Abstract. Deep rolling is a mechanical surface treatment, which main aim is to increase the fatigue life of components by reducing their roughness, increasing the surface hardening and inducing compressive residual stresses. The increase of certain process input parameters such as the applied pressure or the number of overturns leads directly to the raising of the induced compressive residual stresses. Nevertheless, a saturation point is always achieved, where the further increase of the parameters' levels does not change the induced residual stresses. For other mechanical surface treatments, like shot peening, several pre-stress techniques were employed in order to further increase the induced residual stresses without raising the shot intensity or the coverage percentage. Pre-stressed shot peening with the means of bending or torsion is an established processing. Up to now, a few investigations are available regarding the pre-stressing techniques applied to deep rolling. Therefore, this paper offers a newly designed finite element model, built to calculate the induced residual stresses by bending, consequent deep rolling and springback. A four point bending setup with different pre-stress levels was employed and the influence of pre-stress levels on the induced residual stresses was investigated. Additionally, the applied deep rolling pressure was also varied in order to optimize this hybrid processing. At the end, the anisotropy of the induced longitudinal and transverse residual stresses due to the bending and deep rolling was analyzed.

As a rule, deposits of phosphates contain radioactive elements. Studies made in the laboratory of samples from North America and north Africa had shown that this radioactivity is due to the presence of uranium, and occasionally of thorium, either in the form of vaandate or in a diffuse state. Surface measurements carried out with a portable scintillometer had enabled some deposits to be outlined, but radiometric prospecting was only a supplementary method at this stage. From the results of these surface studies, it could be considered that the relations emitted by phosphates were sufficiently intense to be detected from a certain altitude. Consequently, a scintillometer was installed aboard a helicopter, and experimental tests were carried out on the known deposit of Djebel Honk, Algeria. Three profiles, flown perpendicular to the existing layers at 45 metres, permitted us to ascertain the validity of the method, and to define the working standards. Despite the small width of these outcrops (30 metres at most), it was established that “helicopter radiometry” could be used for phosphate exploration. Fourteen thousand kilometres of profiles were flown in northern Algeria. Since the phosphate deposits known in this area are located at the contact of the Cretaceous and Eocene (Dano‐Maestrichtian, Thanetian, Ypresian), a systematic coverage of these geological series was undertaken. It was then possible to draw up a rapid inventory of the series. Airborne radiometry, and helicopter radiometry in particular, now seems to be the most efficient, quickest, and least expensive method that can be applied to systematic phosphate exploration.