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Linear Point Load Simulation Query

Question asked by Steven Brooker on Oct 31, 2013
Latest reply on Nov 19, 2013 by Jared Conway

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hi am just new to this forum and looking a bit of advice on simulating point loading. i am currently booked in for a 3 day course through pentagon solutions but is not happening for another 4 weeks. i am currently designing a ductile iron cover which needs to withstand a point load of 12.5 tonnes.

the cover itself rests in a fixed frame and so i put fixtures on all the contact point but i am un sure is this the right way of doing it. the test block size in actual life is a diameter of 250mm. to simulate this i created a split line circle area centre of the top of the cover and applied 12500 Newtons to the area.

I was looking at the ductile iron material properties and am i right in saying, when i run the simulation and if none of the values go over the yield point should this be fine.

If possible, would someone mind if i attached my assembly model with the simulation i have done at the minute and check am i doing this correctly?

Thanks in advance for the help as i have been trying different methods but i am unsure if i am going about it the correct way.

I look forward to hearing your input and many thanks.

Steven

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Jared Conway Nov 1, 2013 12:01 PM
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the cover itself rests in a fixed frame and so i put fixtures on all the contact point but i am un sure is this the right way of doing it. the test block size in actual life is a diameter of 250mm. to simulate this i created a split line circle area centre of the top of the cover and applied 12500 Newtons to the area.

>setup sounds good

I was looking at the ductile iron material properties and am i right in saying, when i run the simulation and if none of the values go over the yield point should this be fine.

>this sounds reasonable but consider that you might want consider what kind of safety factor that you want.

If possible, would someone mind if i attached my assembly model with the simulation i have done at the minute and check am i doing this correctly?

>shouldn't be a problem. just make sure to use pack and go to zip and attach with the advanced editor at the top right hand corner of your posting dialog.
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- Steven Brooker @ Jared Conway on Nov 16, 2013 7:01 AM
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  Hi Jared,
  Sorry for the delayed response. i have been booked in to go on a Simulation 3 day course in December to really get to grips with it but currently i need to use it to see if one of my covers will pass a simple vertical point load test.
  
  I Have aquired the material specs for the ductile iron being usedf and created a custom material for this simulation.
  
  the assembly wll consist of the cover being placed into a fixed frame and 125000N of force applied to a 250mm diameter area centre of the cover. the frame itself will only have seating on the frame on particular areas. am i wrong in saying that the bottom of the cover should be fixed as really in reality, when the load is applied to the centre, as the cover flexes, the bottom of the frame should have the freedom to flex a bit aswell and move but not penetrate through the area of the frame seating.
  
  I have been looking at the Factor of safety plot and i am a little bit confused. it first asks for muliplaction factor and then areas showing where it less than. i am looking this cover to ideally be able to take 40 percent extra of this force so can you please advise how i should this up.
  
  i know you are probably very busy, but if possible would it be ok for me to uplod this cover and frame on what i have done to present in the simulation and have a look at it to see if i am correct.
  
  please let me know and i shall upload
  
  Many thanks in advance
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  - Jared Conway @ Steven Brooker on Nov 18, 2013 11:42 AM
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    so for the load, it sounds like you need to apply a split line. to apply your load. but you'll also want to consider if the shape of the implement will affect the loading condition. if it does, you might wnat to make it a bit smaller to see how it affects the results. or if you want the "exact" solution you'll have to use contact.
    
    for the fixturing, fixed is a good first start but remember that is like supergluing it to the fixture. the only way to allow it to lift is to use contact which is going to increase the time it takes to solve. maybe start with something like a fixture on the inside edges only or an edge created by a splitline along the middle of the fixtured face.
    
    for factor of safety, i'm not sure what you're talking about. can you post a screenshot of what you're looking at.
    
    feel free to post the model using the advanced editor at the top right hand corner.
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    - Steven Brooker @ Jared Conway on Nov 19, 2013 4:06 AM
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      Hi Jared thanks fro your response. i have used a split line to boundary off the 125000N to the top side of the cover. i have attached the frame and cover assembly of what i have done so far. i dont know wether or not the frame is needed in the simulation of i just split line the area off which sits on the frame.
      
      can you please have a look at this as i have not added any fixtures as i am unsure which one to use. the frame in real life situation would be fixed and so it is just supporting the cover. i reckon having the whole underneath of the cover fixed is incorrect as it is only certain parts of the cover resting on the frame. can you please have a look and run the simulation on how you think it should be setup.
      
      as for the factor safety, i ideally want this cover to be safe to take 40% more of the force point loaded. when i run the FOS plot, should i put the multiplication fsactor as 1.4 and then on the next page ask to show areas under 1.4
      
      Thanks in advance for your kind help
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      Frame & Cover.zip1.3 MB
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      - Jared Conway @ Steven Brooker on Nov 19, 2013 12:33 PM
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        so for the fixture, start by using a fixed condition and take a look at how it goes
        you'll want to add a splitline to split the faces on the ribs in the middle so that you can apply fixed restraints only to those locations instead of the whole faces of the ribs
        
        i highly suspect that you'll wnat to look at some forum posts abotu singularities because i think they will start popping up with that type of restraint.
        
        once you get that running you can start looking at contact solutions to get it closer to what actually happens.
        
        extra tip, this looks symmetric, cut the model in half and save yourself half the analysis time.
        
        i'm still not sure what you mean by multiplification factor. are you talking about factor of safety? is so, your logic sounds good.
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Jerry Steiger Nov 10, 2013 5:35 PM
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Steven,

You say the cover rests on the frame and then you say you put fixtures on all the contact points. That sounds wrong to me. If the cover is just resting on the frame, then you ought to be using non-penetration contacts rather than fixing the contact points.

A weight of 12.5 tonnes should generate a force of 12,500*9.8 Newtons, or 122,500 Newtons, not 12,500 Newtons.

Jerry S.
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- Steven Brooker @ Jerry Steiger on Nov 11, 2013 4:07 PM
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  yes i understand now why i dont use permanent fixtures on the feet of the cover and will try using non-penetrating contacts ansd keep the frame as a fixed object. i am trying to replicate a hydraulic point load test which would be testing the force of 12.5 tonnes or 12500 Newtons. Why would the factor of gravity have to be in place if the test block is not being dropped but instead being driven by the force of the hydraulic rams?
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  - Jerry Steiger @ Steven Brooker on Nov 11, 2013 4:40 PM
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    Steven,
    
    Tonne is a unit of weight, not force. A newton is a unit of force that will accelerate 1 kg at a rate of 1 meter per second per second. It takes a force of 9.8 newtons to hold up a mass of 1 kg.
    
    Jerry S.
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    - Steven Brooker @ Jerry Steiger on Nov 11, 2013 5:21 PM
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      hi jerry, i need to apply 12.5 tonnes at a rate of 1kN per second. can this be setup in solidworks
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      - Steven Brooker @ Steven Brooker on Nov 11, 2013 5:34 PM
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        i understand now what you mean, if i was looking to simulate a side wall test, and perform a force, what would you take the acceleration to be?
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        Jerry Steiger @ Steven Brooker on Nov 13, 2013 3:43 PM
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        Steven,
        
        The conversion is always 9.8 from kg force to Newtons. (Actually 9.80665.)
        
        Jerry S.
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Linear Point Load Simulation Query

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