Continuous Extrusion Research Articles

Effect of particle size on the microstructure and tensile property of the Al-28.5Si alloy prepared by continuous powder extrusion

Continuous powder extrusion, a new powder consolidation technology, is used to process alloy powders that are difficult to form. In the paper, Al-28.5Si alloys were successfully prepared by continuous powder extrusion, and the influences of particle size on the microstructure and tensile property have been investigated. In the as-extruded rods, the primary Si phase is dispersed in the α-Al matrix. As the powder size reduces from more than 75 μm to less than 25 μm, the equivalent diameter of the primary Si particles consecutively decreases, but the shape factor increases. Comparing the Si particles in the alloy rod and the powder, it is found that the eutectic Si phase disappears during continuous extrusion. Primary Si particles change from coarse and irregular to round. Specifically, the ultimate tensile strength and elongation at break of the powder-extruded alloy further increase from 211 MPa to 266 MPa and 0.99% to 2.21%. Moreover, the fracture mechanism of alloy rods is the brittle fracture.

Wearable human-machine interface based on the self-healing strain sensors array for control interface of unmanned aerial vehicle

Flexible strain sensors have been widely adopted for wearable systems in detecting the human activities and health. However, the demonstration of controlling interface based on strain sensor is still limited. Herein, a novel wearable human-machine interface (W-HMI) is proposed based on the signal processing system and self-healing strain sensors array. The strain sensor shows high sensitivity with the Gauge Factor max of 20, wide-detection range of 0.2–3000 % and self-healing ability. The proposed flexible and transparent W-HMI is capable of effectively capturing eyes' motions through four-array strain sensors. Based on the coupling effect of different sensors, W-HMI collects and processes the signals of the four sensors under different movements of the eyes, and then outputs different signals to control the right, left, up and down movements of the UAV. Importantly, the destroyed sensor can still show excellent performance due to its self-healing ability and can be used as a W-HMI to control the movement of UAV, which is an important characteristic to compensate for the vulnerability of W-HMI under continuous tension or extrusion. This innovative, cost-effective, simple-designed W-HMI based on the self-healing strain sensors will open a novel way to its application in the human-machine field.

Demonstration of the one-step continuous fabrication of flexible polymer ridge waveguides via nanochannel-guided lithography

We demonstrate a facile one-step fabrication of flexible ridge waveguides by using the nanochannel-guided lithography (NCL) that enables continuous extrusion of a polymer that forms waveguiding core ridge on an undercladding polymer substrate. NCL utilizes a well-cleaved mold edge with microtrench patterns to slide continuously over a UV-curable liquid resin-coated substrate under conformal contact, where the resin and substrate can be chosen for suitable waveguide core and undercladding materials. The local heating of a trench mold can control the viscosity of liquid resin for optimal filling into the microchannels followed by smooth extrusion, which is subsequently UV-cured. Such a smoothly extruded resin core exhibits a very smooth surface potentially promising for the low-loss waveguiding operation which was experimentally confirmed by optical insertion loss characterization. The proposed technique may provide a practical route to the continuous and seamless fabrication of scalable waveguides and photonic elements.

From Biomaterial to Organoid - Bioprinting for Practice

The current state of technology for 3D printing with biomaterials is based on the extrusion of viscous materials. Mostly, extrusion heads utilize pneumatic pressure systems or stepper motors to force the substrate onto a surface. These methods are well developed for high viscouse materials. However, processing low viscous liquids may cause leakages in the system. This could be solved by applying continuous extrusion. Additionally, in order to process gelable substrates, such as gelatine and agar, tempered print heads in combination with a multi stage tempering system are required to prevent the system from clogging. The ongoing work presented in this paper focuses on the development of an extrusion system, which should be able to process multiple viscosities of gelatine sequentially. In order to achieve this, several measurements to examine the properties, as well as the material parameters of different biomaterials are performed. In this process gel point, force resistance and elasticity are the factors of particularly interest. Due to their ability to gel and their availability, the most relevant biomaterials are gelatine and agar. Using this data, an extrusion system involving a peristaltic pump, a heated tube and a nozzle, has been developed. The next step envisaged is to calibrate the extruder based on the obtained data and finally to validate the printing process by printing simple geometric structures. Assuming that a positive evaluation is obtained, the printing system will be tested for printing first organic test structures from patient data using the examined biomaterials.

