bluuebunny/crossref_metadata_2025 huggingface dataset:
Methodology for the Analysis of the Process Behaviour of Advanced High Strength Steels in Bending and Shearing Operations
Authors: Tsoupis Ioannis , Hildering Sven , Merklein Marion
Published: February 2012

In the automotive sector the application of advanced high strength steels (AHSS) for structural and safety relevant components plays an important role. Typical manufacturing processes concerning these parts are bending and cutting operations. However, the forming and cutting potential of these steel grades is different compared to conventional steels, as the process behaviour is changing. For an improved workpiece quality the fundamental knowledge of the damage and failure mechanisms is essential. This study presents a methodology for the analysis of AHSS in bending and out-of-plane shearing operations. Two micro alloyed high strength steels are investigated within this work. First results are presented concerning material characterisation by tensile tests, the material performance in air bending tests and the development of a modular punching tool. The study is closed by summarizing the damage behaviour along the process chain considering both bending and cutting. This shows the applicability of the presented methodology for analysing the process behaviour with respect to occurring failure.
Incremental Forming of Sandwich Materials
Authors: Galdos Lander , Sáenz de Argandoña Eneko , Otegi Nagore , Ortubay Rafael
Published: February 2012

In the last decade, a completely new process has been developed using the existing knowledge in machining and in flow forming and spinning processes, so called the Incremental Sheet Forming. In the process, a spherical tool, governed by CNC incrementally forms a sheet metal to form complex and asymmetric parts using minimum tooling. Several works have been published to study the process limits, optimization of paths for the forming of deep walls and to extent the formability of some alloys using temperature as a process variable. Few studies have been also published where the incremental forming of polymers has been studied. In this work, the forming of steel-polymer-steel hybrid material or Laminate Vibration Damping Steels (LVDS) is considered. Spinnability tests are used to study the process limits and the effects of having two independent sheets in the thickness of the initial blank. The maximum forming angle, forming vertical force and maximum strains near the fracture are presented for the sandwich material in comparison to steel with three different thicknesses and same composition.
Experimental and Numerical Investigation on the Formability of Clad Sheets Copper/Stainless Steel 304L in Spinning Process
Authors: Rezaei Shahreza Amir , Dehghani Farshid , Salimi Mahmood
Published: February 2012

In present study, spinning process of clad sheets composed of Copper and Stainless steel 304L is investigated experimentally. To achieve the Copper-Steel 304L clad sheet the explosive welding method is used. In order to smooth the surface of clad sheets, a cold roll forming process was carried out. The clad sheets were heat treated to improve the metallurgical bounding and formability. The mechanical properties of copper-steel clad sheet were obtained by experimental measurements. Spinning process was performed on Copper-steel 304L clad sheets with internal layer of copper and external layer of steel. Different experimental tests are carried out to investigate the effects of some influential parameters including the tool path and the tool materials on formability of the clad sheets. Moreover, corresponding numerical simulations were made to verify the experimental values. Finally comparison of thickness strain distribution of a perfect product sample shows a reasonable agreement between numerical and experimental data.
Development of Boss Forming Simulation Technologies with a Rotary Tool
Authors: Kobayashi Yoshikazu , Takahashi Susumu , Yukutake Eitaro , Negishi Shigeo
Published: February 2012

Magnesium alloys are light weight and highly recyclable. To use magnesium alloys as parts of products such as automobiles, it is very effective make bosses by using plastic workings because this can reduce material loss and welding for producing parts. The bosses can be produced by a press cylindrical tool with rotation to the surface of the magnesium alloy sheet. To reduce the period of development of the tools in forming condition investigations, numerical simulation with FEM is very useful. FEM technologies have been developed for making bosses with plastic working. Because of the symmetry of the tool, the axisymmetrical FEM is applied as the first step. Bosses were found to increase in height as the friction coefficient increased. To investigate the friction between the tool and the alloy sheets, a ring compression test was conducted. The temperature of the alloy sheets increases as the bosses are formed. Therefore, the compression test was conducted at an elevated temperature. The heat transfer rate also affects the results of the forming simulation. To improve the shape of bosses from the simulation results, 3D simulation was performed. The shape of bosses in the 3D simulation is better than that in the 2D simulation by taking into account the traction at the contact area of the cylindrical tool.
Amorphous Carbon Coatings for Locally Adjusted Tribological Properties in Sheet Bulk Metal Forming
Authors: Hetzner Harald , Tremmel Stephan , Wartzack Sandro
Published: February 2012

In sheet bulk metal forming, locally adapted friction properties of the contact tool/workpiece are an appropriate means for the targeted enhancement of the material flow, enabling an improved form filling and lowered forming forces. However, the implementation of desirable friction conditions is not trivial. And further, friction is inseparably linked to wear and damage of the contacting surfaces. This calls for a methodological approach in order to consider tribology as a whole already in the early phases of process layout, so that tribological measures which allow fulfilling the requirements concerning local friction and wear properties of the tool surfaces, can already be selected during the conceptual design of the forming tools. Thin tribological coatings are an effective way of improving the friction and wear properties of functional surfaces. Metal-modified amorphous carbon coatings, which are still rather new to the field of metal forming, allow tackling friction and wear simultaneously. Unlike many other types of amorphous carbon, they have the mechanical toughness to be used in sheet bulk metal forming, and at the same time their friction properties can be varied over wide ranges by proper choice of the deposition parameters. Based on concrete research results, the mechanical, structural and special tribological properties of tungsten-modified hydrogenated amorphous carbon coatings (a-C:H:W) are presented and discussed against the background of the tribological requirements of a typical sheet bulk metal forming process.
Process-Machine Interaction in Sheet-Bulk Metal Forming
Authors: Behrens Bernd-Arno , Krimm Richard , Salfeld Valerian
Published: February 2012

