Internal Combustion Engine Parts Research Articles

МОДЕЛИРОВАНИЕ ПУСКА ДВС АВТОМОБИЛЯ С БЕССТУПЕНЧАТОЙ КОРОБКОЙ ПЕРЕДАЧ

The aim of the work is to build a computer dynamic model of moving internal combustion engine parts and a continu-ously variable transmission to determine the starting characteristics of the internal combustion engine. The paper objective is to define the characteristics of moving parts of the internal combustion engine and continuously variable transmission when starting the internal combustion engine with an electric starter. The research method is computer modelling of moving internal combustion engine and transmission parts when starting with an electric starter. The novelty of the work lies in building a computer model of moving parts of an internal combustion engine and a contin-uously variable transmission, connected by a torsional vibration damper, considering changes in friction parameters. The results are in developing a computer model to determine the starting characteristics of a four-cylinder in-line four-stroke internal combustion engine with spark ignition and a continuously variable multitronic® 01J transmis-sion. To check the computer model adequacy, the author uses the values of the average friction pressure in accord-ance with GOST R 54120-2010 and empirical data on the unevenness of the angular velocity of the crankshaft. Simu-lating a four-stage start of an internal combustion engine shows that opening the cylinder valves at the 1st stage in-creases the angular velocity of the crankshaft by 4%. Temporary switching on the reverse clutch for 1.4 s reduces the amplitude of angular oscillations of the solar shaft by 2.22 times, eliminates the beating of the contacting gearbox teeth, but slows down the crankshaft speed by 7.6%. After the reverse clutch is turned off, periodic changes in the an-gular velocity of gearbox parts occur.

Improving the physical, mechanical and operational characteristics of cast internal combustion engine pistons made of aluminum alloy using secondary charge

The article is devoted to improving the physical, mechanical and operational characteristics of cast internal combustion engine pistons made of aluminum alloy using secondary charge. The advantage of the proposed approach is that these parts are manufactured from any aluminum alloy using the remelting of failed internal combustion engine parts of the same name. The paper shows that while using a secondary charge in the form of remelting failed parts of the same name, the quality of cast products not only does not deteriorate, but, on the contrary, their physical and mechanical characteristics even increase. It should be noted that the high density of the alloy obtained from remelting failed pistons and the high degree of its modification confirmed the authors’ assumption that in this case refining and modification operations can be avoided. The presented approach using the remelting of failed parts makes it possible not only to save fresh charge materials, but also to preserve the chemical composition of the primary parts, and, consequently, the level of their physical, mechanical and operational characteristics.

THE COMPOSITION OF THE PNEUMATIC SYSTEM FOR LOCAL MULTI-CIRCUIT COOLING ON AUTO TRACTOR DIESEL PARTS JUSTIFICATION

A series of motor bench and non-motorized experiments conducted at the Department of Engines and Hybrid Power Plants of NTU "KhPI" showed the high efficiency of local air cooling of heat-stressed parts of internal combustion engines, in particular, parts of the exhaust valve assembly of the gas distribution mechanism in an automated mode. However, in the tests carried out, a stationary air compressor powered by a ~220 V mains was used with air accumulation in a large-capacity cylinder. The implementation of a local cooling system on power plants, mainly powerful trucks, requires the inclusion in the automatic control system of autonomous cooling, a pneumatic compressor installed on the vehicle with an electric drive, powered by the on-board power supply and accumulating air in a receiver with compact dimensions.
 A review of design solutions and analysis of the component composition of pneumatic systems of autotractor vehicles was carried out. The requirements for the quality and safety of pneumatic systems of vehicles and their elements are considered. The technical characteristics of air compressors are presented. The scheme of the pneumatic system of local multi-circuit cooling on autotractor diesel parts has been chosen. On the example of the selected air compressor with an electric drive Maximum Performance 24V from ARB (Australia), estimates were made of the operating time up to a working pressure in the receiver of 10 bar. The electrical load on the 24 V on-board network of the vehicle was determined in the form of an average current consumption per filling cycle. The maximum current consumption by the compressor is determined, the current consumption per hour is estimated under the condition of a proportional alternation of the cycles of filling the receiver and emptying it.

