Applied Mechanics and Materials Vol. 710

Abstract: In order to decrease the energy consumption of buildings and keep the high thermal comfort of the indoor environment, new types of plasters modified by phase change material (PCM) are developed and experimentally tested. For evaluation of the contribution of PCM admixture to plasters properties, the reference plaster is studied as well. The basic characterization of the tested plasters is done using the measurement of their bulk density, matrix density a total open porosity. For the dry plasters mixtures, the particle size distribution is accessed on laser diffraction principle. Investigation of thermal properties as main parameters affecting the thermal performance of researched materials is done by differential scanning calorimetry (DSC) and transient impulse method. The obtained results proved increased heat storage capacity of the newly developed plasters with incorporated PCM admixture.

Abstract: Fe-Mn-C alloys with different carbon content were investigated. It was found that carbon element effected the SFE of the Fe-Mn-C alloys seriously, SFE increases with increase of carbon concentration. Fe-Mn-C alloys' deformation mechanisms, with SFE increase from 9.04 mJ.m^-2 to 39.99 mJ.m^-2, turn transformation-induced plasticity (TRIP) effect into twinning-induced plasticity (TWIP) effect with carbon concentration increase from 0.16% to 0.98%.

Abstract: This paper investigates the influence of high temperature on geopolymer reinforced by straw fibers from 25°C to 800 °C with a duration of 0 min, 30 min and 60 min, respectively. The effect of straw fiber content on the thermal properties and compressive strength have also been explored. It is found that the optimum range of straw fiber came to be 2-4 % with both excellent thermal insulation properties and a comparable compressive strength. The mechanical strength of the geopolymer with 3% straw fiber subjected to elevated temperatures show that the geopolymer composites possess significantly higher strength and better temperature resistance than the conventional thermal insulation materials. When exposure to 300 °C for 60 min, the specimen gives a satisfied result of 42.08 MPa. And the compressive strength drop is almost under 50% after exposure to 400 °C for 60 min. Thermal analysis is employed to explore the temperature damage.

Abstract: This work examines buckling and kink-band formation in graphene nanosheets (GNSs). GNSs are nanoscale flakes composed of graphene sheets. Expanded graphite was first made, which can be torn apart into GNSs by sonication. A simple but effective approach was adopted to incur buckling in GNSs. Microscopic observations revealed three major modes: the kinking induced by bending, the bulging, and the kink-band caused by in-plane compression. The conditions to cause these modes are discussed. When buckled, the graphene layers undergo sharp kinking. However, the graphene layers can survive kinking without fracture due to their exceptional flexibility. The kink-band in GNSs resembles the kink-band in carbon-fiber composites. However, the scale, the material properties, the micro-structures, and the energy terms involved in forming the kink-band are different.

Abstract: This research is to investigate the properties of compressed building bricks producedfrom Cameron Highlands reservoir sediment. The particle size distribution of the sediments are graded as silt and sand. The sediments used were as total replacement of the normal soils used in the compressed soil bricks. This paper presents the compilation of experimental brick properties; compressive strength, water absorption, microstructure and heavy metal leachingof the compressed sediment bricks. The experimental results shows that increasing use of reservoir sediments decrease the compressive strength andincrease the water absorption. The heavy metal concentrations of the leachates from the leaching test are all within the regulatory limits. The optimum mix is derives from the compressive strength and the water absorption in which in this research is Mix 4, 70% sediment^a, 20% sediment^b and 10% cement,complying with ASTM C129 – Non Load Bearing Bricks [1].

Abstract: The application prospect of conductive rubber composite is introduced. The mechanism of resistance relaxation of conductive rubber composite was expounded. Several representative mathematical models of the resistance relaxation effect of conductive rubber composite were introduced. The influence of external temperature, heat treatment temperature, the amount of conductive filler, the type and the size of stress, nanomodified materials and dispersing additives on the resistance relaxation effect of the conductive rubber composite were discussed respectively. Finally, a brief description of the application status of conductive rubber composite and its summary and outlook were made.

Abstract: The samples with a length of 50mm and cross section area of 20mm2 were machined from extruded P/M Nickel-base superalloy billet and the isothermal deformation tests were carried out at constant strain rate in a vacuum environment using the Thermecmastor. All the samples were deformed to a true strain of 1.04 at deformation temperature 1070°C and 1100°C and strain rate 0.001s-1~1s-1 respectively. The result is the deformation strain rate determine the position and the deformation temperature determine the severity of abnormal grain growth (AGG). The initial grain size and dislocation density is not the only reason to AGG. The AGG is related the recrystallization nucleation process is inhibited in the heat treatment. The AGG region usually has more low energy and low migration rate boundary than other regions.

Abstract: The system damping of electric power systems is influenced by factors of many aspects. In this paper, we analyzed the impact of speed control system on the damping of the whole system in consideration of the Pole-Zero Analysis. The result shows that simple speed control would damp the oscillation, while the power-frequency control would excite the oscillation. Furthermore, the effect of steam turbine response rate on the system damping is analyzed. The time constant of hydraulic servo-motor would determine the response rate of the steam turbine, and as a result, an inflection point exists on the curve which describes the relationship between hydraulic servo-motor time constant and system damping. The result demonstrates that the characteristics of system damping can be used in parameter debugging of steam turbine.

Abstract: According to the requirements of smart substation metering system, a digital interface based on IEC 61850 specification is given, then the functional model of the merging unit is discussed. Meanwhile, according to the actual situation, the author proposes an analog output interface, in order to fit with traditional substation secondary equipment. Then the solution based on TMS320F28335 digital control platform is described, for which the voltage control module of the software and hardware circuits are discussed in detail. The experimental data shows that the proposed merging unit and analog voltage output interface can meet the accuracy standard of electronic transformer in the smart substation.