Papers by Keyword: Fracture Toughness

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Authors: A.J. Morris, R.F. Robey, P.D. Couch, E. De los Rios
Authors: Hang Thi Pham, Takeshi Iwamoto
Abstract: It is considered that fracture toughness of TRIP steel can be evaluated by means of the small punch (SP) test. However, a mechanism of improving fracture toughness in the SP test for TRIP steel under the impact condition might not be clarified through merely experimental works because the effect of strain-induced martensitic transformation (SIMT) coupled with temperature in TRIP steel becomes quite complicated at high deformation rate. Therefore, a computational simulation on the SP test for an evaluation of the mechanism is indispensable. Since the specimen in the SP test will be fractured at a certain level of deformation, it is necessary to express the fracture by incorporating damage model into constitutive equation of the material in simulation of the SP test. In the present study, a finite element analysis is performed for the SP test with a specimen made of type-304 austenitic stainless steel by an inclusion of damage parameter and its evolution equation. After showing the validity of the computation, the effects of deformation rate, temperature, and SIMT on the force-deflection curve and deformation behavior are examined. Then, the mechanism of rate-sensitive fracture toughness in TRIP steel is challenged to be clarified.
Authors: A.P. Newbery, Byung Ahn, P. Pao, S.R. Nutt, Enrique J. Lavernia
Abstract: Mechanical milling of Al alloy powder in liquid nitrogen leads to a large reduction in the scale of the microstructure and results in material with high thermal stability and strength. However, it is important to consolidate the powder and achieve bulk material with sufficient toughness and ductility for structural applications. In this investigation, hot isostatic pressing, followed by quasiisostatic forging and hot rolling, were performed to fabricate Al 5083 plate with a predominantly ultra-fine grained microstructure. Plate produced in this way possessed enhanced tensile strength and ductility, exceeding that of conventionally processed material.
Authors: Gernot Trattnig, Christof Sommitsch, Reinhard Pippan
Abstract: To understand the crack growth in massive forming and to consequentially avoid crack growth in workpieces, it is necessary to investigate its dependence on the crack depth and thus on the state of hydrostatic stress. Prior work shows that the crack opening displacement (COD) for shallow cracked tension specimens with low stress triaxiality is twice as high as for deep cracked specimens with high stress triaxiality. This work examines the crack growth in compression specimens with pre-cracked cylindrical upsetting samples. The compression samples were cut in the stress symmetry plane in order to observe crack initiation and crack growth by a single specimen technique. In this way it is possible to observe blunting, crack initiation and crack growth inside the upsetting specimens. The resulting COD does not differ significantly from the values achieved in tension samples with short surface cracks.
Authors: De Tian Wan, Yi Wang Bao, Yuan Tian, Yan Qiu, Hua Zhao
Abstract: Evaluation of the mechanical properties at ultra-high temperatures for ceramic composites is necessary and important for the safety of designing the ceramic components. In this work, a new and novel test method named as local ultra-high temperature together with applied load method (LUHTAL), was developed to determine the tensile, compressive, bending strength and fracture toughness of ceramic composites. The four point bending load was conducted to measure the bending strength and fracture toughness of ceramic composites after the center of the sample was heated up to about 1500-2000°C by oxygen-assisted spray combustion. To check the availability and reliability for this method, typical ceramic materials including ZrB2/SiC and C/SiC fiber reinforced composite coated with Si, were used as the testing samples. It is indicated that this method is good and feasible for evaluating the mechanical properties of the ceramic composite at ultra-high temperatures in air.
Authors: Hao Chuang Li, Kwang Hyeon Lee, Jae Mean Koo, Chang Sung Seok
Abstract: Tensile and fracture toughness tests of coolant piping materials were performed at various loading rates and temperatures. The crack measurement method for coolant piping materials consisted of the unloading compliance method for quasi-static loading conditions and condition, while the electric potential drop method and the normalization method for quasi-dynamic loading conditions. Tensile and fracture toughness tests of coolant piping materials were performed at the design temperatures of the primary piping system of nuclear power plants, which are 449K (176°C) and 589K (316°C). Also, the plastic η factor considering strength mismatch of welding part was applied to the fracture toughness test results and the J-R curves by the plastic η factor considering strength mismatch of welding part was compared with the J-R curves by the plastic η factor introduced in ASTM E1820-01.
Authors: J. Zhou, Winston O. Soboyejo
Authors: T.L. Becker, Jr., R.M. Cannon, Robert O. Ritchie
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