Gear Technology Manual
Module 4 - DESIGN AND STRESS ANALYSIS OF SPUR AND HELICAL GEARS
Now avalaible on CD-ROM
SYNOPSIS
This module introduces the design of involute spur and helical gears. In Part I it deals with the specification of gears, gear load histograms, gear reliability, metallic and non-metallic gear materials and their fatigue properties.
The sizing of gears for a specific duty using an approximate synthesis method is outlined. In Part II (Section 4.8 onward) the stress analysis to current Gear Standards is introduced, and the stress analysis of a known pair of gears using a method based on BS 436(1986) and ISO/DIN 3990(1987) demonstrated. The derivation of basic stressing formulae is appended, as are some relevant extracts from standards.
CONTENTS
Part 1
Specification, Design Life, Reliability
Design Load
Design Load based on Application Factor KA
Design Load based on Load Histograms
Calculation of Equivalent Load
Example 4.1
Example 4.2
Gear Reliability
Relationship between stress, strength, reliability
Safety Factors for Stress, SF and SH
Selection of Gear Materials and Permissible Stress Levels
Steel Gears
Steel Gears - Heat Treatment
Steel Gears - Fatigue strength
Steel Gears - Material costs
Steel Gears - Permissible stress
Non-metallic Gears
Non-metallic gears - Physical Properties
Non-metallic gears - Permissible Stress
Basic Design Decisions
Spur or Helical Gears
Ratio Split
Facewidth Ratio
Gear Accuracy
Sizing a Metallic Gear Pair - First Estimate
Specification
Permissible Stress
Permissible Surface Stress
Permissible Bending Stress
Facewidth
Approximate Gear Sizing for Contact Stress
Centre Distance not prescribed
Centre Distance fixed
Check of minimum number of teeth on pinion
Minimum module
Approximate Gear Sizing for Bending Strength
Check of Face-Load Factor KHß
Sizing a Non-Metallic Gear Pair - First Estimates
Example, Approximate Sizing
Specification
Permissible Stress
Facewidth
Sizing the Gear for Contact Strength
Check of Minimum Module for Strength
Selecting a Helix Angle
Check of Minimum Number of Teeth
Check of Required Accuracy
Preliminary Gear Specification
Part 2
Gear Stress Analysis
Nominal Contact (Hertzian) Stress, Ho
Zone Factor, ZH
Elasticity Factor, ZE
Contact Ratio Factor, ZE
Helix Angle Factor, Zß
Nominal Bending Stress, 
Fo
Form and Stress Factor, YFS
Contact ratio Factor, YE
Helix Angle Factor, Yß
Real Contact and Bending Stress, H
Dynamic Factor, KV
Face Load Distribution Factor, KHß, KFß
Face Load Distribution Factor for Contact Stress, KHß
Face Load Distribution Factor for Bending Stress, FFß
Transverse Load Distribution Factor, KH
, KF
Example, Stress Analysis
Nominal Contact Stress, Ho
Nominal Bending Stress, Fo
Real Contact and Bending Stress, F, H
Dynamic Factor, KV
Face Load Distribution Factor, KHß, KFß
Transverse Load Distribution Factor, KH, KF
Safety Factors for Contact Stress
Safety Factors for Bending Stress
Design Refinement
Revised Size for Contact Strength
Revised Size for Bending Strength
Gear Stress Analysis to Gearing Standards [BS 436 Pt.31986, DIN 3990 Pt.l-51987, ISO 6336 (Draft)]
Comparison of Gear Fatigue Strength
Comparison of Factors of Safety
Formulae
Literature
Appendices
Derivation of Gear Stress Formula
Root Bending Stress
Contact Stress
Gears as 3 Dimensional Loaded Structures and Lead Correction
Mesh Stiffness and Deflection
Quantifying the Effect of Misalignment
Lead Correction and Crowning
Extracts from BS 436 Pt.2 (1970)
Results of Gear Stress Analysis to BS 436 Pt.3 (1986) and ISO/DIN 3990 (1987)
Index: - Gear Technology Manual
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