Post on 14-Dec-2015
transcript
constant strain rate constant stress (creep)
Deformation tests ( constant T )
Constant strain rate testing
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Extensometer INSTRON 2630-014
(g.l. 10 mm, range 50 %)
At our lab:
Electromechanical (Instron 1123 or 5567)
Universal Electromechanical Testing Machine
Instron 5567 (dual column table top, 30 kN)
Temperature Chamber
Instron 3119(-70 °C / 250 °C )
ServohydraulicTesting Machines(MTS 810)
Constant strain rate behaviour
... details at T = 573 K (Th > 0.6 ! For the Al-alloy)
… why not constant loading-rate experiment?
Creep Testing: top-lever machine
PP
P
10 mm
initial state after creep
Compression Test
Compression Cage
Creep behaviour
The Monkman-Grant Relationship for time to fracture
)exp(1
RTQA
tcn
ssf
MGfss Ct * : time to fracture
: minimum creep rate
ft
ss
or, more general: MGfm
ss Bt * where: 0.77<m<0.93; 0.48<BMG<1.3
for Al, Cu, Ti, Fe and Ni base alloys (from Monkman-Grant research)
Test of Monkman-Grant for Cu
Engineering Estimates of Creep Behaviour
CtTLM r log
Larson-Miller parameter (LM)
ksi
ksi
Fig a