C. Willberg Structural Mechanics Department, Institute of Composite Structures and Adaptive Systems, German Aerospace Center (DLR), Braunschweig 38108, Germany e-mail: christian.willberg@dlr.de S. Duczek Institute for Mechanics, Otto-von-Guericke-University of Magdeburg, Magdeburg 39106, Germany e-mail: sascha.duczek@ovgu.de J. M. Vivar-Perez Structural Mechanics Department, Institute of Composite Structures and Adaptive Systems, Transfer Center MRO and Cabin Upgrade, German Aerospace Center (DLR), Hamburg 22335, Germany e-mail: juan.vivarperez@dlr.de Z. A. B. Ahmad Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Skudai 81310, Malaysia e-mail: zair@mail.fkm.utm.my Simulation Methods for Guided Wave-Based Structural Health Monitoring: A Review This paper reviews the state-of-the-art in numerical wave propagation analysis. The main focus in that regard is on guided wave-based structural health monitoring (SHM) applications. A brief introduction to SHM and SHM-related problems is given, and vari- ous numerical methods are then discussed and assessed with respect to their capability of simulating guided wave propagation phenomena. A detailed evaluation of the following methods is compiled: (i) analytical methods, (ii) semi-analytical methods, (iii) the local interaction simulation approach (LISA), (iv) finite element methods (FEMs), and (v) mis- cellaneous methods such as mass–spring lattice models (MSLMs), boundary element methods (BEMs), and fictitious domain methods. In the framework of the FEM, both time and frequency domain approaches are covered, and the advantages of using high order shape functions are also examined. [DOI: 10.1115/1.4029539] 1 Introduction The academic interest in SHM-related problems has been stead- ily increasing in recent years. These research activities are directed at (i) improving the structural functionality, (ii) decreas- ing the costs, and (iii) prolonging the effective live span of light- weight designs by means of nondestructive inspections and damage detection techniques. The main motivation is to develop an automatic continuous monitoring system. Such a system should provide ample information on the structural state of the examined area of a component. These data can then be evaluated and be used to increase the service life of the structure and to reduce the operating and maintenance costs (O & M costs). Among others, SHM systems are required to reliably detect and localize damages and, if possible, to assess their nature. From that point further measures can be initiated. Their ultimate purpose is to use the measured data to predict the remaining lifetime of the structure. Robust and reliable SHM systems accordingly enable the design engineer to either create safer structures or to fully exploit the material strength. Accordingly, the O & M costs can be reduced and truly lightweight designs can be created, respectively. In the context of hi-tech industries, such as the aeronautical and civil engineering industries, strict safety requirements have to be enforced. This leads to increasing costs as both highly trained and qualified personnel is needed to ensure their compliance. Typi- cally, airplanes, offshore wind energy plants, or bridges are in the focus of such endeavors. Different kinds of SHM systems have been proposed for these purposes during the past decade [1,2]. Among them, ultrasonic guided wave-based SHM systems are a very promising approach and have found numerous applications recently. From the authors’ point of view, efficient numerical tools are of utmost importance in the context of guided wave propagation analysis in lightweight structures. In order to device a robust and reliable SHM system, the physical mechanisms governing the wave propagation in such structures have to be understood in detail. This necessary knowledge can be acquired by employing advanced numerical simulation approaches to support experimen- tal investigations. Effects of particular interest such as the influ- ence of ambient conditions and prestressing can be investigated straightforwardly with the help of numerical models if physical experiments are too costly or bulky. The simulation results can then be used to design, prepare, and develop experimental techni- ques. Additionally, simulation methods can be deployed to design and to qualify the SHM systems itself. To date, there is a wide range of numerical methods suitable for wave propagation analysis—each with its own advantages and disadvantages. Many of these approaches have been specifically tailored to meet the needs of wave propagation analysis. The authors feel that a review of the current state-of-the-art in compu- tational methods for wave propagation analysis with a special focus on SHM-related problems is called for. The objective of the present article is therefore to provide an exhaustive overview dealing with numerical methods being suitable for high frequency structural dynamics. Since different problems are of interest when investigating guided waves for SHM applications, the present paper will evaluate the performance of each method with respect to the given task. In Sec. 2, typical SHM-related problems are discussed. Thereby the challenging tasks that are encountered when dealing with guided wave-based monitoring are illustrated. These informations are used to derive the requirements which are the basis for assess- ing the different modeling techniques with respect to their ability to resolve the physical behavior of ultrasonic guided waves. Sections 3 and 4 deal with analytical and semi-analytical methods, respectively. Section 5 features finite difference schemes, with a special focus on the LISA. Various FEMs are discussed in Sec. 6 of the paper. Here, both time- and frequency-domain approaches are presented. Additionally, high order shape functions are also discussed. Miscellaneous algorithms that are only sporadically Manuscript received March 7, 2014; final manuscript received December 27, 2014; published online February 4, 2015. Assoc. Editor: Chin An Tan. Applied Mechanics Reviews JANUARY 2015, Vol. 67 / 010803-1 Copyright V C 2015 by ASME Downloaded From: http://appliedmechanicsreviews.asmedigitalcollection.asme.org/ on 02/05/2015 Terms of Use: http://asme.org/terms