METHOD FOR THE OPTIMIZATION OF STRESS DISTRIBUTION IN ACOUSTIC THERMOGRAPHY APPLICATIONS

• US 20090204345A1
• Filed: 01/29/2009
• Published: 08/13/2009
• Est. Priority Date: 02/12/2008
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Broddegaard, Mattias, Homma, Christian, Rothenfusser, Max
• Granted Patent: US 7,974,791 B2
• Time in Patent Office: Days
• US Class Current: 702/39
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/2693 Rotor or turbine parts
• CPC Class Codes: G01N 29/12 by measuring frequency or resonance of acoustic waves measuring frequency or resonant frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04, G01H13/00; acoustic resonators G10K11/04; vibration or shock testing of structures G01M7/00
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects
• CPC Class Codes: G01N 29/4418 with a model, e.g. best-fit, regression analysis
• CPC Class Codes: G01N 29/4472 Mathematical theories or simulation

Abstract

In a method for the optimization of stress distribution on an object to be tested for flaws by ultrasound excitation and evaluation based on resulting surface temperature distribution, —a simulation is performed under test conditions on a CAD model of the object prior to a testing an object, —vibrational spectra and modal vibrational forms are calculated, —local mechanical stresses are determined from the vibrational modes, whereby—modes to be excited for the real test are selected from the entirety of the occurring modes such that, —the mechanical stress lies in a selected region above a predetermined minimum stress to enable a reliable proof of defect, —the mechanical stress in all other regions of the inspection part, in particular on easily damaged component structures, is smaller than a predetermined maximum stress by a predetermined factor, in order not to damage the component at weak points.

Claims

1. A method for the optimization of stress distribution on an object to be tested for defects using ultrasound excitation and evaluation on the basis of a resulting surface temperature distribution, with the following steps:

performing a simulation on a Computer Aided Design (CAD) model of the object under test conditions prior to testing an object,

calculating vibrational spectra and modal vibrational forms,

determining local mechanical stresses from the vibrational modes in each instance, wherein

modes to be excited for the real test being selected from the entirety of the occurring modes such that

the mechanical stress lies in a selected region above a predetermined minimum stress in order to enable a reliable proof of defect, and

the mechanical stress in all other regions of the inspection part is smaller than a predetermined maximum stress by a predetermined factor in order not to damage the component at weak points.

2. The method according to claim 1, wherein the all other regions of the inspection part are easily damaged component structures.

3. The method according to claim 1, wherein a finite element simulation method is used to calculate vibrational spectra and modal vibrational forms.

4. The method according to claim 1, wherein all modes are firstly calculated in the frequency range between approximately 15 and 25 kHz and the occurring mechanical stresses are calculated for these modes.

5. The method according to claim 1, wherein selected optimum resonance frequencies are matched to the real component, by the vibrational spectra of the real component being measured and compared with the calculated spectrum of the model.

6. The method according to claim 5, wherein the vibrational spectrum of the real component is measured by excitation with the ultrasound exciter in the case of a low output by detection with a vibrational sensor, for instance laser vibrometer.

7. The method according to claim 5, wherein the two spectra are aligned by means of a correlation algorithm.

8. The method according to claim 1, wherein the site of coupling-in for the ultrasound exciter is adjusted to the component form.

9. A system for the optimization of stress distribution on an object to be tested for defects using ultrasound excitation and evaluation on the basis of a resulting surface temperature distribution, comprising:

means for performing a simulation on a Computer Aided Design (CAD) model of the object under test conditions prior to testing an object,

means for calculating vibrational spectra and modal vibrational forms,

means for determining local mechanical stresses from the vibrational modes in each instance, wherein

modes to be excited for the real test being selected from the entirety of the occurring modes such that

the mechanical stress lies in a selected region above a predetermined minimum stress in order to enable a reliable proof of defect, and

the mechanical stress in all other regions of the inspection part is smaller than a predetermined maximum stress by a predetermined factor in order not to damage the component at weak points.

10. The system according to claim 9, wherein the all other regions of the inspection part are easily damaged component structures.

11. The system according to claim 9, wherein a finite element simulation method is used to calculate vibrational spectra and modal vibrational forms.

12. The system according to claim 9, wherein all modes are firstly calculated in the frequency range between approximately 15 and 25 kHz and the occurring mechanical stresses are calculated for these modes.

13. The system according to claim 9, wherein selected optimum resonance frequencies are matched to the real component, by the vibrational spectra of the real component being measured and compared with the calculated spectrum of the model.

14. The system according to claim 13, wherein the vibrational spectrum of the real component is measured by excitation with the ultrasound exciter in the case of a low output by detection with a vibrational sensor, for instance laser vibrometer.

15. The system according to claim 13, wherein the two spectra are aligned by means of a correlation algorithm.

18. The system according to claim 9, wherein the site of coupling-in for the ultrasound exciter is adjusted to the component form.