Rapid estimation of the long-term hydrostatic strength via short-term burst-pressure tests

Rapid estimation of the long-term hydrostatic strength via

short-term burst-pressure tests

Citation for published version (APA):

Kanters, M. J. W., Erp, van, T. B., Stam, E. J., Engels, T. A. P., & Govaert, L. E. (2014). Rapid estimation of the long-term hydrostatic strength via short-term burst-pressure tests. Poster session presented at Mate Poster Award 2014 : 19th Annual Poster Contest.

Document status and date: Published: 01/01/2014 Document Version:

Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:

• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.

• The final author version and the galley proof are versions of the publication after peer review.

• The final published version features the final layout of the paper including the volume, issue and page numbers.

Link to publication

General rights

Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain

• You may freely distribute the URL identifying the publication in the public portal.

If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement:

www.tue.nl/taverne Take down policy

If you believe that this document breaches copyright please contact us at: openaccess@tue.nl

providing details and we will investigate your claim. Download date: 16. Sep. 2021

Fig.6: Burst pressure‐ (a) and t creep rupture data (b) on Noryl. Lines according to (5) and (6).  

Noryl

Noryl

Fig.4: Burst pressure‐ (a) and creep rupture data (b) on 40% glass fiber reinforced Noryl. Lines according to (3) and (4).  

40% GFR Noryl

40% GFR Noryl

Modelling

In solid polymers, failure occurs once the total amount of plastic strain reaches a

critical value, or:

The equivalent plastic flow rate as function of stress and temperature is described

via the pressure modified Eyring relation:

Where includes the thermodynamic state,

the temperature dependence,

the

stress dependency, and

the influence of hydrostatic pressure.

The expressions for stress and pressure in the geometry of the DETs are:

By substituting these in (2) and solving (1), using

and

_,

, for the

burst pressure as function of pressure rate, this yields:

And for the applied (constant) pressure versus time‐to‐failure in creep rupture:

I.e. by determining

and

in (3), via a simple linear regression model, the

lifetime can be estimated for different applied stresses, using (4).

The approach

With actual products, processing strongly affects the performance, due to effects such

as orientation, cooling history etc. Therefore, to mimic an actual product while

preserving a well‐defined geometry, Dead End Tubes (DETs) are used, see Fig. 1.

These are loaded with an internal pressure up to failure in a water bath at different

temperatures, either in short‐term burst pressure measurements, where the pressure

increases with constant pressure rate in time, or long‐term creep rupture

measurements, where the load is constant.

Polymer Technology

Rapid estimation of the long‐term hydrostatic

strength via short‐term burst‐pressure tests

Marc J.W. Kanters

1

, Tim B. van Erp

2

, Erik J. Stam

2

, Tom A.P. Engels

1,3

, Leon E. Govaert

1

1.

_{Eindhoven University of Technology}      

2.

_{SABIC, Technology & Innovation}       

3.

_{DSM Ahead, Materials Sciences R&D}

Introduction

To estimate a products lifetime, often a complete product is subjected to loads and

temperatures well above service conditions up to failure. Although this works, relevant

test conditions are far from evident; whereas too large loads results immediate failure

and too low loads in impractically long measurement times. So a short‐term method is

required to estimate the outcome of such a long‐term test.

,

,

∗

∗

∗

and

and

Where

Fig.5: Burst pressure‐ (a) and creep rupture data (b) on PC. Lines according to (5) and (6).  

PC

PC

PC+4% MBS

PC+ 4%MBS

Fig.3: Burst pressure‐ (a) and creep rupture data (b) on rubber filled polycarbonate. Lines according to (3) and (4).  

brittle

Include temperature dependence 

Being based on the theory of absolute reaction rates, this description from (3) and 

(4) can be adapted to also include the influence of temperature, which for the burst 

pressure results in:      

,

(5) 

And for the applied pressure as function of time‐to‐failure in creep rupture:

,

      (6)

Multiple deformation processes

at short timescales

Determining long‐

term behavior

Fig.2: Load signal (a) and setup for burst pressure (b) and creep rupture (c).

Creep rupture

,

,

/ department of mechanical engineering

Burst pressure 

b

Fig.1: Dead End Tube (DET)

a

Conclusion

Long‐term creep rupture experiments are quantitatively predicted based on short‐

term burst pressure experiments.

c