Analysis and Research on the Cause of Wind Turbine Blade Bolt Fracture

In 2019, inspection personnel of a wind farm went to the tower and found that a total of 6 bolts of blades in the hub of a wind turbine had broken and failed. In order to find out the cause of fracture, the fracture bolt was comprehensively detected and analyzed by means of appearance morphology analysis, chemical composition analysis, mechanical properties testing, microstructure testing and fracture micro-area analysis. The results show that the main reasons for the bolt fracture are as follows: under the action of the bolt’s constantly changing and repeated wind load impact and the alternating load caused by blade rotation during the operation of the fan, the crack source is formed along the bottom of the thread with serious stress concentration and expands in fatigue mode until the whole fracture fails.

Structure Formation of Butt Joints Made of Aluminum Alloys to Ensure the Quality of Mechanical Engineering Products

The article discusses the problems of ensuring high-quality formation and normative properties of butt joints of the 1560M and 1980T1 (AMg6 and B48) aluminum alloys as applied to engineering. A method is proposed for joining materials by means of EBW using an electron beam sweep. Homogeneous and dissimilar joints have been investigated, heat treatment of joint from the 1980T1 alloy and a dissimilar joint from the 1560M + 1980T1 alloys is recommended. The paper also presents the results of mechanical properties testing, the corrosion resistance and the delayed fracture tests. A welding technology that makes it possible to obtain high-quality butt-welded joints from aluminum alloys in thicknesses up to 40 mm has been developed and implemented.

Designing and fabricating a novel medical insole with universal fluid layer with auto-customizability

Medical insoles play a significant role in pressure reduction, proper stress–strain distribution, and correcting some deformities in the foot. The aim of the present research is to design and fabricate new medical insoles with universal fluid layer. After fabricating two types of insoles including flat silicone insole with shore 17 and flat silicone insole with universal fluid layer (medical silicone with shore 17 and silicone gel with shore 0), PEDAR test using one person in two standing and walking positions in three conditions comprised without the use of medical insole, using of flat medical silicone insole, and flat silicone insole with universal fluid layer was performed. These insoles were also modeled and solved in Abacus software according to the results obtained from mechanical properties testing of silicone and PEDAR test. The results of the finite element analysis showed that absorption of stress and strain in the static state by the silicone insoles with universal fluid layer was 63% and 63%, and in the dynamic state was 84% and 89% more than those obtained by the flat silicone insoles, respectively. The experimental results of the PEDAR system also showed that in the standing state, the silicone insoles with universal fluid layer and the flat silicone insoles had 58% and 30% pressure reduction, respectively, in comparison with without insole condition. Also, in the gait state, the silicone insoles with fluid layer and the flat silicone insole showed 37% and 9% pressure reduction, respectively, in comparison with without insole condition. Eventually, it was found out that the silicone insoles with fluid layer reduce plantar pressure well in comparison to the flat silicone insoles.

Fabrication and Characterization of Particle Board from Coffee Husk Waste

The purpose of this research was to fabricate the particle board from the coffee husk. The coffee husk from Chumphon province of Thailand was collected, prepared and separated into four groups such as outer husk, inner husk, the mixture of inner and outer husk and husk from the milling process. The coffee husk particle sheet was formed by the compression molding with the heater. Then the coffee husk particle sheets were the mechanical properties testing. The results showed the coffee husk particle sheet from milling process pass the Thai industrial standard (TIS.876/2547). However, the results of swelling and water absorption indicated that all the coffee husk sheet were not passed the TIS.876/2547. The effect of coffee husk particle size on mechanical properties was clarified. The coffee husk particle sheet from the particle size of 2, 4 and 6 mm was mechanical testing and follow TIS.876/2547. The coffee particle size of 2 mm showed the passing the standard. Moreover, the effect of isocyanate adhesive on mechanical properties was investigated. The weight percentage range of isocyanate adhesive on coffee husk from 7 to 13 %wt was carried out. The weight percentage of 9, 11 and 13 showed according to TIS.876/2547. From the experiment indicated that the coffee husk could be applied to the wood particle board industrial.

Failure Analysis of Hot Clamp Induced Cracking on Hydrogen Reformer Outlet Pigtail Tubes

Failure analysis of the hot clamped outlet pigtail tubes connected with hydrogen reformer tube in refineries has been carried out. In this paper, hot clamp induced cracking on Incoloy 800HT outlet pigtail tube of a reformer unit is studied by microscopic observation and mechanical properties testing. Metallurgical evaluation and chemical composition analysis have been performed on both hot clamped cracking tube and no cracking one. Results indicated that the most important parameter affecting the high temperature brittleness of pigtails are the Ni/Cr value, surface grain size and impurity atoms grain boundary segregation.

Effects of Yb Addition on the Microstructure and Mechanical Properties of As-Cast ADC12 Alloy

The effects of addition of different amounts of rare earth ytterbium (Yb) on the microstructure and mechanical properties of the casting ADC12 alloy were investigated by mechanical properties testing and microstructure observation. The results indicate that Yb modification had a big influence on the microstructure and properties of the as-cast alloy. The optimum level of Yb content was 0.8 wt %. The coarse dendritic primary α-Al phases were fully refined, leading to the decreasing of the secondary dendrite arm spacing. The morphology of eutectic silicon phases changed from acicular into short rod-like and even granular. There was a structural transformation of β-Fe phases from massive to small rod-shaped morphology. Additionally, the tensile strength, elongation, and microhardness were 267.9 MPa, 4.2%, and 107.3 HV, respectively, increases of 55.4, 121.1, and 41.4%, respectively, compared with the matrix alloy. Fractographic examinations reveal that mainly ductile fracture for Yb addition of 0.8 wt %. The fracture appearances matched the tendency of the tensile properties. Furthermore, the addition of Yb can generate a rare earth phase consisting of the three elements of Al, Si, Yb, with some small iron-rich phases attached around the rare earth phase.