Stress-Independent Microstructure Characterization via Magnetic Field Intersection
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Solution Overview
Problem
Existing non-destructive testing methods for materials, such as electromagnetic testing of steels, face challenges in distinguishing microstructural states from residual stress states, leading to interference and reduced measurement accuracy when stress is considered a target variable.
Innovation Solution
The method involves applying varying load voltages and magnetic fields to determine a characteristic magnetic field strength where measured variables like magnetic flux density or permeability remain constant, allowing for stress-independent characterization of the microstructural state by identifying points of intersection in hysteresis curves or similar values across different load stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic testing methods are used to characterize microstructure, then measurement capability is provided, but stress interference contaminates the measurement
Solution Approach 1:
The patent applies parameter changes by varying the load voltage across multiple levels (at least two different magnitudes) and measuring the electromagnetic response at each voltage level. By analyzing how the measured variable changes with both magnetic field strength and load voltage, the method identifies a characteristic magnetic field strength where the response becomes independent of stress, thereby eliminating stress interference from the microstructure characterization.
Solution Approach 2:
The patent implements feedback by measuring the electromagnetic response at multiple load voltage levels and using this information to determine a characteristic magnetic field strength. The measured variables from different voltage levels are compared and used to identify the specific magnetic field strength where the response is invariant to stress changes, creating a self-correcting measurement approach that eliminates stress interference.
2Measurement precision
If stress is considered a target variable in measurement, then stress characterization is achieved, but structural influences become disturbance variables reducing measurement effectiveness
Solution Approach 1:
The patent segments the measurement process into multiple independent components: measuring the electromagnetic response at different load voltage levels separately, then analyzing the relationships between these measurements. This segmentation allows the method to distinguish between stress-dependent and stress-independent components of the measurement, enabling stress characterization while maintaining reliable microstructure measurement through the characteristic magnetic field strength identification.
3Measurement precision
If multiple load voltages are applied to eliminate stress influence, then measurement independence from stress is achieved, but measurement complexity increases
Solution Approach 1:
The patent applies universality by using the same electromagnetic measurement setup for multiple purposes: characterizing microstructure, determining stress state, and identifying the characteristic magnetic field strength. The method uses the load voltage variation mechanism to achieve stress-independent measurement while also providing stress characterization capability, making the measurement system multi-functional without requiring separate devices for each measurement type.
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 accurate, non-destructive characterization of microstructural states independently of stress conditions, allowing for comparison of multiple materials without suppressing stress influences, thus maintaining measurement effectiveness.
Implementation Method 1
If a magnetic field is applied to a material that is subjected to a voltage or load voltage, various measured variables can be determined that depend on the field strength of the applied magnetic field. Such measured variables can be, for example, the magnetic flux density or the overlay permeability.
Implementation Method 2
The curves of the measurand as a function of the magnetic field strength or the quantity derived from the measurand as a function of the magnetic field strength thus overlap at the characteristic magnetic field strength for at least two load voltages applied to the material
Implementation Method 3
In 'Residual stresses and distortion due to the effects of heat' [Online] 1999, WILEY-VCH Verlag, Weinheim, ISBN: 3-527-27143-0, URL: www3.interscience.wiley.com/cgi-bin/booktext/114029440/BOOKPDFSTART, pages 407-425 describes a device for determining thermally induced internal stresses, which is based on the load-voltage-dependent measurement of Barkhausen noise.
Data Source
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AI summary
The invention relates to a method and a corresponding device for characterizing the microstructure of a material, wherein: - the material is subjected at least partially to at least two load voltages of different magnitudes, - a magnetic field (Ht) is applied to the material subjected to the load voltages, - a measured quantity (B,μΔ) is recorded for each load voltage as a function of a magnetic field strength of the magnetic field, - a characteristic magnetic field strength is determined at which the measured quantity or a quantity derived from the measured quantity has a substantially the same value for at least two of the load voltages, and - the microstructure of the material is characterized by the characteristic magnetic field strength.