International Journal of Computational Materials Science and Surface Engineering (17 papers in press)
Comparative Study on Effects of Slurry Erosive Parameters on Plasma Sprayed FlyashAl2O3 and FlyashSiC Composite Coatings on Al6061 Alloy
by Naveena B E, R. Keshavamurthy, Sekhar N
Abstract: In this present investigation, an attempt has been made to study the potential use of plasma sprayed Flyash-Al2O3 and Flyash-SiC novel composite coatings on Al6061 alloys to mitigate slurry erosive wear. In this Taguchis L27 statistical approach, the influence of various process parameters like, slurry concentration, slurry speed, impinging particle size and testing specimen on the slurry erosive wear in slurry with 3.5% NaCl solution were evaluated and analysed. The results obtained indicate that testing specimen and slurry concentration were greatly influencing on slurry erosive wear than slurry speed and particle size. Under all the test conditions studied, flyash-Al2O3 coatings on Al6061 alloy exhibited higher resistance to slurry erosive wear when compared with flyash-SiC coated and uncoated Al6061. Mathematical models were developed by means of Regressive analysis to predict the slurry erosive wear of developed composite coatings. This will enable the predictive design of important products with the minimum of wastage and maximum utilization of sustainable materials using environmentally friendly processes.
Keywords: Slurry Erosion; Flyash; Al2O3; SiC; Aluminum; Plasma Spray; Taguchi.
Mathematical Model and optimization for Tensile strength of Human Hair Reinforced Polyester Composites
by Divakara Rao P, Udaya Kiran C, Eshwara Prasad K
Abstract: Polymeric based composites were prepared using chopped fibers of human hair in different volume fractions varying from 5 to 25% by weight and in different Fiber lengths ranging from 10mm to 50mm. Experiments are conducted to know the Tensile strength of the composites. Two factor - five level historical data model (DOE) is chosen. In the present study, a mathematical model was developed from the experimental results using Response Surface Methodology (RSM) so as to obtain the optimum tensile strength condition for the composite. The correlation coefficient of the regression model was tested by Analysis of Variance (ANOVA) to check the adequacy of the mathematical model.
Keywords: Composite; Human Hair Fiber; HHRC; Response Surface Method (RSM); ANOVA.
Biological fabrication of silver nanomaterials and their applications in pharmaceutical fields
by Balraj Baskaran, Arulmozhi Muthukumarasamy, Jayapriya Maruthai
Abstract: The antibacterial and anticancer activities were evaluated for the biologically fabricated silver nanomaterials (AgNMs) using Streptomyces sp. The AgNMs were characterised by UV visible spectra at 429 nm and X-ray diffraction pattern in 38.10° (111), 43.68° (200), 63.9° (220) and 79.96° (311) were confirmed the face centred cubic crystal system. The electron microscopic analysis was confirmed that the particles were in spherical shape with an average particle size of 30 nm. The Fourier transform infrared spectra revealed that the Streptomyces sp. was involved in the reduction process of nanomaterial fabrication. The photoluminescence properties of the AgNMs were inspected via PL spectrum and attained prominent emission peak at 544 nm. The AgNMs gave promising antibacterial activity against E-coli comparing with other microorganisms. The anticancer activity of AgNMs was investigated against the human breast cancer cell line and it provides extraordinary toxicity against the cell line. This result confirms the potential scope for the usage of marine bacteria in an effective manner to the pharmaceutical fields.
Keywords: antibacterial activity; anticancer activity; Streptomyces sp.; silver nanomaterials.
Optimisation of cutting parameters on high-speed CNC milling for precision parts of non-ferrous castings using RSM
by N. Parameshwari, M. Ramesh, V.S. Thangarasu
Abstract: This research paper analyses the cutting parameter optimisation suitable for precision parts manufacturing units, which mainly uses non-ferrous cast blocks for their job orders using Box-Behnken's 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 optimisation 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 6,061, 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 minimised cost of manufacturing. The results show that MRR could be maximised by optimisation of input parameters while keeping Ra in the range less than 0.25 microns.
Keywords: non ferrous metals; optimisation; surface roughness; high-speed machining.
Experimental investigation on electrical discharge machining of ceramic composites (Si3N4-TiN) using RSM
by V.P. Srinivasan, P.K. Palani, L. Selvarajan
Abstract: In this work, electrical discharge machining (EDM) of silicon nitride-titanium nitride (Si3N4-TiN) composites which have wide application in heat exchangers, wear-resistant parts, and gas turbines were carried out. Si3N4-TiN composites are fabricated by hot pressing and spark plasma sintering (SPS) process. Selection of appropriate machining parameters in EDM is one of the most important aspects taken into consideration as these conditions to determine the important characteristics such as material removal rate (MRR) and electrode wear rate (EWR) among others. The main machining parameters such as gap voltage (V), current (I) and pulse-on time (Ton) were chosen to determine listed technological characteristics. The characteristic features of the EDM process are explored through response surface methodology (RSM) based on design of experiments (DOE). Moreover, L18 orthogonal array based on DOE to conduct of series of experiments has been adopted. From the results, it is evident that the current is the most significant factor as it influences both MRR and EWR. The high current increases the MRR and the less gap voltage reduces the EWR. The square profile machined with the voltage - 50 volts, current - 5 amps and pulse-on time - 500 µsec exhibits high MRR.
