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 B^N M | V 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 Dpng lire, Trudng Dai hpc Bich Khoa Ha Npi "Khoa Cdng ngh^ td, Trudng Dai hpc Cdng nghi$p Hi Npi TOM TAT Kieh thieh lie mgt du&ng gay nen tdi trpng dpng biin thien lien tuc theo thdi gian ldc dgng ten vd cdu, tr& ihdnh nguyen nhdn tiim Idng gdy nen hign luang hu hdng moi Nhieu cong trinh nghien cieu vi linh vtfc ndy da chung minh linh dung ddn sie dgng mo hinh dao dpng cda d td v&i kich thich tie du&ng Id hdm ngdu nhien di xdc dinh tdi trgng ddt ten vo edu Cdc tdi trpng ndy sau dd dupe sie dtfng ldm dieu kign ddu de ddnh gid dp bin mdi cua vd cdu Trong bdi bdo ndy, ldc gid dd khdo sdt md hinh mgt du&ng ngdu nhien Idc dpng len vd cdu xe tdi ldm nguon kich ddng de ddnh gid dg bin mdi cua xe tdi qud trinh hogt dpng Bdi bdo dua dugrc phuang phdp lugn nghien cuu, edc lieu chudn ddnh gid ve dp ben mdi ciia vd edu th&i gian hogt dpng Tir khia: Bin mdi, vd edu chu dgng, md htnh dpng luc hgc, tieu chudn ISO 8608:1995 ABSTRACT Road roughness excitation apply on rear axle housing of truck in time domain to make variable force and reasonoffatigue failure on it Many researchers on thisfieldshowed that it is trust using random road roughness excitation as input data to solve and analyse problems Dynamic force apply on axle housing to estimate fatigue failure On this research, we calculated input data then using to analysis fatigue during time life of truck This paper showed that the methodology and standazation to estimate life lime of rear axle housing truck Keywords: Fatigue failure, driving axle housing, dyrmmic model, ISO 8608:1995 l.DATVANDE Nghien ciiu dp ben mdi thudng xuit phit tir tai trpng map mo mit dudng Kich thich tu mit dudng gay nen tii trpng dpng biin thien lien tyc theo thdi gian tic dung ien vd ciu vi trd thinh nguyen nhin tilm ting giy nen hi?n tupng hu hdng mdi Nhiiu cdng trinh di cdng bd cic kit qui nghiSn cuu vi Ilnh vyc niy, do, cd tic gia di sii dymg md hinh dao dpng cua d td vdi kich thich tit dudng Ii him ngau nhiSn de xic djnh tii trpng dit Ien vd ciu Cic tai trpng niy sau dd dupc sii dimg lim diiu ki$n diu di danh gii dp bin mdi ciia vd ciu ISSN 0866 - 7056 TAP CHl CO KHl VI|T NAM, Sd nim 2016 WA^^'.cokhivietnam.vn N G H I E N CU'U-TRAO B C I 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 Neu nhu trudc day, m ^ md mat dudng dupc su dving chu yeu 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, dd cd vd cau 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 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) Hi^n nay, phuong phap md ta map md m$t dudng bang ham ngau nhidn dk dupc chuan hod theo tieu chuin ISO 8608:1995 Vi v|y, cac nha nghien cuu thudng su dyng tieu chuSn dh md ta kich thich tu m^t dudng cac md hinh dpng lyc hpc ciia d td Tii tieu chuin ISO 8608:1995, cic nhi nghien ciiu sii dyng cic phucmg phip khac di md ti raip mo mat dudng dudi d?ng: Theo tieu chuan 8608:1995, mAp md m$t dudng dupc md ta thdng qua thdng sd co ban la tin sd khdng gian, bien dang dudng va hilm m^t dd 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: G.:/.) = C.K)(^] (1) Hoic: G,(n)=G,(n„)| (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 Mdi quan h^ giiia tin sd n vi tin sd gdc dupc the hi^n bing biiu thiic: n = Q/2n 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 Thong so md t i mip mo theo tio s6 khdng gian, n k G,(n^[10-'m'] - Trung binh 24 Max A-B B-C 25 26 C-D D-E 27 29 27 29 E-F F-G G-H H+ 211 213 28 210 212 - Mln 215 217 25 211 216 213 215 217 - - 214 Hg = 0.1 chu ky/m Banh gij d$ b^n mdi vd cau chu d$ng: Dd danh gia dd ben ISu ciia chi tidt chiu "^ ISSN 0866 - 7056 TAP CHi CO KHf VI^T NAM, Sd nam 20! www.cokhivietnam.vn NGHieN CU'U-TRAOBOI tii trpng lip cd chu ky, ngudi ta thudng sir dyng dudng cong mdi bing thuc nghiem (cdn gpi li dudng cong S - N) Dd thj tren cho thiy, neu chi tiet chiu img suit thip hon S\ thi khdng xiy hdng mdi ci N ->IJO Gii Ui ung suit S', dupc gpi Ii gidi h?n mdi chuin cua vit li$u, 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 khoang lb'-10' Cic kit qui nghien ciiu thuc nghi$m khic da cho thiy, so chu ky tii tic dpng tuong img vdi gidi ^ mdi ddi vdi thep vi gang thudng nim khoing tir 10* din 10" Vi viy, cic nha nghien ciru cho ting, cd the chip nhin gii thiit Ii chi tiit si khdng hdng mdi sau chju dupc 10* chu ky, dudng cong mdi nim ngang sau d?t 10* chu ky, nhu ben dudi mdi N vi tit dd tinh dupc tudi thp cua nd Tuy nhien, cic chi tiit miy diiu kipn lim viec thuc cua nd khdng chiu tii trpng gidng nhu diiu ki?n thi nghi$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$m vdi cac diuig tii trpng khic ciing cho kit qui thip hon so vdi S'^ chuin tir 10 - 30%, tnidng hpp cy thi Do khdng thi Iim thi nghi?m xic dinh S' cho mpi diiu kipn tii trpng, nen chip nhin vi$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„, TSW^STFT^ Trong dd: k, Ii hp sd kinh nghi$m, phy thupc chil yiu vio lo^i vit lipu Doi vdi cic lo^i gang vi th^p: k, = (0,45-0,65) Hinh I Kit qud Ihi nghigm tren thiet bi tteu chudn Do vi?c tien hinh thi nghidm xiy dyng ducmg cong mdi mit nhieu thdi gian va chi phi, nen ngudi ta di cd ging dya tren cic ket qui thi nghi$m tim mpt sd quy luit d6 tir 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$u: S,=0,5S„ Vdi dudng cong mdi di dupc xay dyng, niu xic djnh dupc gii tri img suit mi chi tiit phii chju la S thi ta cd the dya vio dudng cong mdi de suy sd chu ky tii tic ddng gay hdng Ngoii ra, mdt sd thdng so ket cau, che dd tii trpng vi diiu kipn lim vipc ciia chi tiet ciing gdp phin Iim giim gidi h?n mdi Vi viy, gidi h^n mdi thyc te S,, thudng dupc tinh tit gidi h^n chuin S'^ thdng qua mpt loat cic hp so anh hudng Thdng thudng, ta cd: S< S\ Gidi h?ui b6n mdi thyc te S^ dupc sir dyng Iim ca sd di dinh gii ben mdi ciia chi tiet bing nhiing phuong phip khic Mpt nhiing phuong phip thdng dyng nhat hipn li sur dyng cic tieu chuin bin mdi Cic ket qui nghien cihi thyc n g h i ^ ISSN 0866-7056 TAP CHl CO KHl VI$T NAM, Sd nim 2016 www.cokhivietnam.vn NGHieNCCrU-TRAODd cho thay, hu hdng mdi phy thudc chu ydu vio 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^ (truefracturestress) vdi S < S^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 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 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