NGHIEN c a u TRANG THAI UNG SUAT CUA NONG SUNG PHAO CO RANH XOAN KHI BAN
STUDY ON THE STRESS STATE OF THE RIFLED-BORE BARREL WHEN FIRING
ThS. Biii Quy Vi^t Hgc vien Ky thuat Quan sir
Trong nghien cihi nay, nongphdo co rdnh xodn duac mo hinh hoa vd sir dung phan memAnsys tren ca ca phuang phap phan tic him han dephdn tich nghien cuu. Bdi toan chi xet nong chiu tdi dp suat vd tinh trong truong hap chiu tdi tinh. Ket qua cho thay rdnh xodn co anh huang ddng ke den trgng thai ung sudt ben trong thanh nong. Bdi bao co the dung tham khdo de nang cao tinh chinh xdc trong cong tac tinh toan, thiet ke vd che tao nong sting phdo.
Tir Uioa: Trgng thai img sudt; Nong co rdnh xodn; Hi so cuang do ung sudt.
ABSTRACT
In this study, a rifled-bore barrel has been modeled and investigated by using Ansys software on the basis of finite element method. The problem has only been treated under pressure load in static case. The results showed that twist grooves had a significant influence on the stress state inside the barrel wall.
The article can be used for reference to improve the accuracy in calculating design and manufacture artillery guns.
Keywords: The stress state; The rifled-bore barrel; The stress intensity factor.
. DAT VAN D E dang va cac anh hudng khac dudi dang he sd an Nghien cuu trang thai ung suat cua ndng sung toan [1 ;2]. Thuc te vdi siing va phao cd ranh xoin, phao la ndi dung quan trgng trong tinh toan thilt "^ ph^n dan hudng ndng cd ranh, do dd trang thai k l he thdng phao. Tuy nhien, trong cac tai lieu <^^?> suat ben trong thanh nong khac h i n vdi trang tinh toan, thilt k l vu khi hien nay d i u gia thilt thai ung suat ben trong dng tru iron bdi sir tap ndng la 6ng tru day va dua cac anh hudng ve hinh trung img suat tai cac gdc ciia ranh xoin. ^
TAP CHi CO KHi VIET NAM, S6 3 nam 2014 www.cokhivietnam.vn
NGHIEN cuu-TRAO DOI
Cac nghien ciiu trudc day, cho loai bai toan tap trung ung suat chii yeu tap trung vao cac chi tiet dang tam hoac la tap trung ung suat tai dau cac vet nut [4;6]. Nhu vay, nghien cuu trang thai ung suat ben trong thanh ndng cd ranh xoan trong ndng siing phao la bai toan thuc su cd y nghia trong viec tinh toan thiet ke he thdng phao.
2. BAI TOAN XAC DINH TRANG THAI l]"NG SUAT CUA NONG SUNG PHAO CO RANH XOAN
a. Md hinh bai toan
Cac gia thiet:
- Vat lieu ndng la ddng nhat va dang hudng, bien dang nhd, trong gidi han dan hdi, quan he img suat, bien dang tuan theo dinh luat Hooke.
- Ap suat phan bo deu va tac dung vudng gdc len be mat trong cua thanh ndng. Dudi tac dung cua ap suat cac diem tren thanh ndng d vao trang thai can bang.
- Xet mat cat each dau ndng mot khoang du Idn de cd the bao dam la mat phang va bd qua tac dung cua nhiet dp, do dd viec giai bai toan dua ve giai bai toan phang vdi trang thai biln dang phing. Md hinh tinh nhu hinh 1:
'0 9 0,r,e, Hinh I: Mo hinh bdi toan nong chiu dp sudt trong.
b. Co- sd ly thuyet xac dinh irng suat ben trong thanh nong
De xac dinh h^ang thai img suat trong thanh ndng, ta su dung he cac phuang trinh bao gom cac phuong trinh can bang, phuang trinh lien tuc va cac mdi quan he the hien dieu kien bien.
Phuong trinh can bang:
1 dGg dz^
r de dr Idr^. da, r do '^ dr
Phuang trinh lien tuc:
8- 1 a 1 3 -
0)
dr' ' dr
do'
.(^. +o"e)=0 (2) Trong dd: r, 9: Tga do trong he tga do cue toan cue, o^, o^: ung suat phap hudng kinh, ung suat phap theo phuong tiep tuyin, c^g ^ T^^: ling suat tiep.Dieu kien bien:
\Tj£dS = jp^Su^d
Vdi: S: Tiet dien ngang cua ndng, 1: Chu vi, p^: Ap suat.
Cac dieu kien bien dgng hgc dugc bd qua.
Cac phuong trinh (1), (2), (3) tuong img vdi mot nhiet do nhat dinh.
Tuy nhien, trong truong img suit gin ranh xoan luon cd sir tap tning img suit va ung suit tai mot diem trong thanh ndng dugc tinh [21:
I TAP CHI CO KHI VIET NAM, So 3 nam 2014 www.cokhivietnam.vn
(7^ - , —COS— COS
^,
JlmA'^ 2 4 2
5 . 6 , 3 . 3e, A 1 ^ 1 (4)
K, (l e, 1 39,
: —j=S=\ — C O S ^ H COS
42m^['i 2 4 2 J27I7',
3 . ^, 3 , 3 ^ ,
—sm—' sm—- 4 2 4 2
- ^ i s
^/2;^7•, 4
A:,, f l <9, 3 30, , ^ —cos—^ + —cos—^
, & 4 2 4 2
Vdi: K^ va K^, la cac he sd cudng do ung suit, OjrjOj la he tga do cue cue bd tai gdc ranh xoan.
