What makes a materials scientist tickle?

Back in year 1996 Walter Schütz, in his work “A history of fatigue” told the history on how Gassner in 1941, measuring the fatigue strength of high strength aluminum alloys of the series 7XXX (Al-Zn-Mg), and finding this was not much different from the lower strength, lower cost, alloys of series 2XXX (Al – Cu), warned that if they were used, for example, to build an airplane, this would lead to premature fatigue failures.

This argument is tricky  and seems illogical. Aren’t the alloys of series 7XXX of higher strength compared to alloys 2XXX? And didn’t Gassner find out the fatigue strength was about the same? So why would the fatigue live be smaller if the 7XXX alloys were used?

The explanation for this apparent contradiction is simple. The only possible reason to use a higher strength alloy (especially when it is more expensive) in place of a lower strength one, is to allow higher static stresses. In practice, one is able to reduceaviao-comercial-embraer-175-1334930067222_956x500 the thickness of a sheet, used to build, for example, the fuselage of an airplane. This leads to a lower mass of the structure, which is a good thing for airplanes. The loads acting on the structure, however, are approximately unchanged, since they depend mostly on the overall geometry of the structure. Since stress is the load divided by the cross section area, the material will work at a higher static strength level, and hence this will be inversely proportional to the thickness .

The problem is that the dynamic load (for example, the maximum and the minimum loads in function of time) are also inversely proportional to the reduction in thickness, therefore the difference between the maximum and the minimum stresses, in other words, the stress amplitude will also increase proportionally, leading to a more severe fatigue loading. Therefore fatigue life will be shorter, not because the fatigue strength (the material’s property) decreased, but because the loading became more severe, surpassing the fatigue strength.

This kind of elaborate argument is typical in Materials Science, a similar argument justifies why quenched steels should not be used in the maximum hardness is subject to a hydrogen-rich environment.  Another tricky argument explains also why low stacking fault energy FCC metals present higher strain hardening.

I call this non-linear thinking. A present cause results in an effect as a consequence of a long chain of events, which is not self-evident in principle. As I already wrote, in my opinion the aim of superior education is to prepare the student for this way of thinking.

Non-linear thinking, however, is very common in Materials Science. I believe this is due to the highly interdisciplinary  character of this subject. Of course, other scientific branches are also characterized by interdisciplinarity, but this seems to be more common in Materials Science.

It is this particular way of thinking which motivates the materials scientist. Non-linear thinking is addictive, the first time you get confronted, and understands, one of these long elaborate logical arguments, you will feel the need to learn more of the kind. So, be warned, if you are satisfied with thinking on thing in short cause-effect terms, stay away from Materials Science.


Hydrogen Embrittlement Topic – Special Symposium ICF14 Conference, Rhodes, Greece, June 18-23, 2017, “Fatigue and fracture in aggressive environments: mechanisms and risk assessment”


Hydrogen Embrittlement & Materials Science

Dear colleagues,

14th International Conference on Fracture (ICF14) will be held in the island of
Rhodes (Greece, June 18-23, 2017). For more information about ICF14
please, log on to the conference web page http://www.icf14.org

Prof. Emmanuel Gdoutos, Conference Chairman asked Prof. Robert Akid
(University of Manchester), Prof. Ihor Dmytrakh (Karpenko Physico-Mechanical Institute of National Academy of Sciences of Ukraine) and meas the members of the Scientific Advisory Board of ICF14 to organize the special symposium/sessions titled:

“Fatigue and fracture in aggressive environments: mechanisms and risk

within the frame of the Conference Programme.


We plan that this special symposium will cover the many important and actual
aspects of a general problem “Environmentally Assisted Fracture” including the following three main topic areas:
1. Stress Corrosion Cracking,
2. Corrosion Fatigue and
3. Hydrogen Embrittlement.

Our aim is to bring together top scientists and researchers in the field of  environmentally assisted fracture and hydrogen embrittlement in order to present the lastest achievements in fatigue and fracture in aggressive environments research and the current state of the art in understanding of hydrogen embrittlement phenomena.

