Ultrasonic testing in nde for flaws.pptx

Flaw detection sizing etc

1. A SEMINAR ON ULRASONIC TESTING V.NIVASH M.Tech (II Year I sem ) 23021D0411 CAD/CAM (Flaw Sizing in Ultrasonic Inspection, Flaw location methods , Signal Processing in Ultrasonic NDT, Ultrasonic Flaw Evaluation) ASSIGNMENT-1 1

2. Introduction to Ultrasonic Inspection Ultrasonic inspection is a non-destructive testing (NDT) method used to evaluate the properties of materials by using high-frequency sound waves. It is commonly employed in material testing to detect internal defects, measure thickness, and assess structural integrity without causing damage. In ultrasonic inspection, a transducer emits high-frequency sound waves into the material. 2

3. These waves travel through the material and are reflected back when they encounter a boundary or defect, such as cracks or voids. The time it takes for the waves to return is measured, providing information about the material's thickness, density, and the presence of any internal flaws. Key applications include: Detection of cracks, voids, and weld defects. Thickness measurement of pipes, tanks, and other structures. Material characterization and bonding quality assessment. Ultrasonic testing offers high accuracy, is widely used in industries such as aerospace, automotive, and construction, and can be performed on a variety of materials, including metals, plastics, and composites. 3

4. Flaw Sizing in Ultrasonic Inspection: Flaw sizing in ultrasonic inspection is a critical process that involves assessing the size, location, and orientation of defects in materials or components. Various methods and techniques are used to achieve accurate flaw sizing, and they rely on different principles of ultrasonic wave propagation, signal reflection, and attenuation. Below is an overview of the techniques. Average (AVG) Method: The AVG method involves calculating the average signal amplitude (or time of flight) to determine the flaw size. It typically uses a reference standard (like a known-size defect) for comparison . 4

5. Application: Used in basic ultrasonic testing (UT) for general flaw sizing, especially in situations where precise measurements are not as critical. Principle: The average amplitude is used to estimate the size based on predefined curves or calibration standards. Amplitude: The amplitude of the reflected ultrasonic wave is proportional to the size of the flaw. Larger flaws cause higher amplitudes due to more significant reflection from the surface or the interior defect. Application: It’s often used for initial assessments of flaw size and depth. Principle: The amplitude of the signal decreases with increasing distance from the transducer, so amplitude is used in conjunction with other factors (like distance) to estimate the flaw size. 5

6. Transmission (Through Transmission): The transmission method involves sending ultrasonic waves through the material and detecting the signal that passes through the material. The amount of transmitted energy lost due to a flaw helps in estimating its size. Application: Common in through-thickness inspections, especially when the material is large or thick. Principle: A decrease in transmitted energy indicates the presence of a flaw; the degree of loss helps estimate the size. Time-of-Flight Diffraction (TOFD): TOFD is a technique that measures the time it takes for ultrasonic waves to travel to and from the flaw. It relies on diffraction of ultrasonic waves at the edges of the flaw. 6

7. Application: Commonly used for sizing cracks, especially in welded joints and critical areas. Principle: The time difference between the transmitted and received signals is used to estimate the depth and length of the flaw. TOFD offers high accuracy in depth sizing. Satellite Pulse: Satellite pulse refers to the secondary signals that occur due to the scattering of ultrasonic waves from a flaw. These secondary signals can be analyzed to improve flaw detection and sizing. Application: Used in advanced ultrasonic inspection setups where the primary signal and its satellites are analyzed together to enhance flaw characterization. Principle: Analyzing both the main pulse and satellite echoes allows for more precise sizing and characterization of complex flaws. 7

