scholarly journals Steady-State Thermoelastic Analytical Solutions for Insulated Pipelines

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
M. Fraldi ◽  
L. Esposito ◽  
F. Carannante ◽  
A. Cutolo ◽  
L. Nunziante
Keyword(s):  
Steady State ◽  
Mechanical Response ◽  
Syntactic Foam ◽  
Practical Interest ◽  
Radial Pressure ◽  
Coating Materials ◽  
Laminate Glass ◽  
Geometrical Features ◽  
Von Mises ◽  
Constitutive Parameters

A steady-state thermoelastic analytical solution for a multilayer hollow cylinder, composed of an arbitrary number of phases and subject to both radial pressure and temperature gradient, is presented. By assuming each phase to be homogeneous and thermally isotropic and by varying the mechanical and thermal constitutive parameters, a sensitivity analysis has been performed with the aim of finally applying the study to the mechanical behaviour of an industrial pipeline composed of three phases (steel, insulating coating, and polyethylene) under the action of the above-mentioned load conditions. By making reference to a classical Hencky-von Mises criterion, the stress profiles along the thickness of the layers have been carried out, also localizing the onset of plasticity as a function of the temperature variations, material properties, and geometrical features characterizing the composite structure of interest. At the end, some numerical results of practical interest in the engineering applications have been specialized to three different insulated coating materials (expanded polyurethane, laminate glass, and syntactic foam), to highlight the cases in which thermal properties and loads can significantly interfere with the mechanical response in pipes, in terms of stresses, in this way suggesting possible strategies for avoiding unexpected failure and supporting the optimal structural design of these systems.

scholarly journals Steady-state $$\dot{V}{\text{O}}_{2}$$ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners

2021 ◽  
Author(s):  
Rebekah J. Nixon ◽  
Sascha H. Kranen ◽  
Anni Vanhatalo ◽  
Andrew M. Jones
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Lactate Concentration ◽  
Practical Interest ◽  
Blood Lactate Concentration ◽  
Distance Runners ◽  
Severe Intensity ◽  
The Stability ◽  
Trained Runners ◽  
Over Time

AbstractThe metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 was stable over time from speeds at which a steady-state $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 could not be established. Ten well-trained male distance runners completed 9–12 constant-speed treadmill tests, including 3–5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P < 0.001). Blood lactate concentration was higher and increased with time at a speed 0.5 km/h higher than MLSS compared to MLSS (P < 0.01); however, pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 did not change significantly between 10 and 30 min at either MLSS or MLSS + 0.5 km/h. In contrast, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 increased significantly over time and reached $$\dot{V}{\text{O}}_{2\,\,\max }$$ V ˙ O 2 max at end-exercise at a speed ~ 0.4 km/h above CS (P < 0.05) but remained stable at a speed ~ 0.5 km/h below CS. The stability of $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 at a speed exceeding MLSS suggests that MLSS underestimates the maximal metabolic steady state. These results indicate that CS more closely represents the maximal metabolic steady state when the latter is appropriately defined according to the ability to stabilise pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 .

Force de répulsion entre un courant sinusoïdal linéique et une bande conductrice mince : application aux problèmes de lévitation

1994 ◽  
Vol 72 (9-10) ◽  
pp. 633-638
Author(s):  
M. T. Attaf ◽  
D. Allab
Keyword(s):  
Electromagnetic Field ◽  
Steady State ◽  
Electromagnetic Interaction ◽  
Practical Interest ◽  
Stationary Case ◽  
Electromagnetic Field Distribution ◽  
Conducting Plate ◽  
Conducting Materials ◽  
Sinusoidal Current ◽  
Repulsive Forces

In a previous work, the authors presented a semianalytical treatment of the electromagnetic field distribution in the case of a straight conductor carrying a sinusoidal current parallel to a thin conducting plate. The result of this investigation is extended here to the evaluation of the repulsive forces accompanying this type of electromagnetic interaction. The variation of such forces with geometric parameters is studied in the presence of a single conductor, and in the case of several conductors laying in a plane parallel to the surface of the material submitted to the induction phenomenon. The problem of lévitation in steady-state conditions is examined, in the light of this arrangement, for various conducting materials. Graphs illustrate the results obtained and make evident their practical interest particularly in the stationary case of magnetically levitated vehicles.

