Mass Axial Moment of Inertia

Overview

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Goals

The goal is to determine the mass axial moment of inertia of a body of any shape by using SOLIDWORKS application and experiments.

Learning Objectives

At the end, the students will: • know why it is necessary to know the value of the sought characteristic of each body which rotates; • be able to determine the mass axial moment of inertia by using SOLIDWORKS application ; • acquire experience how to jointly use experimental equipment and specialized software.

Context

In our daily life we come across bodies which rotate – from household devices such as washing machines and blenders to a great number of machines which have very large dimensions. Defining the mass axial moment of inertia plays a key role in the correct design of the rotating parts. Have you ever wondered how skaters spin at a high speed around a fixed axis defined by their own bodies and then suddenly stretch their arms and ….. stop spinning for a very short time? Indeed they change that characteristic of bodies in real time. Actually by stretching their arm, they considerably increase it. With bodies of regular shapes (cylinders, spheres and tubes), there are relatively simple formulae by means of which the mass moment could be calculated. However, in real life rotation or spinning is done by bodies of irregular shapes or by non-homogeneous bodies (car tires, washing machine drums or cutting heads of coffee grinders). Here come two approaches. The first one is to determine the moment of inertia by an experiment. It is based on the law of a body rotation around a fixed axis, applied to bodies of complex shape and bodies of regular shapes. The idea is that we can define the sought characteristic by measuring the oscillation periods of a reference body and a body of an unknown shape and consequent comparison of those values. The second one uses a specialized CAD application – SOLIDWORKS. To determine the axial moment of inertia, it is necessary to build the geometry of the body of a complex shape, to set the material it is made of and to apply a calculation procedure