George Dobre

Study of Car Multi-Link Rear Axle Considering Their Kinematic Incompatibilities

Multi-link rear axles offer some important advantages relative to vehicle handling. But the structure of the multilink split type generally determines kinematic incompatibilities in its operation. The paper studies some aspects surrounding constructive solutions that could minimize these kinematic incompatibilities. Some rear axle mechanisms from different cars were measured and analyzed as component shape by authors; this process allows the geometrical modeling and animation of systems using specialized software (Autodesk Inventor Professional 8). The effects of these modeled structures (the variations of track width and wheel camber angle) have been studied using the above-mentioned software. The variation of track width caused by the studied mechanisms along the compression and relaxation of the suspension spring defines the trajectory of the tyre contact patch. The results are contextualized in diagrams showing that the modifications of the analyzed parameters are very important, with a negative influence on car stability and the comfort of passengers. The interpretation of these diagrams allows the choice of favorable constructive solutions to increase car performance.

Optimal Damping Constant Investigation on a Quarter-Car

This paper shows an investigation on optimal damping constant performed in the frequency domain. The optimal damping constant is meant as that value that minimizes the acceleration of all connected bodies characterizing a two degree of freedom system sketching a quarter car. The connected bodies are sprung and unsprung mass respectively for quarter of chassis and tire, this last keeps the contact with the ground and it is connected with the sprung mass through a shock absorber characterized by spring and fluid damper. Optimal damping constant was determined by imposing analytical conditions on the expression of acceleration of two masses. Afterwards, the variation of acceleration and position in function of frequency for the obtained value of damping constant is plotted numerically in two ways using Wolfram Mathematica and MSC Adams software.

On Evaluation Methods in Product Development. Application on Mechanical Transmissions

Successful companies design and produce products which satisfy optimally the needs and desires of the customer. For this goal new concept ideas need to be generated, optimised and the optimal of them to be selected for production. A literature review considering the state of the art of the systematic approach of product development and of the evaluation methods is realized. Two evaluation methods are considered. One is the classical evaluation method (Pahl et al. 2007) and the second is the fuzzy logic evaluation method proposed by authors. A comparison of the two methods is realized and the principal advantages and disadvantages using a case of study of four variants for a mechanical transmission between a turbine and an electrical generator.

CAD/CAE Approach of the Strain and Stress Static Analysis for Spur Gear Pairs

In the last years there is an increasing demand for the efficiency, compact size, low noise level and reliability of gear transmission. This imposed that gear designers use adequate software for design and verify the product development. The paper aims to evaluate the use of different software for design and test the spur gear transmissions. An algorithm from the concept and geometric profiles of the teeth and linked parts to the models obtained using Finite Element Analysis (FEA) which aims to test and verify the comportment of the involved structures in the meshing process is presented. The paper aims also to demonstrate that ISO or other standards cannot conduct a reliable analysis of the root tooth bending and teeth contact stress. The proposed algorithm shows that o lot of software can be used but also the necessity to generate specific codes to interlink the steps in the algorithm. Also the paper put in discussion the use of 2D and 3D models in the transmission design process. One feature of the algorithm is the necessity of the 3D model in the process. The use of FEM as a numerical method to evaluate the behavior under static load conditions is also one of the necessity in the modern conditions of product development and the paper aimed to demonstrate that feature. Finally the presented FEM software shows a complete suitability for the calculation of spur gears transmission and not only.

On Measurement and Processing Data of the Real Loading: Application to Cement Equipment Components

Considering the real task of modern calculations of strength, reliability and durability of a system (or its components) is an actual and important means to achieve many advantages: (a) more precise calculations of the strength, leading to more accurate dimensions (in general—lower) of the product which in turn causes other cost advantages: lower manufacturing cost and lower operational energy costs; (b) a good assessment of the reliability and durability of the product; (c) as a result a better planned and predictive maintenance. The research in field remains open today because the literature does not provide accurate indications regarding: (a) consideration of real loading in calculations, (b) measuring, processing and interpretation of experimental data to develop models of loading. Research objectives in this field were developed to a good investment programming to modernize or rehabilitate a vibrating screen (1,000 … 1,200 t/h) integrated in cement fabrication flow sheet. Measurements of un-modulated real loadings on one of the lateral case wall of the vibrating screen were made. A measuring methodology procedure and an appropriate measuring chain proposed previously by authors (Dobre et al., On the methods to measure the real loading at mechanical systems. In: The 7th international conference research and development of mechanical elements and systems—IRMES, Nis, Serbia, pp 395–400, 2011). The measurement chain was configured by high performance components with relative low costs (strain gauge signal amplifier, acquisition card, computer with large memory, high frequency processor, etc.). The experimental data are counted after this measurement and mean-amplitude frequency matrix is obtained. The loading spectrum for different stages and conditions of operating resulted. Finally conclusions about the main approaches and results of the paper are noted. The processing methodology of the experimental data could be extended to the entire structure of the cement equipment. The paper continues previous researches developed by the Romanian school in this area (Dobre et al., On the Real loading modelling of the mechanical systems. Fiabilitate si Durabilitate/Fiability and Durability, Nr 1, pp 1–6, Editura Academică Brâncusi, Târgu Jiu, ISSN 1844-640X, 2010), (Mirică et al., On the theoretical-experimental modeling of loading of the mechanical transmissions. In: Proceedings of 3rd international conference on power transmissions, Kallithea—Chalkidiki, Greece, pp 291–296, ISBN 978-960-242-662-2, 2009), (Dobre et al., On the loading modeling of the mechanical systems. In: The 13th international conference on machine design and production, 03–05 Sep 2008, Istanbul, Turkey, vol II, pp 417–480, 2008).

On the Development of Complex Products Containing Sub-Assemblies

The paper analyzes aspects regarding the product development process of a complex product containing sub-assemblies. The sub-assembly is considered as an independent product integrated in a general assembly. The paper proposes new ideas, adding to the state of art in this field. Thus, a proposed scheme of the product development process is applied with new considerations in the case of a complex product containing sub-assemblies. This scheme contains distinct stages for the main developer, aiming with the general coordination and even the development of sub-assemblies, and third-parties, which develop other sub-assemblies (whether manufactured or not by the main developer).