The Dynamic Stiffness of Controlled Hydrostatic Bearings

1969 ◽  
Vol 91 (4) ◽  
pp. 597-608 ◽  
Author(s):  
M. E. Mohsin ◽  
S. A. Morsi
Keyword(s):  
Theoretical Analysis ◽  
Dynamic Stiffness ◽  
Step Function ◽  
Scale Model ◽  
Design Parameters ◽  
Hydrostatic Bearings ◽  
Constant Resistance ◽  
Different Types ◽  
Bearing Design ◽  
Perturbation Solutions

The first part of this paper is concerned with the theoretical analysis of the dynamic behavior of externally pressurized bearings compensated by constant resistance as well as controlled restrictors. The response of the bearing to harmonic and step function loads is considered and perturbation solutions are obtained. The effect of the different bearing design parameters on its dynamic stiffness is studied and recommendations are suggested. The second part of the paper includes a description of an experimental investigation supporting the theoretical analysis. Experiments were conducted on a single bearing as well as on a scale-model machine table supported on four bearings. Results obtained for different types of bearing compensation and loading are described and discussed. Moreover, the effect of oil aeration on the dynamic stiffness of hydrostatic bearings is investigated.

Bearing Performance Limits With Grease Lubrication

2005 ◽  
Author(s):  
P. M. Cann ◽  
A. A. Lubrecht
Keyword(s):  
Surface Damage ◽  
Design Parameters ◽  
Performance Limits ◽  
Grease Lubrication ◽  
Lubricated Contacts ◽  
System A ◽  
Operating Limits ◽  
Bearing Design ◽  
Cage Effects ◽  
Efficient Mechanisms

This paper has examined the influence of bearing design and operation in controlling lubricant supply to the contact zone. Grease lubricated contacts are liable to starvation and as a result the film thickness is reduced, this can result in surface damage or premature bearing failure. It is of obvious importance to know when starvation occurs and the effect of grease type, bearing design and operation on lubrication replenishment. The aim therefore is to develop a starvation parameter capable of predicting the operating limits for a particular bearing/grease system. A number of bearing design parameters are examined in the paper, these include cage design, ball spin and bearing size. Ball spin and cage effects can be efficient mechanisms for maintaining the lubricant supply to the track. Increased bearing size, line contact geometries and high load result in reduced lubricant replenishment of the contact. Using this analysis it will be possible to establish operating limits for families of bearings.

Investigation of sustainability of lubricated journal bearing under relevant design parameters

2018 ◽  
Vol 70 (4) ◽  
pp. 789-804 ◽  
Author(s):  
M.M. Shahin ◽  
Mohammad Asaduzzaman Chowdhury ◽  
Md. Arefin Kowser ◽  
Uttam Kumar Debnath ◽  
M.H. Monir
Keyword(s):  
Aspect Ratio ◽  
Elastic Strain ◽  
Journal Bearing ◽  
Design Parameters ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
Stress Formation ◽  
Bearing Design ◽  
The Stability ◽  
Bearing Friction

Purpose The purposes of the present study are to ensure higher sustainability of journal bearings under different applied loads and to observe bearing performances such as elastic strain, total deformation and stress formation. Design/methodology/approach A journal bearing test rig was used to determine the effect of the applied load on the bearing friction, film thickness, lubricant film pressure, etc. A steady-state analysis was performed to obtain the bearing performance. Findings An efficient aspect ratio (L/D) range was obtained to increase the durability or the stability of the bearing while the bearing is in the working condition by using SAE 5W-30 oil. The results from the study were compared with previous studies in which different types of oil and water, such as Newtonian fluid (NF), magnetorheological fluid (MRF) and nonmagnetorheological fluid (NMRF), were used as the lubricant. To ensure a preferable aspect ratio range (0.25-0.50), a computational fluid dynamics (CFD) analysis was conducted by ANSYS; the results show a lower elastic strain and deformation within the preferable aspect ratio (0.25-0.50) rather than a higher aspect ratio using the SAE 5W-30 oil. Originality/value It is expected that the findings of this study will contribute to the improvement of the bearing design and the bearing lubricating system.

