Đánh giá độ bền mỏi vỏ cầu sau xe tải với kích động mặt đường ngẫu nhiên tiêu chuẩn ISO 8608 1995

NGHllN CCrU - TRAO 06l DANH GIA 0 0 B^N M 6 | V 6 CAU SAU XE TAI V O I KICH DONG MAT OUdNG NGAU NHIEN TIEU CHUAN ISO 8608:1995 ESTIMATION FATIGUE FAILURE OF REAR AXLE HOUSING TRUCK USIN

NGHllN CCrU - TRAO 06l

DANH GIA 0 0 B^N M 6 | V 6 CAU SAU XE TAI V O I KICH DONG MAT OUdNG NGAU NHIEN TIEU CHUAN ISO 8608:1995

ESTIMATION FATIGUE FAILURE OF REAR AXLE HOUSING TRUCK USING RANDOM

ROAD ROUGHNESS EXCITATION ISO 8608:1995

Tran Phuc Hoa'^ Tran Thanh Tiing', Ll H^ng QuSn"

'Vien Co khi Dpng lire, Trudng Dai hpc Bich Khoa Ha Npi

"Khoa Cdng ngh^ 6 td, Trudng Dai hpc Cdng nghi$p Hi Npi

TOM TAT

Kieh thieh lie mgt du&ng gay nen tdi trpng dpng biin thien lien tuc theo thdi gian ldc dgng ten vd cdu, tr& ihdnh nguyen nhdn tiim Idng gdy nen hign luang hu hdng do moi Nhieu cong trinh nghien cieu vi linh vtfc ndy da chung minh linh dung ddn khi sie dgng mo hinh dao dpng cda d td v&i kich thich tie du&ng Id hdm ngdu nhien di xdc dinh tdi trgng ddt ten vo edu Cdc tdi trpng ndy sau dd dupe sie dtfng ldm dieu kign ddu de ddnh gid dp bin mdi cua vd cdu Trong bdi bdo ndy, ldc gid dd khdo sdt md hinh mgt du&ng ngdu nhien Idc dpng len vd cdu xe tdi ldm nguon kich ddng de ddnh gid dg bin mdi cua xe tdi trong qud trinh hogt dpng Bdi bdo dua ra dugrc phuang phdp lugn nghien cuu, edc lieu chudn ddnh gid ve dp ben mdi ciia vd edu trong th&i gian hogt dpng

Tir khia: Bin mdi, vd edu chu dgng, md htnh dpng luc hgc, tieu chudn ISO 8608:1995

ABSTRACT

Road roughness excitation apply on rear axle housing of truck in time domain to make vari-able force and reasonoffatigue failure on it Many researchers on this field showed that it is trust using random road roughness excitation as input data to solve and analyse problems Dynamics force apply on axle housing to estimate fatigue failure On this research, we calculated input data then using to analysis fatigue during time life of truck This paper showed that the methodology and standazation to estimate life lime of rear axle housing truck

Keywords: Fatigue failure, driving axle housing, dyrmmic model, ISO 8608:1995

l.DATVANDE tupng hu hdng do mdi Nhiiu cdng trinh di

cdng bd cic kit qui nghiSn cuu vi Ilnh vyc niy,

Nghien ciiu dp ben mdi thudng xuit trong do, cd tic gia di sii dymg md hinh dao phit tir tai trpng map mo mit dudng Kich thich dpng cua d td vdi kich thich tit dudng Ii him

tu mit dudng gay nen tii trpng dpng biin thien ngau nhiSn de xic djnh tii trpng dit Ien vd ciu lien tyc theo thdi gian tic dung ien vd ciu vi Cic tai trpng niy sau dd dupc sii dimg lim diiu trd thinh nguyen nhin tilm ting giy nen hi?n ki$n diu di danh gii dp bin mdi ciia vd ciu

ISSN 0866 - 7056

TAP CHl CO KHl VI|T NAM, Sd 8 nim 2016

Vi?c md ta map md mat dudng cung

dupc cac nha nghien curu dac biet quan tam

Nhieu cdng trinh nghidn cuu da cdng bd cac

phuong phap mo ta map md m^t dudng khac

nhau Neu nhu trudc day, m ^ md mat dudng

dupc su dving chu yeu trong nghien cuu dao

dgng d td, thi g ^ day Itnh vi;c ung dung cua nd

da dupc md rpng sang bai toan bdn mdi ciia cac

chi tiet lien quan, trong dd cd vd cau

Hi^n nay, phuong phap md ta map md

m$t dudng bang ham ngau nhidn dk dupc chuan

hod theo tieu chuin ISO 8608:1995 Vi v|y, cac

nha nghien cuu thudng su dyng tieu chuSn nay

dh md ta kich thich tu m^t dudng trong cac md

hinh dpng lyc hpc ciia d td

Theo tieu chuan 8608:1995, mAp md

m$t dudng dupc md ta thdng qua 3 thdng sd co

ban la tin sd khdng gian, bien dang dudng va

hilm m^t dd pho nSng lupng (Power Spectra!

