mmme2045 add incomplete notes on polymers

uni/mmme/2044_design_manufacture_and_project/bearings.md

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+---
+author: Akbar Rahman
+date: \today
+title: MMME2044 // Bearings
+tags: [ bearings ]
+uuid: 94cac3fd-c352-4fdd-833d-6129cb484b8a
+lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic Bearings 1.pdf ]
+---
+
+> I don't think I ever finished these notes.
+
+# Types of Bearings
+
+<details>
+<summary>
+
+## Plain Journal Bearings
+
+</summary>
+
+- used to support rotating shafts loaded in radial directions
+- consists of an insert fitted between the shaft and support
+- the insert may be an aluminium alloy, copper alloy, or other material
+- the insert provides lower friction and less wear than if just rotating in the support
+- the bearing may be dry rubbing or lubricated
+
+### Lubrication
+
+- hydrodynamic---a shaft continuously in oil. the load is carried by pressure generated in the oil
+  as a result of the rotation
+- hydrostatic---avoids excessive wear at start up by pumping oil into the load bearing area at a
+  pressure that lifts the shaft
+- solid-firm---a coating of a solid material like graphite or molybdenum disulphide
+- boundary layer---a thin layer of lubricant which adheres to the surface of the bearing
+
+</details>
+
+<details>
+<summary>
+
+## Ball and Roller Bearings (Rolling Element Bearings)
+
+</summary>
+
+- main load is transferred from rotating shaft to its support by rolling contact from balls
+- a rolling element bearing consists of an inner race, outer race, rolling elements and a cage
+
+![](./images/bearings_1-010.jpg)
+
+![](./images/bearings_1-011.jpg)
+
+</details>
+
+<details>
+<summary>
+
+## Plain Rubbing Bearings (Dry Sliding)
+
+</summary>
+
+- does not use liquid lubrication
+- usually polymeric
+- dry lubricants added (e.g. PTFE)
+- reinforcements added (e.g. glass fibre)
+
+</details>
+
+<details>
+<summary>
+
+## Oil Lubricated Porous Bearings
+
+</summary>
+
+- manufactured from sintered metal powders
+- porous and oil impregnated
+- more porous is weaker but allows for high speeds
+- lubricant needs to replenished at regular intervals --- usually every 1000 hours of use
+
+</details>
+
+<details>
+<summary>
+
+# Hydrodynamic Bearings
+
+</summary>
+
+- pressure builds up in the lubricant as a response to the relative motion
+- both journal and thrust bearings may use this principle
+- surfaces touch and rub at very low speeds
+
+
+
+![](./images/vimscrot-2022-11-15T17:56:26,739425867+00:00.png)
+
+
+
+# fun graphs that may be useful for bearing selection
+
+![](./images/bearings_1-035.jpg)
+
+![](./images/vimscrot-2022-11-15T17:33:30,763609479+00:00.png)
+
+![](./images/vimscrot-2022-11-15T17:51:56,506933942+00:00.png)
+
+# $pV$ Factor
+
+- a measure of the bearing's ability to cope with frictional heat generation
+- rapid wear occurs at $pV_\text{max}$
+- if the value is exceeded then overheating, melting, and excessive wear or seizure may follow
+- general operational range should be around $0.5pV_\text{max}$
+
+![$P_\text{max}$ is limited by strength, $V_\text{max}$ is limited by temperature rise](./images/bearings_1-036.svg)
+
+- A - thermoplastics
+- B - PTFE
+- C - PTFE + fillers
+- D - porous bronze + PTF + lead
+- E - PTFE-glass weave + thermoset
+- F - reinforced thermoset + molybdenum disulphide
+- G - thermoset/carbon graphite + PTFE
+
+## Radial Sliding Bearing
+
+$$p = \frac{F_\text{radial}}{bD}$$
+
+$$V = \omega\frac D2$$
+
+![](./images/vimscrot-2022-11-15T17:48:21,486895199+00:00.png)
+
+
+## Axial Sliding Bearing
+
+$$p = \frac{4F_\text{axial}}{\pi(D^2-d^2)}$$
+
+$$V = \omega\frac{D+d}{4}$$
+
+![](./images/vimscrot-2022-11-15T17:48:34,860294942+00:00.png)
+
+# Wear
+
+$$K = \frac{W}{FVt}$$
+
+where $K$ is wear factor (provided by manufacturer), $W$ is wear volume, $F$ is sliding velocity,
+$F$ is bearing load, and $t$ is elapsed time.
