The mechanical properties of epoxy granite composite are extensively influenced by the structure of porosity. The aim of this research work is to establish a mathematical model to estimate the ...correlation among damping and porosity. Also to estimate the correlation among flexural strength and porosity for given epoxy granite composites using experimental methods. The theoretical porosity of epoxy granite in terms of their component properties and volume fraction were determined and verified. Taguchi design of experiments was applied to plan the number of experiments to be carried out. The experimental results obtained from different test were plotted on graph over analytical results. Regression analysis was applied to establish the empirical relation between inherent properties and mechanical properties. Comparison between the analytical model and experimental results was carried out to validate the mathematical model
Composites have become attractive to many industries today and are a good alternative to many traditional materials. Epoxy granite (EG) is used as a competitive alternative to ground ceramics, ...especially as a foundation for machine tools. This is because of their high damping ratio compared to other traditional materials such as cast iron. In the present study, a lightweight and cost-effective EG composite material was developed as a new foundation for machine elements. The composite material EG was prepared by mixing epoxy resin (12 wt %) and granite particles by casting method. The crushed granite particles were sieved and separated into coarse particles ≤2.36 ≥ 1.18 mm, medium particles ≤1.18 ≥ 0.6 and fine particles ≤0.6 mm. Vibration modal analysis is performed using an impact hammer to measure the natural frequencies occurring at each material size and the damping ratios. Microbial and fungal resistance is tested to understand applicability in humid environments, and water absorption and soak resistance were also measured. Scratch tests are performed using a top scratch tester to measure scratch width for fine and coarse samples. The electrostatic discharges generated by friction on the rubber and granite-epoxy composite sole are measured. It was found that as the particle size decreases, the damping ratio increases and the damping capability is improved, both microbial and fungal resistance increases, the scratch width is small for fine particles, while it is difficult to achieve for other granite sizes. Electrostatic discharges show a better feel for the composite material, but it is better with fine particles.
Machine tool structures produced with Epoxy Granite reinforced polymer composites (EGPCs) have gained prominence in recent years and have replaced conventional cast iron materials and other metals ...due to its remarkable damping characteristics. However, machine tool structures manufactured with EGPCs tends to exhibit limited strength, stiffness and stability. Such challenges in EGPCs are resolved by incorporation of steel as additional reinforcement and enhanced mechanical properties are observed in these hybrid machine‐tool structures. Hybrid epoxy granite machine tool structures with enhanced mechanical performance are prone to thermal errors resulting in machining inaccuracies and limited performance. Thermal errors induced in machine tool structures could be attributed due to effect of temperature distribution and displacements at the Tool Center Point (TCP). This review work carried out focuses predominantly on design methods adopted in resolving the challenges identified in development of machine tool structures and further analyses results of several polymer concrete‐based machine tool structures with regard to static, dynamic and thermal characteristics. Several review works conducted earlier have discussed the results of static and dynamic characteristics, whereas this review work provides additional information on thermal based errors induced and discusses the methods adopted in compensation of thermal errors. In this review paper, research studies pertaining to static and dynamic characteristics of different machine tool structures performed in last three decades have been discussed and a wholistic information is provided in relation with static, dynamic and thermal characteristics and properties toward developing a machine tool structure with a novel, newer class or alternative materials.
Challenges in development of machine tool structures – static, dynamic and thermal characteristics.
In Egypt, large quantities of coarse granite wastes are produced annually during the quarrying operations of granite rocks. This waste represents a potentially useful source of material for a variety ...of applications such as a filler material in epoxy granite composite material. In this work a new eco-friendly composite material studied as a substitute for machine tools traditional materials, like cast iron, to produce better efficiency with lower cost. This study aims to investigate the mechanical properties of granite epoxy composite by using the local epoxy (kemapoxy 150) and the granite residues in the Egyptian quarries. The investigated processing variable was epoxy content, and the mechanical characterization ware carried out by compressive and flexural tests according to the ASTM standard method B. Commercially available, Aswan red granite was procured, crushed, and sieved to three size ranges from 0.150 to 8 mm, respectively. Epoxy ratios of 80:20, 85:15 have been used with granite aggregate size mix with small, medium, and coarse size proportions of 50:25:25 respectively for preparing the specimens with granite granular size range (0.150-8) mm. The results show that Epoxy granite composite with granite to epoxy ratio of 80:20% wt. induced the highest compressive strength (72.15 MPa) while the composite with the ratio of 85:15% wt. induced the highest flexural strength (20.1 MPa). Epoxy granite composite show superior results with respect to cement concrete, polyester concrete, and natural granite.
