# Search results

1. ### Programs Is Chemistry a useful minor for a MechEng Major?

Material science would be a most useful minor than chemistry, in my opinion.
2. ### Measuring relative rotation of node - ANSYS WorkBench

Hi all, I have a rather trivial issue I am trying to solve, but it seems like there isn't anything available online that I can find to help me. For this question, imagine I have a 2D annulus with a fixed inner ring and frictionless outer ring. I apply a moment to the outer ring and create...

4. ### How to measure the moment of inertia of a motor's rotor?

I is the Inertia of the object in question i.e. Motor rotor. G is the shear modulus of the spring material, J is the polar moment of the spring - if it's a circular cross-section this would be (pi/32)*d^4, and L is the length of the spring.
5. ### How to measure the moment of inertia of a motor's rotor?

There is a way you can measure MMoI of irregular geometry by attaching it to a spring (say a steel rod) about its centre and then measuring the period. From that you can find the Inertia using fundamental vibration analysis. fN = 1/T = 1/(2*pi)* sqrt(k_theta/I) Natural frequency or period, T...
6. ### Heat Transfer - Conduction/Convection Question - Which area?

Hi Chester, thanks for your reply. Do you mean that the heat transfer area should only be the two faces that are perpendicular to the heat conduction in Figure a, i.e. what were used to derive the Tmax equation, and not the entire surface area of the box? I'm not sure I follow what you mean.
7. ### Heat Transfer - Conduction/Convection Question - Which area?

Homework Statement Its been assumed that the surfaces TL and TR of the same constant temperature. Homework Equations Tmax = TL/R + (qdoto*L2)/(8*k) q = ΔT/R Rconvection = 1/hA The Attempt at a Solution The problem I am having with this question is conceptualising which dimensions to use...
8. ### Other How/where to explain grade discrepancy in job applications?

Hi all, I have a problem. I switched my major nearly two years ago within Engineering, however my university only has one course code for our entire degree which enlists all majors within it. So my issue is that they list ALL of my classes in my academic transcript and weight them all a whole...
9. ### MATLAB Issues Replicating Simulink Model within MATLAB (2DOF)

Hey all, I've been trying to debug a model I've created of a 4DOF geared system within Simulink by reproducing the results in MATLAB going from a 2DOF upwards to verify the dynamics are acting correctly. At the moment I am purely trying to model the stiffness between two gears, my equations...
10. ### Testing Failure on statics exam?

I've had the same experience before and what I can say is that don't dwell on this one test as it is one of MANY. Just keep your head up and work as hard as you have been prior to getting your result. I'd most definitely request a consultation with your lecturer/tutor to go over said exam and...
11. ### 4DOF Spur Gear System - Eigenvalues not corresponding with the Eqns?

Hi Randy, thanks so much for your input! I have updated my stiffness matrix to include the stiffness of the bearings which is now: And by solving the updated dynamic matrix, has yielded three purely positive eigenvalues with one zero. So it seems like its responding as it should, now to see...
12. ### I Finding eigenvalues for 4 DOF system

Thank you for your help Jambaugh!
13. ### 4DOF Spur Gear System - Eigenvalues not corresponding with the Eqns?

Hi there, I am modelling a four degree of freedom system which is the dynamics of two spur gears in mesh, having two rotational and two translation degrees of freedom, respectively, a diagram exhibiting the system can be seen below. I have derived the equations of motion (EOM) and...
14. ### I Finding eigenvalues for 4 DOF system

Hey all, I've derived a fourth order dynamic system as represented by the following: I need to determine the eigenvalues for this system to check whether they're purely real with no imaginary components. How should I go about doing this? I have done eigenvalue problems in the past, but not to...
15. ### MATLAB Passing variables out of ODE45

Sorry, in the mainscript code that I listed I meant to take out the "k_mb = 50;". I have edited it and put it below. Updated mainscript % Mainscript for vibration analysis (19/01/2017). clear all; clc; %% Defining global variables global r_p r_g I_p I_g m_p m_g k_mb r_p = 10; % pinion...
16. ### MATLAB Passing variables out of ODE45

