Extrusion Chamber Research Articles

ADDITIVE MANUFACTURING OF SURLYN SPECIMENS WITH A NANO-REINFORCEMENT OF CARBON NANOTUBES.

This paper explores the self-healing abilty of the ionomer called Surlyn® 8940 (manufactured by DuPont), a partially neutralised poly(ethylene-co-methacrylic acid) (EMAA) ionomer copolymer, and the improvement of the mechanical properties after adding a nano-reinforcement of multiwall carbon nanotubes (MWCNTs) to the structure of the polymer. It begins with the manufacture the nanocomposite material, based on Surlyn® 8940 as raw material, and the mixture process with MWCNTs. Afterwards, an extrusion process was optimized to obtain a homogeneous reinforced filament, which was subsequently used to manufacture the final test samples by means of a 3D printing machine. Specimens with different concentrations of MWCNTs (0.0, 0.1, 0.5, 1.0 % wt.) were manufactured, in order to test the mechanical properties and self-healing ability of unreinforced and nano-reinforced samples. The results show that nano-reinforced samples had an increase of their self-healing ability (increase for 0.5 y el 1% wt. of MWCNTs) and mechanical properties (σTS 18.35, 25.91, 26.92, 28.02 MPa to 0, 0.1, 0.5 y 1 % wt. de MWCNTs respectively). Specimens of 5% of MWCNTs have also been manufactured with different mixing times in the extrusion chamber to study the conductivity of the polymer. Electrical conductivity values ​​for 8 and 10 minutes of mixing times reached S/m units order have been obtained.

Wire arc additive manufacturing of AA5183 with TiC nanoparticles

Aluminium alloys processed by wire arc additive manufacturing (WAAM) exhibit a relatively coarse microstructure with a columnar morphology. A powerful measure to refine the microstructure and to enhance mechanical properties is to promote grain refinement during solidification. Addition of ceramic nanoparticles has shown great potential as grain refiner and strengthening phase in aluminium alloys. Thus, an Al-Mg alloy mixed with TiC nanoparticles was manufactured by the novel metal screw extrusion method to a wire and subsequently deposited by WAAM. Measures to restrict oxidation of magnesium during metal screw extrusion were examined. Purging of CO2 gas into the extrusion chamber resulted in a remarkable reduction in formation of MgO and Mg(OH)2. TiC decomposed to Al3Ti during WAAM deposition, leading to a significant grain refinement of 93% compared to a commercial benchmark. The presence of remaining TiC nanoparticles accounted for an increased hardness of the WAAM material through thermal expansion mismatch strengthening and Orowan strengthening. Exposure of TiC to moisture in air during metal screw extrusion increased the internal hydrogen content significantly, and a highly porous structure was seen after WAAM deposition.

Flow Characteristics and Energy Loss within the Static Impeller of Multiphase Pump

The internal flow is very complex in the multiphase pump, especially in the static impeller, where the flow is more disorganized than that in the impeller wheel, and it will cause greater hydraulic losses. In order to investigate deeply the flow rules within the static impeller, all kinds of the flow losses are analyzed quantificationally in the multiphase pump. Based on the standard SST k-ω turbulence model, selected the helical axial flow multiphase pump as the research object, used the three-dimensional modeling software for the three-dimensional modeling of the flow through parts of the multiphase pump, such as impeller wheel, the static impeller, the suction chamber, and the extrusion chamber. The ANSYS software is used to simulate the three-dimensional flow in static impeller, and the ICEM software was used to divide the mesh of suction chamber, press outlet chamber, moving impeller and static impeller respectively. The results show that the flow within the impeller wheel is more uniform than the static impeller, and larger axial vortexes appear in the static impeller. Compared with the impeller wheel, the effect of the flow rate on the flow within the first static impeller is greater. The friction loss is the largest among all kinds of losses in the static impeller, followed by the turbulence dissipation loss. What’s more, the shock loss and the contraction loss are the smallest, they are all less than 20%, and the main loss within the static impeller are the turbulent dissipation loss and friction loss. The proportion of energy losses in the first and second static impeller is almost the same, which is around 50%, respectively. The results can be used as a reference for the improvement of the hydraulic performance of the multiphase pump.

