Questions tagged [mechanical-failure]

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56 views

Does a change in specimen dimension affect the measured yield strength and tensile strength?

I am having a hard time trying to understand the effect of geometry on a specimen's yield and tensile strength or if there even is one. If there is an effect or not, why is it so? Thanks in advanced!
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36 views

Latch design for home exercise equipment [closed]

I have a latch design problem and need your help - many years in software engineering aren't helping me much here! Two pieces of 60x30mm RHS become parallel/adjacent (on the 60mm face), with a 5mm gap,...
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2answers
80 views

Why does stress act a point instead of on an entire area normal to the stress?

I've often heard stress acts at a point and not on an entire cross-sectional area to which the load is applied normally. Im a little confused here, Let us consider an area of cross-section ...
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1answer
25 views

Length of semi major axis for the ellipse in “Total Strain Energy theory”

The equation describing the "Total Strain Energy Theory" (Haigh & Beltrami's Theory of failure) is given as follows: $$σ_1 + σ_2 - 2μ σ_1 σ_2 ≤ (Syt)^2$$ where $σ_1$ and $σ_2$ are ...
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2answers
441 views

How to prevent screw from loosening?

This is a clevis made for linking the tie-rods to the steering rack. This part is under dynamic loading and is getting loosened. We tried using jam nuts but it did not work well. Due to loosening the ...
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3answers
236 views

Buckling vs. Yielding Failure of Columns

As I have been working through examples of construction projects, I've noticed that in nearly every case of a structural column (sample size considers only homogeneous material columns, no composite ...
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1answer
102 views

mechanical Strength of 3D printed part

If the material is manufactured by 3D printing (laser sintering) then what will be change in its mechanical properties than the properties by casting and machined part? What would be appropriate ...
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0answers
29 views

Is a motor failure caused by a defect bearing considered to be a failure mode or is it higher vibration and speed loss in FMEA/FMECA?

Let us assume we have a motor with a bearing which is exhibited to wear. Over time, we can observe higher vibration, increased noise and the motor speed reduces due to the bearing fault. In the end, ...
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3answers
173 views

DOE analysis or root cause analysis?

For any testing that a part is suppose to pass a test, let's say the leakage test of a seal flange. How should I individualize the cause? I know there is root cause analysis and for different ...
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2answers
32 views

1m3 water container and ice damage prevention

I was looking for data on ice resistance for these kinds of 1000 litres containers. I believe they are made of polyethylene with an outside aluminium structure. Given the physics of ice expansion, ...
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1answer
169 views

Can crosshead movement be used to measure strain in tensile testing instead of an extensometer?

I am trying to design and build a low cost tensile test machine for plastic specimens. Most machines I've seen measure strain data using an extensometer, either the clamp-on type or the noncontact ...
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1answer
64 views

compression buckling under lateral load

I'm trying to figure out what size of round tube to use for a tensegrity structure that'll probably have people climbing on it. The rigid elements are 21' steel tubes, and in normal cases they ...
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4answers
6k views

Would engineering bricks explode if used to build an oven?

I'm building a pizza oven and, to do so, I bought a whole load of engineering bricks (not these but similar). They've got five holes vertically through them, each hole is 2x6x6.5 cm (80 ml) and the ...
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2answers
71 views

Why don't car engine piston-rods (or similar parts) fail as often as other car parts?

Anyone who has owned a car has ultimately dealt with failure of a sensor (parking), or A/C failure, battery shutdown or a tyre puncture. Part breakdowns like these are pretty common, at least ...
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2answers
160 views

Hollow Steel Tubing: Critical Load for Sidewall Buckling

I'm looking to construct a something with hollow steel tubing (e.g. 10ga 2"x3" rectangular tubing) suspended horizontally welded to an outer frame on both sides. I've already calculated the ...
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3answers
158 views

Ductile,Brittle and Malleable

In Callister it says, "two modes of failure are possible ductile and brittle." Why not malleable?Furthermore why is uniaxial tensile test chosen for predicting failure?
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1answer
69 views

Historical data for using supervised learning algorithm in the field of Mechanical Engineering [closed]

Being a student in the field of Mechanical Engineering, I am very new to Machine Learning.I did a couple of basic online courses of Machine Learning (including the one by Andrew Ng on Coursera). So, I ...
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1answer
208 views

Hardening and Brittleness

Why is hardening and brittle nature so related?What is work hardening or strain hardening as far as true stress strain diagram is concerned?
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2answers
36 views

Switch at the back of a battery eliminator

I have this variable voltage battery eliminator and the "switch" to hold the wire in place is broken. Is there any specific name for this "switch" and can I buy it somewhere to replace it or can you ...
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4answers
4k views

What is the difference between tau = VQ/It and tau = V/A?

What is the difference between the formulas $\tau = VQ/It$ and $\tau = V/A$ for finding shear stress due to transverse loading? I understand that the use of first moment of area, is the only reason ...
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32 views

Long term deflection

I've been working with a team of 'designers' that are highly concerned over a potential failure mode of ABS plastic. Their theory is that under a static load well under the yield point of the material ...
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1answer
45 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 ...
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0answers
56 views

Plastic failure evaluation of steel using FEM

I would like to evaluate failure in steel using FEM, especially in geometries with stress concentrations (notches etc.). One possibility is to calculate the stress distribution using a purely linear ...
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1answer
1k views

Actual amount of reinforcement gained by adding gusset to welded steel tube construction

This question bothers me for quite a while and is about bicycle frame construction, specifically a BMX frame and even more specifically it's front triangle. It is a heavy duty frame by definition, and ...
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1answer
104 views

How thick of an oxide might form on a cast zinc part?

