Clevis-Lug Test Fixtures for Tension Failure Under Compression
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Solution Overview
Problem
Conventional methods of testing tension lug joints using compression loading fail to reveal tension failure modes, as laboratories may lack sufficient tensile loading machines but have available compression-loading machines.
Innovation Solution
A fixture comprising three stacked plates with aligned pin-accepting holes and slots, allowing for simulation of tension loading using compression, which includes anti-buckling features to prevent plate deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If compression loading machines are used to test tension lug joints, then sufficient loading capacity is available, but tension failure modes cannot be revealed
Solution Approach 1:
The patent applies inversion by using compression loading (opposite to the required tension loading) to test tension lug joints. The fixture is designed with slots and plates that convert the compressive force into tensile stress on the lug joint, allowing tension failure modes to be revealed while using compression loading machines.
Solution Approach 2:
The fixture acts as an intermediary between the compression loading machine and the tension lug joint. It includes components like outer plates with slots, an inner plate, and a pin that together transform the compression load into a configuration that induces tension stresses on the lug, enabling indirect testing of tension properties through compression loading.
2Force
If conventional compression testing methods are used on lug joints, then compression loading capacity is sufficient, but the testing method does not reveal tension failure modes
Solution Approach 1:
The patent inverts the conventional approach by using compression loading to indirectly test for tension failure modes. The fixture geometry with its slots and movable plates creates a mechanical advantage that transforms compression into tension on the lug joint, making tension failure modes detectable through compression testing.
Solution Approach 2:
The patent changes the loading parameter from direct tension to compression while using a specially designed fixture. The fixture's slot configuration and plate arrangement transform the compression parameter into effective tension stresses on the lug joint, maintaining reliability in failure mode identification despite the parameter change.
3Measurement precision
If tensile loading machines of sufficient capacity are used, then tension failure modes can be revealed, but such machines may not be available in the laboratory
Solution Approach 1:
The patent makes the compression loading machine universal by enabling it to perform both compression testing and tension lug joint testing. The fixture design allows the existing compression machine to serve multiple functions, including revealing tension failure modes, thereby increasing laboratory equipment versatility without requiring additional specialized tensile testing machines.
Solution Approach 2:
The fixture serves as an intermediary that bridges the gap between available compression loading machines and the need to test tension lug joints. It enables laboratories with only compression machines to perform comprehensive lug joint testing, including detection of tension failure modes, by transforming the compression load into the appropriate test configuration.
Data Source
AI summary
Fixtures and methods for testing articles in tension when using compression loading are disclosed. The fixture is formed by three plates that are arranged to simulate a clevis-lug joint. The outer plates form the clevis, and the inner plate forms the lug. The plates each have holes that are aligned to accept the lug pin through all three holes. The center plate is attached to one end of the fixture. The outer two plates are attached to the other end of the fixture. Gaps are provided at one end of the plates to facilitate sliding of the outer plates in one direction and sliding of the inner plate in the opposite direction when compressive forces are applied to the ends of the fixture.