Defect and Diffusion Forum Vol. 419

Abstract: Stress-strain behavior of austenitic stainless steel grade AISI 304 was investigated by means of uniaxial tensile tests and magneto-phase analysis. The test materials were strained in tension within the temperature range of-100 ≤ T ≤ +100 °C. According to the results, intensive strain hardening occurs in austenitic stainless steel when strain-induced α’- martensite is present in the material, and stress-strain behavior is associated with the increase yield strength and tensile strength with decreasing temperature. The analysis of the hardening kinetics reveals that kinetics are affected by the temperature and by the amount of α’- martensite content.

Abstract: As a result of experimental studies, data on the maximum radial loads for a cable with a carbon matrix and the effect of copper conductors on the crack formation process under radial loading of a pusher cable were obtained at the temperature of 20 °C. A finite-element model of a pusher cable is developed, which takes into account the presence of a matrix, copper conductors, and their insulation, which allows us to construct stress and strain fields. The created finite element model allows you to predict maximum loads for composite pusher cables. The design of a stand for testing samples of cables with carbon matrices for radial compressive strength is described. Experimental data on the study of the strength properties of two types of cables at a temperature of 20 °C are presented.

Abstract: Deformation and fracture analysis of the composite elements and structures under high-velocity impact is still associated with many problems. These problems are related not only to the complexity of taking into account the composite layered orthotropic structure and various failure scenarios but also to the problems of instrumented high-velocity impact tests to verify the calculation results. Different requirements for accuracy and numerical efficiency are imposed on the models and their predictive ability depending on the design stage. At the initial design stages, the model should allow one to estimate the energy absorption of the composite structure adequately. At later stages, the size of the damaged area and the fracture pattern also should be predicted with high accuracy. This article describes a simplified approach to the verification of deformation and fracture models of structural composites under high-velocity impact based on low-velocity impact test data. The model with the found parameters makes it possible to predict with satisfactory accuracy the energy absorption of the composite material.

Abstract: The thermodynamic, structural, surface and transport properties of PbSn eutectic alloys at 1050 K have been analyzed employing self association model. The model parameters have been evaluated on utilizing the experimental data of free energy of mixing of PbSn liquid alloys at 1050 K. For the validation of the model parameters, the calculated values of the excess free energy of mixing and activity of the components of PbSn liquid alloys have been compared with the experimentally measured data. Further, the estimated model parameters have been used to determine the thermodynamic functions i.e. the free energy of mixing, thermodynamic activity, entropy of mixing and heat (or enthalpy) of mixing, and the structural properties such as the concentration fluctuations and shortrange order parameter. The theoretical and experimental values are compared. A good agreement is observed. Again, the surface properties of PbSn liquid alloys at 1050 K have been investigated using the Butler model in the framework of self association model. The calculated values of surface tension of PbSn liquid alloys at 1050 K are in reasonable agreement with the data available in the literature. The transport properties like the diffusivity and viscosity of PbSn liquid alloys at 1050 K have been theoretically analyzed. For the computation of viscosity, the simple formula developed by Moelwin- Hughes has been used in conjunction with self association model. The present study reveals that PbSn eutectic liquid alloys at 1050 K are segregating in nature. Further, the model parameters are found to depend on temperature.Keywords: Gibbsfree energy; concentration fluctuations; short-range order parameter; surface tension; diffusivity; viscosity

Abstract: We investigate the structural evolution of the single-walled carbon nanotubes (SWNTs) by molecular dynamics (MD) simulation using the Gao-Weber potential. The structural evolution of SWNTs is analyzed through the total energy per atom, the radial distribution function, coordination number, bond angle and the distribution of ring statistics. The results show that the melting temperature of SWNTs occurs at around T_m=5620 K. This value is in good agreement with the result of Zhang and co-workers. The visualization indicates that the initially perfect SWNTs is broken resulting in the ring of various.

Abstract: The study explores the thermo-physical properties of complex binary liquid potassium-lead alloy at temperature 848 K as a function of concentration by considering complex using different model equations. The Quasi Chemical approximation and the R-K equation are used to investigate features such as free energy, heat of mixing, chemical activity, and concentration fluctuation in the long wave limit at temperature of 848 K. However, at 900 K and 1000 K, these are exclusively examined using the R-K equation. The temperature dependent exponential interaction parameters proposed by Kaptay are taken into account in the RK equation. The study goes on to look at the alloy's viscosity and surface tension using the Budai-Benko-Kaptay model and the Kaptay's improved derivation of Butler equation. The mixing nature of the system is investigated in depth, with a focus on the interaction energy parameters between the alloy's surrounding atoms. The work investigates the fact that the liquid alloy has a moderately interacting as well as ordering character throughout a whole concentration range, and the computed theoretical thermodynamic facts are in reasonable agreement with the corresponding experimental data at 848 K. At greater temperatures, the alloy's tendency goes from ordering to segregating. The alloy's viscosity and surface tension decrease as the temperature rises.

Abstract: The study of amorphous semiconductors is of great interest because they find important applications in many electronic devices, like large area solar cells and photosensors. We have developed a methodology for the analysis of transient response of amorphous photodiodes when switched off from steady-state and when they are exposed to a δ pulse of light. For this purpose continuity equations and the transit time effect have been calculated. For the p-i-n photodiodes, characteristics of photo current decay have been analyzed for an ideal case in which the diode is assumed to have a unit current gain. It is found that characteristics either due to decay from steady-state or due to light pulse excitation is transit time dominated. The short-circuit performance of solar cells resembles to a p-i-n diode because a solar cell is essentially a p-i-n diode which is used as an energy converter. Thus short circuit current decay of solar cells behaves similar to the photocurrent decay of the diode and the same method of analysis can be applied.