Applied Mechanics and Materials Vol. 404

Abstract: Abrasive waterjet machining is one of the non-traditional methods of the recent years which found itself a wide area of application in the industry for machining of different materials. In this paper, the surface roughness of 6061-T6 and 7075-T6 aluminum alloys are being cut with abrasive waterjet is examined experimentally. The experiments were conducted with different waterjet pressures and traverse speeds. It has been found that the surface roughness obtained by cutting material with high mechanical properties is better than that of obtained by cutting material with inferior mechanical properties.

Abstract: In this study, AISI D6 cold work tool steel was machined on lathe by using the CBN tools. AISI D6 work pieces hardness before heat treatment was 22 HRc. Heat treatments were implemented to the work piece at 860-880°C for 40 minutes and it was cooled in oil. In addition the work piece was applied tempering procedure for three times at intervals of 3 hours. The hardness of the work piece after heat treatment was 62 HRc. Experiments were conducted under different depth of cuts, cutting speeds and feed rates by using factorial experimental design on a lathe. The cutting speed of 50, 100 and 150, feed rate of 0.1, 0.15 and 0.2 mm/rev, depth of cut of 0.2, 0.4 and 0.6 125 mm were chosen as the experimental conditions. According to the obtained experimental, it was seen that when the cutting speed, feed rate and depth of cut increases and tool life decreases fast.

Abstract: Based on processing speed and processing accuracy for difficult-to-machine materials, this paper presents a new MEEC processing method, is based on the basic of MEEC increase on-process dressing grinding wheel, grinding wheel non conductive parts won't jam pore, the abrasive dust adhered to the grinding wheel continues to be removed, the grinding wheel always remain sharp, strengthened the grinding effect, greatly improving the grinding efficiency.

Abstract: In this paper microstructure, morphology, elemental composition, phase composition and crystal structure of the sample steel R6M5 were investigate by using the methods of scanning electron microscopy, electron backscatter diffraction (EBSD) analysis and X-ray diffraction (XRD) analysis. Determined that the microstructure of steel R6M5 after hardening and three-time tempering consists of tempered martensite and solid carbide M₆C and MC-type with spherical shape and a diameter of less than 3 μm. Detected that the volume fraction of each carbide amounted to 10.4±0.6% and 2.3±0.4% - for grey and bright carbides, respectively, and that the sizes of bright carbides particles in the microstructure of steel R6M5 are 0.4-4,5 μm, and the sizes of grey carbides particles are 0.5-1.1 μm. XRD analysis showed that the main carbides in the studied steel are carbides М₆С and MC, which have complicated the FCC crystal lattice and the Fd3m spatial group. Determined that carbides are uniform and monocrystalline. ESBD analysis with the support of the XRD analysis showed that carbides spherical shape М₆С fit to Fe₃W₃C composition.

Abstract: The wetting behavior of polymer melts such as HDPE, PP, PC, POM and COC on bulk metallic glass material substrates that are used in polymer micro fabrication like micro injection molding was investigated by sessile drop method at a temperature above the corresponding melting temperatures. Contact wetting angles have been determined on three kinds of bulk metallic glasses: Pd₄₀Cu₃₀Ni₁₀P₂₀, Zr_64.8Cu_15.5Al_8.3Ni_11.4 and La_57.5Al_17.5Ni_12.5Cu_12.5. The equilibrium contact angle has the monotone decrease with the increasing temperature for most polymer melts. Two kinds of wetting behaviors are observed, spanning from 126°, over neutral wetting, to 6°, almost complete wetting. Estimations of the contact wetting angles are presented in different polymer melt temperature. Optimization of process parameter can be chosen according to the wetting ability.

Abstract: Two strength mooring chain steels were used to investigate the stress corrosion cracking (SCC) in synthetic seawater. The resistance of both strength steels to SCC was similar in neutral synthetic seawater. But the failure mechanism was different. For lower strength steel, it is mainly induced by anodic dissolution, while for higher strength steel, by hydrogen embrittlement. The reason was elucidated from their microstructures and corrosion characteristics.

Abstract: In the present work we have studied the phase structure of surface modified layer of austenitic steel 12Cr18Ni10Ti after electrolytic-plasma carbonitriding and nitriding. It was determined that the carbonitriding and nitriding with the subsequent hardening formed carbide and nitride phase. Also it is revealed that steel 12Cr18Ni10Ti after the electrolyte-plasma processing has high hardness. The microstructure of samples surface is presented by martensite and residual austenite. Optimum modes of steel 12Cr18Ni10Ti carbonitriding and nitriding by electrolytic-plasma way have been identified.

Abstract: To obtain the notch strength of the composite modified double base (CMDB) propellant, three-point bending tests on the single-edge U-notched thin plate specimens and uniaxial tensile tests on standard tensile specimens were carried out at 20°C. Experimental data include three parts in different range of the stress concentration factor K_t of specimens. The stress concentration factor K_t of the specimens have a distinct effect on the notch strength in a specific range. When K_t is less than the notch sensitivity factor K_bN which is approximately equal to 1.35, the notch strength of CMDB propellant is approximately equal to its fracture strength and independent of the stress concentration factor of test specimens. When K_t is upper than 2.41, the notch strength change to be steady to a proper value which associate with the fracture toughness of the propellant . This shows that the CMDB propellant is insensitive to notch. The tensile test data is used to predict the value of the notch strength and notch sensitivity factor,and the prediction fit well with the test results of the notched specimens in a specific range.

Abstract: This study deals with the optimization of the process parameters, with regard to multiple performance characteristics, involved in the electrical discharge machining (EDM) of titanium alloy (Ti6Al4V).Based on the grey-Taguchi method were conducted to examine the effect of EDM parameters (pulse current, open voltage, pulse-on-time, and duty factor) on the electrode wear rate, material removal rate and surface roughness. Experimental results indicate that optimal process parameters can be determined effectively so as to improve multiple EDM qualities through this approach. Furthermore, control charts tell us when special causes of variation are impacting machining process. Control charts are basic and powerful tools in statistical process control and are widely used to control various industrial processes. The aim of statistical process control is to explore the predictability of a process. It was found that the EDM process and product characteristics are stable over time.