機械振(zhen)動(dong)(dong)是物(wu)體(或物(wu)體的(de)一部分)在平衡位置(zhi)(物(wu)體靜止時(shi)的(de)位置(zhi))附近(jin)作(zuo)的(de)往復運(yun)動(dong)(dong)。可(ke)(ke)分為 自由振(zhen)動(dong)(dong)、受迫振(zhen)動(dong)(dong)。又(you)可(ke)(ke)分為無(wu)阻尼(ni)(ni)振(zhen)動(dong)(dong)與 阻尼(ni)(ni)振(zhen)動(dong)(dong)。常(chang)見的(de)簡(jian)諧運(yun)動(dong)(dong)有彈簧振(zhen)子模型、單擺模型等。振(zhen)動(dong)(dong)在機械行(xing)業中的(de)應用

   振動(dong)在機(ji)械中(zhong)的應用非常普遍(bian),例如(ru)在振動(dong)篩分行業(ye)中(zhong)基(ji)本(ben)原理(li)系(xi)借電(dian)機(ji)軸(zhou)上下端所安裝(zhuang)的重錘(不平(ping)蘅重錘),將(jiang)電(dian)機(ji)的旋轉運(yun)動(dong)轉變為水平(ping)、垂直(zhi)、傾(qing)斜的三次元(yuan)運(yun)動(dong),再把這個運(yun)動(dong)傳達給篩面。若改變上下部(bu)的重錘的相(xiang)位角可改變原料的行進方向。

   拋體(ti)運(yun)動則可以分解為:正交(jiao)的(de)一個(ge)(ge)勻(yun)(yun)速直(zhi)線(xian)運(yun)動和另一個(ge)(ge)勻(yun)(yun)變(bian)速直(zhi)線(xian)運(yun)動,所(suo)以,拋體(ti)運(yun)動比勻(yun)(yun)變(bian)速直(zhi)線(xian)運(yun)動復雜得(de)多。

   在勻速(su)圓周運動(dong)(dong)作正交分解[1]的(de)過程(cheng)中,原來(lai)大(da)小(xiao)不變(bian)的(de)向心力,變(bian)成大(da)小(xiao)和方向都(dou)作周期性變(bian)化的(de)回復(fu)力。簡諧(xie)(xie)振(zhen)(zhen)動(dong)(dong)已經夠復(fu)雜了(le)。所以(yi),振(zhen)(zhen)動(dong)(dong)就定(ding)量研(yan)究到簡諧(xie)(xie)振(zhen)(zhen)動(dong)(dong)為止。然而通常我們遇到的(de)振(zhen)(zhen)動(dong)(dong)的(de)微(wei)觀情(qing)況,都(dou)要比簡諧(xie)(xie)振(zhen)(zhen)動(dong)(dong)復(fu)雜得多。所以(yi),研(yan)究簡諧(xie)(xie)振(zhen)(zhen)動(dong)(dong)過渡到研(yan)究振(zhen)(zhen)動(dong)(dong)、熱振(zhen)(zhen)動(dong)(dong)等(deng),需要洞察力、想象力和抽象思維(wei)、邏輯推(tui)理等(deng)能力。

   參(can)照物本(ben)來就(jiu)應(ying)該是(shi)在研究過程中保持(chi)靜(jing)止(或假定(ding)為靜(jing)止)的點(dian),我們(men)的物理思路,就(jiu)是(shi)"從(cong)確定(ding)的量、不變(bian)的量出發進行(xing)研究"。確定(ding)的量和不變(bian)的量有(you)本(ben)質的區別,在對(dui)勻(yun)變(bian)速直線運(yun)動(dong)和拋體(ti)運(yun)動(dong)進行(xing)研究時,基準點(dian)選擇在運(yun)動(dong)的始點(dian)。這是(shi)確定(ding)的量,卻不一(yi)定(ding)是(shi)不變(bian)的量。特別在我們(men)進行(xing)分段研究時,每一(yi)階(jie)(jie)段的終點(dian),就(jiu)是(shi)下一(yi)階(jie)(jie)段的始點(dian)。

