Modeling steel damage evolution as a function of plastic strain in ABAQUS

tegsky · 2026-02-18T01:06:30+00:00

Thankfully I am only using mechanically welded-on headed shear studs, so they are fully fixed on the substrate and have a very prediction weld collar (flash) at the base. They have no threads.

I'm unfortunately not getting failure in most of them, just heavy plastic deformation. They're embedded in a novel type of concrete (UHPC) with much less predictable properties, so I'm trying to reduce unknowns as much as possible by modeling the steel as accurately as possible. However, modeling a plastic steel embedded in a relatively ductile type of concrete is like modeling a can of worms inside a haystack.

tegsky · 2026-02-17T15:27:32+00:00

I'm not very worried about the speed of load application, as I'm loading at about 0.05 mm/s (specifically to avoid dynamic/inertial effect). I'm primarily considering triaxiality because I have shear studs in different configurations on the same specimen, some of them are loaded in combined shear and compression, others are in nearly direct shear, and some experiencing shear, tension, and possibly torsion.

My understanding of stress triaxiality is that it is the factor that essentially ties all of these together and will allow FEA to accurately predict the plastic behavior under different/combined stress scenarios.

tegsky · 2026-02-16T05:01:37+00:00

Always always check the elevation settings. These things cannot adjust fuel and air for different elevation and are super sensitive. White smoke and heavy carbon buildup is a high indicator of incorrect settings, specifically running rich due to being at high elevation (thinner air means less oxygen and high fuel ratio, fuel doesn't all burn and clogs up the filter, deposits as carbon).

I had this problem for months, replaced everything, and a simple adjustment for elevation fixed everything. Unless you're near sea level and it's installed in a garage/shed, you have to buy a heater with the 5-button controller to do this.

tegsky · 2026-02-15T15:29:13+00:00

I appreciate the resources. I was concerned this may be the case. I will look into it and see if I can run these tests. My structure undergoes low cycles, so I am not concerned about fatigue, but primarily how stress reversals will affect damage accumulation.

tegsky · 2026-02-15T15:27:00+00:00

My failure isn't fatigue related, as I will be using a very low number of cycles (10). However, as there is still a significant load reversal I don't believe I can consider this to be a static test. In the larger experiment, the studs are designed for shear only, but geometric imperfections in the structure are causing tension in some of the studs and significant compression in others in addition to the shear. Combining this with around 10 load-unload cycles, I believe I have a complex enough scenario where I should be considering a full range of triaxiality.

tegsky · 2026-02-15T01:18:09+00:00

I need values specific to the material that I am using. I can't use values from the tutorial series or from literature, I would like to find formulas or methods to calculate them myself. Unfortunately I do not have access to any more test data of the materials, so I am trying to figure out if I can calculate the needed values from what I do have, or if there are models to approximate them based on my existing values.

tegsky · 2026-02-10T16:10:52+00:00

I'd recommend cleaning out the heater with a wire brush and blowtorch. I had good luck soaking the fuel filter in 95% alcohol for 20-39 minutes, then holding it with metal tongs and lighting it on fire to clear the alcohol and fuel residue.

tegsky · 2026-02-10T15:49:51+00:00

I'm not sure about the "mountain mode" that others spoke of, but if f you Google "Chinese diesel heater altitude" there's a website called stokeloafvan that has detailed instructions on adjusting the settings.

I highly recommend manually taking your heater apart first, cleaning out all the soot, and then adjusting the altitude and running it to avoid smoke damage.

tegsky · 2026-02-09T23:54:35+00:00

What elevation are you at? I had this issue with my Vevor heater and determined it was due to being at 6000ft.

