砂轮 英语

Literature reviewIn precision grinding, conditioning of grinding wheels has always been a major topic of research as quality and economy of the grinding operation are directly related to grinding wheel conditioning. Under conditioning the operations profiling (indicated by truing for straight profiles), sharpening and cleaning are considered. For super-abrasive grinding wheels (CBN and diamond)profiling is most challenging because the lifetime and accuracy of the profiling tools are strongly limited by the inherent wear-resistance and abrasiveness of the considered grinding wheel. Below, available methods are discussed followed by the development of a profiling device and form disc drive system. Eventually the profilability of different grinding wheels is investigated and demonstrated with two cases.The resin-bonded diamond wheels have been usually used for grinding various cemented tungsten carbides. Based on the environmental consideration, the dry condition will be sometimes employed to grind these materials. However, the poor machinability of tungsten carbides causes difficulties in dry grinding. Especially in a dry machining process, all the grinding power is dissipated as heat in the grinding zone, at the interface between the wheel and the workpiece. This heat causes the wheel and workpiece temperatures to rise, which may cause thermal damage. Under such a condition, increasing material removal rates and obtaining high-quality surfaces would be limited.In order to improve the machinability of tungsten carbides in a dry grinding process, many studies have been conducted. Torrance and Metzger stated that in dry grinding of carbide, the resulting predominant mode of wheel wear is heat related. Furthermore, the wheel loss in wet grinding is mainly mechanical wear, and the grinding ratio increases with increase of the wheel speed. In addition, Metzger indicated that frequency of the wheel/workpiece entry impacts during grinding of cemented tungsten carbide would accelerate diamond wheel wear. The drop in grinding ratio can reach values as high as 70% in reciprocating face grinding with resin bond wheels.For best results in dry grinding cemented carbides, the following guidelines are adopted: (1) a low wheel speed of around 18 m/s; (2) a low table speed of 2–3 m/min; (3) a low depth of cut in the 0.01–0.05 mm range;(4) reduction in the area of contact .Furthermore, in the selection and use of wheels operated under a dry condition, metallic additives and lubricants would be added into the resin bond, which facilitates the dispersion of heat and the reduction of friction inthe contact zone. Besides, the irregular metal clad diamond particles with the moderate strength are also recommended to improve heat dissipation and retention in the resin bond . In turn these benefits result in increased tool life and enhanced performance.Even though several studies on the performance of the diamond wheels in the grinding of carbides had been investigated. However, studies relating the effects of the filler of the resin bond on the dry grinding of tungsten carbide are little reported. In this paper, the effects of several fillers of the resin-bonded diamond wheel on the performance of dry grinding of tungsten carbide are studied.A new kind diamond grinding wheel with Al-based bonding agent was prepared in this paper. The influence of sintering temperature to the relative density , hardness and service life of diamond grinding wheels with Al Sn Ti, Al Sn Ti Ni Co, Al Sn Ti Ni and Al Sn Ni Co bonding agent was studied. The microstructure of different bonding agent sintered at different temperature was observed. The service life of the Al-based grinding wheels was compared with Cu-based or resin-based ones. The results showed that the Al Sn Ti Ni Co is the best composition system in this research. The best sintering temperature is 300 ?C. The sample has a high relative density after sintered at 300 C. The retention of Al-based bonding agent to diamond grit is strong. The service life of this Albased diamond grinding wheel is about three times as long as that of resin-bonded grinding wheel.A new kind of grinding wheel has been fabricated with Albased bonding agent. The optimal system of Al-based agent in this research is Al Sn Ti Ni Co. Relative density, hardness hardness and service life of Al-based diamond tools are effectively influenced by sintering temperature. For these Al-based systems, the optimal sintering temperature is about 300 C. The grindingeffect of ceramic tile squared by Al-base wheel is as good as that by resin-based wheel. The service life of Al-based grinding wheel is three times as long as that of the resin based.Epoxy resins have been commercialized for 50 years. There are thousands of epoxies available in the markets. The basic properties of epoxy resins can be modified in many ways: by blending of different resins, by selection of curing agents and by the use of modifiers and fillers. The