Key Engineering Materials Vols. 353-358

Abstract: Based on the mathematical similarity of the eigenvalue problem of the Reddy’s third-order plate theory (RPT) and the classical plate theory (CPT), relationships between the solutions of axisymmetric vibration or buckling of functionally graded material (FGM) circular plates based on RPT and those of isotropic homogeneous circular plates based on CPT are presented, from which one can easily obtain the RPT solutions of axisymmetric vibration or buckling of FGM circular plates expressed in terms of the well-known CPT solutions of isotropic circular plates without much tedious mathematics. Effects of rotary inertia are not considered in the present analysis. The relationships obtained from the present analysis may be used to check the validity, convergence and accuracy of numerical results of FGM plates based on RPT, and also show clearly the intrinsic features of the effect of transverse shear deformation on the classical solutions.

Abstract: The current method of soil nail construction in Hong Kong is both labour intensive as well as expensive and a search for new soil nail material is required. In the present pilot test, light weight high strength and high corrosion resistance GFRP pipe with Tube a’ Manchette grouting technique is used as soil nail instead of the conventional steel reinforcement. It is found that this material can be handled easily on site with difficult access. From extensive laboratory as well as field tests, it is demonstrated that this new soil nail technique has various advantages for use in Hong Kong and many developed cities. The field test results on this innovative soil nail will be discussed in this paper.

Abstract: The viscosity-temperature curve of Bi melt showed that the viscosity values deceased with the increase of temperature. However, the discontinuous changing pattern took place on the viscosity curve. Viscosity of Bi melt can be divided into three parts as high temperature zone, moderate temperature zone and low temperature zone according to its change rate with temperature. The temperature ranges of the abnormal viscosity change were about 400~430°C and 610~640°C. With the DSC analysis, the abnormal phenomenon was explored from the microscopic structure viewpoint. It was assumed that the change from inhomogeneous atom configuration to homogeneous one led to the discontinuous variation, which is related to the bond transformation with the increase of temperature in melt Bi.

Abstract: A series of numerical model tests were performed to investigate the behaviour of the anisotropic rock surrounding circular excavations under high confining pressures. The aim was to provide information on the formation of fractures and failure around deep level rock tunnels under controlled conditions. Solid cubes containing a circular hole were confined to a vertical pressure with same as the confinement in the horizontal directions. In this modeling, the inhomogeneous rock is generated by using Weibull parameters which are related to the microstructural properties determined by crack size distribution and grain size. The fracture angle is assumed to be 45o. The observed failure zone around the excavation was simulated using both the maximum tensile strain criterion and Mohr-Coulomb criterion respectively (as the damage threshold). And RFPA (Realistic Failure Process Analysis) code was used as the calculating tool in this modelling, three opening modes are simulated and compared. Computational model predictions that include crack propagation and failure modes of rock show a good agreement with those of the observation in site. It is pointed out that the damage evolution of EDZ strongly depends on the inhomogeneous, the excavation mode, anisotropic property, and the various loading conditions. Concerning the existence of a weak plane, the amount of displacement at the side wall of the tunnel was quite large, since the shear deformation occurred in EDZ. The model is implemented in RFPA code and is able to represent the change in fracture patterns between the solid and jointed parts. This provides confidence for the application of the numerical model to the design of rock tunnels at great depth.

Abstract: Based on Green and Lindsay’s generalized thermoelasticity theory with two relaxation times, a two-dimensional coupled problem in electromagneto-thermoelasticity for a rotating half-space solid whose surface is subjected to a heat is studied in this paper. The normal mode analysis is used to obtain the analytical expressions for the considered variables. It can be found electromagneto-thermoelastic coupled effect in the medium, and it also can be found that rotation acts to significantly decrease the magnitude of the real part of displacement and stress and insignificantly affect the magnitude of temperature and induced magnetic field.

