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An Accelerated testing program can be broken down into the following steps:

Define objective and scope of the test

Collect required information about the product

Identify the stress(es)

Determine level of stress(es)

Conduct the Accelerated test and analyze the accelerated data.

Common way to determine a life stress relationship are

Arrhenius Model

Eyeing Model

Inverse Power Law Model

Temperature-Humidity Model

Temperature Non-thermal Model

1.Discuss Reliability requirements for an automobile.

2.Read and discuss information about System of reliability parameters:

System reliability parameters

Requirements are specified using reliability parameters. The most common reliability parameter is the Mean Time Between Failures (MTBF), which can also be specified as the failure rate or the number of failures during a given period. These parameters are very useful for systems that are operated on a regular basis, such as most vehicles, machinery, and electronic equipment. Reliability increases as the MTBF increases. The MTBF is usually specified in hours, but can also be used with other units of measurement such as miles or cycles. In other cases, reliability is specified as the probability of mission success. For example, reliability of a scheduled aircraft flight can be specified as a dimensionless probability or a percentage referred to system safety engineering.

A special case of mission success is the single-shot device or system. These are devices or systems that remain relatively dormant and only operate once. Examples include automobile airbags, thermal batteries and missiles. Single-shot reliability is specified as a probability of success, or is subsumed into a related parameter. Single-shot missile reliability may be incorporated into a requirement for the probability of hit.

For such systems, the probability of failure on demand (PFD) is the reliability measure. This PFD is derived from failure rate and mission time for

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non-repairable systems. For repairable systems, it is obtained from failure rate and mean-time-to-repair (MTTR) and test interval. This measure may not be unique for a given system as this measure depends on the kind of demand. In addition to system level requirements, reliability requirements may be specified for critical subsystems. In all cases, reliability parameters are specified with appropriate statistical confidence intervals.

Discuss the possible illustrations and graphics for the article

A.“Reliability modeling”;

B.“Reliability test requirements”;

C.“Design for reliability”.

Reliability modeling

Reliability modeling is the process of predicting or understanding the reliability of a component or system. Two separate fields of investigation are common: The physics of failure approach uses an understanding of the failure mechanisms involved, such as crack propagation or chemical corrosion; The parts stress modeling approach is an empirical method for prediction based on counting the number and type of components of the system, and the stress they undergo during operation.

For systems with a clearly defined failure time (which is sometimes not given for systems with a drifting parameter), the empirical distribution function of these failure times can be determined. This is done in general in an accelerated experiment with increased stress. These experiments can be divided into two main categories:

Early failure rate studies determine the distribution with a decreasing failure rate over the first part of the bathtub curve. Here in general only moderate stress is necessary. The stress is applied for a limited period of time in what is called a censored test. Therefore, only the part of the distribution with early failures can be determined.

In so-called zero defect experiments, only limited information about the failure distribution is acquired. Here the stress, stress time, or the sample size is so low that not a single failure occurs. Due to the insufficient sample size, only an upper limit of the early failure rate can be determined. At any rate, it looks good for the customer if there are no failures.

In a study of the intrinsic failure distribution, which is often a material property, higher stresses are necessary to get failure in a reasonable period of time. Several degrees of stress have to be applied to determine an acceleration model. The empirical failure distribution is often parameterized with a Weibull or a log-normal model.

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It is a general praxis to model the early failure rate with an exponential distribution. This less complex model for the failure distribution has only one parameter: the constant failure rate. In such cases, the Chi-square distribution can be used to find the goodness of fit for the estimated failure rate. Compared to a model with a decreasing failure rate, this is quite pessimistic. Combined with a zero-defect experiment this becomes even more pessimistic. The effort is greatly reduced in this case: one does not have to determine a second model parameter (e.g. the shape parameter of a Weibull distribution, or its confidence interval (e.g. by an MLE / Maximum likelihood approach) - and the sample size is much smaller.

Reliability test requirements

Because reliability is a probability, even highly reliable systems have some chance of failure. However, testing reliability requirements is problematic for several reasons. A single test is insufficient to generate enough statistical data. Multiple tests or long-duration tests are usually very expensive. Some tests are simply impractical. Reliability engineering is used to design a realistic and affordable test program that provides enough evidence that the system meets its requirement. Statistical confidence levels are used to address some of these concerns. A certain parameter is expressed along with a corresponding confidence level: for example, an MTBF of 1000 hours at 90% confidence level. From this specification, the reliability engineer can design a test with explicit criteria for the number of hours and number of failures until the requirement is met or failed.

The combination of reliability parameter value and confidence level greatly affects the development cost and the risk to both the customer and producer. Care is needed to select the best combination of requirements. Reliability testing may be performed at various levels, such as component, subsystem, and system. Also, many factors must be addressed during testing, such as extreme temperature and humidity, shock, vibration, and heat. Reliability engineering determines an effective test strategy so that all parts are exercised in relevant environments. For systems that must last many years, reliability engineering may be used to design an accelerated life test.

