scholarly journals Rationale for Selecting a Method for Determining Parameters of the Contact Spot of Pneumatic Wheel Mover With Support Base

2019 ◽  
Vol 5 (6) ◽  
pp. 212-228
Author(s):  
A. Lipkan ◽  
◽  
A. Panasyuk ◽  
R. Kashbulgayanov ◽  
◽  
...  
Keyword(s):  
Contact Spot ◽  
Pneumatic Wheel

scholarly journals The Contact Mechanics of Novikov’s Surface-Hardened Gearing during Running-in Process

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Alexey Beskopylny ◽  
Nikolay Onishkov ◽  
Viktor Korotkin
Keyword(s):  
Cold Deformation ◽  
Contact Fatigue ◽  
High Hardness ◽  
Contact Spot ◽  
The State ◽  
Contact Strength ◽  
Friction Forces ◽  
Contact Surfaces ◽  
Defective Surface ◽  
The Impact

The article is devoted to the analysis of the state of the contact surfaces of the higher kinematic pair in the general case of relative motion, that is, in the presence of rolling, sliding, and twisting, which is characteristic of Novikov’s circular-screw gears. The purpose of the work is to assess the impact of friction forces, the state of contact surfaces after tool processing, and the localization of the instantaneous contact spot on the level of contact—fatigue durability of gears. Power contact in the presence of geometric slippage of the mating surfaces leads to a significant change in the initial geometry and the mechanical properties of surface layers. In the existing methods of calculations of contact strength, the effect of running-in is investigated insufficiently, which leads to an incorrect result, especially for gear with high hardness of the teeth. In this work, the conditions of contact interaction close to the real requirements are studied on the basis of experimental material, numerical solution of the contact problem, determination of the terms of the contact areas of slip, and adhesion within the instantaneous spot. The shape of the instant contact spot has asymmetry and can be approximated by an ellipse with the introduction of a correction factor. The running-in period is of a plastic nature with cold deformation and reduction of the roughness of surfaces. As a result of the run-in period, the area of actual contact (tooth height) is increased by 2 or more times. It is not desirable to spread the area of contact at the area of adhesion that initiates the formation of pitting. The presence of defective surface area on the level of contact strength does not have significant influence, because of the running-in period, but increases the risk of spalling and brittle fracture.

scholarly journals BASIS OF MATHEMATICAL INTERACTION MODELS OF WHEEL PROPELLERS OF FORESTRY MACHINES WITH SLIDING SURFACES

2020 ◽  
Vol 10 (1) ◽  
pp. 173-184
Author(s):  
Olga Burmistrova ◽  
Elena Teterevleva ◽  
Igor Grigorev ◽  
O. Kunitskaya ◽  
Andrey Manukovskiy ◽  
...  
Keyword(s):  
Soil Mechanics ◽  
Physical And Mechanical Properties ◽  
Soil Mass ◽  
Contact Spot ◽  
Time Value ◽  
Partial Load ◽  
Forestry Production ◽  
The Impact ◽  
Number Of Passes ◽  
Contact Spots

The purpose of the research, the results of which are presented in this article, is to analyze the scientific description of the properties of weak bearing movement surfaces of forest machines. The analysis has showed that universal mathematical models of the wheel propeller interaction with soil are based on the provisions of soil mechanics. This approach has been tested in the science of forestry production. It is successfully used by modern domestic and foreign researchers. However, with regard to the development and implementation of a mathematical description of interaction of ultra-low pressure wheeled mover (for example, in all-terrain wheeled vehicle) with supporting surfaces, it is necessary to take into account the ratio of the sides of the mover’s contact spot with the soil, since: mover pressure on the ground is defined as the partial load of a single mover and the area contact spots; the distribution of compressive stress over the depth of the soil mass depends on the ratio of the length and width of the contact spot; the bearing capacity characterizing the resistance to shear of the soil layers depends not only on its physical and mechanical properties, but also on the parameters of the contact spot, which is taken into account by special correction factors, the values of which depend on the aspect ratio of the contact spot. Soil rheology is considered to take into account the number of passes of a wheeled all-terrain vehicle along the route and its speed. One of the characteristics of the impact of the mover is exposure time. Value of the length of the contact spot is also used when determining the impact time of the mover on the soil.

scholarly journals Matching the Traction Qualities of Agricultural Mobile Power Vehicles with the Permissible Maximum Pressure on the Soil

