HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
<<  <  Page 3/3
Dave Palmer
User Rank
Platinum
Re: Commonplace Chemicals
Dave Palmer   2/3/2012 11:50:24 AM
NO RATINGS
@Alex: When it comes to environmental stress cracking, there is not necessarily any advantage to making the plastic thicker or thinner.  The key variables are stress and chemical exposure.  If by making the plastic thicker, you can reduce the stress below the threshold, then it might be a solution.  But often the threshold stress is so low that this is impractical.  And if the internal stresses in the material are high enough, it doesn't matter what you do with the external stress.

Here is a good introduction to residual stress in plastics.  At some risk of oversimplification, thin-wall sections are more likely to have flow-induced residual stresses, while thick-wall sections are more likely to have thermal-induced residual stresses.  But either way, molded-in stresses can be significant.

Alexander Wolfe
User Rank
Blogger
Commonplace Chemicals
Alexander Wolfe   2/3/2012 11:16:41 AM
NO RATINGS
I never realized the commonplace chemicals like oil and grease were precursors to stress cracking in plastics. Good to know. Also didn't realize there's some built-in prestress. It seems that, in consumer systems, the plastic always ends up cracking at some point. Is that because thin(ner) plastics are always prone to cracking (and on the other side of the design equation, making them thick enough to be more crack resistant doesn't comport with weight and cost requirements. Or are the thicker plastics just as stress-crack prone?)

<<  <  Page 3/3


Partner Zone
Latest Analysis
During a teardown of the iPad Air and Microsoft Surface Pro 3 at the Medical Design & Manufacturing Show in Schaumburg, Ill., an engineer showed this "inflammatory" video about the dangers of maliciously mishandling lithium-ion batteries.
The Window Watcher stops the burglar before he does damage or enters the house. House alarm service companies set off alarms and call the service only after the burglar has damaged and entered the house.
If you’re designing a handheld device or industrial machine that will employ a user interface, then you’ll want to check out the upcoming Design News Continuing Education Center course, "Engineering Principles Behind Advanced User Interface Technologies.”
Brooke Williams of Texas Instruments explains how TI’s new TDA3x chip will help future vehicles “see” all around themselves.
It's been two years since the Mac Mini's last appearance on iFixit's teardown table, but a newly revised version joins Apple's lineup this week.
More:Blogs|News
Design News Webinar Series
10/7/2014 8:00 a.m. California / 11:00 a.m. New York
9/25/2014 11:00 a.m. California / 2:00 p.m. New York
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Oct 20 - 24, How to Design & Build an Embedded Web Server: An Embedded TCP/IP Tutorial
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: 10/28-10/30 11:00 AM
Sponsored by Stratasys
Next Class: 10/28-10/30 2:00 PM
Sponsored by Gates Corporation
Next Class: 11/11-11/13 2:00 PM
Sponsored by Littelfuse
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service