Questions tagged [stresses]

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23
votes
5answers
5k views

Why exactly does a washer help distribute the stress around a bolt?

Usually the reason for having a washer under a bolt head is stated to be that it helps to evenly distribute the stress to the clamped material surface. But why is this? I would understand if the ...
15
votes
2answers
11k views

Why do we even use engineering stress?

Surprisingly this hasn't been asked before, so I must be missing something simple. We use engineering stress and engineering strain in this eq. Stress = (Young's modulus) × (strain). This eq. is ...
14
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1answer
1k views

Why does prestressing in trees make them stronger?

In "Structures: or Why Things Don't Fall Down" James Gordon talks about trees being prestressed with the outside in tension and the inside in compression. Why does it make a tree stronger to have it ...
12
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5answers
6k views

What is the difference between pressure and stress?

Since the units are the same ($\frac{N}{m^2}$), what's the difference between pressure and stress?
10
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3answers
3k views

Strength of a welded steel gate with vertical bars vs. crossed diagonal bars

Looking for some hints on how to create a rough estimate for the following problem. Given two steel gates with the same dimensions, same material - e.g. everything is the same. The only difference ...
10
votes
3answers
14k views

What is the difference between the Polar Moment of Inertia, $ I_P $ and the torsional constant, $ J_T $ of a cross section?

This question is so fundamentally basic that I am almost embarrassed to ask but it came up at work the other day and and nearly no one in the office could give me a good answer. I was calculating the ...
10
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3answers
4k views

How do you select the correct area to consiser for first moment of area calculations?

I have just begun studying mechanics of materials and I am struggling to understand intuitively how to select the area in first moment of area calculations. I was hoping someone has a relatively easy ...
8
votes
2answers
8k views

Interpretation of shear flow/shear center of L-profile

I have calculated the shear flows and center of an L shaped profile. I assume they are correctly calculated (I followed the same steps as during the lectures for an I shaped profile). However, I have ...
8
votes
1answer
1k views

How can I calculate the stresses and limits for the physical lowering of in-service pipelines?

Sometimes underground pipelines are exposed due to vertical scour or lateral migration of streams (or other erosion). One option is to lower the (in-service) pipeline to a new depth that provides ...
7
votes
3answers
691 views

How do large turbines deal with asymmetry and beat arising from those?

A large turbine used in an electric plant can easily have 10+ meters in diameter and rotate at 70+ RPM. Should any asymmetry occur the rotating turbine will produce beat which will sooner or later ...
7
votes
4answers
2k views

Why do stress concentrations really occur?

From doing some research I've learned that internal stresses inside an object can "concentrate" on sharp edges, as shown in the above picture. For that reason we often make fillets so that the change ...
7
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1answer
3k views

Principle of Virtual Work vs Castigliano's (Second) Theorem

I had a look online and into some literature however I did not seem to find a good comparison for the two different methods. They are both used for determining displacements and slopes (rotation by ...
6
votes
3answers
600 views

Is a distributed load in two parts equal to a full distributed load?

I have a structure like such: Due to my lack of knowledge of ANSYS, I have made the singular distributed loading (GI) represented as two distributed loadings (GH and HI). Would this be an accurate ...
6
votes
1answer
461 views

Do outer fillets|chamfers also reduce stress as inner ones do?

I kind of have an intuition or at least imagination about how fillet|chamfer of inner edges|vertexes reduce stress (concentration). But does that apply to outer edges|vertexes aswell? Maybe to a ...
6
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1answer
116 views

Yield properties of plastic material

What is meant by yield of isotropic plastic material? How is yield of Isotropic plastic material different from the term normal yield which is referred as transition from elastic behaviour to plastic....
5
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3answers
201 views

Do scaled models reflect strength characteristics of full size

Lets say you want to build a bridge out of carbon fiber. This has never been never been done before, and it's super expensive stuff. So your goal is to use as little material as possible, but ...
5
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2answers
5k views

Difference between Precipitation Hardening and Tempered Martensite

The textbook "Materials Science and Engineering An Introduction" mentions that: "Precipitation hardening and the treating of steel to form tempered martensite are totally different phenomena, even ...
5
votes
1answer
273 views

Physical interpretation of the relative displacement tensor?

