Abstract

Start

Mr Meyers's speech in Seattle about this chapter. (7 min, 818k, a streaming Real Audio file. Download the Player) ASNT prohibits the further distribution of the audio record. Since we don't want to escalate the matter into the legal arena, we have decided to delete it - Sorry. See also ASNT Policies taken to Extemes. Conventional UT Techniques Longitudinal or Mode Converted Shear Wave Inspection Interrogation Along a Line Through the Part Limitation: Mechanical Scanning is Necessary to Inspect the Entire Part "New" Concept Applications Involving Sheet or Tubular Geometries Guided Waves Can Interrogate Large Areas (perhaps the entire part) from a Single Location Guided Waves What Are They? How Are They Generated? What Are the Defining Variables? What Are the Limitations? Guided Waves Are: Waves whose propagation characteristics depend on a structural boundary (Lots of reflections, mode conversion, hence wave superposition to form packets of energy, or modes, that depend on wave input angle and frequency) i.e. rods, tubes, and embedded layers, etc. Fig.1: Guided Waves: Generation of Symmetric Modes. Fig 1 and Fig 2 as Animated Image Fig.2: Guided Waves: Generation of Antisymmetric Modes Fig.3: Particle Displacements for a Perfect Plate Particle Displacements Motion ???? Fig.4: Guided Wave Dispersion Curve Wave Structure: Describes the Distribution of Particle Motion Through the Thickness of the Plate When Multiple Layers Exist, the Wave Structure Can Become More Complex Fig.5: Possible Wave Structures (depends on the location on the dispersion curve) Fig.6: Other Possible Wave Structures Fig.7: Guided Wave Dispersion Curve Different Modes Have Different Regions of Sensitivity Through the Thickness of the Material Selection of the Appropriate Mode is Very Important to Inspection Optimization Limitations Not Practical for Materials Thicker Than 0.25 inch Requires a Basic Understanding of the Flaw Geometry Multiple Modes Broad Bandwidth Transducers Permit the Generation of More Modes More Available Modes Improve Probability of Detection, Classification, and Sizing <-- Speech end

Piezocomposite Transducer Technology

Desirable Characteristics of UT Transducers for Guided Wave Applications

• High Pulse Amplitude (and Low Noise)
• Broad Bandwidth
• Conformability
• Good Acoustic Impedance Match to Testpiece

Historical Design Perspective

• Theoretical Modeling Helps Us Understand Current Transducer Performance
• Piezoceramic Ceramic Properties Have Been Limited
• Can Improved Piezoceramic Properties Improve Transducer Performance Theoretically?

KLM MODEL RESULTS

Fig.8: Waveform and Spectrum of a PZT Element in Water

Fig.9: Waveform and Spectrum of heavily backed PZT Element in Water

Fig.10: Waveform and Spectrum of heavily backed PZT Element with a matching Layer

Fig.11: Waveform and Spectrum of an Low Acoustic Impedance Piezoelement in Water

Fig.12: Waveform and Spectrum of an electrically matched Air backed Low Acoustic Impedance Piezoelement in Water

Why Investigate New Piezoelectric Materials?

• Theoretical Modeling Indicates Significant Performance Improvements Can Be Achieved!

Structural Composite Material

• Combination of Two or More Materials
• Properties Not Available in Any Constituent Material

Piezocomposite Material

• Combination of a Piezoelectric Material and Some Other Material
• Improved Piezoelectric Performance

Fig.13: Rods Ceramic in a PolymerMatrix	Fig.14: Acoustic Impedance as a Function of Ceramic Volume Fraction	Fig.15: Thickness Coupling Factor as a Function of Ceramic Volume Fraction	Fig.16: Bandwidth Comparison of Piezocomposite and Conventional PZT Transducers on an IIW Test Block
Fig.17: Received Signal Spectra (No Attenuation)	Fig.18: Received Signal Spectra (Attenuation Factor =0.05)	Fig.19: Received Signal Spectra (Attenuation Factor =0.1)	Fig.20: Experimental Correlation with Theory

What Can We Do With This "New" Technique?

Guided Wave Applications

• Aging Aircraft Inspection
• Steam Generator Tubing Inspection
• Manufacturing


Aging Aircraft Inspection


Fig.22: Lap Splice Joint Inspection. Large Amplitude = Good Bond

Fig 23: Handheld Guided Wave Probe

Fig 24: Effect of Frequency Tuning


Fig.25: Tear Strap Inspection. A Large Reflection From the Distant Side of the Tear Strap Indicates a High Quality Bond

Fig 26: Tear Strap Inspection

Fig 27: Tear Strap Inspection - Results

Steam Generator Tubing Inspection

Fig 28: Conventional and Guided Wave Inspection Techniques

Fig 30: Schematic of Segmented Probe

Fig 31: Boreprobe Waveform

Fig 32: Boreprobe Segment Response

Manufacturing

Fig 33: losed Loop Monitoring and Control Powder Metal Part Characterization
Article: Advances in Ultrasonic Inspection Techniques for Monitoring the Powder Injection Molding Process
Recently, guided waves have been considered as potential tools for monitoring the powder injection molding process. This work relies on the integration of guided wave mechanics modeling and viscoelasticity. Using the theoretical model as a guideline, guided wave modes with optimum sensitivity to PIM defects can be selected for inspection purposes. This technology is applied to in- situ inspection of a powder injection molded part, a cylindrical motor component, for defect detection. Joseph L. Rose*, Randall M. German, and Derrick D. Hongerholt* Engineering Science and Mechanics, The Pennsylvania State University .

Fig 34: Wave Propagation Analysis in a Cylinder

Summary

• Guided Wave Techniques May Be Faster and More Effective for Ultrasonic Inspection of Certain Geomitries
• Piezocomposite Transducer Technology Enhances These Methods
• Experimental Results Demonstrate the Usefulness of the Technique

Authors:

Paul A. Meyer, Ph.D.