Search Results (35)

Polylactic acid (PLA) has gained attention as a sustainable, compostable polyester, but process-induced degradation in single- and twin-screw extruders reduces PLA’s molecular weight and affects its properties. In addition, PLA is often blended with other materials to improve its properties. A continuous mixer, which provides tighter control of shear levels and lower processing temperatures, produces less degradation of heat-sensitive polymers like polyvinyl chloride, but there is limited information about the effects of machine design and processing parameters. Therefore, this work investigated three parameters in the mixer section (rotor design, rotor speed, and orifice position) and screw speeds in the extruder section when processing PLA using a continuous mixer. The resultant PLA samples were characterized for their rheological, thermal, and chemical structure properties. It was found that higher rotor speeds and smaller orifice openings resulted in lower molecular weights, whereas varying the screw speed in the extruder did not significantly affect the molecular weight. Rotor design substantially impacted degradation, with rotors that provided lower shear stress and residence time producing very low reductions in molecular weight. Overall, this work provided insight on how to select rotors and processing parameters to reduce degradation of PLA for continuous mixer Full article

The eccentric rotor extruder (ERE) is polymer processing equipment that exhibits excellent processing capabilities for materials with extremely high viscosity, which are difficult to plastically deform and transport efficiently. However, the mass transfer mechanism in the solid conveying section of this new device is fundamentally different from that of traditional extruders, and no related research has been reported. This study uses discrete element method (DEM) simulation technology to model the solid conveying process of the ERE. By visualizing the positive displacement conveying process, and with an analysis of the output parameters, the study clarifies the mass transfer principles and quantifies the conveying capacity, providing guidance for optimizing the extruder design. The simulation results show that the ERE exhibits positive displacement conveying characteristics, with the conveying process achieved by the forward movement of the cavities (closed cavities between the rotor and stator) in a helical manner. However, differences in the dual-cavity (two types of cavities) feeding process and low fill level can lead to significant fluctuations in extrusion output and reduced conveying capacity. To address these issues, an improvement scheme for the dual-cavity feed opening is proposed, with feed openings designed with different opening lengths. Then, by analyzing the particle coordinate data from the simulation output, the conveying capacities of different feed opening structures are quantified and optimized. Finally, experimental and simulation verification results indicate that the optimized structure significantly improves the issues of uneven filling and low fill level, with good correspondence between the simulation and experimental results. Simulation results show that, compared with the original structure, the optimized dual-feed opening structure increases the feed capacity from 3953 particles per cavity to 5132 particles per cavity, an improvement of 29.8%, and it achieves balanced filling between the two cavities. Experimental validation indicates that the UPE4040 output can be increased from 165.3 g/min with structure op-00 to 231.7 g/min with the optimized structure op-05. Full article

Whole grain foods have been recommended to preserve biologically active components and benefit human health. The effect of the addition amount of whole sweet potato flour (WSPF, 25%, 51%, and 75%) on the physicochemical and structural properties of extruded whole-grain noodles was evaluated. Compared with traditional wheat flour (WF), the increased content of WSPF led to an enhancement in the dough’s water retention capacity, resulting in the reduction of dough development time and stability time. The modulus of elasticity and the modulus of loss of the dough exhibited a positive correlation with the proportion of WSPF added, while the tangent value and maximum creep flexibility were negatively correlated. Confocal laser scanning microscopy (CLSM) observed that WSPF induced protein aggregation in the dough. Compared to conventional WF, the increased incorporation of WSPF resulted in improved textural characteristics of the extruded noodles. Sensory evaluation indicated that the addition of WSPF could enhance the quality of the noodles by imparting a sweet potato aroma, a distinctive color, and a satisfactory taste. These characteristics were correlated with their enhanced relative crystallinity, enthalpy, and short-range ordered structure. Additionally, 75% whole-grain sweet potato noodles exhibited the highest relative crystallinity (11.05%), enthalpy of pasting (ΔH, 22.6 J/g), and short-range ordered structure (0.78). SEM results indicated that the presence of holes in the cross-section of the sweet potato extruded noodles facilitated their rapid rehydration. Overall, the whole-grain sweet potato noodles have great potential in promoting the textural, sensory, and nutritional properties compared to traditional wheat noodles. Full article

This article presents the first use of shape forming elements (SFEs) to produce architected composites from multiple materials in an extrusion process. Each SFE contains a matrix of flow channels connecting input and output ports, where materials are routed between corresponding ports. The mathematical operations of rotation and shifting are described, and design automation is explored using Bayesian optimization and genetic algorithms to select fifty or more parameters for minimizing two objective functions. The first objective aims to match a target cross-section by minimizing the pixel-by-pixel error, which is weighted with the structural similarity index (SSIM). The second objective seeks to maximize information content by minimizing the SSIM relative to a white image. Satisfactory designs are achieved with better objective function values observed in rectangular rather than square flow channels. Validation extrusion of modeling clay demonstrates that while SFEs impose complex material transformations, they do not achieve the material distributions predicted by the digital model. Using the SSIM for results comparison, initial stages yielded SSIM values near 0.8 between design and simulation, indicating a good initial match. However, the control of material processing tended to decline with successive SFE processing with the SSIM of the extruded output dropping to 0.023 relative to the design intent. Flow simulations more closely replicated the observed structures with SSIM values around 0.4 but also failed to predict the intended cross-sections. The evaluation highlights the need for advanced modeling techniques to enhance the predictive accuracy and functionality of SFEs for biomedical, energy storage, and structural applications. Full article

The main aim of this work is to evaluate the mechanical properties of additive manufactured polymeric parts joined with standard plastic parts through structural adhesives. The primary advantage of this technique is its ability to significantly increase the size of the final assembly by using additive manufacturing (AM) for complex joints and inexpensive, reliable extruded plastic parts for load-bearing components. This hybrid assembly combines the flexibility and shape adaptability of AM with the structural strength and cost-effectiveness of extruded polymer parts, resulting in a final design that performs comparably to the base material. The materials used in the paper are rigid acrylic adhesive and toughened acrylic, both applicable with almost no surface preparation and fast curing. The 3D-printed parts are produced in ABS, while the standard parts are in PVC. First, the work is devoted to estimating the performance of the adhesives using pin–collar joints and a combined numerical and experimental methodology. The second section presents and discusses the results of two more realistic applications of adhesive bonding to hybrid complex joints. For the pin–collar joints, the results show failure mostly in the adhesive, with an average shear stress of 11.5 MPa and 5.22 MPa and a stiffness of 4449 N/mm and 3649 N/mm for the rigid and toughened adhesives, respectively. The results of the adhesive bonding of structural joints show that the adhesive is always capable of providing the load-carrying capacity required to achieve the strength of traditionally manufactured polymeric parts. The paper shows that adhesives are a feasible way to expand the potential of 3D-printed equipment to obtain larger hybrid parts partially realized with traditional technology, especially with inexpensive off-the-shelf bars and sections. Full article

The growing global demand for healthy, gluten-free snacks has driven the food industry to explore innovative products that fit consumer preferences. This study focused on developing a gluten-free, energy-dense, and crunchy snack called Quispiño, made from quinoa (Chenopodium quinoa Willd.), an ancient crop native to the Andes and particularly significant in Puno, Peru. Natural and desaponified quinoa samples were compared, revealing decreased carbohydrate content (69.75 g to 64.02 g per 100 g) and protein content (13.27 g to 12.90 g per 100 g) after desaponification. Moisture remained around 11.5%, while fiber content significantly decreased in the desaponified quinoa (from 4.39 g to 2.76 g per 100 g). The extrusion process influenced the color of the extrudates, reducing the L* value (from 75.28 to a range of 63.70–69.12), indicating darkening due to the Maillard reaction. Moisture in the extrudates ranged from 3.08% to 6.12%, while firmness varied between 7.25 N and 25.86 N, significantly influencing extrusion temperature. The water solubility index (WSI) ranged from 0.17% to 71.61%, with high values attributed to starch dextrinization during extrusion. The water absorption index (WAI) showed a significant increase, highlighting the physical changes induced by extrusion. The sectional expansion index (SEI) also varied considerably, ranging from 7.33 to 13.08, reflecting the impact of the extrusion process on the final product structure. The optimal sample was identified and subjected to an acceptability test with an untrained panel of 45 evaluators who assessed flavor, color, odor, appearance, and texture. The best-performing treatment was further analyzed for proximate composition, calcium, and iron content to compare with the raw material. The results demonstrate the potential of quinoa as a key ingredient in developing new, expanded, gluten-free snacks that meet the growing demand for nutritious and appealing food products in the global market. Full article

