GB/T 4732.5-2024 Pressure vessels design by analysis - Part 5: Elastic plastic analysis method
1 Scope
This document specifies the design-by-analysis approach of pressure vessels based on elastic plastic theory, including terms and symbols, basic requirements, load combination conditions, and evaluating steps of five failure modes, i.e., plastic collapse, excessive local strain, buckling, fatigue and ratchet.
This document is applicable to pressure vessels specified in GB/T 4732.1-2024.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 4732.1-2024 Pressure vessels design by analysis - Part 1: General requirements
GB/T 4732.2-2024 Pressure vessels design by analysis - Part 2: Materials
GB/T 4732.3-2024 Pressure vessels design by analysis - Part 3: Formulae method
GB/T 4732.4-2024 Pressure vessels design by analysis - Part 4: Stress classification method
GB/T 4732.6-2024 Pressure vessels design by analysis - Part 6: Fabrication, inspection and testing and acceptance
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 4732.1-2024 and the following apply.
3.1.1 forming strain
residual strain caused by component forming
3.1.2 uniaxial strain limit
strain limit of materials under unidirectional stress
3.1.3 triaxial strain limit
strain limit of materials under three-dimensional stress
3.1.4 twice yield method
fatigue evaluating method of elastic plastic analysis under monotonic loading condition using cyclic stress-strain curve expressed by stress range-strain range with zero as starting load and load range as ending load
3.1.5 cycle-by-cycle analysis method
fatigue evaluating method of elastic plastic analysis on given load cycle one by one until the stress and strain at the cyclic return point are stable using cyclic stress-strain curve expressed by stress amplitude-strain amplitude based on the follow-up strengthening model
3.1.6 elastic plastic analysis
Theoretical or numerical analysis on elastic deformation, stress distribution of structures under given loads as well as plastic deformation, stress redistribution and failure behavior of materials after entering yield using appropriate elastic and plastic mechanical constitutive models based on elastic and plastic properties and parameters of materials
3.1.7 dual criterion
dual evaluating criteria to prevent plastic collapse and excessive plastic deformation simultaneously
3.1.8 collapse load
load when a vessel or component is subjected to plastic collapse under monotonic loading conditions, which is the maximum load that the vessel or component can bear
3.1.9 quasi-limit load
load of the vessel or component when it moves from the local plastic deformation stage to the overall plastic deformation stage under the condition of considering the strain hardening and geometric strengthening effects
Note: Under the assumption of ideal plastic material and small deformation, the quasi-limit load is the limit load.
3.1.10 zero-curvature load
load on the zero-curvature point, i.e., critical point on the load-deformation curve from the arc transition section representing the local plastic deformation stage of the structure to the linear section representing the overall plastic deformation stage of the structure
Note: The zero-curvature load is the quasi-limit load.
3.1.11 strain limiting load
load at which the maximum total equivalent strain within the structure reaches 5%
3.1.12 limit load boundary
load boundary where the component does not lose its load carrying capacity when the component is subjected to a proportional loading action within a domain
3.1.13 shakedown load boundary
load boundary where the mechanical load, thermal load, or both cyclic loads experienced by the component vary within a domain, the component is in a shakedown state
3.1.14 ratchet load boundary
load boundary where the mechanical load, thermal load, or both cyclic loads experienced by the component vary within a domain (in a specific form), the component does not undergo a ratcheting
3.1.15 residual stress field
stress field that exists inside the object to maintain balance when the external load is cancelled Note: The residual stress field is a self-balancing stress field.
3.1.16 direct computational method
method, when performing limit, shakedown and ratchet analysis, by using lower limit theorem and the upper limit theorem, for directly determining the maximum load that the component can bear according to the final state of the component under a given load form, rather than tracking the loading history of the load and the evolution process of the stress and strain response of the component
3.2 Symbols
For the purposes of this document, the following symbols apply.
D——Vessel dead weight, and gravity loads of materials contained, auxiliary equipment and external fittings.
E——Seismic load.
L——Incidental load.
p——Design pressure, MPa.
ps——Static pressure caused by liquid or materials contained (e.g. catalyst), MPa.
pT——Pressure for pressure test, MPa.
Ss——Snow load.
Sm——Allowable stress for material at the pressure test temperature, MPa.
——Allowable stress of material at the design temperature or operating temperature, MPa.
T——Thermal and displacement loads.
W——Wind load.
Wpt——Wind load under the pressure test conditions to be determined by the user.
a——Load adjustment factor.
4 Basic requirements
4.1 The five failure modes of plastic collapse, excessive local strains, buckling, fatigue and ratchet of the pressure vessel shall be evaluated in accordance with the evaluating method based on elastic plastic analysis specified in this document. When the vessel design temperature enters the material creep temperature range, high temperature creep design by analysis shall be performed according to Annex A.
4.2 In addition to the failure modes covered by this document, designers shall also check other failure modes that may occur during the life cycle of the vessel during design.
4.3 The design unit shall be responsible for the correctness and completeness of the vessel design documents. The design calculation sheet includes vessel or component design parameters, detailed structure, material properties, mechanical model, calculation results and evaluating conclusions.
4.4 The elastic plastic analysis requires the following material property parameters, see GB/T 4732.2-2024.
Contents
1 Scope
2 Normative references
3 Terms, definitions and symbols
4 Basic requirements
5 Plastic collapse
6 Excessive local strains
7 Buckling
8 Fatigue
9 Ratchet
Annex A (Normative) Design-by-analysis approach for high temperature creep
Annex B (Normative) Dual evaluation criterion of plastic collapse
Annex C (Normative) Direct computation method of limit, shakedown and ratchet load boundaries
Annex D (Normative) Elastic-plastic stress-strain relationship of materials
GB/T 4732.5-2024 Pressure vessels design by analysis - Part 5: Elastic plastic analysis method
1 Scope
This document specifies the design-by-analysis approach of pressure vessels based on elastic plastic theory, including terms and symbols, basic requirements, load combination conditions, and evaluating steps of five failure modes, i.e., plastic collapse, excessive local strain, buckling, fatigue and ratchet.
