Article Evaluation (Week 3)

Article Chosen: Conductive Heat Transfer

Is everything in the article relevant to the article topic? Is there anything that distracted you?
- I would agree that everything in this article is relevant to the topic however I was distracted a little bit when the article spoke about detailed classifications in regards to smooth and solid surfaces.
Is the article neutral? Are there any claims, or frames, that appear heavily biased toward a particular position?
- No, the article appears neutral to me.
Are there viewpoints that are overrepresented, or underrepresented?
- I feel like the Free or Natural convection section went into a little more detail than the forced convection section.
Check a few citations. Do the links work? Does the source support the claims in the article?
- The links do work and the items that I could check seem to support the article.
Is each fact referenced with an appropriate, reliable reference? Where does the information come from? Are these neutral sources? If biased, is that bias noted?
- No not all of the facts are referenced however some are. The sources appear to be neutral.
Is any information out of date? Is anything missing that could be added?
- No I feel the article encompass everything as far as my knowledge.
Check out the Talk page of the article. What kinds of conversations, if any, are going on behind the scenes about how to represent this topic?
- There are a lot of conversations going on behind the scenes. Some back and fourth in regards to the opening paragraph and definition of convection.
How is the article rated? Is it a part of any WikiProjects?
- The project is rated as Start-Class and is within scope of the WikiProject Meteorology.
How does the way Wikipedia discusses this topic differ from the way we've talked about it in class?
- This article goes a lot deeper than our classroom discussions but not in a bad way. What we have leaned in class is just relevant to the welding topic.

Potential Topics (Week 4)

Fatigue of a Welded Joint

I was not able to find information regarding fatigue of a welded joint. Ideally this would be a subheading under the Welded Joint page. I would be able to speak a little but about metallurgy plus information which will be presented in lecture on 11/29.

Welding Distortion

I was not able to find any information on this topic either in Wikipedia. This may be a topic in itself where as my previous topic would be an add on. I would be able to link some topics such as Welding and Distortion. I do not have many sources on this topic to they will have to be researched but it is a fairly well known topic within manufacturing. We have not covered this topic in class but it is coming. I have discussed it in other classes as well as in application at work/industry.

Thermal Conduction

Thermal Conduction subheading "Applications" can be updated to include welding. Here we can expand a little but from the earlier portion of class and how it applies to welding and review various papers/studies.

Welding Cooling Rate

This may be a good topic because it is not represented on Wikipedia, however I do not have any good references other than class notes at this time so I will keep this as a low priority.

Instructor Comments

Adding an article on fatigue of welded joints would be excellent.

Fatigue of a Welded Joint (DRAFT)

Welding is a manufacturing method used to join various materials in order to form an assembly. During welding, joints are formed between two or more separate pieces of material. A welded joint subjected to cyclic loading could fail due to fatigue.^[1] Fatigue results from this cyclic loading, as well as strains, in the material.^[1] Throughout a welded assemblies life, cracks, which reduce the fatigue life of a joint, could initiate, propagate, and grow causing the assembly to fail even if these cyclic stresses are low and smaller than the base material and weld filler material yield stress.^[1] Hence, the fatigue strength of a welded joint does not correlate to the fatigue strength of the base material.^[1] Incorporating design considerations in the development phase can reduce failures due to fatigue in welded joints.^[2]

Stress Life Method

Similar to high cycle fatigue analysis, the stress life method utilizing stress-cycle curves (also known as Wöhler curves) can be used to determine the strength of a welded joint under fatigue loading. Welded sample specimens undergo repeated loading at a specified stress amplitude, or fatigue strength, until the material fails.^[3] This same test is then repeated with various stress amplitudes in order to determine its corresponding cycles, N, to failure. With the data collected, fatigue strength can be plotted against the corresponding number of cycles for a specific material, welded joint and loading.^[3] From these curves, the endurance limit, finite-life and infinite-life region can then be determined.^[3]

Factors Affecting Fatigue

Welding Residual Stresses

During the welding process, residual stresses can present themselves in the area of the weld, either in the heat affected zone or fusion zone. The mean stress a welded joint may see in application, can be altered due to the welding processes implementing residual stresses, changing the fatigue life and can render S-N laboratory testing results.^[2] Welded assemblies, with geometrical imperfections, can also introduce residual stresses.^[2] Removal of residual stresses by stress relief methods can only be partially achieved.^[2] Residual stresses can still remain in a welded joint even after some of these stress relief methods have been achieved.^[2]

