Saladin S-N data points for plain fatigue 86 4.16 Comparison of Ownby and Saladin S-N data points for fretting fatigue 87 4.17 Comparison of Ownby...and Saladin S-N data for all tests 88 4.18 Plot comparing ΔQ vs Nf from Ownby, Saladin & Madhi data points 89 4.19 Plot from Kawagoishi et al. [21...in this study 93 4.3 Madhi fretting and plain fatigue testing data 94 4.4 Saladin fretting and plain fatigue testing data 94 4.5 Comparison of
Savalle, S.; Cailletaud, G. (ONERA, 75 - Paris (France))
It is now well known that, on the microscopic scale, the fatigue failure process can be partitioned in two main stages: microinitiation and micropropagation. We show here the advantage in introducing these two successive steps in life prediction models for high temperature fatigue and creep. In a first part, we show that there is a non-interaction field between these two phenomena. Then, an extensive application is made using data on the Nickel-base alloy IN100: for some tests, creep and fatigue interact simultaneously, and for some others, they act consecutively. Finally, the same concepts are applied to the case of a loading corresponding to the superposition of vibrations and a large mean stress.
Pillhoefer, H.; Track, W.; Wege, R.
Creep values of the nickel-based cast alloys IN 100 and IN 713C were determined at the Institute for Materials of the Darmstadt Technical College on behalf of the FVV Working Party on 'Long Term Creep' and these were evaluated with the aim of: Producing documentation of structural changes, documentation of changes of the ..gamma.. separation phase depending on temperature, stress and time. Clearing up the stress to which ..gamma.. separation particles remain stable; from this one can judge how sensible it is to produce a defined hardened structure in IN 100 by heat treatment. Formulating subjects and tasks for an FVV Research Project 'Creep equations'. (orig./IHOE).
The influence of γ\\' size on critical resolved shear stress in alloy IN100 at 650. °C has been examined by considering dislocation/precipitate interactions involving particle shearing and Orowan by-passing mechanisms. To achieve this, heat treatment procedures were carried out on smooth specimens to produce materials with variations in secondary and tertiary γ\\' size, while maintaining their respective volume fractions. These specimens were subjected to strain-controlled fully reversed cyclic loading at 650. °C. Thin foils extracted from these specimens, post-testing, were examined by transmission electron microscopy to identify the nature of the precipitate/dislocation interactions during plastic deformation. Results indicated the presence of shearing and Orowan by-passing mechanisms. These observations have been used as a basis to calculate the critical resolved shear stress as a sum of components contributed by solid solution and by γ\\' particles being sheared and looped. In this analysis, a critical particle size defining the shearing/looping transition has been determined and this has been used to calculate the relative volume fraction and size of particles contributing to the critical resolved shear stress. These analytical results have been compared with those experimentally obtained at 650. °C using smooth specimens with different precipitate sizes. © 2013 Elsevier B.V.