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NDT Glossary: Terms Used in Non-Destructive Testing
This glossary brings together terms commonly used in NDT (non-destructive testing) and inspection, with concise English definitions and Turkish equivalents where relevant. Designed as a reference resource for inspection firms, technicians, and quality managers.
A
A-Scan
The most fundamental display in ultrasonic testing (UT). The horizontal axis represents time (depth) and the vertical axis represents echo amplitude. The depth and approximate size of a discontinuity are interpreted from the A-scan. Most conventional UT instruments produce A-scan output. (TR: A-Tarama)
Acceptance Criteria
The limit values used to make an accept/reject decision on an inspection result. Defined by the applicable standard (e.g., ISO 5817, ASME, EN 12062), customer specification, or regulation. The same discontinuity can yield different outcomes under different acceptance criteria. (TR: Kabul Kriteri)
Accreditation
The formal recognition that an inspection body has demonstrated it meets the requirements of a specific standard (e.g., ISO/IEC 17020). In Turkey, accreditation is granted by TÜRKAK. Accreditation documents the impartiality and technical competence of inspection results. (TR: Akreditasyon)
AUT (Automated Ultrasonic Testing)
Ultrasonic inspection performed with mechanized or robotic systems rather than by hand. Used for consistent, high-speed scanning of pipelines and large weld seams. Can employ PAUT or conventional UT probes. (TR: Otomatik Ultrasonik Muayene)
B
B-Scan
A cross-sectional image in ultrasonic testing, showing the side profile of the material in the scan direction. Used alongside A-scans to better evaluate the depth and extent of discontinuities. (TR: B-Tarama)
C
C-Scan
A top-view (plan view) image in ultrasonic testing showing the location of discontinuities across the scan surface — similar to a map. Commonly used in automated scanning of large plates or weld seams. (TR: C-Tarama)
Calibration
The process of adjusting and verifying a measurement instrument or inspection equipment against known reference values. Calibration of NDT equipment (UT instruments, RT tubes, MT yokes) is mandatory for accreditation and standards compliance and must be renewed at defined intervals. (TR: Kalibrasyon)
Couplant
A liquid or gel material applied between a UT transducer and the test surface to eliminate the air gap and allow sound to pass into the material. Water, glycerin, or proprietary gels are used depending on the application. (TR: Bağlaç / Temas Malzemesi)
CR (Computed Radiography)
A radiographic testing method that uses phosphor plate detectors to capture the image digitally. Faster than conventional film but slower than DR; no chemical processing required, making it an environmentally friendlier intermediate solution. (TR: Bilgisayarlı Radyografi)
D
DAC Curve (Distance Amplitude Correction)
A reference curve in ultrasonic testing constructed from the echo amplitudes of known reflectors at varying depths. Compensates for the natural decrease in sound intensity with depth; used to evaluate discontinuity size against the applicable standard. (TR: Mesafe-Genlik Eğrisi)
Discontinuity
The general term for any structural irregularity in a material — crack, porosity, slag inclusion, lamination, and similar. Not every discontinuity is a defect: a discontinuity that exceeds the acceptance criterion is classified as a defect (flaw). (TR: Süreksizlik)
DR (Digital Radiography)
A radiographic testing method in which X-rays or gamma rays strike a digital detector rather than film. The image is captured instantly, no film processing is needed, and image quality can be enhanced digitally. (TR: Dijital Radyografi)
E
ET (Eddy Current Testing)
A non-destructive testing method based on electromagnetic induction. Used to detect surface and near-surface cracks, corrosion, and wall thinning in conductive materials. Widely applied in tube inspection and aircraft component control. (TR: Eddy Akımı Muayenesi / Akım Girdabı Muayenesi)
H
HAZ (Heat Affected Zone)
The base metal region that is not melted during welding but whose metallurgical properties are altered by heat exposure. The HAZ is a critical zone for inspection alongside the weld itself; a significant proportion of weld discontinuities originate here. (TR: Isıdan Etkilenmiş Bölge)
I
Indication
A signal or image detected in non-destructive testing that requires interpretation. An indication may represent a genuine discontinuity (relevant indication) or a misleading signal caused by material geometry or the inspection technique (false indication). (TR: İndikasyon)
IQI (Image Quality Indicator)
A reference device placed on the film or detector in radiographic testing to verify image quality. The visibility of the wire or hole in the IQI confirms whether the image meets the minimum quality threshold. Also called a penetrameter. (TR: Görüntü Kalite Göstergesi / Penetremetre)
ISO 9712
The international standard for qualification and certification of NDT personnel. Defines three certification levels (Level 1, 2, 3), each with specified requirements for theoretical knowledge, practical skill, and experience.
ISO/IEC 17020
The international standard used as the basis for accreditation of inspection bodies. Defines Type A, B, and C inspection bodies; covers requirements for independence, impartiality, and technical competence. In Turkey, TÜRKAK grants accreditation under this standard.
