فهرست مطالب fattaneh morshedsolouk

Recently, a new type of artificial muscle called thermally activated twisted and coiled polymer actuators (TCPAs) has garnered significant attention. These actuators are primarily made from fishing lines or sewing thread, and when actuated by heat, they can contract along their length to produce linear displacement. The low production cost, silent operation, high power-to-weight ratio, and the ability to generate significant displacement in response to thermal stimuli are among the advantages that have made these actuators more appealing compared to other conventional actuators. They are thus emerging as a suitable option for various applications, such as robotics, smart textiles, energy harvesting systems, and more. These actuators (TCPAs) operate by leveraging the expansion and contraction properties of polymer fibers, which are initially twisted by an electric motor and then coiled into a spring-like structure. This construction method enhances the strength and efficiency of the TCPAs. Additionally, these actuators can maintain their performance in diverse environments, including underwater and high-temperature settings. This review explores the fabrication methods, underlying principles, and thermal actuating techniques of these actuators. It also discusses their innovative and emerging applications. Furthermore, the study addresses the challenges in exploiting this technology and proposes possible solutions to optimize their performance.

In this paper, the quasi-static compressive strength of two different sandwich structure designs in which cores consist of trapezoidal corrugated panels is investigated. In one design, the core consists of a cross-corrugated multilayer structure, while in the other design the core is consists of two interlocking bidirectional cross-corrugated panels. For each design, three different trapezoidal wave profiles are studied and one of them is constructed and tested. The results of specimens' crushing tests under quasi-static compressive loads are compared with the numerical modeling results. Afterward, the mechanical behavior of the other four designs is evaluated numerically. The results showed that the ultimate strength of the sandwich structures with an interlocked corrugated core is higher than the ultimate strength of the other design. It was also found that, in a given design, the ultimate strength depends on the corrugation profile geometry. These results can be used in the design of high-strength light-weight structures. Measures that can be taken to improve the ultimate strength of sandwich panels include the use of polyurethane foam, which is light in weight but has high strength, or the geometry of the structure be changed.

This review article delves into the intricate mechanical behaviors exhibited by metal hydrides within hydrogen storage tanks during hydrogen absorption and release processes. The metal’s crystal structure undergoes expansion upon hydrogen absorption, leading to the liberation of energy—an exothermic phenomenon. Conversely, during hydrogen release, the metal contracts, necessitating an intake of energy from the surroundings—an endothermic occurrence. These cyclic processes give rise to two significant mechanical implications: firstly, the initiation of a decrepitation mechanism; secondly, the material undergoes rhythmic expansion and contraction, often referred to as "hydride breathing." These dual mechanisms collectively contribute to the escalating strain and stress imposed on the walls of the metal hydride container, thereby impacting its structural integrity. This review delves into the comprehensive landscape of experimental studies, measurement techniques, and modeling approaches employed in analyzing stress and strain within metal hydride hydrogen storage tanks. The report encompasses an exploration of the factors amplifying mechanical stresses within the metal hydride bed, alongside proposed strategies for their mitigation and control. Furthermore, the article concludes by presenting pragmatic and experimental recommendations aimed at the development of secure hydrogen storage tanks grounded in metal hydride technology.

This research investigates the amount of energy absorption in a sandwich panel with a corrugated core of an egg comb with two different dimensions. Sandwich panels with different core shapes are widely used in the transportation industry due to their lightweight, and many studies have been conducted on their properties, one of which is the study of energy absorption. Investigating the amount of energy absorption in these types of cores will help to increase the safety of the passengers. In this research, the cores with the ratio of the angle of the leg to the base of 30 degrees (T30) and 40 degrees (T40) were made through sheet cutting and bending and were connected to each other using spot welding. ST 37 steel sheet was used for the core and surface. The samples were subjected to a quasi-static uniform load. The force-displacement curves were obtained and the peak force value, energy absorption rate, specific energy absorption, and energy absorption efficiency were calculated from the crushing behavior of the sample. It was found that the angle ratio has an effect on the amount of energy absorption. The amount of energy absorption in T40 was about 1.5 times that of the T30 model.

The strength of a laser-welded steel corrugated sandwich panel with a circular opening at the center under compressive in-plane load is studied using finite element method. The opening is stiffened with a ring and the effect of the stiffening ring on the strength of the sandwich panel is assessed. Corrugated sandwich panels are structural components that have good mechanical behavior under the impact, bending, and in-plane loading. Thus, they are widely used in structures that operate in severe loading conditions such as marine and aerospace structures. The sandwich panel is modeled in Ansys software using shell elements and the welding connection between the faceplate and corrugated core is modeled with shell elements. The contact between the faceplate and corrugated core is defined as a frictionless contact, so the faceplate and core panel are both thin-walled structures that are free to buckle independently. It was deduced that the ring’s thickness can change the strength of the sandwich panel, but it does not increase the strength up to the strength of the intact plate. It was also found that the opening diameter can decrease the strength of the sandwich panel dramatically.