Influence Of Softening Research Articles

Effects of La<sup>+3</sup> and Sc<sup>+3</sup> Ions on Structure and Microstructure of PZT Ceramics for Energy Storage Applications

Solid solutions of PZT ceramic at Zr/Ti ratio of 0.56/0.44 having various content of softener (La+3) and hardener (Sc+3) ions according to chemical formula (Pb1-y Lay) (Scx Zr0.56-x Ti0.44) O3, [y= (0.0 and 0.02); x= (0.02, 0.04 and 0.06)], were prepared via conventional solid state reaction methods. Structural and microstructural characteristics were investigated systematically. The measurements of XRD diffraction spectra showed occurring of phase transformation after doping with Sc+3 ions in both, PZT and PLZT ceramics, through emerging of tetragonal phase to coexist with the rhombohedral phase. Their fraction varied depending on content of Sc+3 ions. SEM mages display a different influence of softener and hardener ions, at 0.02 % mole, on the grain size. Doping with La+3 causes reduction in grain size, whereas Sc+3 increase the grain size. However, further increase in Sc+3 content in both (PZT and PZT) ceramics causes sharp decreasing in grain size. The latter feature is preferable in terms of increasing in the energy storage values.

Evaluation of possibilities of application of web-based tool for effective identification of mechanical properties of materials

The main purpose of the work is to present and test the developed web-based tool to identify parameters of rheological equations, whose functionality according to the presented results is comparable to existing desktop applications. The developed web-based application with a user-friendly interface uses selected optimization methods (Powell and Hooke-Jeeves algorithms). Criteria for selecting optimization methods are: robustness and frequent application to identification problems described in literature. Testing the developed application consists of comparing the identified stress-strain curves obtained from mechanical tests using the developed tool and commercial desktop application, and performing efficiency tests for the analyzed examples of rheological equations and optimization methods. For this purpose, two material models were used: a simple Hollomon’s model and a multi-parameter model used for steel, in which the influence of softening during the dynamic recrystallization is insignificant. The presented software is implemented in technologies such as JDK 1.8, Spring Framework and PrimeFaces, and passes the efficiency tests successfully.

Influence of Softener on Rheological Characteristics of the Nanostructured Modifier

Article is devoted to studying of influence of additives on rheology of the nanostructured modifier on the basis of silica-containing raw materials. Optimum technological combinations of the plasticizer were defined, which allow to change flow character of a suspension and to give to a material necessary properties. Basic possibility to use additives on a melamine-formaldehyde basis for plasticization of the nanostructured modifiers of silicate structure is proved.

New strength formulae for rock surrounding a circular opening

In this paper, the unified strength theory proposed by Yu Mao-hong in 1991 is used to develop new strength formulae for rock surrounding a tunnel. The new formulae can be applied to an elastic–plastic material. The formulae have a series of expressions with the unified parameter, especially variations such as the well-known Kastner and Airy formulae, which are widely used in rock mechanics and engineering. These formulae are derived on the basis of the Mohr–Coulomb strength criterion. For the strength-weakening (plastic-softening) of geomaterials, the analytical solutions for the radius of the plastic residual zones, radius of the plastic-softening zones, and displacement around the opening are presented according to the elastoplastic-softening – residual plastic, tri-linear stress–strain model. In addition, the derivation for the stress state in the surrounding rock is given. The Kastner formula, Airy formula, and available solutions can be considered as special cases in the new strength formula. The influence of softening, shear dilatancy, and different strength models on the results is analyzed. The results presented in this paper are useful for analyzing surrounding rock with various stress conditions and reinforcement of caves.

New Evaluation Methods Discussion of Softening–Melting and Dropping Characteristic of BF Iron Bearing Burden

Based on the analysis of the existing evaluation methods and with the combination of the characteristic of cohesive zone characteristic in blast furnace (BF) and softening–melting and dropping experimental result of iron bearing burden, a new evaluation method of softening–melting and dropping characteristic of iron bearing burden was put forward, which can be used for evaluating various kinds of iron bearing burden. The softening–melting and dropping characteristics of the mixed burden and the high metalized burden are evaluated through the new method, which verified that the new method is reasonable and feasible. The results showed that the new method can judge not only the corresponding relation between the shrinking percentage and the unit charge column pressure drop, but also the influence of softening and melting temperature interval, melting temperature interval and dropping temperature interval on the softening–melting and dropping characteristic value of iron bearing burden. This new method is expected to provide technical guidance for BF smelting.

