Accepted Manuscripts

Kai Soon Fong, Tan Ming Jen, Fern Lan Ng, Atsushi Danno and Beng Wah Chua
J. Manuf. Sci. Eng   doi: 10.1115/1.4036529
In this study, an AZ31 magnesium alloy plate was processed by constrained groove pressing (CGP) under three deformation cycles at temperatures from 503 to 448 K. The process resulted in a homogeneous fine grain microstructure with an average grain size of 1.8 µm. The as-processed microstructure contained a high fraction of low angle grain boundaries of subgrains and dislocation boundaries that remained in the structure due to incomplete dynamic recovery and recrystallization. The material’s yield strength was found to have increased from 175 to 242 MPa and with a significant weakening of its initial basal texture. The microstructure stability of the CGP-processed material was further investigated by isothermal annealing at temperature from 473 to 623 K and for different time. Abnormal grain growth was observed at 623 K and this was associated with an increased in non-basal grains at the expense of basal grains. The effect of annealing temperature and time on the grain growth kinetics was interpreted by using the grain growth equation, D^n ?+D?_0^n=kt, and Arrhenius equation, k=k_0 exp(-Q/RT). The activation energy (Q) was estimated to be 27.8 kJ/mol which was significantly lower than the activation energy for lattice self-diffusion (QL=135 kJ/mol) and grain boundary diffusion (Qgb=92kJ/mol) in pure magnesium. The result shows that grain growth is rapid but average grain size still remained smaller than the as-received material, especially at the shorter annealing time.
TOPICS: Stability, Annealing, Magnesium alloys, Pressing, Temperature, Grain size, Yield strength, Texture (Materials), Cycles, Dislocations, Grain boundary diffusion, Diffusion (Physics), Magnesium (Metal), Deformation, Recrystallization, Grain boundaries
Murali Sundaram and Sagil James
J. Manuf. Sci. Eng   doi: 10.1115/1.4036559
Vibration Assisted Nano Impact-machining by Loose Abrasives (VANILA) is a novel nanomachining process to perform target specific nano abrasive machining of hard and brittle materials. An atomic force microscope (AFM) is used as an experimental platform in this process, wherein, nano abrasives injected in slurry between the workpiece and the vibrating AFM probe, impact the workpiece and cause nanoscale material removal. Molecular dynamic (MD) simulations are performed in this study to understand the nanoscale material removal mechanisms involved in the VANILA process. The simulation results revealed that the material removal for the given impact conditions happens primarily in ductile mode through three distinct mechanisms which are nanocutting, nanoplowing and nanocracking. It was found that domination by any of these mechanisms over the other mechanisms during the material removal process depends on the impact conditions, such as angle of impact and the initial kinetic energy of the abrasive grain. The transition zone from nanocutting to nanoplowing is observed at angle of impact of near 60° while the transition from the nanocutting and nanoplowing mechanisms to nanocracking mechanism is observed for initial abrasive kinetic energies of about 600-700 eV. A material removal mechanism map is constructed to illustrate the effects of the impacts conditions on the material removal mechanism. Confirmatory experimentation on silicon and borosilicate glass substrates showed that all the three nanoscale mechanisms are possible, and the nanoplowing is the most common mechanism.
TOPICS: Machining, Abrasives, Vibration, Molecular dynamics simulation, Nanoscale phenomena, Atomic force microscopy, Kinetic energy, Heat resistant glass, Brittleness, Simulation, Molecular dynamics, Abrasive machining, Engineering simulation, Slurries, Borosilicate glasses, Probes, Silicon, Simulation results
Grant Brandal and Y. Lawrence Yao
J. Manuf. Sci. Eng   doi: 10.1115/1.4036530
The combination of a susceptible material, tensile stress, and corrosive environment results in stress corrosion cracking (SCC). Laser shock peening (LSP) has previously been shown to prevent the occurrence of SCC on stainless steel. Compressive residual stresses from LSP are often attributed with the improvement, but this simple explanation does not explain the electrochemical nature of SCC by capturing the effects of microstructural changes from LSP processing and its interaction with the hydrogen atoms on the microscale. As the hydrogen concentration of the material increases, a phase transformation from austenite to martensite occurs. This transformation is a precursor to SCC failure, and its prevention would thus help explain the mitigation capabilities of LSP. In this paper, the role of LSP induced dislocations counteracting the driving force of the martensitic transformation is explored. Stainless steel samples are LSP processed with a range of incident laser intensities and overlapping. Cathodic charging is then applied to accelerate the rate of hydrogen absorption. Using XRD, martensitic peaks are found after 24 hours in samples that have not been LSP treated. But martensite formation does not occur after 24 hours in LSP treated samples. TEM analysis is also used for providing a description of how LSP provides mitigation against hydrogen enhanced localized plasticity, by causing tangling and prevention of dislocation movement. The formation of dislocation cells is attributed with further mitigation benefits. A finite element model predicting the dislocation density and cell formation is also developed to aid in the description.
