Dynamic Torque Measurement for Viscoelastic Shear Properties
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Solution Overview
Problem
Current methods for measuring dynamic shear properties of viscoelastic materials are limited by their sensitivity to boundary conditions and frequency range, making it challenging to accurately determine shear modulus and loss factor, especially for materials with high loss-factors and varying properties with frequency and temperature.
Innovation Solution
An apparatus and method using Kibble's method, which applies dynamic torque and measures the proportionality constant to calculate shear modulus and loss factor by fitting mechanical models to transfer functions between applied torque and torsional response, allowing measurements over a large frequency range beyond the sixth torsional resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resonant methods are used to measure dynamic shear properties, then measurement precision is improved at specific frequencies, but the frequency range is limited and boundary condition sensitivity increases
Solution Approach 1:
The system transitions from static resonant frequency measurements to dynamic frequency sweeping across a broad range (0.1 Hz to 1000 Hz). The apparatus applies oscillatory torque at varying frequencies and measures the torsional response dynamically, enabling continuous adaptation to different frequency conditions rather than being locked to specific resonant frequencies.
Solution Approach 2:
The measurement system varies the frequency parameter continuously across more than six torsional resonant frequencies. By changing the operating frequency parameter and measuring the proportionality constant between applied torque and torsional response at each frequency, the system determines frequency-dependent shear properties throughout a broad spectrum rather than at fixed points.
2Measurement precision
If sandwich shear plates or torsion rheometers are used, then shear properties can be measured, but the frequency range is limited to tens to hundreds of Hertz and boundary condition sensitivity increases
Solution Approach 1:
The patent replaces traditional mechanical measurement systems (sandwich shear plates, torsion rheometers) with an electromagnetic actuation system. A voice coil motor generates oscillatory torque through electromagnetic forces, eliminating direct mechanical contact and associated boundary condition sensitivities. The system measures torque indirectly through electrical parameters, substituting mechanical measurement with electromagnetic measurement.
Solution Approach 2:
The apparatus measures dynamic shear properties across a universal frequency range from 0.1 Hz to 1000 Hz, encompassing and extending beyond the limited ranges of traditional methods. The system can handle materials with varying loss factors and frequency-dependent properties, making it universally applicable to diverse viscoelastic materials regardless of their specific mechanical characteristics.
3Adaptability or versatility
If traditional methods are used for materials with high loss-factors, then measurement becomes even more challenging, but accuracy of shear modulus and loss factor determination deteriorates
Solution Approach 1:
The system employs feedback through measuring the torsional response and comparing it with the applied torque to determine the proportionality constant. By continuously monitoring the relationship between input torque and output response across different frequencies, the system adjusts measurements to account for high loss factors and frequency-dependent behavior, maintaining accuracy for materials with varying damping characteristics.
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 accurate determination of frequency-dependent shear properties of viscoelastic materials over a broader frequency range, improving the measurement of shear modulus and loss factor with enhanced precision and applicability to materials with high loss-factors.
Implementation Method 1
a first coil interacts with the magnetic field and the current to apply a force to the specimen
Implementation Method 2
a second coil fixed to the motor and configured to measure voltage
Implementation Method 3
a mirror secured to the motor; a laser source focused on the mirror and configured to produce a laser, such that the mirror reflects the laser
Data Source
AI summary
Embodiments relate to an apparatus and method for determining the complex shear modulus of compliant viscoelastic specimens. The apparatus comprises at least one magnet configured to provide a magnetic field; a specimen and a motor secured to the end of the specimen, wherein the motor is positioned proximate to the magnet such that the motor is in the magnetic field; a first coil fixed to the motor; an amplifier configured to provide a current in the first coil, such that the first coil interacts with the magnetic field and the current to apply a force to the specimen; a second coil fixed to the motor and configured to measure voltage; a mirror secured to the motor; a laser source focused on the mirror and configured to produce a laser, such that the mirror reflects the laser; and a photodetector configured to detect the laser reflected from the mirror.