The structure and composition of natural bone show gradient changes. Most bone scaffolds prepared by bone tissue engineering with single materials and structures present difficulties in meeting the needs of bone defect repair. Based on the structure and composition of natural long bones, this study proposed a new bone scaffold preparation technology, the dual-phase composite forming process. Based on the composite use of multiple biomaterials, a bionic natural long bone structure bone scaffold model with bone scaffold pore structure gradient and material concentration gradient changes along the radial direction was designed. Different from the traditional method of using multiple nozzles to achieve material concentration gradient in the scaffold, the dual-phase composite forming process in this study achieved continuous 3D printing preparation of bone scaffolds with gradual material concentration gradient by controlling the speed of extruding materials from two feed barrels into a closed mixing chamber with one nozzle. Through morphological characterization and mechanical property analysis, the results showed that BS-G (radial gradient long bone scaffolds prepared by the dual-phase composite forming process) had obvious pore structure gradient changes and material concentration gradient changes, while BS-T (radial gradient long bone scaffolds prepared by printing three concentrations of material in separate regions) had a discontinuous gradient with obvious boundaries between the parts. The compressive strength of BS-G was 1.00 ± 0.19 MPa, which was higher than the compressive strength of BS-T, and the compressive strength of BS-G also met the needs of bone defect repair. The results of in vitro cell culture tests showed that BS-G had no cytotoxicity. In a Sprague–Dawley rat experimental model, blood tests and key organ sections showed no significant difference between the experimental group and the control group. The prepared BS-G was verified to have good biocompatibility and lays a foundation for the subsequent study of the bone repair effect of radial gradient long bone scaffolds in large animals. Full article

This study investigates the impact of varying extrusion ratios on the microstructure and mechanical properties of AlSiCuFeMnYb alloy. Following hot extrusion, significant enhancements are observed in the microstructure of the cast rare earth aluminium alloy. Within the cross-sectional microstructure, the α-Al phase is reduced in size, and its dendritic morphology is eliminated. The morphology of the eutectic Si phase transitions from long strips to short rods, fine fibres, or granular forms. Similarly, the Fe-rich phase changes from a coarse skeletal and flat noodle shape to small strips and short skeletal forms resembling Chinese characters. The CuAl₂ phase evolves from large blocks to smaller blocks and granular forms, while the Yb (Ytterbium)-rich rare earth phase shifts from large blocks to smaller, more uniformly distributed blocks. In the longitudinal section, the structure aligns into strips along the extrusion direction, with the spacing between these strips decreasing as the extrusion ratio increases. At an extrusion ratio of 22.56, the alloy demonstrates superior mechanical properties with a tensile strength of 325.50 MPa, a yield strength of 254.44 MPa, a hardness of 143.90 HV, and an elongation of 15.47%. These represent improvements of 27.8%, 36.5%, 38.9%, and 236.4%, respectively, compared with the as-cast rare earth alloy. In addition, the fracture surface of the extruded rare earth alloy exhibits obvious ductile fracture characteristics. Additionally, the alloy undergoes dynamic recrystallisation and dislocation entanglement during hot extrusion. The emergence of a twinned Si phase and a dynamically precipitated nanoscale CuAl₂ phase are critical for enhancing deformation strengthening, modification strengthening, and dynamic precipitation strengthening of the extruded alloys. Full article

Traditional metal–plastic dissimilar welding methods directly heat the metal workpiece, which may cause potential thermal damage to the metal workpiece. Ultrasonic extruded weld-riveting (UEWR) is a relatively new method for dissimilar joining of carbon fiber-reinforced thermoplastic (CFRTP) and metal. In this method, the CFRTP workpiece is melted using the ultrasonic effect and is squeezed into prefabricated holes in the metal workpiece to form a rivet structure. In this method, the metal workpiece is not directly heated, and potential high-temperature losses can be avoided. This paper investigates the process characterizations of UERW of AZ31B magnesium alloy to carbon fiber-reinforced PA66. The process parameters are optimized by the Taguchi method. The joint formation process is analyzed based on the fiber distribution in the cross-sections of joints. The effects of welding parameters on the joint microstructure and fracture surface morphology are discussed. The results show that a stepped amplitude strategy (40 μm amplitude in the first stage and 56 μm amplitude in the second stage) could balance the joint strength and joint appearance. Insufficient (welding energy < 2600 J or amplitude-A < 50%) or excessive (welding energy > 2800 J or amplitude-A > 50%) welding parameters lead to the formation of porous defects. Three fracture modes are identified according to the fracture surface analysis. The maximum tensile shear strength of joints at the optimal parameters is about 56.5 ± 6.2 MPa. Full article

