A Semi-Analytical Model for Prior Strain in Ballistically Perforated Steel Plates
K. Moyano (TU Delft - Mechanical Engineering)
C. L. Walters – Mentor (TU Delft - Ship and Offshore Structures)
Okko Coppejans – Mentor (TNO)
Milan Veljković – Graduation committee member (TU Delft - Steel & Composite Structures)
W.J. Wong – Graduation committee member (TU Delft - Ship and Offshore Structures)
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Abstract
High-strength marine grade steel is often used in naval applications where ballistic impact poses a critical threat to structural integrity. Perforation by a projectile leaves behind a hole surrounded by plastically deformed material, which alters the stress redistribution capacity of the impacted structural component and reduces its residual strength. Understanding and predicting these effects is essential for reliable damage assessment and safe structural design.
This work develops a semi-analytical stress field model for perforated EH36 steel plates that incorporates prestrain effects derived from Vickers hardness measurements around ballistic holes. The model builds upon Stowell’s elastoplastic stress concentration framework, extended with a Swift-type hardening law to capture strain hardening from prior plastic deformation.
The analytical solution results are compared with finite element analysis (FEA) and limited experimental Digital Image Correlation (DIC) data. While the validation dataset is not sufficient for full generalization, the comparisons indicate that incorporating prestrain reduces the stress concentration factor at the edge of the hole compared to analyses without prior strain.