Mechanical Vibration (eBook)

Ivana Kovacic, University of Novi Sad, Serbia Ivana Kovacic graduated in Mechanical Engineering from the Faculty of Technical Sciences (FTN), University of Novi Sad, Serbia. She obtained her MSc and PhD in the Theory of Nonlinear Vibrations at the FTN. She is currently a Full Professor of Mechanics at the FTN and the head of the Centre of Excellence for Vibro-Acoustic Systems and Signal Processing CEVAS at the same faculty. Kovacic is the Subject Editor of three academic journals: the Journal of Sound and Vibration, the European Journal of Mechanics A/Solids and Meccanica. Her research involves the use of quantitative and qualitative methods to study differential equations arising from nonlinear dynamics problems mainly in mechanical engineering, and recently also in biomechanics and tree vibrations. Dragi Radomirovic, University of Novi Sad, Serbia Dragi Radomirovic graduated in Mechanical Engineering from the Faculty of Technical Sciences (FTN), University of Novi Sad (UNS), Serbia. He obtained his MSc and PhD in Analytical Mechanics at the FTN. He is a Full Professor of Mechanics at the Faculty of Agriculture, UNS. His research interests are directed towards Mechanical Vibrations and Analytical Mechanics.

About the Authors ix

Preface xi

1 Preliminaries 1

Chapter Outline 1

Chapter Objectives 1

1.1 From Statics 1

1.1.1 Mechanical Systems and Equilibrium Equations 1

1.1.2 Constraints and Free-Body Diagrams 1

1.1.3 Equilibrium Condition Via Virtual Work 2

1.2 From Kinematics 4

1.2.1 Kinematics of Particles 4

1.2.2 Kinematics of Rigid Bodies 5

1.2.3 Kinematics of Particles in Compound Motion 7

1.3 From Kinetics 8

1.3.1 Kinetics of Particles 8

1.3.2 Kinetics of Rigid Bodies 9

1.4 From Strength of Materials 13

1.4.1 Axial Loading 13

1.4.2 Torsion 14

1.4.3 Bending 14

2 Lagrange's Equation for Mechanical Oscillatory Systems 17

Chapter Outline 17

Chapter Objectives 17

2.1 About Lagrange's Equation of the Second Kind 17

2.2 Kinetic Energy in Mechanical Oscillatory Systems 19

2.3 Potential Energy in Mechanical Oscillatory Systems 21

2.3.1 Gravitational Potential Energy 22

2.3.2 Potential Energy of a Spring (Elastic Potential Energy) 24

2.4 Generalised Forces in Mechanical Oscillatory Systems 27

2.5 Dissipative Function in Mechanical Oscillatory Systems 28

References 30

3 Free Undamped Vibration of Single-Degree-of-Freedom Systems 31

Chapter Outline 31

Chapter Objectives 31

Theoretical Introduction 31

4 Free Damped Vibration of Single-Degree-of-Freedom Systems 67

Chapter Outline 67

Chapter Objectives 67

Theoretical Introduction 67

5 Forced Vibration of Single-Degree-of-Freedom Systems 101

Chapter Outline 101

Chapter Objectives 101

Theoretical Introduction 101

6 Free Undamped Vibration of Two-Degree-of-Freedom Systems 127

Chapter Outline 127

Chapter Objectives 127

Theoretical Introduction 127

7 Forced Vibration of Two-Degree-of-Freedom Systems 153

Chapter Outline 153

Chapter Objectives 153

Theoretical Introduction 153

8 Vibration of Systems with Infinite Number of Degrees of Freedom 183

Chapter Outline 183

Chapter Objectives 183

8.1 Theoretical Introduction: Longitudinal Vibration of Bars 183

8.2 Theoretical Introduction: Torsional Vibration of Shafts 197

8.3 Theoretical Introduction: Transversal Vibration of Beams 207

9 Additional Topics 225

Chapter Outline 225

Chapter Objectives 225

9.1 Theoretical Introduction 225

9.2 Equivalent Two-Element System for Concurrent Springs and Dampers 226

9.2.1 Concurrent Springs 227

9.2.2 Concurrent Dampers 231

9.3 Nonlinear Springs in Series 238

9.3.1 Purely Nonlinear Springs in Series 239

9.3.2 Equal Duffing Springs in Series 239

9.3.3 Two Different Nonlinear Springs 240

9.4 On the Deflection and Potential Energy of Nonlinear Springs: Approximate Expressions 242

9.4.1 Duffing-Type Spring Deformed in the Static Equilibrium Position 242

9.4.2 Duffing-Type Spring Undeformed in the Static Equilibrium Position 242

9.5 Corrections of Stiffness Properties of Certain Oscillatory Systems 244

9.5.1 One-Degree-of-Freedom Systems 245

9.5.2 Two-Degree-of-Freedom Systems 248

Appendix: Mathematical Topics 255

A.1 Geometry 255

A.2 Trigonometry 257

A.3 Algebra 258

A.4 Vectors 258

A.5 Derivatives 259

A.6 Variation (Virtual Displacements) 260

A.7 Series 260

Index 261