+
+# Manufacture
+
+- nominal diametral clearance is commonly 1 $\mu$m  per mm
+- manufacturing tolerance
+
+  - close running fit (H8/f7)
+  - free running (H9/d9)
+

uni/mmme/2044_design_manufacture_and_project/pneumatics_and_hydraulics.md

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+---
+author: Akbar Rahman
+date: \today
+title: MMME2044 // Pneumatics and Hydraulics
+tags: [ uni, mmme2044, pneumatics, hydraulics ]
+uuid: 9df953f9-13bc-40df-916a-dccaf9a338cf
+lecture_slides: [ ./lecture_slides/Lecture 4 Pneumatics and Hydraulics.pdf ]
+---
+
+> I don't think I ever finished these notes.
+
+# Actuation Systems
+
+Actuation systems are the elements of control systems which are responsible for transforming the
+output of a control system (such as a microcontroller or microprocessor) into a controlling action
+on a machine or device.
+
+![](./images/vimscrot-2022-10-24T15:48:55,638854990+01:00.png)
+
+# Typical Hydraulic Power System
+
+The pump pumps oil from a sump through a [non return valve](#non-return-valve) and an
+[accumulator](#accumulator) to the system, from which it returns to the sump.
+
+![](./images/vimscrot-2022-10-24T16:12:01,516571507+01:00.png)
+
+## Advantages and Disadvantages of Hydraulic Power Systems
+
+Advantages:
+
+- Able to generate extremely large forces from compact actuators
+- Easy to control speed
+- Easy to implement linear motion
+
+Disadvantages:
+
+- Large infrastructure (high pressure pump, tank, distribution lines)
+- Potential fluid leaks
+- Noisy operation
+- Vibration
+- Maintenance
+- Characteristics of fluids change with temperature and moisture
+
+## Components of the System
+
+### Hydraulic Pump
+
+This provides the pressure and flow of the liquid in the system.
+
+[More information about pumps](#types-of-pumps)
+
+### Pressure Relief Valve
+
+This is a safety system that safely let's out the fluid of a pressurised system if the pressure
+exceeds a specified safe pressure.
+
+### Non-return Valve
+
+### Accumulator
+
+The accumulator is a container in which the oil is held under pressure against an external force.
+This smoothes out any short term fluctuations in the output oil pressure of the pump.
+
+![](./images/vimscrot-2022-10-24T16:12:23,213636592+01:00.png)
+
+- oil pressure rises → gas bladder contracts → more volume for oil to occupy → pressure reduces
+- oil pressure reduces → gas bladder expands → less volume for oil to occupy → pressure increases
+
+
+# Types of Pumps
+
+## Gear Pump
+
+A gear pump uses the meshing of gears to pump fluid by displacement.
+They are one of the most common types of pumps for hydraulic fluid power applications.
+
+They are also widely used in chemical installations to pump high viscosity fluids.
+
+![](./images/vimscrot-2022-10-24T16:00:04,751432198+01:00.png)
+
+## Vane Pump
+
+A rotary vane pump is a positive displacement pump that consists of vanes mounted to a rotor that
+rotates inside of a cavity.
+
+In some cases these vanes have have variable length and/or be tensioned to maintain contact with
+the walls as the pump rotates.
+
+![](./images/vimscrot-2022-10-24T16:02:06,595981120+01:00.png)
+
+## Radial Piston Pump
+
+The working pistons extend in a radial direction symmetrically around the drive shaft to take in
+fluid and output it at the outlet port.
+
+![](./images/vimscrot-2022-10-24T16:04:18,644075219+01:00.png)
+
+## Axial Piston Pump with Wash Plate
+
+An axial piston pump is a positive displacement pump that has a number of pistons in a circular
+array within a cylinder block.
+It can be used as a stand-alone pump, a hydraulic motor or an automotive air conditioning
+compressor.
+
+![](./images/vimscrot-2022-10-24T16:08:20,920351717+01:00.png)
+
+# Typical Pneumatic Power System
+
+![](./images/vimscrot-2022-10-24T16:17:26,097345700+01:00.png)
+
+1. (Filter, Silencer) The air inlet to the compressor is likely to be filtered silenced to reduce
+   the noise level.
