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Accepted Manuscripts

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research-article  
Davood Rahmatabadi, Bijan Mohammadi, Ramin Hashemi and Taghi Shojaee Shojaee
J. Manuf. Sci. Eng   doi: 10.1115/1.4040542
In this study, ultra-fine grained Al5052/Cu multi-layered composite is produced by accumulative roll bonding (ARB) and fracture properties are studied using plane stress fracture toughness. The fracture toughness is investigated for the unprocessed specimens, primary sandwich and first, 2end and 3rd cycles of ARB process by ASTM E561 and compact tension specimens. Also, the microstructure and mechanical properties are investigated using optical microscopy, scanning electron microscopy, uniaxial tensile tests, and microhardness measurements. The value of plane stress fracture toughness for the ultra-fine grained Al5052/Cu composite increased by increasing the number of ARB cycles, continuously from the primary sandwich to end of the 3rd cycle, and the maximum value of 59.1 MPa.m1/2 is obtained that it is about 2.77 and 4.05 more than Al5052 and pure Cu (unprocessed specimens). This indicates that ARB process and the addition of copper to aluminum alloy can increase the value of fracture toughness to more than three times. The results showed that by increasing the ARB cycles, the thickness of copper layers reduced and after the 5th cycle, the good uniformity of Cu layers achieved. By increasing the number of ARB cycles, the microhardness of both aluminum and copper layers are significantly increased. The tensile strength of the sandwich is enhanced continually, and the maximum value of 566.5 MPa is achieved.
TOPICS: Composite materials, Bonding, Fracture toughness, Cycles, Copper, Stress, Microhardness, Optical microscopy, Tensile strength, Tension, ASTM International, Mechanical properties, Scanning electron microscopy, Aluminum, Aluminum alloys
research-article  
Brandon Smith, Mahdi Ashrafi, Mark Tuttle and Santosh Devasia
J. Manuf. Sci. Eng   doi: 10.1115/1.4040545
This paper investigates an out-of-autoclave (OoA), embedded-resistive heating method to precisely control the bondline temperature when curing high strength adhesives for joining composite adherends. A challenge with OoA methods is that non-uniform heat loss, e.g., due to substructures that act as local heat sinks, can lead to non-uniform temperatures in the bondline, which in turn, results in uneven curing and potentially weak joints. The main contribution of this work is to apply a voltage pattern at the boundary of the embedded heater to control the distribution of the electrical power at the interior bondline, and thereby reduce temperature variations. Additionally, this work devises an empirical model (that can be applied when material parameters and models are not readily available) to predict the desired power generation, and to design the embedded heater and voltage pattern that minimizes the bondline temperature variation. The technique is demonstrated experimentally for bonding a single-lap joint, and the maximum temperature variation in the bond area was reduced by 5 times from 31.6 ?C to 6.0 ?C.
TOPICS: Joining, Composite materials, Temperature, Hardening (Curing), Design, Energy generation, Heat losses, Heat sinks, Heating, Adhesives, Bonding, Electricity (Physics)
research-article  
Mohammad Montazeri, Reza Yavari, Prahalada Rao and Paul Boulware
J. Manuf. Sci. Eng   doi: 10.1115/1.4040543
The goal of this work is to detect the onset of material cross-contamination in laser powder bed fusion (L-PBF) additive manufacturing (AM) process using data from in-situ sensors. Material cross-contamination refers to trace foreign materials that may be introduced in the powder feedstock due to reasons, such as poor cleaning of the AM machine after previous builds, or inadequate quality control during production and storage of the feedstock powder material. Material cross-contamination may lead to deleterious changes in the microstructure of the AM part and consequently affect its functional properties. Accordingly, the objective of this work is to develop and apply a spectral graph theoretic approach to detect the occurrence of material cross-contamination in real-time during the build using in-process sensor signatures, such as those acquired from a photodetector. Inconel alloy 625 test parts were made on a custom-built L-PBF apparatus integrated with multiple sensors, including a photodetector (300 nm to 1100 nm). During the process the powder bed was contaminated with two types of foreign materials, namely, tungsten and aluminum powders under varying degrees of severity. Material cross-contamination is detected by tracking the process signatures from the photodetector sensor hatch-by-hatch invoking spectral graph transform coefficients. These coefficients are subsequently traced on a Hoteling statistical control chart. Using this approach, the error in detecting the onset of material cross-contamination was < 5% , in contrast, traditional stochastic time series modeling approaches had corresponding error exceeding 15%.
