Mechanical Stability and Brittleness of Metals and Alloys. Pt. 3. Physical-Mechanical Concept of Strength and Destruction of Metals and Alloys

This work offers the fundamentals of a new approach to the nature of strength and failure of metallic materials under the conditions of stress-strain state (SSS) of a general type, which occurs within the local zones of non-uniform force fields (NFF) due to the stress raisers (SR). Basic foundation of the physical and mechanical concept of structural strength of metals and alloys, sigma(NF), is considered based on the comparison of the proposed strength margin (SM) parameter for two cases: Delta S for uniform force fields (UFF) and Delta sigma(N) for non-uniform force fields (NFF) near the SR. Exhaustion of each type of SM means a transition to brittle fracture, which, for SM at NFF, manifests itself in a steep fall in structural strength: sigma(NF) < sigma(0.2). Exhaustion of strength margins Delta S and Delta sigma(N) may occur due to both physical (alloy structure, temperature conditions) factors and purely mechanical ones (type of SSS, SR), which cause embrittlement of metals. A special mechanical characteristic is proposed-break resistance b(r) (basic one for the uniform SSS) and b(rN) (structural one for the non-uniform SSS), the ratio between which governs the regularities of influence of strength sigma(0.2) (conditional yield strength) and strength margin Delta S on such manifestations of brittleness of metals as cold brittleness, when the temperature is decreased, or 'mechanical brittleness' due to the SR at room temperature T-& Kcy;. Examples of the application of parameters Delta S, Delta sigma(N) and b(r), b(rN) are given for the analysis of experimental evidence published by various authors. A conclusion is made about the effectiveness of using structural strength parameters in investigation of the nature of brittleness and embrittlement of metal alloys caused by their extra hardening, the temperature decrease, or the SR effect (cracks, etc.). has context menu