Papers by Keyword: Grains

Abstract: Effects of Cerium (Ce) addition on solidification structure of a low-carbon 42CrMo4 steel was investigated. The addition of up to 0.067 wt.% of Ce in the steel produced greatly improved solidification structure with a suppressed columnar grain zone, finer grain size in an equiaxed grain zone and zero area fraction of casting shrinkage cavity. The added Ce occurred in the steel both in the form of Ce oxy-sulfide inclusions and as dissolved atomic Ce segregated together with other elements at prior austenite grain boundaries and at interdendritic spacing. The Ce oxy-sulfide inclusions were found to play a major role in the observed improved grain structure meanwhile dissolved Ce had pronounced effects on morphology of dendritic networks. The fraction of Ce dissolved in the melt appeared to bring about increase in fluidity of the molten steel, leading to total elimination of interdendritic shrinkage porosity in solidification structure of the steel with added Ce. Ce addition can be considered as a potential solution for grain structure refinement in heavy-weight castings of 42CrMo4 steel grade.

Abstract: The article presents the results of the study of the quality parameters of the precise hole, depending on the size, spatial location and condition of the contacting surfaces, the parameters of the state of the contact zone, during finishing grinding. The correlation between the processing modes and the current parameters of the contact zone during internal grinding is established. Dependencies describe the flow cross-feed for the i-th turn increment of the depth of micro-cutting, compensation of radial material removal previous turn, deterioration of the wheel, the increment of the elastic and thermal strains. At the same time, the depth of micro-cutting and the increment of elastic and temperature deformations affect the values of the radial wear of the tool and the radial removal of the material. The equation of displacement balance is developed for discrete processes of hole processing with abrasive tools, during which the analyzed surface area comes into contact with the abrasive tool periodically.

Abstract: Barium titanate (BTO) samples were prepared by nanomilling based solid state reaction method. Dielectric behavior of BTO sample has been investigated by temperature dependent impedance spectroscopy. The impedance analysis of BTO samples confirm that hopping of electrons and defects coexisted in sample and contribution of grain and grain boundary to dielectric behavior is discussed. A single semicircular arc obtained by Nyquist plots whose radius decreased with increase in temperature illustrates the prominent role of grains. The activation energy of defects was calculated from Arrhenius plot. These defects may be due to oxygen vacancies and hopping between Ti⁺⁴ to Ti⁺³ ions.

Abstract: In the previous papers, the author discussed the role of r-value (anisotropic parameter in plasticity) on the surface roughening after plastic deformation. In the present paper, discussion is made on the effects of mutual constraint of deformation between neighboring grains at the grain boundary on the surface roughening. A characteristic parameter called constraint ratio is introduced to express the degree of the mutual restriction between grains. The well-known Coffin-Manson relation in low cycle fatigue is deduced considering to the surface roughening after cyclic deformation.

Abstract: Probability occurrence between two successive 2-d granular materials configuration, which are related to their entropy, can be used to check history line of the materials configurations. As an example, a well-known Brazil-nut effect will be presented. In small region it seems that this effect violates principle of minimum energy but not as the whole system, where the energy does decrease. In this work effect of temperature is considered constant since the configurations are observed in frozen states instead of dynamic or fluidized states.

Abstract: The objective of this study was to investigate numerically heat and mass transport during drying of grains with particular reference to bean and rough rice. The proposed mathematical models based on the Fick’s and Fourier’s Laws consider constant physical properties and convective boundary condition at the surface of the solid. The solutions of the governing equations were performed using ANSYS CFX^® software. The grains were regarded as an ellipsoid of revolution. Results of the drying and heating kinetics and moisture content and temperature distributions in the grains along the drying process are presented and analyzed.

Abstract: This paper describes the work performed on a small-scale dryer designed to allow agricultural product to be dried by farmers via usage of slanted plates for grains transportation. This work involves the prototype design, computational simulation using Comsol Multiphysics and study of the results. The computational simulation results are plotted in temperature contour-plots based on the prototype modelling and boundary conditions. The results illustrate the difference in opening and closing of grains inlet and also effects of the temperature distribution within the dryer. Air-flow relative humidity is also introduced to allow observation of the drying air-flow on the grains. The simulation results are shown and elaborated here. From the results, it is evident the grains can be dried as the injected heated air-flow is projected onto the plates. It can also be concluded here that farmers may need to close the grains inlet of the dryer to prevent heat loss and non-uniform distribution of heat.

Abstract: In this work, the effect of isothermal heat treatments on microstructure evolution and mechanical properties after welding by induction of A37 pipeline steel have been studied by scanning electron microscopy, hardness measurements, and tensile tests. Microstructural evolution in welded joint was identified after isothermal annealing from 200 until 900 °C.

Abstract: When the depth-sensing (nano)indentation is applied to sintered samples, measured properties, which are expected to represent the material of an individual grain, seem to depend on the overall porosity of the macroscopic sample. To understand such a result, it is assumed that while the nanoindenter penetrates into the surface grain and probes the properties of its material, the grain itself serves as another, larger indenter indenting the rest of sample and probing the properties that represent the bulk of material rather than individual grains. Load vs. displacement curve reflects the synergetic response of these two “indenters” and so it contains information about the sample’s mechanical properties at both microscopic and macroscopic scales. Obtained theoretical results agree qualitatively with the experimental data (the dependence of the indentation modulus on the porosity of sample; the indentation size effect).

Abstract: This paper provides an automatic barn-entering system for grains. Based on the technologies of microwave and PLC, the system may detect the grain moisture on line and control the directions of grain flows on conveyor. For the flows with moisture below the specified threshold, the grains may be made their way into the barn, otherwise rechannel the direction automatically and not permitted into the barn.Thus can avoid effectively grains' from going mouldy due to the high moisture content.