Advanced bolt assessment through process automation

Transcription

1 Titelmasterformat Bolt Assessment inside durch ANSYS Klicken bearbeiten Advanced bolt assessment through process automation

2 Contents Short presentation of VDI 2230 Workflow with Bolt Assessment inside ANSYS (BAIA) Demo Comparison with reference examples Additional informations

3 Titelmasterformat VDI 2230 Part 1 durch Klicken bearbeiten

4 Brief Overview of Guideline VDI 2230, Part 1: Calculation Steps R0 Nominal Diameter and Limiting Size R7 Assembly Stress R1 Tightening Factor R8 Working Stress R2 Minimum Clamping Force R9 Alternating Stress R3 Subdividing the working load/load factor R10 Surface Pressure R4 Changes in Preload R11 Length of Engagement R5 Min. Assembly Preload R12 Sliding, shearing R6 Max. Assembly Preload R13 Tightening Torque

5 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) The load introduction factor 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 5

6 Titelmasterformat VDI 2230 Part 2 durch Klicken bearbeiten

7 Assessment of bolted connections via FEM VDI 2230 Part 2 1. Scope 2. Normative references 3. Terms and definitions 4. Symbols and abbreviations 5. Calculation method and approaches to solutions 6. Analytical calculations 7. FEM-Application 7.1 Fundamental Approach 7.2 Modeling 7.3 How to derive the solution quantities from the FE Analysis 7.4 Verification of loading capacity supported by guideline VDI 2230 Part 1 7

8 Model Class I Objective of the Calculation Internal forces at the joint used as an input for calculations through VDI 2230 Part 1 Equivalent Model Modeling the assembly contains resilience of the structure which means that load distribution on the full assembly is taken into account. In the vicinity of the interface parts will be bonded (no pretension applied) Postprocessing At connection reaction forces will be post processed from FE Analysis. According to VDI 2230 Part 1 -> Dimensioning -> Verification 8

9 Model Class II and III Calculation Goal Internal forces of the screw calculated in the FE-analysis are used as input quantity for the calculation analogous to VDI 2230 Part 1 Modeling Screw is considered as a dummy element analogous to VDI 2230 Part 1 Preload is considered The interface is represented by a contact The calculation considers max. respectively min. preload based on the type of bolt 9

10 Model Class II Modeling Represent resilience of bolts and all preloaded parts Bolt through beams -> d N shaft diameter -> d 3 screw thread Depending on connectivity the resilience of thread, screw and head has to be taken into account Include preload -> F m_fe_min, F m_fe_max 2 calculations Consider the loss of preload 10

11 Model Class III Modeling Reproduce resilience of bolts and all parts involved Bolt represented as a solid -> d N diameter of the shaft -> d 3 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 -> F m_fe_min, F m_fe_max 2 calculations Consider loss of preload Multi-zone mesh 11

12 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 slipping In addition a sufficient length of engagement has to be provided. 12

13 Model Class IV Bolt completely modeled including thread Verification through local stress This will not be discussed further here

14 Titelmasterformat Bolt Assessment inside durch ANSYS Klicken (BAIA) bearbeiten Functionality and workflow 14

15 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 WB, open the protocol 15

16 Post Pre Functionality: Bolt Assessment inside ANSYS Graphical User Interface Background calculated forces parameters safety factors 16

17 Titelmasterformat Demo durch Klicken bearbeiten Example from VDI

18 Case Study (Live-Demo) Modified example 2 of VDI 2230 Analysis setup Loads setup Torsion and bending moment Results display Bolt Assessment inside ANSYS on YouTube

19 Titelmasterformat Comparison durch Klicken bearbeiten VDI 2230, Example 1

20 1 st Analysis: 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 MPa at step 3 Note: steps 1 and 2 are reserved for the pretension and embedding

21 Example 1: Results and comparison with reference solution Values VDI 2230:2003 VDI 2230:2014 FEM FMperm Deviation 2003 [%] Deviation 2014 [%] FEM FMmin Deviation 2003 [%] Deviation 2014 [%] FKmin [N] F_Z [N] F_SA_max [N] F_Smax [N] S_F S_D S_p M_A [Nm] Minimal clamping force FK is slightly greater than 1000 N. The sealing function is guaranteed. Loss of preload F_Z due to embedding is correctly evaluated.

