The article presents results of comparative tests performed to verify the conformity of geometric deviation measurements of a crankshaft carried out at a test bed equipped with a system of elastic support with measurements adopted as reference values. A number of simulation tests were carried out with varied shaft support conditions using the proposed measuring system. The selection criteria were established for support parameters. Meeting these criteria guarantees that shaft elastic deflections and strains are eliminated. Consequently, such strains will not affect the estimation of geometrical deviations of the measured object. The comparative evaluation measurement of roundness profiles and values of roundness deviations of main crankshaft bearing journals of a marine medium speed engine was performed using a correlation calculus. The results have revealed high conformity of both determined roundness deviation values and measured profiles compared to the reference ones.
The form, waviness and roughness components of a measured profile are separated by means of digital filters. The aim of analysis was to develop an algorithm for one-dimensional filtering of profiles using approximation by means of B-splines. The theory of B-spline functions introduced by Schoenberg and extended by Unser et al. was used. Unlike the spline filter proposed by Krystek, which is described in ISO standards, the algorithm does not take into account the bending energy of a filtered profile in the functional whose minimization is the principle of the filter. Appropriate smoothness of a filtered profile is achieved by selecting an appropriate distance between nodes of the spline function. In this paper, we determine the Fourier transforms of the filter impulse response at different impulse positions, with respect to the nodes. We show that the filter cutoff length is equal to half of the node-to-node distance. The inclination of the filter frequency characteristic in the transition band can be adjusted by selecting an appropriate degree of the B-spline function. The paper includes examples of separation of 2D roughness, as well as separation of form and waviness of roundness profiles.
The paper relates to the problem of adaptation of V-block methods to waviness measurements of cylindrical surfaces. It presents the fundamentals of V-block methods and the principle of their application. The V-block methods can be successfully used to measure the roundness and waviness deviations of large cylinders used in paper industry, shipping industry, or in metallurgy. The concept of adaptation of the V-block method to waviness measurements of cylindrical surfaces was verified using computer simulations and experimental work. The computer simulation was carried out in order to check whether the proposed mathematical model and V-block method parameters are correct. Based on the simulation results, a model of measuring device ROL-2 for V-block waviness measurements was developed. Next, experimental research was carried out consisting in evaluation of waviness deviation, initially using a standard non-reference measuring device, and then using the tested device based on the V-block method. Finally, accuracy of the V-block experimental method was calculated.
At the Kielce University of Technology a new concept of accurate measurements of sphericity deviations of machine parts has been developed. The concept is based upon measurement of roundness profiles in many clearly defined cross-sections of the workpiece. Measurements are performed with the use of typical radial measuring instrument equipped with a unit allowing accurate positioning of the ball. The developed concept required finding a solution to numerous problems relating to the principle of the radial measurement. One of the problems to be solved was matching of measured roundness profiles. The paper presents an outline of the developed concept of sphericity measurement, a mathematical model of profile matching and results of the verification of the model.
The paper discusses a method of quantitative comparison of cylindricity profiles measured with different strategies. The method is based on applying so-called Legendre-Fourier coefficients. The comparison is carried out by computing the correlation coefficient between the profiles. It is conducted by applying a normalized cross-correlation function and it requires approximation of cylindrical surfaces using the Legendre-Fourier method. As the example two sets of measurement data are employed: the first from the CMM and the second one from the traditional radial measuring instrument. The measuring data are compared by analyzing the values of selected cylindricity parameters and calculating the coefficient of correlation between profiles.