# Presentation: 745530

## STEP-Enabled CAD-CAE Integration

**STEP-Enabled CAD-CAE Integration**
**Stephen Gordon**
**NASA’s STEP for Aerospace Workshop**
**JPL, Pasadena, CA**
**January 17, 2001**

## Outline of Topics 

**CAD-CAE Integration Domains**
**Purpose, Scope, and Scale of Analysis**
**CAD-Centric vs. CAE-Centric Processes**
**Categories of Integration (What is truly ‘Seamless’?)**
**De-Featuring Geometry (Content, Amount of Detail)**
**Geometry ‘Gender Changing’ Needs and Tools**
**“****Simulation-Specific Geometry” vs. CAD Geometry**
**Collaboration (Inter- and Intra-Company)**
**ISO STEP 10303 is not just about Data Exchange**
**AP209 is an Enabler for CAD-CAE Integration**
**AP209 = CAD + CAE + FEM + FEA + PDM  ****(Mnemonic)**
**Backup Slides**

**Outline of Topics**** **

## CAE Functionality 

**Computer-Aided Engineering (CAE) is made up of many varied and diverse functions, depending upon one’s organization and it’s structure.**
**My focus will be on the exchange and sharing of design and engineering data (largely geometry and material information) for use in computational analysis tools, specifically finite element method codes.**
**My purpose today is to define where I see, as an analyst, the potential and growing use for ISO STEP AP209. **
**There is no attempt to slight many other important (non-analytical) engineering functions in the CAD-CAE domain related to the overall design, approval, and life-cycle of the products we create.**

## CAD and CAE  Integration

**It is **_**not**_** simply related to the existence of captured CAD geometry, a perception unwittingly left during product model ‘walk-throughs’.**
**The closer the scale, scope and purpose of an engineering analysis is to the type and detail of the existing CAD product model geometry, the greater the likelihood that a **_**closely-coupled**_**, **_**automated**_**, or even **_**seamless**_** integrated CAD-CAE process can be implemented.**

**CAD and CAE****  ****Integration**

## Scope, Purpose, and Scale

**Small-scale, single part optimization**
**“****Widgets & Gadgets”**

**Large-scale simulation, e.g. vehicle crash-worthiness**

**These may both employ the same software, but with significantly different models!**

## Large-Scale Simulation, Full Vehicle Models

**Large-Scale Simulation, Full Vehicle Models**
**Part of the CAE Domain**

**Such analyses and simulations likely include multi-physics and media-structure interaction**

## CAD and CAE Integration

**We have found that the time and cost to change, re-work, and de-feature CAD geometry can sometimes be greater than that for creating analysis models from readily-generated “idealized” geometry. (Not a popular view in today’s world!)**
**The more abstract, idealized geometry used for analysis is also referred to as “Simulation-Specific” or “FEA-Specific Geometry”.**

**CAD and CAE**** ****Integration**

## Analysis Model Creation (e.g. FEA)

- Geometry

- Derived
- Idealized
- Geometry

- Engr. Anal.
- Model (FEM)

- Simplify
- Idealize
- De-Feature

- Pave
- Mesh
- Discretize

**Analysis Model Creation (e.g. FEA)**

- Change
- Type or
- “Gender”

**Geometry is not always the same!**

**A mechanical engineer, a structural engineer, and a piping engineer may each require different forms of geometry capture.**

## Geometry Representation

**Geometry Representation**

**Same Object ...**

**Multiple/Different Forms of Geometry Capture**

**1D Line (Curve)**

**3D Solid (Volume)**

**2D Surface (Shell)**

## Exploded View - Same Geometry, Different Data Capture

**Exploded View - Same Geometry, Different Data Capture**

**1D Line (Curve)**

**3D Solid (Volume)**

**2D Surface (Shell)**

**“****Gender Changing”**

## Integrated CAD-CAE Process

**Unfortunately, there is often the perception (sometimes from MCAD vendor hype) that engineering analysis is a totally seamless process within CAD.**
**This view can be a disservice to many sectors of business, where solid product models have become the CAD approach of choice, but the wrong geometry for analysis.**
**Fortunately, articles in the literature have recently begun to reflect some of these different views on delivering analysis.**