Density, vidt t4t 1^ PSD) Tan sd khdng gian n

dupc tinh bang sd chu ky tren mpt met dudng

(chu ky/m) Bien d^ng dudng dupc hidu \k

bidn thien chidu cao map md theo tryc dpc cua

dudng PSD la ham m§t dp phd nSng lupng cua

chidu cao map md cua m$t dudng tinh theo tan

so n ho$c tin sd gdc Q:

:/.) = C.K)(^]

G

Hoic:

G,(n)=G,(n„)|

(1)

(2)

Tix)ng cdng thiic tren, n la tan sd khdng

gian (chu ky/m), n,, li gii tri tham chiiu ciia n

(dirpc liy n,, = 0,1 chu ky/m), G^ (n„) Ii mat dp

phd d tin sd Uj (dupc liy theo bing I), n la

tin sd gdc (lad/m), n,, =lrad/m Klii tinh toin

cic lo9i dudng d td, chi sd w thudng dupc chpn

bing 2 Mdi quan h^ giiia tin sd n vi tin sd gdc

dupc the hi^n bing biiu thiic: n = Q/2n

Tieu chuin ISO 8608:1995 phin biet cic d?mg dudng (dudng phd, cao tdc vi dia hinh khdng dudng xi) theo mit dp phd ning luong va chia chiing thanh 8 losu vdi ky hieu quy udc tii A din H Trong dd, A Ii loai dudng chit lupng tdt nhit, cic chii cii tiip theo md ta cac loji dirdng

cd chit Iupng kem din vi H li loiii dudng xiu nhit Mdi loai dudng dupc die trung bdi mit dp phd ning Iupng G^ (n^ (xem bing 1.1) Tii tieu chuin ISO 8608:1995, cic nhi nghien ciiu sii dyng cic phucmg phip khac nhau

di md t i raip mo mat dudng dudi d?ng:

h = f{x) hoic A = / ' ( ' )

Vdi h Ii chiiu cao mip mo, t la thdi gian

vi X li dich chuyin theo hudng chuyin dpng Him mip md mjt dudng tten day dupc sir dyng lim kich thich diu vio cho md hinh dpng lyc hpc d td, nhim xae dinh tii trpng tir mip md mit dudng tic dyng Ien ciu chu dpng

Bdngl Tieu chudn ISO 8608:1995 phdn logi du&ng:

Lo^i duimg

A - B

B - C

C - D

D - E

E - F

F - G

G - H

H +

Thong so md t i mip mo theo tio s6 khdng gian, n

k

3

4

5

6

7

8

9

-G,(n^[10-'m'] Mln

-25

27

29

211

213

215

217

Trung binh

24

26

28

210

212

214

216

-Max

25

27

29

211

213

215

217

-Hg = 0.1 chu ky/m

Banh gij d$ b^n mdi vd cau chu d$ng:

Dd danh gia dd ben ISu ciia chi tidt chiu "^

ISSN 0866 - 7056

TAP CHi CO KHf VI^T NAM, Sd 8 nam 20! 6

NGHieN CU'U-TRAOBOI

tii trpng lip cd chu ky, ngudi ta thudng sir dyng

dudng cong mdi do bing thuc nghiem (cdn gpi

li dudng cong S - N)

Dd thj tren cho thiy, neu chi tiet chiu

img suit thip hon S\ thi khdng xiy ra hdng

do mdi ngay ci khi N ->IJO Gii Ui ung suit S',

dupc gpi Ii gidi h?n mdi chuin cua vit li$u, do

dupc xic dinh bing thiet bi vi quy oinh chuin

S6 chu ky tii tic dpng len chi tiet tuong iing vdi

gii tri S' theo kit qui tren hinh 1, nim trong

khoang lb'-10'

