8 Replies Latest reply on Nov 24, 2016 4:14 PM by Maurits De Wolff

    simulation settings

    Maurits De Wolff

      Hello,

       

      I am trying to run a 'light' simulation on an auto crane. The school assignment is about the driveline of the crane system (electromotor, hydraulics, etc). I like Solidworks but I should not deviate too much from the real subject.

       

      The problem is I'm guessing the simulation is taking too much time. Guessing is all I can since I'm a solidworks rookie.

       

      I've read things about solidworks not taking advantage of multiple cores, contact sets not the right connectors for simulation, applying mesh control which tend to use more than one core amongst other things. Settings for this simulation are mesh controls of 15mm at the hinge parts and load bearing welds around the flanges at both sides. I put the global mesh at approximately 300mm (large beam parts mostly). I selected direct sparse for solver. Also, my sense is that I don't need a fixed point at the foot of the column (under the slewing ring). Two bearing features as assigned should be okay, as they are under real life conditions. Am I correct?  I calculated on paper that 25mm pins through the forked hinge parts should be good for the applied weight. Can someone knowledgeable look at my setup and comment please?

       

      Thanks maurits

        • Re: simulation settings
          Gian Flavio Violi

          Maurits,

           

          Downloading right now. I'll give you an update in a few hours since I have a couple of meetings.

           

          Right of the bat though, I can see that you used Solid Mesh for the problem. As I haven't actually see the 3D CAD, I think using shell meshing (or actual beam meshing) if posible would be better. How are all the elements of the ASM/PART held together?

           

          GF

            • Re: simulation settings
              Maurits De Wolff

              You mean 'connections' in the statics tree to left? The hydrailic cilinder has a mate distance of 32mm I believe which alows the piston to retract completely. Since the distance mate locks the hydraulic assembly I did not fix the front face of the piston to the bottom of the cilinder in static mode.

               

              Under component contacts I have the global contact @ no penetration. And all moving (sliding, rotating) parts @ no penetration. Again, because of the vertical down pressure I figured there is no need to secure these parts for simulation. Solidworks would have complained about this if it were a problem. So I think this should be fine. But there is a whole lot that I don't know.

               

              I appreciate your looking at it.

                • Re: simulation settings
                  Gian Flavio Violi

                  Maurits,

                   

                  When you define every connection as a global connection it makes the simulation so much longer to run, isn't even worth it to save time not defining local contacts set-up. You are telling SolidWorks that every node of the model is bonded with all the rest of them, this isn't efficient computationally speaking.

                   

                  What I suggest you should do is set up propper contact sets for the interacting parts and leave the global contact to bonded (just in case you missed one contact). This way your sim should be abble to run even if you have a few mistakes and you can check all the stresses on contact regions to see if you slip up one; most of the time its pretty obvious to see if you have a bonded contact instead of the no penetration because of the stress concentrations you see on faces that are pulling way from each other.

                   

                  Another thing you should do is chaging the pins you use to connect the hidraulics of your system. Instead of using an actual part, use pin connectors (or even bolts is you want to check for pre-loading stress and bolts failures). This should make your sim run a lot smoother and faster.

                   

                  I would tackle this issues first before moving forwards.

                   

                  Keep posting me updates so I can help you get to the finish line. Since this is a school project I don't think is fair I give you a handout (just kidding)!

                   

                  Regards,

                  GF

                    • Re: simulation settings
                      Maurits De Wolff

                      I can't run the study, Gian.

                       

                      I replaced each hinge part with 2 pins (both sides). I did not change the rotational stiffness of the pins. They should slightly rotate under stress. I meshed the boom parts as beam and the hydraulic components and column as solids. The solver is FFEplus.

                      When I hit Run This Study SW complains it wants bonded contact sets between beam and solid. That's the pins I just put in.

                       

                      What do I do wrong here?

                        • Re: simulation settings
                          Gian Flavio Violi

                          Maurits.

                           

                          Yes, beam meshing isn't an option now. Gotta switch to a shel messhing, thats why I said "if posible" on beam meshing... I wasn't 100% sure you could because of contacts limitations. The next thing to do would be setting up shell meshing for those beam elements. 

                           

                          There is a series of videos in youtube made by SolidWorks Technical Specialist called the Simulation Step-up series. I suggest watching them all and subscribe to the SolidWorks channel as they are still posting new videos on this series (last one was updated 2 days ago). Particularly this section of the series could help you a lot going forward, its about how to set-up beams for shell meshing. Also, take a look into contact set-up videos.

                           

                          Also, I'm gonna take a really deep look into your model and what you are doing to provide you further assistance going forward and pointing out where you could improve your model. As of right now I'm a little busy setting up my week long traning session for a customer, maybe in a few hours I can post you an update on that, if not tomorrow at last.

                           

                          Lets take this one step at the time.

                           

                          Regards,

                          GF

                            • Re: simulation settings
                              Maurits De Wolff

                              I've on the internet in the meantime.

                               

                              I have a love/hate relationship with Solidworks Knowledge Base. Every so often in those tutorials some path (click here, select that from submenu, then click on pulldown menu and select  .... well it isn't listed. What tutorial version is this anyway, 2003 ? No, it's 2016. What it says I should find 3 layers down in some submenu just isn't there. Check tutorial again, maybe I missed something. Maybe SW people don't update carefully their Knowledge Base and I am looking at last years tutorial. Well, the option doesn't show in my menu. End of story.

                               

                              There is little info on bolts, almost nothing on pins. I ran into the video series you mentioned. I have a hard time following the Indian accent, but this guy (Ramesh I believe) isn't so bad. The tutorial is good and thorough. A bit too thorough since I'm in a hurry (deadline 30 november and other assignments waiting). So I skipped it but I should go back and watch them videos.

                               

                              Meshing is a murky business for the rookie. Multimeshed bodies or assemblies should be adjoined tutorial tells me. Knowledge Base explains what you can do with meshing but is not so clear on how to execute it, where to go in the menu's. Or the menu's don't line up with the online tutorial and I'm getting lost again. Same story with those pins. I cannot assign a value lager than 0 to the pins, or I don't know where to look. Ramesh goes into detail about extruding a pin of the same material and size, evaluate it and apply the tensile strengh, stiffness etc to the pins in the model. Solidworks doen't let me assign a value to the pins. During simulation there is going to be 570 kN on the hydraulic piston. While at the same time there is 'nothing' in those holes. I find that weird.

                               

                              I  will watch those videos again.

                               

                              Thanks for helping out.