In this work,anisotropic fatigue crack growth rate(FCGR)behaviour in a hot-rolled Mg-3wt%Al-0.5wt%Ce alloy was investigated using compact tension(CT)specimens with notch(an)parallel to the rolling direction(RD)and tra...In this work,anisotropic fatigue crack growth rate(FCGR)behaviour in a hot-rolled Mg-3wt%Al-0.5wt%Ce alloy was investigated using compact tension(CT)specimens with notch(an)parallel to the rolling direction(RD)and transverse direction(TD).The FCGR tests were conducted at a constant load ratio(R=0.1)and maximum stress intensity factor(KMax=15.6 MPa√m)to investigate the crack closure effect.For both constant R and KMax conditions:(i)the load-displacement curves for every loading cycle were linear for a_(n)∥ to RD and TD,indicating no crack closure;(ii)the FCGR was found to be lower for an∥RD than an∥TD over the entire stress intensity factor range(△K).The hot-rolled sample contained long-aligned Al11Ce3 intermetallic phase within grain boundaries that are elongated along RD.During the FCGR test,{10.12}<10.11>extension twins(ET)with lamellae∼⊥and c-axis∼∥to these elongated intermetallics along RD developed irrespective of the notch orientation.During the loading cycle,these intermetallics along RD generate back-stresses,reducing the in-plane tensile stress∼||and∼⊥to crack-tip to∼0 for a_(n)∥to RD and TD,respectively.Hence,lenticular ET∼||⊥and∼||,with c-axis∼||and∼⊥to crack path activates,leading to trans and inter lamellar crack for anto RD and TD,respectively,and anisotropic FCGR.Translamellar crack in a_(n)∥RD reduces the FCGR due to plastic energy dissipation as perceived by comparatively more geometrically necessary boundaries(GNBs).On the other hand,faster FCGR was obtained for a_(n)∥TD due to interlamellar cracking.Thus,the crack growth through the matrix-ET interfaces was favoured due to strain incompatibility.The Fractography for a_(n)∥RD shows smaller elongated grooves along crack propagation,which indicates crack arrest.However,larger elongated grooves for a_(n)||TD indicated easy crack propagation due to favourable interlamellar crack.展开更多
Single-edged notched tension （SENT） specimen is used to study the fatigue crack growth rate （FCGR） behavior of AISI 50100 steel using MTS 810. Calibration tests are run to get plots of crack mouth opening displace...Single-edged notched tension （SENT） specimen is used to study the fatigue crack growth rate （FCGR） behavior of AISI 50100 steel using MTS 810. Calibration tests are run to get plots of crack mouth opening displacement （CMOD） vs. load and CMOD vs. crack length-to-width ratio with the known crack lengths. Numerical simulation is also done to try to establish a relation between crack length and CMOD. FCGR of welded and un-welded specimens are plotted against stress intensity factor range to show the effect of welding on fatigue crack growth rate of AISI 50100 steel. The experimentally obtained CMOD values are compared with values obtained by numerical simulation using ABAQUS/StandardTM software package. Results show that numerical values are in good agreement with experimental data for small crack lengths and lower values of applied load,展开更多
基金support provided by the Science and Engineering Research Board(Ref.no.:ECR/2016/000125)Department of Science and Technology,Government of India.SB acknowledges the funding by Alexander von Humboldt Foundation,Germany.
文摘In this work,anisotropic fatigue crack growth rate(FCGR)behaviour in a hot-rolled Mg-3wt%Al-0.5wt%Ce alloy was investigated using compact tension(CT)specimens with notch(an)parallel to the rolling direction(RD)and transverse direction(TD).The FCGR tests were conducted at a constant load ratio(R=0.1)and maximum stress intensity factor(KMax=15.6 MPa√m)to investigate the crack closure effect.For both constant R and KMax conditions:(i)the load-displacement curves for every loading cycle were linear for a_(n)∥ to RD and TD,indicating no crack closure;(ii)the FCGR was found to be lower for an∥RD than an∥TD over the entire stress intensity factor range(△K).The hot-rolled sample contained long-aligned Al11Ce3 intermetallic phase within grain boundaries that are elongated along RD.During the FCGR test,{10.12}<10.11>extension twins(ET)with lamellae∼⊥and c-axis∼∥to these elongated intermetallics along RD developed irrespective of the notch orientation.During the loading cycle,these intermetallics along RD generate back-stresses,reducing the in-plane tensile stress∼||and∼⊥to crack-tip to∼0 for a_(n)∥to RD and TD,respectively.Hence,lenticular ET∼||⊥and∼||,with c-axis∼||and∼⊥to crack path activates,leading to trans and inter lamellar crack for anto RD and TD,respectively,and anisotropic FCGR.Translamellar crack in a_(n)∥RD reduces the FCGR due to plastic energy dissipation as perceived by comparatively more geometrically necessary boundaries(GNBs).On the other hand,faster FCGR was obtained for a_(n)∥TD due to interlamellar cracking.Thus,the crack growth through the matrix-ET interfaces was favoured due to strain incompatibility.The Fractography for a_(n)∥RD shows smaller elongated grooves along crack propagation,which indicates crack arrest.However,larger elongated grooves for a_(n)||TD indicated easy crack propagation due to favourable interlamellar crack.
基金supported by University of Engineering and Technology, Taxila
文摘Single-edged notched tension （SENT） specimen is used to study the fatigue crack growth rate （FCGR） behavior of AISI 50100 steel using MTS 810. Calibration tests are run to get plots of crack mouth opening displacement （CMOD） vs. load and CMOD vs. crack length-to-width ratio with the known crack lengths. Numerical simulation is also done to try to establish a relation between crack length and CMOD. FCGR of welded and un-welded specimens are plotted against stress intensity factor range to show the effect of welding on fatigue crack growth rate of AISI 50100 steel. The experimentally obtained CMOD values are compared with values obtained by numerical simulation using ABAQUS/StandardTM software package. Results show that numerical values are in good agreement with experimental data for small crack lengths and lower values of applied load,
