Toughness Study Of Different Jades Based On Type I Fracture Toughness

At present,jade research mainly focuses on optics,mineralogy and commercial value,but less on its mechanical toughness.In this paper,the Brazilian disc splitting test is used to test the fracture toughness of nephrite,Xiu jade and Lantian jade,and the fracture toughness is used to analyze and study the toughness of three kinds of jade;the relationship between the fracture toughness and the crystal texture of jade is studied;and combined with the fracture toughness and the model of statically determinate cylindrical beam with surface crack,the application analysis is carried out.Research findings:1.The average values of fracture toughness of three kinds of jade are as follows:Nephrite is 9.52 MPa·m^1/2,Xiu jade is 3.59 MPa·m^1/2,Lantian jade is 1.60 MPa·m^1/2,and the toughness values are:nephrite>Xiu jade>Lantian jade.The toughness of the three kinds of jade is superior to that of the general rock.2.The texture,content,grain size and cleavage of the jade minerals have influence on the fracture toughness of the jade samples.Nephrite is mainly composed of tremolite with felt like interwoven texture,and the content of fiber like tremolite grain and the degree of bonding affect its fracture mode,which is dominated by transgranular fracture and intergranular fracture,leading to the maximum fracture toughness;Xiu jade is mainly composed of serpentine and tremolite with scaly crystalloblastic texture and fibrous aggregate,and intergranular fracture is the main mode of fracture,followed by fracture toughness value;Lantian jade is mainly composed of calcite and serpentine with unequal granular,fibrous and leaf like textures,that are loose,and the cleavage development of calcite minerals is dominated by cleavage fracture,which leads to the minimum fracture toughness value.3.When three kinds of jade are carved into a model of statically determinate cylindrical beam with surface cracks,the crack depth,crack half arc length are related to the slenderness ratio of the beam.When the ratio of crack half arc length c to crack depth a is 1,0.8 and 0.6,and the ratio of crack depth a to beam diameter D is 0.05,0.125,0.20,0.275 and 0.35,The maximum ratio of the square of the length l² to the1/2 power of the height D of carved nephrite,Xiu jade and Lantian jade should not be greater than 261.19?110.81?51.84,that of the simple supported beam should not be greater than 1044.76,443.23 and 207.35,that of the overhanging beam(i=0.71l)should not be greater than 3109.4,1319.13 and 617.12;under the same conditions,nephrite has the longest limit length and Lantian jade is the shortest,and the deeper the surface crack is,the smaller the slenderness ratio is.Therefore,for the jade with small fracture toughness and deep surface cracks,the overhanging beam model should be used as far as possible for carving,and the carving works can show the beauty of slender,slender and beautiful;and to ensure that the crack is located at the edge of the compressive stress of the statically determinate beam,and the midpoint of the beam support point and the beam support point is as far away from the crack as possible,that can prevent the crack on the statically determinate beam model from extending due to propagation;...