bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical and Experimental Study of Sheet Metal Bending by Pulsed Nd:Yag Laser with DOE Method
Authors: Hosseinpour Gollo M. , Naeini Hassan Moslemi , Liaghat G.H. , Jelvani S. , Torkamany M.J.
Published: December 2009

Metal forming by a laser source is an efficient and economical method for forming sheet metal into straight bend and doubly curved shape. It can be most useful in the automation of sheet metal forming. This paper presents an FEM model for three dimensional thermo-mechanical simulation of the laser forming. The aim of this simulation and experimental study is to identify the response related to deformation and characterize the effects of process parameters such as laser power, beam diameter, scans velocity and pulse duration, in terms of bending angle for a square sheet part. Extensive experimentation, including a design of experiments, is performed to address the above-mentioned aims. From these experiments it has been determined that laser forming using Nd:YAG laser is a flexible manufacturing process for steel sheet bending.
Effects of Grain Size on Micro Backward Extrusion of Copper
Authors: Chang Chao Cheng , Wang Teng Chiao
Published: December 2009

This study investigates the effects of grain size on the micro backward extrusion of copper cups. An equal channel angular extrusion (ECAE) technique was applied to refine the grain size in copper. Commercial available copper was annealed, deformed by six-pass ECAE at room temperature and then heat treated to obtain a microstructure with a grain size of about 4μm. Microstructure was examined and mechanical properties including hardness and stress-strain relationship were also investigated. The processed copper was then used in a micro backward extrusion of cups with the diameter of 3 mm and the wall thickness of 0.1 mm. The extruded cups were compared with those resulting from the coppers with larger grain size prepared by different heat treated processes. This study shows that the quality of the micro extruded cup increases as the grain size decreases. By using the refine-grained coppers for the micro backward extrusion, the cups with even rim height and uniform wall thickness can be easily produced.
Effects of Welding Positions on Mechanical Properties and Microstructure in Weld Metal of High Strength Steel
Authors: Masoumi F. , Shahriari D.
Published: December 2009

In this study the effects of two welding positions included in flat and upward vertical on the mechanical properties and microstructure of high strength weld metal deposited with shielded metal arc welding (SMAW) using an electrode of ASME SFA 5.5-96 E9018B3 type have been investigated. The aim of the present work is to study the effects of these two welding positions for a weld metal alloyed with 1%Mo, 2%Cr, 0.79%Mn, and 0.08% C in the stress relieved condition. For studying mechanical properties Tensile, Impact and hardness experiments have been conducted; meanwhile chemical analysis and microstructure studying have been carried out on specimens. The results show that welding position does not have any significant effect on tensile and hardness of the weld metal but in vertical position welding metal toughness is lower than toughness in flat position in all temperatures. Transition temperature of ductile fracture to brittle fracture is -50 °C for E9018B3 in welding of high strength micro alloyed steels.
Effect of Dwell Time on Friction Stir Spot Welded Dual Phase Steel
Authors: Al-Shahrani A. , Wynne Bradley P.
Published: December 2009

Friction stir spot welding (FSSW) is a relatively new welding technique which has already been successfully commercially applied on automotive aluminum alloys which, in turn, lead to significant energy savings and infrastructure cost-reductions. Due to the success of FSSW on Al alloys FSSW has generated tremendous interest in the automotive industry as an alternative joining process to resistance sport welding for steel body panels. Currently there is limited data on the mechanical properties and microstructure of friction stir spot welded steel thus the current aim was to investigate how these parameters chamged as a function of some critical process variables. In this instance spot welding of 2 mm thick high strength dual phase steel (DP800) was undertaken using a 3.5mm pin length tungsten rhenium tool with a tool rotation speed of 1000 rpm and plunge rate of 100 mm/min. Different dwell times of 0, 0.5, 1, 2 and 4 seconds were then applied prior to tool retraction to study the effect of dwell time on the microstructure and mechanical properties of the spot welds. Investigation of the weld spot joints revealed three distinct microstructural zones; a) thermo-mechanically affected zone (TMAZ), b) heat affected zone (HAZ), and c) parent material zone. The TMAZ shows an acicular martensite microstructure while the HAZ shows a ferrite/martensite structure in a very fine scale when compared to parent material zone. The Parent material is a typical dual phase structure which is ferrite matrix with a dispersion of martensite. Therefore, the TMAZ was harder while HAZ was softer when compared with parent material zone. The tensile strength obtained from tensile tests and the bonding ligament which has been reported to be measures of strength were also found to increase with dwell time.
Effects of Isothermal Aging on Tensile Properties and Fracture Behavior of 316L Austenitic Stainless Steel Weld Metal
Authors: Karimian A. , Farhangi Hassan , Amari Allahyari A.
Published: December 2009

