Remember to epoxy your woofer magnets!

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  • F1nut
    F1nut Posts: 46,272
    The sheer strength of any adhesive depends primarily on the materials it is used on. So, unless one can find a spec for its use with ferromagnetic material and steel all the other sheer strength ratings are useless. In fact, the sheer strength rating is pretty much useless as we are not bonding two materials in the traditional sense. What we are doing is called a fillet. A fillet is a continuous bead of adhesive applied in an angle between two parts.
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  • audioluvr
    audioluvr Posts: 3,706
    Definition of tensile strength. Doesn't mention anything about adhesion properties.

    a) the tensile strength, also known as the ultimate tensile strength, the load at failure divided by the original cross sectional area where the ultimate tensile strength (U.T.S.), σmax = Pmax /A0 , where Pmax = maximum load, A0 = original cross sectional area. In EN specifications this parameter is also identified as 'Rm';
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  • Gardenstater
    Gardenstater Posts: 2,015
    edited October 9
    The 3 common methods of measuring adhesive bond strength are tensile strength, shear strength, and peel strength. There is also tensile -shear (lap joint strength) and compressive shear. I would think peel strength would be a good one for us to know since, as f1 said, this is a fillet. It's also something the manufacturers don't ever seem to give info on. Shear strength and tensile strength are good too because, if the speaker is knocked over on its side or dropped in transport, the weight of the pole piece is going to try to break the bond at the magnet in shear and the weight of the magnet is going to try to break the bond at the inner plate in tension. That's only on the downward sides. There is actually a combination of shear and tensile failures occurring at different places. The only way that the fillet can fail is for the material to lose its grip and internal adhesive failure but they usually both happen at different places (base materials are stronger than adhesive), either because of a sudden shock, just plain poor bonding to the materials, and degradation due to material ageing and thermal cycles gradually weakening the grip over time. Here's a basic rundown of the main 3:

    https://www.applicheminc.com/blog/adhesive-strength-test-terms

    Also this is a really good video where he measures 10 different construction adhesives for tensile strength (wood and pvc) and shear strength (wood only) and he even throws in JB-Weld which is pretty cool. Too bad he didn't do them with ferrite and cadmium plated steel lol.

    Post edited by Gardenstater on
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  • audioluvr
    audioluvr Posts: 3,706


    That would be a good start on a comparison if they weren't using wood since a single board of wood varies greatly in porosity and strength. He should have used something like aluminum or steel.
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    There is about a 5% genetic difference between apes and men …but that difference is the difference between throwing your own poo when you are annoyed …and Einstein, Shakespeare and Miss January.

    by Dr. Sardonicus