Its theme is 'Innovate or Enervate', and it is intended that the symposium will address some of the problems that have prevented the Australian aviation manufacturing industry from achieving the same status that other national aviation industries have.

Areas that will be examined include: • aircraft design • structures, including static design,

fatigue, nondestructive inspection • propulsion systems.

Enquiries relating to the symposium should be sent to: The Conference Manager, 1987 Australian Aviation Symposium, The Institution of Engineers, Australia, 11 National Circuit, Barton A C T 2600, Australia.

A symposium on Fatigue and Fracture testing of Weldments is to take place in the week commencing 24 April 1988 in Las Vegas, NV, USA.

The symposium will focus on specimen design and preparation, test

procedures unique to welded specimens, and interpretation of test results.

Contact: Theresa Smoot, ASTM, 1916 Race Street, Philadelphia, PA 19103, USA.

Publications

The use of fracture mechanics to predict the behaviour of cracked structures and to analyse failed structures is the subject of Case Histories Involving Fatigue and Fracture Mechanics, recently published as STP 918 by ASTM.

The experiences of engineers and scientists in applying fracture mechanics to engineering components in real-life situations are described in 22 articles. The book is 431 pages long, costs £66.00 and can be ordered from: American Technical Publishers Ltd, 68a IVilbury IVay, Hit&in, Herts SG4 OTP, UK.

Another recent publication from

ASTM is entitled Fatigue in Mechanically Fastened Composite and Metallic joints (STP 927). It comprises 12 basic and applied research papers covering bridge structures, airframes, adhesive bonding, welding, and metallic and composite materials.

Cost of the 288-page book is £48.00. Orders to the address above.

Fatigue Behaviour of Offshore Structures is volume 22 of Springer's Lecture Notes in Engineering Series.

Written by A. Gupta and R. P. Singh, the book aims to characterize the various uncertainties involved in estimating the fatigue life of an offshore steel jacket platform.

Two structural models are used in the stress analysis, and the results are compared. A detailed description is presented of the fatigue damage at each joint in the structure. The book is available for DM49 from: Springer- Verlag GmbH & Co KG, Heidelberger Plat~ 3, Postfach, D-IO00 Berlin 33, FRG.

Fatigue of Welded Constructions

Brighton, UK, 7-9 April 1987

This international conference, organized by the Welding Institute, was held at the Bedford Hotel in Brighton, 18 years after the last similar meeting took place. At that time it was thought that the way ahead in life prediction techniques lay with the development of fracture mechanics methods. This has certainly proven to be the case, and was the focus of many of the present talks.

Approximately 140 participants were presented with 42 papers, 25 of which were from outside the UK, mainly the USA and Western Europe.

Delegates were welcomed to Brighton by the conference Technical Director, S. J. Maddox (Welding Institute, UK), who opened the meeting. The first session comprised three papers concerned with residual stresses and a fourth that described the fatigue behaviour of T-welded joints between a clad steel plate and a stainless steel attachment.

In the first presentation J. L. Overbeeke (Eindhoven University of

Technology, The Netherlands) asked whether the additional costs of stress relieving paid off in terms of increased fatigue resistance. Most design rules for calculating fatigue life do not allow any bonus for stress relieving, but there are welded structures that are designed outside these rules, such as those in the automotive industry. Tests on stress-relieved specimens showed that crack closure at low R-ratios was more effective than for as-welded specimens, resulting in higher endurances and fatigue limits.

A strategy to reduce weld failures in Thermit welded rail joints by joint straightening was described by J. C. Sinclair (British Rail, UK). Straightening of these rails by bending alters the dynamic and residual stresses present. A simplified probabilistic fracture mechanics model showed that the technique could possibly result in 50% fewer failures.

In the second session S. J. Maddox summarized a series of investigations into the fatigue

behaviour of specimens representing deck to longitudinal stiffener connections in steel orthotropic bridge decks. There are currently no standards which give rules for the fatigue design of such decks, although many examples of in-service fatigue cracking have been observed.

As a result of the tests, three modes of failure due to wheel loading were identified, namely fatigue cracking in the weld toe in the deck plate, in the weld toe in the trough, or in the weld root through the weld throat. It was found that the fatigue life for toe failure could be improved by shot peening or plasma dressing, whereas disc grinding was less effective. Maddox also suggested that, for design purposes, the stress in both the stiffener and the weld throat at the root should be in accordance with the Class D S/N curves of the BS 5400 (Part 10) fatigue rules.

