Utmattningsprovning av kamringar : Framtagning av testutrustning för utmattningsprovning av kamringar

Sammanfattning: Bosch Rexroth in Mellansel develops and fabricates Hägglunds hydraulic motors among other things. One important component of the motor is the cam ring, which commonly affects the life span of the motor. The aim is to create the basis of a testing equipment where a loose cam ring can be tested. Previously, a complete motor has been used in order to test the fatigue resistance of the cam ring. In order to load the cam ring similar to the real case. FEM-analysis was performed to investigate how the cam ring is affected during loading and how the rig should be built for the strains to be similar to the real case. The result of this simulation was compiled in a Haighdiagram in order to get an indication of the magnitude of the stresses. The solution is a testing equipment which consist of a cylinder block which usually is in the motor. The cylinder block is bolted onto a bottom plate where the cam ring has a given position. The cam ring is fixated using a sloted spring pin and a dowel pin that keeps the cam ring in position and prevents potential torque. All pistons should be pressurised by pulsation at the same time using the same pressure, thus, the torque is expected to be zero. One of the holes which is holding the cam ring is oval, this is to allow deformation of the cam ring. The result of this work is a basic plan for the components included which affects the mechanical function of the testing equipment. A limitation of this work has been that the residual stresses in the clearance holes is unknown. These residual stresses have a great importance for fatigue resistance of the cam rings. As a consequence of this, it has been difficult to estimate which working pressure the test rig has to use in order to achieve the desired life span. Experimental testing when using the rig will indicate this. Task monotoring  The testing equipment will generate 1-10 million loading cycles before failure of the cam ring occurs. Will be achieved through experimental testing  Testing time should be reasonable, result would preferably be achieved within 2-4 weeks. Will be achieved through experimental testing  The testing equipment should be customised for a CA 50-50 cam ring. (CA 50 motor series strongest motor 50 Nm/bar) Achieved  Testing equipment should be usable with the current laboratory equipment of Bosh Rexroths (420 bars maximum preassure). Probably achieved  The crack needs to be detected in an appropriate way, to stop the testing. Achieved  The testing equipment needs to be able to be manufactured by using the developed blueprints. Achieved