- TITLE:
INVESTIGATION OF THE INFLUENCE OF THE INITIAL MICROSTRUCTURE UNDER DIFFERENT REGIMES OF HEAT TREATMENT ON THE MECHANICAL PROPERTIES OF 42CrMо4 STEEL
- AUTHOR(S):
V. Todorov
- ABSTRACT:
In this article, the impact of heat treatments - normalization and a combination of normalization, quenching and high-temperature tempering - on the microstructure and mechanical properties of 42CrMo4 steel specimens is investigated. Three groups of samples were studied: 1) asreceived; 2) after normalization at temperature of 860� � with holding time of 20 minutes and cooling in air; 3) after normalization (860��/20 minutes), quenching at 850�� in oil and then tempered at 590��, followed of cooling in air. The phase and microstructural analysis revealed the presence of retained austenite in the samples subjected to normalization. The resulting microstructure is ferrite-sorbite, containing about 10% retained austenite. The mechanical properties for the three investigated groups of samples showed the highest values for tensile strength (Rm=1147 MPa) and hardness (324 HBW) after normalization, and the highest elongation (12.9%) was obtained with the combination of normalization, quenching and high temperature tempering.
- DOI:
https://doi.org/10.62853/PHAV2471
- PAGES:
49-53
- DOWNLOAD:
INVESTIGATION OF THE INFLUENCE OF THE INITIAL MICROSTRUCTURE UNDER DIFFERENT REGIMES OF HEAT TREATMENT ON THE MECHANICAL PROPERTIES OF 42CrMо4 STEEL
- HOW TO CITE THIS ARTICLE:
V. Todorov. Investigation of the influence of the initial microstructure under different regimes of heat treatment on the mechanical properties of 42CrMo4 steel. Journal of Technical university of Gabrovo. 68 (2024) 49-53.
- TITLE:
EFFECTS OF ELECTRON BEAM TREATMENT ON MICROSTRUCTURE OF TI6AL4V ALLOY
- AUTHOR(S):
M. Atanasova
- ABSTRACT:
The effect of changes in the electron beam current on the microstructure of Ti6Al4V was investigated. Processing was applied with 6 different beam current values: 5, 10, 15, 20, 25 and 30 mA. A rectangular blank with dimensions thickness 10 mm, width 70 mm and length 100 mm was used. The change of the microstructure and the appearance of defects during electron beam treatment of a titanium alloy were investigated. The conducted experimental studies confirm the tendency that as the magnitude of the current increases, both the depth of penetration and the width of the treated area increase proportionally. The average measured value of grain size in fusion zone is in the range (0.72 -1.48) mm.
- DOI:
https://doi.org/10.62853/WAWB1418
- PAGES:
43-48
- DOWNLOAD:
EFFECTS OF ELECTRON BEAM TREATMENT ON MICROSTRUCTURE OF TI6AL4V ALLOY
- HOW TO CITE THIS ARTICLE:
M. Atanasova. Effects of electron beam treatment on microstructure of Ti6Al4V alloy. Journal of Technical University of Gabrovo.68 (2024) 43-48.
- TITLE:
GENETIC SYNTHESIS OF HYBRID ELECTRO-MECHANICAL SYSTEMS FOR MOTOR-SPINDLE UNITS WITH ADAPTIVE SPATIAL STRUCTURE
- AUTHOR(S):
V. Shynkarenko, Y. Kuznetsov, L. Soos, A. Shevchenko
- ABSTRACT:
The results of fundamental research carried out at the Department of Electromechanics of KPI named after Igor Sikorsky, it was established that the structural organization and evolution of arbitrary classes of technical systems that function on the principles of electromechanical energy conversion is determined by the principles and laws of genetically organized systems. Motor-spindles (M-�) also belong to the category of such systems. The energy and genetic core of technical systems with electromechanical energy converters is the active zone of the energy converter, which is a physical and information carrier of genetic information and the corresponding genetic code. The trend of creating multi-coordinate motor-spindle units with a spatially adaptive structure, designed to function as part of metalworking centers and machines with digital control systems, is analyzed. In genetically organized systems, the processes of structuring objects of any level of complexity are implemented on the basis of the elemental information base of genetic programs using genetic synthesis operators. From the point of view of the theory of genetic structure formation, spatial adaptation is the result of chromosomal transformations using the principles of hybridization, mutation, replication, and isomerism. The problem of synthesizing a hybrid multifunctional EM structure for motor-spindle units with a spatially adaptive modular structure was formulated and solved. A generalized genetic model of chromosomal synthesis of hybrid electromechanical modules of motor-spindle units according to a given function has been developed. The structural formulas of hybrid electromagnetic chromosomes, which determine the population structure of original technical solutions, have been determined. Based on the simulation results, the structures of spatially adaptive motor-spindle units with two-, three-, and four-coordinate movement of the working body were synthesized. Based on the results of the research, a genetic catalog was created, which serves as a system basis for the development of original technical solutions for motor-spindle units.
