Fatigue Mac OS

Statistics for the operating system market come in different flavors and from a variety of sources but they all have one thing in common: indicating that Windows is losing ground to Mac OS X and Linux. As far as Microsoft is concerned, it reached the apex of the operating system market with the launch of Service Pack 2 for Windows XP back in 2004. Since then, it has been all down hill for the Redmond giant. Sure, the slope is by no means steep enough for a hard Windows fall, just sufficiently inclined through the erosion produced by Mac OS X and Linux that the ground is slipping from under Microsoft's proprietary platform, slowly but surely...

Women are more likely to have non-cavitary, nodular MAC. Diagnosis of MAC lung disease usually requires: Medical history with records of symptoms: Cough, sputum production, shortness of breath; Loss of appetite (anorexia is the medical term) weight loss; Severe fatigue or tiredness with inability to perform daily tasks. Oct 12, 2015 Simulation of a fatigue crack problem in electronic devices 1. Simulation of a fatigue crack problem in electronic devices using cohesive zone modelling approach Bala Karunamurthy. KAI Kompetenzzentrum Automobil- und Industrieelektronik GmbH, Villach. Grygoriy Kravchenko. ILSB, TU Wien ACUM’15.

While Windows is not at risk from a landslide, it has been on a downward trajectory for the past years, with consumers suffering from Windows fatigue, and increasingly looking for alternatives. Recent releases such as Windows Vista in 2007, and Vista Service Pack 1 as well as Windows XP Service Pack 3 have done little to impact the general trend. As of May 2008 Windows is credited with 91.13% of the operating system market according to Net Applications, with 91.11% by W3Counter and with 95.94% by OneState (but only as of April 2008).

In January 2007, when Windows Vista hit the shelves, Net Applications revealed a share of 93.33% for Windows, approximately two percent higher than in January 2008. Back in July 2007, OneStat gave Windows a share of 96.97%, also larger than the 95.94% from a couple of months ago. W3Counter seem to be on par with Net Applications indicating that Windows was at 93.6% of the market in May 2007, and as low as 91.11% in the past month.

Windows Saturation

The release of Service Pack 1 for Windows Vista and of Service Pack 3 for Windows XP has done little to help break what appears to be a generalized and accentuating case of Windows fatigue. Net Applications stated that SP3 for XP failed to impact the operating system's continuous market share lost for over a year. Even with SP3 available as of May 6, 2008, XP continued to lose audience and is down from 73.07% in April to 72.12% the past month. Vista continues to climb in statistics, but SP1 didn't deliver the kick needed to accelerate growth to the levels where focus will no longer shift to XP SP3, Windows 7 or rival products. Vista only climbed from 14.02% in March to 15.26% in May.

Statistics from W3Counter indicate a similar trend with XP dropping from 78.56% to 78.24% in the past two months while Vista jumped from 7.34% to 7.69%. It's not that Microsoft can't spare a few tens of millions of users, and it's not that a large proportion of the Windows audience is shifting toward Mac OS X and Linux, but the Redmond company is finding it harder and harder to boost its share on a market already saturated by its operating system. The software giant is indeed at the top, but the only way is not necessarily down, even if the general trend seems to contradict this perspective.

Windows Vista, the Default Growth

Windows Vista climbed up in the space occupied by Windows XP to claim the second most used operating system on the market since mid-2007. Since the January 2007 launch, Vista's growth has somewhat stabilized at around 10 million units per month. At the end of March 2008, Microsoft revealed that it had sold over 140 million Vista licenses worldwide. As of May, Chief Executive Officer Steve Ballmer claimed that Vista had passed the 150 million mark.

W3Counter puts Vista at 7.69% in May 2008 compared to 1.91% the same month of the past year. In March 2008, OneStat indicated that in its statistics, Vista is at 13.76% up from July 2007 when it accounted only for 12.72%. Net Applications reveal the most consistent growth for the latest Windows client, from 0.93% in February 2007, to 15.26% in May 2008.

