scholarly journals Research on the Tensile Mechanical Properties of a Braided Corrugated Hose and Its Axial Stiffness Model

2021 ◽  
Vol 9 (9) ◽  
pp. 1029
Author(s):  
Dacheng Huang ◽  
Jianrun Zhang
Keyword(s):  
Simulation Experiment ◽  
Structural Parameters ◽  
Physical Property ◽  
Nonlinear Effects ◽  
Accurate Method ◽  
Axial Stiffness ◽  
Vibration Absorption ◽  
Stiffness Model ◽  
Braiding Angle ◽  
Good Agreement

Braided corrugated hoses are widely used in displacement compensation and vibration absorption environments due to their excellent flexibility and energy dissipation properties; however, the axial stiffness has rarely been discussed before as an important physical property of braided corrugated hoses. In this paper, the theoretical axial stiffness model for braided corrugated hoses is established based on the energy method and the theory of the curved beam. The influences of the braiding parameters of the metallic braided tube and the structural parameters of the bellows on the axial stiffness are also discussed. Through finite element tensile testing, the axial stiffness curves of the braided corrugated hose under different braiding angles and different wire diameters are obtained. The theoretical axial stiffness model is in good agreement with the simulation experiment, which reflects the nonlinear effects of the braiding angle and wire diameter on the braided corrugated hose. This paper provides an accurate method and basis for the design of braided corrugated hoses in the future.

scholarly journals Электронная структура и нелинейная диэлектрическая восприимчивость γ-фазы оксида теллура

2020 ◽  
Vol 62 (4) ◽  
pp. 547
Author(s):  
Е.М. Рогинский ◽  
М.Б. Смирнов
Keyword(s):  
Structural Parameters ◽  
Correction Term ◽  
Accurate Method ◽  
Quantum Mechanical ◽  
Wannier Functions ◽  
Direct Band Gap ◽  
Valence Electrons ◽  
Direct Band ◽  
Ab Inito ◽  
Good Agreement

The structural electronic and nonlinear optical properies of the γ-TeO2 crystal is studied by ab inito quantum mechanical calculations. The incluence of 5d electrons localization effect is taken into account in calculations by using Habbard-like correction term (LDA+U approximation). The obtained within such approach structural parameters are obtained in a good agreement with experimental data. The electronic bund structure is studied within quasiparticle G0W0 approximation, which is known as the most accurate method. It was found that the γ-TeO2 crystal is wide gap semiconductor with non-direct band gap. The analysis of the chemical bond is performed using Maximaly Localized Wannier functions. It is established that the valence electrons of ozigen atoms are belong to sp3-hybridization states and valence of tellurium atoms are equal to four.

An efficient procedure to predict the dynamic loads for piston liner systems in marine engines

2021 ◽  
pp. 146808742199698
Author(s):  
Lyu Xiuyi ◽  
Abdullah Azam ◽  
Wang Yuechang ◽  
Lu Xiqun ◽  
Li Tongyang ◽  
...  
Keyword(s):  
Simulation Analysis ◽  
Structural Parameters ◽  
Computation Time ◽  
Primary Source ◽  
Cylinder Liner ◽  
Accurate Method ◽  
Friction Behavior ◽  
Accuracy Requirement ◽  
Precise Prediction ◽  
Friction Prediction

The piston ring-cylinder liner (PRCL) is one of the most important parts of marine diesel engines and contributes 25% to 50% of total friction loss. The lubrication simulation analysis of the PRCL system is a challenging task. Complete understanding and precise prediction of lubrication loads is a key to understanding the friction behavior of PRCL systems as the accuracy of the friction prediction depends upon precise prediction of lubrication loads. Therefore, this paper focuses on the gas pressure calculation which is the primary source of lubrication loads. The procedure presented combines the advantages of two mainstream methods to predict loads in the PRCL system. The result is a significant reduction in the computation time without compromising on accuracy. Firstly, a comparison of both approaches is presented which suggests that each technique has its limitations (one is time-bound, and one is accuracy-bound). Then, the results from both calculation methods are verified against literature and a parametric study is performed to identify the key structural parameters of PRCL system that affect the calculation efficiency. Finally, a correlation coefficient is introduced into the analysis to combine the two approaches which then identifies the conditions under which the use of the faster method becomes invalid and replaces it with the more accurate approach. This ensures optimum performance of the calculation procedure by switching between the fast and the accurate method depending upon the accuracy requirement under given conditions, thereby, simplifying the dynamic and lubrication model of PRCL systems. The study has direct implications for the tribological design of the PRCL interface.

