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Federal Highway Administration Research and Technology
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Publication Number: FHWA-HRT-04-042
Date: July 2004 |
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Guidelines for Ultrasonic Inspection of Hanger PinsPDF Version (1.29 MB)
PDF files can be viewed with the Acrobat® Reader® FOREWORDIn June 1983, a failed hanger pin initiated the tragic collapse of one span of the Mianus River Bridge on the Connecticut Turnpike near Greenwich, CT. This incident resulted in the deaths of three motorists. Following the collapse, there was an immediate increase in interest in the inspection and condition evaluation of bridge hanger pins. Ultrasonic inspection is one of the most reliable methods used to inspect hanger pins, and it has become the primary method of performing a detailed inspection of an in-service hanger pin. This report provides background information regarding hanger pins in general and discusses the field ultrasonic techniques, including methods, results, and limitations of each method. The report provides a comprehensive document describing the fundamentals of ultrasonic hanger pin inspection and can be used by State transportation agencies that are either inspecting pins themselves or contracting for inspection services. In addition, a limited experimental program was utilized to emphasize, and more completely explain, some important aspects of ultrasonic pin inspection. This report will be of interest to bridge engineers, designers, and inspectors who are involved with the inspection of hanger pin assemblies used in our Nation's highway bridges. T. Paul Teng,
P.E. NOTICE This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for its contents or use thereof. This report does not constitute a standard, specification, or regulation. The U.S. Government does not endorse products or manufacturers. Trade and manufacturers' names appear in this report only because they are considered essential to the object of the document. Technical Report Documentation Page
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized TABLE OF CONTENTS1. INTRODUCTION 1.1. BACKGROUND 1.2. OBJECTIVE 2.1. ULTRASONIC TESTING EQUIPMENT 2.1.1. Fundamentals of Ultrasonic Waves 2.1.1.1. Pulse-Echo Technique 2.1.1.2. Pitch-Catch Technique 2.1.2. Decibel Scale 2.1.3. Transducers 2.1.4. Ultrasonic Beam Characteristics and Important Formulae 2.1.4.1. Beam Attenuation 2.1.4.1.1. Beam diffraction 2.1.4.1.2. Beam absorption 2.1.4.2. Beam Spread (Beam Divergence) 2.1.4.3. Beam Centerline Location 2.1.5. Distance Amplitude Correction 2.2. GENERAL HANGER PIN INSPECTION REQUIREMENTS 2.2.1. Cleaning and Coupling Requirements 2.2.2. Scanning Patterns 2.2.3. Application and Sensitivity of Straight and Angle Beam Transducers 2.2.4. Interpretation of Ultrasonic Testing Signals 2.2.5. Defect Sizing Techniques 2.2.5.1. Probe Movement Techniques 2.2.5.1.1. The 6-dB drop technique 2.2.5.1.2. The 20-dB drop technique 2.2.5.1.3. The time-of-flight diffraction technique 2.2.5.2. Amplitude Techniques 2.2.5.2.1. The comparator block technique 2.2.5.2.2. The distance amplitude correction technique 2.2.5.2.3. The distance grain size technique 2.2.6. Wear Grooves 2.2.7. Acoustic Coupling 2.3.1. Physical Measurements 2.3.2. Visual Assessments 2.3.3. Ultrasonic Testing Data Collection 2.4. INSPECTOR QUALIFICATIONS AND CERTIFICATIONS 3.1. INTRODUCTION 3.2. INSPECTION SPECIMENS 3.2.1. Side-Drilled Hole Test Block 3.2.2. Manufactured Cracked Pins 3.2.3. Pin/Hanger Mockup 3.3. TESTING PROGRAM 3.3.1. Beam Diffraction 3.3.2. Distance Amplitude Correction 3.3.3. Angle and Straight Beam Sensitivity to Cracks 3.3.4. Defect Sizing 3.3.5. Acoustic Coupling 4.1. BEAM DIFFRACTION 4.2. DISTANCE AMPLITUDE CORRECTION 4.3. ANGLE AND STRAIGHT BEAM SENSITIVITY TO CRACKS 4.4. DEFECT SIZING 4.5. ACOUSTIC COUPLING LIST OF FIGURESFigure 1. Model of