Surface Property Measurement with In-Process Distortion Compensation
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Solution Overview
Problem
Conventional surface property measurement instruments face significant uncertainties due to instrument frame and stage distortion, which are difficult to detect and compensate for, especially under non-linear, non-repeatable, and time-dependent conditions, leading to size-dependent and inaccurate measurements.
Innovation Solution
The apparatus and method utilize a reference sensor to measure the relative location of a stylus and the specimen surface under known loading conditions, minimizing the dependency on instrument frame and stage characterization by maintaining a constant relative proximity between the sensor and the surface, thereby compensating for distortions in the measurement process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional instruments use distortion calibration with amorphous material, then measurements can be compensated for instrument frame distortion, but the stiffness of the amorphous material differs from the specimen, adding uncertainty to the calibration process
Solution Approach 1:
The patent changes the calibration approach by using a rigid reference object with known geometric properties instead of amorphous material. This allows the instrument to measure distortion effects independently of material stiffness variations, as the reference object's geometry provides stable, repeatable reference points that are not affected by the compliance differences between calibration and measurement materials.
Solution Approach 2:
The patent introduces a rigid reference object as an intermediary element that mediates between the indenter and the specimen. This reference object serves as a stable geometric baseline that allows the system to separate and compensate for instrument distortion from the actual material response, enabling accurate measurements without being affected by the compliance mismatch between calibration and measurement samples.
2Measurement precision
If conventional instruments use force sensor displacement calculation, then depth of penetration can be measured, but additional uncertainties arise from deconvolving which displacements are related to distortions and which are related to depth of penetration
Solution Approach 1:
The patent segments the measurement system into distinct functional components: a rigid reference object that provides geometric reference, a force sensor that measures applied load, and a proximity sensor that measures stylus position. This segmentation allows each component to be independently characterized and compensated for, simplifying the overall measurement process by separating distortion effects from penetration depth measurements.
Solution Approach 2:
The patent replaces the conventional mechanical displacement measurement approach with a hybrid system that uses proximity sensing to directly measure stylus position relative to the specimen surface. This substitution eliminates the need to deconvolute force sensor displacements into distortion and penetration components, as the proximity sensor directly measures the geometric relationship between the stylus and surface independent of mechanical compliance effects.
3Adaptability or versatility
If conventional instruments perform measurements under non-linear, non-repeatable, time-dependent loading conditions, then real-world material behavior can be characterized, but instrument frame and stage distortion becomes difficult to detect and compensate for
Solution Approach 1:
The patent employs dynamic measurement capabilities that allow the system to adapt to varying loading conditions while maintaining measurement accuracy. The rigid reference object provides a stable geometric baseline that remains valid under non-linear, time-dependent loading, enabling the system to characterize real-world material behavior without being compromised by instrument distortion. The proximity sensor continuously monitors stylus position, allowing real-time compensation for any frame or stage distortion that occurs during dynamic testing.
Data Source
AI summary
The present invention provides an apparatus and method for performing surface property measurements, such as workpiece hardness and other material property measurements, with in-process compensation for instrument frame distortion and the like. The apparatus includes a substantially rigid base; a stylus coupled to the substantially rigid base, the stylus configured and selectively positioned to interact with a surface of a specimen at points along a central axis of the stylus; a proximity detector sensor coupled to the substantially rigid base, the proximity detector sensor disposed at a predetermined distance from the surface of the specimen and operable for sensing the predetermined distance between the proximity detector sensor and the surface of the specimen; and a proximity detector actuator coupled to the substantially rigid base, the proximity detector actuator operable for maintaining the predetermined distance between the proximity detector sensor and the surface of the specimen as the substantially rigid base and the stylus are moved with respect to the surface of the specimen along the central axis of the stylus.