The present contribution deals with the process-machine interaction and its impacts on the workpiece quality by forming parts with sheet-bulk metal forming. It focuses on the manufacturing of complex asymmetrical parts with functional elements. The functional applications of these elements such as fixation, motion and load transmission require compliance with high geometrical accuracy as well as high precision regarding the final mechanical properties of the part. The high process forces in horizontal as well as in vertical direction to form these elements cause displacements of the tool and press components, which lead to workpiece defects retroactively. Although the interaction between the forming machine and process affects the quality of the finished part significantly, the machine influence is usually ignored in the analysis of the forming process with the Finite-Element-Method. The challenges mentioned are demonstrated by forming of a complex asymmetrical part with gear teeths and carrier elements. As typical for sheet-bulk metal forming, the dimensions of the finished gear teeths (4mm) are much higher as the initial thickness of the sheet metal (3mm). The displacements of the press components during the process have been determined by means of optical measuring systems. The results are presented in all three spatial directions. The conclusions about the acting process forces in horizontal and vertical direction have been made by analyzing the press displacements by means of a new developed three-axial load device. Finally, this paper introduces a suitable approach to represent the machine characteristics in order to improve the computational accuracy of sheet-bulk metal forming simulations and gives an overview about the possibilities to improve the process stability by improving the mechanical components of forming machines.
Processing and Characterization of AA2195 Al-Cu-Li Alloy Bars Processed through Vacuum Induction Melting and Caliber Rolling
Authors: Nayan Niraj , Murty S.V.S. Narayana , Sharma S.C. , Sreekumar K. , Sinha Parameshwar Prasad
Published: February 2012

A novel technique of pure Lithium addition has been adopted for the processing of Al-Cu-Li alloy AA2195 cast ingots (7-8 kg each) in VIM under dynamic inert atmosphere, which gives more than 95% recovery of Lithium. The cast billets were homogenized, forged and converted into 12mm diameter rods by caliber rolling in the temperature range of 250°C, 300°C, 350°C and 400°C. The caliber rolled rods were treated to T8 (Solution Treatment+WQ+CW+Aging) condition. Mechanical properties were evaluated for T8 tempered bars at room temperature and correlated with microstructural observations. Highest mechanical properties in T87 temper have been obtained for rods caliber rolled at 350°C temperature.
Processing and Characterization of Al-Cu-Mg Alloy Rivets for Aerospace Applications
Authors: Nayan Niraj , Murty S.V.S. Narayana , Agarwal Alok , Sharma S.C. , Sinha P.P.
Published: February 2012

Al-Cu-Mg (Russian grade V65) alloys are used for riveting applications in aerospace industries due to their relatively high shear strength of the order of 25 kg/mm2 combined with a high plasticity. This paper presents the processing of V65 aluminium alloy rivets from wire rods. It was observed that wire rods which have not been intermittently annealed and having more than 25% cold working prior to heading operation, cracked on the free bulged surface of the head. In view of this, it is recommended that a maximum of 25% of cold work is allowed in the wire rods to be used for rivet fabrication to successfully realize defect free rivets.
Optimisation of Laser Process Parameter on Laser Transformation Hardening of AISI440C
Authors: Jain Anil Kumar , Alias A.V. , Jha Abhay Kumar , Sinha Parameshwar Prasad
Published: February 2012

High yield strength and good wear resistance of hypereutectic steels in hardened and tempered condition made them attractive to manufacture rotating parts of mechanical systems. However, they suffered with poor corrosion, owing to high carbon content. The need for a material with improved strength, wear resistance and corrosion resistance for bearing application resulted in the design of a new steel having 17 wt.% Cr, up to 0.75 wt.% Mo and 1 wt.% C, which was christened as 440C. This martensitic grade of stainless steel was surface hardened by laser transformation hardening (LTH) technique using Pulsed Nd: YAG laser. Optimised process parameter could result in 300 µm thick hardened layer consisted of martensite, retained austenite and fine carbide with an average hardness of 540 VHN, while it was about 220 VHN in the core. Laser process parameter like energy/power density, pulse width, scanning speed and overlap ratio were responsible in influencing the microstructural constituents, hardness achievable and in turn dictates the wear resistance capability of the material. Experimental results such as temperature distribution, depth of hardening have been verified analytically. A reasonable agreement between the theoretical and experimental measurements was obtained. This paper highlights the details of experimental work.
Simulation of Cooling Rate of Gray Cast Iron Casting in a Sand Mold and its Experimental Validation
Authors: Kumar Vinod , Kumar Amitesh
Published: February 2012

