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The isothermal tensile test of medium carbon steel material was conducted at deformation temperatures varying from 650 to 950 ∘ C with an interval of 100 ∘ C and strain rates ranging from 0.05 to 1.0 s − 1 . In addition, the scanning electron microscopy (SEM) procedures were exploited to study about the surface morphology of medium carbon steel material. Using the experimental data, the artificial neural network (ANN) model with a back-propagation (BP) algorithm was proposed to predict the hot deformation behavior of medium carbon steel material. For model training and testing purpose, the variables such as deformation temperature, strain rate, and strain data were considered as inputs and the flow stress data were used as targets. Before running the neural network, the test data were normalized to effectively run the problem and after solving the problem, the obtained results were again converted in order to achieve the actual data. According to the predicted results, the coefficient of determination ( R 2 ) and the average absolute relative error between the predicted flow stress and the experimental data were determined as 0.999 and 1.335%, respectively. For improving the model predictability, the constrained nonlinear function based optimization procedures was adopted to obtain the best candidate selections of weights and biases. By evaluating each test conditions, it was found that the average absolute relative error based on the optimized ANN-BP model varied from 0.728% to 1.775%. Overall, the trained ANN-BP models proved to be much more efficient and accurate by means of flow stress prediction against the experimental data for all the tested conditions. These optimized results displayed that an ANN-BP model is more accurate for flow stress prediction than that of the conventional flow stress models.

Consistent and reasonable characterization of the material behavior under the coupled effects of strain, strain rate and temperature on the material flow stress is remarkably crucial in order to design as well as optimize the process parameters in the metal forming industrial practice. The objective of this work was to formulate an appropriate flow stress model to characterize the flow behavior of AISI-1045 medium carbon steel over a practical range of deformation temperatures (650&ndash, 950 ∘ C) and strain rates (0.05&ndash, 1.0 s &minus, 1 ). Subsequently, the Johnson-Cook flow stress model was adopted for modeling and predicting the material flow behavior at elevated temperatures. Furthermore, surrogate models were developed based on the constitutive relations, and the model constants were estimated using the experimental results. As a result, the constitutive flow stress model was formed and the constructed model was examined systematically against experimental data by both numerical and graphical validations. In addition, to predict the material damage behavior, the failure model proposed by Johnson and Cook was used, and to determine the model parameters, seven different specimens, including flat, smooth round bars and pre-notched specimens, were tested at room temperature under quasi strain rate conditions. From the results, it can be seen that the developed model over predicts the material behavior at a low temperature for all strain rates. However, overall, the developed model can produce a fairly accurate and precise estimation of flow behavior with good correlation to the experimental data under high temperature conditions. Furthermore, the damage model parameters estimated in this research can be used to model the metal forming simulations, and valuable prediction results for the work material can be achieved.

Performance of elevated temperature grain refinement and texture analysis are investigated in the temperature range of 500 °C, 600 °C, 700 °C and 800 °C in this study. Electron Back Scattered Diffraction (EBSD) was used for observation of grain distribution of Inconel 718. Tensile test was performed for all the heat treated samples and the fractrographic was examined using Scanning Electron Microscope (SEM). In addition, the texture of Inconel 718 was examined using crystallographic textures and Orientation Distribution Function (ODF) plots. The results indicate that Inconel 718 heat treated with 800 °C shows better grain refinement and provide optimum texture. Furthermore, it also indicated that decreased grain size contributed to the decreased cleavage size that leads to increased ductility.

The electrolytic ZnO based alloy coating with admixed interfacial blend of Mg have been successfully coated on medium carbon steel (AISI 4140) substrate by spray coating technique over a range of applied current density and dwell time. The structural and morphological properties of the coated samples are characterized using Optical Microscope (OM), Scanning Electron Microscope (SEM), X-ray Diffraction Analysis (XRD) and Energy Dispersive Spectroscopy (EDS) analysis. The adhesion test was carried out using scratch testing. The corrosion behavior is evaluated in a chloride environment (NaCl) by Tafel exploration as a function of coating thickness. The results revealed that the introduction of ZnO-Mg particles increases the adhesion strength of the AISI 4140. During scratching, cracks parallel with the scratch channel, external transverse cracks, adhesive spalling, and complete breaking of the coating within the scratch channel were observed. The acquired results exhibit that the introduction of ZnO - Mg coating improves corrosion resistance of AISI 4140 in NaCl solution. Equally, deposition thickness significantly affected the adhesion and corrosion properties. Increasing the coating thickness from 30 µm to 90 µm leads to decreasing the adhesion and corrosion properties.

