Application of Probability to Mechanical Design
107
Safety factor
as 78,056
as
37,416
The gear
1.
2.
3.
- 2.0862 3 = N safety factor on other solutions
will be mounted on the shaft and
It may be keyed on the shaft with one or more keys
A spline may be the more efficient method with locknuts etc.
The gear could be flanged and the shaft mounted to it. This interface should be checked.
The shock load should be incorporated.
Complete the back
checking on sizes
Calculate a critical speed and include any base vibration motions
Include the axial force and check the factor of safety.
D. Fatigue Considerations in Design Codes
National codes and standards frequently provide methods of analysis that
address the problem of fatigue, or cyclic loading. In applications where
use of such codes is mandatory, the rules must be followed in detail. A
notable example of this is provided by the ASME Boiler and Pressure Vessel
Code [2.61] which contains detailed procedures for evaluating the fatigue
behavior of pressure vessels and pressure vessel parts. This is an excellent
treatment of the subject and is recommended to the reader for study
and use (see also [2.56]). Information on the American Institute of Steel
Construction Code (AISC) is presented in [2.51,2.64]. An excellent source
of fatigue data for aircraft materials is also presented in [2.65].
In the example in Fig. 2.37 allowable stress can be developed for comparison. If the impact constant kk is placed in the stress calculations, the
allowable stress is 0.31
E. Summary For Fatigue Calculations
1. When designing a system or a component, the critical frequencies,
deflections, shock and vibration levels, operating temperatures, and surrounding environment must be known. The system must meet the overall
requirements while often components must exceed them, as in deflections.
Components with maximum deflections A when assembled will always have
larger maximum deflections, as do springs in series.
2. Determine the component critical parameters such as deflections,
stresses, frequency, or failure modes. Attempt to assign a value to these
parameters even though it is understood that they will often change.
107
Safety factor
as 78,056
as
37,416
The gear
1.
2.
3.
- 2.0862 3 = N safety factor on other solutions
will be mounted on the shaft and
It may be keyed on the shaft with one or more keys
A spline may be the more efficient method with locknuts etc.
The gear could be flanged and the shaft mounted to it. This interface should be checked.
The shock load should be incorporated.
Complete the back
checking on sizes
Calculate a critical speed and include any base vibration motions
Include the axial force and check the factor of safety.
D. Fatigue Considerations in Design Codes
National codes and standards frequently provide methods of analysis that
address the problem of fatigue, or cyclic loading. In applications where
use of such codes is mandatory, the rules must be followed in detail. A
notable example of this is provided by the ASME Boiler and Pressure Vessel
Code [2.61] which contains detailed procedures for evaluating the fatigue
behavior of pressure vessels and pressure vessel parts. This is an excellent
treatment of the subject and is recommended to the reader for study
and use (see also [2.56]). Information on the American Institute of Steel
Construction Code (AISC) is presented in [2.51,2.64]. An excellent source
of fatigue data for aircraft materials is also presented in [2.65].
In the example in Fig. 2.37 allowable stress can be developed for comparison. If the impact constant kk is placed in the stress calculations, the
allowable stress is 0.31
E. Summary For Fatigue Calculations
1. When designing a system or a component, the critical frequencies,
deflections, shock and vibration levels, operating temperatures, and surrounding environment must be known. The system must meet the overall
requirements while often components must exceed them, as in deflections.
Components with maximum deflections A when assembled will always have
larger maximum deflections, as do springs in series.
2. Determine the component critical parameters such as deflections,
stresses, frequency, or failure modes. Attempt to assign a value to these
parameters even though it is understood that they will often change.