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Research Papers

J. Manuf. Sci. Eng. 2018;140(7):071001-071001-16. doi:10.1115/1.4039383.

Barrel-shaped surfaces are widely used in industries, e.g., blades, vases, and tabular parts. Because a part such as an aero-engine blade is typically quite large, the efficiency of its measurement becomes a critical issue. The recently emerged five-axis sweep scanning technology offers to be a powerful means to significantly increase the efficiency of measurement. However, currently it still mostly relies on humans to manually plan a five-axis sweep scanning path, and in most cases, the surface is simply divided into a number of smaller open patches for which the sweep scanning is then individually planned. We present an algorithm for automatically planning the five-axis sweep scanning for an arbitrary barrel-shaped surface in the form of either a compound, a trimmed, or a simple surface. The planning algorithm is novel in that no partitioning of the surface is needed and a single continuous five-axis sweep scanning path will be generated for the entire surface. By eliminating the nonsweeping time spent by the stylus due to its air-moves between multiple patches and also the time-costly approach-retraction operations required for each patch, the proposed algorithm is able to significantly reduce the total inspection time, sometimes more than 50%, as validated in our physical inspection experiments.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071002-071002-11. doi:10.1115/1.4039556.

Like many other additive manufacturing (AM) processes, fused deposition modeling (FDM) process is driven by a moving heat source, and temperature history plays an important role in determining the mechanical properties and geometry of the final parts. Thermal simulation of FDM is challenging due to geometric complexity of manufacturing process and inherent computational complexity which requires numerical solution at every time increment of the process. We describe a new approach to thermal simulation of the FDM process, formulated as an explicit finite difference method that is applied directly on as-manufactured model described by a typical manufacturing process plan. The thermal model accounts for most relevant thermal effects including heat convection and radiation to the environment, heat conduction with build platform and between adjacent roads (and adjacent layers). We show that the proposed simulation method achieves linear time complexity both theoretically and numerically. This implies that the simulation not only scales to handle three-dimensional (3D) printed components of arbitrary complexity but also can achieve real-time performance. The approach is fully implemented, validated against known analytic solutions, and is tested on realistic complex shapes.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071003-071003-10. doi:10.1115/1.4039649.

The manufacturing of low-density paper such as tissue and towel typically involves a key operation called creping. In this process, the wet web is continuously pressed onto the hot surface of a rotating cylinder sprayed with adhesive chemicals, dried in place, and then scraped off by a doctor blade. The scraping process produces periodic microfolds in the web, which enhance the bulk, softness, and absorbency of the final tissue products. Various parameters affect the creping process and finding the optimal combination is currently limited to costly full-scale experiments. In this paper, we apply a one-dimensional (1D) particle dynamics model to systematically study creping. The web is modeled as a series of discrete particles connected by viscoelastic elements. A mixed-mode discrete cohesive zone model (CZM) is embedded to describe the failure of the adhesive layer. Self-contact of the web is incorporated in the model using a penalty method. Our simulation results delineate three typical stages during the formation of a microfold: interfacial delamination, web buckling, and post-buckling deformation. The effects of key control parameters on creping are then studied. The creping angle and the web thickness are found to have the highest impact on creping. An analytical solution for the maximum creping force applied by the blade is derived and is found to be consistent with the simulation. The proposed model is shown to be able to capture the mechanism of crepe formation in the creping process and may provide useful insights into the manufacturing of tissue paper.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071004-071004-9. doi:10.1115/1.4039439.

