有效面積的概念和有效面積的變化有效面積是一個等效的面積,壓力作用在這個面積上將產生相等的軸向力。一般情況下,跟著內壓力的增大,鋼波紋管有效面(mian)(mian)積變小,面(mian)(mian)隨外壓力的增加,有效面(mian)(mian)積變大。
一篇文章讓你學會鋼波紋管的應力計算
波(bo)紋管用于力(li)平衡(heng)式儀(yi)(yi)表時,其有效(xiao)(xiao)面積的不(bu)亂性會直接影響著儀(yi)(yi)表的精度(du)。所以(yi)在(zai)(zai)這種場(chang)合不(bu)但要求波(bo)紋管具有公道的有效(xiao)(xiao)面積,而且還要求有效(xiao)(xiao)面積在(zai)(zai)工(gong)(gong)作過(guo)程中不(bu)隨工(gong)(gong)作前(qian)提而變化。
美國EJMA 應力(li)計(ji)算(suan)方(fang)法波紋(wen)(wen)管(guan)的(de)有(you)效(xiao)面(mian)積計(ji)算(suan)有(you)效(xiao)面(mian)積是波紋(wen)(wen)管(guan)的(de)基本機能參數之一,它表征波紋(wen)(wen)管(guan)將壓力(li)轉換(huan)為集中(zhong)力(li)的(de)能力(li),在利用(yong)波紋(wen)(wen)管(guan)把壓力(li)變成(cheng)集中(zhong)力(li)輸出的(de)場合,有(you)效(xiao)面(mian)積就是一個重要參數。
數(shu)值(zhi)法計(ji)算波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)管(guan)應力假定(ding)(ding)(ding)波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)管(guan)的(de)(de)(de)(de)全部波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)都(dou)處于(yu)統一前(qian)提下,在(zai)計(ji)算時只研究波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)管(guan)波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)的(de)(de)(de)(de)單個半(ban)波(bo)(bo)。這樣,在(zai)研究中(zhong)(zhong)(zhong)就不(bu)考慮端(duan)部波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen),固(gu)然端(duan)部波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)的(de)(de)(de)(de)邊界(jie)前(qian)提與中(zhong)(zhong)(zhong)間波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)有所不(bu)同(tong)。數(shu)值(zhi)法是根據E.列(lie)(lie)斯涅(nie)爾(er)對于(yu)變(bian)壁厚回轉(zhuan)薄殼產生(sheng)軸向(xiang)對稱(cheng)變(bian)形時所列(lie)(lie)的(de)(de)(de)(de)非線(xian)性(xing)(xing)(xing)(xing)方程來解(jie)的(de)(de)(de)(de)。在(zai)推(tui)導E.列(lie)(lie)斯涅(nie)爾(er)方程時,應用了薄殼理論(lun)的(de)(de)(de)(de)一般假定(ding)(ding)(ding),其中(zhong)(zhong)(zhong)包(bao)括:與環殼曲率主半(ban)徑比擬厚度(du)很小的(de)(de)(de)(de)假定(ding)(ding)(ding);材料的(de)(de)(de)(de)均一性(xing)(xing)(xing)(xing)和(he)各向(xiang)同(tong)性(xing)(xing)(xing)(xing)的(de)(de)(de)(de)假定(ding)(ding)(ding)。采用上(shang)述假定(ding)(ding)(ding)也會給計(ji)算帶來一定(ding)(ding)(ding)的(de)(de)(de)(de)誤差。由于(yu)在(zai)制造(zao)波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)管(guan)時,管(guan)坯的(de)(de)(de)(de)軋制,拉(la)深和(he)隨(sui)后的(de)(de)(de)(de)波(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)(wen)塑性(xing)(xing)(xing)(xing)成形會造(zao)成材料力學機能(neng)上(shang)的(de)(de)(de)(de)各向(xiang)異性(xing)(xing)(xing)(xing)和(he)不(bu)平(ping)均性(xing)(xing)(xing)(xing)。
