毕业设计小论文翻译部分含封面(恒应利压力机设计)
(学号):
学校
毕 业 设 计(论 文)译文
恒应力压力机设定
姓 名
学 院 专 业 班 级 指导教师
2012 年 4
月 5 号
Cement constant stress press set
ABSTRACT
This paper introduces a kind of testing machine using electro-hydraulic servo control system, control precision, high frequency ring ac servo motor, drive the precision the ball screw vice test, can realize the test range of speed regulation, test process stable and efficient. The liquid crystal display controller, independent completed in the testing of experimental parameters set, test process control, data acquisition, processing, analysis and display; Can realize single test, also can undertake group trial; Control and measurement precision, accurate and fast, convenient and reliable. According to user requirements external microcomputer, the test data are statistics and processing, and then output print various requirements of the test curve and test report, may realize the storage, print networking, intelligent and flexible. After testing has to return to the initial position of the function, high efficient and fast. Has the work of the position limit protection function and overload, over current protection function, reliable, safe.
This tester is mainly used in cement grinding the compressive strength test. Configuration suitable test affix, can complete tiles, metal products, components and other material performance test. Widely used in building material industry, is the building materials industry and technology supervision, inspection arbitration, scientific research institutions department ideal test equipment.
Keywords: Electro-hydraulic servo control liquid crystal display and control external microcomputer limit overload over current protection
One.Pressure test machine speed control
Cement strength test method for GB/T 17671-1999 pressure test of the cement, cement specimens of test requirements with lotus in the provision of compression speed on the area, with 2 400 N/s speed increase until the moment of destruction. The test process, in specimens of unit time increase stress should be the same, namely 400 ÷ 2 (40 x 40) = 1. 5 MPa/s. So in order to with and without constant speed of the press and jose ability separation, we call it a "constant stress and lotus pressure test machine".
According to GB/T 17671-1999 sets, its add lotus speed allows error for 200 N/s, namely 0. 125 MPa/s.
In order to achieve such add lotus speed, currently has two measures:
1) ordinary pressure test machine. It is equipped with a kind of and press readings dish with one, with the mark of the fixed speed dish to guide, when the press after startup, fixed speed dish can turn, the angular velocity (force value said) just 2 N/s for 400. Pressure test, the operator through the fuel-efficient valve, let the machine needle always follow speed indicator for pressure plate some go, the specimens pressed and jose is able to meet the prescribed requirements speed.
2) by pressure sensor, pressure to be automatic control unit and pressure system and automatic control of speed by pressure test machine. Its speed can add lotus free choice, once chosen, add lotus speed test according to the speed of the selected always. Second.with the meaning of speed regulation charge
According to the modern research of fracture mechanics, constant strain rate and lotus, cement grinding (σ) specimens of stress and strain (ε) relations as curve. Figure 1 for chao lake 525 ordinary cement grinding specimens in the same ε relation curves.
Figure 1 can see, the same ε for the non-linear relationship, and the strain of the increase in the increase of stress fast. Because of the cement hydration is a time and related processes, different varieties, cement, different maintenance specimens of cement in the same ε relationship are also different. At the same time, the same specimens in different strain rate cases in the same ε relationship will be apparent change. Figure l of strain rate of 1 x 10-3 m / (m • s), if the strain rate bigger or smaller, the same ε relation curve will appear on top of the existing curve or below, the ultimate stress (strength) will also be different.
We determine cement grinding try the limit of the body is to build strength value of the mechanical properties of cement contrast system. This system not only for different varieties,
different grades, different) are comparable specimen, and in different regions due also and comparability. So according to cement specimens of sand in the same ε relationship features of the strength parameters is obtained, σ ε and must be in the choice in a parameter, and fixed the increase rate.
Fixed rate increase if the strain, then we present the use of the press will be difficult do, and test the demand is very high also, so all countries in the world using simple fixed rate to me to limit stress increase the intensity. Our country the latest concrete strength test standard also has stipulated the fixed rate increased stress to strength test.
Three.the press and the speed of detection and Hollywood standards
Cement grinding try body compressive strength, the fixed determination of stress increase rate, as we add charge for constant speed. A press, whether a manual operation or computer control, in the test to do add lotus speed is constant, in addition to the provisions of the need to increase the stress outside, still must go at any time during the test specimen for the compensation to reduce stress strain.
Can see from figure 1: specimens to stress damage can be points to four stages, in less than 40 MPa stress, the specimen strain rate is almost equal, strain and stress increase the proportion of increased almost equal proportion; In the 50 ~ 60 MPa strain the proportion of increase between began more than the proportion of stress increase; About 70 MPa strain increased rates of increase soon, and stress small percentage increase; More than 70 MPa are destroyed when near stress almost no longer increases.