A New Composite Biomaterial Made from Sunflower Proteins, Urea, and Soluble Polymers Obtained from Industrial and Municipal Biowastes to Perform as Slow Release Fertiliser

Controlled-release fertilizers (CRF) are needed under current agriculture practice to decrease the environmental impact caused by fertilizer doses applied in excess of plants’ uptake rate. Commercial CRF are available. They are manufactured from mineral fertilizers encapsulated into a synthetic polymer matrix or coated by a polymer layer. However, substitution of fossil sourced organic polymers with biopolymers is a major environmental concern. In the present paper, we describe the manufacture by a continuous twin-screw extrusion process, and the mechanical and chemical properties of injection-molded composite pellets containing 90% sunflower protein concentrate (SPC) matrix, and 5–10% of a biopolymer (BP) obtained from municipal biowastes (MBW), and/or urea (U). The reported results show that SPC-BP-U behaves as an efficient eco-friendly CRF. BP contributes to several benefits to the performance of the composite pellets, upon increasing surface hardness, and controlling the formation of ammonia from urea hydrolysis and the release of organic nitrogen. The SPC-BP-U appears a powerful eco-friendly CRF to supply organic C and the three major N, P, and K nutrients to soil and plants. It offers worthwhile scope for being tested in the cultivation of specific plants under the real operational conditions of agriculture practices.

Numerical study of radiative non-Darcy nanofluid flow over a stretching sheet with a convective Nield conditions and energy activation

Abstract Numerous industrial processes such as continuous metal casting and polymer extrusion in metal spinning, include flow and heat transfer over a stretching surface. The theoretical investigation of magnetohydro-dynamic thermally radiative non-Darcy Nanofluid flows through a stretching surface is presented considering also the influences of thermal conductivity and Arrhenius activation energy. Buongiorno’s two-phase Nanofluid model is deployed in order to generate Thermophoresis and Brownian motion effects [1]. By similarity transformation technique, the transport equations and the respective boundary conditions are normalized and the relevant variable and concerned similarity solutions are presented to summarize the transpiration parameter. An appropriate Matlab software (Bvp4c) is used to obtain the numerical solutions. The graphical influence of various thermo physical parameters are inspected for momentum, energy and nanoparticle volume fraction distributions. Tables containing the Nusselt number, skin friction and Sherwood number are also presented and well argued. The present results are compared with the previous studies and are found to be well correlated and are in good agreement. The existing modelling approach in the presence of nanoparticles enhances the performance of thermal energy thermo-plastic devices.

Microstructure and mechanical properties of ZM6 magnesium alloy after continuous variable cross-section direct extrusion

Microstructure and mechanical properties of ZM6 magnesium alloy after continuous variable cross-section direct extrusion

Upcycling of post-consumer polyolefin plastics to covalent adaptable networks via in situ continuous extrusion cross-linking

Post-consumer plastic bags were upcycled to covalent adaptable networks (CANs) based on internally catalyzed anhydride monoester transesterification.

Graph-based Optimization of Continuous Extrusion Path in FRP-AM for Compliant Mechanism Fabrication

Graph-based Optimization of Continuous Extrusion Path in FRP-AM for Compliant Mechanism Fabrication

Preliminary Finite Element assessment of residual stresses in dissimilar AA6082-S355 butt welded joints produced with the Hybrid Metal Extrusion and Bonding (HYB) technique

Hybrid Metal Extrusion & Bonding (HYB) is a new solid-state joining method for metals and alloys that utilizes continuous extrusion as a technique to enable aluminum filler metal additions. Previous works showed that this method is well suitable for joining dissimilar metals such as steel and aluminum. In the present paper a Finite Element model for the thermal residual stresses were implemented employing the FE code WELDSIM. As a starting point, the results of a semi-analytical heat generation model previously implemented for HYB process of aluminum butt welds were used to estimate the net power input as a sum of contributions that are dependent on the welding parameters i.e. the welding speed, the rotational speed and the material properties. Subsequently, the thermal stresses occurring in the material and finally the residual stresses were determined. In the present work, predictions of the FE model for different sets of welding parameters are presented and discussed.

