Abstract. Neutron diffraction and curvature measurements were conducted to investigate the residual stresses associated with Plasma Transferred Arc Cladding (PTA) of Ti-6Al-4V on a substrate of the same material. The wire-feed PTA coupled with 3-axis CNC machine was used as an Additive Manufacturing (AM) technique to build parts. A combination of the process parameters was chosen to investigate their effects on residual stress evolution. Neutron Diffraction (ND) measurements of residual strains were performed on the SALSA instrument at the Institut Laue-Langevin (ILL), Grenoble, France. Longitudinal stresses were also inferred by using a Coordinate Measurement Machine (CMM) and Euler-Bernoulli beam theorem. Furthermore, Optical Microscopy (OM) of the cross section of the parts was used to analyse the microstructural evolution. The results show the effect of shorter and longer 'dwell time' between layers on the evolution of residual stresses.
IntroductionTitanium alloys have become a material of great interest for different industrial applications due to their excellent corrosion resistance, low density, excellent high temperature mechanical properties and biocompatibility [1,2]. Manufacturing components in a layer-by-layer fashion offers a high geometrical flexibility and great potential for time and cost savings in comparison to conventional manufacturing technologies [3]. The Additive Manufacturing (AM) of small and medium-sized Ti-6Al-4V parts represents an interesting business case for a number of industrial applications.
Defect propagation and material degradation affect both the performance and safety of energy storage systems. Both processes may accompany operation over time, be nucleated during manufacturing, or be initiated rapidly by external stimuli. This raises particular concerns in lithium-ion cell technologies, where the consequences of faults can be dramatic. However, to date, we have limited capability to detect and/or predict these critical lifetime- and reliability-determining events, especially during operation under real-world operating conditions.
In this paper we present our work related to embedding sensors within and around commercially available pouch and cylindrical format cells. The types of sensors include reference electrodes for measuring half cell voltages during operation, optical fibres to measure mechanically and thermally induced strain, and magnetoresistive sensors to measure the local magnetic field resulting from the flow of charge. Embedding of these sensors is not trivial as the performance of the cell must be unaffected by the modifications. Furthermore, the embedded sensors must survive the cells internal environment. Methodologies for embedding sensors in pouch and cylindrical cells are discussed.
These instrumented cells collectively provide a powerful suite of in-situ and in-operando diagnostics for assessing performance, detecting defect propagation and materials degradation. These diagnostic methods are of great academic interest allowing ageing and failure mechanisms to be studied in greater detail. Furthermore, such diagnostic methods would also be useful in industry allowing systems reliant on lithium battery technology to be characterised in relation to battery operation. Here we present examples of the use of instrumented cells to understand the changes occurring within the cells when operated outside manufacturers’ guidelines and under abuse conditions. Data showing progression of failure is also presented.
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