Rubber Failure Analysis: Inner Tube Failure

 California failure analysis lab performs rubber failure analysis on a failed bicycle inner tube. The rider was braking while descending a long steep hill. Toward the bottom of the hill his inner tube failed, and he heard a loud pop. The wheel rim was too hot to touch. A failure analysis was performed and the failure originated at a point on the tube that would have been in contact with a spoke "nut". It is believed that the tube was heated to the highest temperature at this location, and it softened to the point of failure. In addition, the tire pressure was elevated due to the heating of the rim from the friction of the brake pads. Upper right is a 40X photo-micro graph of the failure origin.

California Failure Analysis Lab Examines Stainless Steel Corrosion Failure

Stainless steel corrosion failures often result from grain boundary sensitization. Many 300 series stainless steel alloys come in two grades or more. For example 304 stainless steel comes as 304, 304L and 304H. Each grade has a different amount of carbon (C). the 304 grade allows up to .0.08% C; whereas
304 L allows a maximum of 0.03% C. In corrosive environments, this is critical if the piece is welded or heated in the temperature range from 459°C to 850°C. As the carbon content increases in the alloy, the time for grain boundary sensitization decreases. Grain boundary sensitized stainless steels exhibit rapid corrosion  failure at the grain boundary because the chrome has been tied up by the carbon in the grain boundaries.
In this case the California failure analysis expert performed a corrosion failure analysis on a jacketed pipe made from 304 stainless steel which corroded rapidly as a result of grain boundary sensitization. The alloy was not specified correctly. The design drawings should have specified solution treated 304L or 316L plate for the manufacture of the industrial pipe. The plumbing failure expert  contends that if this were done, the plumbing failure would not have occurred. The equipment designer cannot rely on the supplier to pick the proper materials..  

Glass Expert Witness Services

Read Consulting is a California failure analysis laboratory that provides a complete line of glass expert witness services. These include glass failure analysis, window damage assessment,  patent expert witness support and stress testing. In addition Read Consulting also offers glass expert witness support in all areas of glass and ceramic machining and processing.  Process and device patent expertise is also provided.