Papers by Keyword: Compression

Abstract: In this study the effect of adding different weight ratio (0.5, 1, 1.5, 2)% of TiO₂ nanoparticles powder extend the life of removable partial dentures made by PMMA was studied.The PMMA has low mechanical properties. Then the life is relatively short. After adding these different weight ratios, it found that the highest ultimate compressive stress was at the weight ratio 1.5% . The chewing force measured using a special sensors F-scan, which represents a mat of micro-sensors.When the value of the chewing pressure was 312 kPa. To measure the life of partial dentures, a special device was manufactured that applied a force that simulated the force generated during chewing . It measured by the f-scan sensor, and the best life of 1.5% TiO₂ was added by weight. The lifetime of dentures increased by about 80% after adding 1.5 wt% of TiO₂ nanoparticles.

Abstract: Due to the seismicity of the country and especially to the geology of the province of Pichincha, it was considered important to obtain this equation in order to improve the structural design of future constructions since we do not have our own parameters to determine the mechanical properties of concrete. Based on previous investigations of the modulus of elasticity carried out in the country, it was identified that the current formula does not reflect the reality of the existing conditions since the derivation of this equation was determined in the USA whose characteristics of the materials are totally different from those of Ecuador. Therefore, it was considered convenient to carry out a complete study of the properties of the aggregates to obtain the equation of the modulus of elasticity of concrete that represents the attributes of the province of Pichincha.

Abstract: Reliability and behaviour of composite columns is influenced by many factors. This paper presents a comparative study of the reliability and performance of square composite columns under axial compression, taking into account mechanical and geometric variability. The choice is opted for metal hollow profiles filled with ordinary concrete and high-performance concrete. In this study, a mechanic-reliability model to calculate the reliability index and the probability of failure of different columns is presented. The response surface method is used to accomplish this coupling in order to describe the uncertainties in a suitable model and to study their influence for a reliability assessment. The results show that the material and geometric characteristics of the columns have a significant influence on strength and reliability. The sensitivity of the random parameters of structural reliability is assessed from the proposed method.

Abstract: In the search for a dosage that allows us to design a sustainable concrete with greater resistant capacity. Different solutions are proposed that allow us to find the right addition to achieve a better performance in the physical and mechanical characteristics of concrete in fresh and hardened state. For the development of the research, the influence of the addition of coconut fiber in concrete is evaluated. For this reason, various mix designs were developed: The pattern and with the addition of coconut fiber in partial replacement of fine aggregate with designs of 0.50 %, 1.00%, 1.50% and 2.00%, making a total of 90 concrete specimens which are represented in cylindrical and rectangular specimens. For each mixture, tests were carried out for its fresh state and hardened state. From the analysis it is concluded that the most optimal relationship is achieved with 1.00% coconut fiber addition, achieving compressive and flexural strengths at 28 days of 231.60 kg / cm2 and 83.10 kg / cm2, representing percentages of increase in 11.00% and 9.00% respectively.

Abstract: The paper presents compression tests of stocky and slender masonry pillars strengthened in bed joints with PBO fibres and an inorganic matrix. Five stocky pillars and four slender pillars were tested under static loading. Physical models were prepared using lime mortar similar to that used in historical structures. Fibres were applied in the grooves that were made after the mortar setting period in order to recreate real-world conditions. One of the models was subjected to preloading before the strengthening was applied. The failure modes, load-bearing capacity, cracking stresses, stiffness and deformations (longitudinal and transverse) were all determined through experimental testing. Strengthening effectiveness in terms of the increase in load-bearing capacity and stiffness, as well as anti-cracking was determined on the basis of the experimental results. The results obtained for the stocky and slender pillars were also compared, indicating the influence of slenderness on strengthening effectiveness. Special attention was also paid to failure modes and the interaction of the PBO fibres with the bed joint. Methods that strengthen pillars in their bed joints using PBO fibres increase their load-bearing capacity, stiffness and cracking resistance, while maintaining a satisfactory visual appearance which is especially important in heritage structures.

Abstract: During recent years, the rapid growth of the population in urban areas has promoted the development of housing, roads, shopping centres and industries; having increased the consumption of tap water in the concrete industry. A solution to this problem, is to use domestic wastewater treated, due to the large quantities produced and the need to include them within the life cycle of the water; thus bridging the gap of service in urban and rural areas. The present research seeks to use the domestic wastewater treated in the production of concrete for construction; the results show slightly for the slump, initial setting time and splitting tensile increase, and that the resistance to compression and flexural is decreased.

