Incremental sheet forming (ISF) process has gained massive popularity due to its die-less nature. The process shows greater flexibility in making customized sheet metal parts economically and more effectively as compared to the traditional forming processes. This paper mainly focuses on investigating the behavior of commercially pure (CP) titanium grade 2 sheet. Single point incremental forming process has been used to deform the sheet. Workpiece geometry has been chosen as conical rectangular shape, using the unidirectional spiral tool path profile. The deformation of the titanium sheet has been performed with and without the use of lubricating fluid. The finite element analysis (FEA) for the von Mises stress and sheet thickness variation has been carried out on ABAQUS ® simulation software. Also, the stretching of the deformed sheet has been examined along the side wall and corner of the deformed surface. The ISF has limitation with respect to the geometrical accuracy and surface finish quality of the formed part. To study the surface quality of the deformed surface, scanning electron microscopy (SEM) has been utilized. Stress triaxiality is another important parameter to investigate the crack initiation and fracture during forming, it has been predicted using Finite element analysis.

The mechanics of chip formation involves a complex interplay between surface plastic flow, material microstructure and tool-chip interface dynamics. At the continuum scale, this process has often been approximated as being one of pure shear along a very narrow zone — the shear plane. The primary assumption behind this approximation is that of steady or time-independent plastic flow. This approximation addresses the exception rather than the rule, since most metal cutting processes involve unsteady time-dependent plastic flows. In this work, we attempt to develop parallels with an analogous problem in fluid mechanics — flow past a rigid fixed body — to quantify the unsteady nature of plastic flow. Here the role of the body is played by the tool, and the flow field corresponds to the plastically deforming material. The prerequisite for fully exploiting this kinematic analogy is full-field material flow measurements. This is provided by digital image correlation (DIC), a family of techniques that use in situ imaging of the cutting process to obtain instantaneous full-field material displacements. Given this kinematic flow information, we show how one can describe the cutting process more accurately using the fluid flow analogy, and without having to resort to specific preconceived models. For steady flows, the analogy is more than merely cosmetic — the pathlines, streamlines and streaklines, all determined kinematically, coincide exactly. The analogy also allows consideration of time-dependent unsteady plastic flows that are usually beyond the purview of theoretical analyses. One can, for instance, ask the question of whether the transition from steady to unsteady plastic flow observed in metal cutting can be described by a dimensionless parameter, analogous to the Reynolds number for fluids. We show that in the case of unsteady flows, the actual deformation field is far removed from that described by conventional shear plane or slip line field models. Now the streaklines develop undulations or folds for the same boundary conditions as for the steady case (cutting velocity, depth of cut). Of the three flow lines, we attempt to extract information from streaklines, since they contain information about both spatial and temporal gradient. We present analyses of these streakline curvature features using simple geometric techniques that reflect both the spatial and temporal flow evolution. Our results shed light on the importance of considering unsteady flows in chip formation and machining. Borrowing ideas from fluids to describe these flows appears to hold significant promise for quantifying unsteady flows and their consequences for practical machining operations.

Magnetic field-assisted finishing process is a hybrid nanofinishing process that combines the advantages of both magnetorheological finishing process and chemical mechanical polishing process. This process uses magnetorheological fluid combined with chemicals as the polishing medium. The developed novel tool is made of mu-metal which encloses a permanent magnet. The femoral component of the prosthetic knee joint made of titanium alloy is used as the workpiece material in the present study. The surface finish requirement of the femoral knee joint is at the nanometer level. Finishing of the femoral component of the knee joint is a difficult task due to its complex surface conditions. The best final surface roughness of 0.02 μm is obtained after finishing of the knee joint. Also, the femoral knee joint should be hydrophilic in nature. Surface wettability test is conducted using the goniometer to prove the hydrophilicity nature of the finished surface. The formation of the oxide layer is observed on the finished surface. The oxide layer increases the biocompatibility of the implant. The present study proves the capability of the novel tool to provide the required surface properties of the femoral knee implant. Hence, the magnetic field-assisted finishing process can be used to finish the complex freeform surface of the femoral knee implant.

