scholarly journals Reduced order numerical modeling for calibration of complex constitutive models in powder pressing simulations

2017 ◽  
Vol 49 (3) ◽  
pp. 331-345
Author(s):  
Shwetank Pandey ◽  
Vladimir Buljak ◽  
Igor Balac
Keyword(s):  
Ceramic Powder ◽  
Constitutive Models ◽  
Industrial Applications ◽  
Reduced Order ◽  
Discrepancy Function ◽  
Numerical Instabilities ◽  
Powder Pressing ◽  
Cap Model ◽  
The Difference ◽  
Constitutive Parameters

Numerical simulations of different ceramic production phases often involve complex constitutive models, with difficult calibration process, relying on a large number of experiments. Methodological developments, proposed in present paper regarding this calibration problem can be outlined as follows: assessment of constitutive parameters is performed through inverse analysis procedure, centered on minimization of discrepancy function which quantifies the difference between measurable quantities and their computed counterpart. Resulting minimization problem is solved through genetic algorithms, while the computational burden is made consistent with constraints of routine industrial applications by exploiting Reduced Order Model (ROM) based on proper orthogonal decomposition. Throughout minimization, a gradual enrichment of designed ROM is used, by including additional simulations. Such strategy turned out to be beneficial when applied to models with a large number of parameters. Developed procedure seems to be effective when dealing with complex constitutive models, that can give rise to non-continuous discrepancy function due to the numerical instabilities. Proposed approach is tested and experimentally validated on the calibration of modified Drucker-Prager CAP model, frequently adopted for ceramic powder pressing simulations. Assessed values are compared with those obtained by traditional, time-consuming tests, performed on pressed green bodies.

scholarly journals Calibration of Drucker–Prager Cap Constitutive Model for Ceramic Powder Compaction through Inverse Analysis

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4044
Author(s):  
Vladimir Buljak ◽  
Severine Bavier-Romero ◽  
Achraf Kallel
Keyword(s):  
Inverse Analysis ◽  
Ceramic Powder ◽  
Calibration Procedure ◽  
Powder Compaction ◽  
Alumina Powder ◽  
Compaction Test ◽  
Calibration Protocol ◽  
Cap Model ◽  
The Difference ◽  
Constitutive Parameters

Phenomenological plasticity models that relate relative density to plastic strain are frequently used to simulate ceramic powder compaction. With respect to the form implemented in finite element codes, they need to be modified in order to define governing parameters as functions of relative densities. Such a modification increases the number of constitutive parameters and makes their calibration a demanding task that involves a large number of experiments. The novel calibration procedure investigated in this paper is based on inverse analysis methodology, centered on the minimization of a discrepancy function that quantifies the difference between experimentally measured and numerically computed quantities. In order to capture the influence of sought parameters on measured quantities, three different geometries of die and punches are proposed, resulting from a sensitivity analysis performed using numerical simulations of the test. The formulated calibration protocol requires only data that can be collected during the compaction test and, thus, involves a relatively smaller number of experiments. The developed procedure is tested on an alumina powder mixture, used for refractory products, by making a reference to the modified Drucker–Prager Cap model. The assessed parameters are compared to reference values, obtained through more laborious destructive tests performed on green bodies, and are further used to simulate the compaction test with arbitrary geometries. Both comparisons evidenced excellent agreement.

Constitutive Modeling of Porcine Coronary Arteries Using Designed Experiments

2003 ◽  
Vol 125 (2) ◽  
pp. 274-279 ◽  
Author(s):  
Stacey A. Dixon ◽  
Russell G. Heikes ◽  
Raymond P. Vito
Keyword(s):  
Coronary Artery ◽  
Internal Pressure ◽  
Coronary Arteries ◽  
Axial Strain ◽  
Constitutive Models ◽  
Parameter Study ◽  
Dependent Variables ◽  
Measured Force ◽  
The Difference ◽  
Constitutive Parameters

