Hollow Cylindrical Test Specimen for Thin-Walled Material Fatigue Analysis
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Solution Overview
Problem
Existing test specimens, such as solid round bar coupons and flat coupons, fail to accurately represent the strength and fatigue properties of thin-walled materials, particularly in the aerospace industry, due to edge effects and surface finish influences, making standard testing methods like ASTM E8 and ISO 1143 inadequate for correlating surface finish effects with material thickness.
Innovation Solution
A hollow cylindrical test specimen with grip portions and a void extending from one axial end, configured to be secured to a test machine, allowing for load testing that minimizes edge effects and enables accurate measurement of surface finish impacts on mechanical properties, using a continuous thin circular wall with predetermined surface thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If solid round bar coupons are used as test specimens, then standard material property test methods can be applied, but the test specimen does not accurately represent thin wall material properties and surface finish effects
Solution Approach 1:
The patent changes the geometric parameters of the test specimen by introducing a hollow cylindrical configuration with a void extending from one end, creating a thin-walled structure that accurately represents the geometry of interest. This allows the specimen to model thin-wall components while maintaining manufacturability and testability
Solution Approach 2:
The patent transitions from a solid 3D bar to a hollow cylindrical structure by introducing an internal void dimension. This dimensional change creates a thin-walled geometry that better represents actual thin-wall components while preserving the cylindrical symmetry that eliminates edge effects
2Measurement precision
If flat coupons are used for material tests, then surface finish effects can be tested, but edge effects at the cross section make results highly inaccurate
Solution Approach 1:
The patent uses a cylindrical geometry with curved surfaces instead of flat surfaces. The circular cross-section eliminates sharp edges that cause stress concentrations and edge effects, while the curved surface still allows for controlled surface finish conditions to study their effect on material properties
3Productivity
If standard test methods are used for thin wall materials, then testing can be conducted, but surface finish effects cannot be accurately correlated with material thickness
Solution Approach 1:
The patent creates a specimen where the wall thickness is uniform and controlled throughout the cylindrical structure, while allowing independent control of surface finish conditions. This local quality control enables separate optimization of thickness uniformity and surface finish characteristics to accurately study their interaction
Data Source
AI summary
A test specimen is provided. The test specimen includes a coupon. The coupon includes a test portion and grip portions. The grip portions are located on opposite axial ends of the coupon. The test portion is located between the grip portions. The coupon further includes a void extending into the coupon from at least one of the axial ends. The void is defined by a wall having a surface thickness at the test portion that corresponds to a predetermined surface thickness of interest. The coupon is configured to be secured to a test machine for conducting load tests on the coupon.