the automatic creation and optimisation of structural fixings using hyperworks

7/29/2019 The Automatic Creation and Optimisation of Structural Fixings using HyperWorks

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Altair Engineering 2013 1

The Automatic Creation and Optimisation of StructuralFixings using HyperWorks

Darren AshbyGroup Leader Model BuildAbbey Road, Whitley, Coventry CV3 [email protected]

Matt CarrollAltair ProductDesignImperial House, Holly Walk, Leamington Spa, CV32 [email protected]

Abstract

Body in White (BIW) joining assumptions form an important part of BIW development whereimprovements in structural and manufacturing efficiency can often be realised throughcarefully engineered joining. During the early stages of BIW development where theavailability of detailed CAD data may be limited, the joining of a Finite Element BIW modelcan be a time consuming process, often leading to an incorrectly constrained model as aresult of not taking into consideration design and manufacturing rules. With an ever-

increasing demand to reduce model build timings the availability of reliable connection databecomes an important factor in delivering quicker and more accurate models.

This paper describes the use of a concept joining tool, developed in collaboration with AltairProductDesign using HyperWorks, to take a Finite Element BIW with no associated joiningdata and automatically assemble the structure in a manner that replicates the manufacturingprocess as well as applying logic to the joint definition. In addition to outputting a validatedFE and CAD-ready joining file, the tool also has the capability to optimise the number, andlocation of joints in the structure through a process of ranking each connections contributionto CAE attribute performance and redistribute the joining entities in order to maximiseefficiency.

Keywords: Body in White, Finite Element, HyperWorks

1.0 Introduction

During 2012 Altair ProductDesign developed a customised HyperWorks joining tool forJaguar Land Rover (JLR) to provide the ability to automatically identify and createmanufacturing feasible joint locations in a Finite Element Body structure. In addition thejoining tool is able to optimise the number and location of connections in a body through aprocess of extracting, manipulating and ranking attribute specific data.

With the current joint creation process, simplistically shown in Figure 1, the time taken forCAE to generate valid connection points varies depending on whether a full or partial joining

of a structure is required. The process can often be iterative with reviews taking place with
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Altair Engineering 2013 The Automatic Creation and Optimisation of Structural Fixings using HyperWorks 2

design or manufacturing to validate the CAE assumptions, however, delays can occur wherereviews need to be scheduled.

Figure1 : Current CAE Join t Creation Proc ess

By using the joining tool the joint creation process can be shortened by up-to 60% due to thecreation of feasible connection points that require less reviews as a result of following thedesign and manufacturing rules. Figure 2 shows the revised process and the addition of anoptimisation loop which has now been included.

Figure2 : Revised CAE Jo int Creation Pro cess

The joining tool runs from within the existing HyperWorks software utilising the processmanager where the user follows a step by step process in the joining of a body structure.The process itself can be broken down into four principal stages, shown in Figure 3, and willbe described in more detail in the following sections.


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Figure3 : Principal Stages of th e Joining Too l

2.0 Joining Tool

2.1 Manufacturing Data

To enable the automatic joining of a BIW structure the tool requires a number of facilityspecific inputs.

Bill of Materials

Rivet/Spotweld Pitch Library

Gun/Frame Surface data

Manufacturing Sequence (section 2.2)

The Bill of Materials (Figure 4) provides the tool with key information regarding materialproperties, gauge, component type (cast/sheet/extrusion) and the body structure partnumbers.

Figure4 : Bil l of Materials

The Rivet/Spotweld pitch library defines the joining pitch rules for material composition,individual panel gauges and panel stacks. Figure 5 shows an example of a pitch database.

Figure5 : Pitch Database


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The Spotweld or Rivet gun and frame surface data (Figure 6) is required for clashverification during the joining process. The surface data is converted from the supplied CADinto a HyperMesh format file to enable the tool to align the gun/frame.