Estimation of cooling rates of gray cast iron casting in the sand mold and its dependency on design and process parameters is one of the keys for achieving best processing conditions to produce quality castings. The estimation of cooling rate involves modeling of fluid flow, heat transfer and solidification of molten metal inside the mold. Prediction of heat transfer has been carried out from filling of mold but the estimation of cooling rate has been carried out after complete filling of the mold. In the present work fluid flow, heat transfer and solidification of molten metal in a sand mold model has been developed on a Pro-Cast 2008 platform. A stepped bar pattern with different thickness has been fabricated to carry out the experiment. Stepped bar pattern has been selected because gray cast iron castings are thickness sensitive as well as different section of castings have different cooling rate. Cooling rates have been determined experimentally by measuring the Dendritic Arm Spacing (DAS) and Secondary Dendritic Arm Spacing (SDAS) from the microstructure of different steps. Results show that the morphology of graphite, dendritic arm spacing and secondary dendritic arm spacing as well as the interlamellar spacing of eutectic structure depend on the casting thickness. These decreases as the thickness of castings decrease because thinner section of casting has higher rate of cooling than the thicker section. The estimated cooling rate matched well with the experimentally measured cooling rate.
Friction Stir Processed Rare Earth Containing Magnesium Alloy for High Temperature Application
Authors: Govindaraju M. , Rao K. Prasad , Uday Chakkingal , Balasubramanian K. , Ravindran Comondore
Published: February 2012

Friction stir processing was performed on rare earth containing magnesium alloy AE42 with the aim of improving the mechanical properties. The resultant stir zone mechanical and metallurgical properties were analyzed to determine the application temperature of the zone. Stir zone microstructure was refined to 5 micron and the grain morphology was completely changed. Second phase intermetallics Al11RE3 Al2RE were refined to submicron level tiny pieces and homogenously distributed throughout magnesium matrix. As a major achievement, both toughness and strength of the stir zone was improved by 15 to 25%. High temperature properties up to 250°C were better than base metal. The stir zone was capable of withstanding more temperature and stress than the base metal.
Surface Modification of Steels Using Friction Stir Surfacing
Authors: Janakiraman S. , Reddy Jayachandra , Kailash Satish V. , Udaya Bhat K.
Published: February 2012

Friction stir surfacing is done to deposit commercial pure Al on medium carbon steel under open atmosphere conditions. Roughness of the substrate, normal load and tool rotation are the variables. Deposition is analysed with respect to continuity, width, composition and phase parameters. Good deposition is observed under a limited set of load and rotation speed. The deposit contains a mixture of steel and aluminium particles.
Ultrafine-Grained HSLA Steel Processed Using MAF: Dry Sliding Wear and Corrosion Behaviour
Authors: Padap Aditya K. , Chaudhari Gajanan P. , Nath Sameer K.
Published: February 2012

As ultrafine grained (UFG) steels obtained by severe plastic deformation (SPD) are useful for structural purposes and micro devices, it is necessary to establish the relation of microstructure with wear and corrosion properties. Very few studies are available that correlate the microstructural changes and the mechanical properties of UFG steels to the degradation phenomena such as wear and corrosion. In present work a HSLA steel was severely deformed by warm (500°C) multiaxial forging (MAF) technique using up to nine strain steps. Submicron sized grain size was obtained after warm MAF. The hardness and strength improved significantly. The MAF processed UFG HSLA steel did not show any improvement in wear resistance. Low pull-off-work and fragmented nanosized pearlitic cementite particles were the two factors found responsible for it. The corrosion resistance of HSLA steel after warm MAF remained largely unaffected.
Microstructure and Mechanical Property of Fe-Al2O3 Nanocomposites Synthesized by Reactive Milling Followed by Spark Plasma Sintering
Authors: Ravi K.R. , Murugesan A. , Udhayabanu V. , Subramanian R. , Murty B.S
Published: February 2012

The in-situ Fe based nanocomposite containing Al2O3 particle is synthesized by reactive milling of Fe2O3-Al-Fe powder mixture in toluene medium followed by consolidation of powders using Spark Plasma Sintering process. Transmission electron microscopy investigation of consolidated Fe-Al2O3 nanocomposites has shown heterogenous grain structure of Fe consisting of nano, submicron and micron size grains together with nanometer Al2O3 particles. The hardness of Fe-Al2O3 nanocomposites consolidated at 800°C is 795 MPa.
Processing and End Milling Behavioural Study of A356-SiCp Composite
Authors: Jayakumar K. , Mathew Jose , Joseph M.A. , Kumar R. Suresh , Chakravarthy P.
Published: February 2012

Machining process such as milling receives less attention in the study of machinability of composites due to its interrupted cutting and the complexity of the process. In the present study, A356 aluminium alloy powder reinforced with 10 volume % SiC particles of various sizes (1,12.5 and 25 µm) were synthesized by vacuum hot pressing method and the effect of particle size on the composites were analysed for its mechanical properties and machinability. End milling of these composites were carried out and the surface roughness and resultant cutting force were analysed with the change of machining parameters and varying SiC particle sizes. The minimum cutting force and surface roughness were obtained for a finer particle (1 µm) reinforced composite with higher cutting speed, low feed and depth of cut.
Rheological Behavior of Various Al Alloys during Solidification
Authors: Suéry Michel
Published: February 2012

