Papers by Keyword: Fracture Mode

Abstract: The effect of a small amount of Sb addition to Sn-3.0Ag-0.5Cu (mass%) solder on microstructures and impact properties of the solder ball joint was investigated. Cross-sectional microstructural observation revealed that scalloped Cu₆Sn₅ is formed at the solder/Cu interface, and Cu₃Sn is formed at the interface between Cu₆Sn₅ and Cu with aging. It was confirmed that the growth of the reaction layer is suppressed by the addition of Sb. Moreover, the result of the impact ball shear test showed that the decrease in impact properties with aging can be suppressed in Sn-3.0Ag-0.5Cu-1.5Sb (mass%). It was also suggested that the suppression of linear crack propagation at the Cu₃Sn/Cu₆Sn₅ interface is effective to prevent the reduction of absorbed energy.

Abstract: The compressive behavior of ME20M alloy along rolling direction (RD) at a wide strain rates under low temperatures is investigated in this paper. Compressive stress-strain results reveal that the effect of strain rate on yield strength and flow stress is not obvious, especially at low temperatures. Moreover, the temperature plays an important role in compressive responses. SEM observations indicate that brittle fracture is the main fracture mode at low strain rate, and ductile fracture occurs in the failure of the alloy at high strain rate.

Abstract: This article presents the effect of weld zone shapes on microstructure and tensile properties of weld joints in friction stir welding. Experiments are conducted using four different tool pin profiles that are cylindrical, conical, cylindrical-conical and stepped-conical for analysing the weld zone shape. The weld zone shape properties are defined by characteristic length. Grain size and mode of fracture surface behavior are analysed by optical microscope and scanning microscope respectively and tensile strength is measured by universal testing machine. It is also observed that the weld zone shape of all pin profile tool is vase shape. In which, cylindrical, conical and cylindrical-conical pin profile tools produce basin dominant vase shape and stepped-conical pin profile tool produces cylinder dominant vase shape. The experimental result shows that the weld joint fabricated by stepped-conical pin profile tool produces the smallest grain, good ductile fracture mode and highest tensile properties as compared to other pin profile tool. This analysis shows that cylinder dominant vase shape produces high tensile properties and enhance ductile fracture mode in the weld joint.

Abstract: The creep damage tolerance factor λ as an important outcome of the continuum damage mechanics approach has been used to asses the creep fracture mode and the susceptibility of material to localized cracking at strain concentrations. In this work, using sets of our earlier published creep data of three advanced ferritic creep-resistant steels (T23 low alloy steel, P91 and P92 chromium steels) are analysed in terms of the creep damage tolerance factor λ. It was found that the value of the creep damage factor λ is not constant and depends on the creep loading conditions. The data analysis is followed by fractographic investigations, which is used to identify the creep fracture mode (s) experimentally.

Abstract: Analysis of the absorbed impact energy of an Al-Mg-Sc alloy after different thermo-mechanical processing routes was investigated between-196°C and 20°C. The material with a grain size of ∼ 22 μm in cast condition and with an average grain size of 0.7 μm produced by was produced by equal-channel angular pressing (ECAP) exhibits well-defined ductile-brittle transition in the temperature interval-60...-100°C, however, even at-196°C the value impact energy of fine-grained alloy is higher by a factor of 2 in comparison with coarse-grained state. The impact toughness of the hot rolled alloy linearly decreases with decreasing temperature. The influence of different microstructures on impact toughness and fracture behavior of alloy is discussed.

Abstract: The purpose of this paper is to investigate the fracture modes of the crack propagation of fourteen sandstone samples under Cracked Chevron Notch Brazilian Disc (CCNBD) test conditions through the use of image analysis and the high speed camera. The fracture mode is characterized by the displacement of 0.5mm glass beads placed on the sandstone surface relative to the approximate orientation of the fracture propagation. Using a Phantom v2011 High Speed Camera the fracture generation and propagation of the samples are recorded and processed for image analysis. ImageJ with Multi-Tracker and Manual Tracker, as well MATLAB® software were used to analyze the movement of particles during fracture propagation. It was found that the ImageJ software was able to track the movement of the particles and the output of the MATLAB® script was able to plot vector trajectories of the particles. For the analysis of samples tested under different orientations it was found that both shear mode and mixed-mode were evident in the fracture propagation.

Abstract: High temperature thermoplastic of 50Mn2V casting slab was tested by Gleeble-1500 thermal simulator machine. The morphology, microstructure and composition of fracture surfacewere observed and analyzed by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).The results show that, there are two brittle temperature zones of 50Mn2V casting slab at the temperature of 600~950°C and 1300~1465°C, respectively, The section shrinkaging rate is less than 60%. The fracture mode changes from mixed one dominated by intergranular to toughness transgranular one with the increase of temperature at the range of 600~1250°C. However, the fracture is along with the solid-liquid phase at the range of 1300°C~ melting point.

Abstract: The effect of strain rate up to nearly = 10²/s on the tensile stress-strain properties of isotropic fine-grained nuclear-grade graphite IG-11 was investigated. Cylindrical tensile specimens machined out of graphite bars were used in both static and dynamic tests. The dynamic tensile stress-strain curves up to fracture were determined using the split Hopkinson bar (SHB). The low and intermediate strain-rate tensile stress-strain relations up to fracture were measured on an Instron 5500R testing machine. It was demonstrated that the ultimate tensile strength increases slightly, while the fracture strain and absorbed energy up to fracture decrease dramatically with increasing strain rate. Macro and microscopic examinations revealed a slight difference in the fracture surfaces between the static and dynamic tension specimens.

Abstract: The temperature effects on the ultimate strength of 93WNiFe alloy have been investigated systematically through tensile tests, fracture surfaces and microstructure. The temperature ranges from 10 to 900 degrees. The results show that the ultimate strength decreases with the increase of temperature, and there is a platform in 300 to 600 degrees .The deposition has been observed in fracture surfaces from 500 to 600 degrees. The fracture modes influence the ultimate strength,deposition can improve mechanical properties of W-W and W-M interfaces, it is the cause of the ultimate strength platform.

Abstract: Based on the existing test results of single shear bolted connection fabricated with cold-formed ferritic stainless steel, in this study, the experiment for double shear bolted connections with bolt arrangements(1×2, 2×2) and end distance parallel to the loading direction as main variables has been performed. Specimens were planed with a constant dimension of edge distance perpendicular to the loading direction, bolt diameter, pitch and gauge. Ultimate strength and fracture mode obtained from test results were compared with those predicted by current American and Japan design codes such as AISI and AIJ.