Change of Ice Resistance of Ice-Breaking Tanker According to Frictional Coefficient

Selecting an optimal bow configuration is critical to the preliminary design of polar ships. This paper proposes an approach to determine the optimal bow of polar ships based on present numerical simulation and available published experimental studies. Unlike conventional methods, the present approach integrates both ice resistance and calm-water resistance with the navigating time. A numerical simulation method of an icebreaking vessel going straight ahead in level ice is developed using SPH (smoothed particle hydrodynamics) numerical technique of LS-DYNA. The present numerical results for the ice resistance in level ice are in satisfactory agreement with the available published experimental data. The bow configurations with superior icebreaking capability are obtained by analyzing the sensitivities due to the buttock angle γ, the frame angle β and the waterline angle α. The calm-water resistance is calculated using FVM (finite volume method). Finally, an overall resistance index devised from the ship resistance in ice/water weighted by their corresponding weighted navigation time is proposed. The present approach can be used for evaluating the integrated resistance performance of the polar ships operating in both a water route and ice route.

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Analysis of Chemisorbed Tribo-Film for Ceramic-on-Ceramic Hip Joint Prostheses by Raman Spectroscopy

Journal of Functional Biomaterials ◽

10.3390/jfb12020029 ◽

2021 ◽

Vol 12 (2) ◽

pp. 29

Author(s):

Risha Rufaqua ◽

Martin Vrbka ◽

Dušan Hemzal ◽

Dipankar Choudhury ◽

David Rebenda ◽

...

Keyword(s):

Raman Spectroscopy ◽

Hyaluronic Acid ◽

Hip Joint ◽

Total Joint Replacement ◽

Film Formation ◽

Frictional Coefficient ◽

Synovial Fluids ◽

Frictional Coefficients ◽

Joint Prostheses ◽

Ceramic On Ceramic

To understand the possible lubricant mechanism in ceramic-on-ceramic hip joint prostheses, biochemical reactions of the synovial fluid and the corresponding frictional coefficients were studied. The experiments were performed in a hip joint simulator using the ball-on-cup configuration with balls and cups made from two types of ceramics, BIOLOX®forte and BIOLOX®delta. Different lubricants, namely albumin, γ-globulin, hyaluronic acid and three model synovial fluids, were studied in the experiments and Raman spectroscopy was used to analyze the biochemical responses of these lubricants at the interface. BIOLOX®delta surface was found less reactive to proteins and model fluid lubricants. In contrast, BIOLOX®forte ball surface has shown chemisorption with both proteins, hyaluronic acid and model fluids imitating total joint replacement and osteoarthritic joint. There was no direct correlation between the measured frictional coefficient and the observed chemical reactions. In summary, the study reveals chemistry of lubricant film formation on ceramic hip implant surfaces with various model synovial fluids and their components.

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Formulation of Ice Resistance in Level Ice Using Double-Plates Superposition

Journal of Marine Science and Engineering ◽

10.3390/jmse8110870 ◽

2020 ◽

Vol 8 (11) ◽

pp. 870

Author(s):

Liang Li ◽

Qingfei Gao ◽

Alexander Bekker ◽

Hongzhe Dai

Keyword(s):

Elastic Plate ◽

Approximate Model ◽

Ice Thickness ◽

Full Scale Test ◽

Ship Resistance ◽

Bending Resistance ◽

Level Ice ◽

Scale Test ◽

Coulomb Criterion ◽

Ice Resistance

The estimation of ship resistance in ice is a fundamental area of research and poses a substantial challenge for the design and safe use of ships in ice-covered waters. In order to estimate the ice resistance with greater reliability, we develop in this paper an improved Lindqvist formulation for the estimation of bending resistance in level ice based on the superposition of double-plates. In the developed method, an approximate model of an ice sheet is firstly presented by idealizing ice sheeta as the combination of a semi-infinite elastic plate and an infinite one resting on an elastic foundation. The Mohr–Coulomb criterion is then introduced to determine the ice sheet’s failure. Finally, an improved Lindqvist formulation for estimation of ice resistance is proposed. The accuracy of the developed formulation is validated using full-scale test data of the ship KV Svalbard in Norway, testing the model as well as the numerical method. The effect of ice thickness, stem angle and breadth of bow on ship resistance is further investigated by means of the developed formulation.

