Our client was a designer of advanced spark plugs, who required support to design and validate a new product. Due to the flexibility of our analysis setup and model, it was possible to quickly run multiple iterations of the geometry. We assessed assembly forces to identify the optimum process while also incorporating the sensitivity of specific parameters. Our approach saved our client significant amounts of money by reducing the need for expensive prototyping and testing.
Our client was a designer of advanced spark plugs (working with a leading Formula 1 works team) who required support to design and validate a new spark plug. Traditionally our client utilised physical testing as a means to validate their new designs; this incurred significant costs regarding the manufacture of small volumes of prototype parts, but more importantly took an extended period of time, in an industry where being ‘ahead of the curve’ is critical to success.
We were asked to determine the optimal manufacturing loads and to verify the sealing pressures within the spark plug assembly after it had been installed into the cylinder head and exposed to combustion pressures and temperatures. The purpose of the work was to confirm that the spark plug was structurally sound while ensuring that sufficient residual compression continued to be ‘locked in’ within the assembly. Many tolerances and variables needed to be considered to ensure that the recommended manufacturing loads would be achievable within the design limits, as constrained by geometry and materials. Additionally, some exotic materials were used in the manufacture of the components, so we helped to obtain the relevant input parameters and characteristics, which were critically important in achieving accurate and representative results.
Following the creation of a detailed analysis plan, we developed axi-symmetric Finite Element Analysis (FEA) models in ANSYS Parametric Design Language (APDL) to simulate the full manufacturing process of the spark plug. It was essential to accurately determine the residual stresses present in the assembly, post-manufacturing, to fully capture the response of the spark plug once in operation. Our analysis used a coupled thermal, electrical and structural approach to model the assembly process, which included electrical heating of the shell, followed by a swaging operation and the subsequent cooling and shrinkage of the components.
All stages of the analysis considered temperature dependant elastic-plastic material properties to capture the material response accurately. Following the analysis of the manufacturing process, we modelled the installation into the cylinder head and the exposure to operational temperatures and pressures. Throughout every stage of analysis, the residual compressive force within the assembly was monitored to ensure the spark plug remained leak tight.
Due to the flexibility of the analysis setup and model, it was possible to quickly run multiple iterations of geometry and assembly forces to identify the optimum process, while also understanding the sensitivity of specific parameters. We optimised the design and manufacturing process and generated a 3D half symmetry model to assess non-axis-symmetric effects and loads.
We presented the output of the task to our client, giving them the opportunity to scrutinise the results in detail and ask clarification questions. We then developed a detailed technical report that the client could adopt as part of the technical documentation.
- We reduced timescales to obtain optimal design parameters
- We reduced cost by a significant saving in prototype manufacture and testing
- We enhanced performance, by identifying optimal design and critical limits