Ram Coin Dimpling: Assessment of Modern Dimpling Methods

Abstract

Given the increasing necessity of improving the structural assembly methods especially in the aviation industry; a proper study by comparison of the currently used methods could reveal to be helpful in choosing the right method to achieve one’s manufacturing goals. It could also incite further researches to solve the existing deficiencies in this domain or make more efficient the existing ones. With the above-mentioned motives, this paper is a close look at dimpling methods. This paper will revise the key characteristics of hot dimpling and cold dimpling by experimental results on sheet materials with different properties. Tensile test and shear test were carried out to evaluate the strength of the sheet material after each dimpling method and study diverse failures remarked while doing experiments. The dimples’ status, fatigue and especially radial cracks and hole sizes, is evaluated. We wish to achieve dimples that permit the rivets to sit flush with the surface of the surrounding material and rivet’s head to fit with no defect. Due to the increasing complexities encountered in the manufacturing and assembly of air and space vehicles, missile systems and associated equipment, this research is provided to be used as an enlightenment to dimpling processes; especially ram coin dimpling. The ram coin dimpling method is divided into cold dimpling (room temperature) and hot dimpling (increased temperature). Comparing this research paper to the studies previously done, we found that hot dimpling though requiring a lot more attention proves to be more efficient on thick or brittle sheet materials, where cold dimpling would produce radial cracks.