Design of the hydraulic shock absorbers characteristics using the acceleration of the sprung mass

The force-velocity characteristics of the air-pressure-controlled shock absorbers produced in BRANO a.s. were designed on the basis of the relative deflections of the air springs. These characteristics are verified by means of another approach – the acceleration of the sprung mass criterion. The reference vehicle is the same as in the previous case – the SOR C 12 intercity bus. The bus multibody models created in the alaska simulation tool are used for the designed characteristics verification. The results of both approaches are compared

Základní model pádu regulačního orgánu v jaderných reaktorech

This paper is focused on the modelling and dynamic analysis of a nonlinear system representing a control assembly of the VVER 440/V213 nuclear reactor. A simple rigid body model intended for basic dynamic analyses is introduced. It contains the influences of the pressurized water and mainly the e ects of possible control assembly contacts with guiding tubes inside the reactor. Another approach based on a complex multibody model is further described and the suitability of both modelling approaches is discussed.Článek je zaměřen na modelování a dynamickou analýzu nelineárního systému, který reprezentuje regulační orgán jaderného reaktoru VVER 440/V213. Je představen jednoduchý model tuhého tělesa určený pro základní dynamické analýzy. Model zahrnuje vliv stlačené vody a zejména vliv možných kontaktů regulačního orgánu s vodicími trubkami uvnitř reaktoru. Dále je popsán jiný přístup k modelování založený na komplexním multibody modelu a je diskutována vhodnost obou přístupů k modelování

Influence of the fibre damping computational model in a mechanical system on the coincidence with the experimental measurement results

Experimental measurements focused on the investigation of fiber behaviour are performed on an assembled weight-fibre-pulley-drive mechanical system. The carbon fibre driven by one drive is led over a pulley. At its other end there is a prismshaped steel weight which moves in a prismatic linkage on an inclined plane. In the presented case, the position of the weight is symmetric with respect to the plane of drive-pulley symmetry. Drive periodic excitation signals can be of different shapes with the possibility of variation of a signal rate. Time histories of the weight position and the force acting in the fibre are measured. The same system is numerically investigated by means of multibody models. In the  computational model, the influence of the fibre damping coefficient exerted both on the coincidence of the simulation results and the experimental measurement results is evaluated. The main aim of  simulations is to create a phenomenological model of a fibre which will be utilizable in fibre modelling in the case of more complicated mechanical or mechatronic systems

Non-uniform quaternion spline interpolation in vehicle kinematics .

editorial reviewe

Modelling of dynamic behaviour of fibres and cables

In this paper there are presented some possible approaches suitable for the modelling of the fibre and cable dynamics in the framework of various mechanical systems: force representation of a fibre, a pointmass model and an absolute nodal coordinate formulation. Experimental measurements focused on the investigation of the fibre behaviour were performed on the assembled weight-fibre and weight-fibre-pulleydrive laboratory mechanical systems. These mechanical systems were modelled using some of the mentioned methods and simulations of the experimental measurements were performed. The simulations aim was to create a phenomenological model of a fibre (cable). The obtained results are discussed

Selected results of the CESEN project solving

V příspěvku jsou stručně představeny dva vybrané výsledky řešení projektu Centra kompetence Technologické agentury České republiky „Centrum výzkumu a experimentálního vývoje spolehlivé energetiky“ (akronym CESEN) dosažené v roce 2018: porovnání vlastností žárových nástřiků s jinými typy povrchových ochran komponent energetických zařízení a pokročilé numerické řešení vibrací lopatek parních turbín.TE01020068 „Centrum výzkumu a experimentálního vývoje spolehlivé energetiky“The paper presents in brief two selected results of the Competence Centre Project of the Technology Agency of the Czech Republic “Centre of research and experimental development of reliable energy production” (CESEN acronym) achieved in 2018: comparison of properties of thermally-sprayed coatings with other types of surface treatment of power producing equipment parts and advanced numerical solution of steam turbines blade vibration

3D projection of the LuGre friction model adapted to varying normal forces

In this paper, we develop an adaptation of the LuGre friction model so as to allow the development of the friction force and its application in any directions on systems subjected to varying normal forces. This is achieved by projecting a modified LuGre model adapted to varying normal forces in 3D along an arbitrary orthogonal system. Consequently, the direction of the friction force is automatically oriented in the correct direction, thus stick, stick-slip, and slip behavior can be represented in all directions. The projected friction model has the following friction features: stick-slip, presliding displacement, frictional lag, varying break-away force, viscous friction, Stribeck effect, and is adapted to varying normal forces. The equivalence of this projected LuGre model with the modified one is proven analytically. The friction model is then applied to simulate the friction on two mechanical systems. The first system consists of a cube sliding on a plane with a transition from stick to slip due to varying normal forces and with a pulling force oriented in multiples directions of the contact plane. The second one is a more complex system consisting of three turbine blades that uses friction to damp their resonance. The results obtained for both systems are consistent with literature

Spatial revolute joints with clearance and friction for dynamic analysis of multibody mechanical systems

A study on the effects of dry spatial revolute joints with clearance and friction is delivered through this work. Both radial and axial clearances are taken into consideration which makes the model more realistic for three-dimensional motion. The kinematics of the contact between the journal and bearing are assessed, and used to evaluate the intra-joint normal and tangential contact forces. Moreover, a spatial slider-crank mechanism is used as an application example. The ideal case, the frictionless clearance joint and the joint with clearance and friction were compared, and the results show that clearance and friction have a significant impact in the dynamic response of the mechanical system

Dynamics of rotating systems with rolling element bearings

This paper deals with a suitable approach to the computational modelling of rolling element bearings in the framework of rotating systems dynamics. Various alternative approaches are briefly summarized and a chosen moderately complex approach is described in more detail. The presented bearing model respects real number of rolling bodies and roller contact forces acting between the journals and the outer housing