Effective reduction of stiffness at peak frequency in hydraulic engine mounts by using magneto-rheological fluids

Hydraulic engine mounts are generally used in aerospace and automotive applications for the purpose of cabin noise and vibration reduction. By careful selection of hydraulic mount design parameters, at a certain frequency, namely the notch frequency, the dynamic stiffness will be smaller than the static stiffness and cabin vibration and noise reduction is provided at that frequency. Literature review indicates that in all previous designs of hydraulic engine mounts the dynamic stiffness increases after the notch frequency. This phenomenon undesirable because of the increase in the force transmitted to the cabin. This paper proposes a new hydraulic engine mount that uses two working fluids. The new design has two notch frequencies and two peak frequencies. In this study, effective reduction of the peak frequencies has been demonstrated by using a controllable fluid as one of the working fluids and a non-controllable fluid as the second working fluid. As a result, one can obtain a hydraulic engine mount design with only one notch frequency but having no peak frequency. The new hydraulic engine mount design and its mathematical model are presented in detail and some discussions on the simulation results are provided

Parametric study of the corrosion of API-5L-X65 QT steel using potentiostat based measurements in a flow loop

Low-carbon steel is widely used in industrial pipelines, and corrosion studies are focused mostly on erosion-corrosion, its prediction and control. In this paper, the corrosion rate in pipelines is modeled using a flow loop and measured by linear polarization resistance method (LPR) using a 3-electrode corrosion setup for API-5L-X65 QT steel. Optical microscopy and SEM studies are conducted to examine the surface of the sample and the corrosion products. The effect of NaCl concentration on the corrosion rate is studied at different pH, temperature range, and flow velocities with dissolved oxygen content in the solution maintained at 6 mg/L (6ppm). The corrosion rate is found to be varying from 1 mil per year (0.0254 mmyr−1) to 10 mils per year (0.254 mmyr−1), and the corrosion rate increases with the flow velocity and reaches a maximum at Reynolds Number above 10,000. Further increase in fluid velocity shows corrosion is flow insensitive, and uniform corrosion is predominant in the region

IMECE2003-43254 AN ANALYTICAL EVALUATION OF THE TRANSIENT DYNAMICS OF SEMIACTIVE DAMPERS

ABSTRACT This paper provides an analytical evaluation of semiactive dampers, which have been more increasingly used for vehicle applications i

Variable Volumetric Stiffness Fluid Mount Design

Passive fluid mounts are commonly used in the automotive and aerospace applications to isolate the cabin from the engine noise and vibration. Due to manufacturing and material variabilities, no two identical fluid mount designs act the same. So, fluid mounts are tuned one by one before it is shipped out to customers. In some cases, for a batch of fluid mounts manufactured at the same time, one is tuned and the rest is set to the same settings. In some cases they are shipped as is with its notch frequency not being in its most optimum location. Since none of the passive fluid mount parameters are controllable, the only way to tune the mount is to redesign the mount by changing fluid, changing inertia track length or diameter, or changing rubber stiffness. This trial and error manufacturing process is very costly. To reduce the fluid mount notch frequency tuning cycle time, a new fluid mount design is proposed. In this new fluid mount design, the notch frequency can be easily modified without the need for any redesigns. In this paper, the new design concept, and its mathematical model and simulation results will be presented

Hybrid Secondary Suspension Systems

Abstract. Passive fluid mounts are used in the fixed wing applications as engine mounts. The passive fluid mount is placed in between the engine and the fuselage to reduce the cabin's structure-borne noise and vibration generated by the engine. To investigate the benefits of passive fluid mounts used in conjunction with tuned vibration absorbers (TVA), a simple mathematical model is developed. This mathematical model includes the mathematical model of a passive fluid mount, a TVA, and a spring representing the fuselage structure. The simulation results indicate that when passive fluid mounts are used in conjunction with TVAs, an active suspension system behavior is nearly created

Hybrid Secondary Suspension Systems

Passive fluid mounts are used in the fixed wing applications as engine mounts. The passive fluid mount is placed in between the engine and the fuselage to reduce the cabin's structure- borne noise and vibration generated by the engine