- DOI:
https://doi.org/10.62853/VMPU4498
- PAGES:
37-42
- DOWNLOAD:
GENETIC SYNTHESIS OF HYBRID ELECTRO-MECHANICAL SYSTEMS FOR MOTOR-SPINDLE UNITS WITH ADAPTIVE SPATIAL STRUCTURE
- HOW TO CITE THIS ARTICLE:
V. Shynkarenko, Y. Kuznetsov, L. Soos, A. Shevchenko. Genetic synthesis of hybrid electro-mechanical systems for motor-spindle units with adaptive spatial structure. Journal of Technical University of Gabrovo. 68 (2024) 37-42.
- TITLE:
METHODS FOR INCREASING THE FATIGUE LIFE OF STRUCTURAL COMPONENTS WITH FASTENER HOLES - STATE OF THE ART
- AUTHOR(S):
G. Duncheva, P. Daskalova
- ABSTRACT:
The article reviews the main approaches and the methods that implement them to improve the fatigue behavior of metal structural elements with fastener holes. A generalized classification scheme is proposed, in which established methods in engineering practice and new methods are systematized. The generalized scheme was developed based on the differential-morphological method. In accordance with the differentiation of the methods in the generalized scheme, the principle schemes of the different groups are visualized and an analysis of their advantages and disadvantages was made from the point of view of their functional capabilities and in a technological aspect.
- DOI:
https://doi.org/10.62853/JNWG1335
- PAGES:
21-36
- DOWNLOAD:
METHODS FOR INCREASING THE FATIGUE LIFE OF STRUCTURAL COMPONENTS WITH FASTENER HOLES - STATE OF THE ART
- HOW TO CITE THIS ARTICLE:
G. Duncheva, P. Daskalova. Methods for increasing the fatigue life of structural components with fastener holes - state of the art. Journal of Technical University of Gabrovo. 68 (2024) 21-36
- TITLE:
POROSITY DISTRIBUTION AND MICROHARDNESS OF A COLD ARC PULSE™ WIRE ARC ADDITIVELY MANUFACTURED AlSi x MECHANICAL PLATE
- AUTHOR(S):
Nikolay Petrov, Maria Ormanova , Iliya Zhelezarov
- ABSTRACT:
Porosity is known as the main problem of aluminum alloys regardless of the method for formation of aluminum components due to the unique thermophysical properties of this metal. The larger the heat input is, the higher the likelihood is of formation of pores within the structure of the components, whether be they caused by the gas adsorption or due to the expansion and then shrinkage of the material during the heating/cooling cycle. Since the pore formation mechanisms of additively manufactured specimens is still unclear, during the present work a wire arc additively manufactured specimen was used in order to study the concentration of pores within the structure of the last along its volume. Additionally, the less studied cold arc pulse (CAP) mode was employed during the specimens manufacturing. Since the structure directly influences the mechanical properties of the components, a microhardness map was prepared as well as investigation of the microhardness as a function of the specimen�s height. The results were summarized and indicated an increasing trend of the porosity of the specimen towards its top section. The larger defects were observed closer towards the bottom of the specimen due to the lower interpass temperature, this the worse fusion of the aluminum. Despite this the microhardness along the face-wall of the specimen and its cross section remained the same within the margin of error. The possibility of decreasing the porosity and increasing the quality of the deposited components was discussed.
- DOI:
https://doi.org/10.62853/HAEA7843
- PAGES:
2-07
- DOWNLOAD:
POROSITY DISTRIBUTION AND MICROHARDNESS OF A COLD ARC PULSE™ WIRE ARC ADDITIVELY MANUFACTURED AlSi x MECHANICAL PLATE
- HOW TO CITE THIS ARTICLE:
Petrov N., Ormanova M., Zhelezarov I. Porosity distribution and microhardness of a cold arc pulse wire arc additively manufactured AlSix mechanical plate. Journal of the Technical University of Gabrovo. 68 (2024) 2-7