This paper presents research results on biocomposites made from a combination of extruded apple pomace (EAP) and potato starch (SP). The aim of this work was to investigate the basic properties of biocomposites obtained from extruded apple pomace reinforced with potato starch. The products were manufactured by hot pressing using a hydraulic press with a mould for producing samples. The prepared biocomposites were subjected to strength tests, surface wettability was determined, and a colour analysis was carried out. A thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and cross-sectioning observed in a scanning electron microscope (SEM) were also performed. The obtained test results showed that the combination of apple pomace (EAP) and starch (SP) enabled the production of compact biocomposite materials. At the same time, it was found that each increase in the share of starch in the mixture for producing biocomposites increased the strength parameters of the obtained materials. With the highest share of starch in the mixture, 40%, and a raw material moisture content of 14%, the material had the best strength parameters and was even characterised by hydrophobic properties. It was also found that materials with a high content of starch are characterised by increased temperature resistance. The analysis of SEM microscopic photos showed well-glued particles of apple pomace, pectin, and gelatinised starch and a smooth external structure of the samples. Research and analyses have shown that apple pomace reinforced only with the addition of starch can be a promising raw material for the production of simple, biodegradable biocomposite materials. Full article

Large-Scale Material Extrusion (LS-MEX) is increasingly being used in small-scale production and prototyping due to its ability to create components in new temporal and spatial dimensions. However, the use of this manufacturing process poses microscopic and macroscopic challenges not encountered in previous small-scale production systems. These challenges arise primarily from the prolonged retention of heat in the material, which leads to insufficient strength in the extruded strands at the macrostructural level. As a result, the component can collapse, a phenomenon known as ‘slumping’. Thermal energy also influences microstructural changes, such as crystallisation kinetics, which affect properties such as the strength and stiffness of the final product. The duration and dynamics of thermal energy are influenced by manufacturing parameters and the possible use of additional peripheral equipment, which affects component quality. In this study, the influence of thermal energy on structural processes through simulations of polyamide 6 with 40% carbon fibres (PA6 wt.%40 CF) is investigated. The results show that by adjusting the process parameters and using modification units, the thermal profile of the material can be accurately controlled, which allows the microstructural processes to be precisely controlled. This leads to the targeted modification of the macroscopic material properties. The focus of this work is on the combination of numerical simulations of the LS-MEX process with semi-empirical methods for the analysis of crystallisation processes. The application of the Nakamura model, which is used throughout similar investigations, allows a detailed description and prediction of the crystallisation kinetics during the manufacturing process. The study shows that the absolute degree of crystallisation can be determined with simplified assumptions using a combination of thermal simulations and semi-empirical approaches. It was found that the absolute degree of crystallisation increases from the outer interface of the strand to the print bed across the cross-section. This can be attributed to the specific thermal boundary conditions and the resulting temperature profiles at different points. Full article

With the rapid development of the new energy vehicle market, the demand for extruded profiles for battery trays, mainly characterized by significant wall thickness differences in multiple chambers, is increasing, posing new challenges to production and quality control. This study examines the multi-objective optimization problem in the design process of aluminum profile dies with multi-cavity profiles and significant wall thickness differences. Using QFORM-extrusion professional aluminum extrusion finite element analysis software and the response surface analysis method, the standard deviation of the velocity (SDV), standard deviation of the pressure (SDP), and thick wall hydrostatic pressure (TWHP) on the profile section at the die exit are optimized. By analyzing the functional relationship between the key die structure parameters (the height of the baffle plates, the length of the bearing, and the height of the false mandrel) and the optimization objective, the optimal combination scheme of die structure parameters was obtained using the NSGA2 (non-dominated sorting genetic algorithm-2) multi-objective genetic optimization algorithm. The results show that, compared with the initial design scheme, the standard deviation of profile section velocity was reduced by 5.33%, the standard deviation of pressure was reduced by 11.16%, and the thick wall hydrostatic pressure was increased by 26.47%. The die designed and manufactured using this scheme successfully completed the hot extrusion production task, and the profile quality met the predetermined requirements, thus verifying the effectiveness of this study in optimizing the design of a multi-cavity aluminum profile die with significant differences in wall thickness for complex structures. Full article

