Forces distribution in thread and external altering load factor in thread joint under structures vibration

According to teaching literature sources and in an engineering practice there is the rule to use the same type distribution of variable dynamic load in thread as the static one for thread strength calculation under variable acting load. Performed numerical investigation shows that it is not quite right and distribution of the dynamic load in thread can be different from the static distribution depends on thread joint elements stiffness and elastic and inertial properties of whole structure as well. External variable load factor and load distribution in thread in structures with thread joints have to be defined taking into account whole structure dynamic properties. In order to increase endurance strength of thread joints subjected to vibration it is necessary to tune off a design from any resonances.