Cic kit qui nghien ciiu thuc nghi$m

khic da cho thiy, so chu ky tii tic dpng tuong

img vdi gidi 1 ^ mdi ddi vdi thep vi gang

thudng nim trong khoing tir 10* din 10" Vi

viy, cic nha nghien ciru cho ting, cd the chip

nhin gii thiit Ii chi tiit si khdng hdng do mdi

sau khi chju dupc 10* chu ky, dudng cong mdi

nim ngang sau khi d?t 10* chu ky, nhu ben

dudi

TSW^STFT^

Hinh I Kit qud Ihi nghigm tren thiet bi tteu chudn

Do vi?c tien hinh thi nghidm xiy dyng

ducmg cong mdi mit nhieu thdi gian va chi phi,

nen ngudi ta di cd ging dya tren cic ket qui thi

nghi$m tim ra mpt sd quy luit d6 tir do cd the

xiy dyng dudng cong mdi bing cich tinh toin

dya tr^n cic thu$c tinh ciia vit Ii$u Ching h ^ ,

tren hinh 1,gii tri gidi han mdi cd the dupc tinh

tir gidi h^n bin cua vit Ii$u:

S,=0,5S„

Vdi dudng cong mdi di dupc xay dyng,

niu xic djnh dupc gii tri img suit mi chi tiit

phii chju la S thi ta cd the dya vio dudng cong

mdi de suy ra sd chu ky tii tic ddng gay hdng

do mdi N vi tit dd tinh dupc tudi thp cua nd Tuy nhien, cic chi tiit miy trong diiu kipn lim viec thuc cua nd khdng chiu tii trpng gidng nhu diiu ki?n thi nghi$m chuin trin diy

Vi vjiy, gii tri gioi hsm mdi sS khdng cdn li S'^ nhu hinh I,mi thudng thip hon Ching h?n, thi nghiem miu thir vdi tii trpng kdo - nen diing

tim s6 cho gii tri g'^ h?" ™°' * ^ P ' ' " " ^° ^*'

S'^ chuin khoing 10% Thi nghi$m vdi cac diuig tii trpng khic ciing cho kit qui thip hon

so vdi S'^ chuin tir 10 - 30%, tuy tnidng hpp cy thi

Do khdng thi Iim thi nghi?m xic dinh S' cho mpi diiu kipn tii trpng, nen chip nhin vi$c xic dinh gidi h ^ bin mdi S'^ theo ling suit gidi hsm cua vit Ii?u S (ultimate tensile strength) thdng qua m0t he so kinh nghipm:

S', = k,.S„,

Trong dd: k, Ii hp sd kinh nghi$m, phy thupc chil yiu vio lo^i vit lipu Doi vdi cic lo^i gang vi th^p:

k, = (0,45-0,65) Ngoii ra, mdt sd thdng so ket cau, che

dd tii trpng vi diiu kipn lim vipc ciia chi tiet ciing gdp phin Iim giim gidi h?n mdi Vi viy, gidi h^n mdi thyc te S,, thudng dupc tinh tit gidi h^n chuin S'^ thdng qua mpt loat cic hp so anh hudng Thdng thudng, ta cd:

S< S\

Gidi h?ui b6n mdi thyc te S^ dupc sir dyng Iim ca sd di dinh gii ben mdi ciia chi tiet bing nhiing phuong phip khic nhau Mpt trong nhiing phuong phip thdng dyng nhat hipn nay

li sur dyng cic tieu chuin bin mdi

Cic ket qui nghien cihi thyc n g h i ^

ISSN 0866-7056 TAP CHl CO KHl VI$T NAM, Sd 8 nim 2016

NGHieNCCrU-TRAODd

cho thay, hu hdng do mdi phy thudc chu ydu

vio 2 thdng sd d ^ tnmg cua iing su5t ma chi

tidt phai chiu: Gi^ tri trung binh o^ va bien dp

o^ cua nd Vi vky, cac tieu chuin bdn mdi dupc

xay dyng dua trdn gii thiet ve mdi quan he giira

cdc ucng suat o^ va a vdi cac gia tri umg suat

gidi h ^ cua vat lieu nhu gidi han biln d^ng

deo Sy (yield strength), gidi hgn bdn pha huy

Su (ultunate tensile strength) va img su4t pha

huy thyc o^ (true fracture stress) vdi S < S^<Oj

Cac tieu chuan bdn mdi thudng dupc

thh hi^n dudi dang db tlq quan h§ giCta o^ va

o^vdi ten gpi Ik "ducmg ddng thudi thp" Viing

ben trai cua dudng cong la vijng an toan (khdng

hdng do mdi), cdn viing ben phai la vung cd

tu6i thp gidi han (sg hdng sau N chu k^ tai tac

dpng)

Tren hhih 2, the hi^n 4 tieu chuin b ^

mdi ciia cdc tac gia Goodman, Gerber, Soderberg

va Morrow

Ohg mdt tnmg bl/th

Hinh 2 Cdc tieu chudn ben mdi

Neu su dyng tieu chuin Goodman thi

dudng ddng thudi thp dupc md ta bang bidu

thuc:

-2- + ^=- = l

Khi dd, h^ so an toin n dir^ tinh nhu sau:

