Mahmoud Hammou, Ahmed Bouzidane, Marc Thomas, Aboubakeur Benariba and Mohamed Bouzit
The purpose of this study is to examine the dynamic performance of an orifice-compensated three-pad hydrostatic squeeze film damper.
Abstract
Purpose
The purpose of this study is to examine the dynamic performance of an orifice-compensated three-pad hydrostatic squeeze film damper.
Design/methodology/approach
A numerical model has been developed and presented to study the effect of eccentricity ratio and pressure ratio on the static and dynamic characteristics of an orifice-compensated three-pad hydrostatic squeeze film damper. It is assumed that the fluid flow is incompressible, laminar, isothermal and steady-state. The finite difference method has been used to solve Reynolds equation governing the lubricant flow in film thickness of hydrostatic bearing. The numerical results obtained are discussed, analyzed and compared between three- and four-lobe hydrostatic journal bearings available in the literature.
Findings
It was found that the influence of eccentricity ratio on dynamic characteristics of an orifice-compensated three-pad hydrostatic squeeze film damper appears to be essentially controlled by the concentric pressure ratio. It was also found that the three-pad hydrostatic squeeze film damper has higher stiffness than three and four-lobe hydrostatic journal bearings.
Originality/value
In fact, the results obtained show that this type of hydrostatic squeeze film damper provides hydrostatic designers a new bearing configuration suitable to control rotor vibrations.
Details
Keywords
Mohamed Benadda, Ahmed Bouzidane, Marc Thomas and Raynald Guilbault
This paper aims to propose a new hydrostatic squeeze film damper compensated with electrorheological valve restrictors to control the nonlinear dynamic behavior of a rigid rotor…
Abstract
Purpose
This paper aims to propose a new hydrostatic squeeze film damper compensated with electrorheological valve restrictors to control the nonlinear dynamic behavior of a rigid rotor caused by high unbalance eccentricity ratio. To investigate the effect of electrorheological valve restrictors on the dynamic behavior of a rigid rotor, a nonlinear model is developed and presented.
Design/methodology/approach
The nonlinear results are compared with those obtained from a linear approach. The results show good agreement between the linear and nonlinear methods when the unbalanced force is small. The effects of unbalance eccentricity ratio and electric field on the vibration response and the bearing transmitted force are investigated using the nonlinear models.
Findings
The results of simulation performed that the harmonics generated by high unbalance eccentricities can be reduced by using hydrostatic squeeze film damper compensated with electrorheological valve restrictors.
Originality/value
The numerical results demonstrate that this type of smart hydrostatic squeeze film damper provides to hydrostatic designers a new bearing configuration suitable to control rotor vibrations and bearing transmitted forces, especially for high speed.
Details
Keywords
Jacques Masounave, Youssef A. Youssef, Yves Beauchamp and Marc Thomas
Investigates the effects of the most influential cutting parameters (cutting speed, feed rate, depth of cut, tool nose radius, tool length and work piece length) on surface…
Abstract
Investigates the effects of the most influential cutting parameters (cutting speed, feed rate, depth of cut, tool nose radius, tool length and work piece length) on surface roughness quality and on the formation of built‐up edge in a lathe dry turning process of mild carbon steel samples. A full factorial design (384 experiments), taking into account the three‐level interactions between the independent variables has been conducted. The results show that the following three‐level interactions: feed rate × cutting speed × depth of cut, feed rate × cutting speed × tool nose radius and tool nose radius × depth of cut × tool length have significant effects on surface roughness in this type of machining operation. Shows that the analysis of main effects alone and even two‐level interactions could lead to a false interpretation of the results. The analysis of variance revealed that the best surface roughness is achieved with a low feed rate, a large tool nose radius and a high cutting speed. The results also show that the depth of cut has no significant effect on surface roughness when operating at cutting speeds higher than 160m/min. Furthermore, it is shown that built‐up edge formation deteriorates surface roughness when machining mild carbon steel at specific feed rate, tool nose radius and cutting speed levels. Proposes a new model for evaluating the limiting cutting speed to avoid the built‐up edge formation. Finally, shows through experimentation that an increase in depth of cut would lead to improved surface roughness when tool vibration is increased.
Details
Keywords
Yulan Sun, Marc Thomas and Jacques Masounave
The purpose of this paper is to present experimental research on the behaviour of a new electrorheological fluid (ETSERF).
Abstract
Purpose
The purpose of this paper is to present experimental research on the behaviour of a new electrorheological fluid (ETSERF).
Design/methodology/approach
The ETSERF is a suspension based on diatomite powders dispersed in silicon oil with a surfactant. A design of experiments is conducted to investigate the effects of electric field strength, particle concentration, surfactant percentage, particle size and shear rate on the efficiency of ETSERFs. The influence of the interactions on shear stresses is analyzed by varying all the combinations of the independent variables. The dielectric properties of the ETSERF are investigated in order to explain the interactions between these independent variables. Furthermore, a quantitative relationship between the dynamic shear stresses and the independent variables is developed.
