What is polymer creep?
Creep is the tendency of a polymeric material to deform permanently under the influence of constant stress, as applied through tensile, compressive, shear, or flexural loading. It occurs as a function of time through extended exposure to levels of stress that are below the yield strength of the material.
What is creep in engineering materials?
In materials science, creep (sometimes called cold flow) is the tendency of a solid material to move slowly or deform permanently under the influence of persistent mechanical stresses. Creep is more severe in materials that are subjected to heat for long periods and generally increases as they near their melting point.
What is creep and its types?
Primary Creep: starts at a rapid rate and slows with time. • Secondary Creep: has a relatively uniform rate. • Tertiary Creep: has an accelerated creep rate and terminates when the material breaks or ruptures.
Why do polymers creep?
Creep is the result of the inherent viscoelastic nature of polymers that causes time dependency. Prolonged static stresses lead to a decay in apparent modulus that is associated with localized molecular reorganization of polymer chains.
What are the factors affecting creep?
Factors Affecting Creep Of Concrete:
- Water-cement Ratio: The rate of creep is increased with increasing water cement ratio.
- Humidity: It is influenced by humidity and drying condition of the atmosphere.
- Age Of Concrete: The rate of creep rapidly decreases with time.
- Aggregate:
- Admixtures:
What do you mean by creep?
to move slowly, quietly, and carefully, usually in order to avoid being noticed: She turned off the light and crept through the door. Someone was creeping around outside my window. The spider crept up the wall. The traffic was creeping along at a snail’s pace.
What is creep in railway engineering?
Creep in rail is defined as the longitudinal movement of the rails in the track in the direction of motion of locomotives. Creep is common to all railways and its value varies from almost nothing to about 6 inches or 16cm.
What are the effects of creep?
Effects of Creep on Concrete and Reinforced Concrete In reinforced concrete beams, creep increases the deflection with time and may be a critical consideration in design. In eccentrically loaded columns, creep increases the deflection and can load to buckling.
Why is creep important in engineering?
While creep resistance often results in the damage or microstructural degradation to a material, for some materials, like concrete, moderate creep is welcomed. This is because it relieves tensile stress that could otherwise lead to cracking.
How do engineers deal with creep?
Engineers use Creep machines to determine the stability and behaviour of a material when put through ordinary stresses. The device generates a creep time-dependent curve by calculating the steady rate of creep in reference to the time it takes for the material to change.
How does creep affect the design of polymers?
Of particular importance in the design process for polymers is an allowance for their susceptibility to creep deformation. Under a constant applied load and at a constant temperature the deformation of the polymer will continue to increase over time. The higher the applied stress or the higher the temperature the faster the deformation.
When does thermal creep occur in a material?
It is a time- dependent deformation under a certain applied load. Generally occurs at high temperature (thermal creep), but can also happen at room temperature in certain materials (e.g. lead or glass), albeit much slower. As a result, the material undergoes a time dependent increase in length, which could be dangerous while in service.
How are creep experiments conducted in Materials Science?
When materials scientists study creep of metals and alloys, much more sophisticated experiments are usually conducted. The alloys are precisely machined into test specimens, the testing temperature is fully controlled, and the elongation of the material is recorded in detail.
How is stress relaxation related to creep in plastic?
Creep is a serious issue in plastic housings or snap fit components, while Stress relaxation is a serious issue in sealing elements. Experimental studies on creep behavior of plastics is carried out using the tensile creep test. The loading is purely under static conditions according to ISO 899-1.