Phase Change Aggregate for Concrete Microcrack Detection

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Solution Overview

Problem

Current methods for non-destructively monitoring the mechanical strength of building materials like concrete and gypsum are limited by complexity, precision, and the inability to detect small changes such as microcracks, often requiring permanent detection and complex sensor setups, which can be invasive and prone to errors.

Innovation Solution

A granular aggregate is developed comprising a compact mass embedded in a switchable phase change material within an outer shell, where the compact mass oscillates based on the material's hardening state, allowing for non-destructive monitoring of mechanical strength by measuring vibrations, which change in response to mechanical stress, including microcracks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If permanent detection with multiple sensors is used to monitor mechanical strength, then detection reliability is improved, but device complexity increases

Engineering Contradiction:
Improvedetection reliabilityVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The monitoring system is segmented into many simple, identical sensor elements distributed throughout the material. Each sensor element is a simple capsule containing phase change material and a compact mass, avoiding the need for complex centralized sensor systems while achieving comprehensive monitoring coverage.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The sensor elements are self-contained and autonomous, requiring no external power supply or complex electronics. The phase change material automatically responds to mechanical stress changes through physical phase transitions, eliminating the need for complex power management and signal processing systems.

Inventive Principle:
Principle #25Self-service

2Measurement precision

If core drilling or local destruction is used to detect microcracks, then measurement precision is improved, but harmful factors increase

Engineering Contradiction:
Improvemicrocrack detection precisionVSAvoidcomponent damage
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The mechanical destruction method (core drilling) is replaced with a non-destructive physical field method. Acoustic waves or vibrations are used to excite the sensor elements, and the phase change material responds to mechanical stress through phase transitions that can be detected without physically damaging the component.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The phase change material acts as an intermediary between the mechanical stress field and the detection system. It translates invisible microcrack-induced stress changes into detectable phase transitions, enabling precise detection without direct mechanical intervention or damage to the component.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Loss of time

If ultrasound or radar radiation is used for snapshot detection, then detection speed is improved, but measurement precision deteriorates

Engineering Contradiction:
Improvedetection timeVSAvoidspatial resolution
Core Design Contradiction:
Loss of timeVSMeasurement precision

Solution Approach 1:

Instead of using a single snapshot method with limited resolution, the system segments the detection space into many discrete sensor element locations. Each sensor element provides localized phase change detection, and collectively they achieve high spatial resolution throughout the entire monitored volume, overcoming the resolution limits of conventional snapshot methods.

Inventive Principle:
Principle #1Segmentation

4Reliability

If many sensors are attached for permanent detection, then detection reliability is improved, but ease of operation worsens

Engineering Contradiction:
Improvedetection reliabilityVSAvoidsensor attachment complexity
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

Multiple sensor functions are merged into a single integrated capsule structure. Each sensor element combines the phase change material, compact mass, and enclosure into one unit that can be easily mixed into the material during production, eliminating the need for separate attachment operations for multiple sensors.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The sensor elements serve multiple functions: they act as both the sensing element and the structural component that can be mixed into the material. The phase change material simultaneously provides the detection mechanism and the response to mechanical stress, eliminating the need for separate sensor attachment and calibration procedures.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 enables simple, non-invasive monitoring of mechanical strength by detecting changes in the vibrational capacity of the compact mass, providing information on mechanical stress states and microcrack detection without damaging the component, while also influencing the acoustic properties of the material.

Implementation Method 1

consisting of an outer shell with a filling of at least one field that acts internally or externally, such as mechanical stress states, acoustic, electrical or magnetic Fields, switchable phase change material and at least one compact mass embedded therein, which oscillates in this filling depending on the aggregate state of the phase change material

Methodology Applied
Scientific EffectPhase change: Phase Change

Data Source

PatentEP2370375B1Vibro-acoustically effective aggregate
Publication Date: 2019.04.10 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV
  • EP2370375B1 patent drawingFigure 1
  • EP2370375B1 patent drawingFigure 2
  • EP2370375B1 patent drawingFigure 3~4

AI summary

The invention relates to a vibro-acoustically effective granular aggregate for materials, e.g. concrete and similar building materials, comprising an external shell (3) with a filler made of a phase transition material (5) that can be switched using internally or externally effective fields, e.g. mechanical stress states, acoustic, electric, or magnetic fields, and at least one compact material which is embedded therein and can vibrate in said filler according to the physical condition of the phase transition material (5), whereby the mechanical state of the surrounding material is characterized and the vibro-acoustic behavior of the surrounding material is influenced.