What Is a Creep Tester?
A creep tester is a device to measure the creep phenomenon that occurs when a certain load is applied to a material.
Creep phenomenon is a phenomenon in which strain increases and deformation progresses when a load is continuously applied to a material. This phenomenon generally occurs in plastic materials at room temperature, but it also occurs in metal materials at high temperatures.
Creep phenomenon causes deformation and rupture of the material, which in turn affects product failure. Estimation of material life by understanding the creep phenomenon is also important for quality control.
Uses of Creep Testers
Creep testers are used to reduce failures of equipment that are subject to high temperatures and to extend the life of metal and plastic materials by understanding and controlling creep phenomena.
One product that is particularly affected is gaskets. Gaskets are a type of sealing material that fixes the joints between pipes, and are often used in equipment through which fluids pass, including plant piping.
Since pressure is applied to the gasket part, the sealing performance may decrease due to the creep phenomenon. In order to prevent the deterioration of sealing, it is possible to select a PTFE resin that is less prone to creep phenomenon by using a creep tester, or to use a gasket under conditions where creep phenomenon is less likely to occur based on the measurement results of the creep tester.
Principle of Creep Testers
The creep tester measures the temperature and strain of a test specimen by heating the specimen in an electric furnace and applying a load to cause the creep phenomenon.
The principles of creep testers include “tensile creep,” “compressive creep,” “torsional creep,” and “creep rupture.”
The creep phenomenon to be tested differs depending on the material of the test specimen. Creep testers for metallic materials are generally uniaxial tensile. The metal specimen is set in an electric furnace and tensile load is applied in one direction by a rod.
Creep testers for plastic materials are designed to deal with the viscoelastic properties of plastics. Due to its sensitivity to test temperature and humidity, it is necessary to test a larger number of specimens or over a longer period.
Additional Creep Tester Information
Creep Testing Challenges
The creep phenomenon of plastic materials is influenced by the viscoelasticity of the resin. Viscosity is a property whereby strain increases when an external force is applied to an object and does not disappear when the external force is removed. Viscosity is a liquid-like property.
Elasticity is a property in which a certain amount of strain occurs when an external force is applied to an object and the strain disappears when the external force is removed. Elasticity is a solid-like property.
Viscoelasticity is the combination of liquid and solid properties, with an increase in strain when an external force is applied and a partial loss of strain when the external force is removed. Understanding creep phenomena is important for product control, but care must be taken to avoid the following challenges in measurement.
1. Obtaining Data
Creep phenomena of plastic materials are not well described in public information on the Internet or in literature, making it difficult to obtain the data you want. If you need the data, you need to measure it by yourself.
2. Time Consuming
It takes several weeks to several months to measure the creep phenomenon. Also, since it depends on measurement conditions such as temperature, it is easy for variations to occur, and in some cases, measurements need to be redone.
3. Not Easy to Perform
Many companies do not have their own creep testers due to the size of the equipment. In such cases, measurement requires external testing, which is costly.