Envalior

Quickly and accurately calculate creep curves for every condition

When selecting resins for specific application types, design engineers want to compare creep properties of the resins they have to choose from. With our Creep Tool you can easily check the creep behavior of a material at any given temperature and stress level. You can also use the tool to run simulations, for which material data is needed as input, to validate and optimize a design.

As a design engineer, who designs parts that need to sustain continuous loads over a long period of time, you need to check whether resulting creep deformations are acceptable or not, and to do this, you need material creep data as input for simulations. As a customer of Envalior, you can get all the creep data needed for your evaluations without any delays. Plus, our CAE/engineering services team is ready to support you in case you need assistance on how to use our creep data or help interpreting creep simulation results. 

You can obtain accurate creep curves immediately  

The Creep Tool is most important to utilize during the concept and detailed design stages of an application design project. There are requirements for the part in terms of creep and evaluating these are best done by FE (finite element) simulations. The quality of the outcome is governed by the availability and quality of the material data input (=creep curve). 

There is not just one creep curve per material. There are many parameters that influence creep curves, such as temperature, relative humidity, stress level, and duration of load, fiber orientation, etc. Our Creep Tool currently considers the effects of temperature (T) and stress (σ). 

With our Creep Tool, you can enter the specific temperature and stress level you are interested in and generate the creep curve. The range of valid temperatures and stresses are indicated by the tool. You can also do this for many of our materials and compare their performance in an efficient manner, so you can pick the best material for your specific application.

You can output the creep performance in different formats, like the resulting strain (=deformation) as a function of time, or as creep modulus (=applied constant stress divided by time dependent deformation) as a function time. Time considered is now limited to 1000 hours. The creep response is measured on an injection moulded ISO5271A specimen. All the Creep Tool predictions are based on creep data measured on these types of specimens.

We have measured many creep curves for many grades at several temperatures and stress levels. These are all available in our datasheets. You can also find the curves on plasticsfinder.com. However not every condition, for temperature and stress, has been measured. 

In such cases, you have a few options: 

  1. Ask the material supplier you are working with to measure the missing creep curves, which requires time and investment. The lead time is typically 8-12 weeks, based on a standard creep measurement running for about 1000 hours.  
  2. Perform an interpolation on the existing data to estimate the creep curve for the missing condition/s. 
  3. Thankfully a third option is available to you —our Creep Tool, which offers a quick and efficient way to solve these challenges. Based on a few user inputs, the required creep curve can be estimated by our tool. Once you have the output you can download the curve/s in an Excel file and continue your project without any delay.

The technology behind the Creep Tool

We have measured and collected all creep curves for many of our grades in one database, and developed models based on polymer-physics to assess the effects of stress, temperature, moisture, glass fiber content, and glass fiber orientation on the level and shape of the creep curve. 

This results in creep deformation predictions by our Creep Tool to have a high degree of accuracy, typically within 10% when applying to not too high loads. If the load is increased to more than 50% of the initial tensile strength, deviations can occur. In the online Creep Tool, the applied load is limited to 45% of the tensile strength.

We are continuing to improve the Creep Tool by measuring more creep curves. This includes temperature and stress ranges not yet covered, as well as including more of our material grades.

Get instant answers to your material challenges

Learn about the latest materials innovations  

ABOUT THE AUTHOR

Lucien Douven

Senior Design Engineer

Lucien Douven is responsible for the development of advanced CAE tools, based at the Envalior Materials Center in the Netherlands. He holds a PhD degree in Mechanical engineering, from Eindhoven University of Technology.

Creep Tool

Published on

01 June 2023

Tags

  • Blog
  • Basic material property prediction
  • Overall

Share

Leveraging thermoplastic expertise to optimize system designs