Selected CEC Legal Projects


Some legal case work involves computer modeling/simulation and /or laboratory testing to reproduce failures, quantify design strengths, or quantify material properties. Some such cases are briefly described. CEC endeavors to use simulations and tests to maximize benefit to cases yet minimize costs (so test setups are usually simple and straightforward).


Legal Consulting

  

Metal Chair Failure Modeling

One area of work at Convergence is expert witness testimony in cases involving mechanical hardware and failure analysis. This particular project involved detailed finite element modeling of a welded chair frame, and prediction of stress levels in normal use. The results in graphical form are excellent visual aids for arbitration or trial use. The analysis results corroborated the hypothesized failure mode, and supported a design defect case.

Chair Failure Test

Pullout tests were conducted to determine strength of seat mount screw attachments in a plastic office chair. Load was measured using our data acquisition system, and the inserts were loaded until failure. CEC uses computer controlled hydraulics and chain winches to apply loading.

Lagbolt Pullout

CEC simulated a situation where a lag bolt was pulled out of a wall (resulting in a fixed roof ladder failure). In plane loading was used to represent a downward force and then progressive loading was used to pull the lag bolt out of the wood. Different hole sizes and pre-existing conditions were used to show how a degraded hole would drastically reduce the load carrying capability.

Nut/Bolt Failure

A simple fixture was utilized to characterize the force requirement to strip out the threads of different grade bolts and nuts for a pool filter explosion case. CEC’s 20,000 lbf capacity computer controlled hydraulic load frame was used with closed loop displacement control to load the bolts and nuts. From recorded data, we compared the maximum load carrying capability of each subject nut or bolt. The data was useful to show a design defect in the equipment in question.

Standoff Test

This test consisted of pulling on the end of a mechanical standoff (chopper motorcycle part) with a hydraulic cylinder and cable, to measure the bending load sustainable before breakage. The standoff with different length attachment stud engagement and different grade stud materials were tested. Multiple tests were performed and statistical analysis was conducted to support the case.

Bench Test

A poorly built bench was subjected to load capacity testing. CEC provided testing for both fatigue life of the bench with an oscillating load applied and a maximum load carrying test. Multiple exemplar benches were built and tested with different fastener configurations from screws to large carriage bolts.