Preparation and properties of gradient structure concrete member
Based on the dense packing powder theory, the refining and self-healing principles, and hydrophobic treatment, the special surface-layer materials and design are proposed in gradient structure concrete (GSC) member. According to service behavior, the GSC member is divided into serial structure and parallel structure. And it is fabricated corresponding to structural parameters by stacked press process, or pulled clapboard method, or suspended nets method. Use of small and full scale specimens for testing, the results are shown that: 1) the surface-layer strength of the GSC component improved by 30%, compared to that of a conventional single-layer component; 2) the width of the crack ranges from 0 to 0.1mm in the GSC component, whereas a conventional single-layer component are distributed with visible cracks(0.2–0.5mm);3) The permeating depth and chloride diffusion coefficient of the GSC component is respectively 0mm and 6.3×10–13 m2/s, whereas a conventional single-layer component is 15mm and 12.8×10–13 m2/s.
EFFECT OF THE COMPONENT GRADIENT DISTRIBUTION ON THE STRENGTH OF CEMENT-BASED COMPOSITE MATERIALS
A structural model of cement - based functional gradient materials is put forward based on the concept of gradient structure. The relationships between the gradient distributions of the components and fibers in the cement-based materials were investigated. The results indicate that the continuous gradient change in the components can be obtained using multi-layer vibration method. The bending and compressive strengths of concrete and mortar (FGDCM) reinforced with fibers with gradient distribution were greatly increased in comparison with homogeneous distribution.
Surface roughness monitoring by singular spectrum analysis of vibration signals
Abstract This study assessed two methods for enhanced surface roughness (Ra) monitoring based on the application of singular spectrum analysis (SSA) to vibrations signals generated in workpiece-cutting tool interaction in CNC finish turning operations i.e., the individual analysis of principal components (I-SSA), and the grouping analysis of correlated principal components (G-SSA). Singular spectrum analysis is a non-parametric technique of time series analysis that decomposes a signal into a set of independent additive time series referred to as principal components. A number of experiments with different cutting conditions were performed to assess surface roughness monitoring using both of these methods. The results show that singular spectrum analysis of vibration signal processing discriminated the frequency ranges effective for predicting surface roughness. Grouping analysis of correlated principal components (G-SSA) proved to be the most efficient method for monitoring surface roughness, with optimum prediction and reliability results at a lower analytical-computational cost. Finally, the results show that singular spectrum analysis is an ideal method for analyzing vibration signals applied to the on-line monitoring of surface roughness.