De loai bd diem ky di trong trudng ung suat, Siebel va Stieler [6] da dua ra khai niem vd hudng, gradient ung suSt, x, dugc tinh tir sir phan bd ung suat theo ling suat Idn nhat a^^^, tai gdc rSnh xoan. Gradient ung suat, x, dugc tinh theo (5) va the hien tren hinh 2.
da dx (5)
Siress gradicni x. nim"'
Hinh 2: Quan he giira gradient ung sudt vd img sudt dan hoi l&n nhat tgi mot dinh ranh.
Khi dd, su thay ddi ung suat tir gdc ranh xoan vao ben trong thanh ndng (phan phdi ung suat) dugc the hien nhu hinh 3.
Giai cho bai toan ung suat ben trong thanh ndng cd the su dung phuong phap sd tren ca sd ly thuyet phan tir him han.
Hinh 3: Suphdn bo img sudt tir goc ranh vdo thdnh nong.
3. VI DU TINH TOAN CHO MOT LOAI N6NGCOfl22MM
Giai bai toan thuat phdng trong vdi cac dilu kien nhdi h-ong [1] d cac nhiet do tieu chuin (+15"C), tj - +50"C va t^ = -50°C, ta dung dugc dudng cong ap suit khi thudc Idn nhit ben trong thanh ndng (hinh 4):
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NGHIEN cuu-TRAODOI
Hinh 4: Duong cong dp sudt l&n nhat trong long nong.
Su dung phan mem Ansys de xem xet trang thai ung suat ddi vdi mot mat cat. Cac tinh toan dugc thuc hien vdi cac du lieu ban dau sau day [1]: Thong s6 hinh hgc chi tiet: Ban kinh trong: i^
- 61 mm, ban kinh ngoai: r^ ^ 95 mm; Thdng sd vat lieu: Md dun dan hdi Young E ^ 2.1 * 10" N/m^
= 2.1*10^ N/mm^, he so Poison: |i = 0.3; Thdng sd tai: Ap suat p ^ 130 MPa. Vdi cac thdng sd da cho, ket qua tinh cho trudng hgp ndng khdng cd ranh xoan duoc the hien tren hinh 5.
H'lnh 5: Trgng thdi ung sudt nongphdo 122 mm khong CO rdnh xodn.
Khi cd ke den ranh xoan, vdi cac thdng sd ranh: sd ranh xoan n ^36, chilu rgng ranh xoin a ^ 6,6 mm, chieu rgng song ndng b = 4,04 mm, chieu sau ranh t - 1 mm, ban kinh gdc luon ranh
p - 0,5 mm; k i t qua tinh toan trang thai img suat dugc the hien tren hinh 6.
Hinh 6: Trgng thdi ung sudt nongphdo 122 mm CO rdnh xoan.
Ta thay, ung suat Idn nhat trong trudng hgp nay Idn han 1.17 lan so vdi tru'dng hgp ndng troti va ung suat nhd nhat cung nhd hon, bang 0.97 lan.
Ung suat Idn nhat tap trung tai gdc ranh xoan, ling suat nhd nhat tap trung tai dinh song xoan.
4. KET LUAN
Ket qua cd the dugc su dung de danh gia kha nang chiu tai cua ndng chiu tai ap suit khi thuoc.
Ket qua cho thay, dudi anh hudng cua tai trgng ap suit khi thudc, ndng phao cd sy tap trung ung suat tai gdc cac ranh xoan va su phan bd ung suit khong d i u ben frong thanh ndng. Gia fri ung suit Idn nhit phu thugc vao he sd cudng do ung suat. He so cudng do ung suat la ham kit hgp ciia 2 dang I va dang II do dieu kien chiu tai cua ranh xoan. Nd phu thudc vao sd lugng ranh xoin n, chilu rgng ranh xoan a, chieu sau ranh t, ban kinh gdc luon ranh p.
Bai toan cd the dimg de tham khao nang cao tinh chinh xac hrong cdng tac tinh toan thilt kl va c h i tao ndng sung phao.'t*
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Ngay nhan bai: 05/02/2014 Ngay phan bien: 20/3/2014
Tai lieu tham khao:
[1], Khong Dinh Tuy, Nguyen Viet Trung, Nguyen Van Diing, Ca sa thiet ke he thong phao. Hoc vien Ky thuat Quan su, (2009).
[2]. Phan Nguyen Thieu, Khong Dinh Tuy, Nguyen ly thiet ke vii khi co nong, Quan dpi Nhan dan, (2000).
[3]. Hoang Xuan Lugng, Pham Tien Dat, Nguyen Thai Chung, Ly thuyet dan hoi-deo-tir bien., Hoc vien Ky thuat Quan su, (2008).
[4]. E.'E.Gdoutos, Fracture Mechanics An Intj-oduction. Kluwer, London, (1993).
[5]. Yukitaka Murakami, Metal Fatigue Effects of small defects and Nonmetallic Inclusions. Elseviei" Science, Oxford, (2002).
[6].E. Siebel and M. Stieler, Ungleichjormige Spannungsverteilung bei Schwingender Beansprvchung.VDlZ., 1955.
[7]. E.M.Mopo30B, A.lO.MyHseMHeK, A.C.LUa;icKnii, Ansys e pyxax unoiceHepa- MexauuKa paspymemm.
JlenaHa, MocKsa, (2008).
[8]. Vii Qudc Anh, Tinh toan ket can bang phan mem ANSYS, Xay dung, (2006).
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