Study On Shock Reflection Wave Characteristics Of Aqueous Simulated Lunar Soil

China’s Chang’e-5 lunar sampling and return vehicle has successfully completed its lunar sampling and return mission,and will conduct in situ sampling of the South Pole of the moon in the following phase 4 lunar exploration project.Around the lunar polar resources,countries have obtained direct evidence of the existence of water ice in the permanent shadow area of the lunar South Pole by means of remote sensing.How to realize automatic unmanned drilling and sampling in the lunar polar environment is an important part of the polar resources exploration mission.In the future lunar exploration plans of various countries,the lunar South Pole water ice exploration will be the focus,and the lunar soil sampling mission in the ultra-low temperature environment is very urgent to the physical and mechanical properties of the lunar soil.In this paper,the dynamic mechanical properties of the simulated lunar soil containing water under ultra-low temperature were studied.Scanning electron microscope(SEM)was used to observe the microscopic morphology of the water-bearing lunar soil under low temperature environment.Parameterized calculation was carried out on the microscopic morphology of the water-bearing lunar soil using image processing method,and the calculation results of the microscopic pore area and circumference were obtained.Based on Bishop’s formula of saturated frozen soil and one-dimensional stress wave propagation theory,the characteristics of stress wave propagation in water-bearing lunar soil were obtained.A finite element model was established to simulate the dynamic mechanical tests of the simulated lunar soil with water content.The dynamic mechanical responses of the simulated lunar soil under different loading rates,water content,temperature and density were studied.By comparing the reflected wave curves under different conditions,the influence of different sample parameters on the reflected wave shape is obtained,which provides a comparative basis for subsequent experimental research.The thermal simulation of sample temperature change in the ultra-low temperature environment was carried out,and the effect of the temperature retaining system was analyzed,and the conclusion was drawn that the temperature retaining system could ensure the sample to be tested in the ultra-low temperature environment.Ultra-low temperature sample temperature keeping equipment and sample temperature measuring system were designed and manufactured to achieve the purpose of sample cooling and test temperature monitoring.Using the high-speed impact of space debris research center of Harbin Institute of Technology of large diameter of 40 mm hopkinson pressure bar test rig,respectively in different density and moisture content of simulated lunar soil under different temperature and dynamic mechanics test,get a different density,moisture content,temperature and so on under the condition of the incident wave,reflected wave and transmission wave form,and record the super dynamic strain gauge and the oscilloscope to collect the signal data.The test data curves are analyzed in time domain and frequency domain.Based on second wave method has carried on the test data processing,get water cut of simulated lunar soil under dynamic impact stress-time curve,the stress-strain curve,the research of time domain curves under different test conditions as a result,it is concluded that water simulated lunar soil density and moisture content and stress strain curve of stress-time had a greater influence on the amplitude,is to change the main factors of water simulation on soil dynamics.The waveforms of the reflected wave obtained from the test are converted in time-domain to frequency domain,and the frequency domain curves of the reflected wave under different conditions are compared,and the amplitude of the reflected wave at different frequencies is different.