scholarly journals Fracture Estimation in Ship Collision Analysis—Strain Rate and Thermal Softening Effects

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1402
Author(s):  
Burak Can Cerik ◽  
Joonmo Choung
Keyword(s):  
Strain Rate ◽  
Large Scale ◽  
Failure Modes ◽  
Weighting Function ◽  
Internal State ◽  
Thermal Softening ◽  
Flow Rule ◽  
Proportional Loading ◽  
Rate Dependent ◽  
Ship Collision

This study examined the effects of the strain rate and thermal softening on large-scale ductile fracture in ship collisions using a rate-dependent combined localized necking and fracture model. A Johnson–Cook type-hardening model, consisting of strain hardening, rate-sensitivity, and thermal softening terms, was adopted together with an associated flow rule. The temperature was treated as an internal state variable and was calculated from the plastic strain energy using a strain-rate-dependent weighting function under fully isothermal and adiabatic conditions. At every time increment, the fracture locus was updated based on the temporal strain rate, whereas the necking locus was coupled with the hardening law, which was dependent on both the strain rate and temperature. The damage indicator framework was used to consider the non-proportional loading paths. The dynamic shell-element failure model was verified through plate-panel penetration tests and applied to a large-scale ship collision analysis involving a struck ship/ship-shaped offshore installation and a supply vessel. The effects of the loading rate and impact energy were assessed in terms of the global behavior of the structure and observed failure modes.

scholarly journals Strain rate dependent plasticity and fracture of DP1000 steel under proportional and non-proportional loading

2021 ◽  
pp. 104446
Author(s):  
Sarath Chandran ◽  
Wenqi Liu ◽  
Junhe Lian ◽  
Sebastian Münstermann ◽  
Patricia Verleysen
Keyword(s):  
Strain Rate ◽  
Proportional Loading ◽  
Dependent Plasticity ◽  
Rate Dependent

A Numerical Study on Ductile Failure of Porous Ductile Solids With Rate-Dependent Matrix Behavior

2019 ◽  
Vol 87 (3) ◽  
Author(s):  
Lars Edvard Blystad Dæhli ◽  
David Morin ◽  
Tore Børvik ◽  
Ahmed Benallal ◽  
Odd Sture Hopperstad
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Strain Localization ◽  
Ductile Failure ◽  
Unit Cell ◽  
Strain Rates ◽  
Proportional Loading ◽  
Loading Paths ◽  
Rate Dependent ◽  
Constitutive Formulation

Abstract This work examines the effects of loading rate on the plastic flow and ductile failure of porous solids exhibiting rate-dependent behavior relevant to many structural metals. Two different modeling approaches for ductile failure are employed and numerical analyses are performed over a wide range of strain rates. Finite element unit cell simulations are carried out to evaluate the macroscopic mechanical response and ductile failure by void coalescence for various macroscopic strain rates. The unit cell results are then used to assess the accuracy of a rate-dependent porous plasticity model, which is subsequently used in strain localization analyses based on the imperfection band approach. Strain localization analyses are conducted for (i) proportional loading paths and (ii) non-proportional loading paths obtained from finite element simulations of axisymmetric and flat tensile specimens. The effects of strain rate are most apparent on the stress–strain response, whereas the effects of strain rate on ductile failure is found to be small for the adopted rate-dependent constitutive model. However, the rate-dependent constitutive formulation tends to regularize the plastic strain field when the strain rate increases. In the unit cell simulations, this slightly increases the strain at coalescence with increasing strain rate compared to a rate-independent constitutive formulation. When the strain rate is sufficiently high, the strain at coalescence becomes constant. The strain localization analyses show a negligible effect of strain rate under proportional loading, while the effect of strain rate is more pronounced when non-proportional loading paths are assigned.

scholarly journals Strain-rate-dependent properties of short carbon fiber-reinforced acrylonitrile-butadiene-styrene using material extrusion additive manufacturing

2020 ◽  
Vol 26 (10) ◽  
pp. 1701-1712
Author(s):  
Wilco M.H. Verbeeten ◽  
Miriam Lorenzo-Bañuelos ◽  
Rubén Saiz-Ortiz ◽  
Rodrigo González
Keyword(s):  
Carbon Fiber ◽  
Strain Rate ◽  
Acrylonitrile Butadiene Styrene ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Flow Rule ◽  
Content Type ◽  
Short Carbon Fiber ◽  
Rate Dependent ◽  
Short Carbon

