International Journal of Computational Materials Science and Surface Engineering (10 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 P. Divakara Rao, C. Udaya Kiran, K. Eshwara Prasad
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.
The deformation and residual stress simulation of dual laser-beam bilateral synchronous welding for Al-alloy aircraft panel structure
by Xiaohong Zhan, Yun Liu, Yao Meng, Wenmin Ou, Yanhong Wei
Abstract: This paper reports a numerical investigation of dual laser-beam bilateral synchronous welding (DLBSW) for T-joint structure of aircraft fuselage. Finite element numerical simulation of DLBSW is carried out to obtain suitable matching of welding parameters for civil aircraft panels which composed of 6156 aluminum alloy skin and 6056 aluminum alloy stringer. The distribution of welding residual stress and welding distortion on the aircraft panels are predicted and discussed. Three-dimensional finite element model of the panel containing three stringers has been developed to simulate the temperature field, residual stress distribution and welded panel distortion. It is simulated that three stringers are welded to base plate of the specimen through different welding sequences and the welding sequence with the smallest distortion is acquired.
Keywords: Aluminum; Numerical Simulation; Aircraft Panel.
Comparison of RSM and ANN model in the prediction of the tensile shear failure load of spot welded AISI 304 /316 L dissimilar sheets
by Vigneshkumar Murugesan, Ashoka Varthanan Perumal
Abstract: Resistance spot welding process is broadly used for joining sheet metals in automobile, aerospace, chemical and biomedical industries. In this research work, mechanical property, macro and microstructure of resistance spot welded dissimilar steel sheets of grades AISI 304 and high corrosion resistance AISI 316 L are studied. Experiments are conducted by changing the process parameters such as Welding current, Electrode pressure, Welding time and Squeeze time using central composite design of Response surface methodology. The empirical model predicted by the Response surface methodology (RSM) is compared with Back propagation algorithm model of Artificial neural network (ANN). By numerical optimization tool of design expert software, the optimal process parameters setting for attaining the maximum tensile shear failure load is identified. The results of the properly trained ANN model (R2 value of 99.04 percent) proved that it is more accurate than RSM model (R2 value of 96.33 percent)
Keywords: RSW ; resistance spot welding; RSM; response surface methodology; ANN; artificial neural network; TSFL; tensile shear failure load; dissimilar metals; optimization techniques; austenitic stainless steel; failure mode; microstructures; macrostructures.
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.
Numerical analysis of stress-induced and concentration-dependent carbon diffusion in low-temperature surface carburization of 316L stainless steel
by Yawei Peng, Jianming Gong, Yong Jiang, Dongsong Rong, Minghui Fu
Abstract: A kinetic model based on stress-induced and concentration-dependent carbon diffusion was developed for simulating the carbon concentration-depth profile of carburized austenitic stainless steel. The model considers that the diffusivity of carbon is dependent of carbon concentration and the stress induced by diffusion of the dissolved carbon atoms can affect the diffusion behavior in turn. In order to check the validity of the model, 316L stainless steel was treated by low-temperature surface carburization at 470 ℃ for different times, and the carbon concentration along the depth direction was measured by scanning electron probe micro-analyzer (EPMA). The results show that in carburized 316L stainless steel, the predicted carbon concentration-depth profile based on stress-induced and concentration-dependent carbon diffusion model is in good agreement with experimental results, which indicates that the stress and concentration-dependent diffusivity play important roles in carbon diffusion. As a result of carburization, large compressive residual stress is generated and gradiently distributes in the carburized layer, meanwhile, the diffusion of carbon atoms can be accelerated by stress. Although, the compressive residual stress is not the dominant reason for total carbon diffusivity increases significantly with increasing carbon concentration, the stress gradient as the next driving force cannot be ignored during low-temperature surface carburization. The proposed model can only be used to describe the carbon diffusion in austenitic stainless steel during low-temperature surface carburization without obvious carbides precipitation.
Keywords: Austenitic stainless steels; Low-temperature surface carburization; Carbon diffusion; Stress-induced diffusion; Concentration-dependent diffusivity.
The Simulation for Ultrasonic Testing Based on Frequency-Phase Coded Excitation
by Xinyu Zhao, Jiaying Zhang, Tie Gang
Abstract: Large time-bandwidth product coded signal and pulse compression in radar field have been introduced into ultrasonic testing. Linear frequency modulation (LFM) excitation, that LFM is a kind of frequency coded signals, is usually used to improve the time resolution, but the sidelobe of LFM should be suppressed to detect smaller flaws nearby. Barker coded excitation, that Barker is a kind of binary phase coded signals, is usually used to suppress the sidelobe, but the time resolution of results is lower than LFM excitation. So a frequency-phase coded excitation is proposed to obtain good testing results with higher time resolution and lower sidelobe level. The proposed excitation signal combines the frequency and phase coded signal. LFM is applied to each sub-pulse of Barker code, and it is called LFM-B13. The simulations are carried out using K-wave toolbox in Matlab software. The results of simulations demonstrate that, the time resolution of LFM-B13 excitation is approximately 40% higher than that of LFM excitation, and the main sidelobe level of LFM-B13 excitation is approximately 4dB lower than that of LFM excitation, when 60% bandwidth of 5MHz central frequency transducers are used in the simulations of penetrating experiments.
Keywords: simulation; ultrasonic testing; coded excitation; pulse compression; K-wave.
Effect of Ni content and brazing temperature on the self joining of ZrB2-SiC
by JIayin Liu, Jie Zhang, Chunfeng Liu, Tianpeng Wang
Abstract: Pd-Co-Ni filler alloy was adopted to braze ZrB2-SiC to itself. The reliable ZrB2-SiC joints were obtained. The effects of Ni content and brazing temperature were investigated on the microstructure and properties of the ZrB2-SiC joints using SEM and four-point bending method. All the joints consist of diffusion zone in ZrB2-SiC ceramic, Pd-Si phase, Co-Si phase, and Ni-Co solid solution. During the brazing, Ni and Co can solute into each other, a certain control over the reaction between SiC from the ceramic and Co from the brazing alloy was obtained, which was beneficial for the joint strength.
Keywords: ZrB2-SiC; Pd-Co-Ni; brazing temperature; microstructure; mechanical properties.