Lesson 5 Flashcards
It could be said to be the backbone of many engineering decisions and designs. It underpins the considerations for safety, longevity, and efficiency in engineering works.
Material Failure
is a technical term in the field of engineering used to describe the state where a material used in the design of an engineering component or structure ceases to perform the purpose for which it was designed. When this happens, the component or structure itself becomes unfit for its intended use.
Material Failure
Material Failure can occur due to several causes. Some of the more common ones include:
Stress concentration
Overload
Corrosion
Fatigue
This occurs when the load on a material is unevenly distributed, causing stress to concentrate in a particular area.
Stress concentration
This refers to the gradual degradation of a material’s properties due to chemical reactions with its environment.
Corrosion
This happens when a material finally breaks or fails after being subjected to cyclic loading over a long period.
Fatigue
This simply happens when the weight or force borne by a material is greater than it is designed to carry.
Overload
) is an essential part of evaluating why a failure occurred, so that action can be taken to prevent a similar incident in the future. It involves several steps, from initial observations to the final analysis, carried out by highly skilled technicians and engineers.
Material Failure Analysis (MFA)
helps find the underlying cause for a failure, either on an individual part level or a series production level. The idea is to keep investigating the chain of events that led to the ultimate failure until you find the fundamental reason.
root cause analysis (RCA)
The Process of Material Failure Analysis
Failure identification
Information gathering
theoretical failure prediction
Physical testing
comparison of theoretical and experimental results
final analysis and recommendations
the first step in Material Failure Analysis. During this stage, the problem is described in detail, which might include any unusual behaviour before the failure.
Failure identification
involves collecting all relevant information about the failed material’s manufacturing, history, and application. This might also include collecting pieces of the failed component for further testing.
Information gathering
the gathered information is used to formulate a hypothesis about the possible causes of failure, using knowledge of material behaviour and failure mechanisms.
theoretical failure prediction
such as visual inspections, non-destructive testing, and mechanical testing, provides a more in-depth understanding of the material’s properties and the failure’s features, leading to a refined hypothesis.
Physical testing
the results from physical testing are compared against the theoretical predictions, which can either validate or refute the initial hypothesis about the failure’s cause.
comparison of theoretical and experimental results
phase, the results are interpreted, and steps to prevent future failures are proposed. In the realm of material failure, it is often the case that,
final analysis and recommendations
Types of Manufacturing Failure Analysis
Failure Modes and Effects Analysis (FMEA)
Fishbone Diagram
Logic Fault Tree
The 5 Whys
Data Analytics
This manufacturing failure analysis technique predicts the likelihood of potential failures, while also quantifying their consequences. A _______ mode is a physical process that leads to a failure, while “__________” refers to the potentially destructive consequences caused by these failures.
Failure Modes and Effects Analysis (FMEA)
diagram is a visual tool that graphically represents the potential root causes. The illustration consists of 2 key elements: the head represents the effect or failure, and each “bone” represents a category of potential causes. They are as listed:
Machines
Methods
Materials
Manpower
Metrics
Minutes (time).
Fishbone Diagram
is a manufacturing failure analysis technique that uses a top-down tree structure where the defined fault is at the top of the structure and the base roots represent the underlying cause of the fault. A logic fault tree helps identify the physical, human and organizational roots of a failure.
Logic Fault Tree
This manufacturing failure analysis technique is a simple way of quickly getting to the root cause. The process starts with a failure, and you ask the question ‘why’ each time there is an identified cause. This activity repeats until there is an identified root cause or an uncontrollable process. The number five is not a hard limit but rather a guideline. You can determine a root cause after two to 10 whys, depending on the complexity of the problem.
The 5 Whys
With the ever-expanding “fourth industrial revolution,” modern manufacturing facilities have increasing access to rich data sets with data collected from a range of inexpensive IoT sensors used to monitor process-defining parameters such as machine temperature or vibration. Determining the root cause of a production line is analyzed through historical data. Statistical techniques are also used on these datasets to predict potential failures on equipment before they cause a costly breakdown.
This method of manufacturing failure analysis is becoming more prevalent with cheaper sensors and more capable software tools. Affordable and convenient failure analysis tools with proven statistical process modeling techniques allow companies to focus on prevention through preventative maintenance.
