Success stories
Success stories
On-site test data analysis helps get optimized exhaust flex-joints to market faster and reduce design risk
- Automate and simplify complex test data analysis.
- Handle test data and CAE fatigue analysis within a single environment.
- Evaluate design options and change the design if necessary in the early stages of the design process.

On-site test data analysis helps get optimized exhaust flex-joints to market faster and reduce design risk
- Automate and simplify complex test data analysis.
- Handle test data and CAE fatigue analysis within a single environment.
- Evaluate design options and change the design if necessary in the early stages of the design process.


BOA Group is a leading system developer and supplier of flexible element technology, bellows, hoses and decoupling devices worldwide. Its customers include almost all European and North American, and many Asian manufacturers of passenger cars and commercial vehicles. BOA pioneered the multi-ply bellows design which absorbs thermal expansion and vibration in engine and compressor piping systems. The multi-ply bellows is manufactured from a laminated tube that consists of thin gaugestainless steel plies. This tubular body is formed into corrugations by a hydroforming process that delivers close tolerances. The use of thin gauge material combined with a large number of corrugations per unit length reduces deflection forces acting on and increases the flexibility of the bellows
Importance of physical testing
The primary purpose of physical testing for BOA is to validate the critical tradeoff between static manufacturing/assembly offset and dynamic range. The exhaust flex joint has a certain amount of flexibility, or dynamic range, which is needed to accommodate the relative motion of the engine and the exhaust system. However, the initial variation in alignment between the engine and exhaust system, called the static offset, takes up a certain amount of that dynamic range. Physical testing is needed to determine the dynamic range required by the vehicle’s operating envelope to ensure it is within the flex hose’s dynamic range.
Physical testing is also performed to determine the fatigue life of the flex joint on this particular vehicle. The required life of the flex joint might be 150,000 miles, yet there is rarely time to drive the prototype for this full distance. In any case, the life of the flex joint is determined not by how many miles the vehicle is driven but by the number and magnitude of severe loads it receives, such as when the vehicle goes over a pothole. The amount of damage produced by these events is estimated by driving a prototype with the flex joint installed over potholes, Belgian blocks, or other hazards designed to generate severe loads on the flex joint. The loads from each event are recorded by the sensors.
The damaging events are converted to stresses and strains. The vehicle OEM determines a duty cycle that defines how many of each of these damaging events the vehicle is expected to see during its warranty life. The test data is compressed and accelerated to generate a damage profile that corresponds to the OEM’s duty cycle and is used as input for a fatigue analysis that predicts the life of the flex joint.
Previous test data analysis process
Data was then converted to the proprietary format used by a fatigue analysis software package. The data conversion and manual processes caused analysis delays, so a considerable period of time was required to determine whether or not the RLDA had captured all of the necessary data. By this time everyone involved had usually traveled back from the proving ground to their offices and were often involved in other projects, hence producing further delays.

“In the past, we were working with software that was more laborious and manual for the task and had difficulty handling test data,tools like Excel and MATLAB also require considerable effort to make them work.”
Switching to new test data analysis tool
BOA also switched from its previous fatigue analysis software to nCode DesignLife which integrates with GlyphWorks to enable test data analysis and CAE fatigue analysis in one environment. BOA is able to accurately predict the failure location by using capabilities in DesignLife such as hot spot detection in 3D, stress distribution in 3D, and virtual strain gauge analysis.

“GlyphWorks is designed from the ground up for test data so it fits the task perfectly.”
BOA engineers also use GlyphWorks to perform post-processing of raw sensor data to 6 degree of freedom (DOF) relative motion data of an exhaust flex hose using complex mathematical algorithms. The data is automatically converted into reports that were defined by BOA engineers to expedite the design decisionGlyphWorks enables visualization of bellows frequency response using frequency modules making process. The reports make it easy to determine whether or not the original flex hose design has sufficient dynamic range to accommodate the vehicle’s relative motion.




Optimizing the design
Engineers have developed a custom process within GlyphWorks to generate accelerated drive files for a 6 DOF simulation used to test the part without having to install it in a prototype vehicle and run it on the proving ground. This approach can be used after RLDA is performed on a vehicle to evaluate other flex hose designs without having to re-run the RLDA.
High frequency data acquisition is also performed using a microphone inside the passenger cabin to evaluate the impact of the flex joint on noise/vibration/harshness (NVH). BOA uses GlyphWorks to process the data and perform order analysis, which involves matching the accelerometer data to the speed of the motor and makes the data much easier to interpret.
“Improvements seen from using nCode GlyphWorks and DesignLife make it possible to completely process and analyze the data more efficiently. The result is that the post-RLDA analysis can be completed in real time while the proving ground testing is conducted. Engineers that are gathered together at the proving ground can study the test data and fatigue analysis results and make decisions on the spot. If the data indicates a problem with the design, a new design can quickly be fabricated and tested, avoiding the need for another round of testing at a later date. The ability to evaluate design options and if necessary change the design in the early stages of the design process increases confidence, reduces risk and helps get products to market faster."