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To property inspect a part for cracks or other defects, it is important to become familiar with the different types of magnetic fields and the equipment used to generate them. As discussed previously, one of the primary requirements for detecting a defect in a ferromagnetic material is that the magnetic field induced in the part must intercept the defect at a 45 to 90 degree angle. Flaws that are normal (90 degrees)  to the magnetic field will produce the strongest indication because they disrupt more of the magnet flux. Therefore, for proper inspection of a component, it is important to be able to establish a magnetic field in at least two directions. A variety of equipment exists to establish the magnetic field for MPI.One way to classify equipment is based on its portability.  Some equipment is designed to be portable so that inspection can be made in the field and some is designed to be stationary for ease of inspection in the laboratory or manufacturing facility....

     French automotive group Citroen has launched a new electric car, which is actually an off-road vehicle, on the world market. It's called My Ami Buggy. It has a very compact design. The design was also inspired by the My Ami electric car. It also has a 5.4kWh battery pack and an 8hp generator motor. The company has set the original price of the My Ami Buggy at around $13,029 (roughly Rs 10.78 lakh).  It is reported that this is a limited edition model, only 1000 will be produced. The electric car will also be available in more than 10 countries. In June, it will also launch in some European countries including France, Spain and Italy. It will launch in Morocco and Türkiye, but it won't be available in the US for now.       Best of all it is very compact and easy to drive. Launched as a rugged EV, the off-roader will be available in a khaki and black color combination. Equipped with an 8 hp electric motor and a 5.4 kWh battery, it can re...

Why your car's muffler leaks water: You've probably noticed frequently that water sometimes leaks out of your muffler when you start a stationary car. So is there a need to panic when something like this happens? No, actually getting water out of your car's muffler is a sign that the engine is fine. A lot of people don't realize this and think that if water is coming out of the muffler in their car, it means there is a problem with the engine, but this is not the case. So don't worry, it's completely normal. Why does water flow out of the car muffler?  There are two main reasons for a car engine to leak water. The first reason is condensation. When an internal combustion engine is running, carbon dioxide is released. Water vapor will also escape. It turns watery when the car is stopped after driving and the engine cools down. Now, when you start the car again, this water will come out of the muffler.  Another reason is the catalytic converter. The c...

Magnetic field orientation and flaw detectable.  The type of magnetic field established is determined by the method used to magnetize the specimen. Being able to magnetize the part in two direction is important because the best detection of defects occurs when the lines of magnetic force are established at right angles to the longest dimensions of the defect. This orientation creates the largest disruption of the magnetic field within the part and the greatest flux leakage at the surface of the part. As can be seen in the image, if the magnetic field is parallel to the defect, the field will see little disruption and no flux leakage field will be produced. An orientation of 45 to 90 degrees between the magnetic field and the defect is necessary to form an indication. Since defects may occur in various and unknown directions, each part is normally magnetized in two directions at right angles to each other. If the component below is considered, it is known that passing curr...

THE HYSTERESIS LOOP AND MAGNETIC PROPERTIES.  A great deal of information can be learned about the magnetic properties of a materials by studying it's hysteresis loop. A hysteresis loop shows the relationship between the induced magnetic flux density (B) and the magnetizing force (H). It is often referred to as the B-H loop. The loop is generated by measuring the magnetic flux of a ferromagnetic material while the magnetizing force is changed. A ferromagnetic material that has never been previously magnetized or has been throughly demagnetized will follow the dashed line as H is increased. As the line demonstrates the greater the amount of current applied (H+), the stronger the magnetic field in the component ((B+). At point  "a" almost all of the magnetic Domains are aligned andante additional increase in the magnetizing force will produce very little increase in magnetic flux. The material has reached the point of magnetic saturation. When H is reduced to zero,...

MAGNETIZATION USING DIRECT INDUCTION.  With direct magnetization, current passed directly through the component. Recall that whenever current flows, a magnetic field is produced. Using the right-hand rule, which was introduced earlier, it is known that the magnetic lines of flux form normal to the direction of the current and form a circular field in and around the conductor. When using the direct magnetization method, care must be taken to ensure that good electrical contact is established and maintained between the test equipment and the test component improper contact can result in arcing that may damage the component. It is also possible to overheat component in areas of high resistance such as the contact points and in areas of small cross - sectional area.   There are several ways that direct magnetization is commonlyaccomplished. One way involves clamping the component between two electrical contacts in a special piece of equipment. Current is passed ...

MAGNETIZATION USING INDIRECT INDUCTION.  Indirect magnetization is accomplished by using a strong external magnetic field to establish a magnetic field within the component. As with direct magnetization, there are several ways that indirect magnetization can be accomplished. The use of permanent magnets is a low cost method of establishing field. However, their use is limited due to lack of control of the field strength and the difficulty of placing and removing strong permanent magnets from the component. Electromagnetes in the form of an adjustable horseshoe magnet ( called a yoke) eliminate the problems associated with permanent magnets and are used extensively in industry. Electromagnetes only exhibit a magnetic flux when electric current is flowing around the soft iron core. When the magnet is placed on the component, a magnetic field is established between the north and south poles of the magnet. Another way of indirectly inducing a magnetic field in a ma...

