Questions related to Failure Analysis
Researchers and materials practitioners often come across the stress-strain diagram, which is a popular tool used to select materials based on their mechanical properties.
While the diagram is a useful resource for many applications, it is an issue that it is 𝐧𝐨𝐭 𝐜𝐨𝐫𝐫𝐞𝐜𝐭 to use the stress – strain diagram for fracture analysis - a fatal beginner's mistake. The reason behind can be understood in our today’s illustration below!
Let me know the comments below.
I have plenty of ideas but need to start one that really crucial and on-demand in this field and some advice from experts will be appreciated. on the welding cracking and failure analysis specifically.
In fracture mechanics, the obsolete principle of stress intensity factor K (SIF) is still used, even though it has a limited validity and questionable interpretation.
What experience do you have and what is your opinion?
I am trying to use machine learning algorithms to predict whether a pipe has broken or not and I also want to predict the time to failure of a particular pipe. So, I need a dataset that contains the pipe installation year, the date of recorded failure for failed pipes and also some other parameters such as pipe length, operating pressure, type of material and pipe diameter among others.
When applying Maximum Stress Criterion on ANSYS composite PrePost, I noticed that interlaminar stress limit (S3) accounted for by the software is 50% of the out-of-plane stress limit (Z) defined by the laminate properties. However, I didn't find any thing in the documentation that refers to the value of this weakening factor.
Can any one provide me with a reference for this assumption?
The Poisson’s ratio is linear and increases slightly at the softening region. Could anyone show light on this? Is there any material model available to simulate this behavior? Thanks!
Looking for a motivated Ph.D. candidate to work in the field of additive manufacturing with the background of mechanical engineering and material science.
Deadline for application: February 14, 2020
I am working on developing a micromechanical FE model for predicting kink-band formation in UD composites. To model matrix plasticity, which model, out of Concrete Damaged Plasticity and Drucker-Prager, is preferred? Any insights particularly on the differences between the two models will be really helpful.
I am trying to predict the preload loss in a bot using the analytical relation ( Equation-(28)) given in the paper:
It will be of great help if you could suggest something here.
Factors of safety (FoS) are a part of engineering design. For bolts joining, some value of FoS is required to ensure the system safety. Thus, which range value of FoS is suitable for the bolts joining according to its application.
1. In a Low-velocity impact test, I have got Force vs Time response. There were two peaks in cross-ply and angle-ply orientation. In cross-ply, its peak to peak distance is lesser when compared to angle-ply. What is its significance?
2. Another was, steep rise in the cross-ply but the linear increment in angle -ply. What might be the reason?
I am looking for datasets that contains the all potential failure of a component. For example in autonomous vehicular domain, If want to see the failure causes of "Camera Sensor", the datasets should contain all possible list of failure cause (Power Outage, Short-circuit, or bad weather condition (reduced perception due to dense fog may be)) of "Camera Sensor"
I want to simulate & analyze the fracture and fatigue (crack growth) in the rear axle housing of heavy tracks (Volvo company) in Abaqus.
My question is which method is suitable for this research and how I can find the geometry and the mechanical & fatigue properties for this specific vehicle?
(If there is any related paper/thesis or anyone can help me, please let me know.)
For a dynamic Bayesian network (DBN) with a warm spare gate having one primary and one back-up component:
If the primary component P is active at the first time slice, then its failure rate is lambda (P) and the failure rate of back up component S1 is [alpha*lambda (S1)].
If the primary component P fails at the first time slice, then its failure rate is lambda (P) and the failure rate of back up component S1 is [lambda (S1)].
My question is, above are the conditional probabilities of primary and backup component. In a DBN, prior failure probability is also required. What will the prior failure probability of back up component? Will it be calculated using lambda (S1) or alpha*lambda (S1)?
I am looking for a wear detection method for a pipe that goes under intense heat and pressure for short instances at intervals. this process has an average cooldown time of 8 seconds between each cycle.
I am working on analysis of failure in safety valve springs.
I have faced to a special case, wondering if someone could help me.
The pressure relief safety valve hasn't worked (didn't pop) but the spring has failed.
The tank pressure is 90 psi (6.2 bar) and safety valve operating pressure is 150 psi (10.3 bar).
What can be the cause of spring fail?
What are the most important methods to quantify risk (failures, uncertainties...) for production systems ?
Especially for production systems, We look also on other fields ...
Fracture surface after Uni-axial tensile testing of pure aluminium sub-size tensile specimen shows the presence of elongated dimples instead of equi-axed dimples. What could be the reason behind this? Does it imply that the material failed by shear?
