AWS A9.5:2013

An American National Standard

Guide for Verification and Validation in Computation Weld Mechanics

AWS A9.5:2013

An American National Standard

Approved by the American National Standards Institute

October 30, 2012

Guide for Verification and Validation in Computation Weld Mechanics

1st Edition

Prepared by the American Welding Society (AWS) A9 Committee on Computerization of Welding Information

Under the Direction of the AWS Technical Activities Committee

Approved by the AWS Board of Directors

Abstract

This standard provides guidelines for assessing the capability and accuracy of computational weld mechanics (CWM) models. This standard also provides general guidance for implementing verification and validation (V&V) of computa- tional models for complex systems in weld mechanics.

International Standard Book Number: 978-0-87171-830-3

American Welding Society 8669 Doral Blvd., Suite 130, Doral, FL 33166

© 2013 by American Welding Society

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Statement on the Use of American Welding Society Standards

All standards (codes, specifications, recommended practices, methods, classifications, and guides) of the American Welding Society (AWS) are voluntary consensus standards that have been developed in accordance with the rules of the American National Standards Institute (ANSI). When AWS American National Standards are either incorporated in, or made part of, documents that are included in federal or state laws and regulations, or the regulations of other governmen- tal bodies, their provisions carry the full legal authority of the statute. In such cases, any changes in those AWS standards must be approved by the governmental body having statutory jurisdiction before they can become a part of those laws and regulations. In all cases, these standards carry the full legal authority of the contract or other document that invokes the AWS standards. Where this contractual relationship exists, changes in or deviations from requirements of an AWS standard must be by agreement between the contracting parties.

AWS American National Standards are developed through a consensus standards development process that brings together volunteers representing varied viewpoints and interests to achieve consensus. While AWS administers the process and establishes rules to promote fairness in the development of consensus, it does not independently test, evaluate, or verify the accuracy of any information or the soundness of any judgments contained in its standards.

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This standard may be superseded by new editions. This standard may also be corrected through publication of amend- ments or errata, or supplemented by publication of addenda. Information on the latest editions of AWS standards includ- ing amendments, errata, and addenda is posted on the AWS web page (www.aws.org). Users should ensure that they have the latest edition, amendments, errata, and addenda.

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AWS does not monitor, police, or enforce compliance with this standard, nor does it have the power to do so.

Official interpretations of any of the technical requirements of this standard may only be obtained by sending a request, in writing, to the appropriate technical committee. Such requests should be addressed to the American Welding Society, Attention: Managing Director, Technical Services Division, 8669 Doral Blvd., Suite 130, Doral, FL 33166 (see Annex C). With regard to technical inquiries made concerning AWS standards, oral opinions on AWS standards may be rendered. These opinions are offered solely as a convenience to users of this standard, and they do not constitute professional advice. Such opinions represent only the personal opinions of the particular individuals giving them. These individuals do not speak on behalf of AWS, nor do these oral opinions constitute official or unofficial opinions or interpretations of AWS. In addition, oral opinions are informal and should not be used as a substitute for an official interpretation.

This standard is subject to revision at any time by the AWS A9 Committee on the Computerization of Welding Information. It must be reviewed every five years, and if not revised, it must be either reaffirmed or withdrawn. Comments (recommendations, additions, or deletions) and any pertinent data that may be of use in improving this standard are required and should be addressed to AWS Headquarters. Such comments will receive careful consideration by the AWS A9 Committee on the Computerization of Welding Information and the author of the comments will be informed of the Committee’s response to the comments. Guests are invited to attend all meetings of the AWS A9 Committee on the Computerization of Welding Information to express their comments verbally. Procedures for appeal of an adverse decision concerning all such comments are provided in the Rules of Operation of the Technical Activities Committee. A copy of these Rules can be obtained from the American Welding Society, 8669 Doral Blvd., Suite 130, Doral, FL 33166.

