Strength of materials

2012-10-19

Projekt „Inżynier mechanik – zawód z przyszłością”

Lecture #1 - Introduction

Zajęcia współfinansowane ze środków Unii Europejskiej w ramach Europejskiego Funduszu Społecznego

Strength of materials Instructor: PhD eng. Olejarczyk Krzysztof Krasickiego 54 street, room 306 Telephone: (48) 361 71 16 e-mail: [email protected]

CZŁOWIEK – NAJLEPSZA INWESTYCJA

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• Theoretical background 1. Timoshenko S. Strength of Materials, 3rd edition. Krieger Publishing Company, 1976 2. Hibbeler, R.C. Statics and Mechanics of Materials, SI Edition. PrenticeHall, 2004 3. Mott, Robert L. Applied Strength of Materials, 4th edition. PrenticeHall, 2002 4. Beer & Johnston (2006). Mechanics of Materials, 5th edition. McGraw Hill. 5. Fedynand L., Pytel A., Strength of materials. Singer 6. Warren C.Young Richardd G.Budynas Roark’s formulas for stress and strain, 7th edition. McGraw-Hill 2002. 7. Guide to mechanics 8. Internet’s web pages

• Extension • Torsional • Bending • Buckling • Strength hypothesis

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This course has two specific goals: 1. To introduce students to concepts of stresses and strain; shearing force and bending; as well as torsion and deflection of different structural elements.

1. Introduction:

- Course objectives - What is strength of materials, stress, strain …. - Why …

2. Main body:

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2. To develop theoretical and practical skills relevant to the areas mentioned in 1above.

Fundamental concepts Fundamental principles Major classes of materials Properties of materials Systems of units Types of loading Boundary conditions

3. Summary 5

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Upon successful completion of this course, students should be able to: 1.

Understand and solve simple problems involving stresses and strain in two and three dimensions.

2.

Understand and carry out simple experiments illustrating properties of materials in tension and compression.

The science of durability typical structural elements under load

3. Draw shear force and bending moment diagrams of simple beams and understand the relationships between loading intensity, shearing force and bending moment. 4. Compute stresses.

A load applied to a mechanical element will induce internal forces within the element called stresses.

5.Calculate the deflection. 7

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The strength of any material relies on three different type of analytical method: strength, stiffness and stability, where:

The stresses acting on the material cause deformation of the material. Deformation of the material is called strain, while the intensity of the internal forces is called stress.

-strength refers to the load carrying capacity, -stiffness refers to the deformation, -stability refers to the ability to maintain its initial configuration.

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… becouse YOU WILL DO ANYTHINK LIKE THAT

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Space

- Euclidean coordinates

space:

length,

width,

height,

three

• Time - definition of an event requires specification of the time and position at which it occurred. • Mass - used to characterize and compare bodies. • Force - represents the action of one body on another. A force is characterized by its point of application, magnitude, return and direction.

Mesh

In Newtonian Mechanics, space, time, and mass are absolute concepts, independent of each other. Force, however, is not independent of the other three. The force acting on a body is related to the mass of the body and the variation of its velocity with time.

-10at pressure - Different thickness -Uniform stress distribution 13

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• An alternative to major classes, you may divide materials into classification according to properties. • Metals

• One goal of materials engineering is to select materials with suitable properties for a given application.

• Ceramics • Polymers

Mechanical properties A. Elasticity and stiffness B. Plasticity C. Strength D. Brittleness or Toughness E. Fatigue

• Electronic Materials • Composites • Biomaterials

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• Kinetic Units: length, time, mass, and force.

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• International System of Units (SI): The basic units are length, time, and mass which are arbitrarily defined as the meter (m), second (s), and kilogram (kg). Force is the derived unit,

F

ma

• Three of the kinetic units, m 1 N 1 kg 1 2 referred to as basic units, may be s defined arbitrarily. The fourth unit, referred to as a derived unit, • U.S. Customary Units: must have a definition compatible The basic units are length, time, and with Newton’s 2nd Law, force which are arbitrarily defined as the foot (ft), second (s), and pound   (lb). Mass is the derived unit,

F

ma

m 1slug

F a 1lb 1ft s 17

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Boundary condition-definitions Y

Translations

Axial loading

R y ,My

Tx, Ty Tz (1, 2, 3)

Transverse loading

T y ,F y

Rotation Rx, Ry, Rz (4, 5, 6)

R x ,Mx T z ,F z

T x ,F x

Forces

Torsional loading

Fx, Fy, Fz

Moments Mx, My, Mz

X

R z ,Mz

Z

Cartesian coordinate system

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An end release allows either or both ends of a beam to rotate about or translate along one or more of the local axis of the beam.

Some examples to introduce topics you will learn.

Without the right material, a good engineering design is wasted. Need the right material for the right job!

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In 1949, the COMET aircraft was a newly designed, modern jet aircraft for passenger travel. It had bright cabins due to large, square windows at most seats. It was composed of light-weight aluminum.

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In early 1950's, the planes began falling out of the sky.

These tragedies changed the way aircraft were designed and the materials that were used.

- Materials properties are responsible for helping achieve engineering advances. - Failures advance understanding.

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The square windows were a "stress concentrator" and the aluminum alloys used were not "strong" enough to withstand the stresses.

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Until then, material selection for mechanical design was not really considered in designs.

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    

1. Autodesk Algor’s materials on: www.autodesk.algor.com 2. MSE Illinois. Introduction to engineering materials. D.D. Johanson 2004 3. Hibbeler, R.C. Statics and Mechanics of Materials, SI Edition. Prentice-Hall, 2004 4. J. S. Rossmann, C. L. Dym. Introduction to Engineering Mechanics a Continuum Approach, CRC Press 2009

Tubular constructed building. Well designed and strong. Strong but not from buckling. Supports lost at crash site. Heat from burning fuel adds to loss of structural support from softening of steel (strength vs.T).

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Thank you for your attention For further information please contact:

dr inż. Olejarczyk Krzysztof Phone +48 48 361 71 14 mobile +48 606 142 641 e-mail: [email protected] 27

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