TOPICS: Lasers, Contamination, Sensors, Errors, Feedstock, Aluminum powders, Storage, Time series, Tungsten, Additive manufacturing, Quality control, Machinery, Alloys, Quality control charts, Modeling, Theoretical methods
research-article  
Ze Liu, Benxin Wu, Rong Xu, Kejie Zhao and Yung Shin
J. Manuf. Sci. Eng   doi: 10.1115/1.4040483
Previous investigations on "double-pulse" nanosecond (ns) laser drilling reported in the literature typically utilize double pulses of equal or similar pulse energies. In this paper, "double-pulse" ns laser drilling using double pulses with energies differing by more than 10 times has been studied, where both post-process workpiece characterizations and in-situ time-resolved shadowgraph imaging observations have been performed. A very interesting physical phenomenon has been discovered under the studied conditions: the "double-pulse" ns laser ablation process, where the low-energy pulse precedes the high-energy pulse (called "low-high double-pulse" laser ablation) by a suitable amount of time, can produce significantly higher ablation rates than "high-low double-pulse" or "single-pulse" laser ablation under a similar laser energy input. In particular, "low-high double-pulse" laser ablation at a suitable inter-pulse separation time can drill through a ~0.93-mm thick aluminum 7075 workpiece in less than 200 pulse pairs, while "high-low double-pulse" or "single-pulse" laser ablation cannot drill through the workpiece even using 1000 pulse pairs or pulses, respectively. This indicates that "low-high double-pulse" laser ablation has led to a significantly enhanced average ablation rate that is more than 5 times those for "single-pulse" or "high-low double-pulse" laser ablation. The fundamental physical mechanism for the ablation rate enhancement has been discussed, and a hypothesized explanation has been given.
TOPICS: Lasers, Drilling, Laser ablation, Ablation (Vaporization technology), Drills (Tools), Separation (Technology), Aluminum, Imaging
research-article  
Saeed Farahani, Alireza Fallahi Arezodar, Bijan Mollaei Dariani and Srikanth Pilla
J. Manuf. Sci. Eng   doi: 10.1115/1.4040429
In this paper, a theoretical approach to model free deformation of sheet metal via polymer injection pressure is presented. It is a general methodology that can be applied for any situation where a non-uniform pressure distribution is responsible for free deformation of sheet metal within a circular cavity. This approach is composed of two iterative approximation loops. In the outer loop, the radius of curvature at the tip of dome shape was optimized based on the boundary condition at the edge of clamped area while in the inner successive loop, principal stresses determined from plasticity theories were used to satisfy the equilibrium equations. While forming sheet metal via polymer injection is a revolutionary yet complex process, its modeling is challenging. Hence, before implementing this general approach to this process, the modeling methodology as such necessitates a simplified solution for melt flow analysis to obtain a pressure distribution encompassing the entire cavity. To evaluate the proposed model, a customized experimental setup was designed and fabricated, which allows sheet metal bulging with the plastic injection. The deformation of the AA1100-O sheet was investigated during the injection of the Polypropylene-Olefin compound. The comparison of the theoretical and experimental results shows that the general approach formulated here can be successfully applied to predict the surface strains and thickness distributions with maximum error of 6% while the deformed geometry remains within ± 0.35mm deviation in the final deformation stage.