TOPICS: Stress corrosion cracking, Martensitic transformations, Hydrogen, Laser hardening, Dislocations, Stainless steel, Tension, Failure, Finite element model, Microscale devices, Dislocation density, Plasticity, Phase transitions, Atoms, Lasers, Absorption, Residual stresses
Xinyan Ou, Jorge Arinez, Qing (Cindy) Chang and Guoxian Xiao
J. Manuf. Sci. Eng   doi: 10.1115/1.4036522
In last decade, global competition has forced manufacturers to optimize logistics. An innovative containerization method (CM) provides a new perspective for optimizing logistics cost saving, where collapsible containers are used to reduce the frequency of shipping freight. However, optimization of logistic cost is complicated due to the interactions in a system, such as market demand, inventory, production throughput and uncertainty. Therefore, a systematic model and accurate estimation of the total cost and system performance are of great importance for decision-making. In this paper, a mathematical model is developed to describe deterministic and stochastic scenarios for a closed-loop container dynamic flow system. The uncertainties in a factory and a supplier are considered in the model. The performance evaluation of the collapsible container system and total cost estimation are provided through model analysis. Furthermore, fuzzy control method is proposed to monitor the processing rate of the supplier and the factory, and to adjust the rate of the supplier operation and further reduce the logistic cost. A case study with a MATLAB simulation is presented to illustrate the accuracy of the mathematical model and the effectiveness of the fuzzy controller.
TOPICS: Fuzzy control, Supply chains, Containers, Logistics, Uncertainty, Control equipment, Simulation, Optimization, Decision making, Matlab, Performance evaluation, Flow (Dynamics)
Kyung-Min Hong and Yung C. Shin
J. Manuf. Sci. Eng   doi: 10.1115/1.4036521
This paper reports on numerical and experimental investigations involving examination of the effects of an interfacial gap in the range of 0-0.3 mm on keyhole and molten pool dynamics. A numerical model was developed to investigate the three-dimensional transient dynamics of the keyhole in lap welding processes with an interface gap. The model was able to reliably predict the weld profile. In addition, the modeling results provided detailed information regarding the interaction between the molten pool and the solid/liquid boundary that led to the extended weld width. Experimentally, AISI 304 stainless steel was joined in a lap welding configuration using an IPG YLR-1000 fiber laser. The tensile shear and T-peel testing of the lap joints showed that adding an adequate amount of interface gap improves weld strength.
TOPICS: Dynamics (Mechanics), Laser welding, Stainless steel, Dynamic models, Welding, Computer simulation, Shear (Mechanics), Transients (Dynamics), Modeling, Testing, Fiber lasers
S. M. Saqib and R. J. Urbanic
J. Manuf. Sci. Eng   doi: 10.1115/1.4036488
To understand the different aspects of the laser cladding (LC) process, process models can be of aid. Presently, the correct parameters settings for different manufacturing processes, such as machining, casting, etc. are based on simulation tools that can evaluate the influence of the process parameters for different conditions. However, there are no comprehensive, focused simulation process planning tools available for the LC process. In the past, most of the research has focused on the experimentally based optimization strategies for a process configuration, typically for a single track bead in steady state conditions. However, an understanding of realistic transient conditions needs to be explored for effective process planning simulation tools and build strategies to be developed. A set of cladding experiments have been performed for single and multiple bead scenarios, and the effects of the transient conditions on the bead geometry for these scenarios have been investigated. It is found that the lead-in and lead-out conditions differ, corner geometry influences the bead height, and when changing the input power levels, the geometry values oscillate differently than the input pulses. Changes in the bead geometry are inherent when depositing material; consequently real time adjustments for the process setting are essential. The dynamic, time varying heating and solidification, for multiple layer scenarios, leads to challenging process planning and real time control strategies.