8. Multimode Transducer: Multimode transducers generate and receive multiple ultrasonic wave modes (such as longitudinal, shear, or surface waves) to provide more comprehensive information about the flaw. Application: Useful in complex geometries and for detecting and sizing different types of flaws (e.g., surface and subsurface defects). Principle: By using multiple modes of ultrasonic waves, multimode transducers can provide better coverage and more detailed sizing of flaws, especially when the flaw orientation is unknown. Zonal Method Using Focused Beam: In this method, a focused ultrasonic beam is used to interrogate a specific zone of the material, with the inspection area divided into zones for precise localization of the flaw. 8

9. Application: Used in situations where high-resolution imaging is required, such as in weld inspections or when inspecting thin materials. Principle: A focused beam allows for improved resolution in specific regions, reducing the beam width to pinpoint the location and size of the flaw with high accuracy . Summary of Methods and their Applications: AVG and Amplitude: Basic and quick assessments for general flaw sizing. Transmission: Effective for through-thickness inspections and large defects. TOFD: Highly accurate for depth and length sizing, especially for cracks. Satellite Pulse: Enhances flaw detection and characterization by analyzing secondary signals. Multimode Transducer: Provides a multi-faceted view of flaws for complex geometries. Zonal Focused Beam: Improves resolution for high-accuracy flaw sizing in localized zones. 9

10. Flaw location methods "Flaw location methods" can refer to a variety of techniques used in engineering, materials science, and nondestructive testing (NDT) to detect, locate, and evaluate flaws or defects in materials, structures, and components. These flaws could be cracks, voids, corrosion, or other forms of material degradation that can compromise the integrity of a structure or product. Below are some common flaw location methods: Ultrasonic Testing (UT) X-ray or Gamma Ray Radiography Magnetic Particle Testing (MT) Dye Penetrant Testing (PT) Eddy Current Testing (ET) Acoustic Emission Testing (AE) Infrared Thermography (Thermography) Visual Inspection (VI) Laser Shearography Acoustic Wave Propagation (Surface Wave Methods) Guided Wave Testing (GWT) 10

11. 1. Ultrasonic Testing (UT) Principle : Uses high-frequency sound waves (ultrasound) to detect flaws. The waves are introduced into the material, and their reflection (echo) is analyzed to locate flaws. Applications : Common for detecting cracks, voids, and material thickness measurements in metals and composites. Advantages : High sensitivity, can detect subsurface flaws, and provides quantitative measurements (e.g., depth, size of the flaw). Limitations : Requires skilled operators and calibration, and is more effective on materials with good acoustic properties. 11

12. 2. X-ray or Gamma Ray Radiography Principle : Uses ionizing radiation (X-rays or gamma rays) to penetrate the material and create an image of the internal structure. Flaws will appear as dark spots on the radiographic image. Applications : Frequently used in aerospace, welding inspections, and inspecting welds, castings, and composites. Advantages : Can detect both surface and internal flaws, creates permanent records (film or digital), and is relatively fast. Limitations : Limited to thin or low-density materials, requires safety precautions due to radiation hazards, and can be expensive. 12

13. 3. Magnetic Particle Testing (MT) Principle : A magnetic field is applied to ferromagnetic materials, and magnetic particles are sprinkled over the surface. If a flaw (e.g., crack) is present, it will distort the magnetic field, causing the particles to accumulate, revealing the flaw. Applications :Used for surface and near-surface defect detection in ferromagnetic materials (e.g., steel). Advantages : Relatively inexpensive, portable, and simple to perform. Limitations : Limited to ferromagnetic materials and primarily detects surface or near-surface flaws. 13

14. 4. Dye Penetrant Testing (PT) Principle : A liquid dye is applied to the surface of the material. The dye penetrates cracks or voids, and after wiping off the excess, a developer is applied, which draws the dye out of the flaws, making them visible. Applications : Common for surface-breaking defects in metals and non-porous materials. Advantages : Simple, inexpensive, and effective for detecting surface cracks and discontinuities. Limitations : Only works on surface-breaking flaws and requires clean surfaces to be effective. 14

