V 1/ la cac ma Iran dudne eheo
De t( ?:-[/] +A CK
tran C
- 0 (4.4.3.2) Phuang trinh dae trung (4.4.3.2) la phuong trinh bae n ciia iri rieng / ' . Do ma
khons doi xuns nen nshiem ciia phuons trinh dae truna co eia tri am. va
tuc la gia trj A xuat hien dudi dang cap sd phuc lien hgp: /^-, - //, ± / OJ^ (4.4.3.3) Nghiem cua phuang trinh (4.4.3.2) la su lo hgp cua 2n nghiem theo cae
dane dao dgng rieng cua ket cau:
{c\=^a,{^,]e /J
(4.4.3.4
/ =
Trong đ : ^i la hang sd dang
{(p^ ] la vecta dang dao dgng rieng thu i
Cac vecta rieng [(p] va hang sd ^i cung xuat hien dudi dang cap sd phue lien
hgrp :
Phan une ciia he co dane sau:
• " r
fe} = X [(«. + ' ^ ) ({/^} + 'M) ế ''"' + {a, - i/3,) ({p} - iU) e- " - 1
(4.4.3.6) Khai trién (4.4.3.6) va chu y i- = -I ta dugc ket qua sau:
n
fe} = Z ^ " ' ' [ - 2 ( / ? , {p,}+ a,{q,])s^nco,t + 2(.., {^, } - /?, {p, }) cos . . , / ]
/ = I
(4.4.3.7) Nhan xet nghiem (4.4.3.7) ciia phuong trinh vi phan khi dgng luc Flutter (4.4.2.2):
- Phuang trinh dae trung (4.4.3.2) eo cac nghiem tri rieng t6n tai a dang cac cap
so phuc lien hgp. Day la ly do giai thfeh tai sao cac dang dao dgng xuat hien
theo cap a trana thai mat on dinh khf dons luc.
- Nghiem (4.4.3.7) la su tdng hgp thanh phan thue ciia cac nghiem don le theo cac dang dao dgng rieng ciia ket eaụ
Khao sat su 6n dinh cua nghiem (4.4.3.7):
- Neu thanh phan thue ciia tat ca cac tri rieng dt:u am thi gia tri eiia nghiem bi gidi
ban va ket cau d trang thai 6n dinh. Dieu kien dn dinh \/p^ < 0 (VRe(A )<0 ).
Neu chi can ton tai mot tri rieng ed phan thue duang thi gia tri eiia nghiem tang nhanh dot bien va bien do dao dgng bi phan ky, kel cau d trang thai mat 6n dinh . Didu kien mat on dinh 3 / / > 0 (3Re(/lJ>0).
- 6 trang thai tdi han ton tai mgl tri rieng cd phan thue bang 0. Lay dieu kien tdi han
đ đ lim mat 6n dinh khf de>ng lire eiia kel eau va .\ae dinh van ide gid tdi ban.
Dieu kien d trang thai tdi ban 3//^ = 0 ( 3 R e ( / ) = 0 ). (adsbygoogle = window.adsbygoogle || []).push({});
Nhu vav d trang thai tdi han, se luon luon ton lai ii nhat mot cap eiia 2 dang dao đne id hap eav mat 6n dmh dudi eung mgl tan sd, ggi la tan sd Flutter
- 5 9
dao dgng rieng cu the dua vao id hgp hoae id hgp đng thdi nhieu dang dao done rieng d trang thai tdi ban.
4.5. Ma tran phan tu cua lire khi đng lire
Cac thanh phan luc khf dgng gdm luc nang L^, luc ngang Dp va md men xoan
M^ xac la cac luc dai deu tren mot dan vi chi6u dai dam eaụ Trong phuang phap
PTHH cac thanh phan luc khf dgng phai duac quy doi tuang duang va nut phan tirdam.
Nguyen ly quy đi tuang duang cac luc khf dgng v6 mil bang each tap trung tuyen tmh luc khf dgng dai d6u tren phan lu dam v6 hai nut xac dinh phan tụ Dc cd ihê bieu di6n luc khf dgng tren phfin tu thong qua cac chuyen vi tai mil ciia phan tu đ ngudi ta lam
dan gian hoa bang each lap trung lire khi dgng \t eae mil dau va cudi eiia phan lir. hinh
4 . 2 .
l/2.Lh.L
l/2.Lh.L :/ạDL
Hinh 4.2. Md hinh lap trung cae lue khi đng tren phan tu dam ve mil
Bien doi luong dirong xe irai bieu thue la eae lue khf đng. edn ve phai la each bi^u dien quan he khae giua lire khi đng viet dang ma Iran kh. đng va ehuyen M nui (4.4.1.2) la dirge:
pU--L 2B ^^ .. 2 5 -