Preliminary study on the measurement of maximum fi

2022-07-27
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Preliminary study on vibration aging and thermal time effect stress test

after solidification, the casting will produce residual stress in the cooling process. The residual stress has a great impact on the quality of the casting. Especially for the workpiece under alternating load, when the direction of the load is consistent with the direction of the residual stress, the sum of the internal and external stresses may exceed the strength limit of the material, and in serious cases, the casting will break locally or as a whole; The castings with residual stress often deform or reduce the accuracy of parts after machining. Therefore, it is necessary to eliminate or reduce the residual stress in the casting

the traditional aging method is thermal aging, which consumes a lot of energy and costs a lot; Serious environmental pollution; Long production cycle, difficult to match furnace; More importantly, the uniformity of furnace temperature is poor, the speed of temperature rise and drop is not easy to control, and it is easy to produce secondary residual stress, micro cracks, and even scrap castings

vibration aging can eliminate 20% ~ 80% of the internal residual stress of castings, and 50% ~ 80% of the internal residual stress of castings can be eliminated by thermal efficiency. The energy consumption of vibration aging is only 5% of that of thermal aging

in order to create higher economic benefits for the enterprise after the experiment, the factory adopts the new technology of vibration aging, and first selects the cast iron z01.1.18 base (material HT 200, unit weight 900kg, maximum wall thickness 50mm, minimum wall thickness 20mm). The aging results were measured by X-ray diffraction

1 determination of aging process scheme 1.1 thermal aging process scheme

thermal aging refers to the temperature range in which the casting is heated to the plastic state. At this temperature, it is held for a certain time to eliminate the stress, and then cooled slowly. The thermal aging process of the base is shown in Figure 1. 1.2 vibration aging process scheme

(1) the selection of support points, the determination of excitation points and the placement position of sensors are shown in Figure 2. Fig. 1 heat aging process of frame Fig. 2 process parameters of frame (2) are shown in Table 1. Table 1 process parameter gear main vibration frequency excitation time vo/vio/avt/vit/a34820r/min301293.51262.8

(3) the characteristic curve is shown in Figure 3. 2 Determination of aging results 2.1 test equipment

the test equipment is an X-ray stress measuring instrument, as shown in Figure 4. Fig. 3 characteristic curve Fig. 4 X-ray stress measuring instrument 2.2 stress test

according to the structure of the base, the residual stress at point a (see Fig. 2) is large, which is a crack prone part. Therefore, the stress at point a is measured before and after vibration aging, before and after thermal aging, and the test data are shown in Table 2. Table 2 test data pre cast aging

(MPA) post aging

(MPA) elimination

(%) average

(%) thermal aging 3393

339414.8

13.77.0

5.453

6157 vibration aging 3395

339615.7

15.48.1

9.048

424 45 note: this test result is the analysis of 2.3 test results completed in april1993

according to the test data in Table 2, the thermal efficiency eliminates 51% of the residual stress at point a of the base, Vibratory stress relief can eliminate 45% of the residual stress, and the result is ideal, which is also in line with the information

3 the stress test results of other cast iron castings, in addition to the stress test of the base, are also tested by the same method for castings such as feedback process workbench and drawing that emphasize organizing economic activities into a "resource 1 product 1 renewable resource" in the industrial circular economy model, and the results are also consistent with the expectations (see Table 3). Table 3 name of test results before aging

(MPA) after aging

(MPA) elimination (%) thermal aging workbench

drawing 23

107

570

50 vibratory aging workbench

drawing 21

138

662

54

4 economic benefit analysis through statistics, the comparison of energy consumption and cost between thermal aging and vibratory aging is shown in Table 4. Table 4 thermal aging, vibration aging and cost comparison energy consumption (yuan/t) cost (yuan/t) thermal aging 21.14119.20 vibration aging 0.762.00

from table 4, vibration 3. The equipment uses X-ray aging to save energy (21..67) ÷ 21.14 compared with thermal aging × 100%=96.8%, cost reduction (119.20- at this time, 1 helmet should be placed on the head mold for isolation 2.00) ÷ 119.20 × 100%=98%。 From this point of view, compared with thermal aging, the new vibration aging technology has very significant economic benefits

5 conclusion by measuring the residual stress of iron castings before and after thermal aging and vibration aging by X-ray diffraction, it shows that thermal aging can eliminate 50% ~ 70% of the residual stress, vibration aging can eliminate 42% ~ 62% of the residual stress, vibration aging can save 96.8% energy and reduce the cost by 98%. Vibratory stress relief is a new technology which can be widely used

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