This paper is concerned with the tensile behavior of various Al alloys during solidification obtained by using an initially solid specimen heated locally until it becomes fully liquid and then partially solidified at a controlled cooling rate. It is shown that for Al-Cu as well as for Al-Si-Mg alloys, a similar behavior is observed with a sharp transition on the stress-solid fraction curve when the coalescence solid fraction of the dendrites is reached. Below the transition fracture occurs along liquid films for very low stresses whereas beyond this transition, ductile fracture is observed leading to higher stresses.
Synthesis of Porous SiC Preform and Squeeze Infiltration Processing of Aluminium-SiC Metal Ceramic Composites
Authors: Manu K.M. Sree , Resmi V.G. , Brahmakumar M. , Anand N. , Rajan T.P.D. , Pavithran C. , Pai B.C. , Manisekar K.
Published: February 2012

Metal-Ceramic Composites with high volume fraction of reinforcement find wide applications in the area of tribology and high temperature resistant components like piston, brake pads, heat shields etc. Most of these components can be made by infiltration processing of porous ceramic preforms. The present investigation is to synthesize porous ceramic preform based on SiC particles using inorganic salt as a pore forming agent and Squeeze infiltration is applied to fabricate the Al-SiC metal-ceramic composites. The direct squeeze infiltration of 6061 aluminum alloy on SiC preform is successfully carried out with the controlled process parameters of initial preform temperature, liquid metal superheat, squeeze pressure and its rate of application, and die temperature. The preform and composites are characterized using XRD, optical microscopy, electron microscopy, and hardness and compression strength. Porous ceramic preform with more than 50% porosity has been fabricated by sodium chloride as pore former. The infiltrated composite have shown uniform and complete infiltration of Aluminium alloy in between SiC particles and posses very high hardness of 147 BHN in as cast condition compared to 57 BHN for the 6061 Al alloy.
Processing and Microstructure of Magnesium In Situ Composite with Titanium and Boron Based Reinforcement
Authors: Ajith Kumar Kumaraswamy Kaliamma , Raghukandan Krishnaswamy , Pillai Uma Thanu Subramonia , Pai Bellambettu Chandrasekhara , Chakraborty Madhusudan
Published: February 2012

The present work is aimed to investigate the in-situ TiB/TiB2 particle formation in Mg and Mg-Al alloy via the chemical reaction between Mg, Al, K2TiF6 and KBF4. The feasibility to produce the Mg and Mg-Al matrix with in-situ TiB2 and TiB particles have been studied with respect to processing parameters. The XRD, optical microscopy and SEM-EDX analyses have been carried out on the synthesised composites. Significant improvement in the hardness values are obtained for the in-situ composite compared to the base alloys.
Tribological Behavior of Mg-Mg2Si In Situ Composite
Authors: Ajith Kumar Kumaraswamy Kaliamma , Pillai Uma Thanu Subramonia , Pai Bellambettu Chandrasekhara , Chakraborty Madhusudan
Published: February 2012

Mg-Mg2Si in-situ composites by the addition of Si in Mg have become more attractive since the Mg2Si phase impedes the grain boundary sliding at elevated temperature because of its inherent properties which greatly improve the heat and wear resistances. In the present work, Mg-Mg2Si composites have been prepared by the liquid state processing with different amount of silicon additions. The microstructure and dry sliding tribological behavior of the composites have been studied. SEM studies reveal the wear mechanisms involved in these composites. The results indicate that wear rate of the composites is a function of Mg2Si content in the composite. The effect of Mg2Si morphology and distribution on the overall mechanism is also discussed.
Mechanical Characterization of Multi Phase Steel at Different Rates of Loading
Authors: Singh Nilamber K. , Cadoni Ezio , Singha Maloy K. , Gupta Narinder K.
Published: February 2012

The purpose of the present paper is to investigate the mechanical properties of multi phase 800 high yield strength (MP800HY) steel under compressive loading at different strain rates (-4700s-1to-0.001s-1). Specimens of MP800HY steel are tested on universal testing machine to study their stress-strain behavior under quasi-static (-0.001s-1) condition. Then, the specimens are tested undersplit Hopkinson pressure bar(SHPB) to study the strain rate sensitivity of the material under different rates of compressive loading (-4700s-1, -4300 1/s, -3800 1/s, -2900s-1and-1600s-1). The effect of pulse shaper in SHPB experiments has been studied. Thereafter, the applicability of the existing Johnson-Cook material model to represent the flow stress of MP800HY is examined.
Study of LCF Behavior of IN718 Superalloy at Room Temperature
Authors: Sudarshan Rao G. , Sharma V.M.J. , Thomas Tharian K. , Ramesh Narayanan P. , Sreekumar K. , Sinha Parameshwar Prasad
Published: February 2012

nconel 718 is an age hardenable nickel base supper alloy with high strength at elevated temperatures, and excellent creep properties. It is used extensively in turbine discs, blades where components experience elevated temperatures for prolonged duration, leading to coarsening of the microstructure. To evaluate the life of such components after prolonged exposure to service conditions, LCF properties at such large grain sizes are essential. For this purpose, low cycle fatigue (LCF) behavior of forged Inconel 718 turbine rotor disc having large grain size was studied at room temperature. Total strain controlled fatigue tests were conducted in air at ambient temperature on this alloy in solution treated and aged condition. The results indicated that the material exhibits cyclic strain softening and the cyclic yield strength is lower by 40% compared to the monotonic yield strength. The deformation takes place by multiple planar slip.
Correlation of Mechanical Properties with Ferrite Number in 0.07C-16Cr-6Ni Stainless Steel
Authors: Gangwar Narendra Kumar , Venkateswaran T. , Sivakumar D. , Pant Bhanu
Published: February 2012

