Optical Scaling Factor Determination for Strain Measurement Accuracy
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Solution Overview
Problem
Conventional methods for determining scaling factors for strain measurements on machine elements are costly, time-intensive, and often inaccurate due to limitations in measuring maximum strains at precise locations and accounting for geometric deviations.
Innovation Solution
A method and apparatus that utilize optical measurement techniques to determine scaling factors by measuring strains on a machine element, calculating displacement and strain fields, and deriving a scaling factor based on these measurements, thereby improving accuracy and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional strain gauges are used to measure maximum strains at predefined positions, then the measurement process is simple and direct, but the accuracy deteriorates due to geometric deviations and inability to capture true maximum strain locations
Solution Approach 1:
The patent replaces the mechanical strain gauge measurement system with an optical measurement system. Instead of using strain gauges that require physical contact and precise positioning, the invention uses optical methods (such as speckle interferometry or digital image correlation) to measure surface displacements and calculate strains non-contactly. This substitution enables accurate capture of maximum strain locations without being constrained by geometric deviations, as the optical system can measure the actual deformed state of the component surface.
Solution Approach 2:
The patent transitions from point-based strain measurements (one-dimensional location) to full-field surface measurements (two-dimensional surface). By measuring displacements across the entire surface and calculating strain fields, the system captures the spatial distribution of strains, identifying true maximum locations regardless of predefined positions. This dimensional expansion from discrete points to continuous surface measurement resolves the accuracy issue caused by geometric deviations.
2Measurement precision
If extensive laboratory analyses with additional strain gauges are conducted to determine scaling factors, then the accuracy of scaling factor determination improves, but the time consumption and costs increase significantly
Solution Approach 1:
The patent replaces the time-consuming mechanical process of applying multiple strain gauges during laboratory calibration with a rapid optical measurement system. The optical system captures full-field displacement data in a single measurement cycle, eliminating the need for tedious manual gauge application and multiple measurement setups. This substitution reduces calibration time from potentially days to minutes or seconds, while maintaining or improving accuracy through comprehensive field measurement.
Solution Approach 2:
The patent performs preliminary optical scanning and full-field measurement before the actual strain measurement is needed. By capturing the complete displacement field and calculating strain distributions in advance, the system establishes accurate scaling factors prior to operational use. This preliminary action eliminates the need for repeated laboratory analyses and allows for rapid determination of scaling factors.
3Ease of manufacture
If strain gauges are applied at positions defined by finite element calculations, then the measurement setup is straightforward, but the reliability deteriorates when geometric deviations cause displacement of maximum strain positions
Solution Approach 1:
The patent replaces the calculation-based positioning approach with measurement-based positioning. Instead of relying on finite element calculations to predict maximum strain locations, the optical system directly measures the actual strain distribution on the component surface. This substitution makes the measurement setup equally straightforward (requiring only optical access) while dramatically improving reliability by capturing the true maximum locations regardless of geometric variations from the nominal model.
Solution Approach 2:
The patent changes the measurement parameter from predefined positional coordinates to actual measured displacement fields. By measuring the complete surface displacement pattern and deriving strain fields from actual measurements rather than theoretical calculations, the system adapts to geometric deviations. The maximum strain locations are identified based on measured data, not calculated predictions, ensuring reliability despite manufacturing tolerances.
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 method enhances the accuracy and validity of scaling factor determination, reduces the need for extensive laboratory analyses, and shortens turnaround times for compressor blisks, leading to more efficient and reliable strain measurement validation.
Implementation Method 1
measuring a displacement of at least one detection surface portion of the machine element that differs from the measurement surface portion of the machine element, in particular by optical scanning of the machine element
Data Source
AI summary
The present invention relates to an apparatus and a method for determining a scaling factor for a strain measurement in a machine element, comprising steps for measuring a strain in a measurement surface portion by means of a strain measuring device; for measuring a displacement of a detection surface portion of the machine element by an optical scanning; for determining a displacement field on a surface of the machine element on the basis of a model of the machine element and the measured displacement of the at least one detection surface portion; for determining a strain field on the surface of the machine element on the basis of the determined displacement field and the model of the machine element; and for determining a scaling factor of the strain measuring device on the basis of the determined strain field and the measured strain in the measurement surface portion.