BS ISO 3046-5:2001 pdf – Reciprocating internal combustion engines — Performance — Part 5: Torsional vibrations.
1 Scope This part of ISO 3046 establishes general requirements and definitions for torsional vibrations in shaft systems of sets driven by reciprocating internal combustion (RIC) engines. Where necessary, individual requirements can be given for particular engine applications. This part of ISO 3046 covers sets driven by reciprocating internal combustion engines for land, rail-traction and marine use, excluding sets used to propel road construction and earthmoving machines, agricultural tractors, industrial types of tractors, automobiles and trucks, and aircraft. 2 Normative references The following normative documents contain provisions, which, through reference in this text, constitute provisions of this part of ISO 3046. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this part of ISO 3046 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 2041:1990, Vibration and shock — Vocabulary ISO 2710-1, Reciprocating internal combustion engines — Vocabulary — Part 1: Terms for engine design and operation ISO 2710-2, Reciprocating internal combustion engines — Vocabulary — Part 2: Terms for engine maintenance 3 Terms and definitions For the purposes of this part of ISO 3046 the terms and definitions in ISO 2710-1 and ISO 2710-2 as well as the following apply. 3.1 set assembly of mechanisms including one or more RIC engines and the driven machinery 3.2 shaft system assembly of all the components of a set connected so that they can rotate (see Figure 1) NOTE When the torsional vibrations are calculated, it is the complete shaft system that is considered.
3.3 torsional vibrations oscillatory angular deformation (twist) of a rotating shaft system 3.4 torsional vibration amplitude maximum angular displacement measured in a section perpendicular to the axis of the shaft system between the angular position considered and a given arbitrary reference position 3.5 natural frequency parameter that can be calculated for each solution of the equation of motion for the undamped system See 2.80 of ISO 2041:1990. NOTE It is usually not necessary to calculate the natural frequency for a damped system. 3.6 natural vector relative amplitude for the whole section where the system is vibrating at its associated natural frequency and an arbitrary section of the system is chosen as a reference and given an amplitude of unity 3.7 elastic line envelope of the natural vector amplitudes in each section (see Figure 2) 3.8 vibratory node point of elastic line where relative natural vector amplitude is equal to zero 3.9 natural mode of torsional vibration natural frequency and its elastic line that characterizes each mode of torsional vibration NOTE Examples are first mode of vibration or one node mode of vibration or second mode of vibration or two node modes of vibration. 3.10 excitation torque torsional periodic torque generated by the RIC engine or driven components that excites torsional vibration of the shaft system 3.11 harmonic each term of a series of sinusoidal terms (Fourier series) into which the excitation torque may be subdivided See 2.26 of ISO 2041:1990. NOTE Each of these harmonics is theoretically capable of producing resonance at the appropriate rotational velocity of the shaft system. The Fourier series terms are written in increasing order. The first harmonic is related to the first term of the series (even if it had zero magnitude) and so on (see Figure 3).
3.13 resonance speed speed at which the whole shaft system resonates (as the natural frequency of a vibration mode equals the frequency of one of the harmonics of the excitation torques) See 2.73 of ISO 2041:1990. 3.14 synthesized torsional stress torsional stress generated in a given section of the shaft system by the total of all the harmonics of the excitation torques, taking account of the magnitude and phase of the stress generated by each harmonic (see Figure 4) NOTE Mean torque is not used when elaborating the synthesized torsional stress. 3.15 additional torsional stress stress due to the torsional vibrations of a given harmonic which is superimposed on the torsional stress corresponding to the mean torque transmitted in the given section of the shaft system being considered 3.16 barred speed range speed range over which the stress caused by the torsional vibration exceeds the stress value permitted for continuous operation NOTE Continuous operation in this speed range is forbidden, but passing through in transient operation is permissible provided that it offers no danger or damage to the shaft system.