MAGNETIZING CURRENT IN MAGNETIC PARTICLE INSPECTION.  Half wave Alternative current (HWAC) :- When single phase alternative current is passed through a rectifier, current is allowed to flow in only one direction. The reverse half of each cycle is blocked outsourcing that a one directional, pulsating current is produced. The current rises from zero to a maximum and then returns to zero. No current flows during the time when the reverse cycle is blocked out. The HAWC repeat at same rate as the unrectified current (60hertz typical). Since half of the current is blocked out, the amperage is halftone the unaltered AC. This type of current is often referred to as half wave Dc or pulsating DC. The pulsation of the HWAC helps magnetic particle inspection form by vibrating the particles and giving them added mobility. This added mobility is especially important when using dry particles. The pulsation is reported to significantly improve inspection sensitivity. ...

Longitudinal Magnetic Fields in Magnetic Particle Inspection.  When the length of a component is several times larger than its diameter, a longitudinal Magnetic field can be established in the component. The component is often placed longitudinally in the concentrated magnetic field that fills the center of a coil or solenoid. This magnetization technique is often referred to as a coil shot. The magnetic field travels through the component from end to end with some flux loss along its length as shown in the image to the right. keep in mind that the magnetic lines of flux occur in three dimensions and are only shown in 2D in the image. The magnetic lines of flux are much denser inside the ferromagnetic material than in air because ferromagnetic materials have much higher permeability than does air. When the concentrated flux within the material comes to the air at the end of the component, it must spread out since the air can not support as many lines of flux per unit ...

When a component is magnetized along its complete length, the flux loss is small alongside length. Therefore, when a component is uniform in cross section and magnetic permeability, the flux density wellbeing relatively uniform throughout the component. Flaws that run normal to the magnetic lines of flux will disturb the flux lines and often cause a leakage field at the surface of the component. When a component with considerable length is magnetized using a solenoid, it is possible to magnetize only a portion of the component. Only the material within the solenoid and about the same width on side of the solenoid will be strongly magnetized. At some distance from the solenoid, the magnetic lines of force will abandon their longitudinal direction, leave the part at a pole on one side of the solenoid and return to the part at a opposite pole on the other side of the solenoid. This occurs because the magnetizing force diminishes with increasing distance from the...

As discussed previously, when current is passed through a solid conductor, a magnetic field forms in and around the conductor. The following statements can be made about the distribution and Intensity of the magnetic field. 1)    The field strength varies from zero at the centre of the component to a maximum at the surface. 2)    The field strength at the surface of the conductor decreases as the radius of the conductor increases when the current strength is held constant.( However, a larger conductor is capable of carrying more current.) 3)    The field strength outside the conductor is directly proportional to the current strength. Inside the conductor, the field strength is dependent on the current strength, magnetic permeability of the material, and if magnetic, the location on the B-H curve. 4)    The field strength outside the conductor decreases with distance from the conductor. In the images below, the magnetic field strength is gr...

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 nonma...

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 demagneti...

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 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 sh...

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 ...

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 appl...

                      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 ...

Summer has wreaked havoc, as soon as you come home, you feel like having cold water or a cold drink to enjoy yourself.  But none of us is unaware of the condition of electricity in the cities.  In such a situation, getting some cool water is very useful.          Summer has wreaked havoc, as soon as you come home, you feel like having cold water or a cold drink to enjoy yourself.  But none of us is unaware of the condition of electricity in the cities.  In such a situation, it becomes very difficult to get any cold water.  To solve this problem, we have come up with an idea that will work to keep water and other drinks cool without electricity.  Yes, we are talking about home made fridge.  With this fridge, you can keep drinks and water cool.  So let us tell you how to make this fridge. 1. For this, first of all you will need two pots (one big pot and one small pot) and sand. 2. Now fill some sand in the big po...

To inspect a part using a head - shot, the part is clamped between two electrical contact pads. The magnetic solution,called a bath, is then flowed over the surface of the part. The bath is then interrupted and magnetizing current is applied to the part for a short duration. typically 0.5 to 1.5 seconds.(precautions should be taken to prevent burning or overheating of the part)  A circular field flowing around the circumstances of the part is created. Leakage fields from defects then attract the particles to form indications. When the coil is used to establish a longitudinal Magnetic field within the part is placed on the inside surface of the coil. Just as done with a head shot, the bath is then flowed over the surface of the part. A magnetizing current is applied to the part for a short duration, typically 0.5 to 1.5 seconds, just after coverage with the bath is interrupted. (Precautions should be taken to prevent burning or overheating of the part) Leakag...