(4)

Trong dd, S^ la gidi h ^ mdi thyc te (thudng nhd hon nhieu so vdi a do dupc tren dudng cong mdi thuc nghifm)

2 XAC DINH TAI TRQNG TAC DVNG LEN VO CAU CHU D Q N G 6 TO TAI

De md ta ham kich thich tir m$t dudng

tac ddng ldn ckc hanh xe ciia clu chu dpng,

ngudi ta thudng sii dyng cac lo^ map md khac

nhau t>h phan anh dung trgng Uiai chju tai cua

vd cau, mlp md theo bien dgng ducmg ngau nhidn tiiudng dupc sur d ^ g Hi^n nay, ISO 8608-1995 la tieu chuan ve mip md m§t dudng dupc su dyng phd bien nhat trong cac tinh toan dpng luc hpc d td Tidu chuin nay, phin bift cac dgng dudng theo mat dp phd nang lupng (PSD)

va chia chung thanh 8 toai vdi k;^ hieu quy udc tir A ddn H

Theo tieu chuin ISO 8608:1995, bidu thurc md ta chidu cao mlp md cua m$t dudng dupc viet nhu sau:

MJ:) = y VAn.2*.10"'.f-^ l.cos(2;r.i.An_c+a) (5) Vdi A^ la bien dd, n la tin s6 khdng gian

va <p la pha (bien thien ngiu nhien trong khoang 0-27t)

Neu coi d td chuydn dpng deu vdi v ^ toe V thi bidu thuc tinh dp cao mlp md theo bidn

X cd the viet lgi theo bien thdi gian t nhu sau:

A(0 = X•^/AJ^.2^I0"^f-^|.cos(2;^.i.A«.^'i+^J (6)

Mo hinh d$ng 1 ^ hpc xe tai:

Md hinh xae djnh cac tai trpng dpng tac dung len vd cau trong trudng hpp xe chuydn dpng tren dudng dupc xae djnh tir md hinh dpng luc hpc cua xe tai 2 cau Trong nghien cuu nay, tdc ^ a sii dung phuong phap tach clu tnic h?

nhieu vat dd thiet lap hf phuong trinh vi phan

md ta dpng lyc hpc xe tai »

ISSN 0866 - 7056

T ^ CHf CO KHl VI$T NAM, Sd 8 nim 2016

NGHieN c u u - T R A O D 6 I

Hinh 3 Md hinh khdng gian xe tdi

Md hinh dpng lyc hpc khdng gian cua

xe tii nhe 2.45 tan, cd 2 true (cau sau chii dpng)

dupc md ti d hinh 3 Trong đ, thin xe dupc

coi nhu mpt tim phing cd khdi Iupng M dat

t^i trpng tam Trong trudng hpp tdng quit, than

xe cd 6 chuyen dpng (6 bic ty do), bao gdm: 3

chuySn dpng tinh tien theo cac tryc x (tryc dpc),

y (tryc ngang), z (tryc thing diing) vi 3 gdc

xoay tuong img: cp (gdc lie dpc - Quay quanh

tryc y), y (gdc Ifich ben - Quay quanh true z),

P (gdc lie ngang - Quay quanh tryc x) Cic ciu

xe (ciu trudc - 1 , ciu sau - 2) Ii cic Ichdi lupng

khdng dupc treo dupc coi nhu cic thanh phing,

cd khdi Iupng m^,, m„ dat tai trpng tim ciia

chiing M6i cau xe cd 3 chuyin đng tinh tiin:

Theo tryc dpc (x,, Xj), theo tryc ngang (y,, y^),

theo tryc thing diing {^^^, ^^) vi I chuyin vi

gdc lie ngang quanh true dpc (P^,, p^) Thin

xe dupc ndi vdi cic ciu xe thdng qua hp thing treo (die trung bdi cic dp cirng C vi hp sd cin giam chin K^.) (chi sd i: 1 - trudc; 2-sau; chi si

j : I -trai; 2-phii) Cau xe lidn ket vdi mit dudng bing binh xe din hdi, die trung bdi dp ciing

Hp phuang trinh vi phin tong quit m6

ti dpng lyc hpc cua xe tai 2 ciu nhim xic dinh cic tii trpng dpng I6n vd ciu dupc md ti d h$ (7), bao gdm: 10 phuang trinh vi phin A& ^ i ? , , + F ^ + i ? y + i r j j + i T j j + i r ^ + 1 ^ + i r ^

''<y+Ví>-F,i,iosS„*F^„caS„+F,^^S„+F,,,!iiS^i-F^*F^

-',*—'i(''m*'iii+''co*'iii)*'!('Jii-fF„+J^j,*ii„)