Reliability engineering must also address requirements for various reliability tasks and documentation during system development, test, production, and operation. These requirements are generally specified in the contract statement of work and depend on how much leeway the customer wishes to provide to the contractor. Reliability tasks include various analyses, planning, and failure reporting. Task selection depends on the criticality of the system as well as cost. A critical system may require a formal failure reporting and review process throughout development, whereas a non-critical system may rely on final test reports. The most common reliability program tasks are documented in

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reliability program standards, such as MIL-STD-785 and IEEE 1332. Failure reporting analysis and corrective action systems are a common approach for product/process reliability monitoring.

Design for reliability

Design For Reliability (DFR), is an emerging discipline that refers to the process of designing reliability into products. This process encompasses several tools and practices and describes the order of their deployment that an organization needs to have in place in order to drive reliability into their products. Typically, the first step in the DFR process is to set the system’s reliability requirements. Reliability must be "designed in" to the system. During system design, the top-level reliability requirements are then allocated to subsystems by design engineers and reliability engineers working together.

Reliability design begins with the development of a model. Reliability models use block diagrams and fault trees to provide a graphical means of evaluating the relationships between different parts of the system. These models incorporate predictions based on parts-count failure rates taken from historical data. While the predictions are often not accurate in an absolute sense, they are valuable to assess relative differences in design alternatives.

One of the most important design techniques is redundancy. This means that if one part of the system fails, there is an alternate success path, such as a backup system. An automobile brake light might use two light bulbs. If one bulb fails, the brake light still operates using the other bulb. Redundancy significantly increases system reliability, and is often the only viable means of doing so. However, redundancy is difficult and expensive, and is therefore limited to critical parts of the system. Another design technique, physics of failure, relies on understanding the physical processes of stress, strength and failure at a very detailed level. Then the material or component can be re-designed to reduce the probability of failure. Another common design technique is component derating: Selecting components whose tolerance significantly exceeds the expected stress, as using a heavier gauge wire that exceeds the normal specification for the expected electrical current.

Many tasks, techniques and analyses are specific to particular industries and applications. Commonly these include:

Built-in test (BIT)

Failure mode and effects analysis (FMEA)

Reliability simulation modeling

Thermal analysis

Reliability Block Diagram analysis

Fault tree analysis

Root cause analysis

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Sneak circuit analysis

Accelerated Testing

Reliability Growth analysis

Weibull analysis

Electromagnetic analysis

Statistical interference

Avoid Single Point of Failure

Results are presented during the system design reviews and logistics reviews. Reliability is just one requirement among many system requirements. Engineering trade studies are used to determine the optimum balance between reliability and other requirements and constraints.

Language practice

1. Match English words with their Russian definitions:

2.Rephrase the following sentences and translate them into Russian:

Example: This wire is made of copper.

This is a copper wire.

1.This rod is made of metal.

2.This handle is made of rubber.

3.This tin is made of aluminum.

4.This beaker is made of glass.

Example: This is a steel blade.

This blade is made of steel.

1.This is a plastic cover.

2.This is a copper pipe.

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3.This is a plastic ruler.

4.This is an iron bolt.

3.Give instructions to your groupmates:

Example: Steel\ruler\wooden

Helen, do not use the wooden ruler. Use the steel one.

1.Metal\tray\plastic

2.Rubber\pipe\copper

3.Glass\rod\plastic

4.Iron\bolts\steel

5.Copper\nuts\steel

6.Wooden\beams\concrete.

Writing

1.Using all phrases and word structures from section “Language practice” describe the role of different materials in the car reliability.

2.Using phrases and word structures from section “Language practice” write your own report about:

1)Software reliability

2)Reliability organizations

3)Reliability engineering education

4)Preventive maintenance

3.Find appropriate supporting information, illustrations and graphics for the following articles and make a presentation of it:

Human reliability

Human reliability is related to the field of human factors engineering, and refers to the reliability of humans in fields such as manufacturing, transportation, the military, or medicine. Human performance can be affected by many factors such as age, state of mind, physical health, attitude, emotions, propensity for certain common mistakes, errors and cognitive biases, etc.

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Human reliability is very important due to the contributions of humans to the resilience of systems and to possible adverse consequences of human errors or oversights, especially when the human is a crucial part of the large sociotechnical systems as is common today. User-centered design and error-tolerant design are just two of many terms used to describe efforts to make technology better suited to operation by humans.

Human Reliability Analysis Techniques

A variety of methods exist for Human Reliability Analysis (HRA) (see Kirwan and Ainsworth, 1992; Kirwan, 1994). Two general classes of methods are those based on probabilistic risk assessment (PRA) and those based on a cognitive theory of control.