APPLICATION OF VACUUM SUCTION CASTING OF IRON-CARBON ALLOYS FOR THE PRODUCTION OF ENGINE PARTS

The use of vacuum suction casting technology for iron-carbon alloys for the production of internal combustion engine parts will improve their quality and wear resistance, preserve metal, and reduce emissions. The technology is widely used for non-ferrous alloys. At the same time, its implementation for iron-carbon alloys (including cast iron) in modern engine construction requires careful scientific and practical preparation. Problematic tasks arise when improving the pneumatic system of vacuum suction (large volumes of gas release), the stability of the metal pipeline (thermal overload in a high-temperature cast iron melt), and the stabilization of the casting microstructure (high-speed crystallization). The authors suggest using a specialized titanium alloy VT3-1 for the metal pipeline, for which the article calculates thermal loads during cyclic operation in the “Deep – take-out” mode for the use of cast irons of the SCH25 and VCH50-1.5 grades. For reliable operation of the metal pipeline and the absence of solidification of the melt on its inner surface, a thermal calculation method was develop, which allows determining the time of heat removal of overheating of the melt according to the diameter of the metal pipeline. The pneumatic system of the vacuum unit is supplement with a patented gas jet ejector, which, in combination with a powerful shop compressed air system, provides a full gas outlet. Applying the developed law of change in the discharge between atmospheric pressure and pressure in the mold cavity, the authors of the article regulate the rate of crystallization of castings, which makes it possible to form much smaller phases of perlite in the microstructure and reduce the presence of Ferrite. At the Enterprise "Pervomaiskdizelmash" using vacuum casting technology, blanks of guide bushings of engine valves 6CHN25/34 made of cast iron SCH25 and VCH50-1,5, as well as oils of piston rings made of cast iron VCH50-1,5 were obtained. The obtained parts showed an increased service life by 15-30%. Vacuum casting technology is recommend for iron-carbon alloys in the production of engine parts.

Evaluation of the influence geometric parameters of a cylindrical specimen for tensile adhesion testing of thermally sprayed coating

The problem of calculating the required adhesion strength and the accuracy of measuring the adhesive/cohesive strength of thermally sprayed coatings (thermal barrier, electrically insulating, irradiation) on a cylindrical test specimen is of practical interest from the point of view of improving the reliability of highly loaded parts of internal combustion engines of agricultural machines, various parts of the aerospace and nuclear industries. There have been carried out a set of studies on the application in practice of standard test method for assessing adhesion or cohesion strength of electrically insulation plasma sprayed coating Al2O3 on standard and elongated specimens with a diameter of 25 mm in accordance with standards ASTM C633-13, GOST 9.304-87. In order to assess the influence of witness specimen’s geometry at common coating adhesion, there were selected 6 types of cylindrical specimens. A finite-element stress analysis was used to evaluate stress-strain state of the two bonded cylindrical specimens of the same geometry with coating by tensile testing. The uniformity of stress distribution at the interface coating/substrate was found for three elongated specimens. Compared to standard tensile testing of a cylindrical specimen, the applied significance of the conducted studies that it is possibility to obtain more accurate experimental data of bond strength. There is also needed further research in the field of determining the most optimal geometry of the witness specimen for evaluating the tensile adhesion strength of thermal spray coating.

