Effect of Initial Volume Fraction of Voids and Specimen Size on Ductile Fracture

AbstractCompressive yield stresses have been measured for pastes (0.35 ≤ w/c ≤ 0.50) of portland cement, calcium aluminate cement, and weakly and strongly flocculated alumina (Φ0 = 0.20) using the centrifuge sediment height technique. Equilibrium sediment heights are reached quickly, allowing all measurements to be taken during the cement's induction period. The compressive behavior showed little dependence on the compressive history. Compressive yield stress was, however, dependent upon initial volume fraction, decreasing as the initial volume fraction increases. This behavior was observed in both the cements and alumina suspensions, implying that strong dependencies on initial structure may be a general property of the compressive behavior of flocculated suspensions.

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Numerical Evaluation of Micro- to Macroscopic Mechanical Behavior of Plastic Foam

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.340-341.1025 ◽

2007 ◽

Vol 340-341 ◽

pp. 1025-1030

Author(s):

Isamu Riku ◽

Koji Mimura

Keyword(s):

Mechanical Behavior ◽

Strain Hardening ◽

Loading Condition ◽

Volume Fraction ◽

Plastic Foam ◽

Uniform Compression ◽

Initial Volume ◽

Initial Volume Fraction ◽

Characteristic Value ◽

Initial Modulus

In this study, we employ the two-dimensional homogenization model based on molecular chain network theory to investigate the micro- to macroscopic mechanical behavior of plastic foam under macroscopic uniform compression. A parametric study is performed to quantify the effect of a characteristic value of matrix, distribution and initial volume fraction of voids, and the macroscopic triaxiality of loading condition on the deformation behavior of the foam. The results suggest that the onset of localized shear band at the ligament between voids together with the microscopic buckling of the ligament leads to the macroscopic yield of the foam. The initial modulus and the macroscopic yield stress of the foam have no dependence on the characteristic value of matrix. Furthermore, as the microscopic buckling of the ligament is promoted in case of high initial volume fraction of voids and high triaxiality loading condition, the macroscopic yield point appears at early deformation stage. After the macroscopic yield, macroscopic strain hardening appears in the macroscopic response and a remarkable strain hardening is shown in case of high initial volume fraction of voids and high triaxiality loading condition due to the considerable increase of the density of the foam in these cases.

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Initiation of Submarine Granular Avalanches: Role of the Initial Volume Fraction

10.1063/1.2964899 ◽

2008 ◽

Author(s):

Mickaël Pailha ◽

Olivier Pouliquen ◽

Maxime Nicolas ◽

Albert Co ◽

Gary L. Leal ◽

...

Keyword(s):

Volume Fraction ◽

Initial Volume ◽

Initial Volume Fraction

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Granular collapse in a fluid: Role of the initial volume fraction

Physics of Fluids ◽

10.1063/1.3594200 ◽

2011 ◽

Vol 23 (7) ◽

pp. 073301 ◽

Cited By ~ 83

Author(s):

L. Rondon ◽

O. Pouliquen ◽

P. Aussillous

Keyword(s):

Volume Fraction ◽

Initial Volume ◽

Initial Volume Fraction ◽

Granular Collapse

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A two-phase flow description of the initiation of underwater granular avalanches

Journal of Fluid Mechanics ◽

10.1017/s0022112009007460 ◽

2009 ◽

Vol 633 ◽

pp. 115-135 ◽

Cited By ~ 80

Author(s):

MICKAËL PAILHA ◽

OLIVIER POULIQUEN

Keyword(s):

Critical State ◽

Two Phase Flow ◽

Volume Fraction ◽

State Theory ◽

Phase Flow ◽

Two Phase ◽

Initial Volume ◽

Initial Volume Fraction ◽

Critical State Theory

A theoretical model based on a depth-averaged version of two-phase flow equations is developed to describe the initiation of underwater granular avalanches. The rheology of the granular phase is based on a shear-rate-dependent critical state theory, which combines a critical state theory proposed by Roux & Radjai (1998), and a rheological model recently proposed for immersed granular flows. Using those phenomenological constitutive equations, the model is able to describe both the dilatancy effects experienced by the granular skeleton during the initial deformations and the rheology of wet granular media when the flow is fully developed. Numerical solutions of the two-phase flow model are computed in the case of a uniform layer of granular material fully immersed in a liquid and suddenly inclined from horizontal. The predictions are quantitatively compared with experiments by Pailha, Nicolas & Pouliquen (2008), who have studied the role of the initial volume fraction on the dynamics of underwater granular avalanches. Once the rheology is calibrated using steady-state regimes, the model correctly predicts the complex transient dynamics observed in the experiments and the crucial role of the initial volume fraction. Quantitative predictions are obtained for the triggering time of the avalanche, for the acceleration of the layer and for the pore pressure.

