The Investigation of the First Order Size Effect in Micro-Plastic Forming

Abstract

With the rapid development of MEMS and electronic industry, the demands for micro-parts are increasing gradually. However, size effects make the traditional forming theories and deformation mechanism not suitable in micro forming field. In this paper, we introduced the classification of the size effects. It pointed out that the size effects can be divided into the first order and the second order size effects in the micro-forming. For the first order size effects, the theory model was established based on the surface layer model. It also clarified the phenomenon that flow stress of the blank reduced with the increase of the ratio of grain size and thickness (t decreases or d increases). Finally, the model was verified with the experimental results of the first order size effects in the references, confirming the effectiveness of the theoretical model. It provides a method to theoretically and experimentally study the micro-plastic forming.

Effect of Emission Points on Ultrasonic Testing Accuracy of Log Internal Decay

“…Therefore, how to detect the log internal decay effectively and accurately is significant to protect our forest resource and to reduce property damage. From previous research results [3,4], it is known that the ultrasonic wave can detect log internal defect quantitatively by searching the ultrasonic paths that are tangent over the edge of the defect according to the principles that the velocity of ultrasonic wave will decrease when it passes through deficiency [5]. Based on this, the relationship between the number of ultrasonic emission points and the detection accuracy of log internal decay was analyzed in this paper, which could provide some reference value and theoretical basis to further log grading and reasonable bucking as well as the accurate detection of internal defect in wood materials [6].…”