In-process simulation of the extrusion to support optimisation and real-time monitoring in fused filament fabrication

A simulation model is presented in this work, capable to predict temperature and velocity of the extrudate as well as the compressive force acting on the filament in a fused filament fabrication (FFF) machine operating with a Bowden extruder. The simulation model is developed for future incorporation into a larger on-machine apparatus designed for process monitoring and adaptive control and destined to the fabrication of high value-added parts. The simulation model captures mechanical aspects of the extruder (including slippage at the drive gear, filament compression into the hot end), as well as temperature and pressure changes within the extrusion chamber, where the filament is liquefied and transformed into the extrudate. The model is implemented so that it can react to changes in the part program as it is being executed, offering predictions on the extrusion process that can be compared with sensor measurements. The simulation model is implemented in prototype form and calibrated on a multi-sensor FFF machine working with a PLA filament within a range of predefined operating conditions (heating temperatures and print feed rates). Load cells, high-speed optical imaging and infra-red thermal imaging of the extrudate mounted on the FFF machine are used to verify the predictions of the simulation model.

Numerical simulation of the 3D flow field in a ring die pellet mill considering viscous heating

Viscous heating has a substantial influence on the extrusion forming process and product quality of powder materials. This study selected the MUZL420 ring die pellet mill as the research object, from which a 3D flow physical model was established. The numerical simulation of 3D nonisothermal flow in the extrusion pelletizing process of granulated alfalfa was performed with POLYFLOW. The distribution laws of pressure, velocity, shear rate, viscosity, viscous heating and temperature in the flow field were revealed to thoroughly investigate the pelletizing process and provide a reference for structural optimization and process control. The results showed that two extrusion zones in the pelleting chamber were symmetrical with respect to the center, and the significant pressure gradient along the rotating direction of the ring die and the roller caused the material to flow back in the opposite direction. There were larger velocity gradients, shear rates and viscous heating levels in the deformation and compaction zone, the negative pressure zone behind the extrusion zone and the die holes. The distribution of viscosity was opposite to that of the shear rate. The temperature increase area caused by viscous heating gradually expanded from the material inlet to the bottom of the extrusion chamber along the [Formula: see text]-axis direction, and the temperature increased accordingly. The extrusion force and the forming temperature in the extrusion forming zone were captured in the numerical simulation. The extrusion forming density was calculated with the regression prediction model established through the simulation experiment of pelletizing with a ring die. Through a comparison with the results of mean alfalfa pellet density from the ring die pellet mill experiment, the relative error was less than 5%, which indicated that the numerical simulation method was reliable.

Texture formation process of 6063-type aluminium alloy during hot extrusion

This study investigated the texture formation process of A6063 alloy hot extruded material using electron backscatter diffraction (EBSD) measurements. The cube component that becomes the main orientation during hot extrusion was formed near the bearing inflow in the extrusion chamber and grew with continuous recrystallization. The Goss component with the same ED // <100> relationship as the cube component was not formed in the chamber or the bearing but was formed by discontinuous recrystallization after passing through the bearing. The TD // <111> orientation component of the surface layer was formed in the bearing and then grew with discontinuous recrystallization. However, because the internal cube and Goss components expanded preferentially, the surface layer TD // <111> components were replaced by the cube and Goss components after passing through the bearing. The cubic texture formation of extruded aluminium alloys is noted to be analogous to the formation of rolling sheet materials, formed by recovery and recrystallization from a plane strain deformation structure. However, for the A6063 alloy extruded under conditions close to industrial production, the cube components were mainly formed by recovery and continuous recrystallization.

Simulating the dependence of the filler wire feeding on the wire size in the hybrid metal extrusion & bonding (HYB) process

HYB is a new solid-state joining method for metals and alloys that utilizes continuous extrusion as a technique to enable aluminium filler metal (FM) additions. In the present work, a finite element (FE) model for the filler wire feeding inside the HYB PinPoint extruder has been developed and implemented within the commercial software package DEFORM 3DTM. Adaptive remeshing is used to handle the high mesh distortions occurring during simulation. Moreover, modelling of the FM flow stress as a function of strain, strain rate and temperature is done by employing a modified version of the Johnson-Cook constitutive equation and experimental tensile test data for the AA6082 filler wire. In the numerical simulations, the feeding behaviour of filler wires with diameters of 1.2, 1.4 and 1.6 mm, respectively has been explored. The results show that the filler wire feeding is sensitive to variations in the extrusion chamber geometry. For the specific combinations of wire diameters and extrusion chamber geometries examined, the ɸ1.4 mm wire appears to be the best choice when it comes to reducing feeding problems related to buckling & breaking of the filler wire during extrusion & joining.

