Shakedown as a Guide to the Design of Pressure Vessels

1969 ◽  
Vol 91 (3) ◽  
pp. 799-806 ◽  
Author(s):  
F. A. Leckie ◽  
R. K. Penny
Keyword(s):  
Linear Programming ◽  
Lower Bound ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Design Decisions ◽  
Programming Techniques ◽  
Standard Linear ◽  
Standard Linear Programming

Using the theorems of plasticity lower bound estimates of shakedown loadings have been calculated for a number of shell-like structures commonly found in the pressure vessel industry. These have been determined by making use of elastic solutions, already available, in conjunction with standard linear programming techniques. Combinations of loadings and temperatures have been considered with a view to illustrating how calculations of these types can help in making design decisions.

A Geometric Algorithm for Hybrid Workpiece Localization/Envelopment Problem

1998 ◽  
Author(s):  
Y. X. Chu ◽  
J. B. Gou ◽  
Z. X. Li
Keyword(s):  
Linear Programming ◽  
Localization Problem ◽  
Euclidean Group ◽  
Geometric Algorithm ◽  
Hybrid Localization ◽  
Programming Techniques ◽  
Standard Linear ◽  
Workpiece Localization ◽  
Present Simulation ◽  
Standard Linear Programming

Abstract The problem of aligning the CAD model of a workpiece such that all points measured on the finished surfaces of the workpiece match closely to corresponding surfaces on the model while all unmachined surfaces lie outside the model to guarantee the presence of material to be machined at a later time is referred to as the hybrid localization/envelopment problem. The hybrid problem has important applications in setting up for machining of partially finished workpieces. This paper gives a formulation of the hybrid localization/envelopment problem and present a geometric algorithm for computing its solutions. First, we show that when the finished surfaces of a workpiece are inadequate to fully constrain the rigid motions of the workpiece, then the set of free motions remaining must form a subgroup G0 of the Euclidean group SE(3). This allows us to decompose the hybrid problem into a (symmetric) localization problem on the homogeneous space SE(3)/G0 and an envelopment problem on G0. While the symmetric localization problem is solved using the Fast Symmetric Localization (FSL) algorithm developed in one of our early papers, the envelopment problem is solved by computing the solutions of a sequence of linear programming (LP) problems. We derive explicitly the LP problems and apply standard linear programming techniques to solve the LP problems. We present simulation results to demonstrate efficiency of our method for the hybrid problem.

scholarly journals An Improvement for Fuzzy Stochastic Goal Programming Problems

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Shu-Cheng Lin ◽  
Han-Wen Tuan ◽  
Peterson Julian
Keyword(s):  
Linear Programming ◽  
Goal Programming ◽  
Random Environment ◽  
Solution Process ◽  
Lower Side ◽  
Stochastic Goal Programming ◽  
Linear Programming Problems ◽  
Standard Linear ◽  
Standard Linear Programming

We examined the solution process for linear programming problems under a fuzzy and random environment to transform fuzzy stochastic goal programming problems into standard linear programming problems. A previous paper that revised the solution process with the lower-side attainment index motivated our work. In this paper, we worked on a revision for both-side attainment index to amend its definition and theorems. Two previous examples were used to examine and demonstrate our improvement over previous results. Our findings not only improve the previous paper with both-side attainment index, but also provide a theoretical extension from lower-side attainment index to the both-side attainment index.

An Evaluation of ASME Ellipsoidal Heads

1969 ◽  
Vol 91 (3) ◽  
pp. 636-640 ◽  
Author(s):  
R. R. Gajewski ◽  
R. H. Lance
Keyword(s):  
Linear Programming ◽  
Lower Bound ◽  
Programming Problem ◽  
Lower Bounds ◽  
Limit Analysis ◽  
Digital Computer ◽  
Linear Programming Problem ◽  
Pressure Vessels ◽  
Asme Code ◽  
Bound Theorem

The ASME Code specifications for unfired cylindrical pressure vessels are examined from the viewpoint of the lower bound theorem of limit analysis. The problem is formulated as a linear programming problem and numerically solved using well-established algorithms on a digital computer. It is shown that lower bounds for collapse are less than the ASME Code specifications for such structures.

scholarly journals Unit Price Contracts: A Practical Framework For Determining Competitive Bid Prices

2011 ◽  
Vol 14 (3) ◽  
pp. 63 ◽  
Author(s):  
John E. Burnett ◽  
Bruce M. Wampler
Keyword(s):  
Linear Programming ◽  
Objective Function ◽  
Capital Budgeting ◽  
Analytical Framework ◽  
Unit Price ◽  
Competitive Bidding ◽  
Bidding Strategy ◽  
Standard Linear ◽  
Bid Prices ◽  
Standard Linear Programming

<span>A general analytical framework within which to solve the competitive bidding problem is developed by considering a unit price contract. By viewing the problem in the standard capital budgeting framework and exploiting the linearity of the firms objective function and constraints, the problem can be formulated as a standard linear programming (LP) application whose solution is the optimal bid. We also investigate a so-called unbalanced bidding strategy as an effective way for bidding firms to hedge the risk, or uncertainty, inherent in may unit price contracts.</span>

