Parametric Analysis of the Mandrel Geometrical Data in a Cold Expansion Process of Small Holes Drilled in Thick Plates

Abstract

Cold expansion technology is a cold-forming process widely used in aeronautics to extend the fatigue life of riveted and bolted holes. During this process, an oversized mandrel is pushed through the hole in order to yield it and generate compressive residual stresses contributing to the fatigue life extension of the hole. In this paper, a parametric analysis of the mandrel geometrical data (inlet angle straight zone length and diametric interference) and their influence on the residual stresses was carried out using a finite element method (FEM). The obtained results were compared with the conclusions presented in a previous parametric FEM analysis on the influence of the swage geometry in a swaging cold-forming process of gun barrels. This process could be considered, in a simplified way, as a scale-up of the cold expansion process of small holes, and this investigation demonstrated the influence of the diameter ratio (K) on the relation between the mandrel or swage geometry and the residual stresses obtained after the cold-forming process.

Cold Expansion Process with Multiple Balls—Numerical Simulation and Comparison with Single Ball and Tapered Mandrels

“…For the specific case of the mandrel geometry, there are a wide published research focused on the tapered models [13][14][15][16] but limited investigations on ball geometries [17,18]. The motivation behind the use of ball geometries, as an alternative to tapered mandrels, comes from its consolidated manufacturing process based on their use for ball bearings industry.…”

“…Calaf-Chica et al [13] showed the significance of selecting the optimal geometry for tapered mandrels. Three parameters were targeted: length of straight zone (SZ), inlet angle (IA) and outlet angle (OA) (see Figure 7).…”

“…This calculation was executed considering a similar level of pushing loads needed for the process (comparing with cold expansion performed with a single ball geometry; around a maximum load of 500 N). From Reference [13], it was deduced that an increment of the length of the straight zone or a reduction of the inlet angle increase the pushing load. In this iterative process, three different SZs were evaluated (SZ = {0.50, 0.75, 1.00} mm) obtaining the appropriate IA to reach the most similar pushing load (IA = {1.0, 1.5, 5.0} • ).…”

Special Issue of the Manufacturing Engineering Society 2019 (SIMES-2019)

“…In this Special Issue of the journal Materials, 29 contributions to cutting-edge advances in different fields of the manufacturing engineering have been collected. In particular, in additive manufacturing and 3D printing [4][5][6][7][8][9][10][11]; sustainable and green manufacturing [12][13][14][15][16]; metrology and quality in manufacturing [17][18][19][20][21]; advances and innovations in manufacturing processes [22][23][24][25]; manufacturing of new materials [26][27][28]; design, modeling, and simulation in manufacturing engineering [29,30] industry 4.0 [31] and manufacturing engineering and society [32]. Among all of them, the topic additive manufacturing and 3D printing stands out for the number of contributions it has had in this Special Issue showing the interest that this topic arouses, currently, among researchers, the industry and the public in general.…”

“…Concretely, two about thermoplastic carbon fiber composites C/TPU [26,27] and, other, about an Al-SiC metal matrix composite [28]. It counts also with two works in design, modeling, and simulation in manufacturing engineering about the indentation process [29] and the cold expansion process [30]; one, in the topic industry 4.0 about the application of the supply chain to shipbuilding [31] and the other in the topic manufacturing engineering and society about a new risk methodology based on control charts to assess occupational risks in manufacturing processes [32].…”