Impact Mechanics of a Lap Joint: A Theoretical-based Parametric Study.

摘要

The failure of a single connection can cause overload on other structural members, which may consequently fail. Thus, the behavior of damaged or worn joints is of particular concern. In order to represent a loose lap joint, a beam impacting four springs with gaps is modeled. A basis analysis reveals impulse frequency responses with unique dynamic phenomena. Using steady state response, six influential parameters are studied: damping ratio, contact stiffness, position of intermediate springs, gaps, excitation amplitude and beam height. For all parameters, the system response was highly controlled by modes with two contacting springs. Regarding damping, increasing damping ratio reduces transient response, response amplitude, and impulse, except in regions of instability. Regarding contact stiffness, increasing spring stiffness increases system resonant frequencies. The impulse at the first system resonance decreases and at the second system resonance increases. Location of the intermediate spring defines the length of the joint's overlap: the effect is complex. Gap defines the looseness of the joint: increasing gap generally means the joint has more wear. Increasing gap decreases the contribution of contact as well as decreases the impulse, except in unstable regions. Regarding excitation amplitude, less excitation is always more desirable, and unique changes in instabilities result. Increasing the beam's height increases the natural frequencies and changes mode shapes; general recommendations highly depend upon excitation frequency, which stems from operating conditions.