In this research, variations of tensile properties and fracture behavior of 316L austenitic stainless steel weld metal as a function of aging temperature and time have been investigated. Stainless steel plates were butt-welded using GTAW process. Weld metal tensile specimens were subjected to various aging heat treatments at temperatures of 750 and 850°C for periods of 1 to 100 hours prior to tensile tests at 25 and 500°C. Dissolution of delta-ferrite and formation of sigma phase network during aging resulted in a mild increase in tensile strength and significant reduction in ductility, particularly at 25°C. Although fracture surfaces exhibited ductile features, the dimple morphology and the macroscopic fracture mode were found to be affected by aging. The unaged weld metal exhibited a classic mode of cup and cone fracture, whereas slant and flat types of fracture modes were observed in the aged weld metals, with the slant mode being dominant at 500°C. The slant mode was associated with deformation localization along arrays of primary voids, nucleated at cracked sigma phase particles, oriented at about 45° to loading direction. The transition in the fracture mode is further discussed based on variations in the dimple morphologies and strain hardening exponent.
Plasma from Electron Beam Evaporation of a Metal Target
Authors: Ho Ching Yen , Wen Mao Yu , Ma C.
Published: December 2009

Transport variables in plasma column are analytically investigated in this paper.
Low-energy electrons and ions are produced from electron beam evaporation of a metal target in the
technological vacuum chamber of an electron beam welding machine. Assuming collisionless plasma
motion in the radial direction, the electrostatic potential is obtained from model of plasma expansion.
Transport variables such as ion density, electron density, conduction heat of the ions and electrons are
calculated using the electrostatic potential and are compared with the available experimental data.
The Influence of Welding Parameters on Tensile Behavior of Friction Stir Welded Al 2024-T4 Joints
Authors: Mahmudi E. , Farhangi Hassan
Published: December 2009

In the present study, the relationships between friction stir welding parameters and the tensile behavior of Al 2024-T4 joints was investigated. The aluminum alloy plates were butt-welded using a hardened steel tool with a threaded and fluted cylindrical pin at various tool rotation speed to advancing speed ratios. Metallographic observations, EDS analysis and microhardness measurements show that the band spacing in the periodic microstructure of the stir zone and the average microhardness of this region decrease with increasing speed ratio. Tensile ductility is strongly affected by welding parameters and final elongation increases significantly with speed ratio at the constant rotating speed of 900 rpm. This behavior is found to be associated with a change in tensile fracture location. Formation of microscopic voids at low speed ratios leads to premature fracture in the nugget zone, while in the defect-free joints produced at higher speed ratios the fracture location shifts into the HAZ on the retreating side, which exhibits the lowest microhardness value within the weld joint. At the optimum rotation speed of 900 rpm and speed ratio of 11.2 rev/mm the tensile strength and final elongation of the joints are equivalent to 97% and 77% that of base metal, respectively.
Resistance Spot Welding of Unequal Thickness Low Carbon Steel Sheets
Authors: Pouranvari Majid , Marashi Pirooz
Published: December 2009

Resistance spot welding is the dominant process for joining sheet metals in automotive industry. Even-thickness combinations are rarely used in practice; therefore, there is clearly a practical need for failure behaviour investigation of uneven-thickness resistance spot welds. The aim of this paper is to investigate and analyze the failure mode and failure mechanism of dissimilar thickness low carbon steel resistance spot welds during tensile-shear overload test. Microstructural investigations, microhardness tests and tensile-shear tests were conducted. Mechanical properties of the joint were described in terms of peak load, energy absorption and failure mode. It was concluded that weld nugget size and the strength of the thinner base metal are the controlling factors of the peak load and energy absorption of dissimilar thickness spot welds.
Effect of Temperature Field on Flexural Wave Characteristics of a Bar Resembling Welding to Rigid Body
Authors: Alzaharnah Iyad T. , Al-Kaabi S. , Yilbas Bekir Sami
Published: December 2009

The flexural motion of a bar changes during the welding process because of the temperature field, which modifies the modulus of elasticity. Depending on the duration of heating during the welding process, the wave characteristics of the flexural motion changes; therefore, the wave characteristics can be related with the heating durations. In the present study, welding of one end of a bar to a rigid body is simulated and flexural motion generated at the free end of the bar through impulse force is analyzed. Temperature field and flexural wave characteristics are computed for different heating durations. It is found that temperature decays sharply in the region next to the heat source, and this decay becomes gradual as the heating progresses. The effect of temperature decay on the characteristics of the flexural wave is significant in the early heating period and gradual decay of temperature in the bar modifies the wave characteristics considerably.
Multiaxial Mechanical Strength of AA-2024-T3 Aluminium Alloy Sheets Joined by Friction Stir Welding Processes
Authors: Cerveira R.L.L.P. , Batalha G. F.
Published: December 2009

The aim is to analyze a junction produced by a Friction Stir Welding (FSW) joining process under multiaxial loading, employing a modified Arcan test that allows an angle variation of the loading in order to evaluate the failure of the FSW weldment as compared to the base material. A short review of the earlier studies and relevant theories about the FSW processes and fracture modes I and II under multiaxial loading are presented and were experimentally evaluated for an AA2024-T3 aluminum alloy sheets (t = 1.6 mm) processed by FSW. The results obtained can serve as a basis to compare the junctions made using FSW and conventional joint methods such as rivets (very common practice in the aeronautical industry).
Characterization of Surface Defects Associated with Flash Butt-Welded Pearlitic Rails and their Contribution to Overload and Fatigue Failures
Authors: Mousavizade Mostafa , Farhangi Hassan
Published: December 2009