A Semi-Analytical Model for the Heat Generation during Hybrid Metal Extrusion and Bonding (HYB).

Hybrid Metal Extrusion and Bonding (HYB) is a novel solid-state welding method for metals and alloys that utilises continuous extrusion as a technique to enable aluminium filler metal additions. In the present study, a new semi-analytical model for the heat generation during aluminium butt welding is presented. As a starting point, the classical Rosenthal thin plate solution for the pseudo-steady-state temperature distribution around a fully penetrating line source is invoked. Then, the associated heat generation is calculated by considering the individual contributions from the tip of the rotating pin, the pin shoulder, and the filler metal additions on the net power input. In a calibrated form, the model yields thermal efficiency factors that are in close agreement with those obtained from more sophisticated finite element analyses but with considerably less computational effort.

Microstructure, mechanical properties and deformation characteristics of Al-Mg-Si alloys processed by a continuous expansion extrusion approach

In the present work, a double-pass continuous expansion extrusion forming (CEEF) process was proposed for an Al-Mg-Si alloy, in which the diameter of rods was gradually expanded. The microstructural evolution, mechanical properties and deformation characteristics were investigated by utilizing microstructural observations, mechanical testing and a finite element method coupled with a cellular automata model. The results showed that the strength and ductility of the double-pass CEEF processed Al-Mg-Si alloys were improved synchronously, especially in artificially aged alloys. The grain size of the processed Al-Mg-Si alloy rods was refined remarkably by continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), and the homogeneity of microstructure was gradually improved with increasing number of processing passes. The artificially aged alloy processed with double-pass CEEF and water quenching contained fine (sub)grains and high-density dislocations, which resulted in more needle-shaped β” precipitates and a larger precipitate aspect ratio than the as-received and air-cooled CEEF alloys owing to the different precipitation kinetics. The severe cumulate strain and microshear bands were found to accelerate CDRX and GDRX for grain refinement between adjacent positions of the parabolic metal flow due to the special temperature characteristics and large shear straining during the CEEF process.

Formulation of Heat-Induced Whey Protein Gels for Extrusion-Based 3D Printing.

This study investigated the extrusion-based 3D printability of heat-induced whey protein gels as protein rich food inks. In particular, the effects of ionic strength by the addition of NaCl (0–250 mM), protein content (10%, 15%, 20%), fat content (0%, 10%), and partial substitution of whey protein isolate (WPI) with microparticulated whey protein (MWP) or micellar casein isolate (MCI) on printability were assessed. Texture analysis, specifically Young’s modulus, rheological measurements including yield stress, and creep–recovery behavior were used to characterize the gels. Modifications of the formulation in terms of ionic strength, increased protein content, and the formation of emulsion gels were insufficient to maintain a continuous extrusion process or shape stability after printing. However, the substitution of WPI with MWP created more viscoeleastic gels with improved printability and shape retention of the 3D cube structure after deposition. The partial replacement of WPI with MCI led to phase separation and 3D-printed cubes that collapsed after deposition. A narrow range of rheological material properties make WPI and MWP emulsion gels promising food inks for extrusion-based 3D printing.

