Fracture tensile test piece

Reduction of area is the proportional reduction of the cross-sectional area of a tensile test piece at the plane of fracture measured after fracture. 

Equation (10.5) is more generally applicable than Eq. (10.6) because it is not restricted to linearly elastic materials. It constitutes a criterion for tensile rupture of a highly elastic material having a cut in one edge of length, /, in terms are of the fracture energy, Gc- Two important examples of test pieces of this type are (1) the ASTM tear test piece for vulcanized rubber (ASTM D624-54) and (2) a typical tensile test piece that has accidental small nicks caused, for example, by imperfections in the surface of the mold or die used to prepare it. 

Rupture of a tensile test piece may be regarded as catastrophic tearing at the tip of a chance flaw. The success of the WLF reduction principle for fracture energy, G, in tearing thus implies that it will also hold for tensile rupture properties. Indeed, a/, and may be calculated from the appropriate value of G at each rate and temperature, using relations analogous to Eqs. (10.6) and (10.7). The rate of extension at the crack tip will, however, be much greater than the rate of extension of the whole test piece, and this discrepancy in rates must be taken into account (Bueche and Halpin, 1964). 

The Tensile Strength is defined as the maximum stress supported by the test piece before fracture takes place. 

A great deal can be learned about the mechanical properties of materials by stressing them until they fracture or break. The most common mechanical test involving metals or polymers is the tensile test, in which a sample of the solid is stretched. The test uses a standard test piece with a shape dependent on the material to be tested. Metals usually have a central cylindrical section, of known gauge length. 

Both the previous two methods require the test piece to be sufficiently rigid for buckling of the specimen under test to be negligible. For thinner section materials and for those exhibiting a high elongation before fracture, the tensile impact test may be the only viable... 

The tensile strength of a cellular material is determined by measuring the uniformly applied force required to break the sample. The test piece is usually dumbbell-shaped (Fig. 13) and is cut or stamped (clicked) out of a sheet of foam with a test piece cutter. The rectangular cross section specimen should be prepared with care, since any snags or imperfections may cause premature fracture of the material under test. The cutting out of the material may also be useful in obtaining an indication of the clickability" of the foam. 

The result shows that the determined values for the tensile adhesion strength are extremely low. The tensile adhesion strengths of all cement stone samples are significantly lower than the tensile strengths of both stones and the cement stones themselves. When judging the fracture pattern it could be observed that above all it had come to a cohesion failure of the stones. The examination of the test pieces before test start showed a pre-damage on all samples which had not been there on the stone slices after demoulding (Fig. 7). 

Fig. 6 SEM of tensile fractured injection molded test pieces of tBu-HQ/Cl-PEC(15.1 GPa).

Fracture toughness and tensile properties are summarized in Table 1 below. The ductile IPNs showed substantial drawing and yielding in the impacted test>pieces compared with either smooth or sometimes locally crazed fracture surfaces for the more brittle polymers. 

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