Research On The Dynamics Of Milling Drum For Asphalt Concrete Pavement

Milling drum is the core component of asphalt concrete pavement cold milling machine.At present, milling drum structure design, milling operating parameters selection and milling power configuration are carried out mainly by experience and analogy method in domestic.Milling drum operating performance, power utilization, milling drum and component life need to be improved. The milling drum dynamics of asphalt concrete pavement are studied.Using a combination of theoretical model and indoor full-scale test method, a further study for the mechanical law of the interaction between milling drum and asphalt concrete pavement and the milling energy consumption law is carried out, and the milling resistance calculation and milling energy consumption forecast for single-tool and rotary multi-tool are achieved,which provides the theoretical basis for milling drum design, milling parameter selection,milling machine's power control. The main research contents are as follows:Based on the milling force mode and the translational cutting resistance characteristics of asphalt concrete,the model for three-dimensional space milling resistance of single tool is established with shear failure, which includes the material characteristic parameters of asphalt concrete, the milling operation parameters, and the structure parameters of milling drum and milling tools. The vector superposition of the milling resistance of each tool simultaneously involved in the milling at any time is taken as the revolving multi-tool milling resistance, and the theoretical calculation methods for milling resistance and milling power of the revolving multi-tool are obtained.In order to validate the theoretical model and study the dynamics of interaction between milling tool and asphalt concrete, a dynamics tes't bench for research on dynamics of milling drum for asphalt concrete pavement is developed. The tool changer components with adjustable installation angle and three-component force (tangential force, radial force and lateral force) sensor for single-tool milling are designed. The test data acquisition system is set up with single-tool milling resistance, milling drum speed, rotation angle, driving torque,milling operation speed and milling drum hydraulic motor pressure as the main test values,and the single-tool milling resistance data wireless transmission is achieved. Three kinds of asphalt pavement board (typical AC-10 ? AC-13 and AC-20) are made and their compressive strength, splitting strength and shear strength tests are carried out.The single-tool's milling experiments of milling drum for asphalt concrete pavement are carried out, and the single influence law of milling linear velocity, milling operation speed,milling depth, installation angle, milling mode and shear strength on milling resistance are obtained. The undetermined coefficient and milling mode coefficient for the milling resistance model are determined, and the theoretical calculation of milling resistance and milling power of single-tool and rotating multi-tool are realized. The experiment data show that the milling tangential force has no obvious trend with the milling speed when the milling feed pitch and milling depth are kept constant. The milling tangential force of single-tool is a monotonic function of milling distance and milling depth respectively. The effect of milling feed pitch on milling tangential force of single-tool is most significant.The single-tool milling experiment data also shows that the peak value of tangential force for single-tool milling decreases with the increase of asphalt concrete shear strength when the milling parameters are constant, but there is no obvious correlation with compressive stength and splitting strength. The shear strength obtained by direct shear test can accurately characterize the damage difficulty level of asphalt concrete's milling. When the half-angle value of the tool nose is 55 °,the optimal value of installation angle is 42°.The angle between the tangential force and the milling resistance force under different working conditions varies from 26° to 32 ° .The milling mode coefficients corresponding to different tool space are determined by experiment.Milling drum design and the selection of milling parameters must also take into account the energy consumption in the process of milling drum operation. The theoretical calculation and experimental data of energy consumption parameters show that single-tool milling productivity, average power, specific energy consumption are increasing or decreasing monotonic function of milling drum radius, milling linear speed, milling feed pitch and milling depth. Under the same operation conditions, the difference between the theoretical calculation value and the measured value of the single-tool milling productivity and specific energy consumption is small, so the theoretical calculation model can reflect the actual energy consumption accurately. Considering the milling stability and the average power of single-tool's milling,the milling linear speed should be 6?7 m/s and the impact extrusion effect of milling tools on asphalt concrete is used When the milling depth is constant, the milling feed pitch should be appropriately increased to reduce the specific energy consumption and increase the productivity. The theoretical model provides theoretical support for the design of cold milling machine, milling drum and revolving multi-tool's milling power control of cold milling machine.