Parameter design of PLA/Wood Fused Filament Fabrication using Taguchi optimization methodology

This study investigates the effects of four variables during fused filament fabrication of organic biocompatible composite material, PLA with coconut flour, at the ultimate tensile strength and elasticity module of the printed parts. The parameter optimization uses Taguchi L18 design and regression models. The examined deposition variables are the layer thickness, the nozzle temperature, the raster deposition angle, and filament printing speed. The effects of the above variables on the strength of the parts are essential to enhance the mechanical response of the printed parts. The experimental outcomes are investigated using the ANOM and ANOVA analysis and modeled utilizing linear regression models. In addition, an independent experiment was repeated three times at optimum parameters' levels to evaluate the methodology, giving predictions errors less than 3%.

Procedure for determining the thermoelastic state of a reinforced concrete bridge beam strengthened with methyl methacrylate

This paper reports the analysis of methods for determining temperature stresses and deformations in bridge structures under the influence of climatic temperature changes in the environment. A one-dimensional model has been applied to determine the temperature field and thermoelastic state in order to practically estimate the temperature fields and stresses of strengthened beams taking into consideration temperature changes in the environment. The temperature field distribution has been determined in the vertical direction of a reinforced concrete beam depending on the thickness of the structural reinforcement with methyl methacrylate. It was established that there is a change in the temperature gradient in a contact between the reinforced concrete beam and reinforcement. The distribution of temperature stresses in the vertical direction of a strengthened reinforced concrete beam has been defined, taking into consideration the thickness of the reinforcement with methyl methacrylate and the value of its elasticity module. It was established that the thickness of the reinforcement does not have a significant impact on increasing stresses while increasing the elasticity module of the structural reinforcement leads to an increase in temperature stresses. The difference in the derived stress values for a beam with methyl methacrylate reinforcement with a thickness of 10 mm and 20 mm, at elasticity module E=15,000 MPa, is up to 3 % at positive and negative temperatures. It has been found that there is a change in the nature of the distribution of temperature stresses across the height of the beam at the contact surface of the reinforced concrete beam and methyl methacrylate reinforcement. The value of temperature stresses in the beam with methyl methacrylate reinforcement and exposed to the positive and negative ambient temperatures increases by three times. It was established that the value of temperature stresses is affected by a difference in the temperature of the reinforced concrete beam and reinforcement, as well as the physical and mechanical parameters of the investigated structural materials of the beam and the structural reinforcement with methyl methacrylate

Free Span Analysis for Submarine Pipelines

Pipelines are one of the most important and key elements that align with transferring hydrocarbon products in coastal and offshore industries which are exposed at various risks during their servicing. In this project, we are studding and describing free spanning of marine pipeline based on DNVGL-RP-F-105 regulation applying the finite element method by Abaqus software. For modeling, case studies of Gorze to Kish oil pipeline have been used. In order to provide and study the integrity of the structure against fatigue, the exact place as well as the free span length using software under environmental loading based on DNVGL-RP-F205 has been determined. Since based on DNVGL-TS-F101 free span causes local buckling, fatigue, and pipe burst then given to the servicing as well as environmental conditions, pipe condition has been monitored. Finally, using sensitivity analysis, the effect of different soil classes, elasticity module, and temperature on the pipe condition has been studied. At the end, the question if it is allowed to use a cross model for bed has been answered in previous studies.

Determining the parameters for a 3D-printing process using the fused deposition modeling in order to manufacture an article with the required structural parameters

The mass application of FDM technology is slowed down due to the difficulty of selecting 3D printing parameters in order to manufacture an article with the required characteristics. This paper reports a study into the impact of 3D printing parameters (temperature, print speed, layer height) on mechanical parameters (strength, elasticity module), as well as on the accuracy of printing and roughness of the surface of a specimen based on thermoplastic (PLA plastic). Several batches of specimens were fabricated for this study in accordance with ASTM D638 and ASTM D695, which were tested for tension, geometric accuracy, and roughness. Based on the experimental data, regression analysis was carried out and the functional dependences of the strength, elasticity module, printing precision, roughness of a surface on 3D printing parameters (temperature, speed, thickness of the layer) were constructed. In addition, the derived mathematical model underlying a method of non-linear programming has established such printing parameters that could provide for the required properties of a structure. The analytical dependences reported in the current work demonstrate a high enough determination factor in the examined range of parameters. Using functional dependences during the design phase makes it possible to assess the feasibility of its manufacture with the required properties, reduce the time to work out the process of printing it, and give recommendations on the technological parameters of 3D printing. The recommendations from this study could be used to make PLA-plastic articles for various purposes with the required properties

TECHNOLOGICAL CHARACTERIZATION OF Mezilaurus itauba WOOD: APPLICATION AND MACHINING TESTS

Brazil has several forest species that can be used for sustainable wood production. However, finding materials with technological quality is still a challenge. Wood is an excellent building material, however, there are few studies that have investigated the technological characterization, machining and processing of these species, including Mezilaurus itauba (Meisn.) Taub. Ex Mez. Thus, this study aimed to evaluate the technical characteristics and application potential of M. itauba wood from two distinct commercial lots, by analyzing its mechanical properties and performing machining tests. For this, static bending, dynamics and machining tests were carried out. The perpendicular compression tests of the evaluated fibers presented mean values of 9899.77 Mpa and 10670.74 Mpa for the elasticity module of lot 1 and lot 2, respectively. The average value observed for the L1 rupture module was 96.02 Mpa, while for L2 it was 113.85 Mpa. For the shear tests, low variation was observed between the specimens as well as between the evaluated lots. As for machining tests, M. itauba wood was classified as excellent for manufacturing furniture and internal openings. The M. itauba lots have acceptable mechanical strength, and the density is indicated for structural works, as well as for manufacturing furniture and interiors.

Influence of Injection Molding Parameters on the Mechanical Properties of Injected PC/ABS Parts

This study optimized the influence of process parameters on the mechanical properties during injection molding (IM) of PC/ABS blend. The Taguchi method of design of experiments (DOE) was employed to optimize the process parameters and to increase the tensile strength and the elasticity module. Taguchi’s L9 (34) orthogonal array design was employed for the experimental plan. Process parameters of the injection molding such as material temperature, injection pressure, holding time, and mold temperature were studied with three levels. The Signal to noise (S/N) ratio for mechanical properties of PC/ABS blend using the Taguchi method was calculated. Taguchi’s results proposed two sets of optimal injection parameters conditions to achieve the best mechanical characteristics (σ, E). The (S/N) ratio results proved that the injection pressure was the more prominent than the other IM process parameters for the tensile strength, and the material temperature was the more prominent for the elasticity module.

Production and Characterization of the Ti-12Mo-30Nb Alloy

With the increasing quality of life, the growing advancement of medicine and thus greater longevity of the population, the need for the development of biomaterials becomes increasingly necessary. Titanium alloys are widely used for biomedical application because they have corrosion resistance, biocompatibility, high hardness and low elasticity modulus compared to other metallic biomaterials. In the market, the titanium alloy most used for orthopedic purposes is the Ti-6Al-4V that despite its good mechanical and structural properties, present cytotoxic elements related to the presence of Al and V, pointing out the need for the development of new materials. In the current scenario, the most outstanding alloys are β Titanium alloys, which stand out due to their low elasticity modulus, which allows a high hardness/modulus ratio. Therefore, the objective of this work was to develop new studies on the Ti-12Mo-30Nb alloy, looking for good mechanical and structural characteristics and not cytotoxicity. Therefore, this alloy was produced by arc fusion with non-consumable tungsten electrode in an argon inert atmosphere. The material was characterized by X-ray Diffraction, Scanning Electron Microscopy, Vickers Hardness and Ultrasonic Elasticity Module. According to the results, it was verified that the alloy presented only the phase β in the microstructure and a hardness/modulus ratio superior to commercial alloy.

THE INFLUENCE OF THE USE OF RECYCLED GYPSUM ON THE PROPERTIES OF GYPSUM PRODUCTS IN LABOR CONDITIONS

The article presents the first results from research, which is deal with recycling of plaster boards and use of the resulting material. The research is carried out within the project MPO Trio c. FV30359 “Recyklace sádrokartonových desek a nová materiálová využití s pridanou hodnotou – GIPSRec”. The plasterboards are produced of stucco, which is calcinated of Flue Gas Desulfurization Gypsum (FGD Gypsum). There is possibility to replace a part of this stucco with recycled material. There is opportunity for saving costs for production. The question how this utilization can change the properties of the products is very important and it is necessary to find the possible improvement or deterioration. This is the objective of this research. The effect on properties was monitored on the samples which was prepared of only pure stucco and of stucco with part of recycled material. There was observed water ratio (splash test), setting times, volume changes, flexural strength, compressive strength and elasticity module.

Monobloco – cimentação de pino e preenchimento em único passo em dente tratado endodonticamente

The literature reports several materials for the restoration of endodontically treated teeth, with coronal destruction that requires an intra-root fiber post to stabilize the prosthetic part. The intra-radicular post of composite resin reinforced with fiberglass can be used as retainers in rehabilitating endodontically treated teeth due to their adhesiveness, pleasing aesthetics, and elasticity module close to the dentin less wear on the remaining structure. This clinical case reports the step-by-step application of dual resin cement (Rebilda DC Dentine - Voco) used as the cementation material of the post and material for the filling core in a single step, in an upper right lateral incisor. Moreover, it describes the advantages and indications of the post-and-core technique, also called “monobloc” which can be used in both anterior and posterior teeth. This protocol minimizes the adhesive interfaces, the chair time, and the steps of the clinical procedure.

Developing viscoelastic contact models and selecting suitable creep function for spherical biological cells

In most contact theories, the most popular of which are the three models of Hertz, Derjaguin, Muller and Toporov (DMT) and Johnson, Kendall and Roberts (JKR), biological cells were considered as an elastic material which is not a proper assumption. The elastic assumption in the case of biological cells could lead to neglecting the loading history as a result of which the stresses and strains applied to the material would not be studied accurately. In this paper, developing the three mentioned elastic models into viscoelastic models, simulating and comparing them with empirical data obtained through the indentation test of the MCF-7 cancer cell showed that the viscoelastic state presents a better prediction of biological cell behavior compared to that of an elastic state. The selection of the suitable creep function for objects in contact is another issue that has a significant importance in the viscoelastic case and this was investigated. Different mechanical models of a cell were studied and simulated for all three named theories among which the creep function obtained from the Kelvin model, a parallel combination of spring-damper, simplified the simulation and gave more precise results for modeling due to the fact that the obtained results from this model are closer to experimental ones and simpler than other models. On the other hand, for a more exact prediction of cell behavior, this model was modified by an equivalent elasticity module which considered cell components instead of the cell cortex only. The results of the simulation confirmed that a new elasticity module can improve the accuracy of cell models. After choosing the suitable mechanical model for the cell, we scrutinized the capability of the developed theories in predicting the results for biological liquid environments. Although the results of the Hertz and DMT viscoelastic models are closer to experimental ones in comparison with viscoelastic JKR, neglecting adhesion makes their prediction in biological liquid environments weak and erroneous. Therefore, it can be concluded that the developed viscoelastic model of JKR is more accurate and has a better performance in different environments than the other mentioned models.