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Research Papers

J. Manuf. Sci. Eng. 2016;139(3):031001-031001-13. doi:10.1115/1.4033928.

Cutting stress field in machining process plays a significant role in the understanding of cutting mechanics and prediction of surface integrity, tool wear, and failure. It is in great need to get accurate and reliable cutting stresses in the chip formation zone. In this paper, a new methodology to obtain the cutting stress field is proposed. The deformation field containing elastic as well as plastic parts can be obtained via digital image correlation (DIC) technique. The orthogonal cutting stress field can be obtained with the experimental determined deformation field and material constitutive model as inputs. However, the challenge is to handle the inaccuracy of infinitesimal elastic deformation involved in the total deformation due to the inaccuracy of the obtained images. We develop a method to modify the hydrostatic pressure field based on mechanical equilibrium equations to compensate the inaccuracy of elastic deformation part. Besides, Eulerian logarithmic strain based on a least square plane fit on a subset of displacement data is adopted to reduce the image noise. The stress distribution along the shear plane and tool–chip interface can be extracted and integrated to calculate cutting forces. A feasibility study is performed by comparing the cutting forces predicted based on this new method against the experimental measurements. The comparison of cutting parameters obtained through DIC technique with finite element method (FEM) predictions is also made.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031002-031002-14. doi:10.1115/1.4034476.

On-the-fly laser machining is defined as a process that aims to generate pockets/patches on target components that are rotated or moved at a constant velocity. Since it is a nonintegrated process (i.e., linear/rotary stage system moving the part is independent of that of the laser), it can be deployed to/into large industrial installations to perform in situ machining, i.e., without the need of disassembly. This allows a high degree of flexibility in its applications (e.g., balancing) and can result in significant cost savings for the user (e.g., no dis(assembly) cost). This paper introduces the concept of on-the-fly laser machining encompassing models for generating user-defined ablated features as well as error budgeting to understand the sources of errors on this highly dynamic process. Additionally, the paper presents laser pulse placement strategies aimed at increasing the surface finish of the targeted component by reducing the area surface roughness that are possible for on-the-fly laser machining. The overall concept was validated by balancing a rotor system through ablation of different pocket shapes by the use of a Yb:YAG pulsed fiber laser. In this respect, first, two different laser pulse placement strategies (square and hexagonal) were introduced in this research and have been validated on Inconel 718 target material; thus, it was concluded that hexagonal pulse placement reduces surface roughness by up to 17% compared to the traditional square laser pulse placement. The concept of on-the-fly laser machining has been validated by ablating two different features (4 × 60 mm and 12 × 4 mm) on a rotative target part at constant speed (100 rpm and 86 rpm) with the scope of being balanced. The mass removal of the ablated features to enable online balancing has been achieved within < 4 mg of the predicted value. Additionally, the error modeling revealed that most of the uncertainties in the dimensions of the feature/pocket originate from the stability of the rotor speed, which led to the conclusion that for the same mass of material to be removed it is advisable to ablate features (pockets) with longer circumferential dimensions, i.e., stretched and shallower pockets rather than compact and deep.

Topics: Lasers , Machining , Errors
Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031003-031003-12. doi:10.1115/1.4034593.

At the end of roll-to-roll (R2R) manufacturing process machines, the web substrate must be wound into rolls. Winding is the only means known to store and protect vast lengths of very thin webs for subsequent processing. Web thickness variation in wound rolls is a root cause of large manufacturing loss due to residual stress-related defects. Minute thickness variations down the length and across the web width can induce large residual stress variations and defects within the roll. Winding models allow the exploration of winding residual stresses whose variation has been affected by web thickness or coating imperfections. Knowledge of these stresses is used to mitigate manufacturing defects. Spot web thickness sensors are employed in R2R process lines that scan over the web width while the web is moving downstream through the process machine. Spatially, this provides a measure of web thickness in a zig-zag pattern. During manufacturing, the thickness variation is used as a control feedback parameter to manipulate a forming or coating die lip to reduce the web or coated web thickness variation. The thickness variation acceptable in process may be very different than that which is acceptable based on the residual stresses in the wound roll. It will be determined whether the thickness test data captured spatially for process feedback are sufficient to characterize the residual stresses in the wound roll. A winding model will be developed and verified that is used to characterize these residual stresses.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031004-031004-10. doi:10.1115/1.4034718.
OPEN ACCESS