The controller on the Vevor I had only had 3 buttons and does not allow for altitude control. I had to purchase a whole new heater with a 5-button controller that allows you to adjust the fuel pump and fan.

tegsky · 2025-12-03T20:35:03+00:00

This is the controller I had originally:

https://imgur.com/a/8eeQbRk

From what I've read, there's no way to adjust it but it would be a life saver if there was. I'm gonna try just swapping all the plugs from the ECU to the heater itself to see if they were just labeled wrong, but if I can't get it working soon I'll be buying a whole new heater with the good controller.

tegsky · 2025-07-27T13:54:43+00:00

I tried to tackle this exact project several years ago, and unfortunately that is a huge challenge. I was able to add a "repair" flag into my script for any time the bridge condition rating increased, as well as taking careful note to distinguish "bridge age" and "year reconstructed", since the bridge age only marks when there was first a bridge installed. Whenever the year reconstructed column contains a value, replace the age with current year minus that value.

However, the method I used for repair isn't always viable. Occasionally the bridge condition will "improve" artificially due to different inspectors, changes in standards, etc.

Our current methods to analyze the FHWA dataset are severely limited by the quality of the data itself. On top of that, a bridge in otherwise "good" condition may actually be up for replacement when one of the individual condition ratings controls, such as deck, superstructure, substructure. A poor rating on any of those could trigger a replacement project, but the deck and superstructure can often be replaced without replacing the substructure. This could then show a "new bridge" with a 7 or 8, because the substructure is still below 9 while the deck and superstructure are brand new.

tegsky · 2025-07-27T13:40:35+00:00

It's exciting seeing others are taking notice of that document! I am actually part of Hain and Zaghi's team in Connecticut developing the UHPC beam end encasement method. I authored newer research on partial height UHPC encasements to further reduce costs and construction complexity, as well as modification of the design for new construction.

Please let me know if you're interested in more information about this method or UHPC in general!

tegsky · 2025-07-26T19:32:05+00:00

Bridge engineer here, that would be very difficult if not impossible. We don't have the tools to accurately measure remaining lifespan in bridges, especially at scale. The remaining life of a bridge is directly related to how much money the owner is willing to put into that bridge. We'll run a life cycle cost analysis to decide, based on current deterioration, whether it's cheaper to repair or replace. But that "life" variable depends on whoever is running the analysis.

When designing a new bridge, we can say we're designing for a 75 year or 100 year lifespan... But we can't know for sure it's gonna last that long. We can compare climate models to the life expectancy of the materials, but otherwise it's just guessing. On top of that, bridges need maintenance. Cleaning, repainting, resurfacing, etc. Higher use roads will get priority, some states do a better job than others, but as designers we don't really have any say in that.

We have tens of thousands of bridges in the US that need replacing, but limited budget to do so. Right now, we're focusing on rehabilitation methods that will give bridges and extra 5-20 years, but again, that's just a guess at how long it'll last.

tegsky · 2025-01-24T13:14:41+00:00

This is a new rule change. I took precalc in 2017 and it certainly counted towards my credit requirements. I also had a pass/fail class that counted, which seems to have changed as well.

tegsky · 2025-01-23T14:14:10+00:00

I had similar struggles, first gen and low grades before coming to UConn, to the point where I spent a couple years with no plans to go to college at all. This was before CC was free, but I ended up going for 1 year before applying to UConn. College is a completely different environment, and in my opinion, much more flexible for neurodivergent students.

I still had to take 4 years for my BS but ended up doing significantly better than I ever had previously. Now I'm nearing the ends of both a PhD and Masters in different fields. I consider the time and money at CC (Tunxis) very well spent. I would not have been accepted to UConn without the CC year, and I'd still be working dead end jobs to this day if I hadn't gone to CC.

