International Journal of Computational Materials Science and Surface Engineering (15 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.
FRICTIONAL BEHAVIOUR OF AA7050/B4Cp HYBRID COMPOSITES
by Ranjith Rajamanickam, Giridharan P.K., Subramanian M
Abstract: In this work, AA7050 aluminium alloy reinforced with SiCp was fabricated through liquid stir casting technique. The influence of %reinforcement, sliding speed, applied load and sliding distance on friction co-efficient was investigated using pin on disc equipment with tests based on design of experiments. The results revealed that the friction coefficient increases with increase in % reinforcement. Sliding speed, load and distance follows the similar trend that is at saddle point it registers maximum and after that COF decreases with increase in any of the above said parameters. The result showed that the presence of mechanical mixed layer reduce the coefficient of friction and its broke down leads to increase in friction factor. The presence of mechanical mixed layer was conformed through EDAX analysis. A mathematical model for friction co-efficient was developed using response surface methodology and combined effect of process parameters was thoroughly analysed.
Keywords: Co-efficient of friction; ANOVA; Mathematical modelling; Stir Casting; K2TiF6.
COMPUTATIONAL EVALUATION OF BLENDING RATIO ON THE FLUIDISED BED GASIFICATION SYSTEM: A CORRELATION STUDY
by Saravanakumar P.T, Suresh Vellingiri, Vijayanand P, Ramarao M, Hariharan N, Vellingiri S
Abstract: The intention of this current research work was to calculate the collective effects of the Corn Stalk, wheat and coconut shell in a fluidized gasification process, where the focus was to enumerate the relationships between the response variables and imperative operating factors. With a view to the shortcomings of the traditional “one-factor-at-a-time” process in the identification of the effect of experimental factors and their interactions, a statistical design of the experiment based on response surface methodology (RSM) was used. The response variables used in this work were gasification efficiency, tar yield and carbon adaptation with different bed materials such as silica and limestone. Using RSM, the possessions of individual operating factors and their interactions were firmly gritty, which were not otherwise probable by the traditional design of experiment methodology. Using the consequential response variable correlations, gas efficiencies were optimized as a function of the dissimilar blending ratios and bed materials using respectively. In order to authenticate the optimized parameters, a complete three-dimensional numerical model is developed to simulate gasification in a fluidized bed reactor using the Eulerian-Lagrangian approach. The model predicts product gas efficiency and carbon conversion efficiency in good agreement with experimental data. The arrangement and development of flow regimes and distributions of gas compositions inside the reactor are also examined.
Keywords: Corn Stalk; Wheat Husk, Coconut Shell, Fluidized bed gasifier; Response Surface Methodology(RSM); Computational Fluid Dynamics(CFD).
Special Issue on: ICPNS'2016 Physical and Numerical Simulation of Materials Processing
LATEST DEVELOPMENTS IN VIRTUAL CASTING OF LIGHTWEIGHT METALS
by Qigui Wang, Peggy Jones, Yucong Wang, Dale Gerard
Abstract: The increasing use of lightweight metal castings in critical automotive and aerospace structures has required improved quality, with more reliable and quantifiable performance. Metal casting processing is very complex and often involves many competing mechanisms, multi-physics phenomena, and potentially large uncertainties. The most effective way to optimize the processes and achieve the desirable mechanical properties is through the development and exploitation of robust and accurate computational models. This paper reviews the latest advances in computational tools for lightweight shape casting processing and discusses the opportunities and challenges for future development of virtual casting.
Keywords: Computational Tools; ICME; Virtual Casting; Lightweight Metals.
Deformation control study on H-Beam welded by a finite element model
by Xiaojie Wang, Zhaoxia Qu, Liqian Xia, Zhongqu Sun
Abstract: With the demand of safety and lightweight for truck industry, the welded H-beam structure used for truck frame trends to be fabricated by ultra high-strength steel gradually. However, deformation and stress is still a big issue for welding manufacture of H-beam by ultra high-strength steel. In this study, H-beam deformation of BS960E, which was recently developed by Baosteel Group Corporation, was investigated by numerical simulation and experimental test. A three dimensional (3D) thermo-mechanical finite element model of submerged arc welding(SAW) on H-beam structure of BS960E was proposed, which considered double ellipsoidal heat source, temperature-dependent material physical and mechanical properties, and stress relaxation in the weld molten pool. The simulation results including temperature and residual deformation were both validated by experimental test. Based on the developed model, the effect of heat input and welding sequence on welding deformation of H-beam structure were studied. The optimal welding parameters were finally obtained by the numerical analysis and the experimental verification. The results showed that combining with numerical model and experiment test the welding deformation of H-beam welded by ultra high-strength steel could be controlled effectively.
Keywords: H-beam welded structure; ultra high-strength steel; welding deformation; numerical simulation.
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.