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You searched for subject:(Percussive drilling). Showing records 1 – 2 of 2 total matches.

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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

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 · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

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

Due to the overall process complexity, studies about percussive drilling usually focus on a limited set of the (sub)processes underlying it, e.g., the hammer thermodynamics or the interaction between the bit and the rock. Following this paradigm, the assessment of the process performance is typically performed by considering a single percussive activation and a single interaction cycle between the bit and the rock, from arbitrary initial conditions.The need for an integrated approach to evaluate drilling performance, based on the dynamical interaction of the (sub)processes underlying drilling, is evident. Such an approach requires simplified models, however, as the computational cost associated with full scale models is simply unbearable. In this thesis, three dynamical integrated models are proposed and a preliminary analysis is conducted for a reference configuration and around it. The models couple three modules that represent: (i) the dynamics of the mechanical system, (ii) the interaction between the bit and the rock, and (iii) the activation of the mechanical system. For each module, simple representations are considered; of particular importance is the bit/rock interaction model which is a generalization to repeated interactions of experimental evidence observed for a single interaction.In the first model, the dynamics of a rigid bit is cast into a drifting oscillator and the activation modeled as a periodic impulsive force. The second and third models account for the dynamics of the piston and the activation results from the impact of the piston on the bit. They are respectively based on elastic and rigid representations of the two bodies. In the rigid model, analytical results of wave propagation in thin rods are used to represent the contact interaction between the piston and the bit. In the elastic model, wave propagation is resolved.Their preliminary analysis has revealed the occurrence of complex dynamical responses in the space of parameters. Expected trends are recovered around a reference configuration corresponding to a low-size hammer, with an increase of the rate of penetration with the feed force and the percussive frequency. An important sensitivity of the rate of penetration to the latter parameter is uncovered. Interestingly, our analyses show that when the activation period has the same order of magnitude as the timescale associated with the bit/rock interaction, a lower power consumption is observed, indicating a possible resonance phenomenon in the drilling system. Also, the predictions of the rigid model are shown to be in good agreement with the ones of the elastic model, in the explored range of parameters.Given the piecewise linear nature of the proposed models, dedicated numerical tools have been developed to conduct their analysis. As such, the thesis proposes a high-order time integration scheme for linear structural dynamics as well as a novel framework to evaluate the accuracy of such schemes, and a root-solving module to perform event-detection, for coupling with event-driven…

Subjects/Keywords: Bit/rock interaction; Dynamical systems; Percussive drilling; Piecewise smooth; Structural dynamics; Civil engineering

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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

.