Materials Science Forum Vols. 773-774

Abstract: V-sections were roll formed from two grades of steel, and the strain on the top and bottom of the strip near the edge was measured using electrical resistance strain gauges. The channels were bent to a radius of 2 and 15 mm along the centerline. The steel strips were of mild and dual phase steel of yield strength 367 MPa and 597 MPa respectively. The longitudinal bow was measured using a 3-dimensional scanning system. The strain measurements were analysed to determine bending and mid-surface strains at the edge during forming. The peak longitudinal edge strain increased with material yield strength for both profile radii. For the 15 mm radius, the bow was larger in the dual phase steel than in the mild steel. For the 2 mm profile radius, the bow was smaller compared with the 15 mm profile radius and it was similar for both steels. It was observed that the difference between the peak longitudinal edge strain and yield strength to Youngs modulus ratio of the material is an important factor in determining longitudinal bow.

Abstract: Equal channel angular pressing (ECAP) has attracted a lot of interest due to its ability for fabrication of bulk ultrafine-grained materials. With the development of computer skills, the computer-aided methods become very important and useful in understanding the deformation mechanism of ECAP. In this study, the influence of mesh size during finite element simulations of ECAP has been examined based on the plane strain condition assumption. Four different meshes have been compared and these results indicate that Mesh 600 and Mesh 2400 fail to capture the deformation features of ECAP accurately. Large corner gaps develop in these two cases and the simulated strains are smaller than the analytical calculations. Similar results have been obtained between Mesh 6369 and Mesh 12000 and the predicted features of plastic deformation and texture evolution are consistent with the experimental results.

Abstract: Refinement of the grain diameter of the micro structure of Aluminium foil with a thickness of 300μm has been done through the ARB process up to fourth cycles with 72 layers that are proven to increase formability in micro forming a cup. Grain size was measured from the full annealed condition, of the ARB process, and the results of ARB process followed by stress relieved. Formability of the formation of a cup which is expressed as the LDR has increased from 1.87 for the material conditions of full annealed to 2.00 for the ARB process followed by stress relieved in a single step process. In addition to improved formability obtained in a cup formation, grain refinement in the microstructure can also reduce cup earing and wrinkle on the cup wall.

Abstract: During an Aluminium extrusion process, the extrusion parameters, i.e. friction, heat transfer, etc. are significantly influence by the temperature gradients produced in the billet during transfer to the container and after upsetting the container. The heat transfer at the tool/billet interface governs the temperature profile throughout the billet and tools during extrusion and consequently has a critical influence on the results. Although FEM technique offers great potential, care must be taken when applying the analysis to the hot extrusion of rate sensitive alloys. The most useful approach of an FEM simulation would thus be to include both the tooling and the billet in the calculation as discretised meshes. Because of the occurrence of the conductive and convective heat transfer, the deformation during hot extrusion is not adiabatic and estimation of the temperature increase is alloy dependent. The aim of this paper is to investigate and to compare how commercial FEM codes assign and deal with the heat transfer parameter at the tool/material interface. Three commercial FEM codes were investigated and compared; Simufact, Deform and Forge. The usefulness and limitation when using commercial FEM codes are discussed. Methods to assess difficulty of comparison are presented. The work illustrates the essentials of numerical analysis in the comprehension of the thermo-mechanical events occurring during large deformation. Results are presented for velocity distribution and temperature evolution in both materials and tools. It is shown that the heat transfer parameter to be extremely sensitive when attempting to simulate the hot deformation. Moreover, the accuracy of the results does not only depended on the geometric definition of the tooling and material data but also the governing boundary conditions between the material and tooling.

Abstract: Ferrite rolling of interstitial free steel strip in the temperature range 650-850°C can effectively reduce furnace costs and scale formation as a result of lower strip reheating temperatures. Different lubrication conditions of lubricating oil, solid lubricant and dry condition were used during ferrite rolling tests of thin interstitial free steel strip on a 2-high Hille 100 experimental rolling mill. Different rolling speed, rolling temperature and reductions were applied to the rolling process. The rolling force and roll roughness were affected by the lubrication conditions and rolling parameters. Solid lubricant indicated an improved performance in terms of the roll roughness, as well as the oxidation property of the strip surface during ferrite rolling.

