Science topic

Structural Integrity - Science topic

Explore the latest questions and answers in Structural Integrity, and find Structural Integrity experts.
Questions related to Structural Integrity
  • asked a question related to Structural Integrity
Question
13 answers
There have been many classical fatigue life assessment methods, but most of them have their own limitations. For example, the method of material fatigue life assessment is often not suitable for complex engineering components. If we want to accurately predict the fatigue life of engineering structure, which aspects should we start from? Welcome to leave a message.
Relevant answer
Answer
Fatigue analysis refers to one of three methodologies: local strain or strain life, commonly referred to as the crack initiation method, which is concerned only with crack initiation (E-N, or sigma nominal); stress life, commonly referred to as total life (S-N, or nominal stress); and crack growth or damage tolerance analysis, which is concerned with the number of cycles until fracture.
The method for calculating fatigue life is sometimes called the Five Box Trick, including material, loading, and geometry inputs, and analysis and results. The three main inputs for fatigue life analyses are processed using various life estimation tools depending on whether the analysis is for crack initiation, total life, or crack growth.
Best regards,
  • asked a question related to Structural Integrity
Question
5 answers
Recently, I came into contact with a new discipline named chemo-mechanical coupling. I found that chemo-mechanical coupling phenomena exist in many research areas, ranging from development of advanced batteries, biomechanical engineering, hydrogen embrittlement, and high temperature oxidation, etc. Although it is very important in engineering field, I can't know the main mechanisms of coupled chemical and mechanical interactions. Can you give me some suggestions? Such as, some related publications or research project. Thanks very much.
Relevant answer
Dear Gang Zhu
The applications of chemo-mechanical coupling discipline are going on for the time being into two directions that covering by materials research and development activity:
Designing and manufacturing a multifunctional components that characteristics in a variety of applications e.g. artificial organs.
Highlight the mechanism of material degradation and failure case study e.g. high temperature oxidation process.
Now, in the case of high temperature oxidation the mechanical coupling with the oxidation chemical reaction results in stress generation in the oxide scale formed which in turn affects the chemical reaction rate and the diffusion process of the reactants and therefore, the process become a complex chemo-mechanical as the stress is diffusion dependent during the oxidation and the oxide growth is stress induced.
In other hand, the story may be different with the hydrogel coupling behavior as external mechanical load can induce redistribution of ionic concentration, while a chemical stimulus lead to swelling or shrinking of the hydrogel.
So for this multi-field coupling behavior in a medium, there are many approaches that have been proposed by many researchers leading to a bundle of knowledge for the same coupling behavior .Thus, I think that makes the topic appears as foggy to understand by many of the followers.
I hope the above contribution is helpful.
Best regards
  • asked a question related to Structural Integrity
Question
14 answers
In engineering, the damage that can be detected is usually called crack. But how to describe the small cracks which cannot be measured in the early stage of damage? Can we give a universal definition? Greatly appreciate your review.
Relevant answer
Answer
Gang:
How to define a crack? Your question is essentially how small can a crack be to still be considered as a crack, and more specifically what dimensions preclude the use of continuum and fracture mechanics to analyze such a crack. In general, for a continuum approach, which has the advantage of being widely applicable, a crack naturally needs to have at least one dimension larger than an atomic (or lattice) spacing.
As there are no size-scales in elasticity, in principle any sized elastic crack could be analyzed. However, from a fracture mechanics perspective, for the use of linear-elastic fracture mechanics (LEFM), its is any violation of the elastic constitutive law used that must be considered, i.e., this region of violation needs to be small enough to be ignored, e.g. the crack size (and the remaining uncracked ligament) should to be some 10 to 15 times larger than the crack-tip plastic zone.
For nonlinear elastic fracture mechanics (NLEFM) approach, the crack size (and remaining uncracked ligament) need to be at least a order of magnitude larger than the region of unloading, i.e., increment of crack advance) and the crack-tip zone of non-proportional loading. Indeed, the prevailing constitutive laws used to develop the fracture mechanics approach which is utilized will be in general determine what sized cracks (and what sized components) can be analyzed, as in the LEFM and NLEFM examples given above.
The physical definition, however, of when a crack is actually a crack is very relevant to the question of crack initiation for fatigue analysis and life prediction. Traditional total life (S/N) approaches to fatigue life estimation of course include initiation, but one doesn't generally need to know the dimensions of any crack formed as only the applies stress (or strain) and the number of cycles to failure are measured. For damage-tolerant life-prediction strategies, conversely, the crack size does become important, as conventionally the lifetime is calculated in terms of the cycles for the largest undetected crack to grow to failure. LEFM approaches work well here, e.g., by integration of the Paris law for fatigue-crack growth, but there are problems with small cracks which can display non-conservative behavior, i.e., faster growth rates (and lower fatigue thresholds) than larger cracks at the same applied stress-intensity range. For a brief classification of the relevant crack sizes here, the reader is referred to the attached reference on small fatigue cracks.
If we could perform such damage-tolerant life-prediction calculations and include crack initiation, this would dramatically enhance predicted lifetimes but, in addition to the question at hand as to when a crack is actually a crack, this is a tall order as the initiation life is invariably a marked function of the nature of the component surface, and to reliably characterize the surface condition in, for example, every turbine blade in every gas turbine, would be impossible. However, a recent study has attempted to characterize the precursor microstructural damage prior to the formation of an actual crack (Lavenstein et al., Science, 370 (2020) 190), and if this approach can ever be feasibly harnessed industrially, then maybe the question of when a crack is actually a crack may not be so important!
ROR
  • asked a question related to Structural Integrity
Question
18 answers
With Climate Change and all, I will tell you what I think is a minimum needed for survival and that is: literally a completely, fully, entirely new outlook on life AND that being FOR EVERY HUMAN BEING and involving all our work-a-day pursuits -- a wholly new way of life (and "full-blown" way of action/work) and a source of wholesomeness and great actions and GOOD:
Every hour/day/week/month/year, etc. you wake up mindful, informed (and get more informed as ever needed to proceed ASAP), dedicated, and completely persistent and consistent in acting for the earth-life-dignity of your CAUSES and related CAUSES. Serious life as pursued will be nothing but your involvement and active-dedication to CAUSES (maintaining rational, workable consistencies, and AS MUCH IN ACTION as possible, to actually achieve or actualize the causes). Satisfaction will have nothing to do with "being easy-going" NOR with typical or traditional ideas (notions) of happiness, nor with any [supposedly] other way of (or toward, or for) "satisfaction" -- "rewards" of life many of you, much of the time, thought likely would come with "freedom" and "general happiness" (as historically thought about) but such will be clearly seen as blatant, flagrant, and shameful irresponsibility of old ways considered not worth even thinking about FOR ANY GOOD PURPOSE or any goal in the world (you will have plenty else to think about and with integrity and dignity AND FOR DIGNITY AND INTEGRITY)(plus, there is inherent irrationality in the old views: one way or others of expecting -- and basically even counting on -- MAGIC). BUT, now, all the old happiness/play/satisfaction/fun in-and-with any other "things" or activities will naturally and rationally and personally come to be seen as that which eliminates true dignity and integrity and any worthwhile (or even real) satisfactions -- now with you having the dignity and integrity of work on AND for your CAUSES. With this new way (for all we see for ourselves and for any decent folk we will associate with), SOON nothing else will will "do"; we will have a new way to real dignity, better understandings, and some true, real, good lasting, progressive satisfaction, and with greater loving kindness and equanimity (as we accept we do what we do and others do as their own best in the same vein). As indicated, the way is to operate (LIVE) IS ONLY in terms of CAUSES and inter-related or necessarily simultaneous or successive CAUSES. Developing and accomplishing (in action as much as possible and necessary) will be ALL for the CAUSES which will be your life -- the "all" of your life that matters or has any implications for yourself or others. And, this is also at least as all other decent human beings doing all major things of working life will know you, and that is how you will know them. This is all simply a commitment to understandings, and engaging in wholesome pursuits (which, AGAIN, will be in terms of CAUSES). The causes will be shared only as well, rationally, and wholesomely pursued through group action BUT may well be otherwise that which is done alone (individually), if that is how things are going to get done.
This is the formula for self-breeding of the species and for any real decency and for the survival of the species itself. I cannot imagine how anything else will be sufficiently adaptive; in fact, anything else breeds ignorance, confusion, chaos and irresponsibility (an easy logical and sound argument to make). (I want to live, I want humans who follow me to live; DO YOU?)
Relevant answer
Answer
We need to have the interest of others by maintenaning balance in the ecosystem.
  • asked a question related to Structural Integrity
Question
7 answers
  • Generally, fracture mechanics parameters and terms (CTOD, J, C*, stress, load line displacement, plastic zone size) have relevant & respective dimensional units. The physical significance of their units is easily understandable like, energy per unit area or energy rate per unit area of crack growth. In case of K, why its (meter)1/2 i.e. square root of crack size, a and not simple a or 1/a or a-2 ? What is the physical significance of including square root of crack size, a in K formula?
Relevant answer
Answer
Mr. Kumar,
As explained by many others, the unit of K is due to the sqrt(r) singularity.
Describing a similar parameter for HRR singularity might have a unit with MPa.m^n, where n can have a fraction value.
