1.
Destructive Testing (DT)
Destructive Testing involves testing materials to failure to determine their mechanical properties.
These tests are typically used in research, material selection, and quality control.
Common DT Methods:
1. Tensile Testing:
o Measures the material’s tensile strength, yield strength, and elongation by pulling it
apart until it breaks.
2. Hardness Testing:
o Determines a material's resistance to deformation or indentation.
o Methods: Brinell (HB), Rockwell (HR), Vickers (HV), Knoop (HK), and Mohs hardness
tests.
3. Impact Testing:
o Evaluates the material’s toughness (resistance to sudden shock loads).
o Methods: Charpy and Izod impact tests.
4. Bend Testing:
o Tests ductility and soundness of welds by bending the material to a specified angle.
5. Fatigue Testing:
o Determines the ability of a material to withstand cyclic loading without failure over
time.
6. Fracture Toughness Testing:
o Measures a material’s resistance to crack propagation.
o Used for materials exposed to extreme conditions (e.g., aerospace, marine).
7. Creep Testing:
o Evaluates how a material deforms over time under constant stress and temperature.
8. Corrosion Testing:
o Assesses a material’s resistance to corrosion under specific environments (e.g., salt
spray test, electrochemical tests).
Advantages of DT:
✔ Provides accurate mechanical properties (e.g., strength, hardness, ductility).
✔ Ensures material suitability for specific applications.
Disadvantages of DT:
❌ Destroys the test specimen.
❌ Costly for expensive materials and components.
2. Non-Destructive Testing (NDT)
NDT evaluates materials without causing damage, making it ideal for in-service inspection and
quality control.
Common NDT Methods:
1. Visual Inspection (VT):
o Uses direct visual examination or optical instruments (borescopes, magnifiers).
o Detects surface defects like cracks, corrosion, and weld discontinuities.
2. Ultrasonic Testing (UT):
o Uses high-frequency sound waves to detect internal defects.
o Identifies cracks, voids, thickness variations in metals and composites.
3. Radiographic Testing (RT/X-ray):
o Uses X-rays or gamma rays to detect internal flaws in materials.
o Common in weld inspections and aerospace applications.
4. Magnetic Particle Testing (MT):
o Detects surface and near-surface cracks in ferromagnetic materials using a
magnetic field and iron particles.
5. Dye Penetrant Testing (PT):
o A liquid dye is applied to detect surface cracks in non-porous materials.
o Common in weld inspections.
6. Eddy Current Testing (ET):
o Uses electromagnetic induction to detect cracks, corrosion, and material thickness
in conductive materials.
o Common in aircraft and pipeline inspection.
7. Acoustic Emission Testing (AE):
o Monitors stress-induced crack formation using sensors.
o Used for structural health monitoring.
8. Thermographic Testing (Infrared - IR):
o Detects heat variations to identify defects, such as insulation failure and hidden
cracks.
o Used in electrical and mechanical inspections.
Advantages of NDT:
✔ Non-destructive – No damage to materials.
✔ Allows in-service inspection.
✔ Cost-effective for expensive components.
Disadvantages of NDT:
❌ Requires skilled personnel for interpretation.
❌ Some methods (e.g., RT, UT) need specialized equipment.
Comparison of DT and NDT
Criteria Destructive Testing (DT) Non-Destructive Testing (NDT)
Damage to
Yes, tested to failure No, material remains intact
Material
Purpose Determines mechanical properties Detects internal/external defects
Cost High (material loss) Lower (no damage)
Testing Location Usually in a lab Can be done in-service
Material selection, research, Maintenance, quality control, safety
Applications
certification inspections