Updating Substructure Models With Dynamic Boundary Conditions

1995 ◽  
Author(s):  
Michael Link ◽  
Zheng Qian
Keyword(s):  
Boundary Conditions ◽  
Dynamic Stiffness ◽  
Design Parameters ◽  
Physical Parameters ◽  
Model Parameters ◽  
Dynamic Boundary Conditions ◽  
Main Structure ◽  
Modal Data ◽  
Residual Structure ◽  
Dynamic Boundary

Abstract In recent years procedures for updating analytical model parameters have been developed by minimizing differences between analytical and preferably experimental modal analysis results. Provided that the initial analysis model contains parameters capable of describing possible damage these techniques could also be used for damage detection. In this case the parameters are updated using test data before and after the damage. Looking at complex structures with hundreds of parameters one generally has to measure the modal data at many locations and try to reduce the number of unknown parameters by some kind of localization technique because the measurement information is generally not sufficient to identify all the parameters equally distributed all over the structure. Another way of reducing the number of parameters shall be presented here. This method is based on the idea of measuring only a part of the structure and replacing the residual structure by dynamic boundary conditions which describe the dynamic stiffness at the interfaces between the measured main structure and the remaining unmeasured residual structure. This approach has some advantage since testing could be concentrated on critical areas where structural modifications are expected either due to damage or due to intended design changes. The dynamic boundary conditions are expressed in Craig-Bampton (CB) format by transforming the mass and stiffness matrices of the unmeasured residual structure to the interface degrees of freedom (DOF) and to the modal DOFs of the residual structure fixed at the interface. The dynamic boundary stiffness concentrates all physical parameters of the residual structure in only a few parameters which are open for updating. In this approach damage or modelling errors within the unmeasured residual structure are taken into account only in a global sense whereas the measured main structure is parametrized locally as usual by factoring mass and stiffness submatrices defining the type and the location of the physical parameters to be identified. The procedure was applied to identify the design parameters of a beam type frame structure with bolted joints using experimental modal data.

scholarly journals Theoretical and Experimental Investigation of Two-to-One Internal Resonance in MEMS Arch Resonators

2018 ◽  
Vol 14 (1) ◽  
Author(s):  
Feras K. Alfosail ◽  
Amal Z. Hajjaj ◽  
Mohammad I. Younis
Keyword(s):  
Internal Resonance ◽  
Nonlinear Response ◽  
Multiple Scales ◽  
Hopf Bifurcations ◽  
Chaotic Motions ◽  
Different Types ◽  
Quadratic Nonlinearities ◽  
Multiple Scales Perturbation Method ◽  
Good Agreement ◽  
Perturbation Solutions

We investigate theoretically and experimentally the two-to-one internal resonance in micromachined arch beams, which are electrothermally tuned and electrostatically driven. By applying an electrothermal voltage across the arch, the ratio between its first two symmetric modes is tuned to two. We model the nonlinear response of the arch beam during the two-to-one internal resonance using the multiple scales perturbation method. The perturbation solution is expanded up to three orders considering the influence of the quadratic nonlinearities, cubic nonlinearities, and the two simultaneous excitations at higher AC voltages. The perturbation solutions are compared to those obtained from a multimode Galerkin procedure and to experimental data based on deliberately fabricated Silicon arch beam. Good agreement is found among the results. Results indicate that the system exhibits different types of bifurcations, such as saddle node and Hopf bifurcations, which can lead to quasi-periodic and potentially chaotic motions.

