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  • Aluminum 6061 Stress calculation.

    Discussion in 'The main mechanical design forum' started by kaarvannan, Jul 27, 2012.

    1. kaarvannan

      kaarvannan Member

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      Hello,

      I have designed a dovetail clamp. We machined it out of aluminum 6061 and tested it. While we were pleased with its clamping ability, the dovetail rail shown in the attached image developed these strange stress marks. The dimensions of the part have not changed. There are no visible marks on any other parts. Have any of you seen these type of stress marks before? What does this mean? Will there be pre-mature failure? How to strengthen this part?

      Regards,
      kaar.

      [​IMG]
       
      Last edited: Jul 27, 2012
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    3. GarethW

      GarethW Chief Clicker Staff Member

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      Photo doesn't work
       
    4. leiswyyy

      leiswyyy New Member

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      The photo is not available.

      The photo is not available.
      Why you use aluminum 6061? Could you change the material to steel?

      BR.
      leiswyyy
      --------------------------------------------------------------

       
    5. kaarvannan

      kaarvannan Member

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      [​IMG]

      We use Aluminum predominantly in all of our parts. If I choose steel instead, this would be the only part made of steel. Also, since we anodize (black) our parts, steel will standout from the rest of the components.
       
    6. leiswyyy

      leiswyyy New Member

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      Are these marks caused by manufacturing process?

      I wondered whether these marks come from manufacturing process (forming process?, pressing portion of fixtures?). If not, do these marks come from frition when this dove tail goes through rails?
      Steel can also be surface-treated to be black! Of course, you are right concerning the density of steel is different from that of other component(AL).

      Best Regards.
      leiswyyy
      -------------------------------------------------------------------------------------------------
       
    7. kaarvannan

      kaarvannan Member

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      Thank you for your observation!
      I am pretty sure these marks did not come from the manufacturing process. It couldn't have come from movement of the dovetail, as it is minimal. The rail merely allows the dovetail to be clamped at different positions on the rail. I barely moved it during testing. These marks have shown up at the only region on the rail, I tightened the dovetail on. So I am fairly certain that this is a strength issue.

      I couldn't begin to quantify the strength of that piece. I am completely lost as to what strength should I try to improve; shear? tensile? and how to go about doing it?

      Regards,
      Kaar.
       
    8. leiswyyy

      leiswyyy New Member

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      What about change the materials to aluminum 5052.
       
    9. Erich

      Erich Well-Known Member

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      5052 is not any stronger than 6061.

      2024-t3 and 7075-t6 are significantly stronger than 6061-t6. 7075 has strength approaching cold rolled mild steel.
       
    10. kaarvannan

      kaarvannan Member

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      leiswyyy is right. These marks have been formed during the manufacturing process. Being a prototype, the part was being held in two parallel vises, instead of dedicated pocket jaws. The marks have been formed in the region in between the two vises due to end mill chatter. Thank you.
       
    11. mechgo1977

      mechgo1977 New Member

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      I agree with kaarvannan, these are definitely machining marks, not stress.
       

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