Research Papers

J. Manuf. Sci. Eng. 2016;139(4):041001-041001-6. doi:10.1115/1.4034630.

In this paper, we develop and apply feature extraction and selection techniques to classify tool wear in the gear shaving process. Because shaving tool condition monitoring is not well-studied, we extract both traditional and novel features from accelerometer signals collected from the shaving machine. We then apply a heuristic feature selection technique to identify key features and classify the tool condition. Run-to-life data from a shop-floor application is used to validate the proposed technique.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041002-041002-7. doi:10.1115/1.4034890.

To enhance mechanical and/or electrical properties of composite materials used in additive manufacturing, nanoparticles are oftentimes deposited to form nanocomposite layers. To customize the mechanical and/or electrical properties of the final composite material, the thickness of such nanocomposite layers must be precisely controlled. A thickness model for filter cakes created through spray-assisted vacuum filtration is presented in this paper, to enable the development of advanced thickness controllers. The mass transfer dynamics in the spray atomization and vacuum filtration are studied to derive solid mass, water mass, and filter cake thickness differential area models. A two-loop nonlinear constrained optimization approach is used to identify the unknown parameters in the model. Experiments involving depositing carbon nanofibers in a sheet of filter paper are used to measure the ability of the model to mimic the filtration process.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041003-041003-11. doi:10.1115/1.4034792.

Free abrasive diamond wire saw machining is often used to cut hard and brittle materials, especially for wafers in the semiconductor and optoelectronics industries. Wire saws, both free and fixed abrasive, have excellent flexibility, as compared to inner circular saws, outer saws, and ribbon saws, as they produce a narrower kerf, lower cutting forces, and less material waste. However, fixed abrasive wire saw machining is being considered more and more due to its potential for increased productivity and the fact that it is more environmentally friendly as it does not use special coolants that must be carefully disposed. The cutting forces generated during the wire saw process strongly affect the quality of the produced parts. However, the relationship between these forces and the process parameters has only been explored qualitatively. Based on analyzing the forces generated from the chip formation and friction of a single abrasive, this study derives an analytical cutting force model for the wire saw machining process. The analytical model explains qualitative observations seen in the literature describing the relationship between the cutting forces and the wafer feed rate, wire velocity, and contact length between the wire and wafer. Extensive experimental work is conducted to validate the analytical force model. Silicon carbide (SiC) monocrystal, which is employed extensively in the fields of microelectronics and optoelectronics and is known to be particularly challenging to process due to its extremely high hardness and brittleness, is used as the material in these experimental studies. The results show that the analytical force model can predict the cutting forces when wire saw machining SiC monocrystal wafers with average errors between the experimental and predicted normal and tangential forces of 9.98% and 12.1%, respectively.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041004-041004-10. doi:10.1115/1.4034891.

Laser peen forming (LPF) is a promising method to fabricate fiber metal laminates (FMLs) with its design flexibility to produce complex shapes. Eigenstrain-based modeling is a helpful method to predict deformation after LPF, while determining eigenstrain is very difficult because of its complex constituents and high-dynamic loading of process. An effective experiment-based method is proposed in this work to obtain eigenstrain induced by LPF in metal layers of FMLs. An analytical beam model is developed to relate the deflection profile generated by specific scanning strategy to equivalent bending moment. Based on the determined bending moment from the measured deflection profiles, the generated eigenstrain can be inversely calculated by the proposed beam model describing the relationship between the eigenstrain and the bending moment. Chemical etching to remove sheets layer by layer is used to obtain the relaxed deflection profile to calculate the eigenstrain in each metal layer. Furthermore, an approximate model of plate is established to predict deformation after LPF based on determined eigenstrain. The results show that the predictive deformed shape agrees very well with both experiments and finite model prediction.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041005-041005-6. doi:10.1115/1.4034712.