Thermal spray coating has the ability to enhance the lifetime of engineering components by reinforcing the surface properties. The surface roughness of the as-sprayed coatings needs to be suitably finished for its end use. The nanofinished WC-Co coatings are widely used in aerospace and automobile industries. In this present investigation, surface grinding followed by the magnetorheological finishing (MRF) processes is employed for finishing of WC-Co coating. Boron carbide (B 4 C) powder is used as the abrasive particles in the MRF process. MRF spot finishing technique is performed on the ground coating. The plastically deformed layer from the ground surface is removed completely by the gentle mechanical abrasion of MR fluid ribbon. The surface roughness and volume of material removed are measured over the finishing time. It is perceived that the surface roughness of the finishing spot is increased after a threshold machining time. This is attributed to the aging of MR fluid and the mechanical abrasion of wear debris. The experiment is also performed with the assistance of Murakami’s reagent to perform etching and finishing, simultaneously. A comparatively higher finishing rate is observed in this case.

In metal cutting processes the use of cutting fluids shows significant effects on workpiece surface quality by reducing thermomechanical loads on cutting tool and workpiece. Many efforts are made to model these thermomechanical processes, however without considering detailed heat transfer between cutting fluid, tool and workpiece. To account for heat transfer effects, a coupling approach is developed which combines CFD (Computational Fluid Dynamics) and FEM (Finite Element Method) chip formation simulation. Prior to the simulation, experimental investigations in orthogonal cutting in dry and wet cutting conditions with two different workpiece materials (AISI 1045 and DA 718) are conducted. To measure the tool temperature in dry as well as in wet cutting conditions, a two color pyrometer is placed inside a EDM drilled cutting tool hole. Besides tool temperature, the cutting force is recorded during the experiments and later used to calculate heat source terms for the CFD simulation. After the experiments, FEM chip formation simulations are performed and provide the chip forms for the CFD mesh generation. In general, CFD simulation and experiment are in reasonable agreement, as for each workpiece setup the measured temperature data is located between the simulation results from the two different tool geometries. Furthermore, numerical and experimental results both show a decrease of tool temperature in wet cutting conditions, however revealing a more significant cooling effect in a AISI 1045 workpiece setup. The results suggest that the placement of drilling holes has a major influence on the local tool temperature distribution, as the drilling hole equals a thermal resistance and hence leads to elevated temperatures at the tool front.

An experimental study of shear band formation in cutting of metals is made using a low melting point Bi-based alloy as a model material system. High-speed imaging is used to capture the transition in the plastic flow, from laminar to shear banded flow, as a function of cutting speed. The dynamics of shear band nucleation is captured in situ and temporal evolution of localized plastic flow during shear band growth is quantitatively analyzed using an image correlation method, particle image velocimetry (PIV). The observations show that shear band nucleation is governed by a critical shear stress criterion, and accompanied by a large drop in the flow viscosity by several orders of magnitude, analogous to the phenomenon of yielding in yield-stress (Bingham) fluids. Likewise, the displacement field around a freshly nucleated shear band evolves in a manner resembling the boundary layer formation in planar flow of a Bingham fluid with a very small viscosity. Surprisingly, temperature has little influence on shear band nucleation or growth.

Minimum Quantity Lubrication or MQL is an increasingly used technique for metal cutting operations and it has become an attractive alternative for machining parts at big scale production. However, fully lubricated conditions are still in use for machining special materials so that surface finish, tool wear, and temperature distribution levels remain at optimum levels. On the other hand, dry condition machining is in use as well although with some restraint due to issues with material burr, surface roughness, and tool wear. The main purpose of this work is to analyze the effects of cutting fluid flow rate, its application mechanisms, and cutting speed on surface roughness and establish the lowest possible cutting fluid flow rate that yields to minimum surface roughness (Ra). To achieve the objective, a set of experiments was performed using a Computer Numerical Control (CNC) lathe instrumented with a Kistler 9121 dynamometer and a customized cutting fluid application system to obtain coefficients of friction and cutting forces. Finally, a previously 2D finite element analysis (FEA) simulation from Akbar et al. [1] is applied and compared to experimental results to find out if the cutting force can be predicted. A first regression model that correlates cutting force and surface roughness is posed, so that FEA simulation can be implemented to predict the final surface roughness. AISI 4140 machinery steel in annealed condition is used to carry out the simulated and experimental work.

