Disk and Strip Forging with Side Surface Foldover—Part 2: Evaluation of the Upper-Bound Solutions

1978 ◽  
Vol 100 (4) ◽  
pp. 428-433 ◽  
Author(s):  
R. A. Kohser ◽  
B. Avitzur
Keyword(s):  
Upper Bound ◽  
Side Surface ◽  
Thin Specimen ◽  
Load Pressure ◽  
Interface Friction ◽  
Relative Simplicity ◽  
Lower Upper ◽  
Field Solution ◽  
Power Load ◽  
Triangular Field

The upper-bound solutions developed in Part 1 are evaluated with regard to their ability to produce a lower value for required power (load, pressure, or work). Comparisons made with existing solutions such as the triangular field solution and one-zone bulge solution show that for strip, each solution has a domain of geometry and friction in which it is superior. The new solution produces a lower upper-bound for conditions of high interface friction and relatively thin specimen, the area where foldover is the observed mode of flow. For solid cylindrical disks, the solution fails to improve upon existing analyses, but comes sufficiently close to warrant additional study. After evaluation, these solutions were then used in an incremental technique to model the geometry and flow as a function of reduction in height. Results appear most encouraging, and the relative simplicity of the technique when compared with present alternatives is quite attractive.

scholarly journals Fast and accurate exercise policies for Bermudan swaptions in the LIBOR market model

2016 ◽  
Vol 03 (01) ◽  
pp. 1650005 ◽  
Author(s):  
Patrik Karlsson ◽  
Shashi Jain ◽  
Cornelis W. Oosterlee
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Monte Carlo Simulations ◽  
Upper Bound ◽  
Market Model ◽  
Monte Carlo Approach ◽  
Lower Upper ◽  
Libor Market Model ◽  
Bermudan Swaptions

This paper describes an American Monte Carlo approach for obtaining fast and accurate exercise policies for pricing of callable LIBOR Exotics (e.g., Bermudan swaptions) in the LIBOR market model using the Stochastic Grid Bundling Method (SGBM). SGBM is a bundling and regression based Monte Carlo method where the continuation value is projected onto a space where the distribution is known. We also demonstrate an algorithm to obtain accurate and tight lower–upper bound values without the need for nested Monte Carlo simulations.

Experimental Study of the Operation Conditions of Stability on a Gamma Stirling Engine

2016 ◽  
Author(s):  
Houda Hachem ◽  
Ramla Gheith ◽  
Fethi Aloui ◽  
Sassi Ben Nasrallah
Keyword(s):  
Experimental Study ◽  
Rotational Speed ◽  
Heat Engine ◽  
Industrial Process ◽  
Stirling Engine ◽  
Load Pressure ◽  
Operation Conditions ◽  
Receiver System ◽  
Power Load ◽  
Time Required

Considering Stirling engines modern applications and cogeneration recovery energy from industrial process, the power of a Stirling prime mover is to be provided at a speed of rotation adapted to the operation of the receiver system (usually a generator) to exploit the performance of this machine under the conditions of its use (ie lowering of the rotational speed and torque transmitted rise or, more rarely, elevated speed and lowering the torque transmitted). Knowing that the hot air engine cannot change speed quickly and in order to have a well designed system, it is important to study the unsteady state conditions. In this work we present an experimental stability analysis of an irreversible heat engine working at different conditions. The experimental study aims at analyzing the effect of working parameters disruption on the stability of the Gamma Stirling engine. Parameters involved in this experimental study are the load pressure of the motor and the load applied to the Stirling engine. The influence of engine operating parameters on its torque and rotational speed is investigated. The time required by a gamma type Stirling engine to stabilize operation after disruption is estimated. Results show that after a small disruption, speed and temperature evolutions decays exponentially to the steady state determined by a relaxation time. It is assumed that the decrease of the applied power load to the engine or the increase of the load pressure leads to a speed up. And that the increase of the applied power load to the engine or the decrease of the load pressure leads to a speed down.

Disk and Strip Forging with Side-surface Foldover—Part 1: Velocity Field and Upper-Bound Analysis

1978 ◽  
Vol 100 (4) ◽  
pp. 421-427 ◽  
Author(s):  
B. Avitzur ◽  
R. A. Kohser
Keyword(s):  
Velocity Field ◽  
Upper Bound ◽  
Plastic Material ◽  
Relative Size ◽  
Side Surface ◽  
Friction Material ◽  
Material Strength ◽  
Upper Bound Analysis ◽  
Zone Ii ◽  
Bound Analysis

With the assumptions of a Mises’ rigid, perfectly-plastic material and constant shear stress friction prevailing between the forge platens and deforming solid, the upper-bound analysis technique was applied to the upset forging of rectangular strip and solid cylindrical disks in an effort to incorporate the combined phenomena of bluge and fold. A two-zone velocity field was proposed for each geometry with Zone I occupying the interior volume and Zone II, the region near the free-surface periphery. The velocity field in Zone I was chosen as the exponential cusp-type used successfully in several previous analyses. Zone II was represented by a velocity field compatible with a foldover phenomenon and kinematically admissible with respect to boundary conditions and compatibility with Zone I. Solutions based on the above assumptions provide the forging pressure as a function of specimen geometry, interface friction, material strength, rate of bulge formation and relative size of Zone II. Minimization with respect to the last two variables provides the optimum rate of barreling or bulging and determines the degree of foldover expected.

A novel method based on lower–upper bound approximation to predict the wind energy

2020 ◽  
Vol 259 ◽  
pp. 120458
Author(s):  
Peng Wen ◽  
Su Zhang ◽  
Yazhou Xing ◽  
Limin Huo ◽  
Navid Bohlooli
Keyword(s):  
Wind Energy ◽  
Upper Bound ◽  
Lower Upper ◽  
Novel Method

Limit Analysis of Flow Through Inclined Converging Planes

1980 ◽  
Vol 102 (2) ◽  
pp. 109-117 ◽  
Author(s):  
M. Kiuchi ◽  
B. Avitzur
Keyword(s):  
Lower Bound ◽  
Plane Strain ◽  
Upper Bound ◽  
Limit Analysis ◽  
Velocity Fields ◽  
The Body ◽  
Design Flow ◽  
Upper And Lower Bounds ◽  
Lower Upper ◽  
Flow Through

A variety of mathematical models may be used to analyze plastic deformation during a metal-forming process. One of these methods—limit analysis—places the estimate of required power between an upper bound and a lower bound. The upper- and lower-bound analysis are designed so that the actual power or forming stress requirement is less than that predicted by the upper bound and greater than that predicted by the lower bound. Finding a lower upper-bound and a higher lower-bound reduces the uncertainty of the actual power requirement. Upper and lower bounds will permit the determination of such quantities as required forces, limitations on the process, optimal die design, flow patterns, and prediction and prevention of defects. Fundamental to the development of both upper-bound and lower-bound solutions is the division of the body into zones. For each of the zones there is written either a velocity field (upper bound) or a stress field (lower bound). A better choice of zones and fields brings the calculated values closer to actual values. In the present work, both upper- and lower-bound solutions are presented for plane-strain flow through inclined converging dies. For the upper bound, trapezoidal velocity fields, uni-triangular velocity fields, and multi-triangular velocity fields have been dealt with and the solutions compared to previously published work on cylindrical velocity fields. It was found that in different domains of the various combinations of the process parameters, different patterns of flow (cylindrical, triangular, etc.) provide lower upper-bound solutions. The lower-bound solution for plane-strain flow through inclined converging planes is newly developed.

Sign in / Sign up

Export Citation Format

Share Document