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Abstract

In this paper, the energy losses in big band saw machines are investigated. These losses are caused by the geometric and angular inaccuracies with which the leading wheels are made. Expressions for calculating the kinetic energy of the mechanical system in the ideal and the real cases are obtained. For this purpose, expressions for calculating the velocities of the centers of the masses in two mutually perpendicular planes are obtained. A dependence for calculation of the kinetic energy losses of the mechanical system in final form is received. Optimization procedure is used to determine the values of the parameters at which these losses have minimum values. The proposed study can be used to minimize energy losses in other classes of woodworking machines.

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Bibliography

[1] M. Sarwar, M. Persson, H. Hellbergh, and J. Haider. Measurement of specific cutting energy for evaluating the efficiency of band sawing different workpiece materials. International Journal of Machine Tools and Manufacture, 49(11-12):958–965, 2009. doi: 10.1016/j.ijmachtools.2009.06.008.
[2] M. Mandic, S. Svrzic, and G. Danon. The comparative analysis of two methods for the power consumption measurement in circular saw cutting of laminated particle board. Wood Research, 60(1):125–136, 2015.
[3] Z. Kopecký, L. Hlaskova, and K. Orlowski. An innovative approach to prediction energetic effects of wood cutting process with circular-saw blades. Wood Research, 59(5):827–834, 2014.
[4] K. Orlowski, T. Ochrymiuk, A. Atkins, and D. Chuchala. Application of fracture mechanics for energetic effects predictions while wood sawing. Wood Science and Technology, 47(5):949–963, 2013. doi: 10.1007/s00226-013-0551-x.
[5] P. Iskra, C. Tanaka, and T. Ohtani. Energy balance of the orthogonal cutting process. Holz Als Roh- und Werkstoff, 63:358–364, 2005. doi: 10.1007/s00107-005-0021-8.
[6] P. Obreshkov. Woodworking Machines. Publishing House ``BM'', 1995. (in Bulgarian).
[7] A. Pisarev, Ts. Paraskov, and C. Bachvarov. Course in Theoretical Mechanics. Second part – Dynamics. State Publishing House Technics, 1988. (in Bulgarian).
[8] R.M. Dreizler, and C.S. Lüdde. Theoretical Mechanics: Theoretical Physics 1. Springer, Berlin, Heidelberg, 2010. doi: 10.1007/978-3-642-11138-9.
[9] F. Scheck. Mechanics. From Newton's Laws to Deterministic Chaos. 5th edition, Springer, Berlin, Heidelberg, 2010.
[10] B. Marinov. Dynamic and Shock Processes in Some Classes of Woodworking Machines. Analysis and Optimization. Omniscriptum Publishing Group-Germany/LAP LAMBERT Academic Publishing, 2018.
[11] B. Cheshankov. Theory of the Vibrations. Publishing House in TU, 1992. (in Bulgarian).
[12] B. Marinov. Spatial deformations in the transmissions of certain classes of woodworking machines. Mechanism and Machine Theory, 82:1–16, 2014. doi: 10.1016/j.mechmachtheory.2014.07.010.
[13] Zh. Gochev. Handbook for Exercise of Wood Cutting and Woodworking Tools. Publishing House in LTU, 2005. (in Bulgarian).
[14] Yo. Tonchev. Matlab, Part 3. Publishing House Technique, 2009. (in Bulgarian).
[15] R. Peters. Band Saw Fundamentals: The Complete Guide. Hearst Communications Inc, 2006.
[16] L. Bird. The Bandsaw Book. Taunton Press Inc, 2000.
[17] W. Turner. A Comprehensive Handbook on Uses and Applications of the Band Saw and Jig Saw. Literary Licensing LLC, 2013.
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Authors and Affiliations

Boycho Marinov
1

  1. The Institute of Mechanics, Bulgarian Academy of Sciences, Sofia, Bulgaria.
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Abstract

In this paper, the computer modelling application based on the modal expansion method is developed to study the influence of a sound source location on a steady-state response of coupled rooms. In the research, an eigenvalue problem is solved numerically for a room system consisting of two rectangular spaces connected to one another. A numerical procedure enables the computation of shape and frequency of eigenmodes, and allows one to predict the potential and kinetic energy densities in a steady-state. In the first stage, a frequency room response for several source positions is investigated, demonstrating large deformations of this response for strong and weak modal excitations. Next, a particular attention is given to studying how the changes in a source position influence the room response when a source frequency is tuned to a resonant frequency of a strongly localized mode.