Keywords: electrical discharge machining; EDM; silicon nitride-titanium nitride; Si3N4-TiN; material removal rate; MRR; electrode wear rate; EWR; response surface methodology; RSM; design of experiments; DOE.
Application of numerical simulation during the development of ductile iron bearing seat
by Ping Li, Yanjie Zhao, Junquan Wei, Fengjun Li, Jitai Niu
Abstract: The study deals with the casting defects of shrinkage and dispersed shrinkage appeared during the development of ductile iron bearing seat due to the original process of conventional side-riser feeding on the basis of general casting design method. The bearing seat was cast using automatic air-impact moulding production line with green-sand. The commercial software of InteCAST was used to simulate casting solidification process and to analyse the reason for the casting defects. Further, the optimised process was proposed in conjunction with three pieces of arc-type chills and a side-rider every casting. The result of mass production shows that the casting defects of bearing seat were effectively eliminated by the optimised process. Consequently, the development cycle of bearing seat was significantly shortened and business opportunities of new market are obtained for the foundry enterprise.
Keywords: bearing seat; ductile iron; numerical simulation; solidification; casting defect.
Effect of friction stir welding parameters on mechanical and micro structural behaviour of AA7075-T651 and AA6061 dissimilar alloy joint
by K.P. Yuvaraj, P. Ashoka Varthanan, C. Rajendran
Abstract: This article reports the effect of FSW tool parameters on tensile properties of the friction stir welded AA7075-T651 and AA 6061 butt joint. Aluminium is a widely used material in many engineering applications ranging from packaging material (cans, foil) to transportation (automobiles, aircraft, trucks). Nowadays titanium and composites are growing in use, most of commercial civil aircraft airframes are made from aluminium alloys. Without aluminium, civil and aviation would not be economically viable. In this work, dissimilar aluminium alloys such as AA7075-T651 alloy and AA 6061 alloy of 6mm thickness plate has been friction stir butt welded incorporating FSW tool parameters such as tool tilt, tool offset and pin diameter with central composite design (CCD) by using response surface methodology. It consists of three factors and five levels having 20 experimental runs. From this research, it is found that the joint fabricated with 6mm pin diameter, 0.9 mm tool offset and 3 degree tilt angle exhibited the acceptable tensile strength of 267 N/mm2 compared to other joints. SEM analysis on the tensile fractured surface along with dimples clearly reveals the failure due to ductile behaviour.
Keywords: friction stir welding; pin diameter; tool offset; tool tilt angle; response surface methodology; ultimate tensile strength.
Study on fatigue reliability evaluation method of mechanical system with damage structure under variable amplitude load
by Yuanyuan Ma, Liyang Xie, Xiaohang Xiong
Abstract: The parts of large-scale machinery equipment are mostly welded with each other. Welded structures with internal defects can be regarded as damage structures, which is much easier to suffer from fatigue damage under the action of variable amplitude loads. In this paper, the scale welding structure system - hydraulic support is taken as the object of study. Firstly, combining with the characteristics of its workload, it adopts a new angle: The probabilistic characteristics of the load history of hydraulic support are described and the reliability evaluation of the structure is carried out from 'macro' and 'micro'. Secondly, the equivalent cyclic loading with equivalent stress amplitude is equivalent to the equivalent cyclic loading by applying the damage equivalent mechanism. Based on this, the calculation of the total probability and the statistical average algorithm, the fatigue reliability model was built. It can objectively reflect the real failure, the correlation between the sites of injury.
Keywords: variable amplitude loading; damage structure; probabilistic fatigue; structural reliability; system failure modelling.
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.
THERMO-MECHANICAL ANALYSIS IN SAE-AISI 1524 CARBON STEEL GAS TUNGSTEN ARC WELDS
by Edison Bonifaz
Abstract: A thermo-mechanical analysis was conducted in SAE-AISI 1524 carbon steel Gas Tungsten Arc Welds (GTAW). The sequentially coupled thermal-mechanical finite element modeling approach was used to simulate the thermal and stress evolution during the GTAW process. The analysis procedure was divided into two major steps. First, a 3D transient nonlinear heat flow analysis was performed to determine the temperature distribution for the entire welding and cooling cycle of the process. In the second step, the thermal history from the heat flow model was included into the mechanical elasto-plastic calculation of the stress and deformation in the weldment. Temperature-dependent material properties and the effect of forced convection due to the ﬂow of the shielding gas were included in the model. It is encouraging to note that the model is sufficiently accurate to predict the FZ and HAZ weld profiles as evidenced for the good agreement observed between numerical cross-sectional and metallographic temperature profiles. The successful in the results can be attributed greatly to the characteristic heat distribution parameter c selected from the complementary experimental work. For further experimental comparison purposes, numerically predicted residual stresses obtained in three different locations of two different weld situations are presented.
Keywords: Finite element method; thermal cycles; residual stresses; heating and cooling curves; weld profiles.