1、PDF外文http:/ 6680 字 The Two-Dimensional Dynamic Behavior of Conveyor Belts Ir. G. Lodewijks, Delft University of Technology, The Netherlands 1. SUMMARY 1-In this paper a new finite element model of a belt-conveyor system will be introduced. This model has been developed in order to be able to simulat
2、e both the longitudinal and transverse dynamic response of the belt during starting and stopping. Application of the model in the design stage of long overland belt-conveyor systems enables the engineer, for example, to design proper belt-conveyor curves by detecting premature lifting of the belt of
3、f the idlers. It also enables the design of optimal idler spacing and troughing configuration in order to ensure resonance free belt motion by determining (standing) longitudinal and transverse belt vibrations. Application of feed-back control techniques enables the design of optimal starting and st
4、opping procedures whereas an optimal belt can be selected by taking the dynamic properties of the belt into account. 2. INTRODUCTION 2-The Netherlands has long been recognised as a country in which transport and transhipment play a major role in the economy. The port of Rotterdam, in particular is k
5、nown as the gateway to Europe and claims to have the largest harbour system in the world. Besides the large numbers of containers, a large volume of bulk goods also passes through this port. Not all these goods are intended for the Dutch market, many have other destinations and are transhipped in Ro
6、tterdam. Good examples of typical bulk goods that are transhipped are coal and iron ore, a significant part of which is intended for the German market. In order to handle the bulk materials a wide range of different mechanical conveyors including belt-conveyors is used. 3-The length of most belt-con
7、veyor systems erected in the Netherlands is relatively small, since they are mainly used for in-plant movement of bulk materials. The longest belt-conveyor system, which is about 2 km long, is situated on the Maasvlakte, part of the port of Rotterdam, where it is used to transport coal from a bulk t
8、erminal to an electricity power station. In addition to domestic projects, an increasing number of Dutch engineering consultancies participates in international projects for the development of large overland belt-conveyor systems. This demands the understanding of typical difficulties encountered du
9、ring the development of these systems, which are studied in the Department of Transport Technology of the Faculty of Mechanical Engineering, Delft University of Technology, one of the three Dutch Universities of Technology. 4-The interaction between the conveyor belt properties, the bulk solids prop
10、erties, the belt conveyor configuration and the environment all influence the level to which the conveyor-system meets its predefined requirements. Some interactions cause troublesome phenomena so research is initiated into those phenomena which cause practical problems, 1. One way to classify these
11、 problems is to divide them into the category which indicate their underlying causes in relation to the description of belt conveyors. 5-The two most important dynamic considerations in the description of belt conveyors are the reduction of transient stresses in non-stationary moving belts and the d
12、esign of belt-conveyor lay-outs for resonance-free operation, 2. In this paper a new finite element model of a belt-conveyor system will be presented which enables the simulation of the belt's longitudinal and transverse response to starting and stopping procedures and it's motion during ste
13、ady state operation. It's beyond the scope of this paper to discuss the results of the simulation of a start-up procedure of a belt-conveyor system, therefore an example will be given which show some possibilities of the model。 3. FINITE ELEMENT MODELS OF BELT-CONVEYOR SYSTEMS 6-If the tot
14、al power supply, needed to drive a belt-conveyor system, is calculated with design standards like DIN 22101 then the belt is assumed to be an inextensible body. This implies that the forces exerted on the belt during starting and stopping can be derived from Newtonian rigid body dynamics which yield
15、s the belt stress. With this belt stress the maximum extension of the belt can be calculated. This way of determining the elastic response of the belt is called the quasi-static (design) approach. For small belt-conveyor systems this leads to an acceptable design and acceptable operational behavior
16、of the belt. For long belt-conveyor systems, however, this may lead to a poor design, high maintenance costs, short conveyor-component life and well known operational problems like : excessive large displacement of the weight of the gravity take-up device premature collapse of the belt, mostly due t
17、o the failure of the splices destruction of the pulleys and major damage of the idlers lifting of the belt off the idlers which can result in spillage of bulk material damage and malfunctioning of (hydrokinetic) drive systems Many researchers developed models in which the elastic response of the bel
18、t is taken into account in order to determine the phenomena responsible for these problems. In most models the belt-conveyor model consists of finite elements in order to account for the variations of the resistance's and forces exerted on the belt. The global elastic response of the belt is mad
19、e up by the elastic response of all its elements. These finite element models have been applied in computer software which can be used in the design stage of long belt-conveyor systems. This is called the dynamic (design) approach. Verification of the results of simulation has shown that software pr
20、ograms based on these kind of belt-models are quite successful in predicting the elastic response of the belt during starting and stopping, see for example 3 and 4. The finite element models as mentioned above determine only the longitudinal elastic response of the belt. Therefore they fail in the a
21、ccurate determination of: the motion of the belt over the idlers and the pulleys the dynamic drive phenomena the bending resistance of the belt the development of (shock) stress waves the interaction between the belt sag and the propagation of longitudinal stress waves the interaction between the id
22、ler and the belt the influence of the belt speed on the stability of motion of the belt the dynamic stresses in the belt during. passage of the belt over a (driven) pulley the influence of parametric resonance of the belt due to the interaction between vibrations of the take up mass or eccentricitie
23、s of the idlers and the transverse displacements of the belt the development of standing transverse waves the influence of the damping caused by bulk material and by the deformation of the cross- sectional area of the belt and bulk material during, passage of an idler the lifting of the belt off the
24、 idlers in convex and concave curves The transverse elastic response of the belt is often the cause of breakdowns in long belt-conveyor systems and should therefore be taken into account. The transverse response of a belt can be determined with special models as proposed in 5 and 6, but it is more c
25、onvenient to extend the present finite element models with special elements which take this response into account. 3.1 THE BELT A typical belt-conveyor geometry consisting of a drive pulley, a tail pulley, a vertical gravity take-up, a number of idlers and a plate support is shown in Figure 1. This
26、geometry is taken as an example to illustrate how a finite element model of a belt conveyor can be developed when only the longitudinal elastic response of the belt is of interest. Since the length of the belt part between the drive pulley and the take-up pulley, Is, is negligible compared to the length of the total belt, L, these pulleys can