Vacuum arc remelting (VAR) is a melting process for the production of homogeneous ingots, achieved by applying a direct current to create electrical arcs between the input electrode and the resultant ingot. Arc behavior drives quality of the end product, but no methodology is currently used in VAR furnaces at large scale to track arcs in real time. An arc position sensing (APS) technology was recently developed as a methodology to predict arc locations using magnetic field values measured by sensors. This system couples finite element analysis of VAR furnace magnetostatics with direct magnetic field measurements to predict arc locations. However, the published APS approach did not consider the effect of various practical issues that could affect the magnetic field distribution and thus arc location predictions. In this paper, we studied how altering assumptions made in the finite element model affect arc location predictions. These include the vertical position of the sensor relative to the electrode–ingot gap, a varying electrode–ingot gap size, ingot shrinkage, and the use of multiple sensors rather than a single sensor. Among the parameters studied, only vertical distance between arc and sensor locations causes large sources of error and should be considered further when applying an APS system. However, averaging the predicted locations from four evenly spaced sensors helps reduce this error to no more than 16% for a sensor position varying from 0.508 m below and above the electrode–ingot gap height.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071005-071005-12. doi:10.1115/1.4039491.

A heterogeneous object (HO) refers to a solid component consisting of two or more material primitives distributed either continuously or discontinuously within the object. HOs are commonly divided into three categories. The first category has distinct material domains separating the different materials. The second, called functionally graded materials (FGMs), has continuous variation of material composition that produces gradient in material properties. The third category allows for any combinations of the first two categories within the same part. Modeling and manufacturing of HOs has recently generated more interest due to the advent of additive manufacturing (AM) technology that makes it possible to build such parts. Directed energy deposition (DED) processes have the potential for depositing multiple powdered materials in various compositions in the process of creating a single layer of material. To make this possible, tool paths that provide proper positioning of the deposition head and proper control over the material composition are required. This paper presents an approach for automatically generating the toolpath for any type of HO considering the material composition changes that are required on each layer. The toolpath generation takes into account the physical limitations of the machine associated with powder delivery and ability to continually grade the materials. Simulation results using the toolpath generation methodology are demonstrated by several example parts.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071006-071006-15. doi:10.1115/1.4039555.

Fiber waviness is one of the most significant defects that occurs in composites due to the severe knockdown in mechanical properties that it causes. This paper investigates the mechanisms for the generation of fiber path defects during processing of composites prepreg materials and proposes new predictive numerical models. A key focus of the work was on thick sections, where consolidation of the ply stack leads to out of plane ply movement. This deformation can either directly lead to fiber waviness or can cause excess fiber length in a ply that in turn leads to the formation of wrinkles. The novel predictive model, built on extensive characterization of prepregs in small-scale compaction tests, was implemented in the finite element software abaqus as a bespoke user-defined material. A number of industrially relevant case studies were investigated to demonstrate the formation of defects in typical component features. The validated numerical model was used to extend the understanding gained from manufacturing trials to isolate the influence of various material, geometric, and process parameters on defect formation.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071007-071007-15. doi:10.1115/1.4039646.

Gear shaping is, currently, the most prominent method for machining internal gears, which are a major component in planetary gearboxes. However, there are few reported studies on the mechanics of the process. This paper presents a comprehensive model of gear shaping that includes the kinematics, cutter–workpiece engagement (CWE), and cutting forces. To predict the cutting forces, the CWE is calculated at discrete time steps using a tridexel discrete solid modeler. From the CWE in tridexel form, the two-dimensional (2D) chip geometry is reconstructed using Delaunay triangulation (DT) and alpha shape reconstruction. This in turn is used to determine the undeformed chip geometry along the cutting edge. The cutting edge is discretized into nodes with varying cutting force directions (tangential, feed, and radial), inclination angles, and rake angles. If engaged in the cut during a particular time-step, each node contributes an incremental force vector calculated with the oblique cutting force model. Using a three-axis dynamometer on a Liebherr LSE500 gear shaping machine tool, the cutting force prediction algorithm was experimentally verified on a variety of processes and gears, which included an internal spur gear, external spur gear, and external helical gear. The simulated and measured force profiles correlate closely with about 3–10% RMS error.

Topics: Gears , Cutting , Kinematics
Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071008-071008-10. doi:10.1115/1.4039651.

