Research To The Improved Damage Tolerance Fatigue Theory Based On Interval Analysis And Its Application

Fatigue failure is the main form of the early destruction failure of mechanical parts. As modern machinery improved toward the direction of large-scale and high-speed, a lot of parts work in the harsh environment of heavy duty, high pressure, high temperature and corrosion, and the fatigue failure event is not uncommon. Therefore, the study on the fatigue life and the prevention of fatigue failure of the parts has a very important significance.Traditional fatigue design methods are premised on no defects in parts, but in actual production assembly, the parts internal or surface inevitably generate the initial defects. The damage tolerance design method can consider these initial defects, according to fracture mechanics and non-destructive testing techniques we can correctly estimate the remaining life of crack-containing components. The damage tolerance design method has many advantages, but it relates lots of the material parameters, and many parameters cannot be determined, so the method cannot be easily widely used in practical engineering applications, but can only be used in aviation and a few other areas.Interval analysis is also called interval mathematics, it is a branch of mathematics which uses interval variables instead of point variable, and it was originally developed from the study of computational mathematics theory of error. In order to solve the problems above, this thesis is groundbreaking combine interval analysis theory whit the damage tolerance design method, and use interval variables instead the uncertain parameters. Damage tolerance design method in practical applications involving a large number of material parameters, most of these parameters need to be measured by the test method, and more often, because of the constraints cannot be measured using test method, so we need to find a manual value. As we know, the manual parameter values corresponding experimental values of specific heat treatment, but always it is different, so people usually get approximate parameters. In addition, some parameters directly given Interval value by manual. For these cases, here we used Interval Valued alternative the exact value, making damage tolerance design method can facilitate applied to the practical engineering. In this thesis, I first proposed the concept of life interval. The conventional method to descript batch components of life is the mean life. Actually, all parts of the life is not the same, the life of some parts A far cry from the mean life. However, use the life interval instead of the mean life will be more accurate, more practical to describe a batch of parts of life, and with non-destructive testing technology we ensure that all parts of life are in the range of the life. Moreover, we use automobile horizontal hollow stabilizer bar as an example, through the fatigue test, to verify that the new theory correctness and feasibility.