Findings
The relationship provides a very useful explanation for the contributions of each independent variable to the viscosity and yield stress.
Originality/value
A new empirical model is proposed to explain the rheological behaviour of the ER fluids with a shear‐thinning behaviour.
Details
Keywords
Otis W. Gilley and Marc C. Chopin
Although most labor and microeconomic textbooks contain a theoretical discussion of the backward‐bending labor supply curve, scant empirical evidence of this phenomenon exists. In…
Abstract
Although most labor and microeconomic textbooks contain a theoretical discussion of the backward‐bending labor supply curve, scant empirical evidence of this phenomenon exists. In this paper we investigate the behavior of PGA golf professionals as they make labor‐leisure choices for performing on the PGA Tour. Using tournament theory to model this labor market and data from tournament performances over three seperate years, we find significant evidence that higher paid PGA Tour players do indeed operate in the backward‐bending region of their labor supply curves.
Details
Keywords
Marc C. Chopin and Craig T. Schulman
Analysis of management compensation has focused on the principal — agent problem. We address the problem confronting owners who must choose a manager without knowing the…
Abstract
Analysis of management compensation has focused on the principal — agent problem. We address the problem confronting owners who must choose a manager without knowing the productivity of individual managers. We find performance contingent contracts may result in a separating equilibrium in which high productivity managers accept contracts low productivity managers find unacceptable.
Edeltraud Guenther, Timo Busch, Jan Endrikat, Thomas Guenther and Marc Orlitzky
The purpose of this literature review is to reorient empirical research on the causal links between corporate ecological sustainability (CES) and corporate financial performance…
Abstract
The purpose of this literature review is to reorient empirical research on the causal links between corporate ecological sustainability (CES) and corporate financial performance (CFP). Toward this end, we summarize the findings of four meta-analyses (conducted between 2012 and 2016), which indicate that there is, on average, a small positive association between CES and CFP. In addition, these empirical associations seem to be contingent on the firm’s strategic approach with regard to ecological sustainability (e.g., proactive vs reactive approach) and on the operationalization of both constructs. We conclude that future research may benefit from an even more explicit, analytic shift to the circumstances under which it pays for firms to go green. The main research limitations we point out are model misspecifications, endogeneity, and problems in the measurement of both CES and CFP.
Details
Keywords
Outlines the benefits of humour in the workplace. Briefly looks at the place of humour in advertising and the effect of it in areas such as attention, comprehension, persuasion…
Abstract
Outlines the benefits of humour in the workplace. Briefly looks at the place of humour in advertising and the effect of it in areas such as attention, comprehension, persuasion and likeability. Discusses humour in the workplace and provides some suggestions for employers. Covers humour in training and concludes that modest investment in all these areas can bring benefits to the workplace.
Details
Keywords
A history of twentieth‐century censorship. Shakespeare's company staged the first production of The Merchant of Venice sometime between 30 July 1596 and 22 July 1598. From the day…
Abstract
A history of twentieth‐century censorship. Shakespeare's company staged the first production of The Merchant of Venice sometime between 30 July 1596 and 22 July 1598. From the day of that presentation, it is probable that the play has annoyed, perhaps even offended, many who have seen or read it, the source of the offense being the disparaging portrait of a major character, Shylock. On the stage for many years, there have been radically discrepant interpretations of the Jewish usurer. Since the day of Sir Henry Irving, actors and directors have often chosen to present Shylock in a way that transforms the role from that which Elizabethan playgoers may have seen and heard, or may have thought they had seen and heard, to the complex, ambivalent personality depicted in all productions since Irving first projected Shylock as a tragic hero.
Philippe Eiselein and Nikolay A. Dentchev
Purpose: This literature review aims to answer the calls for further exploration of scaling challenges and opportunities for social entrepreneurs (SEs). We address the scaling…
Abstract
Purpose: This literature review aims to answer the calls for further exploration of scaling challenges and opportunities for social entrepreneurs (SEs). We address the scaling issue of social entrepreneurship through the theoretical lens of sustainable business models. Methodology: This paper investigates, on a multilevel approach, 340 journal articles published in one of the 20 peer-reviewed journals in management, entrepreneurship, CSR, organizational behavior, and nonprofit. It also considers influential articles due to their relatively high citation count (i.e., more than 150 times) outside of those selected journals. This paper furthermore analyses in-depth 32 scaling articles. Findings: This study positions the topics of social entrepreneurship over the last decades, together with the six types of scaling strategies: scaling up, scaling down, scaling across, scaling deep, scaling out, and diversification. It also discusses 15 challenges related to the scaling efforts by SEs. It furthermore elaborates on potential leads for research and practice regarding scaling social impact. Social Implications: There are many pathways for SEs to increase their impact on society, even though it remains quite challenging to achieve for most. Understanding what possibilities or limitations apply to individual SEs is but a first step in developing the full potential of social entrepreneurship. Originality: This paper approaches scaling from three complementary levels of analysis, i.e., individual, organizational, and institutional. Thus we provide more clarity and a nuanced perspective on past and future research regarding scaling challenges and opportunities.