Study of the character and causes of destruction of the cardan shaft of the propeller engine

2019 ◽  
Vol 85 (12) ◽  
pp. 43-50
Author(s):  
D. A. Movenko ◽  
L. V. Morozova ◽  
S. V. Shurtakov
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Yield Point ◽  
Protective Coating ◽  
Fracture Pattern ◽  
Corrosion Cracking ◽  
Tempered Martensite ◽  
Neck Formation ◽  
Static Mechanism ◽  
Shaft Surface

The results of studying operational destruction of a high-loaded cardan shaft of the propeller engine made of steel 38KhN3MFA are presented to elucidate the cause of damage and develop a set of recommendations and measures aimed at elimination of adverse factors. Methods of scanning electron and optical microscopy, as well as X-ray spectral microanalysis are used to determine the mechanical properties, chemical composition, microstructure, and fracture pattern of cardan shaft fragments. It is shown that the mechanical properties and chemical composition of the material correspond to the requirements of the regulatory documentation, defects of metallurgical origin both in the shaft metal and in the fractures are absent. The microstructure of the studied shaft fragments is tempered martensite. Fractographic analysis revealed that the destruction of cardan shaft occurred by a static mechanism. The fracture surface is coated with corrosion products. The revealed cracks developed by the mechanism of corrosion cracking due to violation of the protective coating on the shaft. The results of the study showed that the destruction of the cardan shaft of a propeller engine made of steel 38Kh3MFA occurred due to formation and development of spiral cracks by the mechanism of stress corrosion cracking under loads below the yield point of steel. The reason for «neck» formation upon destruction of the shaft fragment is attributed to the yield point of steel attained during operation. Regular preventive inspections are recommended to assess the safety of the protective coating on the shaft surface to exclude formation and development of corrosion cracks.

scholarly journals THE INFLUENCE OF MICROSTRUCTURAL FACTORS AND HEAT TREATMENT ON THE CORROSION RESISTANCE OF REINFORCING STEEL CLASS A 600

2018 ◽  
Vol 22 (2) ◽  
pp. 52-63 ◽  
Author(s):  
N. N. Sergeev ◽  
V. V. Izvol'skiy ◽  
A. N. Sergeev ◽  
S. N. Kutepov ◽  
A. E. Gvozdev ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Corrosion Resistance ◽  
Chemical Composition ◽  
Carbon Content ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Steel Reinforcement ◽  
Reinforcing Steel

Currently, hot rolled bar reinforcement class A600 of low-alloy steels in the delivery condition has a high tendency to this very specific kind of destruction as stress corrosion cracking under tension (SCC). However, there are cases of collapse of pre-stressed concrete structures, in most cases initiated corrosion cracking under stress, put the problem this type of fracture is particularly acute. In stress corrosion cracking cracks occur, the occurrence of which depends not only on the structural state of the material, the type and level of stress, but also on the degree of aggressiveness of the environment in which the operation occurs. In this regard, it is very important to establish how the corrosion resistance of class A600 reinforcing steel varies depending on the change in the chemical composition, microstructure, the level of applied and residual micro-stresses, and various modes of heat treatment. The purpose of this paper is to study the effect of the above factors on the resistance of low-alloyed reinforcing steel class A600 stress corrosion cracking It is shown that the sensitivity of the reinforcement to stress corrosion cracking is largely determined by the chemical composition (mainly carbon content), the type of microstructure and the level of residual micro-stresses. The influence of heat treatment regimes on the corrosion resistance of A600-grade reinforcing steel in nitrates solutions is investigated. It is shown that the use of additional heat treatment (normalization and improvement) increases the corrosion resistance of steel. High corrosion resistance steel reinforcement has only a carbon content at the lower limit of the vintage composition, which is provided by the structure of homogeneous bainite with mechanical properties at the level of strength class A600. With higher mechanical properties, the steel reinforcement has lower corrosion resistance.

Structural features and strength behavior of TRIP/TWIP steels

2020 ◽  
pp. 5-18
Author(s):  
D. V. Prosvirnin ◽  
◽  
M. S. Larionov ◽  
S. V. Pivovarchik ◽  
A. G. Kolmakov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Thermomechanical Processing ◽  
Maximum Load ◽  
Structural Features ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Structural And Functional Properties ◽  
Twip Steels ◽  
The Creation

A review of the literature data on the structural features of TRIP / TWIP steels, their relationship with mechanical properties and the relationship of strength parameters under static and cyclic loading was carried out. It is shown that the level of mechanical properties of such steels is determined by the chemical composition and processing technology (thermal and thermomechanical processing, hot and cold pressure treatment), aimed at achieving a favorable phase composition. At the atomic level, the most important factor is stacking fault energy, the level of which will be decisive in the formation of austenite twins and / or the formation of strain martensite. By selecting the chemical composition, it is possible to set the stacking fault energy corresponding to the necessary mechanical characteristics. In the case of cyclic loads, an important role is played by the strain rate and the maximum load during testing. So at high loading rates and a load approaching the yield strength under tension, the intensity of the twinning processes and the formation of martensite increases. It is shown that one of the relevant ways to further increase of the structural and functional properties of TRIP and TWIP steels is the creation of composite materials on their basis. At present, surface modification and coating, especially by ion-vacuum methods, can be considered the most promising direction for the creation of such composites.

