Papers by Keyword: Vibration

Abstract: Aiming at a 1220 strip surface, where the Cold Rolling Mill had chatter marks, on which the reasons for the formation was tracked tested for in-depth study. Based on the vibration test, the analysis was given to the dynamic characteristics of the rack ^[1-3]. It was found that had reaction to the mill that caused the forced vibration mill to further accelerate the formation of chatter marks. In the analysis of the mechanism on the chatter marks, the relationship between chatter marks spacing and vibration source was considered in successfully finding out the cause of the 1220 mill chatter marks generated, and then the chatter marks suppression measures were proposed with satisfied effects.

Abstract: Using the geometric non-linear theory (The Total Lagrange Description) in dynamics we can establish the problem of the natural vibration of the structure including the effects of the structural and geometrical imperfections. The incremental stiffness matrix can take into account the residual stresses (structural imperfections) and the geometrical initial displacements (geometrical imperfections) as well. The behaviour of columns, frames and thin-walled structures is sensitive to imperfections. This theory and results can be used as a base for the non-destructive method for the evaluation of the level of the load and the imperfections.

Abstract: In the developed countries, waste cooking oil has proven to be a problematic material since people usually pour waste cooking oil into the kitchen drainage because they unaware that this waste can be recycled. In this study, the waste cooking oil was converted into polymer, fabricated by using hot compression machine and named as waste biopolymer (WB). WB characteristics before and after UV-irradiated such as vibration damping, density and surface morphology were analysed in this study. Total damping ratio of WB changes more than 5% after 1000 hour UV-irradiation. UV-irradiation does not give major influence to the WB morphology since there is no big change for overall structure of UV-irradiated WB after 1000 hours of UV. Even though the density of UV-irradiated WB is decreasing with increasing exposure time to UV, but it gives good influence to the damping ratio. WB is expected to have a good service life even in a harsh UV environment thus it can be applied in many applications especially in automotive field and manufacturing packaging.

Abstract: Waste cooking oil has proven to be a problematic material in the developed countries since people usually pour waste cooking oil into the kitchen drainage because they unaware that this waste can be recycled. Thus, in this study, the converted waste cooking oil into polymer was fabricated by using hot compression machine and named as waste biopolymer (WB). Vibration transmissibility test was conducted to determine the WB characteristics before and after UV-irradiated. It is revealed the similar vibration transmissibility responses curves were obtained at 1mm, 0.1g and 0.15g base excitation levels for the entire testing frequency except for the displacement transmissibility from base to moveable top plate at 1.5 mm. There was only one resonance peak occurred over the testing frequency which was 15 - 23 Hz for the displacement transmissibility and 15 – 25 Hz for the acceleration transmissibility test on shaking table. No other variation used on the displacement and acceleration amplitude to control the transmissibility test of UV-irradiated WB system based on shaking table. Evidently, small changes on the frequency of the vibration transmissibility were shifted to higher value of UV-irradiated WB with overall percentages of changes are below 5% except for displacement transmissibility at 1.5 mm. This shows the photo-stability of WB after UV-irradiation is high and could be used for further study.

Abstract: A marine steam turbine control valve is taken as the research object in this paper, the vibration response is studied under pressure pulse excitation. The transient flow field analysis is made using the method of large eddy simulation to obtain the time-domain information of the pressure pulsation. Then, the analysis of vibration based on coupled modes, research vibration response and resonance problems of the control valve. The study found that the vibration of control valve is strongly in low frequency excitation, but high-frequency excitation makes relatively little impacts on it; The diffuser and downstream of valve is the main area of generating vibration.

Abstract: To highlight the main factors, only the crowding shaft was taken as elastic component, while the other crowding system parts, such as girth, driving shaft and swing arm were taken as rigid components; the effects of damping were ignored; the dynamical model of excavator’s crowding system was simplified to a two degree of freedom model; mathematical and mechanical models were derived by Lagrange equation method; the locked rotor condition, when the bucket rod was perpendicular to the boom, was used as the calculation condition; the calculated dynamic load coefficient of the crowding system was compared with that in multi degree of freedom model and the result shows: to simplify calculation, it is practicable to replace multi degree of freedom models with two degree of freedom models in the preliminary design stage.

Abstract: Based on UG and Automatic Dynamic Analysis of Mechanical System (ADAMS), the 3D model of differential was constructed and the real-time dynamic simulation of differential was achieved. The effects of gear backlash between half axle gears and planetary gears on the vibration of differential are studied. To increase the credibility of simulation results , the contact forces between half axle gears and planetary gears were calculated based on the Hertz elasticity impact theory.

Abstract: To obtain the concise relationship between the dynamic load and its influence factors, the single degree-of-freedom system was applied to simplify the crane working mechanism. Based on the sloping load, this paper analysed the main influence factors on the dynamic load and two relations were obtained:the relation between the dynamic load coefficient and the loading time;the other between the dynamic load coefficient and the natural vibration period. Due to the previous calculation and analysis, the suitable loading time and the dynamic load coefficient within the engineering permissible range were also obtained. The stiffness formula based on the loading time of the system’s elastic component was originally put forward. The result provided not only reliable basis to obtain the geometric parameter of the elastic component, but also feasible measures to prevent the dynamic load from increasing. Hence, it is effective to ensure the stable running of the equipment.

Abstract: A crankshaft is the most critical component, and it can dominate the life of the engine. Nowadays an orbital grinding is widely used to grind a crankshaft. In this study, static analysis is done to find deformation of an orbital grinding system due to weight, modal analysis is done to obtain the natural frequencies, and harmonic analysis is done to investigate the compliance. It is found that all the results show that first frequencies are found to be near 70-80Hz. The machine will be weak to vibration near 70-80Hz. It is also found that the peak value of x compliance is smaller than that for other axes, and grinding in the x direction will be more stable than grinding in other direction.

Abstract: The objective of this study is to develop a process of treatment of the vibratory signals generated during a horizontal high speed milling process without applying any coolant in order to establish a monitoring system able to improve the machining performance. Thus, many tests were carried out on the horizontal high speed centre (PCI Météor 10), in given cutting conditions, by using a milling cutter with only one insert and measured its frontal wear from its new state that is considered as a reference state until a worn state that is considered as unsuitable for the tool to be used. The results obtained show that the first harmonic follow well the evolution of frontal wear, on another hand a wavelet transform is used for signal processing and is found to be useful for observing the evolution of the wavelet approximations through the cutting tool life. The power and the root mean square (RMS) values of the wavelet transformed signal gave the best results and can be used for tool wear estimation. All this features can constitute the suitable indicators for an effective detection of tool wear and then used for the input parameters of an on-line monitoring system. Nevertheless we noted the remarkable influence of the machining cycle on the quality of measurements by the introduction of a bias on the signal; this phenomenon appears in particular in horizontal milling and in the majority of studies is ignored