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編號
無錫太湖學(xué)院
畢業(yè)設(shè)計（論文）
相關(guān)資料
題目： 十噸位橋式起重機(jī)總體設(shè)計
信機(jī) 系 機(jī)械工程及自動化專業(yè)
學(xué) 號： 0923283
學(xué)生姓名： 夏宇峰
指導(dǎo)教師： 陳炎冬（職稱：講師）
（職稱： ）
2013年5月25日
目 錄
一、畢業(yè)設(shè)計（論文）開題報告
二、畢業(yè)設(shè)計（論文）外文資料翻譯及原文
三、學(xué)生“畢業(yè)論文（論文）計劃、進(jìn)度、檢查及落實表”
四、實習(xí)鑒定表
無錫太湖學(xué)院
畢業(yè)設(shè)計（論文）
開題報告
題目： 十噸位橋式起重機(jī)總體設(shè)計
信機(jī) 系 機(jī)械工程及自動化 專業(yè)
學(xué) 號： 0923283
學(xué)生姓名： 夏宇峰
指導(dǎo)教師： 陳炎冬 （職稱：講師）
（職稱： ）
2013年5月25日
課題來源
生產(chǎn)實踐所得 。目前國外起重機(jī)械總的發(fā)展趨勢是：發(fā)展快，水平高。如國外起重機(jī)在集成電路、微處理器、微型計算器及電子監(jiān)控技術(shù)等方面都有廣泛的運(yùn)用，一些節(jié)能新技術(shù)得到了推廣，可靠性、安全性、舒適性、環(huán)保性能得到了高度重視，并向大型和微型化方向發(fā)展。經(jīng)過多年的發(fā)展，我目前國外起重機(jī)械總的發(fā)展趨勢是：發(fā)展快，水平高。到目前，我國起重機(jī)械行業(yè)的產(chǎn)品種類已經(jīng)超過1000個，并不斷有新的起重機(jī)械設(shè)備問世。借鑒國外起重機(jī)發(fā)展趨勢，我國起重機(jī)發(fā)展走勢應(yīng)是：大力發(fā)展機(jī)電一體化產(chǎn)品，實現(xiàn)裝載機(jī)工作狀態(tài)的自動監(jiān)測和控制，實現(xiàn)平地機(jī)的激光導(dǎo)平自動控制，實現(xiàn)在有毒、有危險環(huán)境下起重機(jī)作業(yè)的遙控，大力提高產(chǎn)品的質(zhì)量、可靠性和技術(shù)水平，大力發(fā)展起重機(jī)品種，加強(qiáng)新技術(shù)的應(yīng)用，改善駕駛員的工作條件。
科學(xué)依據(jù)
（1）課題科學(xué)意義
起重機(jī)械用來對物料作起重、運(yùn)輸、裝卸和安裝等作業(yè)的機(jī)械設(shè)備，它可以完成靠人力無法完成的物料搬運(yùn)工作，減輕人們的體力勞動，提高勞動生產(chǎn)率，在工廠、礦山、車站、港口、建筑工地、倉庫、水電站等多個領(lǐng)域部門中得到了廣泛的使用，隨著生產(chǎn)規(guī)模的日益擴(kuò)大，特別是現(xiàn)代化、專業(yè)化的要求，各種專門用途的起重機(jī)相繼產(chǎn)生，在許多重要的部門中，它不僅是生產(chǎn)過程中的輔助機(jī)械，而且已成為生產(chǎn)流水作業(yè)線上不可缺少的重要機(jī)械設(shè)備，它的發(fā)展對國民經(jīng)濟(jì)建設(shè)起著積極的促進(jìn)作用。起重機(jī)械是起升，搬運(yùn)物料及產(chǎn)品的機(jī)械工具。起重機(jī)械對于提高工程機(jī)械各生產(chǎn)部門的機(jī)械化，縮短生產(chǎn)周期和降低生產(chǎn)成本，起著非常重要的作用
在高層建筑、冶金、華工及電站等的建設(shè)施工中，需要吊裝和搬運(yùn)的工程量日益增多，其中不少組合件的吊裝和搬運(yùn)重量達(dá)幾百噸。因此必須選用一些大型起重機(jī)進(jìn)行吊裝工作。通常采用的大型起重機(jī)有龍門起重機(jī)、門座式起重機(jī)、塔式起重機(jī)、履帶起重機(jī)、輪式起重機(jī)以及在廠房內(nèi)裝置的橋式起重機(jī)等。
在道路，橋梁和水利電力等建設(shè)施工中，起重機(jī)的使用范圍更是極為廣泛。無論是裝卸設(shè)備器材，吊裝廠房構(gòu)件，安裝電站設(shè)備，吊運(yùn)澆注混凝土、模板，開挖廢渣及其他建筑材料等，均須使用起重機(jī)械。尤其是水電工程施工，不但工程規(guī)模浩大，而且地理條件特殊，施工季節(jié)性強(qiáng)、工程本身又很復(fù)雜，需要吊裝搬運(yùn)的設(shè)備、建筑材料量大品種多，所需要的起重機(jī)數(shù)量和種類就更多。在電站廠房及水工建筑物上也安裝各種類型的起重機(jī)，供檢修機(jī)組、起閉雜們及起吊攔污柵之用。
(2) 國內(nèi)外研究概況、水平和發(fā)展趨勢
經(jīng)過多年的發(fā)展，我目前國外起重機(jī)械總的發(fā)展趨勢是：發(fā)展快，水平高。到目前，我國起重機(jī)械行業(yè)的產(chǎn)品種類已經(jīng)超過1000個，并不斷有新的起重機(jī)械設(shè)備問世。借鑒國外起重機(jī)發(fā)展趨勢，我國起重機(jī)發(fā)展走勢應(yīng)是：大力發(fā)展機(jī)電一體化產(chǎn)品，實現(xiàn)裝載機(jī)工作狀態(tài)的自動監(jiān)測和控制，實現(xiàn)平地機(jī)的激光導(dǎo)平自動控制，實現(xiàn)在有毒、有危險環(huán)境下起重機(jī)作業(yè)的遙控，大力提高產(chǎn)品的質(zhì)量、可靠性和技術(shù)水平，大力發(fā)展起重機(jī)
