2014 hbm ncode products user group meeting · 2017-05-02 · 2014 hbm ncode products user group...

2014 HBM nCode Products User Group Meeting

May 14-15, 2014 2014 HBM nCode Products User Group Meeting Livonia, MI (USA)

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Including Bolt Pre-tension Effects in DurabilityAnalyses

Daniel Ramos C.Chassis CAE, Ford Motor Company


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• Ford Motor Company is a multinational automaker whose headquarters are located in Dearborn, MI. The company was founded by Henry Ford and incorporated on 1903.

• Ford has important manufacturing facilities in the United States, Canada, Mexico, China, the United Kingdom, Germany, Turkey, Brazil, Argentina, Australia and South Africa.

• The Chassis CAE group from FoM currently works in the development and analysis of truck frames, brakes, suspension among other components. nCode has been used for more than 5 years in this group for durability analyses.

Intro to Ford Motor Company – Chassis CAE


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• As an initiative to improve confidence in durability analyses for sheet-metal brackets, several conditions are being modeled to reproduce durability tests. Bolt pre-tension effects were modeled to include their contribution to fatigue.

• Variations of more than 10% in fatigue results show a major contribution of bolt tightening effects. The major effects of bolt tightening include modal shape change and initial stresses at the surrounding areas.

• More than 30 of these brackets are found in each vehicle, which need to be optimized while making sure that they reach the durability targets.

Challenge/project scope


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• From physical testing, the effect of bolt tightening in natural frequencies was demonstrated using several torque conditions using a sheet metal bar to find a simple way to evaluate Gain vs. Frequency.

From tightening to fatigue calculation

0.010.020.030.040.050.060.070.080.0

80.0 85.0 90.0 95.0100.0105.0110.0115.0120.0

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Frequency [Hz]

Gain vs. Frequency

5 Lb Ft10 Lb Ft15 Lb Ft20 Lb Ft25 Lb Ft


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• From physical testing, the effect of bolt tightening in natural frequencies was demonstrated using several torque conditions.

• The CAE analyses were then conducted using HBM nCode for E/E component brackets.


Modal shape changecan be appreciated in detail in this run.

170.75 [Hz] 161.32 [Hz]

169.83 [Hz] 147.61 [Hz]


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• Displacements shift to different areas because of bolt tightening, thus giving different stress distributions and magnitudes, which will affect the durability results.

• The combination of different torques can have a greater effect in damage than having unified torques with higher values in some cases because of the alterations in modal shapes.


236.38 [Hz] 234.02 [Hz]

235.48 [Hz] 196.46 [Hz]


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• The effects of bolt tightening were then demonstrated with a Taguchi DOE running 16 experiments , which consider 4 bolts (factors) with 4 different torques (levels).


TORQUE - TAGUCHI RUNS TABLEbolt1 bolt 2 bolt 3 bolt 4 run #80 80 80 80 180 60 60 60 280 40 40 40 380 20 20 20 460 80 60 40 560 60 80 20 660 40 20 80 760 20 40 60 840 80 40 20 940 60 20 40 1040 40 80 60 1140 20 60 80 1220 80 20 60 1320 60 40 80 1420 40 60 20 1520 20 80 40 16


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• As seen previously from the modal analysis, run #14 has the major effect in terms of displacement due to a combination of different torques in the bolts that attach the module to the bracket.

From tightening to fatigue calculationZ

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• Original torque FRF is represented by dotted blue curve, while run #14 FRF is represented by the light green curve.

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• The analysis uses HBM nCode because of its capability to handle results from static and dynamic analyses from different solvers, while providing the analyst the opportunity to set a number of parameters that best fit the analysis needs.

• The analysis is divided into 3 stages: Abaqus dynamic analysis, conversion of the results from Abaqus, Durability analysis using nCode.

Durability analysis

1 – Run an initial static step in Abaqus which pre-tensions bar elements.2 – Modal analysis with pre-tensioned elements as an initial condition.3 – Modal transient analysis is executed with an acceleration signal. Generalized displacements (a.k.a modal participation factors) are extracted as a result and written to .odb file. 1 – Using the provided python script, generalized displacements are extracted from .odb and written to a file compatible with nCode. 2 – With a pre-set nCode flow, the newly created file is used to generate a time-series file to be used as input for EN-Analysis glyph.1 – EN-Analysis is set-up in nCode to use modal analysis results as an FE Input and the recently created signal as Time Series Input.2 – The EN-Analysis is run, which at the end displays the results and writes them to an output file.

nCod

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Pyt

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Aba

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Durability analysis

• With the correct Time Series, nCode runs a durability analysisusing the corrections established in corporate procedures for theseanalyses (Neuber, SWT, etc).


