Transient Response Dynamic Module Modifications to Include Static and Kinetic Friction Effects

A methodology that supports forced transient response dynamic solutions when both static and kinetic friction effects are included in a structural system model is described. Modifications that support this type of nonlinear transient response solution are summarized for the transient response dynamics (TRD) NASTRAN module. An overview of specific modifications for the NASTRAN processing subroutines, INITL, TRD1C, and TRD1D, are described with further details regarding inspection of nonlinear input definitions to define the type of nonlinear solution required, along with additional initialization requirements and specific calculation subroutines to successfully solve the transient response problem. The extension of the basic NASTRAN nonlinear methodology is presented through several stages of development to the point where constraint equations and residual flexibility effects are introduced into the finite difference Newmark-Beta recurrsion formulas. Particular emphasis is placed on cost effective solutions for large finite element models such as the Space Shuttle with friction degrees of freedom between the orbiter and payloads mounted in the cargo bay. An alteration to the dynamic finite difference equations of motion is discussed, which allows one to include friction effects at reasonable cost for large structural systems such as the Space Shuttle. Data are presented to indicate the possible impact of transient friction loads to the payload designer for the Space Shuttle. Transient response solution data are also included, which compare solutions without friction forces and those with friction forces for payloads mounted in the Space Shuttle cargo bay. These data indicate that payload components can be sensitive to friction induced loads

Suppression of axionic charge density wave and onset of superconductivity in the chiral Weyl semimetal Ta₂Se₈I

A Weyl semimetal with strong electron-phonon interaction can show axionic coupling in its insulator state at low temperatures, owing to the formation of a charge density wave (CDW). Such a CDW emerges in the linear-chain-compound Weyl semimetal Ta2Se8I below 263 K, resulting in the appearance of the dynamical condensed-matter axion quasiparticle. In this paper, we demonstrate that the interchain coupling in Ta2Se8I can be varied to suppress the CDW formation with pressure, while retaining the Weyl semimetal phase at high temperatures. Above 17 GPa, the Weyl semimetal phase does not survive, and we induce superconductivity, due to the amorphization of the iodine sublattice. Structurally, the quasi-one-dimensional Ta-Se chains remain intact and provide a channel for superconductivity. We highlight that our results show a near-complete suppression of the gap induced by the axionic charge density wave at pressures inaccessible to previous studies. Including this CDW phase, our experiments and theoretical predictions and analysis reveal the complete phase diagram of Ta2Se8I and its relationship to the nearby superconducting state. The results demonstrate Ta2Se8I to be a distinctively versatile platform for exploring correlated topological states. © 2021 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society

An Experimental Study on the Ordered Alloy Ni_2Cr

The ordered alloy Ni_2Cr has been investigated by means of electron diffraction, electron microscopy, calorimetry, resistometry and tensile tests. The formation of the Pt_2Mo type superstructure is revealed by an electron diffraction study on the single crystalline specimens. The size of ordered domains is of the order of magnitude of several hundred A even in the well annealed state. The so-called \u27K-state\u27 which is characterized by the initial increase in electrical resistivity upon isothermal annealing is attributed to the existence of very fine ordered domains. Superdislocations consisting of triple dislocations are sometimes observed in various stages of ordering, and the mechanical properties are briefly discussed in the light of electron microscopic observation. The energy and entropy of transformation are evaluated as about 1.0 kcal/g・atom and 1.2 cal/g・atom-deg on the alloy of 32.1 at% Cr annealed at 500℃ for about 3000 hr

EFFECT OF THE VANADIUM ADDITION ON THE GRAIN SIZE AND MECHANICAL PROPERTIES OF THE COPPER-ALUMINIUM-ZINC SHAPE MEMORY ALLOYS

The effects of vanadium addition on the β-grain size, pseudo-elastic and shape memory behaviour and fracture mode of the copper-aluminium-zinc shape memory alloys with different vanadium contents were investigated. It was found that the vanadium addition is very effective in reducing β-grain size. In the specimen hot-rolled and recrystallized for several ten minutes at 1073K, the maximum mean grain size was only 300 µm. When the annealing time is shorter, i.e. a few minutes, it reaches 200 µm. The minimum β-grain size 100 to 150 µm of the specimen in the recrystallized state was obtained by combination of vanadium addition and cold-rolling. The recoverable pseudo-elastic strain of the specimen having four-five grains along its thickness was found to be up to 5%, and recoverable shape memory strain up to 5.5%, both are near the mean theoretical values of polycrystalline materials. It was found that grain boundary cracking, which is usually observed in copperbase β-brass alloys and is considered to be the most undesirable failure of these alloys, was remarkably suppressed by vanadium addition

SURFACE ENERGY AND EQUILIBRIUM SHAPE OF L12-TYPE A3B ORDERING ALLOYS

Calculation of surface energy of L12-type A3B ordering alloy was made on the basis of a broken bond model using Bragg-Williams approximation. Prior to the calculation of surface energy, calculation of broken bond density in the same alloy was made. Numerical results for Cu3Au alloy were presented as functions of surface orientation and degree of order. Applying Wulff's theorem to calculated γ-plots of the alloy, their external equilibrium shapes for the alloy with various degree of order (η) were predicted

EFFECT OF WEATHER ON WILD TURKEY POULT SURVIVAL

Abstract: Weather conditions are partly responsible for annual variations in poult production, but the specific effects of weather on the survival of eastern wild turkey poults (Meleagris gallopavo silvestris) are not well documented. Understanding the relationships between weather and poult survival might permit predicting fall populations from the preceding spring weather. Weather conditions and poult survival were monitored daily during 2 breeding seasons. The impact of weather on poult mortality included both age‐specific and random effects. Rain and low temperatures (3.8 cm, 7‐8 C) over an 18‐hour period produced mortality in 12‐ and 15‐day‐old broods, but not in 4‐ and 6‐day‐old broods. One hen abandoned her nest during this storm. The disappearance of 8 of 11 poults in another brood coincided with a heavy thunderstorm that occurred about 1 hour after the birds left the nest. Predation and accidents were additional causes of poult mortality. Systematic brood counts provide the best means for predicting fall populations because spring weather accounts for only part of the annual variation in productivity

GROWTH PARAMETERS AND SEX AND AGE CRITERIA FOR JUVENILE EASTERN WILD TURKEYS

Abstract Most information on the growth and development of juvenile wild turkeys (Meleagris gallopavo) has been obtained from game‐farm stock and little data is available for young poults. One or more of the following data were recorded from hatching to approximately 210 days of age for 97 hand‐reared wild turkeys: body weight, leg length, primary molt patterns, and length of postjuvenile primaries 7 and 8. From hatching to 35 days, age could be determined from leg length or juvenile primary patterns but sex could not be distinguished.. Between 35 and 56 days of age, weights and leg lengths of males and females began to diverge but not enough to positively determine sex. Age was most accurately determined from the postjuvenile primary molt pattern. Between 56 and 98 days, there was sexual dimorphism in leg length, body weight, and molt sequence, and both sex and age could be determined. Beyond 98 days of age, leg length alone separated the sexes. Age could be determined up to about 177 days for females and 190 days for males by measuring the length of postjuvenile primaries 7 and 8. Use of the combination of body weight, leg length, and primary molt pattern provided the most accurate method for determining sex and age. Data from hand‐reared poults compared favorably with that from wild‐trapped, known‐age poults from several northeastern states. The data indicate that techniques now used in the Northeast are overaging juveniles