International Journal of Computational Materials Science and Surface Engineering (15 papers in press)
Theory analysis of grinding fluid jet and its effect on surface roughness of workpiece
by WANG Yu-gang, Xiu Shichao
Abstract: In grinding process, a small amount of grinding fluid can be injected into the contact area for cooling and lubrication. This leads to decrease of the grinding fluid utilization efficiency and workpiece surface integrity. Based on fluid mechanics theory, a mathematical model of two-phase flow field is established and the simulation of the grinding fluid jet is carried out by FLUENT. The distribution of grinding fluid and the pressure variation curve of the jet process are obtained. The results show that less utilization efficiency of the grinding fluid in contact area is a combined effect of high pressure airflow, severe backflow and large pressure difference. The utilization efficiency of the grinding fluid can be improved, when jet occurs at the middle position with higher velocity. In addition, in the grinding experiment of surface roughness, the suitable supply parameters are proved by analyzing Ra values of the parts.
Keywords: Grinding fluid; Jet; Two-phase flow; simulation; surface roughness; supply parameters.
Biological fabrication of silver nanomaterials and its applications in Pharmaceutical Fields
by Arulmozhi Muthukumarasamy, Balraj Baskaran
Abstract: The antimicrobial potentials like antibacterial, antifungal and anticancer activities were evaluated for the biologically synthesized silver nanoparticles (AgNPs) using Streptomyces sp. The AgNPs were characterized by UV visible spectra at 429nm and X-ray diffraction pattern in 38.10(111), 43.68 (200), 63.9(220), 79.96(311) were confirmed the Ag crystal system. The electron microscopic analysis was confirmed the particles were in spherical shape with an average particle size of 30nm. The Infrared spectra revealed that the Streptomyces sp. was involved in the reduction process. The photoluminescence properties of the AgNPs were inspected via PL spectrum and attained prominent emission peak at 544nm. The AgNPs gave promising antibacterial activity against Mycobacterium tuberculosis comparing other microorganisms. The antifungal and anticancer activities of AgNPs provide extraordinary toxicity against the human pathogenic microorganisms. These results confirms the potential scope for the usage of marine bacteria in an effective manner to the pharmaceutical industries.
Keywords: Antibacterial activity; anticancer activity; Antifungal activity; Streptomyces sp.; Silver nanoparticles.
Simulation study on rapid solidification of eutectic Al-Cu alloy: A Molecular Dynamics approach
by Seshadev Sahoo
Abstract: It has been found out that, the metals and alloys produced by rapid cooling techniques have better structural and mechanical properties. The cooling rate is a critical factor affecting the resulting structure of a liquid-solid transition. The solidification of Al-33wt. % Cu is studied with the constant-volume and constant-temperature molecular dynamics technique to obtain an atomic description of structural transformation. The system is modeled by using embedded atom method (EAM) including many body interactions. Molecular dynamics simulation study based on the EAM potential is carried out to study the unidirectional solidification behavior of Al-33wt. % Cu alloy. The radial distribution function during cooling and heating processes provides a good picture of the structural transformation i.e., solid to liquid and again solid which has crystalline in nature. From the simulation result it was found that, the solid/liquid interface moves smoothly unidirectionally with an interface velocity of 9 m/s. This simulation study gives a clear picture of the rapid solidification of Al-Cu alloy at atomic level.
Keywords: Solidification; Simulation; Molecular Dynamics; LAMMPS; Eutectic alloy.
EXPERIMENTAL AND NUMERICAL INVESTIGATIONS ON PLASMA SPRAYED CERAMIC COATINGS WITH VARYING COATING THICKNESS
by Kalayarasan M, Prabhu Raja V, Shankar S, Nithin V, Karthik V
Abstract: Coatings are extensively used in many tribological applications in order to reduce the wear rate. Despite its advantages, life of the coatings has been limited by the stresses arising at the interfacial region. The purpose of this work is to study three different types of ceramic coatings grown by plasma spraying method on titanium substrate by ball indentation and finite element method (FEM). Micrometer-sized powders of the following compositions were plasma sprayed on to the Ti6Al4V (TAV) substrate (flat plate): (i). Al2O3 (AO), (ii). 8 mol% yttrium stabilized Zirconia (8YSZ) and (iii). Al2O340 wt% 8YSZ (A4Z). The effect of type of material and coating thickness on stress distribution and contact pressure has been investigated. The dimensionless parameters which aid in the comparison of the behaviour of the elastically coated sphere and coating thickness with different material properties were identified and used for further investigation. The investigation has revealed that Al2O340 wt% 8YSZ coating on titanium substrate is the most desirable one for protecting the substrate against yielding and hence it could be used as a protective layer.
