Terahertz Sensor Offset for Tube Wall Deformation Detection
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Solution Overview
Problem
Terahertz measurement methods face challenges in accurately measuring the wall thickness of extruded tubes, particularly due to sagging effects and non-ideal surface conditions, leading to imprecise detection of inner surface deformations like sagging, eccentricity, and ovality.
Innovation Solution
A THz measurement device with a main sensor and an additional sensor, where the additional sensor is offset by a sensor angle relative to the main sensor, allows for detection of reflection peaks on deformed inner surfaces, enabling precise measurement of wall thickness deformations by distinguishing between proper and improper reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single THz sensor is positioned perpendicular to the pipe axis to measure wall thickness, then the measurement setup is simple, but the inner surface deformations like sagging cannot be detected accurately
Solution Approach 1:
The measurement system is segmented into multiple sensors positioned at different angular locations around the pipe. Each sensor measures a specific wall region, and by combining measurements from multiple segments, the system achieves complete coverage and accurate detection of inner surface deformations while maintaining relatively simple individual sensor setups
Solution Approach 2:
The measurement approach transitions from a single perpendicular measurement dimension to multiple angular dimensions around the pipe circumference. By positioning sensors at different angles and rotating them around the pipe axis, the system captures three-dimensional wall thickness information, enabling detection of sagging and other deformations that cannot be detected from a single perpendicular viewpoint
2Measurement precision
If multiple pairs of transmitters and receivers are rotated around the object to focus THz radiation onto the longitudinal axis, then wall thickness changes can be determined, but reflection peaks cannot be determined for non-perpendicular interfaces
Solution Approach 1:
Different measurement locations around the pipe are treated with local quality principles. Sensors positioned at specific angular locations are optimized for detecting specific types of wall deformations. The system adapts the measurement approach locally at each angular position to account for the specific geometry and deformation characteristics at that location, improving overall measurement accuracy
Solution Approach 2:
The measurement system incorporates dynamic rotation of sensors around the pipe axis during operation. This dynamic positioning allows the system to capture wall thickness information from multiple angles and to track the movement of deformation features like sagging as they occur during pipe extrusion, enabling accurate determination of reflection peaks from varying interface orientations
3Measurement precision
If THz radiation is emitted perpendicular to the pipe axis to detect reflection peaks, then outer surface measurements are accurate, but deformed inner surfaces cannot be properly detected
Solution Approach 1:
The measurement system introduces asymmetry by positioning sensors at non-perpendicular angular locations around the pipe axis. This asymmetric arrangement allows detection of inner surface deformations that would be invisible to perpendicular sensors. The asymmetric sensor positions create varied measurement perspectives that reveal sagging and other deformations while maintaining accurate outer surface measurements through complementary sensor placements
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 qualitative and quantitative detection of sagging and other deformations with minimal effort, differentiating between acceptable deformations and defects, and allowing for wide-area measurements with reduced equipment and energy usage.
Implementation Method 1
The THz radiation incident along the optical axis is partially reflected at the pipe's interfaces, so that, when incident perpendicularly along the optical axis, it is reflected back and can be detected as a reflection peak in the recorded signal amplitude
Implementation Method 2
The layer thicknesses can be determined as time-of-flight measurements of the THz radiation
Data Source
Figure 1~5
Figure 6~8
Figure 9~10
AI summary
The invention relates to a THz measuring device (7) for measuring at least a wall thickness (d) of a tubular object (1) having an inner surface (1b) and an outer surface (1a), comprising a THz main sensor (8) for emitting a THz main beam (12) along a first optical axis (A1) through an axis of symmetry (B) of the object (1) and for receiving THz radiation reflected at the outer surface (1a) and the inner surface (1b) along the first optical axis (A1), a THz auxiliary sensor (9) for emitting a THz auxiliary beam (14) along a second optical axis (A2), which is offset relative to the first optical axis (A1) by a sensor angle (a) and does not pass through the axis of symmetry (B) at least temporarily, and for detecting the THz auxiliary beam (14) reflected back along the second optical axis (A2), and an evaluation- and control device (16) which receives a first signal amplitude (S1) from the THz main sensor (8,30-8) and a second signal amplitude (S2) of the THz auxiliary sensor (9, 18, 19, 30-i), determines reflection peaks in the signal amplitudes (S1, S2) and detects an internal wall thickness deformation (2) if it - in the first signal amplitude (S1) determines an outer reflection peak (P1) of the outer surface (1a) of the wall region (5, 6) without the inner reflection peak of the inner surface (1b) of the wall region (5, 6), and - in the second signal amplitude (S2) determines an inner reflection peak (P2) of the inner surface (1b) of the wall region (5, 6).