scholarly journals Analysis of the reasons for the formation of under-collar cracks in the bushing of medium-speed combustion engines

2021 ◽  
pp. 48-53
Author(s):  
И.Н. Рубан ◽  
В.П. Булгаков ◽  
О.В. Федорова
Keyword(s):  
Metal Structure ◽  
Combustion Engines ◽  
Surface Layers ◽  
Plastic Properties ◽  
Tensile Stresses ◽  
Stress Cracking ◽  
Medium Speed ◽  
Piston Displacement ◽  
Low Sensitivity ◽  
Diffusion Of Hydrogen

Вибрация цилиндровой втулки, вызванная перекладкой поршня, развивает колебания вдоль по длине втулки от бурта до основания и акустические колебания внутри втулки, которые приводят к возникновению растягивающих напряжений и деформаций в поверхностных слоях металла; при взаимодействии с водой создаются условия для диффузии водорода во втулку. Диффузия водорода повышает внутреннее давление, что вызывает растрескивание структуры металла под действием напряжений. Происходит деградация металла – снижение прочностных и пластических свойств. Причиной появления подбуртовых трещин и кавитационные разрушения цилиндровой втулки является усталость деградированного металла от «водородного растрескивания под напряжением» и действия циклических растягивающих напряжений. Для повышения долговечности втулок по подбуртовым трещинам необходимо: 1. Увеличение износостойкости скользящей поверхности втулки для стабилизации величины теплового зазора; 2. Повышение жесткости втулки за счет увеличения толщины втулки в подбуртовой зоне; 3. Применение метала втулки с малой чувствительностью к «водородному растрескиванию под напряжением» (замена чугуна с пластинчатой формой графита на сферическую). The vibration of the cylinder bushing caused by the piston displacement develops the vibrations along the length of the bushing from the collar to the base and acoustic vibrations inside the collar, which lead to tensile stresses and deformation in the surface layers of the metal; when interacting with water, conditions for the diffusion of hydrogen into the bushing are created. The diffusion of hydrogen increases internal pressure, which causes the cracking of the metal structure under stress. The degradation of the metal that is the decrease in strength and plastic properties occurs. The reason for the formation of under – collar cracks and cavitation destruction of the cylinder bushing is the fatigue of the degraded metal from "hydrogen stress cracking" and the action of cyclic tensile stresses. To increase the durability of the bushings along the under – collar cracks, it is necessary to: 1. Increase the wear resistance of the sliding surface of the bushing to stabilize the value of the thermal gap; 2. Increase the stiffening effect of the bushing by increasing the thickness of the bushing in the under – collar zone; 3. Apply the metal of the bushings with low sensitivity to "hydrogen stress cracking" (replace the cast iron with lamellar graphite for the spherical one).

Analysis of the stress-strain state of a vertical ground electrode system for permafrost soils under pushing loads

2021 ◽  
pp. 77-89
Author(s):  
I. S. Sukhachev ◽  
P. V. Chepur ◽  
A. A. Tarasenko ◽  
A. A. Gruchenkova ◽  
Yuhai Guan
Keyword(s):  
Equivalent Stress ◽  
Side Surface ◽  
Metal Structure ◽  
Vertical Displacement ◽  
Soil Mass ◽  
Electrode System ◽  
Plastic Properties ◽  
Design Scheme ◽  
Permafrost Soils ◽  
Vertical Ground

The article proposes the design, design scheme and model of a vertical ground electrode system with lobe lugs for permafrost soils. The model was implemented using the ANSYS software. In the design scheme, the soil — ground electrode system is taken into account, the elastic-plastic properties of the soil are taken into account by the Drucker — Prager model. When modeling the work of the foundation soils, the Mises strength condition was adopted, according to which the equivalent stress is calculated under the condition of the material hydrostatic compression. The following boundary conditions are accepted: a cylinder-shaped soil mass is rigidly fixed along the lower face and along the side surface of the cylinder. Calculations are made for 5 standard sizes of grounding conductors. Maps of the distribution of stresses in the metal structure of the ground electrode (the rod and petals-emphasis) are received, the movements of the ground electrode in the soil mass are determined. The dependences between the maximum equivalent stresses in the ground electrode lobes and the value of vertical displacement in the ground base are established, as well as the amount of movement of the earthing pad, at which the effective equivalent voltages reach critical values in the area where the paddles are adjacent to the rod.

