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Defence Technology（防务技术） 2019年第2期15卷 216-226页

作者： B.venkata Ramudu C.Jayarami Reddy v.madhu Armour Design and Development Division Defence Metallurgical Research Laboratory

In the present paper, the high velocity impact of 9 mm soft lead projectile on 10 mm and 30 mm thick Eglass/epoxy composites was studied using a 450 kv Flash X-ray radiography(FXR) system. The basic parameters of FXR imaging, such as effect of ratio of target to film(TF) and source to target(ST) distances and X-ray penetration thickness of the composite material were optimized based on clarity and the actual dimensions of the objects. The optimized parameters were used in the FXR imaging of the ballistic event of 9 mm soft projectile on E-glass/epoxy composite. The real time deformation patterns of both the projectile and composite target during the ballistic impact were captured and studied at different time intervals. The notable failure modes of the 10 mm thick target with time include fibre breakage, bulging on the back side, delamination, recovery of the bulging, reverse bulging and its recovery. However, with increase in thickness of the target to 30 mm the only failure mechanism observed is the breaking of fibres. The ballistic impact event was also numerically simulated using commercially available LS-DYNA software. The numerically simulated deformation patterns of the projectile and target at different time intervals are closely matching with the corresponding radiographic images.

关键词： Flash X-ray radiography E-Glass/epoxy composite Ballistic impact Numerical simulation

An experimental investigation of wire electrical discharge machining of hot-pressed boron carbide

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Defence Technology（防务技术） 2015年第4期11卷 344-349页

作者： Ravindranadh BOBBILI v.madhu A.K.GOGIA Defence Metallurgical Research Laboratory

The present work discusses the experimental study on wire-cut electric discharge machining of hot-pressed boron *** effects of machining parameters,such as pulse on time(TON),peak current(IP),flushing pressure(FP) and spark voltage on material removal rate(MRR)and surface roughness(R_a) of the material,have been *** parameters are found to have an effect on the surface integrity of boron carbide machined *** rate of brass wire increases with rise in input energy in machining of hot-pressed boron *** surfaces of machined samples were examined using scanning electron microscopy(SEM).The influence of machining parameters on mechanism of MRR and R_a was *** was demonstrated that higher TON and peak current deteriorate the surface finish of boron carbide samples and result in the formation of large craters,debris and micro *** generation of spherical particles was noticed and it was attributed to surface tension of molten ***-ridges were also observed on the surface due to protrusion of molten material at higher discharge energy levels.

关键词：电火花加工碳化硼热压制实验扫描电子显微镜材料去除率表面粗糙度电火花线切割

Development of cost effective personnel armour through structural hybridization

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Defence Technology（防务技术） 2020年第6期16卷 1089-1097页

作者： P.Rama Subba Reddy T.Sreekantha Reddy I.Srikanth Juhi Kushwaha v.madhu Defence Metallurgical Research Laboratory Hyderabad500058India Advanced Systems Laboratory Hyderabad500058India

The objective of the present study is to develop cost effective thermoplastic hybrid laminate using Dyneema®HB50 and Tensylon®HSBD 30A through structural hybridization *** having 20 mm thickness were fabricated and subjected to 7.6239 mm mild steel core projectile with an impact velocity of 730±10 ms*** such as energy absorption,back face deformation and rate of back face deformation were measured as a function of hybridization *** was observed that hybrid laminate with 50:50 ratio(w/w)of Tensylon®and Dyneema®with Tensylon®as front face showed 200%more energy absorption when compared to 100%Tensylon®laminate and showed equal energy absorption as that of expensive 100%Dyneema®***,hybrid laminate with TD50:50 ratio showed 40%lower in terms of final back face deformation than Dyneema®*** of back face deformation was also found to be slow for hybrid laminate as compared to Dyneema®*** mechanical analysis showed that,Tensylon®laminate has got higher stiffness and lower damping factor than Dyneema®and hybrid *** interface between Tensylon®and Dyneema®layers was found to be separating during the penetration process due to the poor interfacial *** behaviour of laminates for different hybridization ratios were studied by sectioning the impacted *** was observed that,the Tensylon®laminate has undergone shear cutting of fibers as major failure mode whereas the hybrid laminate showed shear cutting followed by tensile stretching,fiber pull out and *** inputs are highly useful for body armour applications to design cost effective armour with enhanced performance.

关键词： Dyneema® Tensylon® Hybrid laminate Ballistic impact Energy absorption Back face signature

Neural network modeling to evaluate the dynamic flow stress of high strength armor steels under high strain rate compression

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Defence Technology（防务技术） 2014年第4期10卷 334-342页

作者： Ravindranadh BOBBILI v.madhu A.K.GOGIA Defence Metallurgical Research Laboratory Hyderabad 500058 India

An artificial neural network(ANN) constitutive model is developed for high strength armor steel tempered at 500 C, 600 C and 650 C based on high strain rate data generated from split Hopkinson pressure bar(SHPB) experiments. A new neural network configuration consisting of both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on Johnsone Cook(Je C) model and neural network model is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tempering temperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB, over a range of tempering temperatures(500e650 C), strains(0.05e0.2) and strain rates(1000e5500/s) are employed to formulate Je C model to predict the high strain rate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the high strain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient(R) and average absolute relative error(AARE). R and AARE for the Je C model are found to be 0.7461 and 27.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with the experimental data for all tempering temperatures.

