Metall, Ceramics, textiles

Question 1

Metals - general

Answer 1

• Very heavy and robust (not brittle)
• Isotopic properties
• Based upon different alloys to manipulate properties:
  1. Provide solid-solution strengthening
  2. Improve corrosion resistance
  3. Improve hardenability

Question 2

Ferrous Alloys

Answer 2

• Based on iron-carbon alloys
• Includes cast irons and different steels like:
  __Stainless steel__: Good resistance to corrosion and conatins chromium to make it stainless
• Steels properties can be manipulated by heat treatment and quench-and-heat treatment (hot to cold making steel very hard)

Question 3

Aluminum alloys

Answer 3

• Aluminum = third most common element
• Lower density than steel
• Used for: joints in assistive devices, AFO, KAFO

+Quite good corrosion resistance
+Strong relativley to it’s weight

-Lower tensile strength than steal
-Low hardness resulting in poor wear resistance

Question 4

Magnesium alloys

Answer 4

• Lighter than aluminum
• Lower Tm

+Comparable strength to aluminum but a bit weaker

-Sensitive to salt exposure
-Low modulus with poor resistance to fatigue, creep, and wear

Question 5

Titanium alloys

Answer 5

+Good corrosion resistance
+High specific strength
+Good high-temp. properties

-Expensive

Question 6

Metal - manufacturing

Answer 6

• Casting = shaping: die-, sand-, and investment casting
• Shape rolling and Die forging = squeezed to shape by massive rolls
• Extrusion = metal forced through a shaped die
• Press forming, roll forming, and spinning: fast but has geometry restrictions

Question 7

Die-casting - process

Answer 7

• Widely used to shape aluminum
  1. Molten metal under high pressure is injected into a metal die
  2. Pressure is maintained until metal solidifies
  3. Die opens and product comes out

Question 8

Ceramics - types and manufacturing

Answer 8

• Not as used as steel and composites
• Silica = most used ceramic
• Titanium dioxide = electronic ceramics
• Manufacture process:
  1. Ceramic powder
  2. Agglomerates
  3. Extrusion and tape casting (ex) to convert processed powder into green ceramic (desired shape)
  4. Sintering (high temp. treatment) to make cermaic dense

Question 9

Cermaics - properties

Answer 9

+High temperature resistance
+Good compression strength
+Very hard

-Very brittle to impact

Question 10

Textiles - structure

Answer 10

• From variety of fibers/filaments depending on wanting properties
• Natrual fibers: 60 %, ex. jute, cotton, silk
• Synthesizes fibers: 40 %, ex. nylon (strong!)

Question 11

Textiles - usage

Answer 11

Assisstive devices:
* Support knee and ankle
* Insoles - textile on top
* Straps
* Knitted textiles can help with movement

Other:
* Masks
* Can affect properties to make hydrophobic

Question 12

Technical textiles

Answer 12

• Protective textiles: contamination, impact (bullet-proof vest), temperature (fire fighters), UV
• Sport textiles: sports wear like breathing clothing and hydrophobic shoes
• Medical textiles: dipers where liquid is stored
• Electronic textiles: conductive materials, ex. heart rate
• Mobile textiles: ex. air bags, belts