TOPICS: Lasers, Transients (Dynamics), Cladding systems (Building), Stainless steel, Geometry, Production planning, Simulation, Corners (Structural elements), Machining, Casting, Manufacturing, Steady state, Heating, Optimization, Real-time control, Solidification
William J. Emblom
J. Manuf. Sci. Eng   doi: 10.1115/1.4036489
A stamp forming die, whose flexible blank holder was designed using FEA was built. The tooling also included active draw beads, local wrinkling sensors, and local force transducers. Wrinkling was controlled using a PID feedback loop and blank holder force. Local forces in the tooling could be controlled using blank holder forces in a PID feedback loop. A third closed-loop control system that could be used to control local punch forces near draw beads featured an advanced PID controller with a Smith Predictor and Kalman Filter. A Bang-bang controller was also incorporated into that control system in order prevent control saturation. Fuzzy logic was used to transition from once controller to the other. Once closed-loop was implemented, tests were performed to evaluate the strains in the pans for various forming conditions. These results were compared to open-loop tests and it was found that the strains from closed-loop control tests resulted in more uniform strains and that the strains were further from the forming limit curves than strains from tests that were performed under open-loop conditions. Furthermore, it was seen that the strains in the regions were local force were controlled resulted in more uniform strain fields. Hence it was concluded that controlling local punch forces resulted in the strain control of critical regions.
TOPICS: Aluminum, Sensors, Control systems, Control equipment, Fuzzy logic, Finite element analysis, Transducers, Feedback, Kalman filters, Tooling, Blanks, Forming limit diagrams
Guangyu Hou and Matthew C. Frank
J. Manuf. Sci. Eng   doi: 10.1115/1.4036423
This paper introduces a new method that uses slice geometry to compute the Global Visibility Map (GVM). Global Visibility Mapping is a fundamentally important process that extracts geometric information about an object which can be used to solve hard problems; for example, the setup and process planning in CNC machining. In this work, we present a method for creating the GVM from slice data of polyhedron models, and then show how it can help determine around which axis of rotation a part can be machined. There have been various methods of calculating the GVM to date, tracing back to the well-known seminal methods that use Gaussian Mapping. Compared to the considerable amount of work in this field, the proposed method has an advantage of starting from feature-free models, like STL files. Also, it has solutions of adjustable resolution. Moreover, since it is built upon slicing the model, the method is embarrassingly parallelizable in nature, thus suitable for high performance computing. Using the GVM obtained by this method, we generate an axis of rotation map to facilitate the setup planning for 4-axis CNC milling machines as one implementation example.
TOPICS: Geometry, Rotation, Machining, Production planning, Resolution (Optics), Computer numerical control machine tools, Machining centers
Jingyuan Yan, Ilenia Battiato and Georges M. Fadel
J. Manuf. Sci. Eng   doi: 10.1115/1.4036424
During the past few years, metal based additive manufacturing technologies have evolved and may enable the direct fabrication of heterogeneous objects with full spatial material variations. A heterogeneous object has potentially many advantages and in many cases can realize appearance and/or functionality that homogeneous objects cannot achieve. In this work we employ a pre-process computing combined with a multi-objective optimization algorithm based on the modeling of the Direct Metal Deposition (DMD) of dissimilar materials to optimize the fabrication process. The optimization methodology is applied to the deposition of Inconel 718 and Ti-6Al-4V powders with prescribed powder feed rates. Eight design variables are accounted in the example, including the injection angles, injection velocities, and injection nozzle diameters for the two materials, as well as the laser power and scanning speed. The multi-objective optimization considers that the laser energy consumption and the powder waste during the fabrication process should be minimized. The optimization software modeFRONTIER® is used to drive the computation procedure with a MATLAB code. The results show the design and objective spaces of the Pareto optimal solutions, and enable the users to select preferred setting configurations from the set of optimal solutions. A feasible design is selected corresponds to a relatively low material cost, with laser power 370 W, scanning speed 55 mm/s, injection angles 15º, injection velocities 45 m/s for Inconel 718, 30 m/s for Ti-6Al-4V, and nozzle widths 0.5 mm under the given condition.
