fast and reliable bolt assessment inside ansys
TRANSCRIPT
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© CADFEM 2015
Fast and reliable Bolt Assessment “inside ANSYS”
Vincent Constantin, CADFEM (Suisse) AG
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien
© CADFEM 2015
Agenda
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 2
• Introduction
• VDI 2230
• Bolt Assessment inside ANSYS
• Verification Examples
• Application Example
• Conclusion
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VDI 2230 Part 1
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 3
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Limitations of VDI 2230 Part 1
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• Nonlinear material behavior (e.g. plasticity, creeping)
• Nonlinear status (i.e. load dependent contacts, sealings incl. fluid
penetration)
• Geometric nonlinearities (large deflections during upward movement)
• Plates stiffness has to be estimated
• The load introduction factor n has to be estimated
• Finding the length of lever arm a for an eccentric force transmission can be
quite difficult, calculations are cumbersome…
Source: User Manual KISSsoft
Source: User Manual KISSsoft
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VDI 2230 Part 2
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 5
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Assessment of bolted connections via FEM
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• VDI 2230 Part 2, Chapter 7
• Modeling
• Using FEM-results
• Verification of bolts
• 4 model classes
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Model Class III
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• Modeling
• Reproduce resilience of bolts and all parts
involved
• Bolt represented as a solid
-> dN diameter of the shaft
-> d3 diameter of the thread
Head and screw nut will not be modeled in
detail, thread resilience will not be modeled,
this will result from the local displacement
• Preload is included
-> Fm_FE_min, Fm_FE_max 2 Calculations
• Consider loss of preload
• Multi-Zone Mesh
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Realization: verification of load capacity based on VDI 2230 Part 1
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For a verification in dependence upon VDI 2230 the following loads must be
below the acceptable threshold:
• Working stress
• Alternating stress
• Surface pressure at the bolt head and nut bearing area
• Safety factor against sliding
In addition a sufficient length of engagement has to be provided.
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Bolt Assessment inside ANSYS
Functionality and Workflow
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Automation
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• Goals:
• Automation of bolt calculation for the model class III
• Forces and moments in the bolts are automatically measured
• Using external database to simplify the user‘s work
• What is needed?
• New load object: bolt pretension with additional properties
• New result object: post-processing, display of calculated safety factors
• Accessing database and calculation module of KISSsoft
• How to implement it?
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Automation
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 11
• How to implement it?
• Application Customization Toolkit (ACT)
• Enhance usage of ANSYS by integrating own
functionality
• Implement load and result objects
• Define special settings in details view
• Access the graphics window
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Workflow
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 12
1. Model preparation: Solid Bolts and Mesh
2. Add new Bolt Load to project tree
• Insert parameters
3. Add new Bolt Assessment to post processing section of project tree
• Select Type of Result
4. Solve
5. Review results in WB, open the Protocol
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Functionality: Bolt Assessment inside ANSYS
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 13
Calculated Forces
Parameters
Pre
P
ost
Back-
ground
Graphical User Interface
Safety factors
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Verification
VDI 2230, Example 1
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Example 1: Boundary conditions and load case
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• Fixed Support at the end of the rod
• Frictionless Support around the
piston
• Pressure:
• 0 MPa at steps 1 and 2
• 5.5 MPa at step 3
• Note: steps 1 and 2 are reserved for
the pretension and embedding
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Example 1: Results and comparison with reference solution
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Values VDI 2230 FEM FMperm Dev. [%] FEM FMmin Dev. [%]
F_Kmin [N] 1000.00 36592.35 - 1203.11 20.31 F_Z [N] 2415.00 2491.61 3.17 2501.33 3.57
F_SA_max [N] 1394.40 1423.60 2.09 1729.57 24.04 F_Smax [N] 66194.00 66223.60 0.04 28650.57 -
S_F 1.15 1.15 -0.28 2.66 - S_D 5.89 5.79 -1.79 4.76 -19.17 S_p 1.77 1.68 -4.76 3.89 -
M_A [Nm] 108.00 109.15 1.06 - -
• With the values of the KISSsoft’s database, the calculated contact surface is smaller than in the reference solution. Thus the safety factor against surface pressure (S_p) is more conservative.
• With the minimal preload, the additional bolt load is greater because of a partial separation at the interface. This leads to a smaller safety factor against fatigue failure (S_D).
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Verification
VDI 2230, Example 2
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Example 2: Model
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• Flange connection with 12 screws
• Lateral loading on bolts
• Lower part: fixed
• Upper part: torsion moment
• 13 000 Nm
• Relevant safety factors:
• S_P: Pressure
• S_G: Sliding
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Example 2: Results: Surface Pressure
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 19
Values VDI 2230:2014 FEM FMperm Deviation [%]
F_Smax [N] 118800.00 118800.00
ApK [mm^2] 151.50 151.20 -0.20
SP 1.08 1.08 -0.22
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Example 2: Results: Safety factor against sliding
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VDI 2230:2014 FEM FMmin / bolt min FEM FMmin / bolt max Deviation min [%] Deviation max [%]
SG 1.26 1.26 1.29 0.01 1.96
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Bolted assembly
Application of Bolt Assessment inside ANSYS
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Problem Description
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• 25 Bolts M12 – 8.8
• Preload: • max 40 000 N
• min 16 000 N
• 2 Analysis in 3 load steps: • preload
• embedding
• external loads
• Questions: • M12 – 8.8 strong enough?
• Safety factors?
• Working stress (S_F)
• Alternating stress (S_D)
• Surface pressure (S_P)
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Using Bolt Assessment inside ANSYS
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• Results
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Comparison with a classic evaluation
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• Safety factor against exceeding
the yield point S_F
• Safety factor against surface
pressure S_P
• Safety factor against fatigue
failure S_D
0
50
100
150
200
250
1 Bolt 25 Bolts
Time needed by the user [min]
Standard FEA calculation Bolt Assessment inside ANSYS
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Conclusion
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 25
• Standards & regulations
• Reproducible methodology
• Streamlined, automated workflow
• No more in-house solutions
0
50
100
150
200
250
1 Bolt 25 Bolts
Time needed by the user [min]
Standard FEA calculation Bolt Assessment inside ANSYS
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Wanted: examples and case studies
ANSYS Conference & 10. CADFEM Users' Meeting, 29.-30. April 2015, Wien 26
• Would you like to learn more?
• We are looking for your bolt calculations and cases!
• You provide your model including all hand calcs
• We will verify the bolts using our Bolt Assessment inside ANSYS
• We compare your results with the ones from Bolt Assessment inside ANSYS.
• Conditions: your test case will be published
• Contact us:
• Matthias Alberts ([email protected])
• Vincent Constantin ([email protected])
Bolt Assessment inside ANSYS auf YouTube
https://youtu.be/wQYN5S9PHus