Keywords: Ceramic coatings; Ball indentation; Experimental analysis; Finite element analysis.
The potential of Using Superhydrophobic Surfaces on Airfoils and Hydrofoils: A Numerical Approach
by Seyed Farshid Chini, Mostafa Mahmoodi, Mehran Nosratollahi
Abstract: Fluids at their interface with ordinary solids are motionless. This condition is referred to as no-slip condition. On superhydrophobic surfaces, fluids have slip velocity which is quantified using Naviers slip length definition. On a superhydrophobic surface, slip velocity can be as large as 50% of the free-streams velocity. We have studied the potential of using superhydrophobic surfaces to improve the performance of airfoils. For that, NACA 4412, 4418, and 4424 were studied numerically. The chord-based Reynolds number was approximately 5000. We found that increasing the slip from 0 to 50% results in up to 66% increase in the lift, and 45% decrease in the drag force when angle of attack is small (i.e. <5o). For larger angle of attack values (i.e. >5o), using superhydrophobic airfoil is still worthy, but its effectiveness becomes smaller. The less efficacy of superhydrophobic airfoils is explained by the laminar separation bubble phenomenon which can have an adverse effect on lift and drag. For small angle of attack values, by increasing the slip from 0 to 50%, the bubble length becomes smaller which is favorable and explains the well-behaviour of superhydrophobic airfoils at small angle of attacks. However, for larger angle of attack values, by increasing the slip, bubbles length grows which results in less efficacy of superhydrophobic airfoils at larger angle of attack values.
Keywords: Surface Engineering; Superhydrophobic; Lift and Drag; Airfoil;Laminar Separation Bubble.
IDENTIFYING THE MINIMUM CORROSION CONDITIONS FOR FRICTION STIR WELDED DISSIMILAR JOINTS OF ALUMINIUM-MAGNESIUM ALLOYS
by Kamal Jayaraj Rajagopal, Malarvizhi S, Balasubramanian Visvalingam
Abstract: Joining of dissimilar metals is very much need of the hour in the fields of automobile manufacturing and industrial construction, where the characteristic features of the different metals are optimized for the desired application to result in weight reduction and cost effectiveness. Due to continuous efforts of researchers, sound friction stir welded joints of 6061-T6 aluminum alloy to AZ31B magnesium alloy were obtained. However, the presence of intermetallics (Al12Mg17 and Al3Mg2) in the nugget zone and formation of intercalated microstructure lead to severe corrosion attack. Chloride ion concentration, pH value and immersion time are reported to be the more influencing parameters on corrosion attack. The present work aims to identify the minimum corrosion conditions for friction stir welded joints of Al/Mg alloys by statistical tools such as design of experiments, analysis of variance and response surface methodology. From the results, it is found that the pH value has greater influence on corrosion rate than other two parameters.
Keywords: Friction stir welding; Dissimilar joint; Aluminium alloy; Magnesium alloy; Response surface methodology; Corrosion rate.
Optimization of Cutting Parameters on High-Speed CNC Milling for Precision parts of Non-ferrous Castings using RSM
by Parameshwari N, Ramesh M, Thangarasu V S
Abstract: This research paper analyses the cutting parameter optimization suitable for precision parts manufacturing units, which mainly uses non-ferrous cast blocks for their job orders using Box-Behnkens response surface method. This solution method developed based on case studies conducted from industrial units involved in precision components manufacturing in 100% export oriented units around Coimbatore. The problem is converted into a simultaneous optimization model for getting better material removal rate (MRR) on high-speed CNC milling process while maintaining the surface roughness requirements less than 20 microns. The experiments were carried out for different alloy materials of non ferrous group frequently used for manufacturing precision components Aluminium 6061, Brass, Gunmetal, Phosper bronze. The group of materials is of heterogeneous but they share similar mechanical properties required for a precision component, it is generally difficult to machine these material due to either soft ductile / hard brittle characters. However this research is to give an adaptable solution to the small and medium type job order companies, which struggle to maintain the precision at a minimized cost of manufacturing. The results show that MRR could be maximized by optimization of input parameters while keeping Ra in the range less than 0.25Microns.
Keywords: Non ferrous metals; optimization; surface roughness; high-speed machining.
