Failure Definition and 248 Threads

My resident theoretical physicist, who I love dearly, is often very distraught. He describes his days of wracking his brains as painful, unproductive, and, at worst, a tedious backtrack through a bunch of stuff that he got wrong and must redo or unthink. Please help me to understand what he...

The failure of so-called "no-communication" theorems In what we commonly refer to as "no-communication" theorems of quantum mechanics (QM), we make assumptions which are consistent with QM and with our knowledge of physical systems. But are these assumptions appropriate to a potentially would...

i have a machine which runs for exponential duration with mean alpha,and fails. once it fails, to repair it, it takes an exponential duration with mean beta then again it comes back to service and this continues. what is the probability that it is in non working(repair) state.

I used to think this question would be a simple question, but I haven't been able to get a good explanation from anyone (including two electrical engineers). So, here goes During a brownout (periods where a building does not receive it's normal level of voltage) motors can potentially...

In the case of a power grid or generator failure, the former which chernobyl was testing for and the later which occurred at Fukushima - why can't you stay online, use the electricity your producing to power the pumps and sink the excess electricity into the ground? I have no engineering...

If a hypersonic jet (Mach 10) were to experience sudden engine failure at high altitude what would happen? Would it continue traveling forward, slowly decelerating and descending, thereby giving the pilot chance to attempt a controlled engine restart? Or would the jet experience catastrophic...

Hello, Thought I would share this link to "Lockharts Lament" It basically talks about how the way math is being taught in schools is a terrible way to teach it and that it takes all of the real mathematics out of it. http://www.maa.org/devlin/LockhartsLament.pdf

Hey Physicists! This post may be relatively long, but thank you to anyone that will actually read it. I have always been interested in Physics and the way things work in general. During my Freshman year, I barely passed Freshman level Physics, but I did. It was during my second year...

Greetings. First a little introduction; I am a current high-school senior, and this time of year is very stressful. It seems that it is the time of my life where I will be measured up, so to speak, with my peers, and perhaps have to decide my goals and future plans. I don’t want everyone to...

I'm not posing this to be a forum troll or to insult the excellent ongoing work in Physics. It's a serious question based on the following: * Most of relativity and QM theory was completed within 20 years by a few dozen scientists. * Their tools were very primitive-not even electric...

Homework Statement Hi all, I have been trying to go over this problem for sometime now.. yes I have easily browsed over +200 articles, lectures , etc on google. The question is related to delong petit law and wants me to find out the temperature at which it fails i.e when quantum effects...

Hi, I'm currently trying to work through a problem about calculating the most likely time for a hard disk to fail: Hard disks fail with a probability per unit time: \alpha (t) = \alpha _0 t where \alpha_0 = 0.5 years. I know that the answer is t_{modal} = \frac{1}{\sqrt{\alpha_0}}, but am...

Hi all, This is not really a homework problem, more of a 'what-if' scenario but I'm not sure which section to put it in. For a science project we have been asked to look at material properites and come up with a project (which will have a presentation :eek: but that's another story). I'm looking...

Apparantly we have missed this event some weeks ago. Careful when walking on cliffs. (Look at the right top at 10 seconds.) Looking forward to comments from geologists.

Calculating the equation of time and the declination of the sun Hi, I'm trying to calculate the equation of time and the declination of the sun in the prettiest way possible: https://gist.github.com/1278755" But right now I'm getting some unexpected values: 1) Failure...

Homework Statement This example comes straight out of the book. Can someone show intermediate steps? Fx = 0: -0.0933Tab - 0.0846Tac + P = 0 Fy = 0: +0.778Tab + 0.705Tac - 1962N = 0 Fz = 0: +0.622Tab - 0.705Tac = 0 Book solution: P = 235 N, Tab = 1401N, Tac = 1236N Homework...

