Experimental Techniques for Shear Testing of Thin Sheet Metals and Compression Testing at Intermediate Strain Rates

A new specimen geometry for the characterization of thin sheet metals in simple shear is introduced. The objective of this work is to develop methods to generate experimental data that populate material models for numerical simulations. The new simple shear specimen, based on ASTM B831, can be tested in both quasi-static and dynamic conditions using a servo-hydraulic load frame and tension Kolsky bar, respectively. Specimens are fabricated from a 0.5in Al2024-T351 plate with their gage sections orientated in various directions. Tests are conducted at shear strain rates ranging from 0.01(1/s) to 9000(1/s). Traditionally, shear characterization is performed through torsion tests on thin walled tube specimens, which are impossible to fabricate from thin sheet metals. The proposed specimen geometry is evaluated by comparing data obtained using the new specimen to existing torsion data. Three-dimensional Digital Image Correlation (DIC) is used to directly measure deformation on the surface of specimen gage sections for all tests. Stress versus strain curves obtained from tests using both specimen geometries agree, indicating that the new specimen geometry is suitable for use in characterizing thin sheet metals in shear. Additionally, the new specimen geometry is able to capture anisotropic effects which are averaged in torsion data on thin walled tube specimens. A parallel LS-DYNA simulation is conducted to investigate the strain state within the gage section during a test and compare to experimental data measured with DIC. Results show that a nearly uniform state of shear strain exists until large strains are developed.An intermediate strain rate apparatus is used to characterize Al2024-T351 and Cu-101 in compression at a strain rate of 100(1/s). The proposed intermediate strain rate apparatus consists of a linear hydraulic actuator to generate the loading and a long transmitter bar. The specimen is placed on the end of the transmitter bar and loaded directly by the actuator. When the specimen is loaded, a compression wave propagates down the transmitter bar and reflects back towards the specimen when it reaches the end of the bar. A long transmitter bar allows the test to continue until the reflected wave reaches the specimen. Ample time (16ms) is provided to accumulate significant strain at intermediate strain rates without inertial effects (ringing) that are common to other intermediate strain rate testing techniques. Two materials, Al2024-T351 and Cu-101 are tested. Previous data shows Al2024 does not exhibit strain rate sensitivity below 5000(1/s) while Cu-101 does. Specimens from both materials are tested in compression at strain rates ranging from 0.01(1/s) to 5000(1/s) using a load frame, the proposed intermediate strain rate apparatus, and a compression Kolsky bar. DIC is used to measure deformation on the surface of the specimen for all tests. Experimental data shows the intermediate strain rate apparatus is able to capture the expected data trends and is not subjected to the ringing observed by other common intermediate strain rate test techniques.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Gardner, Kevin Alexander

Contributors dc:contributor

• Gilat, Amos

• Mechanical Engineering
• shear testing
• intermediate strain rate testing
• dynamic testing
• digital image correlation

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1366199322

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1366199322