邢浩,楊軍
??獙?dǎo)彈武器貯存延壽
考慮延緩糾正的雙應(yīng)力加速可靠性增長試驗方法
邢浩,楊軍
(北京航空航天大學(xué) 可靠與系統(tǒng)工程研究院,北京 100191)
縮短傳統(tǒng)加速可靠性增長試驗時間,以及考慮延緩糾正方式對產(chǎn)品可靠性的影響。提出考慮延緩糾正的雙應(yīng)力加速可靠性增長試驗方法,首先,采用基于延緩糾正AMSAA模型跟蹤可靠性增長過程,并采用極大似然估計方法估計模型參數(shù);其次,以溫度和振動作為加速應(yīng)力為例,開展加速壽命試驗,獲得試驗數(shù)據(jù),基于廣義艾琳模型,通過最小二乘估計方法得到加速系數(shù);然后,將產(chǎn)品可靠性外推到正常應(yīng)力水平。航空蓄電池應(yīng)用案例分析表明,與基于單應(yīng)力加載的高應(yīng)力加速可靠性增長試驗相比,所提方法能夠縮短29.4%的試驗時間,并且采用延緩糾正方式對產(chǎn)品的可靠性有影響。為產(chǎn)品在雙應(yīng)力加載方式和采用延緩糾正方式下開展高應(yīng)力加速可靠性增長試驗的可靠性評估提供了技術(shù)手段。
雙應(yīng)力;加速可靠性增長;AMSAA模型;廣義艾琳模型;加速系數(shù);延緩糾正文
可靠性增長試驗是通過對產(chǎn)品施加真實的或模擬的環(huán)境應(yīng)力,揭示產(chǎn)品的故障,并采取糾正措施,從而提高產(chǎn)品的可靠性,使其達(dá)到預(yù)定要求的一種試驗。它是一個有計劃的試驗—分析—改進(jìn)過程,其目的是對暴露的問題采取有效的糾正措施,從而達(dá)到預(yù)定的可靠性增長目標(biāo),是提高產(chǎn)品可靠性的有效方法之一[1-6]。然而,隨著科學(xué)技術(shù)的發(fā)展,許多可修系統(tǒng),如動力裝置[7]、控制儀表[8]、航空航天部件[9]等,在可靠性增長試驗前具有較高的可靠性,其故障間隔時間長,在正常應(yīng)力下開展可靠性增長試驗周期長,成本高。為了有效地解決這一問題,將加速壽命試驗[10-13]思想引入到可靠性增長試驗中,得到了加速可靠性增長試驗方法。通過施加比正常應(yīng)力更嚴(yán)酷的應(yīng)力,加速產(chǎn)品的失效,然后進(jìn)行相應(yīng)的分析和糾正,實現(xiàn)產(chǎn)品可靠性的快速增長。
在過去幾十年,加速可靠性增長試驗得到了大力發(fā)展[14-23]。Yu等[14]在Cox的加速壽命模型和Duane可靠性增長模型的基礎(chǔ)上,提出了一種加速可靠性增長模型。Acevedo等[15]對加速壽命試驗進(jìn)行了回顧,發(fā)現(xiàn)執(zhí)行良好的加速壽命試驗是實現(xiàn)產(chǎn)品可靠性增長的有效方法。周源泉等[16]基于Arrhenius和逆冪律模型,給出了恒應(yīng)力加速可靠性增長試驗中單個失效時間數(shù)據(jù)的統(tǒng)計分析方法。Ye等[17]基于AMSAA- BISE模型和廣義艾琳模型,提出了雙應(yīng)力加速可靠性增長試驗方法。Feinberg[18]研究了單應(yīng)力和多應(yīng)力水平可靠性增長壽命數(shù)據(jù)的卡方加速可靠性增長模型。Ruiz等[19]提出了一種貝葉斯加速可靠性增長方法,采用分塊分解技術(shù)對部件的加速壽命試驗數(shù)據(jù)進(jìn)行聚合,估計產(chǎn)品的可靠性。Ruiz等[20]提出了一種貝葉斯框架來分析可靠性增長中的加速壽命試驗數(shù)據(jù)。Anand等[21]在加速可靠性增長試驗的基礎(chǔ)上,提出了一種進(jìn)行磁共振成像系統(tǒng)可靠性試驗的方法。Ruiz等[22]提出了一種在加速可靠性增長計劃中利用退化數(shù)據(jù)進(jìn)行系統(tǒng)可靠性預(yù)測的模型。Ruiz等[23]提出了一種貝葉斯選擇加速可靠性增長方法來加速潛在失效模式的發(fā)生。
然而,上述研究大多集中在單加速應(yīng)力下進(jìn)行加速可靠性增長試驗上,而且在低加速應(yīng)力水平下開展加速可靠性增長試驗時間過長,工程上難以接受。此外,在采用延緩糾正方式下,由于失效沒有立即糾正,因此在試驗結(jié)束時,采取延緩糾正將影響產(chǎn)品的可靠性。因此,為了更有效地縮短試驗時間,并考慮延緩糾正對產(chǎn)品可靠性的影響,本文提出了一種考慮延緩糾正的雙應(yīng)力加速可靠性增長試驗方法。首先,利用AMSAA模型跟蹤最高加速應(yīng)力水平組合下的可靠性增長過程。其次,以溫度和振動為加速應(yīng)力,在不同應(yīng)力水平組合下進(jìn)行加速壽命試驗,得到加速壽命試驗數(shù)據(jù),基于廣義Eyring模型,通過最小二乘估計法得到加速系數(shù)。然后,結(jié)合加速系數(shù),將試驗結(jié)束時的產(chǎn)品可靠性外推到正常應(yīng)力水平。最后,以航空蓄電池為例,驗證了所提方法的有效性。本文針對單加速應(yīng)力下加速可靠性增長試驗時間過長的問題,提出了雙應(yīng)力加載方式下的高應(yīng)力加速可靠性增長試驗方法,在最高加速應(yīng)力水平組合下進(jìn)行可靠性增長試驗,更有效地縮短試驗時間。另外,由于采取即時修正會占用產(chǎn)品較長時間,因此提出在高應(yīng)力加速可靠性增長試驗中采用延緩糾正的方式,并考慮延緩糾正對產(chǎn)品可靠性的影響。
