1,721,021 research outputs found
Stress variability in multilayer composite hydraulic cylinder
No full textThe focus of this research is to evaluate the variability of the stress state in hydraulic cylinder, due to the deviation respect to the nominal values for both the geometrical and the material properties. The element is composed by a multilayer in which the inner layer is made by means of a thin tubular aluminum part, while the coating is made of composite material. The analytical work developed is based on the theory of axial symmetric elements and finds its application in a real hydraulic cylinder made for heavy duty i.e. for an earth moving machine (internal pressure 350 bar). The research is also developed by considering and comparing the results obtained by designing a component made of a single aluminum layer. From the results, it is clear that the multilayer solution has a variability, much higher than the component made by a single layer. This result, therefore, requires at least a complete revision of the safety coefficient evaluated and imposed by standards
Feasibility study of hydraulic cylinder subject to high pressure made of aluminum alloy and composite material
No full textReliability evaluation of critical local buckling load on the thin walled cylindrical shell made of composite material
No full textThe goal of this research is to evaluate the variability of the buckling load in thin orthotropic cylindrical shells due to the deviation with respect to the nominal values, for both the geometrical and material properties. In this research also the fiber orientation i.e the alignment with respect to the cylinder axis was considered. The research is developed by comparing the results obtained through analytical formulas and numerical results (f.e.m.) for isotropic and orthotropic materials. The coefficient of variation for critical buckling load (for symmetrical and non-symmetrical deformation), assumed for comparing the standard deviation values, is linear with the variation of material and geometrical parameters. The standard deviation on critical buckling load considering both the material and geometrical variations and fiber orientation can be very well described by a surface. From these surfaces it is important to underline that to quantify the dispersion values on the critical buckling load, the material properties assume the fundamental role with respect to the fiber orientation. The main implications of these results are correlated to the fact that, for example, during the manufacturing process, the geometrical and material variability is more important than the fiber orientation in order to have a reliability component
EARTHQUAKE EFFECTS ON LOW PROFILE CONTAINER CRANE WITH SEISMIC ISOLATION DEVICE
No full textThe focus of this research is to evaluate and compare the mechanical behaviour of a big ship to shore low profile container crane subjected to earthquake actions, with and without anti-seismic device applied to it. For this purpose, a specific machine was designed considering different load and geometrical configurations. Subsequently, the earthquake actions were studied. The different acceleration spectrums were established by Italian standards. The anti -seismic device was chosen to limit the crane displacement to not compromise the crane performance due, for example, to the increase of the payload swinging effect. The numerical results show that, for each load and geometrical configurations assumed, the anti-seismic device has a positive effect, it reduces the maximum stress values (about 20%). The dynamical crane behaviour is practically unchanged with the isolation device adopted, it was observed a small reduction of the natural frequencies values and a little increase of the magnitude of the maximum displacement. These results are valid also in case of dynamic action applied to the crane due, for example, to the trolley and payload movement
Experimental and analytical study of random fatigue, in time and frequencies domain, on an industrial wheel
No full textIndustrial wheels are components subject to fatigue under a high number of stress cycles, depending on the type of vehicle they are installed to. The reliability of these components is strictly dependent on the accuracy of the fatigue validation method adopted. A common practice in the industry is to test loads under constant amplitude in laboratory through fatigue and test parameters according to the standards used in the industry. The object of this research is to compare the results in terms of damage and the number of failure cycles, adopting both the time domain and frequency domain approach on a real industrial component. Different theories were developed and applied to the real case of study of an industrial wheel, under specific load cases. Eventually, we applied different criteria to the numerical analysis. The added value of this study is the application of the fatigue criteria on a real industrial component, in order to check the reliability of the criteria. Eventually, we determined that the results show that, for these specific experimental load conditions, frequency-domain methods are a bit more conservative than time-domain methods
Feasibility study of a very big crawler crane using composite materials
No full textThe main goal of this research is to design a very big crawler crane adopting composite material to lightweight the machine itself and compare its performance with the one made of classical structural steel. The research starts by sizing the main boom, assuming three different materials: steel, aluminium alloy and composite material. Many load conditions were involved and different criteria were assumed; there are stress safety factors, stiffness, dynamic performance (modal) and buckling phenomenon which is a very important parameter. Then other innovative load conditions were applied to the crane boom: moving load and time-varying wind speed to study the mechanical behaviour of the new solutions. The last step involves the design of additional elements: counter boom, counterweight, ropes, etc., and evaluating the final weight of the entire machine designed with innovative materials. In particular, the weight of the machine in steel configuration is about 5715 kN while this value reduces to 4670 kN and 3830 kN respectively for aluminum and composite material configurations. In other words, for the composite material solution, the final weight is about 67 % of the same machine built with steel, this value decreases to 34 % if only the main boom is evaluated
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