Numerical Simulations of As-Extruded Mg Matrix Composites Interpenetrated by Metal Reinforcement

The interpenetrating magnesium composites reinforced by three-dimensional braided stainless steel wire reinforcement were fabricated and investigated. The extrusion processes of the composites in different conditions were carried out and simulated by finite element method using the DEFORM-3D software. The results show that the matrix and reinforcement of the composites form a good interfacial bonding and the grains were refined by extrusion and the influence of reinforcement, which are in accordance with the enhanced strength and degraded plasticity. The combined quality between the matrix and reinforcement can be strengthened in extrusion chamber where occurred large strain and suffered intense stress, and the effective stress of the material increases continuously with the increase in extrusion ratio and the decrease in extrusion speed until it reaches a stable value.

Polycrystal plasticity simulation of extrusion of a magnesium alloy round bar: Effect of strain path non-uniformity

A flow line model is established and combined with the crystal plasticity method to simulate the extrusion process of a magnesium alloy round bar, and investigate the effect of strain path non-uniformity on development of texture and microstructure in extrusion. A parametric flow line model is established to characterize the material flow corresponding to different strain paths in the extrusion chamber. The polycrystal plasticity method coupled with a phenomenological dynamic recrystallization model is employed to analyze the evolution of texture and microstructure accompanying the deformation. The texture of material deformed near the central extrusion area shows the typical ring fiber texture in the (0001) pole figure, while the basal poles of the material deformed in the side areas tend to rotate backward to the extrusion direction, resulting from an increase of the activities of twinning and slip systems. The more refined microstructure is obtained in the side areas due to the higher strain rate. The difference of mechanical properties between center and side areas of the extruded bar are numerically investigated by simulating tension and compression by using different extrusion textures. Side material shows more isotropic mechanical property than central material, and then less twinning is operative in compression.

Influence of processing parameters and initial temper on Friction Stir Extrusion of 2050 aluminum alloy

Friction Stir Extrusion is an innovative production technology that enables direct wire production via consolidation and extrusion of metal chips or solid billets. During the process, a rotating die is plunged into a cylindrical chamber containing the material to be extruded. The stirring action of the tool produces plastic flow in the extrusion chamber, densifying and heating the charge so that finally, fully dense rods are extruded. Experiments have been carried out in order to investigate the influence of process parameters and initial temper of the base material on the process variables and on the extrudates’ mechanical properties.

Agglomeration Technologies of Processing Powder Wastes

This article deals with the presentation of modern applications for processing powdered, primarily hazardous, waste to an agglomeration form appropriate for subsequent processing by classical methods, for example in the construction, automotive and consumer goods industries. The aim of the research work was to set appropriate operating conditions in order to appreciate currently non-processable wastes resulting from the intensive production of often extremely expensive materials. Technologies which enable returning powder waste back into the primary production cycle were developed and experimentally tested, thus saving raw material resources. When necessary for the fixing of fine airborne particles with a problematic compacting curve (hard to compress, repulsive due to the surface charge) extrusion processes using a patented technology enabling controlled modification of shear forces in the extrusion zone were successfully applied. A new type of axial extruder allows the elimination of the liquid phase and as a result prevents the clogging of the extrusion chamber. In the case of need for granulation of sensitive materials (for example pharmaceuticals not allowing the addition of any kind of agglomerating fluid or reacting strongly in the contact of the two phases), a process of compaction between rolls with different profiled surface was successfully applied. The developed high technologies and the resulting products thus represent a major contribution to environmental protection in the context of not only the work but also the communal environment.

Heat transfer modeling of the friction extrusion process

The present work is focused on understanding the heat transfer phenomenon and the temperature field in the friction extrusion process. A friction extrusion experiment using aluminum alloy 6061 was designed and carried out, in which the mechanical power input during the experiment was recorded and the temperature variations with time at several key points surrounding the process chamber were measured using inserted thermal couples. A numerical thermal model for the experimental system has been developed. The model includes a rotating extrusion die, a material being processed inside an extrusion chamber, a chamber wall, and a back plate at the bottom of the chamber wall. The experimentally measured mechanical power is used as input to the model to predict the temperature field in the experiment. It is found that the predicted temperature variations at the locations of the thermal couple tips agree well with those measured experimentally, suggesting that the thermal model can serve as a reasonable predictive model for the temperature field distribution in the friction extrusion process.

Design, Manufacturing and Welding of Aluminum Alloy UHV Chambers for Taiwan Photon Source

This paper describes the design, manufacturing and welding sequence for the aluminum alloy vacuum chamber for Taiwan Photon Source. The vacuum chamber composes of aluminum extrusion chamber of A6063 and BPM chamber of A6061 aluminum alloys. The straightness and flatness of these extrusion chambers are controlled under 0.1mm/m and 0.2mm/m, respectively. The BPM chambers are manufactured precisely in oil-free environment, which provide clean surface and a precise sealing surface after machining. All the components are assembled in pre-aligned support system through the welding process, and then the results show the straightness of < 0.15mm/m, flatness of < 0.3mm/m, and leakage rates of < 2 × 10-10 mbar‧l/sec. were achieved.

Using contrast material techniques to determine metal flow in screw extrusion of aluminium

Screw extrusion is a new continuous solid state processing method for aluminium. In this process, small pieces of aluminium are continuously inserted into a container wherein a rotating screw pushes the material forward. The material is heated, consolidated and extruded through a die in front of the end of the screw in one single continuous process. Understanding the material flow and the pressure generating mechanism is vital for optimizing screw, container and die designs, thereby increasing capacity, material quality and process stability. Full scale experiments using a prototype extruder were chosen as the means of investigation. In this paper, it is reported on the development of a novel contrast material technique to visualize material flow in the screw channels and the extrusion chamber. Extrusion of Ø 10mm aluminium profiles was performed using both single and double flight screws. The experimental technique provided a means for evaluating the frictional conditions between the aluminium and the surface of the extruder. Different feeding schemes were used to identify regions of high material flow rate together with dead metal zones in the screw channels and in the extrusion chamber. It is demonstrated how newly fed material interacts with and displaces material already present and how the screw pushes material into the extrusion chamber. The instantaneous extrusion velocity was measured and significant variations were detected for all feed rates. An explanatory model of the extrusion pressure generating mechanism in the extrusion chamber and the screw channel is presented linking the material flow and the consolidation process to the extrusion velocity variations.

An Investigation of the Material Flow in a Screw Extruder of Aluminium Using Contrast Material

The material flow in a screw extruder of aluminium was investigated. Screw extrusion of aluminium is a new solid state process where granulate aluminium is consolidated and extruded in a single continuous process using a rotating screw as the pressure generating device. Understanding the material flow is vital for predicting the consolidation and welding process thereby making it possible to optimize screw and container design to increase the capacity, ekstrudate quality and process stability. Using a prototype screw extruder, aluminium alloy AA6060 was extruded together with contrast material using different feeding schemes to visualize the material flow. Material left in the extruder was inspected visually, sectioned and etched in NaOH to reveal the interaction between the contrast material and the AA6060. It was found that newly fed contrast material primarily displaced material in the centre of the screw channel and the extrusion chamber hereby revealing the main paths of the material flow. Areas of sticking friction, material dead zones and zones of slow material displacement rate were effectively identified using this method.

Accurate nano-injection system for capillary gas chromatography

The first version of nano-injection device for capillary gas chromatography (cGC) based on inkjet microchip was developed. The nano-injector could accurately control the injection volume in nano-liter, even pico-liter range. Its configuration and mechanism were discussed in detail. Adopting photolithography and plasma etching technology, we firstly fabricated the inkjet microchip and stuck to a piezoelectric device to eject droplets. Then, a special feedback tube was added to make it function as a nano-injector for cGC, which was an important design to compensate pressure difference between the evaporation chamber of cGC and the sample extrusion chamber of inkjet microchip. The injected volume can be precisely controlled by the number of injected droplets. Excellent precision (RSDs were below 10.0%, n = 5) was observed for the injection of ethanol at elevated pressure. Minimum injection volume was about 1.25 nL at present. Additionally, good repeatability of the calibration curves for the hydrocarbons ethanolic solution (the RSDs of all components were below 5.30%, n = 5) confirmed its feasibility in quantitative analysis regardless of concentration. These results suggested that it can be an accurate nano-injector for cGC.

