1 Mech 260 Presentation

7/28/2019 1 Mech 260 Presentation

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MECH 260,Section 101Introduction to

Mechanics ofMaterials

Clarence W. de Silva, Ph.D., P.Eng.

Professor of Mechanical Engineering

The University of British Columbia

e-mail: [email protected]:// www.mech.ubc.ca/~ial

C.W. de Silva

Presentation Part 1
mailto:[email protected]:[email protected]


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Announcements


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Tutorial Sessions

Objectives of Tutorial Sessions:

1.

Assist the students in problem solution and homework assignments.2. Conduct quizzesote 1: Tutorial sessions will start on September 11th.

ote 2: Assignment 1 and Assignment 2 have been posted on the web site.

Please see the following web site for further details:

http://www.mech.ubc.ca/~ial/MECH260/

Tutorial Schedule and Location:

Tuesdays 13:00 to 14:00

Room MCLD 202

Teaching Assistants: Mr. Muhammad Tufail([email protected])and

Mr. Edward Wang ([email protected])

Teaching Assistant Office: ICICS 065 (Robotics Lab), Tel: 604-822-4850

Office Hours of Instructor and TAs: Please see the web site.


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MECH 260, Section 101, Introduction to Mechanics of Materials3 Credits, 1st Semester 2012/13

(Tuesdays and Thursdays, 8:00-9:30 a.m.); Room: MCLD 202Course Web Site: www.mech.ubc.ca/~ialThe course material including the lecture presentations, homework assignments, and

the solutions to homework problems and exams wil l be posted at this web site.

Instructor:Dr. Clarence de Silva, ProfessorOffice:CEME 2071; Tel: 604-822-6291; e-mail: desi [email protected]

Course ObjectivesThis course deals with the internal effects (primarily stresses and strains) in a deformable solidboy due to external loads acting on it. The subject is also known as Strength of Materials orSolid Mechanics. It is useful in a variety of engineering areas including mechanical, civil, and

mining engineering and biomechanics. It provides theory and formulas that are directlyapplicable in the modeling, analysis, design, and testing of engineering devices and structuressuch as automobiles, airplanes, robots, machine tools, engines, bridges, elevated guideways,and buildings.

Stresses in an object are governed by the internal loading, which are determinedfrom equilibrium equations with external loading. Stresses are a determining factor of thestrength of the object. Strains caused by loading are directly related to the deflection ordeformation or compatibility of the object. The stress-strains relations (or constitutiverelations) determine the stiffness of an object are governed by the physics of the object. Inaddition to strength, deformation, and stiffness, the subject of Mechanics of Materials alsoconcerns stability which studies the possibility of deformations that can grow suddenlywithout limit (in theory).

The course consists of lectures, tutorials, homework assignments, quizzes, an

intermediate examination, and a final examination.Textbook:Philpot, T.A., Mechanics of Materials, 3rd Edition, Wiley, Hoboken, NJ, 2013.
http://../course-364/course-550Y/Activities%202008/www.mech.ubc.ca/~ialhttp://../course-364/course-550Y/Activities%202008/www.mech.ubc.ca/~ial


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MECH 260101 COURSE LAYOUT

Week Starts Topic Read

1 Sept 06 Introduction, Statics Chapter 1

2 Sept 11 Stress Chapter 1

3 Sept 18 Strain Chapter 2

4 Sept 25 Mechanical Propert ies of Materials Chapter 3

5 Oct 02 Design Considerations Chapter 4

6 Oct 09 Axial Load and Deformation Chapter 5

7 Oct 16 Tors ion Chapter 6

8 Oct 23 Bending Chapters 7 and 8

9 Oct 30 Bending Chapter 8

10 Nov 06

Tuesday, Nov 06:

Shear Stress in Bending of Beams

Intermediate Exam (In Class)

Chapter 9

11 Nov 13 Deflection of Beams Chapter 10

12 Nov 20 Statically Indeterminate Beams Chapter 11

13 Nov 27 Stress/Strain Transformations Chapters 12 and 13

Note: The student must pass the final examination in order to pass the course.

Grade Composi tion

Homework Assignments 10%

Quizzes 10%

Intermediate Examination 30%

Final Examination 50%_

Total 100%


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MECH 260 Road Map

Course ObjectivesImportancePlan

Review of Statics

StressStrain

Mohrs Circle:Stress TransformationStrain Transformation

Design Considerations

MechanicalProperties ofMaterials

BendingAxial LoadingTorsion

ExamplesApplications

Beam Bending:Shear StressDeflectionStatically Indeterminate Beams

Examples

Examples

Design ConsiderationsApplicationsRevision


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Importance ofMechanics of Materials


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What is Mechanics of Materials?

Study ofinternal effects (stresses and strains) caused byexternal loads (forces and moments) acting on adeformable body/structure

Also known as: Strength of Materials or Mechanics of Solidsor Mechanics of Deformable Bodies

Determines:

1. Strength (determined by stress at failure)

2. Deformation (determined by strain)

3. Stiffness (ability to resist deformation; load needed tocause a specific deformation; determined by the stress-strain constitutive relationship)

4. Stability (ability to avoid rapidly growing deformationscaused by an initial disturbance; e.g., buckling)


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An Example (Aircraft)

External Loading

on the Aircraft

Engine Thrust

Wing Joint

(Attachment)

Aerodynamic

ForcesGravity

(Stresses and

Strains)

Small Internal

Element

of the Joint

Control Surface

ForcesDynamic Loads


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An Example (Aircraft Disaster)

