Papers by Keyword: Failure Mechanism

Abstract: This study investigates the failure mechanism of a steel pipeline used for transporting methane gas. The investigation revealed extensive pitting corrosion on the pipe's external surface, leading to localized perforation. Analysis of the corrosion products identified iron oxide-hydroxides, primarily goethite and akaganeite, suggesting an oxidizing environment with the presence of chloride ions. Elemental distribution analysis further supported the formation of iron oxides, showing a lower Fe content and a higher oxygen concentration in the corrosion deposit compared to the base metal. The findings highlight the critical role of the three-phase boundary (steel-water-oxygen) in initiating pitting corrosion, emphasizing the importance of effective corrosion prevention and mitigation strategies for ensuring pipeline integrity and safety.

Abstract: In this work, 1200 V SiC JMOS devices with different W_sch (2 μm, 2.5 μm and 3 μm) are fabricated. The single unclamped inductive switching (UIS) tests under different V_{gs_off} (-5 V and 0 V) are carried out to investigate the avalanche capability. The avalanche robustness among various W_sch under same V_{gs_off} is also compared and analyzed by simulation. The different failure mechanisms between different V_{gs_off} are studied by failure analysis and simulation. The method of improving avalanche ruggedness of JMOS is proposed.

Abstract: The technologic characteristics of typical C/SiC rivet connecting unit by chemical vapor infiltration(CVI) is discussed. It is pointed out that many mechanical limitations caused by connection are the important reasons for the huge gap between the development of C/SiC composite material and the actual thermal structure application. The current situation of preparation and mechanical properties of typical rivet joints on C/SiC composites is summarized. The rational dimension of rivet is given through the test of typical rivet units. Finally, the idea of follow-up research on C/SiC connection by combining analysis with experimental verification is put forward.

Abstract: Polyurethane has excellent impact resistance and chemical resistance, so polyurethane coatings are often selected to protect helicopter rotors. but the impact of rainwater when flying in rainy weather can still cause great damage to the polyurethane coating. In order to effectively improve the working life of the polyurethane coating in the rain erosion environment. This paper introduces the failure mechanism of rainwater erosion. The factors influencing the rain erosion performance of polyurethane coatings were discussed from internal and external factors respectively. And the equipment, test methods and standards of rain erosion were summarized. Finally, the problem that the rotation arm of the equipment cannot reach the rotation speed of the helicopter rotor and the incident angle of water droplets cannot be changed, and the future development direction is prospected.

Abstract: Among all additive manufacturing techniques, fused deposition modeling (FDM) has been used the most extensively to fabricate continuous fiber reinforced polymers. Onyx, a short carbon fiber reinforced PA6 composite material developed by Markforged, has received widespread attention, and been employed as matrix in FDM-fabricated composites. This study investigates the tensile properties of continuous glass fiber (GF) reinforced Onyx (CGFRO) composites under quasi-static loading. CGFRO contains three different components, which are short carbon fiber in micrometer scale, continuous glass fiber and polyamide-d thermoplastic. The synergistic reinforcing behavior of these three components was evaluated experimentally by testing Onyx material, and CGFRO with different volume fractions of fibers (Vf). It was found that the failure mode of Onyx was different from that of GF/Onyx and the deformation modes of GF/Onyx varied with the volume fraction of glass fiber. The tensile properties of CGFRO increased with glass fiber volume fractions, where 42% Vf specimens exhibited the highest tensile modulus and strength of 10 GPa and 383 MPa, respectively, which are approximately nine times higher than that of Onyx parent material.

Abstract: In this paper, the post ballistic impact behaviour of kevlar-glass fibre hybrid composite laminates was investigated against 9×19 mm projectile. Eight different types of composite laminates with different ratios of kevlar woven fibre to glass fibre were fabricated using hand lay-up with epoxy matrix. Ballistic behaviour like ballistic Limit (V₅₀), energy absorption, specific energy absorption and Back Face Signature (BFS) were studied after bullet impact. The results indicated that as the Percentage of glass fibre is increased there was a linear increment in the ballistic behaviour. Addition of 16% kevlar fabric, composite sample meets the performance requirement of NIJ0101.06 Level III-A. Since the maximum specific energy absorption was observed in Pure Kevlar samples and the adding of glass fibre increases the weight and Areal Density of the sample, further investigations need to be carried out to utilize the potential of glass fibre for ballistic applications.

Abstract: Since the performance of silver metal oxide (Ag/MeO) electrical contact materials directly affects the reliability and service life of switching apparatus, the related research on high-performance Ag/MeO electrical contact materials has not stopped. And with the rapid development of switching apparatus, higher and higher requirements are put forward for the performance of Ag/MeO electrical contact materials. Thanks to low and stable contact resistance, short arc burning time, good resistance to high current impulse (3000-5000 A) and good anti-arc erosion, silver zinc oxide (Ag/ZnO) more than just serves as an indispensable environmentally friendly alternative to silver cadmium oxide (Ag/CdO) electrical contact material, and has become one of the important research hotspots of Ag/MeO in recent years. Nevertheless, Ag/ZnO is suffering the increasingly serious challenges, especially the poor processability and electrical properties due to the easy segregation of zinc oxide (ZnO) during the process of preparation, which urge scholars at home and abroad to seek favorable methods to optimize the Ag/ZnO. As yet, impressive strides have been made in optimization the preparation process, nano-technology and additive modification of materials, and research on the failure mechanism of materials. Aiming to provide reference for optimizing Ag/ZnO electrical contact material, this review retrospects the research progress in Ag/ZnO electrical contact materials in recent years, and expounds the preparation methods, processing technology, modification research and failure mechanism of Ag/ZnO, and points out the future development directions of Ag/ZnO.

Abstract: In order to study the penetration performance of the tandem warhead composed of a front circular shaped charge and a rear penetration projectile, a grooved steel plate was processed to simulate the effect of circular shaped jets on metal plate, then the failure mechanism of the grooved steel plate impacted by rear projectile was investigated by ballistic experiment, meanwhile, the effect of projectile nose shape on the failure mechanism was also analyzed. The results show that the main failure mechanism of grooved steel plate is ductile tensile deformation or damage when the projectile impacted on the inner plate body and the depth of the pre-splitting groove is not big enough (usually more than 4mm), on the other hand, the circumferential sheared fracture of the bottom of the groove occurred when the depth of the pre-splitting groove is not less than 4mm. The oval projectile body has much greater erosion damage than rod-shaped projectile during the penetration process.

Abstract: In this paper, experimental work on the behavior of composite curved laminate subjected to flexural tensile loading was carried out. Woven roving [∓45] jute, jute-glass, glass-jute and glass/epoxy curved laminates were fabricated by hand lay-up molding. The curved laminate consists of a central circular 90° region connected with two straight arms. Curved laminate length, width and inner radius were 160 mm, 40 mm and 15 mm respectively. Two and four laminate layers were investigated under flexure tensile loading. Test fixture was fabricated to hold the free ends of the curved laminate during the loading process. Effect of stacking sequence, fiber type and number of layers on the tensile load-displacement relation, interlaminar tensile strength (ILTS) and failure mode were investigated. Results show that the maximum tensile load of the glass/epoxy curved laminate is found higher than the glass-jute, jute-glass followed by jute/epoxy curved laminate. Interlaminar tensile strength decreased with the increase in number of layers. The interlaminar tensile strength of glass/ epoxy curved laminate is found higher than the glass-jute, jute-glass followed by jute/epoxy curved laminates. Failure mode is influenced by the material type and number of layers. Increasing the number of layers from two to four leads to interlaminar fracture. Tension and compression fracture were observed respectively on the inner and outer layer of the central region of the curved laminates.

Abstract: In recent years, high speed railway technology has developed rapidly in China. Long routing of high-speed trains, low temperatures, corrosive environments and sand damage are unique to China’s operating environment. As an important safety component of rolling stock, the safety and reliability of the wheels is of deep concern and high value. It is significant to carefully study and systematically summarize the damage from different failure types in high-speed railway wheels under current conditions, and determine the influencing factors and mechanisms of wheel failures in order to improve railway operation safety. In this paper, the damage forms of high-speed railway wheels in China are introduced, and the main influencing factors of wheel failure are discussed in combination with wheel damage characteristics. What’s more, damage mechanism is analyzed aiming at providing theoretical references for reducing failure rate and improving train operation quality.