A constitutive model for the thermo-mechanical behaviour of fusion-relevant pebble beds and its application to the simulation of HELICA mock-up experimental results

2007 ◽  
Vol 82 (15-24) ◽  
pp. 2366-2374 ◽  
Author(s):  
G. Dell’Orco ◽  
P.A. Di Maio ◽  
R. Giammusso ◽  
A. Tincani ◽  
G. Vella
Keyword(s):  
Constitutive Model ◽  
Mechanical Behaviour ◽  
Experimental Results

scholarly journals Experimental results and constitutive model of the mechanical behavior of Ti6Al4V alloy at high temperature

2019 ◽  
Vol 41 ◽  
pp. 723-730
Author(s):  
Jorge Ayllón Perez ◽  
Valentín Miguel Eguía ◽  
Juana Coello Sobrino ◽  
Alberto Martínez Martínez
Keyword(s):  
High Temperature ◽  
Constitutive Model ◽  
Mechanical Behavior ◽  
Ti6al4v Alloy ◽  
Experimental Results

Plastic Flow Stress and Constitutive Model for H96 Brass Alloy

2015 ◽  
Vol 782 ◽  
pp. 130-136 ◽  
Author(s):  
Ping Zhou ◽  
Wei Guo Guo ◽  
Hai Hui Wu
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
Plastic Flow ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Experimental Results ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Brass Alloy ◽  
Plastic Flow Stress

To explore the thermo-mechanical response of H96 brass alloy, the quasi-static (universal-testing machine) and dynamic (the split Hopkinson pressure bar apparatus) uniaxial compression experiments have been performed under the temperatures from 293 K to 873 K and the strain rates from 0.001 s-1 to 6000 s-1, and the strains over 60% are obtained. Results show that, H96 brass alloy has strong strain hardening behavior, and it becomes weaker with the increasing temperature. In addition, this alloy is sensitive to strain rates; and, it has temperature sensitivity, the dynamic strain aging occurs at the temperature of 473 K and a quasi-static strain rate of 0.001 s-1. Based on the thermal activation dislocation mechanism, paralleled with the experimental results, a plastic flow constitutive model with the physical conception is developed. The model is suitable to predict the plastic flow stress at different temperatures and strain rates. According to comparing results, the model predictions are in good agreement with the experimental results.

Numerical Modeling and Analysis of Nonlinear Dynamic Response for a Bolted Joint Beam Considering Interface Frictional Contact

2018 ◽  
Author(s):  
Dongwu Li ◽  
Chao Xu ◽  
Dong Wang ◽  
Lihua Wen
Keyword(s):  
Constitutive Model ◽  
Dynamic Response ◽  
Numerical Results ◽  
Experimental Results ◽  
Bolted Joints ◽  
Interface Element ◽  
Nonlinear Stiffness ◽  
Friction Contact ◽  
Structural Dynamic ◽  
Stiffness And Damping

For an assembled structure with many bolted joints, predicting its dynamic response with high fidelity is always a difficult problem, because of the nonlinearity introduced by friction contact between jointed interfaces. The friction contact results in nonlinear stiffness and damping to a structure. To realize predictive simulation in structural dynamic design, these nonlinear behaviors must be carefully considered. In this paper, the dynamics of a multi-bolt jointed beam is calculated. A modified IWAN constitutive model, which can consider both tangential micro/macro slip and nonzero residual stiffness at macroslip phase, is developed to model nonlinear contact behaviors due to joint interfaces. A whole interface element integrating the proposed constitutive model is developed. The element is used to model the nonlinear stiffness and damping caused by bolted joints. The interface element is placed between the two contact interfaces. The other part of the beam is modeled by linear beam elements. A Matlab code is developed to realize the proposed nonlinear finite element dynamic analysis method. A hammer impact experiment for the bolt-jointed beam is conducted under different excitation force levels. The calculated nonlinear numerical results are compared with experimental results. It is shown that the effect of joint nonlinearity on structural dynamics can be observed from the response predicted by the proposed method. The numerical results agree well with the experimental results. This work validates the necessary of using nonlinear joint model for dynamic simulation of jointed structures.

A framework for the behaviour of unsaturated expansive clays

1992 ◽  
Vol 29 (6) ◽  
pp. 1013-1032 ◽  
Author(s):  
A. Gens ◽  
E. E. Alonso
Keyword(s):  
Key Words ◽  
Mechanical Behaviour ◽  
Unsaturated Soils ◽  
Expansive Soils ◽  
Experimental Results ◽  
Structural Rearrangements ◽  
Expansive Clays ◽  
Clay Model ◽  
Model Predictions ◽  
Low Activity

The paper presents a framework for describing the mechanical behaviour of unsaturated expansive clays. It is an extension of an existing formulation developed for unsaturated soils of low activity. The extended framework is based on the distinction within the material of a microstructural level where the basic swelling of the active minerals takes place and a macrostructural level responsible for major structural rearrangements. By adopting simple assumptions concerning the coupling between the two levels, it is possible to reproduce major features of the behaviour of unsaturated expansive clays. Some selected qualitative comparisons between model predictions and experimental results reported in the literature are presented. Despite the simplified hypotheses made, a very encouraging agreement is obtained. Key words : capillarity, clay, model, unsaturation, suction, expansive soils.