**Integrated CAD-CAE**** ****Process**

## Recent Articles Show Enlightened Views

**“****Three-Dimensional CAD Design and Analyzing with Shell Elements - A Soluble Contradiction?”,**** ****by M. W. Zehn, H. M. Baumgarten, & P. Wehner, NAFEMS 7th Int’l. Conf., Newport, RI, April 1999**
**“****Don’t Change the Model Till the Simulation Finishes”,**** ****by Paul Kurowski, **_**Machine Design**_**, August 19, 1999**
**“****Rookie Mistakes - Over Reliance on CAD Geometry”,**** ****by Vince Adams, **_**NAFEMS Benchmark**_**, October 1999**
**“****Common Misconceptions About FEA”,**** ****by Vince Adams, **_**ANSYS Solutions**_**, Fall 2000**
**“****Eight Tips for Improving Integration Between CAD and CFD”,**** ****by Scott Gilmore, **_**Desktop Engineering**_**, May 2000**

## “Don’t Change the Model Till the Simulation Finishes”

**“****Don’t Change the Model Till the Simulation Finishes”**
**by Paul Kurowski**
_**Machine Design**_
**August 19, 1999**
**When analysis geometry is not the same as design geometry!**
**“****Simulation-specific geometry”or “FEA-specific geometry”**

## CAD-CAE Integration

**Whether CAD-CAE applications can be closely-integrated and automated depends upon:**
** ****The scale, scope, and purpose of the CAE analysis.**
** ****The nature and type (order, or “gender”) of the captured CAD geometry.**
** ****The amount of detail required for the CAE application.**

**Today’s bottleneck in CAD-CAE integration is **_**not**_** automated mesh (grid) generation, it lies with efficient creation of **_**appropriate**_** simulation-specific geometry.**

## The First “Problem” - Geometry Type

**In general, the most automated CAD-to-CAE processes are for MCAE “same gender” geometry classes, eg. widgets and gadgets, or 3D volumes filled with 3D elasticity tet or hex solid elements; or piping analysis employing 1D geometry.**
**In the structures discipline, our ship product lines most often involve large scale, simplified geometry and analysis models, e.g. large assemblages of stiffened 2D plate/shell surfaces and framework structures.**
**However, enterprise CAD product model geometry capture is fundamentally 3D solid modeling supplemented with 1D “structures” entities.**
**Thin-walled structure is more accurately and efficiently analyzed as plates and shells.**

**The First “Problem” - Geometry Type**

## Creating Engineering Analysis Models

**2D Surfaces**
**2D ‘Cut” Surfaces**
**    ****(or Sections)**
**3D Volumes**

**Beams, Trusses**
**Axisymmetric Shells**
**Stiffened Plates & Shells**
**Plates & Shells**
**Plane Stress / Strain Elasticity**
**Axisymmetric Solids**
**(“Quasi-3D”)**
**3D Solid Elasticity**

**Creating Engineering Analysis Models**

_**Geometry Type**_

_**Analysis Model Type**_

**Same “Gender” Geometry**

## CAD-Centric Approaches

_**Idealized**_
_**Geometry**_

_**Analysis Model Type**_
_**(Eg. FEM)**_

**1D Lines, Curves**
**2D Surfaces**
**2D ‘Cut” Surfaces**
**    ****(or Sections)**
**3D Volumes**

**Beams, Trusses**
**Axisymmetric Shells**
**Stiffened Plates & Shells**
**Plates & Shells**
**Plane Stress/ Strain Elasticity**
**Axisymmetric Solids**
**(“Quasi-3D”)**
**3D Solid Elasticity**