   我們選擇(ze)運(yun)(yun)動的(de)(de)(de)始點(dian)(dian)為基(ji)(ji)準(zhun)(zhun)點(dian)(dian),可以(yi)簡化(hua)研(yan)(yan)究(jiu)(jiu)過程,這是(shi)服(fu)(fu)從(cong)于(yu)物理研(yan)(yan)究(jiu)(jiu)的(de)(de)(de)"化(hua)繁為簡"的(de)(de)(de)原則,因此(ci),不(bu)(bu)惜在不(bu)(bu)同的(de)(de)(de)研(yan)(yan)究(jiu)(jiu)階段,選擇(ze)不(bu)(bu)同的(de)(de)(de)基(ji)(ji)準(zhun)(zhun)點(dian)(dian)。在研(yan)(yan)究(jiu)(jiu)勻速(su)圓周(zhou)運(yun)(yun)動和簡諧振(zhen)動時,由于(yu)宏觀上的(de)(de)(de)周(zhou)期性(xing)(xing)和微觀上的(de)(de)(de)拓樸(pu)性(xing)(xing),問(wen)題很復(fu)雜,所以(yi)不(bu)(bu)能(neng)選運(yun)(yun)動的(de)(de)(de)始點(dian)(dian),作(zuo)基(ji)(ji)準(zhun)(zhun)點(dian)(dian)進行(xing)(xing)研(yan)(yan)究(jiu)(jiu),而要(yao)選擇(ze)確定而且不(bu)(bu)變的(de)(de)(de)圓心或者平(ping)衡位置,作(zuo)基(ji)(ji)準(zhun)(zhun)點(dian)(dian)進行(xing)(xing)研(yan)(yan)究(jiu)(jiu),也是(shi)服(fu)(fu)從(cong)于(yu)物理研(yan)(yan)究(jiu)(jiu)的(de)(de)(de)"化(hua)繁為簡"的(de)(de)(de)原則。      

   廣(guang)義上(shang)(shang)(shang)的(de)(de)(de)振(zhen)(zhen)動(dong)(dong)(dong)從(cong)廣(guang)義上(shang)(shang)(shang)說振(zhen)(zhen)動(dong)(dong)(dong)是指描(miao)述系統(tong)(tong)狀(zhuang)態的(de)(de)(de)參量(如位(wei)移(yi)、電(dian)壓)在(zai)其基準值上(shang)(shang)(shang)下交替變化的(de)(de)(de)過程(cheng)。狹義的(de)(de)(de)指機械振(zhen)(zhen)動(dong)(dong)(dong),即力(li)學(xue)系統(tong)(tong)中(zhong)的(de)(de)(de)振(zhen)(zhen)動(dong)(dong)(dong)。電(dian)磁振(zhen)(zhen)動(dong)(dong)(dong)習慣(guan)(guan)上(shang)(shang)(shang)稱(cheng)為振(zhen)(zhen)蕩。力(li)學(xue)系統(tong)(tong)能維(wei)持振(zhen)(zhen)動(dong)(dong)(dong),必須(xu)具有彈(dan)性(xing)和(he)慣(guan)(guan)性(xing)。由(you)于(yu)彈(dan)性(xing),系統(tong)(tong)偏離其平(ping)(ping)衡位(wei)置(zhi)時(shi),會產生回復力(li),促使(shi)系統(tong)(tong)返(fan)回原來位(wei)置(zhi);由(you)于(yu)慣(guan)(guan)性(xing),系統(tong)(tong)在(zai)返(fan)回平(ping)(ping)衡位(wei)置(zhi)的(de)(de)(de)過程(cheng)中(zhong)積(ji)累(lei)了動(dong)(dong)(dong)能,從(cong)而(er)使(shi)系統(tong)(tong)越(yue)過平(ping)(ping)衡位(wei)置(zhi)向另一側運動(dong)(dong)(dong)。正(zheng)是由(you)于(yu)彈(dan)性(xing)和(he)慣(guan)(guan)性(xing)的(de)(de)(de)相互影響,才造成(cheng)系統(tong)(tong)的(de)(de)(de)振(zhen)(zhen)動(dong)(dong)(dong)。