Abstract: Titanium (Ti) alloys are materials of interest in structural and chemical applications due to their low density, outstanding mechanical and chemical resistance properties. However, the mechanical properties still need to be enhanced to make them suitable as a replacement for Ni-based superalloys. There have been significant breakthroughs in the reinforcement of Ti alloy with a small weight percentage (wt.%) of ceramics. This work investigates the effect of TiN nanoparticles’ addition on the densification, phase transformation, microstructure, hardness, and compressive properties of Ti-7Al-1Mo ternary alloy. 3 wt.% of TiN nanoparticles was blended with Ti-7Al-1Mo powder, and the resulting admixed powder was consolidated via spark plasma sintering technique at 50 MPa pressure, 10 min holding time, and 1000 °C temperature. Scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry were used to characterise the microstructure and phase composition respectively. The microstructure of Ti-7Al-1Mo revealed a lamellar structure with alpha (α) phase and minor beta (β) phase with visible grain boundaries, while TiN reinforced Ti-7Al-1Mo composite microstructure shows a bimodal structure with reduction in the lamellar structure. Ti-7Al-1Mo ternary alloy has a hardness value of 352±17 HV0.1 and a compressive yield strength of 985±31 MPa. The composite shows an increment of 74 HV and 323 MPa in its hardness and compressive yield strength respectively in comparison to the ternary alloy.

Abstract: Tensile, compressive and flexural (3-point bending) tests are performed on electromechanical universal testing machine (Zwick/Roell 250kN) to determine mechanical characteristics of an aluminium hybrid composite fabricated through stir casting process at different rates of quasi-static loadings in room temperature 25°C. Influence of heat treatment (annealing) is observed on the material properties. After annealing, the tensile, compressive and flexural strengths decrease while ductility, malleability and bending capability of the composite increase. Bending tests are conducted at different crosshead speeds (1-100mm/min) to study its effects on flexural stresses. It is found that the specimen geometry affects the stress-strain behaviour of the composite.

Abstract: The effect of fabrication methods on polysiloxane (POS) composites were studied by analysing both method of casting (CA) and compression (CO). The POS composites were reinforced with 2-12 wt% of natural derived silica from rice husk (RHA SiO₂) as a filler which incinerated at 700°C. The composites behaviour were analysed through tensile testing (ASTM D412). Through comparison study on both CA and CO composites’s tensile behaviour it shows that both composites strength keep increasing with 2wt% - 10wt% RHA SiO₂ addition but strength decreased at 12wt% due to agglomeration of RHA SiO₂. Moreover, it was found that the tensile strength of CO composites had offer 23.56% higher compared to CA composites. The difference were influenced by the distribution of RHA SiO₂ as filler. The surface morphology of CO composites had showed that the most of RHA SiO₂ were embedded and less agglomeration, compared to CA composites that had lots of agglomeration which lead to higher tendency of crack propagation. The arrangement of filler due to the CO method that helps RHA SiO₂ to distributed homogenously and embedded in a matrix of POS to avoid agglomeration and lead better adhesion respectively. Thus, CO method had potential to offer in enhancing tensile behaviour compared to CA method by influencing filler distribution arrangement for vibration absorber application.

Abstract: Around 1000 million waste tyres are generated annually and over 5000 million more are estimated to be discarded by 2030. It is estimated that one waste tyre is discarded per person in developed areas, hence 1 billion waste tyres are disposed worldwide. Waste tyre is difficult to manage as it takes up space, is difficult to compress and combustion of tyre releases highly toxic substance into the air. Hence, most of them end up in the landfill, as past research data estimated that currently 4 billion waste tyres can be found in landfills. In this study, up to 30% tyre rubber with a fine grind size of 300nm to 500nm was used as partial sand replacement in type N cement mortar. The rubber was treated with 1M NaOH solution to enhance its ability to bond with the other constituent materials. Tests were conducted to determine the properties of rubberised mortar, including consistency, compressive strength, flexural strength, water absorption and acid attack. From the test result, tyre rubber reduced the consistency and strength of mortar. Mathematical regression model showed that reduction of strength occurred in a second-order polynomial function with percentage of rubber. It was concluded that at up to 20% replacement rubberised mortar has the best resistance against water absorption and acid attack while still achieving the target strength.