US 4,895,027 A · Determining plane strain fracture toughness and the J-Integral for solid materials using stress field modified miniature specimens

Abstract

A method of determining the mechanical behavior of solid materials by using stress field modified miniature specimens. The method is an improvement in the method of determining mechanical behavior information from specimens only so large as to have at least a volume or smallest dimension sufficient to satisfy continuum behavior in all directions. Mechanical behavior of the material is determined from the measurements taken during the loading of the specimen resulting in the formation of cracks and/or the further propagation of cracks in the miniature specimen. The specimens include construction features for applying additional stress field modifying loads upon the specimens during the test. These additional loads result in a desired stress state in the specimen which could not be achieved otherwise. A particular example is the introduction of a transverse tensile load during a bend test to increase the transverse stress field to achieve plane strain conditions in a thin specimen. The methods are useful in determining plane strain fracture toughness, dynamic plane-strain crack initiation and arrest fracture toughness, the J-Integral for the material, and the fracture mode transition behavior when the specimen thickness and volume is smaller than previously thought necessary.

Claims23

Dependent claims

A process of determining mechanical behavior of solid material, comprising:

(a) providing a specimen of the material having a volume and smallest dimension sufficient to establish continuum behavior in all directions, and with a volume not more than 10.sup.7 times said sufficient volume;
(b) modifying the stress field of the specimen by applying a first load to the specimen so as to induce and/or modify the existing stress field in the specimen and obtain a selected stress state;
(c) deforming the specimen by applying a second load on the specimen in a direction different than the orientation of the first load of (b) above;
(d) measuring at least one key variable in step c;
and
(e) determining the behavior of the material from the measurements taken according to the principles of the finite element method and/or the principles of linear or nonlinear material mechanics or both.

3 more elements

A process of determining fracture behavior of solid material, comprising:

(a) providing a specimen of the material having a volume and smallest dimension sufficient to establish continuum behavior in all directions, and with a volume not more than 10.sup.7 times said sufficient volume, notching and/or precracking the specimen;
(b) modifying the stress field of the specimen by applying a first load to the specimen so as to induce and/or modify the existing stress field and to result in a selected stress state, the magnitude of the induced stress being defined by analyses according to the principle of the finite element method and/or the principles of linear or nonlinear material mechanics or both,
(c) applying a second load to the specimen in a direction different than the orientation of the first load of (b), the magnitude of the applied load being independent and the load of (c) depending on the load,
(d) measuring K.sub.IC, the plane strain fracture toughness, and/or K.sub.Id, plane strain dynamic crack initiation fracture toughness, and/or K.sub.Ia, plane strain dynamic crack arrest fracture toughness, and/or the J-Integral and/or fracture mode transition behavior, by increasing the loads (b) and (c) applied to the specimen until a crack propagates across a plane of the specimen,
(e) determining the fracture behavior of the material from the measurements taken according to the principles of the finite element method and/or the principles of linear or nonlinear material mechanics or both.

2 more elements

A process of determining fracture behavior of solid material, comprising:

(a) providing a specimen of the material, and notching and/or precracking the specimen thereby providing for a generally planar crack across the specimen:
(b) modifying the stress field of the specimen by applying a first load to the specimen so as to induce and/or modify the existing stress field and to result in a selected stress state, the magnitude of the induced stress being defined by analyses according to the principles of the finite element method and/or the principles of linear or nonlinear material mechanics or both;
(c) applying at least one additional load to the specimen in a direction different than the orientation of the first load of (b), the magnitude of the applied first load being independent, and the magnitude of the additional load of (c) depending on the applied first load,
(d) measuring K.sub.IC, the plane strain fracture toughness, and/or K.sub.Id, plane strain dynamic crack initiation fracture toughness, and/or K.sub.Ia, plane strain dynamic crack arrest toughness, and/or the J-Integral and/or fracture mode transition behavior, by increasing the loads (b) and (c) applied to the specimen until a crack propagates across a plane of the specimen;
and
(e) determining the fracture behavior of the material from the measurements taken according to the principles of the finite element method and/or the principles of linear or nonlinear material mechanics or both.

3 more elements

Dependencies are inferred from the claim text.

Determining plane strain fracture toughness and the J-Integral for solid materials using stress field modified miniature specimens

Life of this patent

Determining plane strain fracture toughness and the J-Integral for solid materials using stress field modified miniature specimens

Life of this patent

Abstract

Claims23