改进剥层应变法测量铝合金预拉伸厚板内部残余应力分布_英文_

Abstract: T he integ rat ed st ructure par ts are widely used in air craft . T he dist or tio n caused by residual str esses in thick pre stret ched aluminum plates dur ing machining integr ated parts is a commo n and serious pr o blem . T o pr edict and contr ol the machining distor tion, t he r esidual stress distr ibutio n in the thick plate must be measur ed fir stly . T he mo dified r emov al metho d for measuring residual st ress in thick pr estr etched aluminum plates is pro po sed and the str ess-st rain r elation matr ix is deduced by elasticity theo ry . T he r esidual st ress distr ibutio n in specim en of 7050 T 7451 plate is measured by using the method, and measur ement results are analy zed and co mpar ed w ith data obtained by ot her met ho ds. T he metho d is effectiv e to m easur e the residual str ess . Key words: pr estr etched aluminum plate; mo val metho d CLC number: V 252. 2; T G146. 2 Document code: A 05 Article ID: 1005-1120( 2004) 04-0286r esidual
N o. 4
W A N G Shuhong , et al. M odified L ayer Remo val M etho d fo r M easur ement of ……
287
t heory . In g eneral, t he layer remo val met ho d means remo val layer-strain met ho d, where a layer is removed f rom t he to p surface of a plat e and t he st rains ar e measured at it s bot t om. T he st resses can be calculat ed by t he str ains. T he [ 3] st ress -st rain relat io nship can be ex pr essed as
1 LIMITATION OF EXISTING LAYER REMOVAL ME THODS
T he layer removal met hod is discussed t o m easure t he residual str ess in t he t hick plat e in
Foundation item : Suppo rted by the N ational N at ur al Science F oundation of China ( 50375072) . Received date: 2004 0622; revision received date: 2004 10-05
( a) = x
E 2( 1 y
2
)
( h - a)
a 0
dx + da
x
dy da
y
plate) .
4(
+
) + 6( h - a )
∫( h -
+
x)2
d x ( 1)
w here x is the strain in x dir ect io n, y t he st rain in y direct ion, a t he dept h of a r em oval layer,
Dec. 2004
T ransactio ns o f N anjing U niver sity of A ero naut ics & A st ro na ut ics
V EMOVAL METHOD FOR MEASUREMENT OF RESIDUAL STRESS DISTRIBUTION IN THICK PRE -STRETCHED ALUMINUM PLATE
x
( a) the st ress at dept h a in direction x .
y
( a)
can be solv ed in a similar way . Because the f it ting funct ion ( a) is oft en diff icult t o be integr at ed, so Eq. ( 1) cannot be direct ly used in practice. Ref. [ 2] put s f orw ard anot her r em oval layer -st rain method . Assumed t hat t he residual st ress pr ofile t hro ug h t hickness co uld be expressed as a po lynomial
x
plane of t he plat e . So t he residual st resses vary only wit h t hro ug ht hickness of t he plat e, and t he dist ribut ion is unifo rm in ev er y plane parall el t o t he middle plane. M oreover , t he str ess distr ibu[ 2, 4] t ion is sy mmet ric about the middle plane , as sho wn in F ig. 1 ( a quart er sect ion of a t hick
W A N G Shu hong , ZUO Dun w en, W A N G M in , W A N G Zong rong
( Co lleg e o f M echanical a nd Electr ical Eng ineer ing, N U A A 29 Yudao Str eet , N anjing, 210016, P. R. China )
x
Fig. 1 P rincipal diagr am of m easur ement
2. 1 Measurement principl e Def ining t hat t he plat e t hickness is H , t he str esses ( z ) v ary w it h t hro ug ht hickness , as show n in Fig . 1. Befor e a layer is remo ved, t he plat e is self -balanced. T he equilix y
dual st ress dist ribut ion in t hick pr e-st ret ched aluminum plat e m ust be measured. T he met ho ds, such as X-ray diff ract ion and hole -dr ill ing m et hods , only can measure t he residual st resses on t he surf ace or subsurf ace of a w orkpiece. T hree-dim ensio nal residual st resses in thick plat es can be dir ect ly m easured by neut ron diff ract ion and hard X-ray met ho ds, but t he t echno logies can be available only in a f ew labs. Alt hough t he residual str esses in t he t hick plat e can be m easured by the crack compliance m et hod, t he measuring and calculat ing processes are t oo complex t o be used in pract ical product ion. U p t o now , t here is no eff ect iv e and mat ure m et hod t o measure residual st ress dist ribut ion in t hick plates . Accor ding to t he char act er ist ics of t he t hick pre-st retched alum inum plat e, a modified lay er remo val m et hod is proposed and t he st ress -st rain relat ion m at rix is deduced by t he elast icit y t heo ry . T he m et hod is v erif ied by ex periment s . It is sho wn t hat t he proposed met ho d is simple and accurate f or measurement of t he residual st ress dist ribut ion in t hick alum inum plat es.