+2. An electric motor drives the compressor
+3. The pressure relief valve protects the system against rising above a safe level
+4. (Cooler, Water Trap) Since the compressor increases the temperature of the air, there may be a
+   cooling system and filter/water trap to cool the air and remove contaminants from the system.
+5. An air receiver increases the volume of air in the system, to smooth out short term pressure
+   fluctuations
+
+## Advantages and Disadvantages of a Pneumatic System
+
+Advantages:
+
+- Cheaper than electrical or hydraulic actuation
+- Non-flammable so can use in harsh environments
+- Simple to implement
+- Controllable
+
+Disadvantages:
+
+- Does not produce a "stiff" system
+- Requires a compressor, air conditioning, and control valves
+- Pressurised air can be dangerous
+
+# Actuators
+
+Actuators generate a Force or Moment.
+Both hydraulic and pneumatic actuators have the same principles, but differ in size.
+Cylinders are the principal actuators for pneumatics:
+
+![A double acting single rod cylinder](./images/vimscrot-2022-10-24T21:27:47,109056338+01:00.png)
+
+![BS ISO 1219 Symbols of a double acting, single rod cylinder](./images/vimscrot-2022-10-24T21:28:10,876277510+01:00.png)
+
+## Terminology
+
+![](./images/vimscrot-2022-10-24T21:29:48,691574340+01:00.png)
+
+Supply to compressed air to one chamber requires exhaust from the other chamber.
+
+#### Positive Stroke
+
+Extends and pushes to + position.
+
+#### Negative Stroke
+
+Retracts to - position.
+
+## Single Acting Linear Actuator
+
+The control pressure is applied to one side of the piston.
+
+![](./images/vimscrot-2022-10-24T21:31:37,439073063+01:00.png)
+
+When  pressure is applied the piston moves along the cylinder.
+
+When pressure is no long applied the piston reverts back to its initial position and the air is
+vented from the cylinder.
+
+## Double Acting Linear Actuator
+
+Double Acting Linear Actuators are used by applying pressure to one of two sides to move a rod in
+one of two directions.
+
+![](./images/vimscrot-2022-10-24T21:35:07,023575068+01:00.png)
+
+## Rotary Actuator
+
+These produce a rotary motion.
+
+A linear cylinder can be used to produce rotary motion with angles less than 360 degrees with the
+correct linkages:
+
+![](./images/vimscrot-2022-10-24T21:38:35,444846789+01:00.png)
+
+You can also have vane type semi rotary, where the difference in pressure causes rotation:
+
+![](./images/vimscrot-2022-10-24T21:37:41,337082140+01:00.png)
+
+# Control Valves
+
+Pneumatic and hydraulic systems use directional control valves to direct the flow of fluid through a
+system.
+
+They may be activated to switch the fluid flow direction by means of mechanical, electrical, or
+fluid signal pressure.
+
+## Valve Flow Symbols
+
+![](./images/vimscrot-2022-10-24T21:41:44,043372779+01:00.png)
+
+## Valve Actuation Symbols
+
+![](./images/vimscrot-2022-10-24T21:42:03,065962564+01:00.png)
+
+### Solenoid Operated Spool Valve
+
+![](./images/vimscrot-2022-10-24T21:47:18,818669077+01:00.png)
+
+## Spool Directional Control Valve
+
+Move horizontally within the valve body to control flow:
+
+![](./images/vimscrot-2022-10-24T21:40:47,390225256+01:00.png)
+
+## Poppet Valve
+
+This valve is normally closed.
+
+![](./images/vimscrot-2022-10-24T21:41:21,917337342+01:00.png)
+
+## Pressure Control Valve
+
+![](./images/vimscrot-2022-10-24T21:48:10,147785815+01:00.png)
+
+## Servo Valve
+
+An electrohydraulic servo valve is an electrically operated valve that controls how hydraulic fluid
+is sent to an actuator.
+
+Servo valves are often used to control powerful hydraulic cylinders with very small electrical
+signal.
+
+Servo valves can provide precise control of position, velocity, pressure, and force with good post
+movement characteristics.
+
+![](./images/vimscrot-2022-10-24T21:50:04,086527638+01:00.png)
+
+## Process Control Valve
+
+Used to control the fluid flow rate.