Application of tuned vibration absorbers in fluid mounts

Abstract. The need to reduce the fuel consumption of vehicles leads to having lighter chassis' with lighter engines yet maintaining engine power. These new design requirements are in contrast with the vibration isolation requirements. To keep the vehicles light yet provide good cabin noise and vibration isolation, requires a new vibration isolation technology. Fluid mounts have been used in the aerospace and the automotive industry to provide cabin noise and vibration reduction for years. With the use of passive fluid mounts, the highest cabin noise and vibration reduction is achieved at a frequency called "Notch Frequency". But typical passive fluid mounts have only one notch frequency. So the best cabin noise and vibration reduction is only achievable at one frequency. In this paper, a new fluid mount design in combination with a tuned vibration absorber is proposed. Bond graph modelling technique is used to model the new fluid mount design. The physical model and simulation results are presented. The effect of the natural frequency of the TVA on the dynamic stiffness of the fluid mount is studied

Serum Cortisol Levels as a Predictor of Neurologic Survival inSuccessfully Resuscitated Victims of Cardiopulmonary Arrest

Introduction: Out-of-hospital cardiac arrest (OHCA) is the most stressful lifetime event for the victims and an important issue for the emergency physicians. The status of the hypothalamic pituitary- adrenal axis (HPA) function in successfully resuscitated victims of cardiopulmonary arrest has been recently of an interest for the researchers. Methods: In a prospective cohort study, 50 successfully resuscitated OHCA victims’ serum cortisol levels were measured 5 minutes and 1 hour after return of spontaneous circulation (ROSC). The data were analyzed comparing the one-week neurologic survival. Results: Fifty blood samples were obtained for serum cortisol levels after 5 minutes of ROSC. Fourteen patients (28%) pronounced death during one hour after CPR. Blood sample from living 36 patients after one hour post-CPR were obtained for second cortisol assay. Eleven patients (22%) were neurologically survived after one week. Seven patients (14%) were discharged finally from hospital with good neurologic recovery. The serum cortisol levels in both the neurologically surviving and the non-surviving after 5 minutes of ROSC patients were 63.4 ±13.6 and 43.2±25.5(microg/ml), (mean±S.D., respectively) and after 1 hour of ROSC patients’ serum cortisol levels were 64.9±13.1 and 47.3±27.1(microg/ml), (mean±S.D., respectively). The difference was significantly higher in neurologically survived group in both 5 minutes and 1 hour after ROSC (P= 0.015 and 0.013 respectively). Conclusion: serum cortisol levels after 5 minutes and one hour of ROSC in victims of cardiopulmonary arrest are significantly higher in neurologically survived than non-survived patients

Two-Mode Operation Engine Mount Design for Automotive Applications

Hydraulic engine mounts are applied to the automotive applications to isolate the chassis from the high frequency noise and vibration generated by the engine as well as to limit the engine shake motions resulting at low frequencies. In this paper, a new hydraulic engine mount with a controllable inertia track profile is proposed and its dynamic behavior is investigated. The profile of the inertia track is varied by applying a controlled force to a cylindrical rubber disk, placed in the inertia track. This design provides a hydraulic engine mount design with an adjustable notch frequency location and also damping characteristics in shake motions. By using a simple control strategy, the efficiency of the proposed hydraulic engine mount in two-mode operation meaning isolating mode in the highway driving condition and damping mode in the shock motions, is investigated

Analytical random vibration analysis of boundary-excited thin rectangular plates

Fatigue life, stability and performance of majority of the structures and systems depend significantly on dynamic loadings applied on them. In many engineering cases, the dynamic loading is random vibration and the structure is a plate-like system. Examples could be printed circuit boards or jet impingement cooling systems subjected to random vibrations in harsh military environments. In this study, the response of thin rectangular plates to random boundary excitation is analytically formulated and analyzed. In the presented method, closed-form mode shapes are used and some of the assumptions in previous studies are eliminated; hence it is simpler and reduces the computational load. In addition, the effects of different boundary conditions, modal damping and excitation frequency range on dynamic random response of the system are studied. The results show that increasing both the modal damping ratio and the excitation frequency range will decrease the root mean square acceleration and the maximum deflection of the plate