Generally about 80 percent of railway tracks are welded by flash-butt welding that consists of electrical heating and hydraulic forging. Fracture of rails specially weld zone fractures are of main concern because of potential risk of a catastrophic derailment. In this paper, surface defects associated with flash butt welding process are examined. Metallographic and fractographic studies show various defects can be formed at the surface of weld zone. Formation mechanism of these defects and their contribution to the observed fatigue and overload weld failures are discussed. Fracture mechanics is also utilized to clarify the role of these defects in fatigue and overload failures.
The Structure and Properties of Carburized and Hardened Vanadium Microalloyed Steels
Authors: Mohar Ali Bepari Md. , Nizamul Haque Md. , Shorowordi Kazi Md.
Published: December 2009

Three 0.15% carbon steel samples containing small additions of vanadium and nitrogen singly or in combination have been carburized in a natural Titas gas atmosphere at a temperature of 9500C and a pressure of about 15 psia for time periods ranging from 1 to 5 hours and quenched in 10% brine from the carburizing temperature of 9500C after pre-cooling to 8600C in the furnace followed by tempering at a low temperature of 1600C. The structure and properties of the carburized and heat treated specimens were studied systematically by optical microscopy, surface hardness and microhardness measurements, X-ray diffractometry and impact tests.
It was found that vanadium without nitrogen does not have any effect in the formation of retained austenite while vanadium with nitrogen is effective in promoting the formation of retained austenite in the case of carburized and hardened steels. It was also found that vanadium alone and vanadium with nitrogen refine the martensite platelets (needles) in the case of carburized and hardened steels, vanadium with nitrogen being more effective. Microhardness measurements have shown that vanadium improves the case hardness and the core hardness values; vanadium with nitrogen is more effective than vanadium alone in increasing the case hardness and the core hardness. The hardenability is found to increase with the increase of austenite grain size and with the extent of carbon penetration of the case of carburized steels. Vanadium as vanadium carbide, VC are detrimental to toughness and vanadium as vanadium carbonitride, V(C, N) are beneficial to toughness of the core of low carbon steels in carburized and hardened condition.
Study of Forming Parameters in Hydroforming of a Thin-Walled ASTM C11000 Copper Tube
Authors: Seyedkashi S.M.H. , Liaghat Golam Hosein , Naeini Hassan Moslemi , Hoseinpour Gollo M.
Published: December 2009

Tube hydroforming technology is still considered a new technique growing fast in automotive and aircraft industries. Many researches on all aspects of this process are still required. Contact friction is one of the most effective parameters on tube wall thinning. To successfully fulfill the process without any common defects, it is very important to determine the proper internal pressure and axial feeding loading paths. In this paper, the effect of lubrication on tube wall thinning on ASTM C11000 copper alloy is discussed as well as the effect of internal pressure and axial feeding. An axisymmetric bulged tube is investigated using theoretical, numerical and experimental methods. Improved linear and non-linear pressure and feeding loading paths are applied and the predicted results are experimentally proved. It is observed that non-linear pressure application gives smoother results. Also proper lubrication plays an important role in success of the process.
Effect of Mold Surface Topography on Uneven Shell Growth in Solidification
Authors: Yigit F.
Published: December 2009

The unstable shell growth pattern in the early solidification stages results mainly from the unevenness of the heat flux drawn from the mold surface. This heat flux is determined either by the size of the air-gaps formed between the solidifying shell and mold surface or from the value of the contact pressure. Present work examines the role of the mold surface topography on gap nucleation and the contact pressure variation in pure metal solidification. The results of the present study can be used to tune mold surfaces for the control of cast surface morphologies.
Nonlinear Finite Element Modeling of Charpy Impact Test
Authors: Ghaith Fadi A.
Published: December 2009

Finite element modeling of Charpy impact test was performed for a normalized carbon
steel specimen based on plane strain geometry and bilinear isotropic hardening plasticity. As the
suggested approach takes into account all aspects of nonlinearity such as geometric, material and
contact nonlinearities, it may describe the conventional destructive impact test accurately with
much less effort and cost. A failure criterion is assumed to be at 10 % of plastic strain based on the
tensile experiment data. Impact energy was estimated at different testing temperatures. It was
found that impact energy required for fracture of the selected steel specimen at room temperature
(i.e. 25 °C) is to be 65.9 Joul. According to simulation results, it is found that the ductile to brittle
transition temperature (DBTT) equals 0 °C. In order to validate the numerical model, a comparison
study was established by comparing the numerical results with the corresponding experimental tests
at the same conditions, which shows good match with maximum deviation of 5 % for all computer
runs.
A Methodology for Control of the Robotic Welding Process Using Infrared Sensors
Authors: Kim H.H. , Kim Ill Soo , Chon K.S. , Shim J.Y. , Kang B.Y. , Kim I.J.
Published: December 2009

