logging in or signing up Rheology-Visco-elasticity Model nitinkadam3 Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: Embed: Flash iPad Copy Does not support media & animations WordPress Embed Customize Embed URL: Copy Thumbnail: Copy The presentation is successfully added In Your Favorites. Views: 864 Category: Science & Tech.. License: All Rights Reserved Like it (1) Dislike it (0) Added: September 01, 2010 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... Premium member Presentation Transcript MODEL FORVISCO-ELASTICITY : MODEL FORVISCO-ELASTICITY Mr. Nitin M. Kadam M.Pharm [Pharmaceutics] firstname.lastname@example.org Slide 2: Non newtonian systems - contineous or steady shear rheometry. Oscilatory and creep measurement are also of considerable importance for investigating the properties of semisolid drug products, foods, cosmetics, etc. The materials are classified as a Viscoelastic materials... INTRODUCTION Slide 3: Materials Shows Viscoelastic Property Systems studied in pharmacy belong to this class are as follows, Creams, Lotions, ointments, suppositories, suspension, Colloidal dispersing, emulsifying, suspending agents , Biological Materials like Blood, sputum, and cervical fluid Slide 4: Deformation of these materials can be divided to two components: Elastic component – Hooke’s law Viscous component – Newton’s law Deformation of such materials combination of Hooke’s law and Newton’s law. Slide 5: The behaviour of solids [elastic] were given by Hooke’s law: E= F/g E= Elastic modulus , g = strain h= viscosity, F= Shear stress G= Shear rate The behaviour of Newtonian fluids were given by Newton’s Law: Hooke’s law & Newton’s Law h = F/G Where, Slide 6: Methods that used to predict the behaviour of visco-elasticity. They consist of a combination of elastic behaviour and viscous behaviour. Two basic elements that been used in this model: Viscous dashpots with viscosity h which follows Newton’s law. Elastic spring with modulus which follows Hooke’s law Mechanical Model Slide 7: The common mechanical model that use to explain the viscoelastic phenomena are: Maxwell Spring and dashpot align in series Voigt Spring and dashpot align in parallel Standard linear solid Maxwell model and Voigt align in parallel. Slide 8: Maxwell model consist of spring and dashpot in series and developed to explain the mechanical behaviour. On the application of stress, the total strain is the sum of strain in spring & dashpot. Elastic spring Viscous dashpot Maxwell Model Slide 9: Can also known as the Kelvin model. It consists of a spring and dashpot in parallel. The compliance of a viscoelastic material following this model is given as a function of time, t, by, J= J∞ (1-e-t/T) Voigt Model Viscous dashpot Elastic spring Strain is expressed in as a deformation or compliance,J. Slide 10: Maxwell model can accurately predict the phenomenon stress relaxation Voigt Model can accurately predict the creep phenomenon Standard linear solid model was developed to combined the Maxwell and Voigt model to describe both creep & stress relaxation e.g. Wool fat behaviour at 30°C. [Creep curve] Standard linear solid Model Slide 11: Oscillatory testing Does not disturb structure. Sample is subjected to oscillatory driving force in an apparatus known as Rheogoniometer. S.S produced results in SR praportional to the surface velocity of the material. The viscoelastic behaviour of materials obtained by oscillatory shear measurements can be analyzed by an extension of the Maxwell spring-and –dashpot model. Slide 12: Write a note on Viscoelasticity Gives a brief description how the chosen mechanical model can be used to estimate the creep or stress relaxation behavior for semisolid materials? Example of the exams question Thank you : Thank you You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.