鋼筋拉直機(jī)的設(shè)計(jì)【鋼筋校直機(jī)】

鋼筋拉直機(jī)的設(shè)計(jì)【鋼筋校直機(jī)】,鋼筋校直機(jī),鋼筋拉直機(jī)的設(shè)計(jì)【鋼筋校直機(jī)】,鋼筋,拉直,設(shè)計(jì),校直機(jī) 學(xué)校代碼：10410 序 號(hào)： 050451本 科 畢 業(yè) 設(shè) 計(jì)題目： 鋼筋拉直機(jī)的設(shè)計(jì) 學(xué) 院： 工 學(xué) 院 姓 名： 學(xué) 號(hào)： 專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 年 級(jí)： 指導(dǎo)教師： 二OO九年 五 月摘 要本人設(shè)計(jì)的鋼筋拉直機(jī)就是以拉直被彎曲的鋼筋為目的的。由于，鋼筋的直徑不是很大，所以，鋼筋的切斷用專用的剪子就可以實(shí)現(xiàn)。該種鋼筋拉直機(jī)主要由電動(dòng)機(jī)，減速器，卷筒,離合器和鋼絲繩組成。本設(shè)計(jì)（鋼筋拉直機(jī)）的工作原理是通過(guò)電動(dòng)機(jī)把電能轉(zhuǎn)變?yōu)闄C(jī)械能，使電動(dòng)機(jī)的轉(zhuǎn)軸轉(zhuǎn)動(dòng)，經(jīng)減速箱變速后帶動(dòng)卷筒旋轉(zhuǎn)，從而使鋼絲繩卷入拉直鋼筋或放出。關(guān)鍵詞：鋼筋拉直 電動(dòng)機(jī) 減數(shù)器 卷筒 離合器 鋼絲繩Abstract I designed steel straightening machine is to straighten the bars were bent for the purpose. As a result, the diameter of steel bars is not very big, therefore, reinforced by the exclusive use of the scissors to cut off can be achieved. Steel straightening machine of the main motor, reducer, drum, clutch components and wire rope. This design (steel straightening machine) is the working principle of electric motors to power into mechanical energy, so that the spindle motor rotation speed by the deceleration after me driven rotating drum, so that involved straightening steel wire rope or release. Key words: steel straightening device subtrahend motor clutch wire rope reel目 錄前 言一、設(shè)計(jì)方案分析和擬訂二、牽引件的選擇2.1 鋼絲繩的選用.2.2鋼絲繩的連接.2.3鋼絲繩夾的選擇三、卷筒的設(shè)計(jì)以及鋼絲繩的固定裝置四、電動(dòng)機(jī)的選擇4.1電動(dòng)機(jī)類型和結(jié)構(gòu)4.2選擇電動(dòng)機(jī)的容量4.3選擇電動(dòng)機(jī)型號(hào)五、減速器的設(shè)計(jì)5.1 選擇減速器的類型5.2 計(jì)算總傳動(dòng)比和各級(jí)傳動(dòng)比5.3 計(jì)算、軸轉(zhuǎn)速、功率和轉(zhuǎn)矩5.4齒輪設(shè)計(jì)5.5軸的設(shè)計(jì)計(jì)算5.6箱體的設(shè)計(jì)六、聯(lián)軸器的選擇七、離合器的確定八、選擇滑動(dòng)軸承8.1 軸承寬度的確定8.2 檢驗(yàn)軸頸的圓周速度8.3 選擇軸承的配合8.4 滑動(dòng)軸承潤(rùn)滑劑的選擇九、夾具的設(shè)計(jì)十、機(jī)座的設(shè)計(jì)總結(jié)參考文獻(xiàn)前 言隨著社會(huì)的發(fā)展進(jìn)步，人們的生活水平的提高，人們對(duì)住房的要求有了不小的提高，由此帶動(dòng)了中國(guó)建筑業(yè)的蓬勃發(fā)展。鋼筋作為建筑業(yè)中極為重要的建筑材料必定會(huì)大批量的生產(chǎn)和運(yùn)輸。運(yùn)輸中為了方便以及節(jié)省運(yùn)輸空間常常會(huì)將10mm以下鋼筋卷成直徑約為1米左右的鋼筋圈。但是，作成了盤狀的鋼筋不能作為建筑工程的材料，所以，我們必須有一樣工具能夠把彎曲的鋼筋拉直以方便施工。由此，可見鋼筋拉直機(jī)是必不可少的的機(jī)械，在建筑業(yè)中有很大的作用。本人設(shè)計(jì)的鋼筋拉直機(jī)就是以拉直被彎曲的鋼筋為目的的。由于，鋼筋的直徑不是很大，所以，鋼筋的切斷用專用的剪子就可以實(shí)現(xiàn)。該種鋼筋拉直機(jī)主要由電動(dòng)機(jī)，減速器，卷筒,離合器和鋼絲繩組成。它結(jié)構(gòu)簡(jiǎn)單，機(jī)身小，可由工作人員單一操作，而且操作簡(jiǎn)單（但要求操作人員進(jìn)行一定的安全技術(shù)培訓(xùn)），安全性比較高，可以在環(huán)境較差的條件下工作，在機(jī)構(gòu)方面本人力求簡(jiǎn)單普及，力求降低維修的難度從而為廣大工作者帶來(lái)了方便，這也是作為設(shè)計(jì)者的最為關(guān)心的事情。因此,在本設(shè)計(jì)的夾具設(shè)計(jì)中本人將鋼筋的彎曲工序和裝夾工序同時(shí)進(jìn)行,這樣可以節(jié)約時(shí)間,減小工作空間。本設(shè)計(jì)主要分為三個(gè)部分：第一是總體結(jié)構(gòu)的設(shè)想；第二是機(jī)體各組成部分的設(shè)計(jì)；第三是總體的設(shè)計(jì)。（在設(shè)計(jì)過(guò)程中多以普通卷?yè)P(yáng)機(jī)為參考設(shè)備）一、設(shè)計(jì)方案分析和擬訂設(shè)計(jì)方案的選擇應(yīng)首先滿足工作機(jī)的工作要求，此外，還應(yīng)具有結(jié)構(gòu)簡(jiǎn)單，尺寸緊工作質(zhì)量和可靠性。我的設(shè)計(jì)方案是工作機(jī)采用齒輪傳動(dòng)。齒輪傳動(dòng)承載能力高，速度范圍大。瞬時(shí)傳動(dòng)，加工方便，成本低廉，傳動(dòng)效率高和使用維護(hù)方便等特點(diǎn)，以保證工作機(jī)的傳動(dòng)比恒定。外廓尺寸小，工作可靠，效率高，是所有機(jī)械傳動(dòng)型式中最常見的一種傳動(dòng)型式。為了達(dá)到以上的要求，總體結(jié)構(gòu)設(shè)計(jì)如圖-1：1電動(dòng)機(jī)；2離合器和制動(dòng)器；3減速箱；4聯(lián)軸器；5卷筒圖-1本設(shè)計(jì)（鋼筋拉直機(jī)）的工作原理是通過(guò)電動(dòng)機(jī)把電能轉(zhuǎn)變?yōu)闄C(jī)械能，使電動(dòng)機(jī)的轉(zhuǎn)軸轉(zhuǎn)動(dòng)，經(jīng)減速箱變速后帶動(dòng)卷筒旋轉(zhuǎn)，從而使鋼絲繩卷入拉直鋼筋或放出。因?yàn)樵瓌?dòng)機(jī)與卷筒之間是剛性聯(lián)接的，卷筒的正反轉(zhuǎn)必須依靠電動(dòng)機(jī)的正反轉(zhuǎn)來(lái)實(shí)現(xiàn)，要求電動(dòng)機(jī)是可逆轉(zhuǎn)的。二、牽引件的選擇經(jīng)過(guò)本人在數(shù)處建筑工地的觀察以及對(duì)一些書籍的查閱，目前，大多數(shù)鋼筋拉直機(jī)都是以鋼絲繩為牽拉件。經(jīng)過(guò)查閱書籍和現(xiàn)場(chǎng)觀察鋼絲繩具有以下一些優(yōu)點(diǎn)：有良好的各方向相同的撓性（過(guò)卷繞裝置時(shí)，容易彎曲），承載能力大，經(jīng)受沖擊大和過(guò)載能力強(qiáng)，自重輕以及在卷繞過(guò)程中平穩(wěn)、無(wú)噪音，并且運(yùn)動(dòng)速度不受限制，使用安全可靠，無(wú)突然斷裂的現(xiàn)象。當(dāng)然鋼絲繩還是有一些缺點(diǎn)的：經(jīng)過(guò)長(zhǎng)期使用繩子的安全性會(huì)有較大的變化，如果工作人員不夠小心的話很容易發(fā)生事故。但是，綜合以上各點(diǎn)，從安全性能等方面考慮，我選擇鋼絲繩作為鋼筋拉直機(jī)的牽拉件。2.1 鋼絲繩的選用.鋼絲繩的選用首先根據(jù)用途、承載情況、工作性質(zhì)和環(huán)境等條件選擇鋼絲繩的類型。然后再根據(jù)鋼絲繩工作時(shí)要承受的最大靜拉力Smax，選擇鋼絲繩的直徑。即S絲KSmax/a式中 S絲鋼絲繩中全部鋼絲破斷拉力總和；K安全系數(shù)，最小安全系數(shù)不小于5.0；a鋼絲繩折減系數(shù)，對(duì)于6W（19）繩，a=0.85。于是有 S絲5.56000/0.85=38823.5 N由表-315線接觸鋼絲繩6W（19）型（GB110274）中選取鋼絲繩直徑d=14.0mm。備注：（根據(jù)國(guó)家標(biāo)準(zhǔn)GB514485的規(guī)定，交捻619鋼絲繩報(bào)廢標(biāo)準(zhǔn)如下斷絲長(zhǎng)度范圍6d時(shí)為10，30d時(shí)為19。）152.2鋼絲繩的連接.鋼絲繩的連接方法有很多，本設(shè)計(jì)采用的是繩卡固定法。即將鋼絲繩繞過(guò)套環(huán)后用繩卡固定。用繩卡固定時(shí)，鋼絲繩直徑為716mm時(shí)，繩卡數(shù)為三個(gè)，間距應(yīng)等于（56）倍鋼絲繩直徑。用此法聯(lián)接處可達(dá)到自身強(qiáng)度地8090%。若繩卡裝反，則固定外強(qiáng)度會(huì)降至75%以下。緊固繩夾時(shí)須考慮每個(gè)繩夾的合理受力，離套環(huán)最近處繩夾不得首先單獨(dú)堅(jiān)固，離套環(huán)最近的繩夾（第一個(gè)繩夾）應(yīng)盡可能地靠近套環(huán)，但仍須保證繩夾的正確擰緊，不得損壞鋼絲繩的外層鋼絲。2.3鋼絲繩夾的選擇由表12.1-417繩夾的型式和尺寸，查得當(dāng)鋼絲繩公稱直徑為14時(shí)，A=29.0，B=32，C=61，R=7.5，H=72。三、卷筒的設(shè)計(jì)以及鋼絲繩的固定裝置卷筒是鋼筋拉直機(jī)用來(lái)卷繞鋼絲繩的卷繞裝置。卷筒將原動(dòng)機(jī)的回轉(zhuǎn)運(yùn)動(dòng)改變?yōu)槲锲返闹本€運(yùn)動(dòng)。按鋼絲繩在卷筒上的卷繞層數(shù)，分為單層繞卷筒和多層繞卷筒。按卷筒的表面結(jié)構(gòu)，分為光面卷筒和帶槽卷筒。由鋼絲繩的長(zhǎng)度，我選擇鑄鐵制成單層繞光面卷筒（如圖-2），它與鋼絲繩與卷筒的接觸面比較隨意。