In heavy duty machine tools, hydrostatic turntable is often used as a means for providing rotational motion and supporting workpiece, so the accuracy of turntable is crucial for part machining. In order to analyze the...In heavy duty machine tools, hydrostatic turntable is often used as a means for providing rotational motion and supporting workpiece, so the accuracy of turntable is crucial for part machining. In order to analyze the influence of load-indcued errors on machining accuracy, an identification model of load-induced errors based on the deformation caused by applied load of hydrostatic turntable of computerized numerical control(CNC) gantry milling heavy machine is proposed. Based on multi-body system theory and screw theory, the space machining accuracy model of heavy duty machine tool is established with consideration of identified load-induced errors. And then, the influence of load-induced errors on space machining accuracy and the roundness error of a milled hole is analyzed. The analysis results show that load-induced errors have a big influence on the roundness error of machined hole, especially when the center of the milled hole is far from that of hydrostatic turntable.展开更多
For reinforced concrete members subjected to high temperature,the degree of in-service loading,commonly expressed as the loading ratio,can be highly influential on the structural behavior.In particular,the loading rat...For reinforced concrete members subjected to high temperature,the degree of in-service loading,commonly expressed as the loading ratio,can be highly influential on the structural behavior.In particular,the loading ratio may be pivotal in relation to the phenomenon of load-induced thermal strain.Despite its potentially pivotal role,to date,the influence of the loading ratio on both material and structural behavior has not been explored in detail.In practice,real structures experience variation in imposed loading during their service life and it is important to understand the likely response at elevated temperatures across the loading envelope.In this paper,the effect of the loading ratio is numerically investigated at both material and structural level using a validated finite element model.The model incorporates a proposed constitutive model accounting for load-induced thermal strain and this is shown to outperform the existing Eurocode 2 model in terms of accuracy.Using the validated model,the specific case of flats slabs and the associated connections to supporting columns at various loading ratios are explored.For the cases examined,a marked difference in the structural behavior including displacement direction was captured from low to high loading ratios consistent with experimental observations.展开更多
基金Projects(51575010,51575009)supported by the National Natural Science Foundations of ChinaProject(Z1511000003150138)supported by Beijing Nova Program,China
文摘In heavy duty machine tools, hydrostatic turntable is often used as a means for providing rotational motion and supporting workpiece, so the accuracy of turntable is crucial for part machining. In order to analyze the influence of load-indcued errors on machining accuracy, an identification model of load-induced errors based on the deformation caused by applied load of hydrostatic turntable of computerized numerical control(CNC) gantry milling heavy machine is proposed. Based on multi-body system theory and screw theory, the space machining accuracy model of heavy duty machine tool is established with consideration of identified load-induced errors. And then, the influence of load-induced errors on space machining accuracy and the roundness error of a milled hole is analyzed. The analysis results show that load-induced errors have a big influence on the roundness error of machined hole, especially when the center of the milled hole is far from that of hydrostatic turntable.
文摘For reinforced concrete members subjected to high temperature,the degree of in-service loading,commonly expressed as the loading ratio,can be highly influential on the structural behavior.In particular,the loading ratio may be pivotal in relation to the phenomenon of load-induced thermal strain.Despite its potentially pivotal role,to date,the influence of the loading ratio on both material and structural behavior has not been explored in detail.In practice,real structures experience variation in imposed loading during their service life and it is important to understand the likely response at elevated temperatures across the loading envelope.In this paper,the effect of the loading ratio is numerically investigated at both material and structural level using a validated finite element model.The model incorporates a proposed constitutive model accounting for load-induced thermal strain and this is shown to outperform the existing Eurocode 2 model in terms of accuracy.Using the validated model,the specific case of flats slabs and the associated connections to supporting columns at various loading ratios are explored.For the cases examined,a marked difference in the structural behavior including displacement direction was captured from low to high loading ratios consistent with experimental observations.