In the present work, the effect of varying subzero treatment temperature on ferrite number and consequent changes in the room temperature mechanical properties of a 0.07C-16Cr-6Ni stainless steel were investigated. In order to study the changes, different subzero treatments were conducted in the range of-10°C to-70°C. The heat treated specimens were characterized for ferrite number, hardness measurements and tensile properties. The results showed a significant increase in the ferrite number with sub-zero treatment and maximum increment was observed in the specimens subjected to-70°C treatment. Both yield strength and UTS follow linear relationships with ferrite number. The increase in yield strength with ferrite number was significant. However, the change in UTS with ferrite number was marginal because of the formation of strain-induced martensite during tensile testing. Hardness could directly be correlated with UTS for higher ferrite numbers (more than 53) only.
Structure-Property Correlation of Rolled ZM21/Al Magnesium Macrocomposite
Authors: Thirumurugan M. , Rao T. Anka , Kumaran S. , Rao T. Srinivasa
Published: February 2012

Cast magnesium alloys are resulting coarse grained structure and micro porosity. In order to improve the formability and ductility in magnesium alloy, it is planned to incorporate aluminum wires as reinforcement through extrusion. In the present paper, ZM21/Al macrocomposites were fabricated by direct co-extrusion process. The extrusion was carried at 450°C with the extrusion ratio of 25:1. Metallurgical bonding of ZM21 magnesium alloy and aluminum was studied with the help of optical metallography and hardness testing. It was observed a white interface layer (intermetallic) formed in between magnesium alloy and aluminum. The same was confirmed by hardness test and SEM-EDS test. The co-extruded macrocomposite was again processed with unidirectional rolling and cross rolling to improve the bonding and grain refinement of the alloy. The composite was rolled at 250°C for 75% reduction in thickness. The microstructure and hardness of the rolled composite were characterized.
Non Destructive Metallographic Technique Used in Indian Space Programme
Authors: Manwatkar Sushant K. , Swathi Kiranmayee M. , Jha Abhay Kumar , Ramesh Narayanan P. , Sreekumar K. , Sinha Parameshwar Prasad
Published: February 2012

Metallography technique is used as an important tool in designing and development of materials. The technique is destructive and hence has its own limitations. Non destructive metallography emerged as a solution for its limitations. The microstructure of the component in the field/service can be replicated and observed under microscope. In the recent past, this technique has drawn the attention of quality control personals due to its non destructive nature. This paper explains the use of nondestructive metallography technique for Ti-6Al-4V alloy domes and low carbon steel static test bed exposed to high temperature.
Electron Beam Welding Studies on Nb-Hf-Ti Refractory Alloy
Authors: Anil Kumar V. , Karthikeyan M.K. , Vinayan E.G. , Gupta Rohit Kumar , Ram Kumar P. , Sinha Parameshwar Prasad
Published: February 2012

Niobium, a refractory metal is mainly used as alloying addition in steels, superalloys, titanium and copper alloys. Being lightest refractory metal with high melting temperature, niobium based alloys are developed for high temperature applications of aerospace systems. However, poor oxidation resistance at elevated temperature limits its fabrication options and also requires oxidation protection in service. Among the fabrication methods, electron beam welding has been found to be a realistic option and the same has been studied in the present work. The paper presents the details of the Electron Beam Welding study carried out in developing the welding procedure for this alloy. An attempt has been made to correlate the weldment microstructure with the mechanical properties.
Microstructural Characterisation of Copper-Stainless Steel Brazed Joint with Copper Based Filler Metal
Authors: Swathi Kiranmayee M. , Jha Abhay Kumar , Manwatkar Sushant K. , Sudhakar D.P. , Ramesh Narayanan P. , Sreekumar K. , Sinha Parameshwar Prasad
Published: February 2012

Copper to stainless steel brazed components are used in the thrust chamber of cryogenic propulsion system of Indian Space Programme. Temperature and time play a major role in the optimization of brazing cycle. An effort has been made to study the influence of the above parameters and correlate with the microstructure and shear strength achieved. In the present work, brazing was performed using Cu based filler metal. Temperature selected was within the range of 1010-1045 °C for two different time durations (20 minutes and 30 minutes) under high vacuum (10-5 Torr). Extensive scanning electron microscopy with energy dispersive spectrometry was carried out to understand the kinetics of elemental diffusion and phase formation at and near the brazed joint. Microhardness was evaluated across the joints to facilitate further understanding of the joint chemistry. The optimized shear strength of the joints was as high as 155 MPa for the joint brazed at 1030 °C for 30 minutes against the required strength of 150 MPa. The joint could retain strength at cryo temperature and meet the minimum expected value of 320 MPa. At the same time, it exhibited good mechanical properties at elevated temperatures. This paper brings out details of the investigation carried out.
Adhesive Joining of Metal to Metal and Metal to Ceramic by Ceramic Precursor Route
Authors: Sreeja R. , Prabhakaran P.V. , Manwatkar Sushant K. , Packirisamy S.
Published: February 2012