-{"„ +Mi -fMa +«i,)-('i-1)(F^, +F^) -(ft-r^XFji+'ị)

Afi-lfcu +'iij-'m-'ii>i +(Fai+Faj-Fa, "ajM +'',,lh'h„J+F^-h,„J

<"j,L -Caii+Faa+faii *'',u,)*Cci,+'iứ'ai +''«u/l

lílFc.+F^-'iu '',u,M,*IF^,+F,^,-F^-F,^Jt,,

'•M,ia-Ca„*Fa!,+F,^+F,^J-(F„+F,^.F,^-F,^J

iA,-tFc*l'.^-F^-F^M,+(F„*F^.F^-F,^)b,

*(lU*F^Jr^*F^(h„-r^

(7)

ISSN 0866 - 7056 TAP CHf COKHf VlfiTNAM Sd 8 nam 2016

NGHieNCCfU-TRAO Ddi

Trong dd:

- m: Khdi lupng dupc treo;

- M: Khoi lupng toan bd;

- m^,, m^: Khdi lupng khdng dupc treo

cau 1 va cau 2;

-5,,, Sj^: Gdc quay banh xe din hudng bdn

trai va ben phai;

"PAP PA2'*^°*^ ' ^ ngang cua cau 1 va cau 2;

- P: Gdc lie ngang cua than xe;

- <p; Gdc lie dpc ciia than xe;

- v: Gdc quay than xe theo tryc dung;

- ^Ai- Chuydn vi ciia khdi lupng khdng

dupc treo clu i (i = 1 -^ 2);

- X, y, z: Chuyen vi theo cac phuong dpc,

ngang va thing dung cua khdi lupng dupc

treo;

- Cj^, Kj.: Dp cung cua nhip va he sd can

giam chin d$t gin vdi banh xe ij (i=l-^2,

J=H2);

- Cj^ij, K^.: D$ Cling hudng kinh vi h^

so cin hudng kinh ciia ldp thir ij (1=1+2,

j=H2);

- J^, Jj J_^: Md men quan tinh tryc z, tryc y,

tryc xcua khdi lupng dupc treo xe tai;

- J^_, J : Md men quan tinh tryc x, y cua

khdi lupng khdng dupc treo clu i (i=1^2);

- Mj,: Md men quay banh xe thu ij quanh

trycy(i=l^2,j=l-5-2);

- F^., F^-, F : Lyc tac dyng len banh

xe meo phuang dpc, phucmg ngang va

phuong thing dung banh xe thu ij(i=l-^2,

j=1^2);

- P- Tai trpng tTnh ung vdi banh xe thii ij

(i=l^2,j=l-^2);

- F(,., F : Lyc dan hdi va lyc can giam

chin h? thdng treo gan banh xe thu ij

(i=K2,j=K2);

- F : Lyc dan hdi l6p banh xe thii ij

(i=K2,j=K2)

De giai h$ phuang trinh toan hpc (7),

hifn nay, Matlab Simulink la mpt phin mem rat

hihi hifu va dupc sir dyng rpng rai trong nudc

va qudc td Trong nghien cuu nay, vifc lgp trinh dupc thyc hien theo clu tnic md dun cho phdp quan ly chuang trinh hay khao sat anh hudng ciia cac thong sd dlu vao mpt each de dang

Du&ng mdp mo theo tiiu chudn ISO 8608:1995:

Map md mat dudng dupc md ta theo tieu chuin ISO 8608:1995, dupc sii dyng trong khao sat tidp theo nhim xae dinh anh hudng ciia tai trpng ddng tren md hinh dudng thuc \^fc khao sat tai trpng dpng tac dpng ldn vd cau khi

xe chay tren cac mat dudng tieu chuan, m^t mat cho phdp xae dinh dp ben ciia vd cau, m^t khdc cho phdp xae dinh cac che dp tai trpng iam thdng sd dlu vao cho bai toan xae djnh dp ben mdi cua vd cau

Map md be m$t cua 7 logi dudng theo ISO 8608:1995, dupc thd hifn tren 1 khoang chi^u dai 250m, nhu tren hinh 4

Hinh 4 Mdp md m^t duang theo tieu chudn ISO 8608:1995

Trong nghien ciiu nay, 4 logi dudng theo ISO 8608:1995, da dupc thii nghifm, bao gdm: loai dudng B-C (dudng tdt), dudng C-D (dudng trung binh), dudng D-E (dudng xiu) va dudng E-F (dudng rit xiu) dupc khao sat Mlp

md m|t dudng dupc dat ddu tren 2 vdt banh xe,

xe chuyen dpng thing Day la trudng hpp khao sat khi khdng cd cac thanh phan lyc ngang tac dung Van tdc ciia xe thay ddi tir 30 ddn 60 km/h '

