Accepted Manuscripts

J. Manuf. Sci. Eng   doi: 10.1115/1.4036289
Fine finishing of cylindrical internal surfaces without affecting geometric form is a critical requirement in several mechanical and aerospace applications. Although various methodologies using flexible abrasive media are reported for the same, many of them demands complex tooling and fixtures to be developed in tune with the internal dimensions to feed the abrasive media. Present paper investigates the feasibility of using magneto-elastic abrasive balls with the aid of a mechanically deployable tool for micro-finishing of geometrically symmetric tubular specimens. The deployable tool used for the present experimentation is designed like an umbrella mechanism, with magnetic pads to hold the elastic abrasive balls, expandable for bore diameter ranges from 45 to 75 mm. The magnetic type elastic abrasive balls proposed in the form of meso-scale balls of diameter 3.5 ± 0.25 mm are capable of finishing the bore surface without altering its roundness. Effects of elastomeric medium, mechanics of material removal and generation of finished profile during the proposed technique have been discussed in detail, through a comprehensive mathematical model. Effect of various process variables on surface roughness was investigated experimentally using response surface methodology and the theoretical predictions were validated at optimum operating condition. 62% reduction in average roughness on brass tubes of initial roughness 0.168µm, with significant improvement in all the associated 2D roughness parameters and without any deviation on roundness, was clearly demonstrating the potential of proposed methodology.
TOPICS: Finishing, Surface roughness, Aerospace industry, Tooling, Response surface methodology, Brass (Metal), Dimensions
Qian Ye and Shikui Chen
J. Manuf. Sci. Eng   doi: 10.1115/1.4036290
Modern computer technology empowers people to simulate additive manufacturing (AM) process at high fidelity, which has turned out to be a valid way to evaluate, anticipate, and design the AM processes. In this paper, we propose a new method to simulate the melting process of metal powder based AM. The physics is described using partial differential equations for heat transfer and Laminar flow. The level set methods are applied to track the motion of free surfaces between liquid and solid phases. The issues, including free surface evolution, phase transitions, and velocity field calculation are explored. The convergence problem is examined to improve the efficiency in solving this multiphysics problem.
TOPICS: Metals, Computer simulation, Additive manufacturing, Physics, Phase transitions, Heat transfer, Laminar flow, Metal powders, Melting, Computer technology, Design, Partial differential equations
Kory Chang and Masakazu Soshi
J. Manuf. Sci. Eng   doi: 10.1115/1.4036224
Sliding guideways are often used as the foundation of linear motion in computer numerical control (CNC) machine tools due to their high damping capabilities especially for heavy duty machining applications. However, the traditional manufacturing process with grinding is time consuming and the product’s sliding performance has not been optimized nor clearly understood. In order to increase productivity, a machining center based manufacturing method with CBN milling tools was introduced and tested by researchers. While greatly reducing manufacturing time and cost, a rougher milled surface, in comparison to traditional grinding, is a possible concern for the performance as well as the life of sliding guideways. In this study, a novel planar honing process was proposed as a post process of CBN milling to create a finish surface on hardened cast iron sliding guideways used for CNC machine tools. A design of experiment (DOE) was conducted to statistically understand significant factors in the machining process and their relationship with surface topography. Effective planar honing conditions were discovered and analyzed with 3D and 2D surface parameters.
TOPICS: Machine tools, Finishes, Optimization, Manufacturing, Machining, Grinding, Milling, Computer numerical control machine tools, Machining centers, Cast iron, Computers, Damping, Design
MD Sarker and Daniel X.B. Chen
J. Manuf. Sci. Eng   doi: 10.1115/1.4036226
Tissue regeneration with scaffold is one of the most promising approaches now a day, where application of dispensing-based rapid prototyping technique is drawing attention due to its capability to offer operational flexibility and print complex structure with utmost uniformity. In a pneumatic dispensing system, it is a critical issue to control the flow rate of biomaterial from dispensing tip, as some variables (material viscosity, temperature, needle geometry, and dispensing pressure) regulates the flow rate . In this context, model equations can play a vital role to control and predict the flow rate of dispensing material, and thus can eliminate the requirement of numerous time consuming trials during biofabrication. Therefore, in this study flow rate model has been developed for medium viscous alginate considering shear and slip flow from a tapered needle. In addition, model equations were also developed from regression of experimental data to predict the flow behavior of alginate at arbitrary concentration. Both flow behavior and flow rate model exhibited close agreement with experimental result, and therefore, indicate the accuracy of the developed model equations. In addition, the slip effect close to needle wall significantly influences the flow rate of alginate with the increase of dispensing pressure.