展起重機(jī)展起重機(jī)品種，加強(qiáng)新技術(shù)的應(yīng)用，改善駕駛員的工作條件。
國外發(fā)展現(xiàn)狀
目前國外起重機(jī)械總的發(fā)展趨勢是：發(fā)展快，水平高。如國外起重機(jī)在集成電路、微處理器、微型計算器及電子監(jiān)控技術(shù)等方面都有廣泛的運(yùn)用，一些節(jié)能新技術(shù)得到了推廣，可靠性、安全性、舒適性、環(huán)保性能得到了高度重視，并向大型和微型化方向發(fā)展。
國內(nèi)發(fā)展現(xiàn)狀和目標(biāo)
應(yīng)開發(fā)一機(jī)多用型的多功能產(chǎn)品，應(yīng)開發(fā)技術(shù)先進(jìn)、可靠性高、壽命長、施工質(zhì)量好而且新技術(shù)含量高的產(chǎn)品。
相關(guān)業(yè)內(nèi)人士指出，未來全球起重機(jī)行業(yè)將向重點(diǎn)產(chǎn)品大型化、高速化和專業(yè)化方向，系列產(chǎn)品模塊化、組合化、標(biāo)準(zhǔn)化和實用化方向及通用產(chǎn)品小型化、輕型化、簡易化和多樣化方向發(fā)展。為此我國起重機(jī)行業(yè)應(yīng)加大研發(fā)投入，注重人才的培養(yǎng)和引進(jìn)，切實增強(qiáng)行業(yè)的核心競爭力，積極參與國際市場競爭，以此來促進(jìn)行業(yè)的進(jìn)一步發(fā)展。
研究內(nèi)容
箱形雙梁橋式起重機(jī)是由一個有兩根箱形主梁和兩根橫向端梁構(gòu)成的雙梁橋架,在橋架上運(yùn)行起重小車,可起吊和水平搬運(yùn)各類物體,它適用于機(jī)械加工和裝配車間料場等場合。本次起重機(jī)設(shè)計的主要參數(shù)如下：起重量10t,跨度22.5m，起升高度為16m起升速度13m/min小車運(yùn)行速度v=43.8m/min大車運(yùn)行速度V=116.8m/min大車運(yùn)行傳動方式為分別傳動;橋架主梁型式,箱形梁.小車估計重量4t，工作級別M6
研究的成果包括
（1）圖紙（CAD完成，包括仿真和機(jī)械系統(tǒng)）A0：4張；
（2）論文打印稿：1.5萬字及中英文摘要、開題報告；
（3）英翻中2000字。
擬采取的研究方法、技術(shù)路線、實驗方案及可行性分析
（1）實驗方案
對橋式起重機(jī)總體結(jié)構(gòu)的布置及橋架結(jié)構(gòu)和電氣部分的設(shè)計
（2）研究方法
對橋式起重機(jī)首先選擇好其基本參數(shù)，大小車及起升機(jī)構(gòu)的布置方案，再對橋架主梁、端梁的尺寸如高度，厚度，加勁板間距等的計算，還有各種載荷，如均布載荷和固定載荷的計算，主梁上最大彎矩和剪力及其組合載荷也要進(jìn)行考慮。電氣部分還需多加了解主要對橋式起重機(jī)變頻調(diào)速的特點(diǎn)包括起升機(jī)構(gòu)大小車機(jī)構(gòu)在變頻調(diào)速上的要點(diǎn)及PLC系統(tǒng)的設(shè)計。
研究計劃及預(yù)期成果
研究計劃：
第1步 熟悉課題的背景，收集資料，閱讀參考書；
第2步 閱讀參考書，翻譯外文資料，完成開題報告；
第3步 方案選擇及總體方案確定；
第4步 機(jī)械傳動系統(tǒng)設(shè)計計算；
第5步 設(shè)計計算及繪制機(jī)械系統(tǒng)裝配圖；
第6步 繪制零件圖；
第7步 整理撰寫論文；
第8步 準(zhǔn)備答辯材料；
第9步 答辯；
預(yù)期成果：
達(dá)到預(yù)期的實驗結(jié)論：據(jù)給定的參數(shù)設(shè)計計算器總體結(jié)構(gòu)的基本尺寸，然后對重要部分的尺寸進(jìn)行大量的計算驗證，如載荷大小，梁的強(qiáng)度、剛度等看是否真正滿足要求以保證能投入實際生產(chǎn)運(yùn)用中。
特色或創(chuàng)新之處
本章主要對箱形橋式起重機(jī)進(jìn)行介紹，確定了其總體方案并進(jìn)行了一些簡單的分析。箱形雙梁橋式起重機(jī)具有加工零件少，工藝性好、通用性好及機(jī)構(gòu)安裝檢修方便等一系列的優(yōu)點(diǎn)，因而在生產(chǎn)中得到廣泛采用。我國在5噸到10噸的中、小起重量系列產(chǎn)品中主要采用這種形式，但這種結(jié)構(gòu)形式也存在一些缺點(diǎn)：自重大、易下?lián)希谠O(shè)計和制造時必須采取一些措施來防止或者減少。
已具備的條件和尚需解決的問題
研究的難點(diǎn)：
（1） 主梁上所受的彎矩和剪力的分布及其組合載荷的考慮
（2） 大小車變頻調(diào)速的特點(diǎn)和整體PLC系統(tǒng)的設(shè)計
指導(dǎo)教師意見
指導(dǎo)教師簽名：
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教研室（學(xué)科組、研究所）意見
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英文原文
Fatigue life prediction of the metalwork of a travelling gantry crane
V.A. Kopnov
