Characterization of mechanical properties and ballistic performance for a customized steel

Morningstar, William Lloyd

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https://hdl.handle.net/2142/115618 Copy

Description

Title

Characterization of mechanical properties and ballistic performance for a customized steel

Author(s)

Morningstar, William Lloyd

Issue Date

2022-04-29

Director of Research (if dissertation) or Advisor (if thesis)

Glumac, Nick G

Committee Member(s)

• Chu, Henry S
• Howell, Ryan A

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Steel
• Material evaluation
• High-strain-rate behavior
• Ballistics

Abstract

Steels and other metallic alloys are versatile materials for achieving different material properties because they can have different types/amounts alloying elements and they can be subjected to different heat treatment schedules. Steels are especially one of the most-used types of metallic alloys in countless applications for industry, so a customized steel, with new alloying and heat treatment methods, was tested and analyzed. The goal of the custom alloying and heat treatment methods was to produce a steel with high hardness and high toughness (HS-HT). This research focused on the mechanical properties and ballistic performance of the steel and compared it to RHA (Rolled Homogeneous Armor) Class 1, ARMOX® 600, and ARMOX® 500T data. These steels were chosen because they are high performing alloys, RHA as a high hardness and the ARMOX® variants are claimed to have high strength and/or high toughness. Mechanical properties and performance metrics at all types of strain rates were conducted because different strain rates determine the varying strength and toughness of a material. Steels also fail differently at low vs. high strain rates, for example, at high strain rates steels fail when the applied load causes strains to localize at Adiabatic Shear Bands (ASBs), and then the material shears to failure. Quasi-static to ballistic tests covered a wide range of performance metrics, that provided a comprehensive understanding of the customized steel. At low strain rates (quasi-static ranges), the customized steel appeared to perform better than the RHA, but not the ARMOX® 600. At dynamic loading ranges, the customized steel had a higher dynamic hardness than RHA for Vickers testing, but it was not as strong as the ARMOX® 600 during Split Hopkinson Pressure Bar Testing (SHPB). During impact toughness testing, the customized steel performed well at extreme cold/brittle temperatures (-40°C). For example, the Charpy toughness value for normal RHA at -40°C is 23-30 [J], and the customized steel achieved 44 [J] at the same temperature. At ballistic strain rates (very high) the customized steel’s ballistic performance was poor compared to the RHA and ARMOX® 500T (not conducted on the ARMOX® 600). The customized steel failed many times through ASBs, and this ASB failure mechanism dominated the material in all the types of ballistic strain rate tests conducted.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 William Lloyd Morningstar

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