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DIN 15018 / FEM 1.001

DIN 15018 / FEM 1.001 performs the static stress check and fatigue check for the steel structures of crane and crane equipment. Fatigue calculations are performed according to the Allowable Stress Design method (ASD).

DIN 15018

FEM 1.001

To add DIN 15018/ FEM 1.001 standard execute Standard - DIN 15018 / FEM 1.001 from the main menu. Alternatively, use the Standard context menu:

To perform the fatigue check three classifications should be defined: Weld Type, Element Group and Material Type.

Weld Type - also called Notch Case, determines which elements belong to what weld type (K0-K4 - joints affected by welding, W0-W2 - elements and joints, not affected by welding). Weld Type depends on the shape, structural design, whole pattern or type and quality of the welds.

Element Group - depends on the Load Spectrum and Class of Utilization (number of cycles). Can be set from B1 to B6.

Load Spectrum:

Load Spectrum Remarks
S0 Very light P=0 Crane by exception loaded with the working load, and as a rule, with very light loads
S1 Light P=1/3 Crane sometimes loaded with the working load, and as a rule with loads of about 1/3 of the working load
S2 Moderate P=2/3 Crane repeatedly loaded with the working load, and as a rule with loads between 1/3 and 2/3 of the working load
S3 Heavy P=1 Crane frequently loaded with the working load

Class of utilization (number of cycles):

Class of utilization Number of expected load cycles Remarks
Over To...incl
N1 - 2 x 105 Irregular use with long periods of rest
N2 2 x 105 6.3 x 105 Regular use in interrupted operation
N3 6.3 x 105 2 x 106 Regular use in continuous operation
N4 2 x 106 - Full, continuous operation

Element Group:

Design load spectrum Class of utilization
N1 N2 N3 N4
S0 B1 B2 B3 B4
S1 B2 B3 B4 B5
S2 B3 B4 B5 B6
S3 B4 B5 B6 B6

For FEM 1.001 standard can be set from B1 to B6.

Symbol Total duration of use number n of stress cycles)
B0 n 16 000
B1 16 000 < n 32 000
B2 32 000 < n 63 000
B3 63 000 < n 125 000
B4 125 000 < n 250 000
B5 250 000 < n 500 000
B6 500 000 < n 1 000 000
B7 1 000 000 < n 2 000 000
B8 2 000 000 < n 4 000 000
B9 4 000 000 < n 8 000 000
B10 8 000 000 < n

Stress Spectrum class Class of utilization
B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10
P1 E1 E1 E1 E1 E2 E3 E4 E5 E6 E7 E8
P2 E1 E1 E1 E2 E3 E4 E5 E6 E7 E8 E8
P3 E1 E1 E2 E3 E4 E5 E6 E7 E8 E8 E8
P4 E1 E2 E3 E4 E5 E6 E7 E8 E8 E8 E8

Material Type - define which steel is used St37 or St52.

Formulas of DIN15018 standard use Yield Stress and Tensile Strength from the materials. It is important to set this value for each material. Standard check if Yield Stress or Tensile Strength is not equal to zero:

If count > 0 then press to edit Yield Stress and Tensile Strength:

Create Tables and Plots for Loads - creates the standard tables and plots for Overall Check for the selected Loads.

Unit system is used for the conversion units in check calculations. By default, MKS (Meter/Kilogram/Second) system is used.

Stress Fatigue is defined in Pa. It is converted in the current stress units:

Press to change the unit system.

By default, the full model is set for the selection, but it is possible edit the selection.

DIN15018 standard performs calculations only on the Load Groups, because the calculation procedure requires the usage of the difference in stress among the loads. Also the Load Group Safety Factor is used in calculations:

ASD Fatigue check contains the calculations of Utilization Factor = Stress / Allowable Stress. If Utilization Factor < 1 then the check is passed.

Mathematical background

The ASD method sets the allowable stress equal to the lower value between the allowable static stress set by the materials characteristics (Yield Stress and Tensile Strength) and the allowable fatigue stress:

For the stress directions X, Y, Z, XY, YZ and ZX the allowable stress can be used:

For the equivalent and the equivalent weld stress the following formula is applied:

Coefficient = 1 – for the normal and equivalent stresses.

Coefficient = – for the shear stress with the weld classification K0-K4.

Coefficient =– for the shear stress the with weld classification W0-W2.

Sallow – the allowable stress for ASD method, Sallow_static and Sallow_fatigue – allowable stresses calculated from the material characteristics and loading conditions.

The Tensile Strength and the Yield Stress can be set for each material in the Material Properties table.

Sallow_fatigue=Stention_fatigue, Abs Maximum Stress >0

Sallow_fatigue=Scompression_fatigue, Abs Maximum Stress <0

Abs Maximum Stress=Smax, |Smax|>|Smin|

Abs Maximum Stress=Smin, |Smax|<|Smin|

Smin and Smax –minimum and maximum values of calculated result stresses;

Stention_fatigue and Scompression_fatigue – the tension and compression stresses that can be expressed using the κ-factor.

The Kappa factor is the ratio between minimum and maximum stresses

For K-factor [-1;0]:

For K-factor (0;1]:

Where Sf – the allowable stress fatigue when K=-1. The Stress fatigue can be set by the exact value or by setting the crane group and the weld type

Warning:

The Stress Fatigue (Sf) for the shear stress is always calculated using the weld type = K0 if the classification weld type is set to K0-K4 and W0 the weld type = W0-W2..

Utilization factor fatigue (is calculated for the directions X, Y, Z, XY, YZ and ZX):

Combined utilization factor fatigue is calculated using the following formula (the sign of Ufx, Ufy and Ufz are taken into the account) :

Maximum Utilization factor fatigue: