scholarly journals Face stability of shield tunnels considering a kinematically admissible velocity field of soil arching

2021 ◽  
Author(s):  
Wei Li ◽  
Chengping Zhang ◽  
Dingli Zhang ◽  
Zijian Ye ◽  
Zhibiao Tan
Keyword(s):  
Velocity Field ◽  
Soil Arching ◽  
Face Stability ◽  
Admissible Velocity

Estimation of Dynamic Forces in Very High-Speed Impact Forging

1966 ◽  
Vol 88 (4) ◽  
pp. 369-372 ◽  
Author(s):  
M. J. Hillier
Keyword(s):  
Approximate Solution ◽  
Velocity Field ◽  
Plane Strain ◽  
Energy Method ◽  
Coulomb Friction ◽  
High Speed ◽  
Admissible Velocity ◽  
High Speed Impact ◽  
Dynamic Forces ◽  
Very High

A study is made of three methods of estimating die loads in impact forging: By approximate solution of the equations of equilibrium; by an energy method, assuming plane sections remain plane; and using the energy method in association with a kinematically admissible velocity field. Results are given for die pressures and die loads for axisymmetric and plane-strain forging of disks and slabs with smooth dies, perfectly rough dies, and for the case of Coulomb friction.

scholarly journals Upper-bound solutions for face stability of circular tunnel in purely cohesive soil using continuous rotational velocity field

2018 ◽  
Vol 58 (6) ◽  
pp. 1511-1525
Author(s):  
Wantao Ding ◽  
Keqi Liu ◽  
Lewen Zhang ◽  
Peihe Shi ◽  
Mingjiang Li ◽  
...  
Keyword(s):  
Velocity Field ◽  
Upper Bound ◽  
Rotational Velocity ◽  
Cohesive Soil ◽  
Circular Tunnel ◽  
Face Stability

A General Velocity Field for Shape Rolling of a V-Sectioned Sheet

1999 ◽  
Vol 122 (1) ◽  
pp. 227-234 ◽  
Author(s):  
Yeong-Maw Hwang ◽  
Hung-Jiun Lin ◽  
J. R. Chen
Keyword(s):  
Plastic Deformation ◽  
Velocity Field ◽  
Rolled Product ◽  
Deformation Behavior ◽  
Thickness Reduction ◽  
Shape Rolling ◽  
Admissible Velocity ◽  
Plastic Deformation Behavior ◽  
Roll Gap ◽  
General Velocity

A general kinematically admissible velocity field has been proposed in this work to examine the plastic deformation behavior of the sheet at the roll gap during shape rolling of a V-sectioned sheet. This velocity field is employed to examine the geometry of the rolled product, which are effected by various rolling conditions such as the sizes of the raw sheet and the vacancy, thickness reduction, etc. Furthermore, experiments on cold shape rolling of aluminum sheet have also been conducted. The rolling forces and the shape of the rolled product were measured to compare with the analytical values. Through the comparisons between them, the validity of this newly proposed velocity field was verified. [S1087-1357(00)71301-3]

Direct Upper Bound Solution to Rectangular-to-Polygonal Extrusion Through Square Die

1999 ◽  
Vol 121 (2) ◽  
pp. 195-201 ◽  
Author(s):  
S. K. Sahoo ◽  
P. K. Kar ◽  
K. C. Singh
Keyword(s):  
Steady State ◽  
Velocity Field ◽  
Upper Bound ◽  
Velocity Fields ◽  
Extrusion Pressure ◽  
Admissible Velocity ◽  
Bound Solution ◽  
Upper Bound Solution ◽  
Aspect Ratios

This paper is concerned with an attempt to find an upper bound solution for the problems of steady-state extrusion of asymmetric polygonal section bars through rough square dies. A class of kinematically admissible velocity fields is examined, reformulating the SERR technique, to get the velocity field that gives the lowest upper bound. This velocity field is utilized to compute the non-dimensional average extrusion pressure at various area reductions for different billet aspect ratios.