Elastic deflection of cutting tools relative to the workpiece is one of the major factors contributing to dimensional part inaccuracies in machining. This paper examines the effect of tool deflection in gear shaping and its effect on the gear's profile form error, which can cause transmission error and noise during gear operation. To simulate elastic tool deflection in gear shaping, the tool's static stiffness is estimated from impact hammer testing. Then, based on simulated cutter-workpiece engagement and predicted cutting forces, the elastic deflection of the tool is calculated at each time-step. To examine the effect of tool deflection on the profile error of the gear, a virtual gear measurement module is developed and used to predict the involute profile deviations in the virtually machined part. Simulated and measured profile deviations were compared for a one-pass external spur gear process and a two-pass external spur gear process. The simulated profile errors correlate very well with the measured profiles on the left flanks of the workpiece teeth, which are cut by the leading edges of the cutter teeth. However, additional research is needed to improve the prediction of the right flanks, which are cut by the trailing edges of the cutter teeth.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071009-071009-9. doi:10.1115/1.4039855.

The Ti–6Al–4V is a widely used alloy in the aerospace industry. In order to improve the grindability of Ti–6Al–4V, a hybrid material removal process is proposed in this study. This process is a combination of ultrasonic assisted grinding (UAG) and electrochemical grinding (ECG), hereafter called ultrasonic assisted electrochemical grinding (UAECG). For confirming the feasibility of the proposed technique, an experimental setup was constructed and the fundamental machining characteristics of UAECG in the grinding of Ti–6Al–4V were experimentally investigated. The results obtained from the investigation can be summarized as follows: (1) the normal and tangential forces in UAECG were decreased approximately 57% and 56%, respectively, comparing with conventional grinding (CG). (2) The work-surface roughness Ra both in ECG and UAECG was negative correlation to the electrolytic voltage, UI, and the surface damage; (3) the wheel radius wear in UAECG was considerably smaller than that in ECG when UI < 10 V. The chip adhesion and the grain fracture mainly affected the working lives of the wheels in ECG and UAECG, whereas the wheel wear in CG was predominantly attributed to the grain drop out; (4) a titanium dioxide (TiO2) layer, which had a 78 nm thickness was achieved on the work surface in the condition of UI = 20 V, leading that the Vickers microhardness of work surface in ultrasonic assisted electrochemical was lower than that in CG by 15%.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071010-071010-9. doi:10.1115/1.4039645.

Zirconia ceramics which are sometimes called “ceramic steel” have gained significant interest because of their excellent properties. However, it is desired to maintain the surface quality while increasing the economics of ceramics grinding process. A hybrid laser/grinding (HLG) process was utilized to grind zirconia ceramics which was irradiated with continuous wave laser before grinding in the hybrid process. The feasibility of hybrid laser/grinding of zirconia ceramics was investigated in terms of grinding force and energy, material removal, and damage formation mechanisms. The results show that laser irradiation can induce lateral cracks, which can help material removal and prevent further crack propagating into the base. The results of grinding tests indicate that grinding force and energy decrease significantly as compared with conventional grinding of ceramics. The combinations of the fractured area, the plowing striations, and seldom debris on the ground surfaces in this work indicate the combined material removal mechanism of both brittle mode and ductile mode.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071011-071011-7. doi:10.1115/1.4039650.

This study aims to investigate the drilling performance of a copper/diamond functionally graded grinding wheel (FGGW) fabricated by centrifugal sintered-casting for carbon fiber-reinforced plastic (CFRP) laminates by originally designed dual-axis grinding wheel (DAGW) system. The copper/diamond FGGW was also originally designed and fabricated by the centrifugal sintered-casting to suppress abrasive-grain wear and reduce the consumption of abrasive grains in our previous study. Drilling tests were carried out over 50 holes in dry machining. Thrust force was evaluated with force sensor during drilling test. Hole diameter, roundness, and roughness were measured to assess hole quality. Drill chips were observed by scanning electron microscope (SEM) to investigate chip morphology. Precision drilling without burring and delamination was achieved in CFRP laminates. Good hole-quality was still obtained over 50 holes due to the low thrust force during drilling. Specific three-dimensional (3D) drilling process of the DAGW system enabled stable and precision drilling with low thrust force in CFRP laminates continuously.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071012-071012-8. doi:10.1115/1.4039062.

