Influence of thick-walled cylinders length on the residual stresses generated during the single-cycle mandrelling

V F Skvortsov,A B Kim,A O Boznak,A Yu Arlyapov

doi:10.1088/1757-899x/91/1/012054

Abstract

The paper presents methodology and results of experimental study by Sachs method the effect of length of mandrelled thick-walled cylinders made of steel grade 50 (0.5% C) with 5 mm diameter hole, outer diameter of 15 and 25 mm on residual stresses. Based on the review of studies, it was noted that this effect may be both due to uneven process of mandrelling along the cylinder length and due to zero axial residual stresses on its faces. It was found that the length of cylinders has the strongest influence on axial residual stresses. With allowances between 0.9 and 7.1% and length reduction from 40 to 10 mm, the largest absolute value of axial residual stresses decreases from 210 to 50 MPa. It was noted that when the outer diameter of cylinders is 15 mm their length significantly influence on both hoop and radial residual stresses. With the above-mentioned decrease in cylinders length, absolute values of hoop and radial residual stresses in the region adjacent to the hole, depending on the mandrelling allowance, increase (from -135 to -205 MPa and from -45 to 55 MPa respectively, when allowance is 7.1%), decrease (from -315 to -235 MPa and from -135 to -95 MPa respectively, when allowance is 0.9%) and remain almost unchanged (when allowance is 3.4%). Impact of length on these stresses is weak when the outer diameter of cylinders is 25 mm.

Highlights

Mandrelling is an effective method of processing holes in parts such as hollow cylinders [1, 2]
Mandrelling is accompanied by generation of considerable residual stresses in hollow cylinders [1, 3, 4]. (Under these stresses hereinafter, as usual, we will understand their average values along the length of the cylinder.) Residual stresses are mainly determined by allowance and number of mandrelling cycles, mechanical properties of the cylinder material and wall thickness ratio, which is characterized by the ratio D/d (D – is outside diameter of the cylinder)
It can be seen that the hoop residual stresses are compressive in the zone adjacent to the hole and tensile in the zone adjacent to external surface in all the cases studied

Summary

Introduction

Mandrelling is an effective method of processing holes in parts such as hollow cylinders [1, 2]. It is used for holes with diameters d=1...150 mm and relative depth L/d≤100. Mandrelling is accompanied by generation of considerable residual stresses in hollow cylinders [1, 3, 4]. The absolute value of residual stresses in the mandrelled hollow cylinders can be close to the offset yield strength 0.2 of the part material. It was established that in order to generate favorable compressive hoop residual stresses in the hole surface layer that enhance performance characteristics of the cylinders, the last mandrelling cycle must be performed with small allowance (about 0.01d)

Objectives

Methods

Results

Conclusion