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Developments in Modelling Bone Screwing

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2020-3029 ◽

2020 ◽

Vol 6 (3) ◽

pp. 111-114

Author(s):

Jack Wilkie ◽

Paul D. Docherty ◽

Knut Möller

Keyword(s):

Material Properties ◽

Frictional Coefficient ◽

Viscous Friction ◽

Model Parameters ◽

General Shape ◽

Bone Material ◽

Bone Material Properties ◽

Modelling Methodology ◽

Recorded Data ◽

Friction Models

AbstractINTRODUCTION: A torque-rotation model of the bone-screwing process has been proposed. Identification of model parameters using recorded data could potentially be used to determine the material properties of bone. These properties can then be used to recommend tightening torques to avoid over or under-tightening of bone screws. This paper improves an existing model to formulate it in terms of material properties and remove some assumptions. METHOD: The modelling methodology considers a critical torque, which is required to overcome friction and advance the screw into the bone. Below this torque the screw may rotate with elastic deformation of the bone tissue, and above this the screw moves relative to the bone, and the speed is governed by a speed-torque model of the operator’s hand. The model is formulated in terms of elastic modulus, ultimite tensile strength, and frictional coefficient of the bone and the geometry of the screw and hole. RESULTS: The model output shows the speed decreasing and torque increasing as the screw advances into the bone, due to increasing resistance. The general shape of the torque and speed follow the input effort. Compared with the existing model, this model removes the assumption of viscous friction, models the increase in friction as the screw advances into the bone, and is directly in terms of the bone material properties. CONCLUSION: The model presented makes significant improvements on the existing model. However it is intended for use in parameter identification, which was not evaluated here. Further simulation and experimental validation is required to establish the accuracy and fitness of this model for identifying bone material properties.

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Experimental evidence for friction-enhancing integumentary modifications of chameleons and associated functional and evolutionary implications

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2013.2334 ◽

2014 ◽

Vol 281 (1775) ◽

pp. 20132334 ◽

Cited By ~ 9

Author(s):

Eraqi R. Khannoon ◽

Thomas Endlein ◽

Anthony P. Russell ◽

Kellar Autumn

Keyword(s):

Experimental Evidence ◽

Frictional Coefficient ◽

Force Transducer ◽

Morphological Convergence ◽

Functional Implications ◽

Smooth Skin ◽

Derivatives Of

The striking morphological convergence of hair-like integumentary derivatives of lizards and arthropods (spiders and insects) demonstrates the importance of such features for enhancing purchase on the locomotor substrate. These pilose structures are responsible for the unique tractive abilities of these groups of animals, enabling them to move with seeming ease on overhanging and inverted surfaces, and to traverse inclined smooth substrates. Three groups of lizards are well known for bearing adhesion-promoting setae on their digits: geckos, anoles and skinks. Similar features are also found on the ventral subdigital and distal caudal skin of chameleons. These have only recently been described in any detail, and structurally and functionally are much less well understood than are the setae of geckos and anoles. The seta-like structures of chameleons are not branched (a characteristic of many geckos), nor do they terminate in spatulate tips (which is characteristic of geckos, anoles and skinks). They are densely packed and have attenuated blunt, globose tips or broad, blade-like shafts that are flattened for much of their length. Using a force transducer, we tested the hypothesis that these structures enhance friction and demonstrate that the pilose skin has a greater frictional coefficient than does the smooth skin of these animals. Our results are consistent with friction being generated as a result of side contact of the integumentary filaments. We discuss the evolutionary and functional implications of these seta-like structures in comparison with those typical of other lizard groups and with the properties of seta-mimicking synthetic structures.