I am using the chi-square funcition to calculate minimal test time (T) in order to demonstrate that the mean time to failure (MTTF) of a product is at least H hours with a confidence level of CL.
I know that I have to use the following formula:
where X(CL,deg) is the chi-square function and deg is the degree number. In all failure analysis text book, deg=2N+2 where N is the number of observed failures. I would like to understand why I have to use this as a degree number.
I am trying to do failure analysis of randomly distributed CNT reinforced composite.Please suggest me how to incorporate the interface properties between polymer matrix and carbon nano tube in abaqus /comsol/ansys ?
I am new to this forum, I hope this topic is in the corrent section.
I followed a tutorial (attached) to analyse ply failure in composites. I submitted the analysis however it didn't converged.
I'm uploading both tutorial document and my model as inp file. Could you give any suggestion for convergence issue?
Does anyone know how can I estimate the NHPP reliability function through Non-parametric method?!
I know the Kernel density estimation is widely used in this area, but seems it has very complicated theory.
I was wondering if you could suggest an example or statistical software directly.
Also, I am just attaching the needed formulas of Kernel model.
Thanks for your attention.
What are the values for 1. Maximum pressure at failure 2. Minimum principal strain at failure 3. Maximum effective strain at failure 4. Volumetric strain at failure 5. Number of failed integration points prior to element deletion 6. Number of failure conditions to satisfy before failure occurs 7.Minimum pressure at failure, and other constant present in MAT_ADD_EROSION card.
I have a metallic rod that is tightened within a metallic tube (with known compression force/pressure applied to the outer surface of the tube). The rod will be moving downwards at a constant displacement (D) by applying axial forces (F) from the top of the rod surface. I am interested in simulating the F-D curve using FEA models and more specifically when the axial slip occurs (failure of the tube gripping capacity.
Could anyone please share any insights on this question? Directions to any relevant papers would be greatly appreciated!
Keywords: Slip, Friction, FEA, Coulomb Law, Finite Element, Yield
I am working on cohesive contact(Between two Aluminium bars). I just have some questions that I am wondering if anyone can help me by answering them.
1. How can I find the the parameters in traction-separation: Knn, Kss, Ktt ( should I consider module of shear and elasticity for them?)
- In damage initiation: normal, shear 1, shear 2 (would I consider tensile and shear strength for these values?)
- In damage evolution: fracture energy. mix-mode ratio 1 and 2
2. From where i can get this parameters ??
I'm looking forward to hearing from you soon.
I've modeled an Eglass/Epoxy composite plate containing a hole in the center and is tensile-loaded from both sides. Hashin progressive failure in Abaqus software is used to see damage in all failure modes. As i excepted , for example Matrix Tension Failure, matrix damaged regions should be shown in HSNMTCRT parameter in Abaqus results but as you see in attachted figure (1), in spite of different amounts of HSNMTCRT parameter, all model have the same gray color .
Why ? Do certain settings are required in the software ?
I am trying to acquire the graph of probability of failure versus factor of safety. In other words, I would like to depict a figure in which the vertical axis shows the probability of failure and the horizontal axis shows factor of safety. As a result of random set theory, the cumulative density function for factor of safety has been calculated. That is to say, there has been a graph in which the vertical axes shows cumulative density function and the horizontal axis shows factor of safety. The question arises here, how the probability of failure for each factor of safety would be derived from cumulative density graph of factor of safety?
Should I use fragility function in order to obtain probability of failure?
I would be pleased to give you any further information that you may request.
It would be nice to have a root cause failure analysis guidebook to validate some of the common failures I am witnessing in pipes and other materials on an industrial plant near me.
I remember an old mini guidebook that one of my professors had in his possession titled "Root Cause Analysis Guidebook" by Chun Choi that he used quite frequently in his reports. However, I was not able to find that book online anywhere for some reason. I am not sure if I have the title correct.
As we may know, non-local plasticity formulations are utilized to reduce mesh subjectivity and eliminate numerical instabilities like snap-back in the response behavior of the materials under plastic regime.
Just wondering which parameter(s) you prefer to "non-localize" to achieve better result? particularly, why averaging the internal variables (hardening/ softening/ cohesive strength modifier) is not recommended compared to plastic strain?
And the most important question: What is your recommendation in implementing strategy of such formulations? I'm trying to implement it in FORTRAN as a UMAT.
I am working on a simulation involving perforation of sheet using LS Dyna 980 but I am unable to get element deletion in simulation.
I really appreciate it if someone could reply my question.
The parameters based on NHPP are Shape= 0.46, Scale= 20.54.
and operation time
0, 50, 100, 200, 300, 400,..., 1000
for more detail, please find the attached file.
