The Magnetic Field Distribution In Alternative Current.

The Magnetic Field Distribution In Alternative Current. 

When the conductor is carrying Alternating Current, the internal magnetic field strength rises from zero at the centre to a maximum at the surface. However, the field is concentrated in a thin layer near the surface of  the conductor. This is known as the "skin effect."  The skin effect is evident in the field strength versus distance graph for a magnetic conductor shown to the right. The external field decreases with increasing distance from the surface as it does with DC. It should be remembered that with AC the fields constantly varying in strength and direction.
In a hollow circular conductor there is no magnetic field in the void area. The magnetic field is zero at the inside wall surface and rises until it reaches a maximum at the outside wall surface. As with a solid conductor, when the conductor is a magnetic material, the field strength within the conductor is much greater than it was in the nonmagnetic conductor due to the permeability of the magnetic material. The external field strength decreases with distance from the surface of the conductor. The external field is exactly the same for the two materials provided the current level and conductor radius are the same.

The Magnetic Field In Distribution In Direct Current.

As can be seen in the field distribution images, the field strength at the inside surface of hollow conductor carrying magnetic field produced by direct magnetization is very low. Therefore, the direct method of magnetization is not recommended when inspecting the inside diameter wall of a hollow component for shallow defects. The field strength increase rather rapidly as one moves in from the ID,so if the defect has significant depth, it may be detectable.However a much better method of magnetizing hollow component for inspection of the ID and OD surfaces is with the use of a central conductor. As can be seen in the field distribution image to the right, when current is passed through a nonmagnetic central conductor (copper bar), the magnetic field produced on the inside diameter surface of a magnetic tube is much greater and the field is still strong enough for defect detection on the OD surface. After conducting a magnetic particle inspection, it is usually necessary to demagnetize the component. Remanent magnetic fields can.
1)    Affect machining by causing to cling to a component.
2)    Interfere with electronic equipment such as a compass.
3)    Create a condition known as arc blow in the welding process. Arc blow may cause the weld arc wonder or filler metal to be repelled from the weld.
4)    Cause abrasive particles to cling to bearing or flying surfaces and increase wear.
Removal of a field may be accomplished in several ways. This random orientation of the magnetic domains can be achieved most effectively by heating the material above its curie temperature. The curie temperature for a low carbon steel is 770 C or 1390 F. When steel is heated above its curie temperature, it will become austenitic and loses its magnetic properties. When it is cooled backdown, it will go through a reverse transformation and will contain no magnetic field. The material should also be placed with it long axis in an east-west orientation to avoid any influence of the earth's magnetic field. 

ELECTROMAGNETS IN MAGNETIC PARTICLE INSPECTION.

Magnetic particle inspection.

Today, most of the equipment used to create the magnetic field used in MPI is based on electromagnetism. That's, using an electrical current to produce the magnetic field. An Electromagnetic yoke is a very common piece of equipment that is used to establish a magnetic field.

It is basically made by wrapping an electrical coil around a piece of soft ferromagnetic steel. A switch is included in the electrical circuit so that the current and, therefore, the magnetic field can be turned on and off. They can be powered with Alternating Current from a wall socket or by direct current from a battery pack. This type of magnet generates a very strong magnetic field in a local area where the poles of the magnet touch the part being inspected. Some yokes can lift weights in excess of 40 pounds.

PRODS IN MAGNETIC PARTICLE INSPECTION

Prods are handheld electrodes that are pressed against the surface of the component being inspected to make contact for passing electrical current through the metal. The current passing between the prods creates a circular magnetic field around the prods that can be used in magnetic particle inspection. prods are typically made from copper and have an insulated handle to help protect the operator. One of the prods has a trigger switch so that the current can be quickly and easily turned on and off. Sometimes the two prods are connected by any insulator (as shown in the image)  to facilitate one hand operation. This is referred to as a dual prod and is commonly used for weld inspections.
If proper contact is not maintained between the prods and the component surface. electrical arcing can occur and cause damage to the component. For this reason, the use of prods are not allowed when inspecting aerospace and other critical components. To help prevent arcing, the prod tips should be inspected frequently to ensure that they are not oxidized, covered with scale or other contaminant,or damaged. 

PORTABLE COILS AND CONDUCTIVE CABLES.

Coils and conductive cables are used to establish a longitudinal Magnetic field within a component. When a preformed coils is used, the component is placed against the inside surface on the coil. Coils typically have three or five turns of a copper cable within the molded frame. A foot switch is often used is typically 00 extra flexible or 0000 extra flexible. The number of wraps is determined by the magnetizing force needed and of course, the length of the cable. Normally, the wraps are kept as close together as possible. When using a coil  or cable wrapped into a coil, amperage is usually expressed in ampere - turns. Ampere - turns is the amperage shown on the amp meter times the number of turns in the coil.

PORTABLE POWER SUPPLIES :- Portable power supplies are used to provide the necessary electricity to the prods, coils or cables. Power supplies are commercially available in a variety of sizes. Small power supplies generally provide up to 1,500A of half - wave direct current or Alternating Current when used with 4.5meter 0000cable. They are small and light enough to be carried and operate on either 120V or 240V electrical service. when more power is necessary, mobile power supplies can be used  These units also operate on 120V or 240V electrical service and can provide up to 6,000A of AC or half - wave DC when 9meters or less of 0000 cable is used 

Advantages and limitation of ultrasonic testing.

