[mactec54]

Hi all you CNC addicts out there - I came across this UHPC that gives you 45GPa out of the bag. Available most places USA. Peter

This is better than Ductal and worth a look they are both connected in a way but different companies, this one has much more development than the Ductal https://cor-tuf.com/about/

[mactec54]

Molds look interesting simple to make using urethane in this video they are Ductal to fill the molds

https://www.youtube.com/watch?v=xCInf88ZPrQ&t=4s

[peteeng]

Hi Mactec - Yes urethane is used as it can be flexed to release the part and to an extent it self-releases but a good wax is needed. With stiff parts like machine parts if you had a stiff mould you would need to do an air or water pressure release. I was thinking about using the HMC for the mould but I'd have to make jacks or use water to release... Plus use good draft angle for easier release although with urethane it could be square. Peter

I looked up cor-tufs modulus and its 45GPa so same as Ductal... seems to be a std number for std UHPC 40-45GPa

[mactec54]

Hi Mactec - Yes urethane is used as it can be flexed to release the part and to an extent it self-releases but a good wax is needed. With stiff parts like machine parts if you had a stiff mould you would need to do an air or water pressure release. I was thinking about using the HMC for the mould but I'd have to make jacks or use water to release... Plus use good draft angle for easier release although with urethane it could be square. Peter

I looked up cor-tufs modulus and its 45GPa so same as Ductal... seems to be a std number for std UHPC 40-45GPa

Yes the standard mix is the same I spoke with the a guy there and it can go to more than double the standard rating the guys name is Doug if you want to contact him they have different mixes and can customize to what ever your needs are but 45 GPa is most likely good enough for any machine parts

[peteeng]

Hi Mactec - Getting a bag of concrete from USA to OZ would be very $$$. I'll test what I have here. I buy a 20kg bag of E45 grout here for $32AUD, freight would be enormous ex US..
Peter

[peteeng]

Evening All - I found a piece of aluminium flat bar today that maybe good to use as a benchmark. Its 80x6mm thick and 1500mm long. I clamped it to the bench and roughly measured its deflection under gravity at about 15.5mm for a 1000mm span. This was a quick and rough attempt. I then modelled it in simsolid and it calculated the deflection under gravity as 15.4mm so were good to go. Making 6mm thick alox epoxy is not a problem but maybe a bit thin for the HMC we shall see. Getting closer to reality now... Peter

[mactec54]

Hi Mactec - Getting a bag of concrete from USA to OZ would be very $$$. I'll test what I have here. I buy a 20kg bag of E45 grout here for $32AUD, freight would be enormous ex US..
Peter

I'm sure you could formulate the same with there help no need for any shipping

[peteeng]

Hi All youz out there and Mactec - I've had help from 2 German companies, one chinese company, a local concrete engineer and a local specialist concrete company. I think I've covered the bases enough, now have to get on with it and prove out all that help... Peter

[ardenum]

I've seen some UHPC recipes have flux added to them, CSA needs that too?

[peteeng]

Hi Ard - Haven't seen anything like flux mentioned. I'd stick with out of the bag mixes... let the chemists do their job... Peter

[peteeng]

Hello All & Sundry - This morning I did a quick deflection test on the aluminium flat bar. Scored 91% of theoretical which is OK. If doing it proper should turn the beam over and repeat to balance out any internal stress. So the quick check gives 63Gpa and 6000 series alloys are 68-69GPa depending on which book you look at... Close enough for now... I used motor mounts and a spindle clamp for weights. So now need to build the test moulds... Peter

[pippin88]

Peter, it hink you are better off getting an alu section that will be easier to mirror in cast parts.

Like 20x20mm section at least.

I only see dial calipers - is that what you used for measurements?

I would use a dial indicator setup and zeroed then add weight.

[peteeng]

Hi Pippin - Need something that can flex easily so the deflection is big. I like a challenge re- part thickness. I did a quick reality check for the AL stiffness a dial guage wouldn't have enough travel in this case so vernier it is. No point in doing a white coat exercise on ally! Trying to illustrate that you don't have to be too technical to get an order of magnitude result. If I go all out white coat, dial indicators, fussy etc then less people will try to do it?? Also I want to put the test piece and alum piece side by side so people can see the difference. If I use a stiff piece this won't work. People get glazed eyes with too much math.

I've rummaged around and found some 6mm MDF I'll slice that up tomorrow and see how it goes for a mould. If no good then I'll get something else. Peter

[ardenum]

So I made the column from E80/E45. E45 price is ~900EUR. E80 probably at least double of that(haven't received a quote yet). I was thinking of running 4 rebars and then grouting the column to the base.

https://i.imgur.com/92AiDcS.png

[peteeng]

Hi Ard - I suggest you don't use steel cages in parts. Machine parts are not like construction beams. Machine parts need to be homogenous and have no preferred strain paths within the part. The cage will create a preferred strain path as its 200GPa stiffness vs the UHPC at E45 or E80. If you connect the cage to the inserts again this can become a preferred path for vibration and strain. I suggest you add steel fibres to the UHPC vs using a cage if you are concerned about cracking. Plus if you look at the photos of mould preps in Rampf and others there are no cages and the inserts and thread inserts are not connected to any internal structure.... Peter

[peteeng]

Hi Al - I have the long moulds sorted. They are white melamine boards. Didn't like the 6mm MDF so got some 11mm pine and will thickness that down to 6mm next week. Moving along ... Peter

[badhabit]

Hi Al - I have the long moulds sorted. They are white melamine boards. Didn't like the 6mm MDF so got some 11mm pine and will thickness that down to 6mm next week. Moving along ... Peter

Any pictures of the moulds?

[peteeng]

Hi Thomas - When I get them set up I'll post some pics. But they are a melamine board top and bottom with some 6mm pine keeping them apart. The mould will make a plank 80x6x1100mm long. I think I'll do an epoxy/ALOX one first then the alox/cement one. The grout supplier has dropped their price from $2.90 AUD /kg to $1.55AUD per kg for E34 out of the bag... They call it high strength grout...Very happy with that...Peter

I was reading through some test results for the grout I'm using. Its self deairing and one test puts air content at 1.3% by volume. That's really low, in the composite world you have to do a lot of work to get to that level in a laminate...

[badhabit]

I think I'll do an epoxy/ALOX one first then the alox/cement one. The grout supplier has dropped their price from $2.90 AUD /kg to $1.55AUD per kg for E34 out of the bag... They call it high strength grout...Very happy with that....

One thing i was wondering: Isn't there a correlation between stiffness and damping somehow? My reasoning tells mere there is. If true, then it is not only a goal of getting the highest possible stiffness, but a compromised between high stiffness and good damping. If so, where that sweetspot is would be interesting, and not just a race to the highest possible stiffness...ergo E34(or EG for that matter) may perform better than some E80 in a real-world machinebase....just a "showerthought"...

[peteeng]

Hi Thomas - With composites I don't think it works that way. Even with metals their dampness ratios are "similar" vs their stiffness. So I'm not concerned that the E80+ material will be less damp then the E35 material I think they will be about the same. Peter

https://durcrete.de/technical-data-nanodur/?lang=en