畢業(yè)論文復雜零件加工工藝設計及數控程序編制

1、 畢業(yè)設計說明書  題 目 復雜零件加工工藝設計及 數控程序編制 專 業(yè) 數 控 技 術 班 級 數 控 班 學生姓名 指導教師 年 月 日目 錄摘要關鍵詞1 設計要求11.1 設計計算說明書部分11.1.1 加工路線方案的擬訂與選擇11.1.2 加工工序的安排與說明11.1.3 毛坯、工藝參數、刀夾具與機床的選擇與說明11.1.4 加工表面的程序清單11.1.5 其他12.2 設計繪圖部分12.2.1 數控加工工序卡片12.2.2 數控加工走刀路線圖12 零件的分析與毛坯的選擇12.1 生產類型的確定12.2 零件的分析12.3 毛坯的選擇23 加工路線方案的擬訂與選擇2

2、3.1 平面加工方法的選擇23.2 凸臺加工方案23.3 孔加工方案23.3.1 擴孔23.3.2 鉸孔23.3 定位基準的選擇33.4 加工階段的劃分33.5 工序的劃分34 工藝參數、刀夾具與機床的選擇34.1 機床的選擇34.2 夾具的選擇44.2.1 三爪卡盤44.2.2 四爪卡盤44.2.3 虎鉗44.3 刀具的選擇44.4 走刀路線的選則54.5 切削用量的確定54.6 加工余量的卻定54.7 主軸轉速54.8 進給量65 加工表面的程序清單66 其它的工序設計66.1 輔助工序的安排66.2 熱處理工序的安排66.3 測量方法67 填寫工藝文77.1 外輪廓加工工序卡片77.2

3、內型腔加工工序87.3 內型腔走刀路線卡片97.4外輪廓走刀路徑108 程序編制109 結論10參考文獻11復雜零件加工工藝設計及數控程序編制摘 要:本課題主要是對復雜零件進行加工工藝分析，采用具體事例分析的方法，說明復雜零件加工工藝的分析步驟，同時對復雜零件進行程序編制的說明，確定本設計通過查閱相關的書籍及對市場及人們生活的調查，分析了復雜零件的數控加工工藝及編程在我國的重要性及所存在的問題，從而做出相應的措施。根據設計要求制定多種方案，完成對復雜零件加工工藝設計及數控程序編制確定裝夾方案，定位及相關的工序內容。復雜零件的工藝設計及程序的編制已是時代的必須，它的發(fā)展將推動我國工業(yè)的發(fā)展。關鍵

4、詞: 復雜零件加工 工藝設計 程序編制 1 設計要求1.1 設計計算說明書部分 加工路線方案的擬訂與選擇 加工工序的安排與說明 毛坯、工藝參數、刀夾具與機床的選擇與說明 加工表面的程序清單 其他2.2 設計繪圖部分 數控加工工序卡片 數控加工走刀路線圖圖名圖幅張數折合零號圖數數控加工工序卡片A32數控加工走刀路線圖A32合計42 零件的分析與毛坯的選擇2.1 生產類型的確定確定生產類型的依據-生產綱領生產綱領 N=Q×n×(1+%+%)式中 N-零件的生產綱領Q-產品的年產量n-每臺產品中，該零件的數量（件/臺）%-備品率%-廢品率根據該公式確定此零件的生產綱領為100-5

5、00件，確定其生產類型為小批量生產，相對來說選取的毛坯精度稍低、加工的余量大。工藝過程卡片比較簡單。需要熟練的技術工人。2.2 零件的分析此零件結構比較簡單，形狀為長方形，主要由平面、外輪廓、內型腔及平行孔系組成。此零件為配合件加工，其中六面已經加工完成，所以只需要進行凸臺形狀的加工，以及相關的孔系的加工。其中內型腔、凸臺的外輪廓以及孔系部分粗糙度為1.6m，既加工精度相對來說要達到很高的要求，一般為7-8級，一般需要進行進一步的加工，以達到加工要求，其中凸臺的外邊的上平面要求與零件的下平面的平行度達到0.02m，孔系的外輪廓面與該零件的右側面的對稱度達到0.04m，其于達到3.2m的粗糙度。