This study reports an experimental investigation for the shallow angle laser drilling of Inconel 718. In this study, a helical laser drilling technique was used to effectively produce holes with a diameter of several hundred microns. The design of experiment (DOE) using the Taguchi method was employed to examine the influence of various process parameters on the geometrical and metallurgical features of drilled holes. A higher laser power, lower speed, and closer focal position to the workpiece surface contributed to the further removal of material by the absorption of more laser energy and larger beam intensity. This resulted in a larger exit hole diameter and less hole taper. The increase in laser power reduced a thickness of the recast layer due to material removal by vaporization. From the DOE result, a regression model to estimate a correlation between experimental factors and hole quality was also suggested. In the second stage of this study, trials to improve drilling performance were made. Using the O2 assist gas of 50 kPa significantly enhanced the drilling performance owing to the delivery of more energy to the workpiece by an exothermic reaction. However, the further increase of O2 gas caused rapid cooling of the workpiece, which lowered the drilling performance. The drilling performance was greatly improved as well using the high laser duty cycle to provide more laser energy. The moving focal position was only beneficial to the drilling performance when a focusing of the beam was moderately maintained on the interaction region of the laser–workpiece.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031005-031005-10. doi:10.1115/1.4034717.

The objective of this study is to investigate hydraulic bulge test in double layer sheets, which is based on experimental tests, analytical investigation, and numerical method. Bulge test due to creating plane stress condition on test sheet is extremely similar to sheet metal forming processes, such as hydroforming, stamping, and deep drawing. The results of the bulge test are more accurate and practical for analyzing the sheet forming process than tensile test. In multilayer sheets, the diverse properties of the constituent layers cause favorable properties on multilayer sheets, such as low weight, high strength, better ductility and corrosion resistance, and good thermal and electrical properties at the same time. For these reasons, multilayer sheets are highly useful in automotive, aviation, and chemical industries. Therefore, the necessity of investigating mechanical properties and formability in multilayer sheets is crucially important. During this study, the hydraulic bulge test has been investigated thoroughly, and then accurate analytical relations have been developed for bulge test in double layer Al–Cu sheet. In addition, the hydraulic bulge test in double layer sheets has been investigated by FEM. Finally, analytical and FE results have been verified by experimental tests. The results from the experimental tests are in good consistency with the extracted analytical relations and numerical method in the bulge test of double layer sheets.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031006-031006-7. doi:10.1115/1.4034494.

In this work, a research on double-direction pressure distributions (DDPD) induced by vaporizing a single metal foil was conducted. The shock pressure in the up direction revealed the same amplitude as that in the down direction. Based on a comparison of pressure amplitudes between double-direction pressure distributions (DDPD) and single-direction pressure distributions (SDPD), the pressure upward in DDPD was found to be smaller than that in SDPD. In addition, an approach to vary the pressure amplitudes in the up and down directions in DDPD was introduced. Using polyurethane plates in different thicknesses leads to various pressure amplitudes on both sides of the foil specimen. Finally, the application of DDPD in metal forming process was examined. A profile forming part with two bulging zones was successfully manufactured.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031007-031007-6. doi:10.1115/1.4034624.

Several biosystems such as leaf veins, respiratory system, blood circulation, and some plant xylem involving multiscale fractal topologies are being mimic for their inherent natural optimization. Three-dimensional fractal structures spanning multiple scales are difficult to fabricate. In this paper, we demonstrate a new method to fabricate structures spanning meso- and microscale in a relatively easy and inexpensive manner. A well-known Saffman–Taylor instability is exploited for the same in a lifted Hele-Shaw cell. In this cell, a thin layer of liquid is squeezed between two plates being lifted angularly leaving behind the fractal rearrangement of fluid which is proposed to be solidified later. We demonstrate and characterize fractal structures fabricated using two different fluids and corresponding methods of solidification. The first one is ceramic suspension in a photopolymer and another is polystyrene solution with photopolymerization and solvent vaporization as methods of solidification, respectively. The fabrication process is completed in period of a few seconds.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031008-031008-10. doi:10.1115/1.4034622.