The theoretical discoveries of the Sanal flow choking [V. R. Sanal Kumar et al., “Sanal flow choking: A paradigm shift in computational fluid dynamics code verification and diagnosing detonation and hemorrhage in real‐world fluid‐flow systems,” Global Challenges 4, 2000012 (2020)] and streamtube flow choking [V. R. Sanal Kumar et al., “Deflagration to detonation transition in chemical rockets with sudden expansion/divergence regions,” AIAA Paper No. 2020-3520, 2020] achieved significant contemplation in all branches of science and engineering for resolving various unanswered scientific questions brought onward from the beginning of this era [V. R. Sanal Kumar et al., “A closed-form analytical model for predicting 3D boundary layer displacement thickness for the validation of viscous flow solvers,” AIP Adv. 8, 025315 (2018)]. The applications of these flow choking phenomena are more significant in aerospace industries [V. R. Sanal Kumar et al., “Nanoscale flow choking and spaceflight effects on cardiovascular risk of astronauts—A new perspective,” AIAA Paper No. 2021-0357, 2021] and medical sciences [V. R. Sanal Kumar et al., “Lopsided blood-thinning drug increases the risk of internal flow choking leading to shock wave generation causing asymptomatic cardiovascular disease,” Global Challenges 2021, 2000076]. Herein, as an offshoot of the Sanal flow choking phenomena, the proof of the concept of boundary-layer-blockage (BLB) persuaded external-flow-choking (EFC) at aircraft-in-ground (AIG)-effect is presented. When the aircraft's ground clearance is relatively low, the evolving BLB factor from both planes (the bottom surface of the aircraft and the ground) creates a transient fluid-throat, leading to the Sanal flow choking and supersonic flow development in the duct flow region. In this physical situation, the pressure ratio (Ptotal/Pstatic) at the external flow choking region is exclusively a function of the specific heat ratio of the fluid. The EFC is more prone for the low wing aircraft flying in the near vicinity to the ground and/or sea with relatively high subsonic Mach number and low angle of attack. At this flying condition, the underside of the aircraft (fuselage and/or wing) and the ground creates the convergent-divergent duct flow effect leading to the EFC at the critical total-to-static pressure ratio. The accurate estimation of the BLB factor at the location of the EFC at AIG effect is presented in this manuscript as a universal yardstick for two-dimensional (2D) in silico simulation. For establishing the proof of the concept of external flow choking and supersonic flow development and shock wave generation, the 2D in silico results are presented for both stationary and moving airfoils in ground effect. In silico results show that the airfoil at stationary position exhibits relatively higher BLB factor and an immediate occurrence of the EFC than the same airfoil moving with the identical inflow Mach number and Reynolds number. We could establish herein that the moving vehicle simulation is inevitable for capturing actual flow physics and further precise examination of the BLB factor and the possibilities of the occurrence of the EFC for credible trajectory optimization of high-speed ground-effect vehicles.

In this paper, two titanium–titanium boride composites aiming at 20 % and 40 % (by volume) of titanium boride reinforcement were processed through spark plasma sintering. The mechanical properties such as fracture toughness, indentation creep, contact stiffness, indentation hardness and Young's modulus of the processed composites were evaluated by means of nano-indentation. The Young's modulus, indentation hardness and contact stiffness increase with the increase in volume fraction of titanium boride, while the fracture toughness and indentation creep decrease. The titanium composite with 38.5 % (by volume) titanium boride showed improved mechanical properties compared to the composite with 24 % (by volume) titanium boride reinforcement. The morphological influence of TiB reinforcement on the mechanical properties was also discussed.

In materials processing, practical understanding of materials behavior at elevated temperatures and high strain rates is necessary for modeling the real system behavior. The tensile deformation behavior of AISI-1045 steel material is investigated at deformation temperatures (923−1223K) and strain rates (0.05−1.0s−1). This paper proposes a detailed research to characterize the material flow behavior based on modified Johnson-Cook (JC) and Zerilli-Armstrong (ZA) models, respectively, as well as the predictability of these two models are discussed. The experimental flow stress-strain data are employed to fit the constitutive equations to estimate the elected model material parameters. To demonstrate the validity and the accuracy of the proposed models, the model adequacies such as coefficient of determination and average absolute relative error are discussed. From the observation made, the authors found that the modified ZA model is more appropriate for predicting the material behavior as the predicted flow stress data and the experimental data displayed better correlation among them. To make this point more concrete, random experiments are conducted to validate the proposed constitutive models and the obtained results also show that the developed modified ZA model exhibits a better relationship with the experimental data. Overall, the proposed research work can be used as an efficient tool in the initial design of numerical model to accurately replicate the experiment in order to save time and cost.

