NISCAIR Online Periodicals Repository Community: IJEMS Vol.18 [2011]

Characterization of fiber distribution in steel fiber reinforced cementitious composites with low water-binder ratio

Mon, 28 Nov 2011 22:58:59 GMT

Title: Characterization of fiber distribution in steel fiber reinforced cementitious composites with low water-binder ratio

Authors: Liu, Jiaping; Li, Changfeng; Liu, Jianzhong; Du, Zhaojin; Cui, Gong

Abstract: Image analysis technique is introduced to characterize fiber distribution in steel fiber reinforced cementitious composites. Through cutting and polishing of specimen, image acquisition of specimen surface, extraction of fiber feature, and measurement of related fiber parameters, i.e., dispersion coefficient and orientation factor, are given to quantitatively analyze fiber distribution. Effects of specimen size, fiber volume fraction and aggregate characteristics on fiber distribution are discussed. Results show that the dispersion coefficient increases with the increase of specimen size and with the decrease of fiber volume fraction and aggregate size, but the changes are small. The orientation factor of fiber is affected by boundary effect, while the influence will get smaller and smaller with the increase of specimen size, especially for the specimen size larger than 50 mm. With the increase of fiber volume fraction, the orientation factor in each direction deviates from 0.5, and the orientation factor in y-direction decreases. Aggregate characteristics have a significant effect on fiber distribution, with the increase of aggregate size, the orientation factors in x- and y- directions increases, while that in z-direction decreases. With the increase of aggregate content, the orientation factors in y- and z-directions increase, while that in x-direction decreases.

Page(s): 449-457

SIMO type universal mixed-mode biquadratic filter

Mon, 28 Nov 2011 22:58:59 GMT

Title: SIMO type universal mixed-mode biquadratic filter

Authors: Liao, Wen-Bin; Gu, Jyh-Cherng

Abstract: A SIMO (single input and multiple outputs) universal mixed-mode (including voltage, current, transadmittance, and transimpedance modes) biquad with one input (a single voltage or current input) and eight outputs (five voltage outputs and three current outputs simultaneously) by using three differential difference current conveyors (DDCCs), four resistors, and two grounded capacitors, is presented in this paper. The proposed biquad filter can realize voltage, current, transadmittance, and transimpedance modes universal filtering responses (lowpass, highpass, bandpass, bandreject, and allpass) from the same topology. Moreover, the new mixed-mode biquad also features the (i) use of two grounded capacitors, (ii) orthogonal control of w₀ and Q and (iii) high output impedance of three current outputs. H-Spice simulation results with TSMC 0.25 μm process and ±1.25 V supply voltages verify the theoretical predictions.

Page(s): 443-448

Analysis of the kerf angle of the granite machined by abrasive waterjet (AWJ)

Mon, 28 Nov 2011 22:58:59 GMT

Title: Analysis of the kerf angle of the granite machined by abrasive waterjet (AWJ)

Authors: Karakurt, Izzet; Aydin, Gokhan; Aydiner, Kerim

Abstract: Abrasive waterjet (AWJ) cutting is one of the fastest growing machining processes which can machine almost any engineering material. However, the cutting capability of AWJ in terms of kerf quality is one of the major obstructions limiting its applications. Kerf angle, an important cutting performance measure, is a special geometrical feature inherent to AWJ machining and its high values are undesirable. It reflects the inclination of the kerf wall from the top surface to the bottom of the kerf. In this study, effects of process parameters and the material properties (i.e. textural properties) of the granites on the kerf angle are experimentally investigated. The design philosophy of Taguchi was followed to conduct experiments. Analysis of variance (ANOVA) was used to evaluate data obtained to determine the major significant process factors statistically affecting the kerf angle of the granites. The results revealed that the grains and their boundaries, the uniaxial compressive strength as well as the mineral compositions (especially feldspar and quartz) play the most important role for the kerf angles in the granites as material properties. Additionally, the most significant process factors influencing the kerf angle of the granites are statistically determined as the traverse speed, and the standoff distance.

Page(s): 435-442

Residual stress evaluation in butt-welded steel plates

Mon, 28 Nov 2011 22:58:59 GMT

Title: Residual stress evaluation in butt-welded steel plates

Authors: Jeyakumar, M; Christopher, T; Narayanan, R; Rao, B Nageswara

Abstract: Thermo-mechanical finite element analysis has been performed to assess the residual stress in the butt-weld joints of 2.25Cr1Mo low-alloy-ferritic steel plates and ASTM36 steel plates utilizing the commercial software package ANSYS, employing 2D plane stress models. Temperature dependant properties of the materials are specified. The radial heat flux distribution is considered on the top surface of the weldment. Convective and radiative heat losses are taken into account through boundary conditions for the outward flux. The present 2D plane stress analysis results are found to be in good agreement with existing 3D finite element analysis and experimental results. 2D welding simulations are not only reducing the complexity of the problem, but also providing the nature of residual stress in weldments with reasonable accuracy.

Page(s): 425-434