       按(an)(an)系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)運動(dong)(dong)(dong)(dong)(dong)自(zi)(zi)由(you)(you)度分(fen)(fen)(fen),有單自(zi)(zi)由(you)(you)度系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)(如(ru)鐘(zhong)擺(bai)的(de)(de)(de)振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong))和(he)(he)多(duo)(duo)自(zi)(zi)由(you)(you)度系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)。有限多(duo)(duo)自(zi)(zi)由(you)(you)度系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)與(yu)離散系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)相(xiang)對(dui)應,其振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)由(you)(you)常(chang)微分(fen)(fen)(fen)方程(cheng)(cheng)(cheng)描(miao)述;無(wu)限多(duo)(duo)自(zi)(zi)由(you)(you)度系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)與(yu)連(lian)續系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)(如(ru)桿、梁、板、殼等)相(xiang)對(dui)應,其振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)由(you)(you)偏微分(fen)(fen)(fen)方程(cheng)(cheng)(cheng)描(miao)述。方程(cheng)(cheng)(cheng)中(zhong)不(bu)顯含(han)時(shi)間(jian)的(de)(de)(de)系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)稱(cheng)自(zi)(zi)治系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong);顯含(han)時(shi)間(jian)的(de)(de)(de)稱(cheng)非(fei)自(zi)(zi)治系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)。按(an)(an)系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)受力(li)情(qing)況分(fen)(fen)(fen),有自(zi)(zi)由(you)(you)振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)、衰減振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)和(he)(he)受迫振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)。按(an)(an)彈性(xing)(xing)力(li)和(he)(he)阻尼(ni)力(li)性(xing)(xing)質(zhi)分(fen)(fen)(fen),有線性(xing)(xing)振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)和(he)(he)非(fei)線性(xing)(xing)振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)。振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)又可分(fen)(fen)(fen)為(wei)確定(ding)性(xing)(xing)振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)和(he)(he)隨機振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong),后者無(wu)確定(ding)性(xing)(xing)規律(lv),如(ru)車輛行進中(zhong)的(de)(de)(de)顛簸(bo)。振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)是(shi)自(zi)(zi)然界(jie)和(he)(he)工(gong)程(cheng)(cheng)(cheng)界(jie)常(chang)見(jian)的(de)(de)(de)現象。振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)的(de)(de)(de)消極方面是(shi):影響儀器設備功能,降低(di)機械設備的(de)(de)(de)工(gong)作精(jing)度,加劇構(gou)件磨(mo)損,甚至引起結構(gou)疲勞破壞(huai);振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)的(de)(de)(de)積極方面是(shi):有許多(duo)(duo)需(xu)利用振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)的(de)(de)(de)設備和(he)(he)工(gong)藝(如(ru)振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)傳輸、振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)研(yan)磨(mo)、振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)沉樁等)。振(zhen)(zhen)(zhen)動(dong)(dong)(dong)(dong)(dong)分(fen)(fen)(fen)析(xi)的(de)(de)(de)基(ji)本任務是(shi)討論系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)的(de)(de)(de)激勵(li)(即(ji)輸入,指系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)的(de)(de)(de)外來擾動(dong)(dong)(dong)(dong)(dong),又稱(cheng)干擾)、響應(即(ji)輸出(chu),指系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)受激勵(li)后的(de)(de)(de)反(fan)應)和(he)(he)系(xi)(xi)(xi)(xi)(xi)統(tong)(tong)(tong)動(dong)(dong)(dong)(dong)(dong)態特性(xing)(xing)(或(huo)物(wu)理參數)三(san)者之(zhi)間(jian)的(de)(de)(de)關系(xi)(xi)(xi)(xi)(xi)。