_**Captured CAD**_
_**Geometry**_

**CAD**
**Structures**
**(1D)**

**CAD **
**Solids**
**(3D)**

**CAD-Centric Approaches**

**CAD **
**Surfaces**
**(2D)**

**Can be ‘Seamless’**
**‘****Gender-Changing’ Required**

## CAD-Centric Process with a 3D Solid Product Model

_**Idealized**_
_**Geometry**_

_**Analysis Model Type**_
_**(Eg. FEM)**_

**1D Lines, Curves**
**2D Surfaces**
**2D ‘Cut” Surfaces**
**    ****(or Sections)**
**3D Volumes**

**Beams, Trusses**
**Axisymmetric Shells**
**Stiffened Plates & Shells**
**Plates & Shells**
**Plane Stress/ Strain Elasticity**
**Axisymmetric Solids**
**(“Quasi-3D”)**
**3D Solid Elasticity**

_**Captured CAD**_
_**Geometry**_

**3D Solid Product Model**

**CAD-Centric Process with a 3D Solid Product Model**

**Requires “Gender Changing”**

## The Second “Problem” - Model Content and Amount of Detail

**In general, the captured CAD geometry contains a great deal of detail, necessary for creating drawings and for manufacturing support, but too much detail for most idealized FEA models.**
**Therefore, the idealization portion of FEA requires simplifying the geometry, removing unwanted details which are not commensurate with the scale of the idealized FEA model. Examples include removing small holes, adding or removing fillets, even eliminating whole portions which may be idealized as a rigid mass, or may not be in the analysis at all!**
**This process of simplification is sometimes referred to as “suppressing the details” or “de-featuring” the geometry.**
**For welded structure adding features (weld fillets) to the CAD product model may be required for detailed stress analysis.**

## Welded Thin-Walled Structure with a 3D Solid Product Model

**Welded Thin-Walled Structure with a 3D Solid Product Model**

**Portion of foundation for resilient mounts and shock snubbers**
**Weld material is annotated (e.g.weld symbols), but not explicitly captured as fillets in the product model (as it would be for a machined part)**

- JXXX

**Joint Surface Index**

**Typical de-featuring might include eliminating the small holes but keeping the larger ones.**
**Whereas, a featuring change could be adding weld fillets to avoid stress concentrations or singularities at sharp corners.**

## Categories of CAD-CAE Integration

**Category I -**** ****The CAD Geometry and the Simulation-Specific Geometry are the same (identical).**** This is the truly “seamless” case; there is no change in detail, no de-featuring, and no geometry gender changing required. Analysts and designers use the same (or duplicate copies of the same) geometry.**
**Category II - Existing (available) CAD geometry has the wrong content; it is too detailed and/or of the wrong type to support the scale, scope, and purpose of the required or most appropriate type of analysis.**** Changes are required to add features or remove unnecessary detail from, and/or modify the gender of, the CAD geometry to create Simulation-Specific Geometry amenable to analysis. Automated and semi-automated procedures are required.**
**Category III - Engineering analyses are performed first to define and refine a design concept using idealized geometry prior to establishment of the enterprise (CAD) product model.**** Simulation-Specific Geometry employed for analysis models will require modification and the addition of details and features to support drawings and manufacturing. Automated and semi-automated procedures are desirable.**

**CAD-Centric Process**

**CAE-Centric Process**

## CAD-Centric Approaches

- Engr. Anal.
- Model (FEM)

- Pave
- Mesh
- Discretize

- Captured CAD
- Geometry

- Simulation-
- Specific
- Geometry

- Engr. Anal.
- Model (FEM)

- Simplify
- Idealize
- De-Feature

- Pave
- Mesh
- Discretize

- Change
- Type or
- “Gender”

