Defect and Diffusion Forum Vol. 391

Abstract: The shape memory alloys have been used in the most different sectors such as aerospace, automotive and biomedical due to their ability to return to their original shape when subjected to high temperatures.Modeling and numerical simulation have become great allies in engineering due to the possibility of solving complex problems, especially in cases where experimental research is limited. In the present study, a two-dimensional mathematical model was developed to describe the solidification process of a Ni-Ti alloy in a stainless-steel metal mold sand-confined. It was considered the flow of a refrigerant (air) in the top of the mold. The energy conservation equation, including the phase change term, was discretized using finite volume method (FVM) and a fully implicit formulation. Results of the Ni-Ti alloy and mold temperature distributions over time are presented and analyzed.

Abstract: This study has the purpose to consider a new ignition source in order to increase the inflammable limit of a gasoline engine at its lean region. To analyze flame propagation characteristics, a CVCC (constant volume combustion chamber) was produced, and three types of devices – conventional type, arc type, and jet type – were manufactured to conduct combustion testing. Experimental variables were the air/fuel ratio from 1.0 to 1.8 and charging pressure from 2 bar to 4 bar. The result of flame propagation analysis showed that the spread for jet type was faster than that of conventional type by 10 ms, and that of arc type by 5 ms. Result of combustion pressure experiment showed that, at air/fuel ratio of 1.0, arc type showed the highest value, with 22 bar, while jet type showed 19.4 bar and convention type was 17 bar. At maximum inflammable limit experiment, combustion was possible at jet type and arc type in an area above an air/fuel ratio of 1.8, but the conventional type showed miss fire, where combustion did not occur in the area above 1.6. The Study on new ignition source concluded that the jet type shows superior results in terms of combustion speed while the arc type is excellent in terms of combustion pressure.

Abstract: The paper presents the comparison of the results between the numerical model developed for the simulation of the fluid-structure interaction problem and the experimental tests. The model is based on the so called “partition scheme” in which the equations governing the fluid’s pressures and the equations governing the displacement of the structure are solved separately, with two distinct solvers. The SPH (Smoothed Particle Hydrodynamics) method is used for the fluid and the standard FEM (Finite Element Method), based on shell elements, is used for the structure. Then, the two solvers are coupled to obtain the coupled behaviour of the fluid structure system. The elasto plastic material model for the structure includes some important nonlinear effects like yielding in compression and tension. Previously experimentally tested (on a shaking table) rectangular tanks with rigid and deformable walls were used for the verification of the developed numerical model. A good agreement between the numerical and the experimental results clearly shows that the developed model is suitable and gives accurate results for such problems. The numerical model results are validated with the experimental results and can be a useful tool for analyzing the behaviour of liquid tanks of larger dimensions.

Abstract: The high cycle fatigue behavior of an aluminum alloy of small and large grains was investigated. Samples of small and large grains were provided as rotating bending fatigue test specimens. The samples were tested at eight different stress levels from 103 MPa (15 ksi) to 345 MPa (50 ksi) with a 34 MPa (5 ksi) increase at each level. As-received samples were evaluated for optical microstructural analysis. Scanning electron microscopy (SEM) images were used to evaluate the fractured surface of several samples. High cycle fatigue S-N curves were generated. The fatigue test results showed that grain size has a strong influence on the fatigue life. The high cycle fatigue S-N curves of small grains showed better fatigue life as compared to large grains in the lower stress levels. At higher stresses, the situation was reversed.

Abstract: Though above 70% of the Earth is covered by water, most of the seas and oceans are unusable for drinking. Freshwater lakes, rivers and underground aquifers imply 2.5 percent of the global’s whole freshwater supply. Unfortunately, in addition to being scarce, fresh water is dreadfully unevenly spread. Enhanced demand for freshwater is a global concern. In many countries demanding is further than regular reserves. Sensible use of water, reducing spreading losses and upgraded treatment of recycled water to mitigate the concern, though, water scarcity is still presented consequently desalination of seawater is highly required. Graphene, a single sheet of carbon atoms, possibly will deliver the principal for a novel category of extremely permeable membranes for water purification and desalination. Though, a one atom thickness graphene reveals both brilliant mechanical strength and impermeability to atoms as small as helium. High-density, subnanometer pores within graphene have the potential for ultra-fast water permeance and high solute rejection as the atomic thinness makes slight resistance to stream which deters the transfer of solutes bigger than the pores. The two-dimensional, nanoporous membrane is expected to display orders-of-magnitude permeability and selectivity enhancement over current separation membranes for processes such as brackish water, water softening, or nanofiltration. This study is aimed that the existing desalination methods are not adequate to upgrade water sources unless the desalination technologies are improved significantly. Nanotechnology and utilizing graphene will deliver desalination technology to meet the requirements in the near future. Lately, novel procedures have been technologically progressed by means of nanotechnology and applying graphene for water desalination. This research will emphasize the concept of water desalination for the near futures.

Abstract: Capabilities of application of Mössbauer spectroscopy for determination of grain-boundary diffusion parameters in coarse-grained and ultrafine-grained materials have been analyzed. Application of this method for revealing of non-equilibrium state of grain boundaries in ultrafine-grained materials obtained by severe plastic deformation is demonstrated.

Abstract: Questions regarding the oxidizing roasting of raw iron ore materials (agglomerate and pellets) are studied. Features of the phase structure of raw iron ore materials containing titanium and vanadium are discussed. Reducibility, durability, and temperatures of the softening and melting of metallurgical raw iron ore materials are studied in vitro. Object of research – titaniferous ores with various titanium dioxide content. The behavior of agglomerate and pellets in a blast furnace are studied, as well as the influence of their physical and chemical properties on heat and mass transfer processes using a mathematical model of the blast furnace process [1].

Abstract: Questions of melting of iron ore and raw materials with receipt of cast iron and slag are considered in vitro. The chemical composition of cast iron of slag is studied in vitro. The viscosity of slag is researched. Object of research - titaniferous ores with various contents of titan dioxide. The technical and economic indicators of a blast furnace melting an agglomerate and pellets (a consumption of coke and productivity, a chemical composition of cast iron and slag) received from a concentrate of the Kachkanarsky deposit are calculated. The technique of scientific research is used [1].

Abstract: It has been shown that the plane surface of a stressed solid can become morphologically unstable relative to the perturbations of the electron density. The above instability is referred to as dynamic and evolves under the relaxation mechanism determined by the electron-electron interaction. The development of the dynamic instability is accompanied by the formation of a dynamic pattern differing from that which is formed under elastic-diffusion instability. To describe the dynamic pattern, a method has been proposed which takes into account the dynamic displacements of the atoms caused by a change in the interatomic interaction during the electron density redistribution. The origin of the different types of the pattern earlier observed experimentally on the free surface of the stressed solids has been explained. The dynamic displacements of the atoms have been shown to stimulate the diffusion mass transfer resulting in a change of the value and the sign of the diffusion coefficient.

Abstract: This paper focuses some fundamental aspects of combined convective and microwave drying of prolate spheroidal solids. A transient mathematical modeling based on the diffusion theory (mass and heat balance equations) written in prolate spheroidal coordinates was derived and the importance of this procedure on the analysis of the drying process of wet porous solid, is also presented. Results pointed to the behavior of the moisture migration and heating of the solid with different aspect ratio. Solids with higher area/volume relationships dry and heat faster.