Stiffness Redistribution and Hole-Edge Stress Concentration in Thin-Walled Aluminum Shells Under Impact Loading

Abstract

Thin-walled aluminum shells with mounting holes are widely used in lightweight protective enclosures, but it

remains unclear whether local stiffening or uniform thickening provides a safer balance between global

deformation control and hole-edge stress margin under impact loading. This study compares a 4/4 mm

baseline shell, a 4/4 mm locally stiffened shell, and a 5/5 mm uniformly thickened 6061-T6 shell under the

same 300 g, 2 ms base acceleration using transient finite element analyses with identical geometry, material

data, supports, loading, mesh, and solver settings. Within this linear-elastic relative-comparison framework,

the locally stiffened shell reduces maximum deformation by 16.06%, yet increases the selected hole-edge

peak stress by 27.76% and the unaveraged nodal peak equivalent stress by 32.52%, lowering the minimum

stress-margin indicator to 0.60216. In contrast, uniform thickening reduces deformation by 42.36%, decreases

the selected hole-edge stress by 5.25% and the nodal peak stress by 17.34%, and raises the indicator to

0.96538. Boundary-condition sensitivity confirms that support idealization does not reverse this trend.

Therefore, displacement reduction alone is insufficient for evaluating impact-loaded perforated shells. For

engineering design under the specified impact condition, uniform thickening should be prioritized when

balanced deformation control and local stress-margin improvement are required, while local stiffening should

be paired with hole-edge reinforcement and elastoplastic verification.