Tumble mills are hollow cylindrical shells of large diameter carrying grinding media (a combination of rock/iron ore/chemical flakes and metal balls/rods), which, upon rotation of the mill, will be ground into fine powder. These mills rotate at low speeds using a gear reduction unit and often have vibration problems. These vibration problems result in increased gear wear and occasional catastrophic failures resulting in production loss. The objective of this research is to investigate the effect of oscillation of grinding media on torsional vibrations of the mill. A theoretical model was developed to determine the oscillating frequency of the grinding media. A 12" (0.3 m) diameter tumble mill test rig was built with a 0.5 hp DC motor. The rig is tested with sand and iron bb balls to simulate the industry process application. At low volume levels the grinding media oscillates like a rigid body as compared to higher volumes. It is shown that tumbling action of grinding media causes torsional excitation and hence its effect has to be considered in torsional vibration analysis. At starting, the load on the gears is much higher due to this oscillation.

Tumble mills are hollow cylindrical shells of large diameter carrying grinding media (a combination of rock/iron ore/chemical flakes and metal balls/rods), which, upon rotation of the mill, will be ground into fine powder. These mills rotate at low speeds using a gear reduction unit and often have vibration problems. These vibration problems result in increased gear wear and occasional catastrophic failures resulting in production loss. The objective of this research is to investigate the effect of oscillation of grinding media on torsional vibrations of the mill. A theoretical model was developed to determine the oscillating frequency of the grinding media. A 12" (0.3 m) diameter tumble mill test rig was built with a 0.5 hp DC motor. The rig is tested with sand and iron bb balls to simulate the industry process application. At low volume levels the grinding media oscillates like a rigid body as compared to higher volumes. It is shown that tumbling action of grinding media causes torsional excitation and hence its effect has to be considered in torsional vibration analysis. At starting, the load on the gears is much higher due to this oscillation.

Thesis deals with the calculation of the crankshaft of the cogeneration unit. It deals with the calculation of equity and forced vibration of the crankshaft. Attention is also paid to the influence of elastic couplings on the shape of its own vibration shaft.

The aim of the thesis is to derive a mathematical model of the engine and driveline in a passenger car, capable of describing the wheel speed disturbances related to the engine and driveline. The thesis is conducted in order to improve the disturbance cancelation algorithm in the indirect tire pressure monitoring system, TPI developed by NIRA Dynamics AB. The model consists of two parts, the model of the engine and the model of the driveline. The engine model uses an analytical cylinder pressure model capable of describing petrol and diesel engines. The model is a function of the crank angle, manifold pressure, manifold temperature and spark timing. The output is the pressure in the cylinder. This pressure is then used to calculate the torque generated on the crankshaft when the pressure acts on the piston. This torque is then applied in the driveline model. Both a two wheel and a four wheel driveline model are presented and they consist of a series of masses and dampers connected to each other with stiff springs. The result is a 14 and 19 degrees of freedom system of differential equations respectively. The model is then validated using measurements collected at LiU during two experiments. Measurements where conducted of the cylinder pressure of a four cylinder petrol engine and on the wheel speed of two different cars when driven in a test rig. The validation against this data is satisfactory and the simulations and measurements show good correlation. The model is then finally used to examine wheels speed disturbance phenomenon discovered in the huge database of test drives available at NIRA Dynamics AB. The effects of the drivelines natural frequencies are investigated and so is the difference between the disturbances on the wheel speed for a petrol and diesel engine. The main reasons for the different disturbance levels on the front and rear wheels in a four wheel drive are also discussed.

The diploma thesis ‚Rubber Torsional Vibration Damper Of a Four-Cylinder Diesel Engine‘ covers all the development phases related to a design of a rubber damper for a specified engine. The individual phases of it are discussed in details throughout the thesis. At first, the construction plan of a crankshaft is given. The computational checks for torsional vibrations and forced torsional vibration are performed then. With regards to it there might be derived the basic parameters and dimensions of a rubber torsional vibration damper. The knowledge of them enables to prepare the constructional plan of a rubber torsional vibration damper. By using this damper construction plan the torsional displacements (deviations) and forced vibrations are calculated. Finally, a mechanical and thermal stress test of this damper is performed and a crankshaft production drawing is produced.

