With supercomputers becoming more and more powerful, the magnitude of the simulations and analyses car manufacturers can perform to test new model concepts and designs is rising dramatically. The results include reduced vehicle development times and better optimised solutions, as Anna Kochan reports.

The more powerful a computer, the faster it solves problems. The car industry has been among the first to take advantage of each new generation of more powerful computer to arrive on the market. Initially, crash test simulation was the main application. More recently, as their power has increased, supercomputers have taken on new roles in simulating fluid dynamics, in and around both the car and the engine. The growth rate in the use of these techniques has been phenomenal and new applications are expected to appear in the future.

'Ford has increased its use of supercomputer resources by 50% every year for the past 20 years and will maintain this growth for the foreseeable future,' comments Dr. Gerhard Zellerman, supervisor for vehicle CAD systems at Ford in Cologne. Today, 60% of time spent on computer simulation at Ford relates to safety issues, and the remainder is split between durability and stiffness, and noise and vibration testing.

By the end of the 1970s, Ford had installed its first supercomputer and now operates four at its Cologne, Dearborn and Dunton sites as well as at Jaguar. 'In the beginning, we introduced a supercomputer because the software was available to do CAE (computer aided engineering) simulations which could not be performed any other way,' adds Dr. Zellerman.

The type of CAE simulation to which Dr. Zellerman is referring concerns, for example, a crash test. Historically physical crash testing has been the only way to investigate how a new design behaved during an impact. Today, due to major progress in computer technology, many crash tests can now be performed in the virtual world. This is a major advantage to the automotive industry as ever more stringent safety regulations are imposing greater demands on car companies to test out different forms of impact. The list of tests now includes front impact, side impact, rear impact, oblique impact and car-to-car impact.

The software to perform crash simulation has been available for at least 15 years. The limiting factor has always been computing power. The volume of computation involved in some CAE simulations is so high that the time to complete the simulation becomes too long for it to be worthwhile. With a higher power computer, which is essentially what a supercomputer is, the simulations can become more complex, more detailed and faster. 'When the first crash analysis was done in 1986, the simulation model was very crude because so many assumptions had to be made to keep it within a manageable size,' says Kevin Fox, applications analyst at Silicon Graphics. The models that can be handled today are 60-100 times more detailed, he estimates.

The supercomputers of today are so powerful that they can analyse the fluid flow inside an engine compartment whereas previously it would have been too time consuming to look at anything more complex than a simple duct,' adds Dr. Anthony Baxendale, head of fluid dynamics engineering and research at the UK's Motor Industry Research Association (MIRA) in Nuneaton.

Most large car companies have already invested in supercomputers. In fact, among the top 500 supercomputers in the world today, 11 are installed at sites belonging to car manufacturers. All except two were supplied by Silicon Graphics. Top of the automotive league is Toyota, followed by Audi, GM, BMW, Ford (2) and Nissan, in that order. According to the list, which can be found at www.top500.org, the remaining four are in Japan at un-named companies.

Over the past five or six years, vehicle manufacturers have assessed the usefulness of supercomputers in their research on future techniques departments. It is, however, only recently that they have started to incorporate supercomputer-based analysis into the vehicle development process because it is only recently that simulation run-times have become short enough.

'Car companies want to be able to simulate very large problems early on in the development cycle, and to do it quickly. The only way is with supercomputers. If they can simulate a problem accurately and quickly enough, they can take a lot of cost and risk out of the whole development process,' MIRA's Dr. Baxendale believes.

As a result, the vehicle manufacturers are now re-engineering their whole development process to give simulation techniques an integral role, he comments. While most of the large manufacturers are advanced in this area, Dr. Baxendale says that some have recognised its role in the development process more than others. He highlights GM and Ford as being among the leaders. 'GM has just reviewed how simulation should be integrated into the development process,' he reports. Rover is currently carrying out a similar assessment, he adds.

The benefits a vehicle manufacturer can expect to obtain from the latest computer simulation techniques are varied. It is, however, difficult to assess whether the ability to crash test cars in a virtual world actually reduces the need for physical crash tests, which at an estimated $500,000 a smash, is a very expensive process. Pierre Culière, product manager for design products at French software company ESI, believes that at least the number of generations of physical prototypes is falling. 'In a three-year vehicle development cycle, there is no time for building prototypes and crashing them throughout,' he says. However, the average car company is still crash-testing cars at the rate of at least one a day, he estimates. Ford's Dr. Zellerman talks of claims that computer simulation cuts down the number of physical prototypes by 30% on a vehicle programme compared to the planned number but he is extremely sceptical about them. 'You don't know how they arrive at the planned number,' he says.