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 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 operation
For 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 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 intensity
It 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 as
where 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 blocks
The 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 the normal variable with mean equal to 11.5 min and standard deviation to 1.5 min. unfortunately, this characteristic cannot be simply used for the definition of the number of operation cycles for any work period as the local processing is extremely irregular. Using a total operation time of the crane and evaluations of cycle durations, it is easy to make large errors and increase the number of cycles compared with the real one. Therefore, it is preferred to act as follows.
The volume of a unit load can be modeled by a random variable with a distribution function(t) having mean22 m3 and standard deviation 6;一3 m3, with the nominal volume of one pack being 25 m3. Then, knowing the total volume of a processed load for a month or year, it is possible to determine distribution parameters of the number of operation cycles for these periods to take advantage of the methods of renewal theory [1].
According to these methods, a random renewal process as shown in Fig. 2 is considered, where the random volume of loads forms a flow of renewals:
In renewal theory, realizations of random:，，，having a distribution function F (t), are understood
as moments of recovery of failed units or request receipts. The value of a processed load:，，after
}th operation is adopted here as the renewal moment.
Let F(t)=P﹛＜t﹜. The function F (t) is defined recurrently,
Let v(t) be the number of operation cycles for a transferred volume t. In practice, the total volume of a transferred load t is essentially greater than a unit load, and it is useful therefore totake advantage of asymptotic properties of the renewal process. As follows from an appropriate
limit renewal theorem, the random number of cycles v required to transfer the large volume t has
the normal distribution asymptotically with mean and variance.
without dependence on the form of the distribution function月t) of a unit load (the restriction is
imposed only on nonlattice of the distribution).
