Rotated Flat-Bottom Hole Sample for Mal-Oriented Crack Detection

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Solution Overview

Problem

Existing ultrasonic inspection methods struggle to effectively detect mal-oriented cracks in rotating disk components due to minimized reflection and enhanced diffraction, necessitating the use of traditional flaws like flat bottom holes (FBHs) that are difficult to fabricate for calibration and Probability of Detection (POD) purposes.

Innovation Solution

The development of artificial diffraction inspection samples with flat bottom holes positioned in the axial-radial plane and rotated around an acoustic path vector, featuring a complimentary incidence angle and edges to create diffracted energy, which mimic mal-oriented cracks and are easier to produce.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional flat bottom holes (FBHs) are used for ultrasonic calibration and POD purposes, then volumetric flaws in reflection mode can be detected, but mal-oriented cracks cannot be effectively detected due to minimized reflection

Engineering Contradiction:

Improvedetection capabilityVSAvoidapplicability to mal-oriented cracks

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent changes the geometric parameters of the artificial flaw by rotating the bottom surface of the FBH around an acoustic path vector to create a complimentary incidence angle. This parameter modification transforms the flaw's interaction with the acoustic wave from reflection-dominated to diffraction-dominated, enabling effective detection of mal-oriented cracks while maintaining ease of fabrication

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates artificial flaws that copy the diffraction characteristics of mal-oriented cracks by configuring the FBH bottom surface with specific orientation and incidence angle. This allows the artificial flaw to replicate the diffraction response of real cracks, enabling accurate POD assessment for mal-oriented crack detection

Inventive Principle:

Principle #26Copying

2Measurement precision

If samples are designed with flaws characteristic of target flaws (mal-oriented cracks), then POD reflects real inspection behavior, but fabrication becomes nearly impossible

Engineering Contradiction:

ImprovePOD accuracyVSAvoidfabrication difficulty

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

Instead of attempting to fabricate impossible-to-create internal cracks in samples, the patent inverts the approach by using easily manufacturable FBHs with modified bottom surface orientation. The FBH bottom surface is rotated to create a complimentary incidence angle that produces diffraction responses similar to mal-oriented cracks, achieving POD accuracy without fabrication impossibility

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent modifies the FBH geometry by rotating the bottom surface around the acoustic path vector to establish a complimentary incidence angle. This parameter change transforms the easily manufacturable FBH into an artificial flaw that replicates the diffraction characteristics of mal-oriented cracks, bridging the gap between fabrication ease and measurement precision

Inventive Principle:

Principle #35Parameter changes

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

Facilitates the detection of mal-oriented cracks by maintaining consistent diffraction response and reducing fabrication complexity, thereby enhancing the Probability of Detection (POD) capability.

Implementation Method 1

the diffraction response is based on the crack effective radius and the sound path incidence angle on the crack. The diffraction mode is usually characterized by weaker returned signals versus the reflection mode

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

the edges of the complimentary bottom surface are configured to create diffracted energy received by sensors during testing

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentEP4711757A1Artificial flaw method for ultrasonic diffraction inspection sample

Publication Date: 2026.03.18 RTX CORP

Figure 1~2
Figure 3

AI summary

An artificial diffraction inspection sample including a sample component having a component body with an exterior surface; and a complimentary flat bottom hole formed in the component body, the complimentary flat bottom hole comprising a complimentary bottom surface with a complimentary incidence angle, the complimentary bottom surface being rotated around an acoustic path vector; wherein the complimentary bottom of the complimentary flat bottom hole represents an axial-radial crack.