De xac dinh luc T2 hay tinh cong cat rieng ta phai biet dien tich mat cat ngang ciia kh6i ram sau khi dugc nen den trang thai cat, vai ly do nay ta can nghien ciiu quan he giiia ap lire
Trang 1KET QUA THi NGHIEM XAC DINH MOT SO THONG SO PHU THUOC VAO
DAC TiNH c a LY CUA ROM Tl/Ol TRONG QUA TRINH CAT ROM
Nguyen Vdn Tam ' Le Minh Lir' NguyenXudn Thiet"
TOM TAT
Hien nay ram sau thu hogch lua da vd dang dugc nghien ciru vd xir ly theo nhieu hirdng ldm cho nguon
ram, rg ngay cdng cd gid trj han Trong hdu het cdc phirang dn xu ly viec xdc dtnh cdc dgc tinh ca ly cua ram
la cdn thiet Trong phdn nghien ciru ndy nhdm tdc gid giai thieu mpt so thdng \d phu thupc vda dgc linh ca ly
cua ram tucri nhu: dnh hudng cua gdc cat trugt den dp luc cdt thdi rieng vd cong cdt rieng anh liicdng ciia khe
ha giira mat ben cita dao vai Idm ke den dp lire ep khdi ram dd dm/c cat vdo thanh ben ciia dao; dnh hut'mg
cua dp hrc ep den dp bien dgng ciia khdi ram tirai trong qud trinh ep: he so ma sdt cua ram tuai vdi thep vd
khdi luang rieng cua ram tirai Viec xdc djnh quan he va dgc diem tren lam ca sir de nghien ciru, tinh todn bp
phgn cdt ram dong thdi la ket qud ujig dung cho cdc cdng trinh nghien ciru kliac lien quan den rain tirai
Tir khoa: Ram rg bp phcin cat, mdy cdt ram
EXPERIMENTAL RESULTS DETERMINING SOME OF PARAMETERS DEPENDENT OF
THE PHYSICAL-MECHANICAL PROPERTYOF FRESH STRAW
IN THE PROCESS CUT STRAW
Nguyen Van Tam ', Le Minh Lu \ Nguyen Xuan Thiet"' SUMMARY
The currently straw after harvesting has been much research and treatment direction, make resources straw
increasingly more valuable In most of the straw treatment plan defining the physical-mechanical property of
straw is needed In this study, Uie authors introduce a number of parameters depends on the
physical-mechanical property of fresh straw as: effects of shear cutting angle to specific cutting pressure and specific
cutting public; effects of slot between the side face of the knife with chocking plate to press pressure of straw
blocks were cut on the side face of the knife; effects of press pressure to deformation of fresh straw in the
compression process; coefficient of friction of fresh straw with steel and specific weight of fresh straw With
the relationships and characteristics of fresh straw as the basis for research, calculating the straw cutting parts,
concurrently applied to the results of other studies have a connection with fresh straw
Keywords: Straw, cutters, straw cutters
I DAT VAN DE
Doi vai viec thiet ke che tao cac bg phan Vai nguyen ly cat thai dao co dinh, canh
hoac may cat thai ram, ra cho den nay da co gat (xkn ke) chuyen dgng (hinh 1) dS xac dinh
nhieu mau may sii dung cac nguyen ly cat thai ap luc cat thai rieng qd can xac dinh lire cat thai
khac nhau Song, vai mgi nguyen ly cat thai de cin thiet Pa(N) va do dai doan luai dao cat
xac dinh dugc nSng lugng ck thai trong tinh AS(cm) Khi do ap luc cat thai rieng dugc xac
toan 1^ thuydt, mgt thong so quan trgng can dinh theo cong thurc (Tn'tn Minh Vuang vd
dugc xac djnh la ap luc cat thai rieng qc,(N/cm) Nguyin Thj Minh Thuan, 1999):
Ap lire cat thai rieng q^ la lire can thiet de cat p ^
diit vat thai theo phuang vuong goc vcri luai dao ^" ~ A.9.(l-i-/.tanr).cosr ^'^
tren mgt dan vi chieu dai lam viec ciia ludi dao Trony
do-I ThS Tmimg Cao ding ngha co gioi Ninh Binh P^i- Luc cat thai can thiet theo phuang van
^ TS Trudng D^i hpc Nong nghidp Ha Npi ^^^ ^jg^ ^ ^ j