ISSN 0866 - 7056 TAP CHl CO KHf V I £ T NAM Sd 8 nam 2016

NGHieN CUU - TRAO OOl

Cic kit qui phin tich Ii cic thanh phin

lyc dpc (F^,, i = 1, 2) vi Iuc diing diing (F^, i

= 1,2) dit Ien vd ciu vi cic gii tn cue d^i ciia

cic tii trpng dpng (max(F^,), max(F^i))

tfinhSa Tdi trgng dgng theo phuang dgc

F^, (V = 40 hn/h, du&ng E-F)

V (kmh)

Hinh 5b Tdi trgng dgng euc dgi theo phuang dge

ffmh 6a Tdi trgng ddng theo phmmg thdng ddng

F^, (v = 40 km/h, du&ng E-F)

tftnh 6b Tdi trgng dgng cue dgi theo phuang thdng dirng

Khi xe chiiy vdi y$n tdc v = 40 km/h tren dudng E-F (dudng rit xau), gii tri eye d^ cua Iuc dpc raax(F^) dat 7851 N, gii tri cyc d^ eua Iyc thing dimg max(F^) dat 47616 N Gii tri lyc thing dimg cyc d^i d miic 1,59 lin so vdi trudng hpp tii tinh (xe diing ySn)

3 XAY DVXG M 6 HINH M 6 P H 6 N G V 6

cAu

HyperWorks li mpt trong nhiing phin mem CAE ndi tieng ciia ciia cdng ty Altair (My)

vi dupc ling dyng trong nhiiu Imh vyc vdi khi ning phin tich chinh xic dya tren phuang phip phin tu hiiu h ^ Day Ii mpt phin mim phye vi^ cho vi|c tinh toin, md phdng, tii uu hda chi tiet, ket ciu nhim giim chi phi, giim thdi gian dua sin phim ra thi tnrdng vi ting dp tin c$y cua sin phim

Cic budc xic lip md hinh tinh toin bin mpt chi tiit tronig HyperWorks vi ca bin cung nhu cic phin mem CAE khic, bao gom 6 budc chinh:

- Xiy dyng md hinh 3D cia chi tiit;

- Gin vit li^u;

- Chia ludi;

- Dit ring bupc (diiu kipn bi6n);

- Dit lyc;

- Xuit ket qui

Sau day li cic budc cy thi trong xiy

ISSN 0866-7056

TAP CHl CO KHl VI$T NAM, Sd 8 nim 2016

NGHieNCO'U-TRAOOdi

dyng md hinh tinh tokn bdn vd cSu chii dpng xe

tai bang HyperWoiics

Md hinh 3D vd cku chu d$ng xe tAi:

Vifc xay dyng md hinh 3D cua vd cau

chti dpng xe tai theo phuang phaf} trvc tiep tir

phin mem HyperWoite tuang ddi khd khan,

do md hinh tinh toan yeu cau cd tinh chinh

xae va dp phiic tgp cao Vi the, vifc xay dung

md hinh vd cau dupc tidn hanh trong cac phan

mdm CAD (md hinh 3D^, sau dd dupc dua vao

HyperWorks Trong phan mem HyperWorks

cho phdp lien kdt vdi cac md hinh CAD dd cd

thd nhgn dgng md hinh mpt each chinh xae

Trong nghien ciiu nay, md hinh 3D cua vd cau

chu d$ng d td tai dupc xay dyng bing phan

mem Catia (hinh 2.15)

Hmh 7 Md hinh vo cdu chu dpngxe tdi

Gkn \%t lifu:

HyperWorks cung zip kho vgt lifu ldn

da dupc kidm chiing thyc te Vdi vd clu chu

ddng d td tai, vgt tifu thudng dupc sii dyng la

gang clu vdri cac thdng so nhu sau:

Bdng 2 Thdng so vgt lipu:

Thdng s i

IChoi lupng rieng

Mo dun dan hoi

H$ so Poisson

Ung suit gidi h^n chay cua

gang ciu

U'ng suit gidi b^n phi hiiy

cua gang cau

Dom v|

Kg/m' MPa

MPa MPa

Gii trj

7200 1,7.10=

0.29

490

690

Dinh gii dp ben moi ciia v5 ciu:

Trong bii toin cy thi vi vd ciu, vipc phin tich bii toin mdi vd ciu trong phin mem chuyen dung theo cac thdng so dupc dua la theo tieu chuin Goodman vi dudng cong S-N Diu tien, cic thdng sd ciia dudng cong mdi S-N se dupc dua vio didng qua vi^c xic dinh thdng sd cho vit li$u mdi (material fatigue) trong phin mim

