Kompresör valf yapraklarının darbe yorulması özelliklerinin incelenmesi

A unique automated impact fatigue test system has been designed and produced, which enables to carry out impact fatigue tests of the compressor valve leaves under the desired impact velocities. The test system serves investigations on the impact fatigue characteristics with the ability of crack detection and as the subsequent step of terminating the test system. The crack detection technique incorporates a microphone and a data acquisition system with a non-contact actuation. The impact fatigue experiments were performed on hardened and tempered carbon flapper valve strip steel Sandvik 20C, martensitic stainless chromium steel alloyed with molybdenum Sandvik 7C27Mo2 and Sandvik Hiflex®.The impact fatigue life was determined for various impact velocities. The influence of temperature on the impact fatigue life of Sandvik 20C was investigated in the designed temperature control cabin. Cold-worked edges of the valve leaves were sharpened due to the blanking operation of the valve leaves. Therefore, a tumbling operation is performed in order to round the sharp edges, remove the small manufacturing defects and introduce compressive residual stresses. The edge radius of the specimens was characterized and tumbling duration was correlated with the impact fatigue life. In addition, asymmetrical impact behavior due to the variation in working condition of compressor and the designs of other components were examined. Microscopic and metallographic observations were carried out. It was observed that the impact fatigue failure originated at the edge of the valve leaves on the contact surface of valve leaf and vale plate. The crack propagation results were also presented. The introduced test system and methodology guides the design optimization of valve leaves in terms of compressor performance due to energy consumption and lifetime of the valve leaf.