Mechanical Properties and Durability of Bamboo Fibers/Bamboo-Fiber-Mixed Spray Mortar for Slope Protection

Conventionally, short fibers such as steel and synthetic fibers have been mixed into spray mortar used for slope protection to enhance resistance against cracking and durability. However, in the quest of higher performance fiber-reinforced mortar with reduced impact on the environment, natural fibers such as bamboo fibers may play a vital role. Thus, the tensile strength and the bond strength of bamboo fibers used for spray mortar were examined by laboratory tests. The mechanical properties of bamboo-fiber-reinforced spray mortar were examined under cyclic wet and dry conditions along with its resistance against freezing and thawing by a spray test. It was confirmed that 0.75% mixture of bamboo fibers in spray mortar successfully improved mechanical properties and durability. These include adhesion strength to the base surface following exposure to cyclic wet/dry conditions and overall resistance against freezing/thawing. Moreover, higher compressive strength, flexural toughness and adhesion strength to the base surface were achieved by further mixing in vinylon fibers or fly ash in addition to bamboo fibers.

Modeling of Curvilinear Steel Rod Structures Based on Minimal Surfaces

The article deals with shaping effective curvilinear steel rod roof structures using genetic algorithms by implementing them for the analysis of various case studies in order to find new and efficient structures with positive characteristics. The structures considered in this article are created on the basis of the Enneper surface and minimal surfaces stretched on four arcs. On the Enneper surface, a single layer grid is used, while on the other surfaces, two-layer ones. The Enneper form structure with four supports and the division into an even number of parts along the perimeter of the covered place proved to be the most efficient, and the research showed that small modifications of the initial base surface in order to adapt the structure to the roof function did not significantly affect its effectiveness. However, the analysis and comparison of single and double-shell rod structures based on minimal surfaces stretched on four arcs have shown that a single-shell structure is much more effective than a double one. The paper considers the theoretical aspects of shaping effective structures, taking their masses as the optimization criterion. The optimization helped to choose the best solutions due to structures’ shapes and topologies. However, the obtained, optimized results can find practical applications after conducting physical tests.

DETERMINING THE COEFFICIENT OF FRICTION OF WOOD-BASED MATERALS FOR FURNITURE PANELS IN THE ASPECT OF MODELLING THEIR SHREDDING PROCESS

In order to improve the power selection of the drive unit for the shredding machines,theauthors determine the values of friction coefficients used in the cutting force models. These values consider the friction between steel and such wood-based materials as chipboard, MDF and OSB. The tests concern laminated and non-laminated external surfaces and surfaces subjected to cutting processes. The value of the coefficient of friction for the tested materials is in the range: for the static coefficient of friction 0.77-0.33, and for the kinetic coefficient of friction 0.68-0.25. The highest values of the static and kinematic coefficient of friction were recorded for MDF (non-laminated external surface) and they were equal respectively: 0.77 and 0.68. In turn, thesmallest values of the discussed coefficients were recorded for chipboard (laminated external wood-base surface), which were at the level of 0.33 and 0.25, resp.

Thermal Analysis of Extended surfaces from the Heat sink of Different shape - A Brief Review

This paper introduces a brief review about the way of heat extraction enhancement from heat sink using fins of different types and different shapes and also with different shape of perforation. Extended surfaces from the base plate or heat sink is nothing but they are FINS. There are various types of fin exits. They are Rectangular, Square, Annular, Elliptical, Cylindrical or Pin fin which is utilized with different geometrical combinations. To achieve maximum temperature droop from the base surface or heat sink by using fins numerous trials are completed or being carried out for designing optimized Fin. The optimization of Fin can be achieved by increasing surface contact area with the atmospheric air. In these days there are numbers of experiment is done on fins like Solid fin, Porous fins and Solid fins with perforation, has also been brought off. The various design modifications which are implemented and studied analytically and experimentally by the researchers using ANSYS Work bench is been discussed in this review paper.

