Static and Dynamic Study of 4-Cylinder Diesel Engine Crankshaft using FEM and Analytical Approaches 2016-28-0108

Crankshaft is one of the critical components of an engine (5C: cylinder head, connecting rod, crankshaft, camshaft and cylinder block). It is subjected to repetitive and dynamic loads due to cyclic operation of an engine, inertia forces due to uneven mass distribution with failure zones as fillets and holes in journal locations. Fatigue is most common cause in failure of the crankshaft. Its failure will cause serious damage to the engine so its reliability verification must be performed. The load is applied as per the firing order of the cylinder for 2 revolutions of crankshaft, to cover firing condition of each cylinder. Loads with respect to crank angle or time are applied at respective locations and results are taken on 360 steps for 2 complete revolutions of crank.

The topic was chosen because of increasing interest in higher payloads, lower weight, higher efficiency and shorter load cycles in crankshaft equipment. The present study emphasizes on a CAE based approach for development of crankshaft right from the conceptualization phase. The analysis includes determination of free vibration shapes to adjust the various modal parameters, bending and torsional stiffness analysis for each crank throw, and the SCF (Stress Concentration Factor) calculation to know the localized stress at the web fillets. On the basis of the analysis various design parameters of crankshaft are determined and the dimensions and layout of the neighboring crank-train components are also finalized.

Next, transient analysis was performed on the complete crank-train assembly with flywheel and pulley to deduce the stress distribution pattern at critical locations. The P-θ (Pressure - Crank Angle) diagram was used to calculate the load-cases for dynamic analysis. The stress results obtained from transient analysis is used as input for fatigue solver FEMFAT to evaluate the fatigue life of the crankshaft.