| The Arctic has great value in terms of energy reserves,shipping routes and geographical location.However,perennial sea ice is a serious obstacle to further exploration and development in the Arctic.At present,the mainstream ice-breaking method is still mechanical impact,which requires high strength and power of the ship,and only a few countries have mastered the relevant technology.Laser is a kind of high density energy action mode,which can directly change the temperature stress distribution of ice layer without media,and has high ice breaking potential.At present,the research on laser-assisted ice breaking has not been carried out in depth,and the evolution of ice physical properties during laser irradiation is also lacking.This paper mainly carries out the following research contents:A thermodynamic model of laser energy absorption by ice is established.Based on the Bouguer-Lambert law,the forms and laws of laser energy absorption by sea ice and fresh water ice are analyzed,and the body heat source absorption model of ice to 1070 nm infrared laser is established.Based on the heat conduction equation and the generalized Hooke’s law,the temperature and thermal stress distribution of ice irradiated by laser are analyzed.The effects of laser parameters on temperature distribution and thermal stress are obtained by changing laser power and defocusing amount.The accuracy of theory and simulation is verified by experiments of laser irradiating fresh ice and salt ice.The mechanism of brittle crack propagation in ice irradiated by laser is studied.Based on the theory of linear elastic fracture mechanics,the feasibility of crack propagation induced by thermal stress after laser irradiating ice is investigated,and the initial fine crack propagation process in ice is simulated by extended finite element method(XFEM).The crack propagation mode is demonstrated by analyzing the strain field of adjacent distribution points,and the influence of different distribution point spacing on stress strain and crack propagation is discussed.The effect of laser point distribution parameters on ice breaking effect under static pressure is studied.A set of ice-breaking equipment powered by hydraulic jacks is set up to summarize the damage forms of ice under static pressure and the crack types caused by laser irradiation,and to explore the influence of the number of points,laser power,action time and other parameters on the ice-breaking effect.The interaction of each laser parameter on the ice-breaking effect and the number of crack ripple is determined by orthogonal experiment and result analysis.The influence of laser point distribution parameters on the ice breaking effect of impact load is studied.A set of ice breaking equipment with impact load is built,and the stress curve in the process of ice breaking is collected by sensors.Taking the number of laser points,laser power,laser action time and ice cube size as independent variables,the influence of laser points on ice breaking assisted by impact load is studied.Based on the principle of minimum energy consumption,a method is proposed to induce the overall crack propagation with a predetermined trajectory and cross trajectory,which achieved a good auxiliary ice-breaking effect.Based on the above research content,the principle and action law of laser-assisted ice breaking are basically clarified,which provides a new method for actual ice breaking. |
PDF Full Text Request