I've resolved a relative displacement tensor into a strain tensor and a rotation tensor, where the strain tensor is: $$ \varepsilon_{i,j} =\begin{pmatrix} 0.2 & 0 & 0 \\ 0 & 0.8 &0.4\...
5
votes
1answer
93 views

"Heavy-duty" or not, can my drawer slides really support this weight?

Okay, so recently I got a Dewalt 735 Thickness Planer. It's great at what it does. (It even LOOKS like it's ready to consume the tender flesh of lumber, like some twisted Victorian lumberjack... ...
5
votes
1answer
141 views

Rover Wheels: Convex or Flat?

I was comparing the wheels of the Curiosity rover and the Perseverance rover and noticed that the latter had a very flat cylindrical design as compared to the former. This got me thinking about which ...
5
votes
2answers
845 views

Why is pure shear a "shear"?

If one looks up the meaning of shear strain, most sources talk about this situation: That is, a force acts along a surface of an element at it is elongated, turning a rectangle into a rhombus. ...
5
votes
1answer
106 views

Would a partial space elevator work? [closed]

Background The normal space elevator (that reaches from the Earth's surface to a counterweight beyond geostationary) needs a material that's strength/weight ratio is better than any material we have ...
4
votes
4answers
5k views

How does stiffness/rigidity affect the bending moment of a beam

My question may sound silly as it’s mainly good sense but I may be mixing things up. Let’s consider a flexible cantilever beam of a given length and material is fixed at one end and free at the other ...
4
votes
1answer
4k views

Why is the point of failure load lower than the peak load? [closed]

In a tensile test the peak load was 69kN, but the point of failure load was 60kN. Why is it lower?
4
votes
3answers
471 views

Can the strength of a strut be determined by deflections?

I am interesting in replacing a solid strut with tubing, but I do not want to destructively test the strut to determine its yield point. I do not want to make assumptions about the yield point based ...
4
votes
1answer
19k views

What angle - for a strut - provides the greatest vertical strength/support for a cantilever?

I want to affix a cantilever to wall. I will support the other end of the cantilever with a strut made of wood, that attaches to some point on the wall below the cantilever, as shown in this sketch (...
4
votes
1answer
896 views

Why is the Stress vs strain diagram preferable to the Load vs displacement diagram?

I’m really unsure what is the difference between stress vs. strain and load vs displacement graphs and why stress-strain is better. I know that the units are different: stress is in MPa and the load ...
4
votes
1answer
2k views

Difference between 'plastic yielding' , 'plastic yield strength', plastic strength' and 'plastic stress'?

I am going through a literature where these terms are regularly used and I am confused are they different and if yes then what does each term mean? I also want to know relation of plastic strength of ...
4
votes
4answers
3k views

Calculating maximum internal pressure from maximum rated external pressure?

Is there a calculation / rule of thumb that can determine a containers rough maximum negative pressure (vacuum) from it's rated internal pressure (assuming a single layer construction so there is no ...
4
votes
2answers
5k views

Tensile strength to weight conversion

I read in a documentation to some adhezive: the tensile strength is 13 N/mm2. How many kilograms can the 10x10mm bonding hold? I tried to calculate it by the following: $$\begin{align} F &= m/g \...
4
votes
1answer
3k views

Convert Load Deformation (Extension) Data to Stress-Strain Curve

I am trying to manipulate some data that were obtained from a three point load experiment on a porcine tibia. I would like to obtain a stress-strain curve for the various specimens; however, the only ...
4
votes
1answer
658 views

Why is fillet weld assumed to be in a state of pure shear stress?

According to Building codes, when calculating the maximum load a fillet weld can take, one checks only that the stress in pure shear is below the maximum shear strength. We know that shear yielding ...
4
votes
2answers
472 views

How to determine tensile strength while the normalised tensile strength is known?

I try to design a shaft with yet unknown diameter, i know the distribution of forces and stresses (shear, torsion and normal) in/ along the shaft. I need just one more parameter nl. the tensile ...
4
votes
4answers
2k views

How does a constant load affect the elongation of a steel cable?