In the first phase, maintain stress increase rate unchanged is relatively easy, third and fourth stage can maintain stress increase rate unchanged, the key is to force the system response capacity. Experienced operator should control the throttle the stress increase rate unchanged until the specimens are damaged, or operator always control throttle to add lotus pointer follow speed dish go, also can ensure that add lotus speed meets the requirement. Use the computer to control can do this, also want to see the ability to respond to force system, because the computer can process the information received after instruction rapidly, orders of actuators (dentin system) if there is ability to quickly respond, accurately the instruction execution, it can ensure that add lotus speed requirements, or appear to do a difficult situation. For hydraulic press for, at present more mature actuators is servo valves, but it's too expensive. So the domestic use more developed in recent years electronic proportional valve. Electronic proportional valve response capacity if more than the strain rate increase specimens, the computer instruction will be carried through, otherwise the force
is the actual specimens by rise and fall, before the test results in three stages as dynamic load by specimens, and will appear in the fourth stage stress increase rate drop, appear even the value may, eventually lead to limit stress value (strength) below the standard values.
Therefore how to add lotus speed test process, and its makes assessment is to ensure that the correct test and automatic press qualified key problem. At present domestic haven't a unified, effective detection method, and therefore have this aspect of the standard.
But according to the modern research of fracture mechanics, the stress of the cement concrete strain is due to internal tiny cracks the results of the expansion, this extension speed and by stress size, time and the functions of the role. In standard pressure and fixed and jose state speed and stress related only. We request of the ultimate strain is the stress, but near limit strain of speed increase when strain is really fast, only 1 ~ 1. 5 s or less. In such a short time to test and the change of drying-rate of the Hollywood cannot with normal way, and must have can sense if milliseconds or microseconds to internal force value change sensor, and the force value and time with numerical reflected the relationship, we can understand the test specimen of the true state of stress.
Four. constant stress and lotus pressure test machine should satisfy the conditions
1) maximum load best for 200 kN. According to cement strength achieves 100 MPa plan, specimens in the pressure of the test on the maximum load and only 160 kN, so 200 kN enough to meet the cement strength test requirements.
2) press in 20 to 200 kN within the scope of the value should be not less than 1% accuracy.
3) press an axis of pressure on an axis system should be coincidence, work does not occur in the process of offset.
4) have accord with a standard to ask, fixed by the user or choose to add lotus speed function. The add lotus speed to the extreme stress control error caused should not higher than the press and value error.
5) other configuration and function should comply with the requirements of the universal pressure test machine and cement strength test needs.
Five. The test enginery and old electro-hydraulic servo pressure test machine compared with the following advantages:
1) test force measurement range wider and more accurate, more stable: because
is the actual specimens by rise and fall, before the test results in three stages as dynamic load by specimens, and will appear in the fourth stage stress increase rate drop, appear even the value may, eventually lead to limit stress value (strength) below the standard values.
Therefore how to add lotus speed test process, and its makes assessment is to ensure that the correct test and automatic press qualified key problem. At present domestic haven't a unified, effective detection method, and therefore have this aspect of the standard.
But according to the modern research of fracture mechanics, the stress of the cement concrete strain is due to internal tiny cracks the results of the expansion, this extension speed and by stress size, time and the functions of the role. In standard pressure and fixed and jose state speed and stress related only. We request of the ultimate strain is the stress, but near limit strain of speed increase when strain is really fast, only 1 ~ 1. 5 s or less. In such a short time to test and the change of drying-rate of the Hollywood cannot with normal way, and must have can sense if milliseconds or microseconds to internal force value change sensor, and the force value and time with numerical reflected the relationship, we can understand the test specimen of the true state of stress.
Four. constant stress and lotus pressure test machine should satisfy the conditions
1) maximum load best for 200 kN. According to cement strength achieves 100 MPa plan, specimens in the pressure of the test on the maximum load and only 160 kN, so 200 kN enough to meet the cement strength test requirements.
2) press in 20 to 200 kN within the scope of the value should be not less than 1% accuracy.
3) press an axis of pressure on an axis system should be coincidence, work does not occur in the process of offset.
4) have accord with a standard to ask, fixed by the user or choose to add lotus speed function. The add lotus speed to the extreme stress control error caused should not higher than the press and value error.
5) other configuration and function should comply with the requirements of the universal pressure test machine and cement strength test needs.
Five. The test enginery and old electro-hydraulic servo pressure test machine compared with the following advantages:
1) test force measurement range wider and more accurate, more stable: because
electro-hydraulic servo valve in the static control are zero cover problem (this is electric-hydraulic servo valve itself inherent characteristics), add oil cylinder seal and existing problems of friction, reason in near zero output (displacement and test force) not linear, and low speed easy to crawl, poor stability, starting pressure on the high side, can't achieve small deformation and small test for the power output control (short) is very small, with the sample load control method can't achieve); Adopting electro-hydraulic servo motor control with the ball screw, does not exist the electro-hydraulic servo control problems, combined with a high precision load sensors to force, so test force measurement range wider and more accurate, more stable.
2) control process by temperature effect is small, more stable performance.
3) no hydraulic pressure oil run, run, dripping, and the pollution caused by the leakage problem. No servo valve contaminated stop work problems. Power and drive system and more compact structure more concise and lively, reliability is greatly increased. The long-term use of high reliability, free maintenance (not replace hydraulic oil tedious).
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