Graphene nanoplatelets (GNPs) have many outstanding properties, such as high mechanical strengths, light weight, and high electric conductivity. These unique properties make it an ideal reinforcement used for metal matrix composites (MMCs). In the past few years, many studies have been performed to incorporate GNPs into metal matrix and investigate the properties of obtained metal matrix composites. Meanwhile, fabrication of MMCs through laser-assisted additive manufacturing (LAAM) has attracted much attention in recent years due to the advantages of low waste, high precision, short production lead time, and high workpiece complexity capability. In this study, the two attractive features are combined to produce GNPs reinforced MMC using selective laser melting (SLM) process, one of the LAAM processes. The target metal matrix material is Inconel 718, a nickel-based Ni–Cr–Fe austenitic superalloy that possesses excellent workability and mechanical performance, and has wide applications in industries. In the experiment, pure Inconel 718 and GNPs reinforced Inconel 718 composites with two levels of GNPs content (i.e., 0.25 and 1 wt. %) are obtained by SLM. Note that before the SLM process, a novel powder mixture procedure is employed to ensure the even dispersion of GNPs in the Inconel 718 powders. Room temperature tensile tests are conducted to evaluate the tensile properties. Scanning electron microscopy (SEM) observations are conducted to analyze the fracture surface of materials and to understand the reinforcing mechanism. It is found that fabrication of GNPs reinforced MMC using SLM is a viable approach. The obtained composite possesses dense microstructure and significantly enhanced tensile strength. The ultimate tensile strengths (UTSs) are 997.8, 1296.3, and 1511.6 MPa, and the Young's moduli are 475, 536, and 675 GPa, for 0 wt. % (pure Inconel 718), 0.25 wt. %, and 1 wt. % GNP additions, respectively. The bonding between GNPs and matrix material appears to be strong, and GNPs could be retained during the SLM process. The strengthening effect and mechanisms involved in the composites are discussed. Load transfer, thermal expansion coefficient mismatch, and dislocation hindering are believed to be the three main reinforcing mechanisms involved. It should be noted that more work needs to be conducted in the future to obtain more comprehensive information regarding other static and dynamic properties and the high-temperature performances of the GNP-reinforced MMCs produced by SLM. Process parameter optimization should also be investigated.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041006-041006-6. doi:10.1115/1.4034668.

This paper studies the loading–unloading behaviors of a three-dimensional (3D)-printing built bimaterial structure consisting of an open-cellular plaster frame filled with silicone. The combination of the plaster (ceramic phase) and silicone (elastomer phase) is hypothesized to possess a nonlinearly elastic property and a better ductility. Four-point bending tests with programmed cycles of preceding deformations were conducted. The results show that there exists a linear–nonlinear transition when the bending deflection is around 2 mm in the first cycle bending. As the cycle proceeds, this linear–nonlinear transition is found at the maximum deflection of the previous cycle; meanwhile, the bending stiffness degrades. It is believed that the occurrence of microcracks inside the plaster frame is the mechanism behind the phenomenon. The silicone provides a strong network suppressing the abrupt crack propagation in a brittle material. The effects of the frame structure and plaster–silicone ratio were also compared. A high plaster content and large cell size tend to have a higher stiffness and obvious linear to nonlinear transition while it also has more significant stiffness degradation.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041007-041007-9. doi:10.1115/1.4034888.

Failure analysis of tensile-shear tested bonded composite-based single lap joints (SLJs) that have been subjected to two different levels of cyclic environmental loading is provided. Each test joint has at least one composite adherend which is made of glass fiber-reinforced polymer (GFRP); the second adherend may be aluminum, magnesium, or GFRP composite, and structural epoxy adhesive is used to join two adherends together for creating test joints. Scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) are utilized to investigate the root cause failure of fractured surfaces that gives an insight into the recently published data that showed a significant effect of the cyclic heat on the static load transfer capacity (LTC) of the same SLJs. The SEM and EDS inspections show that the failure mode shifts from interfacial adhesive failure (ADH) to fiber tear (FT) for the GFRP/GFRP joints that have been exposed to cyclic heat with and without high relative humidity as compared to that at ambient condition. Further, failure analysis and discussion are provided.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041008-041008-10. doi:10.1115/1.4034893.

Laser drilling of alumina is a noncontact material processing method, which has great advantages over the traditional mechanical machining. However, the quality of laser drilling is still a challenge. In this study, a 2D transient model is developed to simulate the underwater laser drilling of alumina, considering the recoil pressure which is generated by adjusting the density of water. The distributions of the temperature, pressure, and velocity during the drilling process are examined. The numerical results show that the underwater-drilled hole with smaller taper is obtained compared with that in air, which is attributed to the recoil pressure, higher specific heat capacity, and heat transfer coefficient of water. The experimental results validate the phenomenon in numerical simulation.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041009-041009-9. doi:10.1115/1.4034894.

This paper describes the use of subharmonic sampling to distinguish between different instability types in milling. It is demonstrated that sampling time-domain milling signals at integer multiples of the tooth period enables secondary Hopf and period-n bifurcations to be automatically differentiated. A numerical metric is applied, where the normalized sum of the absolute values of the differences between successively sampled points is used to distinguish between the potential bifurcation types. A new stability map that individually identifies stable and individual bifurcation zones is presented. The map is constructed using time-domain simulation and the new subharmonic sampling metric.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041010-041010-11. doi:10.1115/1.4034681.

