Piezoelectric Element Crack Detection Using Resistive Impedance

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Solution Overview

Problem

Existing crack detection methods for piezoelectric elements in HDD suspensions face challenges due to the difficulty in optical observation and the susceptibility to erroneous detection caused by sharp changes in dielectric loss tangent around resonant frequencies, especially with variations in piezoelectric element types.

Innovation Solution

Measuring the resistive component of impedance between electrodes and using formulas such as F(xi, ai) or F(bi, xi) to calculate a determination value, allowing for accurate crack detection by setting a threshold value based on the resistive component measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If dielectric loss tangent is measured to detect cracks, then crack detection capability is improved, but measurement precision deteriorates due to sharp changes around resonant frequency

Engineering Contradiction:

Improvecrack detection capabilityVSAvoidmeasurement precision

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameter from dielectric loss tangent to resistive component of impedance. This parameter substitution eliminates the sharp variation problem around resonant frequency while maintaining crack detection capability, as the resistive component shows stable characteristics that enable precise threshold-based detection

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the electrical measurement approach (dielectric loss tangent) with an alternative electrical measurement approach (resistive component of impedance). This substitution resolves the measurement precision issue by utilizing a different electrical property that does not exhibit sharp variations near resonant frequency

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If threshold value is set for crack detection, then detection speed is improved, but reliability deteriorates due to difficulty in setting appropriate threshold

Engineering Contradiction:

Improvedetection speedVSAvoidreliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

By changing the measurement parameter to resistive component of impedance, the patent creates a measurement characteristic with clear separation between cracked and non-cracked states. This enables reliable threshold setting because the resistive component exhibits stable and distinct values for different crack conditions, eliminating the uncertainty in threshold selection

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If optical observation is used for crack detection, then measurement precision is improved, but ease of operation deteriorates due to difficulty in observing small piezoelectric elements

Engineering Contradiction:

Improvecrack detection precisionVSAvoidease of operation

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent replaces optical observation with an electrical measurement system that measures the resistive component of impedance. This substitution eliminates the need for direct visual observation of small piezoelectric elements, making the detection process easier to operate while maintaining high precision through electrical property measurements

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Reduces the possibility of erroneous detection by providing clear distinctions between crack-free and cracked piezoelectric elements, irrespective of the type of piezoelectric element used, through precise threshold setting.

Implementation Method 1

applying a resonant-frequency voltage to a piezoelectric element (22)

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

measuring a resistive component of an impedance between a pair of electrodes (22a and 22b) of the piezoelectric element (22) alone due to the application of the voltage

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS20250224357A1Crack detection method for piezoelectric element and crack detection device for piezoelectric element

Publication Date: 2025.07.10 SUNCALL CORP

AI summary

A crack detection device for a piezoelectric element, capable of reducing the possibility of erroneous detection applies a resonant-frequency voltage to a piezoelectric element using an impedance analyzer. A resistive component of an impedance between a pair of electrodes provided in the piezoelectric element due to the application of the voltage is measured by the impedance analyzer. A calculation unit calculates a determination value with respect to the measured value of the measured resistive component of the impedance. A determination unit takes the calculated determination value into consideration and determines whether a crack has occurred in the piezoelectric element on the basis of a preset threshold.