In common with the entire automotive industry, designers of off-highway vehicles are under ever increasing pressure to reduce program development times and costs, while at the same time meeting increasingly rigorous demands of reduced emissions and fuel consumption regulations.

For the off-highway sector those challenges are further compounded by the need to develop platforms that are versatile and robust enough to perform well across all of the many variants that will be spawned from a single base vehicle, some of which will inevitably be required to operate in challenging environments, with regard to temperature extremes, terrain, and dirt management. Finally, but most importantly of all, vehicle designers must provide a safe, quiet, and comfortable working environment for vehicle operators.

Increasingly off-highway OEMs are meeting these demands with the help of extensive engineering simulation, which helps them predict vehicle performance from early in the design process by constructing detailed virtual prototypes of the entire vehicle.

The first, and most difficult, stage in the construction of a virtual prototype is the process of pulling together all of the individual CAD parts that define a vehicle. While this used to be a labor intensive task, most OEMs have invested in comprehensive CAD management solutions that allow an operator to pull up a complete vehicle configuration, including all of the components and their material properties at the click of a button. CD-adapco is investing heavily in this process, working with major OEM’s to collect all the data, and automatically building up a simulation-ready virtual prototype of the vehicle, including every relevant component.

This is particularly challenging in the context of engine compartments, which are subjected to the highest thermal loads, and are comprised of thousands of closely packed components. Indeed, CD-adapco is developing methodologies to account for the heat transfer that occurs between parts in contact, with treatments to deal with bolting, gluing, or welding.

While CD-adapco currently provides the fastest path from CAD database to simulation results, our ultimate intention is to allow the CAD system operator to automatically generate a simulation ready geometry at the click-of-a-button, and passed directly into our simulation tool STAR-CCM+.

Once the simulation-ready virtual prototype of the vehicle is available, the possibilities for testing and improving the vehicle are endless. Most obviously, the virtual prototype can be used to predict the aerodynamic and thermal performance of the vehicle. Challenging modes of operation can be examined, by investigating the performance under extreme operating conditions.

In dirty or dusty environments, STAR-CCM+ can be used to simulate the effect of dirt ingression into the engine compartment. In hot environments the main concern is thermal management, predicting the temperature of each individual component and high loading scenarios, and ensuring that cabin temperatures can be maintained at a comfortable level for the operator. In cold environments the virtual prototype can be used to predict vehicle warmup times, as well as the freezing/thawing of urea tanks or other fluids. For agricultural vehicles, the performance of crop cutting and grain separation can be simulated.

Increasingly engineers are using such tools to understand the performance of the vehicle over entire transient drive cycles rather than a single fixed operating points. Simulation is also being used to optimize the manufacturing process, including e-coating and dipping applications.

Frederick J. Ross, Director of Ground Transportation, CD-adapco, wrote this article for SAE Off-Highway Engineering.