Is it possible to do a failure investigation as well as cfd analysis in a catalytic Converter to determine nature, cause of failure, and how it affects flow.I want to do this a part of my project.

how do i plot the follwing S-N diagram, i am having trouble with what I am supposed to do with the 'cycles to failure' figures: stress amplitude ... cycles to failure (y axis)- .... (x axis) 170 ...... 3.7 x 10^4 148 ...... 1 x 10^5 130 ...... 3 x 10^5 114 ...... 1 x 10^6 92 ..... 1 x...

What will fail if the aluminium impeller rotating at 7500 rpm and powered by 355 kw motor strikes against the stationary 10 mm thick ms plate welded at both the ends having length of 350 and width 200 mm and impeller blade is 12 mm thick. I am confused in first glance we think that blade will...

If the United States expects to compete in the international community it needs competent scientists, engineers, and mathematicians. The articles below show U. S. students falling behind students in many other nations. Even though the U. S. spends more than most countries on education we are...

For those EE that have heard of, but not seen, here is a photo of capacitor failure on a motherboard. I have labelled the relevant material.

I am currently solving a problem (similar to optimal control theory) involving optimization of an integral with mixed and pure constraints. eg: \int F(x,u,t) dt subject to x(t)\geq0 , u(t)\geq0. The problem can be solved by Pontryagin minimum principle by introducing the Hamiltonian function...

For these four practice problems, I had little idea what the hell to do (plugging in seemed worthless), could anyone help? Sorry if this isn't what the board is suppose to be used for. Answers in spoiler tags. If k and h are constants and x2+kx+7 is equivalent to (x+1)(x+h), what is the value...

Hi, could someone explain the following quote to me, please? It explains, why the Kohn-Sham-Scheme of DFT fails to describe transition states. My questions: If N_i ist the occupation number and the wavefunction may be given by \Psi = \sum_I{c_I \Phi_I} where \Phi_I are...

So the starter capacitor in my AC condenser exploded a couple of days ago. I'm headed out to get a new one (found someone open!) and I'm just concerned that the failure could be just a symptom of a bigger problem like a bad compressor or fan motor (its a dual capacity capacitor that serves...

In the thread https://www.physicsforums.com/showthread.php?t=485800&page=17 posz #257 fzero mentions that all known approaches to use gauge theory to describe canonical gravity fail nonperturbatively (Witten in http://arxiv.org/abs/0706.3359 "Three-Dimensional Gravity Revisited"): - gauge...

Are there any general rules of thumb for which to choose? I have a lot of ambigous HW problems which don't specify, they just list a safety factor. For example, if I have a mass hanging on a metal wire with a specified safety factor, then I mean it will buckle at the yield strengh but only...

Say you have a square room with only one door, and the door is as the center of one side of the square. Suppose you put a stereo just outside the door. Can you hear the sound if you are standing in one of the corners of the room that's adjacent to the door? Fraunhofer diffraction predicts that...

Having a hard time with failure theories. Beam length 20 feet, 6"h x 4"w. sigma yield is 40 ksi. How to calculate the maximum distributed load the beam could carry using von Mises and Tresca failure theories. I have my shear and moment diagrams drawn and know they are right. I found that...

Hi Guys, I have some data on a small electric motor being run continuously for a year. The problem is I only have the Headings and numbers and no units or information on what devices were used to measure the data. The variables measured were Time, Speed, Temperature, Power, Powerfactor...

When determining if a beam will fail under a given load, is it correct to first calculate the stress in the beam caused by the load. Then compare that stress to the ultimate tensile strength of the material and this will render a answer of if the beam will fail (break or yeild)

I need to solve the following problem for a school assignment. Let λ(t) denote the failuer rate of a system at time 't'. The failure rate is simple the number of failures in unit time. For example, if the unit time is one day, then λ is the average of failures per day. Let μ(t) denote the...

I need to solve the following problem for a school assignment. Let λ(t) denote the failuer rate of a system at time 't'. The failure rate is simple the number of failures in unit time. For example, if the unit time is one day, then λ is the average of failures per day. Let μ(t) denote the...

