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G. V. Duncheva

Bio: G. V. Duncheva is an academic researcher from Technical University of Gabrovo. The author has contributed to research in topics: Burnishing (metal) & Residual stress. The author has an hindex of 12, co-authored 41 publications receiving 400 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, constitutive models of 2024-T3 aluminium alloy have been developed at room and high temperatures in order to be used in finite element simulations of cold hole working process.

49 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of slide burnishing on the obtained roughness, micro-hardness, residual stress, fatigue strength (life) and wear resistance of chromium-nickel steels is investigated.
Abstract: Chromium–nickel steels are widely used in various fields of the engineering practice because of their increased corrosion resistance. One of the most used chromium–nickel steel is AISI 316Ti. It is known from the engineering practice that processing this steel by cutting creates difficulties and problems. However, there is no information regarding the effectiveness of the slide burnishing (SB) method in terms of quality of the processed surface of this chromium–nickel steel. A comprehensive experimental and FEM study of the surface integrity of slide burnished specimens made of AISI 316Ti austenitic stainless steel has been carried out. The effect of the SB parameters on the obtained roughness, microhardness, residual stress, fatigue strength (life) and wear resistance has been studied. A fully coupled thermal-stress FEM analysis has been conducted to be appreciated the effect of the generated temperature in SB process on the residual stress formation. The SB of AISI 316Ti steel achieves: roughness of Ra = 0.055 μm; micro-hardness increased by more than 32%; significant wear resistance; introduced residual stress with a maximum absolute value, which significantly exceeds the yield limit of the bulk material; increased fatigue strength by 38.9%; fatigue life increasing more than 385 times. The obtained experimental outcomes for the main characteristics of the surface integrity prove that SB can be successfully applied as a mixed burnishing for finishing symmetrical rotational components made of chromium–nickel steels.

40 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of the process parameters on the surface roughness, micro-hardness, and residual stresses obtained in slide burnishing of D16T aircraft aluminum alloy has been analyzed.
Abstract: It is well known that apart from compressive residual stresses, smooth surface and microstructuring of the surface and subsurface layers are beneficial for enhancement of fatigue strength and load-carrying capacity of structural and machine components. This complex of properties can be achieved using surface severe plastic deformation. For symmetric rotational components made of high-strength aluminum alloys, slide burnishing is appropriate because of its simplicity and easy realization. The effect of the process parameters on the surface roughness, micro-hardness, and residual stresses obtained in slide burnishing of D16T aircraft aluminum alloy has been analyzed. The optimal values of the basic governing factors, which ensure minimum roughness (up to $$0.05\,\upmu\,{\text{m}}$$ ), have been established on the basis of a one-factor-at-the-time method, followed by a planned experiment and additional experiments. With the established combination of optimal values, the effect of number of passes and lubricant-cooler on the roughness, micro-hardness, and residual stresses in the surface being treated has been studied for two working schemes. To establish residual stress–depth profiles depending on the tool radius and burnishing force, FEM analysis of the slide burnishing process has been conducted. Thus, an evaluation of the effectiveness of slide burnishing as “mixed burnishing” has been made.

39 citations

Journal ArticleDOI
TL;DR: A review of slide burnishing of metal components is presented in this paper, where the main feature of SB is the sliding friction contact between the deforming element and the surface being treated.
Abstract: This review paper is devoted to the slide burnishing (SB) of metal components—state-of-the-art, achievements and perspectives. SB belongs to the group of static methods for mechanical surface treatment used largely in aerospace, automotive and other industries. By means of the plastic deformation of the surface layers, the surface integrity (SI) of the respective component is improved greatly in terms of minimum roughness, micro-hardness and introduced residual compressive stresses. As a result, fatigue crack resistance, crack corrosion resistance, wear resistance and corrosion resistance increase dramatically. The main feature of SB is the sliding friction contact between the deforming element and the surface being treated. Using the differential-morphological method, an integrated classification of the static methods is created and the area of SB is outlined. The proposed morphological matrix, which can be expanded and supplemented contains existing burnishing methods as well as combinations of elements and interactions that can be used to synthesize new burnishing methods and tools. In addition, a literature review of the publications devoted to SB has been conducted. Further, an analysis of the published studies on different criteria has been carried out and graphic visualizations of the statistical results have been made. On this basis, relevant conclusions have been made and the directions for future investigations of SB have been outlined.

36 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented outcomes from finite element and X-ray diffraction analyses of the cold hole expansion process fulfilled by means of solid mandrel gradually passing through the hole.

28 citations


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TL;DR: In this article, Taguchi optimization results revealed that burnishing force and number of pass were the significant parameters for minimizing the specific wear rate, whereas the burnishing feed and speed play important roles in minimizing the coefficient of friction.
Abstract: The objective of the research was to improve the wear resistance of titanium alloys by ball burnishing process. Burnishing process parameters such as burnishing speed, burnishing feed, burnishing force and number of pass were considered to minimize the specific wear rate and coefficient of friction. Taguchi optimization results revealed that burnishing force and number of pass were the significant parameters for minimizing the specific wear rate, whereas the burnishing feed and speed play important roles in minimizing the coefficient of friction. After burnishing surface microhardness increased from 340 to 405 Hv, surface roughness decreased from 0.45 to 0.12 μm and compressive residual stress were generated immediately below the burnished surface. The optimization results showed that specific wear rate decreased by 52%, whereas coefficient of friction was reduced by 64% as compared to the turned surface. The results confirm that, an improvement in the wear resistance of Ti–6Al–4V alloy has been achieved by the process of ball burnishing.

195 citations

Journal ArticleDOI
TL;DR: In this article, the improvement in the high-cycle fatigue strength of AISI 1045 normalized steel after low-plasticity ball burnishing was quantified, providing engineering data and coefficients useful for fatigue analysis and design.

134 citations

Journal ArticleDOI
TL;DR: In this article, the effects of pre-treatments on aging precipitates and corrosion resistance of a creep-aged Al-Zn-Mg-Cu alloy were investigated by means of transmission electron microscope (TEM), scanning electron microscopy (SEM) and cyclic potentiodynamic polarization experiments.

102 citations

Journal ArticleDOI
TL;DR: In this article, the ball burnishing is applied on sculptured surfaces, aiming at enhance surface roughness, and two different strategies are possible for burnishing, the continuous burnishing (CB) which uses a five-axis interpolation of the machine tool, and the patch burnishing using a more simple 3 + 2 axis interpolation.
Abstract: In this article, the ball burnishing is applied on sculptured surfaces, aiming at enhance surface roughness. Different strategies are possible for burnishing, the continuous burnishing (CB) which uses a five-axis interpolation of the machine tool, and the patch burnishing (PB) using a more simple 3 + 2 axis interpolation. Using both techniques complex parts are burnished and a big improvement in surface roughness achieved, but some differences between both approaches appear. Two parts have been previously machined in a five-axis milling center and finished using the ball burnishing approaches. The first one is a steel AISI 1045 with a hemisphere shape, whose geometry is simple. The second one is a steel DIN 1.2379 part (64 HRC), with more complex features. Surface quality was evaluated for both burnishing approaches, obtaining significant improvements on surface roughness and hardness. The main general conclusion is that ball burnishing reduces roughness without penalizing the manufacturing time or surfac...

84 citations

Journal ArticleDOI
TL;DR: A review on the hole cold expansion technology research status in the last twenty years is presented in this article, where the analysis of the current characteristics and defects of the holecold expansion technology, combined with the actual needs in design and manufacture of new-generation aircraft, development trends and novel research directions are presented for realizing precise and high-efficiency anti-fatigue manufacture.

76 citations