由于本機(jī)械 沒有特殊要求,因此用HT200鑄鐵鑄造即可。圖-2為了保證鋼絲繩的正常，安全的工作以及可以比較容易的更換，本人決定使用以壓板固定（如圖-3）。此種固定法的特點(diǎn)是：結(jié)構(gòu)簡(jiǎn)單和鋼絲繩具有卷入有導(dǎo)入作用。圖-3四、電動(dòng)機(jī)的選擇4.1電動(dòng)機(jī)類型和結(jié)構(gòu)電動(dòng)機(jī)類型和結(jié)構(gòu)型式要根據(jù)電源（交流或直流），工作條件（溫度空間尺寸等）和載荷特點(diǎn)（性質(zhì)大小啟動(dòng)性能和過(guò)載情況）轉(zhuǎn)速來(lái)選擇。由于本設(shè)計(jì)沒有特殊的要求，以及本設(shè)計(jì)本身的要求，本設(shè)計(jì)的電動(dòng)機(jī)均由Y系列電動(dòng)機(jī)中選出，Y系列電動(dòng)機(jī)適用于不易燃不易爆無(wú)腐蝕性氣體的場(chǎng)合，以及要求具有較好啟動(dòng)性能的機(jī)械，在經(jīng)常啟動(dòng)，制動(dòng)和反轉(zhuǎn)的場(chǎng)合。最終本人選用了Y系列三相鼠籠式異步電動(dòng)機(jī)。4.2選擇電動(dòng)機(jī)的容量標(biāo)準(zhǔn)電動(dòng)機(jī)的容量由額定功率表示。所選用電動(dòng)機(jī)的額定功率應(yīng)稍大于工作要求的功率。若容量小于工作要求，則不能保證工作機(jī)正常工作，或使電動(dòng)機(jī)長(zhǎng)期過(guò)載，極易損壞；容量過(guò)大則增加成本從而造成浪費(fèi)。電動(dòng)機(jī)的容量主要由運(yùn)行時(shí)發(fā)熱條件限定，在不變或變化很小的載荷下長(zhǎng)期連續(xù)運(yùn)行的機(jī)械，只要其電動(dòng)機(jī)的負(fù)載不超過(guò)額定值，通常不必校驗(yàn)發(fā)熱和啟動(dòng)力矩。所需功率為： Pd= KW 式中：Pd工作機(jī)實(shí)際需要的電動(dòng)機(jī)輸出功率 PW工作所需輸入功率 電動(dòng)機(jī)至工作機(jī)之間傳動(dòng)裝置的總效率 工作機(jī)所需功率Pw應(yīng)由機(jī)器工作阻力和運(yùn)動(dòng)參數(shù)計(jì)算求得，Pw= KW 或 Pw= KW 式中：F工作機(jī)的阻力，N；v工作機(jī)的線速度，m/s；T工作機(jī)的阻力矩，N.mnw工作機(jī)的轉(zhuǎn)速，r/min；w工作機(jī)的效率?？傂拾聪率接?jì)算：其中分別為傳動(dòng)裝置中的每一傳動(dòng)副，每對(duì)軸承，每個(gè)聯(lián)軸器。由表2-615查得，鋼絲繩平均速度為30-36m/min（JJK-2型）。取v=0.6m/min。 工作機(jī)的（卷筒）的轉(zhuǎn)速nk功率Pw 為nk=44.7 r/minPw=3.325 KW 由表8-24查得，在傳動(dòng)裝置中，兩對(duì)齒輪傳動(dòng)每對(duì)齒輪的效率=0.97，卷筒效率=0.96，四對(duì)軸承每對(duì)軸承的效率=0.98，兩個(gè)聯(lián)軸器每個(gè)的效率=0.99?？傂蕿? =0.972 電動(dòng)機(jī)輸出功率為 Pd=3.58kw4.3選擇電動(dòng)機(jī)型號(hào)對(duì)Y系列電動(dòng)機(jī)，通常多選用同步轉(zhuǎn)速為1500r/min或1000r/min的電動(dòng)機(jī)，如無(wú)特殊需要，不選低于750r/min的電動(dòng)機(jī)。這里我綜合電動(dòng)機(jī)和傳動(dòng)裝置的尺寸、重量、價(jià)格以及總的傳動(dòng)比的特點(diǎn)及大小，我選用960r/min的電動(dòng)機(jī)。由表9-394查得，可選取Y132M1-6型電動(dòng)機(jī)。 Y132M1-6 n=960r/min P=4KW m=71kg 五、減速器的設(shè)計(jì)5.1 選擇減速器的類型在本設(shè)計(jì)中選擇的是二級(jí)展開式圓柱齒輪減速器，它結(jié)構(gòu)簡(jiǎn)單，但齒輪相對(duì)軸承的位置不對(duì)稱，因此軸應(yīng)具有較大剛度。高速軸齒輪布置在遠(yuǎn)離轉(zhuǎn)矩輸入端，這樣軸在轉(zhuǎn)矩作用下產(chǎn)生的扭轉(zhuǎn)變形將能減緩軸在彎矩作用下產(chǎn)生彎曲變形所拉起的載荷沿齒寬分布不均勻的現(xiàn)象，本產(chǎn)品適用于載荷比較平穩(wěn)的場(chǎng)合。5.2 計(jì)算總傳動(dòng)比和各級(jí)傳動(dòng)比總傳動(dòng)比為 i=n/ nk =960/44.7=21.8因?yàn)槭驱X輪傳動(dòng)，由表6-13417查得，高速級(jí)傳動(dòng)比i1=4.5，低速級(jí)傳動(dòng)比i2=4.5，實(shí)際總傳動(dòng)比為i，=i1i2=4.35.0=21.5傳動(dòng)比誤差為i=1.42%4050mm，尺寸系數(shù)=0.84，r=0.78，由附錄表5中查出，當(dāng)B=590mpa,Ra=3.2m時(shí)，表面狀態(tài)系數(shù)=0.94 故（K）D=k/=2.50/（0.940.84）=3.17K）D=k/=1.80/（0.940.78）=2.45D處只有過(guò)盈配合所以：（K）I=k/=2.50/（0.940.84）=3.17K）I=k/=1.80/（0.940.78）=2.45八，求安全系數(shù)。設(shè)按無(wú)限壽命（KN=1）計(jì)算公式為：SI=-1/(k/ac+dm)=1.71SD=-1/(k/aD+dm)=1.78SI=-1/(k/cac+mc)=8.78SD=-1/(k/Da+mc)= 140/（2.456.7+0.16.7）=8.19復(fù)合安全系數(shù)：SI=SS/( S2+S2)0.5=1.74 SD=SS/( S2+S2)0.5=1.69兩個(gè)截面得安全系數(shù)均大于許用安全系數(shù)，軸強(qiáng)度安全，所以軸是合格的。軸一的設(shè)計(jì)（1）軸徑的粗選T=T/WT=T2/0.2d3Tdc*（p/n）1/3=115*（3.96/960）1/3=18.4mm因此選d=20mm圖-9安裝 圓錐滾子軸承，因?yàn)榘惭b處的 為25mm所以選用的型號(hào)為7305E的軸承，其中D=62mmB=17mm C=15mma=13mmE=50.6mm（兩端安裝一樣的軸承）Ft1=2*T2/d2=0.039*106*2/60=1300NFr1= Ft2*tg=1300*tg20=473.2N由此可知軸的總長(zhǎng)為：L=202mm（2）.軸的受力分析圖：圖-10從水平面受力來(lái)看（水平受力圖） 圖-11FAH+ FBH= Ft 51* Ft= FBH*202FAH =971.8N FBH=328.2NC點(diǎn)彎矩MCH= FAH*51=49561.8N.mmD點(diǎn)彎矩MDH= FBH*26=25266.8N.mm從垂直面來(lái)看 圖-12FAV+ FBV= Fr. Fr*51= FBV*LFAV=353.8N FBV=119.4NC點(diǎn)彎矩MCV= FAV*51=18043.8 N.mmD點(diǎn)彎矩MDV= FBV*26=9198.8 N.mm合成彎矩圖-13C點(diǎn)合成彎矩： Mc=(MCH2+MCV2)0.5=52744.2N.mmD點(diǎn)合成彎矩： Mc=(MDH2+MDV2)0.5=26889.2N.mmT2=39000N.mm由此可知軸的結(jié)構(gòu)中D-D . C-C 受的力比較大最有可能因應(yīng)力集中而形成危險(xiǎn)截面。當(dāng)量彎矩由3可知=0.6。 MC=MC2+(aT)20.5=57701.9N.mmMD=MD2+(aT)20.5=35645.3N.mm（3）.下面我們對(duì)軸的強(qiáng)度進(jìn)行校核。由表2-53，當(dāng)45鋼B=590MPa時(shí)按表2-73，以插值法得-1b=54MPaC= MC/W= MC/0.1d3=24.2 MPaD= MD/W= MD/0.1d3=19.5 MPa由此可知本設(shè)計(jì)十分安全，所有截面都十分合格。（4），安全系數(shù)得校核計(jì)算。因?yàn)镃，D兩點(diǎn)都受到了較大得應(yīng)力，應(yīng)力集中。下面來(lái)對(duì)著兩個(gè)截面進(jìn)行安全系數(shù)校核。由表2-53查得45號(hào)鋼正火，回火處理時(shí)。-1=140 MPa -1=255 MPa由表2-2 3查得等效系數(shù)=0.1， =0.2 由前面可知D ，C兩截面得應(yīng)力合成彎矩，轉(zhuǎn)矩分別為：D點(diǎn)合成彎矩： Md=(MDH2+MDV2)0.5=24983.2N.mmC點(diǎn)合成彎矩： Mc=(McH2+McV2)0.5=51007.4N.mmT1=39000N.mmC處有鍵槽，所以由附錄73可知抗彎截面系數(shù)W和抗扭截面系數(shù)WT。（下面是計(jì)算公式及結(jié)果）WC=dC3/32-bt(dC-t)2/2dC=2290.2mm3WTC=dC3/16-bt(dC-t)2/2dC=4940.9mm3選用A型圓頭普通鍵：bh=87，L=40mmt=4mm，t=3.3mm彎曲應(yīng)力幅：a= MC/W=22.2MPa彎曲平均應(yīng)力：m=0扭轉(zhuǎn)切應(yīng)力：=T 2/ WTC=7.9MPa切應(yīng)力幅和平均切應(yīng)力：a=m=/2=3.95MPa因?yàn)镈處沒有鍵槽由表可知：WD=dD3/32=1757.6mm3WTD=dD3/16=3515.2mm3彎曲應(yīng)力幅：a= MD/W=14.2 MPa彎曲平均應(yīng)力：m=0扭轉(zhuǎn)切應(yīng)力：=T 2/ WTD=11.1MPa切應(yīng)力幅和平均切應(yīng)力：a=m=/2=5.55MPa（6），求綜合影響系數(shù)。因（k）D=k/和（k）D=k/，C，D兩截面上有鍵槽和過(guò)盈配合兩種產(chǎn)生應(yīng)力集中的因素，故應(yīng)比較兩者的有效應(yīng)力集中系數(shù)，從中取大植計(jì)算。 C面 鍵槽對(duì)軸的有效應(yīng)力集中系數(shù)，由附錄表13中查出（用插植法），當(dāng)B=590MPa,A型鍵槽時(shí)，K=2.50,K=1.80;過(guò)盈配合對(duì)軸的有效應(yīng)力系數(shù)，當(dāng)B=590MPa，配合為H7/r6時(shí)，Ka=2.50,K=1.80.