on 50% cold-rolled polycrystalline permalloy specimens cut at various angles to the rolling direction, at magnetising frequencies ranging from (I.01 to 0.5 Hz. The peak of the amplitude distribution shifted from 45 to 42.5 dB and the total number of Barkhausen pulses decreased as the specimen angle increased from 10 deg to 70 deg. The power of the frequency spectrum of the Barkhausen noise decreased markedly and the slope of the spectrum decreased from f ~ to f-2 due to the reduction of clustering as the specimen angle increased. As the magnetising frequency increased from 0.0l to 0.5 Hz, the peak of the amplitude distribution shifted towards a high amplitude from 45 to 46.5 dB, the total number of Barkhausen pulses decreased and the power of the frequency spectrum increased due to overlapping of the Barkhausen pulses.

38238 Buttle, D.J.; Scruby, C.B.; Briggs, G.A.D.; Jakubovics, J.P. The measurement of stress in steels of varying microstructure by magnetoacoustic and Barkhausen emission Proceed ings of the Roya l Socie ty of L o n d o n Series A , Vol. 414, No. 1847, pp. 469-497 11987)

Magnetoacoustic emission (MAE) and Barkhausen emission (BE) have been measured as a function of applied magnetic field and tensile stress from mild-steel samples in a wide range of heat treatments, to develop a technique to measure stress without prior knowledge of the microstructure. The results are supplemented by measurements of magnetic coercivity and mechanical hardness. MAE is found to decrease with increasing applied stress, whereas the variation of BE is more complicated. The amplitudes of both MAE and BE, as well as the coercivity and hardness are also found to depend on the

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