Fabrication Sequence Research Articles

Experimental and analytical study of combined bolted-welded lap joints including high-strength steel

Bolting is often combined with welding to supplement the welded joints. However, different opinions are available in literature regarding the combined bolted and welded joint strength. Further, the combined use of bolting and welding in high-strength steel applications has not been extensively studied. In this study, a total of 48 combined bolted-welded lap joints with various test variables including ordinary- and high-strength steel were tested. Depending on the initial installation location of the bolt, there was a difference of by about 100 to 250 kN in strength. When the pre-tensioned bolts were applied, the joint strength increased about 100 kN. The load-deformation relationship of the combined bolted and welded joint was first derived based on deformation compatibility. A new formula that is applicable to both ordinary and high-strength steel was proposed and validated based on the test results. In addition, the effect of the fabrication sequence on the joint strength was also evaluated.

On the fabrication of thin-film artificial metal grid resonator antenna arrays using deep x-ray Lithography

In this paper, a unique microfabrication approach for designing high permittivity, high gain and wideband thin-film artificial metal grid dielectric resonator antenna (GDRA) arrays for mm-wave applications is presented. Fabrication of the GDRAs with a strip template frame is based on deep-x-ray lithography (DXRL) using a 500 µm thick polymethylmethacrylate (PMMA) layer as the photoresist. The simple low-cost fabricated DXRL mask for exposure consisted of gold absorbers patterned by direct-write ultraviolet (UV) laser lithography on a carbon substrate. To avoid the trapping of gas bubbles in the dense, high aspect ratio (HAR) deep grid structures, a novel development approach was introduced utilizing in-vacuum, room temperature dip development to facilitate the collapse of forming gas bubbles. The developed voids were subsequently electroplated to a nickel thickness of 300 µm to obtain high permittivity artificial dielectrics. The paper describes the entire fabrication sequence. Also, the x-ray mask and DXRL structures are examined for dimensional accuracy and structural quality. This strip template frame approach has superior performance in terms of impedance bandwidth, gain and radiation efficiency as compared to the previously published solid template frame approach. For the purpose of the demonstration, a four-element GDRA array sample was fabricated and tested. A wide measured impedance bandwidth of 5 GHz from 58 GHz to 63 GHz and measured broadside radiation pattern with a peak gain of 10.9 dBi was achieved.

Flexible CuO–ZnO nano-bulk junction with photovoltaic response

Nano-Bulk junction grown over flexible Cu substrate demonstrating photovoltaic response has been developed. The structure of the device fabricated by us is Cu/CuO/CuO-ZnO/ZnO/Ag with the entire device fabrication sequence taking place at a temperature lower than 330 K. A nano-crystalline p-type CuO layer was deposited on Cu substrate using chemical bath deposition at 300 K. The n-type ZnO was solution grown and spin coated over the blend of CuO-ZnO deposited as a buffer between p-type CuO an n-type ZnO layer. The optimized device exhibited an open circuit voltage of 0.25 V, a short circuit current density of 2 × 10–6 A cm−2, a fill factor of 8% and efficiency of 0.11%. A space charge limited conduction mechanism was identified for the best device structure. The optimized cell structure had a diode ideality factor of 2.11 and work function of 3.28 eV.

Space-time topology optimization for additive manufacturing

The design of optimal structures and the planning of (additive manufacturing) fabrication sequences have been considered typically as two separate tasks that are performed consecutively. In the light of recent advances in robot-assisted (wire-arc) additive manufacturing which enable addition of material along curved surfaces, we present a novel topology optimization formulation which concurrently optimizes the structure and the fabrication sequence. For this, two sets of design variables, i.e., a density field for defining the structural layout, and a time field which determines the fabrication process order, are simultaneously optimized. These two fields allow to generate a sequence of intermediate structures, upon which manufacturing constraints (e.g., fabrication continuity and speed) are imposed. The proposed space-time formulation is general, and is demonstrated on three fabrication settings, considering self-weight of the intermediate structures, process-dependent critical loads, and time-dependent material properties.

