Solid State Phenomena Vol. 304

Abstract: This research is a comparative study, the use of carbon fiber and steel fiber for Self-Compacting Concrete (SCC). In previous studies, it was proven that the addition of steel fibers can increase the compressive and tensile strength of SCC. While carbon fiber is one of the most widely used materials for structural reinforcement in recent years. Therefore it is necessary to do a comparative study of the use of carbon fiber if applied to SCC. The percentage increase in carbon fiber and steel is 0.5%, 1%, and 1.5%. Then do the testing of: slump test, compressive strength, tensile strength and flexural strength. The results showed the optimal percentage of steel fiber addition of 1.5%, can increase the compressive strength of SCC by 11%. However carbon fiber and steel do not increase the tensile strength of SCC, and tend to reduce flexural strength. Other results show that carbon fiber is not suitable for use in SCC.

Abstract: The great potentials of wood species have not yet been fully tapped in Ecuador in order to propose feasible and eco-friendly alternatives that allow reducing/replacing conventional building materials. This investigation aims to determine the physical-mechanical properties of lightweight bidirectional sandwich-like composite wall panels made of bamboo (Dendrocalamus asper), melina (Gmelina arborea) and balsa (Ochroma pyramidale). To fulfil this purpose, 80 samples from four prototype biopanels were tested in accordance to the current American Society for Testing and Materials (ASTM) standards. The experimental results were validated and compensated by performing a total of 79 finite element analyses (FEA) that in turn allowed evaluating and analyzing both the mechanical efficiency and the biomechanical performance of the proposed biopanels. The results in this investigation showed sandwich-like composite wall biopanels with an enhanced mechanical efficiency that is up to nine times higher than steel, concrete, aluminum, wood and bricks. Results from the biomechanical analyses confirm the practical utilization of the proposed biopanels in low-rise and mid-rise buildings (i.e. between two and ten stories) located in high-risk seismic and windy regions. Thus, its implementation in the actual construction system will definitely implicate important upgrades in terms of structural optimization and sustainable practices. Indeed, the proposed wall biopanels are meant to be used in the rebuilding process of the dramatically affected areas during the 2016 Ecuador earthquake.

Abstract: In this paper, the reaction kinetic mechanism of Fe₂O₃ powder containing carbon was studied by microwave magnetizing roast. Based on the temperature-rise curve and weight loss curve of Fe₂O₃ powder by microwave magnetizing roast, the kinetic parameters of Fe₂O₃ powder microwave magnetizing roast were calculated by non-isothermal methods. The controlling steps of different temperature-rising periods in microwave magnetizing roast process of Fe₂O₃ powder were calculated by the Achar-Brindley-Sharp-Wendworth method. The results indicated that the controlling step of microwave magnetizing roast was phase boundary reaction control of contracted cylinder in 250~450°C, and it was three-dimensional diffusion control of spherical symmetry in 450~650°C. The results showed that the starting temperature of reduction roasting of Fe₂O₃ powder was 250°C, which was lower than that under electrical heating, thereby, it proved in theory that microwave heating can enhance reaction rate.

Abstract: Physical simulation of steel Mn3Ni1CrMo continuous cooling with different speeds from austenitic state was performed using GLEEBLE 3500 complex. The phase transformations are analyzed and the effect of the cooling rate on the structure and hardness is investigated. A continuous cooling transformation diagram of the undercooled austenite decomposition is constructed. It was concluded that it is possible to reduce the hardness of the hot-rolled billet by reducing the cooling rate compared to the existing in the processing at the STELMOR line of PJSC “MMK”, and this will eliminate the heat treatment of welding wire on the hardware processing.

Abstract: Asymmetric rolling with different work roll circumferential speeds is a process that can be used for improvement of mechanical properties of the processed metals and alloys. Development of the model, which allow to calculate the stress-strain state occurring in the microstructure of the ferritic-pearlitic steels during asymmetric rolling, was the main objective of this paper. Macro level models do not take into account the complicated behavior of the ferritic-pearlitic microstructure in the micro scale. Therefore, development of modelling methods, which allow predicting the properties distribution in the metal volume with the behavioral features of the microstructure under the influence of the deformation, was needed. Representative Volume Element (RVE), representing ferritic-pearlitic steel microstructure, was developed. Simulations of the asymmetric rolling process were performed and local deformation of each structural component was predicted. Selected results, as well as discussion of the effect of microstructure on obtained stress and strain distributions, are presented in the paper. Results of multiscale simulation analysis of the deformation characteristics, presented in this study, can be used for optimization of the asymmetric rolling process.