TOPICS: Manufacturing, Flow (Dynamics), Modeling, needles, Pressure, Slip flow, Geometry, Temperature, Viscosity, Biomaterials, Shear (Mechanics), Rapid prototyping, Biological tissues
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
Mohamed Nasr
J. Manuf. Sci. Eng   doi: 10.1115/1.4036122
Finite element modeling (FEM) of machining-induced residual stresses (RS) takes place over two consecutive steps; a cutting step and a relaxation step. In the latter, the workpiece is left to cool down after deactivating all external loads. The current work focuses on the relaxation step, and how different strain components, material plasticity and workpiece edge deflections affect the final state of different RS components. First, a 2D arbitrary-Lagrangian-Eulerian (ALE) plane strain thermo-mechanical explicit model was used to simulate dry orthogonal cutting. After that, the relaxation process was modeled using three approaches; 1) the classical approach, 2) a new approach that is first presented here, and 3) a modified approach that was developed earlier by the current author. In the classical approach, the same exact machined workpiece is relaxed, considering all stress / strain components and material plasticity. On the other hand, the new approach uses a pure elastic 1D thermal relaxation model, in the cutting direction, and assumes that the workpiece edges normal to the cutting direction remain so. The differences between the RS predicted by the new and classical approaches reflected the combined effects of the examined parameters. The role of each parameter was isolated using three different versions of the modified approach. The current findings confirmed that, for orthogonal cutting, the stress relaxation process can be considered as a 1D pure elastic thermal relaxation process. Also, the workpiece edges normal to the cutting direction deflect during relaxation, contributing to the final state of RS.
TOPICS: Plasticity, Machining, Residual stresses, Stress, Finite element methods, Finite element model, Relaxation (Physics), Cutting, Deflection, Plane strain, Finite element analysis, Modeling
Asif Tanveer, Deepak Marla and Shiv G. Kapoor
J. Manuf. Sci. Eng   doi: 10.1115/1.4036123
In this study a heat transfer model of machining of Ti-6Al-4V under the application of atomization-based cutting fluid spray coolant is developed to predict the temperature of the cutting tool. Owing to high tool temperature involved in machining of Ti-6Al-4V, the model considers film boiling as the major heat transfer phenomenon. In addition, the design parameters of the spray for effective cooling during machining are derived based on droplet-surface interaction model. Machining experiments are conducted and the temperatures are recorded using the inserted thermocouple technique. The experimental data are compared with the model predictions. The temperature field obtained is comparable to the experimental results, confirming that the model predicts tool temperature during machining with ACF spray cooling satisfactorily.
TOPICS: Fluids, Machining, Alloys, Sprays, Cutting, Temperature, Heat transfer, Cooling, Film boiling, Thermocouples, Coolants, Cutting tools, Drops, Design
Oguzhan Tuysuz and Yusuf Altintas
J. Manuf. Sci. Eng   doi: 10.1115/1.4036124
The structural dynamics of thin-walled parts vary as the material is removed during machining. This paper presents a new, computationally efficient reduced order dynamic substructuring method to predict the frequency response function (FRF) of the workpiece as the material is removed along the toolpath. The contribution of the removed mass to the dynamics of the workpiece is cancelled by adding a fictitious substructure having the opposite dynamics of the removed material. The equations of motion of the workpiece are updated, and workpiece FRFs are evaluated by solving the hybrid set of assembled equations of motion in frequency domain as the tool removes the material between two consecutive dynamics update steps. The orders of the initial workpiece structure and the removed substructures are reduced using a model order reduction method with a newly introduced automatic master set selection criterion. Both the full and reduced order FRF update models are validated with peripheral milling tests and FRF measurements on a plate-shaped workpiece.