Применение цифровых технологий при диагностировании двигателей энергонасыщенной сельскохозяйственной техники

The development of digital technologies aimed at improving the diagnostic process, increasing the reliability of determining the functional characteristics of agricultural machinery in real time is important and relevant in the technical support of energy-saturated machines. To develop an intelligent system for remote diagnostics of the engines of energy-saturated agricultural machinery, the authors tested a neural network constructor with the ability to use up to ten input and output parameters. An algorithm for a digital system for remote diagnostics, a scheme for predicting failures in online monitoring, and a digital platform for diagnosing energy-saturated agricultural machinery have been developed. The developed platform makes it possible to obtain ICE diagnostic parameters (fuel consumption, engine temperature, and engine shaft speed), which are remotely transmitted in the form of encrypted data to the server using a GPS modem and digitized in the data bank. Then the received data are structured and analyzed using the developed artificial neural network models. The decrypted diagnostic parameters of the internal combustion engine are sent to the operator, who sees graphs of the parameters of the technical condition of agricultural machinery and reports on predicting possible failures of internal combustion engine parts. The article presents a method for collecting and storing diagnostic information obtained as a result of monitoring the technical condition of agricultural machinery. These data are processed using a mathematical model of a neural network. The use of digital technologies in diagnosing equipment with the help of artificial intelligence can significantly reduce the complexity of the operations performed, evaluate the efficiency of the machine as a whole and predict the onset of failures of its mechanisms, perform timely maintenance and repair of machines, and reduce unplanned downtime of energy-saturated agricultural machinery.

ПРИМЕНЕНИЕ НЕЙРОСЕТЕВОГО ПОДХОДА ДЛЯ ДИАГНОСТИКА ДВИГАТЕЛЯ ВНУТРЕННЕГО СГОРАНИЯ ТРАНСПОРТНЫХ СРЕДСТВ

The work is devoted to the problem of diagnosing the internal combustion engine of vehiclesthis problem is now the most relevant due to the constant growth of the car fleet and the tighteningof requirements for safe operation. Timely and accurate control of the internal combustion engineis able to prevent the failure of entire vehicle assemblies, as well as to avoid such serious consequencesas a traffic accident. With the advent of modern technologies the long-known method ofengine condition estimation by sound can become the most advanced, since the human factor isexcluded, for signal processing the computer technique is applied, the analysis of a sound spectrumin which is carried out by means of artificial neural networks. The application of artificialneural networks for analyzing the sound spectrum has found application in speech recognition andfor diagnosing diseases of the respiratory system. The article deals with the failure of one of themain parts of internal combustion engine - the bearing. All possible types of bearing faults and thereasons why they occur are presented. The nodes and mechanisms of the internal combustion enginein which bearings are used are listed. The algorithm of the experimental part is described.The experiment which includes transformation of the received sound signals into spectrogramsand extraction of features with the help of which the classification is carried out, is executed. Theexecuted experimental part has proved the possibility of diagnosing of the internal combustionengine by means of artificial neural networks. Scientific novelty lies in the fact that the diagnosticprocess becomes automated, all the sounds taken by sensors are processed in a computer or in thefuture in a special scanner, the display shows information about the state of certain nodes, unliketraditional methods where the diagnosis is carried out visually or by ear. Thus, the diagnosticaccuracy increases and the overall labor intensity decreases due to the exclusion of partial orcomplete engine disassembly.

The effect of nanoparticle and fiber reinforcement on composites used in some applications of internal combustion engine parts

The effect of nanoparticle and fiber reinforcement on composites used in some applications of internal combustion engine parts

Classification of contaminants in diesel engine oils

Introduction. The deterioration of engine oil in an internal combustion engine (ICE) is directly related to the ingress of various pollutants into the crankcase. Depending on the type of contamination, the type of sediment on engine part surfaces varies. It should be noted that the functioning of the motor oil is extremely affected by the oxidation process, and organic acids produced during the process contribute to corrosion of ICE parts. Water, diesel, cooling fluid, soot particles, asphaltenes, etc. also cause irreparable damage.Materials and methods. This paper presents the results of an extensive literature review aimed at studying the main types of motor oil pollutants. Classifications are given for the aggregate state of pollutants, as well as for possible ways of their penetration into the lubricant. Liquid pollutants are the most narrowly considered in this article. To demonstrate the negative effect of contaminants entering the engine oil, photographs of internal combustion engine parts with sediments on the surfaces of the internal combustion engine components are presented.Results. The classification of the main pollutants of motor oils is given; the consequences arising from the ingress of foreign compounds into the lubricant in question are indicated.Conclusion. The effect of contaminants on the parts of the internal combustion engine and the lubricant has been established. On the basis of the classification, it is possible to judge the causes of entry and the possible consequences of the impact of contamination on the operation of the engine.

