Applied Mechanics and Materials Vol. 421

Abstract: Electrochemical polishing (ECP) is a promising approach to finishing surface to achieve high quality of surface. However, it cannot satisfy requirements of mirror finishing yet. In this paper, a mirror finishing method for cold rolling rollers is proposed. The whole process of the surface finishing can be divided into two phases: electrochemical polishing and mechanical grinding. An anodic film is formed exception for anodic dissolution during ECP. A small amount of the anodic film and metal material are removed by abrasive paper in mechanical grinding. Activated metal surface is exposed again and dissolved in electrochemical reaction after mechanical grinding. Residual of anodic film protects rollers. It is a cyclic process of mirror finishing. Experimental results showed that a mirror finishing surface of up to Ra0.02-0.05μm can be obtained by using this method and that it is effective and efficient.

Abstract: Warm forging is most commonly used for production of die forgings which are manufactured by means of precise forging. As compared to cold forging, warm forging enables to reduce forging forces size considerably. Development of warm forging technology is connected to formability and plasticity research of forged material at warm temperatures. This contribution brings a methodology for optimal forging temperature determination from recommended interval of warm temperatures used for chromium-manganic steel 16MnCr5. The given steel is appropriate for case hardening and precise die forgings production. For the purpose of verification of steel forgeability at the recommended interval of warm forging temperatures 600, 650, 700 and 750 °C technological test of upsetting according to Zidek is used. The main factor of plasticity for optimal warm temperature selection from examined temperature interval is value of reduction of area that was determined by tensile test. Numeric simulation of forging process in closed die confirmed correct plastic flow of steel 16MnCr5 at recommended forging temperature 700 degrees of Celsius.

Abstract: On a 45nm logic product that suffered special pattern function failure, electrical failure analysis identified the failure as soft failure and localized the failure addresses. PVC (Passive Voltage Contrast) was used to narrow down suspected process steps to M1 or below layers, FIB (Focus Ion Beam) and TEM (Transmission Electronic Microscope) approaches were used to identify the actual root cause and failure mechanism.

Abstract: Two-layered microwave absorbers are designed for the achievement of low reflection coefficient for wide angles of oblique incidence at the frequency of intelligent transport system (5.9 GHz). Magnetic composite sheets were fabricated with carbonyl iron (CI) and Co₂Z hexaferrite particles in rubber matrix. On the basis of transmission line theory, reflection loss has been calculated with variation of incident angles for both transverse electric (TE) and transverse magnetic (TM) polarization. The minimum reflection loss (less than-20 dB) is predicted at 5.9 GHz for the laminated composites of Co₂Z/CI. At the optimum thickness of the composite layers, a low value of reflection loss (less than-10 dB) is predicted for wide incidence angles up to 60°. The two-layer composites laminate can be proposed as the high potential microwave absorbers for improvement of electromagnetic environment in ITS operation.

Abstract: In the experiment, 24 samples of data has been tested in real machining by using uncoated, TiAlN coated, and SN_TR coated cutting tools of titanium alloy (Ti-6Al-4v). The fuzzy rule-based model is developed using MATLAB fuzzy logic toolbox. Rule-based reasoning and fuzzy logic are used to develop a model to predict the surface roughness value of end milling process. The process parameters considered in this study are cutting speed, feed rate, and radial rake angle, each has five linguistic values. Nine linguistic values and twenty four IF-THEN rules are created for model development. Predicted result of the uncoated, TiAlN coated, and SN_TR coated has been compared to the experimental results, and it gave a good agreement with the correlation 0.9842, 0.9378 and 0.9845, respectively. The differences of the uncoated, TiAlN coated, and SN_TR coated between experimental results and predicted results have been proven with estimation error value 0.00025, 0.0015 and 0.0008, respectively. It was found that by applying SN_TR coated cutting tools with the recommended combination of linguistic values might gave best surface roughness values.

Abstract: The effects of yttrium (Y) on microstructures and mechanical properties of aluminium alloy were investigated in detail by scanning electronic microscope (SEM), energy dispersive spectrum (EDS),X-ray diffraction and tensile test. The results show that the trend of alloys tensile strength and elongation with increasing of the Y content is a broken line. When the Y content is increased up to 0.30%, the tensile strength and elongation are 105MPa and 10.50% respectively, meanwhile, the fractograph exhibited typical ductile dimple fracture pattern. Then the alloy performance is best. The high strength of aluminum alloy is attributed to the size of Al₂Y phase. Addition of Y above 0.30% in aluminum alloy may generate more the coarse Al₂Y particle. It can induce the decrease in the material performance.

Abstract: A new sintering method which considering the heat storage in iron ore sintering processis put forward in this paper.By means of thermal analysis, the kinetic properties of sintering burden with different proportion of coke are studiedand a few kinds ofreaction models are discussed by the liner correlation calculation.The results suggest that the oxidizingdecomposition of sintering burden can be described as a first - order chemistry reaction.Activation energies of three different sintering burdenswith different proportion of solid fuelare determined in this paper,thus can provide data basefor the new sintering method and heat storage model.

Abstract: To increase the solder joint robustness, researches and studies on composite solder carried out by many researchers in an effort to develop viable lead-free solders which can replace the conventional lead-based solders.This paper reviews the fabrication processes of the lead-free composite solder and its non-metal reinforcing effects to the suppression of intermetallic formation. Most researchers using different solder fabrication methods have found that byadditions of non-metal reinforcement from micron up to nanoparticle size had suppressed the intermetallic compound formations of lead-free composite solders.

Abstract: The aim of this study was to optimize the compaction process of a composite solder fabricated via powder metallurgy route, before details study were conducted in the next stage. Powder of Sn, Cu and Si₃N₄ were carefully weighted, mixed and blended in a mechanical alloying machine. Si₃N₄ were added to the Sn-0.7Cu solder as reinforcement.After 6 hours of mixing and blending, the powders were later compacted into a thin disc at 5 different pressures. Densities and volumes of the compacted samples were then obtained by using MicromeriticsAccuPyc II 1340 Gas Pycnometer. All data were analyzed and compared with each other in order to select the best parameter for compaction pressure. Results showed that at 140 bars, the porosity percentage is the lowest. Hence, it was decided that 140 bars is the best parameter for compaction process.

Abstract: The aim of this study is to investigate efficiency of stainless steel powder inoculation into pure aluminum for microstructure refinement. Refiners consisting of pure aluminum powder (powder size: 106~180m) and stainless steel powder (powder size: 25~53m) have been fabricated through spark plasma sintering (SPS). The stainless steels used in the study include SUS304L, SUS316L and SUS434L. SUS 304L powder has achieved a great grain refinement in cast aluminum, for which fading phenomenon has been considerably avoided. SUS316L and SUS434L powders develop fine dendrite structures, which can lead to high hardness of cast aluminum.