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Authors and Affiliations

Mirosław Meissner
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Abstract

As the duration of a rock burst is very short and the roadway is seriously damaged after the disaster, it is difficult to observe its characteristics. In order to obtain the dynamic characteristics of a rock burst, a modified uniaxial compression experiment, combined with a high-speed camera system is carried out and the process of a rock burst caused by a static load is simulated. Some significant results are obtained: 1) The velocity of ejected particles is between 2 m/s and 4 m/s. 2) The ratio of elastic energy to plastic energy is about five. 3) The duration from integrity to failure is between 20 ms and 40 ms. Furthermore, by analyzing the stress field in the sample with a numerical method and crack propagation model, the following conclusions can be made: 1) The kinetic energy of the ejected particles comes from the elastic energy released by itself. 2) The ratio of kinetic energy to elastic energy is between 6% and 15%. This can help understand the source and transfer of energy in a rock burst quantitatively.
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Bibliography

[1] F. Ren, C. Zhu, M. He, Moment Tensor Analysis of Acoustic Emissions for Cracking Mechanisms During Schist Strain Burst. Rock Mech. Rock Eng. 53, 1-2(2019). DOI: 10.1007/s00603-019-01897-3
[2] G . Su Y. Shi, X. Feng, J. Jiang, J. Zhang, Q. Jiang, True-Triaxial Experimental Study of the Evolutionary Features of the Acoustic Emissions and Sounds of Rockburst Processes. Rock Mech. Rock Eng. 51, 375-389 (2018). DOI: 10.1007/ s00603-017-1344-6
[3] F. Gong, Y. Luo, X. Li, X. Si, M. Tao, Experimental simulation investigation on rockburst induced by spalling failure in deep circular tunnels. Tunn. Undergr. Sp. Tech. 81, 413-427(2018). DOI: 10.1016/j.tust.2018.07.035
[4] S.H. Cho, Y. Ogata, K. Kaneko, A method for estimating the strength properties of a granitic rock subjected to dynamic loading. Int. J. Rock Mech. Min. 42 (4), 561-568(2005). DOI: 10.1016/j.ijrmms.2005.01.004
[5] J. Wang, H.D. Park, Comprehensive prediction of rockburst based on analysis of strain energy in rocks. Tunn. Undergr. Sp. Tech. 16 (1), 49-57(2001). DOI: 10.1016/S0886-7798(01)00030-X
[6] M.N. Bagde, V. Petorš, Fatigue properties of intact sandstone samples subjected to dynamic uniaxial cyclical loading. Int. J. Rock Mech. Min. Sci. 42 (2), 237-250(2005). DOI: 10.1016/j.ijrmms.2004.08.008
[7] M. Cai, H. Morioka, P.K. Kaiser, Y. Tasaka, H. Kurose, M. Minami, T. Maejima, Back-analysis of rock mass strength parameters using AE monitoring data. Int. J. Rock Mech. Min. 44 (4), 538-549(2007). DOI: 10.1016/j.ijrmms.2006.09.012
[8] K. Du, M. Tao, X. Li, J. Zhou, Experimental Study of Slabbing and Rockburst Induced by True-Triaxial Unloading and Local Dynamic Disturbance. Rock Mech. Rock Eng. 49 (9), 3437-3453(2016). DOI: 10.1007/s00603-016-0990-4
[9] R . Simon, PhD thesis, Analysis of fault-slip mechanisms in hard rock mining, McGill University, Quebec/Montreal, Canada (1999).
[10] N .G. Cook, The failure of rock. Int. J. Rock Mech. Min. 2 (4), 389-403(1965). DOI: 10.1016/0148-9062(65)90004-5
[11] P.N. Calder, D. Madsen, High frequency precursor analysis prior to a rockburst. Int. J. Rock Mech. Min. Geomech. Abstr.26, 3-4 (1989). DOI: 10.1016/0148-9062(89)92469-8
[12] Z.T. Bieniawski, Mechanism of brittle fracture of rock: Part II—experimental studies. Int. J. Rock Mech. Min. 4 (4), 407-423 (1967). DOI: 10.1016/0148-9062(67)90031-9
[13] S.P. Singh, Burst energy release index. Rock Mech. Rock Eng. 21 (2), 149-155 (1988). DOI: 10.1007/BF01043119
[14] A. Kidybiński, Bursting liability indices of coal. Int. J. Rock Mech. Min. Sci. 18 (4), 295-304 (1981). DOI: 10.1016/0148-9062(81)91194-3
[15] A. Tajduś, M. Cala, K. Tajduś, Seismicity and Rock Burst Hazard Assessment in Fault Zones: a Case Study. Arch. Min. Sci. 63 (3), 747-765 (2018). DOI: 10.24425/123695
[16] W.D. Ortlepp, T.R. Stacey, Rockburst mechanisms in tunnels and shafts. Tunn. Undergr. Sp. Tech. 9 (1), 59-65 (1994). DOI: 10.1016/0886-7798(94)90010-8
[17] H . Marcak, Seismicity in mines due to roof layer bending. Arch. Min. Sci. 57 (1), 229-250 (2012). DOI: 10.2478/v10267-012-0016-3
[18] T.J. Williams, C.J. Wideman, D.F. Scott, Case history of a slip-type rockburst. Pure Appl. Geophys. 139, 627-637 (1992). DOI: 10.1007/BF00879955
[19] A.A. Griffith, VI. The phenomena of rupture and flow in solids. Phil. Trans. Math. Phys. Eng. Sci. 221 (582-593), 163-198 (1921). DOI: 10.1098/rsta.1921.0006
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Authors and Affiliations