TOPICS: Pressure, Hydrostatics, Sheet metal, polymer melts, Deformation, Cavities, Modeling, Polymers, Approximation, Boundary-value problems, Errors, Geometry, Domes (Structural elements), Stress, Sheet metal work, Equilibrium (Physics), Plasticity, Flow (Dynamics), Shapes
research-article  
Yang Li, Jorge Arinez, Zhiwei Liu, Tae Hwa Lee, Hua-tzu Fan, Guoxian Xiao, Mihaela Banu and S. Jack Hu
J. Manuf. Sci. Eng   doi: 10.1115/1.4040427
Energy directors (EDs) have been widely used in ultrasonic welding of polymers and polymer-based composites. They help concentrate the welding energy and localize the weld at the location where the EDs are present. However, the utilization of EDs increases manufacturing cost and time, especially for complex parts and structures. This paper presents a method for ultrasonic welding of carbon fiber reinforced composite without using EDs. A reusable annular clamp (called a blankholder) is used as part of the weld tool to apply a variable force (called blank holding force) on the composite sheets during the ultrasonic welding. The effect of the blank holding force (BHF) on the weld formation is investigated. The results show that the duration of the BHF had significant impact on the weld formation. There is a critical duration with which a localized weld can form. Suitable durations of BHF at different levels of welding energy are determined by experiments. The main function of the BHF is to create an initial melting area by improving the contact condition. The initial melting area will act as an energy director to concentrate the welding energy, and therefore, promotes the formation of a localized weld.
TOPICS: Composite materials, Carbon fibers, Ultrasonic welding, Blanks, Welding, Melting, Polymers, Manufacturing, Clamps (Tools)
Technology Review  
Yong Huang and Steven Schmid
J. Manuf. Sci. Eng   doi: 10.1115/1.4040430
Additive manufacturing (AM) involves using computer-controlled machines to fabricate three-dimensional (3D) structural and functional parts layer by layer. To date, ample AM application opportunities exist in the health field. Based on the outcomes at the 2016 National Science Foundation AM for Health workshop, this paper summarizes the current state, gaps and research needs, and recommendations related to AM for health, in particular, medical product and hard structure printing and bioprinting. Manufacturing-related knowledge gaps and needs mainly fall into the materials, design, process innovation, part characterization, and policy and education categories. While medical products and hard structures rarely incorporate living cells, they can be designed to integrate with tissues, and their gaps and needs are typically related to the material-process-property-functionality relationship. Bioprinting-specific gaps and needs include build material selection and construct design, printed construct preservation, process selection, scalability and modeling, bioprinting-induced cell injury management, post-printing tissue fusion and maturation, and printed construct evaluation. Research recommendations encompass aspects ranging from fundamental research support to development of suitable standards for clinical use of AM products and are summarized in terms of materials, design, process innovation, modeling, characterization, and policy and education. Medical product and hard structure-specific recommendations are mainly related to build materials and structure design. For bioprinting, recommendations are summarized based on preparation, bioprinting process, and post-bioprinting treatment. Furthermore, a biomedical manufacturing landscape is proposed; the potential of bioprinting as transformative research is introduced, and manufacturing-related scientific challenges are listed.
TOPICS: Additive manufacturing, Bioprinting, Biomedicine, Design, Manufacturing, Modeling, Innovation, Printing, Biological tissues, Education, Wounds, Performance, Computers, Biological cells, Preservation, Machinery, Workshops (Work spaces)
Technical Brief  
Andrea Corrado and Wilma Polini
J. Manuf. Sci. Eng   doi: 10.1115/1.4040426
Tolerance analysis defines a procedure to estimate the resultant variation of the assembly geometry, given the tolerances associated with individual components and the functional relationship between the individual components and the assembly requirements. This aspect is particularly relevant when parts made of composite material are considered, since the research emphasis to date was on the design and fabrication of composite parts, with considerably less attention to quality issues in their subsequent assembly. This work presents a numerical tool to solve the tolerance analysis of assemblies made of compliant parts in composite material; it estimates the geometric deviations of an assembly due to the compliance of the material, the geometrical deviations of the components and the fastening of the parts by adhesive. The comparison between numerical and experimental results obtained for a case study show a good agreement.