Without establishing the records Microsoft was aiming for it, Vista's adoption rate does not qualify the operating system for a failure by any measure. However, the biggest catch behind the uptake of Vista is the fact that it is almost entirely governed by the sales of new OEM computers. Original equipment manufacturers are responsible for over 80% of the revenues of the Windows Client Division, and concomitantly for the largest volumes of sales of the new Windows operating systems.

A very accurate prediction is that Windows Vista adoption will only accelerate after June 30, 2008, when XP is no longer available through retail and OEM channels. With only Vista preloaded on new machines, there is nowhere to go but up for the latest Windows client. Still, even at over 10 million new licenses a month, Vista will remain far from the dominant OS on the market, Windows XP.

Don't Expect Miracles from Windows 7

Even though Windows Vista has taken all the heavy hits, acting as a buffer release for Windows 7, the next iteration of Microsoft's proprietary operating system will drop in a market which has started to experience Windows fatigue for a number of years. But unlike Vista, Windows 7 will benefit from the get go from a mature ecosystem of software and hardware products. Microsoft is essentially promising a Windows 7 apple which will fall far tom the Vista tree, while at the same time featuring the same architecture as its predecessor, in terms of the kernel, and the graphics and audio subsystems, security and search functionality, etc.

In January 2007, data from Net Applications placed Mac OS X at 6.22% of the operating system market and Linux at 0.35%. In over a year, the market share of Windows' rivals went up to 7.83% and respectively 0.68%. OneStat claims that Mac OS X jumped from 1.79% in July 2007 to 2.18% in April 2008, and Linux to just 0.42% from 0.36%, while W3Counter gives OS X 4.73% in May 2008 up from 3.72% in the same month in 2007.

Both Mac OS X and Linux have been slowly converting the default audience of Windows now looking for additional solutions on top of what Microsoft has to offer. The most consistent growth is that of Apple, because of the winning hardware plus operating system combination. This is something that only the Cupertino-based hardware company can deliver, without Microsoft or a Linux distribution vendor being able to match it.

Microsoft is indeed working with its OEM partners harder than ever in order to produce bundles that will rival the Mac computers and OS X in terms of consumer appeal. This month, it has become clear that the Redmond company's main weapon against Apple will be the natural user interface. Delivering an entirely new interaction model as mainstream technology might seem like a big bet for Microsoft, with traditional Windows users experiencing instincts to resist such a move.

However, touch, gestures, voice commands, object and motion recognition will become a standard model of interaction in the future, and Windows 7 has the largest potential to bring this niche technology to the masses and get it adopted fast. At the same time Apple is not exactly standing still, as touch-based interfaces are already widely available in products such as the iPhone and the latest Mac models. At this point in time, it seems that Linux will be the last comment at the natural user interface feast, unless the major developers of Linux distribution take matters into their own hands and convince OEMs to to for the open source operating system what they are doing for Windows 7.

Good, Old XP

Innovation is a mandatory item in the recipe for Windows 7 if the next iteration of Windows attempts to stop its install base from migrating to Mac OS X and Linux. But Windows 7 is planned to drop at the end of 2009, and for the time being Windows Vista proved incapable of not letting the Windows momentum from slowing down. But don't count XP out just yet. Vista's predecessor will continue to have a consistent impact even after Windows 7 will be made available. This because Windows XP is no less than Microsoft's way of reaching the next five billion users.

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The Redmond company has already committed to offering Windows XP Home Edition until 2010 or one year after the release of Windows 7, whichever comes first, on ultra-low-cost mobile and desktop computers. While ultra-low-cost machines will be sold in developed countries, the focus falls on first time users in emerging markets, where Microsoft has identified the next five billion potential customers. But, here, the company has to first fend off Linux, whose biggest advantage is the fact that it is free.

Run Fatlab by executing Fatlab.m in Matlab (source version) or selecting Fatlab from the Windows Start menu (deployed version) to get the main window containing:

Toolbar: Open, save, new analysis. Pan, zoom, rotate view. Select/probe nodes and help.
Model view: 3D view of the FE model (or part of it).
Setup panel: Buttons for setting up and running an analysis + modifying the model view.
Results panel: Specify and view detailed results.

A fatigue analysis consists of the following steps, each activated by a button in the setup panel.

