Strain Isolating Element for Acoustic Transducer Mounting

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Solution Overview

Problem

Existing mounting arrangements for acoustic transducers on substrates subject to high strain, such as naval steel, face issues with delamination and bond failure due to shear stresses, leading to compromised data and power transfer efficiency.

Innovation Solution

A strain isolating element with a narrow stem attached to the substrate and an enlarged head attached to the transducer is used, reducing strain at the attachment interface, and can be acoustically matched to the substrate for improved coupling, with optional flexural mountings and secure attachment methods like welding to minimize defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the transducer is bonded directly onto the barrier or onto a thin carrier plate, then good acoustic coupling is achieved, but the bond is subjected to high shear forces causing delamination and bond failure under high strain

Engineering Contradiction:

Improvebond reliabilityVSAvoidshear stress on bond

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A strain isolating element is introduced as an intermediary component between the transducer and the barrier. This element has a narrow stem portion attached to the barrier and an enlarged head portion attached to the transducer, serving as a mediator that reduces strain transmission to the bond interface.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The strain isolating element changes the mechanical parameters at the bond interface by reducing strain concentration. The narrow stem portion experiences high strain while the enlarged head portion provides a larger attachment area for the transducer, effectively changing the strain distribution parameters.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a thin carrier plate is used to mount the transducer, then acoustic coupling is improved, but the plate stiffness causes high shear forces on the bonding layer during contraction

Engineering Contradiction:

Improveacoustic coupling efficiencyVSAvoidshear force on bonding layer

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The strain isolating element has different local qualities: the narrow stem portion provides structural support and strain isolation at the barrier interface, while the enlarged head portion provides a stable mounting surface for the transducer. This local differentiation allows the element to perform multiple functions simultaneously.

Inventive Principle:

Principle #3Local quality

3Reliability

If the barrier is made from high tensile naval steel to ensure structural integrity, then safety is enhanced, but the material stiffness increases shear forces on adhesive bonds

Engineering Contradiction:

Improvebarrier structural integrityVSAvoidbonding difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The strain isolating element acts as an intermediary that decouples the transducer bond from the high-stress barrier substrate. This allows the use of high-strength materials like naval steel for the barrier while protecting the bonding interface from excessive shear forces.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The strain isolating element significantly reduces strain at the transducer interface by factors of 3 to 1500, achieving low acoustic reflectivity and maintaining efficient data and power transfer even under high compressive strains.

Implementation Method 1

a strain isolating element having a first surface attached to said substrate and a second surface attached to an attachment interface of said active element whereby, when said substrate is subjected to high compressive strain in use, the strain at said second surface is lower than that at said first surface

Methodology Applied

Scientific EffectStrain isolation:

Implementation Method 2

Piezo-electric transducers bonded onto opposite surfaces of a solid barrier by a very thin adhesive layer launch or receive these ultrasonic signals

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 3

NPDT is a technology that permits the transmission of data and power through solid barriers using ultrasonic acoustic waves

Methodology Applied

Scientific EffectAcoustic wave propagation: Sound

Implementation Method 4

Piezo-electric transducers bonded onto opposite surfaces of a solid barrier by a very thin adhesive layer

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Data Source

PatentUS9830898B2Mounting arrangements

Publication Date: 2017.11.28 BAE SYSTEMS PLC

AI summary

In an arrangement for transmitting power or data through a solid rigid substrate without penetrating the substrate, acoustic transducer components are mounted on the substrate by means of strain isolator elements which are welded or otherwise bonded to the substrate and providing an attachment surface to which the attachment interface of the acoustic transducer may be attached. The strain isolator element is of the same or similar acoustic impedance as the rigid substrate and may indeed be formed of the same material. Various geometries of strain isolator are disclosed, including a plain spacer block, and one comprising a stalk attached to the solid rigid substrate and topped by a disc in a ‘mushroom’ configuration.