Hi all, I have the following ode code, and I want to know how I could output the variable "k_mb" within my main script so that I can plot it to see if it's actually active when the solver is integrating. odescript function zdot = odenesttest(t,z) global r_p r_g I_p I_g m_p m_g V k_mb A_or_B =...
17. ### MATLAB MATLAB Repeating Function

Sorry, I'm still an intermediate at using the ode solvers with matlab. I'll list below what I have written (excluding what you have shown me previously). Main script: % Mainscript for vibration analysis (16/01/2017). clear all; clc; %% Defining global variables global k_mb r_p r_g I_p I_g m_p...
18. ### MATLAB MATLAB Repeating Function

One easy way to solve this I think is to make a preset array like 'V' extremely long and then change the current angle to z(2).
19. ### MATLAB MATLAB Repeating Function

Just one more thing (I didn't think it'd be worthwhile beginning a new thread for this when you've responded in here). I'm now trying to incorporate the repeating function into my ODE solving function which obviously requires a bit of modification to the code we have in the previous posts. I'm...
20. ### MATLAB MATLAB Repeating Function

This is great, works perfectly with the addition of this at the end: if V(current_index) ~= max_angle V(current_index) = []; else V(current_index); end Otherwise the last entry in the V array is either over by 5 or 10. But with that, it works nicely. I'll be sure to check out those...
21. ### MATLAB MATLAB Repeating Function

Sorry for the confusion, let me explain. The purpose of this is to simulate the revolution of a pair of gears in mesh, so if the user wants to simulate 10 revolutions the angle will be 3600°, if they want to rotate the gears 1 revolution then the angle will be 360°, etc. So the angle is the only...
22. ### MATLAB MATLAB Repeating Function

Once I start testing the ODE solver, I'll be sure to keep that in mind if it becomes an issue. One further thing, see how the array, V = [0,5,15,20,30,35,45,50,60]; (pre-determined and put in). I want to write something that allows the user to input the angle and then the array is generated...
23. ### MATLAB MATLAB Repeating Function

The addition of 'last' in the lower_index, fixed the problem instantly. Thus, for: angle = 4 -> a_or_b_for_angle = 5 angle = 6 -> a_or_b_for_angle = 10 angle = 46 -> a_or_b_for_angle = 5 angle = 59 -> a_or_b_for_angle = 10 Thank you very much for your help, I'll use this as my base for my ODE...
24. ### MATLAB MATLAB Repeating Function

Again, many thanks. I'm quite sure I know what it is trying to achieve. If I run: angle = 4; V = [0,5,15,20,30,35,45,50,60]; A_or_B = [5,10]; lower_index = find(V < angle, 1); even_or_odd = mod(lower_index,2); a_or_b_for_angle = A_or_B(2 - even_or_odd); The values of each vector are...
25. ### MATLAB MATLAB Repeating Function

Maybe it'll be more clear if I explain the application. I am trying to make a function that allows me to apply a torsional stiffness for gear teeth in mesh, as the gear rotates the gear (in this case) will be in either singular contact or double contact. Where I'm assigning 5° for single and 10°...
26. ### MATLAB MATLAB Repeating Function

Do you mean for each interval there would be an if statement associated with it? This is the nature of the application that I require for an example of 60°: https://postimg.org/image/xcz38o687/ See how the function needs to be able to periodically apply the values dependent on the total angle...
27. ### MATLAB MATLAB Repeating Function

Hey all, I need your help writing the meat of a function that I need for a MATLAB script I'm writing. The jist of it is, starting from 0°, when between 0.0° - 5.0° apply a certain value, when between 5.0° - 15.0° apply another value. However, the relative amount of rotation can be user...
28. ### Undergraduate Thesis - FEA and Quantum Computers

My apologies, I didn't mean FEA on quantum computers. I meant, for example, the vibration of components of the cooling systems required for quantum computers. That sort of application of FEA.
29. ### Undergraduate Thesis - FEA and Quantum Computers

Hey everyone, I've started to do research for my undergraduate thesis topic and I would like to use FEA with an application to quantum computers. I'm thinking of something in regards to mechanical vibrations, however I'm open to consider anything given it's possible at the undergraduate level...
30. ### Increasing the Earth's Rotational speed?

Interesting thought, I'd be inclined to think that if we did have the ability to alter earths rotation by means of rocket propulsion than the emissions from said rockets would impact the climate indirectly.