Ministry of higher education and innovation of the republic of uzbekistan almalyk branch of islam karimov tashkent state technical university

MINISTRY OF HIGHER EDUCATION AND INNOVATION OF THE REPUBLIC OF UZBEKISTAN ALMALYK BRANCH OF ISLAM KARIMOV TASHKENT STATE TECHNICAL UNIVERSITY
Independent work
SUBJECT: ENGLISH
DONE BY: Kozimjonov Farruxjon
CHECKED: Mirzayeva M. U
ALMALYK-2023

Plan:

• Plan:
• Material property.
• Investigating the mechanical properties of materials.
• Determining material properties.
• Performing material tests.

Topic: Properties of materials

A material property is an intensive property of a material, i.e., a physical property or chemical property that does not depend on the amount of the material. These quantitative properties may be used as a metric by which the benefits of one material versus another can be compared, thereby aiding in materials selection.
A property having a fixed value for a given material or substance is called material constant or constant of matter.[1] (Material constants should not be confused with physical constants, that have a universal character.)
A material property may also be a function of one or more independent variables, such as temperature. Materials properties often vary to some degree according to the direction in the material in which they are measured, a condition referred to as anisotropy. Materials properties that relate to different physical phenomena often behave linearly (or approximately so) in a given operating range Modeling them as linear functions can significantly simplify the differential constitutive equations that are used to describe the property.
Equations describing relevant materials properties are often used to predict the attributes of a system.
The properties are measured by standardized test methods. Many such methods have been documented by their respective user communities and published through the Internet; see ASTM International.
To summarize with a simple example: if I give a push to a ball that is initially at rest (fig 1.1a), it will accelerate in that direction at a rate proportional to the force and inversely proportional to its mass. The great step forward in Newton’s scheme was that, together with the inverse square law of gravity, it showed that the force that keeps us down on earth is one and the same with the force that directs the motion of the planets.
INVESTIGATING THE MECHANICAL PROPERTIES OF MATERIALS
If it takes a unit force to stretch a rubber band of a given cross-sectional area a given distance, it can readily be seen that it will take twice the force to give the same stretch to two rubber bands set side by side or to single band of twice the thickness. Resistance to stretching is therefore directly proportional to the cross-sectional area of a sample. To determine the mechanical state of the rubber, the force applied to the sample must consequently be normalized by dividing it by its cross-sectional area. Doing so gives a measurement of the force per unit area, or the intensity of the force, which is known as stress and which is usually represented by the symbol σ, so that σ = P/A, (1.2) where P is the applied load and A the cross-sectional area of the sample.Stress is expressed in SI units of newtons per square meter (N m−2) or pascals (Pa). Unfortunately, this unit is inconveniently small, so most stresses are given in kPa (N m−2 × 103), MPa (N m−2 × 106), or even GPa
DETERMINING MATERIAL PROPERTIES
Many material properties can be determined from the results of a tensile test once the graph of force against displacement has been converted with equations 1.2 and 1.3 into one of stress versus strain. Figure 1.3b shows the stress-strain curve for a typical tough material, such as a metal. Like many, but by no means all, materials, this one obeys Hooke’s law, showing linear elastic behavior: the stress initially increases rapidly in direct proportion to the strain. Then the material reaches a yield point, after which the stress increases far more slowly, until finall failure occurs and the material breaks.
PERFORMING MATERIAL TESTS
Many of the mechanical properties of a material can therefore be readily determined by carrying out one of two sorts of mechanical tests in which materials are put into axial loading: tensile tests and compressive tests. Both of these are most conveniently carried out in universal testing machines on specially prepared samples.