A Simple Dynamic Model For Simulating Draft-Gear Behavior In Rail-Car Impacts

1978 ◽  
Vol 100 (4) ◽  
pp. 492-496 ◽  
Author(s):  
T.-K. Hsu ◽  
D. A. Peters
Keyword(s):  
Dynamic Model ◽  
Static Friction ◽  
Full Scale ◽  
Stick Slip ◽  
Drop Hammer ◽  
Draft Gear ◽  
The Individual ◽  
The Impact ◽  
Good Agreement

A new, simple dynamic model is developed for use in simulating draft-gear behavior in rail-car impacts. The model is based on an analysis of the individual components inside several types of draft gears. The transition from kinetic to static friction during the impact is included. Comparisons with drop-hammer tests and full-scale impacts show good agreement with the experimental forces and deflections. In particular two very important phenomena are correctly simulated: 1) the rise in force just before maximum travel, and 2) the stick-slip-grab phenomenon during impact.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

A Dynamic Model Incorporating Thermal Effect for Piezoelectric Stick-Slip Actuators

2008 ◽  
Author(s):  
J. W. Li ◽  
W. J. Zhang ◽  
Q. S. Zhang ◽  
X. B. Chen ◽  
S. D. Tu
Keyword(s):  
Thermal Effect ◽  
Dynamic Model ◽  
Friction Model ◽  
Significant Rise ◽  
Stick Slip ◽  
Lugre Friction Model ◽  
Identification Approach ◽  
Lugre Friction ◽  
Account Thermal Effect ◽  
Good Agreement

It was found experimentally from our previous study that the operation of the piezoelectric actuator (PEA) and the friction in the piezoelectric stick-slip actuator (PE-SSA) can cause significant rise in temperature, thereby degrading the performance of the actuator. This paper presents a dynamic model for the PE-SSA by taking into account thermal effect. In particular, the dynamic model is developed by integrating the PEA model proposed by Adriaens et al. [1] and the LuGre friction model proposed by De Wit et al. [2]; the parameters involved in the models are determined using a system identification approach. Experiments are carried out to verify the effectiveness of the model. It is shown that the simulation and experimental results are in a good agreement. This study provides a new way to model thermal effect for other micro motion systems.

Vibration analysis of drillstrings with string—borehole interaction

2008 ◽  
Vol 222 (11) ◽  
pp. 2099-2110 ◽  
Author(s):  
Y A Khulief ◽  
F A Al-Sulaiman ◽  
S Bashmal
Keyword(s):  
Dynamic Model ◽  
Drilling Process ◽  
The Finite Element Method ◽  
Stick Slip ◽  
Reduced Order ◽  
Drilling Performance ◽  
Complete Failure ◽  
Contact Impact ◽  
The Impact ◽  
Force Displacement

Drillstring vibration is one of the major causes for a deteriorated drilling performance, and if left untreated may result in a complete failure of the drilling process. Although the variations in the drilling load, stick-slip, and whirling are known to be the primary causes of severe vibrations, they often give rise to excessive flexural deformations and subsequent string—borehole interaction. Drillstring contact-impact interaction with borehole results in high-frequency excitations, which further deteriorate the drilling performance, and may cause damage to the bottomhole assembly. Modelling of impact is crucial to understanding the associated dynamic response, and to providing means for controlling the collision phenomenon. A continuous force—displacement law is introduced to model the impulsive force during the short-lived interval of impact, wherein the material compliance and damping coefficients are determined from energy balance relations. The impact model is integrated to the dynamic model of the whole drillstring; including drillpipes and drillcollars. The dynamic model of the rotating drillstring is formulated using a Lagrangean approach in conjunction with the finite-element method. The model accounts for the torsional-bending inertia coupling and the axial-bending geometric non-linear coupling. In addition, the model accounts for the gyroscopic effect and the effect of the gravitational force field. The generalized eigenvalue problem is solved to determine modal transformations, which are invoked to obtain the reduced-order modal form of the dynamic equations. The developed model is integrated into a computational scheme to calculate time-response of the drillstring system in the presence of string—borehole collisions.

Mechanical Measurements at a Submicrometric Scale: Viscoelastic Materials

2000 ◽  
Vol 651 ◽  
Author(s):  
Charlotte Basire ◽  
Christian Fretigny
Keyword(s):  
Static Friction ◽  
Mechanical Analysis ◽  
Stick Slip ◽  
Dynamical Mechanical Analysis ◽  
Indentation Process ◽  
Mechanical Measurements ◽  
Friction Regime ◽  
Kinetics Of ◽  
Contact Size ◽  
Good Agreement

AbstractAdhesive and tribological properties of the tip of an AFM on viscoelastic samples are studied. The kinetics of the indentation process is shown to be governed by bulk rather than by contact edge dissipations. It is shown that the transition from static to dynamic friction regimes takes place at a critical strain. During the static friction regime, the contact size remains nearly constant. Owing to this property, viscoelastic moduli is measured in this regime. Obtained results, characteristic of a micrometric domain are in a very good agreement with the same properties measured on centimetric samples using dynamical mechanical analysis. Finally, a stick-slip friction regime is observed in a range of velocities.

