73.2 Analysis of excavator failures and countermeasures Xin Zhenwu Xin Zhentao Foreword, 2 Excavators are 7, equipment imported from the Czech Republic, with a bucket capacity of 3, and a weight of 0 tons. Because this type of excavator has a simple operation. , Easy maintenance, less power consumption, heavy loading and weight ratio, etc., are still widely used in open-pit mines. Two 3,2 excavators were deployed in the mine of our group, which is a mine excavation machine. In the course of use, there have been sub-rotary vertical axis fractures. The time interval is according to the calendar time, which is the six-year mine series 3. and the annual mine series 4 whose fractures are typical of torsional fatigue damage. One of the root axis is to add some parts in the domestic processing. Therefore, it is necessary to analyze the fatigue damage of the rotating vertical shaft in order to take corresponding technical measures to improve and extend its service life.
Rotary Vertical Fatigue Failure Analysis 1 Alternating Stress Analysis Rotary motor transmits the torque to the rotary vertical shaft via a rotary speed reducer. The small cylindrical gear at the lower end of the vertical shaft engages with the rotating large gear fixed on the chassis to rotate the rotary platform. After the excavator scoops, it begins to rotate. The upper brake of the motor brakes and stops at the top of the car. After discharging, it returns to the scraper position. During this work cycle, the vertical shaft is subjected to a stress state that is roughly equal to the time from start to average speed and rotation. Because the rotating platform is in an accelerated rotation state, the vertical shaft stress gradually increases from zero, and then becomes smaller and smaller. When the power supply is cut off and the platform is in the inertial rotation state, the stress is almost zero. In the braking phase, the platform moves from inertial motion into slow-rotation motion. Therefore, the absolute value of the stress gradually increases from zero and reaches a maximum, then gradually decreases. When the slewing platform stops, the stress becomes military. The vertical axis is opposite to the direction of torque applied during the start and stop phases. And measured in seconds found that the time required for start-up phase and stop phase is almost the same. Therefore, it can be considered that the vertical shaft is subjected to symmetrical stress change during the entire process of starting and stopping. That is, the maximum torque of the vertical axis is calculated by the cycle 2 maximum stress.
Phase winding AC motor rated power for the number of revolutions 96, transfer points. Check from domestic data. Its maximum starting torque is 2.53.5 times the rated torque. This article takes 3 times.
The speed reduction ratio of the slewing speed reducer is 1=28.8, and its efficiency is 95. The maximum torque applied to the vertical shaft is the nominal shaft diameter of the vertical shaft bearing installation place at the vertical shaft, 160 mm. From the assembly process, the nominal diameter of the middle section of the vertical shaft is 59. Mm. The secondary fractures of the vertical shaft of this type of excavator occurred at the transition between 16 and 159.
The maximum torsional shear stress at 159 section 1 is determined by the strength limit 1 of the following steel. = 6, According to the relevant data, there are the following relationships. The values ​​in parentheses in the formula are taken. However, according to the formula, the lasting fatigue limit of the material specimen is obtained. For parts, consideration should also be given to: Focus on the source dimension surface quality. Heat treatment and other factors. According to the relevant data, the following relational size influence coefficients are the surface mass influence coefficients; the ruler is the effective stress concentration factor. Because there is no thermal burial and no consideration for strengthening coefficient, based on the actual measured vertical axis data and relevant data, various coefficients take the following values ​​K, = 1.48; on behalf of the people from the steel, 7 is the number of cycles It can be seen that fatigue failure does not occur after reaching a certain value. The value corresponding to the team point is the persistent fatigue limit.
According to the relevant data, at that time, that is, limited life fatigue limit time, there are the following Ai system type, which is the number of cycles, the time limit of fatigue; 1 for the permanent fatigue limit; the team for the cycle base; 1 cycle characteristics. For the torsional shear stress, the above formula is still established = there is a large section of steel, take 9 = 107, and take, = team. From the above formula, this result is explained. The rotating vertical shaft was subjected to 1.97,106 cycles of stress transformation. Fatigue damage will occur.
The calculation of the accuracy of the above calculation is performed by determining the operating time of the fatigue failure of the rotating vertical shaft to compare with the calendar time of the actually occurring fatigue failure.
