Comparison of Analysis and Measurement Results for a ST1530 Loader Regarding Dynamic Behavior of Engine Cradle

Sammanfattning: This thesis is a measurement evaluation type of project in which to perform a harmonic response analysis were the results will be compared to measurement data to verify if the ANSYS model is realistic in terms of dynamics. This includes proposing the different parameters that will affect the results of the comparison as well as how to improve further models. In 2014 Atlas Copco received a special customer order of a ST1530 loader with a Detroit engine instead of a Cummins engine which is commonly used in the ST1530. New dynamic analyses had to be performed by the Applied Mechanics Group, regarding harmonic response using data from a measurement of a ST1520 loader with a Detroit engine. A new design of the engine cradle was developed after several analysis iterations. In February 2015, new measurements were performed on the loader with the right Detroit engine and a new engine cradle. There are two different comparison tools/methods used in this thesis, one that consists of comparing the difference between the mean average value of both the ANSYS and the measurements results. The other tool/method is more accurate since it compares both the variation between the peaks and also the offset of the frequency. Results show that the measurement results in 800 rpm were very compatible with the analysis results in ANSYS, meanwhile at high speed the measurement results were only moderately compatible with the analysis results. The vibration in 800 rpm doesn’t exceed the Atlas Copco rule of thumb as opposed to the 2173 rpm. This is only considering the cradle, the cooler however consists of higher vibrations than the measurement data. Their rule of thumb is defined as a boundary for the maximum allowable vibration values. The model could’ve been a lot more accurate if the use of CAD models of both the engine and the cooler were implemented in the analysis. This is desirable but it does not work all the time as companies for these products can not issue a CAD model due to, e.g. Patents and such.