Optimization of asymmetric tooth root generated with protuberance hob

The Direct Gear Design method optimizes various parameters and elements of gear tooth geometry to achieve the required gear drive performance. One such critical element of the tooth profile is the root fillet. Previous publications had considered asymmetric tooth root fillet optimization assuming that the tooth involute flanks and root fillets are processed (machined) simultaneously. However, there are many applications that require high gear tooth flank accuracy and high load capacity in combination with minimized gear production cost. In order to satisfy these requirements, the tooth involute flanks and root fillets are processed separately. A gear blank is machined by a topping protuberance hob that finalizes the root fillet, tooth tip diameter and chamfers, leaving stock for the tooth flank grinding. Then, after the gear’s heat treatment (carburizing + case hardening) and in some cases shot peening of the tooth root, the tooth flanks are processed using highly productive generating grinding, removing the grinding stock. As a result, the full residual stress developed by case hardening is retained. This fabrication sequence is most typical for automotive transmission gears.

Prussian blue-decorated Cs ion exchange resins with polydopamine as a linker

Based on a conventional cation-exchange polymer resin, Cs ion exchange resins were fabricated for the removal of radioactive Cs via two preparation methods. Prussian blue (PB), which have been commonly used to remove radioactive 137Cs, was synthesized on the surface of resins. To provide a strong interaction between the polymer resin and PB, polydopamine (PDA) was used as a linker, present on the surface of the polymer resins. Based on the same principle, two types of Cs ion exchange resins were prepared via different orders of fabrication sequence. From the removal test of Cs ions, it was found that the two types of the resins did not show noticeable difference in adsorption of Cs ions, in which adsorption of Cs ions took place heterogeneously and chemically with multilayer adsorption.

Effect of aluminide coatings on penetration and microstructure of TIG welded 9Cr-1Mo steel for fusion blanket applications

Aluminide coatings with a top alumina layer on 9Cr steels are considered candidates for fusion blanket applications. One of the critical issues associated with such coating is the fabrication sequence. It is therefore important to investigate the effect of aluminide coating on weld properties of 9Cr steels. This work is a preliminary investigation of the weldability of aluminide coated 9Cr-1Mo steels using bead-on-plate welding experiments. Alumina coated GRADE 91 steel samples by hot dip aluminizing followed by normalizing and plasma tempering were generated. Bead-on-plate welding studies were conducted at different heat inputs by varying the weld speed (100,125,150 mm/min) and using a constant current of 200 A by autogenous tungsten inert gas (TIG) welding process. The effect of coating on the weld microstructure was investigated using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive x-rays (SEM-EDX) and microhardness tests. It was observed that the presence of alumina (Al2O3) on the top of coated samples resulted in improved depth of penetration (DOP) due to arc constriction. The presence of Al rich inclusions (AlN) in the weld bead were also observed. The marginal increase in Al concentration of the weld bead appears to reduce the grain size of weld metal for coated sample and microhardness was enhanced compared to the uncoated 9Cr-1Mo steels.

Interfacial characterization and mechanical properties of 316L stainless steel/inconel 718 manufactured by selective laser melting

The multi-material selective laser melting (SLM) technology has been widely studied in recent years. In this paper, 316L stainless steel (316SS) and Inconel 718 (IN718) multi-material parts were manufactured by SLM and their interfacial characteristics and mechanical properties were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electronic universal testing machine and microhardness tester. The interface metallograph and higher comprehensive mechanical performance with elasticity modulus (103 ± 3 MPa), elongation (28.1 ± 2%) and ultimate tensile strength (596 ± 10 MPa) proved good metallurgical bonding at the interfaces (∼100 μm) between 316SS and IN718. Nevertheless, some cracks and holes, which were found at or near the interfaces, suggested special SLM processing parameters (such as laser power, laser scanning speed, layer thickness, hatch spacing, remelting, fabrication sequence and layers of interface) should be applied at the interfaces.

