| Sand therapy is a natural therapy were used the unique sand in Turpan region of Xinjiang province to bury sand for the treatment of diseases.It is a green,healthy and side-free physical therapy that integrates heat therapy,magnetic therapy,phototherapy and mechanical pressure.On the basis of viscoelastic material theory and experiments,this paper studied the effect of sand therapy on the thermal coupling of human lower limbs,conducted experimental research on the temperature and stress of human lower limbs during sand therapy,and applied Maxwell model to fit the elastic modulus and relaxation time of human lower limbs skin under different sand therapy conditions.As an initial condition,the total deformation and equivalent stress of human lower limbs were numerically simulated.This paper will select the sand flow experiment was conducted among 75 subjects were divided into four groups(10cm buried sand thickness,sand body temperature 45℃ group,10 cm buried sand thickness,sand body temperature 50℃group,buried sand thickness of 20 cm,sand body temperature 45℃ group,the buried sand thickness of 20 cm group,the sand body temperature 50℃),collected in turn sand treatment time of 300 s,600s and 900 s,1200s,1500 s and 1800 s of the transient of the lower limbs were temperature and pressure data and statistical analysis,the research of sand treatment on human lower limb of thermal field and force field influence each other.Experimental and numerical simulation studies show that:(1)The influence of stress field on temperature field:when the sand body temperature is 45℃,the buried sand thickness is 20 cm versus 10 cm,and the instantaneous surface temperatures of human lower limbs increase respectively:0.73℃,0.53℃,0.44℃,0.46℃,0.33℃,and 0.31℃;When the temperature of sand body was 50℃,the thickness of buried sand was 20 cm relative to that of buried sand 10 cm,and the instantaneous surface temperatures of human lower limbs increased respectively:0.07℃,0.08℃,0.17℃,0.25℃,0.31℃,and 0.34℃.The experimental results show that the stress field has a certain influence on the temperature field,and the temperature of sand body at 45℃ has a greater influence than that at 50℃.(2)Influence of temperature field on stress field: The experimental study found that when the buried sand thickness was 10 cm,the temperature of sand body was 50℃ relative to that of sand body 45℃,and the instantaneous surface stress of human lower limbs increased respectively:0.001766 Mpa,0.001999 MPa,0.002124 Mpa,0.001952 MPa,0.002032 Mpa and 0.001924 MPa.When the thickness of buried sand was 20 cm,the surface stress of human lower limbs increased by 0.0002555 MPa,0.000574 MPa,0.000839 MPa,0.001022 MPa,0.000882 MPa and 0.000674 MPa when the temperature of sand body was 50℃ compared to 45℃.The numerical simulation found that when the buried sand thickness was 10 cm,the temperature of the sand body was 50℃ relative to that of the sand body 45℃,and the relative changes of the maximum equivalent stress of the lower limbs were 25.330%,25.403%,25.333%,25.326%,25.415%and 25.329% respectively.When the thickness of buried sand was 20 cm,the relative changes of the maximum equivalent stress of lower limbs were as follows:16.611%,16.149%,16.474%,16.604%,16.669% and 16.611% respectively.The experimental results show that the temperature field has an influence on the stress field,and the numerical simulation shows that the influence of the temperatur e field on the stress field is greater when the buried sand thickness is 10 cm than when the buried sand thickness is 20 cm.Through numerical simulation of the maximum total deformation of human lower limbs during sand treatment,it was concluded that when the buried sand thickness was 10 cm,the temperature of sand body was 50℃ relative to that of sand body 45℃,and the relative changes of the maximum total deformation of human lower limbs were 5.801%,5.861%,5.851%,5.845%,5.95% and 6.046%.When the thickness of buried sand was 20 cm,the temperature of sand body was 50℃ relative to that of sand body 45℃,and the relative changes of the maximum total deformation of human lower limbs were5.001%,6.515%,5.275%,10.881%,9.703% and 10.495%.It was found that the relative change of the maximum total deformation of human lower limbs was small when the buried sand thickness was 10 cm and 20 cm,which was consistent with the reality.(3)The elastic modulus of skin of lower limbs under four groups of sand treatment is 0.00313 Mpa,0.00488 Mpa,0.00814 Mpa and 0.009 Mpa,respectively;The relaxation time was 118.59 s,71.66 s,48.76 s and 25.83 s,respectively.The elastic modulus and relaxation time represent the viscoelas tihickness and the temperature of the sand body change,the elastic modulus and relaxation time of the skin of human lower limbs change,indicating that the buried sand thickness and the temperature of the sand body have an influence on the elastic modulus and relax ation time of human lower limbs.(4)Through simulating the four groups of sand therapy,the equivalent stress at each instantaneous monitoring point of human lower limbs was found that the muscle and bone contact place of human lower limbs was subject to the maximum equivalent stress,followed by the skin and muscle contact place,and the skin surface was subject to the minimum equivalent stress,which was consistent with the reality.The simulation results can be used to explore the change of equivalent stress in human lower limbs,so as to provide a basis for studying the mechanical properties of human lower limbs during sand therapy. |
