李文達(dá) 杜敬濤 楊鐵軍 劉志剛
摘要: 建立了彈性約束邊界下旋轉(zhuǎn)薄壁圓柱殼結(jié)構(gòu)自由振動(dòng)行波特性分析模型,通過(guò)在邊界引入四種約束彈簧,任意邊界條件可以通過(guò)設(shè)置剛度系數(shù)而統(tǒng)一得到?;赟anders薄殼理論對(duì)旋轉(zhuǎn)薄壁圓柱殼自由振動(dòng)的振動(dòng)能量表達(dá)式進(jìn)行了推導(dǎo),三個(gè)方向的振動(dòng)位移場(chǎng)通過(guò)一種改進(jìn)傅立葉級(jí)數(shù)進(jìn)行展開(kāi),帶入能量表達(dá)式并利用RayleighRitz法進(jìn)行變換推導(dǎo),得到旋轉(zhuǎn)薄壁圓柱殼自由振動(dòng)的系統(tǒng)特征方程。利用MATLAB編程計(jì)算,得到行波振動(dòng)固有頻率,通過(guò)與現(xiàn)有文獻(xiàn)中其他方法比較,驗(yàn)證了本文方法的正確性,隨后采用不同幾何參數(shù)、不同邊界條件、不同約束彈簧剛度的算例對(duì)振動(dòng)特性的影響進(jìn)行分析, 揭示了轉(zhuǎn)速、長(zhǎng)徑比、厚徑比等幾何條件以及邊界約束彈簧剛度對(duì)旋轉(zhuǎn)薄壁圓柱殼自由振動(dòng)行波特性的影響規(guī)律。關(guān)鍵詞: 旋轉(zhuǎn)薄壁圓柱殼; 自由振動(dòng); 行波特性; 邊界約束; 固有頻率
中圖分類號(hào): O327 文獻(xiàn)標(biāo)志碼: A文章編號(hào): 1004-4523(2016)03-0452-13
DOI:10.16385/j.cnki.issn.10044523.2016.03.011
引言
圓柱殼作為一種基本的結(jié)構(gòu)單元,廣泛應(yīng)用于各個(gè)工程領(lǐng)域,如航空航天、動(dòng)力工程及船舶與海洋工程等,圓柱殼的振動(dòng)特性及動(dòng)力學(xué)響應(yīng)受到國(guó)內(nèi)外學(xué)者的廣泛關(guān)注,然而,現(xiàn)有的研究主要針對(duì)非旋轉(zhuǎn)情況,對(duì)于旋轉(zhuǎn)圓柱殼結(jié)構(gòu)的研究尚不充分。
關(guān)于旋轉(zhuǎn)圓柱殼振動(dòng)特性的研究最早可追溯到1890年,Bryan[1]首次對(duì)旋轉(zhuǎn)圓柱殼的固有特性進(jìn)行了研究,并提出行波振動(dòng)現(xiàn)象。這一發(fā)現(xiàn)引起了研究者的極大興趣,在此基礎(chǔ)上,后續(xù)學(xué)者通過(guò)研究了解到圓柱殼體變形速度方向與殼體轉(zhuǎn)動(dòng)角速度方向會(huì)導(dǎo)致科氏力(Coriolis Force)。隨后,Taranto和Lessen[2]研究了科氏力對(duì)旋轉(zhuǎn)圓柱殼振動(dòng)特性的影響,得出了旋轉(zhuǎn)圓柱殼體振動(dòng)分析中必須考慮科氏力影響的結(jié)論。 Srinivasan和Lauterbach[3]研究了無(wú)限長(zhǎng)旋轉(zhuǎn)薄壁圓柱殼的固有特性, 討論了科氏力和離心力對(duì)前后行波波速的影響規(guī)律。Zohar和 Aboudi[4],Wang和Chen[5]則針對(duì)有限長(zhǎng)旋轉(zhuǎn)圓柱殼進(jìn)行了相應(yīng)的動(dòng)力學(xué)研究。