Special Issue on: ICPNS'2016 Physical and Numerical Simulation of Materials Processing
Simulation investigation of temperature distribution in large aluminium panel during autoclave age forming process
by Yongqian Xu, Lihua Zhan
Abstract: In autoclave age forming process (AAF), temperature uniformity in large aluminum panel is one of the most important factors affecting its final shape and performance. In order to predict the temperature field of the panel, a 3D computational fluid dynamics model for autoclave processing of a large aluminum panel is developed and experimental evaluated. The results, expressed as root mean square error, show that a good fitting between the experimental data and the calculated results is obtained. It indicates that the model can describe the forming process accurately and use to study the temperature distribution in the panel during the non-isothermal AAF. It is found that the slowest heating points are positioned at the intermediate positions between 15-40% and between 55-70% of the panel length. Due to the thermal conduction between the panel and the mold, the panels peak temperature difference was appeared after the beginning of soaking process. It is suggested that the method of partial assisted heating and optimizing the structure and material of mold can improve the temperature uniformity of panel during the AAF.
Keywords: Large aluminum panel; Autoclave age forming; Numerical simulation; Temperature field; Temperature difference.
Plastic deformation and microstructure evolution of bearing ring blank during cold rolling process
by Song Deng
Abstract: Bearing ring blanks of the high-speed rail bearings, machine tool spindle bearings and wind power bearings have been manufactured through the ring rolling technology. Yet, the plastic deformation and microstructure evolution of bearing ring blanks during the cold rolling process remains unclear. In this work, the deformation and damage evaluation of bearing ring blanks made of GCr15 bearing steel are characterized by the electron backscatter diffraction (EBSD) technique. Furthermore, their microstructure changes in cold rolling are investigated through band contrast images, and their texture evolutions after various deformation ratios are analyzed by the technique of 3D-Euler space distribution. This work provides valuable guidelines for enhanced understanding the role of the cold rolling technology on the microstructure evolution of bearing ring blanks.
Keywords: Bearing ring; Plastic deformation; Microstructure and texture evolution; Cold rolling.
The austenitic peak stress model of low alloy steel at elevated temperature based on the valence electron theory
by Xudong Zhou, Xiangru Liu
Abstract: The traditional method of calculating the high-temperature austenite peak stress empirical model proposed by Sellars and McTegart has been used for fifty years. A new method based on the valence electron theory is presented in this paper. This new approach mainly involves three steps.
The first step is to calculate the austenitic valence electron parameters at high temperature. In order to calculate the lattice constant of the metal crystal under high temperature conditions, the average coefficient of thermal expansion of the low alloy steel is calculated with JmatPro software, then the lattice constants for both of no carbon-containing and carbon-containing austenite unit cells are computed at high temperature with the weighted average method. Based on above lattice constants, the austenitic valence electron parameters and their statistical values are calculated in this step.
The second one is to calculate the total binding energy. In this paper, the austenitic unit cells are divided into no carbon-containing unit cell, carbon-containing unit cell, silicon-containing unit cell, manganese-containing unit cell and molybdenum-containing unit cell. Their binding energies are calculated based on the valence electron statistic parameters. Then the total binding energy is defined as the sum of the mole fractions of above elements in low alloy steel and the corresponding binding energy.
The last step is to establish the model of austenitic peak stress at elevated-temperature based on the combination of Hall-Petch formula and Misaka formula as well as the total binding energy. Additionally using the fitted regression relationship of the total binding energy with the iron, carbon, silicon, manganese and molybdenum elements in the low alloy steel, the austenite peak stress model has been simplified as a simple semi-empirical model.
The prediction results show that the austenitic peak stress model presented in this paper has good precision, which means the establishment method of peak stress model of austenite at high temperature is valid based on statistical parameters total binding energy. Since considering the impact of more additional chemical elements in the low alloy steel, this simple austinite peak stress model can provide an effective way for the calculation of low alloy steel deformation resistance.
Keywords: Valence electron theory; Binding energy; Total binding energy; Austenite; Peak stress.
HOT DEFORMATION BEHAVIOR AND HANSEL-SPITTEL CONSTITUTIVE MODEL OF Cr5 ALLOY FOR HEAVY BACKUP ROLL
by Xuewen Chen, Nana Wang, Xiang Ma, Huijun Zhou
Abstract: The heavy backup roll is a key component in large steel rolling production line, as it supports the work roll to prevent any excessive deflection. The backup rolls are traditionally produced by large-scale forging process. To accurately describe the high temperature flow behavior of a newly developed roll material Cr5 alloy for numerical forging simulation, a thermal simulation testing machine, Gleeble-1500D, is used in this work. The isothermal compression experiments are carried out to study the flow behavior of Cr5 alloy at temperature range of 900 to 1200C, and strain rate range of 0.005/s to 5/s. Hansel-Spittel model is thus used to establish the constitutive equation of the material under hot deformation. The accuracy of the constitutive equation is analyzed by using correlation coefficient r. The validation shows that this equation can accurately predict the thermal deformation behavior Cr5 alloy. The Hansel-Spittel model is implemented into the Forge software, and the FE simulation of a compression process is compared favorably with the experimental data.
