The Fatigue Crack Growth calculator allows for fatigue crack growth analysis of a cracked part. Cyclic loading is applied in the form of a stress history. The crack growth rate is calculated at each stress cycle, and the crack is grown until failure. See the instructions within the documentation for more details on performing this analysis. See the reference section for details on the methodology and the equations used.
Options:
Inputs
Input the details for the fatigue crack growth analysis and hit 'Submit' to calculate results:
The results of the fatigue crack growth analysis are detailed below. Refer to the fatigue crack growth reference section for details on how these results were derived.
The total number of cycles in the stress history, Nhist, is cycles. The number of stress histories that can be repeated before failure is:
history repetitions to failure
WARNING: The number of history repetitions to failure is small, so the ordering of the stress ranges in the histry may have a significant effect on the results.
Cause of failure:
NOTE: A factor of safety should be applied to the reported cycles to failure to account for any uncertainty in the initial crack size, the applied stresses, and the fracture and fatigue crack growth properties of the material. It is the responsibility of the engineer to determine the appropriate factor of safety to use in design.
See full result details on the other tabs (above).
Crack Geometry & Stress History
This section details the crack geometry, material properties, and applied stresses.
Crack Geometry
Crack Type:
a
=
c
=
b
=
t
=
Stress History
The table below shows the individual stress ranges that make up the stress history. The stress history is run repeatedly until failure.
Cycles
Tensile Max
Tensile Min
Bending Max
Bending Min
Total number of cycles in stress history:
Nhist =
Equivalent Zero-to-Tension Stress
The crack progression method of "grow a" was selected for this analysis. In this case an equivalent zero-to-tension stress is calculated based on the stress history, and it is used to calculate crack growth. The peak stress from the history is used to check for failure on each cycle.
Below is a plot of crack growth rate, da/dN, versus ΔK for the material used in this analysis. There are several curves shown for varying R-ratios. Note that crack growth rate increases with increasing R-ratio.
The fracture toughness (i.e. critical stress intensity) values for the plane-strain condition and for the current part thickness are provided in the table below:
Plane-Strain Fracture Toughness
K1C =
Fracture Toughness at Part Thickness
Kc =
For this analysis, we have elected to use the :
Kcrit =
fracture toughness considered in this analysis
Results Details
Cycles to Failure
The stress intensities were not sufficient to grow the crack.
The total number of cycles in the stress history, Nhist, is cycles. The number of stress histories that can be repeated before failure is:
history repetitions to failure
WARNING: The number of history repetitions to failure is small, so the ordering of the stress ranges in the histry may have a significant effect on the results.
Cause of failure:
NOTE: A factor of safety should be applied to the reported cycles to failure to account for any uncertainty in the initial crack size, the applied stresses, and the fracture and fatigue crack growth properties of the material. It is the responsibility of the engineer to determine the appropriate factor of safety to use in design.
Crack Growth vs. Cycles
The final crack size is:
af = ,
cf =
The plot below shows the crack size as a function of stress cycles. Since the stress intensity factor, K, is dependent on crack size, the stress intensity increases as the crack grows. Once the crack reaches the critical size (i.e. the crack has grown to the point that the stress intensity equals the critical stress intensity, Kcrit, of the material), the part fails catastrophically due to fracture.
Stress Intensity vs. Cycles
The plot below shows the stress intensity factor, K, as a function of stress cycles. As the crack grows, the stress intensity increases until it equals the fracture toughness (critical stress intensity) of the material, after which the part fails catastrophically due to fracture.
The table below is an abbreviated sampling of the crack growth results. These results were derived using the methodology described here.
N
Stress Range #
a []
c []
Kmax.a []
Kmax.c []
ΔKa []
ΔKc []
da/dN []
dc/dN []
Download Simulation Details to Excel
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Save a formatted Word document to your computer detailing the inputs and results of the analysis.
Download Inputs File
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