Testing methods tensile creep

D-2294. Test Method for Creep Properties of Adhesives in Shear by Tension Loading (Metal-to-Metal) (Fig. 21). The tensile creep counterpart to D-2293. 

ASTM D2990, a. Test Methods for Tensile, Compressive andFlexural Creep and Creep Rmpture of Plastics, Vol. 8.02, ASTM, Philadelphia, Pa., 1993. 

These latter curves are particularly important when they are obtained experimentally because they are less time consuming and require less specimen preparation than creep curves. Isochronous graphs at several time intervals can also be used to build up creep curves and indicate areas where the main experimental creep programme could be most profitably concentrated. They are also popular as evaluations of deformational behaviour because the data presentation is similar to the conventional tensile test data referred to in Section 2.3. It is interesting to note that the isochronous test method only differs from that of a conventional incremental loading tensile test in that (a) the presence of creep is recognised, and (b) the memory which the material has for its stress history is accounted for by the recovery periods. 

It should also be noted that in this case the material was loaded in compre-sion whereas the tensile creep curves were used. The vast majority of creep data which is available is for tensile loading mainly because this is the simplest and most convenient test method. However, it should not be forgotten that the material will behave differently under other modes of deformation. In compression the material deforms less than in tension although the efrect is small for strains up to 0.5%. If no compression data is available then the use of tensile data is permissible because the lower modulus in the latter case will provide a conservative design. 

In conclusion, it may be mentioned that the characterization of the mechanical behaviour of materials has many facets. Different methods of testing pertain to different aspects and conditions. The tensile properties, as determined by the tensile test, correspond to slowly applied single load applications. Rapidly applied and cyclic load applications respectively provide the impact and the fatigue properties. Hardness is an analog of the tensile strength which a tensile test measures. The creep test pertains to mechanical behaviour under long term loading at elevated temperatures. 

Determination of tension set under constant elongation, and of tension set, elongation, and creep under constant tensile load Standard test methods for vulcanized rubber and thermoplastic elastomers-tension Testing of rubber and elastomers... 

A constant tensile-stress method is outlined in ISO 6252, in which a test specimen is exposed to a constant tensile force while immersed in a stress cracking agent so as to determine the time to rupture under a specified stress. This uniaxial test leads to the determination of the lifetime of the specimen with accuracy, but it is time consuming and requires complex equipment. Variations of this test include a tensile creep test that monitors the strain and a monotonic creep test that uses a constant stress rate instead of a fixed stress [1]. 

The objective of this test method is to measure the cohesive stress and the time to failure of a crystalline polymer craze layer under rapid, uniform extension. The method is an impact variant of the Full Notch Creep test used by Fleissner [12], Duan and Williams [13], Pandya and Williams [14] and others. The specimen (Fig. 2), a square-section tensile bar, is injection moulded. At the mid-plane of the gauge length a sharp, deep circumferential notch reduces the cross-section to about one fifth of its original area. This notch plane is formed by a moulded-in, hardened steel washer. Specimens were injection moulded at 210°C into a warm (100°C) mould and air cooled to 40 C using a hold pressure of 45-50 bar. 

ASTM D 2990-77 (1982) Standard Test Methods for Tensile, Compressive, and Flexural Creep and Creep Rupture of Plastics, 11 pp (DOD Adopted) (FSC 9330) (MR) (Comm D-20)... 

Note that the isochronous test method is quite similar to that of a conventional incremental loading tensile test and differs only in that the presence of creep is recognized and the memory of the material for its stress history is overcome by the recovery periods. Isochronous data are often presented on log-log scales because this provides a more precise indication of the nonlinearity of the data by yielding a straight-line plot of slope less than unity. 

C1291-95 Test Method for Elevated Temperature Tensile Creep Strain, Creep Strain Rate, and Creep Time-to-Failure for... 

Standard test method for tensile, compressive, and flexural creep and creep-mpture of plastics... 

The US practice uses the creep compliance and indirect tensile strength test, according to AASHTO T 322 (2011), as a suitable performance test for low-temperature cracking in hot mix asphalt mix design. The same procedure was selected as the material characterisation test method for the prediction of low-temperature cracking of flexible pavements in the AASFITO (2008) Mechanistic-Empirical Pavement Design Guide. 

The test method determines the creep compliance, D(f), the tensile strength, S , and Poisson s ratio, v, of hot mix asphalts. The procedure is applied to test specimens having a maximum aggregate size of 38 mm or less. 

For these three reasons it is not possible to eonsider the time-to-failure in the long-term tensile creep shear test as a eriterion for the quality of the weld seam and the welding method in geomembranes at all. 

EN 1542 Products and systems for the protection and repair of concrete structures. Test methods. Measurement of bond strength by pull-off. EN 1544 Products and systems for the protection and repair of concrete structures. Test methods. Determination of creep under sustained tensile load for synthetic resin products (PC) for the anchoring of reinforcing bars. 

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