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Questions tagged [mechanical-engineering]

Questions within the problem domain of mechanical engineering. Mechanical Engineering can be a broad field; consider choosing more specific tags if they apply.

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15 views

Type of Engineer

I am a mechanical engineer by education (master's degree). I have been working for 6 years in industry. However, I am beginning to search for a new job. I work at NASA as an instrumentation engineer. ...
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1answer
22 views

What is the reason for forbidding liquids for cooling in drilling on cfrp/Al or cfrp/Ti stacks?

I recently did some research on the effect of cooling on CFRP/Al7075 drilling.But I read somewhere that liquids are forbidden for cooling operations on these multi layer plates !!! , And I wanted to ...
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1answer
19 views

Homogeneous materials and direction dependence of properties

A homogeneous material is a material which has a uniform composition throughout. What do we mean when we say "uniform composition"? I have learnt about pure substances in Thermodynamics ...
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2answers
38 views

What is the best time interval in condition monitoring programs for checking rolling bearings?

The time intervals between observing or measuring the vibration of rolling bearings in industrial plants are so important in condition monitoring programs. For instance, some experts measure the ...
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2answers
66 views

A problem with quantifying ductility of a material

The textbooks I'm referring to for studying strength of materials say that we can quantify ductility using percentage elongation or percentage reduction in area up to failure point. The higher the ...
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1answer
15 views

Where can I find information on the SONY ERS AIBO robodog? [closed]

I have an assignment relating to the 4th industrial revolution, but mainly focussed on the Sony AIBO Robot Dog. I need to discuss the evolution of it and principle and practical aspects of system ...
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1answer
37 views

Why not put an air compressor on an exhaust to store co2? [closed]

For short-distance drives in a car, why not put an air compressor to store the co2 and dispose of later?
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0answers
12 views

Pv Diagram of a pressure cooker

For a bit of self training in thermodynamics, I've been trying to think of some random systems and go ahead and try to solve them, some of these things I've stolen from random googling of university ...
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1answer
35 views

Automated Opening and Closing of hinge

I am trying to design a mechanism that puts tension on a string. The purpose is to dip this string in a solution for a stipulated amount of time, and once the time is up, the string is pulled back up! ...
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3answers
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Difference between fast or slow rising force on materials' breaking strength

Assume that force is applied to a material like a rope, steel cable or a beam until it tears apart. Does it make any difference for the breaking point if the force rises slowly or really fast?
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5answers
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Mechanical mechanism that regulates gear's rotational velocity

Please do note that I am a civil engineer not a mechanical engineer. I have a gear that rotates at a speed that varies with time. Usually, it rotates at speeds higher than the desired speed. Is there ...
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3answers
49 views

How to convert car power into energy (MJ) used per km?

I am currently attempting to do an energy audit regarding how much energy my car uses per kilometer. I am not sure whether my approach to this is right, and it feels like I have made too many ...
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6answers
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How to work on big CAD project in team?

I'm always confused on what is the effective way to work on CAD with multiple team members to make it efficient. So far, as I'm freshly graduated I only work on a project where I'm the only one using ...
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2answers
39 views

What happens when we remove the load, in different regions of the stress strain diagram of mild steel?

A: Proportional limit| B: Elastic limit| C: Upper YP | D: Lower YP Let us say, the gage length was 100mm (random, just for the sake of understanding). I know that if I unload the body anywhere between ...
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5answers
70 views

How can I add the torque of multiple gears?

If I have 3 gears meshed with a gear in the center of the 3 gears as shown in the picture. all of those 3 gears are connected to different power sources. They are free to rotate in the same direction ...
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0answers
27 views

Confusion between Steady flow and Space-Time invariant density field

Let's take the example of a steady flow with velocity field as $u=βr(\tilde{r})$. Now, we can find a density field $ρ(r,t)$ that satisfies the mass conservation equation of $∂ρ/∂t+∇(ρu)=0$. First, ...
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4answers
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What happens from B to C in this stress strain diagram of mild steel?