因過(guò)盈配合的有效應(yīng)力集中系數(shù)均比鍵槽大，取過(guò)盈配合是的有效應(yīng)力集中系數(shù)計(jì)算，由附錄表43中查出，當(dāng)材料為碳鋼，毛坯直徑3040mm，尺寸系數(shù)=0.88，r=0.81，由附錄表53中查出，當(dāng)B=590mpa,Ra=3.2m時(shí)，表面狀態(tài)系數(shù)=0.94 故（K）C=k/=2.50(K）C=k/=1.80/（0.940.78）=1.80D處只有過(guò)盈配合所以：（K）D=k/=3.02(K）D=k/=2.36（7），求安全系數(shù)。設(shè)按無(wú)限壽命（KN=1）計(jì)算公式為：SC=-1/(k/ac+dm)=3.80SD=-1/(k/aD+dm)=5.95SC=-1/(k/cac+mc)= 14.4SD=-1/(k/Da+mc)= 10.35復(fù)合安全系數(shù)：SC=SS/( S2+S2)0.5=3.7 SD=SS/( S2+S2)0.5=5.16兩個(gè)截面得安全系數(shù)均大于許用安全系數(shù)，所以軸是合格的。軸強(qiáng)度安全。軸三的設(shè)計(jì)（1） .軸徑的粗選如同軸一一樣，為了工作以及設(shè)計(jì)維修方便，軸選用了一樣的材料T=T/WT=T2/0.2d3Tdc*（p/n）1/3=115*（3.57/44.7）1/3=49.5mm因此選d=50mm圖-14安裝 圓錐滾子軸承，因?yàn)榘惭b處的 為50mm所以選用的型號(hào)為2007511E的軸承，其D=26.75mm B=25mm C=21mm a=22.5mm E=82.8mm（兩端安裝一樣的軸承）Ft1=2*T3/d2=4736.2NFr1= Ft3*tg=2037.1N由此可知軸的總長(zhǎng)為：L=183mm（2）.軸的受力分析圖：圖-15從水平面受力來(lái)看（水平受力圖） 圖-16FAH+ FBH= Ft 56.5* Ft= FBH*183FAH =3273.9N FBH=1462.3NC點(diǎn)彎矩MCH= FAH*56.5=184975.4N.mmD點(diǎn)彎矩MDH= FBH*16.5=54019.4N.mm從垂直面來(lái)看 圖-17FAV+ FBV= Fr. Fr*56.5= FBV*LFAV=1408.2N FBV=628.9NC點(diǎn)彎矩MCV= FAV*56.5=79563.3 N.mmD點(diǎn)彎矩MDV= FBV*16.5=23235.3 N.mm合成彎矩圖-18C點(diǎn)合成彎矩： Mc=(MCH2+MCV2)0.5=201360.9N.mmD點(diǎn)合成彎矩： Mc=(MDH2+MDV2)0.5=58804.5N.mmT3=763000N.mm由此可知軸的結(jié)構(gòu)中D-D . C-C 受的力比較大最有可能因應(yīng)力集中而形成危險(xiǎn)截面。當(dāng)量彎矩圖-19由3可知=0.6。 MC=MC2+(aT)20.5=500127.0N.mmMD=MD2+(aT)20.5=461561.3N.mm（4），下面我們對(duì)軸的強(qiáng)度進(jìn)行校核。由表2-53，當(dāng)45鋼B=590MPa時(shí)按表2-73，以插值法得-1b=54MPaC= MC/W= MC/0.1d3=27.03 MPaD= MD/W= MD/0.1d3=27.74 MPa由此可知本設(shè)計(jì)十分安全，所有截面都十分合格。（5），安全系數(shù)得校核計(jì)算。因?yàn)镃，D兩點(diǎn)都受到了較大得應(yīng)力，應(yīng)力集中。下面來(lái)對(duì)著兩個(gè)截面進(jìn)行安全系數(shù)校核。由表2-53查得45號(hào)鋼正火，回火處理時(shí)。-1=140 MPa -1=255 MPa由表2-23 查得等效系數(shù)=0.1， =0.2 由前面可知D ，C兩截面得應(yīng)力合成彎矩，轉(zhuǎn)矩分別為：D點(diǎn)合成彎矩： Md=(MDH2+MDV2)0.5=58804.5N.mmC點(diǎn)合成彎矩： Mc=(McH2+McV2)0.5=201360.9N.mmT3=763000N.mmC處有鍵槽，所以由附錄7可知抗彎截面系數(shù)W和抗扭截面系數(shù)WT。（下面是計(jì)算公式及結(jié)果）WC=dC3/32-bt(dC-t)2/2dC=18256.3mm3WTC=dC3/16-bt(dC-t)2/2dC=39462.1mm3選用A型圓頭普通鍵：bh=1811，L=70mmt=7mm，t=4.4mm彎曲應(yīng)力幅：a= MC/W=11.03MPa彎曲平均應(yīng)力：m=0扭轉(zhuǎn)切應(yīng)力：=T 2/ WTC=19.34MPa切應(yīng)力幅和平均切應(yīng)力：a=m=/2=9.67MPa因?yàn)镈處沒有鍵槽由表可知：WD=dD3/32=16637.5mm3WTD=dD3/16=33275.0mm3彎曲應(yīng)力幅：a= MD/W=3.53 MPa彎曲平均應(yīng)力：m=0扭轉(zhuǎn)切應(yīng)力：=T 2/ WTD=22.93MPa切應(yīng)力幅和平均切應(yīng)力：a=m=/2=11.47MPa（6），求綜合影響系數(shù)。因（k）D=k/和（k）D=k/，C，D兩截面上有鍵槽和過(guò)盈配合兩種產(chǎn)生應(yīng)力集中的因素，故應(yīng)比較兩者的有效應(yīng)力集中系數(shù)，從中取大植計(jì)算。 C面 鍵槽對(duì)軸的有效應(yīng)力集中系數(shù)，由附錄表13中查出（用插植法），當(dāng)B=590MPa,A型鍵槽時(shí)，K=2.50,K=1.80;過(guò)盈配合對(duì)軸的有效應(yīng)力系數(shù)，當(dāng)B=590MPa，配合為H7/r6時(shí)，Ka=2.50,K=1.80.因過(guò)盈配合的有效應(yīng)力集中系數(shù)均比鍵槽大，取過(guò)盈配合是的有效應(yīng)力集中系數(shù)計(jì)算，由附錄表43中查出，當(dāng)材料為碳鋼，毛坯直徑50mm，尺寸系數(shù)=0.78 r=0.74，由附錄表53中查出，當(dāng)B=590mpa,Ra=3.2m時(shí)，表面狀態(tài)系數(shù)=0.94 故（K）C=k/=3.41K）C=k/=2.59D處只有過(guò)盈配合所以：（K）D=k/=3.28K）D=k/=2.52（7），求安全系數(shù)。設(shè)按無(wú)限壽命（KN=1）計(jì)算公式為：SC=-1/(k/ac+dm)=6.8SD=-1/(k/aD+dm)=22SC=-1/(k/cac+mc)=5.4SD=-1/(k/Da+mc)= 4.7復(fù)合安全系數(shù)：SC=SS/( S2+S2)0.5=4.2 SD=SS/( S2+S2)0.5=4.6兩個(gè)截面得安全系數(shù)均大于許用安全系數(shù)，所以軸是合格的。軸強(qiáng)度安全。卷筒軸安全性的經(jīng)驗(yàn)算合格。5.6箱體的設(shè)計(jì)箱蓋和箱座是用螺栓聯(lián)結(jié)成一整體。這種箱體結(jié)構(gòu)緊湊、安裝方便，因此應(yīng)用較為廣泛。具體尺寸如下。減速器我選用材料是HT200的鑄造箱體。名稱符號(hào)尺 寸 關(guān) 系結(jié)果/mm箱座壁厚0.025a+389箱蓋壁厚0.888箱蓋凸緣厚度12.箱座凸緣厚度 1.513.5箱座底凸緣厚度22.5地腳螺釘直徑0.036a+1225地腳螺釘數(shù)目a250時(shí)，n=48軸承旁連接螺栓直徑15蓋與座連接螺栓直徑10連接螺栓的間距150-200120視孔蓋螺釘直徑6，至外箱壁距離查表30，至凸緣邊緣距離查表25外箱壁至軸承座端面距離40大齒輪頂圓與內(nèi)箱壁距離110齒輪端面與內(nèi)箱壁距離212箱蓋，箱座肋厚m1mm=m1=8連接螺栓直徑d10通孔直徑d11沉頭座直徑D22底座底面至軸中心線高度H175表-2六、聯(lián)軸器的選擇卷筒軸與減速器的低速軸之間是用聯(lián)軸器聯(lián)接的。聯(lián)軸器是連接軸或軸與其他回轉(zhuǎn)件的一種裝置，使它們?cè)趥鬟f運(yùn)動(dòng)和動(dòng)力過(guò)程中一起回轉(zhuǎn)而不脫開。聯(lián)軸器主要有機(jī)械式、液力式、和電磁式三種。機(jī)械式聯(lián)軸器是應(yīng)用最廣泛的聯(lián)軸器，它借助于機(jī)械構(gòu)件相互間的機(jī)械作用力來(lái)傳遞轉(zhuǎn)矩。聯(lián)軸器可以根據(jù)所聯(lián)軸徑、所傳遞的轉(zhuǎn)矩和軸的轉(zhuǎn)速，從有關(guān)手冊(cè)中選擇合適的型號(hào)。由前述可知，低速軸的轉(zhuǎn)矩T3=763000 N.mm，轉(zhuǎn)速n3=44.7 r/min，所聯(lián)軸徑d=50。 本設(shè)計(jì)選用的是凸緣聯(lián)軸器，這種聯(lián)軸器可傳遞較大轉(zhuǎn)矩，結(jié)構(gòu)簡(jiǎn)單，工作可靠，容易維護(hù)，但要求凸緣端面與軸線有較高的垂直度。6.1 聯(lián)軸器的計(jì)算轉(zhuǎn)矩TC=KT選擇工作情況系數(shù)K，查表14-13，取K=1.5，則計(jì)算轉(zhuǎn)矩TC=KT=1.5763000=1144500 N.mm 6.2 選擇聯(lián)軸器的型號(hào) 查17，根據(jù)軸徑和計(jì)算轉(zhuǎn)矩，最后選用凸緣聯(lián)軸器的型號(hào)為YLD11。七、離合器的確定電動(dòng)機(jī)軸與減速器的高速軸之間是用離合器聯(lián)接的。離合器在機(jī)械運(yùn)轉(zhuǎn)時(shí),把原動(dòng)機(jī)的回轉(zhuǎn)運(yùn)動(dòng)和動(dòng)力傳給工作機(jī),并可隨時(shí)分離或接合工作機(jī).因?yàn)殡x合器在機(jī)器運(yùn)轉(zhuǎn)過(guò)程中可隨時(shí)接合或分離，由相關(guān)材料可知離合器的要求為：1工作可靠，接合平穩(wěn)，分離迅速；2操作和維修方便；3外廓尺寸小，重量輕；4抗磨性和散熱性能好。本設(shè)計(jì)選用的是矩形齒牙嵌式離合器（如圖20），其特點(diǎn)為：制造容易，接合，脫開較困難,停車時(shí)可不關(guān)機(jī)，開機(jī)時(shí)啟動(dòng)平穩(wěn)適于頻繁開機(jī)。為了便于接合，常采用較大的牙間間隙。此離合器適用于重載可傳遞雙向載荷。一般用于不經(jīng)常離合的傳動(dòng)中。應(yīng)在靜止或轉(zhuǎn)差在10r/min以下接合。材料為20Cr，滲碳（0.5-1.0mm）表面硬度HRC=5662，多應(yīng)用于中等尺寸的高轉(zhuǎn)速合中等單位壓力的離合器。根據(jù)所聯(lián)軸徑d=20mm，由 17查得D=50，D1=35，d=20，h0.3=4.3，h1=5，=36。，=5。，K（-0.1）=15.04，K1（-0.1）=15.45，齒數(shù)z=5，同時(shí)接觸齒數(shù)z=3。 