Cosmin Grigoras

Prof. Dr. Cosmin Grigoras

Vasile Alecsandri University of Bacau, Romania, Bacău, Romania
orcid

Research Focus & Metrics

Academic Career Length

12Years (2015-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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7 March 2024 in Machines
Verified
Journal Article
Open access
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Cosmin GrigorasCosmin Grigoras
Cosmin Grigoras
Valentin ZichilValentin Zichil
Valentin Zichil
Vlad-Andrei CIUBOTARIUVlad-Andrei CIUBOTARIU
Vlad-Andrei CIUBOTARIU
SCStefan Marius Cosa
Stefan Marius Cosa
This review focuses on the complex connections between machine learning, mechatronics, and stretch forming, offering valuable insights that can lay the groundwork for future research. It provides an overview of the origins and fundamentals of these fields, emphasizes notable progress, and explores the influence of these fields on society and industry. Also highlighted is the progress of robotics research and particularities in the field of sheet metal forming and its various applications. This review paper focuses on presenting the latest technological advancements and the integrations of these fields from their beginnings to the present days, providing insights into future research directions.

21 September 2024 in Materials
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Journal Article
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Valentin ZichilValentin Zichil
Valentin Zichil
Cosmin GrigorasCosmin Grigoras
Cosmin Grigoras
Vlad-Andrei CIUBOTARIUVlad-Andrei CIUBOTARIU
Vlad-Andrei CIUBOTARIU
The influence of notches and fatigue on the ultimate tensile strength and elongation at break of aluminium alloys (2024-T3, 6061-T4, 6061-T4 uncoated, 6061-T6 uncoated, 7075-T0, and 7076-T6) is presented in this study. A total of 120 specimens were used. On all specimens, notches were made using a CNC machine, with 60 of them subjected to low-cycle fatigue (LCF) before undergoing the tensile test. Based on the statistical examination of the measured data, mathematical prediction models have been established. Compared to their unscratched counterparts, the results indicate a significant decrease in the UTS and elongation at break for both notched and notched-fatigued specimens. The LCF pre-treatment contributes to the negative impacts of the notches, resulting in reduced values for the UTS and elongation at break, thus concluding that surface integrity is critical for maintaining the structural strength of aircraft components.

3 November 2015 in IOP Conference Series: Materials Science and Engineering
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Cosmin GrigorasCosmin Grigoras
Cosmin Grigoras
GBG Brabie
G Brabie
This study was conducted in order to determine the material hardness value due to modification of the milling cutting parameters. The alloy hardness was analysed as a function of different cutting parameters for milling operations (speed, feed and depth of cut), using a face mill. A total number of 17 samples were machined using parameters obtained by combining the input parameters. The total number of combinations is reduced by a preoptimization, using the DesignExpert software. The cutting process was performed in dry conditions, and it was recorded that dry cutting magnesium-aluminium alloy AZ61A with the used parameters did not lead to chip ignition. The surface hardness was determined based on the Vickers scale (HV), its values ranging from 110.59 [HV] to 121.37 [HV]. The obtained results showed that the feed has a significant contribution in the surface harness modification. The application of the Taguchi method reveals that the material hardness can be improved, together with the manufacturing time, by means of the speed, feed and depth of cut maximization.

15 December 2021 in Machines
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Journal Article
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Cosmin GrigorasCosmin Grigoras
Cosmin Grigoras
Valentin ZichilValentin Zichil
Valentin Zichil
BCBogdan Alexandru Chirita
Bogdan Alexandru Chirita
Vlad-Andrei CIUBOTARIUVlad-Andrei CIUBOTARIU
Vlad-Andrei CIUBOTARIU
An industrial process is defined through its quality of parts and their production costs. Labour-intensive operations must be applied to produce high-quality components with inexpensive resources. Recent development in dedicated software allows the industrial sector to rely on more and more autonomous solutions to obtain an optimum ratio between part quality and cost. The stretch forming process is an operation that has a high degree of difficulty, due to the process parameters and the spring-back effect of materials. Our approach to solving several of the shortcomings of this process was to develop a self-adaptive algorithm with computer vision capabilities that adapts to the process in real-time. This experimental study highlights the results obtained using this method, as well as a comparison to a classical method for the stretch-forming process (SFP). The results have noted that the stretch-forming algorithm improves the process, while adapting its decisions with each step.

5 July 2022 in Applied Sciences
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Journal Article
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Vlad-Andrei CIUBOTARIUVlad-Andrei CIUBOTARIU
Vlad-Andrei CIUBOTARIU
MRMaria-Crina Radu
Maria-Crina Radu
EHEugen Herghelegiu
Eugen Herghelegiu
Valentin ZichilValentin Zichil
Valentin Zichil
Cosmin GrigorasCosmin Grigoras
Cosmin Grigoras
Elena NechitaElena Nechita
Elena Nechita
Even though they initially appeared as a method of using waste from other production processes, tailored welded blanks (TWB) presented several advantages by combining materials with different characteristics. On the one hand, this study focuses on minimizing the adverse effects caused by the springback of TWB parts. The proposed method is based on the Taguchi technique using orthogonal type 23 networks. On the other hand, genetic algorithms were applied to obtain maximum performance parameters within the dynamic loadings of tubular structures made of TWB by advantageous positioning of the weld line. The obtained data were compared and evaluated through software platforms such as MATLAB, Design Expert, and Dynaform, and experimental validation. By generating an objective function, the construction of thin-walled tubular structures can be controlled for a predetermined deformation and maximum energy absorption. The data obtained has an error rate of less than 3%, thus considering that this method can be used successfully in the qualitative and quantitative estimation of dynamically loaded TWB tubular structures.

4 December 2020 in Applied Sciences
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Journal Article
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LDLucian Daniel Dobreci
Lucian Daniel Dobreci
Valentin ZichilValentin Zichil
Valentin Zichil
Elena NechitaElena Nechita
Elena Nechita
Cosmin GrigorasCosmin Grigoras
Cosmin Grigoras
Vlad-Andrei CIUBOTARIUVlad-Andrei CIUBOTARIU
Vlad-Andrei CIUBOTARIU
Shockwave therapy is a noninvasive treatment technique used in multidisciplinary fields, such as sports medicine, physical therapy, and orthopedics. This method of treatment is recommended for medical conditions, such as muscle contractions, intramuscular hematoma, or Dupuytren’s contracture. The shockwaves are high-energy pressure waves characterized by nonlinearity, high frequency, and peak pressure followed by low-pressure amplitude which are transmitted through an applicator to the affected tissue. In the case of spinal muscles, the conventional applicator can only be used on one side of the spinal cord at a time. Taking this into consideration, the approach suggested in this paper involves the design of a dedicated dual-tip applicator. This process implied predesign, finite element analysis, statistical analysis of the data, and optimization. We analyzed the input factors, such as frequency, pressure, applicator tip distance, shape, flatness, and material along with their effects, namely induced stress, tissue contact pressure, total strain energy, and propagation velocity. The proposed final design of the applicator uses geometric features suggested by the optimization analysis and also mechanical design features.