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An FEM Based Approach to Crankshaft Dynamics and Life Estimation
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English
Abstract
Crankshafts developed wide applications even before methods to design them got evolved. Initially, they were assumed to be made up of beam segments. Since, the length to width ratios of the segments are of the order of one, these methods were not effective. Therefore, till recently they were designed based mostly on in-house experience and by using empirical formulae. Of late, with the advent of powerful computers, analysis based on finite element method has come into use for crankshaft design. In this work, we generate, from fundamentals, a systematic procedure to design crankshafts for finite life.
Our method uses the advantages of both the classical method and the finite element technique. For the initial and the approximate results, we use the classical method. A software developed, TVAL, based on this method, quickly gives the natural frequencies, critical modes, displacements and stresses. For more accurate results, we model the crankshaft using solid finite elements. The simulated boundary conditions represent both radial and bending stiffnesses of the bearings, which have a large effect on crankshaft dynamics. Time varying radial and tangential forces acting on the crankpin are derived from the cylinder pressures. The model considers the effect of dampers. We find out displacements and stresses at all locations of the crankshaft using the mode superposition method. Stress concentration factors (SCF) are found out by a method based on zooming. We use an engine duty cycle for generating stress histories for accelerated fatigue testing. We conduct rainflow counting on thus obtained variable stress-time history. Life is estimated by assessing the damage by the Miner's rule. We have also discussed variation of lives of crankshafts due to changes in their material properties. Results of analysis of crankshafts belonging to three different classes of engines are presented here.
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Citation
Prakash, V., Aprameyan, K., and Shrinivasa, U., "An FEM Based Approach to Crankshaft Dynamics and Life Estimation," SAE Technical Paper 980565, 1998, https://doi.org/10.4271/980565.Also In
References
- Bargis, E. Garro, A. Vullo, V. 1980 a Crankshaft Design and Evaluation - Part 1: Critical Analysis and Experimental Evaluation of Current Methods Conf. on Reliability, Stress Analysis and Failure Prevention in Mechanical Design ASME International 191 201
- Bargis, E. Garro, A. Vullo, V. 1980 b Crankshaft Design and Evaluation - Part 2: A Modern Design Method: Modal Analysis Conf. on Reliability, Stress Analysis and Failure Prevention in Mechanical Design ASME International 203 211
- Nagamatsu, A. Nagaike, M. 1981 Vibration Analysis of Movable Parts of ICE: Part 1 - Crankshafts Bulletin of JSME 24 2141 2146
- Nagamatsu, A. Nagaike, M. 1983 Vibration Analysis of Movable Parts of ICE: Part 2 - Combined System of Crankshaft and Flywheel Bulletin of JSME 26 827 831
- Bagci, C. Falconer, D. R. 1981 Critical Speeds of Multi-throw Crankshafts using Spatial Line Element Method The Shock and Vibration Bulletin, Analytical Methods, Dynamic Analysis and Vehicle Systems 51 25 41
- Bagci, C. Rajavenkateswaran, S. K. 1987 Critical Speed and Modal Analysis of Rotating Machinery using Spatial Finite Line Element Method Proc. of the 5 th Int. Modal Analysis conference II
- Swanger, L. A. Harris, D. Johnston, P. Derbalian, G. 1986 Advanced Methods for Diesel Component Life Prediction Trans. of SAE, 860885 71 78
- Kim, H. Choi, K. 1991 Crankshaft Stress Analysis Procedures in the Engine Design Proceedings of 6 th International Pacific Conference (SAE), 912489 Oct. 28 Nov. 1 313 319 Seoul
- Vadiraj M. R. Prakash V. Venkatesh D. N. Shrinivasa U. 1996 “Crankshaft Equivalent Length Determination - An FEM Approach” SAE paper no. 961013
- Chen, S. K. Chang, T. 1986 Crankshaft Torsional and Damping Simulation - An Update and Correlation with Test Results Trans. of SAE, 861226 4.964 4.984
- Shimoyamada, K. Iwamoto, S. 1991 A Numerical Simulation Method for Vibration Stress Waveforms of High-Speed Diesel Engine Crankshaft System Proc. of 6th Int. Pacific Conf.(SAE), 912489 Oct. 28 Nov. 1 313 319 Seoul
- Prakash V. Venkatesh D. N. Shrinivasa U. 1994 “Effect of Bearing Stiffness on Crankshaft Natural Frequencies” SAE paper no. 940697 , SAE 1994 Transactions, Journal of Engines 103 1291 1304
- Carrato, P. J. Fu, C. C. 1986 Modal Analysis Techniques for Torsional Vibration of Diesel Crankshafts Trans. of SAE, 861225 4.955 4.963
- Thomson, W. T. 1982 Theory of Vibration with Applications Prentice Hall of India 2nd New Delhi
- Cameron, A. 1971 Basic Lubrication Theory Longman Group Limited London
- Den Hartog, J. P. 1956 Mechanical Vibrations 4th Mc Graw Hill Book Company New York
- ASTM standard