Bar Stool Collapse

Metallurgical examination and failure analysis was requested of a bar stool that collapsed while being used in a retail location. The person seated on the bar stool was severely injured. An overall view of the failed bar stool, with one leg missing is shown in Photograph A.

Photograph A: Overall view of failed bar stool with missing leg.

An overall view of the bottom side of the bar stool is shown in Photograph B. The location of a failed fillet weld used to connect the bar stool foot ring to one of the four legs is denoted with a white arrow.

 
Photograph B: Overall view of bottom side of the subject bar stool. Arrow denotes location of failed fillet weld.

A close-up view of the failed foot ring to leg fillet weld is shown in Photograph C. Note the straight edge of the fillet (denoted with arrows) weld which attached the foot ring to the bar stool leg. Straight edge of failed weld indicates lack of weld penetration into the bar stool leg.

 
Photograph C: Close-up view of failed foot ring to leg fillet weld. Straight edge of weld failure is denoted with arrows.

Underside (side of weld facing bar stool leg) of failed fillet weld, shown in Photograph D. Visual and microscopic examination revealed massive weld porosity. A close-up view of the area where the fillet weld was designed to attach the foot ring to the bar stool leg is shown in Photograph E. White arrows indicate a heat effect from attempted welding, but total lack of weld penetration.

 
Photograph D: Close-up view of underside of foot ring to leg fillet weld showing massive weld porosity.

 
Photograph E: Close-up view of the bar stool leg showing lack of weld penetration.

For reference purposes, a properly and adequately welded leg to foot ring joint is shown in photograph F.

 
Photograph F: Overall view of properly welded leg to foot ring joint.

The failure of the subject bar stool was the result of lack of welding (weld penetration) between the bar stool ring and the bar stool leg. Massive weld porosity was a symptom of defective, improper and inadequate welding.

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