2020 ◽  
Vol 14 (3) ◽  
pp. 9-14
Author(s):  
A. V. Lavrov ◽  
V. G. Shevtsov ◽  
A. V. Rusanov ◽  
V. A. Kazakova
Keyword(s):  
Agricultural Production ◽  
Traction Force ◽  
Contact Spot ◽  
Maximum Pressure ◽  
Navigation Systems ◽  
Tire Pressure ◽  
Main Condition ◽  
Row Crops ◽  
Energy Saturation ◽  
Torsion Bar

Modern highly mechanized agricultural production is characterized by the incompatibility of simultaneous matching of the maximum pressure of agricultural mobile equipment movers on the soil and the possibility of increasing the tractors energy saturation when equipping them with existing wheel engines.(Research purpose) To coordinate the maximum pressure on the soil with the permissible norms, weight utilization factors and the level of tractors energy saturation.(Materials and methods) The authors used a calculated method for determining the maximum pressure on the soil using a universal tire characteristic.(Results and discussion) The authors found that when performing spring works on closing moisture and sowing row crops at a maximum pressure of 80 kilopascals, corresponding to all types of soil, the most mass universal row tractor Belarus 1020 had a maximum pressure of 150 kilopascals, which was 70 kilopascals higher than the permissible one for the corresponding crop shortage. They found that replacing ordinary tires with agrophilic tires could increase the area of the contact spot by 16 percent, while reducing the coefficient of unevenness and increasing the coefficient of use of the adhesion weight. The main condition for replacing ordinary tires with agrophilic tires was to keep the traction force unchanged.(Conclusions) Summarizing the results of the research as agrophilic direction, ensuring the compliance impacts on soil and positively solving the problems of saturation, it is possible to recommend the development of navigation systems in achieving utilization hitch weight equal to 0.5 (low tire pressure), equal to 0.6 (rubber joint with torsion bar suspension) and 0.7 (rubber track). It was found that the conducted research, taking into account the available data on traction tests of the T-250 tractor, would allow to include an agrophilic concept with a hypothetical dependence of the adhesion weight use factor on the longitudinal unevenness coefficient in the revised State Standard 27021-86 “Agricultural and forestry Tractors. Traction classes”.

Analysis of two colliding fractionally damped spherical shells in modelling blunt human head impacts

Open Physics ◽  
2013 ◽  
Vol 11 (6) ◽  
Author(s):  
Yury Rossikhin ◽  
Marina Shitikova
Keyword(s):  
Fractional Derivative ◽  
Human Head ◽  
Contact Spot ◽  
Spherical Shells ◽  
Spherical Object ◽  
Frontal Impacts ◽  
Age Related ◽  
Laplace Transform Technique ◽  
The Laplace Transform ◽  
The Impact

AbstractThe collision of two elastic or viscoelastic spherical shells is investigated as a model for the dynamic response of a human head impacted by another head or by some spherical object. Determination of the impact force that is actually being transmitted to bone will require the model for the shock interaction of the impactor and human head. This model is indended to be used in simulating crash scenarios in frontal impacts, and provide an effective tool to estimate the severity of effect on the human head and to estimate brain injury risks. The model developed here suggests that after the moment of impact quasi-longitudinal and quasi-transverse shock waves are generated, which then propagate along the spherical shells. The solution behind the wave fronts is constructed with the help of the theory of discontinuities. It is assumed that the viscoelastic features of the shells are exhibited only in the contact domain, while the remaining parts retain their elastic properties. In this case, the contact spot is assumed to be a plane disk with constant radius, and the viscoelastic features of the shells are described by the fractional derivative standard linear solid model. In the case under consideration, the governing differential equations are solved analytically by the Laplace transform technique. It is shown that the fractional parameter of the fractional derivative model plays very important role, since its variation allows one to take into account the age-related changes in the mechanical properties of bone.

