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Kahoot Question and AnswersUnit 1What is the threshold failure rate for hull loss ac1 in 10^9 cidents (uncontained engine failures)?Despite this target and technology improvements the More people are flying hull loss accident rate is increasing, why?Propulsive efficiency in the Gas Turbine can be im...

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Kahoot Question and Answers Unit 1 What is the threshold failure rate for hull loss accidents (uncontained engine failures)? 1 in 10^9 Despite this target and technology improvements the hull loss accident rate is increasing, why? More people are flying Propulsive efficiency in the Gas Turbine can be improved by.... Increasing the Turbine Entry Temperature as high as possible before material limitations and optimising Pressure ratio A critical component is a component that... Failure hazards airframe, required failure rate in service < 1 in 108 flights. Failed parts can not be contained within the engine. Discs and shafts fall into this category. A sensitive component is a component that... Failure may result in engine shutdown. No release of high energy debris. Blades, combustion chambers and Outlet Guide Vanes fall into this category. An Unclassified component is a component that Failure results in very low risk to engine operation. Most static parts fall into this category. An example of critical component would be a ... Fan Discs and shafts A typical flight cycle consists of three main elements... Take-off, Cruise and Landing This major flight cycle is associated with which type of fatigue? Low Cycle Fatigue An example of a component that is susceptible to low cycle fatigue is a Fan Disc Unit 2 – Deformations and Dislocations What is Poison's ratio? Ratio of axial to lateral strain for elastic deformation Which of these two curves is the true stress strain curve?

- B Correctly identify the ultimate tensile stress (UTS).

-B

Correctly identify the failure strain (εf)

-C

Correctly identify the yeild stress.

-A

The youngs modulus is calculated from data in region D. What is the correct formula? E = Δδ / Δε What is the correct model for elastic deformation at the atomic / latice scale? Bonds acting as springs Which two of the following would affect elastic deformation behaviour Temperature and Crystal Structure What is the process of plastic deformation at the atomic scale called? atomic scale plastic deformation is achieved via “slip” or the movement of a plane of atoms relative to their neighbours  Slip always occurs under the action of a shear stress and preferably on planes of the closest atomic packing and in directions of closest atomic packing. What is a "Slip System"? combination of slip plane and slip direction is called the slip system. A crystallographic direction on a plane in the lattice What is Schmidd's law? ** RSS = Resolved Shear Stress Slip will occur if the resolved shear stress (RSS) is greater than the critical resolved shear stress (RSS) At what angle to the nominal stress does the RSS reach a maximum. +- 45 degrees What does the Hall-Petch relationship describe?

The increase in yeield stress with reduced grain size Theoretical flow (yeild) stresses below do not match with experimental measurements, why not?

Theory is incorrect.

What is the correct model for slip? Localised debonding of atoms In the picture below, 1) what is b and 2) what does it represent?

Burgers Vector, and the magnitude and direction of slip. What type of dislocation is displayed below and what type of dislocation is it?

Edge and Positive dislocation For an edge dislocation the dislocation line and motion is ............to the Burgers vector Perpendicular and Paralllel What type of dislocation is displayed below and type of screw dislocation is it?

Screw and Right hand dislocation For a screw dislocation the dislocation line and motion is ............to the Burgers vector Parallel and Perpendicular

Identify the type of dislocations below based on their movement

1 Positive, 2 Negative Identify the type of dislocations below based on their movement

1 Right hand screw, 2 left hand screw For the following mixed dislocation identify the components 1) and 2)

1 Edge, 2 Screw 1) What is the name of the pre-existing dislocation network below 2) Name the point highlighted

Frank Network and Node The two diagrams illustrate the two types of dislocation interaction, what are they called?

1 Annihilation, 2 Repulsion

The diagram below shows concentric dislocation loops, where do they originate?

The Frank Read Source What do the black arrows below indicate?

The force of dislocation What happens to internal stress as the dislocation content per unit volume increases?

Increases Which of these two stress-strain curves is for the single crystal?

2 Which of the following are examples of non-conservative dislocation movement (2 answers)? Cross-slip and climb

Unit 3 - Failure Modes in Materials The theoretical strength of a material δc is much higher than the measured value, why? Materials contain defects The characteristics of ductile fracture are that it is.... Shows evidence of deformation prior to fracture What type of failure is pictured above and what is it called?

Ductile Cup and Cone What type of sample is tested here, is it a ductile or a brittle failure?

Single Crystal – Ductile Above is and SEM micrograph of a failed sample. What type of fracture occured?

Bend Fracture Above is an SEM micrograph of a fracture surface from a brittle material, its shows....

transganular cleavage Brittle materials are always weak materials. True or false? False The toughness of a material is a measurement of its....