Setup loads
Setup model
Setup SN curve
Running the analysis

1. Setup loads

The first step in setting up an analysis is to import the loads. Fatlab currently accepts only time series as loading. Therefore to analyse simple cases, e.g. single load ranges, the user must construct a load-time series, e.g. a sine wave having the correct min/max mean values.

The loads file is imported into Fatlab through Setup Loads>Browse… and the content is plotted in the graph. Additional statistical information is provided in the table below. If the loads file have been edited outside Fatlab, the changes can be imported using the Update button.

The load time series can also be manipulated in this window by entering a scale/offset in the table. This is particularly useful for sensitivity studies.

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For longer time series, the computational time can be reduced using the Load reduction popup menu. Here, the user can choose from the following options:

Full time series: Calculate stress at all time instances of input.
All turning points: If the input is oversampled, this option removes all non-peak time instances, without any loss of damage.
Racetrack filtered: The input is subjected to racetrack filtering eliminating cycles smaller than 5, 10, 20, 30 or 40% of the largest range. This causes minor loss in damage.
Single cycle DEL: The input is condensed to a single sinusoidal load cycle with a range corresponding to the damage equivalent load of the input, calculated using the slope (m) specified above.

Notes:

The provided load-time series must contain at least one cycle for one of the load components.
A load component is allowed to be constant, e.g. 0, as long as some other load component experiences at least one cycle.
For constant loads, e.g. gravity, add a constant time series to control this.

2. Setup model

The second step is to import the model file. Select the file using the Browse button and the appropriate file format from the Format popup menu and the model is imported. This processes the FE model by “hollowing it out”, i.e. finding and excluding internal nodes and element faces to enhance performance.

Next, the FE stress files must be imported. Again the file format must be selected. Press Add to select the FE stress files (multiple files can be selected in one go, by holding CTRL while selecting them). Then place the FE stress files in ascending order using the up/down buttons.

The requirements to the FE stress files differ depending on the load-stress relationship (Type) chosen for each load component:

Linear: A single FE stress file is imported.
Bilinear: Two FE stress files is imported (one for negative and one for positive loading).
1D interpolation: A minimum of 2 FE stress files must be given.
2D interpolation: A minimum of 4 FE stress files must be given.
- Var for 2D interp.: No FE stress files is used for this type. This is simply a helper-variable for the 2D interpolation routine, e.g. an angle or similar.

In all cases except 2D interpolation, extrapolation beyond the smallest/largest FE unit load case is supported. Thus, in the case of 2D interpolation, the supplied FE unit load cases must cover the entire loading range, i.e. if the max load is 100kN, an FE unit load case of at least 100kN must be supplied.

Finish by pressing OK. This causes the program to consolidate the inputs, i.e. arranging them in a neat manner for fast access later.

Pressing OK returns to the main window and displays the FE model.

Notes:

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It is an error if the FE stress files are not placed in monotonically increasing order.
The lists of nodes in the FE stress files must be a subset of the nodes in the model.
Currently no sanity checks are performed on the input, e.g. whether the selected format matches the selected file and so forth, so you will have to do that yourself.

3. Setup SN curve

Pressing Setup SN curve brings up the window shown below. Here, the user may supply the SN curve, mean stress handling, fatigue stress, safety factor and so forth for the analysis.

In the Database panel, the user can insert as many SN curves as necessary. Fatlab will use the one that is selected for the overall analysis. The remaining SN curves can be used for analysis of hotspots later on or comparison of different materials. Also the mean stress handling and analysis options are stored individually with each SN curve. A database can be saved to a file and then loaded into another analysis.

Selecting an SN curve will bring up its defining parameters and shows the curve in the diagram. The dashed line SN curve is the one the user defines and the full line SN curve is reduced by the partial safety factor. The latter is of course used in the computations.