圖-20離合器的校核 牙面上的壓強(qiáng) P=2KT/zD0A 牙根彎曲應(yīng)力 b=KTh/zD0W 式中：A每個(gè)牙的接觸面積，mm2；D0牙所在圓環(huán)的平均直徑，mm；h牙的高度，mm；z牙的數(shù)目；W牙根部的抗彎截面系數(shù)，mm3，W=a2b/6。因此，A=h（D-D1）/2=4.3（50-35）/2=32.25 mm2 D0=（D+D1）/2=（50+35）/2=42.5 mma=D0/2z+htg=42.5/254.3*tg5。=13.7mmb=（D-D1）/2=（50-35）/2=7.5 mmW=13.727.5/6=234.6 mm3將以上數(shù)據(jù)代入式、中，得P=21.539103/（542.532.25）=17 MPab=1.5391034/（542.5234.6）=4.35 MPa在運(yùn)轉(zhuǎn)時(shí)接合，取P=40MPa，b= S/3.5=400/3.5=114MPa，按牙面比壓和牙根彎曲強(qiáng)度均小于許用值，離合器強(qiáng)度合格。牙齒嚙合的摩擦角合格。八、選擇滑動(dòng)軸承卷筒的速度v=0.6m/s和pmax=6200N/mm2，屬于低速中載，查表10-11，故選用代號(hào)為ZHSi80-3-3黃銅，其使用性能為：pmax=12N/mm2，vmax=2m/s,pv=10Nm/(smm2),最高工作溫度為200,C軸頸硬度為200HB.8.1 軸承寬度的確定 軸承寬度B可以根據(jù)寬徑比B/d=0.6-1.5來(lái)確定。B/d值過(guò)小，則潤(rùn)滑油易從軸承兩端流失，致使?jié)櫥涣迹p加?。籅/d過(guò)大，則潤(rùn)滑油流失的路程長(zhǎng)，摩擦熱不能很快擴(kuò)散降溫，使軸承溫度升高，而且當(dāng)軸撓曲或偏斜時(shí)勢(shì)必造成軸瓦兩端嚴(yán)重磨損。故選B/d=1.2。8.2 檢驗(yàn)軸頸的圓周速度設(shè)軸頸的圓周速度為v，軸承摩擦系數(shù)為f，則fpv就是軸承單位時(shí)間面積是的摩擦功，摩擦功轉(zhuǎn)變?yōu)闊崃?。通常摩擦系?shù)與軸承局部接觸，此時(shí)即使平均比壓p較小，p和pv值都小于許用值，但也可能由于軸頸圓周速度過(guò)高而使軸承局部過(guò)度磨損或膠合。因此，當(dāng)安裝精度較差，軸的彈性變形較大和軸承寬徑比較大時(shí)，還需檢驗(yàn)軸頸圓周速度v值。V=0.60.025=0.015m/svmax 此數(shù)值遠(yuǎn)小于規(guī)定值，十分安全8.3 選擇軸承的配合 滑動(dòng)軸承根據(jù)不同的使用要求，為了保證一定的旋轉(zhuǎn)精度，必須合理地選擇軸承的配合，以保證有一定的間隙。軸頸與軸承孔間的間隙x，是按以下原則來(lái)選擇的：轉(zhuǎn)速愈高，軸承中的間隙應(yīng)該愈大；在相同的情況下，載荷越大，軸承間隙應(yīng)當(dāng)小一些。由本軸的特點(diǎn)以及數(shù)據(jù)可知 x=（0.00070.0012）d=0.0350.06mm8.4 滑動(dòng)軸承潤(rùn)滑劑的選擇滑動(dòng)軸承必須要潤(rùn)滑劑用來(lái)降低摩擦和磨損，以提高軸承的效率；潤(rùn)滑劑是工作介質(zhì)，同時(shí)對(duì)軸承起冷卻作用。潤(rùn)滑油是滑動(dòng)軸承中應(yīng)用最廣泛的潤(rùn)滑劑，因此選潤(rùn)滑油作為潤(rùn)滑劑。潤(rùn)滑劑的使用原則為：當(dāng)轉(zhuǎn)速高、比壓p小時(shí)，可選粘度較低的油；反之，當(dāng)轉(zhuǎn)速低，比壓大時(shí)，應(yīng)選粘度鋼筋拉直機(jī)的設(shè)計(jì) 院院 系：系：工學(xué)院工學(xué)院 班班 級(jí)：級(jí)：機(jī)制機(jī)制052052班班 姓姓 名：名：肖鈥鑫肖鈥鑫 學(xué)學(xué) 號(hào)：號(hào)：2005045120050451 指導(dǎo)老師：指導(dǎo)老師：吳瑞梅吳瑞梅一、設(shè)計(jì)方案分析和擬訂 n1.1設(shè)計(jì)目的 運(yùn)輸中為了方便以及節(jié)省運(yùn)輸空間常常會(huì)將10mm以下鋼筋卷成直徑約為1米左右的鋼筋圈。但是，作成了盤狀的鋼筋不能作為建筑工程的材料，設(shè)計(jì)的鋼筋拉直機(jī)就是以拉直被彎曲的鋼筋為目的的。一、設(shè)計(jì)方案分析和擬訂1電動(dòng)機(jī)2離合器3減速箱4聯(lián)軸器5卷筒1.2總體結(jié)構(gòu)設(shè)計(jì)一、設(shè)計(jì)方案分析和擬訂 1.3卷筒工作簡(jiǎn)圖二.牽引件的選擇：.1鋼絲繩的選用 鋼絲繩具有良好的各方向相同的撓性（過(guò)卷繞裝置時(shí)，容易彎曲），承載能力大，經(jīng)受沖擊大和過(guò)載能力強(qiáng)，使用安全可靠。從強(qiáng)度及安全性能等方面考慮，選擇鋼絲繩作為鋼筋拉直機(jī)的牽拉件。經(jīng)過(guò)計(jì)算確定選擇線接觸鋼絲繩6W（19）型（GB1102-74），選擇直徑d=14.0mm。二.牽引件的選擇：.2 鋼絲繩的連接 本設(shè)計(jì)采用繩卡固定法。即將鋼絲繩繞過(guò)套環(huán)后用繩卡固定。鋼絲繩直徑為7-16mm時(shí)，繩卡數(shù)為3個(gè)，間距等于5-6倍鋼絲繩直徑。三.卷筒的設(shè)計(jì)以及鋼絲繩的固定裝置.1卷筒的設(shè)計(jì)n卷筒將原動(dòng)機(jī)的回轉(zhuǎn)運(yùn)動(dòng)改變?yōu)槲锲返闹本€運(yùn)動(dòng)。設(shè)計(jì)選擇單層繞光面卷筒。n它與鋼絲繩的接觸面比較隨意，對(duì)其沒有特殊要求，因此選用HT200鑄鐵鑄造。三.卷筒的設(shè)計(jì)以及鋼絲繩的固定裝置.2鋼絲繩的固定裝置 為了保證鋼絲繩的正常安全工作以及易于更換。設(shè)計(jì)使用以壓板固定鋼絲繩。四.電動(dòng)機(jī)的選擇 n選用Y系列三相鼠籠式異步電動(dòng)機(jī) n型號(hào)Y132M1-6型n 轉(zhuǎn)速n=960r/min n輸出功率P=4KW n重量m=71kg 五.減速器的設(shè)計(jì).1選擇減速器的類型n本設(shè)計(jì)中選擇的是二級(jí)展開式圓柱齒輪減速器 n總傳動(dòng)比為 i=n/nk=960/44.7=21.8n高速級(jí)傳動(dòng)比i1=4.5 n低速級(jí)傳動(dòng)比i2=5.0.2減速器齒輪設(shè)計(jì)基本參數(shù)d齒輪1(高速級(jí))實(shí)體圓柱齒輪齒輪2（高速級(jí)）鑄造腹板圓柱齒輪齒輪3（低速級(jí)）實(shí)體圓柱齒輪齒輪4（低速級(jí)）鑄造腹板圓柱齒輪分度圓直徑dd1=60mmd2=258mmd3=63mmd4=315mm不變位齒輪的中心距aa12=159mma34=189mm嚙合角=20=23.27實(shí)際中心距 a34=193mm嚙合角cos20=0.9397cos23.27=0.9187中心距變動(dòng)系數(shù)yY=（a-a）/m=1.24齒高變動(dòng)系數(shù)yy=x1+x2-y=0.1齒頂圓直徑da1=m*（Z1+2*ha*）=66mmda2=264mmda3=m*（Z1+2*ha*+2*x1-y）=74mmda4=326mm齒根圓dfdf1=m*（Z1-2*ha*-2c*）=52.5mmdf2=250.5mmdf3=58mmdf4=311mm軸徑30mm50mm 40mm 60mm節(jié)圓直徑dd1=60mmd2=258mmd3=64.4mmd4=322mm齒寬b 1=50mmb 2=40mmb 3=90mmb 4=80mm五.減速器的設(shè)計(jì).3軸的設(shè)計(jì)n高速軸：總長(zhǎng)為L(zhǎng)=202mm，材料采用45號(hào)鋼n低速軸：總長(zhǎng)為L(zhǎng)=183mm，材料采用45號(hào)鋼 n傳動(dòng)軸：總長(zhǎng)為L(zhǎng)=230mm，材料采用45號(hào)鋼五.減速器的設(shè)計(jì) 4.4箱體的設(shè)計(jì)n箱蓋和箱座是用螺栓聯(lián)結(jié)成一體。這種箱體結(jié)構(gòu)緊湊、安裝方便。n選用材料HT200鑄造箱體六.聯(lián)軸器的選擇 n采用機(jī)械式聯(lián)軸器n根據(jù)所聯(lián)軸徑、所傳遞的轉(zhuǎn)矩和軸的轉(zhuǎn)速，從有關(guān)手冊(cè)中選擇合適的型號(hào)。由前述可知，低速軸的轉(zhuǎn)矩T3=763000 N.mm，轉(zhuǎn)速n3=44.7 r/min，所聯(lián)軸徑d=50。n根據(jù)軸徑和計(jì)算轉(zhuǎn)矩，最后選用凸緣聯(lián)軸器的型號(hào)為YLD11 七.離合器的確定n設(shè)計(jì)選用矩形牙嵌式離合器n特點(diǎn)：制造容易，接合、脫開較困難，停車時(shí)可不關(guān)機(jī)。八.夾具的設(shè)計(jì)n夾具是由三個(gè)部分組成：1.有一個(gè)將鋼筋卡死的鑄鐵棒。2.一個(gè)球體為主體，其中有兩個(gè)通孔一大一小。3.還有一小鐵棒是鋼筋裝夾好了之后用于固定鐵棒。n特點(diǎn)是：裝夾原理比較簡(jiǎn)單，其零部件可以通過(guò)鑄造生產(chǎn)，而且對(duì)工作表面沒有什么要求 八夾具的設(shè)計(jì)八.夾具的設(shè)計(jì)九.機(jī)座的設(shè)計(jì) n本設(shè)計(jì)中，鋼筋拉直機(jī)的機(jī)座是鑄造而成的，其鑄造材料為KTZ60-3，本材料韌性較低，但強(qiáng)度大，硬度高，耐磨性好，且加工性良好 n把底座設(shè)計(jì)成一個(gè)整體，在放置鋼筋拉直機(jī)的地方澆一塊帶有鏍孔的水泥平地，然后用鑼釘直接把底座固定在水泥地上。底座上各個(gè)鏍紋孔的位置由各部件的尺寸來(lái)確定。敬請(qǐng)各位老師批評(píng)指正。敬請(qǐng)各位老師批評(píng)指正！謝 謝！