scholarly journals Methodology for calculating rope drums for stability

2021 ◽  
pp. 83
Author(s):  
Nаtalya Fidrovska ◽  
Viktoria Nesterenko ◽  
Ruslan Karavan
Keyword(s):  
Critical Load ◽  
Stability Margin ◽  
External Pressure ◽  
Shell Shape ◽  
Metal Consumption ◽  
Safety And Reliability ◽  
The Difference ◽  
The Stability ◽  
Stability Issues ◽  
Good Agreement

. The problems of the stability of rope drums are quite urgent. The rope drum is in most cases a thin-walled shell, which, under the influence of external pressure from the rope, can lead to loss of stability. The stability issues of the drum shell, which is loaded with rope turns, are very important, because the safety and reliability of the rope hoist is directly related to them The studies carried out made it possible to obtain a new method for calculating the stability of cylindrical shells, which takes into account not only the length of the shell, but also the rigidity of the connection with the head. In addition, a calculation formula was obtained to determine the critical pressure of the oval shell, which gives a fairly good agreement with the experiments of American scientists. The work also considered the effect of the difference in wall thickness on the critical load of the drum. The studies carried out made it possible to conclude that the parameters of the rope drums make it possible to completely eliminate the need to install rings and stiffeners. Also as a result of research it was found that the shell of the crane drum under the influence of a radial load cannot lose stability. Studies have shown that in all cases the stability margin of the rope drum shell is greater than the strength margin. In this case, the load created by the rope wound on the drum is considered, with the ratios of the radius of the drum and the rope typical for crane construction. In addition, a coefficient was established that takes into account the elasticity of the shell-head joint. The studies carried out have shown that such initial deviations of the drum shell shape as ovality do not give a significant increase in the critical load. The results obtained are quite important, since they allow reducing the metal consumption of the rope drum shell and at the same time ensuring its reliable operation. A decrease in metal consumption is achieved by reducing the thickness of the shell and the absence of the need to install rings and stiffeners. This will lead to a decrease in metal consumption and energy consumption of the crane itself, and also simplifies the technology of manufacturing a rope drum.

Energetics and Structural Effects of Boron Additive to Intermetallic Compound: γ-Tial

1990 ◽  
Vol 213 ◽  
Author(s):  
P.K. Khowash ◽  
D.L. Price ◽  
B.R. Cooper
Keyword(s):  
Intermetallic Compound ◽  
Total Energy ◽  
Site Selection ◽  
Lattice Structure ◽  
Practical Importance ◽  
The Difference ◽  
The Stability ◽  
Experimental Values ◽  
And Behavior ◽  
Good Agreement

ABSTRACTImproving the low temperature ductility of the intermetallic compound γ - TiAl by alloying with small concentrations of an additive is of great practical importance. The difference in site selection energy of the additive plays an important role in the stability and behavior of the alloy. For boron in L10 TiAl, we have calculated the site selection energy using linearized combination of muffin-tin orbitals (LMTO) total energy calculations. For pure γ - TiAl, we found the equilibrium lattice structure by minimizing the total energy, and obtained good agreement with the experimental values. With the introduction of boron, a relaxation of the lattice around the boron additive is expected. For boron additives, we have calculated the forces on each atom leading to the minimization of the total energy as a function of the ionic positions in order to obtain the “true” stable structure of the alloy.

Model Reduction of a Parametrically Excited Drivetrain

2012 ◽  
Author(s):  
Thomas Pumhoessel ◽  
Peter Hehenberger ◽  
Klaus Zeman
Keyword(s):  
Stability Margin ◽  
Original System ◽  
Reduced Model ◽  
Parametrically Excited ◽  
System Parameters ◽  
Additional Stability ◽  
System Equations ◽  
The Difference ◽  
Set Up ◽  
The Stability

The complexity of engineering systems is continuously increasing, resulting in mathematical models that become more and more computationally expensive. Furthermore, in model based design, for example, system parameters are subject of change, and therefore, the system equations have to be evaluated repeatedly. Hence, there is a need for providing reduced models which are as compact as possible, but still reflect the properties of the original model in a satisfactory manner. In this contribution, the reduction of differential equations with time-periodic coefficients, termed as parametrically excited systems, is investigated using the method of Proper Orthogonal Decomposition (POD). A reduced model is set up based on the solution of the original system for a certain parametric combination resonance of the difference type, resulting in an additional stability margin of the trivial solution. It is shown that the POD reduced model approximates the stability behavior of the original system much better than a modally reduced model even if system parameters are subject of change.