TOPICS: Composite materials, Adhesives, Manufacturing, Tolerance analysis, Design, Geometry
Design Innovation Paper  
Daniel-Alexander Türk, Andreas Ebnöther, Markus Zogg and Mirko Meboldt
J. Manuf. Sci. Eng   doi: 10.1115/1.4040428
This paper presents a study combining additive manufactured (AM) elements with carbon fiber-reinforced polymers (CFRP) for the autoclave curing of complex-shaped, lightweight structures. Two approaches were developed: First, structural cores were produced with AM, over-laminated with CFRP, and co-cured in the autoclave. Second, a functional hull is produced with AM, filled with a temperature- and pressure-resistant material, and over-laminated with CFRP. After curing, the filler-material is removed to obtain a hollow lightweight structure. The approaches were applied to hat-stiffeners, which were modeled, fabricated and tested in three-point bending. Results show weight savings by up to 5% compared to a foam core reference. Moreover, the AM element contributes to the mechanical performance of the hat-stiffener which is highlighted by an increase in the specific bending stiffness and the first failure load by up to 18% and 310%. Results indicate that the approaches are appropriate for composite structures with complex geometries.
TOPICS: Composite materials, Hardening (Curing), Tooling, Additive manufacturing, Carbon reinforced plastics, Lightweight structures, Stiffness, Hull, Carbon, Polymers, Failure, Equipment performance, Weight (Mass), Pressure, Temperature, Fibers, Fillers (Materials), Stress
research-article  
Brandt Ruszkiewicz, Laine Mears and John T. Roth
J. Manuf. Sci. Eng   doi: 10.1115/1.4040349
Increasing fuel economy standards are pushing automotive OEMs to lightweight designs, necessitating the use of new materials with good strength-to-weight ratios. These metals come with challenges of decreased ductility and increased springback, making them difficult to form using traditional manufacturing processes. Electrical augmentation is a possible solution for processing these new materials using traditional manufacturing infrastructure. Electrical augmentation increases ductility and decreases forming loads in metals. The electroplastic effect can be predicted and modeled as a 100% bulk heating/softening phenomenon in the quasi-steady state, however, these same models do not accurately predict flow stress in transient cases. In this work, heterogeneous Joule heating is examined as the possible cause for the transient stress drop during the pulsed tension of 7075-T6 aluminum. A multi-scale finite element model is constructed where heterogeneous thermal softening is explored through the representation of grains, grain boundaries, and precipitates. Electrical resistivity is modeled as a function of temperature and dislocation density. In order to drive the model to predict the observed stress drop, the bulk temperature of the specimen exceeds experiment, while the dislocation density and grain boundary electrical resistivity exceed published values, thereby suggesting that microscale heterogeneous heating theory is not the full explanation for the transient electroplastic effect. A new theory for explaining the electroplastic effect based on dissolution of bonds is proposed.
TOPICS: Aluminum, Joules, Stress, Transients (Dynamics), Tension, Heating, Dislocation density, Electrical resistivity, Ductility, Grain boundaries, Temperature, Metals, Manufacturing, Weight (Mass), Flow (Dynamics), Corporate average fuel economy, Microscale devices, Finite element model, Fuel efficiency
research-article  
Jeffrey Plott, Xiaoqing Tian and Albert J. Shih
J. Manuf. Sci. Eng   doi: 10.1115/1.4040350
Flexible thin wall silicone parts fabricated via extrusion-based additive manufacturing (AM) tend to deform due to the AM forces, limiting the maximum build height. The tangential and normal forces in AM were measured to investigate effects of three key process parameters (volumetric flow rate Q, nozzle tip inner diameter di, and layer height t) on the build height. The interaction between the nozzle tip and extruded silicone bead is controlled to prevent interaction, flatten the top surface of the extruded silicone, or immerse the nozzle in the extruded silicone. Results show that tangential and normal forces in AM strongly depend on this interaction. Specifically, the AM forces remained low (less than 0.2 mN) if the nozzle tip did not contact the extruded silicone bead. Once the nozzle interaction with extruded silicone came into effect, the AM forces quickly grew to over 1 mN. The single wall tower configuration was developed to determine a predictive deflection resistance approach based on the measured AM forces and the resultant bending moment of inertia. This approach shows that a smaller di can produce taller towers while a larger di is better at bridging and overhangs. These results are applied to the AM of a hollow thin wall silicone prosthetic hand.