an elastic material Figure 2. Longitudinal wave Figure 3. Shear wave Figure 4. Basic principle of pulse-echo technique Figure 5. Sketch of a typical ultrasonic A-scan Figure 6. Influence of distance on reflected ultrasonic signal Figure 7. Influence of shadow effects on ultrasonic signal Figure 8. Influence of defect orientation on ultrasonic signal Figure 9. Influence of defect size on ultrasonic signal Figure 10. Schematic of direct pitch-catch technique Figure 11. Schematic of indirect pitch-catch technique Figure 12. Piezoelectric effect Figure 13. Schematic of a straight beam piezoelectric ultrasonic probe Figure 14. Schematic of an angle beam piezoelectric ultrasonic probe Figure 15. Concept for generating distance amplitude correction curves Figure 16. Typical pin/hanger assembly Figure 17. Application of a straight beam transducer Figure 18. Application of an angle beam transducer Figure 19. Typical physical measurements Figure 20. Sample ultrasonic test data Figure 21. SDHTB details Figure 22. Photograph of the SDHTB Figure 23. Typical pin geometry Figure 24. Pin 1 defect details Figure 25. Pin 2 defect details Figure 26. Pin 3 defect details Figure 27. Pin 4 defect details Figure 28. Pin 5 defect details Figure 29. Pin/hanger mockup details Figure 30. Beam diffraction results for 8-degree, 5-MHz, 12.7-mm diameter transducer Figure 31. Beam diffraction results for 0-degree, 5-MHz, 12.7-mm diameter transducer Figure 32. Beam diffraction results for 0-degree, 2.25-MHz, 25.4-mm diameter transducer Figure 33. Beam diffraction results for 11-degree, 2.25-MHz, 12.7-mm diameter transducer Figure 34. Beam diffraction results for 14-degree, 2.25-MHz, 12.7-mm diameter transducer Figure 35. Beam diffraction results for 8-degree, 2.25-MHz, 19-mm square transducer Figure 36. Distance amplitude correction curve for 8-degree, 5-MHz, 12.7-mm diameter transducer Figure 37. Distance amplitude correction curve for 0-degree, 5-MHz, 12.7-mm diameter transducer Figure 38. Distance amplitude correction curve for 0-degree, 2.25-MHz, 25.4-mm diameter transducer Figure 39. Distance amplitude correction curve for 11-degree, 2.25-MHz, 12.7-mm diameter transducer Figure 40. Distance amplitude correction curve for 14-degree, 2.25-MHz, 12.7-mm diameter transducer Figure 41. Distance amplitude correction curve for 8-degree, 2.25-MHz, 19-mm square transducer Figure 42. Pin 1 testing results Figure 43. Pin 2 testing results Figure 44. Pin 3 testing results Figure 45 Pin 4 testing results Figure 46. Pin 5 testing results Figure 47. Photograph of pulse-echo setup using 14-degree transducer Figure 48. UT scan utilizing pulse-echo technique with a 14-degree transducer Figure 49. Photograph of pitch-catch setup using 0-degree transducers Figure 50. UT scan utilizing pitch-catch technique using 0-degree transducers Figure 51. Photograph of pitch-catch setup using 0-degree receiving and 14-degree transmitting transducers Figure 52. UT scan utilizing pitch-catch technique using 0-degree and 14-degree transducers LIST OF TABLES Table 1. Defect size data Table 2. Defect sizing error 1. INTRODUCTION 1.1. BACKGROUND A failed hanger pin initiated the tragic collapse of one span of the Mianus River Bridge in Greenwich, CT, on June 28, 1983, resulting in the deaths of three motorists. The collapse sparked an immediate increase of interest in the inspection and condition evaluation of bridge hanger pins. Ultrasonic inspection has become the primary method of performing detailed inspection of in-service hanger pins. 1.2. OBJECTIVE The research objective is to develop a document describing the fundamentals of ultrasonic hanger pin inspection that can be used by State transportation agencies that are either inspecting pins themselves or contracting for inspection services. In addition, a limited experimental program is utilized to emphasize, and more completely explain, some important aspects of ultrasonic pin inspection. |