Abstract: There have been no breakthroughs in ferrous metallurgy for the last 80 years. Automation and digitalization arrived, while the actual steel making processes saw almost no changes. Today, almost all industries experience rapid changes. In 2018 we will see a launch of trains that can travel as fast as1,200 km/h. In 2022 we will see aircrafts capable of flying from London to New York in 1 hour. They already know how to grow human arms and legs. And driverless taxis have become extremely popular. Should we be expecting to see a major breakthrough in metallurgy any time soon? In this paper you will learn about this and other problems, as well as possible ways to solve them. Also, the paper focuses on the results of the development of theory, mathematical models and novel processes, which were helpful in the forming of the ultra-high strength materials by combining the conventional methods of forming such as stamping, plate rolling, plastic bending and asymmetrical rolling. The ultimate aim was to manufacture parts having complex geometries of ultra-high strength sheets. Metalworking techniques like asymmetrical rolling gave rise to very high shear strains and it was used for increasing the strength of the materials. The addition of the incremental sheet forming to the varied combinations of conventional forming processes was used for increasing in the flexibility of the manufacturing process for ultra-high strength. The results of the research project were also encompassing numerical simulation and experimental investigations of the combined process accompanied by the development of the theoretical models for the same.

Abstract: The most comprehensive steel tube portfolio is used to produce all kinds of modern energy production and the corresponding auxiliary unit such as boilers and heat exchangers. Multi-rifled seamless steel tubes are distinguished by maximum pressure, heat resistance, strength and durability. Production of multi-rifled seamless steel tubes by cold draw process using multi-rifled mandrel is quite a new technology. Shape and dimension of the drawing tool depend on drawing tube reduction degree, i. e. on the original diameter of the initial tube and final diameter of the tube. The technology of drawing tubes is influenced by process parameters, dimensions of tools and cold forming process conditions. Optimization of the whole forming process naturally involve the FEM analyses and simulation. One of the most important information of the cold drawing process is the load stroke of the tools. The contribution is concerned at the usability of FEM simulation on an evaluation of cold draw forming process condition and prediction of load stroke of the forming tools. DEFORM 2D/3D FEM software is used to compare the result of the drawing force and to determine the appropriate methodology to set FEM simulation of cold forming.

Abstract: Shot peening process could create compressive residual stress and increase surface hardness and hence also used to improve material surface properties in case thermal effect is to be avoided. The shot peening process parameters such as pressure which result in different shot impact velocity could affect the compressive residual stress distribution which results in different post-process material properties. The ability to understand and predict the effect of process parameters on stress distribution could be very useful to control and obtain material properties as required. In this work, a shot peening process commercially available locally was investigated. The residual stress distribution after shot peening of SKD11 was studied using the finite element (FE) technique. A single shot impact was simulated. A maximum velocity with a miximum impact angle was assumed. The computational predictions showed higher compressive residual stress developed with increasing shot velocity as expected due to higher impact energy. However, experimental results suggested that the process arrangement and machine control highly affect the properties of the material after process. The compressive residual stress and surface hardness obtained experimentally was almost unchanged with an increase in pressure from 0.35MPa to 0.6MPa. It was found that, due to machine arrangement, an increase in impact velocity at higher pressure was relatively small and did not observed in all effected area due to fixed arrangement of nozzle and samples. Hence, research results suggested that a detail computational methodology including the effect of unevent impact velocity and impact angle should be employed to increase the predictive ability of the FE model. The current work could be extended to include such effects with no major difficulty to develop useful information for the design of shot peening process for any specific machine and arrangement.

Abstract: Electromagnetic shielding materials are widely used in engineering. Shielding effectiveness is an important index to measure the shielding effect of electromagnetic shielding materials. A method for calculating the shielding effectiveness of electromagnetic shielding materials is discussed in this paper. This method applies the small reflection theory in transmission line theory. Two kinds of materials are selected as samples. Firstly, the shielding performance is calculated by calculation. Then, shielding performance was measured using a network analyzer and coaxial devices. By comparing the above two results, the feasibility of this method is verified. By using this method, the shielding performance with acceptable accuracy can be obtained when the electromagnetic parameters of the material are known. Thus, the limitation for the application of electromagnetic shielding materials is reduced.