Xác định hệ số ngoại lực của mối ghép ren

NGHIEN CLfU-TRAODPI ^jXAC DINH HE S6 NGOAI LLTC CUA M O I GHEP REN DETERMINATION OF THE EXTERNAL FORCE COEFFICIENT OF THE THREADED JOINTS Nguyen Hflu Loc', Tran Van Thuy^ •Khoa Co khi, TrUdng Dai hpc Bach Khoa TP Hd Chi Minh 'NCS Khpa Co khi, TrUdng Dai hpc Bich Khoa TP Hd Chi Minh Mdi ghep ren gid vai trd quan trgng thilt klhe thong cd SU phdn bd ngoai lUc buldng vi trln be mat ghep cua chi tilt mdy mdi ghep dugc xdc dinh thdng qua hi so ngoai Bii bio trinh bdy phUdng phip xic dinh he so ngoai lUc cua moi ghep ren tren md hinh thi nghilm cic gii tri lUc xilt dUdc bdng cam biln liic loadcell vd miy silu dm Kit qui xic dinh he sd n lUc bang thUc nghiem dugc so sdnh vdi he so ngogi lUc dugc tinh todn bang ly thuylt Qua dd.k chdng gii thuylt true xoay Id true doi xdng di qua trgng tim nhdm bu long Tfl khoa: Mdi ghep ren, lUcxilUhlso ngogi lUc Threaded joints plays an important role in the design of mechanical systems The distributi external force on the bolt and the coupling surface of the mechanical parts in the joints are determ by external force coefficient This paper presents a method to determine the external force coeff of the threaded joints on an experimental model using loadcell force sensor and ultrasonic meter results of external force coefficient are identified from loadcell and ultrasonic meter is compared externalforce coefficient calculated by theory.Besides proven the hypothesis that the axis of rota the axis of symmetry passing through the focus of the group bolts Keywords: Threaded joints, clamping force, externalforce coefficient ISSN 0866-7056 TAP CHl CO KHl VlfiT NAM, Sd nam 2016 www.cokhivietnam.vn NGHIEN C l i u - TRAO B O I va trln md hinh thi nghiem vdi dung cu la cira biln lUc loadcell vi miy sieu im l.GlOlTHlfiU Trong mdi ghep ren, dl hdng hoc khdng xiy xiet va dang lam vile thi vile xic dinh gii tri vi kiem soat cac lUc tic dung mdi ghep ren li het sdc quan trpng [2] De ning cao chat lupng va dp tin cay cua mdi ghep ren qua trinh lam viec thi phai chpn vi stl dung loai buldng (vit) phu hpp, du bin dl giiS chat mdi ghep, chiu dUpe ngoai lUc tic dung qui trinh lam viec [3,4] Ngoai ra, phii xac dinh dung lUc xilt ban diu qui trinh lap ghep de dam bio mdi ghep hoat ddng tdt, khdng bi tich hd vi bi trUpt chiu cic ngpai lUc, rung ddng, qui trinh lam vile [5] CO S6 Lt THUYET Gii siS moi ghep chiu tii trpng cd phUOng bit ky nam trpng mit phang ddi xdng YY (hmh 1) Ngoai lUc F dUac phin hai thinh phan: Vudng gdc be mat ghep F^, vi song spng bl mat ghep F„ Ddi F„ vi F„ vl true qua trpng tim cua nhdm buldng, ta cd mdmen ngiu lUc M Tii trpng F,, vi mdmen M cd xu hUdng tich hd be rait ghep vi duoc chia lim hai phan: Mpt phan la F^ vi M^ tie dungvin buldng, F^ vi M _ tic dung lin cic chi tiet dupc ghep; cdn V^ Trong mdi ghep ren, dUdi tic ddng cua lam tam ghep hi trUpt lUc xiet ban dau, buldng se bi keo va chi tiet ghep Mudn cho cic chi tilt miy dupc ghep bi nen Khi mdi ghep chiu tic dung cua ngoai lUc nam gidi ban khdng tach hd be mat cac khdi bi tach hd va khdng bi trUpt can xilt buldng tam ghep hoie trUpt be mat ghep, buldng giin vdi lUc xilt V: dii them mdt lupng la Al, bien dang nen cua cic - De mdi ghep khdng bi tich hd [1]: tam ghep cung giam bdt mpt lupng tuong tU Nghia la chi mdt phin F cua lUc ngoii F li x? tic dung lira buldng giin dii them, phan cdn lai fe/ MAyc\,^ (1) la (1 - x)F 1^™ B*^^ ^^^^ "^^S ^"^^ ^^^ '•^*- *^"^ ghep, X dupc gpi la be sd ngpai lUc SU phan bd Trong dd: k la he sd an toan de dam bao ngoai lUc trln mdi ghep buldng phu dp mem cua mdi ghep khdng bi hd, k =l,3-^2 buldng va tam ghep Hay ndi each khac li phu thupc vao be sd ngoai lUc [ 1] ?ti\ Fa Hien nay, cd nhieu phuong phap xic dinh true tiep hoac giin tiep lUc xilt hoac ngoai lUc tic dung trongradighep buldng nhU: Mdmen xiet bang cd 11 lUc, lUc xiet bang vdng dim xic dinh lUc, dd giin dai cua buldng bing phuong phip co, may sieu im Tuy vio ylu cau ky thuit cu thi cua tdng loai mdi ghep ma ta chpn phuong phip dp phu hpp nhit, dam bao radi ghep sau dp khdng bi inh hUdng ve chat lUpng Bai bao trinh biy phUdng phap xic dinh he sd ngoai lUc cda mdi ghep ren theo ly thuyet ISSN 0866 - 7056 TAP CHi CO KHi VIET NAM, Sd nam 2016 www.cokhivietnam.vn