最近用Halt试验箱子做HASS测试,目的是剔除缺陷产品;但想做的更多的,可找了很多资料都没有找到随机振动加速因子的计算方法;
哪位兄弟要知道,分享下,谢谢!
请问谁知道Halt的随机振动怎么算加速因子

admin
Lv.6
靓号:8888
可靠性网管理员
没听过Halt试验中的随机振动计算加速因子
做HASS时,根据HALT试验得到的值,取一个百分比而已。
楼主可以再把问题描述清楚一些,为什么要计算随机振动的加速因子。目的是什么,以你的理解,大概如何计算????
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deadxiaoh
Lv.5
有正常的振动的加速因子计算吗?????想交流一下
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fuckit
Lv.5
忘记在哪里看到过的
振动的加速因子使用G值用逆幂模型(PowerLaw)进行计算的
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admin
Lv.6
靓号:8888
可靠性网管理员
[b]回复[url=http://www.kekaoxing.com/club/redirect.php?goto=findpost&pid=77134&ptid=8097]4#[/url][i]fuckit[/i][/b]
了解一下,希望有更多的高手如fuckit一样,来介绍介绍
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i@Suzhou
Lv.2
A_V=T_Use/T_Stress=(W_Stress/W_Use)^(M_b)
(W_Stress/W_Use)^(M_b)=(G_(f_Stress)/G_(f_Use))^(2M_b)
Ln(tf)=C-M_bLn(W)
Where,
A_V=vibrationaccelerationfactor
T_Stress=vibrationduration
T_Use=vibrationduration(nominal)
W=randomvibrationinputPSDacross
theresonancebandwidth(G2/Hz)
W_StressisthePSDteststressand
W_UsenominalusePSD
G_f=resonantGsinusoidvibrationlevel
M_b=b/2wherebisthefatigueparameter
tf=timetofailure
C=constant
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i@Suzhou
Lv.2
Example:UsingtheVibrationmodel
[b]Problem:[/b]
Estimatethetesttimetosimulate10yearsoflifeinthefieldforanassembly
thatistestedtoaLevel4PSDrandomvibrationtestcondition,shownin
below[b]Remark[/b]description.Itisestimatedthattheassemblywillundergoaworst-caseLevel1-
typerandomvibrationexposure1percentoftheassembly’slife.Therestof
theassembly’slifeisrelativelybenignintermsofvibrationexposure.
[b]Solution:[/b]
First,usetheexpressionin[b]previousletter[/b]tofindthevibrationaccelerationfactor.SinceLevel4hasa
PSDof0.12G2/Hz,thenLevel1is0.03G2/Hz.
Therefore,
AV=(WStress/WUse)Mb=(0.12/0.03)4=256.
In10years,thedevicewillbeexposedtoaLevel1vibrationforabout87,600×0.01=876hours.
Therefore,thenumberoftestcyclestosimulatethisis
TStress=TUse/AV=876/256=3.5hours.
[b]Remark:CommonrandomvibrationtestsaremostfrequentlyspecifiedintermsofPowerSpectralDensity(PSD)levels[/b]
Level2:Avg.PSD=0.06G2/HZ(Content11GRMS)
Level4:Avg.PSD=0.12G2/HZ(Content15.5GRMS)
Level8:Avg.PSD=0.24G2/HZ(Content21.9GRMS)
Level16:Avg.PSD=0.48G2/HZ(Content31GRMS)
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pif2216
Lv.6
谢谢,学习了;有相关案例就更好了
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ZICO863
Lv.5
[quote]A_V=T_Use/T_Stress=(W_Stress/W_Use)^(M_b)
(W_Stress/W_Use)^(M_b)=(G_(f_Stress)/G_(f_Use))^(...
[size=2][color=#999999]ice_fang发表于2010-7-1010:56[/color][url=http://www.kekaoxing.com/club/redirect.php?goto=findpost&pid=78194&ptid=8097]
[/url][/size][/quote]
请教:该公式源于哪个标准或文献?