关键词：人工神经网络模型高应变率高强度装甲钢流变应力可预测性压缩评估

Prediction of flow stress of 7017 aluminium alloy under high strain rate compression at elevated temperatures

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Defence Technology（防务技术） 2015年第1期11卷 93-98页

作者： Ravindranadh BOBBILI B.RAMAKRISHNA v.madhu A.K.GOGIA Defence Metallurgical Research Laboratory

An artificial neural network(ANN) constitutive model and JohnsoneC ook(Je C) model were developed for 7017 aluminium alloy based on high strain rate data generated from split Hopkinson pressure bar(SHPB) experiments at various temperatures. A neural network configuration consists of both training and validation, which is effectively employed to predict flow stress. Temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on Johnsone Cook(Je C) model and neural network model was performed. It was observed that the developed neural network model could predict flow stress under various strain rates and temperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB over a range of temperatures(25 e300 C), strains(0.05e0.3) and strain rates(1500e4500 s 1) were employed to formulate JeC model to predict the flow stress behaviour of 7017 aluminium alloy under high strain rate loading. The JeC model and the back-propagation ANN model were developed to predict the flow stress of 7017 aluminium alloy under high strain rates, and their predictability was evaluated in terms of correlation coefficient(R) and average absolute relative error(AARE). R and AARE for the J-C model are found to be 0.8461 and 10.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. The predictions of ANN model are observed to be in consistent with the experimental data for all strain rates and temperatures.

关键词： Aluminium alloy Artificial neural network Johnson-Cook model

Enhancement of wear and ballistic resistance of armour grade AA7075 aluminium alloy using friction stir processing

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Defence Technology（防务技术） 2015年第1期11卷 10-17页

作者： I.SUDHAKAR v.madhu G.madhuSUDHAN REDDY K.SRINIvASA RAO Department of Mechanical Engineering MVGRCE Vizianagaram India Defence Metallurgical Research Laboratory Hyderabad India Department of Metallurgical Engineering Andhra University Visakhapatnam India

Industrial applications of aluminium and its alloys are restricted because of their poor tribological properties. Thermal spraying, laser surfacing, electron beam welding are the most widely used techniques to alter the surface morphology of base metal. Preliminary studies reveal that the coating and layering of aluminium alloys with ceramic particles enhance the ballistic resistance. Furthermore, among aluminium alloys,7075 aluminium alloy exhibits high strength which can be compared to that of steels and has profound applications in the designing of lightweight fortification structures and integrated protection systems. Having limitations such as poor bond integrity, formation of detrimental phases and interfacial reaction between reinforcement and substrate using fusion route to deposit hard particles paves the way to adopt friction stir processing for fabricating surface composites using different sizes of boron carbide particles as reinforcement on armour grade 7075 aluminium alloy as matrix in the present investigation. Wear and ballistic tests were carried out to assess the performance of friction stir processed AA7075 alloy. Significant improvement in wear resistance of friction stir processed surface composites is attributed to the change in wear mechanism from abrasion to adhesion. It has also been observed that the surface metal matrix composites have shown better ballistic resistance compared to the substrate AA7075 alloy. Addition of solid lubricant Mo S2 has reduced the depth of penetration of the projectile to half that of base metal AA7075 alloy. For the first time, the friction stir processing technique was successfully used to improve the wear and ballistic resistances of armour grade high strength AA7075 alloy.

关键词： Armour grade aluminium alloy Friction stir processing Boron carbide Molybdenum disulphide Wear Ballistic resistance

Cr-induced fusion reactions to synthesize superheavy elements

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Nuclear Science and Techniques 2024年第5期35卷 122-130页

作者： S.madhu H.C.Manjunatha N.Sowmya B.M.Rajesh L.Seenappa R.S.Susheela Department of Physics R V College of EngineeringBangalore 560074India visvesvaraya Technological University BelagaviKarnataka 590018India Department of Physics Government First Grade CollegeSrinivasapurKarnataka 563135India Department of Physics Government First Grade CollegeDevanahallyKarnataka 562110India Department of Physics Government First Grade CollegeMulbagalKarnataka 563131India Department of Physics Government First Grade collegeNanjangudOoty RoadMysore 571301India

We investigated ^(50,52-54)Cr-induced fusion reactions for the synthesis of the superheavy element in the 104≤Z≤122 *** cross sections produced in this investigation using ^(54)Cr projectiles were compared with those obtained in prior *** estimated cross sections from this analysis are consistent with the findings of prior *** the current study,the predicted cross section was found to be 42fb at 236 Mev for ^(53)Cr+^(243)Am,23.2 fb at 236 Mev for ^(54)Cr+^(247)Cm,95.6 fb at 240 Mev for ^(53)Cr+248Bk,and 1.33 fb at 242 Mev for ^(53)Cr+***,these projected cross sections with excitation energy and beam energy will be useful in future Cr-induced fusion reaction investigations.

