Mold Casting Research Articles

Preparation and Properties of Polyvinylpyrrolidone/Sodium Carboxymethyl Cellulose Soluble Microneedles.

Transdermal drug delivery is a new means of delivering drugs through the skin to achieve therapeutic effects. Microneedles have several advantages, including low cost, easy self-administration, and high delivery efficiency. Different polymers affect the morphology, mechanical properties, and drug delivery efficiency of microneedles. To study the performance and limitations of microneedles (MNs), we prepared different ratios of polymers. MNs were fabricated from polyvinylpyrrolidone (PVP) and sodium carboxymethyl cellulose (CMC-Na) using the centrifugal molding method. Needle morphology, formability, and other properties of the polymers were evaluated to compare the performances of MNs with different ratios. PVP and CMC-Na were intermixed at different ratios with water as the solvent. The soluble MNs were prepared by mold casting. The morphology, thermodynamic properties, and crystallinity were studied using scanning electron microscopy (SEM), thermogravimetric analysis (TG), differential scanning calorimetric analysis (DSC), and X-ray diffraction (XRD). The results showed that composite microneedles have good thermal stability. Among the different compositions tested, the 10% PVP/2% CMC-Na composite microneedle demonstrated the best performance with a regular surface morphology and relatively high thermal decomposition and melting temperatures. These results indicate that microneedles with appropriate ratios of two different materials possess good formability and other properties.

The Effect of Mold Structure and Cooling Parameters on Heat Transfer during Billet High-Speed Continuous Casting.

Mold structure and cooling parameters are significant factors that affect the heat transfer capacity of high-speed continuous casting molds of billets. Therefore, a three-dimensional fluid flow and heat transfer model of a 160 mm × 160 mm billet mold was established, and its accuracy was verified. Thereby, the characteristics of heat transfer and influences of mold structure and cooling parameters on heat transfer in the high-speed continuous casting billet mold region were revealed. It was found that extending the effective length of a mold is the most valuable method to improve its heat transfer capability and achieve high-speed continuous casting. The total heat and the shell thickness at a mold outlet increased by 19% and 9.21% on average with every 100 mm extension. Enlarging the fillet radius could enhance the uniformity of heat transfer in the mold. Considering the loss of material, the optimal fillet radius of the mold was determined to be R = 10 mm.

Numerical investigation of solidification behavior and inclusion transport with M-EMS in continuous casting mold

The present study deals with the development of a multiphase numerical model of the continuous casting process of steel bloom. Two SEN configurations that differ in port angles are considered for the study of flow pattern, temperature distribution, solidification thickness, interface fluctuation and inclusion behavior during the process. The influence of mold electromagnetic stirring (M-EMS) on the various output parameters is examined. The results show that the upper circulation loop formed in the 15° port angle case is responsible for higher inclusion removal, high interface level, and low solidification thickness in the meniscus region compared to that of the 30° case. The presence of M-EMS completely changes the flow pattern below SEN. Strong rotational flow coupled with oppositely directed swirl flow provides high tangential velocity near the solidification front and high axial velocity in the core region. It results in fluctuation in shell thickness along the casting direction and decreasing the superheated steam penetration. However, flow patterns remain unaffected above the SEN as upwards swirl flow is not able to reach this region. On applying the M-EMS, inclusion entrapment in solidifying shell increases for both 15° and 30° cases. In contrast, inclusion removal at the interface decreases for 15° case and increases for 30° case.

Comprehensive Evaluation Method for Cooling Effect on Process Thermal Dissipation Rate during Continuous Casting Mold

Cooling in the continuous casting mold is the essential process of the molten steel solidifying into a slab shell. The synergistic relationship of casting state, process operation, continuous casting equipment, and other factors is complex and has a significant influence on thermal transfer in the mold. Therefore, a concept of “process thermal dissipation rate” defined by mold system thermal input and output was proposed in this work. The thermal input of molten steel was calculated through the casting temperature, and the slab residual thermal at the outlet of the mold was calculated by the solidification heat transfer model. Consequently, the thermal dissipation rate was calculated to quantify the multi-factor cooperative relationship of mold. The industrial case reflected that the thermal dissipation rates of three stable castings were 12.5%, 14.3%, and 18.8%, respectively, and all of them were obviously abnormal in unsteady casting such as start casting, changing tundish, and end casting. The results above indicated that the thermal dissipation rate could characterize the mold cooling target under the cooperation of complex factors and provide a new method for the dynamic evaluation of the mold system cooling effect with different casting states. Accordingly, the correlation analysis between superheat, casting speed, cooling water flow, and thermal dissipation rate revealed the synergistic influence law of multi-operation on mold cooling effect, which provided a new idea for the precise control of multi-process collaboration in continuous casting.

