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Machine Component Design I(INME 4011)
by
Pablo G. Caceres‐Valencia (B.Sc., Ph.D. U.K.)
GENERAL INFORMATIONCourse Number
INME 4011 Course Title
Machine Component Design ICredit Hours
3Instructor Dr. Pablo G. Caceres‐ValenciaOffice
Luccetti L‐212 Phone Ext. 2358Office Hours
Tu‐Th from 7:30 to 10:45ame‐mail
[email protected]‐site http://academic.uprm.edu/pcaceres
mailto:[email protected]
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AssessmentThe course will be assessed in the following manner:
1st Partial Exam 22%
2nd Partial Exam 24%
Project 22%
Quizzes 24% (*)
Class Participation and Attendance
8% (**)
(*) Date due Moodle
Quizzes and Pop‐Quizzes (max‐8). Missed quizzes will be graded with zero. Lack of access to Internet (Moodle) is not an excuse for not submitting your answers.
(**) Class participation and Attendance. After the third missed class, one point will be deducted in the final grade for each missed class (up to 8 points).
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Grades Final Grade Range
Final Letter Grade100 – 90 A
89 – 80 B
79 – 70 C
69 – 60 D
59 ‐ 0 F
AttendanceAttendance and participation in the lecture are compulsory
and will be considered in the grading. Students should bring calculators, rulers, pen and pencils to be used during the lectures. Students are expected to keep up with the assigned reading and be prepared tosolve problems in class and for the pop‐quizzes. Please refer to the Bulletin of Information for Undergraduate Studies for the Department and Campus Policies.
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TexbooksMy lecture notes are available in the web at
http://academic.uprm.edu/pcaceres“Fundamentals of Machine Elements”
B.J. Hamrock, S.R. Schmid, B. Jacobson
“Machine Design: An Integrated Approach”
Robert Norton, 3er Ed. Prentice Hall
“Mechanical Engineering Design”
J.E. Shigley, C.R. Mischke, R.G. Budynas.
ExamsAll exams will be conducted outside lecture periods on the specified dates. The final project due date is the date for the end of classes. There will be no final exam. Neatness and order will be taking into consideration in the grading of the exams. Up to ten points can be deducted for the lack of neatness and order. You must bring calculators, class notes and blank pages to the exams.
http://academic.uprm.edu/pcaceres
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TENTATIVES DATESWeek Week
09/13
Introduction to Design, Review Load, Stress, Strain.
09/20
10/04
10/18
11/01
11/08 Materials and Manufacturing
Q4
11/15 Materials Selection /Fracture Toughness
12/20 Final Project Presentation
Classes End
12/27 Final Project Presentation
Classes End ‐ GRADES
11/29
12/13
Review Load, Stress, Strain.
Q1
09/27 Basic Elasticity Basic Elasticity.
Q2
10/11 3D Stresses and Strains
Stress Concentration.
Q3
10/25 Static Failure TheoriesExam 1
Mid‐Term Project Presentation
11/22 Fracture Toughness
Q5
Failure Prediction Cyclic & Impact
12/06
Failure Prediction Cyclic & Impact
Q6
Failure Prediction Cyclic & Impact
Q7 –Exam 2
01/10
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OutcomesUpon the completion of the course the student should be able to:
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Calculate the principal stresses and strains in a loaded component
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Identify the location of the critical point on a machine component and calculate the stresses at that point.
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Apply the basic static theories of failure in the designing of machines subjected to static loading.
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Apply the basic fatigue failure theories in the designing of machine subjected to dynamic loading
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Evolution of Engineering Research & Education
1910
1960
2010
Sputnik
Quantum Mechanics
InformationTechnology
“Nano-Bio-Info”
Tables, formulae, etc.
“If it moves, it’s Mechanical,if it doesn’t move, it’s Civil,and
If you can’t see it, it’s Electrical”
The era of science-basedengineering
We are entering an era of integrated science &engineering,
during whichthe boundaries of the disciplines will grow
increasingly indistinct
Engineering disciplines
Engineering disciplines
Sciences
Engineering
Science
?Taken from Tim Sands, Prof. UC. Berkeley
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This approach is driven by the understanding that ME is founded
in and perpetuated through the innovation and creation of products
and therefore ME students should be able to apply learned concepts
and make real-world connections.
