TWI418636B - Resonance Elimination Residual Stress System and Its Method - Google Patents

Description

Resonance elimination residual stress system and method thereof

The present invention relates to a method for eliminating residual stress, and more particularly to a resonance canceling residual stress system and method thereof.

Generally, there are residual stresses in the workpieces of different processing procedures, such as casting, rolling, cold working, heat treatment, welding, etc., and the existence of residual stress not only causes deformation of the workpiece, but also causes difficulty in joining and assembling the components, and also causes the workpiece. The reduction of fatigue resistance and stress corrosion resistance greatly affects the quality of processed products. Therefore, stress relief of the workpiece is an important task for product strength and precision considerations.

At present, the most commonly used method for stress relieving is heat treatment. Generally, the heat treatment method is to uniformly heat the structure to a suitable temperature, and then hold the temperature for a period of time, so that the atoms are rearranged at high temperature, and the residual remains inside the material. The stress is usually controlled by the heating temperature and the holding time. The cooling rate is also critical. Uneven cooling will cause the weldment to shrink unevenly, and the residual stress will increase.

The effect of heat treatment stress elimination is excellent, but relatively large energy is required to be used, and when the volume of the object is too large, a larger furnace must be installed to be able to be processed. In practice, it cannot be applied to each case and has limited use. Missing.

The vibration stress elimination is a technology widely used in the industry at present, mainly by using alternating stress on the workpiece, which can effectively reduce the residual stress in the material, improve the strength of the workpiece, and reduce the deformation of the workpiece. It makes the dimensional accuracy of the workpiece more stable, and has the advantages of energy saving, high efficiency, no pollution, low cost, short production cycle, simple equipment and convenient operation. It has been adopted by Asian countries such as Europe and America.

However, since the vibration frequency is closely related to the resonance frequency of the workpiece, the vibration relieving stress is mainly caused by the superposition of the fluctuation of the workpiece and the fluctuation of the vibration energy, driving the dislocation movement, and the more the fluctuation after the superposition The effect of large-time drive dislocation movement is also greater, and the effect of stress elimination is also the best, and the fluctuation of vibration energy directly affects the effect of eliminating residual stress. Therefore, it is impossible to know the stress elimination and energy fluctuation. In this case, the effect of stress relief cannot be effectively improved at all, and for the setting of the vibration frequency, an objective criterion cannot be obtained because of the fluctuation.

For example, in the application case No. 96113789, "Method for Eliminating Residual Stress by Vibration", the best time for stress relief is when high frequency waves are generated depending on the main vibration wave and the maximum amplitude is generated. It is the position of the resonance point. Therefore, when judging, some people advocate that it is 10 Hz below the resonance point, and some people think that it is about 1/3 of the amplitude of the amplitude. Therefore, it is obvious that there is a sub-resonance point. This residual stress relieving mechanism still has room for improvement in judging the accuracy, and such a state is established for the vibrator of the eccentric cam, and is not suitable for the vibrator that is struck by electromagnetic vibration.

Accordingly, it is an object of the present invention to provide a resonance canceling residual stress system that enhances the residual stress relieving effect for an electromagnetic vibration tapping method. And its method.

Thus, the resonance canceling residual stress system of the present invention comprises an electromagnetic vibrator, a sensing unit, and a monitoring unit. The electromagnetic vibrator is used to strike a workpiece to cause vibration of the workpiece. The sensing unit is for measuring the amplitude and frequency of the workpiece. The monitoring unit has a display screen for displaying the amplitude and frequency of the workpiece, and a controller for controlling the electromagnetic vibrator to continuously apply a predetermined tap frequency to the workpiece, the predetermined tapping frequency is The main vibration wave generated by the workpiece reaches the resonance point.

The method for resolving residual stress by the resonance of the present invention is the above system as a tool, and the method comprises the following steps: Step 1: The electromagnetic vibrator strikes the workpiece to generate a vibration wave of the workpiece. Step 2: The sensing unit measures the amplitude and frequency of the vibration of the workpiece and displays it in the monitoring unit. Step 3: The monitoring unit controls the tapping frequency of the electromagnetic vibrator until the main vibration wave reaches the resonance point. Step 4: Maintain the electromagnetic vibrator to continuously apply vibration to the workpiece at the tapping frequency of the step 4.

The effect of the present invention is to effectively eliminate most of the residual stress when the main vibration wave of the workpiece reaches the resonance point for the electromagnetic vibrator.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Referring to FIG. 1, a preferred embodiment of the resonance canceling residual stress system of the present invention comprises an electromagnetic vibrator 1, a sensing unit 2, and a monitoring unit 3.

The electromagnetic vibrator 1 is directly placed on a workpiece 4. In the embodiment, the electromagnetic vibrator 1 is caused by an electromagnetic telescopic rod (not shown) striking the workpiece 4, and the vibration frequency thereof is The tapping speed is proportional.

The sensing unit 2 has an accelerometer 21 placed directly on the workpiece 4 for measuring the amplitude and frequency of the workpiece 4, and a signal amplifier 22 for amplifying the accelerometer 21 measurement signal.

The monitoring unit 3 is electrically connected to the electromagnetic vibrator and the sensing unit 2, and has a display screen 31 for displaying the amplitude and frequency of the workpiece 4, and is used for controlling the continuous pair of the electromagnetic vibrator 1 The workpiece 4 is applied to a controller 32 of a predetermined tap frequency.

Referring to FIG. 1 and FIG. 2, the following method for eliminating residual stress in the resonance of the present invention is described in conjunction with the steps of the embodiment:

Step 51: The workpiece 4 is struck by the electromagnetic vibrator 1 to cause the workpiece 4 to generate a vibration wave.

Step 52: Measure the amplitude and frequency of the workpiece 2 with the acceleration gauge 21, and amplify the measurement signal of the acceleration gauge 21 through the signal amplifier 22.

Step 53: Display the amplitude and frequency of the workpiece 2 in step 52 with the display screen 31.

Step 54: The controller 32 is used to fine tune the tapping frequency of the electromagnetic vibrator 1, and the predetermined tapping frequency is determined by the waveform displayed by the display screen 31.

Referring to FIG. 3, when the amplitude of the main vibration wave is maximum, that is, the resonance point at that time, at this time, the amplitude of the high-frequency wave attached to the main vibration wave also exhibits a maximum value, and the frequency (ie, the predetermined tap frequency) is about 375 Hz.

Step 55: The workpiece 4 is continuously subjected to vibration for about twenty minutes at a predetermined tapping frequency (375 Hz) of step 54, so that the workpiece 4 effectively eliminates most of the residual stress when the main vibration wave reaches the resonance point.

In the following, the argon-welded test piece is subjected to low-frequency waves (vibration mode A) and intermediate-frequency waves (vibration mode B), and high-frequency waves (vibration mode C) and over-resonance frequencies when the present invention reaches the resonance point. Vibration treatment such as wave (vibration mode D) compares the effect of residual stress relief.

The material test piece used in this embodiment is AISI 304 stainless steel, and the size of the test piece is 100×80×5 (mm). The surface of the test piece was sequentially ground through a sandpaper, and then polished with alumina powder of 1 μm and 0.3 μm, respectively, to measure residual stress.

In the vibration processing, the frequency and the amplitude are displayed via the display screen 31, wherein the position at which the vibration wave amplitude is the highest point is the resonance point of the vibration wave, and the corresponding frequency is the resonance frequency, and the low frequency wave (vibration mode A, input) The frequency is 67Hz, the amplitude value is 1.26V), the vibration waveform is shown in Figure 4; the intermediate frequency wave (vibration mode B, input frequency is 250Hz, amplitude value is 1.36V), the vibration waveform is shown in Figure 5; The frequency of the resonant frequency wave (vibration mode C, input frequency is 375 Hz, amplitude value is 2.57V) of the present invention can be matched with the monitoring unit 3 to determine the frequency. The method is as shown in the foregoing steps, and the vibration waveform is as shown in FIG. 6; the over-resonant frequency wave (Vibration mode D, input frequency is 390 Hz, amplitude value is 1.88 V), and its vibration waveform is as shown in Fig. 7.

After using low frequency wave (vibration mode A), intermediate frequency wave (vibration mode B), and resonant frequency wave (vibration mode C), over-resonant frequency wave (vibration mode D) for 20 minutes, residual stress measurement can be performed. . X-ray is used in this experiment The measurement of the residual stress of the weldment by the diffraction method.

