Traditional Extrusion Research Articles

New rotary piercing process for an AZ31 magnesium alloy seamless tube

ABSTRACTTo address the existing defects in the processing of magnesium alloy seamless tubes (MASTs), a new technology for producing AZ31 alloy tubes using a rotary piercing process was studied. Through the finite-element method and experimental analyses, the distributions of stress and strain and the temperature fields were analysed. The effects of temperature, radial reduction, plug diameter, and advance on the penetration rate, diameter, and wall thickness of the tube were studied. The results showed that temperature is the most important parameter; the penetration rate of the tube was >90% for rolling temperatures of 350–450°C. There was complete dynamic recrystallisation and a uniform distribution of equiaxed grains. This process can potentially replace the traditional extrusion process to produce MASTs.

A Hollow Extrusion Die for Big Square Tube Profiles of Al-alloy

The factors on premature failure of the traditional extrusion die for the big square tube profiles were introduced. And the characteristics of the conventional structure were analyzed. A new type of hollow die structure for these profiles was presented. And the composition elements of the new die structure were described, including its advantages. According to the comparison conventional with new die structure in use, it was shown that the new die structure has obvious advantages, it could greatly improve the die life. This is a type of die structure which is worth promoting.

Assessment of physical properties and sensory attributes of extruded corn snacks mixed with barley and supplemented with (guar and xanthan) gums.

Corn snacks mixed with barley flour in addition to guar and xanthan gumswere evaluated for their physical and sensory properties. Snacks samples were processed using corn grits mixed with 5% barley flour and (0.5-1%) guar gum or xanthan gum using traditional extrusion system conditions. The extruded samples were tested instrumentally direct after processing and at 3, 6, 9 and 12 months' storage (at room temperature) for bulk density, expansion ratio, shear force (hardness) and color. Sensory evaluation was made for snacks color, chewiness, surface characteristics and general appearance. Samples fortified with guar gum recorded the highest value of expansion ratio and shear force 2.82 cm and 16.1kg/cm² respectively. Xanthan gum had the lowest texture shear force values 14.7kg/cm² comparing control 15.3kg/cm² and recorded 2.61cm expansion comparing 2.25cm for control. Adding gum increased bulk density values from 0.52g/cm³ up to 0.69g/cm³. Sample mixed with guar and xanthan gums recorded the higher acceptability scores by panelists than other tested samples.

MICROENCAPSULATION AND ENHANCEMENT OF VIABILITY OF LACTOBACILLUS RHAMNOSUS GG

Probiotics are microorganisms which, when taken orally, give benificial results for human gut wellbeing. In this study, microcapsules loaded with Lactobacillus rhamnosus GG (LGG) were prepared with the traditional extrusion method using low methoxy pectin (3%) alone and in combination with cellulose derivatives and coated with and without Cellacefate (10 % w/V) solution as an enteric coating material. Non capsulated and encapsulated cells were exposed to simulated gastrointestinal fluids for 6 h, and then evaluated for viability using plate counts method. All encapsulated formulations were able to improve the viability of LGG during passage through the harsh condition of GIT and the Cellacefate coated formulations were able to maintain viable bacterial concentration of >107 CFU/g (minimum concentration of probiotics for health benefit).This study reports the viability of encapsulated Lactobacillus rhamnosus GG in LMP coated bead was higher than the controlled and non coated beads.

Using multi-axis material extrusion to improve mechanical properties through surface reinforcement

ABSTRACTDue to the layer stacking inherent in traditional three-axis material extrusion (ME) additive manufacturing processes, a part's mechanical strength is limited in the print direction due to weaker interlayer bond strength. Often, this requires compromise in part design through either adding material in critical areas of the part, reducing end-use loads or forgoing ME as a manufacturing option. To address this limitation, the authors propose a multi-axis deposition technique that deposits material along a part's surface to improve mechanical performance. Specifically, the authors employ a custom 6 degree of freedom robotic arm ME system to create a surface reinforcing ‘skin’, similar to composite layup, in a single manufacturing process. In this paper, vertical tensile bars are fabricated through stacked XY layers, followed by depositing material directly onto the printed surface to evaluate the effect of the skinning approach on mechanical properties. Experimental results demonstrate that surface-reinforced interlayer bonds provide increased yield strength.

Study on processing and structure property of Al-Cu-Mg-Zn alloy cup-shaped part produced by radial-backward extrusion

In this work, three cavity structures of radial-backward extrusion (RBE) have been employed to produce Al-Cu-Mg-Zn alloy cup-shaped part. The effects of the cavity structure on the average effective strain, forming load, and forming damage of cup-shaped part produced by RBE were investigated by finite element simulations, and then the influences of frictional coefficient and ram speed on the forming damage were also studied. Comparisons of mechanical properties and microstructure between cup-shaped part produced by RBE and by traditional backward extrusion (TBE) were conducted by experimental works. The finite element simulation results show that the minimum average effective strain and maximum forming damage were acquired in RBE with type-A cavity (RBE-A); the maximum average effective strain and minimum forming damage were obtained in RBE with type-B cavity (RBE-B), and the forming damage and average effective strain were moderate if RBE with type-C cavity (RBE-C) has been used. For RBE-A, RBE-B, and RBE-C, the forming damage decreases as ram speed increases or frictional coefficient decreases. With the identical frictional coefficient and ram speed, the forming load increases in an order from type-A cavity, type-C cavity, and type-B cavity. The average effective strain in RBE-C is about 1.9 times of that in TBE. The uniform degree of deformation in RBE-C is far better than that in TBE. The experimental results show that after RBE-C, ultimate tensile strength and yield strength of tube length of formed part are significantly larger than that after TBE, and ultimate tensile strengths and elongation of tube length are around 349 MPa and 22%, respectively. Better refinement of grain and more uniform distribution of strengthening phase can be achieved by RBE-C than by TBE.

Fabrication of high-strength Mg-Gd-Zn-Zr alloys via differential-thermal extrusion

A high-strength Mg-Gd-Zn-Zr alloy developed by a novel extrusion method called differential-thermal extrusion (DTE) was detailed characterized, to reveal the effects of the DTE on microstructure and mechanical properties. Different from traditional isothermal extrusion (ITE) with the same billet and mold temperature, the billet temperature for the DTE is remarkably higher than the mold temperature. The finer grains and less long period stacking ordered (LPSO) structure in the DTE sample resulted from its higher cooling speed after deformation. Meanwhile, the stronger precipitation strengthening effect was caused by the higher billet preheat temperature which reserved the precipitation ability before extrusion. As a result, the finer grains and stronger precipitation strengthening led to the strong tensile yield strength (380MPa) and ultimate tensile strength (461MPa) of the aged DTE sample, while those of the aged ITE sample are only 338MPa and 420MPa, respectively. The higher strengths indicate the DTE is a better extrusion process for producing high-strength Mg alloys than the traditional ITE.

Numerical simulation and experimental research of metal dynamic flow in cold extrusion under the electric-hydraulic vibration

With thick-wall cylinders as the researched object, the paper adopts a novel cold-extrusion technology, namely electro-hydraulic cold-extrusion, to apply vibration signals into a traditional cold extrusion technology. With volume effects of vibration processing as the theoretical basis, Deform-3D software was used to conduct numerical simulation of metal materials under a traditional extrusion type and an extrusion mode with vibration respectively. Evolution processes of metal flow lines and metal grid flow under two kinds of extrusion types were analyzed and compared in details. Through experimental research, computational results of numerical simulation were verified. Metal flow lines at corners of molded parts were observed and analyzed in particular. Researched results show that the metal flow velocity increased and the bending level of cross-section flow lines of the metal decreased after applying vibration signals compared with the traditional extrusion type. The research indicated that vibration promoted metal flow, reduced resistance of the metal flow, and obtained more uniform deformation of metal materials during plastic molding. Research achievements obtained in this paper provide important theoretical and practical engineering values for effectively applying vibration in mechanical processing fields.

Investigation on the Hot Tensile Deformation Process of Traditional Extrusion Alloy ZA41 with Different Temperatures and Stain Rates

The hot tensile deformation process of traditional extrusion alloy ZA41 with different temperatures and stain rates is investigated. During the investigation the results show that under the condition of the deformation temperatures ranging from 583 to 613K and strain rates ranging from 5×10-5 to 6×10-4s-1 the alloy exhibits excellent elongation-to-failure of 219.4 % and strain rate sensitivity exponent of 0.35 at temperature of 598 K and strain rate of 5×10-5s-1. The experimental peak stress of ZA41 alloy also shows a decline with the rise of temperature and the decrease of strain rate. Microstructure observations suggest that plastic deformation fracture at high temperature and low strain rate occurs after the connection and expansion of the cavities distributing along triangular grain boundary, and grain boundary movement with cavity coordination makes an important contribution to the superior plasticity.1

Fabrication of biomimetic bone grafts with multi-material 3D printing

Extrusion deposition is a versatile method for the 3D printing of biomaterials such as hydrogels, ceramics, and suspensions. Recently, a new class of emulsion inks were developed that can be used to create tunable, hierarchically porous materials with a cure-on-dispense method. Propylene fumarate dimethacrylate (PFDMA) was selected to fabricate bone grafts using this technology due to its established biocompatibility, osteoconductivity, and good compressive properties. Scaffolds fabricated from PFDMA emulsion inks displayed compressive modulus and yield strength of approximately 15 and 1 MPa, respectively. A decrease in infill (from 100% to 70%) resulted in a six-fold increase in permeability; however, there was also a corollary decrease in mechanical properties. In order to generate scaffolds with increased permeability without sacrificing mechanical strength, a biomimetic approach to scaffold design was used to reinforce the highly porous emulsion inks with a dense cortical shell of thermoplastic polyester. Herein, we present an open source method for printing multi-material bone grafts based on PFDMA polyHIPEs with hierarchical porosity and reinforced with a dense shell of poly(ε-caprolactone) (PCL) or poly(lactic acid) (PLA). A multi-modal printing setup was first developed that combined paste extrusion and high temperature thermoplastic extrusion with high positional accuracy in dual deposition. Scaffolds printed with a PCL shell displayed compressive modulus and yield strength of approximately 30 and 3 MPa, respectively. Scaffolds printed with a PLA shell showed compressive modulus and yield strength of approximately 100 and 10 MPa, respectively. By combining this new paste extrusion of emulsion inks with traditional thermoplastic extrusion printing, we have created scaffolds with superior strength that promote cell viability and proliferation of human mesenchymal stem cells. The development of this technique shows great promise for the fabrication of a myriad of other complex tissue engineered scaffolds.

Ultrasonic-assisted extrusion of ZK60 Mg alloy micropins at room temperature

A new model of ZK60 magnesium micropins formed through ultrasonic-assisted extrusion at room temperature was developed. The billet was transmitted by the ultrasonic wave during the micropin-forming process. A self-designed apparatus was applied for the ultrasonic-assisted extrusion experiments. The effects of amplitude on the load–displacement curve, load reduction, temperature, microstructure, diameter after extrusion, microhardness, and compressibility of micropins were investigated. The results showed that the punch was always in contact with the billet when the displacement of the punch was larger than the amplitude. The maximum reduction of load was approximately 80% because of the dynamic recrystallization and ultrasonic softening. In addition, load reduction was almost similar under different amplitudes when the diameters of micropins after extrusion were 0.3 and 0.5mm as a result of the size effect. The microhardness of the micropins increased at the amplitude of 39 and 42μm as compared with the traditional extrusion. This finding was inconsistent with the results for copper and aluminum. The compression ratio of micropins prepared through ultrasonic-assisted extrusion improved by 14–20% on average at room temperature.

The relationship between reducing sugars and phenolic retention of brown rice after enzymatic extrusion

To investigate the relationship between reducing sugars and phenolic retention of brown rice after enzymatic extrusion, reducing sugars, total phenolic content, total antioxidant activity, and individual phenolic acids of brown rice extruded with different α-amylase concentrations (0.1%, 0.5%, 1%, w/w) were evaluated. Reducing sugars were produced during enzymatic extrusion and significantly increased with the increasing enzyme concentration. Compared with traditional extrusion, the enzymatic extrusion with 1% amylase significantly increased the phenolic retention, DPPH value, FRAP value, and ABTS value by 22.4%, 19.5%, 14.7%, and 41.5%, respectively. The retention of most free phenolic acids was also increased with the increasing enzyme concentration. Besides, the correlation analysis indicated that the content of reducing sugars was positively correlated with total phenolic content (r = 0.915), DPPH value (r = 0.882), FRAP value (r = 0.861), ABTS value (r = 0.867) and free individual phenolic acids (r = 0.595–0.943) of treated brown rice. These results suggested that reducing sugars might protect phenolic compounds during enzymatic extrusion.

Statistical optimization of bambara groundnut protein isolate-alginate matrix systems on survival of encapsulated Lactobacillus rhamnosus GG.

Encapsulation may protect viable probiotic cells. This study aims at the evaluation of a bambara groundnut protein isolate (BGPI)-alginate matrix designed for encapsulating a probiotic Lactobacillus rhamnosus GG. The response surface methodology was employed to gain the optimal concentrations of BGPI and alginate on encapsulation efficiency and survival of encapsulated cells. The capsules were prepared at the optimal combination by the traditional extrusion method composed of 8.66% w/v BGPI and 1.85% w/v alginate. The encapsulation efficiency was 97.24%, whereas the survival rates in an acidic condition and after the freeze-drying process were 95.56% and 95.20%, respectively—higher than those using either BGPI or alginate as the encapsulating agent individually. The designed capsules increased the probiotic L. rhamnosus GG survival relative to free cells in a simulated gastric fluid by 5.00 log cfu/ml after 3 h and in a simulated intestinal fluid by 8.06 log cfu/ml after 4 h. The shelf-life studies of the capsules over 6 months at 4 °C and 30 °C indicated that the remaining number of viable cells in a BGPI-alginate capsule was significantly higher than that of free cells in both temperatures. It was demonstrated that the BGPI-alginate capsule could be utilized as a new probiotic carrier for enhanced gastrointestinal transit and storage applied in food and/or pharmaceutical products.

The role of organic phosphite primary structure in the overall stabilization performance in polypropylene

The role of the primary P3+ functionality in the phosphite overall stabilization performance was re-evaluated. Tris(2,4-di-t-Bu-phenyl)phosphite (P-1) and its oxidation product tris(2,4-di-t-Bu-phenyl)phosphate (P-1ox) were tested both alone and in the presence of hindered phenol during processing in polypropylene. Efficiencies were quantified using the processing degradation index (PDI). The position of the traditional multiple extrusion curve was determined by a single parameter, describing the degree of polymer degradation. Its reciprocal allowed calculating formulations relative efficiencies. It was shown that oxidation of P3+ into P5+ is responsible for 75 % phosphite stabilization performance, regardless phosphite acts alone or in combination with phenol. If P3+ is completely oxidized, stabilizer still works. For the residual performance, the reactions of 2,4-di-t-Bu-phenyl substituents (secondary structure), are responsible. Besides processing, reactions of P3+ also contribute to the long-term stability at 150 °C. Once phosphite is oxidized, the secondary structure does not contribute to the long-term stability at all.

Ultra-high strength Mg-9Gd-4Y-0.5Zr alloy with bi-modal structure processed by traditional extrusion

It is usual to observe that multi-scale structures can lead to combined strength and ductility both in aluminum alloys and steels, but related research has been seldom reported yet in magnesium alloys. In this study, applying traditional one step extrusion, we have successfully obtained a bimodal (Mg-9Gd-4Y-0.5Zr) alloy capable of ultra-high strength. The characterized sample reveal a bi-modal microstructure with two constitutions, i.e. stretched coarse-grain region with strong basal fiber texture and recrystallization fine-grain region. The bi-modal structured sample exhibit excellent mechanical properties with an ultimate strength 508 MPa and elongation 8% via 400 °C extrusion and subsequently 200 °C-60 h peak aging process. Ultra-high strength can be attributed to its strong extrusion texture in stretched coarse grains and dispersed nano-scale precipitates. This unique bimodal structure could be produced easily by one step extrusion, which is quite reliable and low costs in industrial applications of magnesium alloys with ultra-high strength as well as ideal ductility.

Corn proteins solubility changes during extrusion and traditional nixtamalization for tortilla processing: A study using size exclusion chromatography

Changes in the solubility of corn proteins occurring during traditional nixtamalization and extrusion processes used to produce tortillas were studied using size exclusion chromatography, SDS-PAGE and the Dumas method to measure 50% propanol-insoluble protein. Size exclusion chromatography (HPL-SEC) studies furthered the understanding of protein solubility changes during both processes. Extrusion caused more protein aggregation in tortilla intermediate and final products than traditional nixtamalization. Mixing during extrusion and in the intermediate step of masa production in the traditional nixtamalization process was critical in reducing protein solubility. Baking tortillas also considerably reduced the protein solubility for the traditional nixtamalization process. Baking produced aggregation that could not be disrupted with a reducing agent.

Effect of enzymatic (thermostable α-amylase) treatment on the physicochemical and antioxidant properties of extruded rice incorporated with soybean flour

In order to determine the effect of enzymatic extrusion on the physicochemical and antioxidant properties of rice/soybean mixture, different mass ratios (100/0, 95/5, 85/15, 70/30, 50/50 and 25/75%, w/w) were treated with thermostable α-amylase. The reduced special mechanical energy and the enhanced product temperature were closely and regularly linked with the increase of soybean content. The bulk density and water solubility index increased, and the water absorption index and viscosities decreased remarkably after enzymatic extrusion, however, the modification caused by α-amylase were dramatically eliminated with the increase of soybean content to ∼50%. Moreover, the addition of enzyme exhibited an improvement of the total phenolic/flavonoid content (TPC/TFC) and antioxidant capacities compared to traditional extrusion. The TPC/TFC retention of extrudate (ratios of 85/15 and 70/30%) attained over 90%, but dramatically decreased (72.91 and 67.81%, respectively) with soybean added to 75%, probably due to the great reduction of starch substrate for enzymatic hydrolysis.

Study on New Extrusion Route of Equal Channel Angular Processing in High Purity Aluminium

The new extrusion route of ECAP which is called route 135 was put forward in this paper. The grain refinement of the traditional extrusion route BCand the new route of ECAP process in 99.9995% (5N5) high purity aluminum was compared using a die with a channel-intersection angle 90°. It was found through experiment that, the grain was very coarse in the cast ingot of 5N5 high purity aluminum, and the average grain size is about 60mm. High purity aluminum processed by one pass ECAP was refined notably, and average grain size is about 1000 μm. After two ECAP passes, the average grain size is 200μm with route BC, while it is less than 50μm with route 135. The refinement of two passes of route 135 is equivalent to the refinement of eight passes of route BC. It indicates that the route 135 is more effective than route BC. TEM micrograph of 5N5 high purity Al with different ECAP pass under route BCand route 135 was studied.

The Research of Extruded Pressure Auto-Adjustment Method in Abrasive Flow Polishing

Aiming at the quality problems of ‘over polishing’ and ‘insufficient polishing’ in the process of traditional extrusion abrasive flow machining,An abrasive flow polishing method at the constantly small pressure difference is developed, the hydraulic proportional control system is designed, and the mathematical modeling of the hydraulic proportional control system for small pressure difference constant extrusion polishing abrasive flow machining is set up. The simulation results show that the polishing pressure can be well controlled and the stability of polishing velocity is improved, which will improve the extrusion abrasive flow polishing quality.

Influência de variáveis de sinterização na microestrutura de peças de PTFE moldadas por prensagem isostática

O politetrafluoretileno (PTFE) é utilizado em extensa gama de aplicações críticas devido à sua excelente resistência química e térmica, baixa energia superficial e propriedades tribológicas. Devido à sua elevada viscosidade no estado fundido, o PTFE não pode ser transformado pelos métodos tradicionais de extrusão e injeção, sendo o principal método de transformação deste polímero a prensagem sob temperatura ambiente, seguida de sinterização a temperaturas acima do ponto de fusão. O tempo de sinterização é definido de acordo com as dimensões da peça fabricada, podendo variar de poucas horas até vários dias para peças de grande volume. Avaliações sobre a influência dos extremos de tempo e temperatura de sinterização, atualmente adotados na indústria, sobre a microestrutura cristalina do PTFE, são escassas na literatura científica, sendo o principal objetivo deste estudo. Placas em PTFE foram sinterizadas variando-se a temperatura entre 360 ○C e 390 ○C e o tempo entre 10 e 10.000 min. Calorimetria exploratória diferencial (DSC), medidas de perda de massa e de densidade e microscopia eletrônica de varredura (MEV) foram utilizadas. Os resultados das medidas de perda de massa indicaram que a degradação do PTFE aumenta com o tempo e temperatura de sinterização. Análises das entalpias de fusão e medidas de densidade apontam indiretamente a redução na massa molar e aumento no grau de cristalinidade com o aumento do tempo e temperatura de sinterização. As análises em MEV possibilitaram a observação direta da microestrutura cristalina, indicando uma tendência de aumento da largura das lamelas com o tempo e temperatura de sinterização. Os resultados obtidos podem auxiliar no controle da microestrutura do PTFE durante o processamento, o que é bastante útil para a fabricação de peças em PTFE com desempenho otimizado.