An alternative method for small pop-in assessment

Berejnoi, Carlos; Ipiña, Juan E. Perez

doi:10.1016/s0013-7944(97)00105-7

Cited by 10 publications

(4 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For deeper indents (d>10 nm), a striking difference is observed by varying the vacancy concentration. For stoichiometric VN, plastic deformation is indicated by pop-ins -stochastically occurring displacement discontinuities [41,42] which reflect catastrophic mechanical failures on mesoscopic scales, including crack nucleation [43][44][45] and dislocation avalanches [46]. In contrast, nanoindentation load-displacement curves for understoichiometric VN0.8 layers never exhibit pop-ins.…”

Section: Resultsmentioning

confidence: 99%

Adaptive hard and tough mechanical response in single-crystal B1 VNx ceramics via control of anion vacancies

et al. 2020

View full text Add to dashboard Cite

High hardness and toughness are generally considered mutually exclusive properties for singlecrystal ceramics. Combining experiments and ab initio molecular dynamics (AIMD) atomistic simulations at room temperature, we demonstrate that both the hardness and toughness of singlecrystal NaCl-structure VNx/MgO(001) thin films are simultaneously enhanced through the incorporation of anion vacancies. Nanoindentation results show that VN0.8, here considered as representative understoichiometric VNx system, is ≈20% harder, as well as more resistant to fracture than stoichiometric VN samples. AIMD modeling of VN and VN0.8 supercells subjected to [001] and [110] elongation reveal that the tensile strengths of the two materials are similar.Nevertheless, while the stoichiometric VN phase cleaves in a brittle manner at tensile yield points, the understoichiometric compound activates transformation-toughening mechanisms that dissipate accumulated stresses. AIMD simulations also show that VN0.8 exhibits an initially greater resistance to both {110}〈11 ̅ 0〉 and {111}〈11 ̅ 0〉 shear deformation than VN. However, for progressively increasing shear strains, the VN0.8 mechanical behavior gradually evolves from harder to more ductile than VN. The transition is mediated by anion vacancies, which facilitate {110}〈11 ̅ 0〉 and {111}〈11 ̅ 0〉 lattice slip by reducing activation shear stresses by as much as 35%.Electronic-structure analyses show that the two-regime hard/tough mechanical response of VN0.8 primarily stems from its intrinsic ability to transfer d electrons between 2nd-neighbor and 4thneighbor (i.e., across vacancy sites) V-V metallic states. Our work offers a route for electronicstructure design of hard materials in which a plastic mechanical response is triggered with loading.

show abstract

Section: Resultsmentioning

confidence: 99%

Adaptive hard and tough mechanical response in single-crystal B1 VNx ceramics via control of anion vacancies

et al. 2020

View full text Add to dashboard Cite

show abstract

“…For the geometries used in the tests performed under displacement control, this value corresponds to an unstable crack growth smaller than 1% of the uncracked ligament. 24 In this way, most of the first load drops in P±V records in ARALL laminates were critical points. When instabilities were smaller than the critical ones, mostly in GLARE 1, fracture toughness was evaluated at the first attainment of a maximum load plateau.…”

Section: Equations For Calculation Of J-integralmentioning

confidence: 90%

“…The amount of load drop necessary to be considered significant was proposed in a way similar to pop‐in instabilities characterization procedure given by ASTM E 1820, 21 though conservatively establishing at 2% the slope difference between the straight lines instead of the 5% recommended by the standard. For the geometries used in the tests performed under displacement control, this value corresponds to an unstable crack growth smaller than 1% of the uncracked ligament 24 . In this way, most of the first load drops in P–V records in ARALL laminates were critical points.…”

Section: Methodsmentioning

confidence: 98%

Experimental techniques for fracture instability toughness determination of unidirectional fibre metal laminates

Castrodeza

Ipiña

Bastian

2002

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

The aim of this work is to propose procedures for the measurement of the fracture toughness of fibre metal laminates (FMLs) reinforced with unidirectional fibres of aramid or glass. Experimental techniques for fracture toughness evaluation by using Compact (C(T)) and Single‐Edge Bend (SE(B)) specimens obeying ASTM standards are introduced. Procedures from the standard for thick metallic materials were modified in order to overcome problems, which can arise when testing FMLs – that is, specimen buckling, indentations and crack growth in planes other than the plane of the fatigue pre‐crack or notch. The methodology proposed was experimentally tested leading to satisfactory results.

show abstract

“…Equation 10(a)), as shown in Figure 1(b). This usually appears in coarse grain regions (Berejnoi and Perez Ipin˜a, 1998), where the connectivity of the e-substructure is relatively low (and the value of e accordingly relatively high). In fine grain materials the connectivity of the e-substructure is high and its decrease proceeds continuously or in small steps.…”

Section: Cumulative Damagementioning

confidence: 99%

An Overview of Applications of Kafka’s General Mesomechanical Concept to Inelastic Deformation, Cumulative Damage, and Fracture

Kafka

Vokoun

2010

International Journal of Damage Mechanics

View full text Add to dashboard Cite

The previously published applications of the first author’s general mesomechanical concept are surveyed to show a logical integration of the newly presented application to fracture into the general image. The newly presented application models fracture of bodies with cracks. This way of presentation emphasizes that the respective model is not any ad hoc chosen formula, but that it is incorporated in a widely applicable general scheme. In the current study, attention is paid to classical technical materials. The original area of the use of our general model was plasticity, where a number of quantitative comparisons with experimental data corroborated the merits of this approach. The next step was application to cumulative damage and fracture without pre-existing initiators of the fracturing process. The last step, newly discussed in this study, is mesomechanical modeling of the progress of cracks, described by local effect of the deviatoric part of the stress tensor and by a nonlocal effect of the isotropic part of the stress tensor.

show abstract

An alternative method for small pop-in assessment

Cited by 10 publications

References 4 publications

Adaptive hard and tough mechanical response in single-crystal B1 VNx ceramics via control of anion vacancies

Adaptive hard and tough mechanical response in single-crystal B1 VNx ceramics via control of anion vacancies

Experimental techniques for fracture instability toughness determination of unidirectional fibre metal laminates

An Overview of Applications of Kafka’s General Mesomechanical Concept to Inelastic Deformation, Cumulative Damage, and Fracture

Contact Info

Product

Resources

About