Fast and reliable Bolt Assessment “inside ANSYS ......ANSYS Conference & 20. Schweizer CADFEM...

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© CADFEM 2015

Fast and reliable Bolt Assessment “inside ANSYS”

Vincent Constantin, CADFEM (Suisse) AG

ANSYS Conference & 20. Schweizer CADFEM Users' Meeting, 10. September 2015, Zürich

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Agenda


• Introduction

• VDI 2230

• Bolt Assessment inside ANSYS

• Verification Examples

• Application Example

• Conclusion

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VDI 2230 Part 1

ANSYS Conference & 20. Schweizer CADFEM Users' Meeting, 10. September 2015, Zürich 3

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Limitations of VDI 2230 Part 1


• 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


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Assessment of bolted connections via FEM


• VDI 2230 Part 2, Chapter 7

• Modeling

• Using FEM-results

• Verification of bolts

• 4 model classes

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Model Class III


• 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


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


• 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


• 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


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 Workbench Mechanical, open the protocol

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Functionality: Bolt Assessment inside ANSYS


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


• 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


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


• 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


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


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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Problem Description


• 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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Comparison with a classic evaluation


• 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


• 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


• 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:

• Markus Dutly ([email protected])

• Vincent Constantin ([email protected])

Bolt Assessment inside ANSYS auf YouTube

https://youtu.be/wQYN5S9PHus

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https://youtu.be/wQYN5S9PHus

Fast and reliable Bolt Assessment “inside ANSYS ......ANSYS Conference & 20. Schweizer CADFEM...

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