Method of arc activation of the base at increasing the distance plasma spraying

Purpose. To increase the efficiency of the plasma coating by developing a method of ion-arc activation of the base using an activating electrode, which leads to an increase in the adhesion strength of the coating due to the sputtering of surface oxides of the base. Research methods. Experimental and computational, mechanical tests, optical microscopy. The development of the method of ion-arc activation of the part base with an increase in the distance of coating deposition consists in application of an activating electrode located at the surface of the base to create an additional activating arc. The influence of the activating arc on bases for creating an additional activating arc. The influence of the activating arc on the adhesion strength of the coating is determined. The estimation of the current density of the activating arc for the sputtering of surface base oxides is carried out. Results. A method of arc activation of the base surface with an increase in the coating distance is found. It is shown that application of an activating arc of reverse polarity that burns between the additional electrode and the base leads to ion bombardment of the surface by sputtering surface oxides and the creation of microcraters on the base surface. As a result, the bond strength is doubled compared to the bond strength obtained without the use of ion-arc activation of the base. The calculations of the rate of cathodic sputtering of the surface oxides of the base are carried out and the minimum activation current density of the base is determined, which leads to the complete sputtering of a layer of oxides of a given thickness. Scientific novelty. It has been determined that, despite the rapid oxidation of the base under atmospheric conditions, application of the method of ion-arc cleaning of the surface during coating leads to a significant increase in the adhesion strength of the coating to the base. Practical value. The obtained results of increasing the adhesion strength rise the efficiency, the guaranteed service life of the plasma coating on the parts of machines and mechanisms

Statistical optimization of amorphous iron phosphate: inorganic sol–gel synthesis-sodium potential insertion

Iron phosphate, Fe2 (HPO4)3*4H2O, is synthesized at ambient temperature, using the inorganic sol–gel method coupled to the microwave route. The experimental conditions for the gelling of Fe (III)-H3PO4 system are previously defined. Potentiometric Time Titration (PTT) and Potentiometric Mass Titration (PMT) investigate the acid–base surface chemistry of obtained phosphate. Variations of surface charge with the contact time, Q a function of T, are examined for time contact varying in the range 0–72 h. The mass suspensions used for this purpose are 0.75, 1.25 and 2.5 g L−1. The point of zero charge (PZC) and isoelectric point (IEP) are defined using the derivative method examining the variations $$\frac{{{\text{dpH}}}}{{{\text{d}}t}} = f\left( {{\text{pH}}} \right)$$ dpH d t = f pH , at lower contact time. A shift is observed for PZC and IEP towards low values that are found to be 2.2 ± 0.2 and 1.8 ± 0.1, respectively. In acidic conditions, the surface charge behavior of synthesized phosphate is dominated by $$\overline{{ > {\text{POH}}}}$$ > POH ¯ group which pKa = 2.45 ± 0.15. Q against T titration method is performed for synthesized Fe2 (HPO4)3*4H2O in NaCl electrolytes. The maximal surface charge (Q) is achieved at the low solid suspension. Hence, for m = 0.75 g L−1, Q value of 50 coulombs is carried at μ = 0.1 and pH around 12, while charge value around 22 coulombs is reached in the pH range: 3–10. The effect of activation time, Q and pH on sodium insertion in iron phosphate, were fully evaluated. To determine the optimal conditions of the studied process, mathematical models are used develop response surfaces in order to characterize the most significant sodium interactions according to the variation of the pH, Q, the contact time and the contents of the synthesized material.