With the advance of the robotic arc welding process, procedure optimization which selects the welding procedure and predicts bead geometry that will be deposited is increased. A major concern involving procedure optimization should define a welding procedure which can be shown to be the best with respect to some standard and chosen combination of process parameters which give an acceptance balance between production rate and the scope of defects for a given situation. In this paper, bead-on-plate welding using an infrared thermography during robotic CO2 welding process has been conducted to obtain the thermal profile characteristics and develop the empirical models which influence process parameters on bead width with the help of a standard statistical package program SAS. The comparison with values of coefficient of multiple correlations for curvilinear and linear equations presents no differences, which indicate that the developed equations are reasonably suitable.
Development of Scaffold Building Units and Assembly for Tissue Engineering Using Fused Deposition Modelling
Authors: Masood Syed H. , Alamara Kadhim
Published: December 2009

In tissue engineering (TE), a porous scaffold structure of biodegradable material is required as a template to guide the proliferation, growth and development of cells appropriately in three dimensions. The scaffold must meet design requirements of appropriate porosity, pore size and interconnected structure to allow cell proliferation and adhesion. This paper presents a methodology for design and manufacture of TE scaffolds with varying porosity by employing open structure building units and Fused Deposition Modeling (FDM) rapid prototyping technique. A computer modeling approach for constructing and assembly of three-dimensional unit cell structure is presented to provide a solution of scaffolds design that can potentially meet the diverse requirements of TE applications. A parametric set of open polyhedral unit cells is used to assist the user in designing the required micro-architecture of the scaffold with required porosity and pore size and then the Boolean operation is used to create the scaffold of a given CAD model from the designed microstructure. The procedure is verified by fabrication of physical scaffolds using the commercial FDM system.
Aspects of Wear Mechanisms of Carbide Tools when Machine Hastelloy C-22HS
Authors: Kadirgama Kumaran , Noor M.M. , Abou-El-Hossein K.A. , Mohammad B. , Habeeb H.H.
Published: December 2009

In this study the performances of some commercially available carbide inserts when machining Hastelloy C-22HS was investigated under scanning electron microscopy (SEM) for wear mechanisms and other microstructure defects. Carbide inserts coated with TiCN/TiN and TiALN/ TiN experienced severe intergranular fractures and cracks. High temperature causes the layer of the coating to wear off and subsequently the inserts damaged at fast rates. Both types of inserts suffered from high crater wear and thermal cracking. Most of the wear occurred at the nose and flank of the inserts. Generally, it was observed that carbide coated with TiALN/ TiN cutting tool performed better than carbide coated TiCN/TiN cutting tool when milling Hastelloy C-22HS
Modeling the Force, Surface Roughness and Cutting Temperature in Ultrasonic Vibration-Assisted Turning of Al7075
Authors: Nategh Mohammad Javad , Amini Saeed , Soleimanimehr H.
Published: December 2009

The single point cutting tool in ultrasonic vibration-assisted turning (UAT) is made to vibrate under ultrasonic frequency. In present study, the influence of various parameters such as vibration amplitude, depth of cut, feed rate and cutting velocity on the machining force and workpiece's surface roughness in UAT of Al7075 has been investigated. Full factorial experiments were carried out with an ultrasonic frequency range of 20±0.5 kHz. ANOVA was conducted on the experimental results and regression models were obtained for predicting the machining force, surface roughness and cutting temperature. The proposed models were verified by further experiments. The robustness of the proposed models was then investigated whence the optimal parameters were estimated. Similar full factorial experiments were also carried out with conventional turning (CT) in order to compare the results with those of UAT.
Machinability of Bulk Metallic Glass Materials on Milling and Drilling
Authors: Bakkal Mustafa , Nakşiler Veli , Derin Bora
Published: December 2009

In this study, machinability of Zr-based bulk metallic glass (Zr52.5Ti5Cu17.9Ni14.6Al10) (BMG) material was investigated by conducting a set of milling and drilling experiments. In milling, two different tool paths, spiral and slot milling, were used. To investigate the behavior of BMG in drilling by two different tools at different feed rates, two sets of drilling experiments are conducted. Crown shaped exit burr formation are observed in drilling of BMG. Best results on thrust force, exit burr formation and hole surface roughness is obtained while using micrograin WC tool on BMG drilling. No chip light emission was observed during all tests. This study concludes that BMG can be achieved machining with good surface roughness, (Ra=0.113 µm), using conventional cutting tools.
Analysis of Elliptical Cup Drawing Process of SUS304 Stainless Metal
Authors: Huang You Min , Tsai Yi Wei
Published: December 2009