Cylindricity of engine cylinder bore is identified as one of the crucial factors to exert great influence on engine performance including piston friction and wear, energy consumption, and gas emission. Cylindricity at macroscopic level as well as surface roughness at microscopic level such as peak roughness, core roughness, and valley roughness of engine cylinder bore is typically generated by honing operations. However, the selection of the process parameters of honing is currently based on empirical methods since honing is mechanically complex process. It thus makes a significance to analytically investigate honing operation to effectively improve the cylindricity of engine cylinder bore based on its functional requirements. This research aims to explore the methodology on achieving the desired cylindricity for engine cylinder bore through several approaches including simulating honing motion trajectory, improving honing head structure, coordinating cylinder bore honing with its previous boring operation, and optimizing honing parameters such as honing velocity, stroke speed, and overrunning distance. The research presents a systematical thinking to achieve macrogeometrical features in the honing of engine cylinder bore and a theoretical approach for the successful selection and optimization of honing process parameters.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031009-031009-8. doi:10.1115/1.4034791.

With the evolution of modern warfare, there is a constant demand for enhanced soldier protection. The research efforts presented in this paper focus on improving the ballistic performance of composite combat helmets through the control of fiber orientations, reduction of seam density, and preservation of long fiber lengths. To accomplish these objectives, near-net-shape preforming is explored as an alternative method to the traditional cut and dart techniques used in the manufacture of combat helmets. An overview of current fabrication procedures is provided in addition to a discussion of the material selection and preform processing technique. Forming trials are conducted on Dyneema® HB80, a cross-ply thermoplastic lamina, using a laboratory deep-draw setup to explore the effects of processing parameters on the quality of the formed part. Undesirable wrinkling that manifests during deep-drawing of the material is found to be most effectively mitigated through the use of sufficient binder pressure. Furthermore, it is demonstrated that a loose ply stack up is more amenable to the production of high-quality preforms than a preconsolidated charge of material.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031010-031010-10. doi:10.1115/1.4034662.
OPEN ACCESS

In this paper, both software model visualization with path simulation and associated machining product are produced based on the step ring-based three-axis path planning to demo model-driven graphics processing unit (GPU) feature in tool path planning and 3D image model classification by GPU simulation. Subtractive 3D printing (i.e., 3D machining) is represented as integration between 3D printing modeling and computer numerical control (CNC) machining via GPU simulated software. Path planning is applied through visualization of surface material removal in high-resolution and 3D path simulation via ring selective path planning based on accessibility of path through pattern selection. First, the step ring selects critical features to reconstruct computer-aided design (CAD) design model as stereolithography (STL) voxel, and then, local optimization is attained within interested ring area for time and energy saving of GPU volume generation as compared to global automatic path planning with longer latency. The reconstructed CAD model comes from an original sample (GATech buzz) with 2D image information. CAD model for optimization and validation is adopted to sustain manufacturing reproduction based on system simulation feedback. To avoid collision with the produced path from retraction path, we pick adaptive ring path generation and prediction in each planning iteration, which may also minimize material removal. Moreover, we did partition analysis and G-code optimization for large-scale model and high density volume data. Image classification and grid analysis based on adaptive 3D tree depth are proposed for multilevel set partition of the model to define no cutting zones. After that, accessibility map is computed based on accessibility space for rotational angular space of path orientation to compare step ring-based pass planning verses global path planning of all geometries. Feature analysis via central processing unit (CPU) or GPU processor for GPU map computation contributes to high-performance computing and cloud computing potential through parallel computing application of subtractive 3D printing in the future.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031011-031011-7. doi:10.1115/1.4034663.
OPEN ACCESS

In this paper, techniques of direct printing of capacitive touch sensors on flexible substrates are presented. Capacitive touch sensors were fabricated by using electrohydrodynamic inkjet (E-jet) printing onto flexible substrates. Touch pad sensors can be achieved with optimized design of silver nanoink tracks. An analytical model was developed to predict touch pad capacitance, and experiments were conducted to study the effects of sensor design (e.g., number of electrodes, electrode length, and electrode distance) on the capacitance of printed coplanar capacitance touch sensors. Details of the fabrication techniques were developed to enable rapid prototype flexible sensors with simple structure and good sensitivity. The presented techniques can be used for the on-demand fabrication of different conductive patterns for flexible electronics with high resolution and good transparency

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031012-031012-7. doi:10.1115/1.4034664.