Inorganic ceramic adhesives (geopolymers) based on aluminosilicate matrix are versatile candidates for bonding metals to metals or metals to ceramics. On curing, they result in an amorphous, crosslinked, impervious, acid resistant 3D-structures. Alkali activated aluminosilicate based ceramic adhesive was developed for bonding metals to ceramics and metal to metal, for high temperature applications. The bonding is achieved at 175°C for 3 hrs, by solid state reaction of alkaline solution of allkalisilicate precursor with the refractory filler, contributing to the bulk aluminosilicate matrix. Lap shear strength of 2-4 MPa was obtained for bonding stainless steel. The XRD patterns show the amorphous nature of the aluminosilicate matrix, with mullite formation at higher temperatures. Thermogravimetric analysis shows that the weight loss is only due to the removal of water from the system by means of evaporation and polycondensation of Si-OH groups and Al-OH groups. This is followed by structural reorganisation in which aluminium ions are incorporated into the silicate chains forming the Si-O-Al network resulting in the bonding with the metallic surface. The system can withstand the maximum operational temperatures of the substrates and can be used for bonding different metallic or ceramic, joints/interfaces for RLV-TD/TSTO.
Processing, Structure, Texture and Microtexture in Titanium Alloys
Authors: Banerjee Dipankar , Pilchak Adam L. , Williams James C.
Published: February 2012

We review the effect of processing on structure and texture in titanium alloys, focusing on the understanding of this relationship that has evolved over the last decade. Thermomechanical processing cycles for these alloys involve deformation and heat treatment in single phase β and two phase, α+β, phase fields, and involves a complex interplay between deformation and recrystallization textures of the individual phases, textures arising from the crystallographic relationship between the two phases, and the scale of microstructure evolution. We explore these interactions and trace the strong dependence of thermomechanical pathways on the final structure and texture.
Aging and Electrochemical Behaviour of 7017 Al-Zn-Mg Alloy of Various Tempers
Authors: Rout Prasanta Kumar , Ghosh K.S.
Published: February 2012

Artificial aging behaviour of a 7017 Al-Zn-Mg alloy was studied by hardness measurement. The electrochemical behaviour of various alloy tempers, such as under-, peak-, and over-aged, have been evaluated by measuring variation of open circuit potential (OCP) with time and potentiodynamic polarization study in different environments. All the alloy tempers were tested in 3.5 wt. % NaCl solution at neutral (pH 7), at acidic (pH 1) and at alkaline (pH 12) conditions. It has been observed that the OCP values of the alloy tempers shifted toward noble direction with the increase of aging time in 3.5 wt. % NaCl solution. The polarization curves are more or less similar in shape exhibiting only active region in neutral (pH 7) and in acidic (pH 1) conditions, but an active-passive region at alkaline (pH 12) condition. The electrochemical parameters; Ecorr, Icorr, passive potential range (Ep) and passive current (ip), obtained from potentiodyanamic polarization curves for the alloy tempers in acid, neutral and alkaline solution; depend on the alloy tempers and the pH of the solution as well. Attempts have been made to explain the observed electrochemical behaviour of the alloy tempers, which is influenced by the microstructure, presence and distribution of second phase precipitates, accessed by DSC and XRD techniques.
The Role of Electrolyte Additives on the Corrosion Behavior of Ceramic Coatings Formed on ZM21 Magnesium Alloy by Plasma Electrolytic Oxidation
Authors: Sreekanth D. , Rameshbabu N. , Choudary K. Ramaswamy , Rao K. Prasad
Published: February 2012

The present study emphasizes the effect of addition of sodium citrate (C6H5Na3O7.2H2O) and sodium tungstate (Na2WO4.2H2O) to a silicate based electrolyte system on the corrosion behavior of PEO treated ZM21 magnesium alloy. The phase composition of the as-developed coating was evaluated by X-ray diffraction (XRD) analysis, while its surface morphology, thickness and elemental distribution were observed using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Potentiodynamic polarization tests were done in 3.5 wt% NaCl solution to analyze the corrosion behavior of the ceramic coatings in simulated marine environment. The results of XRD showed that the phase composition of all coatings comprised of Mg2SiO4 and MgO irrespective of the additive used. In addition to Mg, Si and O, the presence of W, C in EDS spectrum indicated that these elements were incorporated into the coating from the electrolyte system containing tungstate and citrate. The corrosion test results revealed that the PEO coatings obtained in tungstate containing electrolyte solution showed higher corrosion resistance than those formed in citrate containing electrolyte solution.
Investigative Study of Optical Parameters of Se80.5Bi1.5Te18-yAgy Thin Films
Authors: Kumar Anup , Heera Pawan , Baraman P. B , Sharma Raman
Published: February 2012

The optical constants, like absorption coefficient (α), optical band gap (Eg) and refractive index (n), in Se80.5Bi1.5Te18-yAgy (y= 0, 1.0 and1.5) thin films are calculated using well known Swanepoel’s method in the spectral range of 600-2000 nm. The optical band gap has been estimated by using Tauc’s extrapolation method and is found to increase with increase in Ag content. The present results shows that the large value of nonlinear refractive index and good transparency of these thin films will make them a very promising materials for optical integrated circuits in the optical communication systems.
Development of Zirconia Based Oxygen Sensor for Lead and Lead-Bismuth Eutectic
Authors: Sahu Sulata Kumari , Ganesan Rajesh , Jayaraman V. , Gnanasekaran T.
Published: February 2012

