Effects Of Loading Parameters Research Articles

Strain-induced martensitic transformation in textured austenitic stainless steels

The metastable austenitic steels have a tendency to transform to ɛ (hexagonal) and α′ (tetragonal) martensites during thermomechanical treatment (e.g. under tensile stress). The formation of these martensitic phases affects the strength, toughness, formability and corrosion resistance of the steel. The martensitic transformation of an austenitic steel at various temperatures and strain rates was studied in this work. The effects of loading parameters and temperature on the texture and volume fraction of the martensite were investigated. Also, the effect of various martensitic structures on the stress–strain curve and work hardening was investigated. We have observed a very stable deformation texture feature of austenite (γ) and α′ martensite which was observed even if a small amount of deformation takes place. Finally we will show the texture evolution during transformations.

Physical analysis of the certain results in Z-pinch experiments on the “Qiang Guang-I” generator

Starting from the energy necessary for atomic ionization and plasma maintaining, a method is developed to estimate the required energy and implosion velocity for a material to emit a certain shell X-ray radiation in a Z-pinch. The typical load current and voltage in Z-pinch process on “Qiang Guang-I” generator are analyzed to obtain the inductance and the work done by Lorentz force, as well as the effect of load parameters on them. The inductance is not in good agreements with that calculated from the theory based on the shell model of Z-pinch, possibly due to the over simplification of the model and the measurement limitations, such as the measuring points of the current and voltage are always several centimeters away from the load. It is found in the experiments that the inductance increases with the load current until the end of the X-ray radiation pulse, and is saturated at ～100nH. The work done by Lorentz force is maximal when the diameter of tungsten wire array is 8 mm in our experiments. The work done to the load with more wires is greater than that to the load with less wires if the diameters of the wire arrays are the same, say 8 or 10 mm. At the same time, the calculation for optimized masses per unit length of gas-puff and wire array load was carried out for the “Qiang Guang-I” generator on 1.6MA current level. The optimized results show that the tungsten wire array with 8 mm diameter should be the best load for this generator. This is consistent with the experimental result on the “Qiang Guang-I”.

Modeling effects of nonmetallic inclusions on LCF in DS nickel-base superalloys

Inclusions often play a dominant role in limiting fatigue life in both cast and wrought alloys under nominally elastic cyclic loading conditions. The hierarchical scales of fatigue crack formation and their correspondence to strain–life relations were considered for cast A356-T6 Al in recent work by McDowell and co-workers using a microstructure-property framework that related cyclic plasticity near debonded silicon particle and large casting pores to formation and early growth of microstructurally and physically small fatigue cracks. In this paper, we turn our attention to the analogous role of carbides, oxides or other hard ceramic particles in fatigue crack formation in nickel-base superalloys. Cyclic plasticity of a directionally solidified (DS) nickel-base superalloy is evaluated in the [0 0 1] orientation. The effects of loading parameters (strain amplitude, R-ratio) and microstructural parameters (nonmetallic inclusion shape, spacing, etc.) on local cyclic plasticity at microstructure-scale notches are evaluated. The effect of neighboring grain orientation on intensification of plastic strain around inclusions is analyzed, and functions are determined for relating applied strain to cyclic plastic shear strain near the inclusion/matrix debond (micronotch) that contributes to LCF crack formation. Use of such a framework for predicting microstructure-dependence of fatigue crack initiation life and its variability are discussed, as are additional mechanisms of microfracture associated with cumulative plastic deformation.

Effect of Loading Parameters on Damage-Induced Shear-Extension Coupling in Laminate

The shear extension coupling due to damage in an initially balanced laminate was studied using a damage evolution model developed by the authors. The effects of complex loading application and loading rate and deviation were investigated. It was shown that the combination of shear loading with uniaxial or biaxial tension and compression reduces shear extension coupling when the longitudinal to shear loading ratio is sufficiently high

Effect of loading parameters on damage-induced shear-extension coupling in laminate

Effect of loading parameters on damage-induced shear-extension coupling in laminate

Effects of Load Parameters on the Natural Frequencies and Stability of a Flexible Spinning Disk With a Stationary Load System

The orthogonality properties among the eigenfunctions for a gyroscopic system are derived for a stiffness operator that is not positive definite. The derivatives of the eigenvalues with respect to certain parameters in the system are then obtained. The results are applied to a spinning disk in contact with a stationary load system, which contains such parameters as friction force, transverse mass, damping, stiffness, and the analogous pitching elements, to predict the effects of these parameters and the stiffening of the disk due to the centrifugal force on the natural frequencies and stability of the spinning disk. The results obtained provide a theoretical understanding for previously reported observations based on numerical solutions.

Effect of loading parameters on theophylline release from polystyrene beads

Various parameters of preparation of theophylline loaded by solvent swelling on polystyrene beads were evaluated. The resulting samples were characterized by X-ray photoelectron spectroscopy, differential scanning calorimetry, X-ray diffractometry, electron scanning microscopy and wettability test. The release of drug was carried out in pH 7.5 buffer medium and a biphasic process was seen. An initial phase was adequately described by a cube-root of undissolved drug equation and a terminal phase by a square-root of time equation. Drug-polymer systems, washed with water to remove the surface drug before the release study, exhibit a diffusion mechanism controlled by the Higuchi equation.

Effect of loading parameters on the process of metal fracture during blank production by breaking

Effect of loading parameters on the process of metal fracture during blank production by breaking

Effect of loading parameters on the mechanism of small plastic deformation in tungsten subjected to uniaxial tension

1. Irreversible changes in structure that can be observed by means of a field-ion-microscope occur in the elastic region in samples of tungsten at room temperature. 2. At stresses up to 0.5σ0.2, independently of the strain rate, deformation occurs in localized volumes of the material by means of slip with formation of slightly misoriented blocks. 3. At stresses higher than 0.5σ0.2 and a strain rate of 1.7·10−2 sec−1 the predominant mechanism of small plastic deformation becomes twinning.