ISO 6721-6:2019

ISO 6721-6:2019 pdf free.Plastics – Determination of dynamic mechanical properties-Shear vibration – Non-resonance method.
4 Principle
A test-specimen assembly is subjected to a sinusoidal shear force or deformation at a frequency significantly below the fundamental shear resonance frequency (see 10.2.2). The amplitudes of the
force and displacement cycles applied to the test-specimen assembly and the phase angle between
these cycles are measured. The storage and loss components of the shear complex modulus and the loss factor are calculated using formulae given in Clause 10.
5 Apparatus
5.1 Loading assembly
5.1.1 General
The requirements for the loading assembly are that it shall permit measurements of the amplitudes of, and phase angle between, the force and displacement cycles for a test specimen assembly subjected to a sinusoidal shear force or deformation. Various designs of apparatus are possible: a suitable version is shown schematically in Figure 1. The shear test-specimen assembly consists of two identical specimens S of the polymer bonded to or clamped between metal end-pieces P1 and P2. A sinusoidal force is generated by the vibrator V and applied to the two outer end-pieces P1 of the test-specimen assembly through the clamping device Ci of the shear load stage. The amplitude and frequency of the vibrator table displacement are variable and monitored by the transducer D. The test-specimen assembly is held at its centre P2 by a fixed clamp C2, and thus each specimen S of the polymer is subjected to simple shear deformations of equal magnitude. The sinusoidal force applied in deforming the test-specimen assembly is monitored by a force transducer F connected to C2.
Alternatively, the force can also be calculated from the current supplied to the vibrator.
The members between the clamps C1 and V, and between C2 and F, shall be much stiffer than the testspecimen assembly and shall have a low thermal conductance if the test-specimen assembly is to be enclosed in a temperature-controlled cabinet.
While each member of the loading assembly may have a much higher stiffness than the test-specimen assembly, the presence of clamped or bolted connections can significantly increase the apparatus compliance. It may then be necessary to apply a compliance correction as described in 10.2.4.
A clamping arrangement may be used in which a single specimen of the polymer is subjected to a simple shear deformation, but precautions shall then be taken to ensure that any torque in the loading assembly resulting from the application of load to the specimen does not influence the measurements of the dynamic shear force and displacement. Measurements of the deformation of the specimen may also be made by locating the displacement transducer so as to measure the relative displacement of the two parts C1 and C2 of the load stage. The magnitude of the correction for the compliance of the loading assembly will then become small or negligible (see 10.2.4).
5.1.2 Load stage
The shear load stage shall be capable of gripping the test-specimen assembly with sufficient force to prevent any relative movement between the metal blocks P of the test-specimen assembly and the load stage clamps, and to maintain the force at low temperatures. Any misalignment of the load stage with respect to the force transducer will produce a lateral component of the force applied to the transducer during loading of the test-specimen assembly. The alignment of the loading assembly and test-specimen assembly shall be such that any lateral component recorded by the transducer is less than 1 % of the applied longitudinal force.ISO 6721-6 pdf download.

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