Multifunctional Properties of Bulk Nanostructured Metallic Materials

Abstract

This chapter focuses on multifunctional properties of bulk nanostructured metallic materials and structure-properties relationship therein. The most important structural factors affecting mechanical, physical, and chemical properties of the nanomaterials are discussed, and the strategies to their further improvement are outlined. Special attention is paid to nanostructural design for simultaneous improvement of mutually exclusive properties. Superstrength and Enhanced Mechanical PropertiesAlthough the mechanical and functional properties of all polycrystalline metallic materials are determined by several factors, the grain size of the material generally plays the most significant and often a dominant role. Thus, the strength of different polycrystalline materials is related to the grain size, d, through the Hall-Petch equation which states that the yield stress, σ y , is given bywhere σ o is termed the friction stress and k y the Hall-Petch constant [1,2]. It follows from Eq. 3.1 that the strength increases with a reduction in the grain size and this has led to an ever-increasing interest in fabricating materials with extremely small grain sizes. The fabrication of bulk samples and billets using equal channel angular pressing (ECAP), high pressure torsion (HPT), and other severe plastic deformation (SPD) techniques was a crucial first step in initiating investigations into the properties of bulk nanomaterials because the use of SPD processing permitted, and subsequently fully supported, a series of systematic studies using various nanostructured metallic materials including commercial alloys [3][4][5][6][7][8]

A General Damage Accumulation Model for Multiaxial, Proportional High Cycle Fatigue Loadings With Sines, Crossland and Dang Van Criteria

“…Therefore, a new model parameter μ = 4M 0 (1 + θ)a, corresponding to η, together with a new variable δ = [1 − (1 − D) 1+θ ] a , corresponding to λ, are introduced here to rewrite relation (48) into the following shorter form.…”

“…To verify the performance of the proposed identification procedure, the model parameters and material properties of SM490 steel, given in Table 1, are taken from Refs. [23] and [48]. To those values, we added ζ, the extra parameter of our DAM variants.…”

“…Material properties and fatigue model parameters of SM490 steel taken from Refs [23,48]. Table 2Artificial fatigue database consisting of 30 HCF data points calculated from the pairs of ( σ, σ M ) of each point and parameters ofTable 1plugged into Eq.…”