Contact Analysis of a Soft-Coated Asperity During Loading–Unloading Process in Consideration of Strain Hardening Effects

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Yi Wang ◽  
Yi Cui ◽  
Shuo Liu ◽  
Xinhui Wang ◽  
Xinwei Tian ◽  
...  
Keyword(s):  
Power Law ◽  
Material Properties ◽  
Element Model ◽  
Von Mises Stress ◽  
Main Bearing ◽  
Plastic Properties ◽  
Medium Speed ◽  
Wide Range ◽  
Dimensional Finite Element ◽  
Von Mises

Abstract In this paper, the flattening process of a coated single asperity by a rigid flat is studied based on a two-dimensional finite element model under different contact interferences. The soft coating and hard substrate materials of the main bearing shell in a medium-speed vehicle diesel engine are both considered to follow the power-law hardening elastic-plastic properties. For both loading and unloading processes, the effects of geometrical and material properties, including the coating thickness, Young’s modulus, Poisson’s ratio, yielding stress, and hardening exponent, on the contact behaviors are studied in a wide range to cover the real material properties. The von Mises stress on the interface is also analyzed in order to improve the bonding strength between coating and substrate. The main contribution of this paper is to provide a method to determine the contact properties caused by different material and geometric properties of soft coating and substrate materials, which follow the power-law hardening properties.

Apparent fracture toughness of Si3N4-based laminates with residual compressive or tensile stresses in surface layers

2005 ◽  
Vol 53 (2) ◽  
pp. 289-296 ◽  
Author(s):  
M. Lugovy ◽  
V. Slyunyayev ◽  
N. Orlovskaya ◽  
G. Blugan ◽  
J. Kuebler ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Surface Layers ◽  
Tensile Stresses ◽  
Apparent Fracture Toughness

Intercooler model for unsteady flows in engine manifolds

1998 ◽  
Vol 212 (2) ◽  
pp. 119-132 ◽  
Author(s):  
P A Bromnick ◽  
R J Pearson ◽  
D E Winterbone
Keyword(s):  
Heat Exchanger ◽  
Gas Dynamics ◽  
Internal Combustion Engines ◽  
Unsteady Flows ◽  
Cross Flow ◽  
Combustion Engines ◽  
Medium Speed ◽  
Mass Flowrate ◽  
Flow Heat ◽  
The Relationship

A model has been developed for intercoolers which are used to reduce the temperature of the charge air in turbocharged internal combustion engines. The detailed theory for the intercooler model is presented. The behaviour of the intercooler is characterized by the relationship between the number of transfer units ( NTU) and the effectiveness (ε) of the intercooler, which is assumed to be that of a cross-flow heat exchanger. The structure of the code used to implement the model is presented and the model is applied to simulate the gas dynamics in a medium-speed turbocharged and intercooled diesel engine. The results show the predicted variation of pressure, temperature and mass flowrate across the intercooler and also the variation of intercooler effectiveness with mass flowrate.

Paper 18: Gas Load and Thermal Stresses in Diesel Engine Pistons and Valves

1967 ◽  
Vol 182 (12) ◽  
pp. 176-185 ◽  
Author(s):  
S. M. Ibrahim ◽  
H. McCallion
Keyword(s):  
Diesel Engines ◽  
Internal Combustion Engines ◽  
Thermal Stresses ◽  
Peak Pressure ◽  
Calorific Value ◽  
Combustion Engines ◽  
Stress Distributions ◽  
Average Temperature ◽  
Medium Speed ◽  
Fundamental Understanding

In the field of internal combustion engines, diesel engines have the advantage of a high thermal efficiency and of operating on cheap fuels of high calorific value. To maintain these advantages brake mean effective pressures (b.m.e.p.) are continually being increased, but limitations are imposed by the cylinder head and the piston design. Usually such problems are overcome by development testing. However, these methods give little fundamental understanding of the stress distributions and how they vary under different load and temperature conditions. In this work a method for predicting pressure and steady-state thermal stresses in pistons, of different materials, for medium speed diesel engines is discussed. The pressure is applied to simulate the engine peak pressure loading and the temperature represents the time average temperature distribution in the piston under engine running conditions. The induced stresses and strains are calculated numerically.

scholarly journals Capturing Pressure Oscillations in Numerical Simulations of Internal Combustion Engines

