ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00362.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00363.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Flight simulation fatigue crack propagation tests were carried out on 2024‐T3, 7475‐T761 and mill annealed Ti‐6A1‐4V sheet in thicknesses up to 3 mm and representative for transport aircraft lower wing skin stiffened panels of end load capacities 1·5 and 3 MN/m. The performance of 2024‐T3 was much superior, owing mainly to greater retardation of crack growth after severe flights. The effect of load truncation was also greater for 2024‐T3. The significance of the results for the choice of advanced structural concepts and materials and the choice of truncation level is discussed. A recommendation for further investig

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00364.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Crack tip closure measurements were performed in a 2124 T3 51 aluminum alloy by electronfractography. The technique makes use of high resolution fractography to correlate a closure in striation spacing with a sudden change of the stress intensity factor range following steady state crack growth. The crack growth tests under programmed loads were performed with a servohydraulic machine interfaced to a digital computer. An average value ofKop/Kmaxequal to 0·15 was found in the range of 10 MPa√m<ΔK<35 MPa√m. The higher closure developing after overloads was found a suitable explanation for crack growth reta

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00365.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Two methods are described for inverting the strainrange/life and strainrange/stressrange equations commonly used in fatigue analysis in order to obtain closed‐form expressions for life and stressrange in terms of strainrange. In theCollocationapproach the form used isNf=A(Δε—Δε0)γ orNf=A(Δε)Ψ(Δε—Δε0)γ. In theSpline‐Functionapproach the curve is divided into two regions. At strainranges above where the elastic and plastic lines intersect the equation isNf=NTR1/cexp δRα; at lower strainranges it isNf=NTR1/bexp δRβ, whereNTis transition life,Ris strainrange normalised to transition strainrange, andb, c, α, β, δ are constants determinable from the constants of the equation to be inverted. Similar expressions are derived for the cyclic stress/strain curve in terms of the same constants. The methods are illustrated by an example, and found to have close conformity to the b

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00366.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—High temperature cyclic deformation in nickel is investigated by comparing its cyclic hardening curves at constant strain amplitudes at four temperatures with the monotonic hardening curves and by detailed electron microscopic examination of the bulk. Just as at ambient temperature, there are broad similarities between the cyclic and monotonic hardening of nickel at high temperatures, but there are also significant differences in detail. It is shown that, as in monotonic deformation, increased dynamic recovery with increasing temperature is the main cause for the reduction in flow stress at high temperatures. However, the increased vacancy concentration produced by cyclic straining causes a linear reduction in flow stress (as distinct from the “athermal” behavior observed in monotonic deformation over a limited temperature range). Also the tendency for dislocations to agglomerate into sign‐balanced, low energy configurations requires a temperature higher than that observed for monotonic deformation before high temperature softening is o

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00367.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The cyclic deformation behavior of a commercial grade dispersion strengthened (DS) nickel is reported for four different temperatures in the range from room temperature up to 0·67TMof nickel. This cyclic behavior is compared with the monotonic behavior of the DS‐nickel and also with that of nickel‐200 reported in the preceding article. It is shown that the thoria particles combined with substructure introduced by prior thermomechanical processing contribute substantially to the cyclic flow stress of the material, most strongly at room temperature. Although the DS‐nickel is cyclically stable at all temperatures tested, short circuit diffusion makes it highly susceptible to high temperature recovery and therefore the cyclic flow stress decreases rather rapidly with increasing temperature. However, this decrease soon levels off and at approximately 0·67TMthe cyclic flow stress of the DS‐nickel is shown to be higher than tha

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00368.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The cyclic stress‐strain curves for 1% Cr‐Mo‐V steel and AISI 316 stainless steel were determined under biaxial loading conditions at various temperatures and strain rates. It is shown that these curves may be correlated in terms of the maximum shear stress and strain amplitudes. It is argued that, even though metals obey the von Mises yield criterion for monotonie loading, the micromechanisms of slip which produce the stabilized cyclic stress‐strain behaviour are governed by the Tresca

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00369.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Industrial multi‐pass TIG weldments of HP 9‐4‐20 high strength alloy steel have been found to contain significant volume fractions (around 10%) of retained austenite which are not readily transformed after stress relieving and subsequent refrigeration procedures. To determine whether the presence of such retained austenite in tempered martensitic structures could be detrimental to fatigue resistance in HP 9‐4‐20 steel, fatigue crack propagation behavior was examined over six orders of magnitude in growth rate, in commercially heat‐treated material (containing less than 3% austenite) and in intercritically heat‐treated and tempered material (containing approx. 14% austenite) in an environment of moist, ambient temperature air. Whereas crack propagation rates were unchanged at growth rates exceeding 10−6mm/cycle, structures containing 14% austenite showed somewhat superior resistance to near‐threshold crack propagation at growth rates less than 10−6mm/cycle, the threshold for crack growth (ΔK0) being over 20% higher than in commercially heat‐treated material. The presence of retained austenite further appeared to inhibit the occurrence of intergranular fracture at near‐threshold levels. It was concluded that significant proportions of retained austenite are not detrimental to fatigue crack propagation resistance in HP 9‐4‐20 steel, and may indeed have some beneficial effect at very low, near‐threshold growth rates by increasing resistance to e

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00370.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Low cycle plastic stress‐strain response and fatigue life of low carbon steel in variable amplitude loading is investigated. Repeated block straining with defined probability distribution of strain peaks within a block was chosen. With the help of rain‐flow analysis of a strain block the cyclic hardening/softening curves as well as the service cyclic stress‐strain curves during random amplitude block loading were obtained. The relation between service stress‐strain curves and the basic stress‐strain curve was established. The fatigue life prediction based on the actual cyclic stress‐strain response and rain‐flow analysis was found to be in agreement with exper

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1979.tb00371.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY