Papers by Keyword: ASR

Abstract: A significant number of German concrete motorway pavements have shown damage only a few years after construction. The alkali-silica-reaction (ASR) is often one of the reasons for this damage. German guidelines and regulations focus on the optimisation of the concrete composition to avoid damage due to ASR. Moreover, diverse research projects have dealt with the development and optimisation of ASR performance test methods with and without external alkali supply. However, the influence of other parameters on the occurrence and intensity of a damaging ASR had not yet been taken into account. Such parameters include, e.g., insufficient curing and the modifications of concrete’s porosity due to the use of slip form pavers. Likewise, the increased traf-fic loading had not yet been considered. The Federal Institute for Materials Research and Testing (BAM) assesses these parameters and processes in a number of projects. These projects aim primarily to increase the durability of the concrete pavements, in particular by improving preventive measures that may be taken before or after the construction of concrete pavements. This paper gives a short overview of BAM’s projects concerning ASR in concrete pavements. Furthermore, results regarding the influence of the cyclic traffic loading on ASR are presented.

Abstract: In the present study, several series of pulse current electrodeposition experiment have been carried out at 25 °C in various electrolyte bath under different current densities to find the suitable electrodeposition condition for fabricating Mn-Cu alloys coating. The deposition kinetic of Mn-Cu alloy was assessed from the measurement of cathodic polarization behavior in selected electrolyte bath. The uniformity of Mn-Cu alloy coating, and its composition were studied by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) analysis. The results shows that a dense, adherent, smooth and uniform Mn-Cu alloy coating can be deposited on SUS 430 substrate with relatively high deposition rate. The evaluation of coating area specific resistance (ASR) at 700 °C shows a value of 0.04 Ωcm². This result indicates that Mn-Cu alloy is promising as alternative coating materials for SOFC interconnect.

Abstract: Changing the lamellar morphology of pearlite to a globular morphology significantly enhances the formability of pearlite-ferrite steels. This change is conventionally achieved by soft annealing. Annealed structures possess low yield strength and excellent ductility and this ensures their good cold formability. The problems of these technologies lie not only in long processing times, but also in high energy consumption which makes the final product quite expensive. The time necessary for cementite spheroidization can be shortened by unconventional heat treatment around A_c1 temperature combined with deformation applied at various processing stages. Several processing methods were utilized for spring steel 54SiCr with ferrite-pearlite original microstructure and lamellar pearlite morphology. The hardness of this structure reached 290 HV10. Three main strategies were tested in this work, using either tensile and compression deformation with following hold applied at heating temperature, temperature cycling around A_C1 temperature, or deformation cycles applied at heating temperature. First of all, various heating temperatures in the region of 680-740°C were tested to determine the most suitable heating temperature for this steel. Subsequently, the influence of the character and intensity of applied deformations on cementite spheroidization and ferrite grain refinement were investigated. Carbide morphology and distribution were determined by the means of light and scanning electron microscopy and mechanical properties were determined by hardness measurement. Spheroidized carbides evenly distributed in fine ferrite matrix were obtained after the optimization of processing parameters.

Abstract: Speech feature extraction is discussed. Mel frequency cepstral coefficients (MFCC) and perceptual linear prediction coefficient (PLP) method is analyzed. These two types of features are extracted in Lhasa large vocabulary continuous speech recognition system. Then the recognition results are compared.

Abstract: This paper investigated the effect of clay brick powder (BP) on expansion behaviors of mortar bars using rhyolite aggregates, local volcanic rock from central Thailand. The accelerated test condition (ASTM C 1260) was used in this study. The expansion of samples with varying percentages of BP as cement replacement were compared to those of cement mortar bars. The brick powder significantly reduced expansion of mortar bars. As the percent replacement increased, the larger percentage of expansion reduction was. Due to the possible negative effects on mechanical properties of the mixture, the amount of the supplementary materials should be kept as low as possible. The mixture with 30% BP which yielded expansion below 0.05% at 14 days after acceleration, was chosen to study the effect on strength reduction, compared to the plain mixtures under normal and accelerated conditions. Compressive strength of BP samples under accelerated condition was slightly lower (approx.4%) than that of under normal curing while the strength of control mix was significant lower (of 18%) under similar conditions.

Abstract: It is known for rendering more torque in operation at low speed and suitably attaining high performance dynamic control for the inverter. This paper describes the research of ASR strategy for the spindle inverter control in CNC machine tool. The principles of the vector control and formulas for the coordinate transformation are illustrated. The accuracy of the torque depends on the accuracy of the motor parameters used in the control. So the powerful parameter tuning function should be enabled for all kinds of spindle to run effectively. The response of ASR will be perfect if the switching frequencies is used which is usually constant and set by the user.