We kindly invite you and your colleagues to participation in
this event. Please feel free to submit your Abstracts online before October 30, 2016.

We are looking forward to hearing from you and working closely with
you for the organization of a successful symposium.

Important Conference Dates:
– Second Announcement: December, 2015
– Submission of Abstracts: October 30, 2016
– Notification of Acceptance/Rejection: December, 2016
– Conference: June, 2017

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Materials Matter!

I had the honor and privilege to know Wole Soboyejo, from Princeton. He presented a seminar at the Materials Science and Engineering Department at Texas A&M University where I’m staying this week. During his talk he explained how he was moved by a question his mother (a biologist) stated after he explained the important thins he did for aerospace engineering: “what does this mater for ordinary people?”. He explained how this question directed his later career development. What I found more interesting was the way in which he addressed the young audience, showing how the basic knowledge in Thermodynamics, Fracture Mechanics, helps him in seeking solution to problems like early detection of cancer cells, or increasing the life of OLEDs, or solving the problem of furnishing clean water to the poorest of the poorests. Later I had the opportunity to have a dinner with him, invited by Prof. Alan Needleman, his wife Wanda, Prof. Ibrahim Karaman and Prof. Raymundo Arróyave. It was a pleasant night and I could only confirm the first impression I had, he is a remarkable human being. The whole Department of Materials Science and Engineering in the Texas A&M University also impresses me in good sense. It shows all characteristics of an exciting work ambient.

News about the mechanism of interaction between neurons and Zika virus

Researchers in Brazil mobilized to try to understand the correlation between Zika infection in pregnant women and the development of microcephaly in the babies. Now first reports indicate that the virus attacks preferentially neuron precursor cells inside the uterus. I am not biologist, but it seems that the study used some pretty sophisticated in vitro techniques to obtain these results. This case is an important demonstrations of the correlation between applied and fundamental research. The case has an obvious importance for public health not only in Brazil, but also for the whole world, but it was only possible because someone in the past investigated these neuronal precursors cells and developed the techniques which are used in the study.  As I already mentioned before, I prefer to call this kind of research “useful research”, instead of applied (or fundamental). These two terms sell the idea that these kinds or researches can be disconnected.

Fear of the dark

digitalage Sometime ago I watched a TV program by Deutsche Welle. It was a documentary about the use of social media by kids and “how harmful” the exposure to digital technology in an early age is. I am used to the German fatalism. I lived there for 3.5 years and depending on the documentaries I watched then, one quickly concludes the world was destroyed about 20 years ago 🙂

Is our digital technology dangerous? First of all, I am pretty sure the same accusation was made when Gutenberg showed his movable types to the world, or when Tomas Alva Edison showed how easy it was to record the human voice, or even when that first scientist/priest showed to some King of Uruk that innovative technology called cuneiform writing. Did you get it? All communication technologies which changed the world, and I bet, they were attacked.

I guess we are intrinsically conservative by nature. We learn in an early age the existing communication technology of the time and we have the tendency to stick to this. When something new appears, we approach it cautiously.

I still remember my first experiences with social media. I began, if  remember right, with an Orkut account. This social media was a fever here in Brazil and appeared as quickly as it disappeared. Then I discovered LinkedIn and a social medium maintained by the University of Sao Paulo. Then a colleague from the Philosophy course convinced me to open a Facebook account.

I had my experiences in writing long texts before. I was part of the generation which bothered the friends with long e-mails of analysis of something. This was a pre-blog era and most of the texts produced then were lost. So I decided to create my own blog.

Now I am a constant user of social media. I use most of the tools (but I refused to use Whatsapp, it is too invasive). I discovered friends in the social media (Milos, for example), I discovered ResearchGate, a most useful social medium.

What I want to say with all this is that it is natural to be conservative in the communication, but this does not mean it is impossible to use new technologies. We, professors, in particular, need to stay alive in the social media. This is the language of the youth we teach to. If we want to connect with them, we should share (no pun intended).

As for the kids, my 12 years old daughter os currently addicted to Whatsapp. Am I worried? A bit, but I am also aware that If I was in her position, I would be addicted too. The kids communicate. They will use technology. We must get used to it. And I say more: they will survive.