6、并且根據公差要求來進行調配。2.3 毛坯的選擇工藝設計時，毛坯的選擇是指確定毛坯的種類、制造方法以及余量確定后的毛坯尺寸。零件材料為45號鋼，根據技術要求，要求零件進行去毛刺的處理，即要求外形光潔且美觀，根據零件的結構形狀及外形尺寸以及生產綱領的大小可選擇鍛件，3 加工路線方案的擬訂與選擇3.1 平面加工方法的選擇根據零件的要求，制定如下兩種方案。方案不進行任何處理方案銑床 精加工磨根據零件的技術要求，其中六面已經加工完成，只有加工完凸臺之后剩下的表面，因為它的加工精度需要達到7-8精度，所以需要進行精加工以保證達到技術要求，所以選擇方案。3.2 凸臺加工方案方案粗車半精車方案粗車半精車精車根

7、據零件的精度要求，凸臺達到7-8級精度，要進行精加工。所以選擇方案，方案只能達到8級以上精度，所以它達不到零件的技術要求。3.3 孔加工方案采用銑床加工，加工方案如下：鉆中心孔擴粗鉸精鉸因為零件的圖紙中要求孔的粗糙度達到1.6所以精度要達到7級以上，所以粗鉸仍然達不到技術要求，還要進行精鉸，由于零件有一定的硬度，所以不能直接進行鉆孔，要先進行鉆中心孔，防止鉆頭磨損，以及保持中心度。3.3.1 擴孔擴孔用以擴大已加工出的孔（鑄出、鍛出或鉆出的孔），它可以校正孔的軸線偏差，并使其獲得正確的幾何形狀和較小的表面粗糙度，其加工精度一般為IT9IT10級，表面粗糙度、Ra=3.26.3m。擴孔的加工余量

8、一般為0.24mm。3.3.2 鉸孔鉸孔是用鉸刀從工件壁上切除微量金屬層，以提高孔的尺寸精度和表面質量的加工方法。鉸孔是應用較普遍的孔的精加工方法之一，其加工精度可達IT6IT7級，表面粗糙度Ra=0.40.8m。3.3 定位基準的選擇根據上述零件幾何結構分析及技術分析，平面A以及平面B為重要加工表面，根據粗基準的選擇原則，同時，零件的內型腔以及凸臺的精度要求較高，所以根據精基準的基準統(tǒng)一原則，選則平面B作為基準，進行加工凸臺以及內型腔，保證剩下的表面與平面B的平行度，保證達到20 mm和15 mm的尺寸要求。根據基準統(tǒng)一原則，以平面B為基準加工孔等，同時保證與平面A的對稱度要求，同時保證尺寸

9、的要求。3.4 加工階段的劃分按照零件的加工要求以及加工后所要達到的技術要求,該零件加工階段可劃分為粗加工,半精加工,精加工三個階段 .粗加工階段:由于凸臺部分要求達到1.6m的粗糙度,所以不能夠一次完成,需要經過多次加工,防止應力過于集中,而造成工件的斷列或者工件的使用壽命過短,所以加工過程中,需要進行熱處理.一保證加工要求.半精加工階段:此階段是一個過度階段,為下一步的精加工作好準備,同時,也可防止刀具由于切削量過大而造成的損壞.精加工階段:對于該零件,由于精度要求較高,所以是必須的一步,3.5 工序的劃分根據工件的結構與尺寸要求,按照安裝次數劃分,方案如下方案按照粗精加工劃分，劃分為三道

