Machine dynamics
Machine dynamics refer to the study of a system’s motion based on the forces acting on the system. Machine dynamics apply knowledge of engineering mechanics, especially dynamics, to the problems of real machines.
Examination of different vibrations, e.g. torsional vibrations or natural vibrations on the example of a model.
Basic experiments on mechanical vibration theory
Learning objectives/experiments
- free vibrations
- damped vibrations
- inertia force and displacement excitation
- forced vibrations
- resonance
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Influence of mass, torsional rigidity and damping on the behaviour of a rotary oscillator. Vibrations are recorded on the TM 150/TM 155 recorder.
Learning objectives/experiments
- natural frequency of a rotary oscillator
- influence of torsional stiffness, mass and damping
Illustrative experiments on a torsion test bar with varying masses; multiple mass oscillator
Learning objectives/experiments
- determine the torsional stiffness of a torsion bar
- determine the mass moments of inertia
- decay behaviour of torsional vibrations
- determine the damping in torsional vibrations
- forced torsional vibrations, resonance
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Dynamic behaviour of a ship structure; experiments in air and in water
Learning objectives/experiments
- measure and record natural frequencies and modes of the model ship (in air)
- vibration behaviour of the model shipin air
- comparison between theory (approximation formula for determining the first bending frequency) and practice (measured natural frequency)
- influence of discrete additional masses or ballast on natural frequency and mode (ballast and extra weights not included)
- vibration behaviour of floating model ship (possible with additional tank)
Experimental equipment used to investigate vibrations in rotating components such as shafts.
Investigation of bending vibrations and resonance of a rotating shaft
Learning objectives/experiments
- investigate bending vibrations and resonance of a rotating shaft
- determine critical speeds with different arrangements of the bearing and masses on the rotor shaft and compare with theory
- investigation of the rotor’s self-centring effect
Determination of critical speeds and investigation of natural modes of a shaft
Learning objectives/experiments
- investigation of a Laval rotor
- critical speed
- self-alignment
- natural modes on a shaft with continuous mass distribution with
- different bearing clearances
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- different bearing clearances
Measures such as balancing affect the mass distribution in the machine so that resulting mass forces are avoided or at least reduced to an acceptable level.
Demonstration of the fundamentals of static and dynamic balancing
Learning objectives/experiments
- demonstration of imbalance vibrations at different speeds
- comparison of static, dynamic or general imbalance
- determine an imbalance
- perform a balancing operation
Measurement of imbalance vibrations
Learning objectives/experiments
- measure and assess machine vibrations
- occurrence of imbalance vibrations
- static, dynamic or general imbalance
- dependence of imbalance vibration on position and magnitude of the imbalance
- basic principles of balancing
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Unwanted oscillating and rotating masses in machines are reduced by means of mass balancing or ideally fully compensated.
Investigation of mass forces on a reciprocating piston machine
Learning objectives/experiments
- effect of mass forces
- mass forces in dependence on the speed
- mass forces in dependence on the piston mass
- first and second order mass forces
- comparison of different crank drives
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Comparison of different cam members; recording elevation curves
Learning objectives/experiments
- elevation curves in non-matching engaging member
- elevation curve in sprung-engaging member
- determine the limit speed and compare with theory
- influence of moving mass on the motion of cam member/plunger
- influence of return-spring stiffness and preload on the motion of cam member/plunger
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In vibration insulation, we look at two cases: the transmission of periodic, shock-like or stochastic forces from a machine to surrounding structures or vibrations from the environment to the machine.
Machine foundation and isolation of vibrations
Learning objectives/experiments
- familiarisation with vibration phenomena on machine foundations
- adjust the foundation for different excitation forces
- investigate vibration absorbers
- investigate the effect of additional damping
- compare metal springs and rubber springs
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Used for generating vibrations for the TM 182
Learning objectives/experiments
- in conjunction with trainer TM 182:
- generating vibrations on machine foundations with a “real machine”
The aim of machinery diagnosis, also known as machinery status monitoring or condition monitoring system (CMS), is to conduct needs-based maintenance or repair and therefore to minimise the repair and downtimes of a machine.
