In the present work, thermoset carbon fiber–reinforced polymer (CFRP) was spot joined to magnesium alloy AZ31B by a friction self-piercing riveting (F-SPR) process. Lap shear tensile and cross-tension testing were used to evaluate the mechanical joint performance. An average lap shear tensile load of 5.18 kN was achieved, while an average of 2.81 kN was found from cross-tension testing. All F-SPR samples showed pull-out of AZ31B after mechanical testing, indicating good mechanical interlocking between the steel rivet and AZ31B. Corrosion potential was measured for each material to establish the galvanic corrosion characteristics. As expected, AZ31B was found to be the most active, while thermoset CFRP was the most noble. The steel rivet fell between the AZ31B (active) and the thermoset CFRP (noble). Salt fog corrosion testing (ASTM B-117) was performed to evaluate the corrosion performance of the uncoated F-SPR joint. With up to 200 h of exposure, the post-corroded F-SPR joint integrity retained 81.2% of the pre-exposure F-SPR joint strength with AZ31B pull-out failure mode. From cross-sectional analysis of the F-SPR joint, extensive corrosion of AZ31B was observed at the joint and other exposure areas. However, steel rivet was not significantly corroded potentially due to sacrificial anode effect by which AZ31B corroded first in the galvanic couple.

The synthesis of vertically aligned carbon nanotubes (CNTs), also referred to as CNT forest, by chemical vapor deposition (CVD) is an intricate process that is sensitive to multiple factors other than control of temperature, pressure, and gas flows. In particular, growth is highly sensitive to factors like ambient humidity, as well as small quantities of oxygen-containing species and carbon deposits inside the reactor. These typically uncontrolled factors significantly affect growth reproducibility and hinders the fundamental study of process-structure-property relationship for these emerging materials. Accordingly, universally applicable design modifications and process steps toward improve growth consistency are sought after. In this study, we introduce two new modifications to our custom-designed multizone rapid thermal CVD reactor and demonstrate their impact on growth: (1) reconfiguring the inlet gas plumbing to add a gas purifier to the helium (He) line, and (2) designing a new support wafer for consistent loading of substrates. We use statistical analysis to test the effectiveness of these modifications in improving growth and reducing variability of both CNT forest height and density. Analysis of our experimental results and hypothesis testing show that combining the implementation of He purifier with the redesigned support wafer increases forest height and reduces the variability in height (17-folds), both at statistically significant and practically significant levels.

Hardened steels in engineering applications tend to have gradient microstructures with varying amounts of retained austenite alongside harder phases such as martensite or bainite. However, the metastable austenite can transform into martensite under mechanical loads, resulting in an inelastic strain within the material from the volumetric mismatch between FCC austenite and BCT martensite. In this work, a new constitutive formulation based upon the critical driving force for austenite transformation is presented. The model was implemented into a crystal plasticity formulation, and empirical data from in-situ neutron diffraction was used to determine the local micro-plasticity and transformation plasticity parameters. The results from finite element modeling also show that using a homogenized finite element approach could help to establish a material model that can capture the transformation plasticity within these materials with good accuracy.

In order to rapidly share manufacturing resources among enterprises in a network environment, reduce carbon emissions and production costs, scheduling of cellular manufacturing with intercell moves is studied. Previous researches on cellular manufacturing with intercell moves either supposed that a part can only move between two cells at most one time or supposed that intercell moves of parts were on fixed paths. However, there might be several manufacturing cells with the same processing function or several same machines in different cells in a network environment. Intercell moves of parts might have flexible routes. To make the cellular manufacturing with intercell moves in a network environment, a scheduling model aiming at minimizing total carbon emissions, makespan and total costs is proposed for intercell moves with flexible routes and no restrictions on the number of intercell moves. An improved artificial bee colony algorithm (ABC) is proposed to solve the scheduling model. In order to improve searching ability of ABC, neighborhood search with an adaptive stepsize mechanism is proposed in leader bee phase and onlooker phase of the algorithm. A binary tournament selection method is designed to improve convergence speed in the onlooker bee phase. A case study is used to verify the proposed model and algorithm. The results show that improved algorithm has better performance on convergence speed and searching ability than that of original artificial bee colony algorithm.

