The Experts below are selected from a list of 21183 Experts worldwide ranked by ideXlab platform
R. O. Ritchie - One of the best experts on this subject based on the ideXlab platform.
-
Fracture toughness and R-Curve behavior of laminated brittle-matrix composites
Metallurgical and Materials Transactions A, 1998Co-Authors: D. R. Bloyer, R. O. Ritchie, K. T. Venkateswara RaoAbstract:The fracture toughness and resistance-curve behavior of relatively coarse-scale, niobium/niobium aluminide (Nb/Nb_3Al) laminated composites have been examined and compared to other Nb/Nb_3Al composites with ( in situ ) Nb particulate or microlaminate reinforcements. The addition of high aspectratio Nb reinforcements, in the form of 20 vol. pct of 50- to 250-µm-thick layers, was seen to improve the toughness of the Nb_3Al intermetallic matrix by well over an order of magnitude, with the toughness increasing with Nb layer thickness. The orientation of the laminate had a small effect on Crack-growth resistance with optimal properties being found in the Crack arrester, as compared to the Crack divider, orientation. The high fracture toughness of these laminates was primarily attributed to large (∼1- to 6-Mm) Crack-bridging zones formed by intact Nb layers in the Crack wake; these zones were of sufficient size that large-scale bridging (LSB) conditions generally prevailed in the samples tested. Resistance-curve modeling using weight function methods permitted the determination of simple approximations for the bridging tractions, which were then used to make smallscale bridging (SSB) predictions for the steady-state toughness of each laminate.
-
cyclic fatigue Crack growth in a sic whisker reinforced alumina ceramic composite long and small Crack behavior
Journal of the American Ceramic Society, 1992Co-Authors: Reinhold H Dauskardt, M R James, J R Porter, R. O. RitchieAbstract:The ambient-temperature subcritical growth behavior of both long and microstructurally small Cracks is investigated during cyclic-fatigue loading in a SiC-whisker-reinforced alumina (Al2O3–SiCw) ceramic composite (fracture toughness, Kc∼ 4.5 MPa · m1/2). Based on long-Crack experiments using compact C(T) specimens, cyclic fatigue-Crack growth rates (over the range 10−11 to 10−5 m/cycle) are found to be sensitive to the applied stress-intensity range and load ratio, and to show evidence of fatigue Crack closure. Similar to other ceramic materials, under tension–tension loading the “long”(>3 Mm) Crack fatigue threshold, ΔKTH, was found to be on the order of 60% of Kc. Conversely, “small”(1 to 300 μm) Cracks grown from micro-indents on the surface of cantilever-beam specimens were observed to grow at applied ΔK levels some 2 to 3 times smaller than ΔKTH. similar to behavior widely reported for metallic materials. The observed small-Crack behavior is rationalized in terms of the residual stress field associated with the indent, and the restricted role of Crack-tip shielding (from mechanisms such as Crack bridging, closure and deflection) with Cracks of limited wake, analogous to closure effects with small fatigue Cracks in metals. Consistent with the lack of zone-shielding mechanisms in Al2O3–SiCw, under variable-amplitude cyclic loading Crack-growth rates do not exhibit the marked transient response following block overload sequences as do transformation-toughened ceramics or ductile metallic materials. Possible mechanisms for cyclic Crack advance in reinforced ceramic-matrix composite materials are discussed.
Sana Ullah Balouch - One of the best experts on this subject based on the ideXlab platform.
-
corrosion of steel fibre reinforced concrete from the Cracks
Cement and Concrete Research, 2005Co-Authors: Jeanlouis Granju, Sana Ullah BalouchAbstract:Abstract The corrosion of steel fibres in the Cracked section has been under investigation by many researchers since the last 15 years. It is reported widely that in case of steel fibres reinforced concrete (SFRC), corrosion is less active as compared with steel bars. In the Cracked section, the durability of the material depends on the performance of the bridging capacity of the fibres embedded in the concrete. The corrosion of the fibres not only could produce the spalling of concrete but it could also reduce the sectional area of the fibres, turning the durability of structures in danger. This study focuses on those two aspects of fibre corrosion. The tests were performed on Cracked SFRC samples with 0.5-Mm Crack mouth openings (CMOs) exposed to marine-like environment for 1 year. The results confirm the small sensitivity of SFRC to corrosion. Surprisingly, they made appear an increase of the flexural strength after corrosion. The factors affecting the corrosion of the fibres and the reasons for the increase in flexural strength after corrosion are discussed.