Reactive extrusion and high-temperature oxidation of Ni3Al

The nickel aluminide (Ni3Al) intermetallic has attracted considerable attention over the past few decades due to its desirable properties at elevated temperatures [1]. A considerable amount of work has been reported on the combustion synthesis of nickel aluminides [2–7]. The process (in the thermal explosion mode of ignition) involves uniformly heating an elemental powder compact of nickel and aluminum to an ignition temperature (at or above the eutectic temperature of 640 ◦C) at which the reactant powder spontaneously convert to product(s). A general problem however is the generation of unwanted porosity in the final product, which necessities the application of pressure (hot pressing/hot isostatic pressing) in order to produce highly dense materials [3, 4]. The current approach involves heating the compact to the ignition temperature, and allowing the exothermic reaction to proceed to completion inside the extrusion chamber, thereby raising the compact temperature to the maximum “combustion” temperature. Extrusion is then conducted as the specimen cools down from the combustion temperature. This reactive extrusion (RE) approach offers a number of possible advantages including, the production of completely reacted single phase alloys, consolidation, and grain size refinement through re-crystallization. Recent preliminary work by the authors showed the feasibility of the approach to produce Ni3Al [8]. Away from the die exit, the reactively extruded material was found to have a refined grain structure with an average grain size that increases from 4 to 6.5μm along the extrusion length. In this paper, the effect of extrusion speed on the product microstructure and properties is discussed, together with a preliminary evaluation of the high-temperature oxidation behavior of reactively extruded Ni3Al and a comparison to that of combustion synthesized materials. SHS (selfpropagating high temperature synthesis) extrusion of TiC reinforced with a metallic binder (e.g., Ni) (to facilitate

Statistical evaluation of different technological and rheological tests of Polish wheat varieties for bread volume prediction

SummaryForty‐two Polish wheat flour were used to establish correlation coefficients between protein content, Zeleny test, falling number value, amylograph viscosity, farinograph water absorption, bread volume and rheological properties of dough, as shown by use of a extrusion chamber and alveograph. The equations expressing the changes of bread volume and flour water absorption as a function of significantly correlated parameters were calculated. The correlations and their significance depended on wheat quality and the alveographic parameters were significantly correlated with the dough extrusion parameters. The dough extrusion parameters were significantly correlated only with the water absorption of soft wheats. The dough rheological tests were correlated to a greater extent with the values of the Zeleny test than to the protein content. The prediction of the bread volume as a function of flour quality parameters and dough rheological properties was best done by grouping wheat varieties into specific qualitative classes.

Simulation of bridge die extrusion using the finite element method

This communication reviews previous work on the extrusion of hollow shapes and uses a three-dimensional (FEM) solution to predict load-required, temperature of the extrudate and material flow during the process. A comparison with experiments is made to assess the relative importance of some extrusion parameters in the extrusion process and to ensure that the numerical discretisation yields a realistic simulation of the process. The usefulness and limitations of FEM when modelling complex shapes is also discussed. Methods to assess the difficulty of extrusion of hollow extrusions in general are presented. The paper also illustrates the essentials of numerical analysis to assist the reader in the comprehension of the thermomechanical events occurring during extrusion through bridge dies. Results are presented for velocity distribution in the extrusion chamber, iso-temperature contours and pressure/ displacement traces. These are compared with experiments conducted using a 5 MN press. It is shown that the finite element program predicts the pressure requirement: the pressure/displacement trace showing a double peak which is discussed in some detail. The finite element program appears to predict all the major characteristics of the flow observed macroscopically.

Metal-forming process optimisation by inverse evolutionary search

In this paper, new numerical techniques are developed for the optimisation of steady and non-steady forming processes. These techniques consider the inverse problem formulation together with evolutionary search schemes. The solutions are obtained using numerical algorithms based on a genetic search supported by an elitist strategy. In order to demonstrate the efficiency of the inverse evolutionary search, two specific cases are considered. The first case involves the optimisation of the process parameters aiming for a prescribed pressure distribution at the exit of the extrusion chamber. In the second case, the optimisation objective aims at the reduction of the difference between the realised and the prescribed final forged shape under minimal energy consumption.