Product Realization in Mechanical Engineering
“The key to 21st century competitive advantage will be the
development of products with increasing levels of
functionality.“Smart Materials” will play a critical role in this
development, where we define these as materials that form part of a
smart structural system that has the capability to sense its
environment and the effects thereof and, if truly smart, to respond
to that externalstimulus via an active control mechanism.”
“Smart Materials for the 21st century” a publication of the
Institute of Materials, Minerals and Mining (IOM3)
http://www.iom3.org/foresight/Smart%20materials%20web.pdf
http://www.iom3.org/foresight/Smart materials web.pdf
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DesignTransformation of concepts and ideas into useful
machinery.
MachineCombination of mechanisms and other components that
transforms, transmit or uses energy, load or motion for a specific
purpose
Design of Machine ComponentFundamental practice in
engineering.
Code of Ethics for Engineers (ASME 1997)“Engineers shall hold
paramount the safety, health and welfare ofthe public in the
performance of their professional duties”
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Product Scope and Characteristics
http://www.prz.tu-berlin.de/~www-kt/lehre/hs/ed/dokumente_ed_vl/2005,WS,ED,VL-01.Termin,Vortrag.pdf
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Design• A design must be:
– Functional- fill a need or customer expectation– Safe- not
hazardous to users or bystanders– Reliable- conditional probability
that product will perform
its intended function without failure to a certain age.–
Competitive- contender in the market– Usable- accommodates human
size and strength– Manufacturable- minimal number of parts and
suitable for
production– Marketable- product can be sold and serviced
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Effects of Manufacturing and Assembly
Design of a Reciprocating Power Saw: Effects on Manufacturing
and Assembly
(1) Original Design: 41 parts, assembly time: 6:37min.(2)
Modified Design: 29 parts, assembly time: 2:58min. (Boothroyd
1992)
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Approaches to Product
Development
(a) Over-The-Wall Engineering Approach (from
Kalpakjian[1997]).(b) Concurrent Engineering Approach (adapted from
Pugh [1996]).
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Over-the-Wall (OTW)One designer applies his/her particular skill
and send it OTW to the next step in development. If a problem is
discovered, for example in manufacturing, the product is send back
to be redesigned.
The design is sent to The design is sent to the manufacturerthe
manufacturer
In manufacturing: an Engineer must first design something.an
Engineer must first design something.
The design phaseThe design phaseFor every design there For every
design there is eventually a is eventually a manufacturing
phasemanufacturing phase
Design Manufacture
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In practice, the design may well be impossible to manufacture.In
practice, the design may well be impossible to manufacture.
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Concurrent Engineering Approach
Philosophy of involving many disciplines from the beginning of
adesign effort and keeping them involved throughout product
development.
Design is a multidisciplinary endeavor
Boeing 747 being manufactured in Seattle
Examples of Examples of manufacturingmanufacturing
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Boeing 777
One of the first examples of Concurrent Engineering
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Design Methodology: what engineers do
Define the functioncomponent to carry a load
Material Selection Component Design
Tentative component design
Approximate stress analysis
Tentative choice of material
Assemble Materials Data
Analysis of Materials Performanceiterate
from Ashby and Jones; Engineering Materials 2
Detailed Specifications and Design
Choice of Production Methods
Prototype Testing
Establish Production
Further Development
iterate
iterateiterate
Example: A Cantilever
• This Cantilever Stand is intended for moderate to heavy-duty
use with either the Frontier III or Glas-Hide Boards in certain
lengths on residential pools. There are no unusual climatic
restrictions for this stand's use.
http://www.amerimerc.com/pool_supply/diving_boards/frontierIII_board.asphttp://www.amerimerc.com/pool_supply/diving_boards/glas_hide_board.asp
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Look at the Engineering Science of this design scheme:
Define the functioncomponent to carry a load
Material Selection Component Design
Tentative component design
Approximate stress analysis
Tentative choice of material
Assemble Materials Data
End Load
Uniform Distribution
End Moment Intermediate Load
Triangular Distribution
Choose materials for components from metals, ceramics, plastics,
composites?