Due to continuous push towards environmental regulations to reduce the impact on the environment by reducing the fuel consumption, and concerns on limited resources, the more sustainable manufacturing is in demand. More abundance material like iron-carbon based alloy are higher strength and easily formable but ways are research to reduce the weight of created part by reducing the thickness due to density issue. Some low dense material is the alternatives but they miss the easy to deform spot. The present study is focused on how to make the material more deformable in the process by evaluating the parameters in deformation through the hole expansion process. For this study, four tests were chosen hemispherical dome test, cylindrical tool test, conical tool test, and biaxial test. In all tests, only the biaxial test machine does not use the rigid tool to deform the hole while all other test used the rigid tool punch to deform the hole. Cruciform specimen dimension was used to make the sample, which fits in all of the considered tests. A hole was created at the center of the specimen which will be expanded in all tests. In all tests the deformation mechanics and hole expansion was studied. Force-displacement curves were plotted and discussed. In addition, tests were also performed on annealed material to understand the hole expansion in ductile material. Based on the results it was observed that biaxial tests do not provide any pressurization effect and all test which includes the rigid tool to deform the hole does. Due to the pressurization effect, the hole was expanded more. It was also noted that the hole expansion was more in ductile material and pressurization effect increases with ductile material.

Most researches on process planning optimized machining process routings and cutting parameters independently and ignored their comprehensive effects on carbon reduction. In order to further reduce carbon emissions in manufacturing processes, an optimization model of cutting parameters and machining process routings is proposed to minimize total carbon emissions and total processing time of all processes. Carbon emissions include those caused by energy consumptions of machines in cutting state, material consumption of cutting tools and cutting fluid in all processes. As the optimization of cutting parameters is a continuous optimization problem, but the optimization of machining process routings including machining methods, process sequences, machine allocating and cutter selecting are discrete optimization problems, the whole optimization of process planning is divided into two parts. One is continuous optimization of cutting parameters. Another is discrete optimization of machining process routings. A hybrid optimization strategy of bird swarm algorithm (BSA) and NSGA-II algorithm is proposed to optimize the proposed model. Cutting parameters are optimized using BSA aiming at minimizing carbon emissions and machining time of each process. Machining process routings are optimized using NSGA-II under each optimized group of cutting parameters from the Pareto set. Four kinds of mutation operators in NSGA-II are designed for the discrete optimization of machining process routings. A workpiece with six machining features to be machined in a workshop with two CNC lathes, two CNC milling machines and two drilling machines is taken as a case study. The validity of the proposed model and hybrid strategy is verified by computational and analytical results. Several conclusions are yielded.

Friction stir blind riveting (FSBR) is a recently developed manufacturing process for joining dissimilar lightweight materials. The objective of this study is to gain a better understanding of FSBR in joining carbon fiber-reinforced polymer composite and aluminum alloy sheets by developing a sensor fusion and process monitoring method. The proposed method establishes the relationship between the FSBR process and the quality of the joints by integrating feature extraction, feature selection, and classifier fusion. This study investigates the effectiveness of lower rank tensor decomposition methods in extracting features from multi-sensor, high-dimensional, heterogeneous profile data. The extracted features are combined with process parameters, material stack-up sequence, and engineering-driven features such as the peak force to provide rich information about the FSBR process. Sparse group lasso regression is adopted to select the optimal monitoring features. The selected features are fed into weighted classification fusion to estimate the quality of the joints. The fusion method integrates five individual classifiers with optimal weights. The correct classification rates resulted from various feature extraction and selection methods are assessed and compared. The proposed method can also be applied to other manufacturing processes with online sensing capabilities for the purpose of process monitoring and quality prediction.

The purpose of this work was to develop and analyze different materials that would be able to create the partially carbonized nanofibers through electrohydrodynamic casting followed by heat treatment. Test samples were created with different precursors containing polymer solutions and different added metal salts. After performing a series of steps to create each test sample, the sample was heat-treated to generate carbon nanofiber composites. The morphology of the carbon nanofiber composites was observed using a scanning electron microscope. Hyperthermia tests on typical fiber composites were performed.