Linear Stability Analysis and Buckling of Two-Layered Shells Under External Circumferential Loading: A Numerical Investigation

2009 ◽  
Author(s):  
George Papadakis
Keyword(s):  
Critical Load ◽  
Numerical Investigation ◽  
Engineering Practice ◽  
Pressure Loading ◽  
Layered Shells ◽  
Differential Stability ◽  
The Stability ◽  
Volume Method ◽  
Moduli Of Elasticity ◽  
Good Agreement

The aim of the paper is the numerical investigation of the stability of two-layered shells under the action of imposed azimuthal strain on the external surface. Although this type of loading is not common in engineering practice, it appears often in biomedicine (for example buckling of esophagus, asthmatic airways, gastrointestinal tract etc). The differential stability equations are discretised using the finite volume method and the resulting generalised eigenvalue problem is solved using the QZ decomposition technique. The results show that the buckling behaviour under circumferential loading is entirely different compared to hydrostatic pressure loading. More specifically, it is well known that in the latter case the number of folds with the smallest critical load is equal to 2. In the former case however it depends on the thickness of each layer and their moduli of elasticity. Comparison with experimental measurements shows good agreement. The thickness of the inner layer significantly affects the number of folds and the critical load (it was found that the number of folds is reduced with increasing layer thickness). Comparison of the eigenfunctions of radial and azimuthal displacements also shows more complex behavior compared to pressure loading.

scholarly journals Study on the Stability of Trivalent Cations Doped Zirconia through Atomistic Modeling

2019 ◽  
Vol 22 (4) ◽  
pp. 129-135
Author(s):  
Akram La Kilo ◽  
Triwahyuni S. Umamah ◽  
Lukman A. R. Laliyo
Keyword(s):  
Geometry Optimization ◽  
Lattice Energy ◽  
Atomistic Modeling ◽  
Cell Parameters ◽  
Short Range Potential ◽  
Atomistic Modelling ◽  
Trivalent Cations ◽  
The Difference ◽  
The Stability ◽  
Good Agreement

The aim of this research was to study the stability of the structure of the ZrO2 doped with trivalent oxide Zr1-xMxO2-δ (M = La3+, Nd3+, Sm3+, Eu3+, Gd3+, Y3+, Er3+, Yb3+ and Lu3+ through atomistic modelling and bond valence sum method. Short range potential used in this study was Buckinghams’ potential. Result of geometry optimization at constant pressure shown both cell parameters of ZrO2 was in good agreement with experimental results because of the difference was only 0.11%. Increasing the concentration and the size of substituting dopant of ZrO2 makes the lattice energy of the doped structure was more positive so that the stability of the doped ZrO2 structure decreases. The decrease in the stability of ZrO2 doped with Y3+, Er3+, Yb3+ and Lu3+was smaller than ZrO2 doped with La3+, Nd3+, Sm3+, Eu3+ and Gd3+. BVS results shown that the structure of ZrO2 doped with La3+was not appropriate because it has different value of BVS was more than 0.1

Development of Simple SPD Tight-Binding Models for Transition Metals

1997 ◽  
Vol 491 ◽  
Author(s):  
O. Le Bacq ◽  
F. Willaime ◽  
A. Pasturel
Keyword(s):  
Transition Metals ◽  
Tight Binding ◽  
Pair Potential ◽  
Basis Set ◽  
Atomistic Simulations ◽  
Band Model ◽  
The Difference ◽  
The Stability ◽  
Stability Results ◽  
Good Agreement

