Tube Pure Shear Loading Device Mandrel Segmentation
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Solution Overview
Problem
Current methods for testing the mechanical properties of tubes under pure shear loading fail to maintain a stable pure shear stress state during deformation, leading to unreliable test data due to additional tensile or bending stresses, making it difficult to obtain accurate shear characteristics of tubes.
Innovation Solution
A tube pure shear loading device and method involving a to-be-tested tube composed of a first and second half tube connected with mandrels, where forces are applied in opposite directions to maintain a pure shear stress state, preventing rotation and ensuring the material remains in a stable axial direction, allowing for accurate shear stress-shear strain curve measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional sheet shear test methods (e.g., ASTM B831-05) are used with two long grooves and tensile force applied, then shear loading can be achieved, but additional tensile stress appears in the deformed area as deformation progresses, preventing pure shear stress state
Solution Approach 1:
The tube specimen is divided into three segments: a first half tube, a whole tube, and a second half tube connected in order. The first and second half tubes are processed with grooves and equipped with mandrels, while the whole tube remains intact. This segmentation allows the loading force to be applied only to the half tubes, creating pure shear stress in the whole tube without inducing additional tensile or bending stresses.
Solution Approach 2:
Mandrels are introduced as intermediary elements inserted into the first and second half tubes. These mandrels transmit the loading force from the testing machine to the half tubes, enabling controlled application of opposite forces that generate pure shear stress in the whole tube while preventing unwanted stress components.
2Ease of operation
If tube torsion test is used to obtain shear test characteristics, then shear properties can be measured, but the torsion loading is extremely unstable for thin-walled tubes, making it impossible to obtain effective test data
Solution Approach 1:
Instead of applying torsion loading directly to the tube (conventional approach), the invention inverts the approach by applying tensile loading to the half tubes which indirectly generates pure shear stress in the whole tube. This inversion transforms an unstable torsion problem into a stable tensile loading problem while achieving the same shear stress measurement objective.
3Stress or pressure
If parallel forces are applied to upper and lower parts of a tube to create pure shear stress state, then shear loading is achieved, but the tube twists due to bending moment after plastic deformation, changing the stress state
Solution Approach 1:
The invention creates an asymmetric loading configuration where forces are applied only to the first and second half tubes (which have grooves and mandrels) while the whole tube remains unloaded directly. This asymmetric arrangement generates pure shear stress in the whole tube without creating the symmetric bending moments that cause twisting in conventional approaches.
Data Source
AI summary
Disclosed are a tube pure shear loading device and method. A first mandrel penetrates into a first half tube, and a second mandrel penetrates into a second half tube. The size of the first mandrel matches the size of the first half tube, and the size of the second mandrel matches the size of the second half tube. A first connecting portion of the first mandrel and a second connecting portion of the second mandrel are loaded, and a first protruding portion and a second protruding portion transmit a force to a to-be-tested tube, so that a material of a whole tube in the same plane as a right plane or a left plane of the first half tube and a left plane or a right plane of the second half tube is in a pure shear stress state.