The paper presents a comprehensive method for the elastodynamic analysis of mobile mechanical systems, based on the finite element method. Using Kane’s algorithm, which is employed in the dynamic analysis of mechanical systems with rigid bodies, a method is developed that, by superimposing the rigid body motion over the one of a deformable body, allows to identify the kinematic and dynamic components of the matrices involved in the motion equations namely, the mass matrix, stiffness matrix, damping matrix, and the force vector acting on the system. The method is applied to a high-speed mechanism used for actuating an internal combustion engine with three in-line pistons. Within this method, each kinematic link is considered as a finite element, with corresponding reference frames for which the kinematic and dynamic components of the matrices involved in the motion equations are determined. To solve the differential equations system, a modal superposition method is applied, which enables the decoupling of the equations and to identify the time-varying diagrams for nodal displacements, both longitudinal and transversal displacements, and consequently to determine the accelerations of the kinematic links, which are useful in vibration analysis. The strength force is considered the force exerted by the gas on the piston head, which was experimentally determined under laboratory conditions. The theoretical results obtained are validated through virtual prototyping and experimental tests.

The paper takes a view on different solutions for rotary engine, such as Mallory and Kaeurtz engine, focusing on Wankel engine. For this one is presented the mathematical background used at inner stator curve, based on peritrochoid or epicycloid curve. The authors makes a cinematic analysis for a triangular rotor, using Autodesk Inventor, in conjunction with a two lobs curve at stator. It is mention another case for a rotary machine, with a rectangular rotor which runs in a curve with three lobs, that can be applied at compressors. The study goes further with a similar analysis for a rotary engine with a pentagonal rotor, which rolls in peritrochoid with four lobs. The simulations allows a comparative study between triangular and pentagonal shape rotor, emphasis the influence of constructive parameters on the expected efficiency of the engine. As a main conclusion the last solution is an interesting application that can be further developed for an experimental engine.

The paper presents a method for obtaining the power of thermal source, based on finite element approach, when the temperature distribution is known from an infrared image. The method is solving for the load vector, and extracts the power at element level from this vector.