Nondestructive Testing 211
Nondestructive Testing 211 provides an overview of nondestructive testing and its six most common methods. Nondestructive testing (NDT) is the process of evaluating the quality and integrity of a manufactured part without harming its usability. There are six common NDT methods: visual testing, liquid penetrant testing, magnetic particle testing, eddy current testing, radiographic testing, and ultrasonic testing. Each method requires a certified technician choosing appropriate variables, operating the equipment, and interpreting results.
Despite NDT's many advantages, no one NDT method is capable of finding all types of flaws and defects in every type of part. As a result, manufacturers and inspection personnel must have a proper understanding of NDT and its most common methods in order to ensure it is used both effectively and reliably. After taking this class, users will be able to better understand NDT, its six most common methods, and the appropriate applications of each.
Number of Lessons 14
- Nondestructive Testing in Manufacturing
- NDT: Advantages and Disadvantages
- NDT Certification
- Review: Nondestructive Testing Basics
- Visual Testing
- Liquid Penetrant Testing
- Magnetic Particle Testing
- Magnetic Particle Testing: In Action
- Review: NDT Methods
- Eddy Current Testing: In Action
- Eddy Current Testing
- Radiographic Testing
- Ultrasonic Testing
- Review: Other Common NDT Methods
- Distinguish between destructive and nondestructive testing.
- Describe the advantages and disadvantages associated with nondestructive testing.
- Describe nondestructive testing technician certification.
- Describe visual testing.
- Describe liquid penetrant testing.
- Describe magnetic particle testing.
- Describe magnetic particle testing.
- Describe eddy current testing.
- Describe eddy current testing.
- Describe radiographic testing.
- Describe ultrasonic testing.
The ability to soak up, or absorb, a liquid easily. Developers used during liquid penetrant testing are highly absorbent.
Officially recognized or authorized as meeting a specific standard. Accredited third-party nondestructive training programs are offered through various organizations, including the American Society for Nondestructive Testing (ASNT) and the British Institute of Non-Destructive Testing (BINDT).
An industry that involves machines or vehicles of flight. Nondestructive testing technicians who work in the aerospace industry are required by law to possess minimum certification levels.
AC. A current formed when electrons flow in a one direction and then the opposite direction. Alternating current usually reverses direction 60 times per second.
American National Standards Institute
ANSI. A nonprofit organization that establishes standards and guidelines for several industries and related processes and products. The American National Standards Institute is one of the organizations that sets minimum requirements for nondestructive testing qualification and certification in the United States.
American Society for Nondestructive Testing
ASNT. A professional organization in the United States that researches, supports, and promotes nondestructive testing (NDT). The American Society for Nondestructive Testing offers an accredited third-party NDT training program and aligns with the ANSI/ASNT CP-106 standard for qualification and certification of NDT personnel.
An instrument that measures current flow in an electrical circuit. Ammeters can be used to detect changes in impedance during eddy current testing.
A measurement of voltage level. In ultrasonic testing, the flaw detector displays amplitude signals, which are then interpreted by a certified technician.
British Institute of Non-Destructive Testing
BINDT. A professional organization in the United Kingdom that researches, supports, and promotes nondestructive testing (NDT). The British Institute of Non-Destructive Testing offers an accredited third-party NDT training program and aligns with the ISO 9712:2012 standard for qualification and certification of NDT personnel.
To compare and adjust a device or machine with unknown accuracy to a device with a known, accurate standard. Technicians calibrate some nondestructive testing equipment to specific standards in order to eliminate any variation.
The ability of a liquid to flow into narrow spaces or upwards against the force of gravity. Capillary action draws the liquid penetrant into surface-breaking discontinuities and defects during liquid penetrant testing.
The sudden and complete breakdown of a part or machine. Catastrophic failure can be hazardous to workers as it may result in flying debris, unexpected and fast machine movement, and employee injury.
Validation that an individual has achieved a certain level of expertise in a specific area. Certifications may be awarded by a school, a professional organization, or another governing body.
An interaction between substances that changes the makeup of one or more of the substances. Chemical reactions can occur when two substances come into contact with each other.
Consisting of large crystals that are separated by a greater amount of space. During ultrasonic testing, lower-frequency sound waves penetrate coarse-grained materials better than higher-frequency sound waves.
Brightly colored and clearly distinguishable. Indications made by color-contrast penetrants or detection media are easily visible in ambient light.
Able to act as a path for the movement of electricity. Conductive materials, which include many types of metals, form magnetic fields when energized.
Any material or substance that is used up in a process or wears out over time. A variety of consumables are used during nondestructive testing methods, including liquid penetrant, developer, detection media, x-ray film, and couplant.
The gradual chemical deterioration of a material. Corrosion, which can appear as rust or pitting on the surface of parts, can be detected by visual testing and other nondestructive testing methods.
