An Experimental Study on Mechanical Behaviors of Carbon Fiber and Microwave-Assisted Pyrolysis Recycled Carbon Fiber-Reinforced Concrete

In the last decade, waste carbon fiber-reinforced plastic (CFRP) products have not been properly recycled and reused, and they sometimes cause environmental problems. In this paper, the microwave-assisted pyrolysis (MAP) technology was utilized to remove the resin from the CFRP bicycle frame, which was recycled into carbon fiber. A scanning electron microscope (SEM) and single filament tensile test were used to observe and compare the difference between recycled carbon fiber and normal carbon fiber. The mechanical performances of carbon fiber-reinforced concrete (CFRC) were investigated with static and dynamic tests under three different fiber/cement weight proportions (5‰, 10‰, and 15‰). Three different kinds of carbon fiber were used in this study, normal carbon fiber, carbon fiber without coupling agent, and recycled carbon fiber. The experimental program was tested according to ASTM C39-01, ASTM C293, and ACI 544.2R standards for compression, flexural, and impact test, respectively. From the experimental results, addition of 10‰ of carbon fiber into the concrete exhibited maximum compressive and flexural strength. The impact performance of recycled carbon fiber improved the highest impact number compared with normal carbon fiber under different impact energy.

Application of chaos and extension theory to fault diagnosis of three-phase synchronous generators

This study applied an extension algorithm combined with the Chaos Theory to the fault diagnosis of the three-phase synchronous generator. First, the three-phase synchronous generator is classified, including normal, carbon brush fault, three-phase unbalance, and insulation deterioration, and then by means of hardware measurement circuit and device, electrical signals are measured for each category and a chaotic error scatter map is built through the Chaos Theory to get the chaotic eye coordinates under specific fault categories. Next, the extension algorithm is used to carry out the correlation function and the normalization calculation, evaluating the type of fault to which it belongs. The analysis results show that the proposed method can effectively identify the fault types of three-phase synchronous generators and significantly reduce the amount of feature extraction data, so as to effectively detect the change of fault signals, allowing us to know the operation state of three-phase synchronous generators.

Fabrication of Nanostructured Gradient Tungsten-Cobalt Alloy Using Carbon Deficiency Powder

A nanostructured functionally graded hard alloy was obtained by sintering at temperatures from 1350 to 1410 ° C of two-layer "green bodies", each consisting of layer of powder with normal carbon content (WC-15Co-0.4VC-0.4Cr2C3) and powder layer with deficit of carbon (WC-8Co-0.4VC-0.4Cr2C3). The formation of the η phase (Co3W3C) in the layer with cobalt deficiency causes the migration of cobalt to it and prevents the return of cobalt back in a wide temperature range of temperatures (1350-1410). The porosity of the resulting nanocrystalline hard alloy at 1410 ° C is reduced to 2%, and the maximum hardness of the surface layer with a low cobalt content (10%) reaches 1945HV.

Welded Joint Evaluation for Chromium Controlled Carbon Steel Piping to Improve FAC Resistance

For condensate and feed water piping in nuclear power plants, it is desired to mitigate the pipe wall thinning risk due to Flow-Accelerated Corrosion (FAC). In aspect of material selection, low alloy steels are generally applied to improve FAC resistance. However, low alloy steels are inferior to carbon steels from the point of material cost and construction efficiency due to requirement of post weld heat treatment (PWHT). On the other hand, chromium is known as the most effective element to improve FAC resistance, and it is reported that a certain improvement of FAC resistance is also expected for carbon steels by increasing chromium content to over 0.10 wt%. Such chromium controlled carbon steels are manufactured within the chemical composition range specified by material code of carbon steels, such as ASME B&PV Code Sec.II. Therefore, the amount of alloy content is lower than those for low alloy steels. The authors expect that PWHT can also be exempted for a certain thickness range of chromium controlled carbon steels, according to the exemption condition for normal carbon steels by ASME B&PV Code Sec.III. Furthermore, the chromium controlled carbon steels are generally cheaper than low alloy steels for base materials such as pipe and plate. However, since chromium content of normal welding materials for carbon steels is generally lower than 0.05 wt%, chromium controlled carbon steel welding materials are specially-produced material. It makes the procurability worse compared to normal carbon steel welding materials. Additionally it should be confirmed if the increased chromium content affects the soundness of welded joint. From the above reasons, it is necessary to decide the appropriate welding materials and methods for the chromium controlled carbon steel piping, considering the procurability of welding materials and the soundness of welded joint. In this study, the authors prepared the test pieces which simulate the assumed circumferential butt welded joints, then conducted the mechanical test such as tensile, impact, bend and hardness test to evaluate the soundness of welded joints. Furthermore, the authors evaluated the chromium content distribution of welded joints by using the Electro Probe Micro Analyzer (EPMA), in order to confirm if the chromium content is maintained over 0.10 wt% within the whole expected area.

Evaluation of Risk From Carbon Macro-Segregation in Large Pressure Retaining Forged Nuclear Components

Regions of higher-than-normal carbon content due to carbon macro-segregation have been found in large, pressure retaining forged ferritic steel components in some nuclear reactors. Higher carbon content in ferritic steel can decrease the resistance to fracture from the presence of flaws in the material. Acceptable margins against failure of pressurized components in nuclear safety systems must be maintained throughout their service life to ensure core integrity for all operational and postulated transient loading events. Should carbon macro-segregation substantially reduce the material resistance to fracture in safety components, then the margins against through-wall flaw propagation may fall below those specified by regulatory requirements to ensure adequate component and reactor core integrity. Probabilistic fracture mechanics (PFM) analyses were performed to assess the risk and structural significance of postulated carbon macro-segregation in large, forged pressure retaining components in pressurized water reactors (PWRs). The risk assessment was performed to evaluate several forged components and two classes of loading events. The forged components include the ring and head forgings in the reactor pressure vessel (RPV), steam generator (S/G) and pressurizer. The loading events used in the risk evaluation include pressurized thermal shock (PTS) transient events and a normal RPV cooldown event. The analyses included a range of component dimensions, surface and embedded flaw distributions, various levels of carbon macro-segregation up to and beyond the maximum measured values for the components, and the effects of neutron irradiation, including the effects of potential copper and phosphorus co-segregation. The PFM analyses were performed using the software, Fracture Analysis of Vessels, Oak Ridge (FAVOR). The results from the risk assessment indicate that: acceptable margins against failure are maintained through an 80-year operating interval even if carbon macro-segregation were to be present in RPV, S/G and pressurizer ring and head forgings in PWRs; and the risk associated with the presence of carbon macro-segregation in PWR ring and head forgings is significantly lower than regulatory risk related acceptance criteria.

An Effective Approach Based on Response Surface Methodology for Predicting Friction Welding Parameters

The joining of dissimilar metals is one of the most essential necessities of industries. Manufacturing by the joint of alloy steel and normal carbon steel is used in production, because it decreases raw material cost. The friction welding process parameters such as friction pressure, friction time, upset pressure, upset time and rotating speed play the major roles in determining the strength and microstructure of the joints. In this study, response surface methodology (RSM), which is a well-known design of experiments approach, is used for modeling the mathematical relation between the responses (tensile strength and maximum temperature), and the friction welding parameters with minimum number of experiments. The results show that RSM is an effective method for this type of problems for developing models and prediction.

Blood acid-base balance of sportsmen during physical activity

The aim of this study was to investigate the acid-base balance parameters in blood of sportsmen by physical activity. Before exercise lactate concentration in blood was normal. Carbon dioxide pressure (рСО2), bicarbonate concentration (НСО3 -), base excess (BE), were increased immediately after physical activity lactate concentration increased, while pH, BE, НСО3 -, рСО2 decreased in capillary blood of sportsmen. These changes show the development of lactate-acidosis which is partly compensated with bicarbonate buffering system and respiratory alkalosis. During postexercise recovery lactate concentration decreased, while рСО2, НСО3 -, BE increased. The results of this study can be used for diagnostics of acid-base disorders and their medical treatment for preservation of sportsmen physical capacity.