Investigation of the vibrations of roller bearings
Learning objectives/experiments
- vibrational spectrum of the running noise of roller bearings
- familiarisation with the envelope analysis
- influence of damage to outer race, inner race or roller body, on the spectrum
- estimating service lives of roller bearings
- influence of the lubricant on the vibration spectrum
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Base unit for setting up wide ranging experiments in machinery diagnostics using modular accessory sets
Learning objectives/experiments
- introduction to vibration measuring methods on rotating machinery systems
- fundamentals of measurement of shaft and bearing vibrations
- basic variables and parameters
- sensors and measuring devices
- influences of speed and shaft layout
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Supports all machinery diagnostic experiments of the PT 500 series
Learning objectives/experiments
- within the context of the experiments in the complete PT 500 series, the following learning can be covered:
- familiarisation with vibration signals
- correct application of FFT analysis
- measurement of speed, vibration displacement, vibration velocity and acceleration
- assessment of the vibration state of a machine
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Bending vibrations of elastic shaft
Learning objectives/experiments
- familiarisation with the terms “critical speed” and “resonance”
- influence of unbalanced excitation
- alignment of the elastic rotor
- influence of alignment errors
- understanding and interpreting frequency spectra
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Vibrational behaviour of a shaft with a radial crack
Learning objectives/experiments
- change in characteristic vibration behaviour (natural frequency, resonance speed, amplitude and phase of vibrations) due to a crack
- crack identification from the change in vibration spectrum
- detection of cracks in rotating shafts at the protruding shaft end
- understanding and interpreting frequency spectra
- use of a computerised vibration analyser
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Assessment of bearing condition by vibration analysis
Learning objectives/experiments
- vibrational spectrum of the running noise of roller bearings
- familiarisation with the envelope analysis
- influence of damage to outer race, inner race or roller body, on the spectrum
- estimating service lives of roller bearings
- influence of the lubricant on the vibration spectrum
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Vibration analysis of couplings
Learning objectives/experiments
- effects of alignment errors on different coupling types
- pin coupling with offset
- claw coupling with offset
- effects of production faults such as radial run-out axial run-out and pitch fault, on the running of the machine
- flange coupling with no fault
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- flange coupling with no fault
Vibrations in belt drives
Learning objectives/experiments
- influence of belt tension on vibration behaviour
- influence of speed on vibration behaviour
- influence of pulleys running untrue, and off-track running
- power split across multiple belt drive
- influence of slip on vibration running spectrum
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Vibration analysis of gearing damage
Learning objectives/experiments
- identification of gear damage from vibration behaviour
- influence of gearing type
- spur toothed
- helical
- localisation of damage
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Vibrations on crank drives
Learning objectives/experiments
- experimental modal analysis of mechanical systems
- familiarisation with the envelope analysis
- influence of bearing clearance and shock impact
- inconsistent torque characteristic
- wear measurement on piston rods
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Observation and measurement of cavitation
Learning objectives/experiments
- observing and understanding cavitation in a centrifugal pump
- visually
- stroboscopically (stroboscope available as accessory)
- by vibration analysis
- investigation of the operational vibrations of a centrifugal pump
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Identification of the vibration induced by the blades from the vibration spectrum
Learning objectives/experiments
- vibration measurement on fans
- measurement of blade pass frequency
- identification of the vibration induced by the blades from the vibration spectrum
- effect of dynamic imbalance on the fan
- understanding and interpreting frequency spectra
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Investigation of vibrational behaviour of an electric motor
Learning objectives/experiments
- influence of the gap on vibration behaviour
- influence of electromagnetic asymmetry on vibration behaviour
- influence of the load on the level of vibration
- influence of the gap on electromagnetic losses and efficiency
- influence of speed on vibration behaviour
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