Planetary vertical concrete mixers: Simulation and predicting useful life in steady states and in perturbed conditions

A simulation environment for the dynamics of a concrete mixers has been developed. The mixer is a batch type with a vertical axis. The working rotation motion is planetary and its aim is to physically and chemically mix multiple components in order to make a homogeneous mixture. Actually the mixer distributes all the constituents uniformly in the tank without favouring one or the other. In this paper, a description of the fundamental components of the machine is given followed by the development of a model based method that focuses on the most stressed part of the mixer: the gear reduction unit. On the basis of this model a simulation environment was developed with the aim of evaluating the useful life of a mixer using the lumped parameters analysis and integrating the theory of classical mechanics and life analysis. In addiction a test rig, reproducing working conditions was built to make experimental simulations using destructive tests to evaluate the useful life of mixers. Experimental tests are expensive and accidents are almost impossible to reproduce. Therefore, the early detection, diagnosis, and prognosis of gear-tooth fatigue cracks has always been one of the major technical challenges for safe and cost-effective operation of concrete mixers. The aim of this work is to give a fast and easy to use tool capable of predicting the behavior and the useful life of concrete mixers through geometrical and physical parameters. Simulations were conducted in steady states and in perturbed conditions. Results were compared with data obtained from costumers on building sites.