FE Investigation into Manufacturing- and Design-Related Issues Contributing to the Failure of a Climbing Treestand

Jahan Rasty; Olin Parker; Mathew Mills

doi:10.51501/jotnafe.v39i2.849

Authors

Jahan Rasty Texas Tech University https://orcid.org/0000-0002-9943-3820
Olin Parker Texas Tech University
Mathew Mills Real-World Forensic Engineering https://orcid.org/0000-0002-3577-9750

DOI:

https://doi.org/10.51501/jotnafe.v39i2.849

Keywords:

Treestand, Manufacturing defect, dynamic overload, aluminum weld, forensic engineering

Abstract

The foot platform of a climbing treestand fractured while a user was standing on it in the process of secur-ing his harness to a tree. Analysis of the frame’s fracture surface revealed a manufacturing defect in the form of a ¼-inch diameter hole next to the fracture area, likely created during the welding process. To prove that this defect was the proximate cause of the treestand’s failure (under reasonably expected and foreseeable use conditions), a series of tests on exemplar treestands as well as finite element analysis were performed. It was concluded that the defect reduced the fracture toughness of the treestand by 40%. In addition, it was found that the manufacturer failed to account for additional stress caused by dynamic loading experienced during normal use. The authors opined that both the reduced strength and the omission of dynamic loading in the de-sign resulted in the treestand’s frame failure. Appropriateness of the manufacturer’s reliance on users always wearing their full body harness is also discussed. This paper examines the contribution of the drilled hole to the integrity and suitability of the ASTM-required Factor of Safety (FOS) of 2.

References

DDH Staff “One in Three Hunters Will Fall” Deer and Deer Hunting, https://www.deeranddeerhunting.com/deer-hunt/deer-hunting-tips/p3_one_in_three_hunters_will_fall (Accessed Aug. 23, 2022).

J. Smith et al. “Injuries Due to Falls from Hunters’ Tree Stands in Pennsylvania” American Journal of Preventative Medicine, vol. 37, no. 5, pp. 422-436, Nov. 2009.

M. Metz et al. “Tree stand falls: a persistent cause of sports injury” Southern Medical Journal, vol. 97, no. 8, pp. 715-719, Aug. 2004.

A. Crocket et al. “Tree stands, not guns, are the midwestern hunter's most dangerous weapon” The American Surgeon, vol. 76, no. 9, pp. 1006-1010, Sep. 2010.

C. A. Pierre et al. “Tree stand falls: A persistent cause of neurological injury in hunting” World Journal of Clinical Cases, vol. 2, no. 8, pp. 345-350, Aug. 2014.

Standard Practice for Treestand Manufacturer Quality Assurance Program, TMS Standard 09, 2009.

Standard Test Method for Treestand Static Load Capacity, TMS Standard 11, 1998.

Standard Test Method for Treestand Static Load Capacity, ASTM Standard F2126, 2006.

Fixed Ladders, 29 C.F.R. §1917.118.

Safety and Health Regulations for Construction, 29 C.F.R. §1926.

P. Seddon, “Harness Suspension: Review and Evaluation of Existing Information” Health and Safety Executive, Contract Research Report 451/2002, 2002.

OSHA, “Suspension Trauma/Orthostatic Intolerance” Occupational Safety and Health Administration, Washington, D.C., SHIB 03-23-2004, Mar. 23 2004.

“Hierarchy of Controls” U.S. National Institute for Occupational Safety and Health, https://www.cdc.gov/niosh/topics/hierarchy/ (Accessed Aug. 23, 2022).