Papers by Author: Nicolae Predincea

Abstract: In this study the tangential contact stiffness between two elastic bodies having nominally flat surfaces with different material combinations is investigated. The tangential contact stiffness between these two elastic bodies is first calculated based on the Greenwood-Williamson-McCool contact theory. Then, the tangential contact stiffness is determined by experimental investigation on a tribometer under the effect of different values of normal load and tangential displacement amplitude. The tangential contact stiffnesses obtained from the experimental data show a good agreement with the theoretical results, where the trends are similar and they are in the same order of magnitude.

Abstract: The complex modeling and coordination program has been developed based on quality standards that are in line with the quality requirements specific to the production of turbojet engines and assures the guarantees and confidence of our European Partners in our ability to take part in complex international projects with high levels of scientific and technological difficulty. A particular feature of the project is the quality system integration. For this purpose, the hardware of the existing machine tools is modified to assure the active control of parameters and a report is issued on the actual parameters. The report printed on a barcode card accompanies the component throughout the technological workflow, assuring the traceability of the component history, and a quality report is issued.

Abstract: To achieve high quality and productivity during continuous contouring, it is important to know how the two axes work together to move the machine in a circular or rectangular path. For this reason, we have analyzed circular and linear motion trajectories and the frequency response of the system during milling process. In the same time, is required to analyses simultaneously both mechanical and control subsystems. Based on these problems, the main objectives of this work have been defined to find a way to improve dimensional accuracy.

Abstract: Experimental modal analysis is quickly developed area of science in last years. Experimental approach for solving technical problems is a means to estimate or evaluate modal properties of a mechanical structure. The paper is focused at dynamic properties of milling centers, namely at the resonance frequencies and vibration shapes of a simplified tool-work piece system. All this properties are identified by measurements. The machine tool vibration was excited by impulse force and a response of excited vibration was recorded. The measurement points for vibration were selected at the spindle head, the table and the clamping device. The paper aims to present comparative results of theoretical studies with experimental results obtained from impact test to the machining centers.

Abstract: The present study demonstrates the use of optimization technology in improving the bolted joint design. Design exploration from ANSYS Workbench is used in the study. The objective of the study was to minimize the bolted joint deformation in order to optimize the joint. Variations of the parameters such as bolt pretension force, friction coefficient and pressure were studied. The optimization study provided response charts of the different design variables on the output. Sensitivity analysis of the input variables helped in identifying the importance of each design variable and their respective effects on the output. Finally the different design points were rated based on a goal-driven optimization study and the best design is chosen. Single Graphical User Interface allowed quick learning and ease-of-use.