Equation (4) using Table 2 for each averaged operation month,function of number of load cycles with parameters m,. and 6,., which normal distribution in Table 3. Figure 3 shows the average numbers of cycles with 95 % confidence intervals. The values of these parameters
for a year are accordingly 12,719 and 420 cycles.
3. Strain measurements
In order to reveal the most loaded elements of the metalwork and to determine a range of stresses, static strain measurements were carried out beforehand. Vertical loading was applied by hoisting measured loads, and skew loading was formed with a tractor winch equipped with a dynamometer. The allocation schemes of the bonded strain gauges are shown in Figs 4 and 5. As was expected, the largest tension stresses in the bridge take place in the bottom chord of the truss (gauge 11-45 MPa). The top chord of the truss is subjected to the largest compression stresses.The local bending stresses caused by the pressure of wheels of the crane trolleys are added to the stresses of the bridge and the load weights. These stresses result in the bottom chord of the I一beam
being less compressed than the top one (gauge 17-75 and 10-20 MPa). The other elements of the bridge are less loaded with stresses not exceeding the absolute value 45 MPa. The elements connecting the support with the bridge of the crane are loaded also irregularly. The largest compression stresses take place in the carrying angles of the interior panel; the maximum stresses reach h0 MPa (gauges 8 and 9). The largest tension stresses in the diaphragms and angles of the exterior panel reach 45 MPa (causes 1 and hl.
The elements of the crane bridge are subjected, in genera maximum stresses and respond weakly to skew loads. The suhand, are subjected mainly to skew loads.1, to vertical loads pports of the crane gmmg rise to on the other
The loading of the metalwork of such a crane, transferring full-length logs, differs from that of
a crane used for general purposes. At first, it involves the load compliance of log packs because of
progressive detachment from the base. Therefore, the loading increases rather slowly and smoothly.The second characteristic property is the low probability of hoisting with picking up. This is conditioned by the presence of the grab, which means that the fall of the rope from the spreader block is not permitted; the load should always be balanced. The possibility of slack being sufficient to accelerate an electric drive to nominal revolutions is therefore minimal. Thus, the forest traveling gantry cranes are subjected to smaller dynamic stresses than in analogous cranes for general purposes with the same hoisting speed. Usually, when acceleration is smooth, the detachment of a load from the base occurs in 3.5-4.5 s after switching on an electric drive. Significant oscillations of the metalwork are not observed in this case, and stresses smoothly reach maximum values.
When a high acceleration with the greatest possible clearance in the joint between spreader andgrab takes place, the tension of the ropes happens 1 s after switching the electric drive on, the
clearance in the joint taking up. The revolutions of the electric motors reach the nominal value in
O.}r0.7 s. The detachment of a load from the base, from the moment of switching electric motors
on to the moment of full pull in the ropes takes 3-3.5 s, the tensions in ropes increasing smoothly
to maximum. The stresses in the metalwork of the bridge and supports grow up to maximum
values in 1-2 s and oscillate about an average within 3.5%.
When a rigid load is lifted, the accelerated velocity of loading in the rope hanger and metalwork
is practically the same as in case of fast hoisting of a log pack. The metalwork oscillations are characterized by two harmonic processes with periods 0.6 and 2 s, which have been obtained from spectral analysis. The worst case of loading ensues from summation of loading amplitudes so that the maximum excess of dynamic loading above static can be 13-14%.Braking a load, when it is lowered, induces significant oscillation of stress in the metalwork, which can be }r7% of static loading. Moving over rail joints of 3} mm height misalignment induces only insignificant stresses. In operation, there are possible cases when loads originating from various types of loading combine. The greatest load is the case when the maximum loads from braking of a load when lowering coincide with braking of the trolley with poorly adjusted brakes.
4. Fatigue loading analysis
Strain measurement at test points, disposed as shown in Figs 4 and 5, was carried out during the work of the crane and a representative number of stress oscillograms was obtained. Since a common operation cycle duration of the crane has a sufficient scatter with average value } 11.5min, to reduce these oscillograms uniformly a filtration was implemented to these signals, and all repeated values, i.e. while the construction was not subjected to dynamic loading and only static loading occurred, were rejected. Three characteristic stress oscillograms (gauge 11) are shown in
Fig. 6 where the interior sequence of loading for an operation cycle is visible. At first, stresses
increase to maximum values when a load is hoisted. After that a load is transferred to the necessary location and stresses oscillate due to the irregular crane movement on rails and over rail joints resulting mostly in skew loads. The lowering of the load causes the decrease of loading and forms half of a basic loading cycle.