Image Source: https://mechtics.com/design/strength-of-material/stress-strain-curve-for-mild-steel-with-defination-of-stress-and-strain/ I know that A is the proportional limit, B is the elastic limit. ...
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2answers
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Could the St. Louis Gateway Arch be used as a support structure for a giant vertical axis wind turbine?

I am curious to know if the St. Louis Gateway Arch would be strong enough to act as a support structure for a giant vertical axis wind turbine. I way I am envisioning this being constructed is that a ...
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5answers
5k views

Why are screw holes in most of the door hinges in zigzag orientation?

What advantage does it provide? Explaining with a figure would be helpful. I tried to draw a free body diagram and equated the sum of force and moments to zero, but still was not able to find out.
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3answers
58 views

Why tensile test specimen is enlarged at its ends?

The tensile test specimen used for tension test has an enlarged cross sectional area at the ends. The sources I'm referring to, suggest that this is the case so that the failure occurs in the central ...
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3answers
46 views

Why we needed to relate internal resistive forces with area (stress)?

When we load a body, say a prismatic bar, axially, internal resistive forces are developed within it to oppose the elongation or compression. What was the need of relating these internal resistive ...
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0answers
21 views

gear compatibility specification

I want to build a epicyclic gear system with planetary gears on flat carrier plate and outer ring as internally toothed (geared) slewing bearing. I want to buy a single row slewing bearing of 8 inch ...
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0answers
22 views

Question regarding evaluating 1D heat transfer PDE

My question regards cooling of an object using 1D-heat transfer with fixed surface temperatures. First I need to find the solution to this PDE: Based on the conditions, I worked out that the ...
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2answers
32 views

Clarification on Aluminum Design Manual

I am using the aluminum design manual equations to design an aluminum column that fixed at the base and free at the top, so fixed-free end conditions. Section C.3 of the Aluminum Design Manual says to ...
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0answers
29 views

Bar released from upright position rotates about a lower hinge before being caught by a steel cable, how to calculate the tension on the cable?

I wish to check the safety factor of a steel cable that I've designed to catch a heavy bar that rotates freely due to the gravitational force acting on it. From the upright position, I'm assuming that ...
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2answers
55 views

Shear and Bending Moment

A square tube is slid into a larger square tube. If a load is applied to the end of the inner tube, I would think that inner tube would mainly contact the outer tube in two locations as the load is ...
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2answers
31 views

Do tensile and compressive forces have significance only in pairs?

In strength of materials, there are two types of axial forces which can act on a prismatic bar - Compressive and Tensile. Do they significance only in pairs?
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3answers
33 views

Question about shear force on the beams

Can someone please point me in the right direction. I am a newbie when it comes to statics. I am trying to understand the following diagram. Why on the left side of the beam section, the moment is in ...
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2answers
42 views

What frequency is the low frequency vibration of normal buildings from like elevator or ventilation motor? To avoid equipment resonance vibration

Recently I am building equipment. It is as large as two refrigerators with aluminum extrusion frame. Unfortunately, it has visible resonance vibration. After measuring I find on the floor there is a ...
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3answers
55 views

Can I create a whirlpool/vortex around a horizontal axis in a flat bottle using motor?

I am using this flat bottle: I fixed a motor at the centre of one of the flat sides and attached an impeller. I thought this will create some kind of whirlpool effect but as you can guess, since the ...
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9answers
2k views

Aluminum weight saving

"Aluminum saves weight! Its 3 times lighter than steel!" Also its 3 times weaker and 3 times softer. When comparing stiffness and strenght to weight ratio, aluminum isnt any better than ...
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3answers
278 views

In vibration study, should the reference be necessarily the mean/equilibrium position?

When we determine the natural frequency of free vibration for a system, we start of by defining a reference from where displacements will be measured. I have usually seen in books, taking the ...
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3answers
377 views

Highest point of stress in a multistage gear reducer

Assume a multistage gear reducer (used in forklifts or bed lifts) like the one presented in the following image. Assume that the motor is connected to shaft 1 and the load on shaft 3. Which gear ...
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2answers
100 views

Why is the theoretical formulation not explaining why the graph of the square of the velocity and angular displacement is nonlinear (experimentally)?