10、工序方案按照裝夾次數劃分，分為兩道工序。首先加工上表面的所有內容，然后加工下表面的所有內容。根據以上對零件的結構分析以及技術要求的分析，可知此零件六面以加工完成，只需進行凸臺，內型腔，及孔的加工。根據零件結構特點，此零件需要進行兩次加工，所以選擇方案，裝夾一次完成上表面加工。裝夾第二次，完成下表面的加工，所以根據工序集中的原則，按照裝夾次數劃分為兩道工序，減少了設備的數量，減少了操作工人及生產面積；減少了工序數目，簡化了生產計劃工作，縮短了生產周期。減少了工件的裝夾次數，有利于提高生產力，同時保證表面的加工精度。而方案，總的來說可以實施，但由于裝夾次數過多導致零件精度過低，從而達不到零件的技術

11、的要求，生產起來也復雜，所以從各方面來說，方案 不符合零件的要求。4 工藝參數、刀夾具與機床的選擇4.1 機床的選擇根據零件的形狀與結構選擇YHM1100(A) 數控銑床 ，它適用于鉆、銑、鏜等工序及復雜的二、三維凸凹型腔和表面的自動加工，配合多軸NC回轉工作臺可對工件實現多面體及特殊曲面和復雜型腔，孔位的殼體和模具加工。本機床的鑄件均采用樹脂砂鑄件，且經過兩次人工時效處理，穩(wěn)定性好，強度高，各項精度穩(wěn)定可靠。 三軸滾珠絲桿均采用專業(yè)配套廠商提供的高精度產品，并且均進行預拉伸。 軸承均采用日本進口NSK配對組合的滾珠絲桿專用軸承。超高頻淬火處理的硬軌，采用周邊磨削工藝精磨，與其配合的粘貼Tur

12、cite-B耐磨片并精細研刮，耐磨性好，精度保持長久。機床的潤滑系統(tǒng)均采用定時，定量自動集中供油潤滑系統(tǒng)，可確保每個潤滑部位都得到充分潤滑4.2 夾具的選擇 三爪卡盤根據零件的形狀及加工方法可知，零件不能用三爪卡盤來裝夾，因為三爪卡盤的特點是：三爪卡盤是靠其法蘭盤上的螺紋直接旋裝在車床主軸上。三爪卡盤安裝工件三爪卡盤是車床上應用最廣的通用夾具，適合于安裝短圓棒料或盤類（直徑較大的盤狀工件中，可用反三爪夾持）工件。當轉動小傘齒輪時，大錐齒輪便轉動，它背面的平面螺紋就使三個卡爪同時向中心靠近或退出，以夾緊不同直徑的工件。三爪卡盤裝夾方便能自動定心，但其定心準確度不高，約為0.050.15mm。工件

13、上同軸度要求較高的表面應在一次裝夾中車出。由于零件要求精度很高，所以定位也非常關鍵 ，必須選擇比較精確的夾具，根據以上對三爪卡盤的分析，證明三爪卡盤不可以 四爪卡盤而對于四爪卡盤安裝工件。四爪卡盤有四個互不相關的卡爪，各卡爪的背面有一半瓣內螺紋與一螺桿相嚙合。螺桿端部有一方孔，當用卡盤扳手轉動某一螺桿時，相應的卡爪即可移動。如將卡爪調轉180°安裝，即成反爪。四爪卡盤由于四個卡爪均可獨立移動，因此可安裝截面為方形、長方形、橢圓以及其它不規(guī)則形狀的工件。同時，四爪卡盤比三爪卡盤的夾緊力大，所以常用來安裝較大的圓形工件。由于四爪卡盤的四個卡爪是獨立移動的，在安裝工件時須進行仔細的找正工件

14、，一般用劃針盤按工件內外圓表面或預先劃出的加工線找正，其定位精度較低，為0.20.5mm。用百分表按工件精加工表面找正，其定位精度可達0.020.01mm。 虎鉗虎鉗是用來夾持工件，其規(guī)格以鉗口的寬度來表示，常用的有100、125、150mm三種，使用虎鉗時應注意： （1）工件盡量夾在鉗口中部，以使鉗口受力均勻； （2）夾緊后的工件應穩(wěn)定可靠，便于加工，并不產生變形； （3）夾緊工件時，一般只允許依靠手的力量來扳動手柄，不能用手錘敲擊手柄或隨意套上長管子來扳手柄，以免絲杠、螺母或鉗身損壞。 （4）不要在活動鉗身的光滑表面進行敲擊作業(yè)，以免降低配合性能； （5）加工時用力方向最好是朝向固定鉗身。