Approach to enhance the heat transfer of valve seats through thermal analysis

The valve seat insert is a component of the engine cylinder head, whose primary function is to seal the combustion chamber and absorb the valve's heat, releasing it to the engine cylinder head. The valves experience high temperatures owing to high thermal loading and low heat absorption in the valve seat, which can potentially damage the engine. Therefore, the thermal characteristics of the valve seat must be optimised to increase the heat transmission between the valve and its seat. Here, three copper alloy valve seats, brass, beryllium copper, and bronze copper, were tested against the existing sintered iron valve seat, and their temperature maps were determined using actual engine operation conditions. The instantaneous heat transfer coefficients of the valves, seats, and engine cylinder head during the four-stroke cycle were evaluated using a one-dimensional thermal simulation analysis. The values obtained were used to assess the finite-element model using a three-dimensional thermal simulation in the Ansys software. The results show that the brass, beryllium-, and bronze-copper valve seats increased the overall heat flux by 4.46%, 4.16%, and 2.06%, respectively, compared to those for sintered iron. Thus, the results are essential to improve the thermal characteristics of the copper alloy valve seat imposed on the cylinder head. For validation, an experimental engine thermal survey and uncertainty magnification factors were used to validate the model. The results indicate that the maximum difference between the simulation and experimental values is 8.42%. Therefore, this approach offers a direct and comprehensible application for evaluating the temperature distribution, heat gradient, and heat flux of the cylinder head of air-cooled spark-ignition moped motorcycle engines using copper alloy valve seat materials at intermediate engine speeds. Furthermore, this method is applicable as a platform for the automotive industry to improve the heat transfer of the structural parts of internal combustion engines.

DVDLWC. SMOOTHING THE WORKING SURFACE DURING RESTORATION OF INTERNAL COMBUSTION ENGINE PARTS

When operating internal combustion engines, there is a problem of restoring cylinder liners. After wear, the cylinder liner is bored to the repair size, using boring and honing machines. Finding new effective processing methods is an urgent task. (Research purpose) The research purpose is smoothing the inner surface of cylinder liners by using a vibration-damping extension cord. (Materials and methods) The article proposes an epoxy-based adhesive composition and metal cables to reduce vibration during processing that ensure the compression state of the entire boring system. A special design of the vibration-damping extension of the boring mandrel have been developed. The article presents its description. A 6P12 vertical milling machine was used for research. Prototypes with an internal diameter of 80 millimeters were manufactured of steel 38 HMUA and steel 20. The Mitutoyo profilometer model SJ-410 was used to measure roughness. The rotation speed was changed from 80 to 500 revolutions per minute. (Results and discussion) The roughness of the surface layer of blanks made of 38HMYuA steel treated with a boring mandrel with a vibration-damping extension is four times higher on average than a traditional boring at all stages of the experiment, the roughness parameter Ra is 0.8. The quality of the surface layer of 20 steel blanks processed with a boring mandrel with a vibration-damping extension is twice as high on average as with a traditional boring at 80-315 rpm, the roughness parameter Ra is 1.6 and four times higher at 315-500 rpm, the roughness parameter Ra is 3.2. (Conclusions) The use of a vibration-damping extension will reduce the cost and complexity of restoring parts of internal combustion engines and remove special boring and internal grinding machines from the technological process.

