Failure mode
Encyclopedia
Failure causes are defects in design, process, quality, or part application, which are the underlying cause of a failure or which initiate a process which leads to failure. Where failure depends on the user of the product or process, then human error
must be considered.
, welding
of contacts due to an abnormal electrical current, return spring fatigue failure, unintended command failure, dust accumulation and blockage of mechanism, etc. Seldom only one cause (hazard) can be identified that creates system failures. The real root causes can in theory in most cases be traced back to some kind of human error, e.g. design failure, operational errors, management failures, maintenance induced failures, specification failures, etc.
The (end) or immediate effects of failures can also be diverse depending on the function in the system. So the relay failure might result in a failure (actually a fault) to activate a locking actuator. This is called the sub system effect or sub system functional failure mode. And finally this might result in severe damage to system (the end effect) due to the loss of a protection device. When dealing with causes -> mechanisms -> failure modes -> effects, then it should be realised that all this depends on what system level is looked at. An effect from lower level can be a cause on a higher level. It all depends on the scope of scenario of interest.
Rather than the simple description of symptoms that many product users or process participants might use, the term failure scenario / mechanism refers to a rather complete description, including the preconditions under which failure occurs, how the thing was being used, proximate and ultimate/final causes
(if known), and any subsidiary or resulting failures that result.
The term is part of the engineering lexicon
, especially of engineers working to test and debug
products or processes.
Carefully observing and describing failure conditions, identifying whether failures are reproducible or transient
, and hypothesizing what combination of conditions and sequence of events led to failure is part of the process of fixing design flaws or improving future iterations.
The term may be applied to mechanical systems failure.
, ductile fracture, brittle fracture, impact
, creep, relaxation, thermal shock
, wear
, corrosion, stress corrosion cracking, and various types of fatigue. Each produces a different type of fracture surface, and other indicators near the fracture surface(s). The way the product is loaded, and the loading history are also important factors which determine the outcome. Of critical importance is design geometry because stress concentrations can magnify the applied load locally to very high levels, and from which cracks
usually grow.
Over time, as more is understood about a failure, the failure cause evolves from a description of symptoms and outcomes (that is, effects) to a systematic and relatively abstract model of how, when, and why the failure comes about (that is, causes).
The more complex the product or situation, the more necessary a good understanding of its failure cause is to ensuring its proper operation (or repair). Cascading failure
s, for example, are particularly complex failure causes. Edge case
s and corner case
s are situations in which complex, unexpected, and difficult-to-debug problems often occur.
processes, such as rusting in the case of iron
and steel
. Such processes can also be affected by load in the mechanisms of stress corrosion cracking
and environmental stress cracking
.
Human Error
Human Error is the stage name of Rafał Kuczynski , a polish electronic musician, working mostly in the ambient music genre, produced only with a computer...
must be considered.
Component failure
A part failure mode is the way in which a component fails "functionally" on component level. Often a part has only a few failure modes. Thus a relay may fail to open or close contacts on demand. The failure mechanism that caused this can be of many different kinds, and often multiple factors play a role at the same time. They include corrosionCorrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
, welding
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
of contacts due to an abnormal electrical current, return spring fatigue failure, unintended command failure, dust accumulation and blockage of mechanism, etc. Seldom only one cause (hazard) can be identified that creates system failures. The real root causes can in theory in most cases be traced back to some kind of human error, e.g. design failure, operational errors, management failures, maintenance induced failures, specification failures, etc.
The (end) or immediate effects of failures can also be diverse depending on the function in the system. So the relay failure might result in a failure (actually a fault) to activate a locking actuator. This is called the sub system effect or sub system functional failure mode. And finally this might result in severe damage to system (the end effect) due to the loss of a protection device. When dealing with causes -> mechanisms -> failure modes -> effects, then it should be realised that all this depends on what system level is looked at. An effect from lower level can be a cause on a higher level. It all depends on the scope of scenario of interest.
Failure scenario
A scenario is the complete identified possible sequence and combination of events, failures (failure modes), conditions, system states, leading to an end (failure)system state. It starts from causes (if known) leading to one particular end effect (the system failure condition). A failure scenario is for a system the same as the failure mechanism is for a component. Both result in a failure mode (state) of the system / component.Rather than the simple description of symptoms that many product users or process participants might use, the term failure scenario / mechanism refers to a rather complete description, including the preconditions under which failure occurs, how the thing was being used, proximate and ultimate/final causes
Causality (physics)
Causality is the relationship between causes and effects. It is considered to be fundamental to all natural science, especially physics. Causality is also a topic studied from the perspectives of philosophy and statistics....
(if known), and any subsidiary or resulting failures that result.
The term is part of the engineering lexicon
Lexicon
In linguistics, the lexicon of a language is its vocabulary, including its words and expressions. A lexicon is also a synonym of the word thesaurus. More formally, it is a language's inventory of lexemes. Coined in English 1603, the word "lexicon" derives from the Greek "λεξικόν" , neut...