Abstract: Large particle-size, shallow groundwater level, and large permeate coefficient are the characteristics of gravel stratum, which may results in large ground deformation. Ground deformation depends on several factors. Using the RFPA2D-Flow software exploited by the Center for Rock Instability and Seismic Research of Northeastern University (CRISR), the seepage-stress-deformation coupling rules of soil, which are influenced by different soil distributing, drawdown, enclosure and excavating, were analyzed, and the deformation of gravel in the dynamic balance due to the interaction between seepage and stress is studied.

Abstract: The difference in microstructures of the base metal (BM), weld metal (WM) and heat-affected zone (HAZ) in the weldment is one of the major reasons for the failure of the welded equipments, which can be essentially attributed to the non-homogeneous corrosion occurred electrochemically on the weldment. Therefore, it is necessary to explore the corrosion properties of weldment. In this paper, the electrochemical behavior of SPV50Q steel weldment was investigated. The polarization curves of BM, WM and HAZ in 5wt.%NaCl-0.5wt.%HAc solution containing H2S were measured by potentiodynamic polarization. Interface characterization was also conducted by electrochemical impedance spectroscopy (EIS). The results show the anodic curves are almost same regardless of various pH or H2S content, but the cathodic curves show some difference. Relatively large variation in corrosion current density (icorr) obtained by fitting technique exists among BM, WM and HAZ. icorr of WM and HAZ is larger than that of BM, and icorr of WM is maximum. According to EIS results, polarization resistance (Rp) increases in the orders of WM, HAZ and BM. It is concluded that WM and HAZ are less resistant to corrosion than BM, which can be correlated to the premature failure of the weldment serviced in H2S-containing environment such as sulfide stress corrosion cracking (SSCC) and /or stress oriented hydrogen-induced cracking (SOHIC) etc.

Abstract: Stress corrosion cracking (SCC) of austenitic stainless steel serviced in aggressive environment often occurs in power, petrochemical industry, and leads to premature equipment failure and great economic loss. This paper focuses on the problem of the SCC on the 304L stainless steel nozzle of a hydrogenation reactor, which is caused due to on-line alkali cleaning. Susceptibility for SCC was evaluated by Slow Strain Rate Test (SSRT) for as-rolled and sensitized 304L stainless steel in low concentration sodium hydroxide solution with high temperature. The effects of different strain rates, different concentration of sodium hydroxide and different solution temperatures on SCC were investigated. On the basis of this, the contrast tests were also performed in high temperature pure water. After SSRT, fractograph of the fractured specimens was analyzed by using scanning electron microscopy (SEM).

Abstract: For applying acoustic radiation force to manipulate biomaterials such as cell, DNA, bio-macromolecule without contact, stationary sound field of an ultrasonic transducer was computed numerically. With the numerical data about the sound field, spatial distribution of the acoustic radiation force was analyzed. Besides the radiation force in the axial direction, trapping forces in the lateral direction were discovered. By moving the reflector continuously and carefully, positions of trapping wells were changed simultaneously, as the result, non-contact manipulation of micro cells was implemented.

Abstract: Superelastic shape memory alloys (SMAs) can experience large strains up to 8~10% and restore residual strains just by removing the stress. By employing this unique characteristic of SMAs, a new beam-to-column connection is presented in this paper. The proposed SMA connection consists of an extended end-plate, eight long shank Nitinol SMA bolts, beam flange ribs, beam web stiffeners and continuity steel plates for reinforcing column flanges. In order to predict the behavior of SMA connection, 3-D solid finite element models are set up in ANSYS. The numerical results indicate that the local buckling of beam is avoided and a plastic hinge forms at beam-to-column interface when the moment-carrying capacity of bolt cluster is below the elastic flexural capacity of connecting beam. The SMA connection shows stable moment-rotation hysteresis curves with re-centering capability, which demonstrates the connection’s self-healing deformations function. Far different from energy dissipated by steel yield in traditional connection, the SMA connection shows moderate energy dissipation capacity, and this amount of energy is mainly dissipated by the superelastic behavior of SMA bolts. Moreover, the connection model shows a large inelastic rotation capacity beyond 0.03 rad. The ductility of SMA connection is deeply influenced by the length of SMA bolts, and the 2.2 times length of normal bolt is suggested for SMA bolts.