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Luleå University of Technology
1. Draxler, Joar. Improvements on a Hydraulic Impact Piston for Percussive Rock Drilling.
Degree: 2013, Luleå University of Technology
URL: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-44397
This Master Thesis was done at Atlas Copco Rock Drills AB in Örebro. It treats how the geometry of impact pistons in hydraulic percussive rock drill hammers can be improved. The material in these pistons is highly loaded during each impact and there are cases where fatigue failure has occurred. One critical location for fatigue damage is the fillet between the boom and the tail of the piston. This is because the stress pulse from the impact is amplified in this area. By developing a full transient analysis for a piston in ANSYS, and by using design optimization, a new type of fillet was constructed from a cubic b-spline. This new fillet has the same length as the old fillet, a double radius fillet, on the piston tail, but it has 12‒16% lower maximum stress range, depending on the stress measure. A special feature with this fillet is that it is cut into the material of the boom. In that way it could be longer than the double radius fillet which enables a larger radius of curvature and a longer distance to “lead” in the stress pulse into the tail. This results in lower stress ranges in the fillet. Several multiaxial stress fatigue methods were used to analyze the fatigue damage in the old double radius fillet and in the new undercut fillet. It was found that the double radius fillet has a safety factor of 0.98‒1.08 to infinite fatigue life and the undercut fillet has a safety factor of 1.10‒1.23 to infinite fatigue life, depending on the fatigue method. Because infinite fatigue life normally corresponds to 106 ‒107 equivalent stress cycles, and the piston is desired to withstand close to one billon impacts, the old double radius fillet does not leave any margins to effects which can occur in the giga-cycle regime. The undercut fillet on the other hand leaves some margins to these kinds of effects. Unfortunately, no fatigue parameters were known for the material in the considered piston, so they were estimated from empirical relations. During the work with the undercut fillet it was realized that the weight of the impact piston can be reduced by minimizing the weight of the piston tail without affecting its performance. By using design optimization with the constraint that the maximum stress range in the piston tail should not be larger than the maximum stress range in the double radius fillet, its weight was reduced by 38%. With this change in mass, less energy is needed to accelerate the piston and less reflection energy is needed to be damped out.
Validerat; 20130917 (global_studentproject_submitter)
Subjects/Keywords: Technology; Percussive Rock Drilling; Design Optimization; Elastic Wave Modelling; Teknik
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APA (6th Edition):
Draxler, J. (2013). Improvements on a Hydraulic Impact Piston for Percussive Rock Drilling. (Thesis). Luleå University of Technology. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-44397
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Draxler, Joar. “Improvements on a Hydraulic Impact Piston for Percussive Rock Drilling.” 2013. Thesis, Luleå University of Technology. Accessed January 25, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-44397.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Draxler, Joar. “Improvements on a Hydraulic Impact Piston for Percussive Rock Drilling.” 2013. Web. 25 Jan 2021.
Vancouver:
Draxler J. Improvements on a Hydraulic Impact Piston for Percussive Rock Drilling. [Internet] [Thesis]. Luleå University of Technology; 2013. [cited 2021 Jan 25]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-44397.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Draxler J. Improvements on a Hydraulic Impact Piston for Percussive Rock Drilling. [Thesis]. Luleå University of Technology; 2013. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-44397
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Minnesota
2. Depouhon, Alexandre F.B.E. Integrated dynamical models of down-the-hole percussive drilling.
Degree: PhD, Civil Engineering, 2014, University of Minnesota
URL: http://hdl.handle.net/11299/170117
Subjects/Keywords: Bit/rock interaction; Dynamical systems; Percussive drilling; Piecewise smooth; Structural dynamics; Civil engineering
Record Details
Similar Records
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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager
APA (6th Edition):
Depouhon, A. F. B. E. (2014). Integrated dynamical models of down-the-hole percussive drilling. (Doctoral Dissertation). University of Minnesota. Retrieved from http://hdl.handle.net/11299/170117
Chicago Manual of Style (16th Edition):
Depouhon, Alexandre F B E. “Integrated dynamical models of down-the-hole percussive drilling.” 2014. Doctoral Dissertation, University of Minnesota. Accessed January 25, 2021. http://hdl.handle.net/11299/170117.
MLA Handbook (7th Edition):
Depouhon, Alexandre F B E. “Integrated dynamical models of down-the-hole percussive drilling.” 2014. Web. 25 Jan 2021.
Vancouver:
Depouhon AFBE. Integrated dynamical models of down-the-hole percussive drilling. [Internet] [Doctoral dissertation]. University of Minnesota; 2014. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11299/170117.
Council of Science Editors:
Depouhon AFBE. Integrated dynamical models of down-the-hole percussive drilling. [Doctoral Dissertation]. University of Minnesota; 2014. Available from: http://hdl.handle.net/11299/170117