Papers by Keyword: Tensile Stress

Abstract: The current study proposes to investigate the thermal, wettability and mechanical properties of a low temperature SnBi solder. The main aim is to investigate the performance of the SnBi solder alloy with different Bi composition. The study also establishes the relationship between melting temperature, spreading area and tensile stress of the SnBi with different Bi composition at different low reflow temperatures. The thermal and wettability tests are conducted experimentally, while the mechanical test will be analysed via finite element analyses (FEA). The single shear lap test method was adopted for the simulation. The thermal properties of the SnBi solder are investigated using the differential scanning calorimeter (DSC). The reflow temperature selected ranges from 160 °C to 220 °C to accommodate the purpose of low temperature soldering. Wetting test results showed that spreading area of Sn48Bi solder alloy increased to 28.1 and 42.88 at 180 °C and 210 °C respectively. The increase in the Bi composition reduced the tensile strength regardless of the increase of the reflow temperature. The preliminary results commend the characteristics of the SnBi solder as a possible alternative to the Pb solder.

Abstract: Thus far, our research group has conducted a basic investigation for the development of an artificial ligament, which was performed by utilizing a biogenic secretion that was derived from the Achilles tendon in mice; this was achieved using the film model method. In this study, an attempt has been made to derive a biogenic secretion from the Achilles tendon (tendon gel) and the medial collateral ligament (ligament gel) in rabbits. Subsequently, a discussion was carried out on the possibility of forming a ligament-like structure that was based on the structural, mechanical, and spectroscopic investigations. The tendon gel was successfully formed from a parent tendon that was preserved in vivo for 3, 5, 10, and 15 d. Further, an aligned collagen fiber emerged in the tendon gel, which was subjected to tension on every preservation date. Further, the mechanical behavior of the tendon gel specimens was classified in two groups. The values of the Young's modulus of the specimens preserved for 10 and 15 d were higher than those of the specimens preserved for 3 and 5 d. Within the range of this experimental condition, the aligned collagen fiber structure was formed by applying a tension of approximately greater than 0.05 N. Conversely, only a 10-d preservation period yielded a sufficient amount of ligament gel for the experiment. Notably, the volume of ligament gel was less than that of the tendon gel. In the ligament gel specimen without the synovial membrane, the collagen fiber structure was formed by applying a tension, which was similar to that experienced by the tendon gel specimen. However, the cross-linking and growth of collagen fibers in the ligament gel samples were insignificant as compared with those of the tendon gel samples.

Abstract: With the discovery of high-temperature superconducting (HTS) tape and the improvement of the performance of the second-generation HTS tape, the application of superconductors in power system is gradually unfolding. There have been many demonstration projects at home and abroad. When the HTS tape is applied to the power cable, the mechanical external action of the cable winding, laying and installation operations, and the Ampere force when the current is applied are applied to it. Stress has an important influence on the critical current characteristic of the superconducting tape. In different application scenarios of the tape, different materials and thicknesses reinforcement layers can be chosen. In this paper, for the YBCO superconducting tapes with different reinforcement layers, a set of systems with critical current under tensile stress at cryogenic temperature is used to study the influence of tensile stress on the critical current of superconducting tape at low temperature. We analyze the influence of the structure of the superconducting tape on the characteristics of the tape and studied its degradation characteristics, which have guiding significance for the design and operation of the superconducting cable.

Abstract: The effects Si and Mn addition on the fluidity length, mechanical properties, and casting cracks of a die-cast Al-4.5%Mg alloy were investigated. The Si content was 1, 2, or 3 mass% and the Mn content was 0.3, 0.6, or 0.9 mass%. Both Si and Mn did not affect fluidity. Si content of more than 1 mass% improved casting crack resistance. The effect of Mn on casting cracks was weaker than that of Si. When Si content was 2 mass%, both tensile stress and elongation were good. Mn did not affect the mechanical properties.

Abstract: The aim of the research was to verify whether it is possible to use specific types of treated hazardous waste as a filler in special epoxy based polymer mortars. In particular, it was a neutralizing sludge (NS-HW) with a relatively high content of heavy metals and other hazardous substances. This alkaline sludge is formed as a by-product of galvanic plating of steel elements in the baths, which are subsequently thickened and neutralized with calcium hydroxide. During the experimental verification, it was determined what resulting mechanical properties can be achieved by using 40% of the treated neutralizing sludge as a filler. In order to compare the achieved properties, a reference filler in form of a silica flour was used in the same binding matrix, and the polymer mortar containing waste foam glass of approximately the same fraction. It was discovered that, at the same percent filling, the polymer mortar with neutralizing sludge (NS-HW) had a similar tensile strength similar and cohesion with the concrete substrate as the reference material with the silica flour. Furthermore, it has been shown that this filler lowering the environmental footprint does not affect the chemical resistance of the polymer mortar to aggressive liquid solutions. As part of the microstructure observing, the uniformity of the filler distribution in the hardened polymer mortar, the incorporation of sludge particles into the epoxy matrix, and the quality of the polymer mortar bonding to the concrete was monitored using a high resolution digital microscope.

Abstract: Cement-concrete pavement not only has a long service life even at high loads but also has competitive production costs and fewer significant maintenance costs. The concrete road surfaces, thus, are rather economical. In this article, the Vietnamese Standard TCVN 9382 - 2012 was used to determine the heavyweight concrete composition for rural road construction. Assessment of the crack appearance in the concrete block body was made by the temperature field analysis, the thermal stress and cracking index. The conducted studies' result provided with the possibility of obtaining heavyweight concrete from Vietnam local raw materials regarding to the concrete mixture workability of 11-13 cm standard cone, 31-36 MPa compressive strength of heavyweight concrete at the age of 28 - day - normal hardening and 0.30 - 0.42 MPa average water resistance of samples. Using natural pozzolan to replace 20% of mass cement in the concrete mixture leads to a decrease in the concrete strength characteristics at different ages. The concrete compressive strength of composition No2 decreased mostly by 23% at the age of 3 days and least by 14% at the age of 28 days in comparison these values of composition No1. However, all of these concrete compressive strengths at the age 28 days are higher than 30 MPa. Replacing 20% of the mass Portland cement by natural pozzolan in a concrete mix will decrease price for 1 m³ concrete of 219.96 rubles. By applying the computer program MIDAS CIVIL, the maximum temperature in the concrete block center which was determined after 12 hours from the commencement of mixing of raw materials with water, equals to T_max = 34.61 ⁰С. At the same time, the structure temperature difference between the center (node793) and surface (nodes 120 and 898) of the concrete pavement can be neglected because of its insignificance. Besides, the cracking indexes at three hazardous locations of investigated structure are higher than 1, the cement-concrete pavement will be considered as non-appearance of cracks. However, the cracking index at center (node 793) is always less than this on the surface (nodes 120 and 898), equally to higher thermal crack occurrence at center. Therefore, it is necessary to monitor the development and expansion of thermal cracks to ensure the concrete mixture proper care during the hardening process.

Abstract: The epoxy resins are very popular and plentifully used synthetic resins. The bisphenol A-based (DGEBA) and bisphenol F-based epoxy resins (DGEBF) crystallization is phenomenon which is for that kind of resins natural. They are undercooled liquids and they tend to form the crystal structure at the ambient temperature. The subject of the research is to determine the effect of some crystallinity of DGEBF on chosen mechanical parameters. The degree of crystallinity was counted through the specific weights of crystallized bisphenol F-based epoxy resins. The prepared crystallized samples of DGEBA/DGEBF mixtures were mixed in appropriate weight ratio with isophorondiamine (IPD) based curing agent. Measured was hardness Shore D according to EN ISO 868 standard and tensile parameters according to EN ISO 527-1 standard. Furthermore, the effect of crystallinity on chosen mechanical parameters was observed. It was found out that with the higher crystallinity maximum tensile stress and hardness increased close to the standard parameters amorphous DGEBA and DGEBF.

Abstract: Non-destructive stress measurement methods have been developed. However, there are a few approaches into the effect of stress direction on the nondestructive physical factors. In the present work, a non-destructive and non-contact method using three-dimensional magnet microscopy was applied to stress evaluation of an as-received tool steel (JIS, SKS93). Three-dimensional components of magnetic fields were observed using a scanning Hall probe microscope in order to find the important component which was related to the tensile stress. The observations were carried out under the tensile stress that was less than the yielding stress of the material. It was found that the magnetic field component that was parallel to a tensile loading direction was strongly correlated to stress values.

Abstract: Mechanical effect is one of many causes that influence surface tracking activity of electrical insulation. Mechanical stress is also a main cause that deteriorates the property of cable spacer used in delivered electrical power through transmission line. This paper investigates on surface tracking and tensile stress performance of composite insulator material in order to improve insulator property. Specimen were made from epoxy resin and additive fillers tested under the condition of contamination. The filler ratio were used from 0 to 50% with incremental of 10%.The result showed that fillers have significance improvement on inhibition of the degradation on insulators when the concentration of filler is increased, the tracking time has increased until 40% of filler. Moreover, the improvement on the tensile stress is also increased. It is clearly showed that addition of filler not only improve on the time for surface tracking on insulator surface but also helps improve on mechanical stress property of insulators as well.

Abstract: Duplex stainless steel was nitrided by sodium nitrate, NaNO₃, salt bath from 592°C to 650°C for 1 to 10 hours. The microstructure, microhardness and tensile strength were investigated after nitriding of duplex stainless steel sheets. Microhardness of sample was increased from 279.7 HV to 296 HV after nitriding in bath of NaNO₃+4.8%NaCl salt at 650°C for 8 hours. Tensile strength was increased from 880 to 939.36 MPa and elongation of duplex stainless steel sheet was decreased from 42% to 38% after nitriding in salt bath of NaNO₃ at 650°C for 8 hours. The nitriding effect of NaNO₃ salt is similar with KNO₃ salt in duplex stainless steel sheet. NaNO₃ salt is cheaper than KNO₃ salt. Therefore, NaNO₃ salt is more economical than KNO₃ salt to nitride duplex stainless steel.