Abstract—The paper presents a new testing stand for antifriction bearings, suitable for all types of rolling and sliding bearings, especially for those having small diameters and operating at high rotation speeds. The design of this stand occurred as a necessity of additional equipment to the research endowment required by several research projects developed in partnership by the author’s institutions. It also can be used in proper conditions to test artificial joints for knees or elbows, consistent at model level with cylindrical bearings. Index Terms—bearings, friction, stand, test. I. INTRODUCTION Sliding bearings are involved in wide ranged fields of operation considering their outstanding properties as accuracy, endurance, rigidity, low friction levels, superior behaviour during vibrations or oscillating strains. Besides they are able to work in contaminated environments and the expenses for the manufacturing and maintenance are acceptable. Choosing the most appropriate materials for bearings is a very complex and delicate issue, due to the difficult and sometimes contradictory requirements, high level of mechanical and thermal strains, with complex changes in time, direction and amplitude, possible chemical attacks or radiations influence. As a follow, many types of wear may occur due to metal-metal contact when discontinuities appear within the lubricant film, abrasions due to contaminations with various micro particles or corrosion due to the interaction of aggressive chemical agents resulting from the working environment or even from the lubricant itself. The multitude of the factors acting upon the operating bearings requires a wide range of properties that need to be met by the materials used for their manufacturing and not least optimal possibilities of testing them for all the situations, which may affect their proper functionality, before starting mass production,. Manuscript received March 1, 2009. D. L. Cotoros is with the Transilvania University of Brasov, 500036, Romania, Department of Mechanics, phone: 0040268410525; fax: 0040268410525; e-mail: dcotoros@unitbv.ro or dcotoros@yahoo.com. M.I. Baritz is with the Transilvania University of Brasov, 500036, Romania, Department of Precision Mechanics and Mechatronics, e-mail: mbaritz@unitbv.ro or baritzm@yahoo.com . C.M. Opran is with the Polytechnical University fo Bucharest, Romania, Head of the Composite Materials Laboratory, e-mail: constantin.opran@ltpc.pub.ro . L. Serbina is with the National Research and Development Institute for Nuclear Engineering, Bucharest, Romania, researcher, e-mail: serbina_leon@yahoo.com . The paper is part of the national research projects ID_744/2008, ID_722/2008 and 212/2006. II. THEORETICAL CONCEPTS The testing stand represents the response to the requirement of completing the research endowment of a consortium involved in complex research projects in the field of bearings for different types of applications, not only for mechanical but also for biomechanical purpose. This equipment should be able to determine various performances of bearings, such as: load capacity, endurance, friction moments, for changing load values, even small diameters (starting from 5mm), various rotation speeds from 0 to 60000 rot/min. The loads may be axial or radial, static applied or vibratory. The stand will work within two modes of operation: - continuous operation - repeated turning on and off The main shaft of the equipment works on air bearings, having different diameters, the bigger one being the most strained, as its position is nearer to the tested bearing. For the same reasons, this bearing is supplied with pressured air by means of two rows of holes, while the second bearing is supplied by means of a single row. The number of holes for the second bearing is only three (0,63mm diameter). The main bearing has three holes on each row, with the same size and geometry, plus for each row of holes there is an additional hole, with a 0,25mm diameter, opposed to the supply source,. The holes rows are located at about 12,7mm from the bearing margin, so for a supply pressure of about 1,2atm, we can apply a load of 12kg, the radial clearance being at about 0,025mm. The tested bearing will be positioned on the shaft. If we are dealing with rolling bearings, the external part can be fixed in a floating bearing supplied with pressured air by means of two rows of holes, having the same construction as those above described. A mechanical arm placed on the internal part of the floating bearing allows us to measure the friction moments with high accuracy. For axial loads, a special constructed bearing was designed at the end of the main shaft. This bearing consists of two circular disks, supplied by a central hole, continued with very accurate manufactured conical surfaces. This way, at the border between the frontal and the conical surface, we will get an intermediate pressure among the one near the supply hole and the atmospheric pressure. Testing Stand for Antifriction Bearings with Applications in Biomechanics Diana L. Cotoros, Member, IAENG, Mihaela I. Baritz, Member, IAENG, Constantin M. Opran, Serbina Leonardo, Stanciu Anca Proceedings of the World Congress on Engineering 2009 Vol II WCE 2009, July 1 - 3, 2009, London, U.K. ISBN:978-988-18210-1-0 WCE 2009