Continuum damage based constitutive equations for copper under high temperature creep and cyclic plasticity

1992 ◽  
Vol 437 (1901) ◽  
pp. 545-566 ◽  
Keyword(s):  
Constitutive Equations ◽  
Damage Evolution ◽  
Thermal Loading ◽  
Evolution Equations ◽  
Experimental Results ◽  
Cyclic Plasticity ◽  
Nominal Composition ◽  
Cyclic Thermal Loading ◽  
Temperature Range ◽  
Good Agreement

Viscoplastic constitutive equations without damage for cast copper have been developed for cyclic mechanical and cyclic thermal loading over the temperature range 20-500 °C (nominal composition: 99.99 % Cu, 0.005 % O 2 , B.S. 10355-1037). Model predictions have been compared with experimental cyclic plasticity tests. Good agreement has been achieved. Creep and cyclic plasticity damage evolution equations have been developed. The effect of cyclic hardening on creep damage evolution has been modelled by introducing an internal variable to represent the state of material hardening. A creep cyclic plasticity interaction law has been proposed, and with the creep and cyclic plasticity damage evolution equations, has been combined with the viscoplastic constitutive equations to establish a unified material model for copper over the temperature range 20-500 °C. Predictions of lifetime and deformation history have been made for uni-axial test specimens subject to strain-controlled cyclic plasticity and ratchetting. Good agreement has been obtained with experimental results. The model has been validated for mechanical loading by predicting the response of uni-axial test specimens to strain-controlled cyclic plasticity with strain hold periods, and to combined strain-controlled cyclic plasticity tests with strain holds and ratchetting. The predictions compare well with experimental results. The model has been validated for cyclic thermal loading by predicting the response of uni-axial test specimens subjected to thermal loading cycles. Good comparisons have been achieved with experimental results.

Approximate method for the analysis of components undergoing ratchetting and failure

1998 ◽  
Vol 33 (1) ◽  
pp. 55-65 ◽  
Author(s):  
J Lin ◽  
F P E Dunne ◽  
D R Hayhurst
Keyword(s):  
Approximate Method ◽  
Mechanical Loading ◽  
Thermal Loading ◽  
Cyclic Plasticity ◽  
Processing Unit ◽  
Computationally Efficient ◽  
Element Analysis ◽  
Cyclic Thermal Loading ◽  
Central Processing ◽  
Practical Design

An approximate method has been presented for the design analysis of engineering components subjected to combined cyclic thermal and mechanical loading. The method is based on the discretization of components using multibar modelling which enables the effects of stress redistribution to be included as creep and cyclic plasticity damage evolves. Cycle jumping methods have also been presented which extend previous methods to handle problems in which incremental plastic straining (ratchetting) occurs. Cycle jumping leads to considerable reductions in computer CPU (central processing unit) resources, and this has been shown for a range of loading conditions. The cycle jumping technique has been utilized to analyse the ratchetting behaviour of a multibar structure selected to model geometrical and thermomechanical effects typically encountered in practical design situations. The method has been used to predict the behaviour of a component when subjected to cyclic thermal loading, and the results compared with those obtained from detailed finite element analysis. The method is also used to analyse the same component when subjected to constant mechanical loading, in addition to cyclic thermal loading leading to ratchetting. The important features of the two analyses are then compared. In this way, the multibar modelling is shown to enable the computationally efficient analysis of engineering components.

INVESTIGATION OF THE ENTROPY AND SPECIFIC HEAT CAPACITY OF GaN USING INCOMPLETE GAMMA FUNCTIONS

2008 ◽  
Vol 22 (30) ◽  
pp. 5349-5355 ◽  
Author(s):  
SAVAŞ SÖNMEZOǦLU
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Experimental Results ◽  
Analytical Relation ◽  
Gamma Functions ◽  
Temperature Range ◽  
Incomplete Gamma Functions ◽  
Theoretical Results ◽  
Good Agreement

The aim of this paper is to provide validity and reliable analytical relation for the thermodynamic functions calculated in terms of the Debye temperature using incomplete gamma functions, and examines the entropy and specific heat capacity of hexagonal single crystals of GaN in the 0–1800 K temperature range. The obtained results have been compared with the corresponding experimental and theoretical results. Our results are in excellent agreement with the theoretical results over the entire temperature range. It has also shown that at low temperature, our results are in very good agreement with the experimental results, however, at high temperature, our results are lower than other experimental results.

