Transverse strain response

Cheng ZY, Xu TB, Bharti V, Wang S, Zhang QM (1999) Transverse strain responses in the electrostrictive poly(vinylidene fluoride-trifluoroethylene) copolymer. Appl Phys Lett 74 1901... 

Table 16.2 The transverse strain response and corresponding electromechanical performance of different...

By varying the film processing conditions, the transverse strain in an irradiated P(VDF-TrFE) copolymer can be tuned over a wide range. For instance, the transverse strain response in unstretched films is relatively small ( +1 % at -100 MV/m), with an... 

Cheng Z et al (1999a) Transverse strain responses in electrostrictive poly(vinylidene fluoride-trifluoroethylene) films and development of a dilatometer for the measurement. J Appl Phys... 

There are two quite striking differences in the b-axis and a-axis piezomodulation spectra. First, the sense of the strain response is reversed, i.e. the transverse frequencies appear as minima in the a-axis spectrum rather than as maxima as seen for the b-axis spectrum. Second, the a-axis structure virtually vanishes at frequencies greater than 16,000 cm ... 

The Poisson s ratio can be determined by measuring the transverse strain during uniaxial tension or compression experiments. Due to the small magnitude of the transverse strain, it is difficult to accurately determine the Poisson s ratio. Instead, it is often sufficient to assume a value for the Poisson s ratio of about 0.4. Unless the fluoropolymer component is highly confined, the Poisson s ratio has only very weak influence on the predicted material response. 

For an isotropic, elastic material two elastic constants are sufficient to describe the material response, the elastic modulus E (eq. 7) and the Poisson s Ratio (v), defined as the ratio of the axial to the (negative) transverse strain (- 11/622). 

Load versus strain responses obtained from tests on coupons cut out of a 203 x 203 x 9.5 mm WF profile (a) longitudinal flange coupon tested in tension (b) transverse web coupon tested in compression. 

In general, experimental results on beam-column joints without transverse steel shear reinforcement emphasize a strictly degrading behavior caused, on one hand, by the shear behavior of the joint panels and, on the other hand, by the bond-slip behavior of longitudinal reinforcements anchored in it see Fig. 10. Experimental research on the seismic performance of the beam-column joints (Walker 2001 Alire 2002 Pantelides et al. 2002) has revealed that the joint shear stress-strain response, typically, has a degrading envelope and a highly pinched hysteresis. Moreover, the common practice of terminating the beam s bottom reinforcement within the joints makes the bottom reinforcement prone to pullout under a seismic excitation. Insufficient beam bottom bar anchorage precludes the formation of bond stresses necessary to develop the yield stress in the beam s bottom reinforcement. 

Load Frame, Force and Strain Measurement, Data Acquisition The test method uses a standard load frame with a hydraulic or screw drive loading mechanism and standard force transducers. Force is applied transversely to produce a bending moment. Extension is measured by deflectometers in the gage section and strain is measured using bonded resistance strain gage rosettes to determine both longitudinal and transverse strains. If required, an environmental test chamber may be used to control humidity and ambient temperature. Data collection should be done with a minimum of 50-Hz response and an accuracy of 0.1 % for all data. 

The magnitude of the piezoelectric response owing to applications of stress or strain transverse to the chain axis is much greater than the response owing to application of stress or strain parallel to the chain axis. This anisotropy in electrical response reflects the mechanical anisotropy of extended chain polymer... 

---