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IMCs Microstructure Evolution Dependence of Mechanical Properties for Ni/Sn/Ni Micro Solder-Joints

Materials ◽

10.3390/ma13010252 ◽

2020 ◽

Vol 13 (1) ◽

pp. 252 ◽

Cited By ~ 1

Author(s):

Ning Ren ◽

Heng Fang ◽

Dong Wang ◽

Chenyi Hou ◽

Yatao Zhao ◽

...

Keyword(s):

Mechanical Properties ◽

Brittle Fracture ◽

Ductile Fracture ◽

Solder Joints ◽

Volume Fraction ◽

Tensile Tests ◽

Stress Concentrations ◽

Element Analysis ◽

Scale Down ◽

Long Rod

The current miniaturization trend of microelectronic devices drives the size of solder joints to continually scale down. The miniaturized joints considerably increase intermetallic compounds (IMCs) volume fraction to trigger mechanical reliability issues. This study investigated precise relationships between varying IMC volumes and mechanical properties of Ni/Sn(20μm)/Ni micro-joints. A designed method that followed the IMC volume as the only variable was used to prepare micro-joint samples with different IMC volumes. The continuously thickened Ni3Sn4 IMCs exhibited a noticeable morphology evolution from rod-like to chunky shape. The subsequent tensile tests showed unexpected tensile strength responses as increasing Ni3Sn4 volume, which was strongly associated with the Ni3Sn4 morphological evolutions. Fractographic analysis displayed that the ductile fracture dominates the 20%–40% IMC micro-joints, whereas the brittle fracture governs the 40%–80% IMC micro-joints. For the ductile fracture-dominated joints, an abnormal reduction in strength occurred as increasing IMCs volume from 20% to 40%. This is primarily due to severe stress concentrations caused by the transformed long rod-typed morphology of the Ni3Sn4. For the brittle fracture-dominated joints, the strength appeared a monotonous increase as the Ni3Sn4 volume increased. This may be attributed to the increased crack resistance resulting from continuous coarsening of the chunky Ni3Sn4 without any voids. Moreover, the finite element analysis was provided to further understand the joint failure mechanisms.

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On ductile fracture initiation toughness: Effects of void volume fraction, void shape and void distribution

International Journal of Solids and Structures ◽

10.1016/j.ijsolstr.2005.02.028 ◽

2005 ◽

Vol 42 (18-19) ◽

pp. 5097-5117 ◽

Cited By ~ 72

Author(s):

Xiaosheng Gao ◽

Tianhong Wang ◽

Jinkook Kim

Keyword(s):

Ductile Fracture ◽

Volume Fraction ◽

Fracture Initiation ◽

Void Volume Fraction ◽

Void Volume ◽

Initiation Toughness ◽

Void Distribution ◽

Void Shape ◽

Fracture Initiation Toughness ◽

Ductile Fracture Initiation

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Improvement of an Ellipsoidal Void Model for Simulating Ductile Fracture Behavior

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.577-578.93 ◽

2013 ◽

Vol 577-578 ◽

pp. 93-96

Author(s):

Kazutake Komori

Keyword(s):

Finite Element ◽

Ductile Fracture ◽

Fracture Behavior ◽

Fracture Strain ◽

Volume Fraction ◽

Deformation Gradient ◽

Simple Relationship ◽

The Matrix ◽

The Difference ◽

Deformation Gradients

An ellipsoidal void model for simulating ductile fracture behavior was proposed by the author [K. Komori: Mech. Mater., Vol. 60 (2013), p. 36]. The nominal fracture strain calculated from this model is slightly larger than that calculated from the finite-element void cell when the initial void volume fraction is specified. To decrease the difference, an assumption must be made that the deformation gradient of the void does not coincide with that of the matrix. This study proposes a simple relationship between the two deformation gradients that produces agreement between the nominal fracture strain calculated using the ellipsoidal void model and that using the finite-element void cell.

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