5.4.4.1 Axial Lead Parts in Lateral Vibration
5.4.4.1 Axial Lead Parts In Lateral Vibration
Lateral motion occurs when an axial lead part is vibrated in a direction
perpendicular to its body and parallel with the PWB surface. The parts move
back and forth in an arc. This movement tends to fatigue the metal leads at
the lead bends and ends. In order to prevent this fatigue, a vibration level
must be calculated that will sufficiently vibrate the parts and the leads
without causing fatigue damage. In order to accomplish this, the deflection of
the part, due to a 1 G (static) load, is determined using the parameters in
Figure 55 and Equation 523.
where:
I =
.049d^{4 }W =
weight of the part
Using the deflection due to self weight, the natural frequency of the part
can be calculated using Equation 524.
Next, calculate the bending and shear stresses for the 1 G (static) load.
The two stresses are calculated such that the overall stress on the lead wires
can be determined. The bending stress is calculated by using Equation 525 and
the shear stress by Equation 526.

"1"> 
Eq. 525
Eq. 526 
Figure 55. Axial Lead Parts
Using the principles of Mohr’s circle and the values calculated for bending
and shear stresses, the principal stress due to a static load can be
calculated using Equation 527. Equation 528 represents the principal stress
accounting for a typical radius of the lead bend.

"1"> 
Eq. 527
Eq.
528 
Using Crandall’s equation, a value for Q equal to 62.5, and _{o} equal to .04, the G_{out} level can be
calculated as shown in Equation 529.
This G level is used in Equation 530 to determine the stress on the lead
wires.
The G_{max} of the part is calculated using the endurance limit of
the lead material (_{max}) from Appendix B and the calculated stress level
on the lead wire as shown in Equation 531. The Maximum Allowable PSD level is
obtained from Equation 532.