The development of new coronary artery constitutive models is of critical importance in the design and analysis of coronary replacement grafts. In this study, a two-parameter logarithmic complementary energy function, with normalized measured force and internal pressure as the independent variables and strains as the dependent variables, was developed for healthy porcine coronary arteries. Data was collected according to an experimental design with measured force ranging from 9.8 to 201 mN and internal pressure ranging from 0.1 to 16.1 kPa (1 to 121 mmHg). Comparisons of the estimated constitutive parameters showed statistically significant differences between the left anterior descending [LAD] and right coronary artery [RCA], but no differences between the LAD and left circumflex [LCX] or between the LCX and RCA. Point-by-point strain comparisons confirm the findings of the model parameter study and isolate the difference to the axial strain response. Average axial strains for the LAD, LCX, and RCA are 0.026±0.009,0.015±0.005, and 0.011±0.009, respectively, at all physiologic loads, suggesting that the axial strains in the LAD are significantly higher than in the other regions.

Study of pumping effect in flow-through electrolysers

1983 ◽  
Vol 48 (8) ◽  
pp. 2232-2248 ◽  
Author(s):  
Ivo Roušar ◽  
Michal Provazník ◽  
Pavel Stuhl
Keyword(s):  
Natural Convection ◽  
Balance Equation ◽  
Volume Fraction ◽  
Industrial Applications ◽  
Pumping Effect ◽  
Flow Through ◽  
The Mean ◽  
The Difference

In electrolysers with recirculation, where a gas is evolved, the pumping of electrolyte from a lower to a higher level can be effected by natural convection due to the difference between the densities of the inlet electrolyte and the gaseous emulsion at the outlet. An accurate balance equation for calculation of the rate of flow of the pumped liquid is derived. An equation for the calculation of the mean volume fraction of bubbles in the space between the electrodes is proposed and verified experimentally on a pilot electrolyser. Two examples of industrial applications are presented.

Remaining useful life estimation based on the joint use of an observer and a hidden Markov model

2021 ◽  
pp. 1748006X2110443
Author(s):  
Toufik Aggab ◽  
Pascal Vrignat ◽  
Manuel Avila ◽  
Frédéric Kratz
Keyword(s):  
Markov Models ◽  
Hidden Markov ◽  
Practical Interest ◽  
Markov Property ◽  
Rolling Bearing ◽  
Industrial Applications ◽  
Remaining Useful Life ◽  
Discrete Observations ◽  
Useful Life ◽  
The Difference

We propose an approach for failure prognosis based on the estimation of the Remaining Useful Life (RUL) of a system in a situation in which monitoring signals providing information about its degradation evolution are not measured and no operating model of the system is available. These conditions are of practical interest for industrial applications such as mechanical (e.g. rolling bearing) or electrical (e.g. wind turbine) devices or equipment-critical components (e.g. batteries) in which the addition of sensors to the system is not feasible (e.g. space limitations for sensors, cost, etc.). The approach is based on an estimation of the system degradation using residual generation (where the difference between the system and the observer outputs is processed) and Hidden Markov Models with discrete observations. The prediction of the system RUL is given by the Markov property concerning the mean time before absorption. The approach comprises two phases: a training phase to model the degradation behavior and an “on-line” use phase to estimate the remaining life of the system. Two case studies were conducted for RUL prediction to verify the effectiveness of the proposed approach.

scholarly journals ANALYSIS OF EXISTING METHODS FOR URANIUM-PLUTONIUM MIXED NITRIDE FUEL FAB-RICATION IN RUSSIA AND ABROAD

2020 ◽  
Vol 63 (6) ◽  
pp. 12-18
Author(s):  
Maxim S. Fedorov ◽  
Nikolay A. Baydakov ◽  
Alexander N. Zhiganov ◽  
Dmitry V. Zozulya
Keyword(s):  
High Voltage ◽  
Electric Pulse ◽  
Industrial Applications ◽  
Ceramic Technology ◽  
Laboratory Methods ◽  
Advantages And Disadvantages ◽  
Nitride Fuel ◽  
Powder Pressing ◽  
Uranium Nitride ◽  
Uranium Plutonium

