Mathematisches modell für eine instandhaltungsphilosophie moderner verkehrsflugzeuge

elastic/plastic analysis, the J-integral approach, and many other new techniques. Those of particular interest to this reviewer are the following. The contributions by Leis & Zahoor and Sadananda & Shahinian take a constructive, critical look at the use of the J-integral for cyclic loading. Both include exhaustive lists of references and are of interest to all working in the field of fatigue at very high cyclic plasticity. The problems discussed here are those connected with local residual stresses, displacement fields associated with overloads in variable amplitude service loads, transient material response, and damage process analysis. The paper by Schijve offers an up-todate overview of fatigue prediction methods, together with a very liberal interpretation of Elber's method for variable amplitude loading. However, the two materials reported here had already been extensively investigated and are known to fit Elber's theory well. Experimental results on a wider range of engineering materials would be appreciated by designers in the aircraft industry. Pelloux presented some interesting fractographic results of the crack closure, following in detail the agruments of his recent paper (J Fatigue of Engng Mater and Structures 1 (1979) pp 2 2 - 2 5 ) . The implication of this work is that overloads do not cause an instantaneous reduction in striation spacing. A report by Joyce claims thc development of a direct evaluation of J-curves from load displacement graphs. This may be a more reliable way than the usual unloading compliance method. In any case, it is a good idea if it works. A paper by Orange describes a method of estimating the R-curve from known values of K c. Criteria for small scale yielding for creep problems have been developed in a paper by Rice. It is concluded that in large specimens, the S[F is the loading parameter, while in small specimens the relevant parameter is the path-independent integral C*. In his second paper, Rice presents a discussion on the elastic/plastic analysis of cracks growing in an ideally plastic solid. The evaluation of C* may also be followed by another paper by Saxena. The r61e of elastic/plastic fracture mechanics is discussed in papers by Paris, who not only acted as an able technical director of this meeting, but presented recent advances in the development of the tearing modulus, the stability of circumferential

cracks, and work to fracture (Tumer's ~?-factors); both papers provide a rewarding study. Three papers dealing with dynamic fracture (by Kobayashi et el, Freund et al and Mall) complete this selection. These describe numerical solutions for cracks propagating in real materials, parallel impact loading on the opposite faces of a crack, and

a FEM analysis of cracked bodies with a stationary crack using a simple singular element. This publication offers a valuable account of the present state of our understanding of elasto-plastic fracture mechanics and will be of lasting interest to the wide fracture community. J. C. Radon

Mathematisches modell ftir eine instandhaltungsphilosophie moderner verkehrsflugzeuge ( M a t h e m a t i c a l m o d e l f o r t h e m a i n t e n a n c e p r o g r a m m e o f m o d e r n jet aircraft)

K. H. Galda, J. Kreth, R. Prinz and H. C. Goetting Deutsche Forschungs und Versuchsanstalt fur Luft- und Raumfahrt (1981) DM 10,40 The maintenance of civil aircraft for prevention of structural failure due to fatigue and/or corrosion has been based up to now on a schedule of increasing periods between overhauls with increasing age of the aircraft. This, however, seems somewhat illogical because fatigue and/or corrosion are time dependent and therefore increase with age. So a

better philosophy would be to decrease the periods between overhauls with age. This is the idea of a mathematical model, developed by Dr Galda of Deutsche Lufthansa and his former colleagues at DFVLR, which is already being used by Lufthansa airlines. The booklet under review contains the mathematical background and describes the philosophy used up to now as well as the mathematical model for the new procedure it is available in german. -

14/. Shfitz

Engineering applications of fracture analysis Edited by: G. G. Garrett and D. L. Marriott Pergamon Press (1980) £25.00 The Proceedings of the First National Conference on Fracture - arranged by the South African Institute of Metallurgists, Institute of Physics and the Institute of Welding, under the title 'Fracture '79' in Johannesburg, November 1979 - were published by Pergamon Press, edited by G. G. Garrett and D. L. Marriott and include 27 papers, mostly by South African researchers, although some came from the USA and England. Apart from theoretical analyses, dislocation

methods and fracture initiation models, the contributions also cover the application of fracture mechanics, design problems, testing techniques and future research. Problems related to South African industry are dealt with in detail, and include rock failures, special testing methods and safety problems in nuclear reactors; thus, the contributions offer a good general picture of fracture studies and the application of fracture mechanics in South Africa. The contents of the Proceedings are divided into four parts dealing with the definition of some fracture problems, understanding fracture processes, solutions of fracture

INT. J. FATIGUE January 1982 47