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188 Costică Atanasiu et al.
computer programs, requires knowledge of these characteristics, which are
experimentally determined.
Iosipescu has established the pure shear test specimens shape (Iosipescu,
1962; 1963), the way to accomplish the test, and also the shear fixture. Iosipescu
revealed by photo-elasticity studies that the notches sides should be at 90º
and the notch depth must represent a quarter specimen width, in order the shear
stress be constant on the entire shear section. The pure shear method and the
fixture, designed by Iosipescu, were patented in Romania, U. S. A., Switzerland,
Germany and these were the basis of ASTM (ASTM D5379, 2005) on this
test.
2. Experimental Tests
For determine the mechanical and elastic characteristics of the
chromoplastic SDP2 material (Bălan et al., 1964) tensile tests were performed
on a INSTRON 8801 testing machine, with 10mm diameter specimens load at a
strain rate of 0.1mm/min. The material tensile test characteristic shown in Fig. 1
allowed to obtain the module of elasticity E=3200MPa and the yielding limit
σc=42MPa. This characteristic, resulted from the tensile test, is a slight
hardening Prandtl type curve, having Ep=E/90 slope.
Fig. 1 – The chromoplastic material tensile test characteristic curve.
Shear behavior material research was performed on standard specimens
(ASTM D5379, 2005), shape and size are shown in Figure 2. Specimens were
taken from a 10mm thickness material plate. Loading to pure shear specimens
was performed using a shear fixture (Mareş et al., 2006; Leiţoiu et al., 2007)
mounted in a WDW50 testing machine, as is shown in Fig. 3.
A special strain-gauge rosette N2A-06-C032A-500 (Micro-
Measurements) was installed in the shear section between the specimen notches
for determining the shear module of the chromoplastic material. This rosette
contains two strain gauges, with side-by-side grids, each aligned to the principal