Embedded Optical Fiber Sensors for Railway Concrete Sleeper Stress Monitoring

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Solution Overview

Problem

Railway track supports face challenges with measuring stresses and aging due to high loads, climatic hazards, and maintenance issues with existing strain gauges, which are sensitive to electrical environments, require frequent recalibration, and have limited durability and accuracy.

Innovation Solution

Embedding optical fiber strain sensors within the concrete of railway track supports allows for comprehensive stress measurement, including compression and bending moment evaluation, with embedded temperature sensors and a data collection system, providing long-term durability and reduced maintenance needs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If strain gauges are attached to the surface of rail supports, then stress measurement capability is provided, but the measurement system requires electrical power supply and is sensitive to electrical environment

Engineering Contradiction:

Improvestress measurement capabilityVSAvoidelectrical environment sensitivity

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces traditional electrical strain gauges with optical fiber sensors that use optical principles instead of electrical resistance changes. The optical fiber sensor measures strain through changes in light propagation characteristics, eliminating sensitivity to electrical environments while maintaining stress measurement capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the measurement parameter from electrical resistance (in traditional gauges) to optical properties (light transmission characteristics). This parameter change makes the sensor immune to electrical interference while preserving the ability to detect mechanical stress through physical deformation of the optical fiber.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If traditional strain gauges are used on rail supports, then stress measurement is possible, but frequent maintenance and recalibration are required

Engineering Contradiction:

Improvestress measurementVSAvoidmaintenance interval

Core Design Contradiction:

Measurement precisionVSDuration of action of moving object

Solution Approach 1:

The optical fiber sensor is designed as a robust, maintenance-free measurement device that eliminates the need for frequent recalibration and maintenance. The sensor's passive optical nature and embedding in concrete protect it from environmental degradation, effectively creating a long-lasting measurement system.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The optical fiber sensor is embedded within the concrete structure during manufacturing, providing inherent protection against environmental factors before exposure occurs. This preemptive embedding shields the sensor from weather, mechanical damage, and contamination that would otherwise require maintenance.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Measurement precision

If strain gauges are placed on contours of rail support, then surface stress measurement is achieved, but it is difficult to account for deformations and internal stresses

Engineering Contradiction:

Improvesurface stress measurementVSAvoidinternal stress information

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The optical fiber sensor is nested within the concrete matrix, allowing it to measure both surface deformations and internal stress states. The sensor is embedded at strategic locations within the concrete volume, enabling simultaneous detection of external loading and internal stress distribution that cannot be obtained from surface-mounted gauges alone.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 embedded optical fiber sensors enable precise, long-lasting stress measurement and deformation analysis, reducing maintenance and improving measurement accuracy by being immune to environmental factors and power supply requirements, allowing for real-time monitoring of rail support conditions.

Implementation Method 1

at least one of said measuring instruments is a extensometric optical fiber sensor embedded in the concrete of said support in order to measure the stresses undergone by the concrete

Methodology Applied

Scientific EffectOptical fiber sensing: Optical Fibre

Data Source

PatentEP2602169B1Instrumented concrete sleeper for railway rails

Publication Date: 2017.08.30 DE TRAVERSES & BETON ARME SYST VAGNEUX

Figure 1a~1b
Figure 2a~2b
Figure 3a~3b

AI summary

The sleeper (1) has a set of positions (7) that is utilized for supporting railway rails (2), where the rails comprise a set of measuring instruments that are embedded into the sleeper. One of the set of measuring instruments is arranged as an extensometric sensor (3) i.e. interferometric sensor, or a temperature sensor, whose optical fiber is embedded in the concrete to measure stresses undergone by the concrete. The extensometric sensor comprises a sensitive element arranged according to a direction of arrangement of the railway rails. An independent claim is also included for a rail measurement system.