Slip line method for sintered powder materials under condition of axial symmetry is proposed based on the simplified yield condition of sintered powder materials and Haar-von Karman perfect plastic criterion. The equa...Slip line method for sintered powder materials under condition of axial symmetry is proposed based on the simplified yield condition of sintered powder materials and Haar-von Karman perfect plastic criterion. The equations of slip line and stress along slip line are derived, and numerical solutions are given. Deformation load in closed die upsetting of sintered copper cylinder is calculated by slip line method, and theoretical solutions are compared with experimental results.展开更多
Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination o...Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.展开更多
This paper presents the elastic and plastic deformation of the steel helmet with coldextrusion moulding. The plastic streamline of the plastic mould-making process for ellipse thinplate is described. The distribution ...This paper presents the elastic and plastic deformation of the steel helmet with coldextrusion moulding. The plastic streamline of the plastic mould-making process for ellipse thinplate is described. The distribution of slip-line is established based on the plastic streamline. Theextrusion force of plastic moulding of the steel helmet is calculated by using of slip-line method.Furthermore, an applied example is given.展开更多
At present,associated flow rule of traditional plastic theory is adopted in the slip line field theory and upper bound method of geotechnical materials. So the stress characteristic line conforms to the velocity line....At present,associated flow rule of traditional plastic theory is adopted in the slip line field theory and upper bound method of geotechnical materials. So the stress characteristic line conforms to the velocity line. It is proved that geotechnical materials do not abide by the associated flow rule. It is impossible for the stress characteristic line to conform to the velocity line. Generalized plastic mechanics theoretically proved that plastic potential surface intersects the Mohr-Coulomb yield surface with an angle,so that the velocity line must be studied by non-associated flow rule. According to limit analysis theory,the theory of slip line field is put forward in this paper,and then the ultimate bearing capacity of strip footing is obtained based on the associated flow rule and the non-associated flow rule individually. These two results are identical since the ultimate bearing capacity is independent of flow rule. On the contrary,the velocity fields of associated and non-associated flow rules are different which shows the velocity field based on the associated flow rule is incorrect.展开更多
The axi-symmetric active earth pressure for layered backfills was investigated using the slip line method. Due to different soil properties, the interfaces of the soil layers were considered as discontinuity surface. ...The axi-symmetric active earth pressure for layered backfills was investigated using the slip line method. Due to different soil properties, the interfaces of the soil layers were considered as discontinuity surface. Accordingly, the change of the major principal direction was obtained and a new computation scheme was proposed to deal with the discontinuity in the calculation, finally the slip line method was extended to layered backfills. Results indicate that, the major principal direction, as well as the earth pressure, has a finite jump on passing the soil interfaces. The magnitude of the jump depends on the soil properties mainly. Generally, the active earth pressure when a strong layer is overlying a weak layer is much larger than that when the weak layer is lying on the strong layer. The present solution can be reduced to plane strain case and it has been compared with Rankine's and Coulomb's results, and a good agreement is observed.展开更多
文摘Slip line method for sintered powder materials under condition of axial symmetry is proposed based on the simplified yield condition of sintered powder materials and Haar-von Karman perfect plastic criterion. The equations of slip line and stress along slip line are derived, and numerical solutions are given. Deformation load in closed die upsetting of sintered copper cylinder is calculated by slip line method, and theoretical solutions are compared with experimental results.
基金supported by National Natural Science Foundation of China (Grant No. 50675145)Shanxi Provincial Key Project of Science and Technology of China (Grant No. 2006031147)+1 种基金Shanxi Provincial Innovation Project for Graduate Students of China (Grant No. 20061027)Shanxi Provincial Key Project for Studied-abroad Returnee of China
文摘Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.
文摘This paper presents the elastic and plastic deformation of the steel helmet with coldextrusion moulding. The plastic streamline of the plastic mould-making process for ellipse thinplate is described. The distribution of slip-line is established based on the plastic streamline. Theextrusion force of plastic moulding of the steel helmet is calculated by using of slip-line method.Furthermore, an applied example is given.
文摘At present,associated flow rule of traditional plastic theory is adopted in the slip line field theory and upper bound method of geotechnical materials. So the stress characteristic line conforms to the velocity line. It is proved that geotechnical materials do not abide by the associated flow rule. It is impossible for the stress characteristic line to conform to the velocity line. Generalized plastic mechanics theoretically proved that plastic potential surface intersects the Mohr-Coulomb yield surface with an angle,so that the velocity line must be studied by non-associated flow rule. According to limit analysis theory,the theory of slip line field is put forward in this paper,and then the ultimate bearing capacity of strip footing is obtained based on the associated flow rule and the non-associated flow rule individually. These two results are identical since the ultimate bearing capacity is independent of flow rule. On the contrary,the velocity fields of associated and non-associated flow rules are different which shows the velocity field based on the associated flow rule is incorrect.
基金the National Natural Science Foundation of China (No. 50679041)the Shanghai Leading Academic Discipline Project (No. B208)
文摘The axi-symmetric active earth pressure for layered backfills was investigated using the slip line method. Due to different soil properties, the interfaces of the soil layers were considered as discontinuity surface. Accordingly, the change of the major principal direction was obtained and a new computation scheme was proposed to deal with the discontinuity in the calculation, finally the slip line method was extended to layered backfills. Results indicate that, the major principal direction, as well as the earth pressure, has a finite jump on passing the soil interfaces. The magnitude of the jump depends on the soil properties mainly. Generally, the active earth pressure when a strong layer is overlying a weak layer is much larger than that when the weak layer is lying on the strong layer. The present solution can be reduced to plane strain case and it has been compared with Rankine's and Coulomb's results, and a good agreement is observed.
