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.

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 Process characterization and analysis of ceramic powder bed fusion

2021 ◽  
Author(s):  
Kevin Florio ◽  
Dario Puccio ◽  
Giorgio Viganò ◽  
Stefan Pfeiffer ◽  
Fabrizio Verga ◽  
...  
Keyword(s):  
High Speed ◽  
Ceramic Powder ◽  
Integrating Sphere ◽  
Alumina Powder ◽  
Powder Bed Fusion ◽  
Single Track ◽  
Ceramic Powders ◽  
Pure Alumina ◽  
Powder Bed ◽  
Melt Pool

AbstractPowder bed fusion (PBF) of ceramics is often limited because of the low absorptance of ceramic powders and lack of process understanding. These challenges have been addressed through a co-development of customized ceramic powders and laser process capabilities. The starting powder is made of a mix of pure alumina powder and alumina granules, to which a metal oxide dopant is added to increase absorptance. The performance of different granules and process parameters depends on a large number of influencing factors. In this study, two methods for characterizing and analyzing the PBF process are presented and used to assess which dopant is the most suitable for the process. The first method allows one to analyze the absorptance of the laser during the melting of a single track using an integrating sphere. The second one relies on in-situ video imaging using a high-speed camera and an external laser illumination. The absorption behavior of the laser power during the melting of both single tracks and full layers is proven to be a non-linear and extremely dynamic process. While for a single track, the manganese oxide doped powder delivers higher and more stable absorptance. When a full layer is analyzed, iron oxide-doped powder is leading to higher absorptance and a larger melt pool. Both dopants allow the generation of a stable melt-pool, which would be impossible with granules made of pure alumina. In addition, the present study sheds light on several phenomena related to powder and melt-pool dynamics, such as the change of melt-pool shape and dimension over time and powder denudation effects.

Microstructure and Properties of Composites Prepared by Reactive Pressure Infiltration of Aluminium into Metal and Ceramic Powder Preforms

2014 ◽  
Vol 782 ◽  
pp. 523-526
Author(s):  
Andrej Opálek ◽  
Karol Iždinský ◽  
Štefan Nagy ◽  
František Simančík ◽  
Pavol Štefánik ◽  
...  
Keyword(s):  
Ceramic Powder ◽  
Nickel Aluminides ◽  
Gas Pressure ◽  
Alumina Powder ◽  
Pressure Infiltration ◽  
X Ray ◽  
Reactive Infiltration ◽  
Melting Temperatures ◽  
Ni Powder ◽  
Properties Of Composites

Nickel aluminides exhibit very attractive high temperature properties. However, due to high melting temperatures they are difficult to prepare. Gas pressure reactive infiltration is a relatively cheap technology that provides composites where nickel aluminides are formed due to mutual reaction between Ni powder and molten aluminium forced to penetrate into powder preform. The feasibility of this concept is demonstrated in this work. Ni powder and/or Ni+25 vol. % Al2O3 powder mixture, respectively, were mechanically pressed and then infiltrated with aluminium using 5 MPa argon gas pressure at the temperature of 750 °C for 120 s. Al/Al2O3 composite using loose alumina powder was prepared in similar manner for comparison. The microstructure of composites was observed by scanning electron microscopy and newly formed intermetallic phases were analysed by energy-dispersive X-ray spectroscopy. Relative elongations during additional thermal cycling up to 800 °C had been recorded. Composites were additionally characterized by hardness measurements.

scholarly journals Integration algorithms of elastoplasticity for ceramic powder compaction

2014 ◽  
Vol 34 (11) ◽  
pp. 2775-2788 ◽  
Author(s):  
M. Penasa ◽  
A. Piccolroaz ◽  
L. Argani ◽  
D. Bigoni
Keyword(s):  
Ceramic Powder ◽  
Powder Compaction ◽  
Integration Algorithms

scholarly journals A Nelder–Mead algorithm-based inverse transient analysis for leak detection and sizing in a single pipe

2021 ◽  
Author(s):  
Oussama Choura ◽  
Caterina Capponi ◽  
Silvia Meniconi ◽  
Sami Elaoud ◽  
Bruno Brunone
Keyword(s):  
Transient Analysis ◽  
Experimental Tests ◽  
Leak Detection ◽  
Calibration Procedure ◽  
Second Phase ◽  
Viscoelastic Parameters ◽  
The Difference ◽  
Single Pipe ◽  
The University ◽  
Nelder Mead Algorithm

Abstract In this paper the results of an experimental validation of a technique for leak detection in polymeric pipes based on the inverse transient analysis (ITA) are presented. In the proposed ITA the Nelder–Mead algorithm is used as a calibration tool. Experimental tests have been carried out in an intact and leaky high-density polyethylene (HDPE) single pipe installed at the Water Engineering Laboratory (WEL) of the University of Perugia, Italy. Transients have been generated by the fast and complete closure of a valve placed at the downstream end section of the pipe. In the first phase of the calibration procedure, the proposed algorithm has been used to estimate both the viscoelastic parameters of a generalized Kelvin–Voigt model and the unsteady-state friction coefficient, by minimizing the difference between the numerical and experimental results. In the second phase of the procedure, the calibrated model allowed the evaluation of leak size and location with an acceptable accuracy. Precisely, in terms of leak location the relative error was smaller than 5%.