Assemble Materials Data?Cost, density, elastic properties,
yield
stress, hardness, tensile stress, strength to weight ratio,
ductility, fracture toughness, fatigue stress, thermal expansion
coefficient, thermal conditioning, specific heat, thermal shock
resistance, creep, oxidation/corrosion rates
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Codes and Standards• Code- a set of specifications for the
analysis, design, manufacture,
and construction of something• Standard- a set of specifications
for parts, materials, or processes
intended to achieve uniformity, efficiency, and a specified
quality
Product Liability• “Strict liability” concept prevails in the
U.S.
– Manufacturers are liable for any damage or harm that results
from a defect.
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OrganizationsAluminum Association (AA)American Gear
Manufacturers
Association (AGMA)American Institute of Steel
Construction (AISC)American Iron and Steel Institute
(AISI)American National Standards
Institute (ANSI)American Society for Metals
(ASM)American Society of Mechanical
Engineers (ASME)American Society of Testing
Materials (ASTM)American Welding Society (AWS)
American Bearing Manufacturers Association (ABMA)
British Standards Institute (BSI)Industrial Fasteners Institute
(IFI)Institution of Mechanical
Engineers (I. Mech. E.)International Bureau of Weights
and Measures (BIPM)International Standards
Organization (ISO)National Institute for Standards
and Technology (NIST)Society of Automotive Engineers
(SAE)American Society of Agricultural
and Biological Engineers (ASABE)
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Design Philosophy
Also check deflection!!Also check deflection!!
Design•If the load is known and the geometry is specified,
determine the material and the safety factor. • If the load is
known and the material is specified, determine the safety factor
and the geometry (dimensions).
Analysis•If the load is known and the material and geometry are
specified, determine the safety factor – Is it safe??
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Critical Section
The critical section is the location in the design where the
largest internal stress is developed and failure is most
likely.
In general, the critical section will often occur at locations
of geometric non-uniformity, such as where a shaft changes its
diameter along a fillet.
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Safety Factors
•N = 1.25 to 2.0 Static loading, high level of confidence in all
designdata
•N = 2.0 to 2.5 Dynamic loading, average confidence in all
designdata
•N = 2.5 to 4.0 Static or dynamic with uncertainty about
loads,material properties, complex stress state, etc…
•N = 4.0 or higher Above + desire to provide extra safety
FOR DUCTILE MATERIALS:
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Uncertainty• Stochastic Design Factor Method- uncertainty in
stress
and strength is quantified for linearly proportional loads
Stress AverageStrength Average
==σsnd
Measures of Strength
• S – Strength• Ss – Shear Strength• Sy – Yield Strength• Su –
Ultimate Strength• - Mean StrengthS
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Measures of Stressτ – Shear Stressσ – Normal Stressσ1 –
Principal Stressσy – Stress in y-directionσr – Radial Stressσt –
Tangential Stress
Stress Allowable (AISC)• Tension: 0.45 Sy ≤ σall ≤ 0.60 Sy•
Shear: τall = 0.40 Sy• Bending: 0.60 Sy ≤ σall ≤ 0.75 Sy• Bearing:
σall = 0.90 Sy
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SUGGESTED SAFETY (DESIGN) FACTORS FOR ELEMENTARY WORKbased on
yield strength - according to Juvinall & Marshek op cit.
1.25 - 1.5 for exceptionally reliable materials used under
controllable conditions and subjected to loads and stresses that
can be determined with certainty - used almost invariably where low
weight is a particularly important consideration
1.5 - 2 for well-known materials under reasonably constant
environmental conditions, subjected to loads and stresses that can
be determined readily.
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2 - 2.5 for average materials operated in ordinary environments
and subjected to loads and stresses that can be determined.
2.5 - 3 for less tried materials or for brittle materials under
averageconditions of environment, load and stress.
3 - 4 for untried materials used under average conditions of
environment, load and stress. It should also be used with
better-known materials that are to be used in uncertain
environments orsubject to uncertain stresses.
Repeated Cyclic loads : the factors established above are
acceptable but must be applied to the endurance limit (ie. a
fatigue strength ) rather than to the yield strength of the
material.
Impact forces : the factors given above are acceptable, but an
impact factor (the above dynamic magnification factor ) should be
included.
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Brittle materials : the ultimate strength is used as the
theoretical maximum, the factors presented above should be doubled.
Where higher factors might appear desirable, a more thorough
analysis of the problem should be undertaken before deciding on
their use.
Need to take into account the statistical nature of materials
properties
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Design Methodology: what engineers doSafety Factors
