.

0 (hodnocen0 x )

EB

EB

ONLINE

[Pardubice] : Univerzita Pardubice, 2018

1 online zdroj (133 stran)

ISBN 978-80-7560-166-7 (online ; pdf)

ISBN 978-80-7560-165-0 (print) ISBN !978-80-7560-166-0 (chyb.)

This book deals with the mechanics of impacts and vibrations and mitigation of their effects. It brings the expressions for impacts and for velocity, displacement and force in various cases of braking or stopping, and pays attention to the fact that force impulses propagate in bodies only with limited velocity. Then, it shows how various materials respond to load, how they absorb energy and how they can fail. Further it describes technical means for impact energy absorption, such as bend parts, compressed shells, composites, air cushions and hydraulic shock dampers with constant deceleration. One chapter is devoted to vibrations and mitigation of their effects. Formulae are presented for free and forced vibrations, without or with damping, and attention is also paid to the transmission of forces into foundations and to kinematic exciting, appearing during a vehicle´s ride on a wavy road. Also a dynamic absorber of vibrations is described and vibrations of a system of several bodies. More complex analysis needs numerical methods, such as the finite element method. The last chapter is devoted to the dimensional analysis and theory of similarity, which can spare work during the development of appliances for the damping of impacts and vibrations. The book contains explanatory examples, numerous figures and references..

* rázy * nárazy

001643036

Jaroslav Mencík: Impacts and vibrations // Contents // 1. Introduction 7 // 2. Impacts and hits 9 // 2.1 Introduction 9 // 2.2 Direct collision of mass points 10 // 2.3 Elastic impact 11 // 2.4 Inelastic impact 13 // 2.5 Partly elastic impact 13 // 2.6 Oblique impact 16 // 2.7 Forces at impacts - simplified solution 19 // 3. Wave character of stress increase 23 // 3.1 Longitudinal waves in a prismatic bar 23 // 3.2 Elastic waves in a bar hit by a body of finite size 27 // 3.3 Elastic waves in a three-dimensional body 27 // 3.4 Plastic waves 28 // 3.5 Hydraulic shock 29 // 4. Courses of stopping for various resistances 31 // 4.1 Braking with constant resistive force 31 // 4.2 Impact on a spring with linear characteristics 34 // 4.3 Impact on a spring with linear characteristics // and friction damping 39 // 4.4 Impact on a spring with linear characteristics // and damping proportional to velocity 41 // 4.5 Impact on a spring with linear characteristics and // damping proportional to velocity squared 44 // 4.6 Changes of kinetic energy during braking 45 // 5. Response and damage of materials // and components 47 // 5.1 Introduction 47 // 5.2 Elastic - plastic response of ductile materials 48 // 5.3 Load response of viscoelastic materials 51 // 5.4 Brittle and ductile failure 52 // 5.5 Ductile materials - elastic-plastic bending 54 // 5.6 Loss of stability by buckling 58 // Jaroslav Mencík: Impacts and vibrations // 5.7 Influence of notches and other stress concentrators 60

5.8 Influence of cracks, principles offracture mechanics 62 // 5.9 Failure of bodies from brittle materials 65 // 6. Structural elements for impact damping 73 // 6.1 Rings and systems of rings 73 // 6.2 Zig-zag structures 76 // 6.3 Axisymmetric shells loaded by axial force 77 // 6.4 Materials with cellular structure 78 // 6.5 Axisymmetric tearing and inversion // of metal tubes 80 // 6.6 Composites 82 // 6.7 Air-or gas bags and cushions 84 // 6.8 Hydraulic shock absorbers of constant force 86 // 7. Vibrations and mitigation of their effects 92 // 7.1 Free vibration without damping 92 // 7.2 Free vibration with damping 94 // 7.3 Forced vibration 95 // 7.4 Forces transmitted from the vibrating body // to the frame or foundations 101 // 7.5 Vibration caused by kinematic excitation 103 // 7.6 Transverse vibration of beams 105 // 7.7 Circular vibrations 107 // 7.8 Rotation of a shaft with eccentric load 108 // 7.9 Balancing of rotating objects 109 // 7.10 Energy in vibrating systems with damping 110 // 7.11 Dynamic absorber of vibrations 112 // 7.12 Vibration of systems with more degrees of freedom 114 // 8. Dimensional analysis and similarity theory 118 // 8.1 Dimensional analysis 118 // 8.2 Similarity 120 // 8.3 Further recommendations 122 // 8.4 Limitations of similarity principle 124 // 8.5 Examples of dimensionless quantities 125 // 8.6 Examples of similarity numbers 126 // Index 127