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---
author: Akbar Rahman
date: \today
title: MMME2044 // Linkages
tags: [ mmme2044, linkages, uni ]
uuid: ae955a7e-bc65-4055-a79d-38b57c5a00a5
---
# Freedom and Constraints
A body that is free in space can move in three, independent perpendicular directions and rotation
in three ways about those directions.
It is said to have 6 degrees of freedom (DoF).
The number of degrees of freedom are the number of components of motion that are required in order
to generate the motion.
If a joint is constrained to move along a line, it has 1 degree of freedom.
If a joint is constrained to a plane with no rotation then it has two degrees of freedom.
## Gruebler's Equation of Degrees of Freedom
$$M = 3L - 2J - 3G$$
where $M$ is degrees of freedom, $L$ is number of links, $J$ is number of joints, and $G$ is number
of grounded links.
![](./images/vimscrot-2022-10-17T16:33:52,261209255+01:00.png)
- if DoF > 0, it is a mechanism with relative motions
- if DoF = 0, it is a structure without motion
- if DoF < 0, it is a preloaded (or overly constrained) structure without motion but possibly
additional stress
![](./images/vimscrot-2022-10-17T16:36:24,581871695+01:00.png)
## Grashof Condition
Four bar linkage is the simplest possible pin-jointed mechanism.
The Grashof condition is a simple relationship that predicts the linkage behaviour based only on
the lengths of the links.
A linkage is a Grashof linkage if at least one link is capable of making a full revolution and
the following equation holds true:
$$S + L < P + Q$$
where
- $S$ is the length of shortest link
- $L$ is the length of longest link
- $P$ is the length of one remaining link
- $Q$ is the length of other remaining link
### Triple Rockers
If $S + L > P + Q$ then it is not a Grashof linkage and is known as a triple rocker.
![](./images/vimscrot-2022-10-17T21:50:13,068568249+01:00.png)
### Double Cranks / Crank Rockers
$$S + L = P + Q$$
![](./images/vimscrot-2022-10-17T21:50:29,856118739+01:00.png)
## Limit Conditions
Toggle is an important test to check if the linkage can reach all specified positions without
encountering a limit or toggle position, also called a station configuration.
Toggle positions may be determined by collinearity of two links
![](./images/vimscrot-2022-10-17T21:53:02,839579659+01:00.png)
## Transmission Angle
Transmission angle, $\mu$, is the angle between the output link and the coupler.
It is a useful test to check the quality of the force transmission in a linkage.
Ideally $\mu = 90$ deg but at minimum $\mu \ge 40$ deg.

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- Rigid Body - Distances between any two particles on a body remain constant---in real life we are - Rigid Body - Distances between any two particles on a body remain constant---in real life we are
looking for negligible deformation looking for negligible deformation
# Lecture 2 (W04/41)
## Relative Motion
![](./images/vimscrot-2022-10-17T09:09:23,080550083+01:00.png)
where $_{BA}$ is read as "$B$ as seen by $A$".
These equations must be treated as vectors.
# Lecture 3 (W05/42)
## Instantaneous Centre of Rotation
This is a point with zero velocity at any particular moment.
![](./images/vimscrot-2022-10-17T09:13:09,972195575+01:00.png)
$$v_A = 0$$
$$v_B = v_{BA}$$
To find the centre of rotation you can draw to perpendicular lines to velocities from two non
stationary points.
The centre of rotation will be where the lines intersect.
![](./images/vimscrot-2022-10-17T09:14:37,194818034+01:00.png)
## Point Velocity Projections on Joining Axis
Take two points $A$ and $B$ and their velocities at one instant
\begin{align}
v_B &= v_A = v_{BA} \\
\text{then } \pmb{v_B} || AB &= \pmb{v_A} || AB + \pmb{v_{BA} || AB \\
\text{but } \pmb{v_BA} || AB &\equiv 0 \text{(since $\pmb{v_BA} \perp AB$)} \\
\text{or } \pmb{v_B| || AB &= \pmb{v_A} || AB \\
v_B\cos\beta = v_A\cos\alpha \\
\end{align}
# zack.jpg
![zack.jpg](./images/zack.jpg) ![zack.jpg](./images/zack.jpg)