近幾年,劉彥琦等人[67]基于Love殼體理論研究了不同邊界和幾何參數(shù)對(duì)旋轉(zhuǎn)薄壁圓柱殼振動(dòng)特性的影響,然而并未對(duì)前、后行波特性進(jìn)行分析。韓清凱等[8]對(duì)旋轉(zhuǎn)薄壁圓柱殼的高節(jié)徑振動(dòng)特性以及篦齒結(jié)構(gòu)的影響進(jìn)行了分析。項(xiàng)松等[9]則基于Love理論給出了旋轉(zhuǎn)功能梯度圓柱殼的固有頻率計(jì)算方法。項(xiàng)爽[10]對(duì)旋轉(zhuǎn)功能梯度材料圓柱殼的振動(dòng)特性進(jìn)行了研究。
目前,國(guó)內(nèi)外已有大量關(guān)于旋轉(zhuǎn)圓柱殼動(dòng)力學(xué)特性的研究文獻(xiàn),然而對(duì)具有除簡(jiǎn)支簡(jiǎn)支邊界以外其他復(fù)雜邊界條件的旋轉(zhuǎn)薄壁圓柱殼動(dòng)力學(xué)特性的研究還比較少見(jiàn)。對(duì)于不同邊界條件下的旋轉(zhuǎn)圓柱殼,可以采用不同的分析方法對(duì)其振動(dòng)特性進(jìn)行分析。Saito和Endo[11]應(yīng)用三角函數(shù)和Galerkin法求得了兩端固支條件下的旋轉(zhuǎn)圓柱殼振動(dòng)固有頻率;Penzes和 Kraus[12]利用復(fù)指數(shù)函數(shù)研究了具有不同邊界條件的旋轉(zhuǎn)圓柱殼的固有特性;Lam和 Loy[1314]對(duì)比了分別采用Donnell,F(xiàn)lügge,Love,Sanders四種殼體理論的兩端簡(jiǎn)支邊界條件下旋轉(zhuǎn)圓柱殼的前、后行波特性,并將廣義微分求積法(Generalized Differential Quadrature Method)引入到旋轉(zhuǎn)圓柱殼的振動(dòng)分析中來(lái),在考慮離心力、科氏力和初始張力的情況下分析了轉(zhuǎn)速、厚徑比等因素對(duì)兩端簡(jiǎn)支(SS)、兩端固支(CC)、一端固支一端簡(jiǎn)支(CS)、一端固支一端自由(CF)四種邊界條件下的圓柱殼固有頻率的影響。Li等[15]綜合分析了旋轉(zhuǎn)薄壁、厚壁圓柱殼、圓錐殼的振動(dòng)固有特性。
第3期李文達(dá),等: 邊界條件對(duì)旋轉(zhuǎn)薄壁圓柱殼結(jié)構(gòu)自由振動(dòng)行波特性的影響分析振 動(dòng) 工 程 學(xué) 報(bào)第29卷除上述經(jīng)典的解析方法外,傳遞矩陣法和有限元法在殼體動(dòng)力學(xué)分析中也大量應(yīng)用。洪杰等[1617]通過(guò)傳遞矩陣法離散求解了轉(zhuǎn)動(dòng)薄壁殼體的行波振動(dòng)頻率,并采用瞬態(tài)激振方法對(duì)殼體進(jìn)行了振動(dòng)測(cè)試,驗(yàn)證了理論分析結(jié)果。曹航和朱梓根[18]通過(guò)擴(kuò)展商用有限元軟件的分析功能,實(shí)現(xiàn)了對(duì)轉(zhuǎn)動(dòng)殼體行波振動(dòng)的分析。Chen和Zhao[19]等人采用有限元法對(duì)高速旋轉(zhuǎn)圓柱殼的固有特性進(jìn)行了研究。Padovan[20]利用有限元法研究了旋轉(zhuǎn)圓柱殼的行波振動(dòng)特性。Guo,Zheng和Chu[21]利用有限元法分析了旋轉(zhuǎn)圓柱殼的振動(dòng)特性, 比較了大撓度變形、邊界條件和旋轉(zhuǎn)速度對(duì)旋轉(zhuǎn)圓柱殼的固有頻率和模態(tài)的影響。
