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
Human error refers to something having been done that was " not intended by the actor; not desired by a set of rules or an external observer; or that led the task or system outside its acceptable limits".Senders, J.W. and Moray, N.P. (1991) Human ...
must be considered.
Component failure / failure modes
A part failure mode is the way in which a component failed "functionally" on the component level. Often a part has only a few failure modes. For example, 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
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
,
welding of contacts due to an abnormal electric 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.
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 Causes, or causality, is the relationship between one event and another. It may also refer to:
* Causes (band), an indie band based in the Netherlands
* Causes (company)
Causes.com is a civic-technology app and website that enables users to orga ...
(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
In computer programming and software development, debugging is the process of finding and resolving '' bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems.
Debugging tactics can involve ...
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
Iteration is the repetition of a process in order to generate a (possibly unbounded) sequence of outcomes. Each repetition of the process is a single iteration, and the outcome of each iteration is then the starting point of the next iteration. ...
. The term may be applied to mechanical systems failure.
Types of failure causes
Mechanical failure
Some types of mechanical failure mechanisms are: excessive deflection,
buckling
In structural engineering, buckling is the sudden change in shape (deformation) of a structural component under load, such as the bowing of a column under compression or the wrinkling of a plate under shear. If a structure is subjected to a ...
,
ductile fracture,
brittle fracture,
impact, creep, relaxation,
thermal shock,
wear
Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology.
Wear in ...
, 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
In solid mechanics, a stress concentration (also called a stress raiser or a stress riser) is a location in an object where the stress is significantly greater than the surrounding region. Stress concentrations occur when there are irregulariti ...
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
A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a measure.
Models c ...
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
A cascading failure is a failure in a system of interconnected parts in which the failure of one or few parts leads to the failure of other parts, growing progressively as a result of positive feedback. This can occur when a single part fails, in ...
s, for example, are particularly complex failure causes.
Edge cases and
corner case
In engineering, a corner case (or pathological case) involves a problem or situation that occurs only outside normal operating parameters—specifically one that manifests itself when multiple environmental variables or conditions are simultaneou ...
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
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
processes, such as
rusting
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH), ...
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.
See also
*
Failure analysis
*
Failure mode and effects analysis (FMEA)
*
Failure modes, effects, and diagnostic analysis Failure modes, effects, and diagnostic analysis (FMEDA) is a systematic analysis technique to obtain subsystem / product level failure rates, failure modes and diagnostic capability. The FMEDA technique considers:
* All components of a design,
* The ...
(FMEDA)
*
Failure rate
Failure rate is the frequency with which an engineered system or component fails, expressed in failures per unit of time. It is usually denoted by the Greek letter λ (lambda) and is often used in reliability engineering.
The failure rate of a ...
*
Forensic electrical engineering
Forensic 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 cau ...
*
Forensic engineering
*
Hazard analysis
A 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 different types of hazards. A hazard is a potential condition and exists or not (probability is 1 or 0). It may ...
*
Ultimate failure
In mechanical engineering, ultimate failure describes the breaking of a material. In general there are two types of failure: fracture and buckling. Fracture of a material occurs when either an internal or external crack elongates the width or len ...
Notes
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Failure
Reliability engineering
Maintenance