A methodology of formulating an elasto-plastic three-dimensional finite element model, which is based on Prandtl-Reuss flow rule and von Mises yield criterion respectively, associated with an updated Lagrangian formulation. An extended r-min algorithm is proposed to formulate the boundary conditions, such as the yield of element, maximum allowable strain increment, maximum allowable rotation increment, maximum allowable equivalent stress increment, and tolerance for nodes getting out of contact with tool.
In order to verify the reliability and accuracy of the FEM code, the fractured thickness of a specimen in the simple tension test is adopted as the fracture criterion of forming limit in simulation. A set of tools was designed to perform the elliptical cup drawing experiment on the hydraulic forming machine. According to the simulation and experimental results, the minimum thickness is concentrated on the contact regions between work-piece and punch major axis, because the camber radius is relatively large along the minor axis, the ones that bear are relatively small to the circular tensile stress, so the thickness does not change much. The limit drawing ratio (LDR) amounts to about 2.136 for penetration in the elliptical cup drawing process of this study. According to the definition of LDR, when the die radius is increased from R3.0mm to R9.0mm, the LDR would increase from 2.11 to 2.157. When the punch radius is increased from r3.0mm to r9.0mm, the LDR would increase from 2.07 to 2.181. This paper has provided a better understanding of the elliptical cup drawing process for improving the manufacturing processes and the design of tools.
Rice Husk/High Density Polyethylene Bio-Composite: Effect of Rice Husk Filler Size and Composition on Injection Molding Processability with Respect to Impact Property
Authors: Rahman Wan Aizan Wan Abd. , Isa N.M. , Rahmat A.R. , Adenan N. , Ali Roshafima Rasit
Published: December 2009

The compounding of rice husk and high density polyethylene (HDPE) was undertaken on a Sino PSM 30 co-rotating twin screw extruder. Four sizes of rice husk were studied at various compositions. The size ranged from 500 μm and below (coded A, B, C and D) while the content of rice husk in the composite varies from 30, 40 and 50 percent of weight. A fixed amount of Ultra-Plast TP10 as a compatibilizer and Ultra-Plast TP 01 as lubricant, were added into the bio-composite compound. The injection molding process ability of the bio-composite was studied through flow behavior on melt flow indexer and analyzed on JSW N100 B11 Injection Molding. Size A which has the largest particle is the most appropriate size as the bio-composite filler based on thermal stability test. The melt flow rate of rice husk/HDPE (RHPE) decreases with the increased in rice husk compositions and apparent viscosity also increases with composition for all filler size. Melt flow rate above 4g/10 min was found to be the lower limit for injection molding process. The smaller the filler size, the lower is the impact strength and the increased in the filler composition lowers the impact strength. A bio-composite at 30 weight percent rice husk size A (RH30PEA) was found to have optimum rheological properties with respect to impact strength.
Experimental Investigations of Nd:YAG Laser Welding of 630 and 321 Stainless Steel and their Effects on Process Parameters
Authors: Akbari Mousavi Seyed Ali Asghar , Sufizadeh A.R.
Published: December 2009

In this paper, the laser welding of the 630 precipitation hardening stainless steel with the 321 austenitic stainless steel was considered. The experiments were carried out with the pulsed Nd: YAG laser under various welding parameters. The effects of power of laser, voltage, duration of pulse, welding speed, beam diameter and frequency, on the weld volume are investigated. The results show that the weld volume increases with voltage and frequency. The weld volume decreases with welding speed and beam diameter. Moreover, the study shows two effects for the duration of pulse. Up to some value of duration of pulse, the weld volume increases. Exceeding, this limit reduces the weld volume. The optical and scanning electron microscopic tests were carried out. The results show that the martensitic structure is produced in the 630 stainless steel side and the austenitic stainless steel is produced in the 321 stainless steel side. The microhardness tests across the samples were carried out. The results show the maximum hardness is for the 630 stainless steel side and the minimum weld hardness is for the 321 stainless steel side. The high voltage may cause hot cracks in the 321 stainless steel side. The effects of gas flow rate on the microstructure were also considered.
Wear Behavior of White Layer in Plasma Nitrided H13 Steel at Ambient and Elevated Temperatures
Authors: Mahmoudi Amir , Esmailian Mohamad
Published: December 2009

In this study, AISI H13 steel was plasma nitrided in two different atmospheres, containing 25%N2-75%H2 and 4%N2-96%H2 at a constant temperature of 530oC and 6h-holding time. Dry wear behavior of nitrided samples was determined with pin-on-disc method at 25oC and 500oC, under 10N and 30N loads. The results indicated that the nitrided steels, which had a thin multiple phases white layer (produced at 4%N2-96%H2 atmosphere), didn’t have any wear resistance in ambient and elevated temperatures. However, the nitrided steels, having thick single phase white layer (produced at 25%N2-75%H2 atmosphere), showed better wear resistance in ambient temperature than in elevated temperature.
Evaluation of the Role of Alloying Elements in Austemperability of Heavy Section Ductile Iron
Authors: Heydarzadeh Sohi M. , Nili-Ahmadabadi Mahmoud , Bahrami Vahdat A. , Amirsadeghi A.
Published: December 2009