15、所以根據以上的介紹可以知道，該零件選擇精密虎鉗進行夾緊以及定位。4.3 刀具的選擇根據零件的形狀結構，選擇刀具如下：凸臺的輪廓粗加工用直徑為30 mm的銑刀 ，精加工選擇直徑為20 mm的銑刀，內型腔粗加工選擇直徑為10 mm的銑刀，精加工選擇直徑為5 mm的銑刀。平面的精加工選擇直徑為5 mm的平面銑刀，因為此零件內型腔的寬度只有20 mm，所以選擇直徑較小的刀具這樣可以保證零件平面的精度，同時也可以防止加工好的零件輪廓由于刀具過大而造成損壞。都采用環(huán)行加工的方法，一層一層的銑削，可以提高零件的精度，也為最后的精加工做好準備?？椎募庸?，首先選擇直徑為10 mm的鉆頭進行鉆中心孔，以保證同軸度

16、等要求，然后選擇直徑為19 mm的鉆頭做粗加工，然后選擇直徑為20 mm的鉆頭進行最后的鉸孔，以保證質量。4.4 走刀路線的選則為了防止零件輪廓的損壞，保證零件表面的光整，不出現刀痕，切削時采用按照零件的輪廓線切向切入切出，以保證零件的技術要求 ，達到圖紙要求。采用層銑削的方法。進一步保證零件的質量。4.5 切削用量的確定切削用量一般包括背吃刀量，進給速度，主軸轉速等，具體安排見下面的分析。4.6 加工余量的卻定根據 零件的結構為旋轉表面，加工余量從直徑上考慮，既雙邊余量。實際所切除的金屬厚度為直徑上的加工余量的一半，計算公式如下：對于外表面 Zi=Li-1-Li 對于內表面 Zi=Li-Li

17、-1對于軸 2Zi=di-1-di對于孔 2Zi=Di-1-Di式中 Zi- 本道工序的單邊余量；Li- 本道工序的工序的尺寸Li-1- 上道工序的工序 尺寸Di - 本道工序的孔直徑Di-1 - 上道工序的孔直徑di - 本道工序的外圓直徑di-1 - 上道工序 的外圓直徑；各道工序的余量之和為加工總余量。所以確定加工余量為：凸臺進行多次加工，粗加工余量為2 mm。根據零件的精度要求，精加工已經能夠達到要求，所以精加工時為最后的一步，不留加工余量內型腔分進行幾次加工， 粗加工余量為2 mm， 半精加工余量為0.5 mm對于平面半精加工余量為 1 mm。精加工時為最后的一步，不留加工余量。對于

18、孔，擴孔時加工余量為2 mm。鉸孔為最后一步，不留加工余量。4.7 主軸轉速主軸轉速的計算公式如下： V=Dn/1000式中 V 主軸轉速D 刀具的直徑N 切削速度切削速度在機械手冊上可以查到，主軸轉速如下：粗銑輪廓時，主軸轉速為800，精銑的時候為1200。內型腔粗加工時為800，精加工時為1000。鉆中心孔時為800，鉆19的孔時轉速為500，鉆20的孔時轉速為1200銑平面時精加工時主軸轉速為1000。4.8 進給量進給量的計算公式如下：f=nzfz式中： f 進給量n 切削速度fz 每齒進給量具體看工序表。5 加工表面的程序清單根據加工順序選擇原則，表面 程序加工清單安排如下表21加工

