Developing More Cost Efficient Cast Components

Background

Topology optimisation is a mathematical design method that can be used to identify and remove redundant material in a structure while maximising stiffness, strength or other performance metrics for a given set of loads and constraints. Topology optimisation has seen rapid adoption by the Additive Manufacturing (AM) industry, due to its ability to accurately manufacture the often complex, organic looking shapes that the technique produces. Indeed, TWI has used topology optimisation to design innovative and lightweight parts for the additive process in the aerospace, medical and automotive sectors. However, the design approach is not limited to AM and TWI is exploring its potential in for cast components

Overview

This case study demonstrates the use of topology optimisation to design a bracket for casting; using the state-of-the-art casting simulation solution, Altair Inspire Cast to simulate and optimise the manufacturing process. This included the working conditions under which material porosity is reduced to an acceptable level. This general methodology demonstrates the power of emerging numerical modelling software for streamlining design-to-production workflows, allowing users to rapidly design cost efficient cast parts that are right first time.

Objective

To lightweight and optimise a structural bracket, followed by the use of Altair Inspire Cast casting simulation solution to demonstrate that the new design will result in acceptable levels of porosity during the casting process.

Outcomes

Figure 1 shows the design space of the bracket (the area where the topology optimisation solution can add or remove material based on the given loads and constraints). Alongside is the suggested design solution exhibiting a 75% reduction in mass without compromise to performance. This represents a potentially significant material and cost saving compared to the original design.

Compared to AM, the casting process is fast, reliable and less susceptible to distortion and tolerance sensitivity. Therefore, accurate casting modelling using Altair Inspire Cast can help to predict: a) the pulling velocity field, fundamental to verify that the molten material is uniformly distributed across the mould; b) the distribution of solid fraction, which helps to evaluate the presence of porous regions in the material; and

c) the temperature distribution over time, which is of importance to predict regions of possible hot crack nucleation and subsequent propagation. In this way, the casting process can be improved to obtain more durable and cost-effective components.

Figure 1. Bracket component before (left) and after (right) topology optimisation

Figure 2. Casting simulation of the AM bracket

Alessio Basso Project Leader - Numerical Modelling and Optimisation

Alessio has joined the NMO Group at TWI in October 2018, as a Project Leader. He has obtained his Master's Degree in Aerospace Engineering in 2011 with dissertation in CFD-BEM Validation for Vertical Wind Turbines (VWT). Subsequently, Alessio enrolled to the annual, 9-month, Research Master course in Fluid Dynamics at Von Karman Institute, Belgium, where attended and passed examinations on Experimental Measurements and Computational Methods in Fluid Dynamics. In 2013 Alessio joined the University of Nottingham where he worked on Turbulent Flow Control (TFC) finalised to skin friction reduction, and where he achieved the Master of Phylosophy Degree in Mechanical Engineering. In 2017 Alessio worked in CFD methodology on multiphase flows at Teesside University, where he developed and improved performances of current microbubble aeration systems.

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