ПЕРСПЕКТИВИ ВИГОТОВЛЕННЯ ЛИТИХ ЛЕГКОВАГИХ МЕТАЛОКОНСТРУКЦІЙ ДЛЯ БУДІВНИЦТВАСПОРУД МОДУЛЬНОГО ТИПУ

A review of prefab modular building metal structures with a list of their advantages and an assessment of reuse compared to building structures made of concrete and wood is carried out. An analysis of the cost structure of such metal structures and their nstallation is given. It is noted that the most effective means of reducing the cost of metal structures is to reduce metal consumption. Unlike welded for bolted structures, installation is simplified and bolted connections provide the possibility of disassembling the structure with transportation to another place, which is important for hangars, warehouses that change location. The use of cast metal structures, in particular, made by gasification model casting (LGM) in vacuum molds made of loose sand,has significant opportunities. The motivation, methods and examples of optimization of constructions, as well as imitation of constructions of nature, in particular crystalline materials, for man-made metal products are considered. Cellular spatial materials obtained by the LGM method expand the existing range of properties compared to compact materials. And cast lattice materials,in particular, the analogues of which are taken from the macro-and microworld of nature, from prefabricated model elements, will simplify construction and allow the production of cellular materials and frame lightweight products, which are often called "materials of the future." Ukraine obtains metal from its own ores and is able to transform it into a high-tech, knowledge-intensive product in the form of machines, mechanisms and metal construction structures. The development of such technologies opens up ways to borrow the structural properties of natural materials known to us not only to copy them, but also to obtain new materials and structures with optimization for specific mechanisms or buildings. At the same time, construction with the use of metal structures has all the prerequisites to become an effective solution in the construction industry, which will contribute to the reconstruction of the country

Chondrogenic Differentiation of Adipose-Derived Stromal Cells Induced by Decellularized Cartilage Matrix/Silk Fibroin Secondary Crosslinking Hydrogel Scaffolds with a Three-Dimensional Microstructure.

Finding an ideal scaffold is always an important issue in the field of cartilage tissue engineering. Both decellularized extracellular matrix and silk fibroin have been used as natural biomaterials for tissue regeneration. In this study, a secondary crosslinking method of γ irradiation and ethanol induction was used to prepare decellularized cartilage extracellular matrix and silk fibroin (dECM-SF) hydrogels with biological activity. Furthermore, the dECM-SF hydrogels were cast in custom-designed molds to produce a three-dimensional multi-channeled structure to improve internal connectivity. The adipose-derived stromal cells (ADSC) were seeded on the scaffolds, cultured in vitro for 2 weeks, and implanted in vivo for another 4 and 12 weeks. The double crosslinked dECM-SF hydrogels exhibited an excellent pore structure after lyophilization. The multi-channeled hydrogel scaffold presents higher water absorption ability, surface wettability, and no cytotoxicity. The addition of dECM and a channeled structure could promote chondrogenic differentiation of ADSC and engineered cartilage formation, confirmed by H&E, safranin O staining, type II collagen immunostaining, and qPCR assay. In conclusion, the hydrogel scaffold fabricated by the secondary crosslinking method has good plasticity and can be used as a scaffold for cartilage tissue engineering. The multi-channeled dECM-SF hydrogel scaffolds possess a chondrogenic induction activity that promotes engineered cartilage regeneration of ADSC in vivo.

The Effect of Casting Technique and Severe Straining on the Microstructure, Electrical Conductivity, Mechanical Properties and Thermal Stability of the Al-1.7 wt.% Fe Alloy.

