توصيفگر ها :
دستگاه ايزوكينتيك , آلياژ حافظهدار , فنر آلياژ حافظهدار , نايتينول , فنر , بيومكانيك , تمرينات ايزوكينتيك
چكيده انگليسي :
Today, according to the progress of science, there is an effort to create a bridge between experimental sciences and engineering. Due to the old age of most people, physiotherapy has become very important in the world. Therefore, performing rehabilitation exercises, as well as endurance and strength exercises are essential. Isokinetic devices are used for rehabilitation treatments, accelerating injury recovery, and performing endurance and strength exercises in physical therapy and gyms. An isokinetic device can be used to perform hand, leg, and back exercises. This device is designed so that the force applied to the part of the device in contact with the person's body is almost constant. Previous isokinetic devices used ordinary torsion springs, weights, and gearboxes to apply force. Most of the previous devices used a normal spring with constant stiffness or a gearbox with constant power, voltage, and speed. Usually, devices that work in sports clubs use a series of fixed weights to apply force. The required weight is chosen according to the type of exercise that the person intends to do and also to the person's physical ability level. Limitations in the force application range and the impossibility of changing the weight during the process are disadvantages of the mentioned devices. In general, the high cost of supplying this device and the lack of change in the amount of input power based on the person's ability are among the disadvantages of the devices in the market. Smart materials can adapt themselves to the environment with intelligent performance against environmental changes like living organisms. A group of these materials is called shape memory materials, which can "remember" a shape even after relatively severe deformations. After deformation at low temperatures, these materials will not deform until heating, and thus
they naturally return to their original shape (the shape before the deformation process). Therefore, using springs made of smart materials that react by applying stimuli such as temperature change, voltage change, etc., can solve some of the mentioned problems. The stiffness of a normal spring depends on the diameter of the wire, the diameter of the spring, its material, and the number of spring rings; thus, the stiffness of a normal spring cannot be changed after manufacturing. Therefore, the amount of force produced by a normal spring is only a function of its displacement. The stiffness of a shape memory alloy spring is a function of the percentage of nickel and titanium compounds, working temperature, applied voltage, wire diameter, spring diameter, the number of spring rings, and the amount of applied shear stress. Therefore, the force produced in a shape memory alloy spring is a function of the working temperature, the applied voltage, and the tension of the corresponding spring. Due to the non-uniformity of a shape memory alloy spring stiffness, the design of the isokinetic device presented in this thesis has been made to keep the resultant force applied to the connection point between the device and the person's body nearly constant. For this purpose, according to the shape memory properties and superelasticity of the shape memory material (Nitinol), the proposed design employs a combination of normal and shape memory alloy springs. Due to the variability of the stiffness of the shape memory alloy spring, the resultant applied force is almost constant. Using a combination of a normal and a shape memory alloy spring reduces the supply cost, makes this device lighter, and thus makes it portable. It should be noted that the device operator can reduce or increase the number of shape memory alloy springs or normal springs considered in parallel. This capability causes a more comprehensive range of force to be applied, which leads to professionally performing the isokinetic exercises.
