Fracture toughness

About: Fracture toughness is a research topic. Over the lifetime, 39642 publications have been published within this topic receiving 854338 citations.

Ductile Fracture of Metals

Abstract: An account of the recent developments in research into ductile fracture in metals and alloys. Aspects covered include localized fracture at the root of notches and sharp cracks, and fracture in bulk plastic-deformation processes of the metal and metal forming type. Also discusses various theoretical

Kinking of A Crack Out of AN Interface

Abstract: Kinking of a plane strain crack out of the interface between two dissimilar isotropic elastic solids is analyzed. The focus is on the initiation of kinking and thus the segment of the crack leaving the interface is imagined to be short compared to the segment in the interface. Accordingly, the analysis provides the stress intensity factors and energy release rate of the kinked crack in terms of the corresponding quantities for the interface crack prior to kinking. Roughly speaking, the energy release rate is enhanced if the crack heads into the more compliant material and is diminished if it kinks into the stiff material. The results suggest a tendency for a crack to be trapped in the interface irrespective of the loading when the compliant material is tough and the stiff material is at least as tough as the interface.

Structural basis for the fracture toughness of the shell of the conch Strombus gigas

Abstract: Natural composite materials are renowned for their mechanical strength and toughness: despite being highly mineralized, with the organic component constituting not more than a few per cent of the composite material, the fracture toughness exceeds that of single crystals of the pure mineral by two to three orders of magnitude The judicious placement of the organic matrix, relative to the mineral phase, and the hierarchical structural architecture extending over several distinct length scales both play crucial roles in the mechanical response of natural composites to external loads Here we use transmission electron microscopy studies and beam bending experiments to show that the resistance of the shell of the conch Strombus gigas to catastrophic fracture can be understood quantitatively by invoking two energy-dissipating mechanisms: multiple microcracking in the outer layers at low mechanical loads, and crack bridging in the shell's tougher middle layers at higher loads Both mechanisms are intimately associated with the so-called crossed lamellar microarchitecture of the shell, which provides for 'channel' cracking in the outer layers and uncracked structural features that bridge crack surfaces, thereby significantly increasing the work of fracture, and hence the toughness, of the material Despite a high mineral content of about 99% (by volume) of aragonite, the shell of Strombus gigas can thus be considered a 'ceramic plywood' and can guide the biomimetic design of tough, lightweight structures