In this investigation the role of alloying elements on austemperability of heavy section ductile irons was studied. Four different chemical compositions were chosen in a way to specify an optimal chemical composition with suitable austemperability. Austempering was carried out at 315 and 350oC for 1 hour on specimens prepared from cast Y-blocks with 75 mm thickness. Metallographic examinations and hardness tests indicated that thickness of bainitic layer was positively dependant on the amount of the alloying elements which deferred pearlitic transformation in TTT diagram to the longer time. In addition, by increasing the amount of alloying elements, the morphologies of ferrite in bainitic structure changed from featherlike to acicular. According to the results of this study, in order to achieve a full bainitic structure (in the specimens whit 75mm thickness), the optimal amounts of alloying elements were: 0.35 % Mn, 0.22 % Mo, 1.1-1.4% Ni and 0.6% Cu. In addition, regarding to the thick sections of Y-blocks, graphite degeneration defect was also studied, and it was noticed that this defect could be completely eliminated by adding 50ppm of antimony.
Low Temperature Thermochemical Surface Treatment of Austenitic Stainless Steel for Improved Mechanical and Tribological
Authors: Triwiyanto A. , Mridha S. , Haruman E.
Published: December 2009

This paper describes the results of four thermochemical surface treatments of austenitic stainless steels carried out at 450oC in a fluidised bed furnace and they are nitriding, carburizing and the newly developed hybrid process involving the simultaneous and sequential incorporation of nitrogen and carbon to form a dual layer structure in order to achieve much enhanced surface hardness and wear resistance without compromising the corrosion resistance of the steel. In all these treatments there formed alloyed layers with a common feature of being precipitation-free and supersaturated with nitrogen, or carbon or both in the austenite lattice which is known as S Phase or expanded austenite. However the layer thickness was not uniform in any of these treatments and an effective layer was produced after 8h treatment duration. The nitriding treatment produced thicker and harder layer compared to other treatments; the maximum hardness was over 1500 Hv for nitriding and the minimum hardness of 500 Hv for carburizing treatment. The nitriding treatment sample gave high wear resistance which corresponded to high hardness values.
Characteristics of CFRP Structure of Bending Strength and Rigidity According to Stacking Orientation Angle
Authors: Kim Ji Hoon , Jeong Joo Yeung , Bang Jung Min , Kim Jung Ho , Yang In Young
Published: December 2009

Carbon fiber reinforced plastics (CFRP) have high strength in comparison with dimensional stability, invariability of material property, high strength and rigidity, corrosion resistance. Therefore, CFRP is widely used in various fields including space and aviation industries, sports and leisure industries, and general structural members and parts. To achieve structural members of CFRP with high strength and rigidity, theoretical approaches is limited to isotropic material, and empirical studies have been conducted. As with other composite materials, CFRP shows different rigidity and strength due to difference in properties in fiber and matrix material. In this study, CFRP specimen with changing stack orientation angle was manufactured as general structural application, and bending strength and rigidity of the corresponding composite was measured. In addition, square aluminium tube reinforcement is applied to prevent the shortcoming of CFRP. Vacuum compressed CFRP via autoclave with square aluminium tube reinforcement material (Hybrid) was evaluated by changing of orientation angle.
A High Corrosion and Wear Resistant Interior Surface Coating for Use in Oilfield Applications
Authors: Lusk D. , Gore M. , Boardman B. , Upadhyaya D. , Casserly T. , Oppus M.
Published: December 2009

A novel technique for depositing thick DLC based films on the inside of cylindrical substrates, like pipes, tubes and valves, has been developed. A plasma enhanced chemical vapour deposition (PECVD) technique has been used to engineer and optimize the above mentioned films for maximum coating performance. Of particular importance is the corrosion and wear resistant qualities of these films. Changes in film chemistry, structure and thickness are attributed to the improved corrosion and wear resistance. Details will be given of the corrosion testing which has taken place, such as exposure to HCL (hot and ambient temperature), NaCl and H2S environments. One such test is a very aggressive sour autoclave test where the film is exposed to an aqueous, organic and gas phase over a 30 day period and no damage to the film was found. In depth details of this sour autoclave test will be shown including photographs of the film before and after testing. Wear testing has also been carried out in dry and wet sand slurry environments where very low coefficient of friction (COF) and wear rates were found. It is believed that this thick DLC based film can increase the component life in applications where internal surfaces are exposed to highly corrosive and abrasive media, in particular the oil and gas industry. Examples of such applications are mud pump sleeves, deep well components, directional drilling, abrasive flow spools, pump barrels and in sour fields (H2S).
Quality Assessment and Metallurgical Examination of Laser Welded Sheets
Authors: Abu-Dheir Numan , Yilbas Bekir Sami
Published: December 2009

Laser welding of steel 316L sheets is considered and the effects of laser welding parameters on the laser weld quality and metallurgical changes in the weld section are presented. The laser weld quality is assessed through careful examination of weld geometrical features, and the resulting weld microstructure. Metallurgical changes in the weld sites are examined using optical, and electron scanning microscope (SEM). Two levels of heat inputs are used-1500W and 2000W; and two scanning speeds of 2cm/s and 4cm/s are used to laser weld 316L sheets. It is found that at the high laser power intensities, evaporation takes place in the irradiated region and as the laser power intensity increases further, a cavity is formed at the top surface of the welding cross section. A similar situation is also observed as the laser scanning speed reduces. The low diffusivity of the alloying elements at high temperatures preserves the segregation profile. The scattered partitioning of the cells and dendrite boundaries are observed due to the presence of Cr and Mo.
ITO Thin-Film Removal Process Using Design of Rolling Tool
Authors: Pa Pai Shan
Published: December 2009

