Advanced Materials Research Vols. 154-155

Abstract: In this article, the nonlinear dynamic responses of drilling shaft system with hydrodynamic forces of cutting fluid were analyzed in deep slot hole drilling. A numerical method is presented to observe the states of the drilling shaft system. Using the proposed method, the periodic orbit of the drilling shaft motion and its period are calculated when the design parameters of drilling shaft system are subject to change, then the stability for dynamic responses of the drilling shaft system can be determined by the Floquet theory. According to the physical character of cutting fluid, the variational constraint approach is introduced to continuously revise the variational form of Reynolds equation at every step of iteration process. The nonlinear hydrodynamic forces of cutting fluid and their Jacobian are solved simultaneously without the increasing of computing efforts. The numerical examples show that the scheme of this study saves computing efforts but also is good precision, and can make a good reference for the dynamic design of drilling shaft system in deep slot hole drilling.

Abstract: A phase field model is used to describe the microstructural development during the ceramic sintering. The evolution of the density is governed by Cahn-Hilliard equation, while the long-range order (lro) parameter fields by the time-dependent Ginzburg-Landau equation. In the simulation, green microstructures that consist of circular particles with different particle-size distributions and green densities have been produced by the stochastic growth model. The porosity of 25.6% was considered. The formation and growth of sintering neck, the seal, spheroidization as well as disappearance of pores and growth of grains are observed during simulation. The simulation results show grain boundary diffusion and surface diffusion are the dominate mechanism at the initial sintering stage. The predicted growth exponent of sintering neck and grain is consistent with the existing theoretical analysis.

Abstract: The effects of multiple ultrasonic frequencies on grinding surface quality of Al2O3-ZrO2 nano-composite ceramics are researched to provide optimization laws for ultrasonic grinding parameters. Some SEM photographs of ultrasonic grinding surface with different frequencies are provided to research the surface quality. The enhanced surface quality of ceramics with ultrasonic grinding is explained as the transition of single abrasive particle removal mode from brittle to ductile, which is resulted from the reduction of equivalent rigidity on surface under ultrasonic vibration. And this phenomenon becomes more evident as frequency increases. Through the XRD experiment, the phase transition from tetragonal phase t-ZrO2 to monoclinic phase m-ZrO2 becomes increasingly obvious by the action of ultrasonic vibration. The compressive stress generated during this phase transition can suppress the initiation and expansion of microcracks on the processing surface. The research shows that, the grinding surface quality with ultrasonic vibration is superior to that without ultrasonic vibration, and increasing ultrasonic frequency can contribute to the improvement of the surface quality.

Abstract: The effect of carbon content on primary austenite stability of high chromium white cast iron(15.0wt.%) was investigated by means of optical microscopy(OM) and energy spectrum spectrometry(EDS).The results indicate that with increasing the concentration of carbon,the carbon of solid solution in the primary austenite increased, while the chromium was on the contrary, The increase of carbon content stabilized primary austenite under the condition that no secondary carbides precipitated, however, once secondary carbides precipitated, the stability of primary austenite deteriorated with the increase of carbon contents. 2.63wt.% C was the critical value of the secondary carbides precipitation in high chromium white cast iron(15.0wt.%).

Abstract: The semi-circular parallel cracks appeared on the film surface with the angles of 45 degree to the sliding direction of SiC ball and the delamination of film quickly occurred after cracking by using a “ball-on-disk” type testing machine. Stress distribution before and after cracking in the film was calculated by FEM analysis. The maximum tensile stress existing in the film at the back-contact edge of ball is the reason for the initiation of semi-circular parallel cracks. The tensile stress normal to interface as well as the shear stress along interface appears at crack tip, and the alternate generation of these two stresses is the main reason for the delamination. The longitudinal normal stress σxx and the maximum principal stress σ1 become bigger after cracking, so that the crack propagation is faster.

Abstract: Through silicon vias (TSVs) provide advanced vertical interconnections solutions for system-in-package (SiP) (such as chip to chip, chip to wafer, and wafer to wafer stacking), wafer-level packaging, interposer packaging. At present the shortest electrical path (vertical electrical feed through) between two sides of a silicon chip is one of the important applications. In order to achieve high density and high performance package, TSVs technology has been developed. And for three-dimensional (3D) MEMS (Microelectromechanical System) packaging, TSVs are the most important enabling technology. In this paper, some advantages of TSVs technology are described, and process flow of TSVs module is introduced firstly. Subsequently, a novel electricity test method of Non-Ideal Planes for TSVs is introduced. Finally, many critical issues and challenges of TSVs are reviewed.

Abstract: The creep rupture behaviour,hardness distribution and microstructure of weldment made by submerge arc welding for W strengthened P92 steel are described in this paper. The cross-weld creep tests were carried out at 923K under stresses in the ranges 130-100MPa. For stress below 120MPa, weld-joints were ruptured by the Type crack, which located in their fine-grained heat affected zone(FGHAZ)with the smallest measured cross-weld hardness. A strong drop in creep rupture strength of weldment was induced by brittle type failure. In addition to coarsening of M23C6 carbides and an equiaxed fine grains in FGHAZ, intermetallic Fe2(Mo,W)Laves phase precipitated on grain boundaries during creep is probably the significant factor caused the type failure.

Abstract: In this paper we have presented an assembly unit equipped with electrothermally actuated microclamps (MCs), piezoelectric pad and rotary table to provide an environment for micropositioning and microclamping of submilimeter parts. The structural material of the system is considered to be <100> oriented Si with 20 µm thickness. Activating MCs, two approaches performed in the simulation procedure and results showed that utilizing 140 nm deposited Chromium thin layer on the U-shape structure as active material, reduces the overall input voltage and temperature in comparison with direct applying of potential difference to Si structure. To obtain more realistic results, both of these methods are simulated using finite element software in line with considering temperature-dependent thermophysical properties for structural and active material due to high operating temperatures. Design strategies and other advantages of using thin layer of chromium as active material are highlighted in the text.

Abstract: The effect of machining conditions on the rolling contact fatigue (RCF) strength of PEEK polymer bearings was investigated. RCF tests were carried out by using bearings machined by different conditions. The surface profile and roughness were observed before and after testing by laser confocal microscope. Pitting and cracking were associated with the different initial surface conditions. From the obtained results, we found that the RCF strength of machined surfaces decreases when the surface becomes rougher.

Abstract: In order to meet the requirements of laser processing technology and quality, the laser bean oblique incidence technique is put forward and focusing laser spots with different shape and incident direction are realized. The relation between the output laser beam spot shape and laser power of high power CO2 laser is studied through the organic glass sampling method. The result indicates that the laser beam cross-section shape presents rectangle and the long-axis length of laser beam has nothing to do with the laser power changes, but the short-axis width increases with the laser power improving. The two-dimension rotary laser head is designed and the laser bean tilt incidence is realized. The formula of the relation between focusing spot coordinate in the processing plane and laser head turn angle, also swinging angle is deduced. The relation between the focusing spot shape and the laser power, defocusing amount, laser head turn and swinging angles is researched through the single-side gummed paper sampling method. The result indicates that the focusing laser spot form is affected by the parameters of laser power, defocusing amount, laser head turn and swinging angles.