Figure6 : Manufacturing Gun Sur faces

2.2 Manufacturing Sequence

The manufacturing sequence is a critical aspect of the joining process and describes theassembly sequence of the body structure through the definition of structured sub-assembliesand their integration into assemblies and ultimately the BIW. The tool can also assess anynumber, or combination of manufacturing sequences, as a means of providing valuableupfront assessments during the planning of manufacturing facilities.

Another powerful feature of the joining tool is the ability to define specific manufacturingfacilities at a given sequence, for example, certain joining guns. The tool mimics themanufacturing sequences to enable it to understand when and where a joint can be made inthe process.

Figure 7 shows an example of a manufacturing sequence where a number of individualparts are pulled together to form a higher level front member assembly. A number ofcompleted assemblies are then pulled together to form the under frame complete assembly.A similar sequence would exist to create the upper structure and roof assemblies beforefinally coming together to produce a complete body structure.


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Figure7 : Example Assembly Sequence

2.3 Processing CAD Geometry

With all of the standard inputs having been defined the tool will absorb all the geometric andproperty data from the FE model for subsequent joining checks and placement. The toolautomatically detects geometric features suitable for joining, including recognition of flangesand matched surfaces. In addition to this the tool identifies holes in panels that may be usedfor joining gun access or fixing bolts.

Figure 8 shows examples of the geometric features that are identified by the tool, on the leftareas that would be detected as flanges and on the right, fixing holes and a gun access hole.

Figure8 : Examp les of Geometric Features Recognised by the Tool

2.4 Joint Creation

When all of the input data has been processed the joining of the structure can take place. Abenefit of the tool is that it can be left to run overnight providing further time savings. Shownin Figure 9 is an image of an understructure assembly automatically joined by the tool whichtook around 3 hours to complete including checks. During benchmarking of the tool, thenumber of virtual connections created was typically within 2% of the manufacturing intent,and located at comparable positions. To join an entire body structure will take around 6hours to complete.


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Figure9 : Automatical ly Joined Under Structur e Assembly

Looking more closely at some of the detail on the joined structure, the tool creates bothACM2 connections as well as CAD Rivet buttons, shown in Figure 10, which can beimported into CATIA for package checks and to identify proposed locations that the CAE toolhas generated. The tool will also check for symmetry and where found will create identicalconnection points on both hands of the structure to maintain joining quality.

Figure10 : Examp le of CAD Rivet Button Representat ion

Also shown in Figure 11 is an example where the tool has correctly recognised engineeredgaps on the structure and created connections either side (ACM2)


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Figure11 : Examp le of Engineered Gap Recogn it ion

There will be instances where the tool is unable to produce a connection automatically, for

example, failing to meet one or more of the quality criteria, and in such cases the tool hasthe ability to create connections in a manual mode. Where a location is selected the tool willcarry out the same quality checks as it would in automatic mode, however, where a failureoccurs this can be overruled to force the connection. Figure 11 shows the tool in manualmode with the quality checks displayed during the creation process. The display of thequality check can also be a useful guide as to why a connection may not have been madeoriginally.

Figure12 : Joining Tool Manual Mode with Qual i ty Check

2.5 Feedback

With the joining completed the tool produces a database containing information that will beof value for design and manufacturing. Figure 13 shows two examples of the type ofinformation produced by the tool, the first is a table identifying the number of unique stacks

and the associated number of connections points; in addition the number of 2T and 3Tconnections would be output (not shown). The second table identifies all the possible


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rivet/die combinations and the number of connections that would have been possible witheach. One of the benefits of this being to identify the number of connections that eachcombination could create, useful in determining the most efficient options for manufacturingfacility planning.

Figure13 : Manufacturing Feedback

3.0 Pitch Optimisation

As part of the Concept Joining Tool developed for JLR, an additional suite of tools has beentailored, again utilising the process manager functionality in HyperWorks, to post processNVH, durability and crash attribute performance data, and to rank each joining entity for itsprimary function requirements. The ranked data can then be used to adjust joining pitch andplacement which is later fed back into the auto Joining tool, with a view to not only reducingthe joining count but also assist in optimising manufacturing facilities. As the tool usesmultiple sources of attribute data, the models are correlated back to a master Bill ofMaterials and connection file.