A real example of this type of failure was described in the next paper by J. R. Cuninghame (Transport and

Int J Fatigue July 1987 187

Road Research Laboratory, UK). Fatigue cracks had been found in three welded connections of the structures that comprise the Severn Crossing: the Severn Bridge, the Beachley Viaduct and the Wye Bridge. Assessment of the joints showed that the remaining life of each was less than 10 years. In repairing the welds, greater fatigue strength was also imparted to the joints, leading to an acceptable predicted life for the structures.

The next session was concerned with fatigue under variable amplitude loading. Some of those members of the audience actually involved in the design of welded structures subject to random loading, such as bridges, ships, offshore installations etc, might have found the papers in this session disturbing, for there was some doubt cast on the validity of Miner's linear damage rule, upon which all the current design rules are based. However, Y. Tomita (Osaka University, Japan) said that Miner's rule leads to estimates of fatigue life that are conservative rather than optimistic.

In a session on fatigue life prediction, F. V. Lawrence (University of Illinois at Urbana-Champaign, USA)

explained how a fatigue design methodology based on crack initiation and early growth could estimate the fatigue strength of weldments at long lives when fatigue crack initiation becomes the dominant fraction of the total fatigue life. The use of smooth, polished specimens in this model to represent conditions at the weld toe was questioned, and the ensuing debate continued long after the session had finished.

Improving the fatigue life of welded structures was the subject of another session. The audience was told by I. F. C. Smith (Swiss Federal Institute of Technology) how shot, needle and hammer peening can increase the fatigue life of specimens with longitudinal welded attachments, but that stress relieving may not guarantee any substantial increase. P. J. Haagensen (University of Trondheim, Norway) proposed that, in view of the evidence that improvement techniques can increase fatigue strengths, future design rule revisions should take these into account.

On a more negative note, examples were described of instances when repairing welds had actually decreased the fatigue strength, for

example by introducing defects. G. E. Nordmark (Alcoa Laboratories, USA) explained how repairing discontinuities in welds in aluminium alloy 5456 plate reduced the fatigue life by as much as 75%, unless the repair terminations were suitably ground or peened, which are costly processes.

Repair of welds was the focus of the final session of the conference. Techniques such as grinding the weld toe, drilling stopholes at the crack tip and groove weld repairing had been applied with varying degrees of success. It was obvious, however, that much work was still required in this area. Indeed, it was suggested by T. R. Gurney (Welding Institute, UK) in summing up that the majority of effort over the next 20 years would be devoted to the development of effective repair methods.

In conclusion, this was a well- organized event that highlighted the need for practical solutions to the problems facing design engineers, for example the questionable validity of Miner's rule and the lack of availability of accurate data on real loading conditions.

A. Burrows

Elastic and plastic fracture Metals, polymers, ceramics, composites and biological materials

A. G. Atkins and Y.-W. Mai

Ellis Horwood, 1985, 819 pp, £75.00

The text of this introductory publication on the mechanics of fracture is well written and straightforward to read (compared with a lot of fracture mechanics publications). As the title suggests, the chapters cover a wide range of (what appears to be) the usual topics of elastic, elastoplastic and plastic fracture. However, an interested purchaser should not be put off by this since Atkins and Mai use a completely fresh and enlightened approach based entirely on energy methods. They rely on the fact that the concept of the requirement of work having to be done to initiate and propogate a crack, whether elastic or plastic, has an actual physical meaning. The whole text ix

developed on the quantity R (specific work of fracture) as fracture toughness, unlike the more conventional texts which use Klc as a measure of fracture toughness. The authors prefer to keep Klc as the critical value of stress intensity for fracture and retain R as an indication of the failure event and the material property that is dependent on the rate of loading and the temperature and condition of the environment.

The book starts with a comprehensive review chapter on the state of the art in fracture. The philosophy of the authors to make the text relevant to all branches of materials technology is clear from the start, as the role of microstructure in

the determination of the mechanics is discussed for crystalline, amorphous, composite and biological materials. The next four chapters deal with the basic theories that have been and are being postulated in linear elastic, elastoplastic and general yielding mechanics consistent with the energy balance approach. An imaginative range of everyday materials and failures is used to illustrate the application of the theory to practical situations from tears in trousers and skin to crack propagation in porous and layered structures, glued interfaces and removing lids from sardine cans, as well as more conventional examples of crack nucleation in metal forming and crazing in polymers.

188 Int J Fatigue July 1987