RESUME

LABORATORY

Jim Aleszka
M.S., P.E.

President and Principal Engineer

Fracture Investigations
4718 Renovo Way
San Diego, CA 92124

Phone & Fax: (858)560-5530
Email us

 

 

NON-METALLIC FAILURES

Metallic materials are not the only types that fail.  Failures often occur in plastic, glass, and composite materials.  Shown below is an example of each type.

  1. Glass
  2. A wine bottle failed in the neck as it was being opened.  The hackle lines on the fracture surface pointed back to a localized crushed area at the lip of the bottle beneath the foil.  Exemplar testing by striking the edge with the corner of a hammer replicated the damage.  It was thus postulated that the lip was crushed from contact with a sharp metal object during or before bottling as the foil cover over the lip was undamaged.  Insertion of the corkscrew created circumferential stresses in the neck, causing a crack to initiate at the crushed area and propagate through the neck.
  3. Plastic
  4. The plastic D-ring from an exercise harness assembly broke.  The harness was used to provide a restraining force during exercise.  Examination of the fracture surface found a large porosity bubble in the center of the surface.  The porosity was caused by incomplete fill of the die during injection molding of the D-ring.  During repeated use of the harness, a fatigue crack initiated at the porosity and eventually propagated through the thickness.

  5. Composite
  6. A composite grinding wheel broke apart. The task was to determine the wheel manufacturer. Energy dispersive x-ray analysis was used to determine the chemical composition of the fibers in the broken wheel. These results were then compared to those from an exemplar disk manufactured by the client. The tests proved that the broken disk was not from the client and the judge dismissed them from the lawsuit.

 

 

 

 

 

 

 

Contact us at info@metalconsult.com