Propagation of guided waves in a hollow circular cylinder application to non destructive testing

In this paper, we study the propagation of guided waves in a tube and their interaction with surface defects. Axisymmetric (longitudinal and torsional) modes and nonaxisymmetric (flexural) modes are found and represented in phase and group velocity dispersion diagrams. The mode chosen to be generated is the second longitudinal mode L (0, 2), for the frequency-thickness product equal to 1 MHz.mm, at this product, the radial component of displacement is very small with regard to the axial component so, the attenuation is less important. According to our experimental results the L (0, 2) mode is sensitive to the depth variation and to the defect circumference. A relation of proportionality between the amplitude of the signal reflected by the defect and its depth was established. The results of the modal decomposition method, concerning the amplitude of the modes diffracted by circumferential defects according to the circumference of the defect, were presented and compared with the experimental measures results

تقییم ثلاثة طرق لتكییس أغاریضالنخیل : دراسة حالة في منطقة ورقلة

L’étude a traité l’évaluation de trois méthodes d’ensachage des inflorescences (papier kraft, polyéthylène perforé et le lif du dattier) de deux cultivars de palmier dattier, après leur pollinisation: Ghars et Deglet Nour. L’essai est mené, au début de la saison de pollinisation, pour diminuer l’effet négatif des températures basses qui bloquent la fécondation.Les résultats montrent que tous les types d’ensachage améliorent la précocité des fruits (notamment le polyéthylène et le papier Kraft), ainsi que les rendements de régime chez les deux cutivars. Le papier Kraft augmente nettement les taux de nouaison et les rendements en fruits chez les mêmes cultivars.Mots clés: Ensachage - Pollinisation -Deglet Nour – Ghars - Palmier Dattier - – Ouargla The study treated the evaluation of three methods of bagging inflorescences (kraft paper, perforated polyethylene and date palm fibrillum) after pollination in two cultivarsof date palm : Deglet Nour and Ghars. The essay is conducted at the beginning of the pollination season, for reduce the negative effect of low temperatures which block fertilization.The results showed that all types of bagging improve early fruits (especially polyethylene and kraft paper), also yield bunches with the two cultivars. The kraft paper increases significantly the rate of fruit set and fruit yield in the same cultivars.Keywords: Bagging-Pollination- Deglet Noor- Ghars- Date palm - Ouargl