STRUCTURE OF THE Cu-NQR SPECTRUM IN Hg-1223 BETWEEN 4.2 K AND 145 K

2000 ◽  
Vol 14 (29n31) ◽  
pp. 3362-3367 ◽  
Author(s):  
H. BREITZKE ◽  
K. LÜDERS ◽  
A. A. GIPPIUS ◽  
E. V. ANTIPOV
Keyword(s):  
Structural Change ◽  
Crystal Lattice ◽  
Liquid Helium ◽  
Spectral Width ◽  
Low Noise ◽  
Experimental Results ◽  
The Other ◽  
Strong Variation ◽  
Temperature Range ◽  
Good Agreement

An extremely low noise RF preamplifier cooled with liquid helium has been developed and is used to perform Cu-NQR measurements for Hg-1223 (T c =134 K ) at temperatures from 4.2 K to 145 K. At temperatures from 4.2 K to 20 K the spectra are centered at 15 MHz with a spectral width of approximately 2 MHz, similar to the Cu-NQR spectra of the other members of the HgBa 2 Ca n -1 Cu n O 2 n +2+δ series. The Cu-NQR spectra in this temperature range exhibit some features indicating an unresolved splitting but they can still be fitted quite well by a set of two pairs of 63/65 Cu lines, as expected for the 1223 structure. The spectra at 40 K and above clearly show a structure that can not be fitted suitable by a set of two pairs of 63/65 Cu lines. However, a fit with a set of four pairs of 63/65 Cu lines is in good agreement with the experimental results. Furthermore, the spectra at 80 K, 85 K and 90 K show a strong variation with respect to each other which might indicate a structural change like the formation of a superstructure, as discussed for other high-T c compounds, instead of a simple disorder in the crystal lattice.

Experimental investigation of cyclic plasticity continuum damage evolution in an engineering component subjected to thermal loading

1993 ◽  
Vol 28 (4) ◽  
pp. 263-272 ◽  
Author(s):  
F P E Dunne ◽  
D B Puttergill ◽  
D R Hayhurst ◽  
Q J Mabbutt
Keyword(s):  
Grain Boundaries ◽  
Thermal Loading ◽  
Cyclic Plasticity ◽  
Test Facility ◽  
Thermal Shock Test ◽  
Continuum Damage ◽  
Loading Test ◽  
Cyclic Thermal Loading ◽  
Slip Bands ◽  
Persistent Slip Bands

A thermal shock test facility is designed and built to enable to enable a copper model slag tap component to be tested under cyclic thermal loading conditions. Infra-red line heaters and pumped cooling water are used to impose temperature loading cycles on to the specimen. Accurate focussing of the line heaters using a two degree of freedom adjustment mechanism, enables a heating area of width 3 mm to be applied to the specimen. Both the heating and the cooling processes are controlled by a proportional, integral, and derivative feedback micro-processor controller. Specimen temperature fields are obtained using thermocouples, and specimen displacements and strains are measured using linear voltage displacement transducers and strain gauges. A cyclic thermal loading test is carried out for approximately 7150 cycles on a model slag tap component. The variations of specimen strains and displacements are recorded and compared with results obtained from a finite element viscoplastic damage analysis. Good agreement between the predicted and experimental results is obtained. Microstructural examination of the specimen reveals the development of persistent slip bands and micro-cracking at grain boundaries. This occurs at the regions of the specimen undergoing cyclic plasticity due to the imposed cyclic thermal loading. The experimental observations of cyclic plasticity damage formation in copper undergoing cyclic thermal loading indicates the suitability of the Continuum Damage Mechanics (CDM) theory to model the evolution of cyclic plasticity damage. The damage is characterized by the development of fields of micro-cracked grain boundaries due to the formation and interaction of persistent slip bands within the grains.

THE DENSITY OF GASEOUS CHLORINE

1940 ◽  
Vol 18b (2) ◽  
pp. 55-65 ◽  
Author(s):  
A. S. Ross ◽  
O. Maass
Keyword(s):  
Equation Of State ◽  
Excellent Agreement ◽  
Industrial Applications ◽  
Experimental Results ◽  
Temperature Range ◽  
Molecular Weights ◽  
Convenient Form ◽  
Good Agreement

The density of gaseous chlorine has been determined over the temperature range 15° to 75 °C. and up to two atmospheres. The values obtained are compared with those extant in the literature, and excellent agreement is found with the very precise measurements of Jaquerod and Tourpaian at 15 °C. and 725 mm. pressure. There is also good agreement, over the temperature range of this investigation, with the measurements of Pier at a pressure of one atmosphere. The equation of state proposed by Maass and Mennie is shown to fit the experimental results over the whole range and to give, for temperatures and pressures outside the region covered by this investigation, values of the density of gaseous chlorine that are in good agreement with the results obtained by Jaquerod and Tourpaian, and by Pier. Tables of calculated and experimentally determined densities and apparent molecular weights show the deviations of gaseous chlorine from ideality. The equation of state is given in a convenient form for the calculation of the density of the gas in industrial applications.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

PHOTOINDUCED NONLINEAR OCTUPOLAR POLARIZATION: TRANSIENT AND PERMANENT REGIMES

1996 ◽  
Vol 05 (04) ◽  
pp. 653-670 ◽  
Author(s):  
CÉLINE FIORINI ◽  
JEAN-MICHEL NUNZI ◽  
FABRICE CHARRA ◽  
IFOR D.W. SAMUEL ◽  
JOSEPH ZYSS
Keyword(s):  
Theoretical Analysis ◽  
Second Harmonic ◽  
Experimental Results ◽  
Polar Field ◽  
Rotational Spectrum ◽  
Dual Frequency ◽  
One Dimensional ◽  
Ethyl Violet ◽  
Disperse Red 1 ◽  
Good Agreement