TOPICS: Elastomers, Extruding, Modeling, Silicones, Thin wall structures, Additive manufacturing, Nozzles, Manganese (Metal), Artificial limbs, Deflection, Inertia (Mechanics), Flow (Dynamics)
research-article  
Kaiyuan Wu, Zhuoyong Liang, Tong Yin, Zuwei He and Min Zeng
J. Manuf. Sci. Eng   doi: 10.1115/1.4040319
A double pulse low-frequency modulation method was proposed to improve heat input control and enhance weld quality during high-power double-wire pulsed gas metal arc welding (GMAW). By constructing a mathematical model, relationships between parameters of double pulse low-frequency modulation and energy input were analyzed. A correction coefficient was added to overcome physical characteristics of charging and discharging in a welding circuit. Thus qualitative relationships between parameters of double pulse low-frequency modulation and energy input were described more accurately. Bead-on-plate welding experiments were conducted in a synchronous phase mode. A stable welding process was achieved and perfect weld bead shapes were acquired. Modulation frequency imposed a significant effect on both weld width and penetration, while modulation duty cycle had a significant effect on penetration and little effect on weld width. Modulation frequency significantly influenced refinement of grain size. Weak and strong pulses of low-frequency modulation improved heat input control, strengthened stirring action of double pulse on weld pool, and enhanced fluidity of molten metals, thereby contributing to optimization of weld quality.
TOPICS: Wire, Gas metal arc welding, Welding, Heat, Metals, Optimization, Circuits, Cycles, Grain size, Shapes
research-article  
Hossein Paktinat and Saeid Amini
J. Manuf. Sci. Eng   doi: 10.1115/1.4040321
In this study, ultrasonic assisted drilling (UAD) is performed to investigate the effect of ultrasonic vibrations on common difficulties existed in conventional drilling (CD). UAD is a promising and advanced technique by which a harmonic movement with frequency in the range of ultrasonic and low amplitude is superimposed in the movement of work material or cutting tool. The study is conducted both experimentally and numerically; at first a UAD system is designed, manufactured and carried out on a milling machine and experimental tests are accomplished and in the following experimental results are supported by the help of 3D finite element simulation. Finally, the dependent parameters such as the burr height and cylindricity of the ultrasonically and conventionally drilled workpiece are measured and evaluated. Briefly, it was proved that intermittent movement of drill bit in the direction of feed rate results in broken and discontinuous chips by which built-up-edge is reduced and hole quality improves. In addition, the burr height which is known as unwanted projection of material at the exit surface of pieces can be decreased notably if UAD is considered.
TOPICS: Drilling, Simulation, Finite element analysis, Vibration, Milling machines, Hole quality, Cutting tools, Bits (Tools)
research-article  
Haidong Yu, Chunzhang Zhao and Xinmin Lai
J. Manuf. Sci. Eng   doi: 10.1115/1.4040323
The accurate calculation of deformation during assembly process is important for deviation propagation of large scale thin-walled hemisphere structures with manufacturing deviations due to the non-uniformed material properties and nonlinear geometrical behavior. In this study, a new irregular quadrilateral plate element based on the absolute nodal coordinate formulation (ANCF) is proposed to discretize the scal-loped segment plates with shape deviations. The high-order shape functions of the new element are de-veloped by considering the variable geometrical boundaries. The generalized elastic forces of the new elements for anisotropic and orthotropic materials are derived based on continuum mechanics approach. The bending deviation mode is defined and the evaluation indexes for assembly quality of thin-walled hemisphere structures are proposed. The force equilibrium equations are employed to study the defor-mation during assembly process for large scale thin-walled hemisphere structures with multiple scalloped segment plates. The numerical results are compared with that from experimental data and ABAQUS. The correlation between the assembly quality and the bending deviation, the clamping methods, the geo-metrical parameters and the material properties of structures is also investigated.
