Inelastic Response of a Deep Crack Single-Edge Notch Specimen Under Impact Loading

1995 ◽  
Vol 117 (3) ◽  
pp. 205-211
Author(s):  
P. M. Vargas ◽  
R. H. Dodds
Keyword(s):  
Strain Rate ◽  
Impact Loading ◽  
Time Integration ◽  
Model Material ◽  
Integration Scheme ◽  
Pressure Vessel Steel ◽  
Single Edge ◽  
Strain Rate Effects ◽  
Vessel Steel ◽  
Dynamic Analyses

Three-dimensional dynamic analyses are performed for a single-edge bend, SE(B), fracture specimen (a/W = 0.5) subjected to impact loading. Loading rates obtained in routine drop tower tests (terminal load-line velocity of 100 in./s or 2.54 m/s) are applied in the analyses. Explicit time integration coupled with an efficient element integration scheme is used to compute the dynamic response of the specimen. Strainrate sensitivity is introduced via a new, efficient implementation of the Bodner-Partom viscoplastic constitutive model. Material properties for A533B steel (a medium strength pressure vessel steel) are used in the analyses. Static analyses of the same SE(B) specimens provide baseline results from which inertial effects are assessed. Similarly, dynamic analyses using a strain-rate insensitive material provide a reference for the assessment of strain rate effects. Strains at key locations and the support reactions are extracted from the analyses to assess the accuracy of static formulas commonly used to estimate applied J values. In ertial effects on the applied J are quantified by examining the acceleration component of J. Results show that dynamic effects for the steel analyzed are negligible after twice a characteristic time that can be defined in terms of the first elastic period of the specimen.

Strain Rate Effects on the Fatigue Crack Growth of SA508 Cl.3 Reactor Pressure Vessel Steel in High-Temperature Water Environment

2000 ◽  
Vol 123 (2) ◽  
pp. 173-178 ◽  
Author(s):  
S. G. Lee ◽  
I. S. Kim
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Strain Rate ◽  
Crack Growth ◽  
Pressure Vessel Steel ◽  
Strain Rate Effects ◽  
Vessel Steel ◽  
Reactor Pressure Vessel Steel ◽  
Rate Effects ◽  
Reactor Pressure

Corrosion fatigue tests were performed in air saturated hot water to assess fatigue crack growth behavior of reactor pressure vessel steel at the LWR operating condition. The main test parameter was loading frequency. Crack growth rate was increased with decreasing frequency until a critical frequency. It was found through fractographic study that the enhancement of crack growth rate was environmentally assisted by the hydrogen embrittlement, since brittle striations and cleavagelike facets with microvoid were formed in the crack growth process. The strain rate effects on crack growth rate were investigated through da/dt versus dε/dt curves. At intermediate range, there is a transient point which corresponds to an onset of dynamic strain aging and abruptly increases the crack growth rate; above the transient point, small-size-particle-enhanced brittle cracks, while only large-size-particle-enhanced brittle cracks before the transient. From the fractography, it is suggested that EAC may be enhanced by specific strain rate, and that EAC may be related to interactions of hydrogen with oxide film and to Luders band movement with a high strain gradient at inclusion/matrix interface.

Dynamic Crack Propagation and Arrest in PWR Pressure Vessel Steel: Interpretation of Experiment With the X-FEM Method

2007 ◽  
Author(s):  
B. Prabel ◽  
S. Marie ◽  
A. Combescure
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Rate ◽  
Thermal Shock ◽  
Crack Growth ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Pressure Vessel Steel ◽  
Vessel Steel

In the frame of analysis of the pressure thermal shock in a PWR RVP and the associated R&D activities, some developments are performed at CEA on the dynamic brittle propagation and crack arrest. This paper presents a PhD work on the modeling of the dynamic brittle crack growth. For the analyses, an important experimental work is performed on different geometries using a French RPV ferritic steel: Compact Tension specimens with different thickness, isothermal rings under compression with different positions of the initial defect to study a mixed mode configuration, and a ring submitted to thermal shock. The first part of this paper details the test conditions and main results. To propose an accurate interpretation of the crack growth, a viscous-elastic-plastic dynamic model is used. The strain rate influence is taken into account based on Cowper-Symond’s law (characterization was made from Split Hopkinson Pressure Bar tests). To model the crack propagation in the Finite Element calculation, eXtended Finite Element Method (X-FEM) is used. The implementation of these specific elements in the CEA F.E. software CAST3M is described in the second part of this paper. This numerical technique avoids re-meshing, because the crack progress is directly incorporated in the degrees of freedom of the elements crossed by the crack. The last part of this paper compares the F.E. predictions to the experimental measurements using different criteria. In particular, we focused on a RKR (Ritchie-Knott-Rice) like criterion using a critical principal stress in the front of the crack tip during the dynamic crack extension. Critical stress is found to depend on crack speed, or equivalently on strain rate. Good results are reported concerning predictive simulations.

Compressive Strain Rate Effects of Concrete

1985 ◽  
Vol 64 ◽  
Author(s):  
P. H. Bischoff ◽  
S. H. Perry
Keyword(s):  
Strain Rate ◽  
Impact Loading ◽  
Maximum Stress ◽  
Compressive Strain ◽  
Plain Concrete ◽  
Strain Rates ◽  
Strain Rate Effects ◽  
Conflicting Evidence ◽  
Rate Effects ◽  
Microcrack Growth

ABSTRACTSince good constitutive laws are required to model correctly the behaviour of concrete under impact loading, it is necessary to determine the complete stress-strain response of concrete at varying strain rates. Conflicting evidence emerges about whether the critical compressive strain (defined as the strain observed at maximum stress) increases or decreases with an increasing strain rate. In this paper, a comprehensive description is given of the brittle fracture process for plain concrete under static and impact loading. The strain rate dependance of tensile microcrack growth is used to explain both the increase in strength and the increase in critical compressive strain that can occur at high strain rates. More extensive experimental results are required to determine the fundamental changes in behaviour that occur as the loading rate is increased and, thus, facilitate the development of a more precise failure model for concrete.

