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Introduction to Machine Design
Lecture 1
Dr./ Ahmed Mohamed Nagib Elmekawy
February 18, 20162
CourseMaterials
drahmednagib.com
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COURSEOUTLINE
• Fundamentalso Introduction - Mechanical Engineering Design o Load Analysiso Materialso Stresses and Strainso Theories of Failure
• Applicationso Bolt Designo Power Screw Designo Shaft Design
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Introduction- MechanicalEngineeringDesign
• Phases and Interactions of the Design Process• Design Considerations.• Design Tools and Resources.• Standard and Codes.• System of Units.• Economics.• Safety.
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LoadAnalysis
This course is concerned with the design and analysis of machine and structural components. Since these are load-carrying members, an analysis of loads is of fundamentalimportance. A sophisticated stress or deflection analysis is of little value if it is based on incorrect loads. A mechanical component cannot be satisfactory unless its design is based on realistic operating loads.
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LoadAnalysis
Sometimes the service or operating loads can be readily determined, as are those on some engines, compressors, and electric generators that operate at known torques and speeds. Often the loads are difficult to determine, as are those on automotive chassis components (which depend on road surfaces and driving practices) or on the structure of an airplane (which depends on air turbulence and pilot decisions).
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LoadAnalysis
Sometimes experimental methods are used to obtain a statistical definition of applied loads. In other instances engineers use records of service failures together withanalyses of strength in order to infer reasonable estimates of loads encountered in service. The determination of appropriate loads is often a difficult and challenging initial step in the design of a machine or structural component.
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LoadAnalysis
• Equilibrium equation
For a nonaccelerating body
For a accelerating body
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LoadAnalysis
• Free Body Diagrams
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LoadAnalysis
• Free Body Diagrams
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LoadAnalysis
• Free Body Diagrams
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LoadAnalysis
• Free Body Diagrams
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LoadAnalysis
• Determination of internal Loads
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Materials
Material Selection
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Materials
Material Selection
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Materials
Material Selection• Strength
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Materials
Material Selection Factors
1. Availability2. Cost3. Material properties—mechanical, physical, chemical, dimensional4. Manufacturing processes—machining, formability, joinability, finishing and coatings
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StressesandStrains
• Free Body Diagrams
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StressesandStrains
• Free Body Diagrams
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StressesandStrains
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StressesandStrains
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StressesandStrains
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StressesandStrains
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StressesandStrains
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Stresses
1. Axial Load
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Stresses
1. Axial Load
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Stresses
2. Torsion Load
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Stresses
2. Torsion Load
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Stresses
2. Torsion Load
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Stresses
3. Bending Load
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Stresses
3. Bending Load
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Stresses
3. Bending Load
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Stresses
4. Combined Loading
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Stresses
4. Combined Loading
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TheoriesofFailure
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TheoriesofFailure
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TheoriesofFailure
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BoltDesign
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BoltDesign
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BoltDesign
The goal of the design is to find the number of bolts, diameter and the material of the bolts for the specific loads applied to the shaft.
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PowerScrewDesign
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PowerScrewDesign
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PowerScrewDesign
The goal of the design is to find the power screw dimensions (pitch, thread depth, mean pitch diameter, and helix).
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ShaftDesign
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ShaftDesign
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ShaftDesign
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ShaftDesign
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ShaftDesign
The goal of the design is to find the diameter and the material of the shaft for the specific loads applied to the shaft.
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References
1. Beer F.P., Johnston E.R and DeWolf J.T., Mechanics of Materials, Seventh Edition in SI Units, McGraw-Hill, 2014.
2. Robert C. Juvinall, Fundamentals of Machine Component Design, Fifth Edition, John Wiley, 2012.
3. Shigley J.E., Mechanical Engineering Design, Eighth Edition, McGraw-Hill, (ISBN: 0-07-056898-7), 2006.
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References
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References
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References
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