在進(jìn)行延緩糾正的雙應(yīng)力加速可靠性增長試驗方法之前,需要給出7個假設(shè)?;谖墨I(xiàn)[24],給出假設(shè)1~4來描述試驗中故障分類、針對故障采取的糾正方式以及故障模式和失效數(shù)服從的分布。根據(jù)工程實際和文獻(xiàn)[16],給出假設(shè)5去描述可靠性如何增長,假設(shè)6去描述產(chǎn)品失效機(jī)理不發(fā)生改變?;谖墨I(xiàn)[10],給出假設(shè)7來描述加速系數(shù)。
假設(shè)1[24]。故障模式可分為A類故障和B類故障,且故障模式彼此獨立,任何故障發(fā)生都會導(dǎo)致系統(tǒng)故障。
假設(shè)2[24]。對于潛在的B類故障,一些B類故障采取即時糾正方法,其余的B類故障則采取延緩糾正方法。
假設(shè)3[24]。發(fā)現(xiàn)的B類失效模式的數(shù)目服從非齊次泊松過程,其均值函數(shù)為冪函數(shù)。
假設(shè)4[24]。試驗段中,持續(xù)試驗時間的每一個A類失效模式下的失效數(shù)目和每一個B類失效模式下的失效數(shù)目均為齊次泊松過程。
假設(shè)5[16]。在最高的加速應(yīng)力水平組合下,采取糾正措施后,產(chǎn)品的可靠性顯著提高。
假設(shè)6[16]。在正常及加速應(yīng)力水平S下,產(chǎn)品故障機(jī)理不變的條件為:過程的某個參數(shù)或過程的某些參數(shù)的函數(shù)不隨S的變化而異。
假設(shè)7[10]。在正常應(yīng)力水平0下,產(chǎn)品的失效分布函數(shù)為0(),t,0為產(chǎn)品達(dá)到失效率的時間,也就是0(t,0)=;在正常應(yīng)力水平S下,產(chǎn)品的失效分布函數(shù)為F(),t,i為產(chǎn)品達(dá)到失效率的時間,也就是0(t,i)=,則加速應(yīng)力水平S對于正常應(yīng)力水平0的加速系數(shù)為:
1)加速壽命模型。本節(jié)以溫度和振動作為加速應(yīng)力為例,產(chǎn)品的特征壽命與加速應(yīng)力水平之間的關(guān)系滿足廣義艾林模型。對于雙應(yīng)力情況,采用溫度和非溫度應(yīng)力同時作用于加速壽命試驗:
2)可靠性增長模型。為考慮采用延緩糾正方式對系統(tǒng)可靠性的影響,本節(jié)采用基于延緩糾正AMSAA模型作為可靠性增長模型。模型原理:該模型相關(guān)參數(shù)估計過程用來評估延緩糾正對產(chǎn)品可靠性的影響。特別是,在第二試驗階段之前,模型和估計過程可以評估系統(tǒng)在采取延緩糾正后的故障強(qiáng)度。失效強(qiáng)度表示為(),其中表示第一階段的試驗時間。該模型對()的估計基于:從試驗階段獲得A、B類失效的失效數(shù)據(jù);在試驗階段發(fā)現(xiàn)的B類失效的d估計值。
在第一試驗階段,沒有采取糾正措施的產(chǎn)品的失效強(qiáng)度為:
式中:obs為試驗段發(fā)生的所有B類失效構(gòu)成的集合。
糾正過程估計()的基礎(chǔ)是試驗段內(nèi)的B類失效模式的失效數(shù)由N減少到(1-d)N,其中d是對失效模式的實際估計。糾正過程對()的估計為:
式中:A為[0,]內(nèi)的A類失效數(shù)。
根據(jù)假設(shè)4,所有的糾正都推遲到試驗段結(jié)束后,B類失效模式的失效率在[0,]內(nèi)保持恒定,估計值為:
式中:N表示[0,]內(nèi)B類失效模式的失效數(shù)。
根據(jù)式(15)可以得到:
對式(17)兩邊分別取對數(shù),得:
然后得到模型的極大似然估計值:
將式(22)轉(zhuǎn)換成矩陣形式:
式(22)可以重新寫為:
通過最小二乘估計方法估計的參數(shù),能夠使得偏差平方和達(dá)到最小值min:
則參數(shù)結(jié)果估計為:
因此,4個參數(shù)估計結(jié)果為:
航空蓄電池作為飛機(jī)發(fā)動機(jī)的起動電源,其可靠性水平的高低直接影響航空產(chǎn)品的使用,因此本節(jié)以航空蓄電池為例(如圖1所示),闡述了所提出方法的有效性,給出了高應(yīng)力水平組合下的加速可靠性增長試驗方法。根據(jù)產(chǎn)品的特性,首先給出加速應(yīng)力和水平大小。選擇溫度和振動作為加速應(yīng)力,每種應(yīng)力都有4個水平,見表1。溫度的正常水平為0=298 K,振動的正常水平為0=0.032/Hz。通過均勻設(shè)計,應(yīng)力水平組合見表2。
圖1 航空蓄電池
表1 環(huán)境應(yīng)力與水平大小
Tab.1 Environment stress and level
表2 均勻設(shè)計下應(yīng)力組合
Tab.2 Stress combinations by uniform design
根據(jù)實際工程背景,航空航天電子產(chǎn)品的特征壽命為11 000 h,該產(chǎn)品的目標(biāo)MTBF為18 000 h。目前產(chǎn)品處于工程研制階段,在高應(yīng)力加速可靠性增長試驗前進(jìn)行了4組可靠性試驗,加速壽命試驗在4種應(yīng)力水平組合下同步進(jìn)行,該產(chǎn)品的特征壽命分別為10 000、8 500、6 500、4 500 h。
加速壽命方程的最小二乘估計為=19.3,=-3 264.7,=5.7,=-1 788.1。然后由式(1)和式(2),計算得出正常應(yīng)力條件下產(chǎn)品的特征壽命和加速系數(shù),見表3。
表3 4組應(yīng)力水平下的特征壽命與加速系數(shù)
Tab.3 Characteristic life and acceleration coefficient under four stress combinations
表4 第一階段B類失效試驗數(shù)據(jù)
Tab.4 Test data of B failure in the first test phase
采取延緩糾正前,產(chǎn)品的失效率為:
相應(yīng)的產(chǎn)品的MTBF值(MTBF)為:
在第一階段末采取延緩糾正后,產(chǎn)品的失效率為:
相應(yīng)的產(chǎn)品MTBF值為:
在第一試驗階段結(jié)束時進(jìn)行糾正后,產(chǎn)品失效率的預(yù)期值為:
在第一試驗階段結(jié)束時進(jìn)行糾正后產(chǎn)品的MTBF值為:
第二試驗階段的截尾失效時間為=6 000 h。B類失效的試驗數(shù)據(jù)見表5。
表5 第二階段B類失效試驗數(shù)據(jù)
Tab.5 Test data of B failure in the second test phase
采取延緩糾正前,產(chǎn)品的失效率為:
相應(yīng)的產(chǎn)品MTBF值為:
在第二階段末采取延緩糾正后,產(chǎn)品的失效率為:
相應(yīng)的產(chǎn)品MTBF值為:
在第二試驗階段結(jié)束時進(jìn)行糾正后,產(chǎn)品失效率的預(yù)期值為
在第二試驗階段結(jié)束時進(jìn)行糾正后產(chǎn)品的MTBF值為:
第二試驗階段的截尾失效時間為=8 000 h,B類失效的試驗數(shù)據(jù)見表6。
表6 第二階段B類失效試驗數(shù)據(jù)
Tab.6 Test data of B failure in the third test phase
采取延緩糾正前,產(chǎn)品的失效率為:
相應(yīng)的產(chǎn)品MTBF值為:
在第三階段末采取延緩糾正后,產(chǎn)品的失效率為:
相應(yīng)的產(chǎn)品MTBF值為:
在第三試驗階段結(jié)束時進(jìn)行糾正后,產(chǎn)品失效率的預(yù)期值為:
在第三試驗階段結(jié)束時進(jìn)行糾正后,產(chǎn)品的MTBF值為:
外推到正常條件下產(chǎn)品的MTBF值為:
為驗證AMSAA模型的合理性,本文使用克萊默- 馮-米塞斯方法[26]。
圖2 產(chǎn)品失效率
將單應(yīng)力下的高應(yīng)力加速可靠性增長試驗方法與所提方法進(jìn)行對比,結(jié)果見表7。從表7可以看出,當(dāng)可靠性增長目標(biāo)值為18 000 h時,高應(yīng)力加速可靠性增長試驗在單應(yīng)力下所需的總試驗時間為10 359.7 h,而所提方法所需的總試驗時間為8 000 h。因此,本文所提方法節(jié)省了更多的試驗時間,效果明顯。
表7 所提方法與單應(yīng)力高加速可靠性增長試驗比較
Tab.7 Comparison between HARGT under single-stress and the proposed method
1)通過采用雙應(yīng)力加載方式下的高應(yīng)力加速可靠性增長試驗,驗證了所提方法的有效性。試驗結(jié)果對比表明,所提方法比單應(yīng)力加載方式能夠節(jié)省29.4%的試驗時間,效果更顯著。