Although the low yield rate of ITO thin-film during the production of semiconductor techniques is easily seen. Current work presents a new modus of electrochemical machining using a design rolling tool as electrodes constructs a precision recycle process offering faster performance in removing the color filter surface’s ITO thin-film. Through establishing an ultra-precise recycling process to remove the thin-film microstructure, this helps the semiconductor optoelectronic industry to reduce both production costs and pollution. The design features of the removal processes for a thin-film and the tool design of rolling electrodes are of major interest. Higher electrical current is not required when an effective feeding electrodes is used to reduce the response area. In the current experiment, the author utilizes a 5th Generation TFT-LCD. The design electrodes (rolling tool) are used with continuous and pulsed direct current in the electrochemical machining experiment. A displays’ color filter with a fast feed rate is combined with enough electric power to provide highly effective removal. High rotational speed of the rolling tool and high flow velocity of the electrolyte elevates the discharge mobility and improves the removal effect. A larger diameter of the fictitious rotation circle of the cathode and a small end radius of the cathode provide better removal effect. A precision recycling process is presented using an effective rolling tool in the electrochemical machining. It only needs a short period of time to remove the ITO thin-film easily and cleanly.
Investigations of Formation of Chatter in a Non-Wavy Surface during Thread Cutting and Turning Operations
Authors: Patwari Mohammed Anayet Ullah , Nurul Amin A.K.M. , Faris Waleed Fekry , Ishtiyaq M.H.
Published: December 2009

An attempt has been made to investigate the chatter formation during two machining operations namely, turning and thread cutting on a non-wavy surface of plain carbon steel with a view to observing the formative mechanisms of chatter. Investigations have been conducted on the chips and common types of discreteness in the form of serrated/saw teeth have been identified. Mechanisms of formation of these teeth have been studied and the frequencies of their formation have been determined at different cutting speeds. The different modes of the vibrating components have been extracted by modal analysis and the vibration responses during cutting conditions have also been recorded using an online data acquisition system. All the experiment were conducted on a no wavy surface and thread cutting was conducted on nascent surface, the existence of chatter observed during the experiments prove that the regenerative effect from the waviness of the previous pass, as postulated by the ‘Regenerative Chatter Theory’ is not correct in explaining the primary cause of chatter during metal cutting. The analysis of amplitude of chatter during machining indicates that noticeable chatter appears in the system when the chip serration frequency is equal to or integer multiple of the prominent natural frequency of the system components.
Constitutive Modelling of Mechanical Behaviour of a Ti-Alloy, Applicable in Metal Cutting
Authors: Habibzadeh A. , Sadeghi M.H. , Davoodi B. , Jabbaripoor B.
Published: December 2009

In order to simulate manufacturing processes, it is essential to have accurate information about mechanical behaviour of material for different deformation conditions depending on the type of the process. In finite element (FE) analysis based techniques for simulation, a constitutive equation is needed to model the mechanical behaviour of material. In the case of metal cutting, the Johnson and Cook (JC) flow stress model is the most suitable constitutive equation to be used in simulation since it contains the effects of strain, strain-rate and temperature. It is needed to evaluate the parameters and constants of the JC model to make it applicable in FE simulations. There are several ways to evaluate the parameters of the equation: experimental such as high strain-rate compression tests called “Split Hopkinson Pressure Bar” which is relatively complicated and expensive technique requiring special testing apparatus; and analytical approach based on Oxley’s theory. An integral method containing quasi-static compression and machining tests have been used in this paper to evaluate the JC equation parameters by fitting data from both tests for a Ti-alloy (Ti6Al4V). Finally the estimated JC model is validated by some other machining tests.
Characteristics of Surface Damage in Micro Electric Discharge Machining of Micro Holes
Authors: Ekmekci Bülent , Sayar Atakan , Tecelli Öpöz Tahsin , Erden Abdulkadir
Published: December 2009

Micro Electric Discharge Machining is mostly used micromachining technique for
manufacturing of micro holes and mini cavities. It is a thermal material removal process achieved
by application of recursive electrical sparks between two conductive materials immersed in
dielectric liquid. There are many electrical and technological parameters, which are effective in the
machining characteristics and machined material surface integrity. In this study, effects of pulse
energy on characteristics of surface damage in micro electric discharge machining of micro holes
are investigated. To observe the influences of investigated pulse forms, a series of micro-holes were
machined and cut from cross sections for metallurgical examinations. Unconventional etching
agents were applied to examine the metallurgical transformations using optical and scanning
electron microscopy. It was observed that heat-damaged segment is composed of three distinctive
layers, have relatively high thicknesses (0.2 to 10 μm) when compared with the size of the micro
holes and varies noticeably with respect to drilling dept. Different morphological structures and
deformations in the subsurface of micro-hole walls at several sections were illustrated. Finally,
analyzed machining parameters and variation of hat damaged layer thicknesses were discussed in
terms of drilling depth.
Pressure and Microstructural Change with Web to Flange Ratio and Die Land Length in Cold Extrusion of I-Shaped Lead Alloy
Authors: Ajiboye J.S. , Balogun S.A. , Agboola A.T. , Eke G.J.
Published: December 2009