Upper yield dynamic stress Time dependent plasticity Split Hopkinson Tension Bar steel. SHTB. by LsDyna code features. Time dependent plasticity has been developed to explain upper and lower yield behavior precise they are the material These instabilities are due to the upper and lower yield stress of the material and have been investigated by several authors. The upper yield stress has been explained with metallic structure parameters such as the dislocation density and velocity 7.In any case, material models involving microstructure parameters are not suitable for engineering purposes. Structural assessment requires relations between the upper and the lower yield value dynamic Hardings for upper The experimental study of the dynamic tensile behavior scale quenched and self-tempered rebar (1640 mm in diameter) is practically impossible, except maybe in the case of very facilities (i.e. the large facility of the Joint Research Centre, Ispra). The unfeasibility of this study has led us to proceed to the charac- terization of the material 13 and the numerical analysis of the dynamic behavior of the material with the present paper. The importance of the numerical simulation is definitely based on the possibility of studying real scale structural elements by means of numerical simulation of tests otherwise not feasible for Corresponding author. Tel.: +41 58 6666 377; fax: +41 58 6666 359. Materials and Design 57 (2014) 156167 Contents lists available and E-mail address: ezio.cadonisupsi.ch (E. Cadoni). In the analysis of the experimental results often it is possible to face difficulties in interpreting the results due to the presence of instabilities (i.e. presence of the first peak), which are not consid- ered in the usual material constitutive laws as JohnsonCook 6. Harding 12, who introduced a linear relation between upper yield stress enhancement and loading rate. proach is the most suitable engineering formulation found in the literature. 0261-3069/$ - see front matter C211 2013 Elsevier Ltd. All rights reserved. http:/dx.doi.org/10.1016/j.matdes.2013.12.049 ap- yield of full- large be properly based on correct experimental data. The difficulties connected to the complexity of the experimental tests can be appropriately understood and solved by numerical simulation. To better comprehend the experimental results it is essential to per- form the simulation of the testing machine 15 in order to obtain mutual verification. Engineering investigations of upper yield were made by Camp- ell and Harding 810. Campbell introduced the delay time and thermal activation theory by which the upper yield occurs after a characteristic time after the start of the loading stress due to the shear band thermal activation 11. The value of the upper yield stress was further investigated by 1. Introduction The understanding of the dynamic reinforcing steels is essential for the reinforced concrete structures when loading rate. These assessment studies means of finite element codes and values of the material resulting into a loading rate sensitivity. Finally, the material model has been used to reconstruct a virtual test over a rebar of 32 mm diameter, as an example of general procedure to cal- culate the global material response. C211 2013 Elsevier Ltd. All rights reserved. of concrete and assessment of existing are subjected to a high usually conducted by models have to with the engineering variables associated to the loading pulse, structure geometry, stress and strain tensor. Models that require the definition of material variables in terms of structure and dislo- cation density/velocity can be considered a phenomenological explanation of upper yield lacking of the complete parameteriza- tion of the stress strain curve including upper, lower yield and its time dependencies. Simulation High strain-rate have been discussed. The elastic and damping dispersion fonts have been introduced into the model to explain the real case variability in SHTB signals. Strain-rate dependent plasticity model has been used Numerical simulation of the high strain-rate and self-tempered reinforcing steel in tension Gianmario Riganti, Ezio Cadoni University of Applied Sciences of Southern Switzerland, CH-6952 Canobbio, Switzerland article info Article history: Received 27 September 2013 Accepted 19 December 2013 Available online 28 December 2013 Keywords: Reinforcing steel bar abstract This paper presents the numerical pered reinforcing steel in tension. imental facility (SHTB-Split interpretation of the experimental tion of the B450C reinforcing and output signals of the Materials journal homepage: www.else behavior of quenched analysis of the high strain-rate behavior of quenched and self-tem- The investigation has been performed properly simulating the exper- Hopkinson Tension Bar), highlighting criticism in the simulation and results. Finite element simulation has allowed a robust model valida- Parametrical finite element model has been used to rebuild the input Physical influence of damping in input wave and modeling strategies at ScienceDirect Design cisms of the SHTB. Section 3 reports the numerical model of the imen geometrical non linearity is included; (iii) the hypothesis of The input stress rising time is another significant characteristic for the