So I did a wind tunnel experiment where I put a rope restrained (1 degree of freedom, so it can wave in the direction of the wind) at one end so that it displaces according to the variation in wind ...
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2answers
27 views

Reaction forces on a three support continuous beam with two of them requiring compatibility equations. Superposition method done wrong!

I need to analyze a continuous beam of length L and three supports: A (at x=0), B (at x=L/2), and C (at x=L). An applied load P is applied at x=3L/4. Now, at A, the continuous beam is bolted to a ...
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3answers
42 views

Can tubes for fits & tolerance be purchased or only manufactured?

I'm currently designing a steel structure for a gym machine. I want to assemble two rectangular tubes, one being able to slide inside the other, for height adjusting. I intend to use a spring ball pop ...
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0answers
24 views

Reference design for a HSK machine spindle?

Is there a reference design somewhere on the web for a HSK milling machine spindle (mainly HSK type A, between 40-63)? I'm mainly looking at the fixating mechanism (drawbar et al) and its tolerances; ...
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3answers
39 views

Find the maximum stress at a point in a machine member

A machine member having a diameter of 50 mm and a length of 250 mm is supported at one end as a cantilever subjected to different forces as shown in the figure. Find the maximum stress at points A and ...
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0answers
18 views

Sign convention for angular velocities in 3D gear train

Consider a Humpage gear train shown above. We are viewing the gear train from right and gear B is rotating in clockwise direction. If we consider clockwise direction as positive what will be the sign ...
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2answers
88 views

Velocity or Speed Ratios in Gears and Gear Trains

I have seen the different definitions of the velocity ratio for Gears and Gear trains. I have referred a book called Theory of machines by S. S. Ratan. In that book the definitions are as following: ...
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0answers
14 views

How would a realistic PV diagram look for a Beta-Type Stirling Engine?

Normally, most textbooks use the diagram below to describe an ideal Stirling Cycle. 1st comes isothermal expansion of gas, 2nd comes isochoric heat transfer to the regenerator, 3rd isothermal ...
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1answer
30 views

How do I calculate the strength of a carbon fiber tube?

I am not a mech engineer and have been struggling with this for a while, I feel like it is pretty straight forward but I'm missing something. The problem is a horizontal tube that is supported at one ...
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3answers
5k views

Why do heavy trucks use air brakes?

I was having a discussion today, which led to the question why do heavy trucks still use air brakes? To my knowledge, it has been used for at least 40 years (I remember that as a kid), and ...
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1answer
59 views

Bushed 3" V-belt pulley with unkeyed 3/4" shaft?

Shortly I will have two 3/4" unkeyed shafts needing 3" type-A V-belt pulleys, one each. They'll each have their own motor driving them, and will need to run to 5000 RPM and possibly higher ...
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1answer
46 views

Utilizing symmetry in statics problem

I am given the structure below, and supposed to find the forces occuring in $A, F, E, D, C$ and $B$. The task hints of using symmetry, as several forces are equal in magnitude. Supposedly, $A=B$, and ...
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2answers
25 views

Force control of pneumatic piston

I am building a small testing device consisting of a double acting pneumatic cylinder. I am using an existing pneumatic line running at 100 psi and I would like to control the force exerted by the ...
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1answer
16 views

trying to find maximum torsional stress

I was wondering how I could get Ttmax (maximum torsional stress) or rather what the formula for it could be
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3answers
64 views

Tensile Force on Line of Bolts

I'm presented with a problem requiring some analysis to determine if an antenna bracket mounted to a concrete blockwork wall is sufficiently strong enough to endure a wind load given the known surface ...
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1answer
67 views

Angular momentum of a multi-body system

I'm trying to compute the total angular momentum of a 3D multi-body, pendulum-like (as in, each body is connected to another one), mechanical system. Let us consider, for a simpler case, a 2D double ...
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2answers
29 views

How to determine the magnitude and direction of a force

I am trying to understand how the solution got the degree of 95, I've done a similar problem with this before, but I had to add the two degrees, when I add the two degrees in this problem I get 75, ...

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