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.

scholarly journals Effect of Additives on Stability of Alumina—Waste Alumina Suspension for Slip Casting: Optimization Using Box-Behnken Design

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1738 ◽  
Author(s):  
Milan Vukšić ◽  
Irena Žmak ◽  
Lidija Ćurković ◽  
Danko Ćorić
Keyword(s):  
Ceramic Powder ◽  
Slip Casting ◽  
Growth Inhibitor ◽  
Poly Vinyl Alcohol ◽  
Alumina Powder ◽  
Suspension Stability ◽  
Concentrated Suspensions ◽  
Grain Growth Inhibitor ◽  
Ph Values ◽  
Weight Content

The green machining of alumina (Al2O3) green bodies generates a certain amount of waste alumina powder. Waste alumina ceramic powder should be disposed of as non-hazardous waste in a legally compliant manner. The influence of additives on the stability of 70 wt.% (≈40 vol.%) alumina—waste alumina water-based suspension was investigated in the presented research. A Box-Behnken three-factor response surface design was used for the preparation of stable highly-concentrated suspensions with the addition of three additives. The optimal amount of each additive was selected according to the obtained results of minimal apparent viscosity: 0.05 wt.% Tiron as dispersant, 0.1 wt.% poly (vinyl alcohol) as binder and 0.2 wt.% magnesium aluminate spinel as abnormal grain growth inhibitor. The analysis of variance was used to identify the contribution of each additive. The zeta potential and sedimentations tests were performed to confirm the suspension stability measurements at different pH values. Alumina particles were optimally dispersed at pH values between 8 and 11. According to the results, the investigated composition of 20 wt.% waste alumina powder (weight content, dry alumina powder), with the addition of optimal amounts of additives, shows a possible application in the production of ceramics by slip casting.

Radiocarbon Distance Between Calendar Dates

Radiocarbon ◽  
2014 ◽  
Vol 56 (02) ◽  
pp. 877-881
Author(s):  
Adam Walanus ◽  
Dorota Nalepka
Keyword(s):  
Calibration Curve ◽  
Calibration Procedure ◽  
Matching Method ◽  
Time Periods ◽  
The Difference ◽  
Calendar Dates

The calibration procedure, and especially the nonlinear shape of the calibration curve, makes analyzing a possible dating result a far from straightforward process. This is especially so if the goal is to distinguish between two relatively close events. Proposed herein is a calculator, or alternatively a graph, which enables reading of the difference between two radiocarbon ages corresponding to their expected calendar ages. The result may surprise the less experienced14C users. Such a calculation also indicates the time periods with high or low potential for application of the wiggle-matching method.

scholarly journals A Comparative Analysis of the Flow Properties between Two Alumina-Based Dry Powders

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Milene Minniti de Campos ◽  
Maria do Carmo Ferreira
Keyword(s):  
Internal Friction ◽  
Moisture Content ◽  
Ceramic Powder ◽  
Morphological Characteristics ◽  
Angle Of Repose ◽  
Wall Friction ◽  
Flow Index ◽  
Alumina Powder ◽  
Flow Properties ◽  
Angle Of Internal Friction

We measured and compared the flow properties of two alumina-based powders. The alumina powder (AP) is irregularly shaped and has a smooth surface and moisture content of 0.16% (d.b.), and the ceramic powder (CP), obtained after atomization in a spray dryer, is spherical and has a rough surface and moisture content of 1.07%. We measured the Hausner ratio (HR), the static angle of repose (AoR), the flow index (FI), the angle of internal friction, and the wall's friction angle. The properties measured using aerated techniques (AoR and HR) demonstrated that AP presents true cohesiveness (and therefore a difficult flow), while CP presents some cohesiveness and its flow might be classified as half way between difficult and easy flow. Their FI values, which were obtained using a nonaerated technique, enable us to classify the alumina as cohesive and the ceramic powder as an easy-flow powder. The large mean diameter and morphological characteristics of CP reduce interparticle forces and improve flowability, in spite of the higher moisture content of their granules. The angles of internal friction and of wall friction were not significantly different when comparing the two powders.

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