Nanocrystalline yttria stabilized zirconia (YSZ) solid electrolyte powders of composition ZrO2-5 mol% Y2O3 were prepared through modified Pechini process and were characterized. Sintered compacts of these powders in form of pellets had 96% of the theoretical density and helium leak rate <10-9 S cc /s. Using a pellet of this electrolyte in a galvanic cell with different oxygen partial pressures across it, emf was measured as a function of temperature and thus qualified for sensor application. Towards the fabrication of the oxygen sensor for Pb and LBE loop, a compact design wherein a YSZ pellet, glass soldered to a metallic component had been chosen for the oxygen meter.
Synthesis of Magnetic Thin Films on Glass Substrates Using NH3 Vapors
Authors: Kumar Pawan , Khah Sunil Kumar , Katyal Subhash Chander , Kumar Rajesh
Published: February 2012

Magnetic thin films in nanometer range have been synthesized on the glass substrates. The synthesis has been carried out using Fe2+ and Fe3+ ions in a PVA solution in H2O. A different approach has been used for the synthesis of the magnetic thin films by using NH3vapors. Obtained films have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and magnetic property measurement system (MPMS). The size and distribution of the magnetite nanoparticles inside the films depends upon the supply of the NH3 vapor. For large exposure time of NH3 vapors, film contains magnetite nanoparticles of size up to 80 nm. While for low exposure time of NH3 vapors, small magnetite nanoparticles of size nearly 20 nm have been obtained. The particles are independent to each other with no aggregation and are uniformly distributed inside the film.
Progress in Understanding the Fatigue Behavior of Ti Alloys
Authors: Pilchak Adam L. , Lu Wei Jie , Williams James C.
Published: February 2012

Titanium (Ti) alloys are used in critical, fatigue limited applications in aircraft and aircraft engines. Current design practices are, of necessity, conservative in order to minimize risk of unexpected failures. Among the sources of this conservatism are the inherent variations in the number of loading cycles the materials can withstand prior to fatigue crack initiation, the uncertainty in crack propagation lifetime prediction and the need to set safe minimum component life values. While the stochastic nature of fatigue is well-known, improved characterization methods have begun to provide a better understanding of the crack initiation process. This paper describes recent work designed to provide an improved understanding of the relationship between thermomechanical processing history, microstructure, texture and the fatigue behavior of α+β Ti alloys. Due to length limitations, the paper focuses on two important aspects of fatigue life variation: the effects of microstructural discontinuities on fatigue and the role of facet formation during crack initiation and the early stages of fatigue crack growth.
Microstructure Evolution of Allotropic Materials during Thermomechanical Processing
Authors: Poletti Cecilia , Warchomicka Fernando , Dikovits Martina , Großeiber Simon
Published: February 2012

The microstructure developed during hot deformation is the result of deformation mechanisms such as dynamic recovery and dynamic recrystallization. Hot deformation can also result in damage and flow localisation, especially in multiphase metal based materials. Several models have been proposed to correlate the parameters of the deformation process (temperature, strain and strain rate) with the flow behaviour such as the processing maps. They were developed based on the dynamic materials model (DMM) and later a modified DMM introduced some changes in the calculation of the processing maps. The correlation of the relevant microstructural changes with thermodynamic parameters are tested and discussed. The data was obtained by using the Gleeble simulator with in situ quenching facilities. Microstructural studies related to the hot deformation of metals were carried out based on alpha-beta and near beta titanium alloys and on low carbon steels. The results are correlated with the efficiency of power dissipation, and the constitutive equations. In diffusion controlled processes such as dynamic recovery, dynamic recrystallization, phase transformation and pore coarsening are related to high power efficiency, and to low n exponent. The efficiency of power dissipation is more sensitive to the deformation parameters than the constitutive equations for materials with phase transformation.
ZnO Nanostructures for Sensor Applications
Authors: Tseng Tseung Yuen
Published: February 2012

The wide-gap semiconductor ZnO with nanostructures such as nanoparticles, nanorods, nanowires has high potential for a variety of sensor applications. This paper reviews the recent developments of ZnO one dimentional nanostructures for future gas sensor applications. Presented first is the factors contributing to the high performances of gas sensors using such nanostructures. Then various fabrication methods of the ZnO nanostructures including vapor phase growth, solution growth, and template-assisted growth are introduced. The characterization and properties of the ZnO nanostructures-based gas sensors are described. The basic mechanisms for explaining the behaviors of the gas sensors are also discussed.
Atomic Layer Deposition of Thin Inorganic Coatings onto Renewable Packaging Materials
Authors: Vähä-Nissi Mika , Hirvikorpi Terhi , Sievänen Jenni , Matilainen Katriina , Salo Erkki , Harlin Ali
Published: February 2012

Biopolymers play still a relatively minor role in the packaging material markets. For this to grow further there are problems to be solved, such as inadequate barrier properties and moisture sensitivity. Atomic layer deposition (ALD) is one potential solution. Atomic layer deposition is a layer-by-layer thin film deposition process based on self-limiting gas-solid reactions. It is well suited for producing pinhole free barrier coatings uniform in thickness at relatively mild process conditions. The purpose of this presentation is to summarize our recent work done concerning atomic layer deposition of thin aluminum oxide layers onto biopolymers.
Fabrication and Characterization of Electrospun Nano to Microfiber Made of Poly(L-Lactide-co-ε-Caprolactone)
Authors: Lin Genevieve , Song Sin Nee , Wong Yee Shan , Tan Lay Poh , Yong Kim Yeow , Jasmen Juliana , Dong Jian Xiang
Published: February 2012