EXPERIENCE IN THE ELECTROSPARK LAYERING TECHNOLOGIES FOR MACHINE PARTS

When the cost of new spare parts has sharply increased, the problems of restoring worn parts are relevant. (Research purpose) The research purpose is to present the most promising technological processes for the restoration of parts of internal combustion engines by the electric spark processing. (Materials and methods) The article presents a description of new generation installations for electric spark processing BIG-5 and their technical characteristics. Tool alloys 65G, SHX15, P6M5, as well as hard alloys and bronzes were used as alloying materials. Conductive materials with high electrical and thermal conductivity, erosion resistance were used to perform the operation of melting the deposited alloying layer. These primarily include copper, tungsten and graphite. (Results and discussion) The article presents developed technological processes and provides a list of details where electric spark processing is successfully used and a detailed description of the technological process of restoring several basic parts, recommends application modes and materials. The main principle of restoring operability is to increase the hardness and bearing capacity of the working surface, as well as the selection of optimal friction pairs. The production tests of technologies confirm 100 percent of the life of the restored parts. The cost of restoration using electric spark processing does not exceed 30-40 percent of the cost of the part. (Conclusions) The examples of restored parts show the effectiveness of the electric spark processing technology, as well as the reduction of labor intensity and cost of work related to the repair and restoration of machines. Electric spark coating is in many ways superior to known technologies in terms of the quality of the resulting surface and labor costs, it is characterized by low energy consumption, simplicity, high utilization of electrode material and environmental friendliness of the process.

Application of MDO technology for internal combustion engines

The prospects of using nano-crystalline ceramic coatings on internal combustion engine parts obtained by micro-arc oxidation (MDO) technology are considered. The tendency of development of engine building on replacement of cast-iron blocks and sleeves on aluminum with the special coverings received by galvanic methods is shown. It is noted that this direction does not involve the use of repair technologies, which significantly affects consumers. Analysis and practical tests have shown the possibility of using MDO technology both in the manufacture of engine parts and for the performance of restoration work. It is concluded that it is necessary to introduce this technology into the mass production of engines and pistons, as well as the need to develop a set of equipment for repair work.

CONTACT INTERACTION OF DISCRETE-CONTINUALLY STRENGTHENED PARTS OF INTERNAL COMBUSTION ENGINES

Studies of the stress-strain state of discrete-continuously strengthening parts of internal combustion engines are described in the paper. A parametric model of a microcell containing a two-part cell has been developed. The first part simulates a fragment of an aluminum part with a surface corundum layer. The second part is a fragment of a cast iron part with a zone of discrete strengthening of steel. Vary: modulus of elasticity of the corundum layer material and the shape of the discrete hardening zone. The dependences of the strength and stiffness characteristics of the studied system on the varied parameters are established. They are the basis for substantiation of rational modes of technology of discrete-continuous strengthening of parts of internal combustion engines.
 In the course of research, it was found that previously determined for discrete strengthening, the effects of a favourable redistribution of contact interaction between parts are preserved for discrete-continuous strengthening. The characteristic dependences of the features of the stress-strain state of the elements of discrete-continuously strengthening parts on the varied properties of the surface layers of the continuously strengthened part, on the one hand, and the shape of the discrete strengthening zone, on the other, are determined. This makes it possible to determine the sensitivity of the characteristics to purposeful or random variation of these factors. It is also expedient to set and solve optimization problems to determine such modes of technological operation of discrete-continuous strengthening, which increase the characteristics of strength, durability, efficiency of internal combustion engines and other machines, units and assemblies containing such strengthened parts.
 The developed approach, models and research methods will be further applied to studies of the stress-strain state of contacting discrete-continuously strengthened parts of structures to improve the technical and tactical and technical characteristics of products of machine-building enterprises.

