Gripping Force Verification via Natural Frequency Measurement
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Solution Overview
Problem
In material testing machines, it is difficult to confirm if a test piece is gripped with an appropriate gripping force, leading to incorrect test results, and existing methods for measuring gripping force are complex and prone to operator variations.
Innovation Solution
A material testing machine that measures and compares the natural frequency of the system including the test piece and gripper before and during the tensile test to determine if the test piece is gripped with an appropriate force, using a force detector and calculating sections to store and compare natural frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual confirmation after testing is used to verify gripping force, then test results can be confirmed, but the complexity of the detection process increases and time is lost
Solution Approach 1:
The patent replaces visual inspection and manual torque measurement with an acoustic measurement system. A vibration generator vibrates the gripper, and a sensor detects the natural frequency of the gripper-test piece system. This acoustic/ vibrational measurement system substitutes for mechanical torque wrenches and visual inspection methods, providing automated, precise gripping force verification without complex manual procedures.
Solution Approach 2:
The system uses the gripper itself as both the actuator (when vibrated) and the sensor (by measuring its natural frequency). The gripper-test piece system's natural frequency inherently reflects the gripping force, eliminating the need for separate measurement devices. The system serves itself by using its own dynamic characteristics to indicate gripping quality.
2Measurement precision
If torque wrench measurement is used to measure gripping force, then gripping force can be measured, but the operation becomes extremely complex and operator variations are introduced
Solution Approach 1:
The patent replaces mechanical torque wrench measurement with an acoustic/vibrational measurement system. By measuring the natural frequency of the gripper-test piece system through vibration and sensor detection, the system eliminates the need for manual torque application and reading. This substitution removes operator involvement from the measurement process, eliminating operator variations and simplifying the operation to automated frequency measurement.
Solution Approach 2:
The system provides automated feedback by measuring the natural frequency of the gripper-test piece system and comparing it against predetermined frequency ranges that correspond to appropriate gripping forces. This feedback mechanism automatically indicates whether the gripping force is appropriate, eliminating the need for operators to interpret torque readings and make judgment calls.
3Productivity
If appropriate gripping force is not confirmed before testing, then testing can proceed quickly, but incorrect test results are obtained
Solution Approach 1:
The patent performs preliminary verification of gripping force by measuring the natural frequency of the gripper-test piece system before the actual tensile test begins. This preliminary action ensures that the gripping force is appropriate before committing to the full test sequence, preventing wasted time on invalid tests while maintaining testing speed through automated quick measurement.
Solution Approach 2:
The system replaces time-consuming visual inspection and manual verification methods with rapid acoustic measurement. By generating vibrations and measuring natural frequency electronically, the system can verify gripping force in seconds, maintaining high productivity while ensuring test reliability through accurate pre-test verification.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables easy judgment of appropriate gripping force, ensuring correct material testing by preventing tests from starting with inadequate gripping force and providing warnings for inappropriate gripping, thus ensuring accurate test results.
Implementation Method 1
a calculating section, which calculates a natural frequency of a system including the test piece and the gripper connected to the force detector, based on a detected value of a force of the force detector when the gripper connected to the force detector is batted
Data Source
AI summary
Provided are a material testing machine and a gripping force detecting method that can easily judge whether a test piece is gripped with an appropriate gripping force by a gripper. A controlling section is connected to a FFT transforming section via a load cell; the FFT transforming section calculates a natural frequency of a system comprising a test piece and an upper gripper which is connected to a load cell based on a detected value of a force of the load cell. In addition, the controlling section is connected to a storing section which stores the natural frequency calculated by the FFT transforming section. Furthermore, the controlling section is also connected to a comparing section which compares the natural frequency calculated by the FFT transforming section and the natural frequency stored by the storing section before a test starts.