epoxy resins have exhibited good thermal properties, chemical resistance and electric insulation through a cross-linking reaction with a curing agent that makes the two-dimensional epoxy structure change to the three-dimensional network structure. These properties of cured epoxies all depend on the structures of curing agents and epoxy resin .Thermal properties differences between rigid rod tetramethyl biphenyl (TMBP) and flexible diglycidyl ethers of bisphenol A(DGEBA) epoxies were studied using modified differential scanning calorimeter (MDSC), thermogravimetric analyzer (TGA)and dynamic mechanical analyzer (DMA) techniques. These epoxies were cured with phthalic anhydride (PA) and phenolic resin (PF5110), respectively. The PF5110-cured epoxy has better thermal properties than the PA-cured epoxy with a higher glass transition temperature (Tg) and a higher decomposition temperature. The good thermal properties of the PF5110-cured epoxy are due to the rigid PF5110 structure on the cured epoxy. DGEBA epoxy has a higher decomposition temperature than the rigid rod epoxy when they are cured with PF5110. But, in the PA curing system, rigid rod epoxy has a better thermal stability. These two different results are due to the different structures of curing agents.Phenolic thermosetting materials were the first major plastic material used by industry. They are still among the most widely used thermosets because they are some of the lowest-cost engineering material on a cost-per-volume basis. Phenolics are formed from the condensation of polymerization reaction between phenol and formaldehyde. The condensation reaction for phenolics can be carried out under two different conditions, resulting in two different intermediate materials. One of the intermediates is called resoles and the other novolacs.In the earlier study about polymer network of phenolic and epoxies resins mixed with linseed oil, only Phencat 15was used as the catalyst for the phenolic resin. In this study, Phencat 382 and UH (a urea hydrochloride solution based on a 1:1 mole ratio of urea: hydrochloric acid 32%) will beused as catalysts to study their effects on the polymer network of phenolicand epoxy resins mixed with epoxidized linseed oil (ELO) (58%). The effect of each one of these catalysts on the curing and the properties of the formed network were investigated. It was discovered that Phencat 382was the best catalyst for the composites. Itwas also discovered that ELO can play its role as plasticiser in the blends of epoxy and phenolic resins and does improve the flexural strength and other mechanical properties of the prepared resins. The storage modulus, flexural modulus, stress at peak and glass transition temperature decreased with increasing percentage by weight of ELO added irrespective of the catalysts used, while the strain yield increased. The cross-link density decreased with the increasing amount of ELO in the resins. The best properties were obtained for the 80/20 epoxy/phenolic resin blends after post-curing for 4h.Imidazole with various molecular weights poly(ethylene glycol)s, including PEG1000, PEG2000, and PEG5000, was blended and evaluated as thermal latent catalysts for the polymerization of diglycidyl ether of bisphenol A (DGEBA) under liquid–liquid or liquid–solid two phase systems. The thermal latency and storage stability properties of DGEBA resin cured by 1–5 wt% of molecular weight imidazole/PEG complexes were measured by viscometer, differential scanning calorimetry (DSC), and TGA.Based on the viscosity–shear rate results, we found the 1–3 wt% amount of imidazole/PEGs showed the better thermal latency in the thermal polymerization system. From the cure activation energy and the viscosity–storage time of these complex catalysts, the order of thermally latent activity was imidazole/PEG1000 (2) > imidazole/PEG5000 (4) > imidazole/PEG2000 (3) > imidazole. Concerning the glass transition temperature (Tg), the use of imidazole/PEG complex catalysts providedcomplete or near complete curing systems in the temperature range about 150.8C.To get a better understanding of the curing process of multi-component thermosets differential scanning calorimetric (DSC) and temperature modulated DSC (TMDSC) measurements were performed during isothermal curing of semi-interpenetrating polymer networks (semi-IPNs) with amounts of 10 or 20 wt.