Cyclic Biaxial Stress Measurement Method Using the Grain Growth Direction in Electrodeposited Copper Foil

Yuichi Ono,Cheng Li,Daisuke Hino

doi:10.1155/2010/928216

Yuichi Ono, Cheng Li + Show 1 more

Open Access

https://doi.org/10.1155/2010/928216

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Abstract

A method that uses grain growth direction in electrodeposited copper foil to measure cyclic biaxial stress is examined in this paper. The grain growth direction is measured by image processing software after a cyclic loading test for various biaxial stress ratios is carried out. Since the grain growth occurs in two directions and its directions correspond closely with the direction of maximum shearing stress when the biaxial stress ratio is negative, the principal stress can be measured using Mohr's stress circle. On the other hand, when the biaxial stress ratio is positive, above-mentioned feature does not occur. Therefore, the first principal stress can be measured based on the grain growth density. The number of grains necessary to measure the biaxial stress is estimated by a statistical approach.

Highlights

The copper electroplating method is used to measure cyclic stress that causes metal fatigue [1,2,3]
If copper foil adhered to a machine element is subjected to repeated loads, grain growth occurs in the copper foil
The maximum shearing stress directions Θ∗ obtained by substituting the values of Table 2 for (3) and (4) are shown in Figures 9(a) and 9(b)

Summary

Introduction

The copper electroplating method is used to measure cyclic stress that causes metal fatigue [1,2,3]. Since the grain growth density is controlled by the maximum shearing stress and the number of cycles, the maximum shearing stress can be measured based on the grain growth density in the prescribed number of cycles [4] This method has the advantage of detecting stress in microscopic regions like the stress concentration region. Since the principal stresses that are important for evaluating metal fatigue cannot be detected by this method, a new method using copper foil with circular holes has been developed [4, 5] This new method is somewhat complex, because the grain growth length at hole edges as well as the grain growth density in the copper foil must be measured. This means that two kinds of copper foils (foil with and without circular holes) are necessary for the principal stress measurement

Methods

Results

Conclusion