Content of this master thesis is analysis of torsional vibration of the three cylinder engine with balancing shaft. In theoretical part of the thesis the kinematic and dynamic description of the cranktrain mechanism is included. The formation of unbalancing of the engine and methods of balancing are described in the theoretical part as well. In practical part of the thesis the analytical calculation of torsional vibration is provided. Simulation of the engine model in multibody software Adams/Engine was used as the other way of torsional vibration analysis. In the result part of the thesis the comparison of the both way of analysis were discussed. Last step of the thesis was design proposal of the torsional vibration damper done by the analytical calculation.

Drill String dynamic behaviour during the oil drilling operation, was a major source for the failure of the Bottom Hole Assembly (BHA). The behaviour produced torsional vibration, which underpins the stick slip phenomena. Besides threatening the safety of the oil drilling process, such failure cause interruptions in the drilling operations and incurred high maintenance cost to the oil drilling company. This issue can be resolved with the implementation of the optimum control mechanism while operating the drill string. In this research, an optimum control mechanism was proposed to suppress the torsional vibration as well as mitigate the risk of stick slip phenomenon from occurring. The mechanism was proposed through a series of rigorous research strategies i.e. updated-mathematical equation modelling, experimentation and simulation. As the first step, a mathematical equation model describing system dynamics was derived to set the parameter of investigation. Representing the freedom torsional of the two degrees - conventional vertical drill string, the model was used to predict the frictional Torque On Bit (TOB) through non-linear friction force, denoting the ground-formation behaviour during drilling activity. Using a velocity feedback system, the drill-string oscillation was reduced while gradually increasing its velocity via gain scheduling method - allowing fast response to load disturbance. To avoid the motor torque from exceeding the maximum threshold, a Weight On Bit (WOB) was introduced. This approach remarks the novel contribution of this research. Next, an experiment on the preliminary test rig within a controlled laboratory set up was conducted. The rotary drill rig was assembled to identify the dynamics (i.e. parameters) of an individual part of the drill string. The results obtained were then applied in the drill string operation experiment, to identify the optimum control mechanism that can avoid the torsional vibration. To enable triangulation of results, a simulation was conducted by applying the same parameters obtained from the test rig experiment in the model- which is the optimum control mechanism that was proposed in this research to minimise torsional vibration, as well as reducing the chance of drill-string failure due to stick-slip phenomenon.

The aim of this work is to evaluate ride quality of a typical passenger car. This requires both identifying the excitation resources, which result to undesired noise inside the vehicle, and studying human reaction t applied vibration. Driveline linear torsional vibration will be modelled by a 14-degress of freedom system while engine cylinder pressure torques are considered as an input force for the structure. The results show good agreement with the corresponding reference output responses which proves the accuracy of the numerical approach fourth order Runge-kutta. An eighteen-degree of freedom model is then used to investigate coupled motion of driveline and the tire/suspension assembly in order to attain vehicle body longitudinal acceleration subject to engine excitations. Road surface irregularities is simulated as a stationary random process and further vertical acceleration of the vehicle body will be obtained by considering the well-known quarter-car model including suspension/tire mechanisms and road input force. Finally, ISO diagrams are utilized to compare RMS vertical and lateral accelerations of the car body with the fatigue-decreased proficiency boundaries and to determine harmful frequency regions. According to the results, passive suspension system is not functional enough since its behaviour depends on frequency content of the input and it provides good isolation only when the car is subjected to a high frequency excitation. Although longitudinal RMS acceleration of the vehicle body due to engine force is not too significant, driveline torsional vibration itself has to be studied in order to avoid any dangerous damages for each component by recognizing resonance frequencies of the system. The report will come to an end by explaining different issues which are not investigated in this thesis and may be considered as future works.

Master 's thesis deals with design of a drivetrain of six cylinder inline engine with cylinder deactivation for heavy agricultural vehicles. In this thesis were devised various possibilities of crankshaft balancing, the best design solution of counterweight was based on optimization in software Catia. Further, the crankshaft was analysed for force and momentum loading and torsional vibration, based on which, the torsional vibration damper was designed. There were considered several options for cylinder deactivation, which were analysed for finest run of engine and the best thermal distribution. Based on these criteria, the best option was to deactivate 2nd and 5th cylinder. The crankshaft was analysed for the fatigue failure by finite element method. The fatigue failure is the most dangerous case for the crankshaft, the resulting safety factor for this limit state is 3,05.

This diploma thesis is called „Rubber damper of a six-cylinder in-line diesel engine“. It consists of brief introduction to crankshaft torsion and dampers, basic analysis of crank vibrations including crank natural frequencies calculation and analytic verification of torsional vibration stress. It contains also a concept of rubber damper and verification of crankshaft with mounted damper.