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Durability analysisNo Torque Effect26.44 life cycles

Original Torque23.98 life cycles

Taguchi #322.99 life cycles

Taguchi #622.89 life cycles

Taguchi #1412.80 life cycles • Bolt tightening effects

can finally be appreciatedin the durability results.

• As seen in the bottom-right image, the stress distribution change seenin the modal analysis has a major effect in durability results.


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Results Summary

• Run #14 shows one of the lowest first natural frequencies and the lowest second frequency, as well as the biggest displacement in the FRF analysis. This is the cause for this run for having the lowest life in the durability analysis (12.8 life cycles).

• The torques used for the DOE are only defined to demonstrate the effect of different bolt pre-tensions in a model.

TORQUE - TAGUCHI RUNS TABLE - MODAL & FRF ANALYSES RESULTS

bolt1 bolt 2 bolt 3 bolt 4 run # 1st Natural Freq [Hz]

2nd Natural Freq [Hz]

Max. FRF Displacement

[mm]80 80 80 80 1 170.57 236.09 0.072980 60 60 60 2 169.93 235.94 0.073580 40 40 40 3 161.32 234.02 0.077980 20 20 20 4 160.37 233.90 0.077860 80 60 40 5 170.45 235.65 0.073160 60 80 20 6 169.83 235.48 0.073660 40 20 80 7 161.43 234.21 0.077960 20 40 60 8 160.50 234.06 0.077840 80 40 20 9 147.95 200.55 0.098640 60 20 40 10 150.93 202.21 0.098040 40 80 60 11 149.62 202.71 0.098240 20 60 80 12 148.99 201.95 0.099320 80 20 60 13 148.21 196.74 0.101120 60 40 80 14 147.61 196.46 0.102320 40 60 20 15 147.36 201.44 0.099320 20 80 40 16 146.36 200.40 0.1014


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Results Summary

• From the DOE analysis, the Main Effects Plot shows that in this particular bracket, Bolt #1 has the major effect in the FRF displacement, which has a direct relationship with Fatigue Results.

• The Interactions Plot shows no interaction between torques at each of the 4 bolts.

4321

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0.08

4321

4321

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Main Effects Plot for MeansData Means

4321 4321 4321

0.104

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0.104

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0.104

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Interaction Plot for YData Means


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• By changing the attachment elements from rigids to bolts with pre-tension, modal shape changes.

• Including contact between bracket to module and bracket to base, initial stresses are taken as initial conditions that affect durability.

• Since contact needs to be modeled, Abaqus was used to solvemodal analysis and modal transient. Python and nCode are used totransform the odb file to Time Series. Durability analysis is finallyset-up in nCode to include the proper corrections.

• Fatigue Life has shown a considerable variation when consideringthe proposed modeling conditions.

• Physical testing was carried out in a simple bar to demonstrateeffect of bolt tightening in natural frecuencies. Physical testing forbracket still needs to be carried out to compare CAE results.

Analysis procedure conclusions


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• nCode is used as a primary tool for fatigue calculations for sheet metal brackets, which gives users the opportunity to set a number of parameters that make it a flexible tool that can help find better correlation.

• nCode with its capability to take results from different FE solvers, gives engineers the opportunity to comply with requirements set inside the company to handle FE dynamic analyses while giving the chance to adjust parameters specific to a given durability analysis.

• By finding a better representation of physical tests in CAE, nCodehas given the opportunity to reduce costs and development time of sheet metal brackets.

Using nCode GlyphWorks for Durability Analyses


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2014 HBM nCode Products User Group Meeting

Thank you!

Daniel Ramos C.Chassis CAE, Ford Motor CompanyTel. 55 1103 [email protected]

Adrián Jordán C.Chassis CAE, Ford Motor CompanyTel. 55 1103 [email protected]

Juan Carlos Martínes L.Chassis CAE, Ford Motor CompanyTel. 55 1103 [email protected]


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2014 hbm ncode products user group meeting · 2017-05-02 · 2014 hbm ncode products user group...

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