機(ji)械振(zhen)(zhen)動(dong)(dong)(dong)是物體(ti)(或物體(ti)的一部分(fen))在平(ping)衡(heng)位置(物體(ti)靜止(zhi)時的位置)附近作的往(wang)復運(yun)動(dong)(dong)(dong)。可(ke)分(fen)為(wei) 自由振(zhen)(zhen)動(dong)(dong)(dong)、受迫振(zhen)(zhen)動(dong)(dong)(dong)。又可(ke)分(fen)為(wei)無阻尼振(zhen)(zhen)動(dong)(dong)(dong)與 阻尼振(zhen)(zhen)動(dong)(dong)(dong)。常見的簡諧運(yun)動(dong)(dong)(dong)有彈簧振(zhen)(zhen)子模型(xing)、單(dan)擺模型(xing)等。振(zhen)(zhen)動(dong)(dong)(dong)在機(ji)械行(xing)業(ye)中的應用

   振(zhen)動在(zai)機械中(zhong)的(de)應用非(fei)常普遍,例如在(zai)振(zhen)動篩(shai)分行業(ye)中(zhong)基本原(yuan)理(li)系(xi)借電機軸上下端所安裝的(de)重錘(chui)(不(bu)平(ping)蘅重錘(chui)),將電機的(de)旋轉運動轉變(bian)為水(shui)平(ping)、垂(chui)直、傾斜的(de)三(san)次元運動,再把這個運動傳達給篩(shai)面。若改變(bian)上下部的(de)重錘(chui)的(de)相位角可改變(bian)原(yuan)料(liao)的(de)行進方向(xiang)。

   拋(pao)體(ti)(ti)運(yun)(yun)動則可以分解為:正交的(de)一(yi)個勻(yun)速(su)直(zhi)(zhi)線運(yun)(yun)動和另一(yi)個勻(yun)變(bian)速(su)直(zhi)(zhi)線運(yun)(yun)動,所以,拋(pao)體(ti)(ti)運(yun)(yun)動比勻(yun)變(bian)速(su)直(zhi)(zhi)線運(yun)(yun)動復雜得(de)多。

   在勻速圓周(zhou)運(yun)動(dong)(dong)作正交分解[1]的(de)(de)過程中,原來大小不變(bian)的(de)(de)向心(xin)力(li),變(bian)成大小和方向都作周(zhou)期性變(bian)化的(de)(de)回復(fu)(fu)力(li)。簡諧(xie)振(zhen)動(dong)(dong)已經(jing)夠(gou)復(fu)(fu)雜(za)了。所(suo)以,振(zhen)動(dong)(dong)就定量研究到(dao)簡諧(xie)振(zhen)動(dong)(dong)為止(zhi)。然而通常我們(men)遇到(dao)的(de)(de)振(zhen)動(dong)(dong)的(de)(de)微觀(guan)情況,都要比簡諧(xie)振(zhen)動(dong)(dong)復(fu)(fu)雜(za)得多。所(suo)以,研究簡諧(xie)振(zhen)動(dong)(dong)過渡到(dao)研究振(zhen)動(dong)(dong)、熱振(zhen)動(dong)(dong)等,需要洞察力(li)、想象力(li)和抽象思維、邏輯推(tui)理等能(neng)力(li)。

   參照(zhao)物(wu)本來就應該是(shi)(shi)在研究(jiu)(jiu)過程(cheng)中(zhong)保持靜止(或(huo)假定為(wei)靜止)的(de)(de)點(dian),我(wo)們的(de)(de)物(wu)理思(si)路,就是(shi)(shi)"從確定的(de)(de)量(liang)、不(bu)變(bian)(bian)的(de)(de)量(liang)出發進(jin)行研究(jiu)(jiu)"。確定的(de)(de)量(liang)和(he)不(bu)變(bian)(bian)的(de)(de)量(liang)有本質的(de)(de)區(qu)別(bie),在對(dui)勻變(bian)(bian)速直線運動(dong)和(he)拋(pao)體運動(dong)進(jin)行研究(jiu)(jiu)時,基準點(dian)選擇(ze)在運動(dong)的(de)(de)始(shi)點(dian)。這是(shi)(shi)確定的(de)(de)量(liang),卻不(bu)一(yi)定是(shi)(shi)不(bu)變(bian)(bian)的(de)(de)量(liang)。特別(bie)在我(wo)們進(jin)行分段研究(jiu)(jiu)時,每一(yi)階(jie)段的(de)(de)終點(dian),就是(shi)(shi)下一(yi)階(jie)段的(de)(de)始(shi)點(dian)。

   我們選(xuan)擇運(yun)動(dong)的(de)(de)(de)(de)始點為(wei)(wei)基(ji)準(zhun)點,可以簡(jian)化(hua)研究(jiu)(jiu)(jiu)過程(cheng),這是服從于物(wu)(wu)理(li)研究(jiu)(jiu)(jiu)的(de)(de)(de)(de)"化(hua)繁(fan)為(wei)(wei)簡(jian)"的(de)(de)(de)(de)原(yuan)則,因(yin)此(ci),不(bu)惜在(zai)不(bu)同的(de)(de)(de)(de)研究(jiu)(jiu)(jiu)階段,選(xuan)擇不(bu)同的(de)(de)(de)(de)基(ji)準(zhun)點。在(zai)研究(jiu)(jiu)(jiu)勻速(su)圓(yuan)周運(yun)動(dong)和簡(jian)諧(xie)振動(dong)時,由(you)于宏(hong)觀(guan)(guan)上(shang)的(de)(de)(de)(de)周期性和微(wei)觀(guan)(guan)上(shang)的(de)(de)(de)(de)拓樸(pu)性,問題很復(fu)雜,所以不(bu)能(neng)選(xuan)運(yun)動(dong)的(de)(de)(de)(de)始點,作基(ji)準(zhun)點進行研究(jiu)(jiu)(jiu),而(er)要(yao)選(xuan)擇確定而(er)且不(bu)變(bian)的(de)(de)(de)(de)圓(yuan)心或者(zhe)平衡位置,作基(ji)準(zhun)點進行研究(jiu)(jiu)(jiu),也是服從于物(wu)(wu)理(li)研究(jiu)(jiu)(jiu)的(de)(de)(de)(de)"化(hua)繁(fan)為(wei)(wei)簡(jian)"的(de)(de)(de)(de)原(yuan)則。      