The Surface Roughness Effect on the Dynamic Stiffness and Damping Characteristics of the Hydrostatic Thrust Spherical Bearings: Part 5 of 5 — Clearance Type of Bearings

2007 ◽  
Author(s):  
Ahmad W. Yacout
Keyword(s):  
Surface Roughness ◽  
Capillary Tube ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Major Effect ◽  
Design Parameters ◽  
Compressibility Effect ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Fluid Compressibility

This study has theoretically analyzed the surface roughness, centripetal inertia and recess volume fluid compressibility effects on the dynamic behavior of a restrictor compensated hydrostatic thrust spherical clearance type of bearing. The stochastic Reynolds equation, with centripetal inertia effect, and the recess flow continuity equation with recess volume fluid compressibility effect have been derived to take into account the presence of roughness on the bearing surfaces. On the basis of a small perturbations method, the dynamic stiffness and damping coefficients have been evaluated. In addition to the usual bearing design parameters the results for the dynamic stiffness and damping coefficients have been calculated for various frequencies of vibrations or squeeze parameter (frequency parameter) and recess volume fluid compressibility parameter. The study shows that both of the surface roughness and the centripetal inertia have slight effects on the stiffness coefficient and remarkable effects on the damping coefficient while the recess volume fluid compressibility parameter has the major effect on the bearing dynamic characteristics. The cross dynamic stiffness showed the bearing self-aligning property and the ability to oppose whirl movements. The orifice restrictor showed better dynamic performance than that of the capillary tube.

scholarly journals Formation of skills to create stories of different type in senior preschool children

2018 ◽  
pp. 111-119
Author(s):  
Alexander Savchin
Keyword(s):  
Preschool Children ◽  
Theoretical Analysis ◽  
School Environment ◽  
Preschool Age ◽  
Different Types ◽  
Definition Of ◽  
Main Definition

The article gives an analysis of problems of formation of skills in children of the senior preschool age to build stories of different types. On the basis of the theoretical analysis of psycho-pedagogical and special literature, based on the main definition of «building a story», a subordinate term is formulated in relation to the topic of the study: «building stories of different types» The psychological and pedagogical conditions of formation of sustainable skills of creation and expedient use of stories of different types in children of the senior preschool age are revealed and substantiated. The components, criteria, indicators and levels of formation of abilities to build a different type of narration in children of the sixth year of life are determined. The stages of formation of persistent skills for building different types of stories by senior preschoolers are singled out. The lack of effective pedagogical technologies in relation to the formation of skills in the children of the senior preschool age to build and expedient use of narration of comprehensive typing significantly reduces the effective preparation of children to school. The proposed pedagogical and motivational technology for the formation of children of the sixth year of a sustainable ability to create stories of various types provides the small person an effective communicative tool, which will definitely promote its self-realization both in school environment and in career, society, own life. The prospects for further research are outlined, such independent types of stories are presented as a story - an instruction and a story - a presentation.

scholarly journals Identification of a Suitable Solid Carrier as a Matrix for the Permeable Reactive Barrier of Laboratory Scale Model Aquifer for Atrazine Degradation

1970 ◽  
Vol 25 (1) ◽  
pp. 119-128 ◽  
Author(s):  
Binita K Shrestha ◽  
Pawan Raj Shakya ◽  
MIM Soares
Keyword(s):  
Laboratory Scale ◽  
Permeable Reactive Barrier ◽  
Scale Model ◽  
Pseudomonas Sp ◽  
Reactive Barrier ◽  
Solid Carrier ◽  
Different Types ◽  
Simultaneous Loss ◽  
Static Conditions ◽  
Atrazine Degradation

Three different types of physical substrata such as sand, granualar activated carbon (GAC) and plastic macaroni beads were selected to identify a suitable solid carrier as a course matrix for the permeable reactive barrier (PRB) in a sand filled two-dimensional laboratory-scale model aquifer. An adhesion experiment was performed and tested with Pseudomonas sp ADP (PASP) under agitated as well as static conditions. In static conditions, adhesion to GAC was the highest (80%) followed by that to beads (60%). No adhesion to sand was observed under static or agitated conditions. Since atrazine is adsorbed by GAC, its bioavailability for degradation by PADP may be affected. To test this, simultaneous loss of atrazine and release of chloride (dechlorination, the first step in the pathway of atrazine degradation by PADP) were determined in the presence and absence of GAC. Although cells remained viable, no significant chloride release was detected. Thus, plastic macaroni beads were identified and selected as the most suitable support for PADP in the biological permeable reactive barrier (BPRB) of the model aquifer.Key words: Suitable Solid; Laboratory Scale; PADPTribhuvan University JournalVol. XXV, No. 1, 2005Page:119-128Uploaded date: 26, September, 2010

scholarly journals THE ROLE OF THE RELATIONSHIP WITH THE MOTHER IN CHILDHOOD IN FORMING A WOMAN'S ATTITUDE TOWARDS HER OWN MOTHERHOOD

