21-40 Flashcards
What is the fatigue limit?
● Maximum stress amplitude below which the material never fails, no matter how large the number of cycles is.
Fatigue is highly affected by the surface quality. Name one solution to how fatigue life can be increased by surface treatment:
● Shot peening
● Case hardening
Name a surface treatment of Al-alloys that is detrimental to fatigue life:
● sulphuric acid anodizing
List two types of molecular structures of polymers:
● Linear polymers
● Branched polymers
● Cross-linked polymers
● Network polymers
What is the glass transition temperature?
● Glass transition is when the polymer becomes a rigid solid on cooling, while retaining the
disordered molecular structure characteristic to liquids.
● The glass transition temperature is between 0.5 and 0.8 of the melting temperature.
The material X10CrNi18-10 is:
● an alloyed steel
The material 1.7734.6 designates:
● hardened and tempered condition.
Which alloying element increases strength?
● Carbon (C)
Which alloying element increases corrosion resistance:
● Nb (Niobium)
● Cr (Chromium)
● Ti (Titanium)
What does the term Nb or Ti stabilize mean in corrosion-resistant materials/welding filler materials:
● A form of intergranular corrosion is weld decay occurs when galvanic corrosion begins from heating the material too long due to welding or improper heat treatment.
● Nb & Ti can be added to form carbides faster than Cr and preventing Cr carbide precipitation and subsequent corrosion.
The material EN AC-51300F is:
● Cast aluminium alloy
1.7734.6 designates:
● Hardened and tempered condition
What is the advantage of Al-Li alloys when compared to Li-free alloys:
● Reduces alloy density
● Increases modulus
● Higher stiffness
● Excellent fatigue and cryogenic toughness properties
● Superior fatigue crack growth resistance
Do Al-alloys have a fatigue limit?
No.
What type of material is preferably used for lightweight complex castings?
● Magnesium alloys
What is the temper designation leading to the highest strength for heat treatable aluminium alloys?
● T6
What are the 2 basic constituents of continuous fibre laminated composite material?
● Composite fibres - usually extremely thin strands of graphite, aramid (kevlar), boron, SiC, quartzor glass. Carry main loads engthwise
● Composite matrix - resin, metal or ceramic. Shields fibres and conveys loads between fibres.
Describe the allotropy of Titanium alloys and its effect on the possible strengthening mechanisms:
● Alpha alloys
● Near-alpha alloys
● Alpha and beta alloys
● Beta alloys
What is valid for thermoset resins?
● Undergo chemical change when cured
● Low viscosity
● Tacky prepreg
● Irreversible processing
Fabric weaves:
● Woven fabrics have in general lower FVC (Fiber Volume Content) than tapes
● UD fiber weave - improved drapability over tape, minimal reduction in fiber strength
● Plain weave - fiber crimping, leads to loss of properties, but improved drapability over UD weave,
improved damage tolerance, speedier layup
● Twill 2x2 / harness satin - improved drapability over plain weave, less crimping of fibers
