Measuring Method Of Dynamic Mechanical Properties Of Coal And Analysis Of Influencing Factors

The dynamic mechanical property test of coal is the basis for studying the stress field and displacement field of mining surrounding rock.It is of great significance for the determination of the surrounding rock damage range and the selection and optimization of support methods.At present,the coal SHPB test needs to be further improved due to the dispersion effect and the non-uniformity of the coal sample stress distribution.In this paper,laboratory experiments,theoretical analysis and numerical simulation are used to systematically study the waveform shaping effect,waveform dispersion effect and coal sample stress uniformity in coal sample impact compression test.The following research results have been obtained.(1)Introduce the basic theory of one-dimensional stress wave and SHPB technology.The general rule of the influence of density and elastic modulus on the uniformity of coal sample stress is obtained by using one-dimensional stress wave theory.(2)The impact compression test was carried out with a copper shaper and a rubber shaper respectively,and different incident stress wave curves were obtained;Finally,a general relationship between the size of the shaper and the waveform characteristics was established.The influence of the size of the stricken bar on the incident waveform is analyzed,and the optimized design of the stricken bar is transformed into a four-factor and three-level coordinated numerical simulation test.The stress wave curve of each group size was simulated by using APDL command stream and Ls-dyna3 D software,and the influence of four sizes on the waveform was obtained.(3)Introduced the contact algorithm in Ls-dyna3 D software.The effects of different scale factors on slave penalty stiffness,scale factors on master penalty stiffness and scale factors for sliding interface penalties on transmitted waves are compared and analyzed,and the parameters suitable for coal-steel contact problems are obtained.(4)The ideal waveform for reducing waveform dispersion is obtained by the comparison analysis of trapezoidal wave,triangular wave and shaping wave propagating in the pressure bar through Ls-dyna3 D software.Through threedimensional numerical simulation,the influence of incident wave waveform and coal sample size on the stress uniformity of coal sample was analyzed,and the diameter and height interval of coal sample satisfying the stress uniformity of coal sample were obtained.The research results can provide reference for improving the accuracy of coal body SHPB test.