Crystallographic texture evolution in high-density polyethylene during uniaxial tension

Abstract

This paper presents experimental measurements of crystallographic texture evolution in high-density polyethylene subjected to very large strains in uniaxial tension (up to a true strain of 2.1). The measurements presented here differ from prior studies in three important aspects: (1) The initial texture in the sample is quite strong with a large fraction of the crystallites oriented in an unstable orientation with the crystal caxis perpendicular to the tensile axis of the sample. (2) Rigorous methods of texture analyses, based on spherical harmonics, have been applied to produce "complete, recalculated" pole figures based on diffraction data from five incomplete pole figures. (3) The measurements were performed while the samples were kept in the deformed state. The results presented here provide several new insights into texture development in tensile straining of high-density polyethylene to large strains. There are at least three distinct preferred orientations: (i) a component with (001) aligned along the extension axis, (ii) a component with (011) aligned close to the extension axis, and (iii) a component with (010) aligned along the extension axis. Note that only the first component has been reported to be stable at high strains in previous studies. The rate of texture evolution in the present study is significantly lower than that reported in previous studies. It was also observed that the natural relaxation of strain following the tensile loading had a significant impact on the texture in the sample. It was observed that the relaxation process mitigated or eliminated the second and third preferred texture components described above, while strengthening the first. ᭧

Effects of high magnetic field annealing on texture and magnetic properties of FePd

“…As a comparison, the same as-prepared FePd samples were annealed in a similar process without the exposure to the magnetic field. Texture was measured using a Philips X'Pert PW3040 MRD X-ray diffractometer, equipped with a pole figure goniometer, operating at 40 kV and 45 mA and employing Ni filtered Cu Ka radiation, as described before [13]. Incomplete pole figures of FePd (0 0 2), (1 1 1), (1 1 3), (2 0 0), (2 0 2) were obtained from the measurements.…”

Self-consistent modeling of large plastic deformation, texture and morphology evolution in semi-crystalline polymers

“…The pole figures are obtained with harmonic series expansion for the intensity functions and plotted in stereographic projection. The experimental data from Li et al (2001) represent the texture of a sample of HDPE after relaxation. 1 It is noted that in Fig.…”

“…Experimentally, the preferred orientations in HDPE at large strains have been found to be (Li et al, 2001): (i) a strong ð0 0 1Þ component aligned with the tensile axis; (ii) a weaker ð0 1 1Þ component aligned close to the tensile axis; (iii) a weaker ð0 1 0Þ component aligned with the tensile axis. From Fig.…”

“…It is noted, however, that the model gives considerably better predictions in tension compared to those reported in Lee et al (1993a, b), where the c component develops much faster than observed and the ð0 1 1Þ and ð0 1 0Þ components along or close to the tensile direction are not predicted at all. 1 Li et al (2001) also measured the in-situ texture evolution during deformation, but we could not use these data because the HDPE sample displayed a strong texture in the undeformed state, which remained stable up to very high strains.…”

High Temperature Texturing of Engineered Materials in a Magnetic Field

“…The equilibrium phase diagram of the FePd system shows five distinguishable regions at low temperature as a function of the atomic content of Pd [12]. The equiatomic FePd undergoes an order-disorder transition at about 923K from a disordered fcc to an ordered L1 0 tetragonal structure.…”