Shock Absorbers Damping Characteristics by Lightweight Drop Hammer Test for Naval Machines

Andrzej Grządziela,Marcin Kluczyk

doi:10.3390/ma14040772

Abstract

The technical requirements for naval ships machine foundations are far more strict in comparison to merchant’s vessels. These requirements are confirmed in the military standardization of many countries. Underwater Explosion (UNDEX phenomena) detonation pulses, force naval engineers to design and implement different shock absorbers made from a wide variety of materials. This study presents the tests results of typical shock absorber designs made of various types of rubber and elastomers. The initial objective of the study was to determine the energy absorption of shock impacts, the choice of materials capable of operating within the temperature range of 0 °C to 70 °C, resistance to contact with oils and marine fuel, performance at frequencies ranging from 5 to 30,000 Hz, and absorption no less than 40% of harmonic vibration energy. Initial studies conducted on tensile testing machine were used to determine the static and dynamic stiffness of a shock absorbers. Considerations of stiffness coefficient for the linear and nonlinear range is typical for shock pulses. Further tests were carried out on a lightweight drop hammer to determine the characteristics of the damping coefficient for high-speed wave interactions—Shock Response Spectrum (SRS). The final aim of the study was to assess the repeatability of the shock absorbers response to multiple impact loads. Mechanical properties describing possibilities of tested dampers materials to absorb energy of UNDEX were also presented.

Highlights

The physical effects of the underwater detonation process have been extensively studied since the mid-20th century [1]
Especially its first whip, can cause brittle fractures for foundations, bearings, and electronics [3,4]. Research on this phenomenon should be divided into two branches, i.e., detonation wave modelling and shock absorbers modelling for naval machines
The deformation velocity is to be in the same order of magnitude of the deformation velocity as the UNDEX effect [1]

Summary

Introduction

The physical effects of the underwater detonation process have been extensively studied since the mid-20th century [1]. Especially its first whip, can cause brittle fractures for foundations, bearings, and electronics [3,4]. Research on this phenomenon should be divided into two branches, i.e., detonation wave modelling and shock absorbers modelling for naval machines. Some publications combine both branches of study, editing recommendations and calculation procedures for naval architects. Sea tests involve measurements and modelling of detonation wave pressure for various sea depths and seabed types. It is called Full Ship Shock Trial (FSST)

Objectives

Methods

Results

Conclusion