' TS Tni6ng Dai hgc Nong nghidp Ha Npi
TAP CHi CONG NGHlfP NONG THON - SO 12 - 2014 27
^^^9/j sr
Trang 2f - he so ma sat cua rom tuai \ a thep;
T - goc cat trugt
Tir (I) ta thay ap lire cat thai rieng qo phu
thugc vao goc cat trugt T va he so ma sat f, do
\ay can nghien ciiu anh huang cua goc cat
trugt T den ap lire cat thai rieng qd
De thuan lgi cho viec phan tich cac thanh
phan lire tac tac dung len dao trong qua trinh cat,
xet sa do qua trinh cat trong truong hgp goc cat
trugt T = O" (hinh 1) Khi cat thai cac vat dan hoi
qua trinh cat co hai giai doan; dau tien la luoi
dao nen ep vat thai mgt doan, roi den cat dut vat
thai Trong qua trinh luai dao di vao vat thai con
phai khac phuc cae lire ma sat do luc dan hoi N2
ctia phan khoi ram da dugc cat tac dgng vao mat
ben cua dao va ly:c N | do vat thai dich chuyen bj
nen ep tac dgng vao mat vat cua canh sac luoi
dao Neu ggi P, la lire can cat thai thi luc cat thai
can thiet Pd la:
P^, = / ^ + 2 r , + 2 , 7 ; c o s / - H 2 A ' i S i n v ; ( N ) (2)
Trong do: y la goc mai dao doi voi cat rom
chgn y = 15"
Hinh I Sa do qud trinh cdt thai bang lirai dao cd dinh
Tu (2) ta thay luc ma sat T; do kh6i roiu da
dugc cat vao mat ben ciia dao co anh huang
den luc ck thai c4n thi^t Pd- Song d6i vai
nguyen 1\ iia\, luc ma sat T: phu thugc vao khe
ha S (5 la khe ho gitra mat ben cua dao va tSm
ke) Vai phan tich nay can nghien ciiu anh
hucmg cua khe ha 5 din ap lire do kh6i ram da
dugc cat tac dgng vao mat ben ciia dao
De xac dinh luc T2 hay tinh cong cat rieng
ta phai biet dien tich mat cat ngang ciia kh6i ram sau khi dugc nen den trang thai cat, vai ly
do nay ta can nghien ciiu quan he giiia ap lire nen va do bien dang tuong doi ciia khoi rom khi nen:
Neu ggi ap luc nen ram la qn (N/cm^), ggi ho
la chieu cao ban dau cua khoi rom a trang thai tu nhien: h,, la chieu dai doan duang nen khi do ty
so nen dugc dinh ngliTa theo cong thiic:
h
e = -^
k
(3)
Neu ggi Sn la dien tich mat cat ngang phan khoi ram dugc nen, de xac dinh dugc chieu cao khoi ram ban dau ho ta phai biet dugc khoi lugng rieng ciia ram tuoi pr Vai phan tich nay can xac djnli dugc quan he giiia ap lire nen q,, voi ty s6 nen s hoac vai khoi lugng rieng ciia rom tuai
De xac djnh moi quan he gifla cac y^u t6
da dugc phan tich trong cac ngi dung tren, can thiet ke thi nghiem va phan tieh ket qua nghien ciixi de xac dinh cac moi quan he nay
IL VAT LIEU VA PHUONG PHAP NGHIEN CUtJ 2.1 Vat lieu
Vat lieu thi nghiem la rom tuai lay tai thoi diem sau khi gat mgt nga> tir gidng lua BCI5 Cac ket qua nghien ciiu ban dau ve dac tinh ciia rom tuoi dugc thuc hien tai Khoa Ca dien -Truong Dai hgc Nong nghiep Ha Ngi
De CO mau ram thi nghiem nhu nhau inoi loai thi nghiem mau rom deu dugc chon theo don vi khoi lugng tren chi^u dai mau rom Doi voi thi nghiem xac dinh anh huang ciia goc cat trugt T den ap luc cat thai rieng qd, moi mau ram co khoi lugng bang lOg voi chieu dai mau rom 20cm Doi vai mau ram thi nghiem xac djnh quan he giira ty so nen e va ap lire nen qn, moi mau ram co khoi lirgng 50g vai chieu dai mau ram 20cm Mau rom thi nghiem dugc xac djnh bang can dien ttr METTLER TOLEDO tai
phong Cong nghe tk bao thuc vat - Khoa Cong
nghe sinh hgc - Truang DHNN Ha Ngi
28
Trang 32.2 Thiet bi va dung cu do
De do va ghi nhan ket qua cac thong so thi
nghiem tren, cac thiet bj va dung cu can thiet
duac trinh ba\ tron^ hinh 2
h) Dv"g c(( (to /(/I
Hinh 2 Cdc dung cy vd thiit bi do
