Phương pháp mới xác định lực cản đào đất của máy xới

NGHIEN CUU - TRAO eO l

Sai sd bien do ciia phuang phap EFG so vdi giai tich:

0,67%

Hinh 8: Anh hutjng ciia kich thuoc support domain len ket qua

Nhan xet cac ket qua:

Trong bai toan nay, phuang phap khdng ludi EFG cho

ket qua kha tdt vdi sd nut it hon phuang phap phan tir hiru

han. Ket qua tir phuong phap khdng ludi EFG kha khdp

vdi ldi giai giai tich khi sd nut du Idn.

Trong qua trinh thyc hien, nhan thay rang kich thudc

suport domain cd anh hudng rat nhieu den ket qua (Hinh

8). Kich thudc suport domain nen chgn Idn hon 2 den 2,5

lan khoang each trung binh giUa cac niit de cho ket qua

chinh xac nhat.

5. Ket luan

Tir cac ket qua tinh toan, cd the ket luan rang phuong

phap Element Free Galerkin hoan toan cd the ap dyng

dugc trong viec tinh toan - md phdng bai toan lan truyen

am. Ben canh mdt sd iru diem, phuang phap nay van tdn

tai mdt sd han che nhat djnh.

Ve uu diem:

Ham dang dugc xay dyng, tinh toan trye tiep trong

chuong trinh.

Dii lieu lun trii cho bai toan chiem it dung lugng hon

phuong phap phan tii hiiu han

Cd nhieu thdng sd tiiy bien (sd lugng niit, ham trgng

sd, kich thudc support domain, hinh dang support domain,

kich thudc d tich phan) nen ngudi nghien ciru cd the de

dang thay ddi de cai tien chuong trinh.

Ve nhugc diem:

Ciing do cd nhieu thdng sd tiiy bien nen thyc te hien

nay chua cd mdt giai thuat cd dinh, tieu chuan cho moi

loai bai toan.

Tuy phuang phap EFG khdng sir dyng phan tir nhung

vin chua mang day dii y nghia "khdng ludi" bdi vi van ton

tai ludi tich phan. •

Tai lieu tham khao:

[1]. Nguyen Hai, 1997, Am hoc va Ki8m tra Tieng on. NXB Giao Due,

[2]. G.R. Liu, 2003, Mesh Free Methods - Moving Beyond The Finite

Element Method. CRC Press.

[3]. Shaofan Li, Wing Kam Liu, Meshfree and particle methods and

their applications.

[4]. Stephane Suleau, Philippe Bouillard, 2000, Accurate acoustic

computations using a meshless method.

[5]. Stephane Suleau, Philippe Bouillard, 1997, Element-Free

Galerkin solutions foe Helmholtz proplem: formulation and numerical

assessment of the pollution affect.

[6]. Stephane Suleau, Amaud Deraemaeker, Philippe Bouillard, 1999.

Dispersion and pollution of meshless solutions for the Helmholtz

equation.

[7]. Juan Fernando Belts. April 29, 1998. Finite Element Study Of

Plane Wave Acoustic Phenomena In Ducts. Thesis submitted to the

Faculty of the Virginia Polytechnic Institute and State University.

[8]. Release 12.0 Documentation for ANSYS, ANSYS, Inc, 2008.

PHl/G^NG PHAP MCn XAC DINH

Ll/C CAN OAO OAT CUA MAY XCH

Tom tat: Bai bao dUa ra cac cong thufc giai tich de xac djnh lUc

can xdi dat theo chi so tich phan do ben cua dat- so va dap cua

mat do ke khi thi cong dat bang may xdi. Dieu nay tranh dirctc

khuyet diem cua cac phuctng phap xac djnh lufc can xdi dat dUa

tren cac cong thiifc thUc nghiem chijfa dUng hang loat cac he so

kinh nghiem. Bai bao cung da so sanh ket qua tinh toan ly thuyet

vdi ket qua thur nghiem ddi vdii cac may xdi dat. Sai sd khdng vUOt

qua 16%. Cac cdng thiiTc dUa ra co the dimg de phan tich djnh

luong va djnh tinh liTc can xofi dat tiiy thudc vao cac yeu td anh

hudng den chi sd tich phan do ben cua dat.

(*) TS. NGUYEN DANH SON

Cac tinh toan lyc can dua tren cac cdng thire

thyc nghiem chira dyng hang loat cac he so

kinh nghiem va cac tinh toan nay chi diing

vdi cac di8u kien, d dd cac he sd nay dugc

xac dinh [1]. Cac lyc can cd thi dugc xac

dinh tren ca sd cac phuong phap co hgc mdi trudng lien

tyc, ca biet la mdi trudng cd dinh bam. Dieu nay cho phep

tranh dugc nhugc diim neu tren. Cac lyc can trong trudng

hgp nay xac dinh qua cac ling suat phap va iing suat tiep

(*) Trucmg Dai hpc Bach khoa TP.HCM

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TAP CHI C 0 KHI VieX NAM • So 03 Thang 03 nam 2010