The Study On Tensile Mechanical Properties Of Caragana Microphylla Roots Under Repeated Stress

To clarify the Ultimate Latticity,Water Content and Elastoplasticity of Caragana microphylla under repeated loading after in vitro,we researched the material mechanics of the roots of Caragana microphylla within the scope of the 1.00 to 4.00 mm diameter.TY8000 servo-controlled tension testing machine(accuracy is 0.01)was used to repeatedly apply 50 times to straight root and lateral root branches.The loading force was 30%and 70%of the root tensile force of the same radius.Simulating the state of roots under repeated external forces under natural disasters such as gale,rainstorm and landslideThe results are as follows:(1)The root activity of Caragana microphylla varied with the time increase.The roots in the range of 1.00～2.00mm,2.00～3.00mm and 3.00～4.00mm root diameter were preserved at room temperature.The activity of roots increased first and then decreased with the time increase.Within 24～25 hours after isolation,the activity increased sharply and reached its maximum value.After 26 hours,the activity decreased sharply.After 27 hours,the overall activity showed a gentle downward trend.(2)The anti-tension force of straight roots and lateral root branch of Caragana microphylla were positively correlated with the diameter of roots with a power function and both of the anti-tension strength were negatively correlated with the root diameter with a power function.There were significant differences in the tensile strength between the straight root and lateral root branches of Caragana microphylla,and both there were significant differences in the tensile strength between the straight root and lateral root branches(P<0.05).In the range of 1.00～4.00mm root diameter,the average tensile strength of straight root was(42.10±8.40)Mpa,the average tensile strength of lateral root branch was(31.52±5.59)Mpa,and the average tensile strength of lateral root branch was 74.87%of the straight root.(3)The water content of root was affected by repeated loading.When the repeated loading force was 30%of the tensile force,the water content of the straight roots in the diameters of 1.00～2.00 mm,2.00～3.00 mm and 3.00～4.00mm decreased by 19.39%,21.49%and 16.06%respectively.When the repeated loading force was 70%of the tensile force,the water content of the straight roots in the diameters of 1.00～2.00 mm,2.00～3.00 mm and 3.00～4.00 mm decreased by 18.35%,18.88%and 9.36%respectively.Under the same loading force,when the root diameter is small,the straight root and lateral root branches can withstand more loading times,showing better elongation.For straight root with the same diameter,the greater the loading force,the smaller the number of times the root can bear the loading.(4)The tensile strength of roots was higher than that of roots under the same root diameter when the ultimate tensile force was 30%.Within the radius range of 1.00～4.00 mm,the tensile strength of roots under repeated stress increased by 39.65%compared with that of roots without stress.When the ultimate tensile force was 70%,the tensile strength of roots was lower than that of roots after repeated stretching Caragana microphylla.The tensile strength of the roots under the same radius was 24.00%lower than that of the roots under the same radius.