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The input parameters is explained in the following table:

Parameter	Description
Primary slope, m1	Slope of the SN curve before the knee.
Secondary slope, m2	Slope of the SN curve after the knee.
Fatigue strength, dsR1	Stress range defining the SN curve [MPa] (at zero mean stress).
Associated cycles, NR1	Number of cycles at which the above stress range is given. Typically 2,000,000.
Knee point stress range, dsR2	Stress range at the knee point [MPa]. Calculated from ds1/N1.
Knee point cycles, NR2	Number of cycles at the stress range. Typically 5,000,000 (EC3) or 10,000,000 (IIW).
Max/min cut-off	Limit value at top/bottom where the SN curve is horizontal [MPa].
Mean stress mode	None: No mean stress correction. Recommended e.g. for welded or bolted joints. Linear: Simple linear mean stress correction. Recommended if M is available. Bilinear: Same as linear until R=0, then follows line down to Rm. Modified Goodman: Recommended for brittle materials. Gerber parabola: Recommended for ductile materials. Soderberg: Similar to Goodman, but using Re instead of Rm. Smith-Watson-Topper: only depends on R 60% compression: Equivalent to EC3 rule using only 60% of compressive loading. IIW, low residual stress: FAT classes are scaled up by up to 1.6. IIW, medium residual stress: FAT classes are scaled up by up to 1.3. FKM: controlled by M and M/3 depending on R.
Mean stress sensitivity, M	Slope of linear mean stress reduction in Haigh diagram.
Yield strength, Re [MPa]	Material yield strength, used if “Observe yield lines” or “Soderberg” mean stress mode is selected.
Tensile strength, Rm [MPa]	Material tensile strength, used by Goodman/Gerber mean stress correction.
Observe yield lines	Limits SN curve to avoid yielding.
Extrapolate in compression	Extend mean stress correction for compressive mean stress (non-conservative).
Fatigue stress	Sx, Sy, Sz, Txy, Tyz, Txz: Stress components in global coordinate system. P1, P2, P3: Principal stresses. Pnmax: Numerically largest principal stress (between P1 and P3). Default. Tmax: Maximum shear stress. CP: Critical plane approach.
Cycle counter	Reservoir: Recommended for short time series (few/single cycles) Rainflow half: Recommended for non-repeating time series (returns a number of residual half cycles). Rainflow full: Recommended for repeating time series (no residual half cycles). Single cycle: No counting, just set number of cycles to 1. Single cycle LC: as above, but using the “Longest Chord” method for determining the shear stress amplitude. Single cycle MCC/MRH: under development.
Partial safety factor	Safety factor scaling down the SN curve.
Multiaxial criterion	Select Fatigue stress = CP to enable these options. Normal stress Modified shear IIW equivalent Findley
Normal search planes	Number of search planes normal to the surface to use in critical plane method.
Inclined search planes	Used for the Findley criterion. 1 = no inclination planes (search planes normal to surface only). 2 = search planes normal to surface and at 45 degrees inclination 3+ = distribute inclination planes evenly between 0 and 90 degrees.
Multiaxiality parameter, k1, k2	Used for the multiaxial criteria. See the Theory reference.

Notes:

Using the critical plane method can be very time consuming (execution time grows linear with no. search planes). It is therefore recommended to perform a simple analysis first, then res-select a few interesting nodes and then switch to critical plane analysis.

4. Running the analysis

After setting up the model, the loading and the SN curve, Fatlab is ready to run fatigue analysis. Pressing Run analysis brings up the dialog shown below. Here it is possible to adjust performance settings and reduce the scope of the analysis.

A Racetrack filter fraction may be entered (default is 0.05, set to 0.0 to disable). This causes Fatlab to discard stress ranges smaller than the given fraction of the maximum occurring stress range (calculated individually for each node).

The Select nodes panel allows for selecting a subset of nodes for analysis:

All nodes: Analyse all nodes in model (element corner nodes only).
All visible nodes: Only analyse the currently visible nodes.
Nodelist from file: An ANSYS NLIST export file is read containing the node numbers to analyse.
Node range: A vector of node number specified using Matlab syntax, e.g. [1 2 3 6:10].
Selected (single) node: Run analysis only for the node selected in the main window.
Nodes from previous result: Selects those nodes from a previous run, that experience a total damage sum larger than the specified value.

The Damage accumulation panel allows the user to add the damage from an analysis to the the damage found in the previous analysis. This is intended for damage monitoring of a structure.