Encontrados 10 documentos, a visualizar página 1 de 1
Residual stresses analysis of ND-YAG laser welded joints
Costa, J. M.; Pires, J. T. B.; Antunes, F.; Nobre, J. P.; Borrego, L. P.http://www.sciencedirect.com/science/article/B6V2X-4V3546Y-2/2/8ee5852dd432955cfe324f9228305af1
Partial crack closure under block loading
Borrego, L. P.; Ferreira, J. M.; Costa, J. M.Fatigue crack propagation tests under high-low and low-high block loading sequences have been performed in aluminium alloy specimens. The tests were carried out at constant [Delta]K conditions. Two stress ratios were analysed: R = 0.05 and R = 0.4. Crack closure was monitored in all tests by the compliance technique using a pin microgauge. The observed transient post load step behaviour is discussed in terms of...
Mould steels repaired by laser welding
Borrego, L. P.; Pires, J. T. B.; Costa, J. M.; Ferreira, J. M.Laser-deposit welding, by using Nd-YAG, is a mould repairing process, which has the advantages relatively to the traditional methods of achieving a less change of the metal composition around the repaired zone and permitting a very accurate deposition of a small volume of the filler material in the area chosen at the work-piece surface. This paper presents a fatigue study in specimens of two base materials used...
Fatigue crack growth in heat-treated aluminium alloys
Borrego, L. P.; Costa, J. M.; Antunes, F. V.; Ferreira, J. M.http://www.sciencedirect.com/science/article/B6V2X-4V42JDW-1/2/7483d2e761bf28c40a5ae2c39c720313
Fatigue behaviour of laser repairing welded joints
Borrego, L. P.; Pires, J. T. B.; Costa, J. M.; Ferreira, J. M.This paper presents a fatigue study in Nd-YAG laser surface repairing welded joints in specimens of two base materials used in mould production. The tests were carried out in a servo-hydraulic machine in tension, under constant amplitude loading, with two stress ratios R = 0 and R = 0.4. Welded specimens were prepared with U notches and filled with laser welding deposits. The fatigue results are presented in th...
Mixed-mode fatigue crack growth behaviour in aluminium alloy
Borrego, L. P.; Antunes, F. V.; Costa, J. M.; Ferreira, J. M.Fatigue crack propagation tests in compact mixed-mode specimens were carried out for several stress intensity ratios of mode I and mode II, KI/KII, in AlMgSi1-T6 aluminium alloy with 3 mm thickness. The tests were performed in a standard servo-hydraulic machine. A linkage system was developed in order to permit the variation of the KI/KII ratio by changing the loading angle. Crack closure loads were obtained th...
Fatigue crack growth in thin aluminium alloy sheets under loading sequences wit...
Borrego, L. P.; Costa, J. M.; Ferreira, J. M.This study analyses the fatigue crack growth behaviour in thin AlMgSi1-T6 aluminium alloy sheets under several loading sequences containing periodic overloads. The observed fatigue crack growth behaviour is compared to constant amplitude loading and discussed in terms of type of loading sequence, intermediate baseline cycles and stress ratio. The crack closure parameter U was obtained for periodic single overlo...
Microstructure dependent fatigue crack growth in aged hardened aluminium alloys
Borrego, L. P.; Costa, J. M.; Silva, S.; Ferreira, J. M.Fatigue crack propagation tests in constant amplitude loading, as well as with single peak overloads, have been performed in AlMgSi1-T6 aluminium alloys with different Mn and Cr contents. Crack closure was monitored in all tests by the compliance technique using a pin microgauge. A moderate stress ratio and a strong material dependence effects on the fatigue crack growth were observed. These effects are discuss...
Analysis of low cycle fatigue in AlMgSi aluminium alloys
Borrego, L. P.; Abreu, L. M.; Costa, J. M.; Ferreira, J. M.In this study low-cycle fatigue tests were performed in two AlMgSi aluminium alloys with different chemical composition, namely 6082-T6 and 6060-T6 alloys, using standard round specimens and tube specimens, respectively. The tests were undertaken in strain control with a strain ratio R[var epsilon]=-1. The cyclic stress-strain curves were determined using one specimen for each imposed strain level. The low-cycl...
Evaluation of overload effects on fatigue crack growth and closure
Borrego, L. P.; Ferreira, J. M.; Pinho da Cruz, J. M.; Costa, J. M.Fatigue crack propagation tests with single tensile peak overloads have been performed in 6082-T6 aluminium alloy at several baseline [Delta]K levels and stress ratios of 0.05 and 0.25. The tests were carried out at constant [Delta]K conditions. Crack closure was monitored in all tests by the compliance technique using a pin microgauge. The observed transient post-overload behaviour is discussed in terms of ove...
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