analiza naprezanja u ucvršcenju polova rotora generatora s ...

Ma{instvo 2(7), 63 – 74, (2003)
N.[virig;....: ANALIZA NAPREZANJA U U^VR[^ENJU...
4. ISPITIVANJE MODELA
4.1 Optere}ivanje modela
Kona~no obra|en model spreman je da se optereti
i da se izvr{e sva potrebna mjerenja. Polo`aj
to~aka na modelu odre|en je pravokutnim
koordinatama ~ija se jedna os poklapa sa osi
simetrije modela. Urezivanje koordinatnih osi u
povr{inu modela nije mogu}e zbog pojave
unutra{njih naprezanja na modelu, koja bi imala
negativnu posljedicu na ispitivanje.
Optere}ivanje svih modela izvr{eno je u zatvorenom
okvirnom nosa~u pomo}u vijka sa trapeznim
navojem.
Prijenos sile na modelima izveden je pomo}u
posebnih ~eljusti koje se sa vijcima pri~vrste na
model, a na drugoj strani ~eljusti nalazi se
simetri~no izbu{ena rupa koja se spaja s
prstenastim dinamometrom pomo}u zatika.
Same ~eljusti su postavljene tako da budu
simetri~ne sa modelom i da se sila prenosi
podjednako na sve rupe modela
Svi modeli optere}ivani su u dva me|usobno
okomita smjera kako bi se {to vjernije simuliralo
stvarno stanje naprezanja na mjestu u~vr{}enja
pola.
Omjer vertikalne i horizontalne sile kojom se
optere}uje model odabran je tako kod svih
modela, da se dobije odnos naprezanja koji
odgovara stvarnom stanju naprezanja u realnim
pogonskim uvjetima.
Iznosi sila F V i F H kojima su optere}ivani modeli
dani su u tablici 4.1. Odabran je uvijek onaj omjer
sila F V / F H koji je za razmatranje pojava u modelu
najpogodniji tj. za taj omjer u modelima se
pojavljuje maksimalni red izokroma. Taj se red
izokroma najlak{e snima u kriti~nom presjeku,
budu}i bi se kod ve}ih iznosa optere}enja
maksimalni red izokroma znatno pove}ao, te bi one
postale toliko guste i nejasne da se ne bi mogle
vi{e razlu~ivati (brojati).
4. TESTING OF THE MODEL
4.1. Loading of the model
When the model is finished it is ready to be loaded
and submitted to all the necessary measurements.
The position of points on the model is defined by
rectangular coordinates. One of their axes agrees
with the model symmetry axes. Cutting in axis
coordinates into the model surface is not possible
because inner stresses occur in the model, which
would have a negative effect on testing.
The loading of all models was carried out in a
closed frame carrier by means of trapeze thread
screw.
The transmission of force on models was carried
out by means of special jaws fixed by screws to
the model. On the other side of the jaw there is a
symmetrically drilled hole which is connected to
the ring dynamometer by means of a pin.
The jaws are symmetrical with the model and the
force is transmitted equally to all holes of the model.
All the models are loaded in two vertical
directions. In that way the simulation of the real
stress on the spot where the pole is fixed is very
reliable.
The ratio between the vertical and horizontal force
by which the model is loaded is chosen for all
models, i.e. the stress ratio (σ v / σ h ) = 1, which
corresponds to the real arrangement of the
generator pole fixing.
Values of the forces F V and F H by which the model
was loaded can be seen in Table 4.1. The force
ratio, F V and F H was chosen so that it would give
the most convenient way of considering the
phenomena in the model, i.e. for that ratio the
maximum order of isochrome appears in the
models. This isochrome order is recorded easily in
the critical cross-section, since at higher loading the
number of maximum isochrome order is increased
considerably. They become so dense and unclear
that they cannot be distinguished (counted).
Tablica 4.1. Iznosi vertikalnih F V i horizontalnih F H sila optere}enja na modele
Table 4.1. Amounts of vertical and horizontal (F V and F H ) loading forces on models
Model I II III IV V VI
F V , N 450 450 450 450 300 1500
F H , N 460 460 460 460 310 500
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