Testing Definitions & Technical Reference

Comprehensive glossary of mechanical testing terminology, stress-strain characteristics, and international testing standards.

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Tensile & Elastic Properties Tensile / UTM

Tensile Strength (Ultimate Tensile Strength - UTS)

UTS = F_max / A_0 (MPa or N/mm²)

The maximum engineering stress a specimen sustains during a uniaxial tension test before necking or fracture occurs.

Standards: ASTM E8, ISO 6892-1, ASTM D638

Yield Strength / Proof Stress

R_p0.2 (0.2% Offset)

The stress level at which a material transitions from purely elastic behavior to permanent plastic deformation.

Standards: ASTM E8M, ISO 6892-1, IS 1608

Modulus of Elasticity (Young's Modulus)

E = Δσ / Δε (GPa)

The ratio of tensile stress to corresponding strain within the linear elastic limit, representing a material's intrinsic stiffness.

Standards: ASTM E111, ISO 527-1

Elongation at Break (% Elongation)

%EL = [(L_f - L_0) / L_0] × 100

The permanent increase in gauge length measured after specimen fracture, expressed as a percentage of the original gauge length.

Standards: ASTM D412, ASTM E8, ISO 37
Creep & Elevated Temperature Testing Creep / Series 9018

Creep Deformation

ε_c = f(time, stress, temperature)

Time-dependent permanent plastic deformation of a material subjected to constant mechanical stress at elevated temperatures over extended periods.

Standards: ASTM E139, ISO 204, BS EN 10291

Stress Rupture Life

t_r (Hours at constant load/temp)

The cumulative time required for a specimen to fracture under continuous static tensile load at a specified temperature.

Standards: ASTM E292, ISO 204

Secondary Creep Rate (Steady-State Creep)

ε̇ = dε / dt (min&sup-1; or hr&sup-1;)

The minimum, constant rate of strain accumulation occurring during Stage II of creep, where work hardening and thermal recovery remain in equilibrium.

Standards: ASTM E139, DIN EN ISO 204
Compression, Flexure, Peel & Dynamic Testing Specialized Modes

Flexural Modulus & Strength (3-Point Bend)

σ_f = 3FL / (2bd²)

A material's ability to resist bending forces. Measured by supporting a beam on two outer spans and applying a central point load.

Standards: ASTM D790, ISO 178

Peel / Adhesion Strength (90° & 180°)

F_peel / width (N/mm or lbf/in)

The average force required to separate bonded, laminated, or adhesive-coated flexible layers from a rigid or flexible substrate.

Standards: ASTM D903, ASTM D3330, ISO 8510

Dynamic Fatigue & Cyclic Endurance

S-N Curve (Cycles to Failure at Frequency f)

Testing component lifespan and fatigue limits under continuous sinusoidal or block loading cycles at frequencies up to 100 Hz.

Standards: ASTM E466, ISO 1099, JIS D4604

Crack Opening Displacement (COD)

δ (mm or μm)

The physical opening displacement between opposing surfaces of a pre-existing fatigue crack under applied load, measured via clip-on COD extensometers.

Standards: ASTM E1290, ASTM E1820, BS 7448