Cradle-to-Grave Life Cycle Prediction of Automotive Materials and Systems in Service: Impact of Ageing on Performance

Material ageing is commonly understood as changes of material properties with time. This physical or chemical alteration has a detrimental effect on the material properties and leads to gradual loss of the design function and unacceptable loss of efficiency or ultimate failure (in some cases ageing may be observed as an improvement, for instance, engine performance). Ageing of a material system under normal service conditions is a difficult case to treat. Many factors can significantly affect its durability, such as temperature, irradiation, moisture, chemicals, mechanical creep and fatigue loading. Synergism in the global ageing often occurs when the simultaneous action of several stresses results in an ageing effect that differs from that which would be observed if the individual stresses were applied sequentially. In an effort to understand the ageing process, the first task is to identify the age parameter that represents, on a macroscopic scale, the micro and sub microscopic features, underlying processes such as nucleation and growth of micro defects, and/or physico-chemical transformations. The second task consists of formulation of a constitutive equation that can mathematically represent ageing. The third task obviously is the experimental examination of the condition that leads to catastrophes such as small perturbation in controlling parameters leading to large variations of the age parameter. A material tensor "g" can be introduced as an age parameter similar to stresses and temperature. A variational principle approach can then be followed to formulate a constitutive equation for ageing. Interestingly, an evolution of "g" in four dimensional material space-time continuum would lead to an inelastic behaviour, which manifests as time dependent material properties recorded by an external observer. For one of the simplest linearized case this approach leads to a semi-empirical creep behaviour model. Currently, most of the studies are based on accelerated ageing test at coupon level and require extrapolation to normal service conditions of the part/component, resulting in many uncertainties, leading to frequent diagnostic tests in the field (visual inspection, chemical measurements, physical measurements), impacting dramatically on cost. The aim of the proposed work is to develop an 'age-aware' comprehensive simulation tool for the prediction and assessment of critically important automotive components and systems during manufacturing, in-service and the end of life.

The emphasis of this research theme is to create, a prediction capability for in-service performance throughout the lifetime of the product. This will ensure that the downstream customer experience can maintain JLR's core brand values and customer experiences. Direct beneficiaries of the outcome from the proposed work are Jaguar Land Rover and their affiliates, where the computer simulation tools are used for improving the design and built of components and vehicles, as well as aerospace, marine and other related industries, where many of the concepts and tools developed will be transferable. The acquired knowledge will lead JLR to the improvement of their simulation innovation capability in relation to ageing that would boost robust design, reducing the dependence on physical prototypes during the product development process and leading to reduction in vehicle emissions through increased design optimisation and robustness of virtual design, verification and validation. The results can be used to establish more realistic and consistent quality assessment and performance criteria and increase cost-effectiveness and endurance (durability) in addition to improving the customer driving experience. More broadly, the concept of optimising product/system design for the duration of product/system life using accurate simulation validated by thorough life performance data offers the opportunity to enhance the performance of products and systems in a wide range of industries from aerospace to healthcare with potential for profound long term benefits. Such benefits could go beyond transportation and include improved long term performance of medical diagnostic instruments such as MRI scanners or life support systems such as ventilators and dialysis machines. The results of the project will be advertised to the widest possible scientific and industrial audience at technical workshops, exhibitions, conferences and meetings with industry and academia such as the annual EPSRC Manufacturing The Future Conference and the annual Advanced Engineering Show at NEC Birmingham (after consultation with our JLR sponsors). At the end of the project, developed predictive tools could be transferred fully to any UK company willing to use them in practical design, e.g. within finite element packages used in analysis of structural components. The proposed project will improve the general understanding of ageing behaviour of metallic and non-metallic materials. The acquired knowledge will help researchers in academia and industry who investigate the dynamic response of advanced materials and structures operating in demanding environments to solve further issues relating to improvement of design and reduction of fabrication and manufacturing costs. The main research results will be published in refereed international journals and presented at international conferences. Web documents will also be placed on the Universities web portal, giving descriptions of the work that can be understood by interested members of the public, including prospective students. The Web presentation format is an extremely efficient way to disseminate scientific information. JLR will be consulted to ensure that any intellectual property rights are properly safeguarded. Direct communication with researchers in the field and attendance at conferences will also be important for the dissemination of results. Terms of engagement will be based on a Collaboration Agreement to be established between JLR, UoM and UoS. This will include non-disclosure of information, intellectual property rights and protocols for exploiting the results of the project. In particular, conditions for publication of results can be delayed at the request of JLR, but not indefinitely. A maximum 12 month delay is suggested. PhD theses of linked PhD projects would also not be included in this type of embargo arrangement.