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---
author: Akbar Rahman
date: \today
title: MMME2047 // Fluid Dynamics
tags: [ mmme2047, uni, fluids, fluid_dynamics, fluid_dynamics ]
uuid: d2b36b74-0661-47d2-8c1f-0bf7747ba7eb
---
As this module builds on MMME1048, content covered in pages tagged [mmme1048](/.tags/mmme1048.html)
may not be covered in these pages.
# Data and Formula Sheet
## International Association for the Properties of Water and Steam (IAPWS)
- <http://iapws.org/relguide/IF97-Rev.html>
- [backup of IF97-Rev.pdf](./data_and_formulae_sheets/IF97-Rev.pdf)
## Thermodynamic Tables to Accompany Modern Engineering Thermodynamics (Robert Balmer)
- [Thermodynamic Tables to Accompany Modern Engineering Thermodynamics](https://ebookcentral.proquest.com/lib/nottingham/reader.action?docID=625295) (paywall)
- [Pages 1-16](./data_and_formulae_sheets/thermodynamic_tables_robert_balmer.pdf)
# Terminology
- State --- condition of a fluid in a particular region, defined by properties
- Property --- a measurable variable characteristic of a fluid
- System --- a region of a fluid contained by real and/or imaginary boundaries

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---
author: Akbar Rahman
date: \today
title: MMME2047 // Thermodynamics
tags: [ mmme2047, uni, thermodynamics ]
uuid: d2b36b74-0661-47d2-8c1f-0bf7747ba7eb
---
As this module builds on MMME1048, content covered in pages tagged [mmme1048](/.tags/mmme1048.html)
may not be covered in these pages.
# Data and Formula Sheet
## International Association for the Properties of Water and Steam (IAPWS)
- <http://iapws.org/relguide/IF97-Rev.html>
- [backup of IF97-Rev.pdf](./data_and_formulae_sheets/IF97-Rev.pdf)
## Thermodynamic Tables to Accompany Modern Engineering Thermodynamics (Robert Balmer)
- [Thermodynamic Tables to Accompany Modern Engineering Thermodynamics](https://ebookcentral.proquest.com/lib/nottingham/reader.action?docID=625295) (paywall)
- [Pages 1-16](./data_and_formulae_sheets/thermodynamic_tables_robert_balmer.pdf)
# Terminology
- State --- condition of a fluid in a particular region, defined by properties
- Property --- a measurable variable characteristic of a fluid
- System --- a region of a fluid contained by real and/or imaginary boundaries
-
# Lecture 1 (W03/40)
## Graphical Representation of Properties
### When is a Graph a Chart?
Graphs plot the relationship between two component characteristics.
A chart has the relationship between the two component characteristics but also plots lines of other
variables on top of them, allowing them to represent more 'dimensions' of the system.
### Temperature vs Specific Entropy
![](./images/vimscrot-2022-10-17T11:11:56,842719958+01:00.png)
The orange line is liquid, the flat blue bit is wet steam, the steep blue bit is superheated steam.
### Specific Enthalpy vs Specific Entropy
![](./images/vimscrot-2022-10-17T11:16:32,326087977+01:00.png)
### Pressure vs Specific Enthalpy
![](./images/vimscrot-2022-10-17T11:21:53,069413177+01:00.png)
## Transport Properties
Transport properties are of use for working out the flow behaviour.
These are:
- density
Density is affected by temperature and pressure. We know perfect gases have equation of
state but we need to use tables for steam an R134a as they are not perfect gases.
- viscosity
Viscosity in all fluids varies with temperature.
On page 10 of the tables there is viscosity of steam and water liquid stated in dynamic form.
$$\nu = \frac\mu\rho$$
(kinematic viscosity = dynamic viscosity / density)
- Prandtl number
- thermal conductivity
# Lecture 2 (W04/41)
![](./images/vimscrot-2022-10-17T12:30:52,395521201+01:00.png)
1. Throttle
2. Evaporator
3. Compressor
4. Condenser

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---
author: Akbar Rahman
date: \today
title:
tags: []
uuid: c0e120ca-08a7-40d2-b72d-d93b7c9cb3b6
---

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