本文首次采用一種改進(jìn)傅立葉級(jí)數(shù)方法和RayleighRitz法對(duì)旋轉(zhuǎn)薄壁圓柱殼行波振動(dòng)特性及邊界約束影響進(jìn)行分析研究,計(jì)算得到不同幾何參數(shù)、不同邊界條件、不同約束彈簧剛度情況下行波振動(dòng)固有頻率,并就上述因素對(duì)振動(dòng)特性的影響進(jìn)行了分析。
3結(jié)論
本文采用一種改進(jìn)傅立葉級(jí)數(shù)和RayleighRitz法相結(jié)合,對(duì)旋轉(zhuǎn)薄壁圓柱殼行波特性進(jìn)行了分析,研究了邊界約束彈簧對(duì)轉(zhuǎn)動(dòng)薄壁圓柱殼行波頻率的影響,得到如下結(jié)論:
(1)本文采用一種改進(jìn)傅立葉級(jí)數(shù)對(duì)旋轉(zhuǎn)薄壁圓柱殼結(jié)構(gòu)三個(gè)方向上的位移函數(shù)進(jìn)行展開(kāi),基于Sanders薄殼理論的能量原理,結(jié)合RayleighRitz方法,建立了旋轉(zhuǎn)薄壁圓柱殼結(jié)構(gòu)自由振動(dòng)行波特性分析模型,數(shù)值結(jié)果表明本文模型有效可行,能夠快速收斂,并具有良好的精確性。
(2)旋轉(zhuǎn)薄壁圓柱殼的行波無(wú)量綱頻率參數(shù)ωf′和ωb′隨著環(huán)向波數(shù)n的增大呈現(xiàn)先下降后上升的趨勢(shì);隨著轉(zhuǎn)速Ω′的增大而升高;隨著厚徑比H/R的增大而升高;隨著長(zhǎng)徑比L/R的增大先下降,當(dāng)長(zhǎng)徑比足夠大后,行波無(wú)量綱頻率趨于穩(wěn)定值。
(3)當(dāng)旋轉(zhuǎn)薄壁圓柱殼一端固定,另一端只存在一種彈簧約束時(shí),隨著軸向約束彈簧k1′、環(huán)向約束彈簧k2′、徑向約束彈簧k3′無(wú)量綱剛度的增大,前、后行波頻率ωf和ωb均在剛度為10-2~102范圍內(nèi)大幅度上升,后趨于穩(wěn)定,但橫向旋轉(zhuǎn)彈簧k4′對(duì)行波頻率影響不大。
(4)對(duì)于旋轉(zhuǎn)薄壁圓柱殼的前、后行波頻率參數(shù)ωf′和ωb′,環(huán)向約束彈簧剛度k2′比徑向約束彈簧剛度k3′對(duì)其影響更大,軸向約束彈簧剛度k1′比橫向旋轉(zhuǎn)約束彈簧剛度k4′對(duì)其影響更大,即軸向和環(huán)向約束彈簧比徑向約束彈簧和橫向旋轉(zhuǎn)彈簧對(duì)轉(zhuǎn)動(dòng)薄壁圓柱殼動(dòng)力學(xué)特性的影響更大。
(5) 在每一種邊界約束變量設(shè)置下,當(dāng)旋轉(zhuǎn)薄壁圓柱殼的無(wú)量綱轉(zhuǎn)速為某一固定值時(shí),前、后行波無(wú)量綱頻率參數(shù)ωf′和ωb′變化趨勢(shì)相同且隨轉(zhuǎn)速的增大變化不大,這說(shuō)明轉(zhuǎn)速的改變對(duì)轉(zhuǎn)動(dòng)薄壁圓柱殼行波頻率隨邊界約束彈簧剛度的變化作用不大。
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