Theoretical Investigations on Mechanical Stability and Electronic Structure of NbN under Pressures

2011 ◽  
Vol 90-93 ◽  
pp. 1264-1271
Author(s):  
Xiao Feng Li ◽  
Jun Yi Du
Keyword(s):  
Debye Temperature ◽  
Density Functional ◽  
Mechanical Stability ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Hexagonal Structure ◽  
Functional Theory ◽  
Theoretical Investigations ◽  
Crystallographic Structures ◽  
Good Agreement

The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

Theoretical Prediction of Motions of High-Speed Planing Boats in Waves

1978 ◽  
Vol 22 (03) ◽  
pp. 140-169
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Nonlinear Effects ◽  
Theoretical Method ◽  
Valuable Insight ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Response Amplitude Operators ◽  
Phase Angles ◽  
Good Agreement

A theoretical method is derived for predicting the linearized response characteristics of constant deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed to length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.

Mechanical and thermal behaviors of ultra-high molecular weight polyethylene triaxial braids: the influence of structural parameters

2018 ◽  
Vol 89 (16) ◽  
pp. 3362-3373 ◽  
Author(s):  
Shenglei Xiao ◽  
Charles Lanceron ◽  
Peng Wang ◽  
Damien Soulat ◽  
Hang Gao
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Mechanical Characteristics ◽  
Structural Parameters ◽  
Tensile Tests ◽  
Tensile Behavior ◽  
Experimental Database ◽  
Strength And Deformation ◽  
Braiding Angle ◽  
Ultra High Molecular Weight

Recently, triaxial braids made from ultra-high molecular weight polyethylene (UHMWPE) have been recognized as one of the most popular composite reinforcements in the aerospace and defense fields. To further explore the mechanical characteristics of this material, a detailed experimental study on tensile behavior is reported in this paper. The triaxial braids show a “double-peak” phenomenon in tensile strength and deformation, caused by axial yarns and the in-plane shearing of bias yarns. The evolution of the braiding angle, measured during these tensile tests, is discussed according to the braiding parameters (initial braiding angle, number of axial yarns). Using the high conductivity properties of the UHMWPE material, the temperature caused by inter-yarn friction during tensile tests is also studied. This temperature is related to the evolution of the braiding angle. The temperature increases with the increasing number of axial yarns and decreases with increasing braiding angle. This study provides an experimental database on the influence of braiding parameters on the tensile behavior of triaxial braids.

scholarly journals Prediction of Dynamic Stability Using Mapped Chebyshev Pseudospectral Method

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jae-Young Choi ◽  
Dong Kyun Im ◽  
Jangho Park ◽  
Seongim Choi
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Pseudospectral Method ◽  
Accurate Method ◽  
Spectral Approach ◽  
Fourier Pseudospectral Method ◽  
Chebyshev Pseudospectral Method ◽  
Fourier Pseudospectral ◽  
Chebyshev Pseudospectral ◽  
Good Agreement

A mapped Chebyshev pseudospectral method is extended to solve three-dimensional unsteady flow problems. As the classical Chebyshev spectral approach can lead to numerical instabilities due to ill conditioning of the spectral matrix, the Chebyshev points are evenly redistributed over the domain by an inverse sine mapping function. The mapped Chebyshev pseudospectral method can be used as an alternative time-spectral approach that uses a Chebyshev collocation operator to approximate the time derivative terms in the unsteady flow governing equations, and the method can make general applications to both nonperiodic and periodic problems. In this study, the mapped Chebyshev pseudospectral method is employed to solve three-dimensional periodic problem to verify the spectral accuracy and computational efficiency with those of the Fourier pseudospectral method and the time-accurate method. The results show a good agreement with both of the Fourier pseudospectral method and the time-accurate method. The flow solutions also demonstrate a good agreement with the experimental data. Similar to the Fourier pseudospectral method, the mapped Chebyshev pseudospectral method approximates the unsteady flow solutions with a precise accuracy at a considerably effective computational cost compared to the conventional time-accurate method.

The Free Energy Simulation Approach to Grain Boundary Segregation In Cu-Ni

1990 ◽  
Vol 209 ◽  
Author(s):  
H. Y. Wang ◽  
R. Najafabadi ◽  
D. J. Srolovitz ◽  
R. Lesar
Keyword(s):  
Monte Carlo ◽  
Free Energy ◽  
Grain Boundary ◽  
Chemical Potential ◽  
Boundary Segregation ◽  
Configurational Entropy ◽  
Accurate Method ◽  
Increasing Temperature ◽  
Atomic Coordinates ◽  
Good Agreement

ABSTRACTA new, accurate method for determining equilibrium segregation to defects in solids is employed to examine the segregation of Cu to grain boundaries in Cu-Ni alloys. The results are in very good agreement with the ones given by Monte Carlo. This method is based upon a point approximation for the configurational entropy, an Einstein model for vibrational contributions to the free energy. To achieve the equilibrium state of a defect in an alloy the free energy is minimized with respect to atomic coordinates and composition of each site at constant chemical potential. One of the main advantages this new method enjoys over other methods such as Monte Carlo, is the efficiency with which the atomic structure of a defect, segregation and thermodynamic properties can be determined. The grain boundary free energy can either increase or decrease with increasing temperature due to the competition between energetic and configurational entropy terms. In general, the grain boundary free energy increases with temperature when the segregation is strongest.

