Non-engineer here so excuse my amateur terminology. I was watching a video on why rebar is put into concrete. It showed how a concrete beam, when pushed down on, compresses at the top and stretches apart at the bottom, and it's the bottom where the crack shows first. I thought this was caused by basic angles, but he said it was because concrete can resist compression excellently but not stretching (i.e. tensile pressures), thus the cracks forming at the bottom where stretching occurs and not at the top where compression occurs.
Is there any solid material that buckles under compression but has great tensile strength, such that it would crumble/fail from above first when a beam is pushed down on? Or is this impossible? If so, would they have any special uses?
According to Wikipedia, bulk modulus is
> a measure of how resistant to compression that substance is.
According to Wikipedia, compressive strength is
>the capacity of a material or structure to withstand loads tending to reduce size (as opposed to tensile strength which withstands loads tending to elongate). In other words, compressive strength resists compression (being pushed together), whereas tensile strength resists tension (being pulled apart).
What's the difference? It seems like both are the same thing - a measure of how resistant to being compressed something is - and yet, substances like aluminum oxide (Al2O3) have drastically different values for bulk modulus and compressive strength.
Why?
Basically pressing clay powder into moulds at around 2000psi to make ceramics. Right now we’re using PTFE due to its easy machinability, but they don’t last very long before deformation begins. An alternative is Aryldite moulds, but we’re needing to use Talcum powder as a release agent between presses. Want to stay away from talc for obvious reasons.
I was thinking about machining steel moulds and then coating it on top with PTFE.
Anyone had experience creating very low stick moulds for hydraulic presses?
Hello! As part of my thesis i casted some mortars of portland cement with some additional/different ingredients and they achieved a compressive strength of 22MPa. I'm trying to find the general uses of Standard 20-30MPa portland cement and anything else i can compare my mortars to. Any useful links? I've only found some blogs
Can anyone tell me how can I show compressive strength analysis of My model in COMSOL? I have done the Von Mises stress analysis which gives me the tensile strength of my model. But what about the compressive strength of it?
Hi all,
I'm playing around with the idea of making a custom dart surround and was looking at pouring a polyurethane into a mold, but I have no idea what kind of densities or compressive strength properties etc a normal surround are made of, or what properties best to look for when selecting a 2 component PU pouring kit for example..Most online sellers just mention "High density PU" or something similar, but no numbers or specifics.
Any advice is welcome, thanks!
Hi all.
I designed a simple 42x42x35 conical foot for a set of Ikea shelving that wasn't quite tall enough to clear a power socket. The shelves themselves have a plastic screw-type foot, which I've designed to fit into the cone. Designed in TinkerCAD, imported into Prusa, and sliced to use what I understood to be the strongest infill option, Gyroid, at 50% infill. Stuck a little rubber circle on the base to make sure they don't slide around on the wood floor.
The shelves themselves aren't that heavy, but do have a bunch of stuff on, ranging from board games to plants. They seem to be working great and have been in place for a month now, but I've noticed that there seems to be a little sway in the shelves that wasn't there when I put them in. Is this just the compressive force taking its toll and giving a little extra play in them, or should I be genuinely concerned about my prints and PLA (or the way I've sliced and printed) won't withstand the force and I should remove them asap?
Pictures of the actual item in situe and a prusa screencap of the type of infill used:
https://imgur.com/a/y8TCZfn
Thanks in advance!
I have a character who is very dense, its her super power. Despite looking normal she weighs roughly 865lbs-1000lbs. Because of this a surface's compressive strength could play a factor depending on the material. In this case another character has made a small bridge about 6 ft long peaking about 15 inches at the highest point with 3 inches of ice beneath that point over a gap. Leading up to this point is a 30-40 degree incline of solid ice. I know that ice gets stronger the thicker it is, but at the edges of this bridge it would crunch more easily under her weight.
At what point does the ice stop breaking as she walks over the bridge, before she reaches the gap. Google keeps giving me answers in MPa and I do not know how that translates to weight.
Hey guys,
I am trying to model behavior of high strength concrete and need data for high strength concrete (90 - 120 MPa). Does anyone have stress strain data for high strength concrete in compression and tension?
I am trying to model the compressive and tensile behavior of C120 concrete in Abaqus, but I cant find tabular data for this material. So I am trying to use a numerical equation which requires max compressive strength and ultimate strain. But I can only find characteristic strength of C120 concrete, and I would guess the ultimate strain would be the corresponding strain at this point?
https://preview.redd.it/c85860u433k41.png?width=634&format=png&auto=webp&s=ff4f8c38ee58bea9320e30a7022505f679768bfd
For the life of me I cannot find a good and consistent answer to this anywhere for some reason. it would be great if someone just linked me a source or something, but I've seen answers that say it's 162GPa to something as nutty as 700GPa+. I find the second one incredibly hard to believe, and I'd like a consistent answer.
I’ve seen those three versions in several codes and documents. I am wondering which one is the correct one, just for consistency in my writing. It seems to me ACI 318 has fc’.
Thank you in advance.
Hi,
I am doing research on biomedical device development, and focusing on devices that work on grasping tissues in the abdominal area. I need some help with applying the concepts of material strength to human tissues.
In simple language, let's assume that the stiffness constant (or the spring constant, K) of a given tissue is known, and we assume that it is a constant and hence the compression of the tissue is linearly proportional to the compressive force applied on it.
Given that we know K, is there a way to figure out the upper limit of the Force or the upper limit of the compression I can allow, before the tissue gets damaged? i.e. can we estimate the compressive yield strength of the tissue given that we know its K?
Another small confusion: If we are talking about the point at which tissue damages, is that the point of yield strength or ultimate strength?
I'm familiar with basic solid mechanics and strength of materials on a very beginner level and I'm getting stuck in applying those concepts in the context of biomechanics. Any help in this direction would be really helpful.
PS: This is not Homework help, I work as an RA and I'm stuck at this issue in my research :)
If to search this question on the internet you will find out that a lot of experimental research has been conducted on this question, but it's extremely difficult, perhaps even impossible, to test all factors that may have an influence on the compressive strength. Therefore, researchers tend to choose 3-4 factors to investigate - but that creates a obvious problem: How should these factors be chosen?
I would like to conduct a simular research for my specific problem, so I have come up with a questionnaire to collect different opinions about what parameters should be investigated and find out the answer based on the experience of the participants.
The questionnaire only consists of a few questions, so it should take like ~3 minutes, but it would help me out tremendously. The link is https://forms.gle/H9wjhadbwjuNq8qL9
I'll be greateful if you can partcipate.
What is the correlation between the concrete thickness and its compressive strength? Is there an equation for this?
