No abstract

No abstract

No abstract

No abstract

Due to the continued interest in reducing weight in both automobile and aerospace structures, interest has grown in magnesium based alloys as a possible materials solution. Despite this interest, these alloys have not been widely utilized due to their relatively poor mechanical properties in comparison to other material systems. However, recent research has clearly indicated that improved mechanical properties can be achieved in these alloys through the use of severe plastic deformation processing methods. In this report, we examine the influence of equal channel angular pressing on the mechanical response of Elektron 675, a Mg-Gd-Y alloy. Results indicate that an appreciable increase in total elongation and absorbed energy can be obtained depending on the selected processing route. However, these improvements in elongation are somewhat offset by a slight reduction in tensile strength. The observed mechanical response is explained through microstructural analysis as well as texture measurements.

No abstract

The presence and quality of welds in metallic structures has the ability to influence their likelihood of failure under dynamic loading. This investigation focused on characterising the behaviour of a welded aluminium structure. Samples were taken from the parent metal, heat affected zone (HAZ) and the weld bead and high strain rate characterisation testing was performed to determine the Johnson-Cook (JC) strength and failure model parameters for each material. However, significant scatter was found in the data for the weld bead due to porosity within the samples. Additional tensile tests were performed using a rotating fly wheel machine with four larger samples, which were machined from the welded aluminium structure and contained HAZs on either side of the weld bead, located in the centre of the specimen. Three of the four samples had the weld bead ground flush to the level of the base plate. Digital image correlation was used to determine the surface strain within each region of the sample and identified significant strain localisation at the interface between the weld metal and the HAZ, as well as within the weld bead. Comparisons between the ground welded specimens and those with the weld reinforcement showed a different failure mode between the two specimens. For the ground specimens, the strain localisation in the weld bead initiated failure prior to the strain localisation occurring at the interface between the weld bead and HAZ. Sectioning of the welds indicated that the strain localisation in the weld bead may have been caused by significant levels of porosity within the weld bead. Preliminary numerical simulations of the ground specimens indicated that the force-time history could be well captured. However, as the strain localisation due to porosity is not captured using a JC model, in addition to the scatter in the characterisation data for the weld bead, failure was not accurately predicted numerically.

This paper gives an overview of different testing facilities and the mechanical material behavior including monoaxial and multi axial testing under high rate loading . Special emphasis is laid on difficult loading conditions and loading states such high temperature and high strain loading ( >1200°C, >1) and multiaxial impact tests. The impact behavior of selected materials is shown and compared under different loading conditions. Furthermore, a distinction is made between virgin and manufactured material behavior (e.g. welding) or predamaged materials. Specifically, if the influence of the manufacturing history is investigated, under certain loading states the impact material properties show a dramatic difference compared to the virgin state of the material. Some examples of different material behavior under the conditions previously described are given.