Can dien tii METTLER TOLEDO tai phong
Cong nghe te bao thue vat - Khoa Cong nghe
sinh hgc - Truang DHNN Ha Npi Can co dai
do tir lOmg -i- 220g Can dung de xac dinh cac
mau ram ed cimg khoi lugng tren ciing mgt
chi^u dai khong doi eiia mau ram
Tu siy FN 500P eo the tieh bu6ng sdy 120
lit, dai nhiet dg tir SO'^C din 250°C, eong sudt
1600W Tu sdy dimg de do do am cua ram tuai
bang each: cho mau ram tuai vai khoi lugng
TAP CHi CONG NGHIEP NONG THON - SO 12
1kg vao til sdy va sdj' 6 nhiet do 70 C sau moi khoang thai gian bo ra can den khi nao mau rom
co khdi lugng khong d6i so vai lan can truac thi dimg lai idy hieu s6 khdi lugng ram trudc va sau khi say ta dugc lugng nude cd trong rom tuai Tinh phan tram lugng nude cd trong mau ram tuai ban dau chinh la do am ciJa mau ram Qua trinh do do am dugc thuc hien lap lai 5 lan va ket qua cho tren bang I
Thi^l bi ma sat GUNT de do ma sat giita rom
va thep tren be mat phang ciia thiet bj dat mgt tdm thep vdi be mat thep phang, do bdng be mat thep d dang tu nhien (khdng danh bdng be mat) Mau ram thi nghiem dugc lay ngau nhien cac cgng ram tir khoi ram va dan len mgt tam bia cimg de tao mat phang ciia mau ram Qua trinh thi nghiem: dat mau ram len tam thep va thay ddi gdc nghieng cua tam thep cho den khi mau rcrm bat dau trugt tren mat phang tam thep, nhin vao
vi tri goc ciia thiet bj GUNT tai vj tri gdc nghieng ling voi khi mau rcrm cd hien tugng trugt ta dugc gia trj gdc trugt cua ram va thep, Cotan ciia goc trugt la he sd ma sat ciia ram tuai va thep Sd thi nghiem dugc thuc hien lap lai 5 lan, ket qua do dugc trinli bay tren bang 1
Dung cu do ap lire nen va ty so nen cd khudn ep dang hinh hop chfl nhat vdi chieu dai day khuon bang 10cm, chieu rdng day khuon bang 1,4cm va chieu cao khudn bang 4cm, khuon ep dang khudn hd ehi cd mat day va hai thanh khudn theo chieu dai khudn Pittong ep cd mat ep chieu dai 8cm, chieu rgng 1,35cm Cac mau ram ep cd ciing khdi lugng tren cimg dan
vi chieu dai mau rom la 50g/20cm Mau ram dugc nap day vao khuon ep ban dau bang tay sao cho mau ram day khudn ep Dung cu do ap luc nen dugc lap tren may keo nen van nang AUTOGRAPH-AGS-20KNG
Dung cu do luc cat: Dung cu gdm cd mdt dao cat dat d vi tri giua khe hd cita hai tam ke
hai ben Dao eat dugc lam tir thep CT45, bk day
dao 5mm, do cao thanh ben dao 50mm, canh sSc ludi dao dugc tao bang each mai hai ben vdi
Trang 4gdc mai dao 15", dao cat dugc tap vao gia lien
k^t vcri may keo nen va dao cd the thay ddi dugc
cac gdc nghieng theo phuong ngang so vdi gia
lien ket Tam ke cat dugc dinh hinh dang khudn
vdi chieu cao thanh khudn 40mm, be rgng day
khudn Mmm nham muc dich xac dinh chieu dai
lam viec ciia canh sac luoi dao AS, tam ke cat
dugc che tao sao cho cd the quay theo gdc
nghieng ciia dao de thi nghiem vdi cac dang gdc
trugt khac nhau, ddng thdi bd phan cat cd the
thay ddi dugc khe hd gifla hai tam ke nham thay
ddi khe hd 8 giua dao va tam ke Mau rom thi
nghiem dugc dat vao hai tam ke va dugc ep chat
hai dau tren hai tam ke nhd vit ep tren tam ke
Dung cu thi nghiem lap tren may keo nen van
nang AUTOGRAPH-AGS-20KNG trinh bay tren
hinh 2g
May keo nen van nang
AUTOGRAPH-AGS-20KNG cd dai do tir 0 -^ 20 kN dugc trang bj bg
CPU xir ly va man hinh Control Display de dieu
chinh che dg van hanh may va hien thj k^t qua
dang sd Tren man hinh cho bi^t luc cat (hoac
nen) va doan dudng di cua dao cdt (hoac
pittong) trong qua trinh thi nghiem Tir k^t qua
