Titelmasterformat durch Klicken bearbeiten Numerical Simulation of Pharmaceutical Powder Compaction using ANSYS Dr. Ahmad Baroutaji, CIT

© CADFEM 2015

Project Background • Dr. Sandra Lenihan,(PI) Dept of Process, Energy and Transport Engineering • Dr. Keith Bryan,(PI) Dept of Mechanical and Biomedical Engineering • Dr. Ahmad Baroutaji, (Postdoctoral researcher) Dept of Process, Energy and Transport Engineering

© CADFEM 2015

Project Targets 1

2

3

Understand the powder behaviour during the compaction

Evaluate the mechanical strength of the final product (tablet)

Improve the tableting process by investigating the effects of tablet tooling geometry and lubrication.

© CADFEM 2015

Computational Modelling of Powder Compaction  Parameters of tabletting process: compaction velocity, die friction coefficient,….  Characterization techniques: a mechanical testing System to obtain the mechanical properties of the powder  Computational modelling techniques: finite element method, discrete element method, and more

To Model the tabletting Process © CADFEM 2015

1

Tabletting Process

Upper Punch

Powder Die

Lower Punch

The Punches movement sequence

© CADFEM 2015

2

Mechanical testing system

Punch Die

Sensor

Lower base © CADFEM 2015

3

Bulk Material Computational modelling techniques  Microscopic ModellingDiscrete element method (DEM)  Consider the discrete nature of the powder by modelling each powder particle as a single object  Simplify the the irregular shape of the particles  Does not provide any information about the global behaviour of the powder  limited to powder compacts with low relative densities  Useful for understanding the physical phenomena of the powder compaction process

© CADFEM 2015

3

Bulk Material Computational modelling techniques  Macroscopic ModellingFinite element method (FEM)

 Treats the powder as a continuous media and characterizes the overall behaviour of the powder  Capable of generating essential information on the macroscopic behaviour of the powder, such as density and stress distributions, and the shape of compacted powders during and after the process. These information are very essential to solve the technical problems associated with the compaction.  Can be performed by application of FEM which account for the large deformations, large strain, compressibility, nonlinear material behaviour and friction phenomena of the powder

© CADFEM 2015

Finite element (FE) Modelling FE Modelling  The behaviour of powder material during the process which can mathematically be described by the material constitutive model.  The interaction between the powder and process tools (i.e. punches and die) which can be described by the friction constitutive model  Geometrical configuration of the die and punches.  The movement procedure of the punches and velocity.  Initial state of the powder

Geometry and FE mesh

© CADFEM 2015

Loading, interaction and Boundary condition

Constitutive Material Model

Validation

Geometry and FE mesh Geometry and FE mesh

Upper Punch

Powder

A

2D

A A

Die

3D Axis Lower Punch

© CADFEM 2015

Loading, Interaction and Boundary conditions Loading, interaction and Boundary condition

Upper Punch (Rigid)

 Define the movement of the upper punch  Define the friction between punches and powder  Define the nature of each component (Rigid/deformable)  Define the friction between die and powder © CADFEM 2015

Die (Rigid)

Powder (Deformable)

Axis

Lower Punch (Rigid)

Constitutive Material Model Constitutive Material Model

q

Transition segment, Ft

Cap segment, Fc

Shear line, Fs

β

Die compaction

R

d P Pa Pb © CADFEM 2015

Drucker-Prager Cap (DPC) Material Model

 It can represent the densification and hardening of the powder  Interaction between particles is incorporated

Constitutive Material Model DPC Material Calibration Elastic Properties E (GPa) Ѵ

Young’s modulus Poisson’s ratio

Instrumented die compaction test, unloading

q

Plastic Properties d (MPa)

