scholarly journals Study of the Tool Geometry Influence in Indentation for the Analysis and Validation of the New Modular Upper Bound Technique

2016 ◽  
Vol 6 (7) ◽  
pp. 203 ◽  
Author(s):  
Carolina Bermudo ◽  
Lorenzo Sevilla ◽  
Francisco Martín ◽  
Francisco Trujillo
Keyword(s):  
Upper Bound ◽  
Tool Geometry ◽  
Upper Bound Technique

Analysis of Strip Rolling by the Upper Bound Approach

1987 ◽  
Vol 109 (4) ◽  
pp. 338-346 ◽  
Author(s):  
B. Avitzur ◽  
W. Gordon ◽  
S. Talbert
Keyword(s):  
Velocity Field ◽  
Rigid Body ◽  
Upper Bound ◽  
Velocity Fields ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Total Power ◽  
Strip Rolling ◽  
Upper Bound Technique ◽  
Independent Process

The process of strip rolling is analyzed using the upper bound technique. Two triangular velocity fields, one with triangles in linear rigid body motion and the other with triangles in rotational rigid body motion, are developed. The total power is determined as a function of the four independent process parameters (relative thickness, reduction, friction and net front-back tension). The results of these two velocity fields are compared with the established solution from Avitzur’s velocity field of continuous deformation. Upon establishing the validity of the triangular velocity field as an approach to the strip rolling problem, recommendations are suggested on how this approach can be used to study the split end or alligatoring defect.

The Study of Distorted Grid Patterns for Flow-Through Conical Converging Dies by the Multi-triangular Velocity Field

1984 ◽  
Vol 106 (2) ◽  
pp. 150-160 ◽  
Author(s):  
J. Pan ◽  
W. Pachla ◽  
S. Rosenberry ◽  
B. Avitzur
Keyword(s):  
Velocity Field ◽  
Upper Bound ◽  
Cone Angle ◽  
Wire Drawing ◽  
Perfectly Plastic ◽  
Distorted Grid ◽  
Upper Bound Technique ◽  
Independent Process ◽  
Flow Through ◽  
Reduction In Area

A variety of velocity fields may be used to analyze the intermediate and final distorted grids for the so-called “flow-through” metal forming processes such as wire drawing, rolling, extrusion, etc. In this paper the triangular velocity field describes the flow of homogeneous, perfectly plastic Mises’ material through a conical converging die. The traditional triangular velocity field was treated and the solution extended. The shape of the distorted grids was uniquely determined by the minimization of the power (drawing or extrusion stresses) required to cause its distortion for a given set of independent process parameters, i.e., process geometry-reduction in area and semi-cone angle, and friction. Actual power (forming stress requirements) was estimated by the upper-bound technique. For the unitriangular velocity field, the power was minimized with respect to the shape of the workpiece (the shape of the triangle). For the multitriangular velocity field, the power was minimized with respect to the shape and the number of triangles. Further, the number of triangles was treated as a real number. Thus, the accurate lower upper-bound was found and the reasonable solution in predicting real distortion grid patterns was then obtained. The analysis determines the severity of the distortion as a function of process geometry and friction.

Closed-Die Forging of Gear-Like Elements

1998 ◽  
Vol 120 (1) ◽  
pp. 34-41 ◽  
Author(s):  
A. El-Domiaty ◽  
M. Shabara ◽  
M. Al-Ansary
Keyword(s):  
Upper Bound ◽  
Pure Aluminum ◽  
Experimental Results ◽  
Frictional Stress ◽  
Die Geometry ◽  
Die Forging ◽  
Closed Die Forging ◽  
Theoretical Predictions ◽  
Upper Bound Technique ◽  
Forging Die

Closed die forging of spur gears is investigated using the slab method and the upper bound technique. The tooth regions are approximated by prismatic rectangular sections. The velocity field comprising three unit deformation regions is used. A constant frictional stress between workpiece and forging die is assumed. The average punch pressure normalized by the flow stress of the gear material is determined theoretically and compared with experimental results. The experimental work is carried out on a commercial pure aluminum (Al 1100) at room temperature. The forging process is carried out using one die geometry without using any additional blocker (preform) dies. The theoretical predictions of forging pressures using slab and upper bound methods agree fairly well with the experimental results.

Stability of Slopes in Anisotropic, Nonhomogeneous Soils

1975 ◽  
Vol 12 (1) ◽  
pp. 146-152 ◽  
Author(s):  
W. F. Chen ◽  
N. Snitbhan ◽  
H. Y. Fang
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Limit Equilibrium ◽  
Equilibrium Analysis ◽  
Stability Factor ◽  
Failure Plane ◽  
Limit Equilibrium Analysis ◽  
Stability Of Slopes ◽  
Upper Bound Technique ◽  
The Stability

The upper bound technique of limit analysis has been found to be very successful in analyzing the stability of cuttings in normally consolidated clays. However, most soils in their natural states exhibit some anisotropy with respect to shear strength, and some nonhomogeneity with respect to depth. It is difficult to obtain the solution based on the classical limit equilibrium analysis with the assumed noncircular failure plane with such soil properties included. This paper establishes an expression for the stability factor Ns, based on the upper bound technique of limit analysis which yields a close-formed solution for sections in which the following conditions are considered: (a) log-spiral failure-plane, through and below toe; (b) non-homogeneity; (c) anisotropy; and (d) general slope.

A new upper bound solution for a hollow cylinder subjected to compression and twist

2004 ◽  
Vol 218 (4) ◽  
pp. 369-375 ◽  
Author(s):  
S Alexandrov ◽  
G-Y Tzou ◽  
S-Y Hsia
Keyword(s):  
Velocity Field ◽  
Angular Velocity ◽  
Hollow Cylinder ◽  
Upper Bound ◽  
Geometrical Parameters ◽  
Parallel Plates ◽  
Compression Force ◽  
Bound Solution ◽  
Friction Factors ◽  
Upper Bound Technique

The upper bound technique is adopted to investigate the effect of angular velocity on the load required to compress a circular hollow cylinder between rough parallel plates. The kinematically admissible velocity field accounts for the asymptotic behaviour of the actual velocity field in a vicinity of the friction surface. The theoretical solution is illustrated by numerical examples for different geometrical parameters and friction factors. In particular, the variations in work rate, torsion moment and compression force with the dimensionless angular velocity are shown.

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