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

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.

Anti-Shock Foundation of Naval Engines for Naval Vessels

“…2. An example diagram of a nonlinear rubber characteristic (13) As the vibration amplitudes (dynamic displacements) are very small compared to the static deflection, changes in the dynamic load cause only a slight oscillation of the vibration isolator deflection in the vicinity of point Z1. The free vibration frequency of the system is then:…”

“…• the height of the rebound. The site's description is presented in Figure 7, and the research methodology is introduced in detail in the earlier publication of the Authors (13).…”

The Fatigue Wear Process of Rubber-Metal Shock Absorbers

“…The analysis of the used rubber and rubber-metal shock absorbers most often concerns three issues, i.e., cyclical changes in properties, reaction to large deformations and non-linearity of the stress–strain curve. In the case of materials used for shock absorbers, these parameters have been theoretically characterized and practically verified [ 7 , 8 , 9 , 10 , 11 ]. The durability of shock absorbers is of fundamental importance in shipbuilding engineering, which is mainly related to the resistance to cyclical loads and environmental impacts, primarily related to temperature and immersion in aggressive liquids [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

“…The deformation and excessive creep will cause large changes in stiffness and dynamic properties. Deformation is determined by compressing a specimen of specified dimensions to a given deflection [ 7 ]. After compression is complete, the sample is left for half an hour and then subjected to an elevated temperature.…”

Theoretical and experimental study of the “superelastic collision effects” used to excite high-g shock environment

“…However, live ammunition tests are difficult to conduct and very costly [3]; therefore, they are impractical for engineering development tasks that require countless iterations to achieve the desired results for individual components as well as for their assemblies. Various high-g shock testing methods can be adopted under laboratory conditions, including the drop table [5,6], Machete Hammer [7,8], Hopkinson Bar [9,10] and gas gun methods, [4,11]. These testing methods have their own advantages and limitations, which will not be repeated here.…”