Moiré interferometry applied to fracture in titanium tubes

Despite there being a substantial body of evidence to the contrary, moiré interferometry is often regarded - even by some adherents - as a curiosity of the optics lab. The present work seeks to demonstrate still further that the method can be an effective tool for practical materials research and assessment, in this case, in a novel and challenging experimental application involving fracture testing of heat exchanger tube material, the work being conducted in a conventional materials test laboratory setting. The key to the utility of the present setup lies with the priority given to its optical efficiency. In standard fracture toughness tests, it is axiomatic that standard specimen geometries be used. A dilemma arises when a material's properties are transformed to a substantial degree by the final stages of its process of manufacture, and when the very nature of the finished form dictates that standard geometries cannot be produced. The focus of this investigation was to measure crack-tip opening displacements (CTODs) in thin-walled titanium tubes. Fringe patterns corresponding to in-plane displacement contours were obtained interferometrically and the method for extracting CTODs from these is described. Significant differences in yield, ultimate strength, elongation, and fracture behaviour were observed for different material orientations

Fatigue testing of a proximal femoral hip component

Published versio

Microstructural and strength study of MIG welded joints of AW7020 aluminium alloy, as a function of joint geometry

[EN] Medium strength AW7XXX aluminium alloys are widely used as welded structures and in transportation. The applications of these alloys are limited by the behaviour of the welded joints. There is no agreement on the joint geometry that must be used on 5 mm welds. The microhardness evolution is one of the most important strength indicators. For this reason, the aim of this work is to study the influence of welded joint geometry on microhardness profile and on the microstructure of a MIG welded AW7020 aluminium alloy, using AW5256 filler.Bloem, C.; Salvador Moya, MD.; Amigó, V.; Vicente-Escuder, Á. (2000). Microstructural and strength study of MIG welded joints of AW7020 aluminium alloy, as a function of joint geometry. Welding International. 14(12):970-974. doi:10.1080/09507110009549300S970974141

Strength-ductility behaviour of Al-Si-Cu-Mg casting alloys in T6 temper

A comparative study of the mechanical properties of 20 experimental alloys has been carried out. The effect of different contents of Si, Cu, Mg, Fe and Mn, as well as solidification rate, has been assessed using a strength-ductility chart and a quality index-strength chart developed for the alloys. The charts show that the strength generally increases and the ductility decreases with an increasing content of Cu and Mg. Increased Fe (at Fe/Mn ratio 0.5) dramatically lowers the ductility and strength of low Si alloys. Increased Si content generally increases the strength and the ductility. The increase in ductility with increased Si is particularly significant when the Fe content is high. The charts are used to show that the cracking of second phase particles imposes a limit to the maximum achievable strength by limiting the ductility of strong alloys. The (Cu + Mg) content (at.%), which determines the precipitation strengthening and the volume fraction of Cu-rich and Mg-rich intermetallics, can be used to select the alloys for given strength and ductility, provided the Fe content stays below the Si-dependent critical level for the formation of pre-eutectic alpha-phase particles or beta-phase plates

Focus on the management of thunderclap headache: from nosography to treatment

Thunderclap headache (TCH) is an excruciating headache characterized by a very sudden onset. Recognition and accurate diagnosis of TCH are important in order to rule out the various, serious underlying brain disorders that, in a high percentage of cases, are the real cause of the headache. Primary TCH, which may recur intermittently and generally has a spontaneous, benign evolution, can thus be diagnosed only when all other potential underlying causes have been excluded through accurate diagnostic work up. In this review, we focus on the management of TCH, paying particular attention to the diagnostic work up and treatment of the condition

Evolution of intermetallics, dispersoids and elevated-temperature properties at various Fe contents in Al-Mn-Mg 3004 alloys

Nowadays, great interests are rising on aluminum alloys for the applications at elevated temperature, driven by the automotive and aerospace industries requiring high strength, light weight and low cost engineering materials. As one of the most promising candidates, Al-Mn-Mg 3004 alloys have been found to possess considerably high mechanical properties and creep resistance at elevated temperature resulted from the precipitation of a large number of thermally stable dispersoids during heat treatment. In present work, the effect of Fe contents on the evolution of microstructure as well as high temperature properties of 3004 alloys has been investigated. Results show that the dominant intermetallic changes from α-Al(MnFe)Si at 0.1 wt. % Fe to Al6(MnFe) at both 0.3 and 0.6 wt. % Fe. In the Fe range of 0.1 to 0.6 wt. % studied, a significant improvement on mechanical properties at elevated temperature has been observed due to the precipitation of dispersoids, and the best combination of yield strength and creep resistance at 573K (300°C) is obtained in the 0.3% Fe alloy with finest size and highest volume fraction of dispersoids. The superior properties obtained at 573K (300°C) makes 3004 alloys more promising for high temperature applications. The relationship between the Fe content and the dispersoid precipitation as well as the materials properties has been discussed