The three-point bending experiments were applied to investigating effects of loading rates on fracture toughness of Huanglong limestone. The fracture toughness of Huanglong limestone was measured over a wide range of ...The three-point bending experiments were applied to investigating effects of loading rates on fracture toughness of Huanglong limestone. The fracture toughness of Huanglong limestone was measured over a wide range of loading rates from 9 × 10-4 to 1.537 MPa.m1/2/s. According to the approximate relationship between static and dynamic fracture toughness of Huanglong limestone, relationship between the growth velocity of crack and dynamic fracture toughness was obtained. The main conclusions are summarized as follows. （1） When the loading rate is higher than 0.027 MPa-ml/2/s, the fracture toughness of Huanglong limestone increases markedly with increasing loading rate. However, when loading rate is lower than 0.027 MPa-ml/2/s, fracture toughness slightly increases with an increase in loading rate. （2） It is found from experimental results that fracture toughness is linearly proportional to the logarithmic expression of loading rate. （3） For Huanglong limestone, when the growth velocity of crack is lower than 100 m/s, the energy release rate slightly decreases with increasing the growth velocity of crack. However, when the growth velocity of crack is higher than 1 000 m/s, the energy release rate dramatically decreases with an increase in the crack growth velocity.展开更多
According to the concept of virtual bending force,a rational explanation for SHOHET's model was presented. Considering the deformation characters of the work rolls in four-high mill,the deformation model of the wo...According to the concept of virtual bending force,a rational explanation for SHOHET's model was presented. Considering the deformation characters of the work rolls in four-high mill,the deformation model of the work roll was regarded as a cantilever beam and new influence coefficients were deduced.The effect of the bending force was taken into account independently. Therefore,the contribution to work roll deflection caused by rolling load,rolling pressure between rolls and bending force can be got from the new formulas.To validate the accuracy of the formulas,the results obtained from the new formulas were compared with those from SHOHET's formulas.It is found that they highly coincide,which illustrates that the formulas are reliable.展开更多
基金Projects(50490275, 50621403, 50778184) supported by the National Natural Science Foundation of ChinaProject(NCET-07-0911) supported by Program of New Century Talents of Ministry of EducationProject(CSTC, 2009BA4046) supported by the Natural Science Foundation of CQ CSTC
文摘The three-point bending experiments were applied to investigating effects of loading rates on fracture toughness of Huanglong limestone. The fracture toughness of Huanglong limestone was measured over a wide range of loading rates from 9 × 10-4 to 1.537 MPa.m1/2/s. According to the approximate relationship between static and dynamic fracture toughness of Huanglong limestone, relationship between the growth velocity of crack and dynamic fracture toughness was obtained. The main conclusions are summarized as follows. （1） When the loading rate is higher than 0.027 MPa-ml/2/s, the fracture toughness of Huanglong limestone increases markedly with increasing loading rate. However, when loading rate is lower than 0.027 MPa-ml/2/s, fracture toughness slightly increases with an increase in loading rate. （2） It is found from experimental results that fracture toughness is linearly proportional to the logarithmic expression of loading rate. （3） For Huanglong limestone, when the growth velocity of crack is lower than 100 m/s, the energy release rate slightly decreases with increasing the growth velocity of crack. However, when the growth velocity of crack is higher than 1 000 m/s, the energy release rate dramatically decreases with an increase in the crack growth velocity.
基金Project(20050216007) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘According to the concept of virtual bending force,a rational explanation for SHOHET's model was presented. Considering the deformation characters of the work rolls in four-high mill,the deformation model of the work roll was regarded as a cantilever beam and new influence coefficients were deduced.The effect of the bending force was taken into account independently. Therefore,the contribution to work roll deflection caused by rolling load,rolling pressure between rolls and bending force can be got from the new formulas.To validate the accuracy of the formulas,the results obtained from the new formulas were compared with those from SHOHET's formulas.It is found that they highly coincide,which illustrates that the formulas are reliable.