Plastic deformation process resulting in ultra fine grained materials which are rapidly grasping applications due to their superior mechanical properties remain an area of continued research interest. Generally, the influence of die land length and web to flange ratio in grain refinement subsequent to plastic deformation process have not being adequately exploited especially in complex die opening geometries. In the present study, the effect of these parameters on extrusion pressure and morphological change in I-shaped die opening geometry is investigated and reported. A forward extrusion rig is designed and manufactured for the purpose of experimental investigation. The upper bound analysis shows that increasing die land length leads to increasing relative extrusion pressure. Optimum web to flange ratio of 0.45 is numerically simulated and recommended to extrude I-shaped lead alloy with minimum load requirement. The experimental results reveal that increasing area ratio leads to quasi-sinusoidal pattern in surface hardness of I-shaped section irrespective of strain rate value. Increasing web to flange ratio, therefore, leads to increasing anisotropy of the I-shaped lead alloy. The extruded sections were examined with optical metallurgical microscope, and it is observed that increasing strain rate results in profound refinement of grain and inclusions in lead alloy even at room temperature.
A Study of Machining Parameters during Electrical Discharge Machining of Steel by a Rotary Copper Electrode
Authors: Satsangi P.S. , Chattopadhyay K.D.
Published: December 2009

The use of thermo-electric source of energy, as in electrical discharge machining (EDM), has greatly helped in machining all types of electrically conductive materials being used in different industrial applications. The present work investigates the different machining characteristics during electrical discharge machining on EN-8 steel with a rotary copper electrode. The effects of three independent machining parameters viz. peak current, pulse on time and rotational speed of tool electrode are chosen as variables for evaluating the output parameters such as metal removal rate, surface finish of work piece. The research focuses on developing empirical models for prediction of metal removal rate and surface finish during rotary electrical discharge machining process with the help of input parameters. The models are developed using linear regression analysis by applying logarithmic data transformation of non-linear equation. Analysis of results using partial and multiple correlation analysis reveals that electrical parameters have more significant effect than the non-electrical parameters on the machining characteristics during electrical discharge machining by a rotary electrode. Furthermore, when high MRR is criterion, high peak current and low RPM with low pulse duration produces better output; whereas, and when smooth surface finish is criterion, low peak current and low RPM with high pulse duration produces better output. In addition, the predictions based on the above developed models are verified with extra experiments and are found to be in good agreement with the experimental verifications.
The Effect of Reinforcement Phase on the Microstructure of Al-SiC Nanocomposite Powder Prepared via Mechanical Alloying
Authors: Rostamzadeh Taha , Shahverdi H. , Sarraf-Mamoory R. , Shanaghi A.
Published: December 2009

Mechanical alloying is one of the most successful methods for the manufacturing of metal matrix nanocomposite powders. In this study, Al/SiC metal matrix composite (MMCp) powders with volume fractions of 5, 10, and 15 percent SiC were successfully obtained after milling the powder for a period of 25 hours at a ball to powder ratio of 15:1 using high energy planetary milling. The Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted to investigate the lattice strain of the matrix phase and the microstructure of the nanocomposite powders after 1, 10, and 25 hours of milling time. Also, the morphology of the Al-5%SiC nanocomposite powder was investigated using transmission electron microscopy (TEM). The results show that with the increase of both milling time and the reinforcement phase volume fraction, the lattice strain increases and the average size of aluminum phase crystallites decreases. Eventually, after 25 hours of milling, the nanocomposite powders show a spherical-like morphology and SiC particles were distributed in an aluminum matrix with appropriate order.
Glass Ceramic Laser Machining for Cooktop Appliances
Authors: Sola Daniel , Peña J.I. , Buñuel Miguel A.
Published: December 2009

This paper presents a study of glass ceramic laser machining for cooktop appliances. Blind holes and special shape cross section blind holes can be created for functional purposes. A Q-switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulsewidths in the nanosecond range has been used. The material can be machined by focusing the laser beam at different depths under the back side of the glass panel, in such a way that blind holes of 2-6 mm diameter and 1-3 mm depth can be drilled. Several cross section shapes can be obtained using additional galvanometric mirrors to deflect the laser beam in the desired direction, controlling the incidence angle. These holes can be used for fastening directly components to the glass panel, avoiding gluing processes, or for approaching thermal sensors to the upper surface, controlling the work temperature in a better way. Several tests have been performed to check the modifications in glass ceramic mechanical properties. Thermal tests have verified the improvement in work temperature accuracy measurement.