   廣義上的(de)振動(dong)(dong)(dong)從(cong)廣義上說振動(dong)(dong)(dong)是指(zhi)描述系(xi)(xi)(xi)統(tong)(tong)(tong)狀態的(de)參量(如(ru)位(wei)(wei)(wei)移、電壓)在其基準值上下(xia)交替變(bian)化的(de)過程。狹義的(de)指(zhi)機械振動(dong)(dong)(dong),即力學系(xi)(xi)(xi)統(tong)(tong)(tong)中的(de)振動(dong)(dong)(dong)。電磁振動(dong)(dong)(dong)習慣上稱為(wei)振蕩(dang)。力學系(xi)(xi)(xi)統(tong)(tong)(tong)能維持振動(dong)(dong)(dong),必須具有彈(dan)性(xing)和(he)慣性(xing)。由于(yu)彈(dan)性(xing),系(xi)(xi)(xi)統(tong)(tong)(tong)偏離其平(ping)衡(heng)(heng)位(wei)(wei)(wei)置(zhi)時,會產生回(hui)(hui)復力,促使系(xi)(xi)(xi)統(tong)(tong)(tong)返回(hui)(hui)原來位(wei)(wei)(wei)置(zhi);由于(yu)慣性(xing),系(xi)(xi)(xi)統(tong)(tong)(tong)在返回(hui)(hui)平(ping)衡(heng)(heng)位(wei)(wei)(wei)置(zhi)的(de)過程中積累了動(dong)(dong)(dong)能,從(cong)而使系(xi)(xi)(xi)統(tong)(tong)(tong)越(yue)過平(ping)衡(heng)(heng)位(wei)(wei)(wei)置(zhi)向另一側運動(dong)(dong)(dong)。正是由于(yu)彈(dan)性(xing)和(he)慣性(xing)的(de)相互影(ying)響,才造成系(xi)(xi)(xi)統(tong)(tong)(tong)的(de)振動(dong)(dong)(dong)。

       按系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)運動(dong)(dong)(dong)(dong)(dong)自(zi)(zi)由(you)度分,有(you)單(dan)自(zi)(zi)由(you)度系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)(如鐘擺(bai)的(de)(de)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong))和多(duo)自(zi)(zi)由(you)度系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)。有(you)限(xian)多(duo)自(zi)(zi)由(you)度系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)與(yu)離散系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)相對應(ying)(ying),其(qi)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)由(you)常微(wei)分方(fang)程(cheng)(cheng)描述(shu);無(wu)限(xian)多(duo)自(zi)(zi)由(you)度系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)與(yu)連續系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)(如桿、梁、板、殼(ke)等)相對應(ying)(ying),其(qi)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)由(you)偏微(wei)分方(fang)程(cheng)(cheng)描述(shu)。方(fang)程(cheng)(cheng)中不(bu)顯含(han)(han)時(shi)(shi)間(jian)的(de)(de)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)稱自(zi)(zi)治(zhi)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong);顯含(han)(han)時(shi)(shi)間(jian)的(de)(de)稱非(fei)自(zi)(zi)治(zhi)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)。按系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)受力情況分,有(you)自(zi)(zi)由(you)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)、衰減振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)和受迫振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)。按彈性(xing)力和阻(zu)尼(ni)力性(xing)質分,有(you)線性(xing)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)和非(fei)線性(xing)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)。振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)又可(ke)分為確定(ding)性(xing)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)和隨(sui)機(ji)振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong),后(hou)者無(wu)確定(ding)性(xing)規律,如車輛(liang)行進中的(de)(de)顛簸(bo)。振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)是(shi)自(zi)(zi)然界和工程(cheng)(cheng)界常見(jian)的(de)(de)現(xian)象。振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)的(de)(de)消極方(fang)面(mian)是(shi):影響儀器設備(bei)功能,降(jiang)低機(ji)械設備(bei)的(de)(de)工作(zuo)精度,加劇構件磨(mo)(mo)損,甚(shen)至引起結構疲勞破壞;振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)的(de)(de)積極方(fang)面(mian)是(shi):有(you)許多(duo)需(xu)利(li)用振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)的(de)(de)設備(bei)和工藝(如振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)傳(chuan)輸、振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)研磨(mo)(mo)、振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)沉樁等)。振(zhen)(zhen)(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)分析的(de)(de)基(ji)本任務(wu)是(shi)討論系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)的(de)(de)激(ji)勵(即輸入,指(zhi)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)的(de)(de)外來擾動(dong)(dong)(dong)(dong)(dong),又稱干(gan)擾)、響應(ying)(ying)(即輸出,指(zhi)系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)受激(ji)勵后(hou)的(de)(de)反(fan)應(ying)(ying))和系(xi)(xi)統(tong)(tong)(tong)(tong)(tong)動(dong)(dong)(dong)(dong)(dong)態(tai)特性(xing)(或(huo)物理參數)三者之(zhi)間(jian)的(de)(de)關系(xi)(xi)。