15. 5. Eddy Current Testing (ET) Principle : Eddy currents are induced in the material by a changing magnetic field. Flaws alter the flow of these currents, which can be detected by a probe to locate the flaw. Applications : Used for detecting surface and near-surface flaws, corrosion, and material property variations (e.g., conductivity). Advantages : Non-contact, fast, and effective for detecting surface or near-surface flaws, especially in conductive materials. Limitations : Limited depth penetration and requires calibration for different materials. 15

16. 6. Acoustic Emission Testing (AE) Principle : Monitors the release of stress waves (acoustic emissions) from the material when it undergoes crack propagation, deformation, or other forms of damage. Applications : Used to detect and locate active flaws, such as crack growth or material failure in pressure vessels, tanks, or large structures. Advantages : Real-time monitoring, capable of detecting active flaws as they occur, and can be used for continuous monitoring. Limitations : Requires specialized equipment and expertise, and is typically used in conjunction with other methods for more detailed analysis. 16

17. 7. Thermography (Infrared Thermography) Principle : Uses infrared cameras to detect heat patterns or temperature variations on the surface of a material. Flaws can cause temperature differences that are visible in infrared images. Applications : Used to detect delaminations , voids, and other subsurface defects in materials like composites, concrete, and metallic structures. Advantages : Non-contact and can cover large areas quickly. Useful for detecting thermal anomalies related to defects. Limitations : Surface conditions and environmental factors (e.g., ambient temperature) can affect the accuracy of the results. 17

18. 8. Visual Inspection (VI) Principle : Direct visual examination of the material or structure, often with the aid of magnifying equipment or cameras. Applications : Used for detecting surface cracks, corrosion, wear, and other visible flaws in materials. Advantages : Simple, fast, and cost-effective. Limitations : Only detects surface defects and requires the flaw to be visible. 18

19. 9. Laser Shearography Principle : Uses laser light to create an interference pattern on the surface of a material. Changes in the surface caused by defects (such as delamination or voids) affect the interference pattern, which can be detected. Applications : Common for inspecting composite materials and structures, such as aerospace components. Advantages : Highly sensitive to subsurface defects and provides real-time results. Limitations : Typically more expensive and complex to implement. 19

20. 10. Guided Wave Testing (GWT) Principle : Guided waves (e.g., Lamb waves or torsional waves) travel along a material (typically a pipe or tube) and are sensitive to changes in material properties or geometry, including the presence of cracks or corrosion. Applications : Commonly used for pipeline inspection, pressure vessels, and long structures. Advantages : Can detect flaws over long distances and requires minimal access to the material. Limitations : Requires specialized equipment and can be complex to interpret. 20

21. The choice of flaw location method depends on factors such as: Type of material (metal, composite, concrete, etc.) Nature of the flaw (surface vs. subsurface) Size and depth of the defect Accessibility of the component Cost and time constraints In many cases, a combination of methods is used to ensure a more comprehensive inspection. For example, visual inspection or dye penetrant testing may be used first for surface flaws, followed by ultrasonic testing or radiography for deeper, subsurface defects. 21

22. Signal Processing in Ultrasonic NDT 1. Mimics (False Echoes): Cause: Non-defective material features (e.g., grain structure, inclusions) or surface irregularities can create echoes that resemble genuine flaws. Signal Processing Solutions : Time-of-Flight ( ToF ) : Differentiates genuine flaws from mimics by analyzing the time delay of echoes. Multi-Angle Scanning : Uses multiple beam angles to confirm the presence and nature of the flaw. Frequency Analysis : Flaws often produce distinct frequency shifts compared to mimics. 22

23. 2. Spurious Echoes: Cause : Unwanted reflections from material boundaries (surface, back wall), transducer ringing, or geometry. Signal Processing Solutions : Echo Filtering : Band-pass filters remove unwanted frequencies outside the defect signal range. Time Gating : Focuses on specific time windows to ignore echoes from non-relevant sources (e.g., surface reflections). Gain Control : Adjusts signal strength to reduce the impact of weak, spurious echoes. 23