ABSTRACTA simple spd tight-binding scheme for atomistic simulations in transition metals is developed using an orthogonal basis set in the two-center approximation. The purpose of the present approach is to cope with the limitations of the canonical d-band model for elements at the beginning or at the end of the transition metal series while keeping a reduced number of parameters, and simple decay-functions. The parameters for the hopping integrals are fitted to FP-LMTO calculations of the volume dependence of band energies and band structures for several selected structures. Constant values are taken for the on-site energies, and the Born-Mayer pair potential is used for the repulsive term. Two approaches are compared for the total energy: the band model and the bond model. First applications are presented in the case of zirconium, where the difference between these models on phase stability results is particularly drastic. The bond model reproduces the stability of the hep phase and displays a good agreement with experiments for the elastic constants.

scholarly journals The effect of pressure on structural, stability, electronic, and optical properties of hydrogenated silicene: A first-principle study

2021 ◽  
Author(s):  
V Kumar ◽  
R. Santosh
Keyword(s):  
Optical Properties ◽  
Binding Energy ◽  
External Pressure ◽  
Optical Parameters ◽  
First Principle ◽  
Electronic And Optical Properties ◽  
External Pressures ◽  
The Stability ◽  
First Time ◽  
Good Agreement

Abstract The structural, electronic, and optical properties of hydrogenated silicene have been studied under different pressures using first-principle calculations. The binding energy and band structure have been calculated for two stable structures: Chair (C-) and Boat (B-) in the range of 0–21 GPa external pressure. The behavior of stability and energy bandgap have been analyzed under different external pressures. The stability has been verified using binding energy and phonon data. The C- and B- structures have zero bandgaps at 21 GPa and become unstable. The optical properties of B-configuration have been studied in the energy range of 0–20 eV. Five optical parameters such as conductivity threshold (σth), dielectric constant ε(0), refractive index n(0), birefringence Δn(0) and plasmon energy (ħωp) have been calculated for the first time under different pressures. The calculated values are in good agreement with the reported values at 0 GPa.

scholarly journals Local Buckling Characteristics of Stainless-Steel Polypropylene Deep-Sea Sandwich Pipe under Axial Tension and External Pressure

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4866
Author(s):  
Jianxing Yu ◽  
Weipeng Xu ◽  
Nianzhong Chen ◽  
Sixuan Jiang ◽  
Shengbo Xu ◽  
...  
Keyword(s):  
Finite Element ◽  
Local Buckling ◽  
External Pressure ◽  
Loading Path ◽  
Finite Element Models ◽  
Collapse Pressure ◽  
Loading Paths ◽  
Axial Tension ◽  
The Difference ◽  
Good Agreement

In this paper, the effects of different loading paths of axial tension and external pressure on the collapse pressure of sandwich tubes are studied by experiments and finite element models. The difference of the two loading paths is investigated. Eight experiments were carried out to study the influence of different loading paths on pipeline collapse pressure under the same geometric and material parameters. Parameterization studies have been carried out, and the results are in good agreement with the experimental results. The test and finite element results show that the loading path of external pressure first and then the axial tension (P→T) is more dangerous; the collapse pressure of the sandwich pipe is smaller than the other. Through parametric analysis, the influence of the axial tension and the diameter-to-thickness ratio of the inner and outer pipe on the collapse pressure under different loading paths are studied.

