| With the development,utilization and protection of various waters,related human activities and the construction of water projects are becoming more and more closely related to ice.The formation and destruction of ice has a great impact on personal safety and engineering safety,so research on ice destruction has important application value.In addition,because ice is very sensitive to geographical environmental conditions,and geographical environmental factors are different,the physical and mechanical properties of ice are very different.In addition,because ice is very sensitive to geographical environmental conditions,geographical environmental factors are different,and the physical and mechanical properties of ice are very different,so the research on ice fracture has not yet formed a universal theory and conclusion.This article will conduct a more systematic study on the fracture toughness and failure modes of freshwater ice.The first part:elaborated the preparation process of artificial fresh water ice in detail.Explain the specific steps and methods of the equipment and experiment required during the experiment.The specific processing procedures of the three-point bending specimen and uniaxial compression specimen required for the experiment are introduced.Using the mass-volume method to measure the density of ice at different temperatures,the result is 0.867g/cm3?0.908g/cm3,indicating that the density of ice at different temperatures has little difference.The second part:fracture toughness test experiment.The fracture toughness of artificial fresh water ice was measured using standard size three-point bending specimens.The ice making temperature is-25?,-30?,-35? and-40?,the loading rate is 0.3mm/min,2.1mm/min and 19mm/min,the a/W value of the sample is respectively 0.45 and 0.55,a total of 145 samples were tested.The results show that:(1)When the loading rate is large,the measured values of fracture toughness of ice are not very discrete,while when the loading rate is small,the measured values of fracture toughness are more scattered,but the general trend is to decrease with the increase of the loading rate.(2)The change of ice making temperature has a significant influence on the fracture toughness of ice.With the decrease of ice making temperature under various loading rates,the fracture toughness of ice will increase,but a/W has no obvious influence on the experimental results.The third part:uniaxial compression strength experiment.Cuboid specimens are used;the ice making temperature is-30?,-35? and-40?;the strain rate range of the experiment is 9.26×10-6s-1?1.11×10-2s-1;the experiment is carried out in 225 groups.According to the experimental data,the stress-strain curves of the artificial freshwater ice and the corresponding different failure modes are obtained.The results showed that the ice samples mainly showed three main failure modes:bulging,shearing and splitting.In addition,the effects of strain rate and temperature on uniaxial compression strength are analyzed.The results show that at a low strain rate,the compressive strength of ice increases with the increase of strain rate,and the ice sample mainly presents a ductile failure mode;when the strain rate is medium,the compressive strength peak will be produced,and the ice sample will appear ductile-brittle transition failure;when the strain rate is high,the ice sample will appear brittle failure mode.Experiments have found that the uniaxial compressive strength of ice will increase with the increase of the elastic modulus,and the two are basically proportional and not affected by the ice-making temperature.The fourth part:the finite element simulation of the three-point bending specimen model using the elastoplastic constitutive.Using the Ludwik hardening model,calculate the three-dimensional J integral and Weibull stress of the three-point bending specimen under different a/W values and different ice making temperatures.The results show that the experimental and prediction curves are generally in good agreement. |
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