, especially of engineers working to test and debug
Debugging
Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware, thus making it behave as expected. Debugging tends to be harder when various subsystems are tightly coupled, as changes in one may cause bugs to emerge...
products or processes.
Carefully observing and describing failure conditions, identifying whether failures are reproducible or transient
Transient
Transience means passing with time or is the state of being brief and short-lived. Something which has the property of transience is said to be transient, or often simply a transient or transient state.Examples include:* Transient...
, and hypothesizing what combination of conditions and sequence of events led to failure is part of the process of fixing design flaws or improving future iterations.
The term may be applied to mechanical systems failure.
Mechanical failure
Some types of mechanical failure mechanisms are: excessive deflection, bucklingBuckling
In science, buckling is a mathematical instability, leading to a failure mode.Theoretically, buckling is caused by a bifurcation in the solution to the equations of static equilibrium...
, ductile fracture, brittle fracture, impact
Impact
Impact may refer to:In science :* Impact , a high force or shock over a short time period* Impact crater, a meteor crater caused by an impact event* Impact event, the collision of a meteoroid, asteroid or comet with Earth...
, creep, relaxation, thermal shock
Thermal shock
Thermal shock is the name given to cracking as a result of rapid temperature change. Glass and ceramic objects are particularly vulnerable to this form of failure, due to their low toughness, low thermal conductivity, and high thermal expansion coefficients...
, wear
Wear
In materials science, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface....
, corrosion, stress corrosion cracking, and various types of fatigue. Each produces a different type of fracture surface, and other indicators near the fracture surface(s). The way the product is loaded, and the loading history are also important factors which determine the outcome. Of critical importance is design geometry because stress concentrations can magnify the applied load locally to very high levels, and from which cracks
Fracture
A fracture is the separation of an object or material into two, or more, pieces under the action of stress.The word fracture is often applied to bones of living creatures , or to crystals or crystalline materials, such as gemstones or metal...
usually grow.
Over time, as more is understood about a failure, the failure cause evolves from a description of symptoms and outcomes (that is, effects) to a systematic and relatively abstract model of how, when, and why the failure comes about (that is, causes).
The more complex the product or situation, the more necessary a good understanding of its failure cause is to ensuring its proper operation (or repair). Cascading failure
Cascading failure
A cascading failure is a failure in a system of interconnected parts in which the failure of a part can trigger the failure of successive parts.- Cascading failure in power transmission :...
s, for example, are particularly complex failure causes. Edge case
Edge case
An edge case is a problem or situation that occurs only at an extreme operating parameter.For example, a stereo speaker might distort audio when played at its maximum rated volume, even in the absence of other extreme settings or conditions.An edge case can be expected or unexpected...
s and corner case
Corner case
A corner case is a problem or situation that occurs only outside of normal operating parameters – specifically one that manifests itself when multiple environmental variables or conditions are simultaneously at extreme levels, even though each parameter is within the specified range for that...
s are situations in which complex, unexpected, and difficult-to-debug problems often occur.
Failure by corrosion
Materials can be degraded by their environment by corrosionCorrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
processes, such as rusting in the case of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
and steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
. Such processes can also be affected by load in the mechanisms of stress corrosion cracking
Stress corrosion cracking
Stress corrosion cracking is the unexpected sudden failure of normally ductile metals subjected to a tensile stress in a corrosive environment, especially at elevated temperature in the case of metals. SCC is highly chemically specific in that certain alloys are likely to undergo SCC only when...
and environmental stress cracking
Environmental stress cracking
Environmental Stress Cracking is one of the most common causes of unexpected brittle failure of thermoplastic polymers known at present. Environmental stress cracking may account for around 15-30% of all plastic component failures in service.ESC and polymer resistance to ESC have been studied...
.
See also
- Failure analysisFailure analysisFailure analysis is the process of collecting and analyzing data to determine the cause of a failure. It is an important discipline in many branches of manufacturing industry, such as the electronics industry, where it is a vital tool used in the development of new products and for the improvement...
- Failure mode and effects analysisFailure mode and effects analysisA failure modes and effects analysis is a procedure in product development and operations management for analysis of potential failure modes within a system for classification by the severity and likelihood of the failures...
(FMEA) - Failure rateFailure rateFailure rate is the frequency with which an engineered system or component fails, expressed for example in failures per hour. It is often denoted by the Greek letter λ and is important in reliability engineering....
- Forensic electrical engineeringForensic electrical engineeringForensic electrical engineering is a branch of forensic engineering, and is concerned with investigating electrical failures and accidents in a legal context. Many forensic electrical engineering investigations apply to fires suspected to be caused by electrical failures...
- Forensic engineeringForensic engineeringForensic engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. The consequences of failure are dealt with by the law of product liability. The field also deals with...
- Hazard analysisHazard analysisA hazard analysis is used as the first step in a process used to assess risk. The result of a hazard analysis is the identification of risks. Preliminary risk levels can be provided in the hazard analysis. The validation, more precise prediction and acceptance of risk is determined in the Risk...