Key Engineering Materials Vol. 1006

Abstract: The development of physiological detection is advancing rapidly, driven largely by the increase in the awareness of sport, healthcare, and biomedical knowledge. Wearable electronics have been integrated into real-world physiological sensing applications, with many recent studies aimed at enhancing their capabilities from both material selection and fabrication perspectives. To create the best fit for specific wearers, three-dimensional (3D) printing is an excellent candidate because of its potential to create structures ranging from simple to highly complex. This work investigates the effect of infill densities (20%, 40%, and 60%) on the electromechanical properties of 3D-printed thermoplastic polyurethane (TPU) using fused deposition modeling (FDM). The printing conditions were consistently controlled throughout the study, specifically using a honeycomb infill pattern. The flexible TPU substrates were successfully 3D-printed, and 1% w/v of multiwalled carbon nanotubes (MWCNTs) were embedded in the 3D-printed samples using an ultrasonic cavitation-enabled treatment and thermal-assisted method. This process aims to prevent CNT fallout while maintaining the compression load-bearing capacity. A compressive load of 10 kN was applied to the samples during electromechanical testing. The results show that a 20% infill density provides the optimum sensitivity of 11.32 MPa^-1 at 2V applied voltage due to its appropriate current path, which is confirmed by scanning electron microscope (SEM). The dimension accuracy of the 3D-printed TPU samples tend to increase with higher infill densities and application of the double treatment.

Abstract: Nowadays, the requirements of scaffolds and bone grafts are increasing along with large defects increasing every year. Furthermore, large defects that occur in human bones are customary. However, this obstacle can be overcome by using 3D printing. This study aims to investigate the morphology, deviation dimension, shrinkage and hardness of hydroxyapatite (HA)/collagen composite, which these materials mimic with human bone. HA/collagen composite was printed using three-dimensional bioprinting based on extrusion with a print speed of 10 mm/min and a layer height of 0.5 mm. The composition of HA and collagen material is 70% and 30%, respectively, where this composition mimics natural bone. Morphology and dimension of HA/collagen composite were obtained by transmission electron microscope. Moreover, the deviation dimension and shrinkage were measured using the Miviewcap optical microscope and software Image J. The resulting HA/collagen composite clearly showed that collagen was in the form of fibers while HA was in an irregular shape. The average width and length of collagen were 5.98 + 0.20 nm and 82.48 + 6.23 nm, respectively. Moreover, the Average width and length of HA were 21.85 + 0.53 nm and 23.30 + 1.33 nm. The average deviation dimension in the X, Y, and Z axes was 2.69%, 1.40%, and 24.12%. Furthermore, shrinkage was 12.27%, 10.18%, and 19.06% on the X, Y, and Z axes. The average hardness of specimen 1 and 2 of HA/collagen composite were 0.0021594 HV.

Abstract: Digital Light Processing (DLP) 3D printing is an additive manufacturing technique that uses a digital light projector to cure photopolymer resin layer-by-layer to create high-precision solid structures. In addition to the planar resolution, the control of curing depth has a critical impact on the success of precise printing and the geometric features of the printed product. This issue is aggravated in the case of projection micro-stereolithography (PμSL), which uses an objective lens to enhance the planar resolution of the projected pattern. In this study, we investigated possible measures to control the cured layer thickness from both material and optical perspectives. As-received commercial resin was used to obtain the raw cured layer thickness, and then Sudan I or carbon black was added separately to study their effects. Eventually, the grayscale of the exposed pattern was adjusted to reduce light intensity and achieve a thinner layer thickness. Combining the above measures reduced the single-layer cured thickness from the raw 250 μm to 5.8 μm, approaching the usual minimum layer dimension setting of 5 μm. By exploring the variables affecting cured layer thickness, the findings in this study are expected to improve DLP 3D printing technology in producing high-resolution structures, especially in the z-direction.

