Pichet Pinit

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MTE 427 MACHINE DESIGN. Pichet Pinit. Design of Spur Gears. 14 Sep, 2008. Template provided by. Lewis Bending Equation. Lewis Bending Equation: Dynamic Effect. Dynamic Factor. As a general rule, spur gears should have a face width F from 3 to 5 times the circular pitch p.

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MTE 427 MACHINE DESIGN

Pichet Pinit

Design of Spur Gears

14 Sep, 2008

Template provided by

Lewis Bending Equation: Dynamic Effect

Dynamic Factor

As a general rule, spur gears should have a face width F from 3 to 5 times the circular pitch p.

Lewis Bending Equation: Dynamic Effect

Do Ex 14-2 as Homework according the changes.

Stress Concentration Factor

In these equations l and t are from the layout in Fig. 14–1, is the pressure angle, is

the fillet radius, b is the dedendum, and d is the pitch diameter.

AGMA Stress Equation

Two fundamental stress equations are used in the AGMA methodology, one for bending stress and another for pitting resistance (contact stress).

AGMA Stress Equation: Bending Stress

Two fundamental stress equations are used in the AGMA methodology, one for bending stress and another for pitting resistance (contact stress).

AGMA Stress Equation: Pitting Resistance

Two fundamental stress equations are used in the AGMA methodology, one for bending stress and another for pitting resistance (contact stress).

AGMA Strength Equation: Bending Stress

Two fundamental strength equations are used in the AGMA methodology, one for bending stress and another for pitting resistance (contact stress).

AGMA Strength Equation: Pitting Resistance

Two fundamental strength equations are used in the AGMA methodology, one for bending stress and another for pitting resistance (contact stress).

AGMA Factors

Important factors of AGMA used for gear analysis are as following,

• Geometry Factor
• Elastic Coefficient
• Dynamic Factor
• Surface Condition Factor
• Size Factor
• Hardness-ration Factor
• Stress Cycle Factors
• Reliability Factor
• Temperature Factor
• Rim-thickness Factor
• Safety Factors

AGMA Factors: Geometry Factors

Bending-strength Geometry Factor, J (YJ)

AGMA Factors: Geometry Factors

Bending-strength Geometry Factor, I (ZI)

AGMA Factors: Elastic Coefficient

Elastic coefficient CP(ZE)

AGMA Factors: Surface Condition Factor

Surface condition factor, Cf(ZR)

The surface condition factor Cf(ZR) is used only in the pitting resistance equation. It depends on

• Surface finish as affected by, but not limited to, cutting, shaving,

lapping, grinding, shot peening

• Residual stress

• Plastic effects (work hardening) Standard surface conditions for

gear teeth have not yet been established.

When a detrimental surface finish effect is known to exist, AGMA specifies a value of Cf(ZR) greater than unity.

AGMA Factors: Size Factor

Size factor, KS

If KS is less than 1, use KS = 1.

AGMA Factors: Hardness-ratio Factor

Hardness-ratio factor, CH

The hardness-ratio factor CHis used only for the gear. Its purpose is to adjust the surface strengths for this effect.

AGMA Factors: Hardness-ratio Factor

Hardness-ratio factor, CH

When surface-hardened pinions with hardnesses of 48 Rockwell C scale (Rockwell C48) or harder are run with through-hardened gears (180–400 Brinell), a work hardening occurs. The CHfactor is a function of pinion surface finish fP and the mating gear hardness.

AGMA Factors: Hardness-ratio Factor

Hardness-ratio factor, CH

When surface-hardened pinions with hardnesses of 48 Rockwell C scale (Rockwell C48) or harder are run with through-hardened gears (180–400 Brinell), a work hardening occurs. The CHfactor is a function of pinion surface finish fP and the mating gear hardness.

AGMA Factors: Stress Cycle Factors

Stress Cycle Factor, YN and ZN

AGMA Factors: Stress Cycle Factors

Stress Cycle Factor, YN and ZN

AGMA Factors: Reliability Factor

Reliability Factor, KR (YZ)

The reliability factor accounts for the effect of the statistical distributions of material fatigue failures.

AGMA Factors: Temperature Factor

Temperature Factor, KT (Y)

For oil or gear-blank temperatures up to 250°F (120°C), use KT = Y = 1.0. For higher temperatures, the factor should be greater than unity. Heat exchangers may be used to

ensure that operating temperatures are considerably below this value, as is desirable for the lubricant.

AGMA Factors: Rim-thickness Factor

Temperature Factor, KB

When the rim thickness is not sufficient to provide full support for the tooth root, the location of bending fatigue failure may be through the gear rim rather than at the tooth fillet. In such cases, the use of a stress-modifying factor KB or (tR) is recommended. This factor, the rim-thickness factor KB, adjusts the estimated bending stress for the thin-rimmed gear.

AGMA Factors: Safety Factor

Safety Factor, SF and SH

To render SHlinear with the transmitted load, it could have been defined as