The maximum nominal stress
decreased slowly in the area of negative a-values, until a minimum was reached for a = -90[degrees], when the stress concentration acted on the flow split area.
with a = crack length, [sigma] = nominal stress
and C = geometry factor (18):
Welded specimens exhibited a large reduction in the maximum nominal stress
compared with nonwelded specimens, an abrupt drop in the stress after maximum and limited elongation capability.
the as-molded materials), the material strain softens: the nominal stress
drop occurs just past the yield point due to the failure and disconnection of the lamellas and remains stationary while the tie molecules are pulled out from the fragmented lamella and become part of the amorphous layers.
Here [[sigma].sub.y] corresponds to the yield stress as conventionally determined for polymers, i.e., the maximum on a nominal stress
versus engineering strain plot.
Zone III is also characterized by a strong dispersion and the nominal stress
at failure is relatively smaller (<16 MPa) compared to the other cases.
The breaking stress can be obtained from the top load basing on the load, deformation and the curve of nominal stress
There are several damage initiation criteria, such as the maximum nominal stress
criterion, the maximum nominal strain criterion, and the quadratic nominal stress
The nominal stress
at which visible water flow started is plotted against cross-head speed in Fig.
The resulting increase in the internal lever arm, a long critical cross section, stands as the reason for the increased nominal stress
. These considerations are not confirmed for the HPFRC specimens.
According to the above theory, if the material element of V-shaped notch bottom is equivalent to the smooth bar, the fatigue life [N.sub.f] for the smooth bar under the action of [DELTA][epsilon] is regarded as the crack initiation time [N.sub.i] under the action of nominal stress
Results of pulsating tension tests Stress Material ratio R [N.sub.G] amorphous 0,1 6,7-[10.sup.5] +/-45[degrees] tissue 2,2-[10.sup.5] unidirectional 45[degrees] 6,7-[10.sup.6] unidirectional 0[degrees] 6,5-[10.sup.5] unidirectional 90[degrees] 4,8-[10.sup.6] Nominal stress
amplitude [sigma] [A.sub.n] [MPa] Material [P.sub.A]=50% [P.sub.A]=10% amorphous 9,0 8,4 +/-45[degrees] tissue 6,7 5,8 unidirectional 45[degrees] 5,2 4,9 unidirectional 0[degrees] 27,1 24,4 unidirectional 90[degrees] 3,2 2,9 Scatter range Material Slope k [T.sub.N] amorphous 4,94 2,02 +/-45[degrees] tissue 7,95 10,80 unidirectional 45[degrees] 17,83 12,73 unidirectional 0[degrees] 16,98 34,34 unidirectional 90[degrees] 16,18 28,02