Session: 01-03-01: Advanced Manufacturing for Aerospace Structures

Paper Number: 110610

110610 - A Metamodel Based on Basis Spline Hyper-Surfaces for Thermal Simulation of the Wire Arc Additive Manufacturing Process 

In the aerospace industry, the amount of wasted material generated during manufacturing is called the buy-to-fly (BTF) ratio, which is defined as the ratio of the mass of raw material to the mass of the finished part (Lockett, 2017). In order to reduce material waste and thereby reduce the BTF ratio, Additive Manufacturing (AM) technology is an environmentally friendly manufacturing alternative to conventional manufacturing processes. Among metal AM processes, wire arc additive manufacturing (WAAM) is one of the most promising technologies in terms of deposition rate (Ding et al., 2015) allowing the production of large near net-shape metal parts with complex geometry by depositing weld beads in a layer-by-layer strategy (Chergui, 2021).

Despite these advantages, the quality of parts manufactured by WAAM is highly affected by the thermal and mechanical phenomena occurring during the process, which are influenced by its main parameters. Furthermore, the understanding of the relationships between the physical phenomena and the parameters governing the process (together with the interaction between these parameters) represents a challenging task (Wu et al., 2018; Ding et al., 2015). Accordingly, process simulation is a powerful tool to address such issues, allowing the simulation of the effect of different deposition parameters and, thus, optimising the process.

From a simulation perspective, WAAM technology is typically simulated using a transient thermomechanical Finite Element (FE) analysis with progressive material addition. However, the computational time associated with this analysis can become prohibitive, especially when the influence of process parameters on the thermomechanical properties of the material must be integrated into the design process. As discussed by Ding et al. (2011), this usually results in a reduction in the effectiveness gains of WAAM process numerical modelling. In addition, due to the prohibitive computational costs related to FE non-linear thermomechanical analyses, such a modelling strategy cannot assess the sensitivity of the temperature field and residual strain/stress fields within manufactured parts to the main process parameters. Therefore, appropriate abaci should be used at the preliminary design phase to predict the behaviour of the resulting material in terms of stiffness, thermal conductivity, thermal expansion coefficients, etc., since calculated values of these parameters cannot be obtained in a reasonable time using this type of modelling strategy. Accordingly, Ding et al. (2011), Montevecchi et al., (2017), Michaleris (2014) proposed different methodologies to reduce computational costs, while keeping a reasonable level of accuracy. Therefore, a trade-off must be found between the computational costs and the precision required for a given application (Wang et al., 2020).

In this context, metamodels are efficiently employed to capture the influence of the main parameters of the process on the manufactured parts and to obtain results having a level of accuracy as good as the one related to non-linear thermomechanical FE models. Generally, a metamodel consists of the definition of a parametric hyper-surface that is capable of approximating (or interpolating) some data (Audoux et al., 2020b; Baillargeon, 2005) without knowing the explicit physical equations of the problem at hand. In comparison with other metamodeling approaches (Baillargeon, 2005), Non-Uniform Rational Basis Splines (NURBS) entities offer many unique advantages (Audoux et al., 2020b).

This research proposes a metamodel based on Basis spline (B-spline) entities (a sub-class of NURBS hyper-surfaces) applied to thermal analyses of the WAAM process. The main goal is to analyse the thermal response of the process as a function of different deposition parameters. The temperature histories are monitored during the simulations at different points on the substrate and approximated through a B-spline hyper-surface. The hyper-surface is built as a result of an optimisation procedure generalising the one proposed in previous works (Audoux et al., 2020a,b). Lastly, a global sensitivity analysis (GSA) is carried out on the metamodel based on the B-spline entities to investigate the influence of the selected parameters of the WAAM process on the temperature histories at the selected locations (corresponding to the position of the thermocouples)

Presenting Author: Mathilde ZANI Ecole Nationale Supérieure d’Arts et Métiers, I2M CNRS UMR 5295

Presenting Author Biography: I am a second year PhD student in Mechanical Engineering at Arts and Metiers Technology school in Bordeaux. My research is mainly involved in thermomechanical simulation of WAAM process and NURBS metamodelling.

I am a graduate in aerospace engineering at the University of Pisa with a master thesis on the cohesive modelling of composite structures with quasi-trivial stacks.

I am passionate about travel, history and photography.

Authors:

Mathilde ZANI Ecole Nationale Supérieure d’Arts et Métiers, I2M CNRS UMR 5295
Marco Montemurro Ecole Nationale Supérieure d’Arts et Métiers, I2M CNRS UMR 5295,
Enrico Panettieri Ecole Nationale Supérieure d’Arts et Métiers, I2M CNRS UMR 5295,