Papers by Keyword: Dynamic Load Coefficient

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 the idea of system theory and highlighting the main aspects of the contradiction, the working device of mechanical excavator is simplified to fewer degrees of freedom dynamic model by analysis, and the main structures of influencing dynamic factors and wire rope are regarded as elastic bodies, other structures as rigid bodies; Starting from the theoretical dynamic characteristic curve of excavator, utilizing typical working conditions as calculation conditions, using Lagrange equation as a method to solve the dynamic integrated constraint system, we can establish the dynamic equations of working device and get the maximum dynamic load and dynamic load coefficient, and provide a reliable basis for selection of the dynamic parameter and calculation of structure strength.

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: This study aims to predict the Dynamic Load Coefficient (DLC) of tyre forces from truck axles. Dynamic Load Coefficient is frequently used to characterise the dynamic loads generated by axles. It is a simple measurement of the dynamic variation magnitude of the axle load, for a specific combination of road roughness and speed. Under normal operating conditions, the DLCs value is typically in the range of 0.05-0.3, and close to zero when the trucks wheels are moving over a perfectly smooth road. To achieve the objectives of this study, which is to determine the DLCs value for seven different types of axles, a simple validated quarter-truck model was excited by a random road surface profile, in order to simulate a vehicle-road interaction. Points are equally spaced along the simulated road to generate dynamic loadings over a broad range of truck speeds. Multiple trucks gross-weight conditions were used to present realistic traffic behaviour. The results showed that irregular road profiles, exciting the vehicle as it travelled, caused continually changing tyre forces. Also, dynamic loading was seen to be fundamentally influenced by the type of suspension (i.e., air and steel), loading condition, and vehicle speed. For example, the DLC value of the tyre forces of the quarter-truck fitted with a steel suspension was found to be more than twice that of the truck fitted with an air suspension. Tyre forces of the one-third laden truck were more aggressive than any other loading condition, due to the uncertain body-bounce generated by the truck, which was strongly dependent on surface irregularities. At low speed, the DLC was greatly decreased if the load was increased. Furthermore, DLC value was always lower for trucks with air suspension over steel suspension, for the same load and vehicle speed. However, air suspension efficiency was clearly better for higher axle loads.

Abstract: Previous research revealed that influence function is strongly influenced the appropriateness of pavement damage prediction and are demanding to be concern in order for better prediction of long term pavement performance. In order to identify the impact of traffic loading condition on the influence function of the pavement toward failure, further stucdy was done to determine the exponential value in the Damage Equivalent Law for varies loading condition and also vehicle speeds. To achieve the aims, the simple quarter truck model was efficiently used with personal computers to predict pavement loading. Towards reality of traffic loading condition will contain a distribution of axles load between unladen and fully laden, the study was further taking into account realistic axle load variation. Results are presented from a study to evaluate the relative influence of truck speed and axle load variation on the stiffness of the asphaltic layer and thus the primary response of the pavement. In conclusion, the exponential value in the Equivalent Damage Law is clearly sensitive to both factor.

Abstract: It applies flight dynamics and vibration principle to create vibration model of aircraft landing gear considering aircraft tire damping, and get the equation of analytical solution based on the impact on airfield pavement roughness. It studies the relationship between dynamic load coefficient and time and speed and roughness. For a special aircraft, it gives the allowable level for pavement roughness based on the influence of pavement and passengers comfort.

Abstract: Stess spectrum serves as prerequisite of analysis on fatigue failure, which is the major cause of malignant industrial accident. The dynamic load coefficient is calculated by allowing for dynamic response of steel structure in complete working cycle and regard steel structure and load as a vibraton system of two degrees of freedom. The load date and its statistical characteristic is collected.through observation of 600t-176m gantry crane in some ship-building base. Then based on Monte Carlo method, the load is simulated and loaded on finite element model. Finally the stress spectrum of key parts of structure is calculated.