Selective Laser Melting (SLM) has been a major subject of study in the field of powder bed additive manufacturing (AM) process. It is desired to know the melt pool size and the associated thermal gradient during the powder melting process. However, there are challenges associated with accurately measuring the melt pool size as a whole by experiment alone. Therefore, the combination of experimental and numerical study may help analyze the melt pool shape in a better way. In this study, a 3D powder scale model using volume of fluid (VOF) approach has been developed using ANSYS FLUENT. A temperature dependent material property is defined and then volumetric heat source is applied to melt the powder particles. The single track results obtained from the simulation are compared with the experiment and the results show that single track width predicted by the simulation is in good agreement with the experimental counterpart. The predicted track width is within 10% error.

Tubular structures of hydrogel are used in a variety of applications such as 3D cell culturing for delivery of nutrient supplies. The wall thickness of the tube determines the speed of diffusion or delivery rate. In this study, we aimed to fabricate tubular structures with varying of wall thicknesses using a thermal-crosslinking hydrogel, gellan gum, with the coaxial needle approach. The wall thickness is controlled by changing the flow rate ratio between the inner (phosphate-buffered saline) and outer needles (gellan gum). A simulation model was developed to estimate the proper extrusion speed to allow the gellan gum to be extruded around its glass transition temperature. While keeping the extrusion rate of gellan gum fixed, different PBS extrusion rates were tested to investigate the printability to form continuous tubular structures, range of printable wall thickness, and possibility to form tubes with closed ends to encapsulate fluid or drug inside the tube. The ranges of printable wall thickness with two pairs of coaxial needle were identified. It was found that at about 200% of the baseline PBS extrusion speed, a maximum of 20% difference in wall thickness can be achieved, while a close end can still be formed.

Hydroxyl ion treatment of different hydroxyapatite-calcium hydrogen phosphate composite in-situ coatings synthesized through pulsed electro-deposition with varying amount of hydroxyapatite phase and degree of crystallinity were carried out with the help of highly basic solution in order to achieve a more chemically stable and corrosion resistance performance under contact with body fluid. The coatings exhibit altogether completely different behaviour in terms of bond formation, surface topography generation, phase transformation and corrosion behaviour. Detailed characterizations of formed top surface layer were carried out with the help of XRD, SEM and FTIR in order to correlate the results with their base surface characteristics. Transformation of <020> and <121> surface parallel planes of calcium hydrogen phosphate in to <002> and <112> planes of hydroxyapatite took place in all the coatings along with formation of nano-crystalline structure. Calcium-rich porous hydroxyapatite scaffold formation takes place in low current density coating which in general exhibits low stability in terms of chemical bonding strength vis-à-vis corrosion protection performance. 10 mA/cm 2 coating, which come with optimum presence of hydroxyapatite phase and crystallinity post electro-deposition, showed significant improvement in terms of increasing hydroxyl and phosphate bond polarization strength of hydroxyapatite phase and the same lead to improvement in the overall corrosion resistance performance of the coating by two times. Despite of formation of highest amount of hydroxyapatite phase during hydroxyl ion treatment in 20 mA/cm 2 coatings, the corrosion protection performance results are negative on account of dilution of mostly low bonding amorphous phases with high internal residual stress.

Most researches on process planning optimized machining process routings and cutting parameters independently and ignored their comprehensive effects on carbon reduction. In order to further reduce carbon emissions in manufacturing processes, an optimization model of cutting parameters and machining process routings is proposed to minimize total carbon emissions and total processing time of all processes. Carbon emissions include those caused by energy consumptions of machines in cutting state, material consumption of cutting tools and cutting fluid in all processes. As the optimization of cutting parameters is a continuous optimization problem, but the optimization of machining process routings including machining methods, process sequences, machine allocating and cutter selecting are discrete optimization problems, the whole optimization of process planning is divided into two parts. One is continuous optimization of cutting parameters. Another is discrete optimization of machining process routings. A hybrid optimization strategy of bird swarm algorithm (BSA) and NSGA-II algorithm is proposed to optimize the proposed model. Cutting parameters are optimized using BSA aiming at minimizing carbon emissions and machining time of each process. Machining process routings are optimized using NSGA-II under each optimized group of cutting parameters from the Pareto set. Four kinds of mutation operators in NSGA-II are designed for the discrete optimization of machining process routings. A workpiece with six machining features to be machined in a workshop with two CNC lathes, two CNC milling machines and two drilling machines is taken as a case study. The validity of the proposed model and hybrid strategy is verified by computational and analytical results. Several conclusions are yielded.

