How can we maximize the absorption of mechanical shock energy in a structural joint?

What is it about?

Optimally employing of natural capability of structural joints for mitigating the undesired dynamics response to the mechanical shock is considered in this paper.

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Photo by NASA on Unsplash

Photo by NASA on Unsplash

Why is it important?

Mechanical shock transmissibility reduction in a structure can lead to more life time and more reliable operation for the sensitive components of other subsystem mounted in a structure and structure itself. Structural joints can play this role without adding any additional weight if their geometry is designed optimally and their parameters are tuned properly. Aerospace systems and subsystems are subjected to impulsive loads due to several reasons, such as engine start and burnout, separation, and others. These loads may cause temporary or permanent failures in sensitive components or subsystems. To avoid these failures, some constraints should be considered in the mechanical design process. Another approach could be to reduce the load level in the transmission path without changing the source of the load or adding any new components, but only by optimizing the design of available components, i.e., structural joints, against destructive effects of impulsive loads. This paper uses an analytical approach to prove that proper design of structural joints can significantly suppress the transmission of undesired excitation. As an example, the following figure shows how micro-slip in the joint with parallel geometry can be employed to reduce impulsive or other types of axial excitation. Parallel geometry refers to that the movement of structural components on both sides of the joint relative to each other at the joint location in the same direction as excitation. This relative motion causes micro-slip and energy dissipation. To achieve this relative motion, it is enough that the slipping surface at the joint is not orthogonal to the direction of excitation. Friction coefficient, fastening pretension, relative stiffness at contact and other parts of the structure in the vicinity of the joint and the angle between excitation and contact surface are control parameters that the designer can use to maximize excitation energy dissipation.