1. introduction to design 2. materials and processes 3. load determination 4. stress, strain, and...

1. Introduction to Design

2. Materials and Processes

3. Load Determination

4. Stress, Strain, and Deflection

5. Static Failure Theories

6. Fatigue Failure Theories

7. Shaft and Shaft Components

Design -- (Dictionary) (1) create and work out the details of .....(2) make a pattern or sketch of .....

----- A process which integrates many diverse technical and nontechnical activities to proceed from product definitions, through conceptualization, to production and ultimately disposal.

A design is some type of information During design is a process Design science will be a science of process

Need

Formulation of specification

Creative synthesis

Drafting Analysis

Manufacture

Testing

Redesign as required

the Need Conceptual Design (concept exploration)

Preliminary Design (demonstration and validation)

Detail Design

Engineering and Manufacturing Development

Production

Operation

During the process of this process, it needs:

* Team Work

* Communication

* Concurrent Engineer (knowledge needed)

* Information Management

Design is a process.

CAD (Computer-Aided Design) packages:

-- Pro/Engineer

-- Unigraphics

-- Catia

-- AutoCAD

-- Microstation

-- Aries ConceptStation

-- IDEAS

-- Cadkey

-- Solidworks

-- DesignCAD

-- ADAMS (Automatic Dynamic Analysis of Multi-bodies Systems)

-- Pro/Mechanica (Motion, Structure, Thermal)

-- Working Model (2D & 3D)

-- Ansys

-- Abcus

-- Nastran

-- Pro/Mechanica

-- Algor

-- TKSolver

-- MathCad

-- Matlab

-- Maple

-- Excel

-- Lotus

Why do we need the design factor of safety?

because of loading variation; value from experiment (Lab.) may differ from reality; reduce probability of failure; might have some defect in the material property; cost.

ndStressAllowable

StrengthfunctionofLostnd

(When stress is linearly proportional to load)"Strength" represents various quantity chosen by the design. e.g. minimum, mean, yield, tensile, shear, fatigue, etc. and have the same unit as stress.

Comparing stress & strength must be of the same reference point.

Taking into account the uncertainty, we have

nd = ns nLwhere

nd = design factor of safety,

ns = accounting uncertainty of strength,

nL = accounting the uncertainty of the load.

(if uncertainty of strength is ±15%, the ns = 1/0.85.

If the uncertainty of allowable load is ±20%, nL = 1.2.

Then, nd = 1/0.85 * 1.2 = 1.41176.)

When the stress is not linearly proportional to the load,

load or force Applied

unit force in Strength = nd

-- ratio of the strength to the actual or computed stress.

S = n or

S = n

srr

where σ & τ are the stresses computed using the final selected size.

Design factor of safety, nd-- represents the aim during the beginning or the design.

Realized factor of safety, nr-- represents what has actually been obtained from the design.

testedpartsofnumberTotal

partsfailedofNumberR 1

e.g. 6 parts failed per 1000 parts tested R = 1- 6/1000 = 0.994

Limits: Max. and Min. Dimensions

Tolerance: Difference between the two limits

Bilateral Tolerance:

Unilateral Tolerance:

in002.0005.1

in000.0

004.0005.1