As American vehicle fuel efficiency requirements have become more stringent due to the CAFE standards, the auto industry has turned to fiber reinforced polymer composites as replacements for metal parts to reduce weight while simultaneously maintaining established safety standards. Furthermore, these composites may be easily processed using established techniques such as injection molding and compression molding. The mechanical properties of these composites are dependent on, among other variables, the orientation of the fibers within the part. Several models have been proposed to correlate fiber orientation with the kinematics of the polymer matrix during processing, each using various strategies to account for fiber interactions and fiber flexing. However, these all require the use of empirical fitting parameters. Previous work has obtained these parameters by fitting to orientation data at a specific location in an injection-molded part. This ties the parameters to the specific mold design used. Obtaining empirical parameters is not a trivial undertaking and adds significant time to the entire mold design process. Considering that new parameters must be obtained any time some aspect of the part or mold is changed, an alternative technique that obtains model parameters independent of the mold design could be advantageous. This paper continues work looking to obtain empirical parameters from rheological tests. During processing, the fiber–polymer suspension is subjected to a complex flow with both shear and extensional behavior. Rather than use a complex flow, this study seeks to isolate and compare the effects of shear and extension on two orientation models. To this end, simple shear and planar extension are employed, and the evolution of orientation from a planar random initial condition is tracked as a function of strain. Simple shear was imparted using a sliding plate rheometer designed and fabricated in-house. A novel rheometer tool was developed and fabricated in-house to impart planar extension using a lubricated squeeze flow technique, where a low-viscosity Newtonian lubricant is applied to the solid boundaries to minimize the effect of shearing due to the no-slip boundary condition. The Folgar–Tucker model with a strain reduction factor is used as a rigid fiber model and compared against a bead–rod model (a semiflexible model) proposed by Ortman. Both models are capable of predicting the data, with the bead–rod model performing slightly better. Orientation occurs at a much faster rate under startup of planar extension and also attains a much higher degree of flow alignment when compared with startup of steady shear.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031013-031013-8. doi:10.1115/1.4034594.

Automotive industries are very much interested in implementing warm forming technology for fabrication of light weight auto-body panels using aluminum alloys without localized thinning or splitting. A nonheat treatable and low formable AA5754-H22 aluminum alloy sheet was selected in the present work, and a laboratory scale warm deep drawing test set-up and process sequences were designed to improve material flow through independent heating of punch and dies. Significant enhancement in cup depth was observed when the temperature of punch and dies were set to 30 °C and 200 °C, respectively. Thermo-mechanical finite-element (FE) model of the nonisothermal deep drawing test was developed successfully to study the improvement in material flow incorporating Barlat-89 yield theory using temperature dependent anisotropy coefficients and Cowper–Symonds hardening model. It was found that a nonisothermal temperature gradient of approximately 93 °C was established within the blank from the center to flange at the start of deformation, and subsequent evolution of temperature gradient helped in improving material flow into the die cavity. The effect of temperature gradient on forming behavior in terms of cup height, ear profile, and thinning development across flange, cup wall, and blank center were predicted and validated with experimental results.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031014-031014-8. doi:10.1115/1.4034665.

It is often desired to increase the machining rate while maintaining the desired surface and subsurface integrity during fabricating high-quality optical glass components. This paper proposed a high-speed high-efficiency low-damage grinding technology for machining brittle optical materials, which consists of three grinding processes: rough grinding, semifinishing grinding, and finishing grinding. Grinding characteristics are investigated with respect to grinding forces, specific cutting energy, surface roughness, ground surface quality, subsurface damage, and material removal mechanisms in grinding of fused silica optical glasses with this technology at grinding speeds of up to 150 m/s. These indications are thoroughly discussed by contacting the undeformed chip thickness. The results indicate that the level of these indications is significantly improved with an increase in the wheel speed due to the decrease of the undeformed chip thickness. It is also found that the improvement of ground surface quality is limited when the wheel speed increases from 120 m/s to 150 m/s, which may be due to the influence of vibration caused by the higher wheel speed. For different grinding processes, these results are also substantially improved with the change of grinding conditions. It is found that the material removal mechanism is dominated by brittle fracture at rough and semifinishing grinding processes, while ductile flow mode can be observed at the finishing grinding process. There are some differences between the experimental results and the previous predicted model of subsurface damage depth.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031015-031015-9. doi:10.1115/1.4034666.
OPEN ACCESS

Porous structure has wide application in industry due to some of its unique properties such as low density, low thermal conductivity, high surface area, and efficient stress transmission. Both templating and foaming agent methods have been used to fabricate porous structures. However, these methods can only fabricate simple geometries. In recent years, many studies have been done to use additive manufacturing (AM), e.g., stereolithography apparatus (SLA), in the fabrication of porous structure; however, the porosity that can be achieved is relatively small due to the limited accuracy in building microscale features on a large area. This paper presents a projection-based SLA process to fabricate porous polymer structures using sugar particles as the foaming agent. With a solid loading of 50 wt.% of sugar in photocurable resin, the method can achieve a structure with much higher porosity. As shown in our results, the method can increase the porosity of fabricated scaffold structures by two times when compared to the current SLA method.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031016-031016-9. doi:10.1115/1.4034669.

