Best common metal for "passing" permanent magnet's magnetic field
Best common metal for "passing" permanent magnet's magnetic field
(OP)
Hi... im currently on a project where i need to design a system to inspect metal crack by using Magnetic Flux Leakage. due to portability and power factor i've decided to use permanent magnet as the system's magnetizer due to its passive properties (does not need external power). The magnet have pulling force of 60kg. This will surely stick very strongly to the metal going to be inspected. so my ideas to solve this is to attach a metal on the magnet surface. this will prevent the metal going to be inspected from sticking to the magnet but at the same time it can still "pass" the magnet's magnetic field to the metal going to be inspected.
So my question is, lets say, the metal going to be inspected is mild steel, what is the best metal to be used as the "passer" metal?
So my question is, lets say, the metal going to be inspected is mild steel, what is the best metal to be used as the "passer" metal?
RE: Best common metal for "passing" permanent magnet's magnetic field
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RE: Best common metal for "passing" permanent magnet's magnetic field
Anyway the best material for the intended use is aluminum: light and not very expensive. Alternatives are plastics or even wood, the latter being likely not compatible with ambient conditions.
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RE: Best common metal for "passing" permanent magnet's magnetic field
RE: Best common metal for "passing" permanent magnet's magnetic field
For both I would suggest you to design a conical type metal part where in you stick the metal part on the magnet pole and the smaller area would be placed on the etal you wish to inspect.
All the Best
N D Senthil Ram
RE: Best common metal for "passing" permanent magnet's magnetic field
the tapezoidal part is the passer metal. the black parts is just attachment to hold the passer metal.
RE: Best common metal for "passing" permanent magnet's magnetic field
Yes the shape confinement will now minimize the attaction and also pass the magnetic flux
The passer metal should be low carbon steel or SS340 magnetic steel to pass magnetic flux through the passer metals
Now let me know how you test the Magnetic Flux Leakage by detecting the crack.
Based on your model the flux will narrow down on the bottom side of the passer metal and the crack which you need to detect should be between the two pole
Its better you measure the magnetic flux after attaching the passer metal on the magnet and still if you need you can confine area at the bottom portion
RE: Best common metal for "passing" permanent magnet's magnetic field
Does low carbon steel and the ss340/430? comes in block form? (it needs to be in block form so it can be machined down to the shape) anyway the passer metal dimension is 15.9mm in width, 85.7mm in breadth and 20mm in depth.
RE: Best common metal for "passing" permanent magnet's magnetic field
The idea to detect defects, e.g. crack, hole, dent, by magnetic flux leakage is also good.
However, unless the hole is very big, no idea how to practically detect the magnetic field changes caused by the defects. Actually, the stronger the magnet, the easier would be to mask the field difference caused by defects. Also, the low reading would indicate a crack, not the opposite.
btw, SS 4xx is magnetic, 3xx is not
RE: Best common metal for "passing" permanent magnet's magnetic field
Is there any simulation software that is suitable to simulate permanent magnet's MFL so that i can find out what is the right depth of the passer metal to detect the crack? all i have is COMSOL Multiphysic, but i have not been able to simulate the MFL for the permanent magnet.
RE: Best common metal for "passing" permanent magnet's magnetic field
RE: Best common metal for "passing" permanent magnet's magnetic field
I have a suggestion here, if you can put a coil near to the crack and increase the current step by step going through the coil which will increase the flux flowing through the metal proportionately. For every step measure the change in the flux leakage. At one point you can optimize how much magnetic field is required to detect the crack with magnetic flux leakage
If you want to do with permanent magnet, you have to increase the thickness of the passer metal, say you’ve multiple passer metal thickness and you can suitable vary the thickness
RE: Best common metal for "passing" permanent magnet's magnetic field
Unless someone can give me the formula for calculating the magnetic flux flowing inside the metal both the permanent magnet and electromagnet... i dont need to do the try and error step. By the way does electromagnet have identical properties like permanent magnet for my case? what i mean is that, does the same amount of magnetic flux flowing inside the metal will yield same result for both electromagnet and permanent magnet cases?
RE: Best common metal for "passing" permanent magnet's magnetic field
Please find the magnetic properties of E818 (Alcomax III)
MDL
Grade DIN Br bHc jHc BHMax
mT Gauss KA/m Oersted KA/m Oersted kJ/m3 MGO
ALCOMAX III 43/5 1260 12600 52 650 53 663 43 5,4
Yes if the magnetic field of electromagnet and the permanent magnet are identical, the flow of flux in the metal will be the same. Right now I don’t have the formula or notes in hand that would help you, however I have the material to calculate.
RE: Best common metal for "passing" permanent magnet's magnetic field
MDL Grade ALCOMAX III
DIN 43/5
Br mT 1260
Gauss 12600
bHc KA/m 52
Oersted 650
jHc KA/m 53
Oersted 663
BHMax kJ/m3 43
MGO 5,4
RE: Best common metal for "passing" permanent magnet's magnetic field
RE: Best common metal for "passing" permanent magnet's magnetic field
Since there is no information about your kind of detection technique, may i propose to take a look at magneto-optical sensors, which are very good suited for that kind of application.
You can use either in in-plane as well as out-of-plane Bias magnetization and since MOs are visualizing flux directions and densities over up to 3 inch areas in real time you can get a very high resoltion regarding your crack inspection.
I am working on some projects regarding that my own, so if you are interested in sharing thoughts as well as you are interested in seeing some results of crack detection, just contact me.
Have a great day,
Marco