Tensile test piece rupture

Physical Properties. Tensile test pieces were cut with an ASTM T50 die, modified by putting a radius as specified in Bell Telephone Laboratories, Inc., drawing B604844, on the junction between the tongues and the reduced section. Dumbbells of this small size were used to facilitate simultaneous irradiation in the water-cooled cell under nitrogen. These dumbbells were pulled at 2 inches a minute for both tensile strength and elongation at rupture measurements at ambient temperature. 

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). 

Tensile strength, both wet and dry BS 4415 1992 ISO 1924 (1992). The maximum tensile force per unit width that a paper or board will withstand before breaking. The stretch at break is the measured elongation at the moment of rupture of a test piece, when tested under specific conditions. 

B1 Tensile stress at rupture 80% of the value obtained on unprestrained. unexposed test pieces... 

Unlike the previous two standard.s, which apply a given strain to the test piece, ISO 6252 [206], which is dual numbered as BS 2782, Method 833A-C [207], uses a dumbbellshaped test piece placed under constant tensile stress and immersed in the test medium until it breaks, time to failure being recorded (Fig. 37). In Method A the tensile stress leading to rupture in 100 hours is determined by interpolating points obtained at various stress levels that encompass the 100 hour point. In Method B the time to failure at a specified stress is found. In Method C the tensile stress versus time to failure is plotted graphically. The test piece normally used for this test is the general purpose plastics dumbbell of ISO 527, but with its dimensions scaled down by a factor of 2. The preferred test temperatures arc 23 and 55 C, but other recommended temperatures include 40. 70 85, and 100 C. 

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