+
+A common form of pneuma

uni/mmme/2045_materials_in_design/polymers.md

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+---
+author: Akbar Rahman
+date: \today
+title: MMME2045 // Polymers (Block P)
+tags: [ uni, mmme2045, polymers ]
+uuid: 22ccabd9-2c10-454c-bf78-cf14c6f96b47
+lecture_slides: [ ./lectures_slides/MMME2045 UNUK BlockP Part 1.pptx, ./lectures_slides/MMME2045 UNUK BlockP Part 2.pptx, ./lectures_slides/MMME2045 UNUK BlockP Part 3.pptx, ./lectures_slides/MMME2045 UNUK BlockP Part 4.pptx, ./lectures_slides/MMME2045 UNUK BlockP Revision and Examples.pptx ]
+exercise_sheets: [ ./questions/Extra Polymer Questions PQ 5-8.pptx ]
+---
+
+> I don't think I ever finished these notes.
+
+# Introduction
+
+- polymers make up a huge range of products in various fields like electricals, packaging,
+  transport, and more
+- they tend to be light, corrosion resistant and low friction
+
+# Case Study: Low Pressure Gas Distribution
+
+- the UK currently depends on a lot of gas for its power (<http://www.gridwatch.templar.co.uk/>, <https://grid.iamkate.com/>)
+
+national scale transmission:
+
+- the National Transmission System (NTS), which is operated by the National Grid, has:
+
+  - 7600 km of large diameter steel pipelines (ranging from 63 mm to 1200 mm)
+  - 20 compressor stations
+
+- gas is transported from terminals to 120 offtake installations at 85 bar
+
+  - 8 regional domestic transmission systems
+  - 40 large scale industrial consumers, like power stations, at 25 bar
+  - 8 large scale storage sites (9 more planned)
+
+regional distribution:
+
+- 275000 km of small diameter pipes
+- pressure is reduced in stages before reaching residential consumers
+- volume of gas flowing in pipleline network acts as buffer storage, called linepack
+
+## Low Pressure Gas Distribution Pipes
+
+Scale                 | Pressure (bar)| Priority                 | Material(s) used
+--------------------- | ------------- | ------------------------ | ----------------
+national distribution | 85            | Max flow                 | high speed steel
+local distribution    | 0.075 to 2    | \phantom                 | cast iron, PE
+inside house          | &lt; 0.07     | Safe and durable         | copper, lead
+laboratory            | &lt; 0.07     | Flexible, easy to change | rubber, PVC
+
+- cast iron used to be used for low pressure distribution until 50s
+- typically 12 foot sections connected by bell and spigot joints
+- sealed by jute fabric and cement or molten lead
+- leaks tend to develop in packing due to overhead traffic, freeze-thaw cycles, shifting soil, and
+  shift to dryer natural gas
+- key problems with cast iron are
+
+  - corrosion
+  - brittleness
+  - leakage
+
+- polymer replacements started in 70s and are ongoing
+- but methane leaks through PE
+
+## Desirable Properties for Pipes
+
+- chemical stability
+- toughness, high yield strength
+- stiffness
+- ease of joining
+- pressure requirements
+- low creep
+- high strength
+- minimal runaway crack growth
+- low cost
+
+## Design against Creep
+
+- radial stress tends to be negligble
+
+$$\epsilon_\theta = \frac{pR}{tE}\left(1-\frac\nu2\right)$$
+
+$$\epsilon_\theta = \sigma_\theta J(t)\left(1 - \frac\nu2\right)$$
+
+### creep compliance:
+
+$$J(t) = \frac{\epsilon(t)}{\sigma}$$
+
+# Selection Criteria for Polymers
+
+## Ductility Factor (Critical Crack Length, $a_c$)
+
+$$M = \frac{K_{Ic}}{\sigma_y}$$
+
+critical crack length is when the cracked structure will fail
+
+$$a_c < \frac1\pi\left(\frac{K_{Ic}}{\sigma_y}\right)^2$$
+
+where $a_c$ is critical crack length, $\sigma_y$ is yield strength, and $K_{Ic}$ is the plane strain
+fracture toughness
+
+$$K_{Ic} = Y\sigma(\pi a)^{\frac12}$$
+
+where $Y$ is the geometry factor (affected by shape of structure), $a$ is the length of the crack,
+and $\sigma$ is applied tensile stress
+
+# Influence of the Material's Structure
+
+## Polyethylene (PE)
+
+- PE is the simplest polymer, with the chemical formula $(C_2H_4)_n$, where $n$ is a large number