Weldability - Behavior of Welded Reinforcement

2019 ◽  
Vol 70 (10) ◽  
pp. 3469-3472
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Mechanical Characteristics ◽  
Mechanical Performance ◽  
Current Work ◽  
Carbon Equivalent ◽  
Work Process ◽  
Ultimate Limit

Weldability involves two aspects: welding behavior of components and safety in operation. The two aspects will be reduced to the mechanical characteristics of the elements and to the chemical composition. In the case of steel reinforcing rebar’s, it is reduces to the percentage of Cech(carbon equivalent) and to the mechanical characteristics: the yielding limit, the ultimate limit, and the elongations which after that represent the ductility class in which the re-bars is framed. The paper will present some types of steel reinforcing rebar’s with its mechanical characteristics and the welding behavior of those elements. In the current work, process-related behavior of welded reinforcement, joint local and global mechanical properties, and their correlation with behavior of normal reinforcement and also the mechanical performance resulted in this type of joints. Keywords: welding behavior, ultimate limit, reinforcing rebar’s

scholarly journals Cellular Orientation on Repeatedly Stretching Gelatin Hydrogels with Supramolecular Cross-Linkers

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2095
Author(s):  
Dae Hoon Lee ◽  
Yoshinori Arisaka ◽  
Asato Tonegawa ◽  
Tae Woong Kang ◽  
Atsushi Tamura ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Cellular Response ◽  
Linear Polymer ◽  
Cross Linking ◽  
Adherent Cells ◽  
Cell Cultivation ◽  
Supramolecular Compound ◽  
Synthetic Materials ◽  
Cyclic Molecules

The cytocompatibility of biological and synthetic materials is an important issue for biomaterials. Gelatin hydrogels are used as biomaterials because of their biodegradability. We have previously reported that the mechanical properties of gelatin hydrogels are improved by cross-linking with polyrotaxanes, a supramolecular compound composed of many cyclic molecules threaded with a linear polymer. In this study, the ability of gelatin hydrogels cross-linked by polyrotaxanes (polyrotaxane–gelatin hydrogels) for cell cultivation was investigated. Because the amount of polyrotaxanes used for gelatin fabrication is very small, the chemical composition was barely altered. The structure and wettability of these hydrogels are also the same as those of conventional hydrogels. Fibroblasts adhered on polyrotaxane–gelatin hydrogels and conventional hydrogels without any reduction or apoptosis of adherent cells. From these results, the polyrotaxane–gelatin hydrogels have the potential to improve the mechanical properties of gelatin without affecting cytocompatibility. Interestingly, when cells were cultured on polyrotaxane–gelatin hydrogels after repeated stress deformation, the cells were spontaneously oriented to the stretching direction. This cellular response was not observed on conventional hydrogels. These results suggest that the use of a polyrotaxane cross-linking agent can not only improve the strength of hydrogels but can also contribute to controlling reorientation of the gelatin.

scholarly journals Controlled atmosphere GMAW welding of transportation vehicles and production machines parts made from 30MnB5 steel

2018 ◽  
Vol 216 ◽  
pp. 03001 ◽  
Author(s):  
Evgeny Ivanayskiy ◽  
Aleksei Ishkov ◽  
Aleksandr Ivanayskiy ◽  
Iakov Ochakovskii
Keyword(s):  
Mechanical Properties ◽  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Chemical Composition ◽  
Controlled Atmosphere ◽  
Shielding Gas ◽  
Reducing Atmosphere ◽  
Metal Composition ◽  
Gmaw Welding ◽  
Welding Materials

The paper studies the influence of shielding gas on the composition and the structure of weld joint metal of 30MnB5 steel applied in essential parts of automobiles and tractors. The welding was performed in inert, oxidizing and reducing atmospheres. It was established that TIG welding with argon used as shielding gas did not provide the required mechanical properties when using conventional welding materials. Carbon dioxide during MAG welding caused partial burning of alloying elements. Carbon monoxide used as shielding gas was proved to form reducing atmosphere enabling to obtain chemical composition close to the base metal composition. Metallographic examinations were carried out. The obtained results provided full-strength weld, as well as the required reliability and durability of welded components and joints.

scholarly journals Influence of the Chemical Composition on Electrical Conductivity and Mechanical Properties of the Hypoeutectic Al-Si-Mg Alloys

2016 ◽  
Vol 61 (1) ◽  
pp. 353-360 ◽  
Author(s):  
B. Dybowski ◽  
J. Szymszal ◽  
Ł. Poloczek ◽  
A. Kiełbus
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Chemical Composition ◽  
Aluminium Alloys ◽  
Mg Alloys ◽  
High Electrical Conductivity ◽  
Transportation Industry ◽  
Proper Selection ◽  
Ti Addition ◽  
Selection Of

Due to low density and good mechanical properties, aluminium alloys are widely applied in transportation industry. Moreover, they are characterized by the specific physical properties, such as high electrical conductivity. This led to application of the hypoeutectic Al-Si-Mg alloys in the power generation industry. Proper selection of the alloys chemical composition is an important stage in achievement of the demanded properties. The following paper presents results of the research on the influence of alloys chemical composition on their properties. It has been revealed that Si and Ti addition decreases electrical conductivity of the Al-Si-Mg alloys, while Na addition increases it. The mechanical properties of the investigated alloys are decreased by both silicon and iron presence. Sodium addition increases ductility of the Al-Si-Mg alloys.

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