ghi nhan nay ta cd dugc do thj quan he giua luc
cat va chuyen vi cita dao trong qua trinh cdt
III KET QUA VA THAO LUAN
3.L Ket qua gia tri cac thong so dac tinh
ciia rem tu'oi
Ket qua do do am, khdi lugng rieng p„ he
sd ma sat f gifla ram tuoi va thep voi sd ldn thi
nghiem lap lai 5 lan cho cac k^t qua do dugc
trinh bay trong bang 1
Bdng I Kit qud do cdc thdng sd dgc tinh cua ram timi
Thong
s6
do
Do am
P
(ks/m')
He so
ma sdt f
So lan do
Lan
1
67
105
0,53
Lan
2
73
95
0,49
Lan
3
75
120
0.58
Lan
4
72
115 0,55
Lan
5
65
90 0,59
Trung binh 70,4
105 0,55
Theo ket qua nghien ciiu (Nguyen Dire Long, 2004) ddi vdi rom khd a do dm 15% co khdi lugng rieng pr = 48kg/m"' va he sd ma sat giiia ram khd va thep f = 0,61 Tir ket qua nghien ciru ve ram tuai 6 do am 70,4% cd kh6i lugng rieng pr = I 0 5 k g W va dac biet cd he s6
ma sat f ^ 0,55 nhd hon so vdi he s6 ma sat giiia rom khd va thep
3.2 Ket qua thi nghiem quan he giira t)
so nen va ap luc nen doi vol rom tuoi K^t qua thi nghiem quan he gifla ap lire nen q„ (N/cm") va ty so nen tuang ddi e dugc trinh bay tren dd thj hinh 3
Tir sd lieu thi nghiem qua phan tich hoi quy
ta cd ham hdi quy md ta quan he gifla ty sd nen
e dugc tinh theo ap lire nen q„ vdi he sd tuong quan R" ^ 0,9693 nhu sau:
E = 0,l644.ln(q„)~ 0,1335 (4)
ai|oumh^i
30
Hinh 3 Do till thire nghiem i/iiun lie £-q„
Ung dung cong thuc (4) de xac dinh chieu cao kh6i rom a trang thai bit d&i cffl Nhu da trinh bay o tren, qua trinh cat co hai giai doan: giai doan nen va giai doan c5t Gia sir ta xac djnh duoc ap lire nen den trang thai cat la q„, khi do tir (4) ta tinh ditgc ty s6 nen e, theo (3) chieu dai doan duong nen hn chinh la do giam chiSu cao cua khoi rom khi nen, khi do chiSu cao ciia khoi rom 6 trang tliai bat diu cat la: h^ = h„ - h„ Bijt dugc he ta xac dinh dugc chi^u dai doan dao lam viec AS
3.3 Kef qua thi nghiem anh hu'olig ciia goc truol den cac thong so trong qua trinh cSt Nhu phan tich 6 tren qua trinh cat co hai giai doan: giai doan nen va giai doan cjt Cac thanh phan luc anh huong trong giai doan cat
Trang 5gdm cd cac thanh phan: Luc cat tac dung true
tiep len canh sac luai dao P,, luc can nen len
mat vat cua canh sac luai dao Ni va lire ma sat
T cua phan khdi ram da dugc cat len mat ben
ciia dao (thanh phan lire T dugc the hien khi
dao da cat het khdi ram va tiep tuc di xudng, gia
trj ghi nhan dugc tir man hinh cua may keo nen)
Tir ket qua thi nghiem, nho thiet bj do luc
cat va do dich chuyen cua dao trong qua trinh
cat bang may keo nen van nang ta cd dugc gia
tri luc cat theo phuang van tde dao Pc tai timg
" ^ l " ' Kal quatHi •ghiem v<n goc tritcrtx'O'
\\ tri cua dao, qua dd ta thu dugc bang gia trj
lire Pc cho timg trudrng hgp gdc trugt, tir ket qua gia tri lire P^ va do djeh chuyen eua dao vao khdi rom trong qua trinh eat ta xay dung dugc
do thi cho cac muc gdc eat trugt T = 0 ; 15 ; 30**: 45"; 60" va 75" Cae giai doan trong qua trinh eat va eae thanh phan lire anh hudng trong qua trinh cat dugc the hien qua ket qua thi nghiem dugc trinh bay bang dd thi thue nghiem (do thj cdng) hinh 4
0 Z 4 6 B 10
''^ W Kel qua Uii nghidm vm goc
.UAfVV\
^
S " 10 IS 20^^ 2 ^ " " " ' O ^10 IS 10 H " ^ » ' 0 5 10-15 30 25 JO 35
Hinh 4 Dd thi quan he giira lire cdt vd chuyen vi cita dao a cdc mirc gdc cdt Innrt r
Trong mgi trudng hgp tren, iing vdi cac
gdc cat trugt khac nhau, cac dd thi hinh 4 deu
md ta dugc cac giai doan ciia qua trinh cat va
dac biet mo ta duge lire ma sat khi khdi ram da
