Influence of superimposed biaxial stress on the tensile strength of perfect crystals from first principles

Abstract

Influence of biaxial stresses applied perpendicularly to the ͓100͔ loading axis on the theoretical tensile strength is studied from first principles. Ten crystals of cubic metals and three crystals of diamond ceramics were selected as particular case studies. Obtained results show that, within a limited range of biaxial stresses, the tensile strength monotonously increases with increasing biaxial tensile stress for most of the studied metals. Within the range, the dependence can be approximated by a linear function. Beyond the range, the dependence shows a maximum that usually appears in the tensile range of biaxial stresses. On the other hand, some of the materials ͑Si, Ni, Cu, and Ge͒ exhibit a maximum tensile strength at nearly uniaxial stress state, and the superposition of both tensile and compressive biaxial stresses reduces the tensile strength. Unlike the other crystals, diamond revealed a maximum under compressive biaxial stress.

Anisotropy of tensile strength and fracture mode of perfect face-centered-cubic crystals

“…According to the analysis above, ideal strength data (r 0 and s 0 ) of six fcc crystals (Cu, Au, Ni, Pt, Al, and Ir) were collected from literature [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] and are listed in Table I. Since for some metals the reported data are dispersive, here we selected the data of r 0 and s 0 to use in the present study from those obtained, as far as possible, by the same group or with the same method, as identified in bold and underlined in Table I.…”

“…21 Several experiments [22][23][24][25][26][27][28] recently claimed that the strengths have approached or even exceeded the ideal strengths calculated by the first principle method. However, raw data of ideal strengths in literature [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] are mostly the ideal cleavage strength (ICS) of low index planes such as f100g, f110g, and f111g and the ideal shear strength (ISS) of f111gh112i and f111gh110i for face-centered-cubic (fcc) crystals. These strength values cannot be simply compared with those measured from the uniaxial loading [22][23][24][25][26][27] or hardness experiments 28 owing to the influence of the competition between fracture along different planes and the obvious normal stress effect for high-strength materials.…”

Alloying effect on the ideal tensile strength of ferromagnetic and paramagnetic bcc iron

“…The ideal tensile strength σm and the corresponding strain ǫm in the [001] direction of FM and PM bcc Fe. The present results (EMTO, FPLO, PAW and FP-LAPW) are compared with previous PAW[1,21,22] and FP-LAPW[24] data for FM Fe. All quoted references employed GGA functionals.…”

[100] Loading of Fcc Based Nanofibre Reinforced Composites

“…The agreement in the case of elastic moduli and Poisson's ratios is mostly also good (within 10%), however, computed Young's moduli for Cu and Au remarkably overestimate the experimental data. Table II together with available literature data [2,4] reported for an equivalent uniaxial loading (using primitive cells). One can note a very good agreement for all listed values.…”

“…Since one of possible explanations dwelled in an eect of transverse stresses (caused by incompatibility strains) acting on the matrix and bres, this eect was systematically studied not only for the ⟨100⟩ crystallographic direction [2] (relevant to the model of nanocomposite loading) but also for tension in ⟨110⟩ and ⟨111⟩ directions [3]. In most cases, the transverse tensile stresses raised the maximum axial stress (i.e.…”