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Personnel

AWS A9 Committee on the Computerization of Welding Information

S. S. Babu, Chair The Ohio State University

S. N. Borrero, Secretary American Welding Society

F. Brust EMC2

D. J. Dewees The Equity Engineering Group, Incorporated

Z. Feng Oak Ridge National Laboratory

J. A. Fleming Bridgestone Americas

J. Goldak Goldak Technologies Inc.

S. P. Khurana Axon Innovations LLC

P. Michaleris Pennsylvania State University

C. Schwenk BMW Group

G. Sonnenberg Huntington Ingalls Industries, Incorporated

W. Zhang Oak Ridge National Laboratory

Advisors to the AWS A9 Committee on the Computerization of Welding Information

1. J. Buijk Simufact-Americas, LLC

   R. Ganta Westinghouse Electric Company

   J. E. Jones EnergYnTech/N.A. Tech, Inc.

   1. Killian Areva NP, Incorporated

      J. S. Noruk Servo Robot Corporation

      H. Porzner ESI GmbH

   2. F. Rybicki University of Tulsa

2. T. Alexandrov The Ohio State University

F. Arnold SIMULIA Erie Region (Abaqus)

P. Dong University of New Orleans

J. C. Kennedy Engineering Mechanics Corp of Columbus

P. F. Mendez University of Alberta

D. H. Roarty Westinghouse Electric Corporation

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Foreword

This foreword is not part of AWS A9.5:2013, Guide for Verification and Validation in Computation Weld Mechanics, but is included for informational purposes only.

A task group was formed in 2007 under the AWS technical committee structure to investigate the need for computational weld mechanics standards. The task group was reorganized as the AWS A9 Technical Committee on the Computerization of Welding Information and began work in 2008. This is the first standard publication by this committee with more related topics on computational weld mechanics (CWM) planned.

Program managers need assurance that computational models of weld mechanics are sufficiently accurate to support pro- grammatic decisions. As there are multiple acceptable approaches to analyzing the welding process using computational models, a step-by-step Verification and Validation (V&V) process is not practical. However, this guide will provide the CWM community with a common language and conceptual framework to enable communication to non-users of CWM to gain a sense of credibility of the CWM models. This guide will cover a wide range of V&V activities, including simplistic and complex model development, verification of numerical solutions, attributes of validation experiments, accuracy requirements, and quantification of uncertainties. Remaining issues for further development of a V&V protocol are identified.

The AWS A9 Committee plans to pursue the publication of additional standards on computation weld mechanics after this standard. Among those planned are:

Recommended Practice for Describing Thermal Boundary Conditions Recommended Practice for Modeling Thermo-Mechanical Phenomena Recommended Practice for Describing Clamps and Fixtures Recommended Practice for Modeling Microstructure

Recommended Practice for Integrated Models

Recommended Practice for Verification, Uncertainty Estimation, and Sensitivity Recommended Practice for Documentation

Exceptions and Modifications with reference to Materials 1: Steels Exceptions and Modifications with reference to Materials 2: Aluminum Exceptions and Modifications with reference to Fusion Welding—Arc Exceptions and Modifications with reference to Fusion Welding—Laser Exceptions and Modifications with reference to Fusion Welding—Resistance

Exceptions and Modifications with reference to Thin and Thick Plate Geometry Exceptions and Modifications with reference to Large Scale Geometries

It is noteworthy that this document is in alignment with similar activities pursued by other international standards organizations such as the German Institute for Standardization (DIN) and the International Institute of Welding (IIW). For example, the readers of this standard are also requested to refer to DIN SPEC 32534–1, Numerical welding simulation— Execution and documentation—Part 1: Overview, published in 2011.

Annex A lists the in-text citations referenced throughout this document.

Comments and suggestions for the improvement of this standard are welcome. They should be sent to the Secretary, AWS A9 Committee on the Computerization of Welding Information, American Welding Society, 8669 Doral Blvd., Suite 130, Doral, FL 33166.

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Table of Contents

Page No.