Rubber Structural Coupon Behaviour Study under Pressure Impulse

2013 ◽  
Vol 198 ◽  
pp. 394-399
Author(s):  
Pawel Baranowski ◽  
Jerzy Malachowski ◽  
Łukasz Mazurkiewicz ◽  
Krzysztof Damaziak
Keyword(s):  
Strain Rate ◽  
Time Integration ◽  
Rate Sensitivity ◽  
Rate Dependency ◽  
Material Behaviour ◽  
Explicit Integration ◽  
Dynamic Simulations ◽  
Central Difference ◽  
Strain Rate Effects ◽  
Behaviour Study

This study focuses on the rubber material behaviour assessment under dynamic loading using numerical methods. Consequently, dynamic simulations of the rubber structural coupon subjected to dynamic velocity loading were performed using the explicit integration procedure with central difference scheme with modified time integration of the equation of motion implementation. During investigations two impulse velocities were used and compared for two different constitutive materials: Mooney-Rivlin without rate-dependency and Mat 181 Simplified Rubber which includes strain rate effects. From the obtained results it was noticed that material behaviour in both cases is different and along with different values of velocity the strain rate sensitivity changes.

scholarly journals Material modelling of tensile steel component under impulsive loading

2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Joao Ribeiro ◽  
Aldina Santiago ◽  
Constança Rigueiro
Keyword(s):  
Strain Rate ◽  
Impact Loading ◽  
Design Methodology ◽  
Ductile Damage ◽  
Fe Model ◽  
Strain Rate Effects ◽  
Displacement Capacity ◽  
Numerical Predictions ◽  
Fracture Simulation ◽  
Rate Effects

Purpose Characterization and modelling of the material properties, as well as the fracture simulation needed for the numerical analysis of bolted T-stub connection under impulsive loads. The strain rate effects are considered on the material law; fracture simulation is explored following “element deletion” technique for a given level of ductile damage. Design/methodology/approach The T-stub model is used in Eurocode 3 – part 1.8 as part of the “component method” for the representation of steel connection’s tension zone and is usually responsible for providing ductility to the connection. Looking forward to establish the “T-stub’s” maximum displacement capacity under impact loading, i) fracture simulation of steel elements is here explored following “element deletion” technique for a given level of ductile damage; ii) material softening and triaxial stress state dependency are assessed by finite element analysis of common uniaxial tension tests, and iii) strain rates effects are used based on results from Split-Hopkinson Bar tests, through the incorporation of the Johnson-Cook’s elevated strain rate law for material strain-hardening description. Numerical predictions of the model describing the “T-stub” behaviour and displacement capacity are compared against experimental results. Findings The FE model developed was found reliable in the description of the T-stub response subject to static and impact loads. Particularly, the strain rate sensitive material hardening following a calibrated Johnson-Cook law proved accurate in the description of the enhancement of the material strength. It was observed that when subject to impact loading regimes, the force-displacement response of T-stubs is: i) enhanced due to elevated strain rate effects, avoiding rupture when subject to a load equal the maximum static; ii) less ductile plastic failure modes in deformable T-stubs are expected, whilst the development of higher strains in the bolt may lead to a reduction in its ductility capacity. Originality/value A non-linear dynamic FE model of simple T-stub configuration using a strain rate effect on the material law and fracture simulation, providing insight of stress, strain, strain rate and damage contours developments, when exposed to impact loading.

Modeling of Dynamically Loaded Open-Cell Metallic Foams: Yielding, Collapse, and Strain Rate Effects

2010 ◽  
Vol 77 (3) ◽  
Author(s):  
Pedro A. Romero ◽  
Winston O. Soboyejo ◽  
Alberto M. Cuitiño
Keyword(s):  
Strain Rate ◽  
Impact Loading ◽  
Unit Cell ◽  
Metallic Foams ◽  
Cell Level ◽  
Effective Response ◽  
Strain Rate Effects ◽  
Open Cell ◽  
Rate Effects ◽  
Dynamically Loaded

Open-cell metallic foams exhibit properties desirable in engineering applications requiring mitigation of the adverse effects resulting from impact loading; however, the history dependent dynamic response of these cellular materials has not been clearly elucidated. This article contributes an approach for modeling the response of dynamically loaded open-cell metallic foams from ligament level to unit cell level to specimen level. The effective response captures the localized chaotic collapse phenomena through ligament reorientation at cell level while maintaining the history of plastic deformation at ligament level. First, the phenomenological elastoplastic constitutive behavior of the ligaments composing the unit cell is modeled. Then, using the constitutive ligament model, the effective unit cell response is obtained from a micromechanical model that enforces the principle of minimum action on a representative 3D unit cell. Finally, the macroscopic specimen response is predicted utilizing a finite element analysis program, which obtains the response at every Gauss point in the mesh from the microscopic unit cell model. The current communication focuses on the ability of the model to capture the yielding and collapse behaviors, as well as the strain rate effects, observed during impact loading of metallic foams.

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