Impact mechanics of friction joints and percussive drills
1986 (English)Doctoral thesis, comprehensive summary (Other academic)
Impact-loaded conical and cylindrical friction joints are studied theoretically and experimentally. The system considered consists of a long, straight, cylindrical and linearly elastic rod which is impacted axially at one end, and which has a body attached by means of a friction joint at the opposite end. The conditions are such that the wave propagation is 1-D in the rod and can be neglected in the attached body. Slip and energy dissipation due to an impact load are determined. The theoretical results of the impact-loaded conical friction joints exhibit phenomena which sometimes have spectacular appearance. The agreement between theoretical and experimental results is fair. The influence of blow frequency and thrust on the performance of a percussive rock drill is studied theoretically. The drill considered consists of hammer, adapter, rod and bit. Two different rock drills are studied. The first is a simple drill with constant characteristic impedance throughout the drill. The second is a prototype of a high frequency percussive rock drill. The efficiency and the maximum (maximum tensile) and minimum (maximum compressive) stresses are determined. For the simple drill the average efficiency in the range from soft to hard rock is only weakly dependent on the blow frequency up to relatively high blow frequencies but strongly dependent for extremely high blow frequencies. It is also found that the maximum and minimum stresses in the drill in the range from soft to hard rock are only weakly dependent on the blow frequency up to high frequencies but strongly dependent for extremely high frequencies. The maximum stress increases and the minimum stress decreases with thrust.
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 1986. , 17 p.
Doctoral thesis / Luleå University of Technologyy… → 31 dec 1996, ISSN 0348-8373 ; 1986:50
Research subject Mining and Rock Engineering
IdentifiersURN: urn:nbn:se:ltu:diva-16974Local ID: 0f806c60-c26d-11db-9ea3-000ea68e967bOAI: oai:DiVA.org:ltu-16974DiVA: diva2:989966
Godkänd; 1986; 20070108 (mlk)2016-09-292016-09-29Bibliographically approved