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dynamic loading & fatigue life

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Dynamic Loading

Dynamic loading of disc springs occurs when the load continuously changes from preload to final load.

The "stress-time" curve of such disc springs which pulsate uniformly is sinusoidal. This is not true in cases of impact loading and therefore it is difficult to predict their life and behavior.

Disc spring "life" may be differentiated into 2 categories:
  1. Limited life: where cycles vary without failure between 40,000 and 2,000,00 cycles.
  2. "Unlimited life": cycles in excess of 2·106 without failure. For virtually indefinite life, the table below indicates the appropriate values required given in percent of travel, relating preload to final load AND considering the disc spring thickness.
Maximum Deflection
Click to enlarge

Fatigue Life

Fatigue life for a disc spring is defined by the effective number of stress cycles that can be sustained prior to failure under certain conditions. This depends on the minimum stress, maximum stress and stress range.

The diagrams presented here are for evaluating fatigue life of single disc springs or series stacks not more than 6 springs. There are three basic groups, depending on thickness (see legend under each diagram).

The horizontal border line enclosing the top portion of the graph (zone) represents the yield strength of the spring steel material.

Intersection points of min/max stress limits which fall outside the graph/zone boundaries are to be avoided as they indicate spring failure is likely at an early stage.
Picture

The graphs were developed based on empirical test data. The test loads were sinusoidally executed. Click on graphs to enlarge.
diagram for disc springs t<.039
diagram for disc springs t<.039
diagram for disc springs .039<t<.236
diagram for disc springs .039
diagram for disc springs .236<t<.551
diagram for disc springs .236

How to Use these Graphs

For standard catalog disc springs
a) Determine preload stress... see Belleville Disc Spring tables for values.
b) Determine final load stress... see Belleville Disc Spring tables for values.
c) The intersection of the stress coordinates will indicate the range of fatigue life that may be expected.

For non-standard or special disc springs
a) Determine the preload stress from formulas for points S2 and S3. Use the HIGHER of the two values for preload and final load.
b) Repeat above procedure for FINAL STRESS... using again the higher of the values found.

Example
M188207: .709 x .323 x .0276( See Belleville Chart)
Preload Stress at Deflection f=.5h : 124000 psi
Final Load Stress at Deflection f=.75h : 174000 psi
Intersection Point between nearby 2MIO-Cycles-Line:
Predicted Cycles: 1.5MIO

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  • Home
  • Spring Selection
    • Precision Belleville Springs >
      • .236 to .394
      • .472 to .492
      • .551 to .591
      • .630 to .709
      • .787 to .886
      • .906 to .984
      • 1.100
      • 1.240 to 1.340
      • 1.400 to 1.770
      • 1.970
      • 2.200 to 2.360
      • 2.480 to 2.800
      • 3.150 to 3.540
      • 3.940 to 4.410
      • 4.920
      • 5.510 to 7.090
      • 7.870
      • 8.860 to 9.840
    • AI Springs >
      • AI .187 to .950
      • AI 1.000 to 1.750
      • AI 2.000 to 2.500
    • SP Belleville Springs >
      • SP .197 to .945
      • SP 1.142 to 3.031
    • CONTACT Disc Springs >
      • CONTACT Narrow
      • CONTACT Regular
      • CONTACT Wide
    • K Disc Springs >
      • Metric for K
      • Inch for K
    • FL Disc Springs >
      • Metric for FL
      • Inch for FL
  • Special Springs
  • Spring Design
    • Tolerances >
      • for Thickness
      • Overall Height
      • Hardness Range
      • OD + ID Guide Clearance
      • OD + ID Tolerance
      • Load Tolerance
    • Load Calculations >
      • Nomenclature
      • Load in Lbs
      • True Radius Factor
      • Corner Radius Factor
      • True Cone Height Factor
      • Flattening at Edge Factor
      • Precise Load Computing
    • About >
      • Contact Us
      • News Releases >
        • Fan Disc Second Patent
        • JPL Selects Fan Disc
        • Fan Disc Wins Patent
    • Load and Stress Calculations
    • Dynamic Loading
    • Materials Properties
    • Tightening Torque Values
    • Typical Disc Spring Apps
  • Site Map