This document is applicable to pressure vessels specified in GB/T 4732.1-2024.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 4732.1-2024 Pressure vessels design by analysis - Part 1: General requirements
GB/T 4732.2-2024 Pressure vessels design by analysis - Part 2: Materials
GB/T 4732.3-2024 Pressure vessels design by analysis - Part 3: Formulae method
GB/T 4732.4-2024 Pressure vessels design by analysis - Part 4: Stress classification method
GB/T 4732.6-2024 Pressure vessels design by analysis - Part 6: Fabrication, inspection and testing and acceptance
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 4732.1-2024 and the following apply.
3.1.1 forming strain
residual strain caused by component forming
3.1.2 uniaxial strain limit
strain limit of materials under unidirectional stress
3.1.3 triaxial strain limit
strain limit of materials under three-dimensional stress
3.1.4 twice yield method
fatigue evaluating method of elastic plastic analysis under monotonic loading condition using cyclic stress-strain curve expressed by stress range-strain range with zero as starting load and load range as ending load
3.1.5 cycle-by-cycle analysis method
fatigue evaluating method of elastic plastic analysis on given load cycle one by one until the stress and strain at the cyclic return point are stable using cyclic stress-strain curve expressed by stress amplitude-strain amplitude based on the follow-up strengthening model
3.1.6 elastic plastic analysis
Theoretical or numerical analysis on elastic deformation, stress distribution of structures under given loads as well as plastic deformation, stress redistribution and failure behavior of materials after entering yield using appropriate elastic and plastic mechanical constitutive models based on elastic and plastic properties and parameters of materials
3.1.7 dual criterion
dual evaluating criteria to prevent plastic collapse and excessive plastic deformation simultaneously
3.1.8 collapse load
load when a vessel or component is subjected to plastic collapse under monotonic loading conditions, which is the maximum load that the vessel or component can bear
3.1.9 quasi-limit load
load of the vessel or component when it moves from the local plastic deformation stage to the overall plastic deformation stage under the condition of considering the strain hardening and geometric strengthening effects
Note: Under the assumption of ideal plastic material and small deformation, the quasi-limit load is the limit load.
3.1.10 zero-curvature load
load on the zero-curvature point, i.e., critical point on the load-deformation curve from the arc transition section representing the local plastic deformation stage of the structure to the linear section representing the overall plastic deformation stage of the structure
Note: The zero-curvature load is the quasi-limit load.
3.1.11 strain limiting load
load at which the maximum total equivalent strain within the structure reaches 5%
3.1.12 limit load boundary
load boundary where the component does not lose its load carrying capacity when the component is subjected to a proportional loading action within a domain
3.1.13 shakedown load boundary
load boundary where the mechanical load, thermal load, or both cyclic loads experienced by the component vary within a domain, the component is in a shakedown state
3.1.14 ratchet load boundary
load boundary where the mechanical load, thermal load, or both cyclic loads experienced by the component vary within a domain (in a specific form), the component does not undergo a ratcheting
3.1.15 residual stress field
stress field that exists inside the object to maintain balance when the external load is cancelled Note: The residual stress field is a self-balancing stress field.
3.1.16 direct computational method
method, when performing limit, shakedown and ratchet analysis, by using lower limit theorem and the upper limit theorem, for directly determining the maximum load that the component can bear according to the final state of the component under a given load form, rather than tracking the loading history of the load and the evolution process of the stress and strain response of the component
3.2 Symbols
For the purposes of this document, the following symbols apply.
D——Vessel dead weight, and gravity loads of materials contained, auxiliary equipment and external fittings.
E——Seismic load.
L——Incidental load.
p——Design pressure, MPa.
ps——Static pressure caused by liquid or materials contained (e.g. catalyst), MPa.
pT——Pressure for pressure test, MPa.
Ss——Snow load.
Sm——Allowable stress for material at the pressure test temperature, MPa.
——Allowable stress of material at the design temperature or operating temperature, MPa.
T——Thermal and displacement loads.
W——Wind load.
Wpt——Wind load under the pressure test conditions to be determined by the user.
a——Load adjustment factor.
4 Basic requirements
4.1 The five failure modes of plastic collapse, excessive local strains, buckling, fatigue and ratchet of the pressure vessel shall be evaluated in accordance with the evaluating method based on elastic plastic analysis specified in this document. When the vessel design temperature enters the material creep temperature range, high temperature creep design by analysis shall be performed according to Annex A.
4.2 In addition to the failure modes covered by this document, designers shall also check other failure modes that may occur during the life cycle of the vessel during design.
4.3 The design unit shall be responsible for the correctness and completeness of the vessel design documents. The design calculation sheet includes vessel or component design parameters, detailed structure, material properties, mechanical model, calculation results and evaluating conclusions.
4.4 The elastic plastic analysis requires the following material property parameters, see GB/T 4732.2-2024.
Contents of GB/T 4732.5-2024
Contents
1 Scope
2 Normative references
3 Terms, definitions and symbols
4 Basic requirements
5 Plastic collapse
6 Excessive local strains
7 Buckling
8 Fatigue
9 Ratchet
Annex A (Normative) Design-by-analysis approach for high temperature creep
Annex B (Normative) Dual evaluation criterion of plastic collapse
Annex C (Normative) Direct computation method of limit, shakedown and ratchet load boundaries
Annex D (Normative) Elastic-plastic stress-strain relationship of materials