+- PE is compact and tightly packed making it insensitive to solvents
+- PE has low polarity, making it a good conductor
+- above $T_g$ the C-C bonds can rotate freely allowing chains to form random coils of amorphous regions
+
+### Types of PE
+
+- low density (LDPE) --- density of 915 to 925 kg per cubic meter
+
+    - processed under high pressure (1 to 2 kbar) and high temps (100 to 300 C)
+    - very branched molecules (low crystallinity (40 to 60%))
+    - $T_m \approx 110$ C
+    - $T_g \approx -120$ C
+    - applications include films, bags, transparent parts, packaging, bubble wrap, flexible caps
+
+- high density (HDPE) --- density of 945 to 960 kg per cubic meter
+
+    - processed with active catalyst at lower pressure (30 bar) and lower temperature (40 to 150 C)
+    - long linear branched molecules (high crystallinity (85 to 95%))
+    - applications include pipes pails, covers, chemical containers jars, tanks
+
+- linear low density (LLDPE) --- same density as LDPE
+
+    - processed at lower temps than LDPE
+    - mostly linear polymer with significant numbers of short branches
+    - commonly made by copolymerisation of ethylene with short chains of alpha-olefins (e.g.
+      1-butene, 1-hexene, 1-oxtene)
+    - advantages include higher tensile strength, impact and puncture resistance than LDPE, lower
+      thickness films can be blown with environmental stress cracking resistance
+    - applications include packaging, bags, cable covering, toys, lids, buckets, containers, pipe
+
+- medium density (MDPE) --- 926 to 940 kg per cubic metre
+
+    - processed by mechanically mixing LDPE and HDPE
+    - has properties of a mix of the two
+    - alternatively can be catalysed by catalysts such as chromium and silica
+    - applications include water and gas pipes (high shock and drop resistance), sacks, shrink film,
+      packaging film, carrier bags
+
+- ulta high molecular weight (UHMWPE) --- density of 930 to 940 kg per cubic meter
+
+    - high molar mass of around 3 to 6 million
+    - gives it high toughness but difficult to form crystal structure (45% crystallinity)
+    - high molecular mass means the long molecules produce more intercrystalline links which
+      increase yield stress through orientation hardening
+    - improved abrasion and chemical resistance, resistance to impact, and cyclical failure
+    - melt flow index is low and cannot be conventionally injection moulded, blow moulded, or
+      extruded
+    - had to be processed by compression moulding or machined
+    - applications include bearing surfaces in biomedical implants, marine barriers, rods, pumps,
+      bearings, gaskets
+
+### Lamellae
+
+- PE molecules can also assume a rod like shape and a more crystalline structure
+- PE contains large numbers of heterogenous nuclei (e.g. from catalyst residues)
+- on cooling from melt, lamellae crystals grow from edges of crystal plates so it expands to seveal
+  micrometers while thickness is about 10 to 15 nanometres
+- lamellae form next to it at a slightly different angle and form a funny shape (p7 of
+  [lecture notes](./lecture_notes/BLOCKP Lecture Notes 20-21.pdf)
+
+## Semi and Non Crystalline Polymers
+
+- semicrystalline---polymer crystals are always separated from each other by amorphous layers
+- non-crysalline (amorphous)---glassy polymers, like polystyrene, PMMA, and polycarbonate are known
+  for transparency
+
+  elastomers or rubbers like polyisoprene or butyl rubber are often filled with particles to
+  increase stiffness and reduce wear, making them opaque
+
+
+# Processing of Polymers
+
+## Melt Flow Index (MFI)
+
+MFI is the output in grams when 2.16 kg is used to extrude a polymer using these exact dimensions:
+
+![](./images/vimscrot-2022-11-10T20:50:05,302396063+00:00.png)
+
+# Stuff
+
+$$P = \text{shear stress} \times \text{shear strain}$$
+
+![](./images/vimscrot-2022-11-10T21:01:22,450954684+00:00.png)
+
+$\Delta P$ is absolute pressure ?? i think (1:12:00 <https://echo360.org.uk/lesson/3c72949d-b5d0-4ffe-b068-9ff663cc4763/classroom#sortDirection=desc>)
+
+
+