Prestressing a Two-Layer Pressure Vessel by Plastic Deformation

1965 ◽  
Vol 87 (1) ◽  
pp. 97-103
Author(s):  
R. W. Schneider
Keyword(s):  
Plastic Deformation ◽  
Internal Pressure ◽  
Pressure Vessel ◽  
Work Hardening ◽  
Design Method ◽  
Strain Curve ◽  
Pressure Vessels ◽  
Stress Strain Curve ◽  
Initial Clearance ◽  
Actual Stress

A method of prestressing two-layer pressure vessels by controlled yielding of the inner layer by internal pressure is described. The required prestressing pressure depends upon the dimensions of the vessel, the initial clearance between layers, and the properties of the material of construction. The design method takes into account the actual stress-strain curve of the material and satisfies the rules of plastic flow with work-hardening. Two-layer, cylindrical vessels are discussed in detail.

Some Properties of a Mechanical Model of Plasticity

1948 ◽  
Vol 15 (3) ◽  
pp. 222-225
Author(s):  
H. F. Bohnenblust ◽  
Pol Duwez
Keyword(s):  
Plastic Deformation ◽  
Potential Energy ◽  
Work Hardening ◽  
Mechanical Model ◽  
Strain Curve ◽  
Hysteresis Curve ◽  
Plastic Range ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Mechanical Models

Abstract Various mechanical models explaining the plastic deformation of metals have been proposed. One of the present authors has shown that in some cases an analytical expression for the stress-strain curve and the hysteresis curve of a metal in the plastic range can be deduced from such a model. The present investigation is a further analysis of the model leading to the computation of the change in potential energy of the metal due to work-hardening.

A Noncyclic Method for Determination of Accumulated Strain in Stainless Steel 304 Pressure Vessels

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Gongfeng Jiang ◽  
Gang Chen ◽  
Liang Sun ◽  
Yiliang Zhang ◽  
Xiaoliang Jia ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Internal Pressure ◽  
Pressure Vessel ◽  
Peak Stress ◽  
Pressure Vessels ◽  
Experimental Results ◽  
Elastic Domain ◽  
Ratcheting Strain ◽  
Stainless Steel 304 ◽  
Accumulated Strain

Experimental results of uniaxial ratcheting tests for stainless steel 304 (SS304) under stress-controlled condition at room temperature showed that the elastic domain defined in this paper expands with accumulation of plastic strain. Both ratcheting strain and viscoplastic strain rates reduce with the increase of elastic domain, and the total strain will be saturated finally. If the saturated strain and corresponded peak stress of different experimental results under the stress ratio R ≥ 0 are plotted, a curve demonstrating the material shakedown states of SS304 can be constituted. Using this curve, the accumulated strain in a pressure vessel subjected to cyclic internal pressure can be determined by only an elastic-plastic analysis, and without the cycle-by-cycle analysis. Meanwhile, a physical experiment of a thin-walled pressure vessel subjected to cyclic internal pressure has been carried out to verify the feasibility and effectiveness of this noncyclic method. By comparison, the accumulated strains evaluated by the noncyclic method agreed well with those obtained from the experiments. The noncyclic method is simpler and more practical than the cycle-by-cycle method for engineering design.

Influence of the Wall Thickness on the Allowable and Failure Pressures of Two- and Tree-Way Globe Valve Bodies

2011 ◽  
Vol 488-489 ◽  
pp. 646-649
Author(s):  
Milan Opalić ◽  
Ivica Galić ◽  
Krešimir Vučković
Keyword(s):  
Internal Pressure ◽  
Wall Thickness ◽  
Design Method ◽  
Equivalent Plastic Strain ◽  
Strain Curve ◽  
Linear Motion ◽  
Valve Body ◽  
Failure Pressure ◽  
Critical Location ◽  
Globe Valve

A globe valve is a linear motion valve used to shut off and regulate fluid flow in pipelines. Depending on the number of process connections, they are produced as two‑ or three-way valves. The main valve component carrying the internal pressure is the valve body. For safe exploitation, the valves are designed with the allowable internal pressure taken into consideration. The aim of this paper is to investigate the influence of the wall thickness on the allowable and failure pressures of two- and tree-way globe valve bodies, DN50 and DN100 respectively. Twice-elastic-slope (TES) and the tangent‑intersection (TI) methods are used to obtain the plastic collapse pressures at the critical location which was determined (Fig. 1a and 1b) at the location where maximum equivalent plastic strain throughout the valve body thickness reaches the outer surface. Obtained values are used afterwards to calculate corresponding allowable pressures according to the limit design method, while the failure pressure at the same location was determined as the highest point from the load-maximal principal strain curve. Calculated allowable pressure values, for both valve bodies, are compared with the corresponding ones obtained using the EN standard.

