Simulation of velocity profile inside turbulent boundary layer

The second-order differential equation with a general polynomial solution [1], is adapted for simulation of complex velocity profile inside the turbulent boundary layer. Consequently, the simulation strategy is suggested

Simplification of laminar boundary layer equations

The laminar boundary layer theory has been involved in two domains of transport phenomena: (i) steady-state flow (via Blasius eq.) and (ii) unsteady state flow and/or nonflow (via Newton, Fourier and/or Fick’s equations). Listed partial differential equations with the similarity of solutions enable the substitution of the observed phenomena by only one-second order differential equation. Consequently, an approach established on the general polynomial solution is described. Numerical verification of the concept is presented. Experimental notifications are documented. Finally, the new simulation strategy is suggested

Prediction of hardness and electrical properties in ZrB2 particle reinforced metal matrix composites using artificial neural network

In the present study, the hardness and electrical properties of copper based composite prepared by hot pressing of mechanically alloyed powders were predicted using Artificial Neural Network (ANN) approach. Milling time (t, h), particles size of mechanically alloyed powders (d, nm), dislocation density (Ï, m-2) and compressive yield stress (σ0.2, MPa) were used as inputs. The ANN model was developed using general regression neural network (GRNN) architecture. Cu-based composites reinforced with micro and nano ZrB2 particles were consolidated via powder metallurgy processing by combining mechanical alloying and hot pressing. Analysis of the obtained results concerning hardness and electrical properties of the Cu-7 vol.% ZrB2 alloy showed that the distribution of micro and nano ZrB2 particles and the presence of agglomerates in the Cu matrix directly depend on the milling time. Also, the results show a strong influence of the milling time on hardness and electrical properties of Cu-7 vol.% ZrB2 alloy. Addition of ZrB2 particles decreases electrical conductivity of copper, but despite this fact Cu-7 vol.% ZrB2 alloy can be marked as highly conductive alloy (samples made of mechanically alloyed powders milled longer than 20 h). Experimental results of the samples have shown a consistency with the predicted results of ANN.  http://dx.doi.org/10.5937/metmateng1404255

Understanding plasma spraying process and characteristics of DC-arc plasma gun (PJ-100)

The thermal spray processes are a group of coating processes used to apply metallic or non-metallic coatings. In these processes energy sources are used to heat the coating material (in the form of powder, wire, or rod form) to a molten or semi-molten state and accelerated towards a prepared surface by either carrier gases or atomization jets. In plasma spraying process, the spraying material is generally in the form of powder and requires a carrier gas to feed the powder into the plasma jet, which is passing between the hot cathode and the cylindrical nozzle-shaped anode. The design of DC plasma gun (PJ - 100) is designed and manufactured in Serbia. Plasma spaying process, the powder injection with the heat, momentum and mass transfers between particles and plasma jet, and the latest developments related to the production of DC plasma gun are described in this article

Structural changes at rotation friction welding of various steel types

Korišćenjem metoda optičke mikroskopije, kvantitativne optičke mikroskopije SEM i EDS analize izvršena su ispitivanja strukture, kao i analiza faznog i hemijskog sastava, kod trenjem zavarenih spojeva brzoreznog čelika Č 7680 sa ugljeničnim čelikom za poboljšanje Č 1730.By using the methods of optical microscopy, quantitative optical microscopy SEM and EDS analysis, the tests of structure were carried out, as well as the analysis of both phase and chemical composition, of joints welded by friction of the HSS steel M-2 with carbon steel for improving 1060

Multilayered nano-foils for low-temperature metal-ceramic joining

Over almost two decades metal-ceramic fusing has been the essential step in obtaining materials which benefit from both ceramic and metal materials, i.e. where the combined properties of the metal and ceramic layers are desirable. Soldering and active metal brazing are the most effective when considering fusing methods. This paper presents a low-temperature process for soldering and brazing ceramics to metals, which is based on the use of reactive multilayer foils as a local heat source. The reactive foils range in thickness from 40 μm to less than 100 μm and contain many nanoscale layers and/or domains that alternate between materials with high mixing heat.

A model for cross-referencing and calculating similarity of metal alloys

This paper presents an innovative model for the comparison and crossreferencing of metal alloys, in order to determine their interchangeability in engineering, manufacturing and material sourcing. The model uses a large alloy database and statistical approach to estimate missing composition and mechanical properties parameters and to calculate property intervals. A classification of metals and fuzzy logic are then applied to compare metal alloys. The model and its algorithm have been implemented and tested in real-life applications. In this paper, an application of the model in finding unknown equivalent metals by comparing their compositions and mechanical properties in a very large metals database is described, and possibilities for further research and new applications are presented

Liquid metal/ceramic interfaces in dental practice and jewellery manufacturing

Metal-ceramic fusing has been the essential step in obtaining materials that benefit from both ceramic and metal constituents. i e where the combined properties of metal and ceramic layers are desirable When considering fusing methods. soldering and active metal brazing are the most effective These processes involve braze melting and flowing between the two pieces of material In the first part the phenomena occurring on the boundary between the ceramics and the active filler metal during the metal-ceramics joining are discussed Three interconnected sub-processes are considered (1) wetting of the ceramic surface. (2) chemical reactions at the Interlace and (3) diffusion with a moving interface Then, the appearances at the grain boundary grooves of the ceramic surface are presented as phenomena on the catalytic surface In the second pan, examples from dental practice and jewellery manufacturing are used for comparative analysis Finally we discuss the composition and properties of the soldering and brazing alloys used for dental practice and jewellery manufacturin

Understanding plasma spraying process and characteristics of DC-arc plasma gun (PJ-100)

The thermal spray processes are a group of coating processes used to apply metallic or non-metallic coatings. In these processes energy sources are used to heat the coating material (in the form of powder, wire, or rod form) to a molten or semi-molten state and accelerated towards a prepared surface by either carrier gases or atomization jets. In plasma spraying process, the spraying material is generally in the form of powder and requires a carrier gas to feed the powder into the plasma jet, which is passing between the hot cathode and the cylindrical nozzle-shaped anode. The design of DC plasma gun (PJ - 100) is designed and manufactured in Serbia. Plasma spaying process, the powder injection with the heat, momentum and mass transfers between particles and plasma jet, and the latest developments related to the production of DC plasma gun are described in this article

Prediction of hardness and electrical properties in ZrB2 particle reinforced metal matrix composites using artificial neural network

In the present study, the hardness and electrical properties of copper based composite prepared by hot pressing of mechanically alloyed powders were predicted using Artificial Neural Network (ANN) approach. Milling time (t, h), particles size of mechanically alloyed powders (d, nm), dislocation density (ρ, m-2) and compressive yield stress (σ0.2, MPa) were used as inputs. The ANN model was developed using general regression neural network (GRNN) architecture. Cu-based composites reinforced with micro and nano ZrB2 particles were consolidated via powder metallurgy processing by combining mechanical alloying and hot pressing. Analysis of the obtained results concerning hardness and electrical properties of the Cu-7 vol.% ZrB2 alloy showed that the distribution of micro and nano ZrB2 particles and the presence of agglomerates in the Cu matrix directly depend on the milling time. Also, the results show a strong influence of the milling time on hardness and electrical properties of Cu-7 vol.% ZrB2 alloy. Addition of ZrB2 particles decreases electrical conductivity of copper, but despite this fact Cu-7 vol.% ZrB2 alloy can be marked as highly conductive alloy (samples made of mechanically alloyed powders milled longer than 20 h). Experimental results of the samples have shown a consistency with the predicted results of ANN. http://dx.doi.org/10.5937/metmateng1404255