轴向振动截割下碟盘刀刃与煤岩作用机制及其载荷模型

Interaction mechanism and load model between disc blade and coal rock under axial vibration cutting

针对现有刀具截割复杂地质条件煤岩(尤其截割硬岩时)损耗高、效率低和易磨损等问题,提出了具有截-楔效应的碟盘刀具复合振动截割破碎煤岩的方法,碟盘刀具径向进给与不同振动形式和姿态来实现复合截割破碎煤岩。以碟盘刀刃为研究对象研究轴向振动截割对煤岩损伤破坏的力学特性,基于剪切破碎理论给出刀刃作用载荷破坏煤岩条件以及刀刃轴向向下振动、向上振动和径向截割煤岩时等效集中载荷的计算方法,采用位移应变等效力合成的方法建立刀刃结构参数与载荷关联模型,模拟研究其径向单作用截割和轴向振动复合截割工况下破碎煤岩的载荷特性,研究碟盘刀具在有振和无振的实验条件下破碎煤岩载荷,对比分析了刀刃载荷的理论计算、数值模拟与实验。结果表明:碟盘刀刃对煤岩的损伤区域面积由中间向两侧逐渐递减与数值模拟应力云图相吻合;振动截割条件下数值模拟和实验的刀刃径向载荷均小于无振条件下的载荷值;轴向振动截割下其数值模拟和实验载荷均与轴向振动位移呈现明显的周期波动规律,且存在超前相位差,径向与轴向载荷幅值与振动位移幅值非同时性,其相位差随振动频率增大而减小;随着截割厚度增大,碟盘刀具径向载荷理论值、模拟值与实验值呈现递增变化规律相吻合,且其误差均值分别为12.01%和6.37%,截割厚度对载荷影响程度从大到小依次为正值轴向载荷、径向载荷和负值轴向载荷;碟盘刀刃轴向向上振动时径向载荷(最大振幅处对应载荷均值)的理论值、模拟值与实验值的误差分别为11.65%和13.99%,其轴向载荷的误差分别为10.46%和13.51%,轴向向下振动时径向载荷的误差分别为13.91%和5.61%,其轴向载荷的误差分别为14.90%和7.88%。结合已有文献碟盘楔面载荷模型共同验证了碟盘刀刃载荷模型的正确性,进而说明了运用位移应变等效力合成的方法建立复合运动破岩载荷模型的可行性。

Aiming at the problems of high loss,low efficiency and easy wear of existing cutting tools by cutting coal rock under complex geological conditions(especially hard rock),a method of cutting broken coal rock under composite vibration of disc cutter with truncation-wedge effect was proposed,and the compound cutting and crushing coal rock was realized by radial feed of disc cutter and different vibration forms and postures.The mechanical characteristics of broken coal rock under axial vibration cutting were studied based on the disc blade study.Based on the shear fracture theory,the failure condition of coal rock under blade load and the calculation method of the equivalent concentrated load when the blade axially vibrates downward,upward,and radially cuts coal rock were given.A theoretical model of the correlation between the blade structure parameters and the load was established by the method of displacement strain-equal force synthesis,and the load characteristics of the crushed coal rock under the conditions of radial single-acting interception and axial vibration composite cutting were studied by numerical simulation.To study the load of disc cutter in crushing coal rock under the experimental conditions of vibration and vibration-free,the theoretical calculation and numerical simulation of blade load were compared with the experiment.The results show that the area of damage to coal rock by the disc blade gradually decreases from the middle to the two sides,which coincides with the numerical simulated stress cloud diagram,the radial load of blade in numerical simulation and experiment under the vibration cutting condition are less than the load value under the vibration-free condition.The numerical simulation and experimental loads show an obvious periodic fluctuation law with the axial vibration displacement under the axial vibration cutting,and which is an advanced phase difference,the amplitude of radial and axial load and the amplitude of vibration displacement are not simultaneous,and the phase difference decreases with the increase of vibration frequency.With the increase of cutting thickness,the theoretical value and simulation value of the radial load of the disc cutter coincide with the increasing change law of the experimental value,the mean error is 12.01%and 6.37%,respectively.The errors between the theoretical,simulated and experimental values of the radial load(corresponding to the mean load at the maximum amplitude)when the disc blade vibrates axially upwards are 11.65%and 13.99%,the errors of the axial load are 10.46%and 13.51%,respectively.When the axial downward vibration,the errors of the radial load are 13.91%,5.61%,the errors of the axial load are 14.90%and 7.88%,respectively.Combined with the load model of disc wedge surface in the existing literature,the correctness of the load model of disc blade was verified,and then the feasibility of establishing the load model of composite motion rock breaking by using the method of displacement strain-equal synthesis was explained.