Ability to absorb energy before fracture Impact testing provides ...... Qualitative ranking data Which material (A or B) would you use for a crash barrier on a highway in the UK.

B Unit 4 The griffith criterion states that a crack will grow if the energy supplied to the system... Exceeds the energy required to form new surfaces What is the difference between Griffith based approaches and fracture mechanics? Fracture Mechanic assesses the stress at the crack tip and obeys similitude What is Kt? Elastic Stress Concentration Factor If σm is the instanteous stress and σ0 is the applied stress, the stress close to the notch....

Increases to UTS or infinity What are these equations called and what is their purpose?

Westergard equations, and calculate stress around crack tip What is stress intensity factor, why does its equation have so few terms?

Stress amplification at crack tip and the geometry at crack tip is simpler so the approximation is more acceptable to be simplified. Is Kcc the same as Ktc? No How do we deal with these problems in reality? Making use of geometry factor Y. Application of a simplified Westergard equations produces the curve below. Is it accurate?

No This is more like reality. Is it possible to calculate plastic zone size using K?

Yes What is plane stress and where does it typically occur?

It is a planar stress and it generally occurs at the surface What is plane strain and where does it typically occur?

It is a planar strain rate and it occurs at the centre It’s a triaxial stress state, it occurs at the centre Below is the critical value of stress intensity factor, what is it called?

Fracture Toughness If K1C and σc are fixed you can calculate... The maximum allowable defect size If K1C and ac are fixed you can calculate... The maximum allowable stress The following test specimen is called.....

Compact Tension

Unit 5 What is metal fatigue? Failure from repeated stress cycles below the UTS Using the fracture surface below name the four stages of fatigue crack growth (CG).

1-overload,2-short crack growth,3-Continuum crack growth,40initiation The features below are characteristic of a fatigue fracture surface, what are they called? Beach Marks What is the R value (or Ratio) of the following wave form?

Rato = -1

Ratio = 0

Ratio = 0.5 What is the chart below called and what do we call the indicated stress (2 answers)?

S-N Curve. Fatigue Limit or Fatigue Strength

Fatigue failures that occur in .. are called....

Zone 1: Low Cycle Fatigue LCF Zone 2: High Cycle Fatigue (HCF) Zone 3: Very high cycle fatigiue(VFCF) As we head towards longer life, what happens to the standard deviation for repeat tests? It increases What type of crack growth is occuring in each of the four zones?

The micrographs show material damage that leads to fatigue crack initiaion. How is it formed?

Development of slip bands, then intrusions and extrusions The image shows a sub-surface initiated fatigue fracture. What is the likely reason for this?

A defect

The image shows striations and indicates direction of crack gowth. How are striations formed?

Intersecting Bulk Shear Peak stress is held constant and the mean stress is increased what happens to the stress range?

Decreases The life above is decreasing as the mean increases, what is the stress range doing? Remains the same What is the diagram below called?

Range-mean diagram Roughly what is the mystery R value? 0.7

What direction does the arrow indicate?

Lower range and mean, increasing life What is the name of loop below and what type of test does it come from?

Hysteresis loop, strain control There are two types of material reponse during a strain control test, what are they? Cyclic hardening and cyclic softening What is the indicated stress called?

Stabilised Stress

Below is a cyclic stress strain curve. This is a curve for a material that...

Cyclic Soften Below is a cyclic stress strain curve. This is a curve for a material that... Cyclic Hardens Unit 6 Which of the following are advantages of Full Component Testing? Representative and certified Which of the following are disadvantages of Full Component Testing? Expensive and variability Which of the following are advantages of Psuedo Component testing? More representative than lab samples and less variable than the full component. Which of the following are disadvantages of Psuedo Component testing? More expensive than lab testing and complex geometries are harder to analyse Which of the following are advantages of plain specimen laboratory testing? More statistically valid and better input data for modelling

What determines the engineering crack size? The inspection method From a lifing perspective which of the two initiation lives is the life to first crack?

B From a lifing perspective which of the two lives is the propagation life?

B Which of the following is an appropriate approach to the fatigue lifing of discs? Safe Life Which of the following is an appropriate approach to the fatigue lifing of blades? Damage tolerance Which of the following are advantages of Safe life approaches? Safety and statistical certainty Which of the following are advantages of Damage Tolerance approaches? Defect tolerant and economic What's missing from the taxis label below and what's the relation called?

Log, the basquin relation In the image below what are 1) σ'f and 2) b called?

1-Fatigue strength coefficient,2-fatigue strength exponent what does the Morrow modification equation below do to the predicted life as σm increases?

Reduces Nf, - Predicted life The goodman method modifies the basquin relation by calculating what?

An effective stress amplitude for a range of mean stresses

What is the name of the most popular strain life method? Coffin-Manson Method For which region below is the Coffin-Manson relation most effective?