The physical significance could be that for an applied stress, K describes by what factor the stress will intensify at a distance of 'r' from the crack tip. The definition of K comes from theory of elasticity, and so it should describe the stress field at the boundary of plastic zone.
As I said another parameter can be described at a boundary of plastic zone and process zone, and that factor would describe the stress field at that boundary.
To make it more fancy, its similar to the Event Horizon, the boudnary of singularity in a Black Hole.
With regards,
Abhishek
  • asked a question related to Structural Integrity
Question
2 answers
What are the main instruments used for measurement of different parameters, such as displacements, strains, etc, during the Structural Integrity Test (SIT) and Integrated Leak Rate Test (IRLT) of Containment Building?
Relevant answer
Answer
Dear Mourad,
Thanks a lot for the relevant documents. These were really very helpful.
  • asked a question related to Structural Integrity
Question
2 answers
Swept area: 1.6 m
Chord and twist are 140 to 40 mm and 90 to 5 mm, respectively.
Relevant answer
Answer
IEC 61400-2 standard presents the calculation procedures but it does not mention the structural design. Further, it is up to you to apply your experience in mechanical design to design the blades probably. 
The 2006 version of IEC 61400-2 is attached for further information. 
  • asked a question related to Structural Integrity
Question
1 answer
Hydrogen is known to diffuse through metals and compromise the structural integrity. Thus, pipelines have to be made with more expensive and thicker high strength steels. Are there any synthetic or metal-based coatings that could reduce the diffusion rate of Hydrogen and thus allow cheaper pipelines to be used?
Relevant answer
Answer
Though Hydrogen is known to diffuse through metals and compromise the structural integrity, yet there inhibitors available. 
Google 
"inhibitors for Hydrogen embrittlement in pipelines" for more references.
  • asked a question related to Structural Integrity
Question
5 answers
I'm trying to do a simple analysis of Timoshenko beam supported by granular layer and excited by impact force. FEM is used and the granular layer is represented by Winkler springs. I want to include damping in the granular layer. Do you have any suggestion how the damping can be represented?
Relevant answer
Answer
Hello Emina Balic
  A Timoshenko beam on a granular layer excited by an impact  force presents an analytically intractable problem of structural dynamics which is why you wish to model the foundation as a Winkler spring model. In problems of statics the foundation reaction on an element  beam of area dA is simply ks*dA*w where ks is a scalar number called the modulus of subgrade reaction and w is the deflection at the given point. However, in dynamic problems ks will be replaced by a complex quantity known as the dynamic impedance that we may represent as kd = ks*( 1+ i*β)  where i = sqrt(-1) and ks retains its previous meaning, where β = loss factor of the granular material due to combined radiation damping and hysteresis.  
  Your problem is solved if you can assign proper values to ks and β. Consider a rigid disc (circular plate) of radius ro on a halfspace of shear modulus G, density ρ and Poisson's ratio  ν undergoing vertical vibration on a halfsapce.  According to the Lysmer analog K= 4Gro/(1- ν )  and viscous damping coefficient  C =  3.4ro2*sqrt(ρG)/ (1- ν ) = 0.85K*ro/Vs where Vs = shear wave velocity of the supporting medium = sqrt(G/ρ).  A damping ratio D can be defined as D = C/Ccr = C/[2sqrt(m*K)] =  0.425/sqrt(B) where B = mass ratio = (1- ν )*m/(4ρro3) with m = mass of disc.
  It can then be shown that  the loss factor β = 2Dω/ωn.  ωn = the natural frequency of disc on a halfspace = sqrt(K/m) and ω = frequency of the exciting force.
With the above I have given you a means for computing the dynamic impedance of a granular medium to a vibrating rigid disc. However, in your problem the element of beam is a rectangle and you need to convert it into a disc using the expression ro = sqrt(dl*b/pai). where b = actual beam width and dl = length of beam element after beam has been divided into elements. On the other hand you can search the literature for the expressions of K and C for a rigid rectangle of dimension dl by b. 
  • asked a question related to Structural Integrity
Question
2 answers
Hi everybody
Can anyone tell us what is the rule of the additional diagonal member in open web steel joist?
Relevant answer
Answer
Salam Mohammad
I have seen such detail in almost all of these joist in American types,so i have a doubt whether this element  works as well {good} as we think
because if we assume there would be any force in this member so at the top point of it there is not equilibrium condition manner  .
ahmad
  • asked a question related to Structural Integrity
Question
12 answers
I cannot find any research which just focuses on the team size, structure, integration, reporting lines etc of an "ideal sustainability team" of a large corporate. Does anyone know relevant research on this or can provide direction for new research?
Thank you.
Relevant answer
Answer
You can follow the following attached file that would be better for your organization.