Experimental Study On Physical And Mechanical Properties Of Artificially Frozen Ice Considering Irradiation Effects

Freezing generally exists in middle and high latitudes,which not only affects people's life and production in cold regions,but also brings various ice disasters.Therefore,ice must be considered in river management and hydraulic structure design.It is of great practical significance to study the physical properties and mechanical parameters of ice for engineering design and protection in ice area.In this paper,the physical properties and mechanical parameters of artificially frozen ice are studied,and the radiation factors created by the indoor solar simulator are innovatively added.The crystal structure,density and thermal conductivity of ice are observed and measured respectively,and the change rules of crystal structure,density and thermal conductivity affected by radiation factors are studied;the strain rate,temperature and radiation are explored,the influence of three factors on the uniaxial compression strength and bending strength of ice is analyzed.The purpose of this paper is to expand and supplement the research on uniaxial compressive strength and flexural strength of artificial freezing and existing mechanical behavior.The conclusions are as follows:(1)In terms of light source selection of solar simulator,the color temperature of four alternative light sources and the energy proportion of each band are compared with the outdoor sunlight,and the long arc xenon lamp which is closer to the sunlight is selected as the light source for this indoor design of solar simulator.In terms of system design,the lamp frame structure of solar simulator is designed as double-layer,and the lamp array is arranged as a square structure;in terms of performance test,the solar simulator has good performance in effective radiation The irradiance in the illumination plane is 115 W/m~2,and the technical performance indexes of the solar simulator meet the requirements of class B in the specification.In terms of heat distribution,the heat flux distribution of the solar simulator is uniform and presents a logarithmic function with the change of irradiation height.Therefore,the solar simulator designed in this paper has reached the set technical parameters and requirements,which can create irradiation conditions for the physical and mechanical properties test of artificially frozen ice considering the influence of irradiation.(2)Through the observation of crystal structure,density measurement and thermal conductivity measurement of artificial frozen ice,it is found that artificial frozen ice is a typical columnar ice structure,and the content of bubbles increases with the thickness.The type of crystal structure of ice crystal does not change after irradiation,but the bubble in ice expands and extends.The average density of artificial freezing is 0.872 g/cm~3?0.919 g/cm~3.The ice density increases first and then decreases with the increase of irradiation time.The thermal conductivity of normal ice and irradiated ice increases with the decrease of temperature.The longer the irradiation time,the smaller the thermal conductivity is,the more significant the law is with the increase of temperature.Because of the anisotropy between ice crystals,the vertical guide thermal coefficient of artificial freezing ice is slightly greater than that of horizontal guide,and the difference between the values is about 3%.(3)In the uniaxial compression strength test of artificial freezing,362 specimens were loaded.The results show that the normal ice is mainly bulged at low strain rate,and split and shear failure occurs at high strain rate;besides the above failure forms,the irradiated ice also presents"columnar failure"(that is,many strip-shaped ice columns are formed when the sample is destroyed).From the stress-strain curve,it is found that there are brittleness curve,toughness curve,ductile brittle transition curve and creep curve for normal ice under different strain rates.Because of the higher strain rate range,there is no creep curve for irradiated ice,and when the irradiation time is longer,there are only brittleness curve and ductile brittle curve.From the curve,it can be seen that with the increase of irradiation time,the extreme value of ice stress gradually decreases down.At the same time,the uniaxial compressive strength of normal ice is power function with strain rate in ductile zone and brittle zone.It is feasible to apply this law to irradiated ice.It is found that the uniaxial compressive strength of normal ice and irradiated ice increases with the decrease of temperature at the same strain rate.The peak value of uniaxial compressive strength of ice moves to the direction of low strain rate with the decrease of temperature,and there is a logarithmic relationship between the peak compressive strength and temperature.Under different irradiation time conditions,the uniaxial compressive strength of ice at the same temperature and the same strain rate decreases with the increase of irradiation time,which is more obvious in the range of low strain rate,and the peak uniaxial compressive strength of ice moves to the direction of high strain rate with the increase of irradiation time.(4)The experimental results show that the bending strength of normal ice and irradiated ice increases with the increase of strain rate at low strain rate,and decreases with the increase of strain rate at high strain rate,indicating that the bending strength of normal ice and irradiated ice is sensitive to the change of strain rate.The bending failure modes of normal ice and irradiated ice are mainly Y-type failure,X-type failure,root failure and splitting failure.The normal ice is mainly Y-type failure,and the irradiated ice is mainly splitting failure.The results show that the bending strength of normal ice and irradiated ice increases with the decrease of temperature.The lower the temperature is,the smaller the strain rate corresponding to the bending strength of ice peak value is;the higher the temperature is,the larger the strain rate corresponding to the bending strength of ice peak value is.The maximum bending strength of normal ice is 2900 kPa?3600 kPa,and that of irradiated ice is 1600 kPa?2500 kPa.The results show that the bending strength of irradiated ice at the same strain rate is lower than that of normal ice at the same temperature,and the phenomenon is obvious in the range of low strain rate,and the bending strength of ice peak value moves to the direction of high strain rate.The higher the temperature is,the more significant the influence of radiation on the bending strength of ice is.This is corresponding to the temperature rising in the melting period or the river opening period,and the solar radiation increasing,which leads to the decrease of ice strength and cracking.