Measurement of standard and off-axis elastic moduli and Poisson's ratios of spruce and yew wood in the transverse plane

It is well known that in the radial-tangential plane of softwoods, the elastic modulus in the principal directions is clearly higher than the off-axis elastic moduli, which decrease to a minimum at a growth ring angle α of about 45°. However, this angular dependency was experimentally proven by only a few early publications. The aims of this study were (1) to analyze this relationship with up-to-date equipment in compression tests on miniature softwood specimens with varying growth ring angles and (2) to compare the experimental results with those calculated by a tensor transformation to assess whether it is admissible to treat the investigated wood species as orthotropic materials. Two softwoods with distinctly different anatomic structures (Norway spruce and common yew) were chosen, and further properties such as Poisson's ratios were determined. The results confirm the above-mentioned angle-dependent tendency for spruce elasticity, but also show that it is not valid for softwoods in general since the behavior of yew was completely different. The tissue textures of both species, particularly density and density distribution, were discussed as possible reason for these observed differences. The determined Poisson's ratios for principal and off-axis load directions may be useful for modeling of material behavio

Orthotropic Strength and Elasticity of Hardwoods in Relation to Composite Manufacture. Part I. Orthotropy of Shear Strength

The orthotropy of apparent shear strength of three Appalachian (aspen, red oak, and yellow-poplar) and two East European (true poplar and turkey oak) hardwood species was investigated. The experimental approach included shear force applications in planes parallel to the grain so that the annual ring orientation and the orientation of the grain relative to the applied force direction were systematically rotated. Statistical analyses of results demonstrated significant effects of grain and ring orientation on the shear strength for all species. Furthermore, interaction between these two factors was detected. Three models, developed to appraise the orthotropic nature of shear strength, were fitted to experimental data demonstrating acceptable to good agreement between predicted and experimental values. A combined model based on tensor theory and a modified version of Hankinson's formula provided the best fit by r2 analysis. The information obtained and the models developed might be used to explore the shear strength of structural composites in which the constituents are systematically or randomly aligned

High-Velocity Features of Calcium and Silicon in the Spectra of Type Ia Supernovae

"High-velocity features" (HVFs) are spectral features in Type Ia supernovae (SNe Ia) that have minima indicating significantly higher (by greater than about 6000 km/s) velocities than typical "photospheric-velocity features" (PVFs). The PVFs are absorption features with minima indicating typical photospheric (i.e., bulk ejecta) velocities (usually ~9000-15,000 km/s near B-band maximum brightness). In this work we undertake the most in-depth study of HVFs ever performed. The dataset used herein consists of 445 low-resolution optical and near-infrared (NIR) spectra (at epochs up to 5 d past maximum brightness) of 210 low-redshift SNe Ia that follow the "Phillips relation." A series of Gaussian functions is fit to the data in order to characterise possible HVFs of Ca II H&K, Si II {\lambda}6355, and the Ca II NIR triplet. The temporal evolution of the velocities and strengths of the PVFs and HVFs of these three spectral features is investigated, as are possible correlations with other SN Ia observables. We find that while HVFs of Ca II are regularly observed (except in underluminous SNe Ia, where they are never found), HVFs of Si II {\lambda}6355 are significantly rarer, and they tend to exist at the earliest epochs and mostly in objects with large photospheric velocities. It is also shown that stronger HVFs of Si II {\lambda}6355 are found in objects that lack C II absorption at early times and that have red ultraviolet/optical colours near maximum brightness. These results lead to a self-consistent connection between the presence and strength of HVFs of Si II {\lambda}6355 and many other mutually correlated SN~Ia observables, including photospheric velocity.Comment: 48 pages (22 of which are tables), 15 figures, 5 tables, re-submitted to MNRAS (after first referee report

Three is the magic number -- distance measurement of NGC 3147 using SN 2021hpr and its siblings

The nearby spiral galaxy NGC 3147 hosted three Type Ia supernovae (SNe Ia) in the past decades, which have been subjects of intense follow-up observations. Simultaneous analysis of their data provides a unique opportunity for testing the different light curve fitting methods and distance estimations. The detailed optical follow-up of SN 2021hpr allows us to revise the previous distance estimations to NGC 3147, and compare the widely used light curve fitting algorithms to each other. After the combination of the available and newly published data of SN 2021hpr, its physical properties can be also estimated with higher accuracy. We present and analyse new BVgriz and Swift photometry of SN 2021hpr to constrain its general physical properties. Together with its siblings, SNe 1997bq and 2008fv, we cross-compare the individual distance estimates of these three SNe given by the SALT code, and also check their consistency with the results from the MLCS2k2 method. The early spectral series of SN 2021hpr are also fit with the radiative spectral code TARDIS in order to verify the explosion properties and constrain the chemical distribution of the outer ejecta. After combining the distance estimates for the three SNe, the mean distance to their host galaxy, NGC 3127, is 42.5 $\pm$ 1.0 Mpc, which matches with the distance inferred by the most up-to-date LC fitters, SALT3 and BayeSN. We confirm that SN~2021hpr is a Branch-normal Type Ia SN that ejected $\sim 1.12 \pm 0.28$ M$_\odot$ from its progenitor white dwarf, and synthesized $\sim 0.44 \pm 0.14$ M$_\odot$ of radioactive $^{56}$Ni.Comment: 16 pages, 17 figures, 11 tables; accepted for publication in A&

Measurement of standard and off-axis elastic moduli and Poisson's ratios of spruce and yew wood in the transverse plane

ISSN:0043-7719ISSN:1432-522

Orthotropic Strength and Elasticity of Hardwoods in Relation To Composite Manufacture. Part II. Orthotropy of Compression Strength and Elasticity

The effect of grain and annual ring orientation on the compression strength (σuc) and modulus of elasticity (Ec) of small clear specimens of hardwood species was investigated. The experimental and analytical works explored the orthotropic nature of three North American (quaking aspen, red oak, and yellow-poplar) and two European (true poplar and turkey oak) hardwood species under uniaxial compression. Apparent compression strength and modulus of elasticity were measured at 15° grain and ring angle increments. The three-dimensional Hankinson's formula and another model, based on orthotropic tensor theory, were evaluated for predicting the anatomical direction-dependent properties of the species. Statistical analyses revealed that both models approximate the compression strength and elastic properties reasonably well. Either the analytical or the experimental results can be used for further modeling the orthotropic properties of structural composites