Calculo de FEA

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description

Análisis de Elementos finitos

Transcript of Calculo de FEA

Page 1: Calculo de FEA
Page 2: Calculo de FEA

ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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FATIGUE & FEA ANALYSIS

“HP TANK 7.8 m3”

(MDI-973-1-1)

METHODOLOGY: FINITE ELEMENT ANALYSIS (FEA)

INDEX:

1. OBJECTIVE

2. DESIGN DATA

3. DEVELOPMENT

4. RESULTS

5. CONCLUSION

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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FINITE ELEMENT ANALYSIS (FEA) FATIGUE

“HP TANK 7.8 M3”

1.- OBJECTIVE

Performing Finite Element Analysis (FEA), to determinate the Fatigue acting stresses in shell, heads and

nozzle sections of pressure vessel named “HP TANK 7.8 M3”. The model will show the strains and stresses

result of the fatigue, the stress concentration zone and global performance. Besides, the peak zone and

global performance.

2.- DESIGN DATA

Design data of baseline for this study were taken from drawing MDI-973-1-1 and 3155 Specification HP Tank.

Equipment location = Wisconsin, USA Equipment size = 60” O.D. X 202” OAL Design pressure = 460 Psig /FV

Design temperature = 450 °F Operation pressure = 29 bars g ( 420.6 psi) (1) Operation temperature = AMB Material of Shell/heads/cones = SA-516-70 Material of flanges and forges = SA-105 Material of neck nozzles = SA-106 B Allowance stress Shell/heads/cones = 1490.5 kg/cm2 Yield stress Shell and flangesbridas = 2672 kg/cm2 (38000 psi ) AT Young´s module = 18.983x 105 kg/cm2 Poisson’s module = 0.3. Material’s density = 7850 kg/m3

(1) The equipment has a cyclical pressure. A pressure cycle corresponds to one depressurization (from 29 bars g to 20 bars g in 5 seconds) + one pressurization (from 20 bars g to 29 bars g in 8 minutes). The total cycle to be taken in account for fatigue sizing: 225,000 cycles. The Finite Element Analysis (FEA) and Fatigue Assessment will be done for the condition requested.

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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3. DEVELOPMENT

Methodology used for developing this study is based on mathematical modeling procedure, of structural

analysis called Finite Element Analysis (FEA). This procedure allows through different models, to evaluate

comprehensively mechanical performance of equipment elements (shell, heads, etc.) and Fatigue. Modeling

and execution analysis are accomplished in an automated way using one of the most important and

recognized analysis software ANSYS release 14.5. Overall model is shown in the following figures:

Fig. 1 Equipment FEA Model

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Fig. 2 Equipment FEA Model

Fig. 3 Cross section

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Finite Elements Models Finite Elements section

Boundary conditions. embedded at base plate

and legs.

Internal pressure = 460.0 psi

Range for fatigue 130.5 psi

Fig. 4 Finite Elements Model and Boundary Conditions

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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3.1 Analysis basis

a).- Criteria basis and mathematical formulation used on the model, below.

In the mathematical model suggested, the following elements were used: “Solid 185”, 8-node structural solid, each node with 3 degrees of freedom per node, and stiffness changes when big deformations and rigidity occur (non-lineal analysis).

Von Mises’ failure criterion was used for getting the acting stresses. Being the most recommendable criteria for cylinder evaluation, it is obtain below:

2ar

2

rt

2

ta2e2

Where:

a= Axial stress.

t = Tangential stress

r = Radial stress.

e = Equivalent stress

b).- Assesssment fatigue was executed applying paragraph 5.5.3 ASME Code Section VIII Division 2. “Fatigue Assesment – Elastic stress and Equivalent Stresses””. Equivalent stres ranges equation:

Alternating stress equation

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Number of cycles equation.

Number of cycles stress-curve

1.00

10.00

100.00

1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09

Esfu

erz

o e

n K

si

Numero de ciclos

Curva S-N

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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4.- RESULTS

Finite Element Análysis gave the followign results: 4.1 Condition 1: Own weight and Internal pressure stresses

Figura 5 Maximum strain 0.58 mm (0.022908 in).

Fig. 6 Maximum Von Mises stress 1149.14 kg/cm2 (16344.6 psi)

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Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Fig. 7 Maximum strain botton head section = 0.25 mm (0.009875 in).

Fig. 8 Maximum Von Mises stress botton head section = 449.91 bars (6523.74 psi)

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Fig 9 Maximum strain in shell 0.34 mm (0.013239 in).

Fig 10 Von Mises stress in flange = 1127.21 bars (16344.6 psi)

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Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Fig 11 Maximum strain in top head = 0.58 mm (0.022908 in)

Fig 12 Von Mises stress in top head = 549.67 bars (7970.18 psi)

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Fig 13 Stress on nozzle section= 1128.19 bars (16358.8 psi)

Fig 14 Stress on top head = 549.67 bars (7970.18 psi)

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ANSYS 14.5

Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Fig 15 Stress on section Shell/nozzle = 934.26 bars (13546.8 psi)

Fig 16 Stress on botton head section = 449.91 bars (6523.74 psi)

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Melter, S.A. DE C.V. {Calle “C” #511, Apodaca, N.L.; México} Customer: ECM TECHNOLOGIES, Winsconsin, USA MC-OT-973-01, Rev. 0 Item:RAP 7.8M3

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Section 5.5.3, ASME Code Section VIII Division 2

Values for Equivalent Primary Stress + Secundary

Element SCL Location SN,K (psi) SN,K (kpsi) Nozzle 1 Inside Nozzle 16358.8 16.3588

Top Head 2 Inside Top Head 7970.18 7.97018

Shell 3 Inside Shell & Nozzle 13546.8 13.5468

Bottom head 4 Inside Bottom Head 6523.74 6.52374

Values for SPS

Element S (kpsi) SY (kpsi) SPS (kpsi) Nozzle 19.5 28.7 58.5

Top Head 21.2 31.75 63.6

Shell 21.2 31.75 63.6

Bottom Head 21.2 31.75 63.6

Efective Alternating of Equivalent Stress Amplitude

Element Location K f= K e,k= Sp,k (kpsi) Salt,k(kpsi) Nozzle Inside Nozzle 1 1 16.36 8.1794

Top Head Inside Top Head 1 1 7.97 3.9851

Shell Inside Shell & Nozzle 1 1 13.55 6.7734

Bottom Head Inside Bottom Head 1 1 6.52 3.2619

Number of Allowance Cycles

Element Location E T (kpsi) E FC (kpsi) SALT,K (kpsi) x NK (CICLOS) Notes Nozzle Inside Nozzle 29000 28300 8.1794 10.2322 17068063254 Passed

Top Head Inside Top Head 29000 28300 3.98509 11.4907 3.09531E+11 Passed

Shell Inside Shell & Nozzle 29000 28300 6.7734 11.4666 2.92796E+11 Passed

Bottom Head Inside Bottom Head 29000 28300 3.26187 11.4907 3.09531E+11 Passed

Nozzle element has the minumum cycles allowance = 1.71 E+10

5.- CONCLUSIONS The number of allowance cycles (1.71 E+10) is higher than cycles (225,000) required, so, the equipment design is accepted for this cycle pressure loads.