High electrical conductivity Al-Ag-Sc-Zr alloy with ultrafine grains processed by accumulative continuous extrusion

Continuous preparation of high-conductivity and high-strength aluminium alloy cable remains a challenge. Here we reveal the scientific significance of high electrical conductivity Al-Ag-Sc-Zr alloy with ultrafine grains prepared by novel processing technologies, the combination of rheo-extrusion and accumulative continuous extrusion forming. Attributed to the continuous dynamic recrystallization during rheo-extrusion, equiaxial microstructure and significantly refined grains (2.8 ± 0.2 μm) were achieved. By means of partially replacing low conductive scandium and zirconium solute atoms with high conductive silver solute atoms, the processed alloy wires exhibit significant higher electrical conductivity (53.5 ± 0.4 %IACS) than the Al-Sc-Zr alloy with similar atomic concentration of alloying elements. Appropriate mechanical properties were also obtained due to the similar solution strengthening effects of silver atoms to scandium and zirconium atoms. These results highlight the potential of this high electrical conductivity Al-Ag-Sc-Zr alloy and its novel processing route.

Fabrication of aluminum–magnesium clad composites by continuous extrusion

Abstract Poor corrosion resistance of Mg alloys extremely limits their industrial applications. Al/Mg clad composites using Al alloy as a protective layer are expected to be an effective approach to combine good corrosion resistance and high specific strength. In this study, novel Al clad Mg composites were developed by continuously extruding 6063 Al alloy tube and AZ31 Mg alloy rod with and without preheating of Mg alloy. The Al/Mg interfacial diffusion, microstructure, texture, and flexural properties of the continuously extruded composites were investigated experimentally. The extruded composites exhibited good metallurgical bonding between Al shell and Mg core even without preheating of Mg alloy, and their fine-grained microstructure contributes to a significant enhancement in ultimate flexural strength (UFS) to 452 MPa. Preheating of Mg alloy caused complete dynamic recrystallization (DRX) of both Al shell and Mg core and modified (0001) texture of the Mg alloy, which leads to a significant improvement in the bendability of the Al/Mg composite.

Nanoribbons fabricated by melt electrospinning

This study focuses on using the multilayer melt electrospinning of polymers in combination with a delamination step to obtain nonwoven webs of ribbon-shaped flat fibers that are ~150 to 200 nm thick. A novel coextrusion system with layer multipliers is used to melt electrospin bicomponent cylindrical microfibers with diameters in the range of ~15–25 μm that have up to 257 alternating layers within each fiber prior to delamination. The diameter of the cylindrical fibers is dependent on the temperature, the flow rate of the polymers, and the die tip-to-collector distance. The fabricated bicomponent layered microfibers are subsequently delaminated using sonication or solvent rinsing to obtain flat nanoribbons whose thicknesses vary from 150 to 200 nm. After delamination, some of the flat nanoribbons are found to roll into cylindrical fibers with diameters ranging from 150 to 250 nm. This bicomponent approach uses a continuous melt extrusion process that can support higher throughputs compared to traditional solution electrospinning and can lead to the fabrication of high surface area nonwoven webs after proper delamination treatments. This study focuses on employing multilayer melt electrospinning of polymers coupled with a delamination step to obtain nonwoven webs of ribbon-shaped fibers. A coextrusion technique with layer multipliers was used to melt electrospin cylindrical microfibers that have up to 257 alternating layers within each fiber prior to delamination. The bicomponent layered cylindrical microfibers are delaminated using sonication or solvent rinsing to obtain flat nanoribbon fibers, that are 150 nanometers to 200 nanometers thick.

Determination of the parameters of viscous fluid flowing in an annular gap during continuous hydrostatic extrusion

The study of deformation of solids by high-pressure liquid (hydrostatic extrusion) is not only an interesting research problem, but an applied one. Hydrostatic extrusion method is currently widely used in various sectors of industry – from mechanical engineering to the food industry. This field of research seems relevant and promising. The paper presents the calculation results for some parameters of continuous hydrostatic extrusion of materials, shows graphs of the dependence of the axial stress in the billet on the total pressure drop along the length and graphs of the dependence of the total pressure drop along the length on the working fluid flow rate in the annular gap. The calculations were performed for the adiabatic fluid flow and for the flow with partial heat transfer. Analysis of the calculation results showed that for fixed flow rates of the working fluid and specified heat transfer conditions, maximum axial stresses can be obtained by optimal values taken for the ratios of the working chamber and the billet diameters.

