Non-destructive testing problems Physical detection is the non-destructive testing without chemical changes. 1. What is nondestructive testing? Answer: Non-destructive testing is a test method for inspecting the surface and internal quality of the parts to be inspected without damaging the working state of the workpiece or raw materials. Second, what are the commonly used methods of flaw detection? Answer: Commonly used non-destructive testing methods include: X-ray inspection, ultrasonic inspection, magnetic particle inspection, penetrant inspection, eddy current inspection, gamma ray inspection, fluorescent inspection, and color detection. Third, the principle of magnetic particle testing? A: Its basic principle is: when the workpiece is magnetized, if there is a defect on the surface of the workpiece, magnetic leakage occurs due to the increase of the magnetic resistance at the defect, forming a local magnetic field, where the magnetic powder shows the shape and position of the defect. Determine the existence of defects. 4. What is the type of magnetic particle inspection? 1. According to the magnetization direction of the workpiece, it can be divided into circumferential magnetization method, longitudinal magnetization method, composite magnetization method and rotating magnetization method. 2, according to the different magnetizing current can be divided into: DC magnetization method, half-wave DC magnetization method, and AC magnetization method. 3. According to the preparation of magnetic powder used in flaw detection, it can be divided into dry powder method and wet powder method. 5. What are the defects of magnetic particle testing? Answer: The magnetic particle inspection equipment is simple, easy to operate, quick to inspect, and has high detection sensitivity. It can be used to find defects on the surface or near surface of ferromagnetic materials such as nickel, cobalt and its alloys, carbon steel and some alloy steels; For the inspection of surface cracks on thin-walled parts or welds, it also reveals incomplete penetration defects of a certain depth and size; however, it is difficult to find the pores, the pinch and the defects hidden deep in the weld. Sixth, the defect magnetic marks can be divided into several categories? Answer: 1. Magnetic traces of various process defects; 2. Hairline magnetic marks caused by material slag; 3. Point-like magnetic marks caused by slag inclusions and pores. 7. What is the reason for the magnetic flux leakage? Answer: Since the magnetic permeability of the ferromagnetic material is much larger than the magnetic permeability of the non-ferromagnetic material, it is analyzed according to the magnetic flux density B=μH after the magnetization of the workpiece, and the B magnetic wire is passed through the unit area of ​​the workpiece, and in the defective area. The unit area cannot allow B magnetic lines of force to pass, forcing a part of the magnetic lines to be squeezed into the material under the defect. Other magnetic lines have to be forced out of the surface of the workpiece to form magnetic flux leakage, and the magnetic powder will be attracted by the magnetic leakage caused by the leakage. . 8. What are the influencing factors of magnetic flux leakage? Answer: 1. Magnetic permeability of defects: The smaller the magnetic permeability of defects, the stronger the magnetic leakage. 2. Magnetization magnetic field strength (magnetization force): The larger the magnetization force, the stronger the magnetic flux leakage. 3. The shape and size of the workpiece to be inspected, the shape and size of the defect, the depth of burial, etc.: When other conditions are the same, the pores buried at the same depth below the surface will produce less leakage flux than the transverse crack. 9. Why do some parts demagnetize after magnetic particle inspection? A: The remanence of some rotating parts will attract iron filings and cause friction damage during rotation, such as shaft bearings. The remanence of some parts will cause the nearby meter to indicate an abnormality. Therefore, some parts should be demagnetized after magnetic particle inspection. 10. What is the basic principle of ultrasonic flaw detection? Answer: Ultrasonic flaw detection is a method of inspecting part defects by using ultrasonic energy to penetrate into the depth of metal material and from one section into another section, and to reflect the defects of the part. When the ultrasonic beam is applied from the surface of the part by the probe When it reaches the inside of the metal, the reflected wave occurs when the defect and the bottom surface of the part are encountered, and a pulse waveform is formed on the fluorescent screen, and the position and size of the defect are judged based on the pulse waveform. 