This paper presents a review and a brief analysis of existing methods for producing mixed uranium nitride and plutonium, developed by both Russian and foreign scientists. The main parameters of the processes are considered, and their advantages and disadvantages are studied. Currently, the main areas of nitride fuel production are the metal hydride method and carbothermic reduction from the starting oxides. The methods are traditional ceramic technology. The starting products for the manufacture of nitride fuel powder can be either oxides (uranium dioxide and plutonium dioxide) or metals (uranium, plutonium and their alloys). To date, the technology for the manufacture of nitride fuel powder has not been finally selected. When considering existing methods, significant emphasis was placed on industrial applications and the simplicity of the hardware design processes. The laboratory methods are reflected in the work, which make it possible to simplify the process and reduce the costs of obtaining powders of mixed uranium and plutonium nitrides. However, they have significant difficulties in the technological implementation and low productivity of the processes. Of special interest among laboratory methods for producing mixed uranium and plutonium nitrides is the method of high-voltage electric pulse consolidation. This method allows sintering of tablets at the stage of powder pressing from mixed uranium and plutonium nitrides by passing a short high-voltage discharge with a power of several kW directly through the powder.

Numerical Simulations of Particle-Laden Flow Based on Given Friction Reynolds Number and Mean Reynolds Number Respectively

2014 ◽  
Author(s):  
Zhenzhong Li ◽  
Jinjia Wei ◽  
Bo Yu
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Wide Spectrum ◽  
Natural World ◽  
Industrial Applications ◽  
Particle Parameters ◽  
The Mean ◽  
The Difference ◽  
Particle Laden Flow

Multiphase flow with particles covers a wide spectrum of flow conditions in natural world and industrial applications. The experiments and the direct numerical simulation have become the most popular means to study the dilute particle-laden flow in the last two decades. In the experimental study, the mean Reynolds number is often adjusted to the value of single-phase flow for each set of particle conditions. However, the friction Reynolds number usually keeps invariable in the direct numerical simulation of the particle-laden flows for convenience. In this study the effect of the difference between given mean Reynolds number and friction Reynolds number was investigated. Two simulations were performed for each set of particle parameters, and the mean Reynolds number and friction Reynolds number were kept invariant respectively. From the results it can be found that the turbulence intensity and the dimensionless velocities are larger when keeping the friction Reynolds constant. And the results calculated from the cases of keeping the mean Reynolds number invariable agree with the experiment results better. In addition, the particle distribution along the wall-normal coordinate was found to be unchanged between two simulation conditions. As a suggestion, keeping the same mean Reynolds number in the direct numerical simulation of particle-laden flow is more appropriate.

Improved Wear Resistance of AISI 304L by Cladding Boride Layers Using the GTAW Process

2014 ◽  
Vol 966-967 ◽  
pp. 386-396 ◽  
Author(s):  
Yuan Ching Lin ◽  
Jia Bin Bai ◽  
Jiun Nan Chen
Keyword(s):  
Wear Resistance ◽  
Energy Dispersive Spectrometer ◽  
Ceramic Powder ◽  
Surface Hardness ◽  
Industrial Applications ◽  
Aisi 304L ◽  
Hardness Tester ◽  
Cladding Layer ◽  
Gtaw Process ◽  
Wear Tests

The austenitic stainless steel (SS) of AISI 304L is widely used in industrial applications because of its superior anti-corrosion resistance. However, the material suffers from a lower hardness, thus reducing wear resistance. In this study, AISI 304L was clad with tungsten boride (WB) ceramic powder using the gas tungsten arc welding (GTAW) process to increase surface hardness and improve wear resistance. The microstructure of the cladding layer was investigated using an X-ray diffractometer (XRD), an electron probe microanalyzer (EPMA), and a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS). The hardness distribution of the cladding layer was measured using a micro-Vickers hardness tester. Wear tests were conducted with a pin-on-disc tribometer at the ambient condition, while simultaneously monitoring friction coefficient variation. Surface frictional temperature was recorded with K-type thermocouples during wear tests. The worn morphology of the tested specimens was observed by SEM to identify wear characteristics. The results show that WB cladding successfully increased the hardness and the wear resistance of AISI 304L. Keywords: GTAW, WB, wear resistance, microstructure