Fully printed, high energy density flexible zinc-air batteries based on solid polymer electrolytes and a hierarchical catalyst current collector

Emerging applications such as flexible electronics and on-body medical devices have created an unmet need for a thin, high energy density, low cost, and low toxicity energy source. We propose here that metal air batteries are particularly attractive for these applications as they eliminate two of the thickness limiting components of other chemistries: the cation-storage cathode and thick encapsulation layers. For the first time, fully printed, ultrathin metal air batteries have been demonstrated with high areal capacities of ∼2 mAh cm−2 for total cell thicknesses, of <160 μm, including the substrate. This provides a volumetric capacity of >140 mAh cm−3 which is among the highest ever reported for cells approaching 100 μm in thickness. The printed cell stack utilizes a printable solid polymer electrolyte based on a non-volatile hydroxide anion ionic liquid and a printed porous hierarchically-structured catalyst layer. The catalyst layer is composed of a porous carbon nanotube cathode current collector network supporting a nanoscale MnCo2O4—decorated reduced graphene oxide air catalyst. This novel combination of materials enables a monolithic, fully printed, and continuous fabrication sequence for ultrathin batteries based on low toxicity materials that does not require an assembled mechanical separator structure or electrolyte filling steps.

Validated prediction of weld residual stresses in austenitic steel pipe girth welds before and after thermal ageing, part 1: Mock-up manufacture, residual stress measurements, and materials characterisation

A series of engineering-scale multi-pass pipe girth weld mock-ups were manufactured using conventional manual metal arc techniques from Esshete 1250 austenitic steel. They were characterised in detail, in order to provide validation benchmarks for finite element prediction of weld residual stresses. The fabrication sequence comprised initial solution heat treatment and quenching, manufacture of five closely spaced girth welds in a single assembly, and then separation into five individual weldments. Detailed welding records were kept, to allow subsequent calibration of weld heat source models. Residual stresses were measured using diverse methods (incremental deep hole drilling and the contour method), in both the as-welded condition and after thermal ageing at 650 °C. The measurements showed good agreement, providing reliable validation targets for predicted residual stresses in both states. Detailed mechanical property characterisation was performed on both parent material and weld metal, comprising monotonic and isothermal cyclic testing over a range of temperatures from ambient up to 1000 °C. The test data were used to derive a range of Lemaitre-Chaboche mixed isotropic-kinematic model parameter sets for use in finite element simulation. These welds and their supporting characterisation comprise a reliable benchmark for weld residual stress simulation in an engineering-scale weldment.

Same day implant bridge for full-arch implant fixed rehabilitation.

To report an alternative clinical and laboratory protocol for same-day implant fixed full-arch provisional rehabilitation that may overcome limitations associated with traditional immediate provisional denture conversion rehabilitation protocols. The traditional denture conversion fabrication method of an immediate full-arch fixed provisional involves the conversion of a complete denture into a provisional fixed implant-support prosthesis. The conversion technique has several shortcomings which compromise structural integrity, longevity, ease of modification, and the need for a silicone impression. The "Same day" implant bridge (SDIB) concept provides clinical and laboratory advantages which overcome the limitations of the traditional denture conversion technique. This article reviews the rationale, clinical stages, and conventional fabrication sequence of the SDIB concept. Compared to the traditional denture conversion method for immediate implant bridge fabrication, the SDIB technique offers the following advantages for implant-supported fixed rehabilitation: rapid fabrication, improved structural integrity and rigidity, elimination of all silicone impressions, ease of modification to promote comfort, function and adaptability, and favorable esthetics.

Construction of self-assembled vertical nanoflakes on CZTSSe thin films

Cu2ZnSn(S, Se)4 (CZTSSe) is a promising alternative absorber material to achieve high power conversion efficiencies, besides its property of involving low-cost and earth-abundant elements when compared to Cu(In, Ga)Se2 (CIGS) and cadmium telluride (CdTe), to be used in solar cell technology. In this study, a novel fabrication technique was developed by utilizing RF sputtering deposition of CZTSSe thin films having a surface decorated with self-assembled nanoflakes. The formation of nanoflakes was investigated by detailed spectroscopic method of analysis in the effect of each stacked layer deposition in an optimized sequence and the size of nanoflakes by an accurate control of sputtering process including film thickness. Moreover, the effects of substrate temperature on the formation of nanoflakes on the film surface were discussed at a fixed deposition route. One of the main advantages arising from the film surface with self-assembled nanoflakes is the efficient light trapping which decreases the surface reflectance. As a result of the detailed production and characterization studies, it was observed that there was a possibility of repeatable and controllable fabrication sequence for the preparation of CZTSSe thin films with self-textured surfaces yielding low surface reflectance.