I do not understand why the reliability values are unreasonable!!
Thanks in advance,
I want to compare the effect of a special heat treatment on LCF behavior of a Ti alloy which is usually being used in aero engin compressor parts.
I am using beam elements to analyze a frame. To simulate deletion of the failed beam elements, I have added *MAT_ADD_EROSION (Element formulation type 1:Hughes Liu with cross section integration) and used maximum principle strain as failure criteria, but simulation does not show element deletion/failure.Does anyone have any ideas about the use of erosion keyword for beam elements?
when post curing applied to thermoset resin, a significant decrease in room temperature storage modulus is observed during my experiments. As far as i know, as the x-link increases , modulus also increases. What should be the explanation? Is this also an indication of decrease in tensile strength, can we correlate these directly?
Loss modulus is decreased and broadened as it is expected. But what happens to Storage modulus?
When joints open while the adhesive is still rather liquid, structures like shown in the pictures can be detected. These structure are very helpful in failure analysis as the prove the rather low viscosity of the adhesive in the moment of the failure. We called them honey on toast structure for the lack of a better term as they resemble the structure of a honey covered toast after falling on the wrong side. But is there somewhere a real/better term for this structure? Are there publications about the dependency of the structures on adhesive thickness and viscosity?
My research is in the field of failure mechanisms of metal components in cyclonic wind events. I am seeking to establish the effect of resonance of steel strucures induced by wind to estimate survivability of a structure.
I want to use AFT models to predict the time of tumor recurrence in an specific cancer type. To be more precise, I want to use regression in order to predict the survival time. Consider the following equation:
where "T" is the survival time, matrix "x" has the features for different samples, "B" must be a sparse weight vector and "e" is the error.
I have used this regression model and the results are poor for the prediction. However if I use the logarithm of "T" the error will fall down and the results will be perfect. But my question is:
For the sake of computing the error of my prediction, should I convert the predicted values (predicted T) by taking exponential of them or not? Or generally, after using AFT should we take exponential to remove the effect of the logarithm in the regression?
any suggestion would be great help to me
Thanks in advance
I've found "Standard Practice for Investigation and Analysis of Physical Component Failures (Withdrawn 2004)" ASTM E2332-04 and "Standard Guide for Corrosion-Related Failure Analysis" ASTM G161 - 00(2013) only.
I would be very grateful for any advice on the following topics:
1) What are the tasks where predictive analytics is most efficient if we are talking about freight operating companies? What predictive analytics methods can be efficiently employed?
2) What are the best publications to start with?
3) Is there any info available about real projects that have been successfully implemented, what ROI can we expect?
I had a reviewer claim that using accelerated failure time models to see how various personal characteristics vary with graduation rates is implausible because they are designed for events that always must happen (e.g., death, failed light bulbs, etc.).
In practice, I've seen both survival models and AFT models used for child welfare placement, foreclosures and other disease outcomes. ' As far as the explicit assumptions I have found from Swindell (2009):
“The AFT approach requires that experimental data satisfy certain assumptions. In particular, the treatment effect on survivorship should be roughly consistent throughout the lifespan, and survival times are assumed to follow a parametric distribution that must be specified (e.g., exponential, Weibull, log-normal, log-logistic).” (p. 3)
It is probably the case that the effect on survivorship is not consistent through the lifespan in the case of graduation, and parametric assumptions are usually false, but at least these assumptions are more or less testable. I also reviewed Allison (2009) and Kalbfleish & Prentice (2002) and cannot find such an asssumption.
I am preparing fused silica ceramics with gelcasting technique. The sample (30 mm diameter X 120 mm length). The samples are failing at the sintering process. Please tell the reasons for the failure? Suggest any methods to find the failure analysis?
The sintering temperature is 1250 oC with an heating rate of 2 oC holding 2 hours and cooled to room temperature with furnace on in the nitrogen environment.
I am attaching the figure of failed sample.
Thanking you in advance.
I have been trying to implement such a model in a UEL in Abaqus for a long time, but I always get unphysical results when the cohesive crack is activated.
I made very simple hypotheses to get it run:
- linear elastic material
- One 2D FE loaded in uni-axial tension
- When the y-component of the stress exceeds the cohesive strength, the cohesive crack is inserted with a pre-defined angle (for simplicity I don't calculate the angle from the stress state at crack activation)
- I am using a linear softening cohesive law (extrinsic, so without an elastic part) in shear and normal directions (so that t_n = t0_n - T_n * [[u]]_n and the same for shear). The initial traction t0_n and t0_t is calculated from the tangential and normal stress projection on the cohesive crack, i.e. t0_n = n*sigma*n and t0_t = t*sigma*n)
- My problem is that I don't get a reasonable solution when the crack is inserted. I guess that it might be due to the non-satisfaction of the traction continuity in the X-FEM leading to the compensation of the traction difference by an unphysical crack opening. But I am not that sure.