- Start

**CAD-Centric Approaches**

**Category I**

**Category II**

## A CAE-Centric Approach

**Category III**

- Create CAD
- Geometry

- Simulation-
- Specific
- Geometry

- Engr. Anal.
- Model (FEM)

- Add
- Details &
- Features

- Pave
- Mesh
- Discretize

- Modify
- Type or
- “Gender”

- Start

**More mature or optimized concept prior to CAD geometry capture; designers add detail later for drawing creation, design disclosure, and manufacturing**

## Category I

**Category I**
**Solids Examples**

**Mechanical parts and components**

## 3D Solids & 3D Elasticity Analysis

**TET Meshing**

**HEX Paving**

**Automated model building options are readily available in almost all CAD and CAE tools**

**3D Solids & 3D Elasticity Analysis**

## Categories II & III

**Categories II & III**
**Thin-Walled Structures**
**(Where the product model is solids)**

## EB Example -Automated Mid-Surfacing

**EB Example -Automated Mid-Surfacing**
**CAD-Centric Category II (Solids-to-Shells)**

**Welded Plate Tank Structure - Multiple Brep Manifold Solids**

## Automated Mid-Surfacing

**Solids**

**Mid-Surfaces**

**Trimmed and Adjusted Mid-Surfaces**

**1**

**2**

**Automated Mid-Surfacing**
**Category II (Solids-to-Shells)**

## Category II

**COTS capabilities now exist for automatic creation of mid-surface geometry and shell FEA mesh.**

**Category II**

**1. Thin-walled solid part**

**2. Mid-surface geometry**

**3. Meshed FEA shell model**

## “DECK_ASSY”

**Section of Stiffened Deck Plate**

**“****DECK_ASSY”**
**Assembly with deck plate and replicated (dittoed) tee stiffeners**

**(Example used in Nov. ‘98 PDES demo using PATRAN and COMMANDS)**

## Automatically created mid-surface geometry

**Automatically created mid-surface geometry**

**Solid geometry**

## FEA Idealization #1

**FEA Idealization #1**
**Explicitly Modeled Stiffeners**
**(8-noded shell elements shown)**

**FEA Idealization #2**
**Eccentric Beam Stiffeners**
**(4-noded shell elements with**
**2-noded eccentric beam elements)**

## Collaboration

**You’ve heard a lot at this workshop about inter-company collaboration, multi-tiered supply chains, even world-wide collaboration.**
**Large companies, such as those many of us work for, often have separate groups and departments which requires intra-company cooperation and collaboration.**
**Integration with standards (such as ISO STEP) is a logical way to build an intra-company architecture of sharing between separate design and analysis organizations.**
**Such an in-house, multi-department business process built on standards is easily transitioned into an external collaborative teaming endeavor, when and if that would be prudent.**

## The ISO STEP 10303 Standards are Enablers for Improved Design-Analysis-Construction Processes

**Today’s business enterprises must have access to enterprise-wide PDM information which integrates design, analysis, construction and life-cycle support.**
**AP209 provides a means to more closely integrate design **_**and**_** analysis, by including nominal (CAD) geometry, various idealized CAE geometries, and associated FEM analysis models and results, along with PDM and separate version control.**
**Mnemonic:****   AP209 = CAD + CAE + FEM + FEA + PDM**

## AP209 = CAD + CAE + FEM + FEA + PDM

**What is ISO STEP 10303 AP209?**

**Nominal CAD Geometry**

**Idealized CAE “Simulation-Specific” Geometry**

**Finite Element Models**

**Finite Element Analysis Controls & Results**

**Product Data Management Info**

**Mnemonic  ****(Engineers like equations!)**
**One can use AP209 with any one or more of these pieces, but the real power lies with the assemblage of all these parts.**

