Polymers exhibit a wide range of stress-strain behaviors as shown in the figure below. ... For polymer materials, this peak stress is identified as the yield stress . As the material is pulled further, fracture occurs. The stress value when fracture occurs is defined as the tensile strength for polymer materials.
What is stress of a material?
Stress is the a measure of what the material feels from externally applied forces . It is simply a ratio of the external forces to the cross sectional area of the material.
What is stress and strain?
Stress and Strain are the two terms in Physics that describe the forces causing the deformation of the objects . Deformation is known as the change of the shape of an object by applications of force. Very small forces can also cause deformation.
What is plastic stress?
The manufacture of plastic parts by its very nature creates stress in the structure. Long polymer molecules that make up the plastics become tangled and aligned along the direction of force during injection molding, extrusion, vacuum forming or other manufacturing process.
What is stress and strain in chemistry?
In chemistry, a molecule experiences strain when its chemical structure undergoes some stress which raises its internal energy in comparison to a strain-free reference compound. ... This extra internal energy, or strain energy, can be likened to a compressed spring.
What is strain explain?
1 : an act of straining or the condition of being strained: such as. a : bodily injury from excessive tension, effort, or use heart strain especially : one resulting from a wrench or twist and involving undue stretching of muscles or ligaments back strain. b : excessive or difficult exertion or labor.
What are the symbols of stress?
| Description Symbol Name | Direct stress σ Sigma | Direct strain ε Epsilon | Shear stress τ Tau | Young’s modulus of elasticity E |
|---|
What are the types of stress?
- anxiety.
- cardiovascular disease.
- depression.
- high blood pressure.
- a weakened immune system.
What is stress in a structure?
The structural stress can also be regarded as the sum of the axial and bending stress in a plate or shell , i.e. the stress at the surface after a stress linearization in the thickness direction. This clearly defined structural stress for plate-type structures can only be determined numerically.
What is unit stress?
The stress or load per unit of area, usually taken per square inch of section . For instance, if a bar is 1 in by 2 in (2.5 cm by 5.1 cm) in section, the unit stress of the bar will be 1,000 divided by 2 (sectional area) or 500 psi (3.4475 MPa).
Where is the stress in plastic?
Look at (and listen to) this example for the word plastic. There are two syllables and the first syllable is stressed . Notice that dictionary A uses a different system to dictionary B to show which syllable is stressed. Of course, it’s the same word (plastic), and the stress is the same (the first syllable).
What makes a polymer brittle?
Fracture of brittle polymers is typically caused by cavitation and crazing . ... The fracture of the amorphous phase through cavitation and crazing competes with plastic deformation. Plastic deformation before breaking is known as plasticity (in metals it is known as ductility).
How do you know if plastic is stressed?
The most basic way to look at stresses in clear plastics is to place a sample of the material between two illuminated polarized sheets . When these elements are properly aligned, the stress pattern becomes visible.
What is the use of stress strain diagram?
A stress strain diagram or stress strain curve is used to illustrate the relationship between a material’s stress and strain . A stress strain curve can be constructed from data obtained in any mechanical test where load is applied to a material and continuous measurements of stress and strain are made simultaneously.
What is strain formula?
Strain occurs when force is applied to an object. Strain deals mostly with the change in length of the object. If the original length of the body L 0 L_0 L0 changes by Δ L Delta L ΔL , then stress can be expressed as. Strain = Δ L L = Change in Length Original Length .
What is strain and its types?
There are three types of strain and they are: Normal strain : Normal strain is defined as the ratio of change in dimension to its original dimension. ... According to normal strain, e = dL/L. Shear strain: The shear strain is defined as the angular distortion between two mutually perpendicular planes.
