Single point incremental forming simulation with adaptive remeshing technique using solid-shell elements

Abstract

Single Point Incremental Forming (SPIF) is a dieless manufacturing process in which a sheet is deformed by using a tool with a spherical tip. This dieless feature makes the process appropriate for rapidprototyping and allows for an innovative possibility to reduce overall costs for small batches, since the process can be performed in a rapid and economic way without expensive tooling. As a consequence, research interest related to SPIF process has been growing over the last years.Numerical simulation of SPIF process can be very demanding and time consuming, mainly due to the the high non-linearity and constantly changing contact conditions between the tool and the sheet surface, as well as the nonlinear material behavior combined with non-monotonic strain paths. To reduce the simulation time, in the present work an adaptive remeshing technique is proposed being implemented in the in-house implicit finite element code LAGAMINE. This remeshing technique automatically refines only a portion of the sheet mesh at the tool's vicinity, therefore following the tool's motion. As a result, uniformly refined meshes required for accuracy purposes are avoided and consequently, the total CPU time can be drastically reduced.In this work, the proposed automatic refinement technique is applied developed within a Reduced Enhanced Solid-Shell (RESS) framework to further improve numerical efficiency. Finally, validations by means of benchmarks are carried out, with comparisons against experimental results. Keywords

Evaluation of the Formability and Dimensional Accuracy Improvement of Ti6Al4V in Warm SPIF Processes

“…After every test, the measurement of the mesh mapped on the parts confirmed there was no dimensional variation in the circumferential direction, see Figure 6. This confirms the existence of plane deformation, as suggested by various authors [33].…”

“…Figure 16 right shows the effect of the temperature on the forces on the main plane of the sheet. The relation between the experimentally obtained Fr and Fz values responds well to the analytical model initially proposed by Silva et al [33] and subsequently developed by Lu et al [48]. This was established by means of Equations (3) to (5), where t is the sheet thickness, rt is the tool radius, µ is the friction coefficient, Φ and θ are the components of the tool-sheet contact angle in the radial and circumferential direction respectively, Sc is the contact surface, Figure 17, and σ eq is the equivalent material yield stress.…”

“…In this context, some research is being carried out with the aim of reducing the computing time in implicit procedures. Thus, other authors have used the Lagamine software based on a Lagrangian method developed expressly for this purpose [31][32][33][34]. In previous works [35], the authors of the present paper have demonstrated the viability of using FEM software of general purpose, as ANSYS Workbench®with an implicit solver, to simulate complete parts made by SPIF.…”

“…The experimental contact surface is greater than the theoretical one due to the springback as the new deformation progresses, in both vertical and radial directions. Furthermore, the previously mentioned analytical models [33,48] establish a rigid-perfect plastic model as the hypothesis of material behavior, without hardening of the material. They also postulate the non-existence of mechanical effects related to bending or stress distribution as simplifying hypotheses, despite it having been demonstrated that in similar relations between forming tool radius and sheet thickness these effects are not insubstantial [40].…”

Damage prediction in single point incremental forming using an extended Gurson model

“…This was later confirmed by a pyramid test simulation by Duchêne et al (2013). Potential reasons for high forces were studied by Sena et al (2016) (boundary conditions, missing blankholder force modeling, friction coefficient, hardening modeling choice, element stiffness, etc.). In particular, for an AA7075-O aluminum alloy using the RESS element the hardening law has an important effect on the force level.…”