dugc eat het len mat ben cua dao:
- Doan OA md ta giai doan nen khdi ram,
lay gia tri trung binh cac gia trj luc cat Pi; 6 giai
doan nay ta dugc gia trj lire nen trung binh P,nb (N),
phan dien tich tao bdi vimg dd thj OAE la cdng
chi phi cho giai doan nen
- Doan do thj AB md ta giai doan eat, luc d
giai doan nay ggi la lire cat gia Ui trung binh luc d
giai doan nay ggi la lire cat can thiet Pet (N), viing
dien tich ABDE tren do thi la cdng cat ddi vdi
mau khdi rom thi nghiem
- Doan tu B den dau eiia dudng ngang C
md ta lire ciia phan khdi ram vua dugc cat song
tac dung len hai mat vat canh xac ludi dao, qua
trinh nay dugc th6 hien rd net khi thi nghiem
vdri khe h<j nhd 8 ^ 1mm (cac trudng hgp khe
hd 6 lorn hau nhu doan nay khdng the hien)
- Duong ngang C la duong md ta luc ma sat Tl lac dung len mat ben cua dao khi khdi ram da dugc cat hoan toan Gia trj luc T2 phu
thudc vao khe ha 5, khe ha 5 cang nhd gta tri
luc T2 cang lon, song vdi khe hd 6 > 5mm thi gan nhu gia trj luc T2 nay khac nhau khdng nhieu a cac truong hgp gdc cat trugt khac nhau, ndi dung nay dugc trinh bay d phan dudi Trong trudng hgp img vcri cac ket qua thi nghiem tren hinh 4, thi nghiem dugc thuc hien voi khe hdf 8 = 5mm va trong mgi gdc cat trugt T khac nliau ta deu nhan dugc lire can ma sat nay bang 3 ON
De xay dung quan he anh hudng ctia gdc cat trugt T den ap suat cat thai rieng qgi(N/cm)
% a tim gia trj gdc cat trugt sao cho cdng cat thai rieng la nhd nhat, ta di tinh trung binh iirc \ a
Trang 6cdng d cae giai doan nen va giai doan cat cho
timg trudng hgp gdc cat trugt T khac nhau
Xet cac thdng sd trong giai doan nen cd chi
sd la i, trong giai doan cat cd chi sd la j , lire nen
d vi tri i ky hieu la Pm, luc d giai doan cat tai v;
tri j la Pcj khi dd lire trung binh va cong d giai
doan nen va eat dugc tfnh theo cdng thuc:
/'„, = lX;,p„,,(N);^„ = io-^X",/^.'-'^'t-') ]
A = A„+A^ ,(J) J
Bdng 2 Luc trung binh vd cong trong giai dogn nen vd cdt img vdi cdc gdc ciu frmrt r
Trong do: n, m lan lugt la sd vj tri luoi dao
trong qua trinh nen va cat, ds = 0,5mm la sd eia
cua doan djch chuyen cua dao trong qua trinh nen va cat, An la cdng nen Ac la cdng cit va A
la cdng toan phan cho ca qua trinh cat Tii kit qua nghien cflu dugc trinh bay bang do thj hinh
4, ung vdi vi tri i cho ta lire Pm, flng vdi vj tri j cho ta luc Pq, thay vao cdng thuc (5) ta co ket qua ghi d bang 2
S(mm)
P.,b(N)
P«(N)
Tong cong A
% (nen/Cat)
x=0°
P
63,333
156,15
40,56
A(J) 0,38 1,015 1,395
t = l S "
Pc
58,571 129,44
45,25
A(J) 0,41 1,165 1,575
t=30°
P
44,24 103,48
42,75
A(J) 0,355 1,19 1,545
t=45"
Po
33,077 76,552
43,21
A(J) 0,215 1,11 1,325
1=60"
P,
25,882
60
4 3 , 1 4
A ( J ) 0,22 1,14 1,36
t=>75°
Pc
19,524 46,825
41,69
A(J) 0,205 1,475 1,68
Tir bang 2 ta thay: Ddi vdi luc cat can thiet
Pel gdc cdt trugt cang Idn thi lire cat cang giam,
song cdng cat cho ca qua trinh dac biet la trudng
hgp cat dang ch^t bd (gdc cat trugt T = O") mac
dii lire cat Pc ldn, song do quang dudng cat S Iai
nhd Iam cho cdng cat cung khdng lon Ddi vdi
trudng hgp gdc cat trugt x - 75" cho ta gia trj
lire cat rat nhd, song quang duong c4t d^ cat hk
khdi rom l^i rat lon lam cho cdng cat ldn Tir
bang 2 ta ti'nh ty sd giira luc nen trung binh va
luc cat can thiet de xac dinh phan tram gia trj
luc nen can thiet so vdi lire cat cSn thi^t, gia trj
tinh toan trong cac truang hgp gdc cat trugt deu
nam trong khoang tir 40% ^ 45%, tuc la lire cSn