An original poling method using purely optical means and based on a dual-frequency interference process is presented. We show that the coherent superposition of two beams at fundamental and second-harmonic frequencies results in a polar field with an irreducible rotational spectrum containing both a vector and an octupolar component. This enables the method to be applied even to molecules without a permanent dipole such as octupolar molecules. After a theoretical analysis of the process, we describe different experiments aiming at light-induced noncentrosymmetry performed respectively on one-dimensional Disperse Red 1 and octupolar Ethyl Violet molecules. Macroscopic octupolar patterning of the induced order is demonstrated in both transient and permanent regimes. Experimental results show good agreement with theory.

scholarly journals A Digital Improvement—Trimming a Digital Temperature Sensor with EEPROM Reprogrammable Fuses

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1700
Author(s):  
Anca Mihaela Vasile (Dragan) ◽  
Alina Negut ◽  
Adrian Tache ◽  
Gheorghe Brezeanu
Keyword(s):  
Standard Deviation ◽  
Power Supply ◽  
Temperature Sensor ◽  
Experimental Results ◽  
Temperature Error ◽  
Thermal Sensor ◽  
Memory Cells ◽  
Temperature Range ◽  
Read Only Memory ◽  
Digital Temperature Sensor

An EEPROM (electrically erasable programmable read-only memory) reprogrammable fuse for trimming a digital temperature sensor is designed in a 0.18-µm CMOS EEPROM. The fuse uses EEPROM memory cells, which allow multiple programming cycles by modifying the stored data on the digital trim codes applied to the thermal sensor. By reprogramming the fuse, the temperature sensor can be adjusted with an increased trim variation in order to achieve higher accuracy. Experimental results for the trimmed digital sensor showed a +1.5/−1.0 ℃ inaccuracy in the temperature range of −20 to 125 ℃ for 25 trimmed DTS samples at 1.8 V by one-point calibration. Furthermore, an average mean of 0.40 ℃ and a standard deviation of 0.70 ℃ temperature error were obtained in the same temperature range for power supply voltages from 1.7 to 1.9 V. Thus, the digital sensor exhibits similar performances for the entire power supply range of 1.7 to 3.6 V.

scholarly journals Comparison of Experimental and Numerical Transient Drop Deformation during Transition through Orifices in High-Pressure Homogenizers

2021 ◽  
Vol 5 (3) ◽  
pp. 32
Author(s):  
Benedikt Mutsch ◽  
Peter Walzel ◽  
Christian J. Kähler
Keyword(s):  
High Pressure ◽  
Visual Analysis ◽  
Imaging Technique ◽  
Extensional Flow ◽  
Droplet Breakup ◽  
Experimental Results ◽  
Drop Deformation ◽  
Droplet Deformation ◽  
Shadow Imaging ◽  
Good Agreement

The droplet deformation in dispersing units of high-pressure homogenizers (HPH) is examined experimentally and numerically. Due to the small size of common homogenizer nozzles, the visual analysis of the transient droplet generation is usually not possible. Therefore, a scaled setup was used. The droplet deformation was determined quantitatively by using a shadow imaging technique. It is shown that the influence of transient stresses on the droplets caused by laminar extensional flow upstream the orifice is highly relevant for the droplet breakup behind the nozzle. Classical approaches based on an equilibrium assumption on the other side are not adequate to explain the observed droplet distributions. Based on the experimental results, a relationship from the literature with numerical simulations adopting different models are used to determine the transient droplet deformation during transition through orifices. It is shown that numerical and experimental results are in fairly good agreement at limited settings. It can be concluded that a scaled apparatus is well suited to estimate the transient droplet formation up to the outlet of the orifice.

Generalized displacement correlation method for mechanical and thermal fracture of FGM

2020 ◽  
Vol 09 (01) ◽  
pp. 2050004
Author(s):  
Y. Ait Ferhat ◽  
A. Boulenouar ◽  
N. Benamara ◽  
L. Benabou
Keyword(s):  
Present Method ◽  
Thermal Loading ◽  
Parametric Design ◽  
Correlation Method ◽  
Functionally Graded ◽  
Mixed Mode Fracture ◽  
Graded Materials ◽  
Displacement Based ◽  
Ansys Parametric Design Language ◽  
Good Agreement

The main objective of this work is to present a numerical modeling of mixed-mode fracture in isotropic functionally graded materials (FGMs), under mechanical and thermal loading conditions. In this paper, the displacement-based method, termed the generalized displacement correlation (GDC) method, is investigated for estimating stress intensity factor (SIF). Using the ANSYS Parametric Design Language (APDL), the continuous variations of the material properties are incorporated by specified parameters at the centroid of each element. This paper presents various numerical examples in which the accuracy of the present method is verified. Comparisons have been made between the SIFs predicted by the GDC method and the available reference solutions in the current literature. A good agreement is achieved between the results of the GDC method and the reference solutions.

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