TOPICS: Metals, Optimization, Lasers, Manufacturing, Design, Pareto optimization, Nozzles, Additive manufacturing, Modeling, Space, Algorithms, Computation, Computer software, Energy consumption, Matlab
Filippos Tourlomousis, Houzhu Ding, Dilhan M. Kalyon and Robert C. Chang
J. Manuf. Sci. Eng   doi: 10.1115/1.4036348
The direct electrostatic printing of highly viscous thermoplastic polymers onto movable collectors, a process known as melt electrospinning writing (MEW), has significant potential as an additive biomanufacturing technology. MEW has the hitherto unrealized potential of fabricating 3D porous interconnected fibrous mesh-patterned scaffolds in conjunction with cellular-relevant fiber diameters and inter-fiber distances without the use of cytotoxic organic solvents. However, this potential cannot be readily fulfilled due to the large number and complex interplay of the multivariate independent parameters of the melt electrospinning process. To overcome the challenge, dimensional analysis was employed to identify a "Printability Number" (NPR), which correlated with the dimensionless numbers arising from the non-dimensionalization of the governing conservation equations of the electrospinning process and the viscoelasticity of the polymer melt. This analysis suggests that the applied voltage potential (Vp), the volumetric flow rate (Q) and the translational stage speed (UT), are the most critical parameters towards efficient printability. Experimental investigations using a poly(e-caprolactone) melt have indeed revealed that any perturbations arising from an imbalance between the downstream and the upstream resistive forces can be eliminated by systematic tuning of Vp and Q for prescribed thermal conditions. This, in concert with appropriate tuning of the translational stage speed, has enabled steady state equilibrium conditions to be achieved for the printing of microfibrous woven meshes with precise and reproducible geometries.
TOPICS: Electrospinning, Fibers, Printing, Steady state, Biomanufacturing, Dimensionless numbers, Dimensional analysis, Viscoelasticity, Equilibrium (Physics), Polymers, polymer melts, Flow (Dynamics)
Chenhui Shao, Jionghua (Judy) Jin and S. Jack Hu
J. Manuf. Sci. Eng   doi: 10.1115/1.4036347
Fine-scale characterization and monitoring of spatiotemporal processes are crucial for high-performance quality control of manufacturing processes, such as ultrasonic metal welding and high-precision machining. However, it is generally expensive to acquire high-resolution spatiotemporal data in manufacturing due to the high cost of the 3D measurement system or the time-consuming measurement process. In this paper, we develop a novel dynamic sampling design algorithm to cost-effectively characterize spatiotemporal processes in manufacturing. A spatiotemporal state-space model and Kalman filter are used to predictively determine the measurement locations using a criterion considering both the prediction performance and the measurement cost. The determination of measurement locations is formulated as a binary integer programming problem, and genetic algorithm is applied for searching the optimal design. In addition, a new test statistic is proposed to monitor and update the surface progression rate. Both simulated and real-world spatiotemporal data are used to demonstrate the effectiveness of the proposed method.
TOPICS: Design, Manufacturing, Spatiotemporal phenomena, Resolution (Optics), Algorithms, Genetic algorithms, Integer programming, Kalman filters, Measurement systems, Metals, Machining, Quality control, Welding
Kai Chen, Xun Liu and Jun Ni
J. Manuf. Sci. Eng   doi: 10.1115/1.4036225
This paper studies a friction stir spot welding (FSSW) process that has been successfully applied to join aluminum alloy 6061-T6 to TRIP 780/800 steel. Cross sections of weld specimens show the formation of a hook with a swirling structure. A higher magnified SEM view of the swirling structure with EDS analysis reveals that it is composed of alternating thin layers of steel and Al-Fe intermetallic compounds (IMCs). To check the effect of different process parameters on the weld strength, the effects of tool plunge speed and dwell time were studied through the design of experiments and analysis of variance. It shows that dwell time is a more dominant parameter in affecting the weld strength than plunge speed. Furthermore, investigation of failure using a lap shear tests reveals that cross nugget failure is the only failure mode. It also shows that cracks are initiated in the swirling structure at the tensile side of the weld nugget. After failure, a cleavage feature can be observed on the fractured surface.
