108
Chapter 2
3. When the components are designed, the maximum and minimum
static loads should be corrected to include the shock and vibration effects
in the design. This does not mean that a vibration analysis can be neglected.
Also, fracture mechanics should be checked to include important
parameters.
4. Free-body diagrams when drawn will determine end conditions at
mating parts. Self-aligning bearings develop simply supported ends while
double bearings approach fixed-end conditions.
5. The determination of the effects of k values, Eq. (2.55),
endurance limits will force the designer to select the materials and/or
the manufacturing process such as machined or cast parts, heat treatment,
and surface coating or treatment.
6. When the ~r - ~m curve is selected or drawn, the proper safety factor
should be determined.
7. When complex systems or parts are designed, a finite element check
for frequencies, deflections, and loads from the known operating conditions will allow a check on a system design before parts are fabricated.
The parts should further be checked using fracture mechanics for
acceptability.
8. When a part or a system is manufactured, finished products should
be tested to failure to verify the designing and manufacturing. However,
there are cases where only one item is produced and used. Then, some form
of non-destructive inspections at servicing must be performed to maintain
a check on the system.
9. Keep a record of successful designs and failures so that design criteria can be modified for a particular class of designs. This is how design
criteria and future design codes will be developed.
EXAMPLE PROBLEM 2.20. An Egitoy metal pulley belt Fig. 2.39
is driven by a sprocket metal pulley of radius r. The ultimate strength is
368,00 psi; eyt = 280,000 psi; and a’e = 128,800 psi. The starting torque of
5 oz-in plus bending of the belt around the pulley creates the stress
5 1
1
at = F/A = r 16°z(0.5333 in)(0.0015
l b
(2.116)
The bending stress due to bending around the pulley is
1 d~y
M
r -- dx ~ E1
Chapter 2
3. When the components are designed, the maximum and minimum
static loads should be corrected to include the shock and vibration effects
in the design. This does not mean that a vibration analysis can be neglected.
Also, fracture mechanics should be checked to include important
parameters.
4. Free-body diagrams when drawn will determine end conditions at
mating parts. Self-aligning bearings develop simply supported ends while
double bearings approach fixed-end conditions.
5. The determination of the effects of k values, Eq. (2.55),
endurance limits will force the designer to select the materials and/or
the manufacturing process such as machined or cast parts, heat treatment,
and surface coating or treatment.
6. When the ~r - ~m curve is selected or drawn, the proper safety factor
should be determined.
7. When complex systems or parts are designed, a finite element check
for frequencies, deflections, and loads from the known operating conditions will allow a check on a system design before parts are fabricated.
The parts should further be checked using fracture mechanics for
acceptability.
8. When a part or a system is manufactured, finished products should
be tested to failure to verify the designing and manufacturing. However,
there are cases where only one item is produced and used. Then, some form
of non-destructive inspections at servicing must be performed to maintain
a check on the system.
9. Keep a record of successful designs and failures so that design criteria can be modified for a particular class of designs. This is how design
criteria and future design codes will be developed.
EXAMPLE PROBLEM 2.20. An Egitoy metal pulley belt Fig. 2.39
is driven by a sprocket metal pulley of radius r. The ultimate strength is
368,00 psi; eyt = 280,000 psi; and a’e = 128,800 psi. The starting torque of
5 oz-in plus bending of the belt around the pulley creates the stress
5 1
1
at = F/A = r 16°z(0.5333 in)(0.0015
l b
(2.116)
The bending stress due to bending around the pulley is
1 d~y
M
r -- dx ~ E1