Abstract: To perform a comparative study of the performance combustion and emission characteristics of pure diesel and mustered blends, a single-cylinder stationary Kirloskar TV1 Engine.xls engine was used. The ratio of mustered oil blends to diesel was 60%. The mustered blend was selected appropriately and the compression ratio was optimized for this study. From this report it is proven that the most favorable of mustered and diesel blends is 60% of mustered and 40% of diesel with compression ratio 14:1,15:1,16:1 & 17.5:1.In comparison, the release of CO was reduced; however, there was a moderate increase in the release of NOx. Therefore, with only a slight alteration in the present diesel engines, the algae blend can be used.

Abstract: Due to the demeaning character of fossil fuels and their detrimental harmful effects on the ecosystem, studies have focused on finding appropriate non-edible replacements. In the present research, the emissions and performance features of the blends of biodiesel generated from the chosen raw materials (flamboyant seed), which includes B25, B50, B75, and B100, were evaluated in the early stages of the research. A diesel engine continues to operate at an authorized rate of 1500 rpm. In the following phase of the research, the focus is on defining the appropriate blend's performance as well as its emission characteristics under the ideal operating circumstances. The FME blend B25 is found to be satisfactory, and the optimal parameters to stated standards have been CR 18.5.With the exception of NOX emission, the ideal blend surpassed alternatives in terms of BSFC and BTHE associated with reduced CO and HC outputs. The optimum fuel's BSFC and BTHE at the maximum load, for CR 18.5, are 0.257 kg/kW-hr and 31.47%, respectively. The emission levels of CO, HC, and NO_X are 0.08%, 51 ppm, and 1029 ppm.

Abstract: Bio-based materials and phase change materials (PCMs) are currently being gradually noticed and emphasized as passive building envelopes. This study focuses on the effect of PCM placement and phase transition temperature on hygrothermal and energy performance. Systematic studies reveal that placing PCM with a phase transition temperature of 24-28 °C in the scenario PCM middle provides considerable results, reducing the summer temperature and relative humidity amplitude, heat load and moisture load by 5%, 0.03%, 8% and 5.8%, respectively. Besides, performance is further optimized with the scenario PCM middle of phase transition temperature of 26-30 °C, with the reductions in temperature and relative humidity fluctuations, heat load and moisture load by 88.6%, 85.4%, 69.65% and 69.63%, respectively. Overall, strategic PCM placement and phase transition temperature improve building energy efficiency and comfort, offering valuable insights for designing bio-based concrete structures.

Abstract: The micro and nano structures of porous material have strong influence on their transfer properties such as porosity, permeability, tortuosity and adsorption isotherm curves. In the construction and building material field, these properties are strongly related to hydro and thermal comfort, due to the fact that heat and mass transfer mechanisms are determined by the micro porous structure. In the present work, we aim to predict heat and mass transfer on such micro-nano structured materials, with a statistical quantification method that is extracted from morphology aspect. A large range of the pore size (from 20nm to 1mm) is covered and investigated by the multiple approaches, including FIB-SEM, X-Ray Tomography, and MIP (Mercury Intrusion Porosimetry). The 3D view of pore structures is obtained in concrete, as well as their size distribution, and pore zones. A reconstruct of 3D view of pore networks is extracted, with the spatial resolution of 20 nm/pixel. A global view of multiple testing methods and the corresponding size ranges are drawn to summarize the multi-scale approaches, for a potential further understanding of relationship between porous structure and thermal-hydro properties.

Abstract: Long-span bridges are generally often needed in the world of civil engineering to reduce the number of the bridge piers. A long span steel box girders with a mid-span of 120-meter and two side-spans of 70-meter is studied. The static bridge deflection needs to be evaluated as the constructed slab thicknesses of the steel I-girder composite slab was not constant along the bridge longitudinal span. Results from numerical simulation with those of loading tests carried out on the bridge after its completion are compared.

Abstract: Questions arise whether construction delay combined with construction method modification of a long-span bridge will affect bridge resistance to withstand the working load in the long term. A continuous bridge with a span of 78 m - 145 m - 77 m that crosses a large river has experienced this condition. In its implementation, there was a difference in construction time compared to the initial design. As a result, it is necessary to conduct an analysis of the effects of the difference in construction time on the bridge structure. An analysis of the stages of bridge construction was carried out using the Midas Civil program to determine the stress and deflection that occurred. Stress and deflection over a long period of time were calculated to determine the effect of construction methods and delays.