Impact Response of a Fractionally Damped Spherical Shell

2014 ◽  
Vol 31 (1) ◽  
pp. 47-53 ◽  
Author(s):  
T.-K. Chang ◽  
Y. A. Rossikhin ◽  
M. V. Shitikova ◽  
C.-K. Chao
Keyword(s):  
Spherical Shell ◽  
Contact Region ◽  
Human Head ◽  
Contact Spot ◽  
Low Velocity Impact ◽  
Strong Discontinuity ◽  
Low Velocity ◽  
Ray Method ◽  
Transform Method ◽  
Contact Domain

AbstractIn the present paper, the problem on normal low-velocity impact of a solid upon an isotropic spherical shell is studied without considering the changes in the geometrical dimensions of the contact domain. At the moment of impact, shock waves (surfaces of strong discontinuity) are generated in the target, which then propagate along the shell during the process of impact. Behind the wave fronts up to the boundary of the contact domain, the solution is constructed with the help of the theory of discontinuities and one-term ray expansions. The ray method is used outside the contact spot, but the Laplace transform method is applied within the contact region. As a result, the exact solution of the contact force is determined as a function of time. This model is intended to be used in simulating crash scenarios in frontal impacts, and to provide an effective tool to estimate the severity of effect on the human head and to estimate brain injury risks.

Particularities of Blading Free Resonance Design for Heavy Duty Gas Turbines With Circumferential Rotor Grooves

2014 ◽  
Author(s):  
Igor Putchkov ◽  
Alexander Arkhipov ◽  
Valery Moskovskikh ◽  
Harald Kissel ◽  
Alexander Laqua
Keyword(s):  
Steady State ◽  
Gas Turbines ◽  
Natural Frequencies ◽  
Contact Spot ◽  
Heavy Duty ◽  
Blade Root ◽  
Lateral Contact ◽  
Start Up ◽  
Blade Frequency ◽  
Engine Start

Blades for heavy duty engines with circumferential rotor grooves are designed such that radial contact is made between the blade teeth and rotor groove at steady state operation conditions. However, sometimes circumferential contact arises between neighboring blade shanks, which is often caused by blade root /rotor thermal expansion. In this case, the radial fixation will give the lower limit of blade frequency band, and the circumferential will give the upper one. The Blade frequency difference between these two fixations might reach about 200–500 Hz depending on blade airfoil and root sizes. When some excitation source (e.g., vane passing frequencies caused by up-stream and down-stream vane counts) has a frequency level situated between blade frequencies caused by radial and circumferential contact, such a case is the subject of the proposed approach. In order to assess how strongly the blade might be fixed under different conditions and how long it might be in resonance during engine start-up and subsequent loading, a 3D elastic-plastic transient analysis and corresponding frequency calculation of blade/rotor assembly is used. At engine start-up the circumferential (lateral) contact between neighboring blade roots is insignificant, and the radial contact between the rotor and the blade is dominant. The lateral contact spot between neighboring blade attachments during start-up appears due to different rates of blade/rotor heating. Further heating leads to an increase of the lateral contact spot areas. The closing of these contact surfaces starts from the outer root edge and spreads toward the inner one, leading to an increase of assembly natural frequencies. Engine loading and further heating lead to the appearance of a circumferential gap between the surfaces, causing the lateral contact to disappear during steady state. The blade root coupling switches again to the usual radial contact state, with the corresponding reduction of natural frequencies. Because the described phenomenon might occur for some time during every start-up and shut-down (from several minutes to couple of hours), it becomes even more severe from a dynamics standpoint if some natural frequency of coupled system crosses the exciting frequency. Examples of assembly frequency tuning are presented.

Simulation of drip-rain effects by tribofatigue loading

2020 ◽  
Author(s):  
A.A. Aliev ◽  
A.Yu. Ampilogov
Keyword(s):  
Polymer Coating ◽  
High Speed ◽  
Erosion Resistance ◽  
High Water ◽  
Contact Spot ◽  
Vertical Load ◽  
Rigid Substrate ◽  
Rain Drop ◽  
The Impact ◽  
Rain Erosion

The outer surfaces of aircraft are periodically subjected during flight to intense rain causing hydroerosion of the outer paintwork. The experimental evaluation of hydroerosion resistance is based on testing in high-speed water flow. The main drawback of such research is the bulkiness of the stands, high water and energy consumption, and, as a result, increased cost. As an alternative to drip-rain tests, their simulation by kinetically similar tribofatigue test according to the “ball on plate” scheme is proposed (vertical load is applied to the polymer coating on a rigid substrate through a steel ball). The process is cyclically repeated until the coating is worn to the specified thickness. The experimentally obtained tribofatigue characteristics then can be converted into close-meaning estimates of erosion resistance. CAAPCOAT-B274-ASP108 polyurethane, previously tested for rain erosion, was selected as the sample. For quantitative evaluation of the transition from drip-rain loading to equivalent tribofatigue one the contact mechanics formulas were used by calculating the force of the drip impact and the stress in the contact spot. Tribofatigue tests were conducted on the UMT-2 TriboLab unit. At equal calculated contact stress levels the wear rate under tribofatigue loading was almost 7 times higher compared to the conditions of rain-drop erosion. The reason may be a scale factor due to the actual difference in contact areas under drip and tribofatigue loading, as well as the failure to take into account the dynamics of waves after the impact of drops. The obtained results of tribofatigue tests can give an estimated value of the hydroerosion resistance of the coating.