11. What are the advantages and disadvantages of ultrasonic flaw detection and X-ray flaw detection? Answer: Ultrasonic flaw detection has higher detection sensitivity, shorter cycle, lower cost, flexibility, high efficiency, and harmlessness to the human body than X-ray flaw detection. The disadvantage is that the inspection surface is smooth and requires experienced inspectors to distinguish Types of defects, no directness to defects; ultrasonic flaw detection is suitable for inspection of parts with large thickness. 12. What are the main characteristics of ultrasonic flaw detection? Answer: 1. When the ultrasonic wave propagates in the medium, it has the characteristic of reflection at different quality interfaces. If the defect is encountered and the size of the defect is equal to or greater than the ultrasonic wavelength, the ultrasonic wave is reflected back on the defect, and the flaw detector can reflect the wave. If the size of the defect is even smaller than the wavelength, the sound wave will bypass the ray and cannot reflect; 2. The directionality of the wave sound is good, the higher the frequency, the better the directionality, and the radiation into the medium with a narrow beam is easy. Determine the location of the defect. 3. The propagation energy of ultrasonic waves is large. For example, the energy propagated by super-waves with a frequency of 1 MHz (100 Hz) is equivalent to 1 million times of the sound waves with the same amplitude and frequency of 1000 Hz (Hz). XIII. What is the relationship between the three main curves on the volatility curve when the thickness of the ultrasonic wave is 14 mm? Answer: Length measurement line 1 Ñ… 6 -12dB Quantitative line Ф 1 Ñ… 6 -6dB Judgment line 1 Ñ… 6 -2dB Fourteen, what is the "soft" and "hard" of the ray? A: The ability of X-rays to penetrate a substance is related to the wavelength of the ray itself. The shorter the wavelength (the higher the tube voltage), the greater its penetration ability is called "hard"; otherwise it is called "soft". Fifteen, when using ultrasonic waves to detect flaws, what is the cause of the disappearance of the bottom wave? Answer: 1. Large defects in the near table; 2. Absorptive defects; 3. Large defects in inclination; 4. The combination of oxide scale and steel plate is not good. 16. What are the main factors affecting development? Answer: 1. Development time; 2. Developer temperature; 3. Shaking of developer; 4. Formulation type; 5. Ageing degree. 17. What is current? Answer: Current refers to the regular movement of electrons under the action of external force in a certain direction; the direction of current is customarily regulated by the positive pole of the power source flowing through the electrical device to the negative pole in the positive direction, that is, opposite to the direction of the electron. 18. What is the current intensity? Answer: The current intensity is the amount of electricity passing through the cross section of the conductor per unit time. The current is sometimes referred to as the current intensity. It can be written as I = Q \ T where I is the current intensity Q is the amount of electricity and T is the time. Nineteen, what is the resistance? Answer: refers to the resistance of current flowing in the conductor. At the same temperature, the resistance of different materials with the same length and cross-sectional area is often very different; the resistance is represented by "R", the unit is ohm, referred to as Europe, Expressed in Ω. Twenty, what is voltage? Answer: It means that under the action of the power supply, the positive and negative charges inside the conductor are pushed to the two ends of the conductor to make it have a potential difference. The unit of the voltage is volt, which is referred to as volt, and is represented by the symbol “Vâ€. Twenty-one, what is AC, what are the characteristics? Answer: AC means that the magnitude and direction of current, voltage and potential in the circuit are not constant, but are alternating. The characteristic is that the magnitude and direction of current, voltage and potential are cyclical changes with time; industrial and mining enterprises The AC motor, civil lighting, and daily electrical equipment used in the equipment are all powered by alternating current; the alternating current has three-phase and single-phase, and its voltage is 380 volts and 220 volts. Twenty-two, what is DC, what are the characteristics? Answer: It means that the current through the cross section of the conductor is equal and the direction is always constant at any different time; the characteristic is that the current, voltage and potential of the circuit do not change with time. It