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Ball screw mechanisms (BSM) and planetary roller screw mechanisms (PRSM) belong to promising energy-saving mechanisms converting rotary motion into linear motion. To calculate and design these mechanisms the static and dynamic load capacities are used. In case a standard size of the mechanism to be designed is available in manufacturer’s catalog, the specified load capacities can be taken from the catalog, and if not, then the static load for the mechanism being designed can be calculated. To determine the dynamic load capacity, long-term and costly experimental studies are to be conducted. Therefore, the crucial task is to forecast the BSM and PRSM dynamic load capacity and, further, the service life of these mechanisms. As follows from the analysis of information provided in manufacturers’ catalogs, there were established correlative relationships of static and dynamic load capacities for BSM and PRSM with the parameters determining their standard sizes. Using these relationships and methods of power regression enable us to obtain empirical dependences linking the factor equal to the ratio of static load capacity to dynamic load capacity with parameters defining standard sizes of the mechanisms. To predict BSM and PRSM service lives the said ratio is calculated using the empirical dependence, static load capacity of the mechanism being designed is determined by means of calculation using known procedures, and then dynamic load capacity is determined as the quotient of static load capacity division by the said factor. Then, having determined the equivalent load acting on the mechanism being designed the service life value is predicted based on known procedures. The developed procedure for predicting dynamic load capacity and service life can be used for calculation of newly developed BSM and PRSM designs when determining reasonable parameters of these mechanisms and their parts. The article cites an example of forecasting PRSM service life with reasoned selection of the most important parameters of its parts, by means of which a substantial economic effect can be obtained. |
