# Plastically Deformed Tubes Subjected to Mechanical Expansion Processes

## TL;DR

This paper studies how mechanical expansion affects stresses in copper and stainless-steel tubes, introducing a new analytical method validated with simulations and experiments.

## Contribution

A novel analytical approach is introduced to evaluate stresses and strains in expanded tubes using a segmented zone analysis.

## Key findings

- Tangential and longitudinal strains were measured in 3/8 inch copper and stainless-steel tubes during mechanical expansion.
- The analytical model's predictions for push force matched well with numerical simulations and experimental data.
- The study validated the model using a finite element approach with multi-linear kinematic hardening behavior.

## Abstract

In engineering, the stress state of expanded tubes is crucial for ensuring structural integrity and preventing stress corrosion cracking. The analysis of stresses and strains in tubes subjected to mechanical expansion using an ogive bullet is essential, yet existing theoretical methods for estimating the stress distributions, especially with spherical and ogive shapes, are sparse. This study explores the expansion of 3/8 inch copper and stainless-steel tubes using an expanding bullet, where tangential and longitudinal strains are measured. A novel analytical approach is introduced to evaluate the stresses and strains, segmenting the tube into three zones, each analyzed with a distinct theory. Validation is achieved through an axisymmetric finite element model that employs a multi-linear kinematic hardening material behavior. The analytical model also estimates the expanding mandrel’s push force, which is then compared with the results from numerical simulations and experimental data, showing good agreement across methods.