Keywords: Cr5 alloy steel; Hot deformation; Hansel-Spittel model;Dynamic recrystallization.
Microstructures evolution and mechanical properties of 5052 aluminum alloy processed by constrained groove pressing
by Kaihuai YANG, Zechang ZOU, Jianmin ZENG, Wenzhe CHEN
Abstract: Commercial 5052 aluminum alloy sheets were subjected to a severe plastic deformation technique known as constrained groove pressing (CGP) at room temperature. The impact of repeated CGP, upon the microstructure refinement was investigated by polarized optical microscope as well as transmission electron microscope. Changes in mechanical properties, measured by tensile test and hardness test, were related to the evolution of microstructures. Moreover, the microhardness, measured on the polished cross-section of each as-pressed sheet, was plotted to provide a pictorial depiction of the homogeneity. The results show that the mechanical fragmentation dominates at grain refinement and a submicron grain size of about 300 nm was achieved in 5052 aluminum alloy sheets by imposing severe plastic strains of 4.64 utilizing the CGP technique. The average microhardness increase dramatically after one pass and then slightly increases with increasing passes, but the homogeneous distribution of microhardness decreases after one pass and then recovers in subsequent passes result in the corresponding uniform distribution of microstructure. In addition, the ultimate tensile strength clearly increases with increasing passes and the elongation decreases after one pass and then remains reasonably constant with further passes.
Keywords: Constrained Groove Pressing; 5052 Al; Microstructures; Grain refinement; Mechanical properties.
Numerical simulation of residual stress in low temperature colossal carburized layer on austenitic stainless steel
by Dongsong Rong, Yong Jiang, Jianming Gong, Yanwei Peng
Abstract: A numerical model is proposed to quantitatively characterize the residual stress evolutions in low temperature colossal carburized layer on austenitic stainless steel. In this model, on the basis of the consideration of concentration and stress dependent carbon diffusivity, prediction of the carbon concentration distribution and growth regularity of carburized layer is performed. The strain rate is discussed taking the compositive effects of residual stress and carbon concentration gradient. Based on the strain compatibility of carburized layer and substrate, the residual stress is calculated. Meanwhile, a low temperature colossal carburization experiment is carried out on 316L austenitic stainless steel, and the carbon concentration and residual stress are measured to verify the validity of the model. The numerical results of carbon concentration and residual stress distributions agree with the experimental data, indicating that the numerical model established in this paper can be used to investigate the process of low temperature colossal carburization.
Keywords: Low temperature colossal carburization; Residual stress; Numerical model; Austenitic stainless steel; Carbon diffusity.
Evaluation of Ductile Fracture Model in Bulk Forming
by Miroslav Urbanek, Antonin Prantl
Abstract: The purpose of this study is to evaluate the parameters of material plasticity and fracture models at room temperature and at rates up to 1 mm/min for steels which are ordinarily used for forging, for instance the 38MnVS6 steel. The behaviour of materials during forming was evaluated and described using MARC/MENTAT and DEFORM software tools. Several fracture models were examined from the perspective of the planned research tasks which involve testing at forging temperatures up to 1100
Keywords: FEM; measurement; triaxiality; normalized Lode angle; Cockcroft-Latham; Oyane.
Simulation of the bite condition of AZ31 sheet rolling
by Zuyan Liu
Abstract: Sheet rolling is a simple plastic deformation, of which there are many formulas to describe its bite condition, however, there is no rigorous theoretical analysis and result, and the applying ranges of these formulas are limited. Although the bite condition is not an important problem in engineering or academy, it is really a term influenced by many factors and it is difficult, maybe impossible to be expressed by an equation. In this paper, by finite element software, the bite condition or the critical friction factor under different thicknesses of AZ31 sheet, rolling reduction, sheet temperature and roller temperature are calculated, and with large result data, the change regulation of the bite condition appears which is shown in a color brick model. This example shows that, avoiding rigorous theoretical analysis, a complex situation can be numerically illustrated well by finite element software.
Keywords: Bite condition; Numerical simulation; Sheet rolling; AZ31.