Acta Polytechnica. 2019, vol. 59
http://hdl.handle.net/10467/81423
2024-03-21T23:19:28ZTHE CHARACTERISTICS OF Al-Si COATING ON STEEL 22MnB5 DEPENDING ON THE HEAT TREATMENT
http://hdl.handle.net/10467/107825
THE CHARACTERISTICS OF Al-Si COATING ON STEEL 22MnB5 DEPENDING ON THE HEAT TREATMENT
Kolaříková, Marie; Chotěborský, Rostislav; Hromasová, Monika; Linda, Miloslav
The coating on the 22MnB5 steel is intended to protect it against oxidation during the forming process. This steel is hot-pressed. A preheating before the pressing and subsequent hardening in the tool affects the properties of the AlSi coating. This study summarizes the results of investigating the effect of heat treatment parameters on the formation of intermetallics in the AlSi coating. The chemical analysis of the coating was performed by the EDX and EBSD method and the mechanical properties were determined by the Hysitron TI 950 TriboIndenter™ system. The result of this study is that, due to a diffusion during the heat treatment, the brittle coating was transformed into a tougher phase.
2019-01-01T00:00:00ZCOMMON CROSSING CONDITION MONITORING WITH ON BOARD INERTIAL MEASUREMENTS
http://hdl.handle.net/10467/107824
COMMON CROSSING CONDITION MONITORING WITH ON BOARD INERTIAL MEASUREMENTS
Sysyn, Mykola; Nabochenko, Olga; Gerber, Ulf; Kovalchuk, Vitalii; Petrenko, Oleksiy
A railway turnout is an element of the railway infrastructure that influences the reliability of a railway traffic operation the most. The growing necessity for the reliability and availability in the railway transportation promotes a wide use of condition monitoring systems. These systems are typically based on the measurement of the dynamic response during operation. The inertial dynamic response measurement with on-board systems is the simplest and reliable way of monitoring the railway infrastructure. However, the new possibilities of condition monitoring are faced with new challenges of the measured information utilization. The paper deals with the condition monitoring of the most critical part of turnouts - the common crossing. The application of an on-board inertial measurement system ESAH-F for a crossing condition monitoring is presented and explained. The inertial measurements are characterized with the low correlation of maximal vertical accelerations to the lifetime. The data mining approach is used to recover the latent relations in the measurement’s information. An additional time domain and spectral feature sets are extracted from axle-box acceleration signals. The popular spectral kurtosis features are used additionally to the wavelet ones. The feature monotonicity ranking is carried out to select the most suited features for the condition indicator. The most significant features are fused in a one condition indicator with a principal component analysis. The proposed condition indicator delivers an almost two-time higher correlation to the lifetime as the maximal vertical accelerations. The regression analysis of the indicator to the lifetime with an exponential fit proves its good applicability for the crossing residual useful life prognosis.
2019-01-01T00:00:00ZEVALUATING SHEAR STRENGTH OF SAND- GGBFS BASED GEOPOLYMER COMPOSITE MATERIAL
http://hdl.handle.net/10467/107823
EVALUATING SHEAR STRENGTH OF SAND- GGBFS BASED GEOPOLYMER COMPOSITE MATERIAL
Al-Rkaby, Alaa Hussein Jassim
Geopolymer has been emerging as a novel and sustainable replacement for the traditional soil improvement materials, such as ordinary Portland cement OPC and lime, which have severe environmental impacts. In this paper, a series of unconfined compression and triaxial tests were conducted on sand and sand - ground granulated blast-furnace slag (GGBFS) based geopolymer. A solution of sodium silicate and sodium hydroxide was employed for the geopolymerization process. Results revealed that adding the GGBFS resulted in a significant increase in the strength properties. This result indicates that geopolymer acted as a cementation agent, providing better bonding between the sand particles and consequently improving the performance of the treated sand.
2019-01-01T00:00:00ZCZECH WW2 CONCRETE FORTIFICATIONS: CORROSION PROCESSES AND REMEDIATION METHOD BASED ON CRYSTALLIZING COATING
http://hdl.handle.net/10467/107822
CZECH WW2 CONCRETE FORTIFICATIONS: CORROSION PROCESSES AND REMEDIATION METHOD BASED ON CRYSTALLIZING COATING
Pazderka, Jiří; Reiterman, Pavel
Concrete is a relatively new structural material, hence the remediation of concrete structures is very rare. There are a lot of concrete fortifications in the Czech Republic, which were built just before WW2. These bunkers formed a long defensive line along the Czechoslovak borders as a protection against Hitler’s army. Today, after 80 years, many of the bunkers are listed as Czech national technical monuments with a strict protection of their historical authenticity. The article describes the technical survey and the possible conservation method of a selected concrete fortification, which exhibits a number of moisture related problems. The studied two-storey, heavily fortified bunker is situated close to the northern border of the Czech Republic, former Czechoslovakia. A detailed survey of the building includes the analysis of the interior environment parameters and laboratory testing of the used concrete. A long-term diagnosis identified the main problem, which lies in the inhomogeneity of the used concrete and the relating massive water ingress. However, the monitored bunker currently does not serve as a military structure and, therefore, a simple solution to improve the internal environment was suggested on the basis of the conducted measurements. With respect to the main causes of failures, the authors suggested a conservation method based on using a crystallizing coating. The suitability of the method was first verified under laboratory conditions and then also on the real bunker.
2019-01-01T00:00:00Z