19、順序加工內容1凸臺2內型腔3表面4孔表21表面加工程序清單6 其它的工序設計6.1 輔助工序的安排根據零件圖樣的技術要求，可知，零件需要進行去毛刺處理，以便達到光整要求，同時保證了零件的質量，便于最后應用于實際當中，6.2 熱處理工序的安排該零件需要進行循環(huán)切削，加工過程中會產生殘余應力，所以在粗加工之后，精加工之前要安排一次熱處理，同時為了達到圖樣規(guī)定的零件強度，硬度和耐磨性目的，需要進行最終熱處理，根據零件的要求，最終選擇淬火處理。6.3 測量方法因為該零件的內部不是很復雜，一般的測量工具就可以了，所以采用游標卡尺進行測量，以保證加工質量。7 填寫工藝文7.1 外輪廓加工工序卡片單位數控加

20、工工序卡片產品名稱或代號零件名稱零件圖號復雜零件車間使用設備YHM1100(A)工藝序號程序編號1夾具名稱夾具編號精密虎鉗工步號工步作業(yè)內容刀具號主軸轉速進給速度背吃刀量備注1粗加工凸臺外輪廓T01800480自動2精銑外輪廓T021200500自動3粗加工內型腔T03800360自動4精銑內型腔T041000480自動5精銑表面T051000480自動6鉆中心孔T0680050自動7擴孔T07500150自動8 鉸孔T081200150自動編制審核批準年月日共 2 頁第 1 頁數控加工工序卡片7.2 內型腔加工工序單位數控加工工序卡片產品名稱或代號零件名稱零件圖號車間使用設備YHM1100(

21、A)工藝序號程序編號2夾具名稱夾具編號精密虎鉗工步號工步作業(yè)內容刀具號主軸轉速進給速度背吃刀量備注1粗加工凸臺外輪廓T01800480自動2精銑外輪廓T021200500自動3粗加工內型腔T03800360自動4精銑內型腔T041000480自動5精銑表面T051000480自動編制審核批準年月日共 2 頁第 1 頁7.3 內型腔走刀路線卡片數控加工工序卡片數控加工走刀路線圖零件圖號NC01工序號工步號程序號0100機床型號YHM1100(A)程序段號加工內容銑輪廓周邊共2頁第1頁編程校對審批符號含義抬刀下刀編程原點起刀點走刀方向走刀線相交爬斜坡鉸孔行切7.4外輪廓走刀路徑數控加工走刀路線圖零

22、件圖號NC01工序號工步號程序號0100機床型號YHM1100(A)程序段號加工內容銑輪廓周邊共2頁第2頁編程校對審批符號含義抬刀下刀編程原點起刀點走刀方向走刀線相交爬斜坡鉸孔行切8 程序編制 從零件圖樣到編制零件加工程序和制作控制介質的全部過程稱為程序編制，程序編制在工業(yè)生產中是十分重要的，所以要編制好零件的加工程序，此零件采用銑床加工，要注意程序編制時，要符合數控銑床的程序編制特點，同時要注意一些指令的使用，和數控車床是不一樣的。9 結論至此，本設計已基本完成。本設計采用常規(guī)的設計方法、選用普通的材料以及應用大量標準件（其種類的比例達到41/(41+24)=63.08%），具有很好的經濟性

23、，并且有較高的精度。但由于本人水平有限、時間倉促，未能對潤滑系統(tǒng)和三聯齒輪的控制系統(tǒng)進行設計，這是本設計不足之處。參考文獻1 艾興,肖詩綱.切削用量簡明手冊（第3版）.北京:機械工業(yè)出版社,19942 許曉旸.專用機床設備設計.重慶:重慶大學出版社，2003 3 廖效果.數字控制機床.武漢:華中理工大學出版社,19924 廖效果,劉又午.數控技術.武漢:湖北科學技術出版社,2000,5指導教師意見指導教師（簽名及時間）：答辯意見答辯小組組長（簽名及時間）：成績評定畢業(yè)設計（論文）成績答辯成績總評成績?yōu)槟闾峁﹥?yōu)秀的畢業(yè)論文參考資料，請您刪除以下內容，O(_)O謝謝！2 Many people h