In order to help manufacturing companies quantify and reduce product carbon footprints in a mixed model manufacturing system, a product carbon footprint oriented multi-objective flexible job-shop scheduling optimization model is proposed. The production portion of the product carbon footprint, based on the mapping relations between products and the carbon emissions within the manufacturing system, is proposed to calculate the product carbon footprint in the mixed model manufacturing system. Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) is adopted to solve the proposed model. In order to help decision makers to choose the most suitable solution from the Pareto set as its execution solution, a method based on grades of product carbon footprints is proposed. Finally, the efficacy of the proposed model and algorithm are examined via a case study.

C-C composite is a kind of typical difficult-to-machine materials due to its high hardness, high strength, and obvious anisotropy features. But, water-based or oil-based coolant cannot be used during its machining process. As a result, the machining defects, including burrs, orifice ripping, and interlayer delamination, are always unavoidable. In this article, taking the liquid nitrogen as coolant, C-C composite cryogenic drilling is researched experimentally. Taking the way of LN2 external spray cooling, a series of cryogenic drilling experiments were designed. Comparing with dry drilling, the thrust force was reduced, the machining defects were significantly inhibited, and a better roundness of holes was achieved in cryogenic drilling. It indicates that cryogenic condition has a positive effect on improving the C-C composite drilling quality.

In the aerospace industry, titanium (Ti) alloys, especially Ti6Al4V, has been extensively used over other light weight alloys due to their high strength-to-weight ratio. However, the material and production costs have been major obstacles in the adoption of Ti alloys for a wide variety of applications. The machining of Ti alloys is one of the most time consuming and expensive mechanical processes in aerospace manufacturing. Based on previous literature on the topic, coated drills have had some degree of success in the drilling of Ti. To further the work, this paper conducts a comparative study in which Ti6Al4V plates are drilled with super hard coated drills such as Diamond-like-Carbon (DLC), AlMgB14 (BAM) and nanocomposite AlCrSiN. The results are compared with those of an uncoated drill bit. Working with a coating supplier, several variations of BAM coating have been applied and used in our drilling experiments. To evaluate the performance of these drills, scanning electron microscopy and confocal laser microscopy were used to assess the wear progress of each drill qualitatively and quantitatively. In drilling Ti alloys, the primary mechanisms of flank wear are abrasion, microscopic fracture (chipping) and attrition, which result in the detachment of the adhesion layer located at the cutting edge. For all the drills, the predominant wear occurs near the margin. From our drilling experiments, it has been observed that AlCrSiN and BAM drills have survived up to 58 holes and over 80 holes, respectively, while both uncoated and DLC drills have experienced catastrophic fracture at less than 40 holes.

Graphene is one of the most promising carbon nanomaterial due to its excellent electrical, thermal, optical and mechanical properties. However, it is still very challenging to unlock its exotic properties and widely adopt it in real-world applications. In this paper, we introduces a new 3D graphene structure printing approach with pure graphene oxide material, better inter-layer bonding, and complex architecture printing capability. Various parameters related to this novel process are discussed in detail in order to improve the printability, reliability and accuracy. We have shown that the print quality largely depends on the duty cycle of print head, applied pressure and travel velocity during printing. A palette of printed samples are presented to demonstrate the effectiveness of the proposed technique along with the optimal parameter settings. The proposed process proves to be a promising 3D printing technique for fabricating multi-scale nanomaterial structures. The theory revealed and parameters investigated herein are expected to significantly advance the knowledge and understanding of the fundamental mechanism of the proposed directional freezing based 3D nano printing process. Furthermore the outcome of this research has the potential to open up a new avenue for fabricating multi-functional nanomaterial objects.