Magnetic source configuration plays an important role in flexible fixturing based on magnetorheological fluid (MRF). In this article, a novel magnetic source connected to spindle of machine tool is designed to generate specific magnetic field in machining region. The magnetic field can follow machining trajectory in real time, solidifying magnetorheological fluid under current machining region and constituting a mirror support to axial milling force. The magnetic field makes magnetorheological fluid work in squeeze mode, thus providing a stronger supporting capability under the same magnetic field. The magnetic source has self-cooling function, permitting a very strong coil current throughout the whole machining process. Compared with other magnetic sources used in magnetorheological fixturing, magnetic source researched in this paper is more universal and economical.

Shear banding is a type of plastic flow instability with often adverse implications for cutting and deformation processing of metals. Here, we study the mechanics of plastic flow evolution within single shear bands in two different (Ti and Ni-based) alloy systems. The local shear band displacement profiles are quantitatively mapped at high resolution using a special micro-marker technique. The results show that shear bands, once nucleated, evolve by a universal viscous sliding mechanism that is independent of microstructural details. The evolution of local deformation around the band is accurately captured using a simple momentum diffusion model by assuming Bingham flow rheology for the band material. The predicted band viscosity is very small, comparable to those of liquid metals. A plausible explanation for this small viscosity and fluid-like behavior at the band, based on phonon drag, is presented.

WC-Co coatings are extensively used in abrasion, sliding, and erosion resistance applications for its favourable mechanical properties. Nanofinishing of WC-Co coating is required for aircraft landing gear cylinder and diesel engine cylinder. Characterisation of surface topography becomes an important aspect in tribological applications as it has significant effect on the functional performance of the surfaces. In this present study, the motif analysis with 5% wolf pruning is applied to identify the significant hills for pattern reorganization of the surface texture generated by different finishing steps such as grinding, shape adaptive grinding (SAG) and chemical assisted SAG (CA-SAG). Several 3D advanced texture parameters are employed to characterize the coated surface before and after finishing in terms of surface roughness, third and fourth moments (skewness and kurtosis) of the probability density function, bearing area ratio curve and fluid retention properties of the surface. Furthermore, power spectral density (PSD) analysis is performed to analyse the unevenness and periodicity of the texture. It is observed that the fluid retention property and the bearing property of the surface improve with the subsequent finishing stage.

Magnetic field assisted finishing process is a nanofinishing process which uses magnetic field for precise control of finishing forces. Magnetorheological fluid mixed with diamond abrasive particles in base medium of glycerol, hydrofluoric acid, nitric acid, and deionized water is used as the polishing medium. The novel tool is a magnet fixture made of mu-metal which is used to hold the magnet during finishing. In the present experimental study, finishing at a spot on flat titanium alloy is carried out to analyze the forces involved in the finishing. Normal force is the main force responsible for the indentation by the abrasive particle on the workpiece surface. Tangential force helps in removing indented material. The measured normal force and tangential force during the spot finishing are 3.285 N and 0.43 N, respectively. The final surface roughness achieved after spot finishing is 10 nm from initial surface roughness of 200 nm. The percentage improvement in surface roughness is 95%.

Organ printing, which utilizes advanced manufacturing technologies to fabricate three-dimensional (3D) functional organs based on layer-by-layer mechanism, is emerging as a promising solution to solve the organ donor shortage problem affecting all over the world. One of the biggest challenges for fabrication of functional and effective thick tissues/organs is the engineering of vascular networks. This paper introduces a Bingham fluid (Carbopol gel) to assist fabrication of 3D vascular-like constructs of interpenetrating network (IPN) hydrogels. Carbopol gel as a Bingham fluid exhibits a characteristic yield stress behavior. As the nozzle moves inside Carbopol, the shear stress is larger than the yield stress and the Carbopol gel behaves like a viscous fluid with a specific viscosity. After the nozzle moves away, the shear stress decreases below the yield stress and the Carbopol gel rapidly solidifies behaving like a solid. This unique rheological property is utilized to support and maintain the shape of the fabricated 3D structures, although the fluid printed is not crosslinked. Finally, the fabricated structures are subject to a two-step gelation process to successfully form 3D vascular-like constructs of IPN hydrogels. This novel approach enables effective and efficient fabrication of complex vascular network of IPN hydrogels.