Abstract: Mechanical vibration was introduced into the Aluminum alloy matrix composite during solidification process. The cooling curves of composite with mechanical vibration were measured and compared without mechanical vibration. The thermal conductivity and thermal diffusivity properties of the Al/TiC composite were investigated. The result indicated that the mechanical vibration reduces the temperature inhomogeneity of melt. The density of the composite with 10.2, 12, 15Hz and 16 Hz of mechanical vibration improved apparently compared with the composite without mechanical vibration. The thermal conductivity and thermal diffusivity properties of composites with mechanical vibration are also both improved significanly.

Abstract: Deep drawing involves conversion of flat thin sheet metal blanks into parts of desired shape. In the present investigation, the process parameters of warm forming are compared with those of Hydromechanical deep drawing. Warm deep drawing process of circular blanks in Ironing stage is investigated using a 20 T hydraulic press. Hydro-mechanical deep drawing is a process for producing cup shaped components with the assistance of a pressurized fluid. There is an increase in the drawability of low Carbon steel by increasing the oil gap (gap between punch and die) but to make exactly cylindrical shape, the cup is subjected to ironing in the later part of drawing operation. Thickness distribution which describes the quality of the drawn cup is compared in both warm and Hydromechanical deep drawing using experiments and finite element simulations. Keywords- Warm forming,Hydromechanical, deep drawing, Drawability.

Abstract: Tailing sand from ex-tin mine in Batu Gajah containing between 95.9 to 98.9% silica. In this research involved the process of, conducting the mechanical sieve grading to identify the size spread, plotting the grain size distribution and calculating the average grain size. Further on with the effects of controlled additions of clay (bentonite) and water and determining the working range on the mechanical properties. The investigation involved comparing the mechanical properties of the tailing sand to the requirement for foundry sand applications listed by Foseco Ferrous Foundrymans Handbook (Foseco). Permeability and green compression strength are the important mechanical properties and considered much in the sand casting mould preparation. These mechanical properties play a vital role in determining the allowable clay and moisture content for working range of tailing sand for making green sand casting mould. Experiments for this investigation were conducted according to American Foundrymen Society (AFS) standard of procedures. Cylindrical test pieces dimensioning of Ø50 mm×50 mm in height from various sandwater ratios bonded with 3.8%wt clay and then 7.4%wt clay, were compacted by applying three ramming blows of 6666 g each using Ridsdale-Dietert metric standard rammer. The specimens were tested for green compression strength using Ridsdale-Dietert universal sand strength machine and permeability number with Ridsdale-Dietert permeability meter. Before the tests were conducted, the moisture content was measured using moisture analyser. Tailing sand with allowable moisture content ranging from 3 to 3.5% (bonded with 3.8%wt clay) and 5.5 to 6% (bonded with 7.4%wt clay) were found to have optimum working range with effective green compression strength and permeability.

Abstract: This work mainly studied the effects of hot extrusion on microstructure, texture and mechanical properties of Mg-5Li-3Al-2Zn alloy. The results show that the microstructures of as-cast and as-extruded alloys both consist of α-Mg matrix and lamellar eutectic structure (α-Mg and AlLi phases). During the hot extrusion, the large eutectic structure of as-cast alloy was crushed into small eutectic structure and the grains were effectively refined. A {0002} basal texture was formed after hot extrusion. The as-extruded alloy exhibits remarkably improved tensile properties, which is mainly attributed to the grain refinement and the formation of texture.

Abstract: The objective of this study is to investigate the surface roughness that effect the capability of adhesive with adding aluminium powder and 63/37 Sn-Pb soft solder powder to the epoxy to increase the mechanical strength of joints. The adhesive strength of the joints was determined by utilizing the single-lap shear test. As seen from the experiments, the surface roughness has an important effect on the strength of adhesive bonded joints. Experimental results show that joints prepared by adhesive which was modified, adding in the amount of 5 wt% 63/37 Sn-Pb powder have more mechanical strength than joints compared to one which is prepared by adding aluminium powder with different ratios as 5, 25,50 wt%.