Cohesion

β

Internal friction angle

Uniaxial compression and diametrical compression test

β

R d Pa

R

Cap shape

Pa

Evolution parameter

Pb

Hydrostatic yield stress

© CADFEM 2015

Instrumented die compaction test, loading

Pb

P

Constitutive Material Model

𝜎𝐷 =

2𝐹𝐷 𝜋𝐷ℎ

4𝐹𝑐 𝜎𝑐 = 𝜋𝐷2

1

𝑅=

𝜎𝑐 𝜎𝐷 ( 13 − 2) 𝜎𝑐 + 2𝜎𝐷

𝛽 = 𝑡𝑎𝑛−1

2

(𝑝𝐵 − 𝑝𝑎 )

6

3 𝜎𝑧 𝐵 − 𝜎𝑧 𝐶 𝐾+ 𝐺= 𝐵 4 𝜀𝑧 − 𝜀𝑧 𝐶 2𝐺 3𝐾

2

𝑝𝑏 = 𝑝𝑎 1 + 𝑅 tan 𝛽 + 𝑅𝐷

2 𝑃𝐷 = 𝜎𝐷 , 𝑞𝐷 = 13𝜎𝐷 3

𝑑=

2 1 + 𝛼 − 𝛼/𝑐𝑜𝑠𝛽 3𝑞𝐵

3(𝜎𝑐 + 𝑑) 𝜎𝑐

7

3

4

=

9

𝑞𝐵 𝑞𝐵 − 𝑞𝐶

10

9𝐺𝐾 3𝐾 + 𝐺 3𝐾 − 2𝐺 𝜗= 2(3𝐾 + 𝐺) 𝐸=

11

12

𝑝𝑎

5

3𝑞𝐵 + 4𝑑 𝑡𝑎𝑛𝛽 1 + 𝛼 − 𝛼/𝑐𝑜𝑠𝛽 2 =− 4 1 + 𝛼 − 𝛼/𝑐𝑜𝑠𝛽 2 9𝑞𝐵 2 + 24𝑑𝑞𝐵 1 + 𝛼 − 𝛼/𝑐𝑜𝑠𝛽 2 tan 𝛽 + 8 3𝑝𝐵 𝑞𝐵 + 2𝑞𝐵 2 + 4 1 + 𝛼 − 𝛼/𝑐𝑜𝑠𝛽 2

1 + 𝛼 − 𝛼/𝑐𝑜𝑠𝛽

2

8

© CADFEM 2015

Validation of FE Model Validation

This can be performed by comparing the numerical predictions against the experimental results

Validated FE Model

© CADFEM 2015

Perform optimization Study

Ref: Han, L. H., et al. "A modified Drucker-Prager Cap model for die compaction simulation of pharmaceutical powders." International Journal of Solids and Structures 45.10 (2008): 3088-3106.

Preliminary FE predications for MCC

Contour plot of Von Mises stress distribution after compaction

MIN

Contour plot of density distribution after compaction

MAX

© CADFEM 2015

Microcrystalline cellulose (MCC) is used widely in pharmaceutical formulations and this particular grade is designed for direct compression formulations. MCC particles are irregular, with a nominal particle size of 100 μm and size distribution between 20-200μm. The bulk and full density of the powder is 300 kg/m3 and 1590 kg/m3 respectively.

Preliminary FE predications for MCC

4.5 mm

7 mm

High stress concentration

The high stress regions are at the top corner, while the low stress regions are placed at the bottom corner. The high stresses concentration at the edge of the tablet may cause Chipping failure mode.

© CADFEM 2015

Von Mises Stress evolution during compaction

Technical Applications of FEM in pharmaceutical industry

1

Estimate and analyse the stress and density distributions within the tablet.

2

Investigate the effect of punch shape and optimize the compaction tools

3

Explore the tablet failure mechanism and assess the origin of defect or crack formation.

4

Estimate the break force of the tablet.

5

Estimate the temperature evolution during compaction

6

Investigate the effect of friction between the powder and compaction tools on the process and tablet structure

© CADFEM 2015

Thank you

© CADFEM 2015