Purpose The purpose of the present paper is to quantify and analyze the strain-rate dependence of the yield stress for both unfilled acrylonitrile-butadiene-styrene (ABS) and short carbon fiber-reinforced ABS (CF-ABS) materials, fabricated via material extrusion additive manufacturing (ME-AM). Two distinct and opposite infill orientation angles were used to attain anisotropy effects. Design/methodology/approach Tensile test samples were printed with two different infill orientation angles. Uniaxial tensile tests were performed at five different constant linear strain rates. Apparent densities were measured to compensate for the voided structure. Scanning electron microscope fractography images were analyzed. An Eyring-type flow rule was evaluated for predicting the strain-rate-dependent yield stress. Findings Anisotropy was detected not only for the yield stresses but also for its strain-rate dependence. The short carbon fiber-filled material exhibited higher anisotropy than neat ABS material using the same ME-AM processing parameters. It seems that fiber and molecular orientation influence the strain-rate dependence. The Eyring-type flow rule can adequately describe the yield kinetics of ME-AM components, showing thermorheologically simple behavior. Originality/value A polymer’s viscoelastic behavior is paramount to be able to predict a component’s ultimate failure behavior. The results in this manuscript are important initial findings that can help to further develop predictive numerical tools for ME-AM technology. This is especially relevant because of the inherent anisotropy that ME-AM polymer components show. Furthermore, short carbon fiber-filled ABS enhanced anisotropy effects during ME-AM, which have not been measured previously.

Modeling Temperature and Strain Rate Dependent Large Deformations of Metals

1990 ◽  
Vol 43 (5S) ◽  
pp. S312-S319 ◽  
Author(s):  
Douglas J. Bammann
Keyword(s):  
Strain Rate ◽  
Large Deformations ◽  
Uniaxial Stress ◽  
Thermal Softening ◽  
Plasticity Model ◽  
Anisotropic Hardening ◽  
Temperature Dependent ◽  
History Effects ◽  
Rate Dependent ◽  
Comparison With Experimental Data

We review the development of a strain rate and temperature dependent plasticity model for finite deformation. In particular we address both the method of determining the parameters of the model and the engineering meaning of the parameters in terms of uniaxial stress-strain curves. The ability of the model to predict some aspects of anisotropic hardening, strain rate history effects, and thermal softening are then illustrated by comparison with experimental data.

A strain rate dependent constitutive model for clays at residual strength

1998 ◽  
Vol 35 (2) ◽  
pp. 364-373 ◽  
Author(s):  
AMP Wedage ◽  
N R Morgenstern ◽  
D H Chan
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Residual Strength ◽  
Plasticity Theory ◽  
Constitutive Relationship ◽  
Plastic Strain Rate ◽  
Flow Rule ◽  
Rate Dependent ◽  
Dependent Part ◽  
Rate Effects

Plasticity theory is extended to incorporate strain rate effects on the residual shear strength of clays. The clay is assumed to behave elastically before yielding and then in a perfectly plastic manner with no volume change during yielding. The Mohr-Coulomb failure criterion is used in the rate-dependent model in which the strain rate affects the mobilized effective friction angle of the material. During initial yielding and subsequent plastic deformation, the stress and strain states at a point will satisfy the rate-dependent yield function (loading function). When the effective plastic strain rate decreases to a threshold strain value, the loading surface moves, or collapses, to the static yield surface. A constant volume flow rule is used to calculate plastic deformation. The computed stress-strain relationship is formulated in two parts, namely a rate-independent part and a rate-dependent part. The rate-independent part is the same as that used in classical elastoplastic formulations, whereas the rate-dependent part is dependent on the current strain rate of the material. The use of the model is illustrated using a numerical example simulating a two-dimensional plane strain test.Key words: constitutive relationship, finite element, plasticity theory, pre-sheared clay, rate effects, residual strength.

Effective constitutive algorithms in elastoplasticity and elastoviscoplasticity

1994 ◽  
Vol 5 (3) ◽  
pp. 313-335 ◽  
Author(s):  
Sia Nemat-Nasser ◽  
Luqun Ni
Keyword(s):  
Finite Element ◽  
Perturbation Method ◽  
Large Scale ◽  
Constitutive Relations ◽  
Numerical Algorithms ◽  
Flow Rule ◽  
Singular Perturbation Method ◽  
Stiff System ◽  
Rate Dependent ◽  
Finite Element Node

The basic constitutive relations for elastoplasticity and elastoviscoplasticity are shown to form a typical boundary layer-type stiff system of ordinary differential equations. Three numerical algorithms are discussed: (i) The singular perturbation method (O'Malley, 1971a, b; Hoppensteadt, 1971; Miranker, 1981; Smith, 1985), which yields accurate results for both the rate-independent and rate-dependent cases, where in the former case, the algorithm is explicit, whereas in the latter case, it is implicit and requires the solution of a nonlinear equation; therefore it is impractical as a constitutive algorithm for large-scale finite-element applications, where the constitutive algorithm is used a great number of times at each finite-element node. (ii) The new constitutive algorithm (Nemat-Nasser, 1991; Nemat-Nasser & Chung, 1989, 1992) which is explicit and accurate for both the rate-independent and rate-dependent cases; the underlying mathematical feature of this new method is investigated, and it is shown that it can be classified as a simplified perturbation method; computable error bounds for this algorithm are obtained, and when the flow rule is given by the commonly used power law, it is shown that the errors are very small, (iii) A modified outer-solution method, which combines the above two techniques, and is simple, explicit, and accurate.

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