Abstract

Elasticity distributions in structure is one of the typical physical quantities that it is desired to measure nondestructively. Indentation testing is a useful method for the nondestructive measurement methods; however, devices are necessary to evaluate the distribution of elasticity. In this report, a technique to evaluate the elastic distribution in solid is introduced by the information obtained from a simple indentation device. The evaluation is based on Hertzian contact theory that is applied to calculate elasticity from force measured by this indentation device. However, the non-uniform nature of elasticity distribution makes it difficult to apply Hertzian theory. As a solution to this difficulty, a correcting method of elasticity is discussed by analyzing the variation of force information obtained from the device. This correction depends on the method for determining the correction factor decided by the area of elastic range distributed in the solid; this decision is numerically defined by finite element method (FEM). The usefulness of this correction method is confirmed by evaluating the hardness distribution of wood grain. Trees are a representative material with hardness distribution, whose mechanical characteristics depend deeply on wood grain. Therefore, evaluating the ability of elasticity distribution in wood grain has been checked by the correction method discussed in this report. Then, for the problem related to evaluation based on basic Hertzian theory, the expected result can be obtained using wood grain size coefficient and the specification of the probe. However, it is also necessary to examine to the choice of device specifications such as probe dimensions because the elasticity of wood is relatively high and any measured information will have high sensitivity in elastic analyses. Those recommendtion are discussed by showing the devices developed for this evaluation in this report.

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