Biomechanical investigations of the secondary stability of commercial short dental implants in porcine ribs

2014 ◽  
Vol 59 (6) ◽  
Author(s):  
Rebecca Wilhelm ◽  
Istabrak Hasan ◽  
Ludger Keilig ◽  
Friedhelm Heinemann ◽  
Helmut Stark ◽  
...  
Keyword(s):  
Dental Implants ◽  
Measurement System ◽  
Experimental Results ◽  
Short Implants ◽  
The Difference ◽  
The Stability ◽  
Secondary Stability ◽  
Good Agreement

AbstractThe use of short implants has increased widely within the last years. However, the stability of these implants has not yet been comprehensively investigated, in particular the difference in geometry and dimension of short implants. The aim of the present study was to investigate experimentally the difference of the secondary stability of different commercial short implants by measuring their displacements. Eleven implant geometries were investigated in this study. A total of 22 implants were inserted in porcine rib segments, two implants for each system. Implant displacements were measured using a self-developed biomechanical hexapod measurement system (HexMeS). The highest displacement was observed with Straumann BL NC 3.3×8.0 mm (266 μm), followed by Straumann Standard 4.1×6.0 mm (156 μm), while the lowest displacement of 61 μm was shown by Dentaurum type 1 implant (4.2×5.0 mm). No obvious difference of displacements was observed between hammered and screw-shaped implants with relevant dimensions. The experimental results were in good agreement with the numerical ones (19–42%) for Dentaurum implants. However, a difference of 70–80% was obtained for the Astra implant (4.0×6.0 mm) and Bicon implant (6.0×5.7 mm). The geometry of short implants directly affects their stability within the bone.

Stability Analysis of a Processor Unit Served in Deep-Sea

2011 ◽  
Vol 697-698 ◽  
pp. 769-773
Author(s):  
D.D. Bian ◽  
H.W. Zhang ◽  
Y.H. Liu ◽  
H.Z. Liu
Keyword(s):  
Critical Pressure ◽  
Autonomous Underwater Vehicle ◽  
External Pressure ◽  
Pressure Vessels ◽  
Wave Number ◽  
Nonlinear Buckling ◽  
Processor Unit ◽  
The Stability ◽  
Nonlinear Buckling Analysis ◽  
Good Agreement

Stability is the key of designing thin-walled external-pressure Vessels. Nonlinear buckling analysis using finite element method has been carried out on a processor unit of an autonomous underwater vehicle to study the stability of the processor unit considering the screw tightening. Effects of the cylinder thickness on the critical pressure are discussed. Results show that the buckling wave number is 4 in the circumferential direction, and the critical pressure decreases with decreasing the cylinder thickness exponentially, which is in good agreement with the theoretical calculation.

Use of a Lyophilized Reference Plasma to Compare Coagulation Test Procedures

1975 ◽  
Vol 34 (02) ◽  
pp. 426-444 ◽  
Author(s):  
J Kahan ◽  
I Nohén
Keyword(s):  
Oral Anticoagulant Therapy ◽  
Repeated Measurements ◽  
Test Procedures ◽  
Coagulation Activity ◽  
Close Relationship ◽  
Measured Activity ◽  
Test Materials ◽  
The Difference ◽  
The Stability ◽  
The One

SummaryIn 4 collaborative trials, involving a varying number of hospital laboratories in the Stockholm area, the coagulation activity of different test materials was estimated with the one-stage prothrombin tests routinely used in the laboratories, viz. Normotest, Simplastin-A and Thrombotest. The test materials included different batches of a lyophilized reference plasma, deep-frozen specimens of diluted and undiluted normal plasmas, and fresh and deep-frozen specimens from patients on long-term oral anticoagulant therapy.Although a close relationship was found between different methods, Simplastin-A gave consistently lower values than Normotest, the difference being proportional to the estimated activity. The discrepancy was of about the same magnitude on all the test materials, and was probably due to a divergence between the manufacturers’ procedures used to set “normal percentage activity”, as well as to a varying ratio of measured activity to plasma concentration. The extent of discrepancy may vary with the batch-to-batch variation of thromboplastin reagents.The close agreement between results obtained on different test materials suggests that the investigated reference plasma could be used to calibrate the examined thromboplastin reagents, and to compare the degree of hypocoagulability estimated by the examined PIVKA-insensitive thromboplastin reagents.The assigned coagulation activity of different batches of the reference plasma agreed closely with experimentally obtained values. The stability of supplied batches was satisfactory as judged from the reproducibility of repeated measurements. The variability of test procedures was approximately the same on different test materials.

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