Embedded Relaxation Modulus Sensor for Viscoelastic Materials

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Solution Overview

Problem

Conventional methods for measuring the relaxation modulus of viscoelastic materials require destructive testing, which is costly and may not accurately represent individual components, such as rocket motor propellants and liners, due to variations in composition and environmental factors.

Innovation Solution

A non-destructive testing method using a sensor with a deformable driver and sensing devices embedded in the material, allowing for in situ measurement of stress and strain to determine relaxation modulus without disassembly or destruction of the item.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional testing methods are used to measure relaxation modulus, then measurement capability is provided, but the test material must be destroyed and disassembled

Engineering Contradiction:

Improverelaxation modulus measurementVSAvoiddestructive testing

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The sensor is embedded in the test material before the material is put into service, allowing future non-destructive measurement of relaxation modulus without requiring disassembly or destruction of the material during testing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sensor acts as an intermediary device that measures stress and strain in the test material through embedded sensing elements, enabling indirect measurement of relaxation modulus without directly destroying the material

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If samples are removed from the application for testing, then measurement can be conducted, but the application must be disassembled or sacrificed

Engineering Contradiction:

Improvematerial property testingVSAvoidtesting procedure

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The sensor is installed in advance within the test material during manufacturing or assembly, eliminating the need for later disassembly or sacrifice of the application to conduct testing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sensor enables the test material to be tested in its original application context without requiring removal from service, allowing the material to serve both its functional purpose and measurement purposes simultaneously

Inventive Principle:

Principle #25Self-service

3Measurement precision

If destructive testing is performed on individual components, then accurate measurement is achieved, but cost and time are increased

Engineering Contradiction:

Improveindividual component testingVSAvoidtesting duration

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The sensor is embedded before service, enabling continuous or periodic non-destructive monitoring of relaxation modulus without requiring time-consuming disassembly and destructive testing procedures

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The sensor enables continuous monitoring of material properties in service, eliminating the intermittent nature of destructive testing and allowing ongoing measurement without disruption to the application

Inventive Principle:

Principle #20Continuity of useful action

4Measurement precision

If conventional testing is used, then relaxation modulus can be measured, but the results may not represent individual components due to variations

Engineering Contradiction:

Improverelaxation modulus dataVSAvoidrepresentativeness of test results

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The sensor provides localized measurement of relaxation modulus at the specific position where it is embedded, capturing the actual material properties at that location rather than providing averaged results from removed samples

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The sensor acts as an intermediary that directly measures stress and strain in the material during service, providing reliable data that reflects the actual conditions and variations in individual components

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

Enables accurate, cost-effective, and non-destructive monitoring of viscoelastic material properties, such as those in rocket motors, providing reliable data on aging trends and mechanical stiffness over time.

Implementation Method 1

The relaxation modulus of a viscoelastic material is a coefficient describing the material's property of releasing or 'relaxing' over time when under constant deformation at a constant temperature

Methodology Applied

Scientific EffectStress relaxation: Stress Relaxation

Data Source

PatentUS7581450B2Relaxation modulus sensor, structure incorporating same, and method for use of same

Publication Date: 2009.09.01 NORTHROP GRUMMAN SYSTEMS CORP

AI summary

A sensor for measuring material properties such as the relaxation modulus of a material in situ and a method of measuring material properties of a material are disclosed. The sensor may be substantially embedded in the material, and includes a deformable driver. When actuated, the deformable driver may create a stress in the adjacent material. The movement or deformation of the driver may be measured with a sensing device, for example a strain gage mounted on a surface thereof. The stress in the adjacent material may be measured with a second sensing device, for example a pressure sensor. The measured movement and stress over a predetermined period of time may he used to determine the relaxation modulus of the material.