Ceramics: Mechanical Properties, Failure Behaviour, Materials Selection

Abstract: 1 Overview and Basic Properties.- 1.1 General Behaviour.- 1.2 Overview of Ceramic Materials.- 1.3 Fields of Application.- 2 Physical Properties.- 2.1 Thermal Expansion Coefficient.- 2.2 Thermal Conductivity.- 2.3 Electrical Conductivity.- 2.4 Specific Heat.- 2.5 Density.- 2.6 Elastic Constants.- 3 Fracture Mechanics.- 3.1 Fundamentals.- 3.1.1 Linear-Elastic Fracture Mechanics.- 3.1.2 Rising Crack Growth Resistance.- 3.2 Experimental Methods for the Determination of the Mode-I Fracture Toughness KIc.- 3.2.1 The Edge-Cracked Bending Bar.- 3.2.2 Specimens with Chevron Notches.- 3.2.3 Specimen with Knoop Indentation Crack.- 3.2.4 Vickers Indentation Cracks.- 3.2.5 Comparison of Different Specimen Types.- 3.3 Experimental Methods for the Determination of Mode-II and Mixed-Mode Fracture Toughness.- 3.3.1 Bending Test with Bars Containing Oblique Notches.- 3.3.2 Three-Point Bending Test with an Eccentric Notch.- 3.3.3 The Asymmetric Four-Point Bending Test.- 3.3.4 Diametral Compression Test.- 3.3.5 Surface Haws in Mixed-Mode Loading.- 3.4 Mixed-Mode Criteria and Experimental Results.- 4 R-Curve Behaviour.- 4.1 Experimental Observation.- 4.1.1 Results for Different Materials.- 4.1.2 Effect of Geometry and Loading Conditions.- 4.1.3 Work-of-Fracture.- 4.1.4 Comparison of Macro- and Microcracks.- 4.2 Determination of R-Curves.- 4.2.1 Specimens with Macrocracks.- 4.2.2 Specimens with Vickers Indentations.- 4.3 Reasons for R-Curve Behaviour.- 4.4 Influence of R-Curves on Strength.- 4.5 Computation of R-Curves.- 4.5.1 Fracture Mechanical Treatment of Bridging Stresses.- 4.5.2 Phase-Transformation Zone and Shielding Stress Intensity Factor.- 4.6 Determination of Bridging Stresses from Crack Profiles.- 5 Subcritical Crack Growth.- 5.1 Basic Relations.- 5.2 Computation of Lifetimes.- 5.2.1 Lifetimes Under Arbitrary Loading History.- 5.2.2 Lifetimes Under Static Load.- 5.2.3 Lifetimes Under Cyclic Load.- 5.3 Methods of Determining Subcritical Crack Growth.- 5.3.1 Double-Torsion Test.- 5.3.2 The Double-Cantilever-Beam Specimen.- 5.3.3 Crack Growth Data from Dynamic Bending Tests.- 5.3.4 Crack Growth Data from Static Bending Tests.- 5.3.5 Lifetime Prediction.- 5.4 Influence of R-Curve Behaviour on Subcritical Crack Growth.- 5.4.1 General Influence.- 5.4.2 Tests with Macroscopic Cracks.- 5.4.3 R-Curves for Subcritical Crack Extension.- 5.4.4 Lifetimes for Natural Cracks.- 5.5 Some Theoretical Considerations on Subcritical Crack Growth.- 6 Cyclic Fatigue.- 6.1 Representation of Cyclic Fatigue Results.- 6.2 Proof of a Cyclic Effect.- 6.3 Methods for the Determination of da/dN-?K Curves.- 6.4 Effect of R-Ratio.- 6.5 Theoretical Considerations.- 6.5.1 Effect of Crack Surface Interactions.- 6.5.2 Effect of Glass Phase Content.- 6.5.3 Effect of Phase Transformation Zones.- 6.6 Differences Between Micro- and Macrocracks.- 7 Determination of Strength.- 7.1 Measurement of Tensile Strength.- 7.1.1 The Tensile Test.- 7.1.2 The Bending Test.- 7.1.3 Test of Pipe Sections.- 7.2 Measurement of Compressive Strength.- 7.2.1 Compression Tests with Cylindrical Specimens.- 7.2.2 Compression Test on Hollow Cylinders.- 7.2.3 Results of Compression Tests.- 8 Scatter of Mechanical Properties.- 8.1 Principal Behaviour.- 8.2 Determination of Weibull Parameters.- 8.3 The Size Effect.- 8.4 Scatter of Lifetimes.- 8.5 Some Specific Problems.- 8.5.1 Three-Parameter Weibull Distribution.- 8.5.2 Multiple Flaw Population.- 8.5.3 Influence of the R-Curve.- 9 Proof Test Procedure.- 9.1 Proof Test Without Subcritical Crack Growth.- 9.2 Proof Test Including Subcritical Crack Growth.- 9.3 Problems in Proof Tests.- 9.3.1 Subcritical Crack Growth During the Proof Test.- 9.3.2 Different Flaw Population at High Temperatures.- 9.3.3 Simulation of the Service Conditions.- 10 Multiaxial Failure Criteria.- 10.1 Representation in Multiaxiality Diagrams.- 10.2 Global Multiaxiality Criteria.- 10.3 Defect Models.- 10.3.1 Cylindrical Pore.- 10.3.2 Spherical Pore.- 10.3.3 Ellipsoidal Pore.- 10.3.4 Circular Cracks.- 10.3.5 Conclusions from Defect Models.- 10.3.6 Statistical Treatment.- 10.3.7 Lifetime.- 10.4 Experimental Methods.- 10.4.1 The Ring-on-Ring Test.- 10.4.2 Ball-on-Ring Test.- 10.4.3 Brazilian-Disk Test.- 10.4.4 Tests with Tubes.- 10.4.5 Triaxial Stress States.- 10.5 Experimental Results.- 11 Thermal Shock Behaviour.- 11.1 Thermal Stresses.- 11.2 Measurement of Thermal Shock Sensitivity.- 11.3 Fracture Mechanical Treatment of Thermal Shock.- 11.4 Thermal Shock Parameters.- 11.5 Size Effect in Thermal Shock.- 11.6 Thermal Fatigue.- 12 High-Temperature Behaviour.- 12.1 Creep Deformation.- 12.1.1 Creep Relations for Tensile Tests.- 12.1.2 Differences in Tensile and Compression Creep.- 12.1.3 Creep Under Variable Stresses.- 12.1.4 Creep Under Bending Load.- 12.2 Failure in the Creep Range.- 12.2.1 Creep Fracture.- 12.2.2 Failure Maps.- 12.3 Creep Crack Growth.- 12.3.1 The C* Integral.- 12.3.2 Experimental Determination of C*.- 13 Plasticity.- 13.1 Plasticity During Contact Loading.- 13.2 Plasticity During Surface Grinding.- 13.3 Plasticity by Phase Transformation in Zirconia.- 13.4 Plasticity by Domain Switching in Piezoelectric Ceramics.- 13.5 Measurement of Plastic Deformations in Bending Tests.- 13.6 Time-Dependent Plasticity Effects.- A.1 Rectangular Bar.- A.2 Comact-Tension (CT) Specimen.- A.3 Round Compact Tension (RCT) Specimen.- A.4 Double-Cantilever-Beam Specimen (DCB).- A.5 Weight Function for Chevron-Notched Bending Bars.- A.6 Specimens for Mixed-Mode Tests.

Methods of analysis and solutions of crack problems : recent developments in fracture mechanics : theory and methods of solving crack problems

Abstract: It is weH known that the traditional failure criteria cannot adequately explain failures which occur at a nominal stress level considerably lower than the ultimate strength of the material. The current procedure for predicting the safe loads or safe useful life of a structural member has been evolved around the discipline oflinear fracture mechanics. This approach introduces the concept of a crack extension force which can be used to rank materials in some order of fracture resistance. The idea is to determine the largest crack that a material will tolerate without failure. Laboratory methods for characterizing the fracture toughness of many engineering materials are now available. While these test data are useful for providing some rough guidance in the choice of materials, it is not clear how they could be used in the design of a structure. The understanding of the relationship between laboratory tests and fracture design of structures is, to say the least, deficient. Fracture mechanics is presently at astandstill until the basic problems of scaling from laboratory models to fuH size structures and mixed mode crack propagation are resolved. The answers to these questions require some basic understanding ofthe theory and will not be found by testing more specimens. The current theory of fracture is inadequate for many reasons. First of aH it can only treat idealized problems where the applied load must be directed normal to the crack plane.