This project aims to optimize the process parameters for fabricating Poly (L-Lactide-co-ε-Caprolactone) (PLCL) electrospun scaffolds to achieve fiber diameters within the ranges of ~500nm, 500nm~1µm and 1~3µm. Electronspun PLCL solutions of different concentrations (4wt% - 12wt%) were prepared using chloroform and dimethylformamide as solvents. The driving voltage and flow rate were varied from 10kV-30kV and 1ml/hr12ml/hr respectively while the gap distance was kept constant at 15cm. The effects of polymer concentration and process parameters on the properties of the scaffolds fabricated such as Youngs modulus, degree of crystallization and porosity were studied. Scanning electron microscopy (SEM) was used to check the structural integrity (absence of beading and uniform diameter) of the fibers. An increase in polymer concentration resulted in an increase in fiber diameter. Flow rate also showed a positive correlation with fiber diameter. Results showed that Youngs modulus decreased with increasing fiber diameter. Porosity of 76% to 94% was achieved. The potential application of PLCL electrospun scaffolds in the tissue engineering of soft tissues was discussed.
Multiwalled Carbon Nanotubes Reinforced Portland Cement Composites for Smoke Detection
Authors: Shukla Prashant , Bhatia Vasuda , Gaur Vikesh , Basniwal Rupesh Kumar , Singh Budhendra Kumar , Jain Vinod Kumar
Published: February 2012

Smoke detection with multiwalled carbon nanotubes (MWCNTs)/cement composites have been studied. Pellets of MWCNTs reinforced Portland cement have been casted with varying MWCNTs %. The DC transient studies depicted an increase in conductivity when exposed to smoke. Responsivity in the range 26-46% has been obtained under smoky environment based on MWCNTs % in the composites. Ionic conductivity increased with frequency at room temperature under ambient and smoky environments. In this paper, we also report fabrication technique of the pellets and the sensing mechanism is explained on the basis of ionic conductivity of the cementitious material in combination with the conductive carbon fibers present in the porous matrix of the cement.
Effect of In Doping on Thermoelectric and Magnetoresistive Properties of ZnO Films Prepared by RF Magnetron Sputtering
Authors: Fang Liang , Ruan H.B. , Peng L.P. , Yang X.F. , Wu F. , Kong C.Y.
Published: February 2012

n-doped ZnO (ZnO:In) thin films with 0~9at.% In content have been prepared by RF high magnetron sputtering on glass substrate. All the films were annealed in N2at 473K for 1h. The effect of In doping concentration on the structure, surface morphology, electrical properties,Seebeck and magnetoresistive effect of the films were investigated. It was found that the crystal quality of the films degrades, and the surface gets rough with increasing In content. The lowest resistivity of the ZnO:In thin films 6.1×10-4Ω.cm occurs at 5at.% in the target doping concentration. All the films show a striking Seebeck effect and the absolute value of the Seebeck coefficient decreases under magnetic field. Meanwhile, a positive magnetoresistance of the films was found. ZnO thin films with 1at.% In-doped is best for the thermoelectric material, which has the largest power factor of 2.1×10-4W/K2m at room temperature.
Fabrication and Spectroscopic Properties of Transparent Yb:YAG Laser Ceramics
Authors: Luo De Wei , Zhang Jian , Xu Chang Wen , Yang Hao , Qin Xian Peng , Ma Jan , Tang Ding Yuan
Published: February 2012

Yb3+ doped YAG ceramics have been successfully fabricated using a vacuum reactive sintering method. High purity Y2O3, Al2O3 and Yb2O3 powders were used as the starting materials. Samples of 5.0 at.% Yb3+ doping concentration have been obtained. The in-line transmittance of the sample reaches 84% at 1100 nm wavelength. The absorption and emission bandwidth were measured to be 19.5 nm and 11.07 nm respectively. The results show that Yb:YAG ceramics will be a promising laser material for high power and ultrafast laser applications.
On the Design of Bi-Layer Armor Materials
Authors: Serjouei Ahmad , Sridhar Idapalapati , Hua Wong Ee
Published: February 2012

A modified Florence model to predict ballistic limit velocity (BLV) for bi-layer armor systems comprising ceramic front and metallic backing plate is proposed based on energy conservation. Maximization of the BLV for a given AD or TT is studied. Comparison between the maximum BLV obtained from new model, two other available models in the literature and experiments is performed. It is shown that the new model, Energy model compares well to the experimental data.
Keywords: Impact; perforation; optimization; bi-layer armor system
Wave Scattering Phenomena for Health Monitoring of Hard-to-Inspect Defects
Authors: Doherty Cain , Chiu Wing Kong
Published: February 2012

Doherty and Chiu reported on the potential use of propagating stress waves for monitoring fatigue crack development in a series of hard-to-inspect weep holes in the wing spar of an aging aircraft. New experimental evidence showed an interesting scattering phenomenon at the defect and demonstrated the ability to use this phenomenon to monitor the development of an upward developing fatigue crack. It was found that a scattered field can be used to highlight the presence of a source of a secondary wave mode arising from the interaction of the incident wave field with the defect. A detailed investigation into these observations will contribute to the creation of new basic scientific understanding of this phenomenon with the potential development of a novel and optimised approach for quantitative inspection of hard-to-inspect regions in a structure.