編號(hào)： 畢業(yè)設(shè)計(jì) (論文 )外文翻譯（原文）學(xué) 院： 機(jī)電工程學(xué)院 專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué)生姓名：學(xué) 號(hào)：指導(dǎo)教師單位姓 名：職 稱：Fatigue life prediction of the metalwork of a travelling gantry craneV.A. KopnovAbstractIntrinsic fatigue curves are applied to a fatigue life prediction problem of the metalwork of a traveling gantry crane. A crane, used in the forest industry, was studied in working conditions at a log yard, an strain measurements were made. For the calculations of the number of loading cycles, the rain flow cycle counting technique is used. The operations of a sample of such cranes were observed for a year for the average number of operation cycles to be obtained. The fatigue failure analysis has shown that failures some elements are systematic in nature and cannot be explained by random causes.卯 1999 Elsevier Science Ltd. All rights reserved.Key words: Cranes; Fatigue assessment; Strain gauging1. Introduction1.1 Characteristics and Developmental Tendency of Modern CranesWith rapid development of modern science and technology, magnification of industrial production scale and improvement of automation level, application of cranes is becoming widespread and its function is obvious. Meanwhile, requirements for cranes are more and more strict. Especially, the widespread use of electronic computer technology spurs lots of subject-crossing advanced design approaches and accelerates the improvement of modern manufacturing and detecting technology. Fierce competition in international market becomes more dependent on the competition of technology. All of these impel technological functions of cranes into a brand-new developmental stage. Cranes are facing a tremendous transformation. Our country is entering global international competitive market at an unprecedented rate and crane manufacture is confronted with a new situation where opportunities and challenges coexist. Thus, it is crucial for cranes to develop and innovate constantly. I want to make a brief explanation about characteristics and developmental tendency of modern cranes with examples, based on new theories, technology and trend of cranes at home and overseas.1)Make the key products large, high speed, endured and specializedBecause of continuous expansion of industrial production scale, increasingly improvement of production efficiency and rising proportion of money spending on loading and unloading and transporting materials in the process of production, required amount of large or high-speed cranes is increasing. Lifting quantities become larger, working speed becomes higher and requirements of energy-consuming and reliability become stricter. Cranes have already become a critical link in the process of automation production. Cranes should be easy to use, maintain and operate and have high security, less troubles and long average time between failures. The central issue in international market production competition is reliability, and many companies abroad have drawn up inter-controlled standard of reliability. The most important for us to catch up with and surpass world advanced level of crane’s function is to improve reliability, to make cranes durable, less troubles, maintainable and economic to be used.At the moment, the biggest floating crane in the world weighs 6500t, chain crane 3000t and bridge crane 1200t. Diversity of industrial mode of production and customers’ need makes crane market expanding and products renewing constantly to satisfy special needs with specific functions and bring its best usefulness into play. Functions of various kinds of cranes are improving. DEMAG ERGOTECH has developed a crane special for aircraft maintenance, which has made its own way into international market. This crane is great in length and lifting height and has accurate halt. When a flexible maintenance platform fixed under lifting cart, it can reach every part of the aircraft. With the fast development of nuclear power stations in the world, cranes which are special for them achieve corresponding development. For example, annular bridge crane in reactors’ space, working under radiative circumstances, is used to lift dangerous load such as top cover of pressure container and components in reactors. It requires high reliability, high security, the ability to determine location accurately and automatically and transfer goods to a lower level, as well as various kinds of protection and particular security devices.2)Make series of production modularized, combined, standardized and practicalMost cranes are produced by series and batch, thus use of systematic multi-objections entire optimization to design series of cranes has already become the key point in development. Through rational matching of series main parameter, its functions can be improved, manufacturing cost can be reduced, and degree of general purpose can be raised. Use less specification spare parts to compose series production with multi-species and multi-specifications. And