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pif2216
Lv.6
[b]回复[url=http://www.kekaoxing.com/club/redirect.php?goto=findpost&pid=78195&ptid=8097]7#[/url][i]ice_fang[/i][/b]
真的非常感谢你的分享!仔细看了下你分享的内容,有些问题还需要向你请教:
1)M_b=b/2wherebisthefatigueparameter这个参数怎么确定?比如你举的例子中AV=(WStress/WUse)Mb=(0.12/0.03)4=256的[b]4[/b]是怎么确定的?
2)G_f=resonantGsinusoidvibrationlevel怎么用的是正玄共振等级?不是随机振动么?正玄共振等级如何确定其值?
3)C=constant如何取值?
4)PSDLevel的值是实验根据具体产品得出还是共用的?比如
Level2:Avg.PSD=0.06G2/HZ(Content11GRMS)
Level4:Avg.PSD=0.12G2/HZ(Content15.5GRMS)
Level8:Avg.PSD=0.24G2/HZ(Content21.9GRMS)
Level16:Avg.PSD=0.48G2/HZ(Content31GRMS)
还有你Level1PSD=0.03G2/HZ是推算的么?还是试验得出的?
5)最后一个问题,和楼上一个兄弟一样的,就是不知道兄弟这些公式和资料是出自什么文件上的阿?能共享下么?
[b]真的再次感谢!!!!!!![/b]
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i@Suzhou
Lv.2
DearAll,
Sorry,mybossoncegivemeapaperliteraturewhichdescribevibrationmodel.SoIshareitwithall.
Iquoteasectionforyourreference.
InVibration,devicesaremountedonadynamicshakertableandsubjecttoeitherarandomorsinusoidal-typevibrationprofile.CommonrandomvibrationtestsaremostfrequentlyspecifiedintermsofPowerSpectralDensity(PSD)levels(seebelowFigure).FigureillustratesthepossiblePSDtestprofilelevelsrelatedtoasimilarparticularuseenvironment.ThePSDfunctiondescribesthedistributionofvibrationenergywithrespecttofrequency.TheamountoftimecompressionthatcanbeaccomplishedisrelatedtothePSDtestlevelanduselevel.Estimatesoftimecompressioncanbemadeoncetheuselevelestimateandspectraldensityprofileareestablished.Thetraditionalclassicaltime-compressionmodel(MIL-STD810E)isapowerlawmodel(seebelowFigure).Inapplyingthismodel,itisimportanttounderstandthefailuremechanismsince,inarandomvibration-loadingenvironment,theresonanceofthematerialcandominatethefatiguelife.Here,maximumvibrationamplitudesandstressoccur.However,fatiguefailuresarenotalwaysdominatedbythefundamentalresonancemode.Inpractice,manyofthestresspeaksintheuseenvironmentmayfallbelowthefatiguelimitofthematerial,whileotherswillbeabovethefatiguelimit.Itfollowsthatanacceleratedlifetestbaseduponthismodelshouldinherentlybeconservative.However,becausemostofthefatiguedamageoccursatthehigheststresspeaksinboththetestandinactualuse,thedegreeofconservatismisnotexcessive.AsnotedinbelowFigure,thePSDisinunitsofG2/Hz.ThesquareoftheGstresslevelattheresonancefrequencyisdirectlyproportionaltothePSDlevel(W~G2),sothemodelcanbeputintermsofeitherrandomorsinusoidal-resonanceG-stressloading.Inthemodel,thefatigueparameterisrelatedtoexperimentalslopeofthestresstocyclestofailuredata.Thisexponentvariesdependingonthefatiguelifeofthematerialsinvolved.Forexample,thevalueofb≈5iscommonlyusedforelectronicboards.However,conservativevalueforthefatigueparameterbisabout8(e.g.,Mb=4).MILSTD-810E(514.4-46)recommendsb=8forrandomloading.
[attach]6890[/attach]

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