Interaction of creep damage and low cycle fatigue damage in a 1Cr0.5Mo steel.

Non-destructive replica studies of creep cavitation in power plant components of low alloy steels is a frequently used tool in order to estimate the reminant life. In addition to creep such components are exposed to thermal stresses and strains during start-ups and shut-downs, which can lead to fatigue damage. In order to study the role of creep-fatigue interactions, the influence of creep damage on low cycle fatigue (LCF) in a 1Cr0.5Mo steel was investigated. LCF-specimens were creep tested to 5% elongation at 560 and 600°C resulting in carbide precipitation, bainite coarsening and a significant amount of creep cavitation. The damage development during LCF was studied using replicas for test series of pre-crept and virgin material. In addition, the influence of a hold time was investigated. The development of creep cavities and micro-cracks, as well as the amount of intergranular crack propagation were evaluated. Creep exposure resulted in a reduction of the number of cycles to failure. The relationship between this reduction and the amount of creep damage as well as the consumed creep life fraction was analysed. The influence of softening and increased inelastic strain range due to creep exposure was also studied.Continuous cycling LCF on creep exposed material resulted in a small increase of the cavity density. Compared to virgin material the number of cycles to failure Nf was smaller at low strain ranges. LCF with 5 min hold time resulted in a reduction of Nf by approximately a factor of 1.8. Creep exposure before hold time LCF resulted in an enhanced development of creep damage during LCF and smaller amounts of intergranular crack propagation whereas no significant further reduction of Nf could be observed.

Mastication of Rubber. I

Abstract Plasticity measurements with the Williams-type (parallel-plate) balance and steam plastometers confirmed the well known influence of time, temperature, and energy consumed on mastication of raw rubber on rolls. Reproducibility of results proved fairly high. The effect of storing plasticized rubber was a slow and unimportant hardening. On hot storing, hardening during the first days took place, followed by slow softening. With the steam plastometer, a stiffening value was determined for several fillers when mixed into masticated rubber. Some experiments were done on the influence of the concentration of such fillers and on the influence of softeners, accelerators and sulfur on plasticity. The influence of the degree of mastication of the mixes on the vulcanized stocks was investigated in a few cases. Apart from the well known influence of extreme mastication on breaking strength, a remarkable influence of the temperature of mastication on modulus was found.

Determination of Resistance to Abrasive Wear. VIII. Influence of Softeners in Tests with the Akron-Croydon and Du Pont Machines

Abstract These experiments indicate that softeners can influence abrasion resistance, as measured by laboratory machines, in some manner other than by altering the stress-strain properties of the rubber. One possible explanation is that the softener acts as a lubricant to the abrasive surface. Since this surface, in laboratory abrasion-testing machines, is relatively small, and comes repeatedly into contact with the rubber under test, it seems possible that it may become coated with a thin layer of softener that reduces its abrasive power. It would be interesting in this connection to try an abrasive machine in which a long continuous strip of abrasive material was used, no part of it being used more than once, so as to eliminate or minimize this lubricating effect. The fact that the effect of the softener is more pronounced on the du Pont than on the Akron-Croydon machine lends support to the lubrication hypothesis, because on the former machine the rate of wear per unit area of abrasive is much greater. Thus in the present tests the volume of rubber abraded per hr. per sq. cm. of abrasive surface ranges from 0.03 to 0.11 cc. on the du Pont machine and from 0.0035 to 0.0045 cc. on the Akron-Croydon machine. On the other hand, if the softener acts as a lubricant, it would be expected to reduce considerably the friction between the abrasive and the rubber and hence the energy used in dragging the rubber over the abrasive surface. The energy figures given in the right-hand columns of Tables 1 and 3, however, show that there is relatively little variation between the different rubbers. As a test of the lubrication hypothesis, it would be of interest to vary the conditions of test so that approximately the same amount of rubber per unit area of abrasive is abraded in a given time on both machines; this should show whether the phenomena observed under the present test conditions are due solely to the difference in rate of wear or to an inherent difference in the type of wear on the two machines. This could most conveniently be done by considerably reducing the load on the du Pont machine. In the original work on this machine the load was standardized at 8 pounds, but no figures are quoted to show how abrasion loss varies with the load. As an addition to the present investigation, it is proposed to examine the effect of this variation with special reference to rubbers containing various amounts and types of softener. Published data on the influence of softeners on the road wear of tire rubbers do not indicate anything like such large effects as are shown by the du Pont machine. This throws some doubt on the value of this machine for testing tire tread rubbers, a conclusion which is confirmed by information obtained from other workers.