Analysis of Stress Distribution for Powder Compression Molding by Finite Element Method

2019 ◽  
Vol 891 ◽  
pp. 269-274 ◽  
Author(s):  
Prakorb Chartpuk ◽  
Chaiwat Chaimahapuk
Keyword(s):  
Stress Distribution ◽  
Natural Frequency ◽  
Ceramic Powder ◽  
Bearing Steel ◽  
Outer Diameter ◽  
Maximum Compression ◽  
Aisi 52100 ◽  
Steel Aisi ◽  
The Difference ◽  
Powder Compression

The ultrasonic mold was designed for the ceramic powder compression. CAD and CAE were used in the design to analyze the mold strength and its natural frequency. The study of stress distribution and compression in upper and lower punch, mold body and waveguide comparison of stresses was analyzed by FEA experiments under maximum compression at 50,000 N to validate the results of both methods and the mold natural frequency. The difference between FEA and experimental analysis was 3-7%, acceptable. The redesign results in a cylindrical mold body with the outer diameter of 80 mm, the height of 100 mm, and the upper punch of 125 mm in length. The six sides are 26 mm of the high waveguide with 100 mm height. The internal and external diameters are 80 and 110 mm, respectively. The mold has been redesigned and can support the maximum compression force of 1,500 kN. with the bearing steel, AISI 52100, obtainable hardness 65 HRC, the stress concentration occurs at the neck of the upper punch using the ultrasonic at 12.00 to 12.45 kHz.

Application of Advanced Constitutive Models to the Simulation of Machining

2009 ◽  
Author(s):  
David A. Miller ◽  
Cameron K. Chen
Keyword(s):  
Elevated Temperatures ◽  
High Strain ◽  
Plastic Material ◽  
Constitutive Models ◽  
Surface Damage ◽  
Machining Process ◽  
Material Response ◽  
Tension And Compression ◽  
Split Hopkinson ◽  
Constitutive Parameters

Advanced constitutive models have long been used to describe plastic material response at high strains and high strain rates. These models include the Johnson-Cook, Zerrelli-Armstrong and Material Threshold Stress (MTS) formulations, each with a separate fidelity. The constitutive parameters for these complex models are commonly identified using laboratory techniques such as quasi-static load frames at room and elevated temperatures, Split Hopkinson Pressure Bars (SHPB) in tension and compression, gas guns, and Taylor impact cylinders. However, while the models are able to adequately describe material response under high strain and high strain rate, the loadings are all uniaxial in nature. The ability of these constitutive models and parameters to describe a different dynamic loading event, namely shear dominated machining, has not been thoroughly investigated. This work will develop numerical simulations applying multiple constitutive models with material parameters experimentally determined for fully annealed copper samples. Ultimately, the machining simulation will be compared with high fidelity experimental machining data. The utility of this research extends to the fundamental questions that surround the machining process, such as tool forces, surface damage, precision and quality.

A Historical Overview of Design Analyses and Experimental Observations of Ratcheting Phenomenon

2020 ◽  
Author(s):  
Jean Macedo ◽  
Stéphane Chapuliot ◽  
Jean-Michel Bergheau ◽  
Eric Feulvarch ◽  
Olivier Ancelet ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
State Of The Art ◽  
Constitutive Models ◽  
Experimental Tests ◽  
Design Codes ◽  
Historical Overview ◽  
Design Rules ◽  
Current Article ◽  
The Difference ◽  
Design Analyses

Abstract In order to investigate the ratcheting behavior and to determine new design rules, some experimental tests were conducted in many countries in the last decades. In France, some tests were carried out under mechanical or thermal cyclic loading to examine this risk. The first section of the current article is addressed to the state of the art concerning the ratcheting effects. The difference between Local and Global Ratcheting is clarified. The second section is dedicated to the experimental observations of ratcheting. The following section describes the constitutive models which are able to simulate material/structural ratcheting responses. The models presented are Linear Kinematic, Armstrong-Frederick, Chaboche, Ohno-Wang and Chen-Jiao-Kim. Finally, the ratcheting rules in design codes are exposed. Both simple and complex rules are presented.

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