Characterization of Sheared Edges in Warm Blanking of Magnesium Alloy AZ31B

This research aims to characterize damage at the sheared edge caused by the blanking operation of magnesium alloy AZ31B sheets. Shearing tests were carried out on an in-house blanking die-set and mechanical press (universal testing machine) by varying punch–die clearance and temperature. Edge damage was distinguished by the geometrical features of the sheared edge and by the distribution of the edge strain hardening (ESH) index. In this account, optical microscopy and scanning electron microscopy were applied to examine the characteristic dimensions of the sheared edge, fracture profile, and sheared edge quality, while the Vickers hardness test was applied to observe the surface micro-hardness in the shear zone (SZ) and the shear affected zone (SAZ). It was concluded that the blanking of magnesium alloy sheets at room temperature results in sheared edge defects, due to premature fracture, referred to here as micro-cracks, loose particles, and a jagged-plus-curved fracture profile. However, such deformities were completely suppressed with the rise in temperature. In addition, based on optical morphology, micro-hardness tests, and microstructure evolution, the recommendation regarding blanking temperature for the magnesium alloy AZ31B has was proposed.

The Quantitative Assessment of the Fracture Profile of Magnesium Alloy QE22 Welded Joint

Magnesium alloys are a part of a group of lightweight and ultra-lightweight alloys, which are important in practical use in constructions. QE22 casting magnesium alloy containing silver, rare earth elements and zirconium is characterized by creep resistance up to the temperature of 200 °C, while during a short exposure it can resist up to the temperature of 250°C. Nowadays, QE22 magnesium alloy are used for casting into sand moulds. In castings of magnesium alloys defects or inconsistencies (such as casting misruns, porosities and cracks) often appear, particularly in huge dimensional castings. Such defects are repaired with the use of padding and welding. Welded joints must ensure suitable operational properties, mainly in terms of creep, so that the repaired casting can work under the same conditions as the correct cast. The basic source of information about the cause and cracking propagation is fracture after creep test. The quantitative fractography, in particular profilomety, allows to describe the fracture and basis on it conclude the causes of destruction. In this paper quantitative procedure for assessing the fracture profile of QE22 welded joints after creep test was worked out. Base on its analysis result, it was found that creep resistant of the QE22 joints is determined by eutectic areas, therefore they must be heat treated after welding joints.

Preparation and Microscopic Analysis of Polyurethane Elastomer Made by Salix psammophila

In this paper, the degradation of Salix psammophila is used to make the polyurethane elastomer and study on the process involving changes in molecules with SPM. Compared with the pure polyurethane, it can be concluded that the polymerization of particles′ size, height and measurement have got bigger visibly. But the cured particles change nothing and retain the natural polymer’s linear permutation. And this polyurethane elastomer′s fracture profile is brittle.

Fractal Analysis of Fracture Surfaces of Steel Charpy Specimens

The article focuses on the technical measurements which could be applied to the fracture surfaces of the steel Charpy specimens in order to apply the Fractal Analysis. One could calculate the fractal dimension not directly for a fracture, but for a profile of the fracture. Most common methods for generation of fracture profile are cross-cut techniques and profile measurements techniques [1-2]. We apply three principal methods: Profilometer, Interferometer Light Microscope and the Vertical Section for a specimen made of XC65 after the Charpy test. We compare the advantages and the limits for each technique. We use the Box Counting algorithm applied in the Image J program for determining the fractal dimension of the fracture surface in all three experimental techniques. Then we could characterize the roughness of the fracture profile at different magnifying power by the estimated fractal dimension.

An Asymptotic Framework for the Analysis of Hydraulic Fractures: The Impermeable Case

This paper presents a novel asymptotic framework to obtain detailed solutions describing the propagation of hydraulic fractures in an elastic material. The problem consists of a system of nonlinear integro-differential equations and a free boundary problem. This combination of local and nonlocal effects leads to transitions on a small scale near the crack tip, which control the behavior across the whole fracture profile. These transitions depend upon the dominant physical process(es) and are identified by simultaneously scaling the associated parameters with the distance from the tip. A smooth analytic solution incorporating several physical processes in the crucial tip region can be constructed using this new framework. In order to clarify the exposition of the new methodology, this paper is confined to considering the impermeable case in which only the two physical processes of viscous dissipation and structure energy release compete.