Engineering Expert Witness Opines on Defective Trailer Strap

Engineering Expert WitnessThis case takes place in California and involves permanent eye injury from a hook snapping into the plaintiff’s eye due to an allegedly defective strap. The plaintiff was preparing a flatbed trailer to haul a load of cinder blocks. In order to ensure that none of the cinder blocks came loose during transit, the plaintiff attempted to secure them using a series of straps. The plaintiff successfully hooked several straps to the trailer before attempting to secure the last remaining strap. He successfully attached the S – hook at one end of the strap to the underside of the trailer. As he was attempting to hook the other end to the other side of the trailer the strap ripped in half, causing the S – hook that was hooked on of the trailer to become unhooked and snap directly into his eye. Not knowing exactly what had happened, the plaintiff removed the S – hook and was in immediate and excruciating pain. He was driven to the ER where he underwent facial reconstruction surgery. He maintained his left eyeball, but he will never see anything more than vague shadows. The plaintiff alleges that the tarp strap was not even close to being stretched to full capacity when he sustained the injury.

Question(s) For Expert Witness

  • 1. Please discuss your familiarity in stretch breakage cases involving tarp straps.
  • 2. In your experience, do you believe S Hooks are defective and unreasonably dangerous?

Expert Witness Response E-007971

I am an expert in analysis of mechanical failures such as described here for the S-Hook. This means examining the failed parts (with a microscope), looking for damage, or material or manufacturing defects, measuring cross-sections and geometry, and ultimately assessing the strength of the design and factors that would reduce the design strength and by how much. S-Hooks in and of themselves are not necessarily defective or unreasonably dangerous. However, a particular S-Hook may be either defective in several ways or dangerous due to factors like prior damage or other abuse. All must be considered. I am a seasoned Mechanical Engineering, PhD and MSME, from Stanford University and a licensed Professional Mechanical Engineer. I have many years of work experience and teaching experience, understanding mechanical failures, knowing how materials fail and characteristic signs of overload, damage, fatigue, etc.

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