thidt cho giai doan nen bing khoang 40% -^ 45%
luc cit thai cin thiSt Vdi kdt luan nay, trong
tinh toan ly thuyet ta xac djnh luc cit cin thigt
Pel, khi dd lire nen trung binh d giai doan nen
dugc tinh la: P„,h = (0,4 -v- 0,45).Pc, DS xac djnh
gdc cit trugt x cho cdng cat rieng nhd, tir bang 2
va edng thuc (I) ta lap bang anh hudng cua gdc
trugt T din gia tri ap lire cit diai rieng qd (N/cm)
va edng cat thai rieng Ar (J/cm'^)
De 'tinh cdng cat thai rieng can xac dinh dien tich mat cat ngang khdi ram sau khi duoc nen den trting thai cat (a day di?n tieh khdi rem dugc cat bdi canh sac luai dao xet d trudng hgp eat thai vdi gdc cat trugt T = O"):
Chieu dai doan dao Iam viec AS xac djnh theo be rgng ranh dat rom cua tam ke la 14mm, song do qua trinh nen ep nen khdi rom mgt phin
bj phinh ra theo chieu dgc luai dao nen doan AS dugc do true tiep khi dao dang trong qua trinJi cat, bang each cho dao dimg lai d giai doan cat trong qua trinh cit va do ta nhan dugc ket qua AS= 16mm
Dien tich khdi rom dugc eit cd the tinh theo cdng thirc (4), song d thi nghiem cit ram voi gdc cit trugt T = O" ta nen ep hai diu nen tai vj tri canh sac ludi dao bat d i u cham vao khdi rcan thi khdi ram da dugc nen mdt phin, do vay chieu day khdi rom da dugc nen dSn trang thai cit cd tha liy bing doan tir E din D tren dd thj irng vdi gdc cit trugt T = O" (hinh 4) Qua dd thi
ta cd chieu day khdi ram da duge nen den trang
thai cat bang 6mm, vdi bk rgng khdi ram bing
32
Trang 7AS=I6mm ta dugc dien tich khdi rcrm can cat
h l t l a F r - 9 6 m m l
Den day tir cdng thurc (I), bang 2 va Fr =
0,96 em ta cd bang gia tri ap luc cat thai rieng
qci(N/cm) va cdng cat thai rieng a cac muc gdc
cat trugt T trinh bay tren bang 3
Bang 3 la ket qua cho ap lire cat thai rieng
va cdng cat thai rieng ddi vdi ram tuoi ung vai
cac truong hgp gde cat trugt thay ddi tir 0 -^ 75"
Gia trj ap luc cat thai rieng qci va cdng cat thai
rieng Ar trinh bay trong bang 3 la hai thdng sd
dac tnmg cho c a tinh cua ram tuai De thuan
Bdng 3 Gid tri dp sudt cdt thai rieng
tien cho viee tinh toan sau nay d gdc cat tnigt x
bit ky va dac biet la xac djnh cdng rieng circ tilu ta lap phuang trinh hdi quy giiia ap lire cat thai rieng va cdng rieng phu thudc vao gde cat trugt T dugc trinh bay theo edng thire (6), (7), trong cdng thuc (6), (7) quan he tuang quan giiJa cac bien d dang thuc nghiem va phuang trinh hdi quy dugc danh gia thdng qua he so tuong quan R^ Dd thj quan he giua ap lire cat thai rieng va cdng rieng phu thudc vao gdc eat trugt T dugc trinh bay tren hinh 5
vd cong rieng a cdc mirc gdc trugt r
^ ^ ^ ^ G o c trugt
Thong s o " " ^ ~ ^
qci (N/cm)
A,(J/cm2)
x(do)
0 97,60 1.453
15 72,83 1,641
30 56,43 1,609
45 43,37 1,380
60 38,07 1,417
75 36,594 1,75
13 30 45 60 75
Hinh 5 S\rphu thupc cua ap lire cdt thdi rieng q^ vd cdng rieng A^ theo goc cdt tnrat r
Phuong trinh hdi quy:
q^^ = -0,8045.r + 87,65 ; R^ =0,901 (6)
4 = lO'^.r' -0,001 l.r' +0,0287.r +1,4493 (7)
R==0
Tir phuang trinh (7) quan he giira cdng cat
rieng va gdc cat trugt dugc md ta bang ham sd
bac ba, gia trj gde cit trugt lam cho Amim euc
tidu tai To = 56,3", thay To = 56,3° vao (7) dugc
cdng rieng cue tieu ^mm = ' 3 6 3 (J/em^)
Tir kdt qua do va phuang trinh (7) ta ed the
thiet k l dao thai sao cho qua trinh eat ed cdng
rieng nhd nhat ho§e tuang ddi nhd, theo (Tran
Minh Vugng va Nguyen Thi Minh Thuan,
1999) gia trj gdc cat trugt T dugc lay sao cho