The robotic riveting system requires a rivet robotic positioning process for rivet-in-hole insertions, which can be divided into two stages: rivet path-following and rivet spot-positioning. For the first stage, varying parameter-linear sliding surfaces are proposed to achieve robust rivet path-following against robot errors and external disturbances of the robotic riveting system. For the second stage, a second-order sliding surface is applied to attain accurate rivet spot-positioning within a finite time required by the riveting process. In order to improve the dynamic performance of the robot riveting system, the motion of robot end-effector between the two adjacent riveting spots has been properly designed. Overall, the proposed control scheme can guarantee not only the stability of the robot control system but also the robust rivet path-following and quick rivet spot-positioning in the presence of the robot errors and external disturbances of the robotic riveting system. The simulation and experimental results demonstrate the effectiveness of the proposed control scheme.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041011-041011-8. doi:10.1115/1.4034713.

A polyacrylonitrile (PAN)-based carbon fiber (CF) manufacturing cost estimation model driven by mass is presented in this study. One of the biggest limiting factors in the large-scale use of carbon fiber (CF) in manufacturing is its high cost. The costs involved in manufacturing the carbon fiber have been formalized into a cost model in order to facilitate the understanding of these factors. This can play a key role in manufacturing CF in a cost-effective method. This cost model accounts for the fixed and variable costs involved in all the stages of manufacturing, in addition to accounting for price elasticity.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041012-041012-11. doi:10.1115/1.4034670.

Little work has been done on quantifying the environmental impacts and costs of sheet metal stamping. In this work, we present models that can be used to predict the energy requirements, global warming potential, human health impacts, and costs of making drawn parts using zinc (kirksite) die-sets and hydraulic or mechanical presses. The methodology presented can also be used to produce models of stamping using other die materials, such as iron, for which casting data already exists. An unprecedented study on the environmental impacts and costs of zinc die-set production was conducted at a leading Michigan die-maker. This analysis was used in conjunction with electrical energy measurements on forming presses to complete cradle-to-gate impact and cost analyses on producing small batch size hood and tailgate parts. These case studies were used to inform a generalized model that allows engineers to predict the impacts and costs of forming based on as little information as the final part material, surface area, thickness, and batch size (number of units produced). The case studies show that the press electricity is an insignificant contributor to the overall impacts and costs. The generalized models highlight that while costs for small batch production are dominated by the die-set, the environmental impacts are often dominated by the sheet metal. These findings explain the motivation behind the research into die-less forming processes such as incremental sheet forming, and emphasize the need to minimize the sheet metal scrap generation in order to reduce environmental impacts.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041013-041013-12. doi:10.1115/1.4034933.

Energy prediction of machine tools can deliver many advantages to a manufacturing enterprise, ranging from energy-efficient process planning to machine tool monitoring. Physics-based energy prediction models have been proposed in the past to understand the energy usage pattern of a machine tool. However, uncertainties in both the machine and the operating environment make it difficult to predict the energy consumption of the target machine reliably. Taking advantage of the opportunity to collect extensive, contextual, energy-consumption data, we discuss a data-driven approach to develop an energy prediction model of a machine tool in this paper. First, we present a methodology that can efficiently and effectively collect and process data extracted from a machine tool and its sensors. We then present a data-driven model that can be used to predict the energy consumption of the machine tool for machining a generic part. Specifically, we use Gaussian process (GP) regression, a nonparametric machine-learning technique, to develop the prediction model. The energy prediction model is then generalized over multiple process parameters and operations. Finally, we apply this generalized model with a method to assess uncertainty intervals to predict the energy consumed by any part of the machine using a Mori Seiki NVD1500 machine tool. Furthermore, the same model can be used during process planning to optimize the energy-efficiency of a machining process.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041014-041014-13. doi:10.1115/1.4034934.

