Measurement of uniform and localized heat dissipation induced by cyclic loading

1998 ◽  
Vol 38 (4) ◽  
pp. 289-294 ◽  
Author(s):  
T. K. Jacobsen ◽  
B. F. Sørensen ◽  
P. Brøndsted
1999 ◽  
Vol 591 ◽  
Author(s):  
H. Rösner ◽  
N. Meyendorf ◽  
S. Sathish ◽  
T.E. Matikas

ABSTRACTDissipated heat has been measured by thermographic technique during fatigue experiments on Ti-6AI-4V. Surface temperature of the specimen was found sensitive to the amount of fatigue damage accumulated in the material. An increased heat dissipation due to fatigue can be related to continuous change in the microstructure (increased dislocation density, stacking faults etc.) of the material. A method based on passive thermography can be proposed to monitor damage accumulation in Ti-6Al-4V due to cyclic loading.


2009 ◽  
Vol 31 (8-9) ◽  
pp. 1407-1412 ◽  
Author(s):  
Charles Mareau ◽  
Véronique Favier ◽  
Bastien Weber ◽  
André Galtier

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3546
Author(s):  
Dragoslav Sumarac ◽  
Petar Knezevic ◽  
Cemal Dolicanin ◽  
Maosen Cao

The Preisach model already successfully implemented for axial and bending cyclic loading is applied for modeling of the plateau problem for mild steel. It is shown that after the first cycle plateau disappears an extension of the existing Preisach model is needed. Heat dissipation and locked-in energy is calculated due to plastic deformation using the Preisach model. Theoretical results are verified by experiments performed on mild steel S275. The comparison of theoretical and experimental results is evident, showing the capability of the Presicah model in predicting behavior of structures under cyclic loading in the elastoplastic region. The purpose of this paper is to establish a theoretical background for embedded sensors like regenerated fiber Bragg gratings (RFBG) for measurement of strains and temperature in real structures. In addition, the present paper brings a theoretical base for application of nested split-ring resonator (NSRR) probes in measurements of plastic strain in real structures.


2020 ◽  
Vol 21 (5) ◽  
pp. 505
Author(s):  
Yousef Ghaderi Dehkordi ◽  
Ali Pourkamali Anaraki ◽  
Amir Reza Shahani

The prediction of residual stress relaxation is essential to assess the safety of welded components. This paper aims to study the influence of various effective parameters on residual stress relaxation under cyclic loading. In this regard, a 3D finite element modeling is performed to determine the residual stress in welded aluminum plates. The accuracy of this analysis is verified through experiment. To study the plasticity effect on stress relaxation, two plasticity models are implemented: perfect plasticity and combined isotropic-kinematic hardening. Hence, cyclic plasticity characterization of the material is specified by low cycle fatigue tests. It is found that the perfect plasticity leads to greater stress relaxation. In order to propose an accurate model to compute the residual stress relaxation, the Taguchi L18 array with four 3-level factors and one 6-level is employed. Using statistical analysis, the order of factors based on their effect on stress relaxation is determined as mean stress, stress amplitude, initial residual stress, and number of cycles. In addition, the stress relaxation increases with an increase in mean stress and stress amplitude.


Author(s):  
R. Z. Aminov ◽  
A. N. Bayramov ◽  
M. V. Garievskii

The paper gives the analysis of the problem of the primary current frequency regulation in the power system, as well as the basic requirements for NPP power units under the conditions of involvement in the primary regulation. According to these requirements, the operation of NPPs is associated with unloading and a corresponding decrease in efficiency. In this regard, the combination of nuclear power plants with a hydrogen complex is shown to eliminate the inefficient discharge mode which allows the steam turbine equipment and equipment of the reactor facility to operate in the basic mode at the nominal power level. In addition, conditions are created for the generation and accumulation of hydrogen and oxygen during the day, as well as additionally during the nighttime failure of the electrical load which allows them to be used to generate peak power.  The purpose of the article is to assess the systemic economic effect as a result of the participation of nuclear power plants in combination with the hydrogen complex in the primary control of the current frequency in the power sys-tem, taking into account the resource costs of the main equipment. In this regard, the paper gives the justification of cyclic loading of the main equipment of the hydrogen complex: metal storage tanks of hydrogen and oxygen, compressor units, hydrogen-oxygen combustion chamber of vapor-hydrogen overheating of the working fluid in the steam turbine cycle of a nuclear power plant. The methodological foundations for evaluating the working life of equipment under cyclic loading with the participation in the primary frequency control by the criterion of the growth rate of a fatigue crack are described. For the equipment of the hydrogen complex, the highest intensity of loading is shown to occur in the hydrogen-oxygen combustion chamber due to high thermal stresses.  The system economic effect is estimated and the effect of wear of the main equipment under cyclic loading is shown. Under the conditions of combining NPP power units with a hydrogen complex, the efficiency of primary reg-ulation is shown to depend significantly on: the cost of equipment subjected to cyclic loading; frequency and intensity of cyclic loading; the ratio of the tariff for peak electricity, and the cost of electricity of nuclear power plants.  Based on the developed methodology for assessing the effectiveness of the participation of nuclear power plants with a hydrogen complex in the primary frequency control, taking into account the damage to the equipment, the use of the hydrogen complex is shown to provide a tangible economic effect compared with the option of unloading nuclear power plants with direct participation in frequency control.


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