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Validation of Numerical Engineering Simulations: Standardisation Actions

Final Report Summary - VANESSA (Validation of Numerical Engineering Simulations: Standardisation Actions)

Executive Summary:
Engineering simulation is an essential feature of the design and manufacture of all engineered products at all scales. However such simulations are not routinely validated, at least in part because technology for rapid, cost-effect validations has not been available. Two previous projects, SPOTS and ADVISE led to the development of appropriate tools. The goal of the VANESSA project has been to establish a validation methodology and the associated calibration procedures within a standards framework and to promote the adoption of the methodology within the European industrial and scientific communities. A CEN Workshop Agreement on the validation of computational solid mechanics models has been developed through a series of public consultations and inter-laboratory studies (ILS). To encourage take up of this innovative approach to design validation by EU industrial base and to gain its international acceptance a series of knowledge exchange events have been organised. In addition, a package of technical and educational materials have been prepared and are available via the project website (www.engineeringvalidation.org) with links to media such as YouTube. The technical approach embedded in the validation process has the potential to stimulate improved quality control for the process chain from design, during production and certification, through to service and maintenance and its adoption would lead to a strengthening of the position of European industry.
Project Context and Objectives:
Context

Engineering simulation is an essential feature of the design and manufacture of all engineered products at all scales. In particular, simulation based on computational solid mechanics models permits designers to optimise the load-bearing components in devices, machines and structures so that a satisfactory level of reliability is achieved for an acceptable cost. The desire for a sustainable society stimulates designers to create elegant, light-weight designs in which embedded energy and material is minimised; however at the same time consumers demand total reliability that often can be achieved most easily by heavy, conservative designs in which additional material provides additional factors of safety. Removal of these safety factors to create light-weight and efficient designs requires a very high level of confidence in the engineering simulations used routinely in design, especially when composite materials or hybrid solutions are adopted. These confidence levels should be acquired through rigorous, quantitative validation of the models employed for the simulations. Although many engineering companies and organisations have developed internal procedures for validating the computational models that are essential to their engineering design activities, there are no standards for the validation of computational solid mechanics models used in engineering design. Consequently, many engineering artefacts are designed using inadequately validated models which when this is recognised leads to conservative design and when it is not recognised leads to unreliable design. The lack of standardisation inhibits the exchange of both data from simulations and of models used for simulation, which in turn slows down innovation, particularly in industries producing engineering systems that are composed of many sub-systems produced by different manufacturers.
The VANESSA project built on two completed projects from FP5 and FP7 with the aim of bridging the gap between the research outputs of these projects and their implementation in engineering industry. The FP5 project SPOTS (Standardisation Project for Optical Techniques of Strain measurement) led to a unified calibration method for all optical systems capable of measuring strain fields on the planar surfaces of engineering components subject to pseudo-static loading . Calibration provides traceability via a continuous chain of comparisons to an international standard, in this case for length, and also allows the minimum measurement uncertainty to be established. Traceability is important in areas such as aerospace and nuclear power, which require certification of designs by regulatory authorities. The establishment of minimum measurement uncertainties is critical in making quantitative judgements about comparisons between datasets. Thus, the SPOTS project provided an initial step in the process of validating computational solid mechanics models by creating a route for providing high quality data from experiments that could be used in the validation process. A set of guidelines were published from the SPOTS project and have been approved by VAMAS TWA26 .
The FP7 project ADVISE finished in November 2011 and extended the research outputs from SPOTS in two important areas, i.e. developing an efficient quantitative method of comparing very large datasets and extending the calibration methodology to include dynamic and out-of-plane loading of engineering components . The SPOTS methodology permitted the calibration of strain fields in static and pseudo-static loading cases in which the area of interest could be approximated as planar. These categories of cases allow a great many engineering analyses to be handled satisfactorily; however the ADVISE work on calibration extends the procedures to important cases in which the rate of deformation and out-of-plane components of deformation are significant. Impact loading occurring either intentionally, such as during landing of an aircraft, or unintentionally, such as in an automotive crash, is one of the most important categories that the ADVISE project considered.
Recent developments in optical measurement have lead to a number of very powerful techniques for acquiring strain data in engineering components subject to service loads , amongst which digital image correlation is becoming ubiquitous. These techniques are capable of generating high-density maps of strain fields containing of the order of 105 to 106 data values, which with careful experimental design could cover the majority of the surface of an engineering component. The quantitative comparison of such data with similar data generated by engineering simulations based on computational solid mechanics models is challenging because the datasets are obtained in different coordinate systems, with different orientations and in data arrays with different pitches. In the ADVISE project, techniques used in image decomposition were used to develop procedures for strain field decomposition that are invariant to rotation, scale and translation and which allow enormous data compression while preserving all of the relevant information6, . These procedures were used to create a validation protocol that involved comparing output from simulations with high-density datasets from optical measurement of strain fields in engineering components or prototypes. The protocol is efficient to apply, takes account of uncertainties and can be adapted to give a quantitative measure of the level of agreement between of the datasets from experiment and simulation.