Effect of Passive Flow Control Devices on Base Pressure for Mach Numbers Between 0.5 and 1.4

Experimental studies are carried out on an axisymmetric cylindrical base body for six freestream Mach numbers between 0.54 to 1.41. Unsteady pressure is measured on the base surface using high-frequency response Kulite pressure transducers. The effect of passive flow control devices on the mean base pressure and the unsteady characteristics of base pressure has been studied. A blunt base, a conventional cavity device and three different ventilated cavity devices have been tested along with four different rounded base lip devices. A total of 20 different base geometric modifications are tested at six freestream Mach numbers resulting in 120 test cases. The cavity devices improve the base pressure as compared to the blunt base case. Among all the cases considered, a maximum increase of 8.6% in the base pressure coefficient is noticed for the Normal Ventilated Cavity device as compared to the blunt base case for freestream Mach number of 1.22. The power spectral density of base pressure fluctuations revealed the dominant peaks on the base surface. The shear layer flapping frequency for all the cases have been found and the Strouhal number based on base diameter varies between 0.2 to 0.27. In the presence of cavity devices, dominant peaks are observed in the range of 2 kHz to 8 kHz which can be attributed to the vigorous action within the recirculation bubble. Maximum reduction in base pressure fluctuation is observed for the Normal & Inclined Ventilated Cavity device configuration test cases.

Can Architectural Surfaces Capture Atmospheric Particulate Matter Like Trees? A Design Strategy to Mimic Leaf Traits

Trees’ ability to capture atmospheric Particular Matter (PM) is related to morphological traits (shape, size, and micro-morphology) of the leaves. The objectives of this study were (1) to find out whether cluster pattern of the leaves is also a parameter that affects trees’ PM capturing performance and (2) to apply the cluster patterns of the leaves on architectural surfaces to confirm its impact on PM capturing performance. Two series of chamber experiments were designed to observe the impact of cluster patterns on PM capturing performance whilst other influential variables were controlled. First, we exposed synthetic leaf structures of different cluster patterns (a large and sparsely arranged cluster pattern and a small and densely arranged cluster pattern) to artificially generated PM in a chamber for 60 min and recorded the changing levels of PM2.5 and PM10 every minute. The results confirmed that the small and densely arranged cluster pattern has more significant effect on reducing PM2.5 and PM10 than the large and sparsely arranged cluster pattern. Secondly, we created three different types of architectural surfaces mimicking the cluster patterns of the leaves: a base surface, a folded surface, and a folded and porous surface. The surfaces were also exposed to artificially generated PM in the chamber and the levels of PM2.5 and PM10 were recorded. The results confirmed that the folded and porous surface has a more significant effect on reducing PM2.5 and PM10 than other surfaces. The study has confirmed that the PM capturing performance of architectural surfaces can be improved by mimicking cluster pattern of the leaves.

Application of Computer-Aided Reverse Engineering System in the Design of Orthotic Boots for Clubfoot Patients

Clubfoot is an abnormal foot as a congenital disability in which one or both feet appear rotated inward and downward. In some cases, the foot and leg sizes may be smaller compared to each other. Accordingly, there is a need for customized shoes designed for clubfoot patients who has difficulty in wearing regular shoes to carry out their daily activities. This study examines using computer-aided reverse engineering system technology to design and manufacture customized boots with specific sizes and shapes. Reverse engineering with a handy scan 3D scanning tool with a tolerance of 0.001 mm was implemented to obtain 3D mesh data of the patient’s clubfoot (male with 65 years). The Curve Base Surface Modeling method provided 3D-CAD drawings of the insole and shoe, the last models, precisely and following the size and shape of the patient’s foot. This CAD data could be appropriately transferred to CNC machines and PowerMill CAM software to obtain patterns of insole and shoe-last from EVA foam rubber and wood. Both ways were well fitted with leather by a shoemaker into a pair of customized clubfoot boots. The field boot-wearing test used feedback from the clubfoot patient wear-testers to assess the functionality and acceptability of the boot products. In this way, the club foot patient can able to perceive wearing comfortably and perfectly. In the field boot-wearing test, the patient could walk at a speed of 83.1% -91.7% faster (2 - 5 minutes/foot) than that when the patient wears the old boot design model. Significantly, the present approach may add knowledge theoretically and practically to use CARE system-based technology in treating clubfoot patients with the need for custom shoes.