Research On The Strength And Stiffness Of The Carbody Of The 12m～3 Electric Shovel

Excavator is necessary producing equipment for lots of strip mine, and it is the most excavating equipment of engineering machine which is broadly used in metallurgy, energy sources, mine etc. It has the characteristic of enduring strike, enduring fatigue and big power. Due to work outside frequently, working environment is very bad.Bottom frame is excavator's leading parts enduring force, whose performance can directly influence excavator's working performance. Its analysis take up all important position. The excavator design often use sample as reference before, which not only has large charge and long cycle, but also can't make change for the project timely. Lately, as development of electronic computer technology, finite element and CAD technology, the research and analysis for the bottom frame also acquire development.So far, finite element is the most economic and effective assistant means, which includes finite element assistant design and finite element assistant analysis. It can greatly reduce resource, shorten working cycle, furthermore, can ensure upper veracity. So importing finite element in the process of excavator design and manufacture is significtive.12m3 excavator is designed by a mechanism factory. The text analyses bottom frame structure analysis and model analysis.Firstly, we analyze and research the whole structure of the excavator. We found three dimension model on base of two engineering drawing. When we assemble the whole vehicle with Pro/ENGINEER software, we must build the assembly center on the rotating center, measure the distance between center of mass of other parts and rotating center in assembly model. In order to calculate the effect of overturning moment and build the Chassis model of 3D finite element model.Secondly establishment of the chassis model mechanical excavator. The bottom frame of excavator is axes symmetry structure toward Y axes symmetry. The stress on the chassis include the deadweight of bottom frame, the vertical force( including upside rotating platform weight ,act arm weight ,the weight of the dipper handle, match weight and so on ), the vertical force toward X axes, Y axes distributed along rotating circle, the overturning moment(it is caused by resistance of digging, soil weight of digging ,weight of act arm ,match weight). Build a finite element model based on the mechanical model of the excavator chassis, a suitable unit type must be chosen. Because the chassis structure is a plate welded structure, SHELL63 is chosen. According to different work condition define the constraints and the work load.Excavators working conditions is more complex. In the walking conditions, the main force on the excavator chassis is caused by gravity of various devices. Relative to Mining conditions is more safe so this paper don't considerate the walking condition. When the excavator dipper is on the most height and full of soil, the stress don't apply on the tooth. Through preliminary calculations, the chassis by a relatively small vertical force and overturning moment, therefore, when calculating the analysis does not consider this condition.Impacting the largest mining power on the excavator dipper is important for chassis structure. This condition may be the biggest stress condition. Choose the relative risk conditions when analyze the structure of the chassis. Excavators work cycle: mining-raising, rotating-unloading-empty, return. In the operating cycle, rotating angle decided by the location of the work place and unloading place. Generally between 90 degree and 180 degree. Shovel parallel to the track mining, shovel dipper perpendicular to the track mining and on the diagonal mining. Dipper Tooth achieves the height of the shipper shaft, speed is zero, the force of hoist cable maintains a fixed value. Dipper handle don't extend all the length. Choose the admission limit condition, dipper handle extend about two-thirds of the total length.Choose three mining conditions,in the first condition the digger parallel to the track(vertical excavation), empty dipper Tooth achieve the height of the shipper shaft, the largest mining force impact on the digger.; In the second condition the digger perpendicular to the track empty dipper Tooth achieve the height of the shipper shaft, the largest mining force impact on the digger; In the third condition the digger is on the diagonal. Empty dipper achieves the height of the shipper shaft, the largest mining force impact on the digger. This paper also process mode analysis under restriction state.The calculation result accord with experience value well, which is recognized by machine factory of the mechanical factory. Real machine experimentation will be actualized. So the model established in this paper is right, and the calculation based on finite element is actual. Improving scheme is brought forward for the result which has serious stress centralization in some place. It has good maneuverability and better effect, because stress value decrease clearly after finite element calculation.