Creep testing fixture and method
AssigneeAutomotive Composites Consortium
InventorsKelly Willson-Hackworth, Steven George Luckey, Jr., Daniel Q. Houston, Edward M. Hagerman, John M. Henshaw
Life of this patent
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Abstract
A creep testing fixture and method for applying a precise amount of constant tensile stress to a creep test specimen to allow for precise measurement of creep in the test specimen. The fixture includes first and second mounting grips for holding opposite ends of a test specimen. A frame supports the mounting grips for relative reciprocal movement toward and away from each other. A tensile spring is connected between the first and second mounting grips. The frame subjects a test specimen held between the mounting grips to tensile stress in response to axially inward force that the tensile spring applies to the frame.
Claims16
A creep testing fixture for applying a precise amount of constant tensile stress to a creep test specimen to allow for precise measurement of creep in the test specimen, the fixture comprising:
- first and second mounting grips for holding opposite ends of a test specimen;
- a frame supporting the first and second mounting grips for relative reciprocal movement toward and away from each other;
- a spring connected between the first and second mounting grips, the frame being configured to subject a test specimen held between the mounting grips to tensile stress in response to force that the spring applies to the frame;
- and
- the spring is a tensile spring and the frame and spring are configured to subject a test specimen to tensile stress in response to axially inward force that the tensile spring applies to the frame such that spring load loss over time is limited by an amount sufficient to allow for accurate tensile creep testing of the test specimen.
A method for applying a precise amount of constant tensile stress to a creep test specimen to allow for precise measurement of creep in the test specimen, the method including the steps of:
- providing a test fixture having first and second mounting grips, a frame supporting the first and second mounting grips for relative reciprocal movement toward and away from each other, a spring connected between the first and second mounting grips, the frame being configured to subject a test specimen held between the mounting grips to tensile stress in response to axially inward force that the tensile spring applies to the mounting grips;
- providing a tensile test specimen having an ultimate strength value;
- providing a tensile spring having a spring rate equal to or less than the ultimate strength of the test specimen;
- connecting opposite ends of the tensile test specimen to the respective first and second mounting grips;
- and
- connecting opposite ends of the spring to respective spring attachment points on the lever arms such that the spring applies a generally constant axial inward load to the lever arms and the lever arms apply a generally constant tensile load to the test specimen.
A method of measuring creep recovery, the method including the steps of:
- providing a test fixture having first and second mounting grips, a frame supporting the first and second mounting grips for relative reciprocal movement toward and away from each other, a spring connected between the first and second mounting grips, the frame being configured to subject a test specimen held between the mounting grips to tensile stress in response to axially inward force that the tensile spring applies to the mounting grips;
- providing a tensile test specimen having an ultimate strength value;
- providing a tensile spring having a spring rate equal to or less than the ultimate strength of the test specimen;
- connecting opposite ends of the tensile test specimen to the respective first and second mounting grips;
- connecting opposite ends of the spring to respective spring attachments points on the lever arms such that the spring applies a generally constant axial inward load to the lever arms and the lever arms apply a generally constant tensile load to the test specimen;
- measuring the resulting strain exhibited in the test specimen;
- returning the spring to a relaxed condition;
- and
- measuring any resulting decrease in strain exhibited in the test specimen.
Dependencies are inferred from the claim text.