2020 ◽  
Vol 11 (87) ◽  
Author(s):  
Tatiana Sidorenko ◽  
◽  
Natalia Grisenko ◽  
Keyword(s):  
Theoretical Analysis ◽  
Adult Age ◽  
Personal Attitude ◽  
Psychological Science ◽  
Factors Influencing ◽  
Different Types ◽  
Main Factors ◽  
Psychological Features ◽  
The Relationship

The article is devoted to the study of such an important psychological phenomenon as an attitude of women to their own motherhood. It is summarizes the study of the problem of motherhood in psychological science in general. The article analyzes the problem of the influence of the relationship with the mother in childhood on the formation of a woman's attitude to her own motherhood in adult age. It is illuminates views of foreign and national researchers on the study of this phenomenon, as well as the essence of different areas of research on this phenomenon. Based on the theoretical analysis of the literature on this topic, the concept of "motherhood", its content and psychological essence is studied. Cultural-historical, biological, physiological and psychological aspects to the study of motherhood are singled out. The main content of scientific views on the formation of the phenomenon of motherhood is generalized. The main factors influencing the development of a woman's maternal sphere and the formation of the attitude to one's own motherhood are analyzed and considered. The content of such basic concepts as "mother's image" and "maternal relations" is revealed. The psychological features of the formation of an adequate image of the mother in the theoretical analysis of the ontogenesis of the maternal sphere are analyzed. The article also reveals the dynamics of motherhood in ontogenesis. The types of maternal relations and their role in the life of a mature woman are determined, as well as the influence of these relations on the formation of a woman's attitude to her own motherhood. The influence of different types of relationships between women and their own mothers on the level of formation of their attitude to personal motherhood has been empirically studied. Two groups of women were studied, one group had a positive relationship with their own mother, and the other had a negative one. In the course of the research the differences between different types of maternal relations and the level of formation of a woman's personal attitude to motherhood are singled out.

scholarly journals Hybrid Bandgaps in Mass-coupled Bragg Atomic Chains: Generation and Switching

2021 ◽  
Vol 8 ◽  
Author(s):  
Shao-Feng Xu ◽  
Zhu-Long Xu ◽  
Kuo-Chih Chuang
Keyword(s):  
Structural Parameters ◽  
Dynamic Stiffness ◽  
Detailed Examination ◽  
Acoustic Metamaterials ◽  
Acoustic Metamaterial ◽  
Chain System ◽  
Different Types ◽  
Atomic Chains ◽  
Amplification System ◽  
Three Degree Of Freedom

In this work, without introducing mass-in-mass units or inertial amplification mechanisms, we show that two Bragg atomic chains can form an acoustic metamaterial that possesses different types of bandgaps other than Bragg ones, including local resonance and inertial amplification-like bandgaps. Specifically, by coupling masses of one monatomic chain to the same masses of a diatomic or triatomic chain, hybrid bandgaps can be generated and further be switched through the adjustment of the structural parameters. To provide a tuning guidance for the hybrid bandgaps, we derived an analytical transition parameter (p-value) for the mass-coupled monatomic/diatomic chain and analytical discriminants for the mass-coupled monatomic/triatomic chain. In our proposed mass-coupled monatomic/triatomic chain system, each set of analytical discriminants determines a hybrid bandgap state and a detailed examination reveals 14 different bandgap states. In addition to bandgap switching, the analytical p-value and discriminants can also be used as a guide for designing the coupled-chain acoustic metamaterials. The relations between the mass-coupled monatomic/triatomic chain system and a three-degree-of-freedom (DOF) inertial amplification system further indicate that the band structure of the former is equivalent to that of the latter through coupling masses by negative dynamic stiffness springs.

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