Data Analytics
The science of analyzing raw data
Data Analytics
is not restricted to high-tech applications or large-scale industrial settings; it can happen anywhere, including in everyday household objects and industrial situations. These failures can range from simple breakdowns to catastrophic disasters.
Material failure
Common Material Failure Examples in Household Items
Glassware:Ever dropped a glass and wondered why it broke so quickly? Thefracture toughnessof glass is low, which means it can fail entirely from a small crack. This is due to the brittle property of glass, which doesn’t allow for muchplastic deformationbefore failure.
Plastic Utensils:Plastic utensils, such as spatulas or spoons, can sometimes fail when used to stir or serve hot food. This deformation is due to a phenomenon called ‘creep’, which is when materials deform under a constant stress over a long period, in this case, the stress from hot food items.
Light Bulbs:Material failure can also lead to the malfunction of light bulbs. The thin tungsten filament inside incandescent bulbs can fail due to a combination of high temperatures (which weaken the metal over time) and the stress induced by electrical currents.
Material Failure Examples in the Industrial Sector
Bridge Collapses:Bridge failures are often caused bystress corrosion cracking(SCC), a process which involves the slow growth of cracks due to a corrosive environment. Such was the case in the infamous Tacoma Narrows Bridge collapse, where high wind speed led to aeroelastic flutter and eventual failure.
Pipeline Ruptures:Pipeline failures can occur due to various reasons, likestress corrosion cracking, hydrogen embrittlement, or even mechanical impact. The regular incidence of pipeline ruptures in the oil and gas industry underlines the significance of selecting materials that can withstand such stresses.
Boiler Explosions:Boilers can fail if substandard materials are used or maintenance procedures aren’t properly followed. The pressure build-up can cause the boiler shell to rupture, leading to an explosion. The Boston Boiler Explosion in 1867 is a tragic example, which resulted from low-quality iron unable to withstand the pressure rise.
External Causes of Material Failure
Mechanical Stress
Temperature Extremes
Corrosion and Wear
Radiation
This covers forces, loads, and stresses applied to a material beyond its load-bearing capacity, leading to behaviours such as deformation, fractures or outright failures. For instance, in structures, cyclic loading leading to fatigue failure is a significant concern.
Mechanical Stress
Extraordinary high or low temperatures can cause materials to fail. High temperatures could lead to the softening or even melting of materials while extremely low temperatures could cause brittleness.
Temperature Extremes
Both these phenomena are responsible for a gradual reduction in the volume of a material, leading to its weakening. Corrosion is mainly due to environmental influences like humidity, while wear results from physical contact with other surfaces over time.
Corrosion and Wear
In severe cases, especially where the material is exposed to high-energy radiation, it can instigate changes in the microstructure of the material and hence can lead to failure.
Radiation
Internal Causes of Material Failure
Inherent Material Flaws
Manufacturing Defects
Material Degradation
Design Errors
Every material has its own set of physical and mechanical properties which define its capacity to withstand certain conditions. If a material’s intrinsic properties are not suitable for a specific application, it could lead to failure.
Inherent Material Flaws
Imperfections introduced during the manufacturing process, such as inclusions, pores, or voids, can serve as stress concentration points leading to premature failure.
Manufacturing Defects
Over time, the material’s properties may degrade due to aging or repeated use, making it susceptible to failure.
Material Degradation
If the design does not accurately take into account the material’s properties or expected loading conditions, it may lead to failure.
Design Errors
How to Prevent Material Failure?
Proper Material Selection
Detailed Design Process
Quality Control
Regular Maintenance
Material Testing
Using a material with the right properties for a specific application is the first step in preventing material failure.
Proper Material Selection
The design phase should take into account the expected loads, environmental factors, as well as the chosen material’s properties. This includes the use of safety factors and design refinement through simulation techniques.
Detailed Design Process
Rigorous ___________ during manufacturing can help identify and rectify any defects or inconsistencies before they lead to failure.
Quality Control
Regular inspection and maintenance can help detect early signs of failure and take corrective action before a catastrophic failure occurs.
Regular Maintenance
Conducting ___________ under different conditions can predict how the material will behave under similar conditions and help evaluate its suitability for a particular application.
Material Testing