material response and it is conditioned by the SHB set up (striker or pre-stressed bar), by the use of pulse shaper, and by other physical parameters out of direct control such as the facilities damping. The pulse shaper technique 17,18 is generally applied to smooth the input signal, in case of stress oscillations typical of stri- ker impact in SHB. By interposition of an intermediate deformable element between striker and input bar, a higher repeatability and a smooth input pulse is obtained. If short rising time is wanted, the input signal will be also affected by high frequency perturbations, especially in SHB configurations. High frequency perturbations widen the repeatability of signals and are subject to the elastic and damping dispersion phenomena. Usually in SHB a ratio length/diameter is adopted, which is always suitable to elastic and damping dispersion 17. The damping influences the input dispersion and its effect should be evaluated such as the elastic dispersion. Damping is not directly controlled in SHB. Different facilities could generate pulses with significant differences in rising time and perturbations. Referring to Fig. 1, three typologies of input signal could be generated: and Design 57 (2014) 156167 157 uniformity of stress/strain through the specimen is overcome; (iv) inertial effects are included; (v) multi material and small struc- ture specimen can be investigated; (vi) possible use of simulation for experimental facilities accuracy enhancement; and (vii) optimi- zation techniques and sensitivity analysis can be applied. 2.2. Effect of perturbations into the signal SHB relations contain several idealizations as the one-dimen- sional wave propagation through bars and specimen, the unifor- mity stress in the specimen, the absence of perturbations and inertial effects. It is well-known as a real input signal of SHTB dif- fers from the ideal trapezoidal pulse due to local perturbations when the real signals are used to obtain the material model param- eters, a series of errors are included due to simplified hypothesis and signal perturbations. The study of perturbed real signal effects to material model response is suitable to enhance the material model correctness. The influence of these factors on the material model response can be checked by means of finite element simulation. The input signal is mainly characterized by amplitude, duration, and rising time. These main characteristics can be adapted to gen- erate the wanted dynamic loading conditions into the specimen reaching the wanted rate during the experiment. experimental set-up. The numerical model results are presented in Section 4 both in terms of FEM and numerical analysis. These re- sults are discussed in Section 5. The model of the real size rebar is presented in Section 6. Finally, Section 7 summarizes the whole work. 2. Critical aspects of the Split Hopkinson Tension Bar 2.1. Signals analysis Signal analysis is usually adopted in the traditionaltheory of the Split Hopkinson Bar (SHB) to calculate stress, strain and strain-rate 17. Another methods consists in the combined use of the simula- tion and experimental test data. The validation of material model is then made by numerical and experimental gauge signal comparison. The advantages in combined use of simulation and experimen- tal data are: (i) accurate final material model verification; (ii) spec- technical or economic reasons. The present work completes, from a numerical point of view, what was started 13 with the experi- mental one, analyzing the various critical aspects regarding both experimental technique used and numerical simulation. The experimental technique used for the high strain rate mechanical characterization of B450C rebar was the Split Hopkin- son Tension bar (SHTB) and was described in 1315. In this par- ticular set-up the input pulse is not generated by a striker who hits the input bar, as in the traditional Split Hopkinson Pressure bar, but using the energy stored in a pre-stressed bar directly con- nected to the input bar 16. This set-up offers several advantages compared to the tradi- tional one, avoiding problems connected to the planar impact be- tween striker and input bar, to the pulse length, etc. The numerical analysis has been performed properly simulating the SHTB, highlighting criticism in the simulation and interpreta- tion of the experimental results. This paper is organized as follows. Section 2 presents the criti- G. Riganti, E. Cadoni/Materials The wanted input amplitude and duration are generated by tun- ing the physical parameters of the input pulse generation method (striker or pre-stressed bar). 1. Low loading rate, high rising time, no apparent wave dis- persion (curve a). 2. High loading rate, dispersion with hypercritical damping (curve b). 