ISO/IEC 17024
The international standard for accreditation of personnel certification bodies. NDT technician certification bodies (e.g., IŞTEC, Türk Lloyd) may be accredited under this standard.
ISO/IEC 17025
The international standard for accreditation of testing and calibration laboratories. In the NDT field, calibration laboratories and some testing activities may fall under this standard.
L
Level 1 / 2 / 3 (NDT Personnel Certification)
Competence levels defined under ISO 9712. Level 1: calibration, scanning, and recording under supervision. Level 2: independent inspection, evaluation, and report writing. Level 3: procedure approval, technical management, training, and methodology development. (TR: Seviye 1 / 2 / 3)
M
MT (Magnetic Particle Testing)
A non-destructive testing method for detecting surface and near-surface discontinuities in ferromagnetic materials. The material is magnetized; iron oxide particles accumulate at discontinuity locations to form visible indications. Cannot be applied to non-magnetizable materials such as aluminum or austenitic stainless steel. (TR: Manyetik Parçacık Muayenesi)
N
NDT (Non-Destructive Testing)
The general name for methods that detect internal and surface discontinuities, dimensional deviations, or material properties without damaging the material or component under test. Primary methods: UT, MT, RT, PT, VT, ET. (TR: Tahribatsız Muayene)
NDE / NDI
Abbreviations used interchangeably with NDT. NDE (Non-Destructive Evaluation) emphasizes sizing and characterization of discontinuities; NDI (Non-Destructive Inspection) emphasizes detection only. (TR: Tahribatsız Değerlendirme / Muayene)
P
PAUT (Phased Array Ultrasonic Testing)
An advanced ultrasonic testing method using multi-element probes to scan simultaneously at multiple angles. Provides more detailed imaging on complex geometries than conventional UT and requires fewer scan passes. (TR: Faz Dizisi Ultrasonik Muayene)
Penetrameter
See IQI.
PT (Liquid Penetrant Testing)
A non-destructive testing method for detecting surface-open discontinuities in non-porous materials. A low-viscosity dye is applied to the surface, allowed to dwell, wiped off, and then revealed with a developer. Applicable to both metallic and non-metallic materials; cannot detect subsurface discontinuities. (TR: Penetrant Muayene / Sıvı Penetrant)
Probe / Transducer
A piezoelectric device in ultrasonic testing that converts electrical energy into sound waves and converts returning sound echoes back into electrical signals. Frequency, diameter, and angle are selected based on the inspection application. (TR: Transdüser / Prob)
R
Reference Block / Calibration Block
Metal blocks of known dimensions and properties used to calibrate ultrasonic testing equipment. The instrument's sensitivity and measurement accuracy are set using known reflectors within the reference block. (TR: Referans Bloğu / Kalibrasyon Bloğu)
RT (Radiographic Testing)
A non-destructive testing method in which X-rays or gamma rays pass through a material to form an image on film or a digital detector. Internal discontinuities (porosity, slag, internal cracks) are detected from the resulting image. The most heavily regulated NDT method from a radiation safety standpoint. (TR: Radyografik Muayene)
T
TAEK (Turkish Atomic Energy Authority)
The government body that regulates and supervises the use of radioactive materials and radiation sources in Turkey. Firms performing RT inspection are required to obtain a license from TAEK and comply with all radiation safety obligations. (TR: Türkiye Atom Enerjisi Kurumu)
TBDS (Technical Document Verification System)
TÜRKAK's central platform that enables digital verification of technical documents (inspection reports, calibration certificates, personnel certificates) issued by accredited bodies. Document authenticity can be verified via QR code or reference number. (TR: Teknik Belge Doğrulama Sistemi)
TOFD (Time of Flight Diffraction)
An advanced ultrasonic technique using two separate transducers that measures the time of flight of waves diffracted from the tips of a discontinuity. Measures weld discontinuity dimensions with high accuracy; the scan image is archivable. (TR: Uçuş Süresi Kırınım Yöntemi)
TÜRKAK (Turkish Accreditation Agency)
Turkey's sole official accreditation body. Accredits conformity assessment bodies including inspection bodies (ISO 17020), testing and calibration laboratories (ISO 17025), and personnel certification bodies (ISO 17024). Member of EA and IAF. (TR: Türk Akreditasyon Kurumu)
U
UT (Ultrasonic Testing)
A non-destructive testing method that uses high-frequency sound waves to detect internal discontinuities and measure wall thickness. Applicable to metals, plastics, and composites; weld seams, pipes, and tanks are among the most common UT applications. (TR: Ultrasonik Muayene)
V
VT (Visual Testing / Visual Inspection)
The examination of a material or component surface by eye or with optical aids (magnifier, endoscope, mirror). The most fundamental inspection method, required alongside other NDT methods; also the only NDT method that requires personnel certification at all levels. (TR: Görsel Muayene)
This glossary is maintained by the ceres-ndt team. If you find a missing term, contact us.
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