TOPICS: Manufacturing, Plates (structures), Shapes, Materials properties, Deformation, Anisotropy, Continuum mechanics, Equilibrium (Physics)
research-article  
Haiyang He, Jie Xu, Xiaoming Yu and Yayue Pan
J. Manuf. Sci. Eng   doi: 10.1115/1.4040322
In projection stereolithography (SL) processes, the separation of a newly cured layer from the constrained surface is a historical technical barrier and still greatly limits its printable size, process reliability and print speed. This paper presents an approach to reduce the separation force in projection stereolithography (SL) processes by texturing the constrained surface with radial microgroove patterns. Separation forces with conventional smooth constrained surface and textured surface are both modeled. The analytical model suggests that a proper design of micro patterns of the constrained surface is capable of reducing separation forces greatly. Furthermore, a projection SL testbed with online separation force monitoring unit is developed for experimental study. Experimental results verified the effectiveness of micro surface textures in reducing separation forces. Test cases also show that with the help of the proposed textured constrained surface, parts with wide solid cross sections that could not be printed using conventional methods were manufactured successfully. The influence of the textured constrained surface on the printed parts' surface roughness is studied, a gray scale projection approach is proposed to eliminate the influence and improve the surface quality of printed parts. Hence, the presented methods can help to improve the manufacturing capability of Projection SL processes.
TOPICS: Separation (Technology), Mask image projection stereolithography, Manufacturing, Reliability, Surface roughness, Cross section (Physics), Design, Surface texture, Surface quality
Technical Brief  
James Garofalo, John Lawler, Daniel F. Walczyk and Nikhil Koratkar
J. Manuf. Sci. Eng   doi: 10.1115/1.4040265
Graphene Oxide slurries were deposited onto copper foil for use in Lithium-Ion battery anodes to determine the best deposition method(s) for research or high-volume manufacturing. Four deposition methods were tested: doctor blade, Mayer rod, slot die, and low volume low pressure (LVLP) spray. Analytical models that link tooling and process characteristics to mass flow rate of slurry and the resulting dry deposition height are developed and validated experimentally. While all methods successfully produced functioning batteries, a number of different qualitative and quantitative metrics from experimental results identified the best method for both situations. Observations were recorded on adhesion, deposition consistency, usability, and cleanability. Data on specific discharge capacity was recorded to show performance over the anode lifetime and at different charge/discharge rates. The data indicates that anodes produced using reduced Graphene Oxide (rGO) deliver a specific charge storage capacity of 50 to 400 mAh/g at charge-discharge rates of 1C to 0.05C. Doctor blading proved to be best for laboratory setups because of its adjustability, while the Mayer Rod shows promise for high-volume manufacturing due to slight better performance and the use of non-adjustable, dedicated tooling. All methods, analysis, and metrics are discussed.
TOPICS: Anodes, Copper foil, Slurries, Graphene, Lithium-ion batteries, Tooling, Manufacturing, Pressure, Flow (Dynamics), Adhesion, Sprays, Blades, Storage
research-article  
Jie Niu, Hui Leng Choo, Wei Sun and Sui Him Mok
J. Manuf. Sci. Eng   doi: 10.1115/1.4040159
Research on materials, design, processing and manufacturability of parts fabricated by Additive Manufacturing (AM) has been investigated significantly in the past. However, limited research on mechanical behaviour of cellular lattice structures by AM was carried out. In this paper, effective tensile Young's modulus, E*, of triangular lattice structures was determined. Firstly, analytical solution was derived based on Euler-Bernoulli beam theory. Then numerical results of E* were obtained by finite element analysis (FEA) for lattice structures classified by three shape parameters. The effects of side length, L, beam thickness, t, and height, h, on E* were investigated individually. FEA results revealed that there is a relationship between E* and the relative density and shape parameters. Among them, t has the most significant effect on E*. Numerical results were also compared with the results from modified general function for cellular structures and modified formula for triangular honeycomb. The E* predicted by the proposed analytical solution shows the best agreement with the numerical results. Finally, tensile tests were carried out using AlSi10Mg triangular lattice structures manufactured by Selective Laser Melting (SLM) process. The experimental results show that both analytical and numerical solutions can predict E* with good accuracy. In the future, the proposed solution can be used to design structures with triangular unit cells.
