فهرست مطالب rasool molhsenzadeh

Basically, gears are an evolved form of friction wheels that have teeth added to them to prevent slippage and ensure relative motion uniformity. The use of polymer gears is increasing due to advantages such as corrosion resistance, injection molding capability, operation without lubricants and low noise. However, the mechanical strength, thermal resistance and durability of polymer gears are lower than metal gears. The locking mechanism in metal gears is different from polymer gears. Among the important damages that lead to failure of polymer gears is thermal deformation, which does not exist in metal gears. In polymer gears, due to the viscoelastic and plastic nature of polymers, a lot of heat is generated during gear engagement and the temperature increases. An increase in temperature causes the ribs to soften and, as a result, change their shape. Pitting, fatigue and wear are other factors that lead to failure of polymer gears. The contact stress resulting from the torque applied to the gear plays the most important role in the intensity of each of the mentioned delays. Investigating the contact stress in polymer gears, including the challenges of industrialists and researchers, will provide a better understanding for the better design of these types of gears, as well as life expectancy. This research is a review of various methods for determining and checking contact stress, including Hertz numerical model, standard method and finite element method.

Plastic gears are widely used in various industries. The advantages of these gears include their lightness, automation, low noise, easy production and low cost. However, the high wear rate, limited working temperature and low mechanical strength in polymer gears, compared to metal types, limit their application. Therefore, extensive research has been done on the performance of polymer gears in order to identify the failure mechanisms. Among the conducted researches, the researchers focus on different parts such as determining the critical torque or in other words, load bearing capacity, gear behavior at lower and higher torques than the critical torque, gear fatigue resistance, gear wear behavior on a micro and macro scale, as well as The thermal resistance of the gear is drawn. In addition, the difference in methods and the provision of new methods for checking the mentioned factors in order to check the performance of the gear can be seen in the research. In general, the type of polymer, torque and work cycle have been recognized as factors influencing the wear of polymer gears. In this research, the method and results of the research conducted on various types of gears made with commonly used polymer materials are presented. In such a way that by comparing the performance of all types of gears, it is possible to reach a general conclusion about their use.