Questions tagged [failure-analysis]

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Are there disadvantages to using a single multispan beam, vs separate simple beams, for materials that tolerate tension as well as compression?

Suppose the following beam situation within a mundane building (viewed from above). Assume vibration and torsion aren't issues. Suppose we have a choice to span a gap in 2 different ways: (Grey = ...
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Inverse Power Law for Accelerated Failure Times

I am working with some subsea cable data. I have $n$ samples that are split into three groups (sized $n_1$, $n_2$ and $n_3$). Each group goes through a different acceleration process until failure. ...
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Incorporating a dichotomous failure model for sustainment analysis

Disclaimer: I am a data scientist, not an engineer. I have been tasked with forecasting failures of a given part and seeing how it affects inventory. Suppose I have historical yearly failure data for ...
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Why does the max principle stress at yielding for a ductile material equal to its yield strength in a uniaxial tensile test?

It is thought that the maximum principal stress for a ductile material is equal to its yield strength, in a uniaxial tensile test. This is also shown in the attached picture. I want to ask why is this ...
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How can I describe cold work and atomic structure?

A copper wire (42 cm x 0.25 cm diameter) twisted to failure did not change its dimensions significantly. How can I visualize or quantify the cold work done (tensile at the exterior, compressive in the ...
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2 answers
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What ASTM standard would be appropriate for testing the breaking strength of nylon ropes

ASTM D4268-93 would appear to be the relevant testing standard, but this was withdrawn in 2002 and is no longer active. Is there a current standard?
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Determining If A Test Article Is Suitable For X RAY Following Shock Testing?

I am interested in putting a small (3"x3"x2") assembly under X-ray, following a shock test, in order to evaluate failures of an internal ceramic piece. Unfortunately, this assembly utilizes quite a ...
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Is a motor failure caused by a defect bearing considered to be a failure mode or is it higher vibration and speed loss in FMEA/FMECA?

Let us assume we have a motor with a bearing which is exhibited to wear. Over time, we can observe higher vibration, increased noise and the motor speed reduces due to the bearing fault. In the end, ...
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3 answers
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DOE analysis or root cause analysis?

For any testing that a part is suppose to pass a test, let's say the leakage test of a seal flange. How should I individualize the cause? I know there is root cause analysis and for different ...
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2 votes
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How to sample Mean-Time-To Failure values from a Weibull Distribution with shape 1.5?

I have a mean time to failure (MTTF) recorded from 100 systems which is 6.5 years. The shape parameter of my component is given with k = 1.3 (based on a list the from literature). Now I want to ...
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Factors favoring crack propagation in the middle of a plate for an extensive length relative to plate thickness (Reasons for < marks on crack surface)

I have a scenario where we have encountered a cracked steel plate where the crack has propagated within the plate longitudinally for an extensive length. The plate thickness is 1", and the crack ...
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stress/shear analysis of components

I am working on analyzing a few problems, but have not really come across this type of stress concentration problem. Does anyone know where I can study the analysis of this situation? Pressing ball ...
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How to calculate the failure rate of a machine with probability and mean failure time?

I dont know how to approach this problem. Suppose that a machine has a probability of failure of 43% at 90 hours of operation. How can you calculate the failure rate and the probability of surviving x ...
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How to determine the maximum internal stress for a material under compression before brittle failure?

Let us consider a ceramic material, $\mathrm{Mg_2SiO_4}$ - Forsterite, with a sphere shape. At room temperature, the ceramic sphere is "trapped" in a matrix which does not expand (null thermal ...
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What does 1 x rpm or 2 x rpm or 3 x rpm in vibration analysis mean?

a description for virbation monitoring of industrial bearings states: peak amplitues at 1 x rpm should be an indicator for a fault in my case. Can somebody explain me what I have to understand ...
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1 answer
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Hardening and Brittleness

Why is hardening and brittle nature so related?What is work hardening or strain hardening as far as true stress strain diagram is concerned?
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Ductile,Brittle and Malleable

In Callister it says, "two modes of failure are possible ductile and brittle." Why not malleable?Furthermore why is uniaxial tensile test chosen for predicting failure?
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What is the difference between tau = VQ/It and tau = V/A?

What is the difference between the formulas $\tau = VQ/It$ and $\tau = V/A$ for finding shear stress due to transverse loading? I understand that the use of first moment of area, is the only reason ...
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1 answer
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How to apply static failure criteria for bending stress in an angled cylindrical surface?

Let’s say I have an irregularly shaped bearing with a cross section that looks like the angled surface of a conical frustum, shown below. If a bending moment is applied which causes the inside ...
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2 votes
1 answer
284 views

Failure due to shear stress on rod lip?

Let’s say I have a circular rod that has an outside lip with a larger diameter and certain height. The rod moves axially, and the intent of the lip is to mechanically stop the rod at a maximum axial ...
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3 votes
2 answers
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What type of failure is this?

The part is a clevis and was insterted in a steering rack . Part was in Tension, torsion and bending. It failed at the end of the threaded bolt part. Is it a common problem for bolted joints ? How can ...
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1 answer
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Historical data for using supervised learning algorithm in the field of Mechanical Engineering [closed]

Being a student in the field of Mechanical Engineering, I am very new to Machine Learning.I did a couple of basic online courses of Machine Learning (including the one by Andrew Ng on Coursera). So, I ...
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1 answer
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How to use failure criteria in isotropic material (NASTRAN)

I'm quite new in NASTRAN enviroment, and I am wondering how to use failure criteria which I can define when creating my isotropic MAT1 material for 1D elements (like CBEAM). From the Quick Reference ...
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mechanical Strength of 3D printed part

If the material is manufactured by 3D printing (laser sintering) then what will be change in its mechanical properties than the properties by casting and machined part? What would be appropriate ...
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What is the longevity of Delrin rollers on aluminum linear rail?

I am in the process of selecting a linear rail system for a 5ft x 10ft cnc laser cutter. Delrin polymer rollers on 2 inch square extruded aluminum tube is an economically attractive solution. I have ...
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8 votes
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How do I properly compute mean time to failure?

I have a product of which we have shipped something like 500 units over the last five years. This product is not intended to be user serviceable; a failure of any component results in the unit being ...
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