Referring to Fig. 8, it can be clearly seen that the residual stress elimination ratio using the low frequency wave (vibration mode A) is 51.1%, and the residual stress elimination ratio using the intermediate frequency wave (vibration mode B) is 54.4%, and the over resonance frequency wave is used. The residual stress relaxation ratio (vibration mode D) is 56.7%, and the residual stress elimination ratio of the resonance frequency wave (vibration mode C) of the present invention is 68.7%, apparently, low intermediate frequency wave (vibration mode A, B) or over resonance frequency The wave (vibration mode D) has less stress relief effect than the resonance frequency wave (vibration mode C). That is, when the main vibration wave reaches the resonance point, the effect of eliminating residual stress is optimal.

According to the above description, the resonance elimination residual stress system and the method thereof of the present invention have the following advantages and effects: The invention acts on the workpiece 4 in a resonant manner, and the timing of the main vibration wave reaching the resonance point is determined not only by the acceleration gauge 21, the signal amplifier 22, and the monitoring unit 3, but also It effectively eliminates most of the residual stress, greatly reduces energy waste, is not limited by the construction site, and can simplify the procedure and reduce the cost, making the invention more practical and convenient.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

1‧‧‧Electromagnetic vibrator

2‧‧‧Sensor unit

21‧‧ ‧ Acceleration regulations

22‧‧‧Signal Amplifier

3‧‧‧Monitoring unit

31‧‧‧ display screen

32‧‧‧ Controller

4‧‧‧Workpiece

1 is a front elevational view showing a preferred embodiment of the resonance canceling residual stress system of the present invention and a method thereof; 2 is a flow chart of the preferred embodiment; FIG. 3 is a waveform diagram of a high frequency wave after the main vibration wave of the main vibration wave of the preferred embodiment is removed; FIG. 4 is a schematic diagram of the preferred embodiment. A vibration waveform diagram of the low frequency wave (vibration mode A); Fig. 5 is a vibration waveform diagram of the intermediate frequency wave (vibration mode B) produced by the preferred embodiment; Fig. 6 is a resonance frequency wave generated by the preferred embodiment (vibration) a vibration waveform diagram of mode C); FIG. 7 is a vibration waveform diagram of the resonant frequency wave (vibration mode D) generated by the preferred embodiment; and FIG. 8 is a residual stress of each vibration mode in the preferred embodiment. Eliminate the ratio map.

1‧‧‧Electromagnetic vibrator

2‧‧‧Sensor unit

21‧‧ ‧ Acceleration regulations

22‧‧‧Signal Amplifier

3‧‧‧Monitoring unit

31‧‧‧ display screen

32‧‧‧ Controller

4‧‧‧Workpiece

Claims (5)

A resonance eliminating residual stress system comprising: an electromagnetic vibrator for striking a workpiece to generate vibration of the workpiece; a sensing unit for measuring amplitude and frequency of the workpiece; and a monitoring unit having a display screen for displaying amplitude and frequency of the workpiece, and a controller for controlling the electromagnetic vibrator to continuously apply a predetermined tap frequency to the workpiece, the predetermined tap frequency being used for the workpiece The generated main vibration wave reaches the resonance point. According to the resonance canceling residual stress system described in claim 1, wherein the main vibration wave generated by the workpiece reaches the resonance point, the high-frequency wave attached to the main vibration wave also reaches a maximum value. The resonance elimination residual stress system according to claim 1, wherein the sensing unit has an acceleration gauge. The resonance canceling residual stress system according to claim 1, wherein the sensing unit further has a signal amplifier. A method for resolving residual stress by using a system as a tool, the system comprising an electromagnetic vibrator for striking a workpiece, a sensing unit for measuring the amplitude and frequency of the workpiece, and A monitoring unit for controlling the frequency of the electromagnetic vibrator and the amplitude and frequency of the workpiece, the method comprising the following steps: Step 1: the electromagnetic vibrator strikes the workpiece to generate a vibration wave of the workpiece; Step 2: the feeling The measuring unit measures the amplitude and frequency of the vibration wave of the workpiece And displayed in the monitoring unit; Step 3: the monitoring unit controls the tapping frequency of the electromagnetic vibrator until the main vibration wave reaches the resonance point; and Step 4: maintain the electromagnetic vibrator with the step 3 The frequency is tapped and the workpiece is continuously vibrated.