Influence of errors of size and details surfaces shape on the nature of their connections

Abstract

Informed choice of tolerances and fits demands probabilistic approach to error estimation of details manufacturing. This work is to extend boundaries of application of the well-known technique of probability calculation for clearances and tension members taking into consideration surface shape errors and size systematic inaccuracy. Accepted standard deviation of fit takes into account form errors for standard level of relative geometric accuracy. It was determined the probability values for clearances and tension members for twelve standard fits and three intervals of sizes within 0...500 mm. Size scattering asymmetry coefficient is used to take into account the systematic errors. Relative characteristics of connections have been obtained for five values of this coefficient with different signs. The corresponding probabilities are calculated under the assumption that the shape of the probability distribution is not very different from the form of the Gauss's law. Calculations have shown that form errors do not affect the average values of clearance and interference though probabilistic characteristics of corresponding connections may increase to 10 %. Systematic errors depending on their sign significantly change the connection character from middle clearance to middle tension member and vice versa. Weak or unpredictable dependence on size intervals can be seen for all relative characteristics. The results of work can be helpful for engineering and accuracy problem solving.дач точности.