COMPARATIVE EVALUATION OF THE CREEP OF PISTON ALUMINUM ALLOYS

The paper deals with the issues of reliability of piston materials in the process of increasing engine power. It is precisely the increase in the liter power of engines while ensuring environmental and economic requirements that is today one of the main areas of work in engine manufacturing. Studies have shown that material creep has significantly affects on the reliability of internal combustion engine parts. The most thermally loaded engine element is a piston. The main critical areas for it can be identified: the edge of the combustion chamber, the area of the piston rings and the piston skirt. The appearance of seizures on the piston skirt is sometimes observed even during the engine initial tests at the engine power increasing. Thus, we can speak about the relevance of the problem of identifying the reasons for reaching the critical state of the piston material. Based on these data, it becomes possible to develop measures to ensure the reliable operation of the piston. Among the most common materials for the manufacture of pistons are aluminum alloys AL25 and AK4. The chemical composition of these alloys varies considerably. The study obtained coefficients for calculating the creep rate for these materials. The identification of the calculation of the creep deformation of aluminum alloys at different stress levels, for different temperatures is carried out. The upper boundary of the region of model adequacy in terms of temperatures and stresses is determined. The creep rate of aluminum alloys is analyzed at different temperatures. In the conclusions, a comparison of the piston materials is made and the advantages of the AK4 alloy in comparison with the AL25 alloy, which are coming out when the engine power is increased, are indicated. The direction of further research is also indicated, which is associated with the analysis of the deformation of the considered materials at the first stage of creep.

Теоретичні дослідження технології обробки циліндрів антифрикційними матеріалами

The article analyzes the research aimed at the use of various materials, additives and additives to oils. It is established that their application is mainly limited to the stages of operation, bench and operational running-in. The use of antifriction materials at the stage of processing the parts of internal combustion engines, limiting the resource, is small, despite the fact that such treatment reduces the running-in time and improves the finish of the friction surfaces. Theoretical calculation of the parameters of the working surface of the engine cylinder liner during their finishing using special antifriction materials showed a 2-fold increase in the bearing surface (from 0.2 to 0.4 of the nominal surface area at the level of the middle line of the profile) and a roughness of 0.27 μm, which is close to the values after the bench run-in. This proves the possibility of using this treatment in order to reduce the time of preparation of CNG and improve the characteristics of the surfaces to be worked. It is established that the finishing of engine cylinder liners with antifriction materials should be carried out at the contact pressure of the working tool (brass bars) on the surface of the sleeve 3 MPa, the speed of the working tool 5.5 m/s, the processing time of the sleeve 20 min. Finishing of sleeves with use of compositions TSK-B100 + SURM-KV, SURM-UO and RVS allows to reduce mechanical losses on friction in TsPG by 5-19% at the beginning of process of running in after processing in comparison with mechanical losses at the end of cold running in without finishing sleeves; to obtain the roughness parameters after finishing the same as after cold running in without additional processing of the sleeves; increase the bearing surface by 2 - 2.5 times (from 0.2 - 0.25 to 0.4 - 0.5 of the nominal surface area at the level of the middle line of the profile), which confirms the calculated data. The final treatment of sleeves with compositions based on antifriction materials TSK-B100 + SURM-KV, SURM-UO and RVS allows to provide values of parameters of a working surface of sleeves (reduction of roughness, increase of a basic surface) approaching their values after cold running in, therefore allows to increase contact loadings. in the connection "sleeve - piston ring" after this treatment and reduce the time of the bench run-in (to the values required for the attachment of other engine connections).

Structure forming and managing of properties of phosphorous cast irons for parts of internal combustion engine