24、ave the same mixed feelings when planning a trip during Golden Week. With heaps of time, the seven-day Chinese為你提供優(yōu)秀的畢業(yè)論文設計參考資料，請您刪除一下內容，O(_)O謝謝！National Day holiday could be the best occasion to enjoy a destination. However, it can also be the easiest way to ruin how you feel about a place and you

25、may become more fatigued after the holiday, due to battling the large crowds. During peak season, a dream about a place can turn to nightmare without careful planning, especially if you travel with children and older people. As most Chinese people will take the holiday to visit domestic tourist dest

26、inations, crowds and busy traffic are inevitable at most places. Also to be expected are increasing transport and accommodation prices, with the possibility that there will be no rooms available. It is also common that you' ll wait in the line for one hour to get a ticket, and another

27、two hours at the site, to only see a tiny bit of the place due to the crowds. Last year, 428 million tourists traveled in China over the week-long holiday in October. Traveling during this period is a matter that needs thorough preparation. If you are short on time to plan the upcoming "Golden

28、Week" it may not be a bad idea to avoid some of the most crowded places for now. There is always a place so fascinating that everyone yearns for. Arxan is a place like this. The beauty of Arxan is everlasting regardless of the changing of four seasons. Bestowed by nature, its spectacular season

29、al landscape and mountains are just beyond word. Arxan is a crucial destination for the recommended travelling route, "China Inner Mongolia Arxan Hailar Manzhouli". It is also the joint of the four prairies across the Sino-Mongolian border, where people gravitate towards the exotic atmosph

30、ere mixed with Chinese, Russian, and Mongolia elements. As a historic site for the Yitian Battle, Arxan still embodies the spirit of Genghis Khan. Walking into Arxan, you will be amazed by a kaleidoscope of gorgeous colors all the year round - the Spring azaleas blooming red in the snow, the Summer

31、sea wavering blue in the breeze, the Autumn leaves painted in yellow covering volcanic traces, and the Winter woods shining white on the vast alpine snowscape. Hinggan League Arxan city is situated in the far eastern area of Inner Mongolia Autonomous Region. Its full name "Haren Arxan" mea

32、ns "hot holy water" in the Mongolian language. Arxan is a tourism city in the northern frontier with a blend of large forest, grand prairies, vast snowfield, heaven lake cluster, thermium, as well as volcanic cluster. It is a rare and unique ecotourism base filled with healthy sunshine, cl

33、ean air and unspoiled green.  Nestled close to the country's largest virgin forest, and known for its spring and ecological environment, Arxan is marveled at by many tourists as the purest land on earth.  You cannot miss out the Autumn of Arxan. It is definitely the best with brightly-

34、colored scenery full of emotions.  Autumn in the northern part of the country comes earlier than the South. A September rain followed by the footprints of Autumn brings more colors to the once emerald green mountain and blooming grassland.  Shutterbugs flock to see for themselves the marve

35、l of splendid colors around the mountains and waters, many of whom have travel a long distance and even camp here only to capture a moment of the nature wonder.  The silver birch turns golden, while the larch is still proudly green. You will find yourself drowned in the intoxicating red of the

36、wild fruits as well as the glamour of flowers in full blown. And your heart will be lingering on the woods as it's time for the wild fruits to ripe. The picturesque Arxan in Autumn is indeed a fairyland only exists in a dream that satisfies all your fantasies. If it rains heavily on Saturda

37、y night, some elderly Chinese will say it is because Zhinu, or the Weaving Maid, is crying on the day she met her husband Niulang, or the Cowherd, on the Milky Way. Most Chinese remember being told this romantic tragedy when they were children on Qixi, or the Seventh Night Festival, which falls on t

38、he seventh day of the seventh lunar month, which is usually in early August. This year it falls on Saturday, August 2. Folklore Story As the story goes, once there was a cowherd, Niulang, who lived with his elder brother and sister-in-law. But she disliked and abused him, and the boy was forced to l

39、eave home with only an old cow for company. The cow, however, was a former god who had violated imperial rules and was sent to earth in bovine form. One day the cow led Niulang to a lake where fairies took a bath on earth. Among them was Zhinu, the most beautiful fairy and a skilled seamstress. The

