Stability analysis of unlined elliptical tunnel using finite element upper-bound method with rigid translatory moving elements

2015 ◽  
Vol 50 ◽  
pp. 13-22 ◽  
Author(s):  
Feng Yang ◽  
Jian Zhang ◽  
Junsheng Yang ◽  
Lianheng Zhao ◽  
Xiangcou Zheng
Keyword(s):  
Finite Element ◽  
Stability Analysis ◽  
Upper Bound ◽  
Upper Bound Method

On Friction of Ploughing by Rigid Asperities in the Presence of Straining—Upper Bound Method

1990 ◽  
Vol 112 (2) ◽  
pp. 324-329 ◽  
Author(s):  
A. Azarkhin ◽  
O. Richmond
Keyword(s):  
Finite Element ◽  
Friction Factor ◽  
Upper Bound ◽  
Plastic Material ◽  
High Accuracy ◽  
The Other ◽  
Periodic Array ◽  
Combined Loading ◽  
Upper Bound Method ◽  
Perfectly Plastic

Upper bound applications traditionally assume that a rigid/perfectly-plastic material moves by rigid blocks, creating discontinuities of velocity at the interfaces between the blocks. In the present version, the elements (blocks) are plastically deformable and there are no velocity discontinuities between adjacent sides. Since this modification incorporates major features of finite element representation employing arbitrary cells, it allows the use of many parameters for minimization, thus achieving high accuracy. On the other hand, it retains the advantage of upper bound techniques in that the incremental procedure for loading is not necessary, and the results for steady processes are obtained directly. Some energy statements for combined loading are derived and a technique for calculating the ploughing force is presented. Examples for a single fully embedded rigid pyramid and a periodic array of asperities ploughing through the rigid/perfectly plastic material in the presence of subsurface straining are given. The friction factor decreased as the rate of subsurface straining increased, as the pyramid angle of the asperities increased, and as the distance between asperities increased.

A Simple Upper-Bound Method for Calculating Approximate Shakedown Loads

1998 ◽  
Vol 120 (2) ◽  
pp. 195-199 ◽  
Author(s):  
R. Hamilton ◽  
J. T. Boyle ◽  
J. Shi ◽  
D. Mackenzie
Keyword(s):  
Finite Element ◽  
Lower Bound ◽  
Spherical Shell ◽  
Upper Bound ◽  
Pressure Vessel ◽  
Simple Approach ◽  
Finite Element Analyses ◽  
Axisymmetric Nozzle ◽  
Upper Bound Method

A simple approach for calculating upper-bound shakedown loads is described. The method is based on a series of iterative elastic finite element analyses (the elastic compensation procedure) applied to Koiter’s upper-bound shakedown theorem. The method is demonstrated for a typical pressure vessel application; an axisymmetric nozzle in a spherical shell. Several geometrical configurations are investigated. The calculated upper-bound shakedown loads are compared with lower-bound results obtained by the authors, simple shakedown criteria, and various results given in the literature.

Face Stability Analysis of Rectangular Tunnels Driven by a Pressurized Shield

2011 ◽  
Vol 378-379 ◽  
pp. 461-465 ◽  
Author(s):  
Xiao Ming Tu ◽  
Yu You Yang ◽  
Gui He Wang
Keyword(s):  
Stability Analysis ◽  
Failure Mechanism ◽  
Upper Bound ◽  
Limit Analysis ◽  
Underground Space ◽  
Face Stability ◽  
Upper Bound Method ◽  
Analysis Theory ◽  
Development And Utilization ◽  
Rectangular Tunnel

With the development and utilization of underground space, some new tunnel forms are emerging, such as the rectangular tunnel, double tunnels, treble tunnels and so on. The aim of this paper is to determine the collapse face pressure of a rectangular tunnel driven by a pressurized shield. The calculation is based on the upper-bound method of the limit analysis theory. A translational kinematically admissible failure mechanism consists a sequence of truncated rigid cones are considered for the calculation schemes. The numerical results obtained by the calculation are presented.

Upper Bound Analysis and Finite Element Simulation of Bi-Metallic Tube Backward Extrusion

2012 ◽  
Vol 445 ◽  
pp. 155-160
Author(s):  
H. Momeni-Khabisi ◽  
H. Haghighat ◽  
M.J. Momeni-Khabisi
Keyword(s):  
Finite Element ◽  
Upper Bound ◽  
Extrusion Process ◽  
Extrusion Force ◽  
Upper Bound Method ◽  
Metallic Tube ◽  
Backward Extrusion ◽  
Element Simulation ◽  
Reduction In Area ◽  
Good Agreement

In this paper, the process of bi-metallic tube backward extrusion through a conical punch, by means of upper bound method and finite element method is investigated. A cylindrical admissible velocity field is developed and by calculating the internal, shear and frictional powers, the extrusion force is estimated. The extrusion process is also simulated by using the finite element code, ABAQUS. Analysis and simulations are done for two types of bi-metallic tubes: aluminum as core, copper as sleeve (Al-Cu) and copper as core, aluminum as sleeve (Cu-Al). The extrusion force from the upper bound method is compared with the Finite Element results. This comparison shows that the upper bound predictions are in good agreement with the Finite Element results. The results also show that, the extrusion force in the case of Al-Cu tube is smaller than Cu-Al tube and in both types of bi-metallic tubes, the aluminum leaves the deformation zone sooner than the copper. Finally the effects of various extrusion parameters, such as the friction factor, reduction in area and semi-punch angle upon the extrusion force are investigated and the optimum semi-punch angle is determined.

A Generalization of the Upper Bound Method With Particular Reference to the Problem of a Ploughing Indenter

1989 ◽  
Vol 56 (1) ◽  
pp. 10-14 ◽  
Author(s):  
A. Azarkhin ◽  
O. Richmond
Keyword(s):  
Finite Element ◽  
Upper Bound ◽  
Plastic Material ◽  
Approximate Solutions ◽  
Upper Bound Method ◽  
Numerical Examples ◽  
Perfectly Plastic

An algorithm based on a combination of the upper bound method and finite element repesentation has been developed. The algorithm is applied to the problem of a rigid indenter ploughing through a rigid/perfectly-plastic material. Numerical examples are given and the results are compared with previous approximate solutions. Limitations of the upper bound method are discussed.

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