This paper features the changes in microstructure and properties of an Al-Fe alloy produced by casting with different solidification rates followed by severe plastic deformation and rolling. Particularly, different states of the as-cast Al-1.7 wt.% Fe alloy, obtained by conventional casting into a graphite mold (CC) and continuous casting into an electromagnetic mold (EMC), as well as after equal-channel angular pressing and subsequent cold rolling, were studied. Due to crystallization during casting into a graphite mold, particles of the Al6Fe phase are predominantly formed in the cast alloy, while casting into an electromagnetic mold leads to the formation of a mixture of particles, predominantly of the Al2Fe phase. The implementation of the two-stage processing by equal-channel angular pressing and cold rolling through the subsequent development of the ultrafine-grained structures ensured the achievement of the tensile strength and electrical conductivity of 257 MPa and 53.3% IACS in the CC alloy and 298 MPa and 51.3% IACS in the EMC alloy, respectively. Additional cold rolling led to a further reduction in grain size and refinement of particles in the second phase, making it possible to maintain a high level of strength after annealing at 230 °C for 1 h. The combination of high mechanical strength, electrical conductivity, and thermal stability can make these Al-Fe alloys a promising conductor material in addition to the commercial Al-Mg-Si and Al-Zr systems, depending on the evaluation of engineering cost and efficiency in industrial production.

Evolution of Microstructure, Mechanical Properties, and Corrosion Resistance of Mg-2.2Gd-2.2Zn-0.2Ca (wt%) Alloy by Extrusion at Various Temperatures.

The current investigation involved casting the Mg-2.2Gd-2.2Zn-0.2Ca (wt%) alloy (GZX220) through permanent mold casting, followed by homogenization at 400 °C for 24 h and extrusion at 250 °C, 300 °C, 350 °C, and 400 °C. Microstructure investigations revealed that α-Mg, Mg-Gd, and Mg-Gd-Zn intermetallic phases were present in the as-cast alloy. Following the homogenization treatment, a majority of these intermetallic particles underwent partial dissolution into the matrix phase. α-Mg grains exhibited a considerable refinement by extrusion due to dynamic recrystallization (DRX). At low extrusion temperatures, higher basal texture intensities were observed. The mechanical properties were remarkably enhanced after the extrusion process. However, a consistent decline in strength was observed with the rise in extrusion temperature. The corrosion performance of the as-cast GZX220 alloy was reduced by homogenization because of the lack of corrosion barrier effect of secondary phases. A significant enhancement of corrosion resistance was achieved by the extrusion process.

A Novel Approach of Optimum Time Interval Estimation for Al-7.5Si/Al-18Si Liquid-Liquid Bimetal Casting in Sand and Metallic Moulds.

This work describes a novel approach for Al-7.5Si/Al-18Si liquid-liquid bimetal casting in sand and metallic moulds. The aim of the work is to facilitate and develop a simple procedure to produce an Al-7.5Si/Al-18Si bimetallic material with a smooth gradient interface structure. The procedure involves the theoretical calculation of total solidification time (TST) of the first liquid metal (M1), pouring the liquid metal (M1), and allowing it to solidify; then, before complete solidification, the second liquid metal (M2) is introduced into the mould. This novel approach has been proven to produce Al-7.5Si/Al-18Si bimetal materials using liquid-liquid casting. The optimum time interval of Al-7.5Si/Al-18Si bimetal casting with modulus of cast Mc ≤ 1 was estimated based on subtracting 5-15 s or 1-5 s from TST of M1 for sand and metallic moulds, respectively. Future work will involve determining the appropriate time interval range for castings having modulus ≥ 1 using the current approach.

Physical and mechanical properties of lightweight concrete with incorporation of ceramic mold casting waste

In the lost-wax foundry industry large amounts of ceramic mold casting waste (CMCW) are disposed of in landfills, which not only pollutes the environment but also leads to the loss of secondary resources. On the other hand, with the improvement of building style and performance, the demand for lightweight concrete is also increasing. Therefore, we recycle CMCW into lightweight concrete for environmental and economic reasons. In this study, two types of expanded clay with different sizes (2–10 mm and 10–20 mm) were used as reference aggregates. From the results, it can be seen that the density of CMCW is about four times higher than that of expanded clay, and the water absorption in 24 h is 1/4 of expanded clay. Then, expanded clay was replaced with three different weight percentages (30%, 60%, and 80%) of CMCW to prepare new lightweight concrete, which was tested for workability. After curing for 28 days at 90% humidity, four compositions were tested for their physical and mechanical properties. Finally, the results showed that with increasing CMCW content, mechanical performance also increased. With 80% CMCW in the lightweight concrete, a density of 1998 kg/m3 and compressive strength of 36 MPa were achieved.

The Influence of Progressive Cladding Technologies on Layers Quality

Experimental work was focused on the restoration of functional surfaces of shaped parts of the molds for high-pressure casting of aluminum alloys. Paper presents results of the research aimed at determination of the quality of renovation layers applied by laser technology and TOP TIG technology. The TruDisk 4002 solid-state disk laser and the AirLiquide TOPTIG 220 welding power source were used to create the layers. Clad was applied to the base material of nickel-chromium-molybdenum vanadium steel 1.2714, DIN-56NiCrMoV7, with a hardness of 44 HRC. Uddeholm Deivar 1.2344, DIN-X40CrMoV51 wire with a 1.2 mm diameter was used as an additive material. The clad quality was evaluated using the light and electron microscopy and EDX microanalysis. The size of the heat affected zone (HAZ) and the presence of internal defects in the clads were determined. HAZ was set as max. a min. Value. Experimental work was supplemented by evaluation of tribological properties of clads by Pin-on-disc method.

Mechanical properties of 3D printed concrete with coarse aggregates and polypropylene fiber in the air and underwater environment

In this study, three-dimensional concrete printing (3DCP) was performed for concrete with coarse aggregates in air and underwater environments for a comparative evaluation of the mechanical properties of the obtained samples. The base concrete mix was selected based on normal weight concrete (NWC) with ordinary Portland cement (OPC) as a binder, and the mechanical properties of the printed concrete applied using 3DCP and mold cast concrete were compared for analysis. For printability, fiber-reinforced concrete (FRC) with polypropylene fiber was additionally considered as a variable, and the fabrication method (printing and mold casting) and conditions (air and underwater environments) were varied. For the specimens fabricated using different materials, fabricating methods, and fabricating environments, the apparent density, compressive strength, splitting tensile strength, and stress–strain curves were comparatively analyzed. Considering the static elastic modulus calculated from the stress–strain curve, the correlation between the values obtained using design codes and those obtained via elastic modulus prediction models presented in previous studies was comparatively analyzed. When the concrete fabricated using the mold casting method was compared with the printed specimen, the density of the mold cast concrete was higher by 34 kg/m3 compared to that of the printed specimen, and the specimen fabricated in the air showed a density that was 45 kg/m3 greater compared to that of the specimen fabricated underwater. The compressive strength (28 days) was found to be approximately 8% higher in NWC compared to that in FRC, and the compressive strength of the underwater specimen was about 72% of that of the air specimen.

Experimental Study on Repairing Peripheral Nerve Defects with Novel Bionic Tissue Engineering.

Peripheral nerve defects are a worldwide problem, and autologous nerve transplantation is currently the gold-standard treatment for them. Tissue-engineered nerve (TEN) grafts are widely considered promising methods for the same, and have attracted much attention. To improve repair, the incorporation of bionics into TEN grafts has become a focus of research. In this study, a novel bionic TEN graft with a biomimetic structure and composition is designed. For this purpose, a chitin helical scaffold is fabricated by means of mold casting and acetylation using chitosan as the raw material, following which a fibrous membrane is electrospun on the outer layer of the chitin scaffold. The lumen of the structure is filled with human bone mesenchymal stem cell-derived extracellular matrix and fibers to provide nutrition and topographic guidance, respectively. The prepared TEN graft is then transplanted to bridge 10 mm sciatic nerve defects in rats. Morphological and functional examination shows that the repair effects of the TEN grafts and autografts are similar. The bionic TEN graft described in this study shows great potential for application and offers a new way to repair clinical peripheral nerve defects.

Role of Nitrogen During Dry-Air Oxidation of TiAlNbCrSi Alloy Produced with Mould Casting (MC) and Electron Beam Melting (EBM)

Role of Nitrogen During Dry-Air Oxidation of TiAlNbCrSi Alloy Produced with Mould Casting (MC) and Electron Beam Melting (EBM)

Biomolecular glass with amino acid and peptide nanoarchitectonics

Glass is ubiquitous in life and widely used in various fields. However, there is an urgent need to develop biodegradable and biorecyclable glasses that have a minimal environmental footprint toward a sustainable society and a circular materials economy. Here, we report a family of eco-friendly glasses of biological origin fabricated using biologically derived amino acids or peptides through the classic heating-quenching procedure. Amino acids and peptides with chemical modification at their ends are found able to form a supercooled liquid before decomposition and eventually glass upon quenching. These developed glasses exhibit excellent glass-forming ability and optical characteristics and are amenable to three-dimensional-printed additive manufacturing and mold casting. Crucially, the glasses show biocompatibility, biodegradability, and biorecyclability beyond the currently used commercial glasses and plastic materials.

Simulation of Commencement and Size of the Hot Spot in Permanent Mould Casting

The foundry casting process is complex and takes various stages to produce the desired component; as a result, simulation is necessary before manufacturing. Hot spots are areas that become thermally isolated and take the longest to cool, resulting in cavities during the solidification of the casting. So it is important to know about the hot spot location and size so that any casting designer can identify the hot spot behaviours before the casting. To predict the initiation of the hot spot, a 3D aluminium permanent mould casting model has been developed by Ansys Fluent. The suitable boundary and initial conditions such as temperature, pressure, convectional heat transfer coefficient, etc. are reasonably established in the simulation of Ansys Fluent. The simulation has been performed for varied pouring parameters i.e. pouring velocity and pouring temperature, to examine the beginning of hot spots. This study can predict the position and approximate size of the hot spots for various pouring conditions and it is found that a hot spot is commonly located below the riser.

Performance of 3D printed columns using self-sensing cementitious composites

Self-sensing cementitious composites can be used as an economical method of structural health monitoring. This is achieved by using the piezoresistivity effect to assist in the detection of defects and enabling repairs to be conducted early which can therefore avoid structural failures. This study uses an established self-sensing cementitious composite mix to 3D print column to examine its structural performance and sensing capabilities in components of large-scale concrete structures. An extrusion-based 3D printer was used to print hollow square column segments. These segments were then joined and filled with steel rebar reinforcement and cast concrete. Another column was created using mould cast concrete for comparison. The specimens were tested under static axial compression to determine their compressive properties, electrical resistivity and piezoresistivity response. The results showed that the 3D printed column performance can be monitored using the self-sensing composite until the printed shell cracks. The 3D printed column did show superior electrical properties with a lower electrical resistance of 274.2 Ω.cm. These results indicate that a different manufacturing approach to creating a 3D printed column should utilise the advantages of 3D printing for use in self-sensing concrete structures.

Influence of transition elements (Zr, V, and Mo) on microstructure and tensile properties of AlSi8Mg casting alloys

ABSTRACT The influence of the additions of transition elements (Zr, V, and Mo) on microstructure, precipitation behaviour and tensile properties of Al–8%Si–0.3%Mg permanent mould castings were investigated. It reveals that the presence of the transition elements increased the solute concentration in aluminium matrix, refined eutectic Si particles, and reduced the length and aspect ratio of intermetallic phases in as-cast microstructure. Moreover, the transition element addition promoted the formation of solute cluster and increased the number density of β′ precipitates and dispersoids during T6 heat treatment. The additions of Zr, V, and Mo considerably improved the tensile strengths and elongation in both as-cast and T6 conditions. The effects of the combined addition of Zr, V, and Mo on the microstructure, precipitation behaviour, and tensile properties were stronger than that of the addition of Zr and V.

Shrinkage Cavities in Conical Mold Castings of Aluminum Alloy

Shrinkage Cavities in Conical Mold Castings of Aluminum Alloy

Medical simulator for the training of traumatologists: pilot work

BACKGROUND: Pelvic fractures are one of the most complex and fatal injuries because numerous large blood vessels are affected. They entail partial or complete loss of working capacity and have a high mortality rate. In medical practice, the number of pelvic fractures is fewer than that of other types of fractures, and specialists often lack practical experience and skills in the treatment. Thus, for the training, or advanced training of specialists, more serious theoretical training is required, which is unproductive without high-quality training simulators and models.
 AIM: The study aimed to develop and manufacture an easy-to-use simulator that mimics human soft tissues and makes it possible to comprehensively prepare and educate specialists in the technique of installing an external fixation device for unstable pelvic fractures.
 MATERIALS AND METHODS: To create the simulator, several main stages were completed: obtaining samples of the pelvic bones, making a mold for casting, and directly assembling the simulator. To obtain bone samples, computed tomography scans and magnetic resonance therapy images were used, on which a three-dimensional (3D) model of the pelvic bones was obtained. Based on this model, anatomically accurate copies of the pelvic bones were made using additive technologies. Then, a 3D digital computer model was developed, and a mold for casting the finished product was made. Bone samples were placed inside the mold, and the mold was gradually filled with a gelatinglycerin compound, which after hardening mimics human soft tissues.
 RESULTS: A prototype of a medical simulator for teaching the installation of the concomitant injury kit apparatus for unstable pelvic fractures was made.
 CONCLUSION: The manufactured simulator can be widely used in educating and training specialists given its sufficiently high anatomical accuracy, ease of maintenance, and good potential for mass production.