With the aim of improving micro-vibration isolation, a hybrid magnetorheological elastomer-fluid (MRE-F) mount with variable stiffness and damping is presented. The proposed mechanism combines a magnetorheological elastomer stiffness unit with a magnetorheological fluid damping unit in a parallel connection. On the basis of a structural design and magnetic circuit analysis, the performance of this prototype was investigated experimentally using an MTS machine under multi-operating conditions. The field-controlled capacities, including resultant stiffness, equivalent damping, as well as the amplitude and frequency dependence were validated based on the experimental data. This work demonstrates the feasibility of applying this hybrid MRE-F mount to isolation systems with a small displacement.

http://iopscience.iop.org/article/10.1088/0964-1726/25/1/015026/pdf

A hybrid magnetorheological elastomer-fluid (MRE-F) isolation mount: Development and experimental validation

Vibration isolation and noise control technologies are used in submarines on multiple systems and there are various reasons for employing these technologies. One of the principal reasons is to minimise the acoustic signature of the submarine so that it is difficult to detect. This paper contains descriptions of conventional and emerging noise and vibration isolation technologies that have and could be applied to submarines.

Recent developments in submarine vibration isolation and noise control

Tilting pad thrust bearings are a key component of marine propulsion shaft systems. The dynamic performance of thrust bearings has a significant influence on the propeller vibration. To investigate the axial oil film stiffness of tilting pad thrust bearings, a two-dimensional thermohydrodynamic model incorporating the vibration frequency is developed. The test apparatus and experimental identification model are also constructed. The axial oil film stiffness is experimentally identified at different speeds, loads, and temperature employing the hammer impulse excitation. The axial oil film stiffness between theoretical and experimental results is compared. The discrepancies are not more than 7% for 30 kN operation cases but increase with axial static load. This is partially because the influence of the pivot stiffness becomes obvious with the axial static load increase and cannot be ignored. The results indicate that axial oil film stiffness is at a magnitude of 109 N·m−1. Compared to foundation sti...

Theoretical and Experimental Study on the Axial Oil Film Stiffness of Tilting Pad Thrust Bearings

Passive-type control devices such as resilient mounts and wire rope isolators are generally used for protecting the shipboard equipment from shoc k loading and for suppressing the mechanical vibration of the equipment in naval ships. To improve the performance of the control device, a new hybrid mount is under development in this study. This mount consists of a passive-type rubber element and an act ive-type piezo-stack element. It can be expected that the mount has enhanced perform ance of about 20 dB or more with respect to transmissibility through a series of perfo rmance tests of prototype mount. ※Keywords: Hybrid mount(하이브리드 마운트), Resilient mount(탄성마운트), Piezo stack(압전 작동기), Naval ship(함정), Vibration control(진동제어), Shock(충격) 1. 서 론 함재에 탑재되고 있는 각종 기계/전자 장비들을 살펴보면, 장비 하부에 다양한 형태의 마운트가 설치되어 있는 것을 알 수 있다. 이러한 마운트는 접수일: 2008년 1월 22일, 승인일: 2008년 4월 10일†교신저자: sjmoon@kimm.re.kr, 042-868-7428 장비에서 발생되는 진동 및 소음이 하부 구조물로전달되는 것을 차단하고, 외부 충격으로부터 장비를 보호하기 위한 목적으로 사용되고 있다. 함정용 마운트로서는 고무요소로 구성된 마운트와 wire rope형 마운트가 널리 채택되고 있으며, 이들 탄성 마운트는 우수한 진동 및 충격 차단성능을 제공하고 있다. 최근 몇 년 전까지도 한국 해군 함정에 탑재되는 장비에 사용되고 있는 마운트

A Study on Development of an Active Hybrid Mount for Naval Ships

This study focuses on the element configuration of hybrid mounts which are combined with passive elements and active elements. The seven configurations are presented according to connection of an active element to a passive element. The dynamic characteristics and control performance of them are investigated qualitatively using Bode plots. With reference to the transmitted force from internal to external, three cases are selected. In addition, some numerical simulations for the three cases are carried out to confirm the performance quantitatively. Based on this research results, a novel hybrid mount with excellent performance will be able to be developed.

A Comparative Study on the Dynamic Characteristics and Control Performances of Hybrid Mounts According to Element Configuration

In naval ships, some methods or devices are acquired both to cut off the transmission of vibration from shipboard machineries and to protect them from external shock loading. One of the approaches is to install the passive mountings between machinery and a flexible supporting structure. More advanced performance has become necessary recently so far as at high frequencies in order to retain the stealth function of certain types of naval vessels. For the purpose of this research, a novel hybrid mount for shipboard machinery installed on naval ships was developed. The mount is combined with a rubber mount and piezostack actuators. The rubber mount is one of the most popular and effective passive mounts to have been applied to various vibration systems to date. The piezostack actuator is featured by a fast response time, small displacement and low power consumption. Through a series of experimental tests conducted in accordance with MIL-M-17185A(SHIPS), MIL-M-17508F(SH), and MIL-S-901D which are US military specifications related to the performance requirements of the mount, it has been confirmed that the hybrid mount shows more effective performance for use in naval ships.

/pdf/a-study-on-the-hybrid-mount-against-vibration-and-shock-for-4qz9cybdbn.pdf

A Study on the Hybrid Mount against Vibration and Shock for Naval Ships

An experiment method has been developed to analyse the vibration characteristics of marine propeller blades, and vibration tests have been carried out on the model scale propeller in air and in water. The driving point transfer function(acceleration/excitation force) has been measured and modified by compensating the attachment effect of the impedance head. The measured natural frequencies in air have been compared with the theoretical results by an in-house FEM code PROSTEC. The added masses have been derived by comparing the measured natural frequencies in air and in water, and the results have been compared to the results using existing formula based on experience.

Experimental Method for the Identification of the Propeller Blade Vibration Characteristics

Development of Hybrid Mount Design Against Shock and Vibration

Free vibrations of strings due to initial conditions have been analyzed by the conventional mode summation method, and the nondimensionalized displacements and velocities have been derived in the form of infinite series. The results show wave propagating phenomena and confirmed by experiments using the high speed camera. Other physical characteristics have been discussed and examined with help of waveform solutions.

/pdf/free-vibration-characteristics-of-a-uniform-string-due-to-28r67g28al.pdf

Hyun-Yup Lee

Papers

A Study on the Hybrid Mount against Vibration and Shock for Naval Ships

A Study on Development of an Active Hybrid Mount for Naval Ships

Experimental Method for the Identification of the Propeller Blade Vibration Characteristics

Development of Hybrid Mount Design Against Shock and Vibration

Free Vibration Characteristics of a Uniform String Due to Initial Conditions