Showing papers by "Hefei University of Technology published in 1998"
TL;DR: In this article, the friction and wear performance of a modified polyacetal or polyoxymethylene (POM) with a toughening phase polyurethane (PU) was analyzed.
Abstract: Compared with other polymers, polyacetal or polyoxymethylene (POM) which is widely used as bearing, guide, gear and other sliding parts, has high strength and stiffness, excellent chemical resistance and superior antifriction and wear resistance. To improve the toughness and self‐lubrication capacity of POM due to its higher crystallizability, other components, which include toughening phase and solid lubricants, are often added to the POM matrix. This paper deals with the friction and wear behaviours of POM which was modified by the toughening phase polyurethane (PU) and filled with polytetrafluoroethylene (PTFE) and silicone oil, during rubbing against MC nylon without liquid lubrication. Friction and wear tests show the tribological performance of the modified POM (M‐POM) with 10 wt% PU is better than those of pure POM and POM blended with PTFE under dry friction. The frictional coefficient of the M‐POM decreases with increasing nominal load. The sliding velocity has a more obvious effect on the tribological properties of the M‐POM than the nominal load. The higher sliding velocity leads to thermal degradation and melting of the experimental polymers because of the frictional heat.
22 citations
TL;DR: An optimal manufactured lot-sizing model is developed under the consideration of learning and shortages, which minimises the sum of labour and material costs, fixed set-up costs, the holding cost and the shortage cost per unit time.
Abstract: In this paper, we develop an optimal manufactured lot-sizing model under the consideration of learning and shortages. Here the learning phenomenon conforms to the De Jong bounded learning curve. A one-dimensional search method is presented for determining the unique optimal production schedule, which minimises the sum of labour and material costs, fixed set-up costs, the holding cost and the shortage cost per unit time. A numerical example is used to illustrate the solution procedure; sensitivity analyses are also shown.
18 citations
TL;DR: In this article, the authors investigated how to improve the toughness of polyoxymethylene (POM) by blending polyurethane (PU) with POM using dual-roller compaction.
Abstract: Polyoxymethylene (POM), one of the major engineering thermoplastics, has high strength and stiffness, excellent chemical resistance and superior antifriction and wear resistance. It suffers, however, from poor impact resistance due to its higher crystallinity. In this study we have investigated how to improve the toughness of POM by blending polyurethane (PU) with POM using dual-roller compaction. The influences of PU, silicone oil, a surfactant, and fillers such as ultra-high molecular weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), graphite and carbon black, on the mechanical properties of oil-containing POM/PU blends and its self-lubrication performance in dry sliding against AISI1045 steel are examined. The results show that blends of POM with 10 wt.% PU reached the maximum notched Izod-impact strength. The best processing method for oil-containing POM/PU blends, and the optimal compositions of modified POM/PU blends were also determined.
10 citations
TL;DR: In this article, the scuffing failure threshold of a piston ring-cylinder lintern was established by using specific oil film thickness and the asperity capacity was evaluated based on the experimental results.
Abstract: The scuffing failure phenomenon of piston ring–cylinder liner is studied theoretically and experimentally. The load and bulk temperature when scuffing failure occurs are measured under different engine speed, lubricant, and environmental temperature in a bench test. Based on the experimental results, the asperity capacity when scuffing occurs is evaluated. Surface contact temperature is determined with the measured bulk temperature and the surface flash temperature calculated by Blok theory. The scuffing failure threshold of piston ring–cylinder liner is established by using specific oil film thickness.
9 citations
01 May 1998
TL;DR: In this paper, the removal of water from oil-in-water emulsion by ultrafiltration (UF) membrane was investigated at 40°C and 3 bar in laboratory and pilot scale.
Abstract: In this study the removal of water from oil-in-water emulsion by ultrafiltration (UF) membrane was investigated at 40°C and 3 bar in laboratory and pilot scale. Hydrophilic polyethersulfone (PES), polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) membranes were used to conduct laboratory tests. The effects of membrane material, nominal molecular weight cut off (MWCO), operating conditions and feed oil concentration in emulsion on UF behavior were studied. For PAN, PVDF membranes their permeate fluxes are much higher than that of PES membrane. The experimental results show that membranes with either high or low MWCO have high separation efficiencies. The PAN membrane has a prominent permeate ability at lower feed oil concentration (0.5 vol%) compared with those of other UF membranes under same MWCO. PES membrane is suitable to remove water of higher feed oil concentration (5 vol%). Comparing the pilot and laboratory results, similar oil and COD rejection are measured, while the permeate flux in pilot is significantly lower.
5 citations
07 Sep 1998
TL;DR: A novel technique is presented for blindly estimating the channel matrix in an M-sensor K-source system using a special estimated higher-order cumulant matrix of the received data.
Abstract: In this paper, a novel technique is presented for blindly estimating the channel matrix in an M-sensor K-source system. A special estimated higher-order cumulant matrix of the received data is first constructed. The channel matrix is then estimated by the eigendecomposition of the cumulant matrix. This method does not need any prior information of the signal. Computer simulation results are presented showing that the proposed algorithm is very promising.
5 citations
5 citations
TL;DR: In this article, the structure, hardness, abrasion, and erosion wear of Cr-Mo white iron (containing approximately 28 % Cr and 1 % Mo) heat treated at certain temperatures were studied.
Abstract: The structure, hardness, abrasion, and erosion wear of Cr-Mo white iron (containing approximately 28 % Cr and 1 % Mo) heat treated at certain temperatures were studied. Results show that the heat treatment of white iron changes the structures and properties; that is morphology, amount, size, and distribution of secondary phases are affected. When white iron was heated at 800 to 850 ‡C the secondary phase precipitated at the phase boundary, making the abrasion and erosion wear worse. When the iron was heated at 900 to 950 ‡C, the secondary phase precipitated dispersively at the matrix, and the corrosion wear was optimum. If the iron is heated at 1000 to 1050 ‡C, the resistance of abrasion is inhibited, as the secondary phases precipitate in large amounts, and the hardness is increased. When the white iron is tempered at 500 to 600 ‡C, the resistance of abrasion is better.
5 citations
TL;DR: In this article, the conditions for the complete dynamic balance of rotor inertial forces in the rotary piston vacuum pump with single cylinder are determined based on motion analysis, and the experiment results show that the pump vibration can be depressed obviously by improving the rotor structure according to the balance conditions.
2 citations
TL;DR: In the design, the key problem is how to find some efficient heuristic algorithms and to solve this problem, a nonliner-discrete-capacity assignment heuristic and a hybrid perturbation heuristic are suggested.
Abstract: In this paper, some problems on the topology design of network are discussed. An exact formula to calculate the delay of a line will be provided. In the design, the key problem is how to find some efficient heuristic algorithms. To solve this problem, a nonliner-discrete-capacity assignment heuristic and a hybrid perturbation heuristic are suggested. Then, a practical CAD system which helps design the topology of network will be introduced.
2 citations
TL;DR: In this article, the formation and source of oil shocking in a vacuum pump chamber is analyzed through tests of the vibration in and noise from a rotary piston pump, and it is believed that the chief source of the shock cell noise comes from the impact of liquid oil moving at great velocity.