Member Thickness

An increase in thickness of a base material decreases the fatigue strength when a crack propagates from the toe of a welded joint.^[2] This is due to an increase in residual stress concentrations in thick material cross sections.^[2]

Material Type

All materials have varying physical and mechanical properties. As a materials ultimate tensile strength increases, this does not lead to an increase in fatigue strength.^[2] This is not the case when evaluating materials that do not contain welded joints.^[2] Therefore stress-cycle curves for welded joints cannot be correlated to the materials ultimate tensile strength. Most design information has been developed for structural steels.^[2]

Welding Process

Many welding processes are available for various applications and environments. Stress-cycle curves are not available for all of these processes and still need to be developed so that proper fatigue analysis can be performed.^[2] The most abundant process found in stress-cycle curves is developed from specimens prepared by arc welding.

Surrounding Environment

The surrounding environment can effect the fatigue life of a welded assembly, often lowering it.^[2] Points such as temperature, moisture, and geographical location are considered part of the surrounding environment. Environments which contain sea water may see decreased fatigue life due to the increase in crack growth rates.^[2] Little information is available in this area, but it is known that if a base material is subjected to corrosion, the fatigue strength can decrease to what is similarly found in welded joints.^[2]

Avoiding Fatigue Failures of a Welded Joint

Since the presence of cracks reduces fatigue life and accelerates failure, it is important to avoid all cracking mechanisms in order to prolong the fatigue life of a welded joint.^[4] Other weld defects, such as inclusions and lack of penetration, should also be avoided due to these defects being the source of where cracks can initiate.^[5] Detailed review of the welded joint during the design is another way to reduce failures. Ensuring that the design is able to handle the cyclic loading profile will prevent premature failures.^[5] Additional resources through design handbooks are also available to aid in designing the welded joint to optimize fatigue life.^[5] Finite element analysis can also be used to successfully predict fatigue failure.^[4]

References

^ ^a ^b ^c ^d Tom., Lassen (2013). Fatigue Life Analyses of Welded Structures : Flaws. RÃ©cho, Naman. Somerset: Wiley. ISBN 9781118614709. OCLC 929525641.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ Maddox, Stephen (January 2000). "Fatigue Design Ruled for Welded Structures". Progress in Structural Engineering and Materials. 2 (1): 102–109. doi:10.1002/(SICI)1528-2716(200001/03)2:1<102::AID-PSE12>3.0.CO;2-A – via John Wiley & Sons, Ltd.
^ ^a ^b ^c Gordon), Budynas, Richard G. (Richard (2008). Shigley's mechanical engineering design. Nisbett, J. Keith., Shigley, Joseph Edward. (8th ed.). Boston: McGraw-Hill. ISBN 9780073312606. OCLC 70836665.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ ^a ^b Martin, T. "Fatigue Design of Welded Joints Using the Finite Element Method and the 2007 ASME Div. 2 Master Curve". Department of Industrial Engineering, University of Pharma (Italy).
^ ^a ^b ^c "What is fatigue failure and how can it be avoided?".

[:0-1] Tom., Lassen (2013). Fatigue Life Analyses of Welded Structures : Flaws. RÃ©cho, Naman. Somerset: Wiley. ISBN 9781118614709. OCLC 929525641.

[:2-2] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ Maddox, Stephen (January 2000). "Fatigue Design Ruled for Welded Structures". Progress in Structural Engineering and Materials. 2 (1): 102–109. doi:10.1002/(SICI)1528-2716(200001/03)2:1<102::AID-PSE12>3.0.CO;2-A – via John Wiley & Sons, Ltd.

[:1-3] Gordon), Budynas, Richard G. (Richard (2008). Shigley's mechanical engineering design. Nisbett, J. Keith., Shigley, Joseph Edward. (8th ed.). Boston: McGraw-Hill. ISBN 9780073312606. OCLC 70836665.{{cite book}}: CS1 maint: multiple names: authors list (link)

[:3-4] Martin, T. "Fatigue Design of Welded Joints Using the Finite Element Method and the 2007 ASME Div. 2 Master Curve". Department of Industrial Engineering, University of Pharma (Italy).

[:4-5] "What is fatigue failure and how can it be avoided?".

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