Machine tool structures fabricated with new alternate material epoxy granite has been developed to enhance the damping characteristics, stability and reduction in weight. Machining of epoxy granite ...composites (EGCs) has been critical by considering its heterogeneous nature. An optimization problem with multiple attributes has become a critical issue in selection of optimal solution due to the varying characteristics among attributes. Decision making model, Analytical hierarchy procedure (AHP) is employed in selection of optimal machining condition in milling EGCs. Evaluation factors consisting attributes that influences machining process such as thrust force, tangential force and surface roughness are only considered. Computation from AHP method reveals that experimental run 3 is the desired optimal solution with the optimal machining conditions of speed 600 rpm; feed rate 0.09 m/min and 4% fiber content.
One of the challenges of machining process is to improve the quality of machined surface by reducing the vibration of cutting tools. The research aims to suppress vibration using composite boring ...bars with an enhanced damping capacity. A new design of boring bars with different cross-sections is considered. Static and dynamic behavior of the proposed tools is investigated. A mathematical model for determining the eigenfrequency is proposed, and it is compared with computer simulation and experimental results. The validity of the proposed models is verified by conducting experimental machining tests in order to study the changes in vibro-acoustic signals depending on the cross-sections of the toolholder. The results show that the composite material significantly improves damping of boring bars, which leads to a reduction in the vibration compared to conventional boring bars.
Polymer concrete or epoxy granite is becoming more popular for beds, bases, and other structures of precision machine tools, owing to its excellent damping characteristics. To realize the same static ...rigidity as that of the cast-iron structures, steel-reinforced epoxy granite (SREG) structures are being used. The vast differences in the thermal properties of steel and epoxy granite (EG) are likely to cause higher magnitudes of thermal error. This work aims to investigate the thermal behaviour of a computerized numerical control (CNC) lathe built with a novel dynamically enhanced SREG bed and compare its performance with the lathe with a cast iron bed. Experimental and numerical investigations have been carried out under cross-feed (CF) drive idle running conditions to determine the TCP deformation. The results reveal that the thermal error in the CNC lathe with SREG bed is 1.68 times that of the lathe with cast iron (CI) bed at 20 ºC and 1.8 times at 40 ºC environmental temperature variation chamber (ETVC) conditions. It could be identified that the heat generated in the CF is conducted to the steel guideways embedded in the SREG bed, but further heat transfer to the EG portion of the bed is impeded, and hence the heat accumulation that occurs in the guideways leads to higher magnitude of the thermal error. The experimentally validated numerical model is used to extend the investigations to study the effect of the idle running of the longitudinal feed drive (LF) and combined cross and longitudinal feed drives, on the thermal behaviour of the lathe.
Thermal error is one of the most influential parameters in precision and ultra-precision machine tool design. In recent decades, machine tool structures made of polymer concrete such as ...steel-reinforced epoxy granite (SREG) have gained popularity due to their superior damping properties, substantial stiffness and good thermal stability to variations in environmental changes. On account of the significant variation in the thermal properties of steel and epoxy granite, the thermal error in a lathe with an SREG bed is found to be 1.6 times that in a lathe with cast iron bed at 20 °C ambient conditions. This paper presents a novel method of reducing the thermal error in the CNC lathe with an SREG bed using a genetic algorithm (GA)-based multi-objective optimization. The proposed thermo-structural optimization is an efficient design model for the SREG bed to enhance heat transfer by maximizing convection area as an objective and required stiffness as one of the constraints. For all analyses, a validated numerical method was adopted. Thermo-mechanical analysis by simulations reveals that a 32% reduction in thermal error can be achieved with the optimized SREG bed. Experimental modal analysis (EMA) on the optimized bed (SREG-2) shows that the dynamic properties have not deteriorated compared to the results of the existing SREG-1 bed.
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