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The mechanics of frictional penetration driven by a blind rivet to sheet metals is analyzed for a friction stir blind riveting process. Analytic models are deduced to calculate the material removal rate, penetration force and torque during the frictional penetration process. Frictional penetration tests with modified rivets and an Al alloy sheet were carried out at various rotation speed–feed rate combinations, where the penetration force and torque were recorded with a data acquisition system. An analysis of the contact condition between the rivet tip and the work material based upon the assumption of pure sliding contact in the initial penetration to partial sticking contact beyond a critical penetration depth of the rivet is completed, and the results are discussed based on the comparison of the analytically calculated and experimentally measured torque–force ratios.

Skin-pass rolling (or temper rolling) is the final forming step in the production of cold rolled steel sheets. Although a large roll radius compared to the contact length is one of the characteristics of skin-pass rolling conditions, numerous studies have been conducted thus far using laboratory mills with small radius rolls. In this paper, the influence of roll radius on the contact condition and material deformation in skin-pass rolling is examined and clarified by numerical analysis by an elastic–plastic FEM analysis as well as experimental rolling tests, which were performed to verify the result of the analysis. Some characteristics of skin-pass rolling related to pressure distribution, contact condition and material deformation are not properly simulated using small radius rolls. Considering characteristic skin-pass rolling conditions, two cases using simplified models, i.e., vertical compression and rolling with a circular, rigid roll, were analyzed.

Burnishing is a cold working, surface treatment process in which plastic deformation of surface irregularities occurs by exerting pressure through a very hard and smooth roller or ball on a surface to generate a uniform and work-hardened surface. In this study, a simple burnishing tool, with interchangeable adapter for ball and roller were designed and fabricated to perform roller burnishing processes on Aluminium 6061 under different parameters and different burnishing orientations. The impact of burnishing speed, burnishing force and burnishing tool dimension on the surface qualities and tribological properties were investigated. It was found that burnishing speed of 330 rpm and burnishing force of 212 N is capable of improving surface roughness as much as 40%. However, an increase in the roller contact width leads to less improvement in the surface roughness. Meanwhile, roller burnishing also enhance the hardness of burnished Aluminium 6061 by 20–30%. In tribo-test, burnished surface using small roller produces the lowest friction coefficient under dry contact condition. A substantial decrease in the friction coefficient and weight loss was obtained under lubricated contact condition. Furthermore, a 46% reduction in the friction coefficient was obtained when sliding took place in the direction parallel to burnishing orientation. These findings are further supplemented by SEM photomicrographs of tested surfaces.

An experimental approach has been employed to ascertain the effectiveness of semi-solid roll strip casting of magnesium alloys by a twin-roll caster. The demand for light-weight products with high strength has grown recently due to the rapid development of automobile and aircraft technology. One key to such development has been utilization of magnesium alloys, which can potentially reduce the total product weight. However, the problems of utilizing magnesium alloys are still mainly related to high manufacturing cost. One of the solutions to this problem is to develop magnesium casting–rolling technology in order to produce magnesium sheet products at competitive cost for commercial applications. In this experiment, magnesium alloys AZ31B, AZ91D, AM50A and AM60B were used for twin-roll strip casting. Temperature of the molten materials and roll speeds of upper and lower rolls, which could be adjusted independently, were varied to find appropriate manufacturing conditions. Effects of cooling and contact condition on possible forming were clarified in terms of contact condition between molten material and the rolls. Microscopic observation of the crystals of the finished casting was performed. It has been found that 2.0–3.0 mm thick magnesium sheets could be produced at a speed of 25 m/min. It has been found that the hot rolled cast magnesium sheets produced by semi-solid manufacturing process could be used for plastic forming.

Bulge tests for the determination of material characteristics are very common in engineering analysis. Apart from test purposes, the bulging technique is utilized for the forming of metal sheet-plate or tubes to various useful shapes. Both theoretical and experimental analysis of this forming technique have been done by several authors for different initial blank forms. Finite-element analysis of bulge forming has been carried out by a few authors. In these analyses, the bulging of diaphragms were simulated with edges clamped and hydraulic pressure applied as forming load. Finite-element analysis of the process incorporating the contact phenomenon between the die and sheet-plate has not been reported in the literature. The application of in-plane compressive load on the sheet-plate has also not been reported in any analysis. This paper attempts to study the effect of combined pressure and in-plane compressive load on the sheet-plate by the finite-element method. The contact condition between the die and the sheet-plate is also taken into consideration in the analysis. Further, the analysis is undertaken also for the pressure-only loading case and the results are compared. It is seen from the analyses that the bulge height obtained in the combined loading situation is much higher than that in the pressure-only loading situation. The bulge from the former has a more straight part and thinned less throughout. It also developed less stress and strain compared to the bulge formed in the pressure-only loading situation.