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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：十噸位橋式起重機大車運行機構(gòu)設(shè)計
信機 系 機械工程及自動化 專業(yè)
學(xué) 號： 0923087
學(xué)生姓名： 葉宏城
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：十噸位橋式起重機大車運行機構(gòu)設(shè)計
信機 系 機械工程及自動 專業(yè)
學(xué) 號： 0923087
學(xué)生姓名： 葉宏城
指導(dǎo)教師： 陳炎冬 （職稱：講師 ）
（職稱： ）
2012年11月25日
課題來源
生產(chǎn)實踐需求
科學(xué)依據(jù)（包括課題的科學(xué)意義；國內(nèi)外研究概況、水平和發(fā)展趨勢；應(yīng)用前景等）
1 課題的科學(xué)意義
橋式起重機廣泛地應(yīng)用在室內(nèi)外倉庫、廠房、碼頭和露天貯料場等處。二十世紀(jì)以來，由于鋼鐵、機械制造業(yè)和鐵路、港口及交通運輸業(yè)的的發(fā)展，促進了起重運輸機械的發(fā)展。對起重運輸機械的性能也提出了更高的要求?，F(xiàn)代起重運輸機械擔(dān)當(dāng)著繁重的物料搬運任務(wù)，是工廠、鐵路、港口及其他部門實現(xiàn)物料搬運機械化的關(guān)鍵。
2 國內(nèi)外研究概況、水平和發(fā)展趨勢
起重機作為一種古老的機械，時至今日，在其承載結(jié)構(gòu)、驅(qū)動機構(gòu)、取物裝置、控制系統(tǒng)及安全裝置等各方面都有了很大的發(fā)展，其設(shè)計理論、制造工藝、檢測手段等都逐漸趨于完善和規(guī)范化，并已經(jīng)成為一種較完善的機械。但由于生產(chǎn)發(fā)展提出新的使用要求，起重機的種類、形式也需要相應(yīng)地發(fā)展和創(chuàng)新，性能也需要不斷變化與究善。由于現(xiàn)代化設(shè)計方法的建立和計算機輔助設(shè)計等現(xiàn)代設(shè)計手段的應(yīng)用，使起重機設(shè)計思維觀念和方法有了進一步的更新，其它技術(shù)領(lǐng)域和相鄰工業(yè)部門不斷取得的新科技成果在起重機上的滲透、推廣應(yīng)用等，更使起重機的各方面不斷地豐富更新。因此，起重機面向現(xiàn)代化、智慧化、更安全可靠方便的方向發(fā)展。
3 應(yīng)用現(xiàn)狀及其前景
加入世貿(mào)組織后，雖然國內(nèi)市場(特別是配套件)將受到較大沖擊，但同時也給我們帶來新技術(shù)的應(yīng)用，使國內(nèi)主機和配套件企業(yè)更清晰認(rèn)識到差距，更多地了解國產(chǎn)產(chǎn)品存在的致命問題，必將引導(dǎo)主機和配套件企業(yè)的技術(shù)創(chuàng)新和技術(shù)進步。隨著工程機械產(chǎn)品近十年來隨著技術(shù)的引進、消化、吸收，有了長足的進步，產(chǎn)品性能、可靠性、外觀都有較大幅度的提高，但同國外工程機械比較來看，還存在較大差距，就工程起重機而言，今后的發(fā)展主要表現(xiàn)在如下幾個方面：
（1）整機性能，由于先進技術(shù)和新材料的應(yīng)用,同種型號的產(chǎn)品，整機重量要輕20%左右。隨著結(jié)構(gòu)分析應(yīng)用和先進設(shè)備的使用,結(jié)構(gòu)形式更加合理
（2）高性能、高可靠性的配套件,選擇余地大、適應(yīng)性好,性能得到充分發(fā)揮
（3）電液比例控制系統(tǒng)和智能控制顯示系統(tǒng)的推廣應(yīng)用
（4）操作更方便、舒適、安全、保護裝置更加完善
（5）向吊重量大、起升高度、幅度更大的大噸位方向發(fā)展。
研究內(nèi)容
十噸位橋式起重機大車運行機構(gòu)設(shè)計
確定機構(gòu)傳動方案
選擇電動機，并驗算電動機的發(fā)熱功率條件
選擇減速器，制動器，聯(lián)軸器
端梁的設(shè)計
運用CAD繪制裝配圖零件圖
撰寫畢業(yè)設(shè)計論文
擬采取的研究方法、技術(shù)路線、實驗方案及可行性分析
去實習(xí)工廠實地研究學(xué)習(xí)，查閱橋式起重機的相關(guān)資料，分析總結(jié)。
按照機械設(shè)計的相關(guān)要求按步驟進行設(shè)計和驗算。
明確設(shè)計要求，調(diào)查研究，收集設(shè)計資料，繪出零件圖，裝配圖。
按照步驟，實驗方案可行。
研究計劃及預(yù)期成果
研究計劃：
2012年11月12日-2012年12月2日：教師下達畢業(yè)設(shè)計任務(wù)，學(xué)生初步閱讀資料，完成畢業(yè)設(shè)計開題報告。
2013年1月21日-2013年3月1日：指導(dǎo)畢業(yè)實習(xí)。
2013年3月4日-2013年3月15日：確定總設(shè)計方案。
2013年3月18日-2013年3月22日：總體設(shè)計（包括參數(shù)計算及結(jié)構(gòu)分析計算）。
2013年3月25日-2013年4月5日：總體設(shè)計（完成參數(shù)計算及結(jié)構(gòu)分析計算后繪制草圖；裝配圖）。
2013年4月8日-2013年4月26日：零件設(shè)計。
2013年4月29日-2013年5月25日：畢業(yè)論文說明書撰寫和修改工作。
預(yù)期成果：
認(rèn)識了解橋式起重機的相關(guān)知識了解和工作方式。
設(shè)計出10噸位橋式起重機的大車部分。
完成畢業(yè)設(shè)計論文和CAD制圖。
特色或創(chuàng)新之處