Different types of toolpaths have been extensively studied with regards to different factors such as energy consumption and tool wear. However, toolpaths have been introduced recently, where high speeds and dynamic movements are combined to provide higher performance. The aim of this paper is to compare a spiral toolpath strategy, which has been studied previously with good results in energy consumption, with a high speed dynamic toolpath strategy, which combines helical and dynamic movements, with regards to energy consumption, tool wear and carbon emissions. Several advantages are identified with a high speed dynamic toolpath strategy over the typical spiral toolpath strategy in terms of tool wear, energy consumption and carbon emissions. The results show that the high speed dynamic toolpath is a better alternative for different milling operations such as slotting, pocketing, and face milling.

Shape memory composites (SMCs) are very interesting for self-deployable structures in aerospace applications. SMCs have been widely developed but not yet fully applied to space. In this study a lab-scale production of SMC prototypes for aerospace is described. Conceptual design of small-scale structures were prototyped with the aim to define several configurations which are able to self-deploy. SMC prototypes were manufactured by using two layers of carbon/epoxy prepreg with a shape memory epoxy resin interlayer. Two different configurations were produced to prototype complex shape for multiple folding and 3D deployments of de-orbiting structures. In particular, the first prototype tests a de-orbiting system without the sail to study the complex folding and de-folding mechanisms. The second configuration evaluates a de-orbiting dual-sail for satellite applications. The SMC structures were produced in the opened shape and subsequently memorized in the closed configuration. The initial deployed configuration is recovered by heating the prototype. The closed configuration increases the packing efficiency of large structures for space orbiting systems. The shape memory properties were provided only to folding zones. Memory-recovery-cycles have been performed to test SMC performances. As a result, the two configurations can successfully self-deploy following the desired design constraints and recovering the original flatness without noticeable defects.

Quenching using a press with controlled die loads, commonly referred to as press quenching, is a specialized technique used to minimize distortion of critical components such as gears and high quality bearing races. Improper press load magnitudes or timing of the load application may restrict part movement during quenching to the point of imposing stresses that cause cracking, especially in a common bearing steel such as AISI 52100, high carbon, high strength steel. This paper applies a finite element based heat treat simulation tool, DANTE ® , to investigate the sensitivity of cracking to press quenching process parameters. The typical method for designing a press quench process to control flatness, out-of-round, and taper is by experience coupled with trial-and-error. This is accomplished by adjusting oil flow rates, flow directions, die loads, and the timing of die loads. Metallurgical phase transformations occur during the quenching process as austenite transforms to martensite and possibly to diffusive phases. Thermal contraction due to cooling and volumetric expansion due to the phase changes therefore occur simultaneously during the heat treating process. A constantly changing stress state is present in the part, and improperly applied die loads, oil flow or oil flow rate can add additional stress to result in cracking. An inconsistent cracking problem in an AISI 52100 bearing ring was evaluated using production trials, but the process statistics were not conclusive in identifying the source of the problem. Heat treatment process modeling using DANTE was used to investigate the effects of quench rate, die load pulsing, and several other process variables to determine how these parameters impact the resulting stresses generated during the press quenching operation.

Wide-spread adoption of carbon nanomaterials has been hindered by inefficient production and utilization. A recently developed method has shown possibility to directly synthesize bulk nanostructured nonwoven materials from catalytically deposited carbon nanofibers. The basic manufacturing scheme involves constraining carbon nanofiber growth to create three-dimensionally featured, macroscale products. Although previously demonstrated as a proof of concept, the possibilities and pitfalls of the method at a larger scale have not yet been explored. In this work, the basic foundation for using the constrained formation of fibrous nanostructures (CoFFiN) process is established by testing feasibility in larger volumes (as much as 2000% greater than initial experiments) and by noting the macroscale carbon growth characteristics. It has been found that a variety of factors contribute to determining the basic qualities of the macroscale fiber collection (nonwoven material), and there are tunable parameters at the catalytic and constraint levels. The results of this work have established that monolithic structures of nonwoven carbon nanofibers can be created with centimeter dimensions in a variety of cross-sectional shapes. The only limit to scale noted is the tendency for nanofibers to entangle with one another during growth and self-restrict outward expansion to the mold walls. This may be addressed by selective placement of the catalyst in the mold.