cdng cat thai rieng Ar nam trong khoang tir Annin din 4 = 4.„,„+6%.4,„,„=I,45 (J/cm^), vdi
Ar - l,45(J/cm^) thay vao phuong trinh (7) duge
hai gia trj gdc cat trugt Tmm = 43** va Tmax = 67" Tren do thi hinh 5 khoang tir imm din Tmax la vung gia trj gdc cat trugt hgp Iy cho cdng cat rieng cd gia trj tuong ddi nhd Vay trong thiet ke
bd phan cat theo nguyen ly (hinh 1) gdc cat trugt hgp ly dugc thiet ke trong khoang T ^ 43" -r 67"
3.4 Anh hirong cua khe hor 5 den ap Iu-c cua khoi rom da dirge cat len mat ben cua dao
Nhu da phan tieh d tren hinh 1, khe hd 5 cd anh hudng den lire ma sat can T2 ciia phin khdi ram da dugc cat len mat ben cita dao va anh
Trang 8hudng den lire can Ni len mat vat cua canh sac
ludi dao De xac djnh dugc anh hudng cua khe
hd 5 den luc ma sat T2 va luc N | , ta lam thi
nghiem vdi cac truang hgp thay ddi khe hd
5 = 1; 2; 3; 4; 5; 10; 20mm, ket qua thi nghiem cho
thiy ddi vdi cac trudng hgp ed khe hd 8 = I -^ 5mm
thi thanh phan luc T2 va N1 cd gia trj khac nhau
va giam dan Song, ddi vdi cac trudng hgp khe
hd 8 > 5mm thi thanh phan luc Ni gan nhu
khdng xuat hien, cdn thanh phan lire T2 cd gia
T]»laaM|MWIUif>»»-1<—'t0-9*6mm*-»
Pe(N)
2 S 0 " ^ '•
trj nhd va gin nhu khdng ddi dr cac mure khe hd khac nhau, liic nay ta coi ap luc do luc N| vao mat vat canh sic luai dao bang ap lue do lire N2 vao mat ben eua dao
D I riit ngin cho viec trinh bay, ket qua thi nghiem dugc md ta bing hai qua trinh cat dai dien cho hai viing: 6 = Imm dai dien cho viing khe hd
8 tir 1 din 5nim va 8 = 10mm dai dien cho viing khe hd 8 > 5mm dugc trinh bay tren hinh 6
niBflM^voiUMlw'«-1«(Hn)d>g«clm9(«- » PC(N)
/ s ^ 'aar
jjwir***yMi«gJ;jJ*|<- • l l f i / i H | l M jjwir***yMi«gJ;jJ*|<- V jjwir***yMi«gJ;jJ*|<- « jjwir***yMi«gJ;jJ*|<- jjwir***yMi«gJ;jJ*|<- * i l
tm:m{^Kit»h^ !•—<™ |mi) • t ^ T
Hinh 6 Anh hirong cda khe hd 5 den luc ma sdt do khdi ram dd duac cdt len hai mgt ben cua dao
Dd thj hinh 6 md td qua trinh anh hudng
ciia luc cat Pc theo khe hd S:
- Vdi khe hd 8 = 1mm ta thay luc cit rat
ldn, luc cit lay trung binh d giai doan cat lit A
den B 1^ Pel = 173 (N), trong truang hgp njiy khi
phan ram cudi cung dugc cat tai \ j tri B, sau khi
cat xong luc Pc khdng chuyen ludn ve dudng
ngang C ma ph^i qua doan BB' doan BB' chinh
la anh hudng do thanh phan lire N | va luc ma
sat T| (hinh 1), dudng ngang C la dudng bieu
dien gia trj ciia lire ma sat T2 len mat ben ciia
dao khi khdi rcrm da dugc cat va thod' khdi hoan
toan mat vat canh sac luoi dao do lire N2 gay ra
- Vdi khe hd 8 = 10mm, khi phan rom eudi
ciing dugc cit xong tai vj tri B luc Pcgiam
ngay xudng dudng ngang C ma khdng cd doan
BB', tuc la anh huoTig ciia khoi rom trong qua
trinh cit ISn m§t vat cua sanh sac ludi dao
khdng ldn va coi nhu bang ap luc ma sat len mat
ben ciia dao, trong truang hgp nay ta coi mat vat
ciia dao nhu mat ben ciia dao Ket qua thi
nghiem cho thay khe hd 8 cang lan thi luc ma
sat ciia khdi ram da dugc cit len mat ben ciia
dao cang nhd, song khi khe ho 8 > 5mm thi cac gia trj luc T2 bieu dien bing dudng ngang C thay ddi khdng nhieu trong khoang tir 20 -f 25N Mat khac khi khe hd 8 > 5mm thi qua trinh ep khdi ram len 2 tam ke hai ben cin luc N ldn han
de tranh hien tugng rut cgng ram trugt doe theo khe hd tam ke(hinh 1)
De mang tinh tdng quat va ung dung, ta cd the coi thanh phan luc N | va lire ma sat T| tac dung len mat vat cua dao cd trong thanh phan luc cit can thilt Pc, vay ta chi xet va trinh bay anh hudng cua khe hd 8 = 1 ^ 5mm den thanh phin luc N2 la thanh phan gay ra luc ma sat T2
