Anisotropic Layer Resonance for Elastic Wave Mode Conversion
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Solution Overview
Problem
Current technologies lack effective methods for converting elastic waves between longitudinal and transverse modes, particularly for ultrasonic applications, due to limitations in mode conversion efficiency and the difficulty in exciting transverse waves using piezoelectric elements.
Innovation Solution
An anisotropic media utilizing transmodal Fabry-Pérot resonance is introduced, allowing for efficient conversion of elastic waves between longitudinal and transverse modes through a layer with specific phase matching and polarization conditions, enabling the development of advanced ultrasound transducers and sound insulating panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a wedge is used to convert longitudinal wave to transverse wave via oblique incident elastic wave, then transverse wave can be excited, but transmission rate is relatively low and dependence on incident media and transmissive media is relatively high
Solution Approach 1:
The patent changes the physical parameters of the media by introducing an anisotropic layer with specific elastic constants (C11, C66, C16) and controlling its thickness (d) to satisfy the phase matching condition. This transforms the wave conversion mechanism from dependency on incident angle and media properties to dependency on controlled material parameters and resonance frequency, thereby improving transmission rate and reducing media dependence.
Solution Approach 2:
The patent utilizes mechanical vibration through Fabry-Pérot resonance at a specific resonance frequency (fTFPR) to enhance the mode conversion efficiency. By tuning the system to resonate at this frequency, the transmission rate of converted waves is significantly improved compared to non-resonant conditions.
2Ease of operation
If mode conversion based on Snell's critical angle is used, then transverse wave can be generated, but incident angle is limited and transmission rate is relatively low
Solution Approach 1:
The patent changes the operational parameters from angle-dependent Snell's law conversion to frequency-dependent resonance conversion. The anisotropic layer is designed with specific elastic constants and thickness to satisfy the phase matching condition at a predetermined resonance frequency, eliminating the need for precise angle control and reducing device complexity.
3Productivity
If anisotropic media with phase matching condition is used for mode conversion, then mode conversion efficiency is improved, but device structure becomes more complex
Solution Approach 1:
The patent employs composite material structure consisting of isotropic outer media and an anisotropic layer in between. The anisotropic layer is characterized by specific elastic constants (C11, C66, C16) that enable mode coupling. This composite structure achieves high mode conversion efficiency while maintaining relatively simple geometry (a layered structure), as the complexity is embedded in the material properties rather than geometric complexity.
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
This solution enhances mode conversion efficiency, allowing for improved ultrasonic wave transmission and sound insulation by effectively converting waves between modes, thereby facilitating more sensitive defect detection and efficient energy dissipation.
Implementation Method 1
capable of converting a longitudinal wave to a transverse wave and vice versa using transmodal (or mode-conversion) Fabry-Pérot resonance
Implementation Method 2
when the elastic wave passes through or is reflected by an anisotropic layer, the longitudinal wave may be easily converted into the transverse wave and vice versa, due to elastic wave mode coupling
Implementation Method 3
different from the electromagnetic wave or the sound wave, a longitudinal (compression) wave and a transverse (shear) wave exist due to solid atomic bonding inside of media
Data Source
AI summary
The anisotropic media has an anisotropic layer, is disposed between outer isotropic media, causes multiple mode transmission on an elastic wave having a predetermined mode incident into the anisotropic media, and has a mode-coupling stiffness constant not zero. A thickness of the anisotropic layer according to modulus of elasticity and excitation frequency satisfies Equation (2) which is a phase matching condition of elastic waves propagating along the same direction or Equation (3) which is a phase matching condition of elastic waves propagating along the opposite direction, to generate mode conversion Fabry-Pérot resonance,Δϕ≡kqld−kqsd=(2n+1)π, Equation (2)Σϕ≡kqld+kqsd=(2m+1)π, Equation (3)kql is wave numbers of anisotropic media with quasi-longitudinal mode.lqs is wave numbers of anisotropic media with quasi-shear mode. d is a thickness of anisotropic media. n and m are integers.