Purpose. Improving the mechanical and operational properties of details of internal combustion engines by managing the structure formation of phosphorous cast irons.
 Research methods. Graphitized and bleached phosphorous cast irons with lamellar and globular graphite of laboratory and industrial melts, melted in electric induction furnaces with alloying modification and fractional casting into dry sand molds were investigated. Chemical composition, microstructure, physical and mechanical properties were determined using standard methods. Non-destructive quality control of engine parts, statistical analysis of experimental data and deterministic factor analysis of the influence of structural components on the properties of the cast irons were carried out according to the methods developed with the participation of the authors. Bench and road motor tests of optimal composition cast irons details were carried out in engines according to standard and factory methods in accordance with state standards.
 Obtained results. The general laws and principles of the formation of the microstructure of cast irons with lamellar and nodular graphite are determined depending on the degree of their alloying with phosphorus and the influence of the scale factor. It has been established that phosphide eutectic in an amount of up to 5.8 % is a strengthening structural component and increases strength, hardness, wear resistance, heat resistance, and machin-ability of phosphorous cast irons with blade tools. The negative effect of phosphide eutectic on plastic properties and cyclic fracture toughness is less significant than the effect of increasing amounts of ferrite, its grain size and graphite. Optimal chemical compositions and microstructures of phosphorous cast irons for internal combustion engines details are recommended.
 Scientific novelty. For the first time, a comprehensive system for managing the properties of phosphorous cast irons has been developed, including the analytical determination of the required characteristics of structural components and the technology for their production.
 Practical value. Methods and technologies for melting, alloying, modifying, heat treatment and surface hardening of phosphorous cast irons have been developed. They make it possible to provide the required level of mechanical and operational properties of internal combustion engines details.

Steady State Unbalance Response Analysis of Internal Combustion Engine Crankshaft Based on Torsional Vibration

Crankshaft is one of the main moving parts in internal combustion engine. The instantaneous gas pressure and effective crank radius of each cylinder of the engine and the ignition interval angle of each cylinder make the torque of each crank change constantly, which causes the torsional vibration of the crankshaft. Based on the lumped parameter model, the transfer matrix method is used to analyze the steady-state unbalance response of internal combustion engine crankshaft, which has a certain reference value for mastering the influence of torsional vibration on the working state and strength safety of crankshaft.

О РЕЗУЛЬТАТАХ ТЕРМОУСТАЛОСТНЫХ ИСПЫТАНИЙ ЧУГУНА И ОЦЕНКЕ ЕГО ДОЛГОВЕЧНОСТИ

The article notes that at present, despite numerous studies of thermal fatigue, the thermal fatigue strength of cast irons due to stresses in parts made of this material requires additional study. Issues of thermal fatigue strength are especially relevant for such heat-stressed parts of internal combustion engines of autotractor diesel engines as the cylinder head. Of particular importance for these parts in their design and restoration is the ability to predict thermal fatigue strength, which is the main criterion that determines their durability. The article describes an approach to solving the problem of predicting the thermal fatigue strength of cast iron parts based on the data on their stress state and the results of thermal fatigue testing of samples on a specially designed and manufactured installation. The setup consists of two massive plates mounted on racks, between which a sample with a hole was rigidly installed. During the tests, the sample was heated by a special annular furnace to a temperature of 550°C for two minutes, and then cooled with running water through the central hole. A sample bounded on both sides during heating and thermal expansion accumulated residual tensile stresses as a result of relaxation processes and, upon reaching critical values and the appearance of fatigue defects in the form of cracks, ruptured. The proposed mode quite accurately repeats the operating conditions of the heat-receiving surface of the cylinder heads in the area of the intervalve jumpers when changing the operating mode at rated power and subsequent engine shutdown. As a result of the tests, the curves of the number of cycles to failure depending on the achieved stresses were obtained and their approximation was carried out. On the basis of approximating expressions and dependences of "limited durability" under low-cycle loading of parts, the thermal fatigue strength of a part made of cast iron can be predicted when its stress state changes as a result of design changes or after restoration.

Analytical study regarding the topological optimization of an internal combustion engine piston

Continuous progress in the automotive field involves the use of new working methods in the calculation and optimization of the internal combustion engine parts. On this occasion, in this paper, the impact of a topological optimization on the piston in the combustion engine of the conventional or hybrid electric car was studied. Starting from the simulation of the Otto cycle, the dimensional calculation is reached, after which a classical FEA analysis is carried out in order to establish the reference values. In the last part, the data of the classical analysis are compared with those of the topological analysis in order to perform a comparison of their results. The purpose of this study is to reduce the volume of the optimized part and to increase its rigidity.