Jeanlouis Granju - One of the best experts on this subject based on the ideXlab platform.
-
corrosion of steel fibre reinforced concrete from the Cracks
Cement and Concrete Research, 2005Co-Authors: Jeanlouis Granju, Sana Ullah BalouchAbstract:Abstract The corrosion of steel fibres in the Cracked section has been under investigation by many researchers since the last 15 years. It is reported widely that in case of steel fibres reinforced concrete (SFRC), corrosion is less active as compared with steel bars. In the Cracked section, the durability of the material depends on the performance of the bridging capacity of the fibres embedded in the concrete. The corrosion of the fibres not only could produce the spalling of concrete but it could also reduce the sectional area of the fibres, turning the durability of structures in danger. This study focuses on those two aspects of fibre corrosion. The tests were performed on Cracked SFRC samples with 0.5-Mm Crack mouth openings (CMOs) exposed to marine-like environment for 1 year. The results confirm the small sensitivity of SFRC to corrosion. Surprisingly, they made appear an increase of the flexural strength after corrosion. The factors affecting the corrosion of the fibres and the reasons for the increase in flexural strength after corrosion are discussed.
Reinhold H Dauskardt - One of the best experts on this subject based on the ideXlab platform.
-
cyclic fatigue Crack growth in a sic whisker reinforced alumina ceramic composite long and small Crack behavior
Journal of the American Ceramic Society, 1992Co-Authors: Reinhold H Dauskardt, M R James, J R Porter, R. O. RitchieAbstract:The ambient-temperature subcritical growth behavior of both long and microstructurally small Cracks is investigated during cyclic-fatigue loading in a SiC-whisker-reinforced alumina (Al2O3–SiCw) ceramic composite (fracture toughness, Kc∼ 4.5 MPa · m1/2). Based on long-Crack experiments using compact C(T) specimens, cyclic fatigue-Crack growth rates (over the range 10−11 to 10−5 m/cycle) are found to be sensitive to the applied stress-intensity range and load ratio, and to show evidence of fatigue Crack closure. Similar to other ceramic materials, under tension–tension loading the “long”(>3 Mm) Crack fatigue threshold, ΔKTH, was found to be on the order of 60% of Kc. Conversely, “small”(1 to 300 μm) Cracks grown from micro-indents on the surface of cantilever-beam specimens were observed to grow at applied ΔK levels some 2 to 3 times smaller than ΔKTH. similar to behavior widely reported for metallic materials. The observed small-Crack behavior is rationalized in terms of the residual stress field associated with the indent, and the restricted role of Crack-tip shielding (from mechanisms such as Crack bridging, closure and deflection) with Cracks of limited wake, analogous to closure effects with small fatigue Cracks in metals. Consistent with the lack of zone-shielding mechanisms in Al2O3–SiCw, under variable-amplitude cyclic loading Crack-growth rates do not exhibit the marked transient response following block overload sequences as do transformation-toughened ceramics or ductile metallic materials. Possible mechanisms for cyclic Crack advance in reinforced ceramic-matrix composite materials are discussed.
P J Withers - One of the best experts on this subject based on the ideXlab platform.
-
evolution of a laser shock peened residual stress field locally with foreign object damage and subsequent fatigue Crack growth
Acta Materialia, 2015Co-Authors: S Zabeen, M Preuss, P J WithersAbstract:Abstract Foreign object damage (FOD) can seriously shorten the fatigue lives of components. On the other hand, laser shock peening improves fatigue life by introducing deep compressive residual stress into components. In this paper we examine how the non-uniform steep residual stress profile arising from FOD of laser peened aerofoil leading edges varies as a function of fatigue Crack growth under high cycle fatigue and mixed high and low cycle fatigue conditions. The ballistic FOD impacts were introduced by impacting a cube edge head-on (at an angle of 0°) to the leading edge. The residual stress distributions have been mapped by synchrotron X-ray diffraction prior to Cracking and subsequent to short (∼1 Mm) and long (up to 6 Mm) Crack growth. The results suggest that the local residual stress field is highly stable even to the growth of relatively long Cracks.