Research On Ice Material Properties And Geometric Profile Optimization Of Ski Jumping Inrun

As an artificial section track,the inrun of ski jumping controls the finished surface with the section shape set precisely in advance.At present,the laying and inspection process of the inrun are determined by foreign experts,and the key technologies are controlled by a few foreign companies.There were few related studies both at home and abroad.The mixture ratio of the ice slurry was determined by engineering experiences.The ice structure of the inrun is affected by repeated loads,temperature loads and other factors in competitions,which leads to the damage of ice over time.The change of the profile also lead to the mechanics change of the athlete in the skiing process.The ice slurry snow water mixture ratio,physical properties,ice constitutive model and damage analysis,mathematics and dynamics analysis of the inrun were studied and analyzed.For the first time,the ice slurry and dynamic differential equations of the third power function were systematically studied and solved.The corresponding results are not only beneficial to reduce the ice structural damage,and also can be used for ice structure repair.It also provides theoretical support for the geometric structure of the ski jumping inrun for Beijing Winter Olympics.The main contents of research are as follows:(1)The determination of the test mixture ratio of the ice slurry.According to the experience of the International Snow Federation expert,five snow water mixture ratios were proposed.The condition of ice slurry mixing,the workability,the forming effect,the surface roughness,the inner pore distribution of the specimen,and the mechanics performance of the specimen under low loading rate were compared.To satisfy the construction workability,the snow water mixture ratio of the ice slurry was determined as snow:water=60%:40%,it can be used for reference in site construction.(2)The research on the mechanical properties of ice based on uniaxial compression test and beam bending test.The ice specimen was prepared with the predetermined test mixture ratio of the ice slurry.Uniaxial compression test and beam bending test were carried out.The influence of the ice temperature and loading rate on the compressive and bending strengths,the significant influence of the ice temperature on the compressive strength of the ice were analyzed.The mathematical models of the ice temperature and compressive strength under different loading rates were established.According to the uniaxial compression test data,the elastic moduli of the ice at different temperature and loading rate were analyzed.The results showed that the maximum compressive strength and bending strength of the ice was at 10 mm/min.The loading rate can be optimized to improve the falling rate of the slide cutter.The ice temperature has a significant effect on the compressive strength.(3)The research on constitutive model and damage mechanism of the ice.Based on the damage mechanics theory,it was assumed that the crack volume of the ice under axial load has the Weibull distribution,and damage variables were introduced to obtain the damage constitutive model of the ice.ABAQUS was used to establish the ice model to simulate the failure of the ice specimen under the uniaxial compression and beam bending test.The results showed that the damage constitutive model could accurately describe the ice constitutive relationship under loading.The extended finite element method can simulate the cracking behavior of ice under different stress conditions.(4)The profile analysis of the inrun based on dynamics.The mathematical and dynamic analysis were carried out of the inrun based on the original constructed parameters,and the athlete skiing states on different profile inruns were studied.The dynamics differential equations were obtained by considering the air resistance and the skiing friction.The influence of the environmental factors and the athlete’s body weight on the skiing velocity were analyzed.The athlete’s skiing velocity and the reaction force on the arc and the third power function were compared.The third power function avoids the instantaneous increase of the force generated by the inrun,so the increase of the force on the athlete is slow.The air density and the ambient temperature have little effect on the skiing velocity.There are a linear increase in athlete body weights and skiing velocity.