(hinh 1) dugc dac trung bdi ap luc q^ cua khoi
ram da dugc cat len hai mat ben cua dao, ap lire
qb dugc tinh theo cdng thiic:
= 0,55
A'
Trong dd: Fr = 0,96 cm^ la dien tich cat, f =
la he sd ma sat cua ram tucri va thep Ket qua anh huong ciia khe ho 8 den ap lire ctia khdi ram da dugc cit len hai mat ben cua dao dugc trinh bay trong bang 4
Trang 9Bdng 4 Gid tri dp luc qb cda khoi ram tdc dung len
thdnh ben ciia dao cdt theo cdc mdc khe gd 5
qb(N/cm-)
Lan 1
l>an2
Lan 3
TB
8(mm)
1
132,55
113,63
132,55
126,24
2
113,64
113,64
3 94,55 75,64 113,64 1 94,55
113,64 1 88,24
4 75,64 56,91 56,91 63,16
5 56,91 56,91 56,91 56,91 Tir ket qua bang 4 ta cd do thj va ham hdi quy
md ta quan he giiia ap lire cua khdi ram da duge
cit len hai thanh ben eua dao d cac muc khe ha 6
trinh bay tren hinh 7 va cdng thirc (9)
Phuang trinh hdi quy vai 6 < 5 mm:
-1,8915.(5 + 1 4 , 6 8 3 ; ( - ^ ) (9)
Phuong trinh hdi quy (9) md ta quan he gija
qt/N/cm^) va 8 (mm) ed he sd tuong quan R^ = 0,9695
IS-giSn-rlAflig
S<mm)
LTinh 7 Do thj dnh hirdng cita khe hd S den dp
lire len thdnh ben ciia dao qb
Tir cdng thirc (9) khi che tao bd phan cat vdi
khe hd 8, cho ta biet dugc ap lire qb, thay qb vao
cdng thuc (9) cimg vdi viec xae dinh dien tich
khdi ram dugc cat F, cho ta k l qua gia trj luc
can ma sat len hai mat ben cua dao do khdi rom
da dugc cat gay ra
IV KET LU^N
- Vdi cac ket qua nghien cim ca ban tren, da
xac djnh dugc mdt sd dac tinh cua ram tuoi d do
am 70,4% nhu: khdi lugng rieng pr = 105kg/m^;
h? sd ma sat vcri thep t~ = 0,55 va quan he giira
t; sd nen vai dp luc nen Tir kit qua nay lam ea
sd cho viec nghien cim img dung trong cac loai
hinh khai thac xir ly ram, ra khac nhau
- Quan he giua gdc eat trugt vcri ap lire cat thai rieng va cdng c i t rieng; quan he giita khe
ha cua dao va t i m ke vdi lire ma sat ciia khdi ram da dugc cit tac dimg len thanh ben cua dao
K i t qua nghien cuu cho thay, voi nguyen Iy cat dao cit cd dinh, canh gat chuyen ddng gat va nen khdi ram trugt tren canh sac luai dao, gdc cit trugt T = 43" ^ 6?" la vimg gdc cit trugt hgp
Iy cho cdng cit rieng A, tuong ddi nhd Do anh hudng ciia lire ma sat vao thanh ben cua dao, vdi ket qua da trinh bay, khi che tao bd phan bam thai ram theo nguyen ly nay khdng nen chgn khe hd 8 < 1mm, khe hd 8 cd the chgn va nghien curu trong viing 5 = 1mm -^ 5imn TAI LIEU THAM K H A O
[1] Nguyen Trpng Hi?p, Nguyin Van Lam (2003),
Thiet ke chi Hit may, NXB Giao due
[2] Nguyen Due Long (2004), Nghien cuu thiet ki
che tgo may dong bdnh rom, co kfio nang sudi 10 kien/gta, Bao cao khoa hpc, Vien Co dien va Cong nghe
sau thu lioach
[3] Le Minh Lu, Nguyen Xuan Thiet v i Nguyin Van
Tam (20! I) Mpt so de xiidl cdi lien bp phgn dgp trong
may thu hogch tua theo huang dap Idch hat dong thai bdm ram de khai thdc hieu qud ram sau ihu hogch a Viet Nam
Tap chi khoa hpc va phSt trien, Tap 9, so 4: 642 - 649 [4] Nguyin Van Tam, Le Minh Lu va Nguyin Xuan
Thiet (2013), Ket qua ihi nghiem dan yeu Id ciia mgi so
thang so ctia b(> phdn cdi rom lien hap vai mdy dap liia
Tap chi khoa hpc v^ phat trien, Tap 1 L so 5: 735 - 744 [5] Tran Minh Vuong va Nguyin Thj Minh Thuan
(1999), Mdy phuc vu chan nuoi, NXB Giao due
Ngay n h a n bai; 18/02/2014
N g a y p h a n bi?ii; 10/3/2014 Nguoi p h a n bien: GS.TSKH Pham Van Lang, Hpi CO khi nong nghiep Viet Nam
TAP CHI CONG NGHIEP NONG THON - SO 12 - 2014