Graphene is one of the most promising carbon nanomaterial due to its excellent electrical, thermal, optical, and mechanical properties. However, it is still very challenging to unlock its exotic properties and widely adopt it in real-world applications. In this paper, we introduce a new three-dimensional (3D) graphene structure printing approach with pure graphene oxide (GO) material, better interlayer bonding, and complex architecture printing capability. Various parameters related to this novel process are discussed in detail in order to improve the printability, reliability, and accuracy. We have shown that the print quality largely depends on the duty cycle of print head, applied pressure, and traveling velocity during printing. A set of printed samples are presented to demonstrate the effectiveness of the proposed technique along with the optimal parameter settings. The proposed process proves to be a promising 3D printing technique for fabricating multiscale nanomaterial structures. The theory revealed and parameters investigated herein are expected to significantly advance the knowledge and understanding of the fundamental mechanism of the proposed directional freezing-based 3D nano printing process. Furthermore, the outcome of this research has the potential to open up a new avenue for fabricating multifunctional nanomaterial objects.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):031017-031017-6. doi:10.1115/1.4034714.

Thermal shrinkage of the added material can distort the manufactured part and generate residual stresses. Experiments are carried out on growing the beams of rectangular cross section. The beams bend with formation of a concave top surface. The distortion is characterized by the curvature radius. The curvature radius significantly increases with the beam height, however, its variation with the layer thickness is within the experimental uncertainty. The proposed mathematical model assumes sequential addition of thermally expanded elastic layers. It explains the experiments and indicates the existence of finite limits for the stress and the deformation fields and the curvature radius at small layer thickness. The proposed model can be applied to predict residual stresses and deformations arising in complicated parts.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(3):031018-031018-8. doi:10.1115/1.4035215.

Metal foams can be fabricated through metallizing nonconductive polymer templates for better control of pore size, porosity, and interpore connectivity. However, the process suffers from a diffusion limit when the pore size is reduced to micro- and nanoscales. In this research, an electropolishing-assisted electroless deposition (EPAELD) process is developed to fabricate open-celled microcellular metal foams. To overcome the diffusion limit, a polishing current is applied in the electroless deposition process to remove metal on the surface of a polymer template, such that the ion-diffusion channels will remain open and the electroless deposition reaction continues deep inside the polymer template. In this paper, a process model of the proposed EPAELD technique is developed to understand the mechanism and to optimize the proposed process.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(3):031019-031019-9. doi:10.1115/1.4035539.

The advancement in the application of light alloys such as magnesium and titanium is closely related to the state of the art of joining them. As a new type of solid-phase welding, ultrasonic spot welding is an effective way to achieve joints of high strength. In this paper, ultrasonic welding was carried out on magnesium–titanium dissimilar alloys to investigate the influences of welding parameters on joint strength. The analysis of variance was adopted to study the weight of each welding parameter and their interactions. The artificial neural network (ANN) was used to predict joint strength. Results show that in ultrasonic welding of magnesium and titanium alloys, clamping force is the most significant factor, followed by vibration time and vibration amplitude; the interactions between vibration time and vibration amplitude, and between vibration amplitude and clamping force also significantly impact the strength. By using the artificial neural network, test data were trained to obtain a high precision network, which was used to predict the variations of joint strength under different parameters. The analytical model predicts that with the increase in vibration time, the increase in optimal joint strength is limited, but the range of welding parameters to obtain a higher joint strength increases significantly; the minimum joint strength increases as well; and the optimal vibration amplitude expands gradually and reaches the maximum when the vibration time is 1000 ms, then shifts toward the low end gradually.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(3):031020-031020-10. doi:10.1115/1.4034896.