Study on the Stress Concentration at the Round Corners of Flat Heads in Pressure Vessels Subjected to Internal Pressure

1996 ◽  
Vol 118 (4) ◽  
pp. 429-433
Author(s):  
H. Chen ◽  
J. Jin ◽  
J. Yu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Intensity ◽  
Stress Concentration ◽  
Internal Pressure ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Stress Index ◽  
Element Analysis ◽  
Approximate Formulas

Results from finite element analysis were used to show that the stress index kσ and the nondimensionalized highly stressed hub length kh of a flat head with a round corner in a pressure vessel subjected to internal pressure are functions of three dimensionless parameters: λ ≡ h/dt, η ≡ t/d, and ρ ≡ r/t. Approximate formulas for estimating kσ and kh from λ, η, and ρ p are given. The formulas can be used for determining a suitable fillet radius for a flat head in order to reduce the fabricating cost and to keep the stress intensity at the fillet under an acceptable limit.

Fabrication of Faucet Using Hydroforming and Bending Processing

2014 ◽  
Vol 626 ◽  
pp. 293-300 ◽  
Author(s):  
Hui Wen Hu ◽  
Ting Yu Chen ◽  
Sheng Yuan Wang ◽  
Tien Yo Ho
Keyword(s):  
Internal Pressure ◽  
Piecewise Linear ◽  
Strain Curve ◽  
Element Model ◽  
Stress Strain Curve ◽  
Forming Process ◽  
Commercial Code ◽  
Simulation And Experiment ◽  
Profile Dimension ◽  
Walled Cylinder

This research aims at the development of faucet using the techniques of hydroforming and bending. In this study, a tube made from stainless steel SUS 304 is used. Finite element model, including tube, dies and punches, are established using a commercial code LS-DYNA. Tensile test is used to obtain the material properties especially in true stress-strain curve. Piecewise linear plasticity model is used to simulate the plastic deformation of material during the forming process. The initial internal pressure is designed by using the theory of thick-walled cylinder subjecting to internal pressure only. Simulation is first used to find the optimal loading conditions for hydroforming and bending forming. Experiment is then performed to fabricate the prototype of faucets using the simulated loading parameters. The results show that good correlation of the distributed thickness and profile dimension between simulation and experiment are obtained.

Elastic-Plastic Stress Analysis of Pressure Vessels

2012 ◽  
Author(s):  
Yang-chun Deng ◽  
Gang Chen
Keyword(s):  
Internal Pressure ◽  
Stress Analysis ◽  
Strain Hardening ◽  
Pressure Vessel ◽  
Plastic Instability ◽  
Pressure Vessels ◽  
Structural Deformation ◽  
Elastic Plastic ◽  
Thin Walled ◽  
Plastic Stress

To save material, the safety factor of pressure vessel design standards is gradually decreased from 5.0 to 2.4 in ASME Boiler and Pressure Vessel Codes. So the design methods of pressure vessel should be more rationalized. Considering effects of material strain hardening and non-linear structural deformation, the elastic-plastic stress analysis is the most suitable for pressure vessels design at present. This paper is based on elastic-plastic theory and considers material strain hardening and structural deformation effects. Elastic-plastic stress analyses of pressure vessels are summarized. Firstly, expressions of load and structural deformation relationship were introduced for thin-walled cylindrical and spherical vessels under internal pressure. Secondly, the plastic instability for thin-walled cylindrical and spherical vessels under internal pressure were analysed. Thirdly, to prevent pressure vessels from local failure, the ductile fracture strain of materials was discussed.

scholarly journals High Strain Rate Behavior of Ultrafine Grained AA2519 Processed via Multi Axial Cryogenic Forging

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 115 ◽  
Author(s):  
Amin Azimi ◽  
Gbadebo Moses Owolabi ◽  
Hamid Fallahdoost ◽  
Nikhil Kumar ◽  
Grant Warner
Keyword(s):  
Plastic Deformation ◽  
Flow Stress ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Strain Curve ◽  
Thermal Softening ◽  
Stress Strain Curve ◽  
Ultrafine Grained ◽  
Cryogenic Forging