Integrated Optoelectronic Device for Detection of Fluorescent Molecules.

This paper presents the development of a compact optoelectronic device suitable for on-chip detection of fluorescent molecules. In order to obtain a highly integrated device, a long-pass multi-dielectric filter has been integrated with thin-film amorphous silicon photosensors on a single glass substrate. Filter rejects the excitation light, allowing the reduction of the distance between the source and the fluorescent site and avoiding the use of external optical component. The compatibility of the technological processes determined the materials and the temporal sequence of the device fabrication. The developed device has been designed for the fluorescence detection of ruthenium complex based molecules and tested, as a proof of concept, for the detection of double-stranded DNA down to 0.5 ng. Results demonstrate the correct operation of the integrated system in both rejecting the excitation light and in detecting the fluorescent signal, demonstrating the suitability of this optoelectronic platform in practical biomedical applications.

Support-free volume printing by multi-axis motion

This paper presents a new method to fabricate 3D models on a robotic printing system equipped with multi-axis motion. Materials are accumulated inside the volume along curved tool-paths so that the need of supporting structures can be tremendously reduced - if not completely abandoned - on all models. Our strategy to tackle the challenge of tool-path planning for multi-axis 3D printing is to perform two successive decompositions, first volume-to-surfaces and then surfaces-to-curves. The volume-to-surfaces decomposition is achieved by optimizing a scalar field within the volume that represents the fabrication sequence. The field is constrained such that its iso-values represent curved layers that are supported from below, and present a convex surface affording for collision-free navigation of the printer head. After extracting all curved layers, the surfaces-to-curves decomposition covers them with tool-paths while taking into account constraints from the robotic printing system. Our method successfully generates tool-paths for 3D printing models with large overhangs and high-genus topology. We fabricated several challenging cases on our robotic platform to verify and demonstrate its capabilities.

Mechanical properties of laminated kenaf woven fabric composites for below-knee prosthesis socket application

Prosthesis is a process of creating artificial human body part. The primary function of below-knee prosthesis is controlling the leg during static and dynamic conditions. The aim of this study is to develop a prosthetic socket made from kenaf-glass fiber composite. The development of prosthetic socket with kenaf-glass fiber was carried out as an attempt to substitute prosthetic socket made from fiberglass polyester composites. Lamination method was adopted to fabricate the prosthetic socket. The laminates contain woven kenaf, glass silk knitted fabric and nylon knitted fabric. The effect of kenaf fabric layering sequence on the volumetric and mechanical properties were evaluated. The flexural and impact strength of 2 layers of kenaf fiber-based laminates are 7.11 MPa and 16.7 kJ/m2 respectively which is higher than the single layer kenaf fabric-based composites. From the results woven kenaf fabric composites has the potential to replace the existing glass fabric-based polymer composites. It is a great initiative to fabricate a prosthetic socket which biodegradable, environmental friendly, locally available, lightweight, comfortable and psychosocially acceptable.

Nonenzymatic determination of glucose at near neutral pH valuesbased on the use ofnafion and platinum black coated microneedle electrode array.

The authors report on a microneedle-based amperometric nonenzymatic glucose sensor for painless and continuous monitoring of glucose. It consists of 3 × 5 sharp stainless steel microneedles micromachined from a stainless steel substrate. The microneedles are 600 and 100μm in height and width, respectively. Nafion and platinum black were sequentially coated onto the tip of gold-coated microneedles and used for nonenzymatic (direct) sensing of glucose. Attractive features of the modified microneedle electrode include (a) a low working potential (+0.12V vs. Ag/AgCl), (b) a linear response in the physiologically relevant range (1-40mM), (c) a sensitivity as high as 175μAmM-1cm-2, (d) a 23μM detection limit, and (e) a response time of 2s. The sensor also exhibits good reproducibility and stability. The sensor is selective for glucose even in the presence of 10-fold higher concentrations of ascorbic acid, lactic acid, dopamine, uric acid, and acetaminophen. Graphical abstract Schematic representation of the fabrication sequence for a nonenzymatic electrochemical glucose sensor using Nafion and platinumblack coated microneedle electrode array. The sensor is based on measuring the faradaic current at +0.12V vs. Ag/AgCl by the direct electrochemical oxidation of glucose to gluconic acid on the surface of aPt black sensing layer.