Control of Onset of Buckling Lobe in Axial Impact of Square Tube

2007 ◽  
Vol 566 ◽  
pp. 173-178 ◽  
Author(s):  
Minoru Yamashita ◽  
Tomohito Okuyama ◽  
Naoya Nishimura ◽  
Toshio Hattori
Keyword(s):  
Tube Wall ◽  
Inertia Force ◽  
Solid Mass ◽  
Rigid Plate ◽  
Axial Impact ◽  
Explicit Finite Element Method ◽  
Explicit Finite Element ◽  
Drop Hammer ◽  
The Impact ◽  
Good Agreement

The method for prescribing the site of the first buckling lobe in the axial impact of the tubular structure is proposed. The inertia force induced by the solid mass attached to the tube during the impact is exploited to trigger the first buckling lobe. When the tube with the solid mass undergoes a large acceleration, the inertia force of the solid mass is expected to bend on the tube wall. In the experiment, the rectangular solid mass was attached to the aluminum alloy square tube. The tube fixed to the drop-hammer was impacted against the stationary rigid plate at the velocity of 5 or 7.7 m/s. For the case of the tube without the solid mass, the site of the first buckling lobe varied and the slight wavy plastic deformation remained further than the buckling lobes. On the other hand, when the tube with the solid mass was impacted, the onset of the first buckling lobe was observed at the portion where the solid mass was attached and the wavy deformation stated above was suppressed. The corresponding computation was also conducted using the dynamic explicit finite element method. The result showed a good agreement with the experimental one.

scholarly journals Hydrodynamic Testing of a High Performance Skiff at Model and Full Scale

2019 ◽  
Vol 4 (01) ◽  
pp. 17-44
Author(s):  
A. H. Day ◽  
P. Cameron ◽  
S. Dai
Keyword(s):  
High Performance ◽  
Open Water ◽  
Full Scale ◽  
Hydrodynamic Performance ◽  
Regression Equations ◽  
Water Testing ◽  
Model Scale ◽  
Speed Range ◽  
The Impact ◽  
Good Agreement

Abstract: This study examines the hydrodynamic performance of a high performance skiff hull using three different physical testing techniques which may be used in early stage design for assessment of the upright resistance of sailing vessels. The hull chosen as a benchmark form is a high-speed hard-chine sailing dinghy, typical of modern trends in skiff design, and is broadly similar to some high performance yacht hulls. The 4.55 m hull was tested at full scale in a moderate size towing tank, at 1:2.5 scale in the same tank, and at full-scale by towing on open water. The work presented here builds on the study of Day & Cameron (2017), with the model tests repeated and re-analyzed in the present study and additional results presented. The challenges of full-scale open-water testing are discussed and several potential improvements in practice are identified for future work. Results show that the open water testing broadly matches well with model-scale tank testing, with the mean discrepancy in the measured resistance between the two around 4% over the speed range tested after correction for the presence of the rudder. Agreement is initially less good for the full-scale hull in the tank for higher speeds, both for resistance and trim. ITTC guidelines suggest that blockage may be an issue for the full-scale boat in this size of tank; comparison of the results suggests that blockage, and/or finite depth effects for the full-scale hull in the tank present a substantial problem at the higher speeds. A correction approach for the wave resistance of the full scale results using a calculation based on a linear thin ship theory is effective in this case, and results show that the full scale and model scale tests agree satisfactorily for the majority of the speed range after this correction. In addition to upright resistance in calm water, results are presented for the impact of small waves, the addition of the rudder, and variations in displacement and trim on resistance for a skiff hull. Finally, the results are compared with predictions from the well-known Delft series regression equations, Savitsky's methods, and a thin ship calculation. The thin ship approach gives good agreement for the case in which the hull is trimmed bow-down and the transom is not immersed, while the Savitsky pre-planing approach gives good agreement for the level trim case. The Delft series and Savitsky planing hull approaches do not give good agreement with physical measurements.