A study of tubular braided structure with negative Poisson’s ratio behavior

2017 ◽  
Vol 88 (24) ◽  
pp. 2810-2824 ◽  
Author(s):  
Ning Jiang ◽  
Hong Hu
Keyword(s):  
Poisson’S Ratio ◽  
Structural Parameters ◽  
Uniaxial Extension ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Yarn Diameter ◽  
Wrap Angle ◽  
Negative Poisson's Ratio ◽  
Braided Structure ◽  
Braiding Angle

Textile structures with negative Poisson’s ratio (PR) behavior are called auxetic textile structures. They have received increasing attention in recent years and have been designed and fabricated through spinning, knitting, weaving and non-woven methods. However, auxetic textile structures fabricated using braiding method have not been reported so far. This paper reported a novel type of auxetic braided structure based on a helical structural arrangement. The geometry of the structure and its deformation mechanism were first introduced and described. Then a special manufacturing process was developed by the modification of commonly used tubular braiding technology. Various auxetic braids were fabricated with different structural parameters and yarns and tested under uniaxial extension conditions. The results showed that all manufactured braids exhibited high negative PR behavior and maintained this behavior until the fracture of the component wrap yarn. Among three structural parameters discussed, namely wrap angle, braiding angle and braiding yarn diameter, the wrap angle had more effects on the tensile properties of auxetic braided structure than the other two parameters. The success of fabricating auxetic braids with commercially available yarns in this study provides an alternative way to manufacture auxetics from positive PR materials.

scholarly journals Theoretical investigation of acoustic wave velocity of aluminum phosphide under pressure

2019 ◽  
Vol 7 (1) ◽  
pp. 3
Author(s):  
Salah Daoud ◽  
Abdelhakim Latreche ◽  
Pawan Kumar Saini
Keyword(s):  
Acoustic Wave ◽  
Wave Velocity ◽  
Elastic Constants ◽  
Structural Parameters ◽  
Theoretical Data ◽  
Aluminum Phosphide ◽  
Semiconducting Material ◽  
Wave Velocities ◽  
Knoop Microhardness ◽  
Good Agreement

The bulk and surface acoustic wave velocities of Aluminum phosphide (AlP) semiconducting material under pressure up to 9.5 GPa were studied. The structural parameters and the elastic constants used in this work are taken from our previous paper published in J. Optoelec-tron. Adv. M. 16, 207 (2014). The results obtained at zero-pressure are analyzed and compared with other data of the literature. In addition, the acoustic Grüneisen parameter and the Vickers and Knoop microhardness are predicted and analyzed in detail. Our calculated results are in good agreement with the experimental and other theoretical data of literature.   

Design guidelines for bump-type compliant conical foil bearing

2021 ◽  
pp. 095440622110127
Author(s):  
Hongyang Hu ◽  
Ming Feng
Keyword(s):  
Load Capacity ◽  
Design Guidelines ◽  
Foil Thickness ◽  
Axial Stiffness ◽  
Structural Stiffness ◽  
Foil Bearing ◽  
Stiffness Model ◽  
Opposite Position ◽  
Stiffness Distribution ◽  
Half Length

The integral bump foil strip cannot optimize the performance for the compliant conical foil bearing (CFB) as the uneven distribution of structural stiffness. To maximize the bearing characteristics, this paper proposed different bump foil schemes. Firstly, the anisotropy of CFB was studied based on the nonlinear bump stiffness model, and the circumferentially separated foil structure was proposed. Moreover, an axially separated bump foil structure with the variable bump length was introduced to make the axial stiffness distribution more compliant with the gas pressure. In addition, the effect of foil thickness was also discussed. The results show that CFB with integral bump foil exhibits obvious anisotropy, and the suggested installation angle for largest load capacity and best dynamic stability are in the opposite position. Fortunately, a circumferential separated bump foil can improve this defect. The characteristics of CFB with axial separated foil structure can be improved significantly, especially for that with more strips and the variable bump half-length design. The suitable bump and top foil thickness should be set considering the improved supporting performance and proper flexibility. The results can give some guidelines for the design of CFB.

Sign in / Sign up

Export Citation Format

Share Document