Bragg Grating Fiber Sensing for Additive Manufacturing Defects
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Solution Overview
Problem
Existing additive manufacturing detection devices face limitations in spatial resolution due to the bulkiness of thermocouples and the space occupied by their connecting wires, making it difficult to achieve high density of measurement points and detect defects between sensors late or inaccurately.
Innovation Solution
The use of a single optical fiber with Bragg gratings at each measurement point, integrated into the support, allows for a high density of measurement points and simultaneous temperature and acoustic signal detection, enhancing sensitivity and spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermocouples are used as temperature sensors, then high temperature measurement capability is achieved, but spatial resolution deteriorates due to the bulkiness of thermocouples and their connecting wires
Solution Approach 1:
The patent replaces mechanical/electrical thermocouple sensors with optical fiber sensors that use light to measure temperature. This substitution eliminates the need for bulky electrical connections and allows for much smaller sensor dimensions, thereby improving spatial resolution while maintaining high temperature measurement capability through the use of temperature-resistant optical fibers and Bragg gratings.
Solution Approach 2:
The patent employs thin optical fiber structures instead of bulky thermocouple assemblies. The optical fibers are sufficiently thin to be integrated into the substrate without occupying significant space, enabling high-density sensor arrays that improve spatial resolution while the fiber materials are selected to withstand high temperature environments.
2Measurement precision
If multiple temperature sensors are integrated into the substrate, then temperature detection capability is improved, but device complexity increases due to the need for separate grooves and wire connections for each sensor
Solution Approach 1:
The patent merges multiple sensing functions into a single optical fiber by incorporating multiple Bragg gratings along its length. Each grating reflects a specific wavelength corresponding to a different measurement point, allowing multiple temperature sensors to be integrated into one substrate without requiring separate grooves or electrical connections for each sensor, thereby reducing device complexity.
Solution Approach 2:
The optical fiber serves multiple functions simultaneously: it acts as both the sensing element and the signal transmission medium for multiple measurement points. The single fiber with multiple Bragg gratings provides universal temperature monitoring across the substrate, eliminating the need for separate electrical wiring infrastructure for each sensor.
3Measurement precision
If a single optical fiber with multiple Bragg gratings is used, then spatial resolution is improved through high density of measurement points, but manufacturing complexity increases due to the need for precise grating positioning
Solution Approach 1:
The patent applies Bragg gratings to the optical fiber before the fiber is integrated into the substrate. This preliminary application allows for precise positioning and spacing of the gratings to be established during the sensor fabrication process itself, rather than requiring complex post-installation positioning procedures, thereby reducing manufacturing complexity while maintaining high spatial resolution.
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 approach enables early and accurate detection of defects such as delamination and fractures by increasing the number of measurement points without increasing the device's size, and allows for high-temperature measurements, improving defect detection sensitivity and spatial resolution.
Implementation Method 1
The support contains an optical fiber with a Bragg grating at each measurement point. Each Bragg grating is characterized by a wavelength which varies depending on the temperature and an acoustic signal measured at the corresponding measurement point.
Implementation Method 2
The support contains an optical fiber with a Bragg grating at each measurement point... an optical signal sent through the optical fiber is reflected by the Bragg gratings
Data Source
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AI summary
This device for detecting a defect during the manufacture of a part by an additive manufacturing process, comprises: - a support having an optical fiber (56) which extends from a proximal end (82) to a distal end (80) passing through measurement points (P1 to P24), this optical fiber having, at each of these measurement points, a Bragg grating, and - a processing unit (50) connected to the proximal end (82) of the optical fiber and configured to obtain a measurement of a temperature or an acoustic signal at each of the measurement points from a measurement of an optical signal which has interacted with the Bragg grating located at that measurement point.