High-moisture extrusion of plant proteins to create meat-like structures is a process that has met with increasing attention in the recent past. In the process, the proteins are thermomechanically stressed in the screw section of the extruder, and the resulting protein gel is structured in the attached cooling die. Various protein sources, notably soy protein isolate (SPI) and wheat gluten, are used to form gels with different networks: SPI creates a physical, non-covalent network, while gluten forms a chemical, covalent one. The food industry frequently adds weak acids to modify taste and shelf life. However, it is known that a change in pH affects the gelation behavior of proteins because the repulsive forces within and between the proteins change. The research reported here was carried out to investigate for the two proteins mentioned the influence of pH modification by the addition of citric acid and acetic acid on gel formation and the meat-like structures produced. For this purpose, materials and parameters were screened using a closed cavity rheometer, followed by extrusion trials at pH 7.36–4.14 for SPI and pH 5.83–3.37 for gluten. The resulting extrudates were analyzed optically and mechanically, and protein solubility was tested in a reducing buffer. For both protein systems, the addition of acid results in less pronounced meat-like structures. At decreasing pH, the complex viscosity of SPI increases (from 11,970 Pa·s to 40,480 Pa·s at 100 °C), the generated gel becomes stronger (strain decreased from 0.62 to 0.48 at 4.5 × 10⁵ Pa), and the cross-linking density grows. For gluten, a decreasing pH results in altered reaction kinetics, a more deformable resulting gel (strain increased from 0.7 to 0.95 at 4.5 × 10⁵ Pa), and a decreased cross-linking density. Solubility tests show that no additional covalent bonds are formed with SPI. With gluten, however, the polymerization reaction is inhibited, and fewer disulfide bonds are formed. Full article

The eastern Kuqa Depression in the northern Tarim Basin, NW China, is rich in oil and gas. However, recent exploration has been hindered by a lack of knowledge on the evolution of the petroleum system. To address this, we conducted hydrocarbon generation and accumulation modeling using both the 2Dmove and PetroMod2017 software for a complex tectonic extrusion section in the Kuqa Depression. The results show that the source rocks in the northern slope zone became mature quite early at around 170 Ma, but the thermal maturity evolution stagnated subsequently because of tectonic extrusion and uplift. The source rocks in the central anticline zone, the southern slope zone, and the deep sag zone were of overall low maturity during the Jurassic to Paleogene but rapidly became mature to highly mature with the deposition of the Neogene Jidike and Kangcun formations. The main hydrocarbon generation periods are in the late Neogene and Quaternary, and the main hydrocarbon generation stratum is the lower Jurassic Yangxia formation. The amount of cumulative hydrocarbon generation gradually increases for carbonaceous mudstone, mudstone, and coal source rocks. Sourced from source rocks mainly in the northern slope zone, oil and gas migrated to anticlinal traps along sandstone transport layers and faults. Recent discoveries, such as the Tudong-2 gas field in the central anticline zone, underscore the richness of this region in petroleum resources. Some gas fields were also predicted in lithologic traps in the southern slope zone and the deep sag zone, as well as in fault-related traps in the northern part of the northern slope zone. Full article

Flare bevel groove (FBG) welds are used in truss bridges with square hollow structural section (HSS) members. To reduce costs, joints can be welded without bevelling, but this negatively impacts the fatigue performance of the connection. This approach is often used in pedestrian bridges made from steel or aluminum. To investigate the fatigue performance of FBG welds, a study was conducted on T-joints made from aluminum square HSS members. The goal was to establish an S–N curve for these welds and present a numerical fatigue life prediction methodology. The study involved cyclic tests supplemented by a fatigue life prediction using linear elastic fracture mechanics (LEFM) coupled with finite element (FE) analysis using the software ABAQUS. Several parameters were varied, including the HSS section size and the corner radius (as extruded and hand ground). Six identical samples were tested for each combination of parameters to generate an S–N curve. The paper ends by drawing conclusions regarding the fatigue performance of aluminum FBG welds and their suitability for use in cyclically loaded structures such as pedestrian bridges. Full article