A Study for the behavior of mechanical property around through defects on the thin tube

Abstract

Background/Objectives: This paper is to investigate the mechanical properties occurring around the penetration defects when the bending moment acts on the thin tube. 

Methods/Statistical analysis: We analyze the stress occurring when a holepasses through a thin tube with regularly arranged tubes of different diameters using the finite element analysis, which is a numerical analysis technique. The hole was treated as a micro-defect. We calculated the maximum stresses in the case of no micro hole and micro hole, and analyzed the influence of the through micro hole by comparing the ratio of the maximum stresses.

Findings: The stress ratio is the same or slightly decreased even if the displacement increases at 0°. Based on this result, the result was obtained that the stress concentration effect is hardly observed even when there is a micro circular hole at 0°.When the twist angle was 0.03°, the stress ratio was 13 or more when the displacement was small. As the displacement increases, the ratio of the stress decreases sharply, and when the displacement exceeds 5 mm, the difference of stresses between the cases with and without defects is not very large. The displacement with the maximum stress ratio gradually decreases with increasing displacement. When the torsion angle is 0.21 or more, it is seen that the stress value increase is low even if there is a micro circular hole. In the presence of defects, the stress is larger than the case where there is no defect as a result of the prediction. When the deformation amount is less than 9 mm, the difference of the maximum stress depending on the presence or absence of the defect is increased. However, when the deformation amount is more than 9 mm, the difference of the maximum stress is not large.

Improvements/Applications: It can be used to reveal the reason of the damage of the defect material and to study the damage prevention technique.

Keywords: Stress Ratio, Through Micro Hole, Torsional Angle, Finite Element Method, Fatigue.