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Nienhuis, Michael D.
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Random Vibration Fatigue Life Assessment of Transmission Control Module (TCM) Bracket Considering the Mean Stress Effect due to Preload

General Motors LLC-Neeraj Carpenter, Sudeep Yesudas, Michael D. Nienhuis
  • Technical Paper
  • 2020-01-0194
To be published on 2020-04-14 by SAE International in United States
Transmission Control Module (TCM) bracket is mounted on the vehicle chassis and is subjected to the random load excitation due to the uneven surface of the road. Assembly of the TCM bracket on the vehicle chassis induces some constant stress on it due to bolt preload, which acts as a mean stress along with the varying random loads. It is important for a design engineer and CAE analyst to understand the effect of all sources of loads on vehicle mount brackets while designing them. The objective of this study is to consider the effect of mean stress in the random vibration fatigue assessment of TCM bracket. The random vibration fatigue analyses are performed for all the three directions without and with consideration of mean loads and results are compared to show the significance of mean stresses in random vibration fatigue life. It was found from this study that mean stress affects the vibration fatigue life and it can increase or decrease the fatigue damage depending upon the nature of the mean stress.
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Simulation Methodology to Analyze Overall Induction Heat Treatment Process of a Crank Shaft to Determine Effects on Structural Performance

General Motors LLC-Nilankan Karmakar, Anoop Retheesh, Pankaj Kumar Jha, Michael D. Nienhuis
  • Technical Paper
  • 2020-01-0506
To be published on 2020-04-14 by SAE International in United States
Steel crankshaft are subjected to an induction heat treatment process for improving the operational life. Hence, to predict the structural performance of a crankshaft using Computer Aided Engineering early in the design phase, it’s very important to simulate the overall induction heat treatment process. Metallurgical phase transformations during the heat treatment process have direct influence on the hardness and residual stress. The objective of this study is to establish the overall analysis procedure, starting from capturing the eddy current generation in the crank shaft due to rotating inductor coils to the prediction of resultant hardness and the induced residual stress. In the proposed methodology, an electromagnetic analysis is performed first to capture the Joule heating due to the surrounding inductor coil carrying high frequency alternating current. Then coupling is done between the electromagnetic and thermal analysis to capture the resultant temperature distribution due to the rotation of the inductor coil by a novel approach. Subsequent quenching operation is simulated then to capture the metallurgical phase changes and hardness using a python subroutine based on continuous…
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Fatigue Tests of Un-Notched and Notched Specimens and Life Prediction Using a Variable Critical Distance Method

General Motors-Neeraj Carpenter, Pankaj Jha, Sudipto Ray, Michael D. Nienhuis
Published 2019-04-02 by SAE International in United States
Fatigue is one of the most common failure mechanism in engineering structures. The statistical nature of fatigue life and the stress gradient are the two challenges among many while designing any component or structure for fatigue. Fatigue lives of the identical components exhibit the considerable variation under the same loading and operating conditions due to the difference in the material micro-structures and other uncontrolled parameters. Stress concentration at the notch causes stress gradient and therefore, applying the plane specimen results for actual engineering components with notches does not give quantitatively reliable results if the stress gradient effects are not considered. The objective of the work presented here was to carry out the fatigue tests of un-notched, U and V-notch specimens which were die cast using aluminum alloy (A380) and to obtain fatigue life using a variable critical distance method which considers the stress gradient due to the notch geometry. Specimens were prepared in the foundry shop in a way to minimize the microstructural variations and a radiography study was carried out to ensure that cast…
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