Doing More With Less: A Digital Twin of state-of-the-art and emerging high value manufacturing routes for high integrity titanium alloy components

Titanium alloy components are strategically important to the future UK aerospace, energy and electric vehicle sectors owing to their high strength-to-weight ratio, excellent fracture resistance and fatigue properties, and compatibility with carbon fibre composites. Current state-of-the-art titanium components are processed through complex non-linear open-die and closed-die hot forging that generates non-uniform microstructure and properties within different regions. This necessitates significantly larger geometries than the final shape to be forged before 70% of the material is machined away to retain the "optimum" microstructure and property set in the final part. This expensive and wasteful approach has led to a sector-wide effort to produce components with more homogeneous microstructures and property distributions from less material. For example, many emerging powder-derived manufacturing routes have been explored extensively. The UK developed, hybrid FAST-forge powder-derived process has shown promise over recent years to produce affordable titanium alloy components. The high-value manufacturing sector now needs the tools to objectively inform which processing route is optimum, be it state-of-the-art or emerging routes, such as FAST-forge, based on key drivers such as cost, volume, energy consumption, resource use, and in-service properties.

Emerging manufacturing techniques such as precision investment casting and additive manufacturing have advantages over forging in terms of material and energy usage and speed of manufacture, but they cannot produce the high integrity properties required for many structure-critical applications. For this century, forging is here to stay, but it needs to have a 21st century makeover to be more agile, economical, less wasteful with better performing products. There is a realisation in industry that in order for UK manufacturing to remain internationally competitive, we need rapid and intelligent process support. For high integrity products there is a drive to create a digital twin of the physical forging process and to empower UK manufacturers to provide a (1) more efficient, less conservative and affordable process route and (2) improved and more consistent properties to reduce design conservatism. This is now possible, owing to recent improvements in control, sensor technology and non-destructive testing characterisation methods, coupled with improved physical understanding and modelling of the material behaviour.

The virtual world of a digital twin that incorporates lubrication, tool wear, temperature, and press dynamics, as well as through-process microstructure and property evolution, will be the closest analogy to an equivalent real-world system or physical twin. We now have the infrastructure and data analysis approaches to create this virtual digital twin. Firstly, this will inform industry on the optimum processing route (i.e. state-of-the-art or FAST-forge) for a given component, enable the assessment of process route and allow the whole supply chain to be involved in the early stages of component design (when changes can still be made cheaply through the virtual digital twin). Secondly, it will enable real-time production decisions, instant troubleshooting and validation for future high integrity forged titanium alloy components, using physics-based models and data analytics. From a sustainability standpoint, a digital twin of the microstructure during forging and press performance will enable the supply chain to do more with less material by providing higher confidence in location-specific properties or utilising the press more efficiently (i.e., using less energy) to achieve the property goals of the design. Creating a digital twin of forging, which is accessible to the whole supply chain will consolidate the UK's world class reputation in the manufacturing of high integrity products and lead to significant business investment.

Being at the leading edge of titanium component manufacture is an important aspect of our UK manufacturing competitiveness, demonstrated through key employers such as Rolls-Royce, BAE Systems, GKN Aerospace, and Safran Landing Systems and their supply chains who manufacture landing gears, bulkheads and compressor disks. Encouragingly, the UK civil aerospace sector (second only in the world to the US) shows signs of major growth: as global demand for aircraft is increasing, it could enjoy a 17% share a new market estimated to be £2.4 trillion over the next 20 years [The Engineer, June 2011].

Overall this proposal will have a substantial impact on the future business and jobs for the UK, particularly in the aerospace sector which currently employs over 110,000 people (second behind the USA) and a further 350,000 indirectly. With an increasing demand for air travel and air cargo it is imperative that the UK strengthen its position as innovators in the industry. A recent report by Boeing stated that between now and 2032 there will be a demand for over 32,000 new airplanes the majority of which will be single-aisle to feed the low-cost carrier sector, particularly in emerging markets such as China. The report goes on to state that 85% of the planes that will exist in 2032 have yet to be built. Pressure to meet the delivery targets of many of these aircraft programmes will require higher productivity, which from a manufacturing standpoint equates to higher production rates and enhanced component property knowledge through improving buy-to-fly ratios, reducing reworking requirements, and quantifying property variation throughout the component. UK manufacturers and their future cost down targets are reliant on new manufacturing practices. To enhance the effectiveness and sustainability of organisations it is imperative that UK research and development provide support and confidence to these new practices. More importantly, the UK has invested heavily in the last few years in the underpinning science and translational infrastructure required for creating and validating a holistic digital twin for titanium forging. Bringing this together will be a game-changing empowerment for the UK supply chain to deliver forged components with enhanced mechanical properties using an energy, material, and economically efficient process.