In this study, laser metal deposition (LMD) additive manufacturing was used to deposit the pure Inconel 625 alloy and the TiC/Inconel 625 composites with different starting sizes of TiC particles, respectively. The influence of the additive TiC particle and its original size on the constitutional phases, microstructural features, and mechanical properties of the LMD-processed parts was studied. The incorporation of TiC particles significantly changed the prominent texture of Ni–Cr matrix phase from (200) to (100). The bottom and side parts of each deposited track showed mostly the columnar dendrites, while the cellular dendrites were prevailing in the microstructure of the central zone of the deposited track. As the nano-TiC particles were added, more columnar dendrites were observed in the solidified molten pool. The incorporation of nano-TiC particles induced the formation of the significantly refined columnar dendrites with the secondary dendrite arms developed considerably well. With the micro-TiC particles added, the columnar dendrites were relatively coarsened and highly degenerated, with the secondary dendrite growth being entirely suppressed. The cellular dendrites were obviously refined by the additive TiC particles. When the nano-TiC particles were added to reinforce the Inconel 625, the significantly improved microhardness, tensile property, and wear property were obtained without sacrificing the ductility of the composites.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041015-041015-8. doi:10.1115/1.4035036.

Butt welding tests of 1.5 mm thickness Ti–6Al–4V were treated by conventional gas tungsten arc welding (C-GTAW) and ultrahigh frequency pulse GTAW (UHFP-GTAW). The low cycle fatigue (LCF) experiments were conducted on the welded joints. The results of fatigue experiment showed that the number of fatigue cycles was increased with UHFP-GTAW. Changes in the microstructure resulting from reduced heat input were expected to enhance the fatigue propagation resistance. The morphology of the martensites in fusion zone was smaller compared to C-GTAW process, and a larger distribution density of basketweave structure was also obtained by UHFP-GTAW. Furthermore, the decreased fatigue crack rate was accompanied as the increased grain boundaries produced by the reduced grain size in fusion zone. Observation of fatigue fractographs revealed that the UHFP-GTAW has obvious slip traces at fatigue initiation sites and more deep secondary cracks in the crack propagation regions associated with the smaller dimples of final fracture zones. The proportion of propagation regions was much larger than C-GTAW. As a result, it can be considered as the representation of the improvement in ductility.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):041016-041016-14. doi:10.1115/1.4035034.

The successful joining of dissimilar metal tubes would enable the selective use of the unique properties exhibited by biocompatible materials such as stainless steel and shape memory materials, such as NiTi, to locally tailor the properties of implantable medical devices. The lack of robust joining processes for the dissimilar metal pairs found within these devices, however, is an obstacle to their development and manufacture. Traditional joining methods suffer from weak joints due to the formation of brittle intermetallics or use filler materials that are unsuitable for use within the human body. This study investigates a new process, Laser Autogenous Brazing, that utilizes a thermal accumulation mechanism to form joints between dissimilar metals without filler materials. This process has been shown to produce robust joints between wire specimens but requires additional considerations when applied to tubular parts. The strength, composition, and microstructure of the resultant joints between NiTi and stainless steel are investigated and the effects of laser parameters on the thermal profile and joining mechanism are studied through experiments and numerical simulations.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(4):041017-041017-8. doi:10.1115/1.4035719.

Torque influences the main phenomena that occur during friction stir welding (FSW) process. However, models for torque have received little attention. In this paper, inverse problem method is used to estimate the parameters for a model for torque, measured during FSW experiments for different combinations of rotational and welding speeds. The experimental results are used as input data to estimate the model parameters. The results showed a good agreement between the experimental data and the model obtained using the inverse problem method. The influence of the tool geometry on torque was observed by comparing previously published experimental results and the experimental data presented.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(4):041018-041018-11. doi:10.1115/1.4035421.

As an important feature of cutting tools, flutes determine rake faces of their cutting edges, their rigidity, chip breaking, and chip space. In industry, flutes are often ground with standard wheels of simple shape (e.g., 1A1 or 1V1 wheels), resulting in flutes without much variation. To make flutes of more complex shape, standard wheels of complex shape (e.g., 1B1, 1E1, 1F1, and 4Y1 wheels), compared to the current ones, should be used. Unfortunately, current commercial software cannot calculate the locations and orientations of these wheels; this is why they are not used to machine flutes. Moreover, grinding wheels are gradually worn out in use, and the flutes lose accuracy accordingly. Therefore, locations and orientations of the worn wheels should be recalculated or compensated in machining; however, no such technique is currently available. To address this challenge, a generic and efficient approach to determining the locations and orientations of complex standard and worn wheels for cutter flute grinding is proposed in this work. First, a parametric equation of the generic wheel surface and its kinematic equation in five-axis flute grinding are rendered. Second, virtual grinding curves are proposed and defined to directly represent the relationships between wheel location and orientation and the flute profile in a geometric way. Then, the characteristics of the virtual grinding curves are investigated and formulated, and a new model of the generic wheel location and orientation is established. Compared to the existing comparative model, this model significantly increases solution liability and computation efficiency. Finally, three practical cases are studied and discussed to validate this approach. This approach can be used to make flutes of more complex shape and can increase flute accuracy by compensating the locations and orientations of worn wheels in machining.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2017;139(4):041019-041019-11. doi:10.1115/1.4035468.