A substance, usually an oil, that coats a test piece in ultrasonic testing. Couplants helps transmit sound waves from an ultrasonic probe into a part.
A fracture or point of separation in a material. Cracks on the surface or interior of a part can be detected with nondestructive testing methods.
A severe discontinuity, or flaw, that can cause a part to be rejected. Defects can be detected through visual inspection or other forms of nondestructive testing.
To eliminate a material's magnetism. After magnetic particle testing, parts often must be demagnetized to remove any residual magnetism.
A measure of the amount of mass within the given volume of an object or substance. The density of a part affects how much radiation it absorbs during radiographic testing.
A category of inspection processes that evaluate a part's properties and performance using methods that lead to part failure. Destructive testing renders a part unusable.
Small particles of ferromagnetic material applied to the surface of a part during magnetic particle inspection. Detection media can be either dry powder or liquid-based.
A highly absorbent substance that helps to draw penetrant to the surface of a part during liquid penetrant testing. Developers help to create clear visible indications of surface discontinuities and defects.
A flaw or imperfection in the specified and expected structure of a part or material. Discontinuities are not always defects.
A period of time when production stops, often due to mechanical failure or maintenance needs. Downtime reduces the efficiency of a manufacturing operation and should always be limited as much as possible.
An intentional delay or pause of a specified length in a process. During liquid penetrant testing, both the penetrant and developer are left undisturbed on the surface of a part for a specified dwell time length.
eddy current testing
ECT. A nondestructive testing method that uses electromagnetic induction to locate surface and near-surface discontinuities and defects. Eddy current testing is limited to use on electrically conductive materials.
An electric current generated when a conductive material is placed near an alternating magnetic field. Eddy currents produce a secondary magnetic field during eddy current testing.
The flow of electrons. Electric current can be used to create a magnetic field within some materials.
The process of generating an electrical current in conductive material by exposing it to an alternating magnetic field. Electromagnetic induction forms the basis of eddy current testing.
Energy emitted in the form of particles or waves. Exposure to electromagnetic radiation, which is used during radiographic testing, can pose significant health hazards if technicians do not take appropriate safety measures.
A portable U-shaped device that establishes a magnetic field in order to detect surface and subsurface discontinuities on a specific section of a test piece. Electromagnetic yokes are powered by alternating or direct current.
electromagnetic yoke technique
A magnetic particle testing technique that uses a U-shaped device to pass an electrical current through a part and create a magnetic field. The electromagnetic yoke technique is a portable and low-cost way of performing magnetic particle testing.
The length of time in which radiation remains in contact with a film or fluoroscopic screen. Exposure time affects the quality of radiographs produced during radiographic testing.
To break, malfunction, or be unable to operate correctly. Destructive testing methods force a part to fail in order to evaluate its properties and integrity.
Progressive structural damage that occurs when a material is exposed to improper load conditions, too many deflections, or extreme temperatures, and eventually results in part failure. Fatigue-related defects can be detected by many nondestructive testing methods.
A material or substance that is easily magnetized and exhibits a strong attraction to magnetic fields. Ferromagnetic materials are often metals, including iron, cobalt, nickel, manganese, and various alloys.
A device that displays voltage level as amplitude signals. Flaw detectors are connected to transducers during ultrasonic testing.
Glowing a bright color. Indications made by fluorescent penetrants or detection particles are only visible under ultraviolet (UV) light.
A screen, lit from behind by fluorescent lights, that displays an x-ray. Fluoroscopic screens allow for immediate viewing of radiographic testing results.
The area where magnetic flux lines leave a part surface and jump over a barrier. Flux leakage attracts magnetic particles of detection media to form an indication on the surface of a part during magnetic particle testing.
The rate at which an alternating current changes direction or a sound wave vibrates within a given amount of time. Frequency is measured in hertz (Hz).
A type of electromagnetic wave with a high frequency and short wavelength. Gamma rays, which have greater penetration depths than x-rays, are sometimes used to view the interior of solid objects during radiographic testing.
Hz. A unit of frequency equal to one cycle per second. Hertz can measure the frequency of alternating current or sound waves.
Hertz. A unit of frequency equal to one cycle per second. Hz can measure the frequency of alternating current or sound waves.
The amount and intensity of light falling onto and spreading over a surface. Specifications for visual testing often require a minimum level of illuminance.
A measure of reactance and resistance in an alternating current (AC) circuit. Impedance is calculated to measure the total opposition to current flow in an AC circuit.
A sign or marking that clearly points out the presence of a discontinuity or defect. Indications in liquid penetrant testing are created with color-contrast penetrant or fluorescent penetrant, while indications in magnetic particle testing are created by particles of detection media.