The present work deals with studies on the dynamic behavior of ultrafine grained AA2519 alloy synthesized via cryogenic forging (CF) and room temperature forging (RTF) techniques. A split-Hopkinson pressure bar was used to perform high strain rate tests on the processed samples and the microstructures of the samples were characterized before and after impact tests. Electron backscatter diffraction (EBSD) maps demonstrated a significant grain size refinement from ~740 nm to ~250 nm as a result of cryogenic plastic deformation showing higher dislocation densities and stored strains in the CF sample when compared to the RTF sample. This microstructure modification caused the increase of dynamic flow stress in this alloy. In addition, the aluminum matrix of the CF alloy is more densely populated with fragmented particles than the RTF alloy due to the heavier plastic deformation applied to the cryogenically forged alloy. The results obtained from the stress–strain curve for the RTF sample showed intense thermomechanical instabilities in the RTF sample which led to a severe thermal softening and the subsequent sharp drop in the flow stress. However, no significant decrease was observed in the stress–strain curve of the CF alloys with ultrafine grains which means that thermal softening would probably not be the most effective failure mechanism. Furthermore, higher level of sensitivity of CF alloys to strain rates was observed which is ascribed to transition of rate-controlling plastic deformation mechanisms. In the post-mortem microstructure investigation, deformed and transformed adiabatic shear bands (ASBs) were identified on the RTF alloy when the strain rate is over 4000 s−1 at which it had experienced a significant thermal softening. On the other hand, circular path and aligned split arcs are the various shapes of the deformed ASB seen at no earlier than 4500 s−1 in the CF alloys. This is associated with the crack failure caused by grain boundary sliding.

Structure of Deformed Iron: Irradiation Softening and Orientation Dependence

1975 ◽  
Vol 33 ◽  
pp. 168-169
Author(s):  
Johsei Nagakawa ◽  
A. Sato ◽  
M. Meshii
Keyword(s):  
Solid Solution ◽  
Plastic Deformation ◽  
Low Temperature ◽  
Dislocation Structure ◽  
Early Stage ◽  
Strain Curve ◽  
Orientation Dependence ◽  
Stress Strain Curve ◽  
Softening Effect ◽  
Solid Solution Softening

Solid solution softening and the orientation dependence of yield stress can be regarded as the two most important phenomena characterizing the low temperature plastic deformation of b.c.c. metals. Recently, the orientation dependence of solid solution softening was reported in electron irradiated pure iron in which self-interstitial atoms simulate the solid solution effect. Single crystals oriented for the hard (112) slip showed the largest softening effect and became the softest crystals after irradiation (Fig. 1). Also, the shape of the stress-strain curve for the irradiation-softened crystal suggests that the irradiation may have influenced the dislocation structure at an early stage of deformation. Specimens oriented for the soft (211) slip showed hardly any effect. In this study, the dislocation structure was investigated to determine the mechanism responsible for the softening effect and the orientation dependence.

Material Test and Analysis for Pressure Vessel Rupture Study Under Fire in Plant

2015 ◽  
Author(s):  
Yoshiyasu Itoh ◽  
Yoshiyuki Waki ◽  
Kazuyuki Kasuya
Keyword(s):  
Internal Pressure ◽  
Pressure Vessel ◽  
Oil And Gas ◽  
Pressure Vessels ◽  
Design Guidelines ◽  
Plant Design ◽  
Design Code ◽  
Safe Level ◽  
Fire Incident ◽  
Vessel Rupture

In case fire incident occurs in Oil and Gas plant, pressure vessels will be exposed to fire. Though entire system will be depressurized when the fire is detected, internal pressure may still remain in the pressure vessels. Therefore, pressure vessels, if leakage of its internal fluids will escalate the incident, shall be confirmed that they will withstand internal pressure without rupture at least until internal pressure is decreased down to safe level. For design for such critical pressure vessel, a pressure vessel rupture study is conducted in addition to design code calculations. As safer plant design is requested in recent projects, demands for the pressure vessel rupture study are also growing. In this research, material data at high temperature range, that are necessary to obtain reliable results by the pressure vessel rupture study, were measured for carbon steel and stainless steel type304 and type304L. In addition, pressure vessel rupture studies were performed for two sample pressure vessels by means of FEM analyses and calculation methods in published design guidelines.

Investigation of Fluid Transients in Centrifugal Pump Integrated System With MultiChannel Pressure Vessel

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Wuyi Wan ◽  
Wenrui Huang
Keyword(s):  
Centrifugal Pump ◽  
Pressure Vessel ◽  
Design Method ◽  
Oscillation Amplitude ◽  
Pressure Vessels ◽  
Integrated System ◽  
Centrifugal Pumps ◽  
Transient Pressure ◽  
Improve Design ◽  
Fluid Transients

A pressure vessel is installed to prevent transient vacuum and overpressure in centrifugal pump integrated system. In order to study the transient response of the pressure vessel with multichannels and improve design approach, an integrated system with two centrifugal pumps and a pressure vessel is presented. Based on the water hammer method of characteristics (MOC), the integrated numerical model and program are established by combining pumps, valves and pressure vessels in the integrated systems. Transient pressure process and gas volume variation are simulated for the pressure vessel. The Oscillation amplitude and frequency are obtained, and then the extreme hydraulic transient pressures are analyzed and compared. An optimal design method is provided to determine the safe and economic mass (SEM) of gas (nitrogen) and corresponding optimal safe and economic volume (SEV) of pressure vessel.

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