BOOK REVIEWS Topics in solid state and quantum electronics

Edited by W. D. Hershberger

John Wiley and Sons Ltd, Chichester (1972) 605 pp f9.25

The material contained in the section on high-frequency ultrasonic devices by R. M. White was presented originally in the spring of 1970 as one of a series of lectures given by eminent researchers organized by the school of engineer- ing and applied science of the University of California, Los Angeles. This lecture, together with the others in the series dealing with solid state physics (an overview; gunn effect; avalanche diode oscillators; superconductivity; solid state light sources-lasers; optical second harmonic generator and parametric oscillation; laser systems; image pick-up and display devices; advances in LSI technology; microwave integrated circuits; and magnetic materials) have been compiled to produce this book.

The section on high-frequency ultrasonic devices naturally draws heavily from the review paper by the same author published in the proceedings of the IEEE for July 1970. It is illustrated liberally by simple explicit line drawings and clear photographs of real devices. This is backed up by an easily readable text which is a little thin in theoretical content.

Specific section headings used by the author include: elastic waves in solids; the piezoelectric effect&bulk and surface wave transducers; passive surface wave devices; ultrasonic amplification; amplifier analysis; amplifier results; ultrasonic amplification in a static magnetic field; and the acoustoelectric effect. The article can be criticized for imbalance between its heavy emphasis on ultrasonic amplification, the very brief discussion of surface wave transducers and the lack of any discussion on the significant topic of pulse compression filters. Although ultrasonic amplifiers have been researched extensively for more than 10 years they have not yet reached practical engineering status, and even if they did, their role is dubious. In spite of this criticism R. M. White’s article can be commended as early reading material for those interested in high-fre- quency ultrasonic devices.

J. H. Collins

Procedures and recommendations for the ultrasonic testing of butt welds

The Welding institute, Abington, Cambridge (1971)

42 pp f 2.20

This is a guide to the ultrasonic testing of butt welds in steel that will be useful to teachers, students and practition- ers. It is an extended, revised edition of a booklet bearing almost the same title published in 1965.

It is a pity that the booklet still confines itself to the testing of butt welds and that the opportunity has not been taken to widen the scope to include fillet welds. A notable omission in a work of this sort is a bibliography. Apart from one reference to a private communication, the only

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references are to British Standards documents, from which material has been heavily drawn. It is also rather surprising to find that publications on ultrasonic testing of welds pre- pared by the International lnstitute of Welding (IIW) have been ignored, including the highly-relevant Lisf of Terms

Used in Ultrasonic Testing.

The quality of the writing varies from section to section. In the main, the text is easy to read and to understand, but there are places where one finds the text disjointed and arguments difficult to follow. Diagrams are extensively used and the majority are clear. However, an exception is Fig.l.5 which is so congested that its salient features arc almost completely obliterated.

One or two erroneous statements have crept into the text and it is perhaps worth mentioning some of these. On page one, the impression is given that the IIW proposed a version of a calibration block which is not of much use. In actual fact, the IIW put forward the basic calibration block design and invited its members-to include in this basic form any additional features they desired. This resulted in the Dutch, French and Germans each producing a slightly different version of this basic design within the general IIW recommendations. In the same section, it is stated that one of these versions (German) is the one in general use. While this may be so in Germany, it is not universally the case. On page two, the impression is given that ‘direct scan’ and ‘one bounce’ are the same thing. Reference to the 11W list of terms will show that this is not so. On page five, it is stated that sound pressure becomes ‘nil at the outermost periphery, which is about 30 dB down’. Although the sound pressure is very small at the outermost periphery, it certainly cannot be nil. On page 25, air is given as an ex- ample of a medium which has ‘infinite acoustic impedance’. Far from having an infinite acoustic impedance, air has a very low acoustic impedance. The definitions of ‘beam emission point/beam index’, and ‘probe index’, given in the glossary are not those generally accepted, or to be found in the IIW list.

A number of typographical errors occur but with the ex- ception of the following, which occur in the glossary, the others arc unlikely to cause any difficulty. ‘Special acoustic impedance’ should read ‘specific acoustic impedance’ and under the definition of decibel, ‘20 log 10 h’/h”‘, should read ‘20 loglo h’/h”‘.

Finally, some note must bc taken of the following state- ment at the top of page 27 which refers to the controversial 20 dB technique:

‘The accuracy of its basic assumptions is open to question but the fact remains that it does work for those who apply it to flaws whose idiosyncrasies they know: using equipment with whose characteristics they are entirely familiar, under conditions which, if not entirely “controlled” are at least forcscen’.

Perhaps this is what critics have been saying ever since the first edition of the booklet was published in 1965, and that it is precisely for these reasons that the technique must be approached rather warily.

H. L. Carson

ULTRASONICS NOVEMBER 1972