## Analysis

**STEP AP209**

**Repository File**

**Archived**

**Design/Analysis**

**AP209**

**Snapshots**

**Design**

**Analysis**

**STEP AP209 File**

**FEA Results**

**FEA Controls**

**FE Models**

**Idealized Geometry**

**Nominal Geometry**

**Design Model - PDM**

**Analysis**

**STEP AP209 File**

**FEA Results**

**FEA Controls**

**FE Models**

**Idealized Geometry**

**Nominal Geometry**

**Design Model - PDM**

**Design**

**The ISO STEP 10303 Standards are not just about data exchange!**
**AP209 captures and integrates design, analysis, and CM/PDM information.**

## Detailed AP209 PDM Concepts

- Part Version

- Design Discipline Product Definition

- Nominal Design Shape

- Idealized Analysis Shape

- Finite Element Analysis Shape

- Analysis

- Analysis Version

- Analysis Design Version Relationship

- Analysis Discipline Product Definition

- Assembly

- Allow Analysis to Revise Independently of Design

**Detailed AP209 PDM Concepts**

## Recommended Practices for AP209

**Recommended Practices for AP209**
**ME007.01.00**
**June 25, 1999**

**Nominal CAD Geometry**

**Idealized CAE Geometry**

**FEA Model**

## CAD-CAE Integration Status

**COTS Vendor Report Card**
**Category I ****	****A ****	****Mature, MCAD for solids good**
**Category II****	****B-,C+****	****Improving, recent mid-surfacing attention**
**Category III****	****D,F****	****Very little for CAE-centric ‘leading design’, need ****	****	****	****shell ‘thickening’ tools, or ‘solids-on-demand’**
**Overall:**
**	****Still too CAD-Centric**
**	****Continued role for traditional FEA pre- and post-processors**
**	****AP209 is ready to support / enable more CAD-CAE integration**
**	****AP209 is more appropriate for CAE than AP203**
**	****Need more vendor support for AP209**

**CAD-CAE Integration**** ****Status**

## Back-up Slides

**PDES & NAFEMS Activities**
**EB’s Prototype AP209**** **

## Working with larger-scale test cases for AP209 coverage

**Working with larger-scale test cases for AP209 coverage**

**PATRAN**
**COMMANDS**

**3847 Nodes**
**6743 Elements**

## Joint PDES & NAFEMS Activity

**NAFEMS Benchmark LE10**
**Thick Plate Pressure**

**NAFEMS Benchmark LE5**
**Z-Section Cantilever**

**Joint PDES & NAFEMS Activity**

**Recasting NAFEMS FEA Benchmarks into AP209 Format**

**NAFEMS Benchmark LE1**
**2D Plane Stress**

## AP209

**AP209**
**Translator**

**AP209**
**Part21**
**File**

**Electric Boat’s AP209 Translator is Interfaced with the COMMANDS FEA System**

**Binary**

**Ascii**

## AP209

**AP209**
**Translator**

**AP209**
**Part21**
**File**

**Ascii**

**COMMANDS**
**Data Base**
**(CDB)**

**Binary**

**EB’s currently implemented prototype AP209 Translator is closely interfaced with EB’s COMMANDS Data Base using binary reads and writes. It was kept separate to enable appending multiple analysis models and results onto a single repository (Part21 file), or selecting and extracting one model with results.**
**Other features (next two slides) were implemented to aid developers as we learned about STEP and Express representation.**

## Slide 45

## Slide 46

## Initial Checkout of AP209 Import to COMMANDS

**Initial Checkout of AP209 Import to COMMANDS**

## Initial Checkout of AP209 Import to COMMANDS

**Initial Checkout of AP209 Import to COMMANDS**

## EB’s AP209 Prototype

**EB’s AP209 Prototype**

**Geometry - Nominal & Idealized**

**FEA Model & Results**

## EB Chart 1

**EB Chart 1**

**EB Chart 2**

**Common Intersection**

**Example = HEX20 Case -Dynamic Version of the MacNeal-Harder Twisted Beam**

## EB Chart 1

**EB Chart 1**

## EB Chart 2

**EB Chart 2**