With the implementation of more stringent emissions standards, ultra-high strength steel has been increasingly used in vehicle body to reduce the carbon emissions, but softening in the heat affected zone is one of the most serious issues faced with in welding of this steel. In this paper, a finite element model (FEM) was developed to estimate temperature distribution in laser welding of ultra-high strength steel M1500 and a carbon diffusion model was then developed to estimate the martensite tempering transformation in the softening zone based on the simulated temperature distribution results. Maximum softening degree, minimum hardness point position and boundary of the softening zone were estimated and validated by hardness measurement experiments. This work provides a better understanding of the mechanism for heat affected zone softening in laser welding of ultra-high strength steel.

A hollow R.R. Moore rotation fatigue sample made of AISI 9310 is processed using vacuum carburization and high pressure gas quenching. The vacuum carburization schedule is designed to through carburize the thin wall section of the fatigue sample to 0.7% wt.% carbon, followed by 10 bar nitrogen quench. Some samples showed significant bow distortion after quench hardening, and further investigations indicated that the unbalanced wall thickness from machining is the main cause of the bow distortion. In this paper, DANTE, a commercial heat treatment software is used to study the cooling, phase transformation, and stress evolution during quenching. The effect of unbalance wall thickness on distortion is also investigated. Residual stress state in the quench hardened sample is critical to the fatigue performance during rotational bending fatigue tests. In this study, the unbalanced geometry has insignificant effect on the residual stresses after quench hardening. However, the unbalanced geometry will affect the applied stress significantly during a rotation fatigue test.

Arterial disease occurs when plaque builds up in the arteries and limits flow of oxygen-rich blood to organs and other parts of the body reducing organ function. Atherectomy is a mechanical process in which plaque is removed from artery walls or modified to change vessel compliance. Various types of atherectomy systems exist to remove or modify plaque depending on plaque morphology. Orbital atherectomy (Diamondback 360® Orbital Atherectomy System) is a sanding process utilizing a diamond abrasive crown mounted eccentrically to a flexible drive shaft. The effects of rotational speed, crown size, centrifugal forces and run time were evaluated. Finite element modeling and bench testing using carbon as a calcified plaque surrogate material were used. The crown-simulated vessel wall force was calculated using a finite element model that included a rigid vessel wall and a rotating crown. Results show a small force when the crown begins to rotate at lower speeds, that increases to a peak force at maximum speed, and decreases as the orbit diameter increases with material removal. A design of experiments plan was created and used to quantify the effects of crown size rotation speed and number of treatment passes on lumen diameter. Increasing the crown diameter increased lumen diameter nonlinearly at an increasing rate with crown rotation speed in the carbon model. Scanning Electron Microscopy (SEM) analysis of the particulate material removed in the bench test demonstrated brittle fracture as the mode of material removal of the carbon surrogate.

There is a need to manufacture advanced composite parts faster, cheaper and with less waste as interest in these materials for lightweighting components used by the aerospace, automotive, marine and energy markets continues to grow. For example, although hot gas torch heating is a well-established process for producing advanced thermoplastic composites parts in automated tape layup (ATL), researchers are looking at other polymer welding methods including laser, infrared and ultrasonic heating in an attempt to improve the process. This paper focuses on benchmarking the capabilities of a new method, ultrasonic consolidation, against another standard process for consolidating thermoplastic composites, i.e. thermal pressing. To accomplish this, 3-point beam bending tests are conducted on specimens made with both methods and flexural strength results were used as an objective comparison. The ultrasonic welding proved to be more effective in welding PET/Carbon tape than thermal, showing an increase of maximum flexural stiffness of 65% for the highest performing ultrasonic consolidation samples, but did not weld HDPE/Glass as effectively with the best ultrasonic samples having 36% lower stiffness. The quasi-isotropic samples showed very similar results. The results show that given suitable process parameters and a compatible thermoplastic composites system, ultrasonic consolidation of prepreg composite tape can be as effective as current thermal methods in terms of performance, but still manage to decrease the time and energy consumed.