Eddy Current Testing
Eddy Current Testing (ET) is a non-destructive testing method that utilizes electromagnetic induction to detect surface and near-surface flaws in electrically conductive materials. Alternating current is passed through a coil, generating eddy currents in the test piece; disruptions in these currents indicate defects such as cracks or corrosion.
- Surface and probe-based inspections identify discontinuities without requiring removal of coatings or paint.
- Rotary probe techniques enable precise examination of fastener holes and confined geometries.
- Additionally, the method allows measurement of material conductivity, corrosion thinning, and non-conductive coating thickness.
This technique is widely applied in aerospace, petrochemical, and power-generation industries where rapid, sensitive inspections are essential.
Ultrasonic Testing
Ultrasonic Testing (UT) employs high-frequency sound waves propagated into a material to detect internal imperfections and measure thickness. A transducer introduces pulses that reflect from discontinuities or opposite surfaces; the time-of-flight and amplitude of returned echoes reveal flaw location, size, and nature.
- Conventional pulse-echo and through-transmission techniques locate voids, inclusions, laminations, and cracks.
- Phased-array and time-of-flight diffraction variants provide advanced imaging and improved defect characterization.
- Thickness gauging monitors corrosion and erosion without access to both sides of a component.
UT is a versatile volumetric inspection method suitable for metals, composites, and welds in structural and pressure-containing applications.
Penetrant Testing
Penetrant Testing (PT), also known as liquid penetrant inspection, detects surface-breaking defects in non-porous materials regardless of material composition.
- A low-viscosity liquid penetrant is applied and drawn into defects by capillary action; excess is removed, and a developer draws the penetrant back to the surface, creating visible indications.
- Water-washable, post-emulsifiable, and solvent-removable systems are available, with fluorescent or visible dye options.
- No magnetization or electrical conductivity is required, making it applicable to metals, ceramics, and plastics.
PT is a cost-effective, sensitive method for identifying cracks, porosity, and leaks in components such as turbine blades, welds, and castings.
Magnetic Particle Testing
Magnetic Particle Testing (MT) is a surface-examination technique for ferromagnetic materials that reveals cracks and near-surface discontinuities through the application of magnetic fields and ferrous particles.
- The component is magnetized, creating leakage fields at defects; fine iron particles applied dry or in liquid suspension gather at these sites, forming visible indications under suitable lighting.
- Techniques include yoke, prod, and coil magnetization to accommodate various geometries.
- Both fluorescent and non-fluorescent particles are used depending on sensitivity and lighting conditions required.
MT offers high sensitivity to fine surface and slightly subsurface defects and is commonly employed on welds, castings, and forgings in manufacturing and in-service inspections.
Visual Testing
Visual Testing (VT) is the oldest and most fundamental non-destructive examination method, relying on direct or remote visual observation to assess surface condition and conformity.
- Direct inspection uses the naked eye or magnification; remote tools include borescopes and drones for confined or hazardous areas.
- Enhanced techniques incorporate illumination, mirrors, cameras, and image recording for documentation and analysis.
- Detectable anomalies include surface cracks, corrosion, misalignment, distortion, and general workmanship defects.
VT serves as the primary or supplementary method across all industries and is typically the first step in any inspection program.