# Factor of Safety (Safety Factor)

Document Sample

```					 Machine Design

What is the importance of Machine Design for
engineers?

What is Machine Design?

Creation of new and better machines AND

Improving   existing ones

So that it is economical in the cost of production and operation.
Machine Design
How a design is born
Market
survey

Aesthetic
marketability
Ease of
Requirement                                  handling

Safety
Availability of
Creation                                     FUNDS
Economical
Model                Available
(Rough idea)              material         Recyclability

Manufacturing
resources
Material/s
Analysis       Force/stress                         Sizes
used
What is the basic knowledge required for Machine
Design?

• Mathematics
•Mathematics
• Mechanics of Machines
• Engineering Mechanics
•Engineering Mechanics
• Mechanics of Materials
•Strength of Materials
• Strength of Materials       • Fluid Mechanics & Thermodynamics

•Workshop Processes
• WorkshopProcesses

•Engineering Drawing
• EngineeringDrawing

• Computing

• Finite Element Analysis, Computational Fluid Dynamics etc
Important considerations in Machine Design

(Tensile, compressive, shear)

• Torsional stresses

• Shock loads (suddenly)     • Bending stress

with some velocity)
Important considerations in Machine Design…..

2. KINEMATICS of the machine (Motion of the parts)

Find the simplest arrangement that would give the most
efficient motion that is required.

3. Selection of MATERIALs

Knowledge of the properties of the materials and their
behaviour under working conditions is required.

Strength, hardness, durability, flexibility, weight, resistance
to heat and corrosion, electrical conductivity, machinability,
etc.
Important considerations in Machine Design…..
3. Selection of MATERIALs

Metal             Non-metal

Ferrous       Non-ferrous

Physical properties: Density, Melting point, Elec/thermal properties

Mechanical properties:
• STRENGTH     – resist externally applied loads without breaking
or yielding
• STIFFNESS    – resist deformation under stress
• ELASTICITY – regain original shape once the force is removed
• PLASTICITY – property which retains deformation (required for
forging etc)
• DUCTILITY    – ability to be drawn into a wire by a tensile force
• BRITTLENESS – sudden breaking with minimum distortion
• TOUGHNESS – resist fracture due to high impact load
• CREEP        – deformation under stress and high temperature
• FATIGUE      – ability to withstand cyclic stresses
• HARDNESS – resistance to wear, scratching, deformation,
machinability etc
Important considerations in Machine Design…..

4. Form and size of the parts

Use I-beam or Angle-iron?

The size will be determined by the forces/torques
applied (stresses on the object) and the material used
such that failure (fracture or deformation) would not
occur
General procedure in Machine Design…..

Need or aim        Recognize and specify the problem

Synthesis        Select the mechanism that would give the desired
motion and form the basic model with a sketch etc

Analysis of the FORCES

Material selection

Determine the stresses and thereby the
Design of elements
sizes of components s.t. failure or
deformation does not occur

Modification       Modify sizes to ease construction & reduce overall co

Detailed drawing                                       Production
Syllabus and method of evaluation

Course content                                     Time allocated
Sessions
ME209 MACHINE DESIGN 1                                 L    T   P    A
Introduction to machine design: Principles and                  01       04
methodology; a field visit.
3
Dynamics of simple mechanism:                                   01       06
Force analysis of a linkage mechanism
Failure analysis of mechanical elements:               3        01       10
Design of a cottered joint
Design of machine elements:                            6        01       16
Design of a flywheel
Design of a simple mechanical device:                  4        01       12
Design of a screw clamp
Design of steel structures:                           10        01       16
Design Project                                         4                      14
Total     30        06       64 14

Course                  Assignments            Coursework
Evaluation
20                       80

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 67 posted: 10/3/2012 language: English pages: 9
Jun Wang Dr
About Some of Those documents come from internet for research purpose,if you have the copyrights of one of them,tell me by mail vixychina@gmail.com.Thank you!