Drawing of Tubes

1980 ◽  
Vol 47 (4) ◽  
pp. 736-740 ◽  
Author(s):  
D. Durban
Keyword(s):  
Exact Solution ◽  
Steady State ◽  
Radial Flow ◽  
Material Behavior ◽  
Wall Friction ◽  
Flow Rule ◽  
Flow Conditions ◽  
Steady State Flow ◽  
Linear Hardening ◽  
Von Mises

The process of the tube drawing between two rough conical walls is analyzed within the framework of continuum plasticity. Material behavior is modeled as rigid/linear-hardening along with the von-Mises flow rule. Assuming a radial flow pattern and steady state flow conditions it becomes possible to obtain an exact solution for the stresses and velocity. Useful relations are derived for practical cases where the nonuniformity induced by wall friction is small. A few restrictions on the validity of the results are discussed.

scholarly journals Biomechanical Behavior Evaluation of a Novel Hybrid Occlusal Splint-mouthguard for Contact Sports: 3D-FEA

2021 ◽  
Author(s):  
Les Kalman ◽  
Amanda Maria de Oliveira Dal Piva ◽  
Talita Suelen de Queiroz ◽  
João Paulo Mendes Tribst
Keyword(s):  
Stress Concentration ◽  
Mechanical Response ◽  
Compressive Loading ◽  
Von Mises Stress ◽  
Occlusal Splint ◽  
Total Deformation ◽  
Contact Sports ◽  
Biomechanical Behavior ◽  
Custom Made ◽  
Von Mises

Orofacial injuries are common occurrences during contact sports activities; however, there is an absence of data regarding the performance of hybrid occlusal splint mouthguards, especially during compressive loading. To evaluate the total deformation and stress concentration, a skull model was selected and duplicated to receive two different designs of mouthguard devices: one model received a conventional custom-made mouthguard (MG) with 4-mm thickness and the other received a novel hybrid occlusal splint-mouthguard (HMG) with the same thickness. Both models were subdivided into finite elements. The frictionless contacts were used, and a nonlinear analysis was performed simulating the compressive loading in occlusion. The results were presented in von-Mises stress maps (MPa) and Total Deformation (mm). A higher stress concentration in teeth was observed for the model with the conventional MG, while the HMG design displayed a promising mechanical response with lower stress magnitude. The HMG de-sign displayed a higher magnitude of stress on its occlusal portion than the MG design. The hybrid mouthguard (HMG) reduced (1) jaw displacement during chewing and (2) the generated stresses in maxil-lary and mandibular teeth.

Influence of Strain-Hardening and Dynamic Recovery on DDRX Steady State

2021 ◽  
Vol 1016 ◽  
pp. 194-199
Author(s):  
Frank Montheillet ◽  
David Piot
Keyword(s):  
Steady State ◽  
Strain Hardening ◽  
Dynamic Recovery ◽  
Constitutive Parameters

Relationships between macroscopic and microscopic constitutive parameters associated with steady state DDRX are derived for a material in which strain-hardening and dynamic recovery are described by the Yoshie-Laasraoui-Jonas equation. First examples are given for illustration.

scholarly journals Constitutive relations for compressible granular flow in the inertial regime

2019 ◽  
Vol 874 ◽  
pp. 926-951 ◽  
Author(s):  
D. G. Schaeffer ◽  
T. Barker ◽  
D. Tsuji ◽  
P. Gremaud ◽  
M. Shearer ◽  
...  
Keyword(s):  
Steady State ◽  
Granular Flow ◽  
Numerical Solutions ◽  
Volume Fraction ◽  
Constitutive Relations ◽  
Practical Interest ◽  
Time Dependent ◽  
Direct Result ◽  
Wide Range ◽  
Inertial Regime

Granular flows occur in a wide range of situations of practical interest to industry, in our natural environment and in our everyday lives. This paper focuses on granular flow in the so-called inertial regime, when the rheology is independent of the very large particle stiffness. Such flows have been modelled with the $\unicode[STIX]{x1D707}(I),\unicode[STIX]{x1D6F7}(I)$-rheology, which postulates that the bulk friction coefficient $\unicode[STIX]{x1D707}$ (i.e. the ratio of the shear stress to the pressure) and the solids volume fraction $\unicode[STIX]{x1D719}$ are functions of the inertial number $I$ only. Although the $\unicode[STIX]{x1D707}(I),\unicode[STIX]{x1D6F7}(I)$-rheology has been validated in steady state against both experiments and discrete particle simulations in several different geometries, it has recently been shown that this theory is mathematically ill-posed in time-dependent problems. As a direct result, computations using this rheology may blow up exponentially, with a growth rate that tends to infinity as the discretization length tends to zero, as explicitly demonstrated in this paper for the first time. Such catastrophic instability due to ill-posedness is a common issue when developing new mathematical models and implies that either some important physics is missing or the model has not been properly formulated. In this paper an alternative to the $\unicode[STIX]{x1D707}(I),\unicode[STIX]{x1D6F7}(I)$-rheology that does not suffer from such defects is proposed. In the framework of compressible $I$-dependent rheology (CIDR), new constitutive laws for the inertial regime are introduced; these match the well-established $\unicode[STIX]{x1D707}(I)$ and $\unicode[STIX]{x1D6F7}(I)$ relations in the steady-state limit and at the same time are well-posed for all deformations and all packing densities. Time-dependent numerical solutions of the resultant equations are performed to demonstrate that the new inertial CIDR model leads to numerical convergence towards physically realistic solutions that are supported by discrete element method simulations.