對橋式起重機進行全面的了解，分析設(shè)計橋式起重機的大車機構(gòu)
已具備的條件和尚需解決的問題
我已學(xué)習(xí)機械數(shù)控專業(yè)三年之久，掌握了一些這專業(yè)的部分知識，老師也給了一些參照資料，可以進行這方面的研究。
尚需解決的問題：（1）車輪的計算及車輪的設(shè)計對各部件之間連接方法和傳動方式的選擇。
（2）進給部件的強度剛度校核
需要對進給部件的強度和剛度有保證，滿足工作時的受力要求，需要進行校核計算。
指導(dǎo)教師意見
指導(dǎo)教師簽名：
年 月 日
教研室（學(xué)科組、研究所）意見
教研室主任簽名：
年 月 日
系意見
主管領(lǐng)導(dǎo)簽名：
年 月 日
外文資料翻譯及原文
英文原文：
Fatigue life prediction of the metalwork of a travelling gantry
crane
Abstract
Intrinsic 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 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 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.
5. Stress concentration factors and element endurance
The elements of the crane are jointed by semi-automatic gas welding without preliminary edge preparation and consequent machining. For the inspected elements 1 and 3 having circumferential and edge welds of angles with gusset plates, the effective stress concentration factor for fatigue is given by calculation methods [3], kf=2.}r2.9, coinciding with estimates given in the current Russian norm for fatigue of welded elements [4], kf=2.9.
The elements of the crane metalwork are made of alloyed steel 09G2S having an endurance limit of 120 MPa and a yield strength of 350 MPa. Then the average values of the endurance limits of the inspected elements 1 and 3 are ES一l=41 MPa. The variation coefficient is taken as 0.1, and the corresponding standard deviation is 6S-、一4.1 MPa.
The inspected element 2 is an I-beam pierced by holes for attaching rails to the top flange. The rather large local stresses caused by local bending also promote fatigue damage accumulation. According to tables from [4], the effective stress concentration factor is accepted as kf=1.8, which gives an average value of the endurance limit as ES一l=h7 Map. Using the same variation coiffing dent th e stand arid d emit ion is =6.7 MPa.
An average S-N curve, recommended in [4], has the form:
with the inflexion point No=5·106 and the slope m=4.5 for elements 1 and 3 and m=5.5 for element 2.
The possible values of the element endurance limits presented above overlap the ranges of load amplitude with nonzero probability, which means that these elements are subjected to fatigue damage accumulation. Then it is possible to conclude that fatigue calculations for the elements are necessary as well as fatigue fife prediction.
6. Life prediction
The study has that some elements of the metalwork are subject to fatigue damage accumulation.To predict fives we shall take advantage of intrinsic fatigue curves, which are detailed in