The Power of Virtual Product Development

Traditional design and verification procedures to develop or improve components and systems for off-highway vehicles often can be time-consuming, costly and, in some cases, physically impractical. Typically, many disciplines will be involved from concept to launch and the number of prototype and test iterations can be staggering. All these challenges have helped accelerate marketplace competencies associated with virtual product development (VPD).

Looking at off-highway drivetrains as a casebook example, VPD technologies have been successfully applied to maximize efficiency, streamline development processes, and increase the reliability of transmissions and gearboxes, final drives and differentials, and hybrid systems.

Advanced simulation tools have additionally been introduced to calculate drivetrain efficiency by accurately simulating gearboxes, power take-off units, and final drives:

• A “virtual test bench” offers the capabilities to analyze rotating parts virtually while they are in the design stage.
• Test strategies can be engaged to verify designs and evaluate the performance of components in prototypes.
• Systems can be modeled using unique computer tools.

Faced with legislation requiring significant reductions in CO2 emissions over the next decade, off-highway OEMs strive for opportunities to improve energy efficiency. A primary area of focus is the vehicle’s driveline. Comprised of complex, interrelated systems — transmission, power take-off unit, and final drive — the driveline holds significant potential for improving overall vehicle efficiency and reducing CO2 emissions.

Using proprietary SKF software called Orpheus, engineers at SKF are able to calculate the efficiency of gearboxes, power take-off units, and final drives. With new Vehicle Environmental Performance (VEP) software, SKF is now able to factor in driver behavior under various operating conditions to quickly and accurately assess potential for real-life CO2 emission reduction. This is an important tool for OEMs and suppliers, because it provides the capability to explore the merits of various design options virtually. Then, the final design can be optimized prior to prototyping.

Simulating bearings and systems

SKF has been developing simulation tools to analyze bearings and bearing systems for more than 45 years.

The first tools focused on an accurate representation of a bearing and were inherently limited by available computational power. In the 1960s and 1970s, models focused primarily on two rigid bodies in contact and were compared with mathematical theories and experiments. This led to the development of a complete bearing model in the 1980s, in which many contacting elements were combined in a single model (bearing rings and rolling elements). These first models were restricted to steady-state calculations and lacked an accurate rolling element retainer (bearing cage). Subsequently, specialized test rigs were constructed to validate unknowns such as bearing dynamics.

Today’s simulation tools have paved the way for unprecedented representations of bearings and complete systems. SKF’s proprietary virtual simulation technology (called BEAST, for Bearing Simulation Tool) illustrates the progress.

Rolling elements form the bridge between rotating and static parts and are often a key element for the behavior of the complete application. The dynamic phenomena that occur in rolling bearings require specialized simulation tools for evaluation. Bearings are inherently challenging to model accurately, due to non-linear behaviors. These behaviors are a function of the infinite number of contact possibilities resulting from the rolling element to ring contacts (and many other influences, such as bearing operating clearance and preload, among others).

To develop an accurate and validated model, many components must be represented. Complex boundary conditions also must be considered, because bearing performance is highly dependent on the application and operating environment.