Accent Policy and Accent Modification Enterprises as Potential Indicators of Intercultural Power Relations: A Call for an Updated Research Agenda

2013 ◽  
Vol 3 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Brynne D. Ovalle ◽  
Rahul Chakraborty
Keyword(s):  
International Relations ◽  
Identity Construction ◽  
Social Theory ◽  
Power Relations ◽  
Linguistic Diversity ◽  
Cultural Organization ◽  
Using Data ◽  
The Individual ◽  
The Impact ◽  
The Relationship

This article has two purposes: (a) to examine the relationship between intercultural power relations and the widespread practice of accent discrimination and (b) to underscore the ramifications of accent discrimination both for the individual and for global society as a whole. First, authors review social theory regarding language and group identity construction, and then go on to integrate more current studies linking accent bias to sociocultural variables. Authors discuss three examples of intercultural accent discrimination in order to illustrate how this link manifests itself in the broader context of international relations (i.e., how accent discrimination is generated in situations of unequal power) and, using a review of current research, assess the consequences of accent discrimination for the individual. Finally, the article highlights the impact that linguistic discrimination is having on linguistic diversity globally, partially using data from the United Nations Educational, Scientific and Cultural Organization (UNESCO) and partially by offering a potential context for interpreting the emergence of practices that seek to reduce or modify speaker accents.

Investigating the Relationship Between Self-Esteem and Stigma Among Young Adults With History of Suicide Attempts

Crisis ◽  
2016 ◽  
Vol 37 (4) ◽  
pp. 265-270 ◽  
Author(s):  
Meshan Lehmann ◽  
Matthew R. Hilimire ◽  
Lawrence H. Yang ◽  
Bruce G. Link ◽  
Jordan E. DeVylder
Keyword(s):  
Young Adults ◽  
Suicide Attempts ◽  
Self Esteem ◽  
High Risk Population ◽  
High Functioning ◽  
People With Mental Illness ◽  
History Of ◽  
The Individual ◽  
The Impact ◽  
The Relationship

Abstract. Background: Self-esteem is a major contributor to risk for repeated suicide attempts. Prior research has shown that awareness of stigma is associated with reduced self-esteem among people with mental illness. No prior studies have examined the association between self-esteem and stereotype awareness among individuals with past suicide attempts. Aims: To understand the relationship between stereotype awareness and self-esteem among young adults who have and have not attempted suicide. Method: Computerized surveys were administered to college students (N = 637). Linear regression analyses were used to test associations between self-esteem and stereotype awareness, attempt history, and their interaction. Results: There was a significant stereotype awareness by attempt interaction (β = –.74, p = .006) in the regression analysis. The interaction was explained by a stronger negative association between stereotype awareness and self-esteem among individuals with past suicide attempts (β = –.50, p = .013) compared with those without attempts (β = –.09, p = .037). Conclusion: Stigma is associated with lower self-esteem within this high-functioning sample of young adults with histories of suicide attempts. Alleviating the impact of stigma at the individual (clinical) or community (public health) levels may improve self-esteem among this high-risk population, which could potentially influence subsequent suicide risk.

The Role of Threat and Economic Uncertainty in Support for Scottish Independence

2014 ◽  
Vol 23 (1) ◽  
pp. 103-124 ◽  
Author(s):  
Daniel Kopasker
Keyword(s):  
Economic Consequences ◽  
Perceived Threat ◽  
Constitutional Change ◽  
Lack Of Information ◽  
Economic Expectations ◽  
Scottish Independence ◽  
The Individual ◽  
The Impact ◽  
Levels Of Support

Existing research has consistently shown that perceptions of the potential economic consequences of Scottish independence are vital to levels of support for constitutional change. This paper attempts to investigate the mechanism by which expectations of the economic consequences of independence are formed. A hypothesised causal micro-level mechanism is tested that relates constitutional preferences to the existing skill investments of the individual. Evidence is presented that larger skill investments are associated with a greater likelihood of perceiving economic threats from independence. Additionally, greater perceived threat results in lower support for independence. The impact of uncertainty on both positive and negative economic expectations is also examined. While uncertainty has little effect on negative expectations, it significantly reduces the likelihood of those with positive expectations supporting independence. Overall, it appears that a general economy-wide threat is most significant, and it is conjectured that this stems a lack of information on macroeconomic governance credentials.

332-OR: Determining the Impact of Additional Macronutrients on the Glycemic-Insulin Dynamic Model

Diabetes ◽  
2019 ◽  
Vol 68 (Supplement 1) ◽  
pp. 332-OR
Author(s):  
BOYI JIANG ◽  
YUXIANG ZHONG ◽  
PRATIK AGRAWAL ◽  
TONI L. CORDERO ◽  
ROBERT VIGERSKY
Keyword(s):  
Dynamic Model ◽  
The Impact
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