is constant; DC motor, electroplating, motor excitation, battery charging, semiconductor circuits, etc. Twenty-three, what is Ohm's law? Answer: Ohm's law reflects the relationship between resistance, voltage and current in a circuit with a steady current. Ohm's law states that the current through the circuit is proportional to the voltage across the circuit and inversely proportional to the resistance in the circuit; ie I = V \ R. Twenty-four, what is electromagnetic induction? Answer: The phenomenon that the magnetic flux changes through the closed loop and the electromotive force is generated in the loop is called electromagnetic induction; thus the electromotive force is called induced electromotive force. If the conductor is a closed loop, there will be current flowing, and the current is called induced current. Transformers, generators, and various inductors are all operating according to the principle of electromagnetic induction. Twenty-five, briefly describe the cause of the attenuation caused by the super-wave propagation in the medium during the ultrasonic wave detection. Answer: 1. The diffusion distance of ultrasonic waves increases, the beam cross section becomes larger and larger, and the energy per unit area decreases. 2, the material attenuation is the absorption caused by the viscosity of the medium; the second is the scattering caused by the messy reflection of the medium interface. Twenty-six, what is the main role of the CSK-IIA test block? Answer: 1. Calibration sensitivity; 2. Calibration scan linearity. 27. What are the main factors affecting photographic sensitivity? Answer: 1. The focus size of the X-ray machine; 2. The rationality of the selection of the transillumination parameters, the main parameters are tube voltage, tube current, exposure time and focal length; 3. Sensing mode; 4. Rationality of film selection; 5, darkroom processing conditions; 6, scattering occlusion and so on. Twenty-eight, using super-wave to flaw detection of large pie forgings, if using the bottom wave to adjust the initial sensitivity of the flaw detection requirements on the working bottom? Answer: 1. The bottom surface must be parallel to the flaw detection surface; 2. The bottom surface must be flat and have a certain degree of finish. Twenty-nine, what are the three principles of ultrasonic probe selection for the K value of the probe? Answer: 1. The sound beam scans the entire weld cross section; 2. The sound beam is perpendicular to the main defect as much as possible; 3. There is sufficient sensitivity. 30. What are the main components of the ultrasonic flaw detector? Answer: There are mainly components such as circuit synchronization circuit, transmitting circuit, receiving circuit, horizontal scanning circuit, display and power supply. Thirty-one, what is the main role of the transmitting circuit? Answer: The synchronous pulse signal input by the synchronous circuit triggers the operation of the transmitting circuit, generates a high-frequency electric pulse signal to excite the wafer, generates high-frequency vibration, and generates ultrasonic waves in the medium. 32. In ultrasonic testing, what is the reason for using a coupling agent between the surface of the wafer and the surface of the workpiece to be probed? A: The air gap between the surface of the wafer and the surface of the workpiece to be inspected will completely reflect the ultrasonic wave, resulting in inaccurate flaw detection results and inability to detect. Thirty-three, what are the three conditions for discriminating defects specified in the JB1150-73 standard? Answer: 1. There are only multiple reflected waves with no defects in the bottom wave. 2. There are only a number of disordered defect waves without bottom waves. 3. The defect wave and the bottom wave exist simultaneously. Thirty-four, the distance specified in the JB1150-73 standard - what is the purpose of the amplitude curve? Answer: Distance-Amplitude curve is mainly used to determine the size of the defect. It provides the basis for the acceptance criteria. It consists of three curves: the waste line, the quantitative line and the long line. The waste line is the maximum allowable equivalent of the defect. ―The control line for determining the size and length of the defect; the length measuring line—the initial sensitivity control line for flaw detection. Thirty-five, what is the ultrasound field? A: The space filled with ultrasonic field energy is called the ultrasonic field. 36. What are the main parameters reflecting the characteristics of the ultrasonic field? A: The important physical quantities that reflect the characteristics of the ultrasonic field are sound intensity, sound pressure acoustic impedance, sound beam spread angle, near-field and far-field areas. Thirty-seven, what is the most important performance indicator of the flaw detector? A: Resolution, dynamic range, horizontal linearity, vertical linearity, sensitivity, signal to noise ratio. 