3. High loading rate, dispersion with sub critical damping (curve c). When a high loading rate is wanted to study loading rate dependent materials, input signal (b) or (c) has to be generated. The phenomena which generate the pulse perturbations can be grouped as: C15 Unlocking(SHTB)/contact(SHB) perturbations/combined use of shaping technique. C15 PochhammerChree wave dispersion 19,20. C15 Damping effects/damping dispersion. input pu lse time b c a Fig. 1. SHB input pulse in the case of: (a) pulse shape technique is used; (b) dispersion and over critical damping; and (c) dispersion and sub critical damping. The non-symmetric static stress due to gravity were several or- ders of magnitude lower than the average stress during the test, and with deformations lower than the geometrical imperfections. The gravity was not modeled but the static shear component at Teflon bearings correspondent to slipping condition is applied as concen- trated loads at bearings location. Static pre-loading acted along the axis direction. The axial-symmetric model was suitable to study the SHTB cause of geometrical and loading conditions. The axial-symmetric model allowed the inclusion of dispersion, damping, pre-loading and axial-stress wave propagation. Axial-symmetric volume weighted elements have been used due to efficiency advantages in computation while ensuring correct solution interpolation with the adequate mesh size. The numerical efficiency of the model was required for multiple runs in parametrical analysis. The element size in radial and axis direction was 2.5 mm. The size of the element was equal to the experimental gauge length to average the stress time history as the real test case. The variation of stresses in radial direction was of the second order influence with respect to the solution of wave propagation in axis direction for SHTB experimental purposes 20. Two ele- ments in radial direction allowed a correct interpolation of the solution. The specimen mesh size was 0.2 mm in axis direction, 0.275 mm in radial direction. The specimen was modeled using C15 Boundary conditions (friction and contact on holders, clamping, etc.). C15 Geometry/alignment errors. C15 Other unknown effects (bar homogeneity and isotropy). During the experiment, all the listed causes act simultaneously. The global effect on the input loading could be easily measured by input/output signal recording. Elastic dispersion occurs by a frequency dependent wave speed propagation. In SHB, the short distance between input/output gauge and specimen is suitable to affect elastic wave to dispersion. Gauge signal correction techniques can be applied to obtain data at specimen location. Those techniques are energy conservative and does not represent the dispersion due to damping. This hypothesis is usually correct because of distance between gauge and specimen is short. Analytical technique cannot be applied for signal correc- tion affected by dispersion damping. A long length of the input bar is suitable to stabilize signal per- turbations, but the input length increases the elastic dispersion ef- fects resulting in smaller loading rate. The influence of damping, dispersion and rising time will be numerically investigated before applying the simulation to the experimental data. 3. Numerical model of the experimental set-up Explicit time integration has been applied to simulate the dy- namic test with rate-dependent material modeling using LsDyna code. The SHTB geometry 1315 is basically axial-symmetric and the non-symmetry is a result of the small geometrical and align- ment imperfections. The axial length of the whole facilities was 15 m consisting of pre-loading bar (6 m), input bar (3 m), and out- put bar (6 m). The bar diameter was 10 mm and the estimated alignment error was 0.1 mm. Bars were horizontally placed and vertical holders consist of Teflon bushing supporting the bars each 500 mm. 158 G. Riganti, E. Cadoni/Materials coincident nodes with bar at outer tread diameter. The axial-symmetric solution excluded non symmetrical geo- metrical perturbations. A full 3D analysis could include the align- ment perturbation and contacts in SHTB holders, with a computation cost increase of two orders of magnitude. Pre-loading was represented by initial stress conditions of pre- loading bar elements. A uniform axis direction stress was assigned. This solution is highly efficient and neglects the pre-loading energy stored closer to the jack joint, which is too far from the specimen side to afflict the input wave shape. Fixed boundary conditions in axis direction were assigned to the jack location. Nodes on axis were automatically constrained in radial direction. Locking was modeled with an instantaneous release free of per- turbation. At the start of the analysis, the pre-stressed elements of the tension bar were free to deform and explicit calculation starts. The absence of unlocking perturbation allowed to focus the influ- ence of material model and dispersion. A full restart technique was applied to increase calculation effi- ciency, adding specimen elements and out bar elements before the arrival of the input wave. Total number of nodes/elements was 19,285/28,955. Calculation time is 15 min at strain-rate 250 s C01 . 