banner ad
Experts Logo

articles

Glass Coffee Pot Failure Analysis: Thermal Shock Failure Of Borosilicate Glass Coffee Carafe - Example of Glass Fatigue

By: Dr. Thomas Read
Tel: (707) 544-2374
Email Dr. Read


View Profile on Experts.com.


Result Summary

The fatigue failure initiated on the outside bottom where the carafe had been scratched with the abrasive scrub pad. As a result of cyclical thermal shock (between 195°C and 15°C), the cracks grew progressively till it reached a critical length. Glass thickness at the origins is approximately 3 mm. One failed after 12.

Introduction

In order to simulate normal, use, coffee carafes were scratched with a chosen abrasive and thermal cycled. In this case a commercial scrub pad was used. It is a sponge with embedded 320-400 grit aluminum oxide.  This scratching is to simulate both cleaning and sliding the carafe on hard counter tops. In this test, the bottom of a new borosilicate coffee carafe was scrubbed with a wet abrasive sponge and then thermal cycled numerous times till a visible crack formed. A carafe that failed after 51 cycles is examined. The progressive crack initiated at an abrasive scratch.

Results
51 Cycle Failure

51 cycle carafe bottom crack photo

Figure #1: Photograph of the failed carafe bottom. The “wavy” nature of the crack indicates that it was driven by thermally generated stress.

 

photomicrograph outside surface photo

Figure #2: Photomicrograph of the fracture origin on the fracture surface. The fracture originated at an abrasive scratch. As a result of thermal shock, the crack grew progressively till it reached a critical length. Glass thickness at the failure origin 2.8mm (Mag. 10X).

 

figure3 high power photomicrograph photo

Figure #3: Higher power photomicrograph of the fracture origin on the fracture surface. The crack initiates on the outside bottom where the carafe had been scratched with the abrasive scrub pad. As a result of stresses from thermal shock, the crack grew progressively till it reached a critical length. Glass thickness at the origin 2.8mm (Mag. 40X.


Dr. Thomas L. Read, CEO of Read Consulting received his PhD. from Stanford University in 1972. He has over 25 years of manufacturing experience in electronics, metallurgy, factory safety, failure analysis, glass fracture, glass failure and bottle failure. As a member of the electronics industry, Dr. Read has earned process patents and has an extensive background in manufacturing techniques. In parallel, he has spent over twenty five years as a consultant to attorneys and engineers in the areas of failure analysis, metallurgy, glass fracture, glass failure, bottle failure, factory safety, manufacturing problems, intellectual property and patent disputes.

©Copyright - All Rights Reserved

DO NOT REPRODUCE WITHOUT WRITTEN PERMISSION BY AUTHOR.

Related articles

thomas_read_photo.jpg

4/12/2021· Failure Analysis

Glass Failure Analysis: Glass Oven Dish Failure

By: Dr. Thomas Read

The annealed borosilicate glass pie plate failed as a result of “thermal shock”. There were multiple origins for the failure, and these all initiated at damage sites on the bottom of the Pyrex baking dish. It appears that the bottom of the pie plate was convex. Thus, setting the dish down and moving it on hard (abrasive) surfaces such as tile or granite counters created bottom “rim” damage.

thomas_read_photo.jpg

7/7/2009· Failure Analysis

Failure Analysis of a Failed Ceramic Water Holding Tank on a Toilet

By: Dr. Thomas Read

The cracked tank was first inspected in the "as received" condition. In this condition it was cracked, but it was still whole. Next, the failed tank was separated by pulling it apart. This was done to expose the fracture surfaces of the main crack. This allowed for a complete failure analysis and for a determination of where the crack initiated.

thomas_read_photo.jpg

7/7/2009· Failure Analysis

Failure Analysis of a Broken Jam Jar

By: Dr. Thomas Read

Glass fractography is the most effective method for determining why a glass object, such as a bottle, failed. This technique consists of examining the fracture surfaces of the failure for artifacts such as Wallner lines and using them to trace the crack back to its origin. Once the origin has been identified, it can be examined in detail with a microscope to determine the cause of the failure.

;
Experts.com-No broker Movie Ad

Follow us

linkedin logo youtube logo rss feed logo
;