Personnel v

Foreword vii

List of Figures x

1. General Requirements 1

   1. Scope 1

   2. Units of Measurement 1

   3. Safety 2

2. Normative References 3

3. Terms and Definitions 3

4. Approach 4

5. Discussion of Computational Weld Modeling Methods and Influences on Analysis 4

   1. Overview 4

   2. Current State-of-the-Art in CWM 6

   3. Key Analysis Inputs 7

   4. Modeling of Heat Transfer During Welding 12

   5. Microstructural Analysis 14

   6. Modeling of Residual Stresses 14

   7. Distortion Prediction 15

6. Validation of Residual Stress and Distortion Models 18

Annex A (Informative)—Cited References 21

Annex B (Informative)—Further Reading 25

Annex C (Informative)—Guidelines for the Preparation of Technical Inquiries 29

List of Figures

Figure Page No.

1. Verification and Validation Activities and Products 2

2. Proposed Methodology to be used for Development of V&V Documents for Different Aspects of Computational Weld Mechanics 5

3. Schematic Illustration of Integrated Computational Weld Mechanics Approach 6

4. Schematic Illustration of Axisymmetry 9

5. Schematic Illustration of Generalized Plane Strain 10

6. Schematic Illustration of Shell Elements 11

7. Hardness Map from a Metallographic Cross Section Made on a Longitudinal

Seam Weld in a High-Strength Pipeline 19

Guide for Verification and Validation in Computation Weld Mechanics

1. General Requirements

   1. Scope. This guide introduces computational weld mechanics methodology through an overview of the current technology. It presents current practices for heat transfer, microstructure, residual stress, and distortion calculations. In addition, a framework for developing verification and validation (V&V) procedures for these models is presented through an example related to the prediction of thermo-mechanical conditions. This document establishes the foundation for future V&V operations to allow for other emerging computational weld mechanics tools.

      1.1.1 Preface. Computational models have been used routinely to great advantage for more than three decades. This technology has been used in many industries to analyze and assist in the design of many items. From architecture to telecommunications, computational analyses (structural to thermal to fluid) have been used to develop objects from the most complex to commonplace everyday items. Numerical analysis has given engineers the capability to make products better, safer, and more functional with less development costs. The growth in the use of computational models shows that commercial industries have confidence in the accuracy of the codes to reduce costs and delivery times while improving quality. In manufacturing, computational solid mechanics (CSM) and computational fluid mechanics (CFM) have been fully adopted; yet, the use of computational weld mechanics (CWM) has not. It has been suggested that the same level of confidence in CWM analyses does not exist due to relative newness of the tools and the lack of experience in their use. In comparison CWM is quite complex involving a coupled phenomena of thermal and nonlinear, transient structural analyses. Information regarding material responses due to thermal inputs, microstructure evolution, and to stresses and strains are needed to perform this type of analysis. It is for these reasons that CWM has emerged about two decades later than CSM.

      The process to develop confidence in computational modeling can be expedited by a process called verification and validation (V&V). Verification testing ensures that a computational code solves the mathematical state equations that describe the phenomenon with sufficient accuracy, robustness, and reliability. Validation tests that a particular computa- tional model predicts a particular event with accuracy and reliability. Such V&V has been developed for computational solid mechanics [1]1 with Figure 1 illustrating a typical methodology used to develop V&V documents for creating mod- els throughout the design process. This approach can be applied to CWM as well. In welding, the relevant phenomenon might be distortion, residual stress, microstructure, or risk of in-service failure. Once through this process, a computa- tional model can be used repeatedly without physical experimentations with confidence that the output will be accurate and reliable.

      Computational models fitted to experimental data before being used are called calibrated models. These types of models cannot be used to predict a particular outcome unless the input values are the same range as the original ‘calibrated’ model. Any changes in the model require the repetition of the calibration process resulting in multiple computational models and experimental tests. As one can easily see, computational approaches that utilize validated codes and verified approaches are much more expansive and usable in multiple cases than their calibrated computational model counterparts.

   2. Units of Measurement. This standard does not require units of measure. Therefore, no equivalents or conversions are contained except when they are cited in examples.

1 See Annex A for in-text citations.