An Analytical Approach to the Problem of Core Fracture During Extrusion of Bimetal Rods

1985 ◽  
Vol 107 (3) ◽  
pp. 247-253 ◽  
Author(s):  
B. Avitzur ◽  
R. Wu ◽  
S. Talbert ◽  
Y. T. Chou
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Analytical Approach ◽  
Upper Bound Theorem ◽  
Numerical Computations ◽  
Bound Theorem

The process of core fracture in bimetals during extrusion was reexamined. The new analysis, based on the upper-bound theorem in limit analysis, eliminated the lengthy numerical computations employed in the previous work [1]. The criterion for core fracture was derived and discussed.

Passive earth-pressure coefficients by upper-bound numerical limit analysis

2011 ◽  
Vol 48 (5) ◽  
pp. 767-780 ◽  
Author(s):  
Armando N. Antão ◽  
Teresa G. Santana ◽  
Mário Vicente da Silva ◽  
Nuno M. da Costa Guerra
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Wall Friction ◽  
Passive Earth Pressure ◽  
Upper Bound Theorem ◽  
Pressure Coefficients ◽  
Bound Theorem

A three-dimensional (3D) numerical implementation of the limit analysis upper-bound theorem is used to determine passive horizontal earth-pressure coefficients. An extension technique allowing determination of the 3D passive earth pressures for any width-to-height ratios greater than 7 is presented. The horizontal passive earth-pressure coefficients are presented and compared with solutions published previously. Results of the ratio between the 3D and two-dimensional horizontal passive earth-pressure coefficients are shown and found to be almost independent of the soil-to-wall friction ratio. A simple equation is proposed for calculating this passive earth-pressure ratio.

Limit Analysis of a Stochastically Inhomogeneous Plastic Medium With Application to Plane Contact Problems

1992 ◽  
Vol 59 (3) ◽  
pp. 477-484 ◽  
Author(s):  
R. P. Nordgren
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Contact Problems ◽  
Yield Function ◽  
Upper Bound Theorem ◽  
Spatial Correlation Function ◽  
Plastic Limit Analysis ◽  
Bound Theorem ◽  
The Mean ◽  
Ice Pressure

The lower and upper bound theorems of plastic limit analysis are extended to a stochastically inhomogeneous medium. The extended theorems provide bounds on the mean safety factor against plastic collapse. A three-parameter yield function is treated by introducing a spatial correlation function for uniaxial yield strength. Application of the stochastic upper-bound theorem is made to the plane problem of a truncated wedge under contact pressure. The results apply to the design of arctic structures against local ice pressure.

Selection of the Optimal Distribution for the Upper Bound Theorem in Indentation Processes

2014 ◽  
Vol 797 ◽  
pp. 117-122 ◽  
Author(s):  
Carolina Bermudo ◽  
F. Martín ◽  
Lorenzo Sevilla
Keyword(s):  
Upper Bound ◽  
Geometric Distribution ◽  
Optimal Choice ◽  
Optimal Distribution ◽  
Upper Bound Theorem ◽  
Modular Model ◽  
Bound Theorem ◽  
Rigid Zones ◽  
Dimensionless Relation ◽  
Selection Of

It has been established, in previous studies, the best adaptation and solution for the implementation of the modular model, being the current choice based on the minimization of the p/2k dimensionless relation obtained for each one of the model, analyzed under the same boundary conditions and efforts. Among the different cases covered, this paper shows the study for the optimal choice of the geometric distribution of zones. The Upper Bound Theorem (UBT) by its Triangular Rigid Zones (TRZ) consideration, under modular distribution, is applied to indentation processes. To extend the application of the model, cases of different thicknesses are considered

Upper Bound Solutions to Plane-Strain Extrusion Problems

1970 ◽  
Vol 92 (1) ◽  
pp. 158-164 ◽  
Author(s):  
P. C. T. Chen
Keyword(s):  
Plane Strain ◽  
Upper Bound ◽  
Material Properties ◽  
Incompressible Material ◽  
Velocity Fields ◽  
Deformation Pattern ◽  
Upper Bound Theorem ◽  
Admissible Velocity ◽  
Die Geometry ◽  
Bound Theorem

A method for selecting admissible velocity fields is presented for incompressible material. As illustrations, extrusion processes through three basic types of curved dies have been treated: cosine, elliptic, and hyperbolic. Upper-bound theorem is used in obtaining mean extrusion pressures and also in choosing the most suitable deformation pattern for extrusion through square dies. Effects of die geometry, friction, and material properties are discussed.

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