Applied Mechanics and Materials Vols. 184-185

Abstract: Polybutyl acrylate (PBA) grafted alumina nanoparticles were synthesized. Polytetrafluoroethylene (PTFE) nanocomposites reinforced with PBA grafted nanoparticles were prepared by compression molding. The effects of PBA grafted nanoparticles on the tribological behavior of the PTFE nanocomposites were investigated on a tribometer. The abrasion mechanisms of the PTFE nanocomposites were investigated by scanning electron microscopy (SEM) of the abraded surfaces. The results show that the addition of PBA grafted nanoparticles maintains low friction coefficient and improves the wear resistance of the PTFE nanocomposites.

Abstract: In single roll rapid quenching molding, especially for the preparation of amorphous ribbons and rare earth permanent magnetic materials, the chilling roll is an extremely important component of the preparation equipment. However, frequent repair of the roll is not conducive to continuous large-scale production because of its poor thermal fatigue resistance. Molybdenum is gradually being used as chilling roll material in some applications, and in the present paper a new approach to study the thermal fatigue resistance of molybdenum is based on laser pulse irradiation on the molybdenum surface. A new designed device effectively prevents the molybdenum to be oxidized during the laser heating test. The experiments of thermal fatigue damage on molybdenum were conducted by the high power laser. The results shows that the fatigue cracks had been propagated in the irradiated region after the specimen was loaded by 200 times pulsed laser heating. There is a greater crack density in the laser heating brim region than in the center of the irradiated region. According to the transgranular mode of crack propagation in the laser heating brim region and intergranular mode in the center of the irradiated region, the maximum stress took place at the intersection region due to the great temperature gradient in the laser heating brim region. Continued basis-oriented experiments are planned, regarding the mechanism of thermal fatigue crack initiation and propagation for chilling roll materials.

Abstract: Knitted protective sleeve mainly deals with the functional development . Using molding technology of knitted fabrics and special coating technology, implemented a full-shaped cuff of production technology and specific coating technology. The results show that the shaped cuff reduces the disadvantages caused by sewing, high fabric elasticity; special coating and coating techniques, reducing the load, at the same time so that the fabric is beautiful, has better properties of waterproof and moisture permeability, improves the wearing comfort.

Abstract: Coal spontaneous combustion is a complex procedure of physical and chemical changing, in which the macro characters is the reflection of micro changes of coal molecule structure in low temperature oxidation. In order to understand the essence of coal-oxygen composition, the Fourier transform infrared spectrum apparatus is used to test and analyze different kinds of coal samples in different oxidation temperature. According to main characteristic spectrum peaks, the activity of coal functional groups is studied. The difference and change of the type and quantity of functional groups in different kinds of coal sample in different temperature are analyzed. The relation between the macro structure change and spontaneous combustion property of coal in low temperature oxidation process is discussed.

Abstract: The tribological behavior of PPS filled with molybdenum-concentrate (MC) deposit from Armenia was studied. The deposit MC was a complex mixture of compounds such as MoS2, SO2, CuS, Al2O3, and others. Whereas MC as the filler in particulate form reduced the steady state wear rate of PPS, the optimum reduction in wear was found to occur with the addition of PTFE along with PPS. The behavior of PPS composites made with MC and PTFE sliding against a steel counterface was investigated as a function of the MC and PTFE proportions, sliding speed, and counterface roughness. Of all the above factors, the change in MC proportion, while PTFE was also present, had the greatest effect on the reduction in wear rate. The variation of the coefficient of friction was found to be in the narrow range of 0.27-0.33. The lowest wear rate was found in the case of PPS+ 17vol.%MC+10vol.%PTFE composite sliding at 1.5 m/s against a counterface roughness of 0.1 μm Ra.

Abstract: This research produced nanofiber membrane with polyethylene oxide (PEO) by electrospinning; the influence of the three parameters —mixture ratio of solution, electric field, and distance between the capillary tip and the collecting plate, on electrospinning was then explored. According to the results of the experiment, the fiber membrane with a diameter of 120 nm could be obtained when the optimum electric filed was 0.6 kV/cm and the distance between the capillary tip and the collecting board was 15 cm. Finally, the spunlace nonwoven was coated with the electrospinning solution with the optimum parameters, creating the asymmetric dressings.

Abstract: The kinetic parameters of thermal explosion tests with five-second delay for 273 energetic materials were analyzed. The compensation effect exists between the two thermal explosion kinetic parameters of these energetic materials, e.g. lnA and Eb. The kinetic parameters of these energetic materials can be expressed by a single linear regression equation for the single compound or mixture under all conditions. The slopes of the regression equation for various systems are in the range from 0.1952 to 0.2413 (mol•kJ-1). The regression equation for single compound or mixture with one type of energetic material as main component has better linearity. Therefore, their “iso-kinetic temperature” Tik is close to their thermal explosion temperature Tb and the “iso-kinetic delay period”τik is also close to the 5 seconds.

Abstract: The numerically simulation of temperature field was carried out by the ANSYS software in multi-layer powder-feeding laser cladding forming.3-D finite element model was found, which nonlinear characteristics of the material thermal properties and the boundary conditions of the convective transfer heat was considered; The process of powder falling into the substrate and cladding element growing was accomplished by “Element Birth and Death technology” in the process of numerical simulation. The result shown that the primarily solidified cladding layer to the following cladding layer has a preheating function in the process of multi-layer laser cladding forming, the initial temperature of following cladding layer is higher than primarily melted cladding layer; The thermal cycling curves of the molten pool nodes takes on periodic variation and basic similar in every layer cladding; The end effect problem is apt to happen in cladding layer, which the phenomenon of edge collapsing or partially burnt is formed; The temperature gradient distribution is divided into two parts, the temperature gradient level distribution along the laser scanning direction in the top and perpendicular distribution in the bottom, The temperature gradient appearances mutation and maximum value in the junction of the substrate and cladding layer, which the crack is apt to be caused in this region.

Abstract: Nowadays, as rising research on biomaterials, the artificial bone scaffold has become the most important part of the study. Moreover, metallic materials have been applied on the artificial bone scaffold; but its high rigidity causes the stress shielding effect in bones. To improve the disadvantages of metallic materials and pursue their better mechanical properties, 304 stainless steel fibers have multi-layer braided into the 3D stainless-steel braid with porous structure and better mechanical properties, using braiding machine. In multi-layer braiding process, with the constant number of take-up gear and varying number of braid gear, the 3D stainless-steel braid was manufactured. Afterwards, its braiding structure and angle were observed by stereo microscope. Also, the optimal braiding parameters can be acquired from tensile strength test.

Abstract: Various jute-based activated carbon fibers were prepared by using jute fibers as raw materials, phosphoric acid as activating agent and activated by microwave heating. The effects of phosphoric acid concentration, microwave radiation power and microwave radiation time on the adsorption properties of activated carbon fibers were investigated to obtain optimum preparation conditions. The pore structure analysis of the activated carbon were carried out on a ASAP 2010 Surface Area and Porosimetry Analyzer. Results showed that optimum preparation conditions were phosphoric acid concentration of 4 mol/L, microwave radiation power of 385 W and microwave radiation time of 10 min. The iodine adsorption value of jute-based activated carbon fiber prepared under optimum conditions is 938.54 mg/g, the specific surface area was 1154.91 m2/g, the pore volume was 0.5997 cm3/g and the adsorption average pore diameter was 2.0772 nm. Majority of large holes in JACF prepared under optimum conditions were distributed in the diameter range of 2-4 nm, demonstrating a mesoporous structure.