The steady-state response of a Maxwell viscoelastic cylinder to sinusoidal oscillation of its boundary

2007 ◽  
Vol 464 (2089) ◽  
pp. 207-221 ◽  
Author(s):  
Panagiotis G Massouros ◽  
Guy M Genin
Keyword(s):  
Steady State ◽  
Mechanical Response ◽  
External Loading ◽  
Loading Frequency ◽  
Peak Strain ◽  
Steady State Response ◽  
Viscoelastic Cylinder ◽  
Sinusoidal Oscillation ◽  
State Response ◽  
Angular Vibration

The steady-state response of a Maxwell viscoelastic cylinder to periodic sinusoidal oscillation of its boundary was studied as a simplified model of the brain responding to low-amplitude angular vibration of an idealized skull. The objectives were to identify conditions in which peak strain occurred on the interior of the cylinder, and to identify ways to scale strains from differently sized cylinders. This latter objective is motivated by the work of Holbourn to inform scaling of intracranial strains experienced under similar acceleration of skulls of different animals. The mechanical response was dictated by two dimensionless parameters that incorporate material properties and external loading frequency. The location and magnitude of maximum strain were examined with respect to these governing parameters in steady state. A frequency-dependent mapping of brain constitutive data to idealized Maxwell models was applied to predict the location and magnitude of peak strains inside a cylinder with mechanical properties representing the adult human brain. Results suggest that peak strains occur on the interior of such a cylinder for skull oscillation within a specific frequency band.

Mechanical Behavior of Alloy AA6111 Processed by Severe Plastic Deformation: Modeling and Experiment

2007 ◽  
Vol 129 (3) ◽  
pp. 380-389 ◽  
Author(s):  
Yuri Estrin ◽  
KiHo Rhee ◽  
Rimma Lapovok ◽  
Peter F. Thomson
Keyword(s):  
Mechanical Response ◽  
Uniform Elongation ◽  
Internal Variable ◽  
Uniaxial Tensile ◽  
Variable Model ◽  
Angular Pressing ◽  
Heat Treated ◽  
Wide Range ◽  
Before And After ◽  
Constitutive Parameters

An established dislocation density related, one-internal variable model was used, with some modifications, as a basis for modeling the mechanical response of aluminum alloy AA6111. In addition to conventional rolling, equal channel angular pressing (ECAP) was used to produce a wide range of grain sizes, down to the submicrometer scale. The samples were heat treated before and after both processes to optimize tensile ductility. Implementation of the model to uniaxial tensile response of the conventionally rolled and the ECAP processed materials confirmed its good predictive capability. The model was further used to formulate simple relations between true uniform strain and the constitutive parameters that allow reliable prediction of the uniform elongation.

Torsional Fatigue of 63Sn-37Pb and Sn-0.7Cu Solders

2007 ◽  
Vol 353-358 ◽  
pp. 2908-2911
Author(s):  
Ning Bai ◽  
Xu Chen ◽  
Xin Li
Keyword(s):  
Steady State ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Equivalent Strain ◽  
Fatigue Tests ◽  
Load Drop ◽  
Torsional Fatigue ◽  
Von Mises ◽  
Fatigue Criterion ◽  
Better Than

A series of torsional fatigue tests were conducted on 63Sn-37Pb and Sn-0.7Cu solders. A continuous load drop was observed during the test. It was found that the load drop percentage had little effect on the elastic strain-life curve but strong effect on the plastic strain-life curve. The fatigue strength coefficient, fatigue strength exponent and fatigue ductility exponent had no great changes with the load drop. However, fatigue ductility coefficient showed a great difference and was linearly varying with load drop. A fatigue criterion of Coffin-Manson type was proposed in relation to load drop. The descending curve of the stress range with cycle was observed to consist of transient, steady state and tertiary regions. The percentage of load drop corresponding to the turning point from the steady state to the tertiary region was about 25% for all strain ranges of 63Sn-37Pb, and 30% for all strain ranges of Sn-0.7Cu. The torsional fatigue lives were correlated with von Mises equivalent strain amplitudes well. The fatigue behavior of Sn-0.7Cu is better than that of 63Sn-37Pb.

Sign in / Sign up

Export Citation Format

Share Document