Bdng 3 Cde thdng sd vgt ligu nhgp vdo de ptidn

tich bdi todn mdi:

e MATMT UMT

VS UTS

e SN sni

01 NCI B2

FL

a

B MPA Gsao

B 29(147 -ai25 looooono i5asi

Trong dd:

- UNIT la dan vi cho iing suit, d day la MPa

- UTS (ultimate tensile strength): Cng suit gidi hgn cua v$t lifu, lly theo bang thdng so vat lifu ban dau bing 690 Mpa

- SRIl: La hf sd chju mdi Trong phin mdm, hf sd nay dupc dinh nghta la iing suit ma tai img suat do vat lifu chi chiu dupc tai trong mpt chu kt, cd gia tri hang 4,263*UTS

- B1 :La hf sd mu chju mdi, the hifn df ddc ciia dudng mdi S-N, dupc tinh toan dua tren tieu ling suat pha huy tai tai chu ki dau tien, cd gia trj bing -0,125

- NCI: La ±dng sd xae dinh so chu ki gidi hgn mdi cua md hinh (tuoi thp chi tiet;

- FL (fatigue limit): La iing suat gidi hgn bdn mdi, vdi iing suat dd vft lifu dupc coi

la ben vd hgn Gia tri ciia FL tuang tuong gia tri S^ trong phin ly thuydt ben mdi phia =

ISSN 0866' 7056

TAP CHl CO KHl VI$T NAM Sd 8 nam 2016

NGHltN CCfU - TRAO D O I

tren FL dupc tinh theo iing suit gidi han

phi huy ciia vit lieu UTS = 690 MPa vi ip

dyng cic cdng thirc thuc nghiem nhu sau:

Ddi v&i vgt lieu bdng gang: S'^ = 0,4*UTS

Tren thuc te, chi tiet thudng chiu img

suit khdng gidng vdi dieu kipn thir nghiem xiy

dyng dudng eong mdi, nen vipc xic dinh gii tri

gidi h ^ bin mdi thyc ti S^ thudng rit phirc t?p

Vi viy, gidi h ^ mdi fliyc ti dupc tinh thdng

qua cic hp sd hieu chinh:

FL = S^=kJ^kk^k^S'^

Trong cdng thire tren:

k^ li hp sd ke den inh hudng cua dp

nhim be mit: k„ = aS,

Mpt sd nghien ciiu di clii ra ring, iing

suit du tjo nen hipu iing ting bin Vi viy, khi

tinh bin mdi ngudi ta thudng liy: k_ = 0,959;

K^ - Hp sd kich thudc: k^ = 6,75;

k^ - Hp sd tii trpng: k^ = 1 khi chju udn;

kj - Hp sd inh hudng cua nhipt dp: k^ =

1 trong dii nhipt dp tit 0 - 250°C;

k^ - Hp sd tip trung iing suit: k^ = 0,8;

Dod6:FL= 158,81 MPa

Sau Ichi di nhip tit ci cic thdng sd tren

vio phin m6m chuyen dyng, la se cd d^ng biiu

do gidi h?n mdi dupc phin mim HyperWorks

dinh nghia nhu hinh 8:

Sau khi di cd thdng sd ciia vit lieu, ta can xic dinh cac thdng sd cho tinh toin mdi, cic thdng sd niy se dupc dinh nghTa qua bing gii tri 3.10 (fatigue parameter)

Bdng 4 Bdng xdc dinh cde thdng sd ddu vdo lieu chudn ptidn tieh bdi todn mdi:

3 STRESS COMBINE CORflECT ' RMNFliW

R n i T GATEREL

B aRTNTY SURVdRT

V 0 N M I S E 5

MM UIAO

as

ITmh 8 Du&ng cong mdi S-W Irong tru&ng hgp xde

dfnh theo ung sudt mdi gi&i hgn eiia vgt ligu FL

Trong do:

- COMBINE: Diing de xic dinh lo^i ling suit sa dupc sii dyng cho tinh toin mdi, d diy ta sir dyng irng suit tuong ducmg Von Misses

- CORRECT li tieu chuin sir dyng cho

tinh toin mdi d day, tic gii chpn tieu

chuin GOODMAN, tieu chuin tinh toin GOODMAN trong phin mim giing nhu

di trinh biy d phin 2.1 vi ly thuyit mdi

- STRESSU: Dan vj iing suit, chpn Mpa

- RTYPE: Xic dinh lojii tii trpng djt vio li6n tyc, d ^ g tii trpng ddng (Rainflow type) day li phin xic dinh Io?i LOAD trong bii toin mdi