24. 3. Noise: Cause : External interference (e.g., electromagnetic), equipment-related noise (e.g., transducer or cables), or surface/material noise. Signal Processing Solutions : Band-Pass Filtering : Removes unwanted frequencies that don't belong to the flaw signal. Averaging : Reduces random noise by averaging multiple measurements. Digital Signal Processing (DSP) : Uses techniques like FFT to isolate flaw signals from noise. Signal Conditioning : Amplifies the signal and suppresses low-frequency noise. These techniques enhance flaw detection accuracy by improving signal clarity and differentiating real defects from artifacts caused by mimics, spurious echoes, or noise. 24

25. Ultrasonic Flaw Evaluation Ultrasonic Flaw Evaluation is the process of analyzing ultrasonic signals to detect, characterize, and quantify defects in materials. It is a key component of non-destructive testing (NDT) used to ensure the integrity of materials without causing damage. The evaluation involves multiple steps, from signal acquisition to interpretation, and is essential in industries like aerospace, construction, and manufacturing. 1.Types of Flaws Detected Cracks : Surface or subsurface fractures caused by stress, fatigue, or defects. Porosity : Air pockets or voids within the material. 25

26. Inclusions : Foreign material embedded within the material (e.g., slag or non-metallic inclusions). Corrosion : Degradation due to chemical reactions, typically seen in metals or pipelines. Delaminations : Separation between layers, especially in composite materials. Weld Defects : Issues such as porosity, lack of fusion, or cracks in welds. 2.Ultrasonic Flaw Evaluation Process a. Signal Acquisition Pulse-Echo Method : The transducer sends out ultrasonic waves, and the returning echoes from flaws are recorded. The time it takes for the echo to return helps determine the flaw's location, while the signal amplitude indicates its size. Through-Transmission : Ultrasonic waves pass through the material, and a drop in signal strength indicates a flaw. 26

27. b. Signal Processing Time-of-Flight ( ToF ) : Measures the time it takes for the ultrasonic wave to travel to and from the flaw, helping to determine its depth. Amplitude Analysis : The strength of the received echo indicates the size of the flaw. Frequency Analysis : Different flaws may affect the frequency spectrum in distinct ways, allowing for further characterization. c. Flaw Sizing and Characterization Flaw Depth : Measured using the time delay of the reflected signal. Flaw Size : Determined by analyzing the amplitude and duration of the reflected signal. Flaw Type : Differentiating between cracks, voids, corrosion, and other defects based on their characteristic signal patterns. 27

28. 3. Evaluation Techniques A-Scan (Amplitude Scan) : A one-dimensional graph showing time vs. amplitude of the received signal. It provides basic information on flaw depth and size. B-Scan (Cross-Sectional Imaging) : A two-dimensional cross-sectional image that combines A-scan data to give a visual representation of the material, revealing flaws in specific layers. C-Scan (Planar Imaging) : A 2D map that shows the distribution of flaw locations over a larger area, often with color coding to indicate severity. Phased Array Ultrasonic Testing (PAUT) : Uses an array of transducers to focus and steer the ultrasonic beam, providing real-time imaging and inspection of complex geometries. Time of Flight Diffraction (TOFD) : Sensitive to crack tips, it provides precise sizing and location of cracks, especially in welds. 28

29. 4. Flaw Evaluation Criteria Size : Larger flaws have more significant impact on material integrity. Location : Flaws in high-stress or critical areas pose a higher risk. Orientation : Cracks aligned with the load direction are more dangerous than those perpendicular to it. Material Properties : Material type and properties (e.g., toughness) influence flaw severity. 5. Standards and Codes Various standards guide flaw evaluation, including: ASME BPVC (Boiler and Pressure Vessel Code) API 1104 (Pipeline welding inspection) ASTM E317 (Ultrasonic testing standards) ISO 17640 (Weld inspection). 29

30. THANK YOU 30