Abstract
When using friction gripping device with a screw drive to move designs from wood there is relaxation of tightening force of the screw with time due to rheological characteristics of wood. Weakening of tightening leads to a reduction of friction forces, holding the floating structure, which can lead to failure and drop of structure. To ensure reliable holding of wooden construction by gripping device within the specified time, prior increase in torque taking into account dynamics subsequent weakening is required. The article presents description of experimental setup to study the rate of weakening of the torque of the screw clamp and development of elastic deformation of samples of wood and plywood of different thickness with clamps of different hardness. Dependence of elastic strain and associated weakening of tightening force from time which samples stay under load, is revealed. The dependence has general nature for all the samples of wood and derivative materials. Regression analysis of the data and graphs of weakening the tightness of the clamps and development of elastic deformations is performed for each experiment. It is established that approximation to exponential function reflects the dependence of attenuation of torque settings on time in the interval up to 24 hours more accurately, than exponential function. To identify factors influencing the rate of weakening of the torque, regression analysis is made. The dependence of the rate of weakening of the torque by on stiffness of the clamp, thickness of wooden construction in the place of installation of gripping device and of the modulus of elasticity of wood is revealed. With the increase in rigidity of clamp and size of cross section of structure, weakening speed increases. Method of determining the rate of increase in force of pre-tightening of friction gripping device with screw drive to move wooden structures is suggested.
Highlights
When using friction gripping device with a screw drive to move designs from wood there is relaxation of tightening force of the screw with time due to rheological characteristics of wood
Предложенная методика позволяет определить коэффициент увеличения усилия предварительной затяжки Kпз фрикционных грузозахватных устройств (ГЗУ) с винтовым приводом для перемещения конструкций из древесины при длительности операции транспортировки до 1 часа по формуле (7) и свыше – по формуле (8)
К вопросу о процессе деформации и деструкции древесины при сжатии поперек волокон // Лесной журнал, 1999, No2-3
Summary
When using friction gripping device with a screw drive to move designs from wood there is relaxation of tightening force of the screw with time due to rheological characteristics of wood. The dependence of the rate of weakening of the torque by on stiffness of the clamp, thickness of wooden construction in the place of installation of gripping device and of the modulus of elasticity of wood is revealed. При использовании фрикционных ГЗУ с винтовым приводом для перемещения конструкций из древесины со временем происходит ослабление усилия затяжки винта вследствие реологических особенностей древесины. Эластические деформации чей гипотезе приняли, что скорость ослабления являются причиной ослабления усилия затяжки усилия затяжки зависит от жесткости зажимного винтовых зажимных устройств, что приводит к устройства, модуля упругости материала образца, уменьшению сил трения на рабочих поверхностях толщины образца и величины приложенной наконтактных элементов ГЗУ.
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