Towards a Unified and Practical Industrial Model for Prediction of Hydrogen Embrittlement and Damage in Steels, ECF21, Paper

This paper will be presented by Milos B. Djukic at the upcoming 21st European Conference on Fracture – ECF21, Catania, Italy, June 20-24, 2016. Towards a Unified and Practical Industrial Model for …

Source: Towards a Unified and Practical Industrial Model for Prediction of Hydrogen Embrittlement and Damage in Steels, ECF21, Paper

Zika, Chikungunya, Dengue

The three names in the title designate viroses which are attributable to the dissemination through mosquitos of the species Aedes Aegypti.  Dengue is the oldest from the three diseases and, at least in Brazil, the first cases were reported between 1851 and 1853 with an epidemic episode in 1923. The name of the disease comes from one of the symptoms, joints pain, which leads people to walk with broken movements, like a puppet.

 Dengue was virtually extinct in Brazil during the campaign to eradicate Yellow Fever, which targeted the vector, by eliminating its habitat  in urban areas. Dengue returned to Brazil in the 1980’s, probably by the dissemination of the vector from neighboring countries which had less success in eradicating it. At the time, however, I heard an alternative explanation: it stated that populations of the vector remained in the forest areas and that the advance of the urban areas (deforestation) lead to the reintroduction of the vector in the cities. Anyway, the mosquito returned and, with it, the Dengue fever. There is no vaccine (contrary to yellow fever) and so, the only way to control the disease is by controlling the vector.
Since the 1980’s we “know” we cannot leave sources of still water exposed to the ambient, because these are preferred sites for reproduction of the mosquito. It is amazing. Last January I was  in the interior of the state of Bahia, an open water reservoir was filled by rain water and in the next day it was already swarming with mosquito larvae. This also shows why it is so difficult to solve the problem, I guarantee about 95% of the population takes the proper measures to avoid mosquito reproduction, the problem is the other 5%.
Dengue is usually not critical, it leads to severe fever (40°C), rashes in the skin, the already mentioned joint pain and some other symptoms, which are similar to influenza. The particularity, however, is that in a second infection there is the risk of development of the hemorrhagic dengue fever and this is very dangerous. There are vaccines in development, but none has been approved to date (as far as I know).
The development of a Dengue vaccine, however, would be no relief to the problem, because of the two other viroses, Chikungunya and Zika. As far as I know, Chikungunya is similar to Dengue (but the virus is different), Zika started as a third virose associated with the mosquito, but supposedly with less severity.
The situation escalated in the second half of 2015, when reports of an increase in cases of microcephaly in the northeast region of Brazil raised the suspicion the there was association with the development of Zika infection in the pregnant women in the first stages of the pregnancy. The brown press started to raise suspicion of relation with the introduction of transgenic mosquitos in the environment, this introduction was an attempt to control the vector.
Although it is possible, the relation between Zika and the microcephaly was not proven, I just read a report telling that only a fraction of pregnant women which had microcephalic babies reported Zika infection during pregnancy. There is the need to investigate this link, and, especially, to identify the mechanism by which a viral infection would affect a baby in the womb (as far as I understood, babies are protected against diseases in the mother). Any pregnant woman traveling through an affected area, however, should take extreme precaution against the mosquito bites.
An important question, however, is our vulnerability to viral infections. Bacterial infections can be combated by antibiotics, micoses can be successfully combated by medicines, even protozoa can be combated by other medicines, but the standard response of a physician to a person with a viral infections is: wait for the body to combat the illness. As we saw in the last Ebola outbreak in Africa, there are powerful antiviral medicines, but these are expensive and their collateral effects are severe.
Here in Brazil we keep trying to control the vector. The situation is critical, but not debilitating. People are not walking ill in the streets and, although the statistics are scaring, not everyone gets these diseases. The scientific community, however, should help, in particular the biologists and the biochemists, to investigate these viruses and their infection mechanisms, and the industry should work in the development of efficient medicines against viral infections.