Measuring and Modeling Density Distributions in Pharmaceutical Tablets Katherine Doyle Advisor: Dr....
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Measuring and Modeling Density Distributions in Pharmaceutical Tablets Katherine Doyle Advisor: Dr. Zavaliangos Mentor: Wenhai Wang
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Transcript of Measuring and Modeling Density Distributions in Pharmaceutical Tablets Katherine Doyle Advisor: Dr....
Measuring and Modeling Density Distributions in Pharmaceutical Tablets
Katherine DoyleAdvisor: Dr. ZavaliangosMentor: Wenhai Wang
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
Background
Die compaction: loose powder pressed in a die by upper and lower punch
Wide range of tablet densities possible by varying compressive force and die shape
Physical analysis coupled with FEA modeling
How do we describe the mechanics of die
compaction?
Schematic of a die/ punch assembly 4
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
BackgroundHydrostatic and Mises Equivalent
Stresses
(First and Second Invariants)321 p
2
)()()( 231
232
221
q
1
23
1
32
Principle Stresses on a Differential Element
Background
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
Simple Tension:
Shear:
Diametrical Compression:
Simple Compression: Simple tests for strength properties 3
Mohr-Coulomb Shear Failure line from simple tension, shear, diametrical
compression, and simple compression:
pq 3
0p
2
123 pq
pq 3
Die Compaction
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
Drucker-Prager/cap Model for powder die compaction
Widely used model because accounts for:
Stronger compact in compression than tension
Cohesion, internal friction angle, and their dependence on relative density (RD)
Shear failure and cap surfaces Drucker-Prager/cap model
showing two failure surfaces and various RD values on P-Q plane 1
Tablet Formation
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
Method for tablet formation
Equipment:
Carbide steel die and punches (flat and convex circular, convex oval)
INSTRON mechanical testing machine
Materials:
Microcrystalline cellulose
Magnesium stearate (die/punch lubricant)
Specimen preparation:
Compacted to 10-120 MPa
Clean or lubricated die/punch
Sliced to show cross section
INSTRON model 1127 General testing machine 5
Current Work
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
Experiments:
Calibration curves: compaction pressure versus RD and RD versus hardness
Microhardness testing and x-ray computerized tomography to map density distribution in tablet slices
Diametrical compression tests
ltheoretica
actualRD
CS
compaction
A
F
Clean and lubricated tablets after diametrical compression 2
Clean and lubricated tablets after diametrical compression. Experiments by K. Doyle.
Current Work
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
Modeling:
Learning ABAQUS FEA software
Graphical interface, coded input files, setting up problem, analysis
Gurson model (simple), Drucker-Prager/cap model
Previous results:
Physical experiment, clean die
ABAQUS simulation, clean die
Density distributions on 4mm slice of convex tablet 2
Future Work
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
Future Experiments and Modeling:
Map density distributions of circular and oval convex tablets (verify previous experiments)
Compare manual results to x-ray tomography and simulation
Repeat and continue diametrical compression testing for wide range of RD
Continue to learn how to model with ABAQUS
Complete die compaction model of 3D oval convex tablet
References
1. Cunningham, J.C, Sinka, I.C., Zavaliangos, A. 2004. Analysis of Tablet Compaction. I. Characterization of Mechanical Behavior of Powder and Powder/Tooling Friction. Journal of Pharmaceutical Science, Vol. 93, No. 8, August 2004: 2022-2039.
2. Cunningham, J.C, Sinka, I.C., Zavaliangos, A. 2004. Analysis of Tablet Compaction. II. Finite Element Analysis of Density Distributions in Convex Tablets. Journal of Pharmaceutical Science, Vol. 93, No. 8, August 2004: 2040-2053.
3. A.T. Procopio, J.C. Cunningham, A. Zavaliangos. 2003. Analysis of the Diametrical Compression Test and the Applicability to Plastically Deforming Materials. Journal of Materials Science. 38, pp. 3629 – 3639, 2003.
4. “Powder Forming Research.” Department of Mechanical Engineering at University of Wales Swansea. http://www.swan.ac.uk/nfa/powdercompaction.htm.
5. “Tensile and Compression Testing.” ETS, North Tower Technologies. http://www.equiptechonline.com/PDetail.cfm?pid=1591&catID=75&subID=38&sid=6
Drucker-Prager/cap Model for powder die compaction
Cap Surface:
Shear Surface:
cohesion
internal friction angle
no physical meaning
determined from experiments
Die Compaction
Agenda
Introduction
Die Compaction
Tablet Formation
Current Work
Future Work
0)tan())
cos1(()(),( 22
aq
ac pdRR
pppqF
tan),( pdqpqFs
Rp
d
a ,