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Sreenivasa Rao Gubba ◽  
Ravichandra S. Jupudi ◽  
Shyam Sundar Pasunurthi ◽  
Sameera D. Wijeyakulasuriya ◽  
Roy J. Primus ◽  
...  
Keyword(s):  
Internal Combustion Engines ◽  
Fuel Combustion ◽  
Dual Fuel ◽  
Combustion Engines ◽  
Cylinder Pressure ◽  
Pressure Oscillations ◽  
Numerical Predictions ◽  
Medium Speed ◽  
Dual Fuel Combustion ◽  
The Mean

In an earlier publication (Jupudi et al., 2016, “Application of High Performance Computing for Simulating Cycle-to-Cycle Variation in Dual-Fuel Combustion Engines,” SAE Paper No. 2016-01-0798), the authors compared numerical predictions of the mean cylinder pressure of diesel and dual-fuel combustion, to that of measured pressure data from a medium-speed, large-bore engine. In these earlier comparisons, measured data from a flush-mounted in-cylinder pressure transducer showed notable and repeatable pressure oscillations which were not evident in the mean cylinder pressure predictions from computational fluid dynamics (CFD). In this paper, the authors present a methodology for predicting and reporting the local cylinder pressure consistent with that of a measurement location. Such predictions for large-bore, medium-speed engine operation demonstrate pressure oscillations in accordance with those measured. The temporal occurrences of notable pressure oscillations were during the start of combustion and around the time of maximum cylinder pressure. With appropriate resolutions in time steps and mesh sizes, the local cell static pressure predicted for the transducer location showed oscillations in both diesel and dual-fuel combustion modes which agreed with those observed in the experimental data. Fast Fourier transform (FFT) analysis on both experimental and calculated pressure traces revealed that the CFD predictions successfully captured both the amplitude and frequency range of the oscillations. Resolving propagating pressure waves with the smaller time steps and grid sizes necessary to achieve these results required a significant increase in computer resources.

Starvation in Dynamically Loaded Flexible Short Journal Bearings

1985 ◽  
Vol 107 (4) ◽  
pp. 516-521 ◽  
Author(s):  
L. van der Tempel ◽  
H. Moes ◽  
R. Bosma
Keyword(s):  
Differential Equations ◽  
Numerical Method ◽  
Dynamic Load ◽  
Journal Bearings ◽  
Important Application ◽  
Combustion Engines ◽  
Connecting Rod ◽  
Supply Pressure ◽  
Continuity Equations ◽  
Medium Speed

A starvation model is incorporated in a previously presented numerical method for calculating film thicknesses inflexible short journal bearings under dynamic load. The system of elastohydrodynamic integro-differential equations is now coupled with continuity equations for the lubricant, considering central circumferential oil grooves and a constant supply pressure. An important application of this method is the connecting rod bearing in medium speed combustion engines. Results for several groove geometries are compared with those for a fully flooded bearing.

Critical Structures of Metal Destruction Under the Process of Wear

1999 ◽  
Vol 122 (1) ◽  
pp. 361-366 ◽  
Author(s):  
I. I. Garbar
Keyword(s):  
Initial Conditions ◽  
Layer Structure ◽  
Low Carbon Steel ◽  
Maximum Level ◽  
Metal Structure ◽  
Wear Intensity ◽  
Relaxation Processes ◽  
Low Carbon ◽  
Surface Layers ◽  
Critical Structure

Resistance to wear is determined by the ability of the metal structure to change in such a way that it can withstand friction stresses. The structure of surface layers which have undergone wear can be identified as a “critical” structure. This is where destruction takes place. To study the surface structure specimens of low-carbon steel, aluminum and copper were subjected to wear tests and then investigated by X-ray. Under certain test conditions it was found that the changes in the surface layer structure, evidenced by the structural broadening of diffraction lines, reach a maximum level. The tests showed that as one progresses from mild wear to harsher friction conditions and correspondingly higher wear intensity, the structural broadening of the diffraction lines is first increased but than reduced. The results show that under low and moderate wear conditions, the structure of the surface layers is changed by the friction process, the surface layers being hardened by fragmentation. The level of metal hardening corresponds to the friction stresses that occur in the surface layers, and reaches a maximum when the fragment dimensions are minimal. As the friction conditions become more severe, the critical structure of the metal approaches the initial conditions, and therefore its strength is less than that of the hardened structure formed under moderate wear conditions. Such results can be explained by the difference in the rates of the plastic deformation and of plastic relaxation processes. Therefore, the critical structure under the process of wear depends on the friction conditions. To put the mechanical properties of the material to best use, one should choose optimal friction and wear conditions so that the metal will be hardened as much as possible. [S0742-4787(00)04801-3]

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