It would be great to find other researchers who have already implemented such a model. It would also be interesting to know whether there are others who had a similar problem at crack activation. And if not, I would be very pleased to have more fruitful discussions on that topic.
I will also upload my UEL and the inp file, in the case that someone is interested to take a look inside.
Thank you very much in advance!!!
Hi, Thank you for any advices.
Assume if I want to estimate the sum value impact of evrey variable in order to select the best variable. It is not sensible to calculate impact of each value in the variable domain beacause of the high computation cost, Are there any methods to reduce that computation cost?
Thank you for any advices.
Hi, I want to know how to put a much greater emphasis on failures during propagation to guide the search in Constraint programming. Are there any good techiques or strategies about this? For example, when propagate the search, I apply the impact of a assignment as reduction of the search space, but when the assignment result in a failure, how can I put a much greater emphasis on the failure. Thank you so much for all of the replies.
There is a Johnson cook model for ductile material deformation. One is material model and one is failure model. when the fracture occurs in ductile material due to shear . Triaxiality is low for that .
Does this model suitable for low triaxiality range.
To mimic loading and unloading phenomenon using Abaqus I have tried applying load (as displacement, say from 0 to 1mm) in 1st step then in 2nd step I have changed it gradually to its initial value (zero). But, I am not getting expected result in terms of load vs deflection plot. I am getting some amount of residual reaction force at the end of analysis, but I want to free the model from it. Also, when the load is decreasing from its peak value (1mm), for the first increment (decrease in terms of displacement) the reaction force is increasing surprisingly. Please suggest me any procedure to get exact result. Thanks.
I am working on stochastic progressive failure analysis of laminated composite plates. Kindly suggest me how to choose degradation model in post first-ply failure.
I am trying to find the probability of failure of each individual volume element of a body, by using Principal of Independent Action (PIA) failure criteria. The problem is that the formula uses the state of stress(SoS) of element but , I have the SoS of all its 8 nodes ( obtained through FEA in ANSYS). How can I use the failure criteria ( PIA )formula now or is there any way to find the SoS of element from the SoS of nodes.
Your advice would be much appreciated . If further details are needed i can submit a report to you .
I am planning to conduct FMEA study for some of the existing equipment/device.This device has several models, most of them have almost same design features. I wish to find out the weak parts/sub component of these device type by conducting the study.
Since number of different models of this device are available in the market, it is not possible to conduct study on all the models.
Whether it would be appropriate to conduct FMEA study on specific model and conclude the results for the whole species of the devices?
I want to do FE model of the failure in material and the literature has used ansys for the analysis , and i want to do the analysis in abaqus and would like to know if there are any equivalent for the same
I would like to know if someone know the data from a white paper/report/research paper about
-> SoftErrors: Failure in Time (FIT) rate (neutron/meoun/proton etc.) for some Flip-Flops which are based on FinFET and/or FDSOI technologies. As there are few papers available on SRAM FinFET FIT rate. Furthermore, there are few papers on CMOS FIT rate for flip flops are also available.
I have to perform the ball on flat reciprocatory wear tests oh IF steel and Mild steel, for the very same purpose I have to select the ball material which should obviously be more harder that the steel itself.
Confusion is between Al2O3 , SiC, Ni and WC balls.
And could you guys please provide me with references ?
Where can I find some reliability data for steam traps? I am looking for Mean life, MTBF and Gamma life for say 250 psi, 1/2" inverted bucket type steam traps. This information is required for the reliability analysis of the steam system. Please share any any information, failure data or any specific experience you may have in this field.
I want to apply cyclic load on the blade to inspect it under fatigue loading.
I want to save the blade and I do not want to causes failure to it.
I'm looking for a methodology that can help me in estimating the number of cycles to failure by certain applied cycles.
I am planning to model a brick masonry wall to check its failure mechanism on non-linear time history and provide RC jackets to retrofit this wall in both in-plane and out-of-plane directions.
I am working on using non-linear ultrasonic parameters, specifically, the ratio of the amplitude of the secondary harmonic to the fundamental to quantify creep damage in austenitic stainless steel.
I have a couple of questions about the results, like the peaks I see in the waveform, etc.
It would be of great help and interest if somebody knows about this particular application of ultrasonic testing.