% of linear polymer and of the corresponding pure networks at temperatures between 333 and 393 K. The network component consists of diglycidylether of bisphenol A (DGEBA) cross-linked with diaminodiphenyl methane (DDM) and the linear polymer component is polysulfone (PSn) or polyethersulfone (PES). The curing time dependence of conversion was estimated from time dependent heat flow measurements during isothermal curing. The curing kinetics is discussed in the framework of different models taking into account the catalytic effects and the influence of diffusion. A lower reaction rate was found in the semi-IPNs compared with the pure networks which is related to a decrease of the diffusion coefficient and/or the density of reacting units due to the linear polymer component. The final conversions were found to decrease with an increasing amount of the linear polymer component and with decreasing curing temperature which corresponds to less perfect network structures. The time evolution of the glass transition temperatures during isothermal curing was determined by the DSC and TMDSC. At the beginning of the reaction only one glass transition—indicating a one phase system—was found whereas at later stages of curing the two phase structure—consisting of a DGEBA/DDM-rich and a PSn-or PESrich phase—was indicated by two glass transition temperatures.The enhancement of the adhesive joint strength of the epoxy–amine system via the addition of a resole-type phenolic resin is investigated. Adhesive blends are formulated from a commercial epoxy and a synthesised resole-type phenolic resin. Phenolic contents are varied from 0% to 30%. The blends are characterized using Fourier transform infrared (FTIR) while the adhesive joint strength and the interfacial fracture toughness are studied for the adhesive blend/aluminium joint using single-lap shear and symmetrical and asymmetrical DCB specimens. It is found that the addition of resole improves the strength of the adhesive joint as well as its fracture toughness. The failure mode is found a function of the resole content. Resole contents less that 10% result in adhesive failure, while for resole contents of 20% and 30% the failure surfaces show adhesive and cohesive regions. The results allow concluding that the addition of resole-type phenolic resins constitutes an effective mean to enhance the adhesive properties of the epoxy–amine systems.Epoxy resins are extensively used in the formulation of adhesives and protective coatings due to their excellent attributes such as chemical resistance, dielectric and insulation properties, low shrinkage on cure, dimensional stability and fatigue resistance . The chemical compatibility of epoxy resins with a rather wide variety of polymers is also of great significance. A number of systems result from the blending of epoxy resins and polymeric modifiers such as nylon, phenolic resins and nitrile rubbers.The variety of chemical and mechanical properties that can be obtained from the combination of currently available epoxy resins and polymeric modifiers enables formulating epoxy-based adhesives and coatings to meet a wide range of specifications and usage criteria. The leading applications of the epoxy-based adhesives are in the field ofstructural metal bonding, particularly in the automotive and aerospace industry, in military equipment and in miscellaneous small-part assembly of plastics and metals.Phenolic modified epoxy resins produce one of the best high-temperature adhesives . On the other hand, epoxybased coatings are mainly used in plant maintenance, container coatings, appliance finishes, pipe coatings and trade sales paints. The most usual curing agents used for the formulation of epoxy-based coatings are amino compounds or formaldehyde condensates with phenols.The curing agents react with the hydroxyl groups of the epoxy backbone at elevated temperatures . The final performance of multicomponent materials and structures depends significantly on the quality of the interface between its components. The need to improve the performance of multicomponent materials and structures has led to significantly progress in the area of interfacial fracture mechanics . During the last few decades, a lot of works have been reported on the fracture of the metal/polymer interface. Most of them have been focused on the aluminium–epoxy interface . Epoxy–phenolic systems have been used for many years in industrial applications, with formulations containing a variety of fillers and additives along with various types of epoxy prepolymers and curing agents. Each formulation can result in a resin which exhibits specific properties. To the authors’ knowledge, there is no information about using the epoxy–amine–phenolic system as adhesive. It is the aim of this work to characterise the epoxy–amine–phenolic systems and to evaluate the adhesive joint strength and the interfacial fracture toughness of the polymer blend/aluminium joint.The formulation and mechanical characterization of adhesives based on epoxy–amine–phenolic blends have been presented in this work. The adhesive blends were formulated from a commercial epoxy and a synthesised resole-type phenolic resin with phenolic contents ranging from 0% to 30%. FTIR analyses allowed concluding that the epoxy reacts with the phenolic resin. The Young moduli of the blends diminished with the increment in the phenolic content, from 4.30MPa for 0% resole to 2.45 GPa for a resole content of 30%.ReferencesJ.M. Derkx a, A.M. Hoogstrate a, J.J. Saurwalt b, B. 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