Advanced Materials Research Vol. 1077

Abstract: This paper presents the results of a systematic dry hobbing experiment performed on a general mechanical transmission type of hobbing machine. All four types of coated HSS hobs demonstrate satisfactory cutting performance applicable enough to practical production. Some related details such as the characteristics of hob wear, the effect of chip crush behavior and cutting speed are also discussed based on the experiment results.

Abstract: As the development of new materials and high speed machining, cutting fluid becomes more and more important because of its functions of cooling, lubrication, corrosion protection and cleaning. The main purposes of cutting fluid are decreasing temperature, reducing friction, extending tool life and improving machining efficiency. In precision machining, high machined surface integrity is the most important. In this paper, a preliminary experimental study on effect of two different cutting fluids on milled surface quality of iron-base superalloy was taken. The surface morphology, roughness, micro hardness and residual stress of the machined surface were investigated. The results showed that the material properties and geometric characteristics of the machined surface were significantly affected by cutting fluid conditions. The effect of cutting fluid on machined surface quality and service performance will become an important research direction. This paper also suggests the main contents of the further research on effect of cutting fluids on machined surface.

Abstract: On the basis of physical oxygen uptake, use the instrument to identify the spontaneous combustion of Yang quan coal, and combination the insulation oxide of coal as well as the TG-DSC experiment to analysis of low-temperature oxidation of coal, though the DSC curves, combined with the insulation oxide experimental to analysis the size of the heat. In the end, we can come to the conclusion about the law and the different temperature parameters of the low-temperature oxidation. At the same time, the temperature when a large number of heat released by coals oxidation were also known ,and laid a theoretical foundation to develop prevention and control measures for the spontaneous combustion of coal mines.

Abstract: The paper deals with disk laser welding of magnesium alloy with the content of rare earth elements. ZE 41 magnesium alloy with the thickness of 2.0 mm was used as experimental metal. TruDisk 4002 solid state laser with a wavelength of 1.03 microns and a maximum power of 2.0 kW was used for welding of magnesium alloy. Laser power which was applied ranged from 0.6 to 1.2 kW. The focal position of laser beam was fixed on the surface of magnesium alloy and the welding speed was set to 70 mm/s. Argon with flow rate of 12 l/min was used as shielding gas. Light microscopy, EDX microanalysis and micro hardness measurements across base metal - fusion zone interface were carried out in order to analyze the weld joints.

Abstract: The paper concerns with welding of copper to stainless steel. Technically pure Cu and AISI 304 austenitic stainless steel with the thickness of 2.0 mm were suggested as experimental metals. TruDisk 8002 laser with the wavelength of 1.03 μm and a maximum power of 8.0 kW was used for production of dissimilar metal welds. Laser power from the range of 2.3 to 2.9 kW and welding speed from 35 to 50 mm/s were used for welding dissimilar metals. Focal position was direct on the surface of welded metals. Helium with flow rate of 17 l/min was used for shielding of molten weld metal. Light microscopy, EDX microanalysis and micro hardness measurements across copper - fusion zone - stainless steel interface were performed in order to study the properties of the weld joints.

Abstract: Contribution deals with soldering of Mg alloy AZ31B by ternary solder ZnAl6Ag6 with ultrasonic support. Suggested solder has been analyzed from many aspects. Microstructure of solder consistutes of solid solution α-Al (FCC_Al), β-Zn (HCP_Zn) and intermetallic phases AgZn₃ and AlAg₃. Melting temperature of solder 386.8 °C has been determined by DSC analysis. Metallurgical process of ultrasonic soldering has run at 410 °C for 3 s. Soldered joint has been constituted by eutectic ternary structure β-Mg₁₇(ZnAl)₁₂, solid solution α - Mg, which contains Al and Ag elements. At solder-substrate interface, there has been formed intermetallic phase Mg₂Zn₁₁. The highest value of microhardness has been 260 HV. To predict lifetime of soldered joint, calculations in software Thermo-Calc has been performed.

Abstract: The contribution is dealing with suggestion of tool geometry affecting weldability of Mg alloy AZ31B at friction stir welding. Four welding tool made of tool steel H13 (X40CrMoV5-1) with different geometry have been used at welding. Weld joints with high quality have been performed at following parameters: tool revolutions 600 rpm, welding speed 40 to 120 mm/min, angle of inclination 3° and pressure force 38 kN. Area of weld metal accounted fine-grained structure with average dimension of grain 13 μm. Structure is formed by solid solution α - Mg, Al-Mn particles and compound MgAl₃Mn₂. Strength of weld joint reaches value 265 MPa. Fracture areas accounted character of ductile fracture.

Abstract: The Carbon-Carbon composites are nothing but the composites, in which Carbon Fibres are reinforced into a Carbon Matrix. The usage of Carbon-Carbon composite materials is gaining the significant position in the fabrication of Missiles, Space Shuttles and other advanced structures. These materials are primarily expensive in nature, and the drilling cost of these materials will increase the manufacturing cost of the final product. Hence care should be taken in drilling of these materials. The cutting process parameters should be chosen carefully to minimize the damage and improve the quality of the hole drilled. Surface roughness is the most serious problem in the drilling process of Carbon-Carbon composites. This paper discusses the comprehensive analysis of surface finish and the influence of various process parameters as spindle speed, feed rate and drill bit point angle on the surface finish of the drilled holes. These experiments were carried out on a CNC drilling machine at Anna university campus, Chennai, India. The drilling of Carbon-Carbon composite material has been done by using three different drill bit materials i.e. TiN coated carbide, Solid carbide and High Speed Steel tools with three different point angles. The Analysis of variance technique is used to study the significance of each process parameter on the performance characteristic surface roughness. A L₂₇ orthogonal array is employed to study the influence of process parameters. This paper also presents the comparison of the surface roughness values of drilled holes obtained by using the three different tool materials.

Abstract: Durability of building structures is one of the most important issues in modern construction. It depends on the all materials which the construct comprises. Thus durability of structures determined by the thermal insulation properties. Using of express methodologies for assessment operational stability of insulation materials allows to obtain reliable results and save time and resources.

Abstract: This article deals with time development of basic mechanical properties of steel fibers reinforced high strength concrete (FRHSC). The basic mechanical properties were studied at different age of the fiber reinforced high strength concrete, exactly at the age 12, 15, 18 and 21 hours and 1, 2, 3, 7, 14, 21 and 28 days. The compressive strength was determined by using cubic specimens (100 x 100 x 100 mm). The tensile strength in bending and fragment compressive strength after bending were determined by prismatic specimens (40 x 40 x 160 mm). Bulk density were determined too. The comparison of mechanical properties of fibers reinforced high strength concrete and high strength concrete is in conclusion of this article.