The analysis of various methods of machining of rope internal thread ISO 10208, DIN 20317 has been carried out and the criteria of high-efficiency machining have been formulated. The concept of the method has been developed, which supposes the designing of the construction of noncore tool and the calculation of the parameters of mechanical trajectory with the purpose of ensuring the machining per one pass on the computer numerical control (CNC) milling machine. The compensation procedure of dimensional wear of insert has been developed. While machining the production batch of the parts in an experimental way, the optimum cutting conditions have been determined which allow ensuring the maximum efficiency on reaching the required roughness and the dimensional accuracy of the profile of rope thread. The performed statistical analysis of the machined parts allowed to establish that dispersions of the actual values of profiles' roughness follow Gauss' law. In an experimental way, it has been proved that the application of the proposed method increased the efficiency of machining of the internal rope thread by 2.5 times. On the basis of comparison of engineering-and-economical performance, the efficient fields of application of high-efficient method of machining of the rope threads have been determined.

Topics: Machining , Thread , Cutting , Ropes , Wear
Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071013-071013-11. doi:10.1115/1.4039653.

This paper presents a new vector-field-based streamline smoothing method in the parametric space and a tool orientation optimization technique for five-axis machining of complex compound surfaces with torus-end cutters. Iso-planar tool path is widely used in the machining of various types of surfaces, especially for the compound surface with multiple patches, but the operations of intersecting the compound surface with a series of planes have depended considerably on the complicated optimization methods. Instead of intersecting the surface directly with planes, a novel and effective tool path smoothing method is presented, based on the iso-planar feed vector fields, for five-axis milling of a compound surface with torus-end cutters. The iso-planar feed vector field in the parametric domain is first constructed in the form of stream function that is used to generate the candidate streamlines for tool path generation. Then, a G1 blending algorithm is proposed to blend the vector fields within the adjacent parametric domains to ensure smooth transition of cross-border streamlines. Based on the smoothened streamlines in the parametric domains, pathlines along with their correspondent side sizes are selected as desirable tool paths. Concerning a high performance machining, detailed computational techniques to determine the tool axis orientation are also presented to ensure, at each cutter contact (CC) point, the torus-end cutter touches the part surface closely without gouging. Both the computational results and machined examples are demonstrated for verification and validation of the proposed methods.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071014-071014-9. doi:10.1115/1.4039888.

Titanium and its alloys are widely used in structural applications owing to superior mechanical properties and corrosion resistance. In the present study, a simple powder metallurgy-based process is developed to fabricate dense components through formation of dough under ambient condition using Ti6Al4V powder along with chitosan powder as dough forming additive and acetic acid as solvent. The prepared samples had ∼66±1.7% green density and 97.3±2.1% sintered density of the theoretical value. The microstructure of Ti6Al4V was investigated using scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) spectroscopy. Micro-CT analysis was carried out for distribution of defects and their influence on flexural strength and microhardness was assessed as well. The prepared green samples had uniform particle distribution that resulted in minimum deformation after sintering. Assessment of mechanical properties revealed that the values of hardness and flexural modulus for sintered samples were comparable to the reported values of Ti6Al4V components prepared using other process. Therefore, the developed method of dough forming for dense titanium components using powder metallurgy route is a simple and viable alternative.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071015-071015-8. doi:10.1115/1.4039767.

Selective assembly is a means of obtaining higher quality product assemblies by using relatively low-quality components. Components are selected and classified according to their dimensions and then assembled. Past research has often focused on components that have normal dimensional distributions to try to find assemblies with minimal variation and surplus parts. This paper presents a multistage approach to selective assembly for all distributions of components and with no surplus, thus offering less variation compared to similar approaches. The problem is divided into different stages and a genetic algorithm (GA) is used to find the best combination of groups of parts in each stage. This approach is applied to two available cases from the literature. The results show improvement of up to 20% in variation compared to past approaches.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071016-071016-13. doi:10.1115/1.4039918.

