Rock Tensile Test Fixture With Self-Centering Vertical Loading
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Solution Overview
Problem
Existing indirect tensile test instruments face challenges in ensuring accurate vertical loading and centering of samples with different shapes and sizes, leading to inconsistent test results and requiring modifications for varying sample specifications.
Innovation Solution
A sample fixture comprising an upper and lower fixture with a ball head, knives, telescopic positioning plates, and guide rods, which ensures accurate vertical loading and centering of samples by using spherical grooves, cutting edges, and telescopic adjustments to accommodate cylindrical and cuboid samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single specification indirect tensile test instrument is used, then the instrument structure is simple, but it cannot be applied to samples with different shapes and sizes
Solution Approach 1:
The fixture is designed with a universal structure that can accommodate both cylindrical and cuboid samples. The upper and lower fixtures include adjustable components (telescopic positioning plates, adjustable positioning blocks) that can be configured to fit different sample geometries, eliminating the need for multiple specialized fixtures or instrument modifications.
Solution Approach 2:
The fixture incorporates dynamic adjustment mechanisms including telescopic positioning plates that can extend or retract, and adjustable positioning blocks that can be repositioned. These dynamic components allow the same fixture to adapt to samples of varying sizes and shapes without requiring structural modifications to the instrument itself.
2Manufacturing precision
If manual sample loading is used, then the operation process is simple, but it is difficult to ensure that the sample is centered in the indirect tensile instrument strictly
Solution Approach 1:
The fixture includes self-centering mechanisms where the spherical groove on the upper fixture and the corresponding spherical surface on the lower fixture automatically guide the sample into the correct position. The telescopic positioning plates and positioning blocks provide automatic positioning that eliminates the need for manual adjustment, ensuring consistent sample centering without complex operational procedures.
Solution Approach 2:
The upper fixture incorporates a spherical groove that receives a spherical surface on the lower fixture. This spherical interface provides automatic centering capability, where the curvature of the spherical surfaces guides the sample into the precise central position, eliminating manual alignment requirements while maintaining simple operation.
3Manufacturing precision
If backing strips are placed at both ends of the sample, then the loading process is simplified, but errors in sample preparation cause the load to act non-vertically on the sample
Solution Approach 1:
The spherical groove and spherical surface interface provide a self-aligning mechanism that ensures the loading force acts vertically on the sample regardless of minor variations in sample preparation. The spherical geometry automatically compensates for misalignment, guiding the load application path to be perfectly vertical without requiring complex fixture adjustments.
Solution Approach 2:
The spherical groove-spherical surface interface provides real-time feedback during loading, where any deviation from vertical alignment is automatically corrected by the spherical geometry. This feedback mechanism ensures that the loading force remains vertically aligned with the sample axis throughout the test, eliminating errors caused by sample preparation variations.
4Adaptability or versatility
If the cutting edge of the knife is exposed, then the loading force can be applied directly to the sample, but the fixture cannot accommodate samples with different shapes and sizes
Solution Approach 1:
The fixture design with telescopic positioning plates and adjustable positioning blocks creates a universal loading interface that can accommodate both cylindrical and cuboid samples. The same fixture structure can be adjusted to fit different sample geometries, allowing direct knife-edge loading for all sample types without requiring multiple specialized fixtures or complex assembly procedures.
Data Source
AI summary
Provided is a sample fixture for an indirect tensile test of rock mass, relating to the technical field of rock mass engineering geomechanics tests. The sample fixture includes an upper fixture, and a lower fixture located below the upper fixture. The upper fixture includes an upper fixing block, a ball head, and an upper knife. The lower fixture includes a lower fixing block, a telescopic positioning plate, and a lower knife. The ball head is in fit with a spherical groove on an upper surface of the upper fixing block to achieve the function of transferring pressure, thus ensuring loading strength acting on a sample. A loading force is transferred by using a cutting edge of the upper knife to make the pressure act on the sample intensively, thus ensuring point or linear loading required by the test.