고체역학 (Gere) — Axially Loaded Members: Problem 2.3-22

2.3-22 A circular aluminum alloy bar of length \( L = 1.8 \text{ m} \) has a slot in the middle half of its length (see figure). The bar has a radius \( r = 36 \text{ mm} \) and modulus of elasticity \( E = 72 \text{ GPa} \). The slot has a height \( 2a = r/4 \). Calculate the elongation of the bar due to forces \( P \) applied at the ends if the axial stress in the middle region is known to be \( 180 \text{ MPa} \).