2016 Volume 65 Issue 10 Pages 745-751
Mass moment of inertia is an important criterion in rating a performance of mechanical systems with rotational motion. In fact, moment of inertia of actual products may be different from design values because manufactured products are uneven. In injection molding, it is important to detect voids occurred after injection process to eliminate inferior products. Even in non-defective products, moment of inertia may vary over time due to factors such as spoilage, corrosion, and drying. In order to improve the inertia moment of the product, the weight and the shape must be modified. Therefore, it is important to evaluate mass distribution and internal shape nondestructively from the view point of quality assurance. Mass distribution and internal shape can be investigated by cutting, but such a destructive method is effective only for sampling inspections. The author proposes a new non-destructive method evaluating mass distribution in the entire component of portable solid even though material densities and dimensions are unknown. In this method, mass distribution is estimated by an inverse analysis from mass moments of inertia measured at several rotational axes nondestructively. Voids in a body can be detected by this method because estimated values at voids become zero. Note that density distribution is also evaluated from estimated masses and the shape. In this study, a new concept estimating mass distribution was shown theoretically. As well, numerical simulations for butt-cylindrical rods were carried out to prove the effectiveness of this method. Furthermore, estimation accuracy of this method was improved using the response surface methodology without any additional measurements of mass moment of inertia.