More important to the car manufacturer is the benefit the computer simulations bring to design optimisation. 'We analyse ten times more different designs than if we did not have computers,' Dr. Zellerman states. In addition, the actual task of developing the theoretical model that is going to be subsequently simulated by computer leads to a better understanding of how the design works and performs, which is quite an advantage in the long term, he believes.

MIRA's Dr. Baxendale also suggests that advanced computer simulation techniques lead to a greater potential for innovation. 'Before using such techniques, car companies used to evolve new designs from old designs that they knew worked. It was quite a successful approach but did not allow for innovation. The market leaders have to do more than just evolve if they are to maintain a competitive position.'

Simulation can also lead to time savings. 'Without it, vehicle companies would not achieve the timescales they are currently targeting,' adds Culière. For the three supercomputers Mitsubishi has installed in Japan over the past six years, the major advantages claimed are improved product quality and faster product development.

While crash testing is the most widespread application of high level computer simulation today, one of the fastest growing areas is in the modeling of fluid flow. 'A very interesting simulation to do is the air flow within the engine compartment to help develop the cooling system,' says Dr. Baxendale. Another application is the simulation of the air and fuel mixing process inside the engine to improve the combustion process, adds Dr. Kent. These calculations are more complex than those involved in crash test simulation because they are non-linear and very dynamic. As a result, they are pushing even today's supercomputers to their limits.

Ford's current hot supercomputer topic is advanced airbag simulation. 'We have simulated airbag deployment for many years. What is new is to simulate the interaction of the airbag with its environment,' says Dr. Zellerman. The goal of this work is to be able to tune the power of the airbag and the force of the seat belt restrainers to the size and weight of the passenger, and thereby minimise injury. Solutions are currently in development.

Also under development are simulation models for assessing pedestrian impact. This is the subject of new legislation being introduced and all car companies are having to look at ways of dealing with the issue.

A growing interest in using high level computers to optimise forging and metal forming processes is reported by Dr Tony Kent, business development manager (UK) at MSC (MacNeal-Schwendler Corporation). He says that, until recently, the mathematical technology was not available to simulate the flow of metals but that the first applications to optimise con rod and crankshaft production processes are being implemented. 'These are non-linear, transient dynamic processes which require the power of a high level computer to model. Car companies are looking to model the forging process in order to minimise the quantity of material in the initial billet and also to better master the flow of the material to ensure that it goes to where it is needed, and only there,' Dr. Kent explains.

MSC/Superforge, the software package MSC has recently developed for 3D simulation of forging operations, is currently being evaluated by a number of major engine manufacturers, Dr. Kent says. By replacing the trial and error methods traditionally used for process and die design, Superforge is designed to help manufacturers reduce time to market and increase profitability.

The pressing of body panels is another area that Ford's Dr. Zellerman anticipates new developments in computer simulation. 'It would be helpful to use computer models to better understand the material flow that takes place during the pressing of a flat blank into a shaped panel. The benefits would mainly be in tool design,' he says.

While Ford continues to develop supercomputer applications in new and varied areas, Dr. Zellerman is still concerned about the time that some of the existing applications take to run. 'Our target is to do simulations that can be completed within a day. However, many of the noise and vibration models are complex and may take a whole weekend to run. If it is longer, we cannot use the application on a production basis,' he says.

Flow simulation is the application which most frequently comes up against this time limitation. The applications which suffer are therefore vehicle aerodynamics, engine cooling and combustion. The solution could be found by replacing the supercomputer with a workstation clustering system which has been developed through a European Community Esprit project. Workstation clustering is not yet mature technology. Software is not yet available for it because of the few number of users. Dr. Zellerman believes it will take up to another two years to become a practical viability. Meanwhile, Ford is to investigate what the benefits would be. 'We have not yet looked at the cost implications but we are really mostly interested in saving time. If we could do in a day the type of flow simulations which would otherwise take three or four days, then it would be worthwhile,' he concludes.

Meanwhile, high level computer technology and applications software are also evolving to improve the viability of complex simulations. 'Crash simulation techniques still need to become faster,' says Pierre Culière. 'The overnight run-times we can achieve today are quite good. However, this is still quite long if a company wants to do multiple simulations covering a range of designs,' he says. As a result, ESI is developing massively parallel versions of its crash test software. Last month, the company announced a new parallel version of PAM-CRASH, a software that ESI claims is already used by 80% of automotive manufacturers worldwide. With this new version of the software, it will be possible to cut down the simulation run-time by using more processors. 'With 16 processors instead of one, the speed of the simulation can be increased by a factor of more than 12. So, with 100 processors, a really significant improvement can be achieved,' Culière expects.


This article was kindly provided by World Automotive Manufacturing, an FT Automotive publication.

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