Irradiation creep of SA 304L and CW 316 stainless steels: Mechanical behaviour and microstructural aspects. Part I: Experimental results

2011 ◽  
Vol 413 (2) ◽  
pp. 63-69 ◽  
Author(s):  
J. Garnier ◽  
Y. Bréchet ◽  
M. Delnondedieu ◽  
C. Pokor ◽  
P. Dubuisson ◽  
...  
Keyword(s):  
Mechanical Behaviour ◽  
Stainless Steels ◽  
Experimental Results ◽  
Irradiation Creep

Progressive Damage Approach to Simulating Low Velocity Impact Response of Plain Weave C/SiC Composites

2010 ◽  
Vol 118-120 ◽  
pp. 241-245 ◽  
Author(s):  
Liu Ding Chen ◽  
Xiao Yan Tong ◽  
Xiang Zheng ◽  
Lei Jiang Yao
Keyword(s):  
Constitutive Model ◽  
Time History ◽  
Composite Plates ◽  
Experimental Results ◽  
Low Velocity Impact ◽  
Progressive Damage ◽  
Low Velocity ◽  
Velocity Impact ◽  
Plain Weave ◽  
User Subroutine

Based on progressive damage theory, a 3D laminated model with an orthotropic property in plane was established to simulate the response of plain weave carbon fiber reinforced silicon carbide(C/SiC) ceramic matrix composites(CMC) under low velocity impact(LVI). Intra-layer damage and inter-layer damage were taken into account, respectively. Three scalar damage variables, associated with the degradation of warp modulus, weft modulus and shear modulus, respectively, were proposed to characterize intra-layer damage evolutions. The intra-layer constitutive model was implemented into MSC.Dytran, via its user subroutine EXFAIL1. The potential delamination region was considered as a discrete cohesive zone. Three vector spring elements were placed into every two adjacent nodes to simulate the inter-layer joints. A scalar damage variables, associated with the degradation of the three vector spring elements, were brought forward to characterize the inter-layer damage evolutions. The inter-layer constitutive model was implemented into MSC.Dytran, via its user subroutine EXELAS. Damage area, indentation depth of C/SiC composite plates and time history of impact force were obtained to compare with experimental results. The numerical results show overall good agreement with experimental results.

scholarly journals Energy-based constitutive modelling of local material properties of canine aortas

2016 ◽  
Vol 3 (9) ◽  
pp. 160365 ◽  
Author(s):  
Kaveh Laksari ◽  
Danial Shahmirzadi ◽  
Camilo J. Acosta ◽  
Elisa Konofagou
Keyword(s):  
Constitutive Model ◽  
Mechanical Behaviour ◽  
Computational Models ◽  
Constitutive Models ◽  
Constitutive Modelling ◽  
Axial Position ◽  
Aortic Tissue ◽  
Nonlinear Constitutive Model ◽  
Local Material Properties

This study aims at determining the in vitro anisotropic mechanical behaviour of canine aortic tissue. We specifically focused on spatial variations of these properties along the axis of the vessel. We performed uniaxial stretch tests on canine aortic samples in both circumferential and longitudinal directions, as well as histological examinations to derive the tissue's fibre orientations. We subsequently characterized a constitutive model that incorporates both phenomenological and structural elements to account for macroscopic and microstructural behaviour of the tissue. We showed the two fibre families were oriented at similar angles with respect to the aorta's axis. We also found significant changes in mechanical behaviour of the tissue as a function of axial position from proximal to distal direction: the fibres become more aligned with the aortic axis from 46° to 30°. Also, the linear shear modulus of media decreased as we moved distally along the aortic axis from 139 to 64 kPa. These changes derived from the parameters in the nonlinear constitutive model agreed well with the changes in tissue structure. In addition, we showed that isotropic contribution, carried by elastic lamellae, to the total stress induced in the tissue decreases at higher stretch ratios, whereas anisotropic stress, carried by collagen fibres, increases. The constitutive models can be readily used to design computational models of tissue deformation during physiological loading cycles. The findings of this study extend the understanding of local mechanical properties that could lead to region-specific diagnostics and treatment of arterial diseases.

Extrusion Process Modeling for Aqueous-Based Ceramic Pastes—Part 2: Experimental Verification

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Mingyang Li ◽  
Lie Tang ◽  
Robert G. Landers ◽  
Ming C. Leu
Keyword(s):  
Constitutive Model ◽  
Response Time ◽  
Rapid Change ◽  
Experimental Studies ◽  
Extrusion Process ◽  
Experimental Results ◽  
Constitutive Law ◽  
Extrusion Force ◽  
Air Bubble ◽  
Highly Nonlinear

In the Part 1 paper, a constitutive law for the extrusion process of aqueous-based ceramic pastes was created. In the study described herein, a capillary rheometer was used to calibrate the viscosity of an alumina paste, and a single extruder system was used to conduct extrusion experiments to validate the constitutive model. It is shown that the extrusion response time and its change both depend on the amount of air in the extruder and the magnitude of the extrusion force. When the extrusion force is small, the rapid change of extrusion response time gives the extrusion dynamic an apparent quadratic response. When the extrusion force is large, the extrusion response time changes slowly, and is dominated by a first-order response. Air bubble release was observed in some of the experiments. A series of simulation and experimental studies were conducted to validate the predictive capabilities of the constitutive model for both steady-state and transient extrusion force behaviors. Good agreements between the simulation and experimental results were obtained. The experimental results demonstrate that the constitutive model is capable of capturing the characteristics of the highly nonlinear response at low extrusion forces and the air bubble release phenomenon. The numerical studies show that the decrease in the extrusion force during an air bubble release depends on the volume of the air bubble.

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