3.1 NVH Data Processing

To enable large amounts of frequency response data to be processed a colour map feature,shown in Figure 14, has been produced that visualises all the load case and response

information. Where the colour is blue, the response is below the guideline, as it turns throughto red it has exceeded the target. The tool scans along the frequency domain looking forcommon issues, identified by the red vertical lines. For a chosen specific issue the strainenergy can be extracted at each joint which the tool then normalises to provide a failurefactor.


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Figure14 : Colour Map Showing Loadcase and Respon se Information

3.2 Durability Data Processing

In a similar manner to the NVH data, the durability results are processed and tabulated in amanner that allows the forces at each joint to be compared across different fatigue orstrength loadcases. The calculated forces can then be compared against an allowablesdatabase to provide a failure factor. Where the score is greater than 1 then the allowable hasbeen exceeded and the joint could fail. Figure 15 shows an example of how the output fromthe durability data extraction would be presented with the failure factors also shown.

Figure15 : Tabulated Output Data from the Durabi l i ty Extract ion

3.3 Crash Data Processing

The crash attribute data is treated differently to the NVH and durability attributes in that thefailure factor data is output directly from the simulation results. The failure factor is a scorebetween 0 and 1 describing the amount of damage a joint incurs during the history of theevent, so for each crash loadcase the tool receives a text file containing the failure factor fora given joint.

The tool can handle any number of crash modes and where for example an OffsetImpacthas been analysed the loading will inevitably be higher on the side the impact occurred. In all


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cases the tool will correlate the XYZ co-ordinates of the joint locations on both sides of thestructure and apply the highest failure factor value measured for each matched pair(enforced symmetry).3.4 Multi Attribute Summary

With the process of collating, normalising and ranking of data from NVH, durability and crash

analysis completed, the data produced can then be used to manually interrogate joints toview their importance against each attribute. The data is displayed in the form of a table,shown in Figure 16, which provides the user with information such as joint family, number ofjoints in the run, spline length and average pitch.

Figure16 : Table Showing Cross Attr ib ute Scores and Asso ciated Conn ections

3.4 Attribute Export

Having interrogated the joint information, the final step of the process is the generation of anattribute database file that captures all the key pieces of cross attribute data for each jointlocation that is then referenced when the auto joiner is re-run. When the tool generatessplines as part of its normal joining process, it consults the cross attribute data for a locationthat could be assigned to the spline. The tool calculates what the minimum number of jointson the spline could be to satisfy the attribute requirements as well as adhering to the

manufacturing standards.

In the example shown in Figure 17, the joining tool has consulted the cross attribute data,which has driven the need to add an additional connection. In the example shown theattribute driven pitch is shown in green versus the original pitch shown in red.


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Figure17 : Joining Tool Autom atic Joiner and Redistr ibuted Connection s

4.0 ConclusionsThis paper has described the process required to automatically create and optimise designand manufacturing feasible connections using customised HyperWorks templates. Thejoining tool has provided the ability to join a Finite Element model following a manufacturingprocess and through recognition of appropriate geometric features. The tool generates bothCAE and CAD compatible data which can be used by design and manufacturing teams forconfirmation of connection locations as well as facility planning. The tool is able to extractand manage large amounts of multi-attribute data to provide feedback on joint criticality andinfluence joining decisions. As a result of this optimisation loops can be incorporated into thedesign phases.

The benefits that the tool provides are the quicker creation of joining assumptions to a CAEmodel which can produce time savings of up-to 60% during model joining. It provides betteralignment between CAE, design and manufacturing as well as reduced manufacturingactivity through fewer joining assumption reviews. Finally there is the potential for reductionsin capital expenditure through better utilisation and minimising of joining facilities.

the automatic creation and optimisation of structural fixings using hyperworks

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