Static strength of welded components

Theory
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: In mechanical engineering and related fields. Mathematical proof for rod-shaped, flat-shaped and volume-shaped components. Static proof and proof of fatigue. Verification with nominal stresses or local stresses. 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

Theory

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:

In mechanical engineering and related fields.
Mathematical proof for rod-shaped, flat-shaped and volume-shaped components.
Static proof and proof of fatigue.
Verification with nominal stresses or local stresses.
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

Stress determination

What stress components

Location of the verification point

Material

Weld seams: Fully welded components

Structural stresses - HAZ / BM
Normal stress x-direction	σ_x	[MPa]
Normal stress y-direction	σ_y	[MPa]
Shear stress y-direction	τ_xy	[MPa]
Main stress 1	σ₁	[MPa]
Main stress 2	σ₂	[MPa]

Structural stresses - Weld
Normal stress perpendicular to the weld seam	σ_⊥		[MPa]
Shear stress parallel to the weld	τ_\|\|		[MPa]

Material characteristics
Equivalent stress¹	σ_v	-	[MPa]
Minimum yield strength	R_p	-	[MPa]
Short term temperature factor²	K_T,m	1	[-]
Long term temperature factor³	K_Tt,p	1	[-]
Construction characteristics
Plastic support number⁴	n_pl	1	[-]
Weld seam factor⁵	α_W	-	[-]
Component strength
Static component strength	σ_SK	-	[MPa]
Safety factors
Safety factors: applied conservatively
Safety factor⁶	j	2	[-]
Proof
Degree of utilization	a_SK	-	[%]

Notes on the factors
Equivalent stress: determined according to von Mises. Short-term temperature factor: This takes into account the influence of increased temperatures on the strength of the material. Long-term temperature factor: This takes into account the duration of the use of the component at very high temperatures. Plastic support number: This takes into account plastic bearing reserves, which allow a higher load on the component. Weld seam factor: takes into account the influence of the load on the weld seam. Safety factor: This takes into account the consequences of the damage and the probability of occurrence.

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