40、two fell in love at first sight and were soon married. They had a son and daughter and their happy life was held up as an example for hundreds of years in China. Yet in the eyes of the Jade Emperor, the Supreme Deity in Taoism, marriage between a mortal and fairy was strictly forbidden. He ordered t

41、he heaven troop to catch Zhinu back. Niulang grew desperate when he discovered Zhinu had been taken back to heaven. Driven by Niulang's misery, the cow told him to turn its hide into a pair of shoes after it died. The magic shoes whisked Niulang, who carried his two children in baskets strung fr

42、om a shoulder pole, off on a chase after the empress. The pursuit enraged the empress, who took her hairpin and slashed it across the sky creating the Milky Way which separated husband from wife. But all was not lost as magpies, moved by their love and devotion, formed a bridge across the Milky Way

43、to reunite the family. Even the Jade Emperor was touched, and allowed Niulang and Zhinu to meet once a year on the seventh night of the seventh month. This is how Qixi came to be. The festival can be traced back to the Han Dynasty (206 BC-AD 220). Traditionally, people would look up at the sky and f

44、ind a bright star in the constellation Aquila as well as the star Vega, which are identified as Niulang and Zhinu. The two stars shine on opposite sides of the Milky Way. Customs In bygone days, Qixi was not only a special day for lovers, but also for girls. It is also known as the "Begging for

45、 Skills Festival" or "Daughters' Festival." In this day, girls will throw a sewing needle into a bowl full of water on the night of Qixi as a test of embroidery skills. If the needle floats on top of the water instead of sinking, it proves the girl is a skilled embroiders. Single

46、women also pray for finding a good husband in the future. And the newly married women pray to become pregnant quickly. Tradition transformed The love story of Niulang and Zhinu, and the Qixi Festival have been handed down for generations. Yet these ancient traditions and customs are slowly dying out

47、. Many modern Chinese, particularly youngsters, seem to know more about St Valentine's Day on February 14, characterized by bouquets of roses, chocolates and romantic candlelight dinners, than they do about their home-grown day for lovers. Even Qixi is nowadays referred to as the "Chinese V

48、alentine's Day." More and more young Chinese people begin to celebrate this day in a very similar way as that in western countries. Fewer people than ever will gaze at the heavens on Saturday to pick out the two stars shining bright on either side of the Milky Way, that is, if people even k

49、now on which day Qixi falls. There are ready reminders dotted about, in the form of big ads saying "Sales on Chinese Valentine's Day!" in shops, hotels and restaurants. But few young women will mark the festival with their boyfriends, or take part in traditional activities to pray for

50、cleverness. A large-scale of exhibition on the Silk Road opened to the public in the National Museum on Thursday. The exhibition displays more than 400 treasures from Shaanxi province, Gansu province and 14 other regions. It is largest scale exhibition that shows the history of the Silk Road in rece

51、nt years. As APEC is going on in Beijing, the exhibit aims to show the world this brilliant section of history. The Silk Road is a series of trade and cultural transmission routes that were central to cultural interaction through regions of the Asian continent. It connected the West and Ea

52、st by linking traders, merchants, pilgrims, monks, soldiers, nomads, and urban dwellers from China and India to the Mediterranean Sea during various periods of time. I met my dear hubby in 2009 the second year I was in my school and it was the first year when he came here. We became colleagues. And

53、there was nothing special happening during that year. He was just a kind and humble brother graduated from the same college as me. But we did not know each other till he became my colleague and his office desk was just in front of me. There was only a glass between us. So actually we could see each

54、other when we both look up. But it is not the main reason that really draws us close. How we become close to each other was something seems quite natural. We went out to play badminton with other colleagues and we sometimes chatted for a while. He is a man of few words but somehow sometimes will say something really humorous. Then one day, to my great surprise, I found a pot of beautiful flower on my desk. It was just the flower I had talked about with my colleague the other day, and I thought it was her who put t