Mean-stress fatigue correction under cyclic loading. Given stress amplitude σ_a, mean stress σ_m, and material σ_uts / σ_-1 (endurance limit) / σ_y, compute safety factors from three classical criteria: Modified Goodman (linear, conservative), Gerber (parabolic, better for ductile metals), and Soderberg (uses σ_y, most conservative). Reports the governing (smallest) value and whether the operating point lies inside the Goodman line.
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Key facts
Category
Math & Numbers
Input types
number
Output type
json
Sample coverage
4
API ready
Yes
Overview
The Fatigue Limit Calculator estimates fatigue safety factors under cyclic loading using the Modified Goodman, Gerber, and Soderberg criteria. Enter stress amplitude, mean stress, and the applicable material strengths to compare criteria, identify the governing minimum safety factor, and check the operating point against the Goodman line.
When to use
Evaluate fatigue safety under cyclic loading with a known stress amplitude and mean stress.
Compare Goodman, Gerber, and Soderberg mean-stress correction criteria during mechanical design.
Check whether an operating point falls inside the Goodman line and identify the most conservative criterion.
How it works
1Enter the alternating stress amplitude σ_a in MPa; this value must be greater than zero.
2Enter the mean stress σ_m and the material properties required for the selected calculations: ultimate strength σ_uts, endurance limit σ_-1, and yield strength σ_y.
3The calculator computes Goodman, Gerber, and Soderberg safety factors when their required inputs are available.
4The result reports the smallest, governing safety factor and whether the point is inside or outside the Goodman line.
Use cases
Preliminary fatigue checks for shafts, brackets, fasteners, and other cyclically loaded components.
Comparison of conservative and less conservative mean-stress correction methods for material selection and design review.
Screening operating points before detailed fatigue testing or a broader mechanical design analysis.
Examples
1. Compare three fatigue criteria for a steel component
Mechanical design engineer
Background
A component experiences a 100 MPa stress amplitude and a 200 MPa tensile mean stress. Its material data are available for all three criteria.
Problem
Determine the safety factor from each criterion and identify the governing result.
Goodman n = 1.7143, Gerber n = 2.8125, and Soderberg n = 1.3636. Soderberg governs, and the point is inside the Goodman line.
2. Screen a high mean-stress fatigue condition
疲劳分析工程师
Background
A cyclic load produces a 150 MPa stress amplitude and a 300 MPa tensile mean stress in a material with σ_uts = 600 MPa, σ_-1 = 250 MPa, and σ_y = 400 MPa.
Problem
Check whether the operating point satisfies the Goodman criterion and find the most restrictive safety factor.