Currently I am studying the mechanical properties of artery tissue, and was tasked with determining if the tissue fails due to shear stress or shear strain. I have always worked under the assumption that they go hand in hand with each other, but the nature of this question obviously suggests...

Hello, Does anyone know how to calculate the cross sectional compressive strength of a piece of pipe? I know as you compress or crush the pipe along the cross section of the pipe it will strain harden at which point compression will be unable to continue experimentally. I need to know what...

Homework Statement A pipe end stop fails when subjected to high pressure and flys of the pipe before impacting with a polycarbonate protective screen. The end stop has a mass of 100g and is 12.7mm dia. as is the internal diameter of the pipe. The instantaneous pressure that the end stop fails...

a steel rod, 40mm in diameter and 1.00m long, is pinned at each end i) calculate the euler buckling for the rod ii) identify three other possible end fixity conditions for the rod and demonstrate how euler buckling load would be affected in each case iii) explain the relation between the...

I am currently taking up a calculus course along with several other courses this semester. I am currently flunking the course and I really want to drop. Now, I'm not terrible at math. I'm actually pretty good. I have had a lot of lec and lab work from my engineering courses pile up in front of...

One of the things I greatly dislike about myself is that before I do something, I always need to research the hell out of it. So, after I finally decided to go ge a BSEE, I searched for any and all online information on what to expect. That search led me to this...

Hi all. Probability definitely isn't my specialty, and I've run across this problem at work. There's one gate valve that isolates two 2400 psi hydrogen gas banks from each other, and I'm trying to find the probability that it fails in one year. I've done some digging and found failure rates...

hi.. I am new to this site. I want to know about reasons of failure of connecting rod of 4 stroke petrol engine. In this case the rod has broken into two parts from the small end of the rod. The manufacturing root of the component is hot forging - hardening - induction softening of the small...

As it happens the legislative branches of the US government have long established a periodic legal limit on the Treasury's ability to raise revenue by issuing debt. I'm told such a limit is somewhat unusual as nations go, but there we are. This year the US Treasury predicts that the current...

I have a broken crankshaft where I am trying to determine the cause of failure. here are some pics of the cracked surface. what is known: 1) the crank shaft was under very light load at time of failure What do you guys think?

Hello everyone, I can understand how liver failure can cause jaundice, but not vise versa. Please help. Thanks :smile:

Homework Statement Hi , I got a MI problem for a given application. I need the failure load of a beam in order to derive the Merit Index. Does anybody knows the equation of the failure load of a beam ?

Unfortunately the piston has disintegrated so we are unable to use that to form an opinion on this failure. Please let me know your thoughts, thank you! http://www.maperformance.com/gallery/pictures/rodfailure1.jpg [PLAIN]http://www.maperformance.com/gallery/pictures/rodfailure2.jpg...

Hi, I am an amtuer engine builder working on offroad race motorcycles. On the Honda Crf450 engines I have been working on, I have been having a large number off con rods failing in numerous ways. I have had the the con rod snap right below the piston with no sign of bearing failure. I've...

I have already drawn the circle and am happy and confident with it, but the question asks me to determine if failure has occurred and I am unsure of how to tell, I guess I don't know how to read the circle and interpret what it means. Can anyone describe to me how you tell if failure has...

Homework Statement A*certain*soil*has*c’*=*12kPa*and*φ’*=*32°.*The*major*and*minor*principal*stresses*at*a*point*in*this* soil*are*348*and*160*kPa*respectively,*and*the*pore*water*pressure*at*this*point*is*96*kPa.*Draw*...

Homework Statement "The compressive strength of a concrete specimen follows a normal distribution with a mean value of 2.8 ksi and a coefficient of variation (COV) of 0.1. If the applied stress is 2.5 ksi, find the probability of failure." Homework Equations normal distribution formula...