Aloha Airlines Boeing 737

Flight 243 on April 28, 1988 with 95 passengers and crewMid-air structural damage and component loss, with onefatality (a crew member was sucked out)

The aircraft landed at Maui airport, Hawaii, without further lossof human life (8 serious injuries)


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Subject Definition

External Forces/

Moments

Reactions, Internal

Forces/Moments

Modeling

Analysis

Computer Simulation

Design Testing/Diagnosis

Operation

Stresses

(Normal, Shear)

Strains

(Normal, Shear)

Deflections

Deformations

(Rectilinear, Angular)

Constitutive(Physical)

Relations

Engineering

Mechanics of

Materials

Statics


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Application of the SubjectUseful in modeling, analysis, simulation, design, and testing of engineering

systems (e.g., automobiles, airplanes, robots, machine tools, engines,

bridges, elevated guideways, and buildings)

Modeling: Determine equations governing stress-strain (or, load-deflection) behavior of an object

Analysis: Determine stresses, strains (internal loads and deformations)

due to external loadingSimulation: Program a model of the system (using both analytical and

experimental equations and parameter values. Run the program underspecified loading conditions. Determine stresses, strains (internal loads,deformations).

Design: Select materials, dimensions, and structure of a device to meet aset of performance specifications (related to strength, size, cost, safety,etc.)

Testing: Apply a specified regime of loading (single or repetitive) andmeasure resulting deformations or determine loading that causesfailure


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Importance of the Subject

Material optimization, energy efficiency, and compact

(light-weight) modern designs of machinery andstructures Thin members; high flexibility; complexgeometry Large deformations can mean poor vehicleride quality (over guideways, bridges, etc.), undesirablecontact between components causing wear, noise, sparks,

hazard, etc.

Increased power levels and longer and varied operatingconditions of modern machinery larger loading; needfor higher strengths

More stringent regulatory requirements on safety,architecture, and esthetics complex and more rigorousanalysis, design, and testing


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Aeronautical and Aerospace Engineering: Design and

development of aircraft and space craftCivil Engineering: Design and evaluation of bridges andbuildings

Electrical Engineering: Electronic hardware structural design,product qualification testing for specialized

applications (e.g., nuclear power plants)Manufacturing Engineering: machine component failure, tool

wear and breakage reduced productivity and productquality, increased costs of operation and maintenance

Proper design of machine tools and componentsMechanical Engineering: Design and testing of engines,

vehicles, aircraft, robots, ships, etc.

Mining and Mineral Engineering: Design, development, andtesting of mining machinery that operate under severe

and risky conditions

Applicable Engineering Fields


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Some Useful TermsForce: A rectilinear load; has a magnitude and a direction (i.e., vector); Units: newton

(N), 1 kN = 1000 N

Normal Force: Force normal (perpendicular) to a considered area; tends to push/pull thebody

Shear Force: Force along the plane of a considered area; causes a shearing (or slidingdeformation along the plane)

Torque: A rotational (angular) load; torsional moment; tends to twist the object towhich it is applied; has a magnitude and a direction (i.e., a vector); Units: newton-

meter (N.m)Bending Moment: A bending load; tends to bend the object to which it is applied; hasa magnitude and a direction (i.e., a vector); Units: newton-meter (N.m)

Stress: Force per unit area; not a vector but a tensor (because same force will causedifferent stresses at a point depending on the area element that is considered)it is atensor; Units: N/m2 (= pascal or Pa), 1 N/mm2 = 1 MPa; normal stress is caused by anormal force component, shear stress is caused by a shear force component

Strain: Deflection per unit length (normal strain) or angle of deformation (shear strain);dimensionless

Free-Body Diagram: Virtually separate the part of interest from the rest of the objectand mark the loads at the interface

Homogeneous: Properties are uniform (do not change from point to point in the body)

Isotropic: Properties are non-directional (do not vary with the direction)


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History


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History of Mechanics of MaterialsArchimedes (287-212 B.C.): Statics, equilibrium of a lever

da Vinci (1452-1519): Concept of moments

Galileo (1564-1642): Effects of loads on beams and rods, virtualdisplacement

Newton (1642-1727): Foundation of mechanics

Bernoulli (1667-1748): Virtual displacement/work, beam bending

Hooke (1635-1703): Hookes law of stress-strain, Hookes joint

Euler (1707-1793): Moment of inertia, beam bending, instability, columnbuckling, rigid body dynamics

dAlembert (1717-1783): Inertia force (converts dynamics to statics)

Lagrange (1736-1813): Mechanics, energy methods

Coulomb (1736-1806): Friction (static and dynamic)

Laplace (1749-1827): Mechanics, etc.

Poisson (1781-1840): Lateral strain, Poissons ratioSaint-Venant (1797-1886): Strain distribution at abrupt changes in section,

strain tensor, torsion

Castigliano (1847-1884): Structural loads and deflections by energymethod

Galerkin (1871-1945): Elastic plates, stresses in dams and retaining walls

Timoshenko (1878-1972): Theory of thick beams


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Applications


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High-Speed Ground Transit(Vehicle/Guideway Design, Material Optimization, Cost, etc.)

The Sky Train

Vancouver, CanadaA Modern Automated

Transit System

Torsional Guideway

Transit System (TGT)

Car

Pier

Guideway

S i i D i


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Earthquake in Kobe, Japan (Magnitude 7.2) on January 17, 1995(Collapse of a Bank Building)

Seismic Design(Safety, etc.)

B ildi D i


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(Design of Members, Joints, Configuration, etc.

for Structural Integrity, Safety, etc.)

Building Design


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(Under Dynamic Loading Conditions)

Joints/Connectors of Machinery

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