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Rheology of the science of deformation and course materials

 

Plan of the lecture:

1. Stages of development of rheology of food products

2. Integral part of the rheology of food products

3. Food materials as a study of rheology

 

Purpose of the lecture: get acquainted with theoretical questions the science of deformation and flow of various phone.

 

1. Stages of development of rheology of food products. Rheology is the science of deformation and flow of various phone the Word «rheology» comes from the Greek «ðåw», which means «flowing». Under deformation is understood relative displacement of particles of the material body, which is not disrupted the continuity of the body. If under the action of finite forces deformation of a body increases in time continuously and permanently, it means that the material flows. During deformation usually occurs a change in the shape or size of the body. The subject of rheology in a General understanding of how science is the study of various types of strain depending on the accompanying stress.

In the definition of rheology, there are two views on the subject of rheology. Rheology, in a broad sense is the study of the deformation and flow of various materials.

Rheology, in the narrow sense is the study of the deformation and flow of materials exhibiting a substantial deviation from the properties of classical models - Gutowski liquids, solids gukovsky and plastic Saint-vannovsky phone.

In the development of engineering rheology distinguish the following stages.

Classic rheology - is the science about the flow and deformation of real bodies, which includes the study of the properties of existing products and develop-ment methods of calculating currents of them in the working bodies of machines.

The management rheology - science, which includes a study and substantiation of combinations of different types of impacts, which provide for a given level of rheological characteristics during the entire technological process.

Physico-chemical mechanics is the study of the ways and regularities of the formation of structures of disperse systems with predetermined properties, the tasks of which include: the establishment of the merits of the formation and destruction of the structures in dispersed and native systems depending on the totality of physical-chemical, bio-chemical, mechanical and other factors; research, study and optimization ways of obtaining structures with predetermined technological properties.

Engineering and physical-chemical mechanics of food production - science, on deformation and flow of products in the working bodies of machines and the methods of the formation of structures of dispersive systems with prescribed technical characteristics, and develops on the basis of physico-chemical mechanics and rheology.

Rheology as a science about the flow and deformation of real bodies were formed in connection with the study of materials, mechanical properties which are intermediate between the properties of elastic solids and viscous fluids. These materials include and food products - meat and meat products, milk and dairy products, fish and fish products, etc. Rheology is also exploring other current variety of visco-plastic materials such as clay pastes and suspensions, greases, resins, building mortars, etc.



The founder of physical-chemical mechanics of a Soviet scientist, academician P.A. Rebinder. A significant contribution to the development of the physico-hee-chemical mechanics and rheology has made many local and foreign scholars M. P. Volarovich, G.V. Vinogradov, V.E. ghoul, M. Reiner and many others A significant contribution to the development of rheological studies in the meat and dairy industry contributed V. Gorbatov, E, Oblique, confectionery, bakery and other food industries Y.A Machikhin, S.A. Machikhin, B.A. and other Nikolaev.

2.Castanie part rheology of food products. Rheology of food products as science includes a wide range of issues, theoretical foundations, various methods and devices of measurement of rheological characteristics of food materials, methods of engineering calculations, design optimization, intensification of technological processes, and also for the control and management of quality of products.

For the purposes of systematization of the material rheology of food production is divided into four parts:

- rheology food materials - contains basic information on the theoretical part of the engineering rheology food materials;

- rheometric food materials -is devoted to the methods of measurement of rheological characteristics of food materials, instrument engineering and presentation of measurement results;

- redynamise calculations - is devoted to the presentation of experimental data in the form of mathematical formulas, graphs (rogramme), mechanical models, providing quantitative assessment of the results of changing food materials as a result of influence of working bodies of machines, as well as engineering and technological equipment;

- rheological basics- of optimization and intensification of control and quality management - focuses on the use of results obtained in the course of experimental research on development issues: optimization of process parameters, intensification of technological processes of manufacturing of products, monitoring of product quality and development of questions of quality control of manufactured products.

Microrheology considers all materials in the form in which they appear in front of the observer at a superficial examination to the naked eye, i.e. as a homogeneous linear structures. However, phenomenologically homogeneous are only pure liquids and perfect crystals.

Microrheology considers the rheological behavior of two - phase and multiphase systems depending on the rheological properties of its components.

 

3. Food materials as a subject of study rheology.In scientific and industrial circles among professionals, and also in studying of special disciplines in universities, colleges, etc. are widely used term «food materials», under which understand the real food raw material of vegetative and animal origin (meat, milk, fish, vegetables, fruits etc), semi-finished products, mixtures, the composition (minced meat, minced fish, bread, pastry, confectionery mass etc.) and finished products (sausage products, dairy products, bread, pasta and confectionery, etc.). This term can be used only to designate that food as the object of study is also considered as a material, but only as a food material.

The purpose of this examination is (clarification) to which science include nutritional materials from the point of view of their study. This question has no definite answer.

Food or food materials: raw materials, semi-products, finished products, most are complex compositions consisting of two, three or more components in different proportions. Each component has in one way or another influence on the properties of the product and not ignore them or skip them cannot. From a scientific point of view of food products (materials) belong to disperse systems, the study of which is an engineering and physical-chemical mechanics of food production.

Food products (materials) are significantly different from others in that they are the materials of vegetable and animal origin. In addition, they cannot long remain in the same form as they were originally. Especially meat and meat products. The study of such materials is engaged in engineering and physical-chemical mechanics of food production.

Food products (materials), as well as others, have different properties, including the group of physical properties provides the most complete picture of the structure of the product. Product structure, its change are defined structural-mechanical properties, which is accepted to Express these characteristics (indicators) as elasticity, viscosity, ductility, stickiness and other If we assume that the material has only one of these properties, such as elasticity, viscosity or plasticity, the study of these materials (see table 1.) provide theoretical mechanics, resistance of materials, hydraulics. The behavior of such materials under the influence of external forces are described by the equations of Newton, Hooke, Saint-Venant and have a linear dependence.

 

 

Table 1 Classification of real bodies

Perfectly solid, Euclidean Elastic body Gukovo   Plastic body, Sain-Venanovo Rheological body True-viscous liquid, Newtonian Ideal liquid, Paskal’evsky
In all normal tangential stresses, deformation zero Voltage proportional to the strain When the limit shear stress begin plastic deformation Linear - composite of bodies in categories 2, 3, 5 and non - empirical Voltage is proportional to the velocity gradient in the first degree Viscosity and compressibility zero
Theoretical mechanics Resistancematerials Resistancematerials Rheology Hydraulics Hydraulics

 

On the basis of the researches found that most of the food materials under influence of external loads are of a different nature. Moreover, the changing nature of elasticity, viscosity and plasticity is not a linear relationship. While dietary materials can simultaneously possess elasticity, viscosity and plasticity. A study of this type of content is engaged rheology (see table 1.), therefore, food products (materials) are the subject of study of rheology.

Checklist

1. Stages of development of rheology of food products

2. Integral part of the rheology of food products

3. Food materials as a study of food products

 


Date: 2015-12-24; view: 1145


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