Microstructural and mechanical characterisation of a second generation hybrid metal extrusion & bonding aluminium-steel butt joint

Hybrid metal extrusion & bonding (HYB) is a joining method that enables solid-state bonding by combining addition of aluminium filler material through continuous extrusion with pressure exerted by a rotating steel tool. This work presents mechanical and microstructural characterisation of a second generation HYB butt joint of aluminium alloy 6082 and structural steel S355. The ultimate tensile strength was measured to be in the range of 184–220 MPa, which corresponds to 60–72% joint efficiency. Digital image correlation analysis of the strain development during tensile testing revealed that root cracks formed, before the final fracture ran close to the aluminium-steel interface. A significant amount of residual aluminium was found on the steel fracture surface, especially in regions that experienced higher pressure during joining. Scanning and transmission electron microscopy revealed that the bond strength could be attributed to a combination of microscale mechanical interlocking and a discontinuous nanoscale interfacial Al-Fe-Si intermetallic phase layer. Analysis of scanning electron diffraction data acquired in a tilt series, indicated that the polycrystalline intermetallic phase layer contained the cubic αc phase. The results give insight into the bonding mechanisms of aluminium-steel joints and into the performance of HYB joints, which may be used to better understand and further develop aluminium-steel joining processes.

Amorphous Polymers' Foaming and Blends with Organic Foaming-Aid Structured Additives in Supercritical CO2, a Way to Fabricate Porous Polymers from Macro to Nano Porosities in Batch or Continuous Processes.

Organic polymers can be made porous via continuous or discontinuous expansion processes in scCO2. The resulting foams properties are controlled by the interplay of three groups of parameters: (i) Chemical, (ii) physico-chemical, and (iii) technological/process that are explained in this paper. The advantages and drawbacks of continuous (extrusion, injection foaming) or discontinuous (batch foaming) foaming processes in scCO2, will be discussed in this article; especially for micro or nano cellular polymers. Indeed, a challenge is to reduce both specific mass (e.g., ρ < 100 kg·m−3) and cell size (e.g., average pore diameter ϕaveragepores < 100 nm). Then a particular system where small “objects” (coreshells CS, block copolymer MAM) are perfectly dispersed at a micrometric to nanometric scale in poly(methyl methacrylate) (PMMA) will be presented. Such “additives”, considered as foaming aids, are aimed at “regulating” the foaming and lowering the pore size and/or density of PMMA based foams. Differences between these additives will be shown. Finally, in a PMMA/20 wt% MAM blend, via a quasi one-step batch foaming, a “porous to nonporous” transition is observed in thick samples. A lower limit of pore size (around 50 nm) seems to arise.

Lignocellulose Pretreatment Combining Continuous Alkaline Single-Screw Extrusion and Ultrasonication to Enhance Biosugar Production

Pretreatment to improve the enzymatic digestibility of highly crystallized lignocellulosic biomass is essential in biorefinery processes. This study investigates the combination of lignocellulose pretreatment with continuous alkaline single-screw extrusion and ultrasonication for biosugar production. Miscanthus sacchariflorus was used because it is a promising bioenergy crop. The results show that ultrasonication with continuous alkaline pretreatment increased the enzymatic digestibility of carbohydrates and reduced the use of chemicals during pretreatment. An hour of ultrasonication following 0.2 M NaOH (2.25 mol-NaOH/kg-biomass) continuous alkaline pretreatment resulted in a 6.7% increase in total biosugar production (83.1% of theoretical yield), a decrease of up to 26.1% in chemical usage, and a 17.0% increase in lignin removal compared with the case without ultrasonication. The developed method can be considered an effective and eco-friendly approach to the production of bio-based materials.