Mesh optimisation for spatial wireframe robotic 3D printing

Most of the polygon meshing system and related algorithm are developed for geometrical optimisation with rarely any practical consideration such as material performance and fabrication process. This paper intends to propose a different approach for mesh optimisation that took practical elements such as material quality, fabrication sequence, and technical restriction into the consideration, developing a novel meshing algorithm. Through our novel nonlinear optimisation process, a data-intensive smart polygon mesh network system is generated that is optimised for a highly efficient construction process in coordination with a robotic fused deposition modelling (FDM) 3D printing system. The mesh network developed from such process and algorithm is structurally rational, cost-efficient with far less construction time.

Analysis of the effects of fabric reinforcement parameters on the mechanical properties of textile-based hybrid composites by full factorial experimental design method

In this study, the effect of some fabric reinforcement parameters (fabric direction, yarn type and stacking sequence) on the mechanical properties of textile based hybrid composites are analysed by using full factorial experimental design method. The analysis of the results is achieved by using Minitab 17 software program. One factor (fabric reinforcement direction) with two levels (warp direction and weft direction) and two factors (yarn type and stacking sequence) with three levels (jute/glass, jute/carbon, glass/carbon and consecutive, low strength inside, high strength inside) are selected as the reinforcement design. Full factorial experimental design analysis results indicate that, the highest tensile and impact strength values among the experimental design are realised when samples are taken from the warp direction and E-glass/carbon combination is chosen as the yarn (material) type. Moreover, it is verified that while higher tensile strength is achieved by placing higher strength fabrics to the inner layers, higher impact strength is achieved by placing high strength fabrics to the outer layers of hybrid composite structures. Analysis of variance tables also show that at 95% confidence level, the effects of the factors are statistically significant ( p &lt; 0.05).

Spin-coating free fabrication for highly efficient perovskite solar cells

A spin-coating-free fabrication sequence has been developed for the fabrication of highly efficient organic-inorganic halide perovskite solar cells (PSCs). A novel blow-drying method is demonstrated to be successful in depositing high quality mesoporous TiO2 (mp-TiO2), methylammonium lead halide (CH3NH3PbI3) perovskite and spiro-MeOTAD layers. When combined with compact TiO2 (c-TiO2) deposited by spray pyrolysis which is also a spin-coating-free process, a stabilized power conversion efficiency exceeding 17% can be achieved for the glass/FTO/c-TiO2/mp-TiO2/ CH3NH3PbI3/spiro-MeOTAD/Au device. This is the highest efficiency for PSCs fabricated without the use of spin-coating to our knowledge. This method provides a pathway towards a scalable process for fabricating high-performance, large area and reproducible PSCs.

A simple fabrication process for disposable interdigitated electrode arrays with nanogaps for lab-on-a-chip applications

In this paper, we introduce for the first time a novel fabrication process for interdigitated electrode arrays (IDA) with nanogaps on polymer substrates. The IDA sensor for disposable lab-on-a-chip (LoC) applications employs an amperometric detection principle which allows a signal amplification by redox cycling. Our fabrication sequence is based on a lift-off free process and therefore, reduces the number of process steps and simplifies the fabrication and increases the yield. This innovative approach consists of an initial structure followed by two deposition processes. The initial structure, which is transferred into the polymer, is in the micrometer range and is formed by hot embossing. A silicon stamp is fabricated by mask aligner lithography and a subsequent dry etching step. An imprint template was prepared from the master and the structures are transferred into a 1mm thick cycle-olefin polymer (COP) sheet. A subsequent sputter deposition process was carried out to form an undercut of the finger structures, which should guarantee a separation of the electrodes. A 90nm thick gold layer was deposited by thermal evaporation to pattern the electrodes. The presented fabrication procedure represents an approach to fabricate disposable nanogap interdigitated electrode arrays allowing high signal amplifications in LoC applications. Furthermore, it demonstrates a low-cost method to fabricate IDAs with nanogaps for high volume mass production.