General presentation of the topic and of the programme of this meeting. Summary of the papers presented during the different sessions. Aspects illustrated by the papers published in this issue.

At the design stage of engineering structures, the fatigue behaviour is generally not included in the analysis. Shoulder reinforcements may be machined with too small blending radii. Even if fatigue is taken into account, the influence of the environment is almost always ignored. This paper shows that corrosion-fatigue is not an uncommon cause of failure in industry and that it may result in significant damages. The survey of such failures and the observation of the fracture surfaces allow to identify the typical features of this phenomenon.

This study concerns the analysis of environmental effects on the behaviour under monotonic and cycling loading of alloys based on FeAl and TiAl intermetallic compounds. Special attention is paid to the coupling of environmental and mechanical effects. In both types of loading, the species which is found to operate at ambiant temperature is water vapour. This species plays also a determining role in fatigue crack propagation at elevated temperature. Effects due to oxygen adsorption are also discussed.

The damaging effect of corrosion-fatigue depends on many parameters. In addition to the influence of the material microstructure, work piece geometry or mechanical loading type, the combined effect of physical-chemical and electrochemical factors has to be considered. After a short presentation of the main parameters and of their effects, the paper concentrates on the outstanding features and the necessary precautions relative to the proper design of corrosion-fatigue test methods. Particular application cases of this approach are then presented.

The coupling effects between mechanics and corrosion which are involved during corrosion-fatigue of metallic materials are analyzed through significant examples. Quantitative approaches for crack initiation and crack propagation are given and discussed in terms of micromechanisms. The introduction of localized corrosion- deformation interactions in damage modellings is proposed and further trends for numerical simulations are introduced.

The common experimental methods used in the laboratory for the study of corrosion-fatigue are based on the evolution of global mechanical and electrochemical variables in relation with environment, mechanical loading or microstructure. For a better understanding and modelling of the physical- chemical processes involved in crack initiation and propagation, it is necessary to make use of techniques giving access to quantitative informations at local scale. Recent results concerning the breakdown of passivity, the morphology and the growth kinetics of potential initiation sites, the corrosion processes at crack tip and quantitative fractography are briefly reviewed.

Mode II fatigue crack growth tests have been carried out at different frequencies, in air and in vacuum, in the case of a maraging steel. By changing the experimental conditions, the tribological behaviour at the fatigue crack sides is modified and changes in mode II crack growth rate and growth stability are obtained. By measuring the displacement profile along the crack sides, ΔKIIeffective can be estimated and data obtained with varying friction conditions can be rationalized.

The paper presents a review of the current knowledge on the influence of gaseous atmospheres, and primarily ambient air, on fatigue crack propagation in metallic alloys. Experimental evidence of the effect of exposure to ambient air or any moist environment on fatigue crack propagation in steels is first proposed. The different interacting processes are analyzed so as to clearly uncouple the influence of the various factors on crack growth resistance. Two distinct mechanisms are identified : the adsorption of vapour molecules and hydrogen assisted fracture at crack tip.

This paper describes a new approach for the functional characterization of the surface topography of metallic products. The aim is to determine in a quantitative and unbiased way the roughness parameter which describes best the property or the function of the material. To achieve this, a new numerical statistical treatment had to be defined and a specific software had to be designed and developed. With these tools, more than 100 roughness parameters can be calculated. The most pertinent one for the description of the relationship between brightness and roughness of cold rolled steel sheets is the fractal dimension.

It is known that age-hardening in lead-calcium alloys proceeds in two stages. The first corresponds to two concomitant hardening transformations of discontinuous type and without precipitation. The second, is a lamellar reaction of precipitation of Pb3Ca. The ageing of lead-cadmium alloys is characterized by a continuous precipitation and a discontinuous transformation. The hardening process is followed by an overaging which consists of a discontinuous transformation with a reprecipitation of the Cd from the fine hardening precipitates of the same phases. With an aim of improving the mechanical and electrochemical properties of Pb-Ca alloys, we undertook a study of the influence of minor additions of cadmium on the age-hardening of these alloys. Two structural states were considered: as-cast condition, rehomogenized condition.