1,720,995 research outputs found
Tensile and bending behavior of sintered alloys: Experimental results and modeling
No full textSintered materials show a different stress-strain behavior when subjected to tensile or compressive loading, the response to compression being characterized by a higher elastic modulus, yield stress, and strain hardening rate. These differences tend to make the bending behavior somewhat more complex to analyze, particularly in the elasto-plastic field, as compared to conventional materials, having equal mechanical properties under tension and compression. As a consequence, the use of widely applied test techniques, such as the Three Point Bending (TPB), becomes more difficult for sintered materials, due to the lack of reliable analytical models capable of evaluating elasto-plastic stress-strain distribution as a function of applied load and deflection. In the present investigation, the results of uniaxial tensile-compressive and bending tests conducted on sintered ferrous alloys characterized by different microstructures and porosity are reported and briefly discussed. Then an analytical model, specifically aimed to analyze the elasto-plastic monotonic behavior of a TPB specimen made with a material having different tensile and compressive properties, is presented. Its predictions as regards load-deflection curves and elasto-plastic stress-strain distributions are compared with the results of TPB tests and of numerical (Finite Element) analysis, showing a fairly good agreement
Influence of post weld treatments on the fatigue behaviour of Al-alloy welded joints
No full textIn this paper the influence of different post welding treatments, such as ageing or shot peening, on the fatigue behaviour of Al-alloy welded joints was investigated. The analysed joints were candidates for car structural applications. Several four point bending fatigue tests were conducted on GMAW specimens subjected to different post weld treatments. The residual stress field acting on specimens was measured by the X-ray diffraction (XRD) technique. The results of tests were discussed with the aid of a finite element model of the specimen aimed to calculate the actual fatigue cycle, also taking account of residual stresses and of their redistribution during the test. This allowed to characterize the fatigue resistance of the joints, taking account of the effective stress acting in the region of crack initiation. (C) 1998 Elsevier Science Ltd. All rights reserved
Investigation of secondary phases effect on 2205 DSS fracture toughness.
No full textThe fracture toughness properties of duplex stainless steels (DSS) are strongly reduced by intermetallic phases, precipitating at 600-1000°C. In this investigation, the embrittlement effect induced by a low content of these phases has been studied in a 2205 DSS, by means of instrumented Charpy V impact testing. Different contents of intermetallic phases have been produced by isothermal treatments at 800-950°C. The microstructure has been analysed by scanning electron microscope/backscattered electron images. The impact test results, the examination of the fracture surfaces and of the cross-sections close to the notch root allows us to elucidate the role of secondary phases contents in reducing impact fracture toughness. When the quantity of secondary phases is 1%, the fracture is completely brittle. The plastic deformation at the notch root and in the resisting section provokes a secondary phase breakage with a high density microcrack formation, inducing an easy nucleation and propagation of the final fracture crack. When the content of secondary phases is between 0·5 and 1%, fracture is mixed. Both the sigma σ and chi χ phases have been found to be responsible for the embrittling of the 2205 DSS, and fracture toughness mainly depends on their density and dimension
Fracture toughness of nitrided layers obtained with different treatment cycles
No full textThis investigation is aimed at developing a methodology for a proper characterization of the fracture toughness of nitrided layers as a function of treatment depth and at assessing the influence of different nitriding cycles on the toughness of nitrided layers
COMPOSITION, MICROSTRUCTURE AND MECHANICAL PROPERTY RELATIONS IN SINTERED STAINLESS-STEEL
No full textStudio dell'effetto delle fasi secondarie della tenacita' a frattura in un 2205 DSS
No full textIt is well known that the fracture toughness of DSS is strongly reduced by the precipitation of various inter- metallic phases occurring in the temperature range 600-1000°C. A large decrease in impact fracture toughness occurs even at room temperature for volume fractions of intermetallic phases lower than 1%, when only small and rare particles are present. In the present investigation, the influence of the intermetallic phases on the impact fracture behaviour of a 2205 grade DSS has been investigated. Samples containing different amounts of the intermetallic phases have been obtained by isothermal aging treatments in the range 800-950°C. The results of the impact tests confirm that the dangerous phase content determine both the toughness and the fracture behaviour of the DSS examined. At content lower than 1%, when precipitates are rare and small, their effect is a reduction of the absorbed energy for the ductile fracture. But the 1% appears as the critical content, when some particles became large enough to operate the nucleation of the brittle fracture. Indeed, at higher content, a number of large particles are present, well sufficient to induce a general brittle fracture. The obtained results allow correlating the absorbed energy values with the intermetallic phases content and dimensions
Danneggiamneto tribologico in compositi a matrice a base alluminio con elevata quantità di rinforzo
No full textDanneggiamento tribologico in compositi a matrice a base alluminio con elevata quantità di rinforzo
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