thus, the requirements of customers can be fully satisfied.By using modularized design instead of conservative entire design, we can make components with similar functions into standard modules which have various uses, similar connective key factors and are interchangeable. Through combination of different modules, we can make different kinds and specifications of cranes. There are only several modules involved when it comes to crane improvement. To design a new style of crane, all that you do is to choose different modules to recompose. Because of improvement in degree of general purpose, single products with small serial production can transform into module production of pretty great batches. As a result, we can achieve specialization production with high efficiency and cut manufacturing cost. It can satisfy marketing demands and increase competitive capacity by composing cranes of various series and specifications using less modularized forms.Bridge crane produced by DEMAG ERGOTECH considered carefully modularization and combination. It makes inter-parameter of series, entirety, mechanism and components matched with each other. The distribution of capacity obtains most economic and suitable effects. To make the main components of lifting mechanism reaches its largest general purpose, the method that the result of lifting weights multiplying lifting speed is a constant has been used. There are more specifications derived through changes of pulley multiplying power. Series of 5-125t bridge cranes only need four basic lifting carts even with various working ranks. Module series of standard wheel cases, which are produced by the company, have various groups of linking holes which can choose different drive unit to form platform carts. They can also combine with metal construction components to be used as running machine of various kinds of cranes; its wheels have several forms of surfaces to be chosen. Because of no basic distance limit and flexible combination, they are widely used. The company’s series of end bridge standard modules have commercialized. It resorts to frictional cycle and high intensity bolt link which improves interchange and accuracy of sizes and reduces machining of connecting covers. It can connect to each main beam quickly and effectively. There are two kinds of end beam modules; one is suitable for single beam and the other is for double beams. According to length and weights, end beam style can be decided.3)Make productions for general purposes small, light, simple and diversifiedThere are quite a number of cranes used in general workshop and storehouse, and thus they have light work and the requirement is not very strict. How to improve application of these cranes and to cut manufacturing cost is critical to win in the marketing competition. Considering comprehensive benefit, the need to decrease the height of cranes as low as possible, to simplify the constructions and to reduce weights and wheel pressure can also decrease structure’s height, lighten structure composition and reduce cost of producing and maintenance. So there will be fast development of electric calabash bridge and light beam cranes, and bridge cranes for general purposes will be replaced by them.The needs of customers advance diversity of cranes. Series parameter scale of cranes expanding and functions enlarging, product of one machine for several uses will obtain further development to increase capacity of dealing with emergencies. The proportion of using wireless remote control under normal conditions will increase.DEMAG ERGOTECH has formed standard crane series of light combinations after long period explosion and innovation. The whole series compose of various productions such as combination “工 ” style single beam, hanging case single beam, horn cart case single beam and case double beams. There are altogether fifteen forms of connection between main beam and end beam. This is suitable for needs of different structure and lifting goods. Each specification of crane has three single speeds and three double speeds to be chosen. There are seven operating ways. In addition, different electric conduction pattern and different electric control pattern can match hundreds and thousands of cranes through different combinations to fully satisfy different needs of customers. Another advantage of the crane is that they are light. Compared to productions at home, its lifting weight is 32t and length 25.5m compared to 46.4t------weight of double beams cranes in our country, 28.3t------ electric calabash bridge cranes. Weight of DEMAG electric calabash bridge crane is only 18.5, which is lighter than domestic productions by 60 percent and 35percent respectively.1.2 Type of CranesCranes can be classified into four kinds, namely, (a) overhead traveling crane; (b) jib crane; (c) bridge or gantry crane; and (d) cantilever crane. Overhead traveling crane. Consists of a girder and a trolley. The girder is supported at each end on trucks