TOPICS: Additive manufacturing, Finite element analysis, Design, Shapes, Mechanical behavior, Density, Lasers, Melting, Honeycomb structures, Euler-Bernoulli beam theory, Young's modulus
research-article  
Zheng Kang, Benxin Wu, Ruoxing Wang and Wenzhuo Wu
J. Manuf. Sci. Eng   doi: 10.1115/1.4039492
Flexible electronic devices involve electronic circuits fabricated onto a flexible (e.g., polymer) substrate, and they have many important applications. However, during their use, they often need to go through repeated deformations (such as bending). This may generate cracks in metallic components that often exist in a flexible electronic device, and could obviously affect the device durability and reliability. Carbon nanotubes (CNTs) have a potential to enhance the metal fatigue properties. However, previous work on the fabrication of CNT-metal composites onto a flexible substrate has been limited. This paper reports the research work on a novel laser-based approach to fabricate CNT-metal composites onto a flexible substrate, where mixtures containing CNTs and metal (silver) nanoparticles are deposited onto the substrate through a dispensing device and then laser-sintered into CNT-metal composites. Under the studied conditions and for the tested samples it has been found that overall the addition of CNTs has significantly enhanced the bending fatigue properties of the laser-sintered material without degrading the material electrical conductivity (which has actually been slightly increased). The laser-based approach has several potential advantages, such as the local, precise and flexible production of CNT-metal composite patterns with small or little thermal effects to the flexible substrate and other surrounding regions, and without using a mask or vacuum. Future work is certainly still needed on this novel fabrication process.
TOPICS: Fatigue, Silver, Lasers, Composite materials, Manufacturing, Carbon nanotubes, Metals, Flexible electronics, Fatigue properties, Electronic circuits, Reliability, Temperature effects, Fracture (Materials), Nanoparticles, Durability, Polymers, Vacuum, Metal fatigue, Electrical conductivity, Deformation
research-article  
Gianfranco Palumbo, Donato Sorgente, Maurizio Vedani, Ehsan Mostaed, Milad Hamidi Nasab, Dario Gastaldi and Tomaso Villa
J. Manuf. Sci. Eng   doi: 10.1115/1.4039110
In the present work, both the surface chemical contamination and the mechanical alteration of Titanium Grade 5 and Grade 23 plates subjected to superplastic forming for the manufacturing of highly customized biomedical prostheses have been investigated. As case study, a cranial implant was considered. Free Inflation tests were conducted in order to determine the material behavior to be implemented in the numerical model used for simulating the implant manufacturing by superplastic forming. Glow Discharge Optical Emission Spectrometry analyses, nano-indentation tests and metallographic analyses allowed to relate the mechanical alteration to the Oxygen enrichment due to the environmental exposition during processing. Finally, real implants were produced and Cytotoxicity tests were conducted on the most oxidized part in order to determine the effect of the oxygen enrichment on the cells viability.
TOPICS: Titanium alloys, Superplastic forming, Surface properties, Biomedicine, Oxygen, Manufacturing, Computer simulation, Nanoindentation, Emission spectroscopy, Contamination, Glow discharge, Plates (structures), Prostheses, Titanium
research-article  
Kai Chen, Xun Liu and Jun Ni
J. Manuf. Sci. Eng   doi: 10.1115/1.4038993
A hybrid friction stir resistance spot welding process is applied for joining aluminum alloy 6061 to TRIP 780 steel. Compared with conventional resistance spot welding, the applied current density is lower and the welding process remains in the solid state. Compared with conventional friction stir spot welding (FSSW) process, the welding force is reduced and the dissimilar material joint strength is increased. The electrical current is applied in both a pulsed and direct form. With the equal amount of energy input, the approximately same force reduction indicates that the electro-plastic material softening effect is insignificant during FSSW process. The welding force is reduced mainly due to the resistance heating induced thermal softening of materials. With the application of electrical current, a wider aluminum flow pattern is observed in the thermo-mechanically affected zone of weld cross sections and a more uniform hook is formed at the Fe/Al interface. This implies that the aluminum material flow is enhanced. Moreover, the Al composition in the Al-Fe interfacial layer is higher, which means the atomic diffusion is accelerated
TOPICS: Welding, Aluminum alloys, High strength steel, Friction, Flow (Dynamics), Electric current, Aluminum, Joining, Steel, Cross section (Physics), Current density, Heating, Diffusion (Physics)

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