Non-Destructive Testing Overview
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Questions and Answers

How many times is the word 'Singapore' presented?

  • 14
  • 12
  • 15 (correct)
  • 16

    • How many times does 'Polytechnic' appear in the given content?

  • 12
  • 15 (correct)
  • 18
  • 9

    • If 'Singapore' and 'Polytechnic' were put together as one phrase how many times does that whole phrase appear?

  • 8
  • 15 (correct)
  • 12
  • 6

    • What is the last letter of the word that appears most frequently?

    <p>c</p> Signup and view all the answers

    How many spaces, including those in between words, does each line have?

    <p>11</p> Signup and view all the answers

    How many times does the letter 'o' appear in the given content?

    <p>30</p> Signup and view all the answers

    How many different letters are used within the two words 'Singapore' and 'Polytechnic'?

    <p>10</p> Signup and view all the answers

    If you were to count the characters in the whole text, including the spaces, which are not part of the word, what is approximately the total number?

    <p>1260</p> Signup and view all the answers

    How many times does the word 'Singapore' appear?

    <p>14</p> Signup and view all the answers

    How many times does the word 'Polytechnic' appear?

    <p>13</p> Signup and view all the answers

    What is the total count of the letter 'e' in all instances of the word 'Singapore'?

    <p>56</p> Signup and view all the answers

    If 'Singapore' + 'Polytechnic' = 'word', how many 'words' are present in total?

    <p>27</p> Signup and view all the answers

    What is the combined count of the letters 'p' and 'n' in all instances of the word 'Polytechnic'?

    <p>39</p> Signup and view all the answers

    Which of the following is the total instance of the letter 'o' from all the words within the text provided?

    <p>26</p> Signup and view all the answers

    What is the total combined count of the letters 'a','p','t' from all the instances of 'Singapore Polytechnic'?

    <p>78</p> Signup and view all the answers

    If the word 'Singapore' is replaced by 'ABC' and the word 'Polytechnic' is replaced by 'XYZ', how many instances of letter 'Z' would be present?

    <p>13</p> Signup and view all the answers

    Study Notes

    Non-Destructive Testing (NDT) Overview

    • NDT is used to inspect materials without destroying them
    • This is important for reusable parts that are valuable or components that need to be reused after testing
    • Testing is done for quality control purposes on components that cannot be harmed during testing, such as a fetus in a mother's uterus.

    NDT Methods

    • Visual Testing: Uses naked eyes or aided devices like magnifying glasses or borescopes for surface defect detection, and reliability depends on the inspector
    • Hydrostatic Testing: Uses water (or helium in high sensitivity tests) at 1.5-2 times the working pressure to check components for leaks. Leaks are detected by pressure changes or seepage
    • Dye Penetrant Testing: Used for finding surface flaws in homogeneous materials. A dye is introduced to surface openings, excess dye is removed, and internal flaws show up as dye penetration
    • Magnetic Particle Testing: Employed to find surface or subsurface flaws only in ferromagnetic materials. The specimen is magnetized, particles are applied, and flaws attract the particles, forming visible indications
    • Radiographic Testing: Uses X-rays (or gamma rays) to detect internal defects in materials. Images are made based on how materials attenuate radiation;
    • Ultrasonic Testing: A technique used for inspecting internal defects and measuring material thicknesses. Ultrasound waves are used to check for flaws that show as echoes.
    • Eddy Current Testing: Detects surface and subsurface flaws in electrically conductive materials, by detecting changes in the magnetic field.

    Visual Testing Specifics

    • Based on visual inspection of surfaces (e.g, using tools, mirrors, mirrors, fiberscopes, etc.).
    • Optical devices like magnifying glasses, and borescopes may be used for more detailed observation.

    Hydrostatic Testing Specifics

    • Components are pressurized with water at 1.5-2 times the working pressure. Seeps or pressure changes indicate leaks.

    Liquid Penetrant Testing

    • Detects surface flaws in homogeneous materials.
    • A dye is used, and excess dye is removed, internal flaws show up as dye.
    • Visible dyes are red hues, observed under white light
    • Fluorescent dyes are viewed under UV or black light

    Liquid Penetrant Testing - Removal of Excess Penetrant

    • Three ways to remove excess penetrants: Water Washable, Post-emulsified or Solvent removable

    Liquid Penetrant Testing - 6 Basic Processing Steps

    • Pre-cleaning, Penetrant application, Excess penetrant removal, Developer application, Inspection and interpretation, Post-cleaning.

    Liquid Penetrant Testing - Methods of Penetrant Application

    • By spraying, immersion or dipping and brushing. For localized inspections or thicker pieces, a thin layer application is preferred.

    Liquid Penetrant Testing - Removal of Excess Penetrant - Specifics

    • Water pressure should not be too high
    • Spray nozzles should not be too closed to allow proper penetrant flow to surface crevices.
    • Removal using solvent-dampened cloth is preferable and wiping direction should only be in one direction.

    Types of Developer for Liquid Penetrant Testing

    • Dry developer is a powder, non-aqueous wet developer is a suspension or solution in a liquid. Wet developer is dissolved in liquid or solution.

    Liquid Penetrant Testing - Inspection and Interpretation

    • Inspecting the test surface under normal white light or black light
    • Identifying and recording type of indication
    • Assessing the indications' relevance

    Types of Penetrant Relevant Indication

    • Fluorescent penetrant shows cracks as fluorescent lines
    • Visible penetrant shows cracks as glowing spots

    Magnetic Particle Testing - Specifics

    • Finds surface or subsurface flaws only in ferromagnetic materials (metals with iron, nickel, or cobalt)
    • Materials are magnetised with strong magnetic fields, causing magnetic lines that run through the component
    • Fine iron particles coated with a dye are applied, particles accumulate on the flaws due to disrupted flux path or leakage field. Indications are visible under proper lighting

    Magnetic Particle Testing - Defect Orientation

    • Cracks between 90° and 45° show correctly
    • Cracks parallel to the magnetic field lines may not be detected

    Magnetic Particle Testing - Magnetisation Techniques

    • Employing permanent magnets or electromagnets in contact with the workpiece or passing electric current through it directly or passing electric current through a coil of wire around the part.
    • The field direction is relevant for defect detection.

    Magnetic Particle Testing - Types of Magnetic Particles

    • Dry magnetic particles (powder): Used for visible inspection. May be coloured to highlight indications more clearly.
    • Wet magnetic particles (liquid suspension): Generally more sensitive than dry particles, use liquids for better mobility enabling more sensitivity

    Magnetic Particle Testing - Limitations

    • Only works well for ferromagnetic materials.
    • Direction of the defect relative to the magnetic field is significant.
    • Current magnetisation may result in marks on the item being inspected.

    Magnetic Particle Testing - Advantages

    • Sensitive for detecting both surface and subsurface defects
    • Simple and inexpensive method
    • Visible indication on surface
    • Unaffected by surface contaminants.

    Magnetic Particle Testing - Post-cleaning

    • Residual magnetism can hinder subsequent processes.
    • Demagnetization is necessary to minimize its impact.

    Magnetic Particle Testing - Demagnetization

    • Demagnetization units can reduce magnetism
    • A gauss meter is used to check for satisfactory demagnetization (below 2 Gauss).

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    Related Documents

    Topic 4 Non-Destructive Testing (Part 1) PDF

    Description

    Explore the fundamentals of Non-Destructive Testing (NDT) and its essential methods such as visual testing, hydrostatic testing, and dye penetrant testing. Understand how these techniques are employed for quality control without damaging materials, making them crucial for reusable components.

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