Region 1 What is the most popular correction method for mean stress effects on strain life methods? The walker method What are the advantages of the damage tollerance lifing methods? They allow lifing of components with defects and obey simlitude Damage tollerance life prediction methods rely on what type of data? Crack Propagation data The central region of this plot is refered to as what?

The paris region or continuum region How is the Paris equation to calculate the remaining life of the component?

Integrate with respect to a

Unit 7 Creep is the process of.... Strain accumulation under constant stress What temperature was this creep test performed at?

0.4Tm Identify the three regions below..

Region 1: Primary Region 2: Secondary Region 3: Teritiary

The arrow indicates....

Increasing temperature and and increasing stress The legend has been removed below identify the correct test temperatures below.

Black = Lowest Temperature, Blue = highest temperature Identify the missing creep senstive area of the engine

High Pressure Turbine Identify the two creep testing setups below.

A = Constant Load, B = Constant Stress What is the name of the equation below, what is D?

Arhenius Equation and D – Diffusion Coefficient What is Q and what does it represent from the equation above? The activation energy, energy for an atom to move into a non-equilibrium state The process of diffusion of an atom in its own lattice is called... Self Diffusion Two types of diffusion are shown below, they are called.....

A- Lattice Diffusion, B – Grain Boundary Diffusion Which of the two modes has the higher activation energy in previous image? Lattice Diffusion Identify the two activation energies in the plot below

A = Grain Boundary Diffusion, B = Self Diffusion High dislocation concentration increase internal stress, which stage of creep is most affected?

Primary Diffusion aids dislocation movement by aiding two mechanisms, what are they called? Climb and Cross Slip What are the two processes below called?

A = Work Hardening, B = Recovery In Region 1 the rate of work hardening is

Greater than recovery In Region 2 the rate of work hardening is The same as recovery In Region 3 the rate of work hardening is Less relevant Identify the creep damage mechanism in (a).

Wedge/ Triple Popint Identify the creep damage mechanism in (b) in image.

Creep Void Formation Why is there an increase in creep life from equiaxied to single crystal alloys?

Less Grain Boundaries Why is directionally solidified alloy better than equiaxed alloy? Less grain boundaries perpendicular to the stress How do single crystal alloys maintain strength with no grain boundaries? (two answers) Precipitation and work hardening

Unit 8 Which of the following best describes an emprical creep lifing method? A numerical correlation between test data and conditions Which of the following best describes a mechanistic creep lifing method? An equation or set of equations describing creep mechanisms Rupture times decrease with larger stress and temperature, what happens to minimum creep rate? It increases The following relationship relates miniumum creep rate to creep life, what is it caled?

Monkman-Grant The following relation relates stress to minimum creep rate, how do you calculate n?

Plot lnσ vs lnCreep rate. N is the gradient The following diagram shows a lnσ vs lnέ0 plot for a metal at moderate stress, roughly n = ..?

5 What is the missing n value below?

It does not obey the power law Name the equation and the paramter Qc below. Norton’s Power Law, Activation for Creep

Is this lifing method empirical or mechanistic? – equation above Both Identify the missing Qc value

Qc = QSD Identify the missing Qc value Qc = QGB Below is a Serby-Dorn plot, what is the prinicple of this and other long term predictions?

Prediction by applying higher temperature at same stress The chart below shows another emprical curve fit, what is it?

Hyperbolic tangent What is difference between these methods and the curve fitting method below (theta projection)?

Theta projection predicts strain accumulation The following equation is mechanistic. What do H, R and W represent?

H = Hardening, R = Recovery, W = Creep damage

Unit 9 Which of the following is a minor flight cycle? Maneuvers Which of the following is a major flight cycle? Takeoff-Cruise-Land Which of the following statements is true for Creep-Fatigue? Mean stress is large compared to stress amplitude Which of the following statements is true for Fatigue-Creep? The mean stress is small compared to the stress amplitude Which of the following types of flight is most succeptible to Creep-Fatigue? Civil Long Haul The key factor controlling the damage mechanism of creep and fatigue interaction is.... Crack Initiation In the following Strain-Life S-N plot the green line represents tests performed at ....

Higher Temperature Identify the benificial effects highlighted below

1 (top) - Slip Dispersal; 2 (below) – elimination of creep

Below is a fracture from a "Cold Dwell" failure, what do we mean by dwell in this case? Tensile or compressive holds in the fatigue cycle The picture thermo-mechanical fatigue (TMF) failure, why has it initiated at the blade tip?

Difference in temperature between tip and body The chart show SN data for Isothermal and Thermomechanical fatigue, which series is isothermal?

Red Series Identify the mystery phase angle

0 degrees Identify the mystery phase angle

180 degrees

Identify the mystery phase angle

90 degrees...