ERRI

Computing Margin of Safety with ERRI B12 RP60.

Margin of Safety (MS) is evaluated using the following equation, derived from the Haigh diagram shown in Figure 1.
Figure 1.
M S = 1 − σ a c t u a l σ a d m i s s i b l e × 100 MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVCI8FfYJH8YrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbb a9q8WqFfeaY=biLkVcLq=JHqpepeea0=as0Fb9pgeaYRXxe9vr0=vr 0=vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaabaaaaaaaaape GaamytaiaadofacqGH9aqpdaqadaWdaeaapeGaaGymaiabgkHiTmaa laaapaqaa8qacqaHdpWCpaWaaSbaaSqaa8qacaWGHbGaam4yaiaads hacaWG1bGaamyyaiaadYgaa8aabeaaaOqaa8qacqaHdpWCpaWaaSba aSqaa8qacaWGHbGaamizaiaad2gacaWGPbGaam4CaiaadohacaWGPb GaamOyaiaadYgacaWGLbaapaqabaaaaaGcpeGaayjkaiaawMcaaiab gEna0kaaigdacaaIWaGaaGimaaaa@53D3@
Figure 2.


σ a MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVCI8FfYJH8YrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbb a9q8WqFfeaY=biLkVcLq=JHqpepeea0=as0Fb9pgeaYRXxe9vr0=vr 0=vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaabaaaaaaaaape Gaeq4Wdm3damaaBaaaleaapeGaamyyaaWdaeqaaaaa@390C@ = Stress Amplitude

σ m MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVCI8FfYJH8YrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbb a9q8WqFfeaY=biLkVcLq=JHqpepeea0=as0Fb9pgeaYRXxe9vr0=vr 0=vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaabaaaaaaaaape Gaeq4Wdm3damaaBaaaleaapeGaamyBaaWdaeqaaaaa@3918@ = Mean Stress

HyperLife calculates Margin of Safety using Haigh Diagram or SN curve assigned to the part.

With single or multiple Haigh Diagrams, mean stress correction should be set to INTERPOLATE. If single SN curve, margin of safety is evaluated based on the mean stress model selected. (Similar to Safety Factor evaluated in Stress Life uniaxial: Uniaxial Fatigue Analysis)

Unwelded evaluation for margin of safety supports identification of worst subcase pair using Range Envelope Configuration. Range Envelope is based on maximum principal range among all the subcases assigned in the fatigue event.
Note: With Event configuration : Range Envelope. Stress range projected in the max principal direction of the worst subcase combination can be used for unwelded evaluation by using the Use projected stress in unwelded evaluation option in preferences.

From the worst subcase tensors projected in the max principal tensor direction can be applied by toggling.

Following are the parameters listed in Assign Material.
Parameter Description
Material Material assigned to the Part.

Material list for selection is created by adding Materials to Assign Material list from Material Db, My Material or HM Material tabs.
Material Units Unit of the assigned material.
Plot Stress Life plot of the assigned material.
FL Fatigue Limit of the assigned material.
SE

Standard Error of Log(N) of the assigned material.

Default = 0.0 (Real ≥ 0.0)
FKMMSS

Mean Stress Sensitivity parameters for mean stress correction based on FKM Guidelines.

Default:

MSS1 = 0.0

MSS2 = 0.15

MSS3 = 0.0

MSS4 = 0.0
Scale Scale is used to modify the calculated stress during the stress history generation.
Offset Offset is used to modify the calculated stress during the stress history generation.
Finish

Material Surface Finish, a result of manufacturing process.

NONE (Default),

POLISH

GROUND

MACHINE

HOTROLL

FORGE

Or USER (any float value between 0.0 and 1.0.)

When it is a float value, it will be used to modify the fatigue limit by multiplied with the original fatigue limit.

Read more: Other Factors Affecting Fatigue
Surf Treatment

Material Surface Treatment for Material S-N Curve, a process used to enhance the fatigue life.

NONE (Default)

NITRIDED

SHOTPEEN

COLDROLL

Or USER any float value greater than 0.0.

When it is a float value, it will be used to modify the fatigue limit by multiplied with the original fatigue limit.

Read more: Other Factors Affecting Fatigue
Temperature factor

Temperature influence can be accounted by applying the temperature factor Ctemp to modify the fatigue endurance limit FL.

Read more: Other Factors Affecting Fatigue
Kf

Fatigue strength reduction factor.

Default = 1.0 (Real ≥ 1.0)

Read more: Other Factors Affecting Fatigue
Note: Stress life for evaluation domain: unwelded is supported only for shell elements via elemental evaluation.

ERRI evaluation supports Time Series loading and allows creation of Superposition/Sequential/Range Envelope fatigue events. Refer to: Create Events.