22 Example 1: Results and comparison with reference solution Values VDI 2230:2003 VDI 2230:2014 FEM FMperm Deviation 2003 [%] Deviation 2014 [%] FEM FMmin Deviation 2003 [%] Deviation 2014 [%] FKmin [N] F_Z [N] F_SA_max [N] F_Smax [N] S_F S_D S_p M_A [Nm] Bolt additional load F_SA is correctly calculated with the permissible preload. With the minimal preload, the additional bolt load is greater because of a partial separation at the interface

23 Example 1: Results and comparison with reference solution Values VDI 2230:2003 VDI 2230:2014 FEM FMperm Deviation 2003 [%] Deviation 2014 [%] FEM FMmin Deviation 2003 [%] Deviation 2014 [%] FKmin [N] F_Z [N] F_SA_max [N] F_Smax [N] S_F S_D S_p M_A [Nm] The maximal bolt load F_Smax is very precise! This leads to a very good evaluation of the safety factors S_F (yield point) and S_D (fatigue failure). The calculation of S_D with the minimal preload gives a smaller value, according to the higher additional bolt load F_SA caused by the partial separation. Note the different reference values of F_SA and S_D between 2003 and 2014 due to differences in the analytical estimation of the load factor.

24 Example 1: Results and comparison with reference solution Values VDI 2230:2003 VDI 2230:2014 FEM FMperm Deviation 2003 [%] Deviation 2014 [%] FEM FMmin Deviation 2003 [%] Deviation 2014 [%] FKmin [N] F_Z [N] F_SA_max [N] F_Smax [N] S_F S_D S_p M_A [Nm] Safety factor S_p (pressure) 5% smaller than the reference. Why? According to the KISSsoft database, the inner diameter of head bearing area is greater than the hole diameter. Consequently the considered surface, where pressure is applied, is about 5 % smaller than in the reference. Result with FE and BAIA is more precise! Required tightening torque corresponds to the reference solution.

25 Titelmasterformat Comparison durch Klicken bearbeiten VDI 2230, Example 2

26 Example 2: Model Flange connection with 12 screws Lateral loading on bolts Lower part: fixed Upper part: torsion moment Nm Relevant safety factors: S_P: pressure S_G: sliding 26

27 Example 2: Surface Pressure Safety margin against surface pressure (SP) is evaluated with the highest preload (FMperm) The safety factor is for every bolt because of the same preload and same parameters for determining the bearing area The determined safety corresponds to the safety calculated in the VDI 2230 Values VDI 2230:2014 FEM FMperm F_Smax [N] Deviation [%] ApK [mm^2] SP

28 Example 2: Safety factor against sliding The safety against sliding (SG) could be critical when the preload is low. Therefore it should be determined with the smallest pretension force. Results vary between and This variation can be explained by the choice of the nodes at the interface that leads to small differences in the measured reaction forces and moments. The minimal safety margin is measured on the geometry of Bolt_2.

29 Example 2: Safety factor against sliding The torsion moment of the interface around the bolt axis is taken into account to calculate the safety factor against sliding when the type is defined as Standard. This leads to a smaller safety than in the reference solution. Element Nodal Forces in the z- direction helps to see why a torsion moment occurs.

30 Example 2: Safety factor against sliding Now let have a look at the safety against sliding Without Torsion Safety factor is between and These values correspond to the reference values Values VDI 2230:2014 FEM FMmin / bolt min FEM FMmin / bolt max Deviation Deviation min [%] max [%] SG (Standard) SG (Without Torsion)

31 Titelmasterformat Additional information durch Klicken bearbeiten

32 Bolt Assessment inside ANSYS Roadmap v1.1: March 2015 Take the Assembly order into account (preload force < valid mounting preload force) Consider several load cases at a time (fatigue- and max. load cases) v1.2: April 2015 Model class I (no actual bolt modeling, only internal forces at interface), prototype available Customer requests?? v1.3: Q Model Class II (bolt modeling via beams)

33 ANSYS 15 ANSYS 16 Bolt Assessment inside ANSYS is fully compatible with ANSYS 15, ANSYS 16 and onwards

34 Conclusion Reproducible methodology KISSsoft calculation procedure is well known and highly regarded Modeling is based on VDI 2230 Part 2 Additional bolt load are calculated directly within the model Accurate estimation of the force transmission factor and eccentricity Cut efforts to maintain in-house stand-alone solutions Uniform handling and streamlined workflow Parameter input directly from the KISSsoft library Automated parameter generation Automated post processing Export reports via interface Stay current with engineering regulations Proof of functionality through standards is increasingly requested by national and international organizations 34

35 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 handmade calculations 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: Engineering: Sales: Roland Rombach Markus Dutly Bolt Assessment inside ANSYS on YouTube 35