Fracture mechanics introduction

In this book no prior knowledge of plastics is assumed. Chapter 1 provides a brief introduction to the structure of plastics and it provides an insight to the way in which their unique structure affects their performance. There is a resume of the main types of plastics which are available. Chapter 2 deals with the mechanical properties of unreinforced and reinforced plastics under the general heading of deformation. The time dependent behaviour of the materials is introduced and simple design procedures are illustrated. Chapter 3 continues the discussion on properties but concentrates on fracture as caused by creep, fatigue and impact. The concepts of fracture mechanics are also introduced for reinforced and unreinforced plastics. 

The analysis of brittle fracture is the very domain of Linear Elastic Fracture Mechanics (LEFM). A comprehensive introduction to its fundamentals and the validity of its application to polymers has been given by Williams [25] and more recently by Grellmann and Seidler [26]. The fracture criteria and relevant test procedures elaborated by the ESIS technical committee TC4 can be found in [27]. 

E.E. Gdoutos Fracture Mechanics. An Introduction. 2nd edition. 2005 ISBN 1-4020-3267-6... 

Applications of linear elastic fracture mechanics (primarily) to the brittle fracture of solid polymers is discussed by Professor Williams. For those not versed in the theory of fracture mechanics, this paper should serve as an excellent introduction to the subject. The basic theory is developed and several variants are then introduced to deal with weak time dependence in solid polymers. Previously unpublished calculations on failure times and craze growth are presented. Within the framework of brittle fracture mechanics and testing this paper provides for a systematic approach to the faOure of engineering plastics. 

Finally, Chapter 17 is about soft solids, a term that applies to the majority of foods. It gives an introduction into solids rheology and fracture mechanics, but otherwise it makes use of many of the theories treated in earlier chapters to explain properties of the various types of soft solids encountered in foods. 

R. Danzer, "Fracture Mechanics of Ceramics - A Short Introduction", Key Engineering Materials, vol. 333, pp. 77-86, 2007. 

Ductile polymers. For ductile polymers, the linear elastic fracture mechanics do not apply. The introduction of the J-integral by Rice(20) has facilitated the application of ductile fracture mechanics for this polymer system.(17) Without detailed discussion, the ductile fracture energy is used instead of in Eq. (5) ... 

Before considering specific classes of rubber-toughened plastics materials and their properties, it is important to have a basic understanding of the fracture behaviour of rigid polymers and to be aware of the methods of fracture mechanics which are used to evaluate toughness. The following two sections provide brief introductions to these topics. 

In Table II, the ultimate stresses of materials calculated from their Young s modulus are compared with the measured values of F ax- It is apparent that the measured values for the failure stress are far below the theoretical values. The situation is worse than it looks, however, because the measured values are partially due to viscoelastic dissipation of the applied stress, while the calculated values assume no such viscoelastic dissipation. Needless to say, this indicates that the theoretical values are far in excess of the measured values. An explanation of these discrepancies is presented in the next section, which gives a short introduction to fracture mechanics. 

Stress cycling tests in imnotched samples do not readily distinguish between crack initiation and crack propagation. Further progress requires a similar approach to that adopted in fracture studies, namely the introduction of very sharp initial cracks in order to examine crack propagation utilizing fracture mechanics concepts. 

Rolf Steinbuch studied Mathematics and Physics at the University of Ulm. After 5 years with Sie-mens/KWU (now AREVA), where he was doing research in the field of fracture mechanics, he moved to Daimler, where he was responsible for nonlinear studies in the field of safety and reliability analysis. Since 1993 he works at Reutlingen University. He teaches mechanics, numerics, and simulation. His research fields cover optimization, acoustics, and nonlinear problems. As consultant he supports the introduction of CAE-tools to the industry. He has been publishing some books and many papers on simulation, acoustics, and optimisation. As visiting Professor he spent time at different universities in Europe and Africa. 

Kaplan (1961) attempted to apply the fracture mechanics approach to cement-based materials. His works were continued by many others, but already Kesler et al. (1971) correctly indicated that LEFM cannot be directly applied to concrete elements. A very comprehensive review of these works and the problems related to the introduction of fracture mechanics to these materials was published by Mindess (1983), and by other authors. 

D. Gross and T. Seelig Fracture Mechanics with an Introduction to Micromechanics. Springer, Berlin, 2006. 

Williams, J.C. (2001). Introduction to elastic-plastic fracture mechanics. In Fracture mechanics testing methods for polymers, adheswes and composites, Moore, D.R. Pavan, A. Williams J.C., (Eds.), pp 119-122, Elsevier Science Ltd. and ESIS, ISBN 0 08 043689 7, The Netherlands. 

WOL Type T specimen is wedge bolt-loaded as shown in Fig. 15.19. Type X specimen is no longer used. The development process continued till the introduction of the third type of specimen worldwide known as the Compact C(T) specimen of Fig. A.9c. Today the C(T) type specimen is the most used one in fracture mechanics applications. However, WOL Type T specimen is still used in see applications for measuring the stress intensity threshold Kj -cc (see Sect. 15.5). The h a/w) and V(a/w) functions for the calculation of the corresponding K and A for types WOL-T and C(T) specimens are listed in the following [6]. The symbols refer to Fig. A.9b and c for types WOL-T and C(T) specimens, respectively. A represents the crack mouth opening displacement (CMOD), i.e., the displacement measured at the notch opening on the specimen surface, as shown in Fig. A.9. 

FRACTURE MECHANICS OF ADHESIVE JOINTS 7.6 EFFECT OF RATE AND TEMPERATURE 7.6.1 Introduction... 

Liu, A. R, Mechanics and Mechanisms of Fracture An Introduction, ASM International Materials Park, OH, 2005. 

The tensile strength of concrete is about 5 to 10 per cent of its compressive strength. Therefore, concrete is a material most suitable to withstand compressive stresses rather than tensile stresses. Nevertheless, interest in the tensile behaviour of concrete increases. The most important reason for this increasing interest in the tensile properties of concrete is the introduction of fracture mechanics in the field of concrete structures and the increasing importance of numerical analyses. 

Williams, J. G., Fracture Mechanics of Polymers , Horwood, New York, 1984. An introduction to the phenomenon of fracture, called fracture mechanics, for polymers and how it is applied to a range of materials and problems. 

In view of the technical relevance the impact resistance of polymers has been intensively investigated. The cited references [88—103] may serve as an introduction into the large body of literature. Vincent [88] and Bucknall et al. [89] give a general survey of the impact testing of polymers. Other references concern the molecular aspects [88-96], instrumentation [97—100], and particle impact [101—103]. The extensive literature on the fracture mechanical analysis of impact bending tests will be referenced in Chapter 9. 

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