A ladder broke in use resulting injury to the user. Metallurgical evaluation of the fracture surface found indication of a brittle fracture (intergranular fracture surface). The cause was attributed to defective metal in terms of chemistry and thermal history. The case was settled out-of-court.
The following examples illustrate some of our contributions to this business sector:
- The body section from a 190 long paper mill roll broke at a point about 15 inches from one end. Examination of the fracture found that the fracture started at the location of a weld used to secure a socket head cap screw in the roll surface. Several cap screws had been used to hold a steel balance weight in place on the roll ID and after assembly the screw heads were arc welded to prevent loosening. The weld left a sharp internal notch beneath the weld bead which, under normal rotating-bending loads, propagated to the surface and then continued circumferentially until the roll failed catastrophically.
- A ladder broke in use resulting injury to the user. Metallurgical evaluation of the fracture surface found indication of a brittle fracture (intergranular fracture surface). The cause was attributed to defective metal in terms of chemistry and thermal history. The case was settled out-of-court.
- Expert testimony for legal action over the failure on installation of steel fasteners. The project included courtroom testimony. The manufacturer of the screw claimed the failures were the result of stress-corrosion cracking caused by over torqueing of the screws upon installation. Our analysis suggested hydrogen embrittlement – a manufacturing flaw. The client, based on our testimony, was awarded an amount equal to the replacement cost of the screws, plus legal and engineering fees.
- Preliminary examination of hydraulic hose specimens for mechanical damages involved a determination of the cause for leakage and eventual rupture of hydraulic hose. Examination of the ends of the broken reinforcement wires found that the wire had worn through before the failure occurred from some surface abrasion. The weakened hose later ruptured under normal operating pressure.
- Another investigation concerned the testing of 3 chain sling specimens. Results from tensile tests in accordance with ASTM procedures for alloy and carbon steel chain specification were provided. The evaluation included measurement of the chain links and mechanical testing to show that at least one sling had been stretched beyond its yield point. In addition, non-standard, repairs had been performed prior to an accident where a load slipped and eventually caused a wreck and two deaths.
- Various locations inside and outside a house displayed a black residue. Specimens were removed and brought to Touchstone Research Laboratory. The specimens were examined using SEM/EDS. The findings indicated that the material was not metallic, but probably carbonaceous. Next, the specimens were examined using GC/MS. The black material was found to contain only carbon, indicating that the source of the soot could include several possibilities. While no statement was provided regarding source, the black residue was presumed to be coming from nearby coke batteries.
The above examples are only a sample of our work in this area. We would be pleased to provide any additional information you may require. We also invite you to review examples on our website of work that we have performed in support of other business sectors.
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