Stress Field Around a Large Opening in a Pressure Vessel During a Major Repair

2009 ◽  
Author(s):  
Erik Garrido ◽  
Euro Casanova
Keyword(s):  
Pressure Vessel ◽  
New Technologies ◽  
Mechanical Design ◽  
General Purpose ◽  
Pressure Vessels ◽  
Mechanical Equipment ◽  
Stress Distributions ◽  
Large Opening ◽  
Von Mises ◽  
Case Basis

It is a regular practice in the oil industry to modify mechanical equipment to incorporate new technologies and to optimize production. In the case of pressure vessels, it is occasionally required to cut large openings in their walls in order to have access to the interior part of the equipment for executing modifications. This cutting process produces temporary loads, which were obviously not considered in the original mechanical design. Up to now, there is not a general purpose specification for approaching the assessments of stress levels once a large opening in a vertical pressure vessel has been made. Therefore stress distributions around large openings are analyzed on a case-by-case basis without a reference scheme. This work studies the distribution of the von Mises equivalent stresses around a large opening in FCC Regenerators during internal cyclone replacement, which is a frequently required practice for this kind of equipment. A finite element parametric model was developed in ANSYS, and both numerical results and illustrating figures are presented.

Effect of Carbide Content on Temper Embrittlement of 2.25Cr1Mo Steel

2016 ◽  
Author(s):  
Yian Wang ◽  
Guoshan Xie ◽  
Zheng Zhang ◽  
Xiaolong Qian ◽  
Yufeng Zhou ◽  
...  
Keyword(s):  
High Temperature ◽  
Pressure Vessel ◽  
High Stress ◽  
Temper Embrittlement ◽  
Damage Mechanism ◽  
Pressure Vessels ◽  
Nondestructive Method ◽  
Operating Conditions ◽  
Low Alloy Steels ◽  
Carbide Content

Temper embrittlement is a common damage mechanism of pressure vessels in the chemical and petrochemical industry serviced in high temperature, which results in the reduction of roughness due to metallurgical change in some low alloy steels. Pressure vessels that are temper embrittled may be susceptible to brittle fracture under certain operating conditions which cause high stress by thermal gradients, e.g., during start-up and shutdown. 2.25Cr1-Mo steel is widely used to make hydrogenation reactor due to its superior combination of high mechanical strength, good weldability, excellent high temperature hydrogen attack (HTHA) and oxidation-resistance. However, 2.25Cr-1Mo steel is particularly susceptible to temper embrittlement. In this paper, the effect of carbide on temper embrittlement of 2.25Cr-1Mo steel was investigated. Mechanical properties and the ductile-brittle transition temperature (DBTT) of 2.25Cr-1Mo steel were measured by tensile test and impact test. The tests were performed at two positions (base metal and weld metal) and three states (original, step cooling treated and in-service for a hundred thousand hours). The content and distribution of carbides were analyzed by scanning electron microscope (SEM). The content of Cr and Mo elements in carbide was measured by energy dispersive X-ray analysis (EDS). The results showed that the embrittlement could increase the strength and reduce the plasticity. Higher carbide contents appear to be responsible for the higher DBTT. The in-service 2.25Cr-1Mo steel showed the highest DBTT and carbide content, followed by step cooling treated 2.25Cr-1Mo steel, while the as-received 2.25Cr-1Mo steel has the minimum DBTT and carbide content. At the same time, the Cr and Mo contents in carbide increased with the increasing of DBTT. It is well known that the specimen analyzed by SEM is very small in size, sampling SEM specimen is convenient and nondestructive to pressure vessel. Therefore, the relationship between DBTT and the content of carbide offers a feasible nondestructive method for quantitative measuring the temper embrittlement of 2.25Cr-1Mo steel pressure vessel.

A Study on Fatigue Life Evaluation of Pressure Vessel Made of ASME SA240-316L Material Using Numerical Analysis

2019 ◽  
Vol 893 ◽  
pp. 1-5 ◽  
Author(s):  
Eui Soo Kim
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Pressure Vessel ◽  
Life Prediction ◽  
Pressure Vessels ◽  
Physical Damage ◽  
Element Analysis ◽  
Internal Damage ◽  
Life Evaluation ◽  
Fatigue Life Evaluation

Pressure vessels are subjected to repeated loads during use and charging, which can causefine physical damage even in the elastic region. If the load is repeated under stress conditions belowthe yield strength, internal damage accumulates. Fatigue life evaluation of the structure of thepressure vessel using finite element analysis (FEA) is used to evaluate the life cycle of the structuraldesign based on finite element method (FEM) technology. This technique is more advanced thanfatigue life prediction that uses relational equations. This study describes fatigue analysis to predictthe fatigue life of a pressure vessel using stress data obtained from FEA. The life prediction results areuseful for improving the component design at a very early development stage. The fatigue life of thepressure vessel is calculated for each node on the model, and cumulative damage theory is used tocalculate the fatigue life. Then, the fatigue life is calculated from this information using the FEanalysis software ADINA and the fatigue life calculation program WINLIFE.

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