The examination of a part during or after its creation to confirm that it adheres to specifications. During inspection, discontinuities may be identified and corrected.
International Organization for Standardization
ISO. A Switzerland-based organization that establishes standards and guidelines for several industries and related processes and products. The International Organization for Standardization is one of the groups that sets minimum requirements for nondestructive testing qualification and certification in Europe.
A nondestructive testing (NDT) certification that indicates a technician is qualified to perform NDT-related tasks under supervision. Level 1 certification requires technicians meet a specific amount of hours in classroom and on-the-job training, which vary according to NDT method.
A nondestructive testing (NDT) certification that indicates a technician is qualified to perform NDT-related tasks as well as interpret and evaluate test results. Level 2 certification also qualifies a technician to perform on-the-job training for Level 1 technicians.
A nondestructive (NDT) certification that indicates a technician is qualified to perform all Level 1 and 2 NDT tasks as well as develop and establish NDT procedures. Level 3 certification also qualifies a technician to supervise, train, and administer tests to Level 1 and 2 technicians.
liquid penetrant testing
LPT. A nondestructive testing method that uses a dye or a fluorescent liquid to locate discontinuites and defects on a material's surface. Liquid penetrant testing relies on capillary action to draw the liquid into minuscule surface openings on a part.
The overall force or pressure placed on a material or structure. Parts are designed to be able to withstand certain types and amounts of loads.
Extending along the length of an object. Longitudinal lines run lengthwise rather than across.
Large enough to be visible to the unaided human eye. Macroscopic surface discontinuities can be detected on parts during visual testing.
A force of attraction that surrounds magnets and current-carrying conductors. A magnetic field is used to help identify discontinuities in magnetic particle inspection.
The force that surrounds a magnet and exhibits the powers of attraction and repulsion. Magnetic flux is described as imaginary lines of force that exit the magnet's north pole and return to its south pole.
magnetic particle testing
MPT. A nondestructive testing method that uses magnetic particles and a magnetic field to locate discontinuities and defects on the surface and near-surface of a ferromagnetic part. During magnetic particle testing, lines of magnetic flux will jump over any discontinuities, creating an area of flux leakage around which magnetic detection media will cluster and form visible indications.
A simple optical instrument consisting of a small, handheld lens that is designed to enlarge an object for the viewer. Magnifying lenses can be used to aid with visual testing of manufactured parts.
An optical instrument consisting of one or more lenses that is designed to greatly magnify, or enlarge, objects that may be too small to seen by the human eye. Microscopes can be used to aid with visual testing of manufactured parts.
Too small to be visible to the human eye without the use of a microscope. Microscopic surface discontinuities can be difficult to detect during visual testing, but they can be easily detected using other nondestructive testing methods.
Nondestructive testing. A category of inspection processes that evaluate a part's properties and performance using methods that do not damage or permanently alter the part. NDT methods include visual testing, liquid penetrant testing, magnetic particle testing, eddy current testing, ultrasonic testing, and radiographic testing.
NDT. A category of inspection processes that evaluate a part's properties and performance using methods that do not damage or permanently alter the part. Nondestructive test methods include visual testing, liquid penetrant testing, magnetic particle testing, eddy current testing, ultrasonic testing, and radiographic testing.
An industry that involves producing energy through the use of atomic reactions. Nondestructive testing technicians who work in the nuclear power industry are required by law to possess minimum certification levels.
A category of devices that processes light waves to enhance an image so it can be viewed more clearly. Optical instruments are sometimes used to enhance visual testing.
An element that, in its gas form, is colorless, odorless, and tasteless and exists naturally in the Earth's atmosphere. Oxygen, which turns to liquid at temperatures below -362 degrees Fahrenheit (-219 degrees Celsius), chemically reacts with many different substances, including almost all organic material and metals.
A low viscosity liquid that is readily drawn into minute cracks, voids, or other discontinuities when applied to a surface. Penetrants create clear, highly visible indications of surface discontinuities and defects during liquid penetrant testing.
A measure of a material's tendency to become magnetized. Permeability affects the depth at which eddy currents can penetrate a part.
Intersecting at a 90° angle. Perpendicular lines form the corner of a square or rectangle.
personal protective equipment
PPE. An article of clothing or a device worn to minimize exposure to hazards and prevent injury. Personal protective equipment may include safety glasses, safety gloves, ear plugs, respirators, or steel-toed boots.
An industry that involves petroleum, natural gas, and related chemicals. Nondestructive testing technicians who work in the petrochemical industry are required by law to possess minimum certification levels.
Either of two oppositely charged ends of a magnet field. Lines of magnetic flux move in a linear path from one pole to the other.
The amount of small spaces or voids within a solid material. Porosity can affect the sensitivity of some nondestructive testing methods, such as eddy current testing.
