Deformation of solid

Physical pharmaceutics -ii
unit-iii
deformation of solid
B-pharmacy

1. DEFORMATION OF SOLID BY- GOURAV SINGH

2. OBJECTIVE Plastic Deformation Elastic Deformation Heckel Equation Stress Strain Elastic Modulus

3. What is deformation of solid? It is defined as change in the size and shape of an object. When applied a external force. It is term of the concept of Strain and stress.

4. What is stress ? Stress ( σ ) is the force per unit area that applies to an object to deform it. Stress ( σ ) = Force/Area Its unit is Nm -2 or Pa Types of stress There are three type of stress Direct stress Indirect stress Combined stress

5. Types of stress Direct Stress: This stress produced under direct loading condition i.e force will be in line with the axis of member. It is force acting on body. It may be tensile or compressive or shear stresses

6. Direct Stress Indirect Stress :- This stress occur due to torque produced in the body. Combined Stress :- This stress are the combination of above two types of stress.

7. What is strain ? Strain is the measure of the amount of deformation. For E.X- If the Bar has original length(L) and when the load is applied on a bar the length of bar will change which is indicated as ( ∆ L) Strain= ∆ L/L It has no unit. Types of strain There are three type of strain Tensile strain Compressive strain Shear strain

8. Types of strain

9. What is Elastic modulus? The constant of proportionality depends on the material being deformed and the nature of the deformation. This constant is called as elastic modulus. Elastic modulus determine the amount of force required per unit deformation. The elastic modulus under the law of H ooke’s law. This law state that “, In an elastic member stress is directly proportional to the strain within elastic limit”. σ α ε σ=E. ε or E= σ/ ε Where, E is constant known as modulus of elasticity or young modulus σ is stress ε is strain

10. Fig- stress strain relationship for elastic solid

11. stress strain relationship for elastic solid Young modulus will have to identify how much the material is elastic. The elastic limit of substance is defined as the maximum stress that can be apply to the substance before it deform permanently.

12. What is Heckle equation? The H eckle analysis is a most useful method for estimating the volume reduction under the compression pressure in pharmacy. Heckle plots can be affected by the time of compression, the degree of lubrication and size of the die. The effect of these variables should be taken into consideration. The basic assumption of heckle equation is that the densification of the bulk powder on applying force obeys first-order kinetics. The Heckle equation is expressed as ; In = KP + A where, ε = Tablet porosity. P = Applied pressure. A = Constant related to particle re-arrangement and fragmentation. K = Slope of the linear part of the relationship reflects yield stress or yield pressure ( Py ) for the particles:  

13. What is Heckle equation? Reciprocal of the K (1/k) value is calculated and reflects yield stress or yield pressure ( Py ) for the particles: In + A Heckle profile depicting on initial curvature (region 1) associated with particle fragmentation and particle rearrangement. The relationship is linear most of the time for a range of pressure applied (region 2) and therby follow the expression. The linear part reveals a situation where compression process is influenced by particle deformation. From the gradient of this linear part, the yield pressure can be determine. When the profile again deviates from the linear relationship (region 3), the resultant curvature suggest deformation of the complete tablet.  

14. What is Heckle equation? Significance of heckle plots: It is used to characterize single material and as well as can also be used for powder mixture. Region 1-Heckle plot usually exhibit a higher final slope than region 2. This indicate that the Region 1 have a lower yield pressure. The two region of Heckle plots in region 2 represent the initial repacking stage and subsequent deformation process 5. The crushing strength of tablets is also correlated with the value of K of the heckle plot. Larger K Values indicate harder tablet. The knowledge of this can be used to select binder during designing of tablets.

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