Machining is the manufacturing process, capable of producing required shape and size by material removal. In recent times industries are striving to enhance the performance of machining processes. One of the problem associated with machining is the amount of heat generation as a result of friction between tool and workpiece. Heat generated may affect the quality of machined surface and tool wear. In order to control it, cutting fluid is applied in large quantity. The problem arises with the use of cutting fluid is its effect on worker’s health and environment. The present investigation is an attempt to explore the use the solid lubricants in machining as an alternative to cutting fluid. The work involves development of minimum quantity solid lubrication set up. Turning experiments has been performed by applying solid lubricants mixed with cutting fluid in minimum quantity. The performance of minimum quantity solid lubrication has been assessed in form of obtained surface finish, power consumption and tool wear during turning. Experimental findings discovered the superiority of minimum quantity solid lubrication over conventional cutting fluid and can be considered as cost effective and sustainable lubrication method.

The hard turning process is widely used in automobile and heavy machinery industries. Extreme cutting conditions like high temperature and tool wear rate, are associated with the hard turning process. Cubic boron nitride (CBN) cutting tool is generally preferred for hard machining operations. However, higher tool cost, and tool failure due to thermal shock limits its widespread usage. In machining performance analysis, tool wear is an important parameter which is directly related to the cost of the machining process. Previous studies have reported the improvement in tool life by using cryogenic coolant as a cutting fluid. Objective of this paper is to investigate the effect of cryogenic cooling on the tool wear of CBN and Ti-coated alumina ceramic cutting tools used in the hard turning of AISI 52100 hardened steel. High pressure cryogenic jet (HPCJ) module was optimized and configured to use it for hard turning case. Computational fluid dynamics (CFD) based simulation was used to test and optimize the nozzle design for the flow of cryogenic coolant. It was validated by fundamental heat removal test. Ceramic and CBN cutting tools were then used for hard turning of parts using HPCJ module. Flank wear lengths for various cooling conditions were measured and analyzed. It was observed that the higher tool life of a Ti-coated alumina ceramic can be achieved under cryogenic cooling technique, as compared to the CBN insert under dry conditions. Cost analysis of these hard turning cases was also conducted to check the feasibility of its usage under realistic shop floor conditions. It was observed that the machining using Ti-coated ceramic under cryogenic jet may reduce the total tooling cost compared to CBN cutting tool conducted under dry conditions.

Additive manufacturing, also known as three-dimensional (3D) printing, is an approach in which a structure may be fabricated layer by layer. For 3D inkjet printing, droplets are ejected from a nozzle and each layer is formed droplet by droplet. Inkjet printing has been widely applied for the fabrication of 3D biological gel structures, but the knowledge of the microscale interactions between printed droplets is still largely elusive. This study aims to elucidate the alginate layer formation process during drop-on-demand inkjet printing using high speed imaging and particle image velocimetry. Droplets are found to impact, spread, and coalesce within a fluid region at the deposition site, forming coherent printed lines within a layer. Interfaces are found to form between printed lines within a layer depending on printing conditions and printing path orientation. The effects of printing conditions on the behavior of droplets during layer formation are discussed and modeled based on gelation dynamics, and recommendations are presented to enable controllable and reliable fabrication of gel structures.

In this study, we investigated the mechanical properties of AZ31B Mg alloy before and after laser shock peening (LSP). The hardness of the AZ31B Mg alloy increased from 57 HV to 69 HV after LSP. The yield strength increased from 128 MPa to 152 MPa. Wear resistance was significantly improved after LSP. Immersion testing showed that LSP did not significantly increase the element release and weight loss in simulated body fluid. We have demonstrated that LSP is an effective way to improve the mechanical properties of the AZ31B Mg alloy.