Evaluation of the Characteristics of Crack Resistance of Materials for Mixed Macromechanisms of Fracture
- PDF / 269,724 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 96 Downloads / 252 Views
EVALUATION OF THE CHARACTERISTICS OF CRACK RESISTANCE OF MATERIALS FOR MIXED MACROMECHANISMS OF FRACTURE Ya. L. Ivanyts’kyi and S. T. Shtayura
UDC 539.375
We propose a procedure of testing materials for static crack resistance for mixed modes of fracture: I + II (tension and transverse shear) and I + III (tension and longitudinal shear). Cylindrical specimens with circular or circular and lateral notches are tested under the conditions of loading by combined tension and torsion. The description of specimens is presented. The procedures of testing, determination of the force and deformation characteristics of crack resistance for the indicated loading conditions, and processing of the results in the form of crack resistance diagrams are proposed. The procedures are developed in conformity with the requirements and regulations of the national standards.
From the viewpoint of fracture mechanics, a crack formed in a material grows according to the macromechanisms of tenson (I), transverse shear (II), or longitudinal shear (III). Loads responsible for the formation of complex stress-strain states in materials promote their fracture according to the mixed mechanisms (I + II), (I + III), (II + III), or (I + II + III). The methods aimed at the evaluation of the characteristics of static crack resistance of structural materials under the conditions of tension [1, 2] and transverse shear [3] are well known. At the same time, there are no standard procedures for the evaluation of the characteristics of crack resistance of materials and residual strength of structural components in the case of mixed fracture under the conditions of complex stressed state. In the present work, we propose to study the state of limiting equilibrium of materials with the help of the diagrams of crack resistance plotted according to the results of testing of cylindrical specimens under the conditions of combined tension and torsion by using force and deformation criteria. Objective of the Work Our aim is to develop a standard procedure for the evaluation of strength of cracked materials subjected to mixed loading by tension and transverse shear (or tension and longitudinal shear) from the viewpoint of fracture mechanics. For this purpose, cracked specimens are simultaneously stretched by a force P and twisted by a torque M to fracture (proportional loading) for different ratios of the stretching force to the torque. The dependences of these characteristics on the displacements of the crack lips are constructed for each mechanism of fracture. The strength of structural elements is evaluated according to the crack-resistance diagrams with the help of two-parameter force or deformation criteria of fracture mechanics. General Conditions The characteristics of crack resistance KIC , KIIC , KIIIC , δIC , δIIC , and δIIIC are determined in the course of testing of specimens with fatigue cracks under loading according to the dependences of the force P on the Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, Lviv. Translated from Fizyk
Data Loading...