38. How can the ultrasonic flaw detector be displayed in several ways? Answer: 1. The A-type display oscillating screen horizontal coordinate represents the ultrasonic transmission time (or distance) ordinate represents the height of the reflected echo; 2, the B-type display oscillography horizontal coordinate represents the ultrasonic transmission time (or distance) This type of display obtains a cross-sectional view of the probe scanning depth direction; 3. The C-type display instrument oscillograph screen represents the projection surface of the workpiece to be inspected, and this display can draw the horizontal projection position of the defect, but cannot give a defect. The depth of burial. 39. What is the main role of the ultrasonic probe? Answer: 1. The probe is an electro-acoustic transducer and can convert the returned sound waves into electrical pulses. 2. Control the propagation direction of the ultrasonic waves and the degree of energy concentration. When changing the incident angle of the probe or changing the diffusion angle of the ultrasonic waves The main energy of the sound wave can be injected into the medium at different angles or change the directivity of the sound wave to improve the resolution; 3. Realize the waveform conversion; 4. Control the working frequency; apply to different working conditions. Forty, the safe operation requirements of magnetic powder probe? Answer: 1. When the workpiece passes directly through the electromagnetic, pay attention to the poor contact between the chucks, or use too much magnetizing current to cause the arc flashing. Wear protective glasses and should not be used in the case of possible gas. 2, when continuous use of wet magnetic suspension, the skin can be coated with protective cream; 3, if used for hydromagnetic suspension, the equipment must be well grounded to prevent electric shock; 4, when using bonfire magnetic powder, the ultraviolet light used Must be filtered to protect the eyes and skin. Forty-one, what is the resolution? A: The minimum distance between images that can be recognized on a ray film or screen, usually expressed as the number of recognizable lines per 1 mm. Forty-two, what is geometric unclear? A: The unsharpness and penumbra caused by the penumbra depends on the focus size, focal length and workpiece thickness. Forty-three, why should we strengthen the investigation and reporting of superwave flaw detection? A: After any ultrasonic flaw detection, any workpiece must be issued as a certificate of the quality of the work. A correct flaw detection report, in addition to establishing reliable detection methods and results, depends largely on the original record. And the final report of the flaw detection is very important. If we check that the workpiece is not recorded or reported, then the flaw detection is meaningless. Forty-four, why use sensitive test strips in magnetic particle inspection? A: The purpose of using sensitive test pieces is to examine the performance of magnetic powder and magnetic suspension and the comprehensive factors such as determining the effective magnetic field strength and direction of the test piece surface and the correct operation method in the continuous method. Forty-five, what is the fixing effect? Answer: The film after development is in the shadow liquid. The film remover dissolves the undeveloped silver bromide on it, and the process of protecting the black metal silver particles is called fixing. Forty-six, what is the basic principle of coloring (infiltration) flaw detection? Answer: The basic principle of coloring (penetration) flaw detection is to use capillary phenomenon to infiltrate the permeate into the defect. After cleaning, the surface permeate is removed, and the defect in the residual tumor, and then the capillary action of the developer is used to adsorb the defect. Tumor permeate to achieve the purpose of testing defects. Forty-seven, what are the main factors of coloring (infiltration) sensitivity? Answer: 1. The effect of the performance of the penetrant; 2. The effect of the emulsification effect of the emulsifier; 3. The influence of the performance of the developer; 4. The influence of the operation method; 5. The influence of the nature of the defect itself. Forty-eight, in the ultrasonic flaw detection, the defects in the weld are divided into several categories? How to classify? Answer: In the ultrasonic flaw detection of welds, the defects in the weld are generally divided into three categories: point defects, line