In the present research work an innovative material, made of steel skin and sheet molding compound core, is presented and is aimed to be utilized for the production of automotive body frames. For a precise description of the laminate structure, the material properties of all the components, including the adhesive utilized as an interlayer, have been carried out, along with the simple tension test of the composite material. The result have shown that the proposed laminate structure has a specific yield strength 114% higher than 6061 T6 aluminum, 34% higher than 7075 T6 aluminum, 186% higher than AISI 304 stainless steel (30HRC) and 42% than SK5 high-strength steel (52HRC), showing its reliability and convenience for the realization of automotive components. After calibrating the material properties of the laminate structure, and utilizing as reference the simple tension results of the laminate structure, the derived material properties have been utilized for the simulation of the mechanical behavior of an automotive B-pillar. The results have been compared with those of a standard B-pillar made of steel, showing that the MS-SMC laminate structure manifests load and impact carry capacity comparable with those of high strength steel, while granting, at least, an 11% weight reduction.

The flow field within the combustor of scramjet engine is very complex and poses a considerable challenge in the design and development of a supersonic combustor with an optimized geometry. In this paper comprehensive numerical studies on flow field characteristics of different cavity based scramjet combustors with transverse injection of hydrogen have been carried out for both non-reacting and reacting flows. The numerical studies have been carried out using a validated 2D unsteady, density based 1st-order implicit k-omega turbulence model with multi-component finite rate reacting species. The results show a wide variety of flow features resulting from the interactions between the injector flows, shock waves, boundary layers, and cavity flows. We conjectured that an optimized cavity is a good choice to stabilize the flame in the hypersonic flow, and it generates a recirculation zone in the scramjet combustor. We comprehended that the cavity based scramjet combustors having a bearing on the source of disturbance for the transverse jet oscillation, fuel/air mixing enhancement, and flameholding improvement. We concluded that cavity shape with backward facing step and 45o forward ramp is a good choice to get higher temperatures at the exit compared to other four models of scramjet combustors considered in this study., {"references":["","J. Tamagno, and O. Lindemann, Experimental Results on Supersonic\nCombustion, General Applied Science Laboratories, Ronkonkoma, NY,\nDecember 1962.","I. T. Osgerby, H. K. Smithson, and D. A. Wagner, \"Supersonic\ncombustion tests with a double-oblique-shock SCRAM jet in a shock\ntunnel\", AIAA J., vol. 8, no. 9, pp. 1703-1705, 1970.","G. Y. Anderson, C. R. McClinton, and J. P. Weidner, \"Scramjet\nperformance\", In: Scramjet Propulsion, E. T. Curran and S. N. B.Murthy\nEds., Reston, VA: AIAA Progress in Astronautics andAeronautics,\n2000, vol. 189, pp. 369-446.","D. C. Hunt, A. Paull, R. R. Boyce, and M. Hagenmaier, \"Investigation\nof an axisymmetric scramjet configuration utilising inletinjection and\nradical farming\", in proceedings of 19th International Symposium on\nAirbreathing Engines Montreal, Canada, September 2009.","J. R. McGuire, R. R. Boyce, and N. R. Mudford, \"Radical farm ignition\nprocesses in two-dimensional supersonic combustion\", J. Propulsion\nPower, vol. 24, no. 6, pp. 1248-1257, 2008.","M. K. Smart, \"Scramjets\", Aeronautical J., vol. 111, no. 1124, pp. 605-\n620, 2007.","M. K. Smart, and C. A. Trexler, \"Mach 4 Performance of hypersonic\ninlet with rectangular-to-elliptical shape transition\", J. Propulsion\nPower, vol. 20, no. 2, pp. 288-293, 2004.","H. Ogawa1, R. R. Boyce1, A. Isaacs and T. Ray, \"Multi-Objective\nDesign Optimisation of Inlet and Combustor for Axisymmetric\nScramjets, The Open Thermodynamics Journal, 2010, 4, 86-91.","Satish Kumar et al., \"Scramjet combustor development,\" Internal\nReport, Hypersonic Propulsion Division, DRDL, India, 2005.\n[10] C. McClinton, A. Roudakov, V. Semenov, V. Kopehenov, AIAA Paper\n96-4571, 1996.\n[11] T. Mathur, M. Gruber, K. Jackson, J. Donbar, W. Donaldson, T.\nJackson, F. Billig, J. Prop. Power 17 (6) (2001) 1305–1312.\n[12] Jeong-Yeol Choi, Fuhua M, Vigor Yang, \"Combustion oscillations in a\nscramjet engine combustor with transverse fuel injection,\" Proceedings\nof the Combustion Institute 30 (2005) 2851–2858.\n[13] J.Y. Choi, I.S. Jeung, Y. Yoon, AIAA J. 38 (7) (2000) 1179–1187.\n[14] A. Paull, R. J. Stalker and D. J. Mee, \"Experiments on supersonic\ncombustion ramjet propulsion in a shock tunnel\", J. Fluid Mech., vol.\n296, pp. 159-183, 1995.\n[15] R. J. Stalker, A. Paull, D. J. Mee, R. G. Morgan, and P. A.\nJacobs,\"Scramjets and shock tunnels – The Queensland experience\",\nProg Aerosp Sci., vol. 41, pp. 471-513, 2005."]}