TOPICS: Welding, Aluminum alloys, High strength steel, Friction, Failure, Swirling flow, Steel, Intermetallic compounds, Cross section (Physics), Shear (Mechanics), Fracture (Materials), Failure mechanisms, Experimental design
Ping Zhou, Ying Yan, Ning Huang, Ziguang Wang, Renke Kang and Dongming Guo
J. Manuf. Sci. Eng   doi: 10.1115/1.4036125
Subsurface damage (SSD) and grinding damage induced stress (GDIS) are the focus of attention in the study of grinding mechanism. Our previous study proposed a load identification method and analyzed the GDIS in a silicon wafer ground [1]. In this paper, a more concise method for GDIS analysis is proposed. The new method is based on the curvature analysis of the chip deformation, and a deterministic solution of residual stress can be derived out. Relying on the new method, the GDIS distribution feature in the silicon wafer ground by a #600 diamond wheel (average grit size 24 ?m) is studied. The analysis results show that the two principal stresses in the damage layer is more close to each other than that ground by the #3000 diamond wheel (average grit size 4 ?m), which indicates that the GDIS feature in ground silicon wafer is related to the depth of damage layer. Moreover, the GDIS distribution presents a correlation with crystalline orientation. To clarify these results, the SSD is observed by Transmission electron microscopy (TEM). It is found that the type of the defects under the surface is more divers and chaotic than that observed in silicon surface ground by the #3000 diamond wheel. Additionally, it is found that most of the cracks generate and propagate along the slip plane maybe due to the high shear stress and high dislocation density instead of the tensile stress which is recognized as the dominant factor of crack generation in brittle materials grinding process.
TOPICS: Semiconductor wafers, Grinding, Stress concentration, Damage, Stress, Diamonds, Wheels, Fracture (Materials), Shear stress, Dislocation density, Silicon, Tension, Transmission electron microscopy, Deformation, Brittleness
De-Lin Huang, Shi-chang Du, Gui-Long Li and Zhuo-Qi Wu
J. Manuf. Sci. Eng   doi: 10.1115/1.4035897
The chamber volumes are very important for some mechanical products. For instance, the volume variations of engine cylinder head combustion chambers directly affect the critical functions (e.g. compression ratio) of an engine. The interior surfaces of the chambers are usually not being machined after casting processes due to high machining cost. Traditional titration methods are only applied off line to evaluate the variations of the chamber volumes since they are considerably time-consuming. Therefore, it is difficult to on line control the volume variations of multiple chambers in machining processes. With the development of new high definition metrology (HDM) technologies, millions of coordinate points of the interior surfaces of the chambers can be on line obtained, and thus great opportunities are provided for on-line controlling volume variations of multiple chambers of a workpiece. However, there are some critical problems urgently need to be solved, such as datum transformation of high-density points, precise volume calculation of multiple chambers, and minimizing the volume difference of any two ones of all chambers. This paper presents a novel systemic approach for on-line minimizing the volume difference of multiple chambers of a workpiece based on HDM. A model for obtaining an optimized machining parameter for depth of chambers is explored to minimize the volume difference of any two ones of all chambers. The results of a case study show that the proposed approach can minimize the volume difference of four combustion chambers of a cylinder head in machining processes.
TOPICS: Machining, Casting, Metrology, Combustion chambers, Density, Engines, Compression, Cylinders, Engine cylinders, Mechanical products
Rianne E. Laureijs, Jaime Bonnín Roca, Sneha Prabha Narra, Colt Montgomery, Jack L. Beuth and Erica R.H. Fuchs
J. Manuf. Sci. Eng   doi: 10.1115/1.4035420
Additive manufacturing is increasingly of interest for commercial and military applications due to its potential to create novel geometries with increased performance. For additive manufacturing to find commercial application, it will have to be cost competitive against traditional processes such as forging. Forecasting the production costs of future products prior to large-scale investment is challenging due to the limits of traditional cost accounting's ability to handle the systemic process implications of new technologies and cognitive biases in humans' additive and systemic estimates. Leveraging a method uniquely suited to these challenges, we quantify the production and use economics of an additively-manufactured versus a traditionally forged GE engine bracket for commercial aviation with equivalent performance. Our results show that, despite the simplicity of the engine bracket, when taking into account part redesign for AM and the associated lifetime fuel savings of the additively-designed bracket, the additively manufactured part and design is cheaper than the forged one for a wide range of scenarios, including at higher volumes of 2,000 to 12,000 brackets per year. Opportunities to further reduce costs include cheaper material prices without compromising quality, being able to produce vertical builds with equivalent performance to horizontal builds, and increasing process control so as to enable reduced testing. Given the conservative nature of our assumptions as well as our choice of part, these results suggest there may be broader economic viability for additively manufactured parts, especially when systemic factors and use costs are incorporated.
TOPICS: Metals, Additive manufacturing, Engines, Forging, Design, Economics , Testing, Defense industry, Commercial air transport, Process control, Fuels

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