capable of traveling on elevated fixed tracks. The trolley is equipped with hoisting and other mechanism, capable of traversing from end to end of such girder. The girder and associated end carriages are known as the bridge. Such cranes vary in lifting capacity from about 2 tons to 400 tons, and in span from 20 ft to 150 ft,or more. Depending on the purpose for which it is to be used, the crane can be operated either from a cabin fixed to the bridge or the trolley, or from the ground. When two trolleys are furnished, these may run on a common tracks arranged side-by-side or one above the other so that each trolley can traverse the entire span. Jib crane: Consists of an inclined member, or jib, capable of suspending a load at its outer end. The jib is supported by a rope or other member attached to a vertical mast of frame. The out reach of the jib can be constant or variable, and the crane as a whole may be either fixed or movable.Included in this kind are: mobile and caterpillar cranes, builders tower cranes, wharf cranes, and movable cranes mounted on high pedestals, gantries, pontoons and barges. Lifting capacities vary from 1/2 ton to 300 tons or more, and outreaches from a few feet to 150 ft. Cranes required for handling heavy machinery and equipment in shipyards and at ports are frequently mounted on pontoons.Bridge or gantry crane: Consists of a bridge girder, connected at near both ends to upright members, which may be fixed or arranged to travel on a fixed track, and the load is suspended from a trolley or crane, capable or traversing from end to end of the bridge. Cranes of this kind have lifting capacities varying from end to end of the bridge. When used in general and bulk-storage yards, the tracks may be of broad or narrow gauge. The tipping moment of the loaded crane is kept within proper limits by a counterweight which is moved along an independent track on the bridge above the trolley. Cantilever crane: Consists of horizontal and vertical members the former, known as the cantilever, being fixed to or totating in a horizontal plane about the axis of the vertical member. On the cantilever is formed a track which supports a movable trolley from which the load is suspended.The mechanism for hoisting and traversing is usually mounted on a rear extension of the cantilever. Although such cranes may be fixed or movable, those of large capacity are usually fixed. Lifting capacities, height of lift and outreach vary between wide limits. When used for the fitting out of ships, light loads are handled by an auxiliary hoist which may be mounted on a jib crane arranged to travel on track. The main lifting mechanism usually consists of two winches which can be operated independently or in concert. A typical fitting-out crane may be of 250 tons capacity with a total outreach of 180 ft and a lifting height of 200 ft. Wharf Cranes: A wharf crane is any crane located on a wharf or pier, and particularly adapted to the transfer of cargo between the wharf or pier and the hold of the vessel alongside; it is also called a cargo crane, although the latter term is more general, as it comprises also parts of the cargo-handling gear of a vessel. Owing to the varying spacing of vessel hatchways, the wharf crane in most cases must be capable of movement along the wharf, and hence is generally mounted on a runway. Other requirements are sufficient horizontal reach to cover the hatchway,sufficient length of host to raise the load from the bottom of the hold to a point entirely clear of the vessel, and rapidity and economy on operation.Types much used as wharf cranes are single or double portal gantries or traveling bridges on the wharf shed roof, carrying rotating bridges on cantilever gantries with folding extensions over the hatchways; gantries with inclined cantilever jibs; also of the derrick type.In the handling of general cargo, as contrasted to bulk cargo, a broader view in analyzing the situation has to be taken. Diversity of shape, size and weight precludes the possibility of using elevators or conveyors to any great extent, while the necessity of sorting and piling in allotted places on the wharf makes the transporter, with its rather limited area of discharge, unsuitable.The traveling portal crane, having a boom capable of being luffed as well swung, is much used as a wharf crane. One of the chief disadvantages, however, which the ordinary luffing crane works under is that when the boom is luffed-in the load suspended from the top of the boom is simultaneously raised; conversely, as the boom is lowered, the load falls by a corresponding amount. This, obviously,is a loss of work and means an unnecessarily large motor to work the luffing gear.To overcome this objection a number of different designs of a type of crane known as the level-luffing crane have been developed, and these cranes are now extensively used as wharf cranes. In this type of cranes a compensating gear in some form or another is provided whereby the load is made