In the 2.5D pocket machining, the pocket geometry (shape of the pocket) significantly affects the efficiency of spiral tool path in terms of tool path length, cutting time, surface roughness, cutting forces, etc. Hence, the pocket geometry is an important factor that needs to be considered. However, quantitative methods to compare different pocket geometries are scarcely available. In this paper, we have introduced a novel approach for quantitative comparison of different pocket geometries using a dimensionless number, “DN.” The concept and formula of DN are developed, and DN is calculated for various pocket geometries. A concept of percentage utilization of tool (PUT) is also introduced and is considered as a measure and an indicator for a good tool path. The guidelines for comparing pocket geometries based on DN and PUT are reported. The results show that DN can be used to predict the quality of tool path prior to tool path generation. Further, an algorithm to decompose pocket geometry into subgeometries is developed that improves the efficiency of spiral tool path for bottleneck pockets (or multiple-connected pocket). This algorithm uses another dimensionless number “HARIN” (HARI is the acronym of “helps in appropriate rive-lines identification” and suffix “N” stands for number) to compare parent pocket geometry with subgeometries. The results indicate that decomposing pocket geometry with the new algorithm improves HARIN and removes the effect of bottlenecks. Furthermore, the algorithm for decomposition is extended for pockets that are bounded by free-form curves.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Manuf. Sci. Eng. 2016;139(3):034501-034501-3. doi:10.1115/1.4034629.

Development of a robust and cost-effective method of joining dissimilar materials could provide a critical pathway to enable widespread use of multimaterial designs and components in mainstream industrial applications. The use of multimaterial components such as steel-aluminum and aluminum-polymer would allow design engineers to optimize material utilization based on service requirements and could often lead to weight and cost reductions. However, producing an effective joint between materials with vastly different thermal, microstructural, and deformation responses is highly problematic using conventional joining and/or fastening methods. This is especially challenging in cost sensitive, high volume markets that largely rely on low cost joining solutions. Friction stir scribe (FSS) technology was developed to meet the demands of joining materials with drastically different properties and melting regimes. The process enables joining of light metals like magnesium and aluminum to high temperature materials like steel and titanium. Viable joints between polymer composites and metal can also be made using this method. This paper will present the state of the art, progress made, and challenges associated with this innovative derivative of friction stir welding (FSW) in reference to joining dissimilar metals and polymer/metal combinations.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(3):034502-034502-5. doi:10.1115/1.4034790.

Research of the microtube hydroforming (MTHF) process is being investigated for potential medical and fuel cell applications. This is largely due to the fact that at the macroscale the tube hydroforming (THF) process, like most metal forming processes, has realized many advantages, especially when comparing products made using traditional machining processes. Unfortunately, relatively large forces compared to part size and high pressures are required to form the parts so the potential exists to create failed or defective parts. One method to reduce the forces and pressures during MTHF is to incorporate electrically assisted manufacturing (EAM) and electrically assisted forming (EAF) into the MTHF. The intent of both EAM and EAF is to use electrical current to lower the required deformation energy and increase the metal's formability. To reduce the required deformation energy, the applied electricity produces localized heating in the material in order to lower the material's yield stress. In many cases, the previous work has shown that EAF and EAM have resulted in metals being formed further than conventional forming methods alone without sacrificing the strength or ductility. Tests were performed using “as received” and annealed stainless steel 304 tubing. Results shown in this paper indicate that the ultimate tensile strength and bust pressures decrease with increased current while using EAM during MTHF. It was also shown that at high currents the microtubes experienced higher temperatures but were still well below the recrystallization temperature.

Commentary by Dr. Valentin Fuster

Expert View

J. Manuf. Sci. Eng. 2016;139(3):034701-034701-8. doi:10.1115/1.4034667.

Information technologies with their strong penetration can provide effective solutions for addressing the challenges faced by the manufacturing industry. Leveraging information technologies to enhance the competitiveness of the manufacturing industry has become a prominent trend worldwide. In this context, two important concepts for manufacturing—Industry 4.0 and cloud manufacturing—have been proposed. Industry 4.0 refers to the fourth industrial revolution, which is characterized by the widespread application of cyber-physical systems (CPS) in the manufacturing environment. Cloud manufacturing is a new service-oriented business paradigm based on the cloud concept and method. Since their inception, there has been a great deal of attention from both academia and industry. However, to date, they have largely been addressed in isolation. The fact is that, although being proposed from different perspectives and embracing different ideas, they each have some key features that can benefit one another. In order to better understand these two concepts, there is a need to compare them and clarify their relationship. To this end, this paper presents basic ideas of Industry 4.0 and cloud manufacturing, gives a brief overview of their current research, and provides a detailed comparative analysis of them from different perspectives.

Topics: Manufacturing
Commentary by Dr. Valentin Fuster

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