As one of emerging novel surface treatment techniques, laser polishing offers a cost-effective and efficient solution to reduce surface roughness of precision components at micro-/mesoscale. Although it has been applied for industrial and biomedical purposes, the underlying mechanism has not been fully revealed. This paper presents a study to understand the basic fundamentals of continuous wave fiber laser polishing of Ti6Al4V samples. A two-dimensional numerical model that coupled heat transfer and fluid flow is developed to illustrate the molten flow behavior. The roles of capillary and thermocapillary flow in the process of laser polishing are investigated to assist the understanding of the contributions of surface tension (capillary force) and Marangoni effect (thermocapillary force) in the polishing process. Capillary force dominates the molten pool at the initial stage of melting, while thermocapillary force becomes predominant when the molten pool fully develops.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Manuf. Sci. Eng. 2016;139(4):044501-044501-5. doi:10.1115/1.4034889.

Metal working fluid (MWF) emulsions are utilized as coolants and lubricants in machining processes like turning or drilling. During their operation life time cycle, MWFs change their properties due to impacting stresses which may influence the machining and tool performance. A frequent refreshing or renewal of MWFs in machining process is thus necessary. This investigation discusses measurement techniques of MWF emulsions to be used for MWF quality assessment and process monitoring. By means of optical spectroscopic measurement techniques (turbidimetry and laser diffraction), the evaluation of the temporal change of the wavelength exponent and the MWF emulsion droplet size is related to the MWF stability. The in-process monitoring of the MWFs in machining during several weeks of operation is shown. Thus, it will be demonstrated that optical spectroscopic measurement techniques may be applied to determine stability change of the emulsion system.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2016;139(4):044502-044502-4. doi:10.1115/1.4034887.

Traditional quality control of resistance spot welds by analysis of the dynamic resistance signature (DRS) relies on manual feature selection to reduce the dimensionality prior to analysis. Manually selected features of the DRS may contain information that is not directly correlated to strength, reducing the accuracy of any classification performed. In this paper, correlations between the DRS and weld strength are automatically detected by calculating correlation coefficients between weld strength and principal components of the DRS. The key features of the DRS that correlate to weld strength are identified in a systematic manner. Systematically identifying relevant features of the DRS is useful as the correlations between weld strength and DRS may vary with process parameters.

Commentary by Dr. Valentin Fuster

Design Innovation Paper

J. Manuf. Sci. Eng. 2016;139(4):045001-045001-12. doi:10.1115/1.4034623.

The production of freeform components is challenging, not only from the point of view of process optimization but also when it comes to the selection and design of the fixturing systems. Currently, most commercially available fixturing systems are difficult to conform to geometrically complex components; while the systems that manage to provide industrially feasible solutions (such as encapsulation techniques) present several limitations (e.g., high complexity, limited reliability, and risk of elastic deformation of the part). In this context, the present work proposes a simple, yet efficient, concept of a fixture capable of holding complex components through the use of compliant/deformable diaphragm elements. The fundaments of this innovative system (i.e., freeform diaphragm-based fixturing system) have been simulated through an experimentally validated finite-element (FE) model, with results showing a good agreement between numerical and measured data (displacement average error ϵav = 4.04%). The main interactions of the system with a workpiece (e.g., contact area and clamping force) have been numerically and experimentally studied, confirming the system's capacity to generate distributed clamping forces in excess of 1000 N. Based on the modeling activities, an advanced prototype for holding a “generic” freeform component was developed. Using this prototype, a repeatability study then showed the capacity of the system to deterministically position and hold complex geometries. Finally, the proposed fixturing system was thoroughly evaluated under demanding machining conditions (i.e., grinding), and the results showed the ability of the fixture to maintain small part displacement (dx < 10 μm) when high cutting forces are applied (Max. FR = 1021.24 N). Design limitations were observed during the grinding experiments, and the lineaments are presented in order to develop improved further prototypes. Overall, the proposed fixturing approach proved to be a novel and attractive industrial solution for the challenges of locating/holding complex components during manufacture.

Commentary by Dr. Valentin Fuster

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