Experimental and calculation study of a tubular part with sections

Abstract

When creating modern engineering products, considerable attention must be paid to strength parameters under dynamic loads. Such parameters include the forms of self-oscillations and their corresponding frequencies. Determining these parameters allows us to identify dangerous modes of operation of the part and predict its strength, as well as the shape and frequency of oscillations, which are the basis for further calculations. This work was devoted to determining the parameters of the dynamic strength of a cylindrical part with a diameter of 105 mm, height of 86 mm, and wall thickness of 2.48 mm made of 40 steel. For this part, the forms of the oscillations and the corresponding frequencies of the solid part were first determined. Then, four slits were made along the axis of rotation 1 mm wide at an equal distance between them. Studies were conducted for slots with depths of 0.25, 0.50, and 0.75 from the height (21.5 mm, 43.0 mm, and 64.5 mm, respectively). For each case, the forms of the oscillations and their corresponding frequencies are determined, as presented in this study. The forms of the oscillations and their corresponding frequencies were determined by finite element modeling in the SolidWorks software complex. The parameters of the created three-dimensional model were as follows: maximum element size of 4.86389 mm; minimum element size of 4.86389 mm; mesh quality: high; total nodes of 16913; total elements of 8096; maximum aspect ratio of 4.7645. To verify the calculated values, experimental studies were conducted to determine natural frequencies and forms of oscillations using the real-time speckle interferometry method. For this purpose, specialized equipment developed at the National University of Shipbuilding named after Admiral Makarov was used, the design of which was protected by a patent from Ukraine. For example, images of interferograms of the oscillating forms of the studied sample with slits of 0.50 height are presented. A comparative analysis of the effect of the depth of cuts was carried out, from which it can be seen that for the first and second forms, the frequency of natural oscillations changes from 474 Hz to 279 Hz, for the third from 722 Hz to 641 Hz, and for the fifth from 1339 Hz to 561 Hz, a decrease in the frequency of occurrence of natural forms of oscillations is explained by a decrease in the stiffness of the studied part, and the corresponding dependences are shown in the form of a graph.