Full of holes or having many voids. Porous materials are able to easily absorb liquids, making them difficult to inspect using liquid penetrant testing.
A device that generates electricity. Power sources include batteries, electric motors, and generators.
Regularly scheduled service and upkeep performed while a machine or component is still in working order. Preventive maintenance can prolong equipment life and increase production.
A specific number of the same part that moves through the production cycle. Destructive testing is performed on a number of sample parts taken at random from a production batch.
The physical and mechanical characteristics of a material that distinguish it from other materials. Properties determine the behavior and performance of a material, including how a material will react under a heavy load or extreme temperature changes.
A device that emits x-rays or gamma rays during radiographic testing. Radiation sources include x-ray machines or certain radioactive elements.
A type of image produced on a sensitive screen or film by x-rays or gamma rays. Radiograph images can allow the interior of a weld to be viewed.
RT. A nondestructive testing method that uses electromagnetic radiation, in the form of x-rays or gamma rays, to produce a picture of the internal structure of a material. In a radiographic testing image, discontinuities and defects in a material appear as dark spots.
A radiation-sensitive device that creates a radiograph image of the interior of a part during radiographic testing. Recording media includes special types of photographic film or fluoroscopic screens.
To be sent backward in the opposite direction. Part discontinuities and defects will reflect sound waves travelling through the part during ultrasonic testing.
The ability of a process to produce consistent and uniform results. Repeatability of visual testing often depends on several variables, including inspector training and testing environment.
The attractive force that exists in an object or substance after it has been removed from a magnetic field. Any residual magnetism in a part must be eliminated after magnetic particle testing.
The process of running a part through an additional and unplanned manufacturing step. Rework is necessary when a part is not produced within the correct tolerance or has poor surface finish or other discontinuities.
Unusable material produced during a manufacturing process. Scrap is a waste product of manufacturing that can increase overall production costs.
The length of time a component or device is expected to be in operation before needing to be replaced. Service life can be increased by performing regular predictive maintenance.
A chemical or combination of chemicals used to dissolve materials. Solvent is used during liquid penetrant testing to remove foreign material or excess penetrant from the surface of a part.
A vibration, or disturbance, of matter caused by the movement of energy. The high-frequency sound waves used in ultrasonic testing are beyond the range of normal human hearing.
A description of the essential physical and technical properties of a finished part. Specifications outline important information, including finished part dimensions and how the part must respond to forces acting upon it.
An established policy regarding specific product requirements or a particular practice or method. Standards cover a range of topics, from the required properties of a material to the documentation necessary across the supply chain.
Below or beneath the exterior of an object. Subsurface discontinuities can only be detected using certain nondestructive testing methods, such as magnetic particle, eddy current, ultrasonic, or radiographic testing.
The degree of roughness and variation on the surface of a part after it has been manufactured. A part's surface finish can affect the use of certain nondestructive testing methods.
A probe-like device that converts one form of energy, such as electrical, into another form of energy, such as mechanical. In ultrasonic testing, transducers convert electrical energy into vibrational sound waves.
UT. A nondestructive testing method that uses high-frequency ultrasonic waves to detect internal part discontinuities and defects. During ultrasonic testing, reflected sound waves are converted into electrical signals, which technicians then evaluate for any indications.
UV light. A wavelength of light that is invisible to the naked eye because it consists of very short wavelengths. Ultraviolet light is necessary in order to view the results from a fluorescent penetrant test or a magnetic particle test that uses fluorescent-coated particles.
Ultraviolet light. A wavelength of light that is invisible to the naked eye because it consists of very short wavelengths. UV light is necessary in order to view the results from a fluorescent penetrant test or a magnetic particle test that uses fluorescent-coated particles.
An optical instrument that consists of a slender fiber-optic tube with a magnifying lens at one end and a video camera on the other end. Video borescopes can be used to aid in the visual testing of manufactured parts, especially inspecting areas that are inaccessible by other means.
A measure of a fluid's resistance to flow. Low viscosity fluids, such as water and mineral oil, flow more easily than high viscosity fluids, which tend to be thick and sticky.
An advanced optical instrument that collects data and forms an image, which is interpreted by a computer to determine an appropriate position or to see an object. Vision systems can aid in the visual testing of manufactured parts.
VT. A nondestructive testing (NDT) method that requires an inspector to closely examine a part for surface discontinuities and defects. Visual testing is often used as a primary inspection method and then followed with other NDT methods.
A measure of electrical pressure or potential that causes current to flow in a circuit. Voltage is measured in volts (V).
An instrument that measures the voltage flowing between two points in an electrical circuit. Voltmeters can be used to detect changes in impedance during eddy current testing.
A type of electromagnetic wave with a high frequency and short wavelength. X-rays are used to view the interior of solid objects during radiographic testing.