One method for analyzing human reliability is a straightforward extension of probabilistic risk assessment (PRA): in the same way that equipment can fail in a plant, so can a human operator commit errors. In both cases, an analysis (functional decomposition for equipment and task analysis for humans) would articulate a level of detail for which failure or error probabilities can be assigned. This basic idea is behind the Technique for Human Error Rate Prediction (THERP) (Swain & Guttman, 1983). THERP is intended to generate human error probabilities that would be incorporated into a PRA. The Accident Sequence Evaluation Program (ASEP) Human Reliability Procedure is a simplified form of THERP; an associated computational tool is Simplified Human Error Analysis Code (SHEAN) (Wilson, 1993). More recently, the US Nuclear Regulatory Commission has published the Standardized Plant Analysis Risk (SPAR) human reliability analysis method also because of human error (SPAR-H) (Gertman et al., 2005).

Erik Hollnagel has developed this line of thought in his work on the Contextual Control Model (COCOM) (Hollnagel, 1993) and the Cognitive Reliability and Error Analysis Method (CREAM) (Hollnagel, 1998). COCOM models human performance as a set of control modes—strategic (based on longterm planning), tactical (based on procedures), opportunistic (based on present context), and scrambled (random) -- and proposes a model of how transitions between these control modes occur. This model of control mode transition consists of a number of factors, including the human operator's estimate of the outcome of the action (success or failure), the time remaining to accomplish the action (adequate or inadequate), and the number of simultaneous goals of the human operator at that time. CREAM is a human reliability analysis method that is based on COCOM.

Related techniques in safety engineering and reliability engineering include Failure mode and effects analysis, Hazop, Fault tree, and SAPHIRE: Systems Analysis Programs for Hands-on Integrated Reliability Evaluations.

Human Error

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Human error has been cited as a cause or contributing factor in disasters and accidents in industries as diverse as nuclear power (e.g., Three Mile Island accident), aviation (see pilot error), space exploration (e.g., Space Shuttle Challenger Disaster), and medicine (see medical error). It is also important to stress that "human error" mechanisms are the same as "human performance" mechanisms; performance later categorized as 'error' is done so in hindsight (Reason, 1991; Woods, 1990): therefore actions later termed "human error" are actually part of the ordinary spectrum of human behavior. The study of absentmindedness in everyday life provides ample documentation and categorization of such aspects of behavior. While human error is firmly entrenched in the classical approaches to accident investigation and risk assessment, it has no role in newer approaches such as Resilience Engineering.

There are many ways to categorize human error (see Jones, 1999; Wallace and Ross, 2006).

exogenous versus endogenous (i.e., originating outside versus inside the individual) (Senders and Moray, 1991)

situation assessment versus response planning (e.g., Roth et al., 1994) and related distinctions in

errors in problem detection (also see signal detection theory)

errors in problem diagnosis (also see problem solving)

errors in action planning and execution (Sage, 1992) (for example: slips or errors of execution versus mistakes or errors of intention; see Norman, 1988; Reason, 1991)

By level of analysis; for example, perceptual (e.g., optical illusions) versus cognitive versus communication versus organizational.

The cognitive study of human error is a very active research field, including work related to limits of memory and attention and also to decision making strategies such as the availability heuristic and other cognitive biases. Such heuristics and biases are strategies that are useful and often correct, but can lead to systematic patterns of error.

Misunderstandings as a topic in human communication have been studied in Conversation Analysis, such as the examination of violations of the Cooperative principle and Gricean maxims.

Organizational studies of error or dysfunction have included studies of safety culture. One technique for organizational analysis is the Management Oversight Risk Tree (MORT) (Kirwan and Ainsworth, 1992; also search for MORT on the FAA Human Factors Workbench.

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d)Primary, secondary and immediate audience

e)Style of the report

Bulldozers can be found on a wide range of small scale and large construction sites, mines and quarries, military bases, heavy industry factories, and large governmental and public Engineering projects.

A bulldozer is a crawler, equipped with a substantial metal plate (known as a blade), and used to push large quantities of soil, sand, rubble, etc, during construction work. The term "bulldozer" is often used to mean any heavy engineering vehicle (frequently loaders and in particular track loaders), but precisely, the term refers only to a tractor (usually tracked) fitted with a dozer blade.

Most often, bulldozers are large and powerful tracked engineering vehicles. The tracks give them excellent ground hold and mobility through very rough terrain. Wide tracks help distribute the bulldozer s weight over large area (decreasing pressure), thus preventing it from sinking in sandy or muddy ground. Extra wide tracks are known as swamp tracks . Bulldozers have excellent ground hold and a torque divider designed to convert the engine s power into dragging ability, letting the bulldozer use its own weight to push very heavy things and remove obstacles that are stuck in the ground. The Caterpillar D9, for example, can easily tow tanks that weigh more than 70 tons. Because of these attributes, bulldozers are used to clear areas of obstacles, shrubbery, burnt vehicles, and remains of structures.

Sometimes a bulldozer is used to push another piece of earthmoving equipment known as a "scraper". The towed Fresno Scraper, invented in 1883 by James Porteous, was the first design to enable this to be done economically,

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