3.1. Damping and numerical model Damping modifies propagation of waves with a frequency dependent function. Damping study is necessary to the following material response verification. The SHTB damping sources were grouped in four physical sources: (i) Material damping: constitutive material of SHTB bar had its own damping parameter. The damping parameter for bars was low compared to the damping induced by other SHTB physical sources, as confirmed by simulation results. (ii) Friction: the static bar weight was distributed along the holders and acted in radial direction. Once the input wave was released, the moving in axial direction through the holder was possible because the axial pre-loading force is greater than the weight multiplied by the static friction coef- ficient. (pre-loading 10 4 N, input and pre-loading bar 50 N weight each, estimated static friction force 5 N). During the wave propagation, the bar hits the holder moving through the Teflon gasket gap several times. The resultant dynamic friction forces are highly dependent on the experimental set up by alignment and bars pre-deformation. (iii) Viscous interface: The bar was in atmospheric air and the high frequency vibration of the bar release energy was in radial direction. (iv) Dynamic contacts: The previously described bar/holder impacted release energy at holder location with a phenom- ena dependent on gap distance, materials, pre-deformation and imperfections. The wave propagation through holders dissipate energy. Damping must be introduced into the numerical model for cor- rect input signal generation. There are two different approaches to model damping in SHTB simulation: (a) The phenomenological approach consists in introducing the single physical effect by modeling the interaction rules with their driven parameters, e.g. contact, vibration, imperfection, influence. This method requires the maximum effort in mod- eling, and is time consuming with regards to the operator and calculator. (b) Model the global effect of damping by assigning a damping Design 57 (2014) 156167 coefficient which converges the numerical results to the experimental ones. A parametric analysis is necessary to identify the correct damping coefficient. As the global result of damping causes is easily detectable by input gauge signal, this method offers the best efficiency in modeling and results. In the present work, the (b) method has been applied. Damping was modeled by using LsDyna keyword C3 damping_global. Damping value was anisotropic in the axial and radial directions, in accor- dance with the two different damping sources 21. Iterative solu- tion of the numerical model compared to the experimental input wave will allow to identify the optimal numerical values. To model the axial damping due to friction of bar over Teflon gaskets, a series of damper elements with damping coefficient pro- portional to the estimated axial friction forces has been defined. These elements act in axial direction. 4. Numerical model results 4.1. FEM analysis The FEM analysis has been performed to verify the dependency imental input pulse and the numerical one has been depicted, 4.1.2. Dispersion and material model verification The input/output gauge signals were generated by interaction between SHTB and specimen. The material model has been tested by fitting the numerical output to the experimental one. If differ- ences are introduced in the numerical stress wave, the fitting of numerical output gauge to real test case by material model param- eters identification will include errors in parameters to compen- sate for input differences. The error propagation is numerically investigated. Material verification was performed by studying a strain-rate dependent material subject to a damped and un-damped input wave. The test material was the B450C type C 13, modeled as ex- plained in the next section. The input wave represents the maximal differences in input stress caused by dispersion error generation using non-damped finite element model. The dispersion oscillations according to the acoustic impedance 1 10 -3 high_damp no_damp experimental 0 1380 1390 1400 1410 1420 1430 1440 time s Fig. 3. Input pulse amplitude and rising time for two pre-loading conditions. 0 200 10 -6 400 10 -6 600 10 -6 800 10 -6 1 10 -3 1300 1400 1500 1600 1700 1800 optimized damp experimental strain - time s Fig. 4. Comparison between experimental and numerical input pulse. G. Riganti, E. Cadoni/Materials and 0 2 10 -4 4 10 -4 6 10 -4 8 10 -4 1380 1390 1400 1410 1420 1430 1440 1450 strain - using the definitive dampi