波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)上的(de)(de)(de)(de)應(ying)(ying)力(li)(li)(li)(li)是(shi)(shi)由系統中(zhong)的(de)(de)(de)(de)壓(ya)(ya)(ya)(ya)力(li)(li)(li)(li)和波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)變形所產生的(de)(de)(de)(de)。壓(ya)(ya)(ya)(ya)力(li)(li)(li)(li)在波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)上產生環(周向)應(ying)(ying)力(li)(li)(li)(li),而在波(bo)(bo)(bo)的(de)(de)(de)(de)側壁、波(bo)(bo)(bo)谷和波(bo)(bo)(bo)峰處產生徑向的(de)(de)(de)(de)薄(bo)膜(mo)和彎曲應(ying)(ying)力(li)(li)(li)(li)。不(bu)(bu)能抗(kang)彎的(de)(de)(de)(de)薄(bo)殼(ke)有(you)時(shi)(shi)稱(cheng)為(wei)(wei)薄(bo)膜(mo),忽略彎曲而算得的(de)(de)(de)(de)應(ying)(ying)力(li)(li)(li)(li)則稱(cheng)為(wei)(wei)薄(bo)膜(mo)應(ying)(ying)力(li)(li)(li)(li)。波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)變形時(shi)(shi)產生徑向薄(bo)膜(mo)應(ying)(ying)力(li)(li)(li)(li)和彎曲應(ying)(ying)力(li)(li)(li)(li)。波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)在工(gong)作時(shi)(shi),有(you)的(de)(de)(de)(de)承受(shou)內(nei)壓(ya)(ya)(ya)(ya),有(you)的(de)(de)(de)(de)承受(shou)外(wai)壓(ya)(ya)(ya)(ya),例如波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)膨脹節和金屬軟管(guan)(guan)在多(duo)數情況(kuang)下其波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)承受(shou)內(nei)壓(ya)(ya)(ya)(ya),而用(yong)(yong)于(yu)(yu)閥門閥桿密封的(de)(de)(de)(de)波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)一般(ban)情況(kuang)下承受(shou)外(wai)壓(ya)(ya)(ya)(ya)在這(zhe)里主(zhu)要分析波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)承受(shou)內(nei)壓(ya)(ya)(ya)(ya)時(shi)(shi)的(de)(de)(de)(de)應(ying)(ying)力(li)(li)(li)(li),波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)承受(shou)外(wai)壓(ya)(ya)(ya)(ya)的(de)(de)(de)(de)能力(li)(li)(li)(li)一般(ban)情況(kuang)下高于(yu)(yu)耐內(nei)壓(ya)(ya)(ya)(ya)能力(li)(li)(li)(li)。跟著波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)的(de)(de)(de)(de)應(ying)(ying)用(yong)(yong),人們(men)對波(bo)(bo)(bo)紋(wen)(wen)(wen)(wen)(wen)管(guan)(guan)的(de)(de)(de)(de)應(ying)(ying)力(li)(li)(li)(li)進(jin)行大量的(de)(de)(de)(de)分析研究和實驗驗證工(gong)作,提(ti)出了很多(duo)供工(gong)程(cheng)設(she)計使用(yong)(yong)的(de)(de)(de)(de)計算公式、計算程(cheng)序(xu)和圖(tu)表。但是(shi)(shi),有(you)的(de)(de)(de)(de)方(fang)(fang)法(fa)(fa)因為(wei)(wei)圖(tu)表或程(cheng)序(xu)繁復使用(yong)(yong)不(bu)(bu)利(li)便,有(you)的(de)(de)(de)(de)方(fang)(fang)法(fa)(fa)假設(she)前提(ti)不(bu)(bu)是(shi)(shi)過(guo)于(yu)(yu)簡化就是(shi)(shi)過(guo)于(yu)(yu)理想,難以保證使用(yong)(yong)上的(de)(de)(de)(de)安全可靠(kao),不(bu)(bu)少方(fang)(fang)法(fa)(fa)未能為(wei)(wei)工(gong)程(cheng)界所接受(shou)。因此(ci),真正(zheng)符(fu)合實用(yong)(yong)要求的(de)(de)(de)(de)方(fang)(fang)法(fa)(fa)為(wei)(wei)數未幾。應(ying)(ying)用(yong)(yong)比(bi)較普遍的(de)(de)(de)(de)方(fang)(fang)法(fa)(fa)有(you)如下兩種:
鋼波紋管作為彈性密封(feng)零件,首先(xian)要(yao)知足(zu)強度前提(ti),即其更(geng)大(da)應(ying)力不超過給定前提(ti)下的(de)許用應(ying)力。許用應(ying)力可(ke)(ke)由極限應(ying)力除以安全系數得出。根據波紋(wen)管的(de)工作前提(ti)和對它(ta)的(de)使(shi)用要(yao)求(qiu),極限應(ying)力可(ke)(ke)以是(shi)屈服(fu)強度,也可(ke)(ke)以是(shi)波紋(wen)管失穩時的(de)臨(lin)界應(ying)力,或者是(shi)疲憊(bei)強度等(deng)。要(yao)計算(suan)波紋(wen)管更(geng)大(da)工作應(ying)力必需分析波紋(wen)管管壁中的(de)應(ying)力分布。
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