TOPICS: Dynamics (Mechanics), Machining, Equations of motion, Structural dynamics, Frequency response, Milling
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
Dakai Bian, Bradley R. Beeksma, Dong-Jin Shim, Marshall Jones and Y. Lawrence Yao
J. Manuf. Sci. Eng   doi: 10.1115/1.4036126
A low concentrated polystyrene (PS) additive to epoxy is used since it is able to reduce the curing reaction rate but not at the cost of increasing viscosity and decreasing glass transition temperature of the curing epoxy. The modified epoxy is co-cured with a compatible thermoplastic interleaf during the vacuum assisted resin transfer molding (VARTM) to toughen the interlaminar of the composites. Using viscometry, the solubilities of thermoplastics polycarbonate (PC), polyetherimide (PEI), and polysulfone (PSU) are determined to predict their compatibility with epoxy. The diffusion and precipitation process between the most compatible polymer PSU and epoxy formed semi-interpenetration networks (semi-IPN). To optimize bonding adhesion, these diffusion and precipitation regions were studied via optical microscopy under curing temperatures from 25?C to 120?C and PS additive concentrations to epoxy of 0% to 5%. Uniaxial tensile tests were performed to quantify the effects of diffusion and precipitation regions on composite delamination resistance and toughness. Crack paths were observed to characterize crack propagation and arrest mechanism. Fracture surfaces were examined by scanning electron microscopy (SEM) to characterize the toughening mechanism of the thermoplastic interleaf reinforcements. The chemically etched interface between diffusion and precipitation region showed semi-IPN morphology at different curing temperatures. Results revealed deeper diffusion and precipitation regions increases energy required to break semi-IPN for crack propagation resulting in crack arrests and improved toughness.
TOPICS: Diffusion (Physics), Glass reinforced plastics, Precipitation, Epoxy adhesives, Epoxy resins, Hardening (Curing), Fracture (Materials), Crack propagation, Fracture toughness, Temperature, Composite materials, Adhesion, Vacuum, Viscosity, Bonding, Glass transition, Optical microscopy, Polysulfone, Polymers, Scanning electron microscopy, Resins, Transfer molding, Delamination
Dakai Bian, Bradley R. Beeksma, Dong-Jin Shim, Marshall Jones and Y. Lawrence Yao
J. Manuf. Sci. Eng   doi: 10.1115/1.4036127
Various methods of toughening the bonding between the interleaf and laminate glass fiber reinforced polymer (GFRP) has been developed due to the increasing applications in industries. A polystyrene (PS) additive modified epoxy is used to improve the diffusion and precipitation region between polysulfone (PSU) interleaf and epoxy due to its influence on the curing kinetics without changing glass transition temperature and viscosity of the curing epoxy. The temperature dependent diffusivities of epoxy, amine hardener, and PSU are determined by using Attenuated Total Reflection- Fourier Transfer Infrared Spectroscopy (ATR-FTIR) through monitoring the changing absorbance of their characteristic peaks. Effects of PS additive on diffusivity in the epoxy system is investigated by comparing the diffusivity between non-modified and PS modified epoxy. The consumption rate of the epoxide group in the curing epoxy reveals the curing reaction rate, and the influence of PS additive on the curing kinetics is also studied by determining the degree of curing with time. A diffusivity model coupled with curing kinetics is applied to simulate the diffusion and precipitation process between PSU and curing epoxy. The effect of geometry factor is considered to simulate the diffusion and precipitation process with and without the existence of fibers. The simulation results show the diffusion and precipitation depths which matches those observed in the experiments.
TOPICS: Computer simulation, Hardening (Curing), Glass reinforced plastics, Epoxy resins, Diffusion (Physics), Precipitation, Simulation results, Polysulfone, Fourier transform infrared spectroscopy, Polymers, Geometry, Glass transition, Temperature, Fibers, Viscosity, Laminates, Infrared spectroscopy, Glass fibers, Bonding, Reflection
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
Hongyue Sun, Kan Wang, Yifu Li, Chuck Zhang and Ran Jin
J. Manuf. Sci. Eng   doi: 10.1115/1.4035586
Aerosol jet printing (AJP) is a direct write technology that enables fabrication of flexible, fine scale printed electronics on conformal substrates. AJP does not require the time consuming mask and postpatterning processes compared with traditional electronics manufacturing techniques. Thus, the cycle time can be dramatically reduced, and highly personalized designs of electronics can be realized. AJP has been successfully applied to a variety of industries, with different combinations of inks and substrates. However, the quality of the printed electronics, such as resistance, is not able to be measured online. On the other hand, the microscopic image sensors are widely used for printed circuit boards (PCBs) quality quantification and inspection. In this paper, two widely used quality variables of printed electronics, resistance and overspray, will be jointly modeled based on microscopic images for fast quality assessment. Augmented quantitative and qualitative (AUGQQ) models are proposed to use features of microscopic images taken at different locations on the printed electronics as input variables, and resistance and overspray as output variables. The association of resistance and overspray can be investigated through the AUGQQ models formulation. A case study for fabricating silver lines with Optomec® aerosol jet system is used to evaluate the model performance. The proposed AUGQQ models can help assess the printed electronics quality and identify important image features in a timely manner.
TOPICS: Aerosols, Modeling, Printing, Electronics, Manufacturing, Inks, Silver, Sensors, Inspection, Printed circuit boards, Cycles
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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