From the analysis of excavator operation statistics, the average operating rate of the two mine excavators is 13.2. According to the relevant information 3, the bucket capacity is the daily average output of the excavator used in the 3 octave excavator factory mine, which is mentioned above. When the excavator completes a working cycle, two alternating stresses are generated. Therefore, the number of alternating stress generated per day is the number of years of fatigue failure of the relevant data because the average operating rate of the excavator is 13.2 which is the twisted circulation channel. In the resource-poor Shantou Special Economic Zone, how to strengthen supervision over bulk cement flow channels and use areas, and resist the entry of poor quality cement unlicensed cement from outside into construction sites to ensure the quality of construction projects is a top priority. Since the city started bulk cement work in 1993, after several years of hard work, it has gradually explored effective methods of supervision and regulation, standardized the management of bulk cement market, and laid a good foundation for the healthy and steady development of bulk cement in the city.
Shantou Special Economic Zone is located on the southeast coast. There is a shortage of raw materials for cement. About 8 or so cements need to be transferred from outside each year. Because the distribution channels of cement varieties are more complicated, counterfeit and inferior cements hit the market from time to time, and they just started to publicize and promote the use of bulk cement. Bring a certain degree of difficulty. Many construction companies believe that bulk cement is not labeled, it is prone to adulteration, and it is short of two. There are misunderstandings and biases in bulk cement, which has led to consciously or unconsciously resisting the use of bulk cement. In response to these questions, we focus on the quality of bulk cement, in-depth construction and construction sites, as well as on-site inspections of bulk cement quality by bulk production and distribution companies, and guidance on the management of production, supply and sales; The society's cement awareness, extensively listened to the urgency of the construction of the theme, understand the use of bulk cement, and the results of random sampling of bulk cement to the public. Through the implementation of various forms of publicity activities, as well as the habit of frequently disregarding the quality of bulk cement and the habit of using bagged cement, the active surnames using bulk cement were mobilized. After many users tasted the sweetness of using bulk cement, they instructed Sifu to fill the water. The use of corpses was changed to the fact that I would like to use the tactics of the 纟2 å¡ å¡ community and the use of the city to increase the use of the unit. In order to effectively strengthen the management of bulk cement distribution channels, standardize the market order of the guideway, maintain the quality of bulk cement, and smash the year of January, the export of Shantou City's bulk cement transit enterprise management provisional law measures have strengthened the distribution channels. The supervisory power in the field of use and use is strictly controlled by the quality assurance measures and after-sales service of the main business of the industry, such as the management and transportation of equipment and equipment for the transfer of cement towels to the business. The bulk cement service service is to implement the annual review system for bulk cement brands, and welcomes the reputable quality products to enter the Shantou market; Xiu strengthens the random inspection of bulk cement quality, and informs the random bulk quality of the unqualified bulk mud brands and prohibits them from continuing. Sell ​​in the market. Blocking the bulk cement from the source into the construction site. Ensure the history of the project; it is to strengthen the statistical work of bulk cement, formulate a series of statistical reporting system, and require the manufacturer to transfer this and use the unit. According to the monthly report, the number of bulk cement brands entering the urban area in a timely manner, as well as the sales use and storage conditions, effectively prevented the approved bulk cement from entering the market or being misled in the circulation process. Phenomenon, but also to prevent the opening of bulk cement checks to withdraw special funds, with this approach to local regulations, so that the city's management in the field of bulk cement circulation in the fast lane in accordance with the law in the past few years, we follow , Fortunately, the provisions of the regulations to manage, according to the administration, improve the quality of bulk cement quality measurement, eliminating the user and the quality of the project after the worry; At the same time increased the bulk cement sales outlets, and expand the sales channels, 4 vast The use of surface, actual proof, only to strengthen the management of the distribution channels, can make the city's bulk cement business healthy and orderly development.
According to the statistics of the calendar time of the year, the result of the application of 365 human-sides is used in the above formula, and the fatigue failure period from the theoretical calculation is 7.4 years.
It is important to point out that, in 1 juice calculation, excavator stack flats and other operations, calendar time to produce fatigue damage should also shorten the improvement measures from the structure and processing technology, can be used as a factory improvement will produce fatigue damage , 159 and a reasonable smooth transition, with tolerance control rule 10, to meet the assembly requirements can reduce stress concentration effects. The surface of the original paragraph 159 belongs to a roughing vehicle. During the processing, the surface finish is improved, such as finisher, so that the surface quality will be reduced. From the current analysis, these two points are feasible and effective. According to the above method, the number of cycles will be greater than the base of the cycle. This means that if no other human factors exist, the vertical shaft will not be fatigued throughout the life cycle of the excavator. From the aspect of operation, we must strive to protect the vertical shaft from the impact of the author's unit, Mudanjiang Cement Group.
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