 ADVANTAGES OF ULTRASONIC INSPECTION: - 

 1)   It is sensitive to both surface and subsurface discontinuities.

       
 2)   The depth of penetration for flaw detection or measurement is superior to the NDT methods.

 3)   Only single sided access is needed when the pulse echo technique is used.

 4)   It is highly accurate in determining reflector position and estimating size and shape.

                                  

 5)   Minimal part preparation is required.

                                                                                

 6)   Electronic equipment provides instantaneous results.

 7)   Detailed images can be produced with automated systems.

 8)   It has other uses,such as thickness measurement,in addition to flaw detection.                                        

LIMITATION:-

 1)  Surface must be accessible to transmit ultrasound.

 2)  skill and training is more extensive than with some other methods.

 3) It normally requires a coupling medium to promote the transfer of sound energy into the test specimen.

 4)  Materials that are rough, irregular in shape,very small,exceptionally thin or not homogenous are difficult.

 

 5)   Cast iron and other coarse gained materials are difficult to inspect due to low sound transmission and high signal noise.                                                                                                                        

 6)  Linear defects oriented parallel to the sound beam may go undetected.

 7)  Reference standards are required for both equipment calibration and characterization of flaws.                                                                                                                                  

Disadvantages of computer.

Disadvantages of computers:

1)  Health issues: Excessive computer use can lead to health problems such as eye strain, back and neck pain, and musculoskeletal disorders. Prolonged sitting and sedentary behavior can also contribute to obesity and other lifestyle diseases.

2)  Security risks: Computers are susceptible to security threats such as viruses, malware, and hacking. Users must take precautions, such as using antivirus software and strong passwords, to protect their personal information and data.

3)  Dependency: As people become reliant on computers for various tasks, there is a risk of dependency and loss of manual skills. Additionally, technical issues or power outages can disrupt productivity and cause frustration.

4)  Social isolation: Spending excessive time on computers can lead to social isolation and a lack of face-to-face interaction. Virtual communication may not provide the same level of human connection as in-person interactions.

6)  Privacy concerns: Computers store vast amounts of personal data, raising concerns about privacy and data breaches. Users must be cautious about sharing personal information online and take steps to protect their privacy.

7)  Environmental impact: The production and disposal of computers contribute to environmental issues such as increased electronic waste and energy consumption. Responsible disposal and recycling of electronic devices are important to minimize the negative impact on the environment.

Computers have undoubtedly revolutionized various aspects of our lives, but it is important to use them responsibly and be aware of the potential drawbacks. Striking a balance between computer usage and other activities is essential for overall well-being.

Stationery Equipment for Magnetic Particle Inspection.

Stationary magnetic particle inspection equipment is designed for use in laboratory or production environment. The most stationary system is the wet horizontal (bench) unit. Wet horizontal units are designed to allow for batch inspections of a variety of components. The units have head and tail stocks (similar to lathe) with electrical contact that the part can be clamped between. A circular magnetic field is produced with direct magnetization.  The tail stock can be moved and locked into place to accommodate parts of various lengths. To assist the operator in clamping the parts, the contact on the headstock can be moved pneumatically via a foot switch.
Most units also have a movable coil that can be moved into place so the indirect magnetization can be used to produce a longitudinal Magnetic field. Most coils have five turns and can be obtained in a variety of sizes. The wet magnetic particle solution is collected and held in a tank. A pump and hose system is used to apply the particle solution to the component being inspected. Either the visible or fluorescent particles can be used. Some of the system offer a variety of options in electrical current used for magnetizing the component. The operator has the option to use AC, half wave DC, or full wave DC.In some units, a demagnetization features is built in, which uses the coil and decaying AC.

If there is a dent in the car.

         

            If you ever buy a new car, there are a few things about it that no one can guarantee, one of which is that your car will definitely get a dent at some point.  This is because no matter how much you save, some person walking on the road sometimes collides with your car a little, due to which your car gets dented, for which you may have to spend thousands of rupees to remove it.  Are.  If you have also bought a new car recently and there is a small dent in it, which you want to get removed but do not want to spend money, then today we are going to tell you a very easy way to remove the dent at home. 

              Once your car gets a dent, you can take it out with boiled water if you want, for this you will have to take about 1 liter of hot water which is boiled, after that pour this water little by little on the dent.  .  As soon as you pour water on the dent the metal sheet starts expanding and you can push it from the back side to get the dent out.  This method is very effective on small dents.

                    

                

Advantages of computer.

Advantages of computer.

1)  Efficiency: Computers can process large amounts of data quickly and accurately, increasing productivity and efficiency in various tasks, including data analysis, calculations, and communication.

2)  Storage: Computers have the ability to store vast amounts of data, eliminating the need for physical paper files and allowing for easy organization and retrieval of information.

3)  Communication: Computers enable instant communication through email, messaging apps, video conferencing, and social media platforms, connecting people globally and facilitating collaboration and information sharing.

4)  Automation: Computers can automate repetitive tasks, reducing human error and freeing up time for more complex and creative work.

5)  Access to information: The internet provides access to a wealth of information and resources, allowing users to search for information, learn new skills, and stay informed about current events.

6)  Entertainment: Computers offer various forms of entertainment, including online gaming, streaming movies and TV shows, and music production. They provide a platform for creativity and relaxation.