S&T objectives

The goal of the VANESSA project was to establish the validation methodology and the associated calibration procedures within a standards framework and to promote the adoption of the methodology within the European industrial and scientific communities. Successful accomplishment of this goal required achievement of the following scientific and technical objectives:
a) To conduct international inter-lab comparison (round-robin) exercises that will generate evidence that the reference material, for calibration of optical systems for strain field measurement, and the validation protocol, for computational solid mechanics models, form a solid basis for standardisation.
b) To prepare a CEN Workshop Agreement on validation of computational solid mechanics models using strain fields from calibrated measurement systems.
c) To raise awareness in the EU industrial base and international engineering community of the validation protocol through a programme of knowledge dissemination and exchange.
The SPOTS calibration procedure has been used extensively and a number of examples of successful calibration published in the scientific literature. It is beginning to be incorporated into experimental design protocols at a number of international companies. However, the ADVISE calibration protocol and associated reference materials have not been tested widely, mainly as a result of their very recent development. Hence, a critical next step in their development is to perform a series of inter-lab comparisons involving organisations from across the range of technology providers and end-users, in order to provide confidence for their incorporation into the standardisation process. A similar exercise has been performed for the validation protocol developed in the ADVISE project, although the nature of the validation process means that some creativity will be required to generate a meaningful and productive inter-comparison exercise. There was collaboration with VAMAS TWA26 in the development of these round-robin exercises use was made of their international network of committee members.
The outputs from the ADVISE and SPOTS projects needed to be integrated into a coherent approach to the validation of the computational solid mechanics models using strain field data acquired using optical measurement systems. Such a coherent approach will facilitate the adoption of the research outputs in the design of marketable products; however the introduction of standards will provide a substantial boost to the process of innovation and to closing the gap between research and market introduction of the technology. Initial steps had been taken in the USA and resulted in a guideline for verification and validation of computational solid mechanics models that describes the requirements without providing a protocol or methodology for their achievement. The recent work in ADVISE filled this gap by providing a powerful means of quantitatively comparing data-rich strain fields and this was used the basis to create a CEN workshop agreement in order to move towards a standard for the validation of computational solid mechanics models using strain field data obtained using calibrated optical systems.
The third objective was concerned with achieving widespread acceptance of the validation protocol and associated calibration procedures in the EU industrial base and the international scientific community. International acceptance of the proposed standard is crucial for its adoption and implementation and thus, a special feature of this project was an effort to reach out to the international community and involve them in the process. Existing strong connections between the partners in SPOTS and ADVISE and members of VAMAS TWA26 were utilised as well as new contacts made at the 1st International Workshop on Validation of Computational Solid Mechanics Models held in Shanghai during October 2011 and organised by the coordinator of the VANESSA project. Similar workshops were used in the VANESSA project to accelerate the process of knowledge exchange, promote acceptance of the new concepts and encourage participation in the inter-comparison and standardisation processes. In addition, a vigorous programme of dissemination was pursued to accelerate the rate of innovation in the EU industrial base. The project included both technology providers and end-users from a number of industries, including ground transportation, nuclear and aerospace, in order to assist in this process.

Project Results:
See attached report
Potential Impact:
See attached report
List of Websites:
www.engineeringvalidation.org

Contact: Professor Eann Patterson, School of Engineering, University of Liverpool, Harrison Hughes Building, The Quadrangle, Liverpool, L63 3GH, UK

Email: eann.patterson@liverpool.ac.uk
Telephone: +44 (0) 151 794 4665