This paper presents a new spiral smoothing method to generate smooth curved tool paths directly on mesh surfaces. Spiral tool paths are preferable for computer numerical control (CNC) milling, especially for high-speed machining. At present, most spiral tool path generation methods aim mainly for pocketing, and a few methods for machining complex surface also suffer from some inherent problems, such as selection of projecting direction, preprocessing of complex offset contours, easily affected by the mesh or mesh deformation. To address the limitations, a new spiral tool path method is proposed, in which the radial curves play a key role as the guiding curves for spiral tool path generation. The radial curve is defined as one on the mesh surface that connects smoothly one point on the mesh surface and its boundary. To reduce the complexity of constructing the radial curves directly on the mesh surface, the mesh surface is first mapped onto a circular region. In this region, the radial lines, starting from the center, are planned and then mapped inversely onto the mesh surface, thereby forming the desired radial curves. By traversing these radial curves using the proposed linear interpolation method, a polyline spiral is generated, and then, the unfavorable overcuts and undercuts are identified and eliminated by supplementing additional spiral points. Spline-based technique of rounding the corners is also discussed to smooth the polyline spiral, thereby obtaining a smooth continuous spiral tool path. This method is able to not only greatly simplify the construction of radial curves and spiral tool path but also to have the ability of processing and smoothing complex surfaces. Experimental results are presented to validate the proposed method.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071017-071017-9. doi:10.1115/1.4039916.

A method of research on the size effect of the specific cutting energy based on the numerical simulation has been proposed. The theoretical model of the research on size effect of specific cutting energy using single grit scratching simulation has been presented. A series of single grit scratch simulations with different scratching depths have been carried out to acquire different material removal rates. Then, the specific cutting energy has been calculated based on the power consumed and the material removal rate. The relationship between the specific cutting energy and the material removal rate has been given which agrees well with that presented by Malkin. The simulation results have been analyzed further to explain the size effect of specific cutting energy.

Commentary by Dr. Valentin Fuster
J. Manuf. Sci. Eng. 2018;140(7):071018-071018-10. doi:10.1115/1.4040025.

Despite the tremendous effort of researchers and manufacturing engineers in improving the predictability of the air bending process, there is still a strong need for comprehensive and dependable prediction models. Currently, available modeling approaches all present some relevant limitations in practical applications. In this paper, we propose a new method, which represents an improvement over all existing modeling and prediction techniques. The proposed method can be used for accurate prediction of the main response variables of the air bending process: the angle α after springback and the bend deduction BD. The metamodeling method is based on the hierarchical fusion of different kinds of data: the deterministic low-fidelity response of numerical finite element method (FEM) simulations and the stochastic high fidelity response of experimental tests. The metamodel has been built over a very large database, unprecedented in the scientific literature on air bending, made of more than 500 numerical simulations and nearly 300 experimental tests. The fusion is achieved first by interpolating the FEM simulations with a kriging predictor; then, the hierarchical metamodel is built as a linear regression model of the experimental data, using the kriging predictor among the regressors. The accuracy of the method has been proved using a variant of the leave-one-out cross validation technique. The quality of the prediction yielded by the proposed method significantly over-performs the current prediction of the press brake on-line numerical control.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Manuf. Sci. Eng. 2018;140(7):074501-074501-8. doi:10.1115/1.4039586.

Deformation machining (DM) is a combination of thin structure machining and single-point incremental forming/bending (SPIF/SPIB). This process enables the creation of complex structures and geometries, which are probably difficult or sometimes impossible to manufacture employing conventional manufacturing techniques. Geometrical discrepancies in thin structure or sheet metal bending and forming are a major obstacle in manufacturing quality components. These discrepancies are more prevalent and complex in nature in incremental or generative manufacturing. In the present work, a comprehensive experimental and numerical study on the parametric effects on various geometrical inaccuracies in DM process has been performed. This study would help in giving an insight in providing necessary geometrical compensation, ensuring a quality product over a wide range of process parameters.

Commentary by Dr. Valentin Fuster

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