defects, and surface defects. In the classification, a defect having a length of less than 10 mm is called a point defect; generally, it is not measured long, and a defect of less than 10 mm is measured by 5 mm. A defect having a length greater than 10 mm is called a linear defect. A defect having a length greater than 10 mm and a height greater than 3 mm is called a planar defect. Forty-nine, how is the film washing process? A: development, stop, fix, wash, dry. Fifty, what is conductivity? A: Refers to the nature of the metal that can conduct electricity. Fifty-one, what is magnetic? Answer: It means that the metal has magnetic permeability. In practical terms, it can be made of permanent magnets and electrical materials made of magnetic materials (metal). It can also be used to check whether there are cracks in the magnetic metal. What is high pressure? Answer: The device whose voltage is above 250 volts is called high voltage. Fifty-three, what is low pressure? A: The device voltage below 250 volts is called low voltage. Fifty-four, what is the safety voltage? Answer: When a person touches a live conductor, the voltage that is not life-threatening is generally referred to as a safe voltage using a voltage below 36 volts. Where the workplace is wet or in a metal container, the tunnel, the electrical lighting in the mine, etc., all use a 12 volt safe voltage. Fifty-five, what is the role of the ultrasonic test block? A: The function of the ultrasonic test block is to verify the performance of the instrument and the probe, determine the initial sensitivity of the flaw detection, and calibrate the scan linearity. 56. What is the correct value of the angle of refraction of the oblique probe? A: The correct value of the angle of refraction of the oblique probe is called the K value, which is equal to the ratio of the horizontal distance of the oblique probe λ to the reflection point and the corresponding depth. 57. What should I do if there are unacceptable defects found in the welds of the local non-destructive inspection? A: Supplemental radiographic inspection should be performed in the direction of extension of the defect or in the suspicious part. There is still doubt about the weld quality after the supplementary inspection that the weld should be fully inspected. 58. What kinds of magnetic marks are caused by non-defects? Answer: 1. Local cold work hardening, magnetic trace accumulation caused by magnetic permeability change of materials; 2. Magnetic powder accumulation at the interface of two different materials; 3. Segregation of carbide layer structure; 4. Mutation of part cross-section size 5. The magnetization current is too high, the magnetic trace caused by the metal flow line; 6, the spot-shaped magnetic mark caused by the surface of the workpiece is not clean or oily. 59. What are the contents of the magnetic particle inspection procedure? Answer: 1. The scope of application of the procedure; 2. Magnetization method (including magnetization specification, preparation of workpiece surface); 3. Magnetic powder (including particle size, color, preparation of magnetic suspension and fluorescent magnetic suspension). 4, test strips; 5, technical operation; 6, quality assessment and inspection records. Sixty, the scope of magnetic particle testing? A: Magnetic particle inspection is a method for detecting defects on the surface and near surface of ferromagnetic materials. Sixty-one, what is the main role of the synchronous signal generator in the ultrasonic flaw detector? It mainly controls which two parts of the circuit work? Answer: The synchronizing circuit generates a synchronizing pulse signal for triggering the simultaneous operation of each part of the instrument. It mainly controls the synchronous transmitting and synchronous scanning two parts of the circuit. Sixty-two, the purpose of non-destructive testing? Answer: 1. Improve the manufacturing process; 2. Reduce the manufacturing cost; 3. Improve the possibility of the product; 4. Ensure the safe operation of the equipment. 63. What are the methods for adjusting the time scan line of the defect positioning instrument during ultrasonic flaw detection? A: There are three methods of horizontal locator, vertical positioning and sound path positioning. Sixty-four, try to compare the main advantages and disadvantages of dry powder method and wet powder test? Answer: The dry powder test has high detection ability for near-surface defects, and is especially suitable for large-area or field detection. The wet powder test has high detection ability for small defects on the surface, and is especially suitable for batch inspection of small parts with irregular shapes.
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