Categories: General Date: Aug 6, 2010 Title: Question for the month

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Why does friction produce a heat?

What is a functionable system type?

What is a Post-Maintenance Flight Test ?

How to estimate Total Packinging Cost?

An O-ring is made from an elastomer with equimolar portions of vinylidene fluoride and hexafluoropropylene. Calculate the weight fraction of each polymer.

Estimate the particle size of a wear fragment produced by the adhesive wear of two 1040 steel surfaces under a load of 50 kg with a sliding distance of 5 mm. (Assume the particle to be a hemisphere of diameter *d*.)

Electromagnetic radiation with photon energies greater than 15 eV can damage semiconductors that are used in a communications satellite. Could visible light be a source of this damage?

What are the mechanisms of the Electrical Insulation Failures?

An extremely dis-organised organization operates n different systems numbered from 1 to n, in n different locations. Once a year these systems must be replaced. A central operator obtains a set of new systems and must transfer them to the appropriate locations. The central operator sends the spare systems in a random manner so that each system may find itself in any location. What is the probability that at least one system will be send to the correct address?

Consider a fleet containing m identical systems. In each system there are k identical modules. It is known that n units are failed in the fleet. What is the probability that exactly r k units are failed in the first system?

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What is Solar Storm ?

What are the effects of thermal shock environments on maintainable systems?

Does ocean tides generate magnetic fields?

Does environmental temperature impact reliability of UK's Type 45 Destroyer?

What is the 2nd Law of Mirce Science ?

What is the 1st Law of Mirce Science?

What is fourth Axiom of Mirce Science?

What is the thirds Axiom of Mirce Science?

What is the second axiom of Mirce Science?

What is the first axiom of Mirce Science?

An automated guided missile hits the target if booster rocket, guidance system and detonator functions properly. The probability of failure of booster rocket, guidance system and detonator is 0.1, 0.3 and 0.2 respectively.

Find

1) Probability of failure of the missile,

2) If the missile fails what is the probability that it failed due to guidance system

What are fundamental physical differences between particles and waves?

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In the jargon of maintenance professionals expression “Easter Egging” is frequently used. What does it mean?

Assume that it is known that the number of parts produced in a specific factory during a week is a random variable with mean of 50.

a) What is the probability that the next week the number of parts produced will exceed 50?

b) If the variance of weekly production is 25, what is the probability that the next week production will be between 40 and 60?

What is Economic Redundancy?

What is the difference between Correlation and Coincidence?

What is the Nature of Probability Theory?

What is Aerotoxic Syndrome?

What is frangibillity?

What is a Discrete Random variable?

Is weather and climate the same?

What is Anti-core Icing ?

What is Impact of Electromagnetic Phenomena on Aircraft Functionabnility ?

The module under consideration consists of two items, A and B whose relevant functionability measures are given in Table 1,

Table 1. RMS Data of Modules Considered

Item Distribution Scale [hrs] Shape [hrs] MTTR [hrs] MLDT [Day]

A Exponential 1000 N/a 6 7

B Normal 800 300 12 1

where, MTTR stands for the mean time to restore and MLDT for mean logistic delay time.

For the initial period of operation of 3000 hours, determine:

1. The expected number of negative functionability events, NNE, for each item;

2. The expected number of NNE for the module, bearing in mind that the consisting items are connected in series from the point of view of reliability;

3. The expected number of maintenance man-hours for the module.

4. The expected logistic delay time for the module if one-for-one spare policy is applied for the consisting items.

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What are the main advantages of building a model of a system, process or activity under consideration?

A European producer is to export a packaging machine to a customer in Brazil. The machine is packaged in wooden box of the following internal dimensions: length=7.00 m, width=2.75 m and height=3.00 m.Calculate a required number of desiccant units that should be used in order to for the machine to arrive to Brazil in the functionable state.

The majority of plastic component failures occur in the mid to long term. Even, in normally tough, ductile plastic materials failures are invariable brittle in nature and result in a short service life. What are the most common causes of such brittle failures?

What are mechanisms for formation of plastics?

What are Non Destructive Methods for Corrosion Monitoring?

What is corrosion?

What are the processes of heat transfer?

What is Infrared Thermography?

What are the main differences between inspection and examination as condition monitoring activities?

For a continuously operating machine, does the increase in the number of spare engines:

- Increases the number of failures of the gearbox?
- Has no impact on the number of failures of the gearbox?
- Decreases the number of failures of the gearbox?

What are the differences between linear and dynamic programming?

Under what conditions are the two random variables X and Y independent?

Suppose that there is a piece of test equipment that could be provided to each base that would enable the base to repair more first-indenture items. The cost of the test equipment has to be weighed against the benefit. Consider the cost as fixed and determine whether the benefit of the test equipment at bases increases or decreases with each of the following:

1. higher target availabilities;

2. projected longer repair times

3. longer order-and-ship times;

4. more years of operation;

5. reduction in unit cost:

6. increase in demand rates;

7. no increase in demand rates but an increase in variability;

8. more failures in the test equipment itself;

9. higher skill requirements for operators;

10. more false positives and negatives in the equipment diagnoses

Functionality and Functionability of machines are:

a) The same properties, just different names?

b) Not the same, but very similar properties?

c) Fundamentally different properties?

Air Transit, a manufacturer of freight aircraft is evaluating the potential benefit of a process improvement programme that should change the applicable learning curve percentage from 85% to 80%. The aircraft on which this programme is to be implemented requires 996 person-years for its first unit (where a person year is defined as work of 52 weeks with 40 hours in each week).

a) Given the following data, approximate the potential cost saving for the 20th aircraft unit manufactured.

Direct labour cost: $25/hr

Direct material cost: $46.7m per unit

Overhead: 100% on direct labour

b) Given the data above, approximate the potential reduction in cost saving for the 20th aircraft unit manufactured if the actual learning curve percentage after programme implementation is 82% rather than 80%.

c) Discuss factors that might influence the extent and rate of time reduction as a consequence of the learning process in manufacturing.

As in all chemical reactions, corrosion reactions occur through an exchange of electrons. In electrochemical reactions, the electrons are produced by a chemical reaction in one area, the anode, travel through a metallic path and are consumed through a different chemical reaction in another area, the cathode. In some cases, such as the common dry cell battery, electrochemical reactions can be used to supply useful amounts of electrical current.

What is the generic chemical formula for the corrosion of metals?

Which of the following failure mechanisms the most frequently causes failure of polymers?

- Biodegradation
- Chemical Attack
- Diffusion, permeation and migration
- Environmental Stress Cracking
- Hydrolysis
- Physical Ageing
- Radiation (ultraviolet radiation most common)
- Shear damage
- Thermo-oxidative degradation

For continuously operating machine, exposed to corrective maintenance policy, the increase in spare parts will:

1. Increase the Number of Failures

2. Decrease the Number of Failure

3. Not affect the Number of Failures.

Is the law of conservation of energy true for phenomena related to:

1. Living world?

2. Non-living world?

3. Both worlds?

Are expressions “complicated system” and “complex system”

a) Two ways to describe the same entity?

b) Two different entities?

c) Irrelevant question?

Bahrain Grand Prix is scheduled for 19-21 April 2013. Due to its closeness to the desert Sakhir, Bahrain International Circuit, during last few years recorded only 5 rainy days per year. However, current weather forecast predicts the rain on the racing Sunday. When it actually rains, the weather forecast is accurate 90% of the time. When it doesn't rain, the incorrect forecasts for rain are 10% of the time. What is the probability that it will rain on the 2013 Grand Prix day?

Among some reliability experts the following statement is commonly accepted “To double reliability you just need to double the Mean Time To Failure.” Is this statement:

a) Correct?

b) Incorrect?

c) Meaningless?

A company has decided to develop a new control processor for a North Sea installation of a wind turbine. The processor will be based on equipment the company already has field reliability data for. It is envisaged that it will consist of the following three elements:

1. Fan, vaneaxial, whose Time to First Failure is defined by W(5000,5)

2. Data processor, whose Time to First Failure is defined by W(10000,1)

3. Mounting tray, whose Time to First Failure is defined by W(10000,7)

The three components are connected in series, from reliability point of view, and no maintenance activities are planned till the first failure of the control processor takes place.

The Solution Requirements

a) What is the Reliability Function of the Control Processor?

b) What is the Mean Time to First Failure of the Control Processor?

c) What is the probability of fault free operation for the first 6 months of continuous operation?

d) Given the difficulty in maintaining off-shore wind turbines, how much of an improvement in the intrinsic Mean Time to First Failure could be expected if another data Processor is added in a parallel configuration?

When asked to define the length of time a customer is going to wait for spare parts for a new type of equipment, the logistics support manager (who has spent seventeen years supporting similar equipment, made the following judgement:

- 33 percent will get it within: 70 hours
- additional 44 percent will get it by 240 hours
- additional 13 percent will get it by 480 hours
- additional 5 percent will get it by 720 hours

a) Making use of the above data, determine the probability that a potential customer will receive the necessary parts within 3 hours of placing an order.

b) Also determine the proportion of customers whose demand for needed spares will be met within two weeks from the placing the order.