Stress Concentration Factor Calculator

A stress concentration factor measures how much a geometric discontinuity raises local stress above the nominal stress in a component. It is defined as Kt = σmax / σnom, where σmax is the peak elastic stress near the feature and σnom is the reference stress calculated without resolving that local peak. Because the numerator and denominator use the same stress unit, Kt is dimensionless. A factor of 2 means the local elastic stress is twice the nominal value. Common stress raisers include holes, grooves, shoulders, keyways, threads, sharp corners, and sudden changes in section. Smooth transitions and larger fillet radii generally reduce concentration. The appropriate nominal stress definition depends on the geometry and the handbook, standard, finite-element model, or test data supplying the peak stress. Both values must refer to the same load case and stress component. Mixing von Mises peak stress with nominal axial stress, for example, may produce a ratio that has no established design meaning. This calculator determines Kt from known maximum and nominal stresses. It does not predict Kt directly from dimensions because each geometry requires a specific chart or equation. The ratio describes theoretical elastic concentration and should not automatically be treated as a fatigue notch factor. In fatigue design, material notch sensitivity means the effective fatigue factor Kf may be lower than Kt. Plastic yielding can also redistribute a sharp elastic peak, although yielding itself may be unacceptable under the applicable design criteria. Use Kt to identify the significance of a local feature, estimate a peak elastic stress from a nominal analysis, or compare alternate geometries. Confirm that a reported peak is not a numerical singularity caused by an idealized sharp corner or point load. Mesh refinement, realistic radii, appropriate boundary conditions, and convergence checks are important when peak stress comes from finite-element analysis. Final design decisions should consider material strength, fatigue life, loading spectrum, safety factors, manufacturing tolerances, environment, and the requirements of the governing code.