High Strength of Powder Magnetic Cores Made from Powders Coated with Low-Melting-Point Glass

Co-hydrolysis of TEOS and DDS to obtain a modified hydrophobic SiO2 insulation layer for FeSiBC amorphous magnetic powder core with low energy loss

Aim: This study was carried out to examine the core strength of athletes and sedentary people between the ages of 13-18. Methods: 200 male athletes from Samsun and 51 sedentary men who did not do any sports participated in this study. The Plank Fitness Test was applied to measure core strength and the time they could stand without disturbing the plank position was recorded. IBM SPSS Statistics 21 package program was used in the analysis of the data. Before the analysis of the data, Shapiro-Wilk normality test was applied and it was determined that the data did not show normal distribution (p<0.05). The Kruskal-Wallis H test was used to compare the averages of core duration between the groups. Results: According to the findings obtained in the study, a significant difference was found when the durations of the groups in the core test were examined [X2(2) =92,158, p<.05]. This finding shows that the core strength between the groups is different according to the branch. When the averages of the groups are examined, it is determined that the branch with the highest core duration is judo (190.53 sec.), followed by taekwondo (158.18 sec.), football (158.01 sec.), sedentary (107.73 sec.) and basketball (69.55 sec.) groups, respectively. In addition, it is seen that the results obtained in core times and the results of training age and body mass index values are similar. Conclusion: According to the results of our study, it is noteworthy that those who do individual sports have higher core scores than those who do team sports and sedentary. We think that this difference is due to the fact that the concentration is constantly high in individual sports and the techniques performed accordingly require more core strength. In addition, we can say that the fact that sedentary people get more core points than basketball players is due to the fact that the training age of the participants and the body mass index values of the basketball players are higher than the other participants. In the light of these results, we think that more core training should be included, especially in sports that require high technical skills and strength. Keywords: Team and Individual Sports, Sedentary, Core Strength

For the commercial production of a claw-teeth motor with three-dimensional powder magnetic cores, the design of motors with high-density and high-strength powder magnetic cores were verified by a test motor. The high strength is to focus on the shaping stress of the press die, and employ the stress values of every part to obtain the design of motor core shapes that can guarantee the desired mold's life that is shown by the relation between stress and mold life according to the material's endurance strength distribution. Furthermore, the high strength, which is obtained by the high-strength process, can make sure that the strength of the flat claw-teeth core that has a complicated shape is at a high level to meet the requirements of factory work. With these considerations, the test motor with the designed claw-teeth cores meets all the design requirements.

Poor performance of local binder of foundry core in casting has been a major concern recently. The effect of some local binder on the mechanical properties of a core has been studied in an attempt to develop a suitable core strength using green compression strength, baked compression strength, permeability and collapsibility test. The effect of temperature, water content, baking time, binder quantity and sand fineness on the core behavior strength was observed. The compression strength of baked cores increased with an increase in the quantity of binder added. The collapsibility of the core is a function of the high permeability obtained in the case of Arabic gum. At baking temperature of 200°C and a baking time of 1.5 h the compression strength after baking increases as the percentage of water decreases. The results obtained showed that the binder of molasses, starch and Arabic gum could serve as effective binder of high core strength for core making processes. Key words: Binders, foundry core, core strength.

Ceramic cores used in the casting must exhibit high heat resistance because they come in direct contact with molten metals. Therefore, in this study, ceramic cores with high heat resistance and fracture strength were fabricated using sodium silicate as the binder instead of a commonly used organic binder. In addition, the prepared ceramic core was coated with Si and Si-Na precursors as the inorganic binder to improve the firing strength of the ceramic core. The thermal stability and firing strength of the sample were investigated. The results revealed that the firing strength of the ceramic core was significantly improved up to 15.2 MPa owing to the formation of a glass phase between the ceramic particles, which was formed by the reaction of sodium silicate and the inorganic binder precursor. In addition, the core was completely decomposed in an NaOH solution at a relatively low temperature of 60°C, indicating the excellent elution properties of the sample. These results indicate that the method proposed in this study is suitable for the preparation of ceramic cores with high fracture strength and excellent elution behavior.

Estimation of insitu strength of concrete

A reply to the discussion of “mix design for optimal strength development of fly ash concrete”

Powder magnetic circuits find more and more application in modern electric machines. These magnetic circuits frequently comprise soft magnetic core and powder permanent magnets as a source of magnetic flux of excitation. It is connected with a lot of advantages of these kinds of materials. The main purpose of the work is to design a brushless DC motor with powder permanent magnet and powder soft magnetic core. It was assumed that the powder magnetic core will be prepared from iron powder bonded by resin and permanent magnet will be prepared from powder of Nd-Fe-B melt-spun ribbon. Investigation of technology of magnetic materials was done and presented. Measurements of properties of magnetic materials were considered in design and analysis of motor. During designing process the dimensions and operational parameters of designing motor were assumed. Permanent magnet DC brushless motor with nominal power 250 W and rotational speed 6000 rpm was designed.

Microstructure and properties evolution of silicon-based ceramic cores fabricated by 3D printing with stair-stepping effect control

Microstructure and magnetic properties of soft magnetic powder cores of amorphous and nanocrystalline alloys

In the late 1980's, a national project of super high-rise reinforced concrete buildings using high strength and high quality concrete and reinforcing steel was promoted by the Ministry of Construction of Japan. The project was simply referred to "New RC". This project aimed at producing high strength and high quality concrete of the specified from 30 to 120MPa and high strength and high quality reinforcing steel bars of yield strength from 400 to 1200MPa. After that many experimental data and knowledge of high strength concrete were provided by many researchers. In the middle of 1990's, high strength concrete of the specified 60MPa Class had been used for high-rise reinforced concrete buildings. And high strength concrete of the specified 100MPa Class had been used for high-rise reinforced concrete buildings in the late 1990's. However, long term data of high strength concrete that cannot obtain by accelerating tests was not collected sufficiently. This paper deals with long term data of high strength concrete. Mechanical properties of 80 to 180MPa class high strength concrete at the age of 20 years were examined. Conclusions are as follows. (1) Long-term strength development ratio of sealed specimen and core specimen of mock up column using high strength concrete are increased when water-binder ratio becomes low.(2) Drying shrinkage ratio of 80 to 180MPa class high strength concrete increases between the age of 10 years and the age of 20 years.(3) Core strength and rebound number of mock up column with 80 to 180MPa class high strength concrete are also increased by increase of the age.(4) Elastic modulus and poisson's ratio of 80 to 180MPa class high strength concrete at the age of 20 years can be estimate by conventional estimate equation.(5) Carbonation has not occurred to surface of mock up column with 80 to 180MPa class high strength concrete at the age of 20 years.

With modified water glass as binder and the introduction of micro silicon powders into the core-making process, an improvement was made to the tensile strength and collapsibility of the sand core. The potassium hydroxide, sodium hexametaphosphate and white sugar were applied as the modifiers of water glass. The optimum proportion of the modifiers was determined through the combination of single factor test and orthogonal test. The optimum proportion of water glass, potassium hydroxide, sodium hexametaphosphate and white sugar is 1000: 40: 5: 5 (wt.). In terms of weight, modified binder and micro silicon powders accounted for 2% and 0.6% of sand, respectively. The sand core was hardened by going through a warm core box process, in which the temperature of core box was 150 °C, and the compressed hot air was blown at 120 °C for 40 s under a pressure of 0.2 MPa. As for the sand core bonded with modified water glass, the tensile strength is 2.46 MPa at room temperature (σ0) and 2.49 MPa at 25 °C and 40% RH for 24 h (σ24), which are 2 times more than that with unmodified binder. The bonded strengths of sand core are increased as a result of the reaction between −OH groups from addition of potassium hydroxide and SiO2 particles widely distributed in the sand core. Comparing with the sand core bonded with unmodified water glass, the high temperature residual tensile strength (σr) of sand core bonded with modified water glass under 600 °C for 5 min, is sharply reduced from 0.20 MPa to 0.01 MPa. By the comparison with unmodified water glass, the dynamic viscosity of the modified water glass and the flowability of molding sand using modified water glass are increased from 74 mPa·s and 2.15 g to 80 mPa·s and 2.21 g, respectively. As revealed by FT-IR analysis, new groups including PO3− , PO43− , and Si-O-C appear in the molecular structure of modified water glass, which are beneficial to the collapsibility of sand core.

Effects of surfactants on the physical properties of silicate binders and the mechanical properties of silicate-bonded foundry sand cores

Finemet nanocrystalline magnetic powder cores: Application of binder and warm compaction process

Internal flow and air core dynamics in Simplex and Spill-return pressure-swirl atomizers