Static strength of unwelded components


FKM stands for mathematical proof of strength of machine components. The guideline was based on former TGL standards, the earlier guideline VDI 2226 and other sources and further developed to the new level of knowledge. The guideline is a calculation algorithm consisting of instructions, formulas and tables. Represents a general method for calculating the strength of components in mechanical engineering.

Area of application of the FKM guideline:

  1. In mechanical engineering and related fields.
  2. Mathematical proof for rod-shaped, flat-shaped and volume-shaped components.
  3. Static proof and proof of fatigue.
  4. Verification with nominal stresses or local stresses.
  5. Can be used for components with or without machining or can also be made by welding.

There are 4 calculation tools on our site, that are based on the FKM guideline :

  • Static strength of (un-)welded components
  • Fatigue strength of (un-)welded components
Static strength of unwelded components

Stress determination

Normal / shear stresses
σx [MPa]
σy [MPa]
σz [MPa]
τxy [MPa]
τxz [MPa]
τyz [MPa]
Main stresses
σ1 [MPa]
σ2 [MPa]
σ3 [MPa]
Equivalent stress
Equivalent stress1 σv - [MPa]
Material characteristics
Component standard value of the yield point Rp - [MPa]
Technological size factor2 Kd 1 [-]
Short term temperature factor3 KT 1 [-]
Long term temperature factor4 KTt 1 [-]
Construction characteristics
Plastic support number5 npl 1 [-]
Component strength
Static component strength σSK - [MPa]
Safety factors
Safety factors: applied conservatively
Safety factor6 j 2 [-]
Degree of utilization aSK - [%]
Notes on the factors
  1. Equivalent stress: determined according to von Mises.
  2. Short-term temperature factor: This takes into account the influence of increased temperatures on the strength of the material.
  3. Long-term temperature factor: This takes into account the duration of the use of the component at very high temperatures.
  4. Plastic support number: This takes into account plastic bearing reserves, which allow a higher load on the component.
  5. Weld seam factor: takes into account the influence of the load on the weld seam.
  6. Safety factor: This takes into account the consequences of the damage and the probability of occurrence.
KONSCHA Simulation GmbH assumes no liability for the correctness, completeness, functionality and topicality of the collection of formulas, calculation programs or their results. The use of the content of the website is at the user's own risk. Liability claims are fundamentally excluded. We are grateful for any information about any errors or improvements.