关键词： Fusion cross sections Compound nucleus formation probability Survival probability Evaporation residue cross sections

Approaches for Optimal Planning of Energy Storage Units in Distribution Network and Their Impacts on System Resiliency

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CSEE Journal of Power and Energy Systems 2020年第4期6卷 816-833页

作者： Balaji venkateswaran v Devender K.Saini madhu Sharma Department of Electrical and Electronics Engineering University of Petroleum and Energy StudiesDehradun 248007India

In the recent decade,a significant increase in the penetration level of renewable energy sources(RESs)into the distribution grid is evident due to the world’s shift towards clean energy and to increase the reliability or inboard manner resiliency of electrical distribution *** based microgrids are the most favorable option available,especially to enhance ***,the integration of RES over the distribution grid would hamper the grid stability due to its stochastic nature under normal *** extreme weather conditions,RES behavior is completely *** there is a need to eliminate the adverse effects caused by the RES and make the distribution grid more reliable and stable under normal and resilient *** address these issues,many researchers proposed several methods to place energy storage units(ESUs)and microgrids(RES integrated),which can support critical loads at an optimal location in the distribution system during normal and extreme conditions,*** aim of this article is to consolidate and review the research towards various approaches to formulate the problem(optimal location,allocation,and operation of ESU and microgrids to face regular and extreme weather condition)and tools to solve it for enhanced system flexibility and *** on the review,a generalized methodology has been designed to adapt the inputs and address both *** the end of the review,future aspects for ESU to strengthen resistance and resiliency of its own are presented,which can be helpful to further improve the reliability and resiliency of the distribution system.

关键词： Energy storage units(ESUs) electrical distribution grid resiliency renewable energy sources(RES)

Influence of TiO_2 on the electrochemical performance of pasted typeβ-nickel hydroxide electrode in alkaline electrolyte

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Journal of Energy Chemistry 2016年第1期25卷 41-48页

作者： B.Shruthi B.J.madhu v.Bheema Raju Department of Chemistry Dr. Ambedkar Institute of Technology Post Graduate Department of Physics Government Science College Department of Chemistry Dayananda Sagar College of Engineering

Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide（β-Ni（OH）2 ） was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO2 additive on the β-Ni（OH）2 electrode performance are examined. The structure and property of the TiO2 added β-Ni（OH）2 were characterized by XRD, TG-DTA and SEM analysis. A pasted–type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni（OH）2 and TiO2 added β-Ni（OH）2 electrodes in 6 M KOH electrolyte. Anodic（Epa） and cathodic（Epc）peak potentials are found to decrease after the addition of TiO 2 into β-Ni（OH）2 electrode material. Further,addition of TiO2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni（OH）2 lectrode,TiO2 added β-Ni（OH）2 electrode is found to exhibit higher proton diffusion coefficient（D） and lower charge transfer resistance. These findings suggest that the TiO2 added β-Ni（OH）2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.

关键词： Nickel hydroxide Electrode material Thermogravimetric analysis Electrochemical properties Impedance spectroscopy

Mini versus ultra-mini percutaneous nephrolithotomy in a paediatric population

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Asian Journal of Urology 2022年第1期9卷 75-80页

作者： Dilip K.Mishra Sonia Bhatt Sundaram Palaniappan Talamanchi v.K.Reddy vinothkumar Rajenthiran Y.L.Sreeranga madhu S.Agrawal Department of Urology Global Rainbow HospitalAgraUttar PradeshIndia Department of Pediatrics F H Medical CollegeAgraUttar PradeshIndia Department of Urology Sengkang General HospitalSingapore

Objective:To evaluate whether there would be a difference in outcome when the smaller ultra-mini 12 Fr sheath was used instead of the mini 16 Fr sheath for percutaneous nephrolithotomy(PCNL)in paediatric patients for stones less than 25 ***:This was a prospective cohort study of patients who underwent PCNL in our hospital in a 2-year period from July 2016 to June 2018 by a single *** was performed in a prone position and tract was dilated to the respective size using single step *** was used to fragment the ***-free outcome was defined as absence of stone fragment at 3 months on kidney,ureter,and bladder ***:There were 40 patients in each *** stone size was comparable between the two groups(14.5 mm vs.15.0 mm).The procedure was completed faster in the 16 Fr group compared to 12 Fr group(24.5 min vs.34.6 min).Stone clearance was highly successful in both groups(97.5%vs.95.0%).There was no difference in complications between the two *** decrease in hemoglobin was minimal in both groups(0.2 g/dL vs.0.3 g/dL).Conclusion:We found that the success rates were similar in both mini PCNL and the smaller ultra-mini PCNL *** significant difference in bleeding was noted in our pilot study,however,operative time was longer in the ultra-mini group as compared to the mini sheath group.

关键词： Percutaneous nephrolithotomy Mini percutaneous nephrolithotomy Ultra-mini percutaneous nephrolithotomy Minimally invasive percutaneous nephrolithotomy Paediatric percutaneous nephrolithotomy Renal stone Urolithiasis