I'm looking into possible failures of a cast zinc part. I'm wondering if the Zinc-oxide that develops after a time would have a thickness great enough to cause dimensional tolerancing issues? ...
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1answer
754 views

Is a gear usually held on a shaft friction or an adhesive?

So, where I work, we have this arcade game, which is a classic claw machine. IN order to raise the claw up and down the machine makes use of a worm gear, like so: (although for the meticulously ...
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0answers
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1answer
14 views

Temperature vs Material Properties - ABS

I'm working on a design that uses fairly large plastic components (ABS, ~400mm longest dimensions). I'm looking at adding a steel component that encapsulates this plastic part. And, the steel part ...
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2answers
2k views

Strength of Welded Joints

When calculating the factor of safety for a fillet weld that is loaded in shear what should be the maximum allowable stress? Some books suggest using the distortion energy (Ssy = 0.577Sy for the ...
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1answer
40 views

Behavior of materials on application of tension

Does a test body subjected to a strain that causes plastic deformation still have elastic recovery?
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1answer
605 views

Coconut Climbing Machine Ideas [closed]

I have been trying to create a machine to climb coconuts as the existing machines are very slow and strenuous to use and frankly, most climbers prefer to climb it manually than use the existing ...
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2answers
9k views

Failure in torsion

Why does a ductile rod in torsion fail at an angle perpendicular to its axis? I know the reason for brittle material failing in pure shear but I don't understand the reason for ductile material.
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2answers
447 views

Moment of force or torque [closed]

Is the moment of force taken in a clockwise and anticlockwise fashion? Why then do we curl our fingers and check it?Explain the equivalence or similarity between the two.
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4answers
228 views

Is radians dimensionless quantity?

Quite often while calculating angular velocity we come across the quantity radians per second. Dimensionally how do i treat radian as?Explain vividly.
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2answers
7k views

What is Saint Venant Principle?

I am having problem with the application of Saint Venant principle.I have heard that quite often we use that knowingly or unknowingly.I would be very greatful to anyone who would explain this very ...
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2answers
124 views

Can buckling failure at the first critical load be avoided by “instantaneous” loading?

Previously, I was told by someone I trust well that a column can avoid buckling at the first critical load by applying the load "instantaneously" with a magnitude between the first and second critical ...
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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 ...
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2answers
7k views

How to calculate the pressure a pipe can withstand?

I was looking at high pressure pipes and their pressure ratings. I'd like to know how these pressure ratings are determined. I assume that pipes are tested until failure, and the failure pressure is ...
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1answer
53 views

Can a mechanic pull apart a strong bolt by hand power alone with an ordinary wrench? [closed]

I am wondering whether a typical mechanic can break a bolt using a wrench. For example, let's say the wrench is 15" long and the force is applied at a radius of 13". The mechanic applies a force of ...
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0answers
129 views

How to compare small and large scale model of an IC engine to predict force, torque, rpm etc generated by actual engine?

I have this 6 cylinder radial engine designed in Solidworks. Rendering Blueprint (Source:Inventor Wizards) And I want to perform some motion analysis on this engine to make some prediction about it'...
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2answers
4k 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 ...
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2answers
976 views

Can anyone verify this wall thickness of a pressure cooker?

I am working on designing a pressure cooker. I've have tried to find, using two different models, the wall thickness based on the following assumptions: Cylindrically shaped container Made of ...
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1answer
2k views

Strength of a Vertical Round Aluminum Tube with load cantilevered off it?

Can a vertical round tube safely support a cantilevered arm mounted near the top of the tube? ROUND VERTICAL TUBE: 6061 Aluminum 2 inch Outside diameter 0.25 inch wall thickness 3 feet height ...
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3answers
1k views

Why do beverage can tabs break when bent?

Most people have had the experience of moving the tab of an aluminum can back and forth until it breaks off. It usually only takes a few complete back and forth motions before the tab breaks off. ...
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1answer
86 views

Are Rolling-Element Bearings Practical for Light Loads?

I have a 5" x 4" x 3/8" plastic panel (wall thickness of 1/8", ribbed). I need to slide the panel over a 12" plastic track that is U-shaped (like a skateboard ramp). This motion could be repeated 2 ...
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1answer
65 views

How does non-electrical ATEX apply to springs?

This question relates to the ATEX directive, which is the European regulation governing the design of products to be used in explosive atmospheres. In particular, I am asking about the part relating ...
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3answers
269 views

What is the [PVC] tube or foam in metal springs for?

There are plenty of springs out there which have either a little PVC tube or a foam inside, when I first saw the tube I thought it was probably to prevent the metal spring from bending, but that ...
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3answers
407 views

How can I apply a fixed and adjustable force to my flexible sample?

I major in microelectronics. I just want to apply a fixed and adjustable force to my flexible sample. 'Fixed' means that the force could be hold for given time without change. 'Adjustable' means that ...
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1answer
3k views

Oblique cutting implemented in Industrial applications

Oblique cutting generates transverse cutting force which reduces tool life. Oblique cutting involves principal and auxiliary cutting edges in the cutting action which increases friction and advances ...
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3answers
2k views

What is the difference between fault tolerance and robustness of a system?

I am trying to understand the difference in the definition of "fault tolerance" and "robustness" when it comes to system design. For instance, what would be the main design ...