Materials & Fatigue Calculators
Fatigue life, fracture, creep, corrosion, and the metallurgy behind allowables.
- Basquin S-N Fatigue LifeHigh-cycle fatigue life from the Basquin power law — enter stress amplitude to get cycles, or cycles to get allowable stress.σa = σ'f · (2Nf)ᵇ Nf = ½ · (σa / σ'f)^(1/b)
- Neuber Notch Stress (Local Strain)Estimate elastic-plastic notch-root stress and strain from nominal load using Neuber's rule and a Ramberg-Osgood curve.(Kt·S)² / E = σ·ε , ε = σ/E + (σ/K′)^(1/n′) → solve σ·ε = Kσ·Kε·(S²/E)
- Paris Law Crack Growth RateFatigue crack growth per cycle from the stress-intensity range using the Paris power law.da/dN = C·(ΔK)ᵐ, ΔK = Y·Δσ·√(π·a)
- Fracture Toughness — Critical Stress / Crack SizeSolve linear-elastic fracture mechanics for critical stress, crack length, or the stress-intensity factor given K_IC.K = Y·σ·√(π·a) , σ_c = K_IC / (Y·√(π·a)) , a_c = (K_IC / (Y·σ))² / π
- Larson-Miller Creep LifeTrade time against temperature for creep-rupture — solve the LMP, remaining life in hours, or allowable metal temperature.LMP = T · (C + log₁₀ t) t = 10^(LMP/T − C) T = LMP / (C + log₁₀ t) — T in K (or °R), t in hours, C ≈ 20 for most steels
- Hardness Conversion (HRC / HV / HB)Cross-convert Rockwell C, Vickers, and Brinell for non-austenitic steel per ASTM E140 Table 1, plus a tensile-strength estimate.Piecewise-linear interpolation of ASTM E140 Table 1 (non-austenitic steel) , UTS ≈ 3.45 · HB (MPa)
- Corrosion Rate (Mass Loss & mm/y ⇄ mpy)Turn a coupon mass-loss test into a corrosion rate, or convert straight between mm/y and mils per year.CR(mm/y) = 8.76×10⁴ · W / (A·T·ρ) , W in g, A in cm², T in h, ρ in g/cm³ , 1 mpy = 0.0254 mm/y
- Galvanic Couple PotentialEstimate the driving voltage and corrosion risk when two dissimilar metals touch in a wet environment.ΔE = | E_A − E_B | (potentials vs SCE, seawater); more-negative metal is the anode
- Hall-Petch Grain-Size StrengtheningPredict yield strength from average grain diameter — σ₀ + k·d^(-½), with the ASTM grain-size number thrown in.σy = σ₀ + k·d^(-½) (d in mm, k in MPa·√mm)
- Hollomon-Jaffe Tempering ParameterTrade soak time against temperature in steel tempering — compute the HJ parameter and solve the equivalent time at a second temperature.HP = T(K) · (C + log₁₀ t), t in hours, C ≈ 20 for most steels Equivalent: t₂ = 10^(HP/T₂ − C)
- Carbon Equivalent (IIW)Weldability index from steel chemistry — flags preheat need and cold-cracking risk before you strike an arc.CEq = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15
- Charpy V-Notch Impact EnergyTurn pendulum release and rise angles into absorbed impact energy — J, ft·lbf, and J/cm² over the notch ligament per ASTM E23.KV = m·g·R·(cos β − cos α) v₀ = √(2·g·R·(1 − cos α)) KV/A = KV ÷ A_ligament
- Thermal Shock Resistance (Kingery R′)First and second thermal-shock parameters for brittle ceramics — the max temperature drop a part survives, and how conductivity buys margin.R′ = σ_f·(1−ν) / (E·α) , R‴ = R′·k
- CTE Mismatch Thermal StressThermal stress at a bonded bi-material interface from a temperature swing — the first-order constrained-strain estimate for die-attach, solder, and coating stacks.ε_free = (α₂ − α₁)·ΔT , σ₁ = E'₁·ε_free·E'₂/(E'₁+E'₂) , E' = E/(1−ν)
- Hydrogen Embrittlement Threshold StressEstimate the sustained-load threshold stress for a high-strength steel from its notched fracture strength and an F519-style threshold ratio.NTS = Ftu · Kt , σ_th = NTS · R_th
- Goodman Mean-Stress CorrectionFold a nonzero mean stress into an equivalent fully-reversed stress and get the Goodman fatigue safety factor, with Gerber for comparison.σₐ/Sₑ + σₘ/Sᵤₜ = 1/n_f (modified Goodman), σₐᵣ = σₐ / (1 − σₘ/Sᵤₜ), Gerber: σₐ/Sₑ + (σₘ/Sᵤₜ)² = 1/n