Kee K.K*, Lim Chin Chin, Michael Tay Ming Kiong
17th Triennial meeting of IAFS, abstract no. A0771 (oral presentation)
Objective: This paper presents a study on damages observed on polyethylene and nylon ropes that have been severed by cuts or under tension.
Nature of study: This study resulted from a case in which a man was found dead at the foot of a building with a polyethylene rope secured to his body. This questioned rope had one fused end and one frayed end. This rope had to be compared with another piece of questioned rope found on the 7th floor of the building to determine if: They were originally one piece of rope which had severed and whether the rope severed as a result of cutting or tension or a combination of both factors.
Methods and results: The frayed ends on both questioned ropes were examined for its damage characteristics using the stereomicroscope and scanning electron microscope. They were found to be irregularly shaped, fibrillated and tapered with striations. Simulation experiments were carried out on control polyethylene and nylon ropes to examine the severance due to cutting or tension. Test cuts were performed on these ropes using single-bladed (i.e penknife) and double-bladed (i.e scissors) tools. The damages observed on the cut ends of the ropes were found to be characteristic of the type of cutting tool. Individual strands and entire ropes (consisting of 3 to 5 strands) were also pulled apart mechanically using a tensile strength tester. Two types of damages were observed: the first type of damage was characteristic of a rope which severed under tension, the second type of damage was characteristic of a rope which severed under a combination of tension, compression and abrasion. The damages observed on these cut/torn ends of these control ropes were compared with those observed on the damaged ends of the two questioned ropes.
Conclusion: The damages observed on the ends of the control ropes severed by cutting or tearing were found to be characteristic of the severance method. These findings are instrumental in the examination of damages observed on ropes.