A Theory on the Mechanics of Axisymmetric Extrusion through Conical Dies

1968 ◽  
Vol 10 (5) ◽  
pp. 367-380 ◽  
Author(s):  
E. R. Lambert ◽  
Shiro Kobayashi
Keyword(s):  
Velocity Field ◽  
Strain Rate ◽  
Effective Strain ◽  
Cone Angle ◽  
Basic Flow ◽  
Deformation Characteristics ◽  
Flow Lines ◽  
Admissible Velocity ◽  
Stress Components ◽  
Good Agreement

For axisymmetric extrusion through conical dies, an admissible velocity field without discontinuities was obtained by superposition of basic flow patterns. Based on this velocity field, the upper bound to the average forming pressure and the detailed mechanics were calculated for the extrusion of a rod with a semi-cone angle of 45° and a reduction of 75 per cent in area. Three different friction conditions along the die were considered and their influence on the deformation characteristics was discussed. Flow lines, velocity components, grid distortion, strain-rate components, effective strain rate, effective strain, and stress components were plotted. A comparison of the present results with those obtained experimentally (visioplasticity) shows good agreement.

An Arbitrarily Inclined Triangular UBET Element and Its Application to Combined Forging

1985 ◽  
Vol 107 (2) ◽  
pp. 134-140 ◽  
Author(s):  
D. Y. Yang ◽  
J. H. Kim ◽  
C. K. Lim
Keyword(s):  
Velocity Field ◽  
Room Temperature ◽  
Field Experiments ◽  
Velocity Fields ◽  
Admissible Velocity ◽  
Forming Load ◽  
Theoretical Predictions ◽  
Triangular Elements ◽  
Al 2024 ◽  
Good Agreement

A kinematically admissible velocity field is derived for a proposed arbitrarily inclined triangular UBET element. The method is applied to combined forging to show the flexibility of application. From the derived velocity fields upper-bound loads on the punch and deformed configurations are determined by optimizing some given parameters related with geometry and velocity field. Experiments on combined forging are carried out with annealed Al-2024 billets at room temperature for several punch shapes. The theoretical predictions both in the forming load and deformed configuration are in good agreement with the experimental results. It is shown that arbitrarily inclined triangular elements proposed in this work can effectively be used for the prediction of the forming load and deformation in combined forging and can be applied to other forming processes with flexibility.

An Upper Bound Solution for a Two-Layer Cylinder Subject to Compression and Twist

2007 ◽  
Vol 345-346 ◽  
pp. 37-40 ◽  
Author(s):  
Gow Yi Tzou ◽  
Sergei Alexandrov
Keyword(s):  
Velocity Field ◽  
Upper Bound ◽  
Additional Condition ◽  
Velocity Fields ◽  
Upper Bound Theorem ◽  
Predictive Capacity ◽  
Admissible Velocity ◽  
Bound Solution ◽  
Bound Theorem ◽  
Formal Requirements

The choice of a kinematically admissible velocity field has a great effect on the predictive capacity of upper bound solutions. It is always advantageous, in addition to the formal requirements of the upper bound theorem, to select a class of velocity fields satisfying some additional conditions that follow from the exact formulation of the problem. In the case of maximum friction law, such an additional condition is that the real velocity field is singular in the vicinity of the friction surface. In the present paper this additional condition is incorporated in the class of kinematically admissible velocity fields chosen for a theoretical analysis of two - layer cylinders subject to compression and twist. An effect of the angular velocity of the die on process parameters is emphasized and discussed.

An Analytical Study of Deformation Behavior of Porous Metals in Uniaxial Tension and Compression

1985 ◽  
Vol 107 (2) ◽  
pp. 175-179 ◽  
Author(s):  
M. Oyane ◽  
S. Shima ◽  
T. Sato ◽  
Y. Tada
Keyword(s):  
Velocity Field ◽  
Deformation Behavior ◽  
Dissipation Rate ◽  
Analytical Study ◽  
Energy Dissipation Rate ◽  
Uniaxial Deformation ◽  
Porous Metals ◽  
Admissible Velocity ◽  
Tension And Compression ◽  
Good Agreement

On the basis of an upper-bound approach, deformation behavior of porous metals is considered. A model for porous metals is employed to describe a kinematically admissible velocity field for uniaxial deformation. By minimizing the total energy dissipation rate obtained from the velocity field, the yield strength, deformation behavior of porous metals, and also distortion of pores are evaluated. In the analysis, porosity, geometry of pores, and environmental hydrostatic pressure are taken into consideration. Calculated results are compared with experimental and/or other theoretical ones and show good agreement.

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