I am sorry if this question has been asked before or if the answer is obvious, but I cannot seem to find the answer. A lot of the structural engineering problems we do involve calculating the ...
4
votes
2answers
1k views

Effect of varying diameter bolts on shear stress under eccentric loading

In my mechanics of materials class we are required to be able to solve problems with bolts in shear. Unfortunately our textbook doesn't cover this subject we only had a little bit of information given ...
4
votes
1answer
50 views

How to apply static failure criteria for bending stress in an angled cylindrical surface?

Let’s say I have an irregularly shaped bearing with a cross section that looks like the angled surface of a conical frustum, shown below. If a bending moment is applied which causes the inside ...
4
votes
1answer
194 views

Is it possible to make very large diamonds using a pressure vessel at several GigaPascal pressure?

Nanocrystalline diamonds can be synthesized by direct conversion of graphite or carbon black mixed with low amount of boron (0.1%-10%) at 8-10 GPa, according to US patent No.20120255236. If some ...
4
votes
1answer
71 views

How to calculate the adhesion I need to keep a 3D printed bending part straight?

3D printed parts cool down during printing, resulting in thermal contraction which causes a bending moment and separation from the printing bed. The issue is solved by increasing adhesion to the ...
4
votes
0answers
75 views

Calculating the bending moment ($M$) of a beam as it relates to stress ($σ$) and strain ($ε$)?

I am trying to learn how to work out the bending moment for progressively complex systems to model a beam. I am assuming only one axis of motion (transverse = $y$). For the basic equations of motion, $...
4
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0answers
66 views

Designing a Safe and Crush-proof Pokemon playing card box using a 3D Super-Elipsoid

My friend has two young Pokemon-addicted sons who carry their 60-card playing decks with them everywhere, typically in a cargo pants pocket. Unfortunately, they have either managed to destroy every ...
3
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3answers
2k views

Does the bearing stress vary along the bolt?

I'm currently working on problems for my mechanics of material course, and I just learned how to calculate the shear stress on a bolt holding stacked plates. That whether it be a single or double ...
3
votes
2answers
139 views

How exactly do forces transfer in different directions?

If we imagine the load being placed at the top of the below triangle, I realise that the downwards force is transferred into one which goes in a 'south east' and 'south west' direction down to the end ...
3
votes
1answer
221 views

What really is so special about principal stresses or stress invariants?

At any point inside a structural element under deformation, we can always find three planes such that when we define a coordinate system with basis vectors lying on those planes, the shear stresses at ...
3
votes
1answer
85 views

Which drawer design can hold more weight?

I want to build drawers for my kitchen. On Youtube I found this Channel, where a guy does woodworking. In a video about making kitchen drawers, he says that the bottom surface of the drawer will be ...
3
votes
3answers
250 views

Different measured strain in beam experiencing pure bending

I have a beam experiencing a pure bending moment. The setup is similar to this image from these lecture notes (with different values). Using the flexure formula, we can determine that the stress (and ...
3
votes
2answers
139 views

Is there any difference between an-elastic and visco-elastic materials?

Most of the sources that I had read about either talks about anelasticity or viscoelasticity, they don't compare both. From what I have read so far ,both anelastic and viscoelastic materials are the ...
3
votes
2answers
67 views

Why is the yield strength of steel assumed to be less for a thicker element?

The above image is part of table 3.1 of Eurocode steel design standard. Looking for example at the first row (steel grade S 235), we see that there are two values for yield strength $f_y$, one for ...
3
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2answers
194 views

Why is the thin-walled cylinder more likely to experience failure along its axis than along its hoop/circumference?

I was watching a YouTube video to understand the concepts of hoop/circumferential stress and axial/longitudinal stress in thin-walled cylinders and their formula derivation. So the formula of the ...
3
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1answer
1k views

Is stress a vector or scalar?

I have seen some theories saying stress is a scalar. I don't understand why. Anyone can explain.
3
votes
2answers
315 views

How to deal with rotation of an element in theory of elasticity?

As you know in linear theory of elasticity equations for strains are given as (according to picture): But what will be if an element will just rotate (strain equation is on the picture): Intuitively ...

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