Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
All trucks produced by Scania are provided with multiple sensors to support various functionality, collecting Controller Area Network (CAN) data from the truck at all times. With this operational data, Scania is able to analyze the usage of the trucks and perform relative comparisons between populations of vehicles. With this it can be concluded if a population of vehicles in one country is used in a more demanding manner than a population of the same vehicle type in another country. Using relative comparison, a general understanding of the usage of the trucks can be obtained. Operational data is also very useful when trying to estimate the load variability, which requires a significant amount of measured samples. Cornering and manuevering are currently not analyzed, since no single sensor have been identified that could serve as a proxy for loads on the vehicle due to such events.
The thesis was constructed with the aim to use operational data for estimating the fatigue damage to the basic chassis caused by curves and maneuvers. It included multi-body simulations as well as physical measurements on both test track and public roads. After the measurements, the data was analyzed with the aim to find a correlation between the frame and the maneuvering, and find a way to describe the correlation with an equation. From the measurements results it could be concluded that there was a clear correlation between the steering angle and strain, showing a similar behaviour for all maneuvers. It was also concluded that the relative change in strain amplitude as a function of the bogie weight was independent of the maneuver.
From the obtained data, showing the behaviour between steering wheel angle and strain, Hans B Pacejka's formula, "the magic formula", could be adapted to represent the strain data, using the steering wheel angle and the bogie weight as input parameters. The formula did not correspond well for all sensor; however, as it was relative damage that was to be determined the formula only had to have the correct behaviour with a scale factor to give the correct results when analyzing the damage.
The adapted formula could estimate the relative damage for the sensors on the front of the chassis (second crossmember and lower flange) relatively well. However, for the sensors in the rear (upper flange and side member web) the formula did not estimate the relative damage as good, especially for maneuvers performed in higher velocities. It was found that the lateral acceleration will impact the strain amplitude for maneuvers in higher velocities, and therefore affect the measured strain in the sensors closer to the fifth wheel. It was also noticed that the formula could not estimate the relative damage when driving on a different road surface than pavement, as the road surface friction is not part of the operational data.
To conclude, the formula should be further investigated and might need to include lateral acceleration in a second term. It is also of most importance to choose populations when performing relative comparison wisely, as the road conditions has to be similar. Lastly, the vehicle configuration should also be evaluated. As of now, there is not known how the vehicle configuration will affect the formula as only one vehicle was used during the measurements.
2023.