Material Testing Machine Chuck Backlash Elimination
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Solution Overview
Problem
Conventional material testing machines experience backlashes in the chuck mechanisms, leading to uneven tensile forces applied to test pieces during biaxial tensile tests, resulting in unnatural test behavior and inaccurate evaluation of material properties.
Innovation Solution
A material testing machine design that applies pretensions to the test piece before the actual tensile test, eliminating backlashes by adjusting the positions of the chucks using screws or wedges to ensure equal tensile forces in both orthogonal directions, ensuring proper alignment and force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gaps are provided between moving members and shafts for mechanical clearance, then ease of assembly and manufacturing are improved, but backlashes occur in the chucks causing inaccurate force application
Solution Approach 1:
The patent applies pretension to the test piece before the formal tensile test begins. This preliminary action eliminates the backlash caused by gaps between moving members and shafts by pre-compressing the connection points, ensuring that subsequent force measurements are accurate without requiring tighter manufacturing tolerances
Solution Approach 2:
The patent introduces a pretension mechanism that applies a preliminary compressive force to counteract the harmful effect of backlash. By applying this anti-action force in advance, the system eliminates the negative impact of mechanical clearance before accurate measurements are required
2Reliability
If backlashes exist in the chuck mechanism, then mechanical tolerance is maintained, but uneven tensile forces are applied to the test piece
Solution Approach 1:
The patent applies pretension to the test piece in advance, which stabilizes the force distribution by eliminating backlash before the formal test begins. This preliminary stabilization ensures uniform force application throughout the subsequent tensile test
Solution Approach 2:
The patent employs load cells to measure the tensile forces applied in each direction and provides feedback control. This feedback mechanism detects force distribution uniformity and adjusts the application of force to maintain stability and eliminate the effects of mechanical backlash
3Ease of operation
If different backlash amounts occur in orthogonal directions, then mechanical play is accommodated, but inappropriate tensile forces are applied to the test piece
Solution Approach 1:
The patent uses load cells in each orthogonal direction to measure the actual tensile forces being applied. This feedback information is used to detect and correct discrepancies in force application caused by differential backlash, ensuring accurate and appropriate tensile forces are applied in both directions
Solution Approach 2:
The patent introduces a dynamic adjustment capability where the force application system can adapt in real-time based on measured backlash conditions. The system dynamically adjusts the force distribution to compensate for different backlash amounts in orthogonal directions, maintaining measurement precision despite mechanical play
Data Source
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AI summary
Seat members 31 are held in a state of being movable with respect to first slide members 21 or second slide members 22 correspondingly. By rotating screws 39 in directions to increase the distances d between surfaces A of the first slide members 21 or the second slide members 22 and surfaces B of the seat members 31, chucks 25 are moved in directions to increase the distance between the chucks to apply pretension to a test piece correspondingly. When backlash in a force transmission system from a support part to the respective chucks 25 is eliminated, a biaxial tensile test is started.