2)采用延緩糾正方式的確對產(chǎn)品的可靠性有影響,因此在實際工程中,應(yīng)該采取合適的糾正措施,更加有效地提高產(chǎn)品服役時間。
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A Double Stress Accelerated Reliability Growth Test with Delayed Corrections
XING Hao, YANG Jun
(School of Reliability and Systems Engineering, Beihang University, Beijing, 100191)
The work aims to shorten the time of traditional accelerated reliability growth tests and consider the effect of de-layed corrections on product reliability. A double-stress accelerated reliability growth test method considering delayed correc-tions was proposed. Firstly, the reliability growth process was tracked with the AMSAA model based on delayed correction, and the model parameters were estimated by the maximum likelihood estimation method. Secondly, with temperature and vibration as the accelerated stress, an accelerated life test was carried out to obtain the test data, and the acceleration coefficient was ob-tained by the least square estimation method based on the generalized eyring model. Then, the product reliability was extrapo-lated to normal stress level. The application case analysis of aircraft storage battery showed that the proposed method could shorten the test time by 29.4% compared with the high-stress accelerated reliability growth test based on single-stress loading and the delayed corrections method had an impact on the product reliability. It provides technical methods for reliability evalua-tion of high-stress accelerated reliability growth tests under double-stress loading and delayed corrections.
double-stress; accelerated reliability growth; AMSAA model; generalized eyring model; acceleration coeffi-cient; delayed corrections
2023-09-14;
2023-09-25
The National Natural Science Foundation of China (72371008, 71971009)
TJ089
A
1672-9242(2023)10-0001-07
10.7643/ issn.1672-9242.2023.10.001
2023-09-14;
2023-09-25
國家自然科學(xué)基金(72371008,71971009)
邢浩,楊軍. 考慮延緩糾正的雙應(yīng)力加速可靠性增長試驗方法[J]. 裝備環(huán)境工程, 2023, 20(10): 001-007.
XING Hao, YANG Jun. A Double Stress Accelerated Reliability Growth Test with Delayed Corrections[J]. Equipment Environmental Engineering, 2023, 20(10): 001-007.
責(zé)任編輯:劉世忠