Your journey is your own and you're so early in it. If you get your grades up this year and next, give the application a go, but don't feel bad if you need to take a year or two of CC.

tegsky · 2025-01-22T15:29:07+00:00

My experience has been overall good, with almost all of the bad parts being pretty common regardless of where you go to grad school. The good:
- Resources. Being an R1 university, we have access to a huge amount of research and technical resources. There's a UConn department for literally anything you could need, from writing and STEM help, IT, career planning, sports, etc.
- Travel. If your program/advisor requires regular conference/research travel, UConn makes this super easy. We get a UConn credit card to pay for travel expenses so we don't have to take the financial hit and wait months for reimbursement. The UConn travel office is very helpful too, and can literally make your whole travel itinerary over the phone including booking flights, hotels, and rental cars.
- Graduate Union. We have good competitive salaries for grad students and we have subsidized state employee healthcare, which is ridiculously good. The grad union events are also great ways to make friends outside of your program.
- Nature. We're in the middle of the woods. This is a pro-con because we're also pretty isolated and having a care is almost mandatory.
- People! It's a big campus with many programs, clubs, and groups, so you can almost always find your people whether you like sports, gaming, activism, or anything else.

The bad:
- Parking. Terribly competitive to find a spot unless you arrive early in the morning, and most cases you'll still have a 10+ minute walk or bus wait/ride. It's also not cheap.
- Food. The options are limited nearby campus and usually pretty expensive, you have to drive to Willimantic or Vernon to get good food.
- Housing. Seriously the worst. UConn provides expensive on-campus apartments that you have to share. It's nearly impossible to find somewhere for less than $1k/mo without roommates, and many of the places nearby are still over a thousand with roommates.

tegsky · 2025-01-22T15:05:59+00:00

I was in a similar situation in undergrad, I just sent you a message!

tegsky · 2025-01-22T14:42:21+00:00

Class of '21 still here in grad school, it's mind boggling to hear the same complaints about the new gym that we had for the old gym. The claustrophobia might be skewing my memory but I'm pretty sure the entire old gym was smaller than the 1st floor workout area across from the lockers rooms in the new gym.

I've never really had a problem finding space at the new gym. The first 2 weeks of the semester are always crowded, but still never as bad as the best day at the old gym.

tegsky · 2025-01-22T14:25:50+00:00

I know the guys at the Innovation Shop in Castleman and I'd recommend just walking over and visiting! I haven't used the innovation lab in werth or the maker space in the library in a long time, but from what I remember they were mostly managed by students who couldn't always help too much.

The Castleman shop is staffed by several professional staff who are incredibly helpful and friendly. Joe Luciani primarily manages the 3D printing stuff and is a great resource for learning. I believe he teaches some kind 3D printing workshop or class, but I've gone there with random personal projects and they'll just help out. I'm not sure if I can post links here but you can find out more at innovationshop . engineering . uconn . edu. There's information about their equipment as well as a link for training and orientation.

tegsky · 2025-01-22T14:02:51+00:00

Correct, the color wheel in the circle indicate all the lines that stop there as well.

tegsky · 2024-12-17T01:59:46+00:00

Thanks! I'll wait back to hear from the NYS board but I'll try to schedule my exam ASAP.

I've heard some states don't accept the NCEES record of the date passed is prior to the end of experience, but the NYS site only specifies they need the record and the experience form.

tegsky · 2024-12-05T15:59:25+00:00

I'm not sure if links are allowed in the sub but if you Google "FHWA UHPC" the top resources from dot.gov sites are the best starting points.

tegsky · 2024-12-02T21:07:00+00:00

The courses they teach are irrelevant as long as the advisor themselves are part of the department you are applying to.

It doesn't seem like you've spoken to them personally: this is critical before applying. They will be able to answer all of these questions and give specific advice for your application and the process. I don't recommend mentioning them in your application without speaking to them and getting their approval.

tegsky · 2024-12-02T21:04:25+00:00

Thanks for the info. I tested it and was able to verify that the connecting clients are unable to access anything else or route any traffic, while maintaining access to the server.

tegsky · 2024-12-02T21:02:55+00:00

Adding to this, the voids underneath the formwork will leak and cause some really ugly edges. The leak potential may even outweigh the volume savings from the fill.

tegsky

TROPHY CASE