4.1. Analysis of loading process amplitudes
Two terms now should be separated: loading cycle and loading block. The first denotes one distinct oscillation of stresses (closed loop), and the second is for the set of loading cycles during an operation cycle. The rain flow cycle counting method given in Ref. [2] was taken advantage of to carry out the fatigue hysteretic loop analysis for the three weakest elements: (1) angle of the bottom chord(gauge 11), (2) I-beam of the top chord (gauge 17), (3) angle of the support (gauge 8). Statistical evaluation of sample cycle amplitudes by means of the Waybill distribution for these elements has given estimated parameters fisted in Table 4. It should be noted that the histograms of cycle amplitude with nonzero averages were reduced afterwards to equivalent histograms with zero averages.
4.2. Numbers of loading cycles
During the rain flow cycle counting procedure, the calculation of number of loading cycles for the loading block was also carried out. While processing the oscillograms of one type, a sample number of loading cycles for one block is obtained consisting of integers with minimum and maximum observed values: 24 and 46. The random number of loading cycles vibe can be described
by the Poisson distribution with parameter =34.
Average numbers of loading blocks via months were obtained earlier, so it is possible to find the appropriate characteristics not only for loading blocks per month, but also for the total number of loading cycles per month or year if the central limit theorem is taken advantage of. Firstly, it is known from probability theory that the addition of k independent Poisson variables gives also a random variable with the Poisson distribution with parameter k},. On the other hand, the Poisson distribution can be well approximated by the normal distribution with average}, and variation },. Secondly, the central limit theorem, roughly speaking, states that the distribution of a large number of terms, independent of the initial distribution asymptotically tends to normal. If the initial distribution of each independent term has a normal distribution, then the average and standard deviation of the total number of loading cycles for one year are equal to 423,096 and 650 accordingly. The values of k are taken as constant averages from Table 3.
7. Conclusions
The analysis of the crane loading has shown that some elements of the metalwork are subjectedto large dynamic loads, which causes fatigue damage accumulation followed by fatigue failures.The procedure of fatigue hfe prediction proposed in this paper involves tour parts:
(1) Analysis of the operation in practice and determination of the loading blocks for some period.
(2) Rainflow cycle counting techniques for the calculation of loading cycles for a period of standard operation.
(3) Selection of appropriate fatigue data for material.
(4) Fatigue fife calculations using the intrinsic fatigue curves approach.
The results of this investigation have been confirmed by the cases observed in practice, and the manufacturers have taken a decision about strengthening the fixed elements to extend their fatigue lives.
References
[1] Feller W. An introduction to probabilistic theory and its applications, vol. 2. 3rd ed. Wiley, 1970.
[2] Rychlik I. International Journal of Fatigue 1987;9:119.
[3] Piskunov V(i. Finite elements analysis of cranes metalwork. Moscow: Mashinostroyenie, 1991 (in Russian).
[4] MU RD 50-694-90. Reliability engineering. Probabilistic methods of calculations for fatigue of welded metalworks.
Moscow: (iosstandard, 1990 (in Russian).
[5] Kopnov VA. Fatigue and Fracture of Engineering Materials and Structures 1993;16:1041.
[6] Kopnov VA. Theoretical and Applied Fracture Mechanics 1997;26:169.
中文譯文
起重機(jī)金屬材料的疲勞強(qiáng)度預(yù)測
v.a.科普諾夫
1.緒論
??頻繁觀測龍門式起重機(jī)LT62B在運(yùn)作時金屬元件疲勞失效。引起疲勞裂紋的故障沿著起重機(jī)的橋梁焊接接頭進(jìn)行傳播，并且能夠支撐三到四年。這種起重機(jī)在森林工業(yè)的伐木林場被廣泛使用，用來轉(zhuǎn)移完整長度的原木和鋸木到鐵路的火車上，有一次裝載30噸貨物的能力。 這種類型的起重機(jī)大約1000臺以上工作在俄羅斯森林工業(yè)的企業(yè)中。限制起重機(jī)壽命的問題即最弱的要素被正式找到之后，預(yù)測其疲勞強(qiáng)度，并給制造商建議，以提高起重機(jī)的壽命。
2.起重機(jī)運(yùn)行分析
??為了分析，在葉卡特琳堡地區(qū)的林場碼頭選中了一臺被安裝在葉卡特琳堡地區(qū)的林場碼頭的龍門式起重機(jī)LT62B， 這臺起重機(jī)能夠供應(yīng)兩個伐木廠建立存儲倉庫，并且能轉(zhuǎn)