Weiyu Zheng
1 2

  1. China University of Mining & Technology (Beijing), School of Energy and Mining Engineering, China
  2. State Key Laboratory of Coal Mining and Clean Utilization, China
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Abstract

As the cost of fuel rises, designing efficient solar air heaters (SAH) becomes increasingly important. By artificially roughening the absorber plate, solar air heaters’ performance can be augmented. Turbulators in different forms like ribs, delta winglets, vortex generators, etc. have been introduced to create local wall turbulence or for vortex generation. In the present work, a numerical investigation on a solar air heater has been conducted to examine the effect of three distinct turbulators (namely D-shaped, reverse D- and U-shaped) on the SAH thermo-hydraulic performance. The simulation has been carried out using the computational fluid dynamics, an advanced and modern simulation technique for Reynolds numbers ranging from 4000 to 18000 (turbulent airflow). For the purpose of comparison, constant ratios of turbulator height/hydraulic diameter and pitch/turbulator height, of 0.021 and 14.28, respectively, were adopted for all SAH configurations. Furthermore, the fluid flow has also been analyzed using turbulence kinetic energy and velocity contours. It was observed that the U-shaped turbulator has the highest value of Nusselt number followed by D-shaped and reverse D-shaped turbulators. However, in terms of friction factor, the D-shaped configuration has the highest value followed by reverse D-shaped and U-shaped geometries. It can be concluded that among all SAH configurations considered, the U-shaped has outperformed in terms of thermohydraulic performance factor.
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Authors and Affiliations

Abhishek Ghildyal
1
Vijay Singh Bisht
1
Prabhakar Bhandari
2
Kamal Singh Rawat
3

  1. Veer Madho Singh Bhandari Uttarakhand Technical University, Faculty of Technology, Dehradun 248007, India
  2. K.R. Mangalam University, School of Engineering and Technology, Department of Mechanical Engineering, Gurugram, Haryana 122103, India
  3. Meerut Institute of Engineering and Technology, Mechanical Engineering Department, Meerut 250005, India

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