- SURVCERT: Survival of certainy Phy thupc vao thdng sd SE trong vjt lipu d diy

SE mic dinh bing 0, nen he so niy di theo m|ic djnh bing 0.5

Tren diy Ii qui trinh nh|p thdng si xic dinh diiu kipn cua bii toin mdi, tic gii di xic dinh dupc ca sd di phin tich trong phin mim chuyen dung Sau dd, dii lipu tinh toin tii bii toin dpng ngau nhien, gom: Cic dil li$u vi lyc, moment theo thdi gian, thii ty cic sy kifn tic dpng vio vd ciu, s6 dupc nhip vio phin

ISSN 08«6-7056

TAP CH! CO KHl VIET NAM, Sd 8 nim 2016

NGHieN CLfU-TRAO 0 6 l

mem de tinh toan tudi thp cua chi tidt (Nc - life

cycles)

4 DANH GIA BQ BEN MOI CUA VO CAU

CHU DONG

Trong n$i dung khao sat nay, vide danh

gia dp bdn mdi ciia ca vd cau nguyen ban va

vd cau sau cai tidn kdt cau dupc thpc hifn

trong trudng hpp tai trpng dpng Idn vdi che dp

thudng xuyen hogt dpng ciia xe (trudng hpp xe

di tren dudng rat xau) Cac che dp map md m^t

dudng khao sat la loai dudng D-E va E-F theo

tieu chuin ISO 8606:1995

cac tai trpng dpng tac dpng ldn vd cau

khi xe chay tren dudng dupc xae dinh tu md

hinh dpng li;c hpc

Hinh 9 Sd chu ky mdi tren md hinh nguyen bdn

v&i logi du&ng D-E

Hinh 10 Sd chu ky mdi tren md hlnh nguyen bdn,

v&i logi du&ng E-F

Bdng 5 So sdnh cdc sd chu ki bin mdi tren md

hinh vd cdu nghien cuu trong 2 logi mgt du&ng

ngdu nhien DE vd EF:

Md hmh

Logi dudng

Vi tri diem moi

nhd nhit

Sh chu ki nho nhat

Yd clu chu df ng

Dudng D-E

374998

2.428x10*

Dudng E-F

374998 3.431x10*

Kdt qua tdng hop ve nghien ciiu dp ben radi ddi vdi md hinh vd clu chu dpng khi xe chay trdn dudng D-E va E-F, dupc the hifn trong bang 5 Khi xe chay tren dudng D-E sd chu ky mdi tai mpi didm tren vd cau deu ldn hem 10*, nen cd thd coi la tren vd clu khdng cd didm mdi va vd clu dug^ coi la ludn dii dp ben radi, vd clu thira bdn trong logi dirdng xau Khi xe chgy tren dudng E-F, sd chu ky mdi tai mpi diem tren vd cau deu ldn hon 10*, nen cd the coi la vd cau du df bdn mdi Tuy nhien, so vdi loai dudng D-E, sd chu ki mdi cua

vd clu da giam han 100 lln, dieu nay hoan toan phil hop quy lugt myen tinh

Vgy, ca 2 logi dudng xiu (duomg ndng thdn) va rat xau (dudng ddi mii) deu du bdn do

dd dd xult cac giai phap cai tien vd cau nfaim tdi uu khdi lupng

5 KET LUAN Bai bao da nghien ciiu df ng tpc hpc md hinh xe tai, xae dinh tai trpng dpng tac dpng ldn

vd clu chii dpng xe tai nh^ san xuat, lip rap tgi Vift Nam Md hinh xae djnh tai trpng dfng va cac kdt qua tinh toan l^c dpng sd dupc sur dpng cho bai toan xae dinh dp ben ciia vd cau chii dpng

Danh gia dp ben mdi ciia vd cau khi xe chgy tren 2 logi dudng xau (dudng D-E) va rat xau (dudng E F) theo tieu chuan ISO Ket qua cho thay, vd cau can dupc cai tidn nham giam khdi lupng do thira ben Thdng thudng, day la cac logi dudng xau, van dam bao didu kifn ben mdi cho vd cau, do dd, cd the iam ca sd nghien Cliu tdi uu cho logi vd ciu nay

Cac nghien ciiu dupc thpc hifn tren 2 phan mem tien tidn hang dau hifn nay tren thd gidi la Matlab va HyperWorks Khi xay dung

md hinh da thpc hifn cac budc theo tieu chuin

va da dupc danh gia bing phin mdm Do dd

ISSN 0866 - 7056

TAP CHf CO KHf V I £ T NAM, Sd 8 nam 2016