On the Effects of Edge Scalloping for Collapsible Spokes in a Non-Pneumatic Wheel During High Speed Rolling

2009 ◽  
Author(s):  
Maya Ramachandran ◽  
Shashank Bezgam ◽  
Lonny L. Thompson ◽  
John C. Ziegert ◽  
Timothy B. Rhyne ◽  
...  
Keyword(s):  
High Speed ◽  
Acoustic Noise ◽  
Contact Region ◽  
Element Model ◽  
Design Criterion ◽  
Mode Shapes ◽  
Time Signal ◽  
Design Strategies ◽  
Pneumatic Wheel ◽  
Out Of Plane

The acoustic signature produced by non-pneumatic wheels with collapsible spokes is a critical design criterion for automotive and other mobility applications. During high speed rolling, acoustic noise may be produced by the interaction of vibrating spokes with a shear deformable ring as they enter the contact region, buckle and then snap back into a state of tension. In order to identify and help understand the causes of acoustic noise for a rolling non-pneumatic wheel, a two-dimensional finite element model with geometric nonlinearity has been utilized. The model consists of a shear ring modeled as two relatively inextensible membranes with high circumferential modulus separated by a hyper-elastic material. The temporal variation in spoke length as the spoke passes through the contact zone is extracted and used as input to a three-dimensional (3-D) model of a single spoke. The 3-D spoke model is able to capture out-of-plane vibration modes of the spoke which may contribute as a source of acoustic excitation and allows for modeling of edge scalloping. Natural frequencies and mode shapes of the various spoke design strategies are computed and correlated with the frequency response of the out-of-plane spoke vibrations. Results indicate that scalloping the edges of the spoke can dramatically reduce the amplitude of vibration, but does not have a strong effect on location of frequency peaks in a FFT of the time-signal. An optimal amount of scalloping was determined which reduces maximum vibration amplitude to an asymptotic value.

scholarly journals Study of cylindrical brush wear effect on its elastic characteristics, on required pressing force and on pressure at the outlet of hydraulic pneumatic accumulator for controlling position of chipping working body

2021 ◽  
Vol 18 (1) ◽  
pp. 106-119
Author(s):  
S. I. Tsekhosh ◽  
B. V. Zhuravsky ◽  
P. I. Tsekhosh
Keyword(s):  
Contact Spot ◽  
Surface Cleaning ◽  
Software Environment ◽  
Pressing Force ◽  
Software Product ◽  
Wear And Tear ◽  
The Cost ◽  
The Relationship ◽  
Elastic Characteristics

Introduction. The article is devoted to a current issue of improving the quality of road surface cleaning and increasing the resource of brush working equipment. Improving the quality of cleaning and the resource of the brush working equipment will reduce the cost of operating a communal machine. In the process of operation, the pile of the cylindrical brush is worns out, while its elastic characteristics change, which is reflected in the required pressing force to maintain the most favorable value of the width of the contact spot from the condition of ensuring high quality cleaning and minimal intensity of pile wear.Materials and methods. The results of studies of the interaction of the pile of a cylindrical brush with the surface to be cleaned are presented at various degrees of wear of the brush pile. The research results are presented in analytical and graphical forms. The calculations were carried out using the Microsoft Excel software product and the Mathkad software environment for mathematical calculations.Results. The paper shows the dependence of the degree of wear of the pile of the brush working equipment on the actual radius of the cylindrical brush. The relationship between the width of the contact spot and the deformation of the cylindrical brush at different degrees of wear and tear is shown as a graph.The influence of the degree of wear on the elastic characteristics of the brush working equipment is considered. The dependences of the average stiffness coefficient on the degree of wear of the pile of a cylindrical brush, as well as the required pressing force on the degree of wear at different values of the width of the contact patch of the cylindrical brush are given.

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