起重机设计外文翻译---龙门式起重机金属材料的疲劳强度预测

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1、1.5万英文字符，3100单词，5400汉字附录 A 英文原文：  Fatigue life prediction of the metalwork of a travelling gantry crane V.A. Kopnov P.O. Box 64, Eknteriuburg 620107, Russian Received 3 April 1998； accepted 29 September 1998 Abstract Intrinsic fatigue curves are applied to a fatigue life prediction problem of t

2、he 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

3、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

4、 assessment； Strain gauging 1. Introduction 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 us

5、ed 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 cra

6、nes' fives, predict their fatigue behavior, and give recommendations to the manufacturers for enhancing the fives of the cranes. 2. Analysis of the crane operation For the analysis, a traveling gantry crane LT62B installed at log yard in the Yekaterinburg region was chosen. The crane serves two

7、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 Sci

8、ence Ltd. All rights reserved. PII: S 1 3 5 0 一 6307(98) 00041 一 7 A 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 cent

9、re 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 maxi

10、mum； 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 intensity It is known that the removal intensity for one yea

11、r is irregular and cannot be considered as astationary process. The study of the character of non-stationary flow of road trains at 23 enterprisesSverdlespromfor five years has shown that the monthly removal intensity even for one enterpriseessentially varies from year to year. This is explained by

12、the complex of various systematic andrandom effects which exert an influence on removal: weather conditions, conditions of roads andlorry 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 betwee

13、n spring and autumn, themore intensively the wood removal should be performed in winter. While in winter the removalintensity exceeds the processing considerably, in summer, in most cases, the more full-length logsare processed than are taken out. From the analysis of 118 realizations of removal val

14、ues observed for one year, it is possible toevaluate 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 theestimation of fatigue life, and, particularly, for an ins

15、pected crane with which strain measurementwas carried out (see later). It would be possible for each crane to take advantage of its loadturnover per one month, but to establish these data without special statistical investigation isdifficult. 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) iswritten as