to travel along a horizontal path irrespective of the rise and fall of the hoisting pulley caused by the luffing-in or out of the boom. In selecting the most economical crane for handling general cargo, the average and maximum weights of the individual pieces of cargo must be taken into consideration. The frequency with which 60-ton lifts are likely to be encountered is exceedingly low, also 20-ton lifts are quite uncommon, so that it would be out of reason to install on any single dock a number of cranes capable of handling such weights. This most popular general-cargo cranes in use at present are from 5~10 tons’capacity. Fatigue failures of elements of the metalwork of traveling gantry cranes LT62B are observed frequently in operation. Failures as fatigue cracks initiate and propagate in welded joints of the crane bridge and supports in three-four years. Such cranes are used in the forest industry at log yards for transferring full-length and sawn logs to road trains, having a load-fitting capacity of 32 tons. More than 1000 cranes of this type work at the enterprises of the Russian forest industry. The problem was stated to find the weakest elements limiting the cranes' fives, predict their fatigue behavior, and give recommendations to the manufacturers for enhancing the fives of the cranes.2. Analysis of the crane operationFor the analysis, a traveling gantry crane LT62B installed at log yard in the Yekaterinburg region was chosen. The crane serves two saw mills, creates a log store, and transfers logs to or out of road trains. A road passes along the log store. The saw mills are installed so that the reception sites are under the crane span. A schematic view of the crane is shown in Fig. 1.1350-6307/99/$一 see front matter 1999 Elsevier Science Ltd. All rights reserved.PII: S 1 3 5 0 一 6307(98) 00041一 7A series of assumptions may be made after examining the work of cranes:·if the monthly removal of logs from the forest exceeds the processing rate, i.e. there is a creation of a log store, the crane expects work, being above the centre of a formed pile with the grab lowered on the pile stack;·when processing exceeds the log removal from the forest, the crane expects work above an operational pile close to the saw mill with the grab lowered on the pile;·the store of logs varies; the height of the piles is considered to be a maximum;·the store variation takes place from the side opposite to the saw mill;·the total volume of a processed load is on the average k=1.4 times more than the total volume of removal because of additional transfers.2.1. Removal intensityIt is known that the removal intensity for one year is irregular and cannot be considered as a stationary process. The study of the character of non-stationary flow of road trains at 23 enterprises Sverdlesprom for five years has shown that the monthly removal intensity even for one enterprise essentially varies from year to year. This is explained by the complex of various systematic and random effects which exert an influence on removal: weather conditions, conditions of roads and lorry fleet, etc. All wood brought to the log store should, however, be processed within one year.Therefore, the less possibility of removing wood in the season between spring and autumn, the more intensively the wood removal should be performed in winter. While in winter the removal intensity exceeds the processing considerably, in summer, in most cases, the more full-length logs are processed than are taken out.From the analysis of 118 realizations of removal values observed for one year, it is possible to evaluate the relative removal intensity g(t) as percentages of the annual load turnover. The removal data fisted in Table 1 is considered as expected values for any crane, which can be applied to the estimation of fatigue life, and, particularly, for an inspected crane with which strain measurement was carried out (see later). It would be possible for each crane to take advantage of its load turnover per one month, but to establish these data without special statistical investigation is difficult. Besides, to solve the problem of life prediction a knowledge of future loads is required, which we take as expected values on cranes with similar operation conditions.The distribution of removal value Q(t) per month performed by the relative intensity q(t) is written aswhere Q is the annual load turnover of a log store, A is the maximal designed store of logs in percent of Q. Substituting the value Q, which for the inspected crane equals 400,000 m3 per year, and A=10%, the volumes of loads transferred by the crane are obtained, which are listed in Table 2, with the total volume being 560,000 m3 for one year using K,.2.2. Number of loading blocksThe set of operations such as clamping, hoisting, transferring, lowering, and getting rid of a load can be considered as one operation cycle (loading block) of the crane. As a result to investigations, the operation time of a cycle can be modeled by