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Research on Modeling Method of Runway Frictional Coefficient Measuring Vehicle Based on Impedance Diagrams

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.214.133 ◽

2011 ◽

Vol 214 ◽

pp. 133-137 ◽

Cited By ~ 1

Author(s):

Xu Dong Shi ◽

Shou Wen Shi ◽

Lu Zhang ◽

Jian Li Li

Keyword(s):

Surface Roughness ◽

Friction Coefficient ◽

Measurement Data ◽

Frictional Coefficient ◽

Modeling Method ◽

Measuring System ◽

Discrete Fourier Transformation ◽

Measuring Error ◽

Impedance Diagram ◽

Airport Runway

Airport runway friction coefficient is an important parameter to evaluate the quality of runway which is usually measured by runway friction coefficient measuring vehicle. In order to reduce the airport runway friction coefficient measuring error which comes from runway vibration caused by road roughness and vehicle its own structural characteristics, an impedance diagram is used to model the suspending system and measuring system of the measuring vehicle. The power spectral density of pavement and inverse discrete Fourier transformation are introduced to model runway surface roughness as excitation input. The rationality of the stimulating established model is validated by comparing with an airport runway surface roughness measurement data. Runway friction coefficient measuring vehicle′s measuring error can be reduced and the measurement accuracy can be improved by using the impedance diagram modeling method.

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Vibratory Conveying by Harmonic Longitudinal and Polyharmonic Normal Vibrations of Inclined Conveying Track

Journal of Vibration and Acoustics ◽

10.1115/1.4051228 ◽

2021 ◽

pp. 1-14

Author(s):

Ihor Vrublevskyi

Keyword(s):

Inclination Angle ◽

Normal Vibration ◽

Longitudinal Vibration ◽

Frictional Coefficient ◽

Material Point ◽

Normal Vibrations ◽

Dimensionless Parameters ◽

Optimal Values ◽

Vibration Parameters ◽

Angle Parameter

Abstract Vibratory conveying of a material point by harmonic longitudinal and polyharmonic normal vibrations of an inclined conveying surface is considered. The dependence of dimensionless conveying velocity – a ratio of velocity to the product of frequency and amplitude of longitudinal vibration – on several dimensionless parameters is investigated in the moving modes without hopping. Maximal conveying velocity is achieved at the certain values of normal vibration amplitudes and phase difference angle between the longitudinal and normal vibrations, which are called optimal. Their values are dependent on two dimensionless parameters: the inclination angle parameter – a ratio of an inclination angle tangent to a frictional coefficient, the intensive vibration coefficient – a ratio of the longitudinal amplitude of vibration to the amplitude of the first harmonic of normal vibration and frictional coefficient. In a condition of the intensive longitudinal vibration, when its amplitude significantly greater than amplitudes of normal vibration, dimensionless velocity is almost independent of the intensive vibration parameter and it depends only on inclination angle parameter, i.e. on inclination angle and frictional coefficient. The optimal values of harmonics' amplitudes of polyharmonic normal vibration are determined in dependence of inclination angle parameter with the number of harmonics from 2 to 7. The graphs of considered dependencies are presented and the most important values of parameters are presented in the table. Conclusions are made to determine the optimal vibration parameters and the problems of further research are indicated. The considered vibrations can be used in different vibratory conveying devices with electromagnetic drives.

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Stability of a String in Axial Flow

Journal of Energy Resources Technology ◽

10.1115/1.3231213 ◽

1985 ◽

Vol 107 (4) ◽

pp. 421-425 ◽

Cited By ~ 23

Author(s):

G. S. Triantafyllou ◽

C. Chryssostomidis

Keyword(s):

Stability Analysis ◽

Frictional Coefficient ◽

Axial Flow ◽

Added Mass ◽

Equation Of Motion ◽

Bending Stiffness ◽

Diameter Ratio ◽

Constant Speed ◽

Hamilton’S Principle ◽

The Stability

The equation of motion of a long slender beam submerged in an infinite fluid moving with constant speed is derived using Hamilton’s principle. The upstream end of the beam is pinned and the downstream end is free to move. The resulting equation of motion is then used to perform the stability analysis of a string, i.e., a beam with negligible bending stiffness. It is found that the string is stable if (a) the external tension at the free end exceeds the value of a U2, where a is the “added mass” of the string and U the fluid speed; or (b) the length-over-diameter ratio exceeds the value 2Cf/π, where Cf is the frictional coefficient of the string.

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