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Jan K. Spelt - One of the best experts on this subject based on the ideXlab platform.
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Combined effect of strain-rate and Mode-Ratio on the fracture of lead-free solder joints
Materials & Design, 2015Co-Authors: Amir Nourani, Jan K. SpeltAbstract:Abstract The critical strain energy release rate for the solder joint fracture was measured as a function of the strain rate and the Mode Ratio of loading. These data are useful in predicting the fracture of solder joints loaded under arbitrary combinations of tension and shear during the impact conditions typical of falling portable electronic devices. In this study, strain rates from quasi-static (close to 0 s − 1 ) to 61 s − 1 were investigated at phase angles from 0 to 60°, typical of the range found in microelectronic devices. Copper–solder–copper double cantilever beam (DCB) Model specimens were prepared using SAC305 solder at cooling rates and times above liquidus typical of actual ball grid arrays (BGAs). A drop tester was designed and built to achieve different strain rates at various Mode Ratios. The critical initiation strain energy release rate, J ci , increased about 70% from quasi-static to intermediate strain rates, before decreasing by more than 67% from intermediate strain rates to 42 s − 1 .
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Effect of geometry on the fracture behavior of lead-free solder joints
Engineering Fracture Mechanics, 2011Co-Authors: Siva P.v. Nadimpalli, Jan K. SpeltAbstract:Abstract Copper bars were soldered along their length with a thin layer of lead-free Sn3.0Ag05.Cu alloy under standard surface mount processing conditions to prepare double cantilever beam (DCB) specimens. The geometry of the DCBs was varied by changing the thickness of the solder layer and the copper bars. These specimens were then fractured under Mode-I and two mixed-Mode loading conditions. The initiation strain energy release rate, G ci , increased with the relative fraction of Mode-II, but was unaffected by the changes in either the substrate stiffness or the solder layer thickness. However, the steady-state strain energy release rate, realized after several millimeters of crack growth, was found to increase with the solder layer thickness at the various Mode Ratios. The crack path was found to be influenced by Mode Ratio of loading and followed a path that maximizes the von Mises strain rather than maximum principal stress. Finally, some preliminary results indicated that the loading rate significantly affects the G ci .
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Crack path selection in the fracture of fresh and degraded epoxy adhesive joints
Engineering Fracture Mechanics, 2011Co-Authors: Amir Ameli, Marcello Papini, S. Azari, Jan K. SpeltAbstract:The crack paths and fracture surfaces of aluminum–epoxy adhesive joints were characterized as a function of the Mode Ratio of loading and the amount of degradation that had been generated using the open-faced aging technique. A finite element (FE) Model was used to predict the extent of the plastic zone at different crack growth lengths and Mode Ratios, and a close relationship was found between the evolution of the plastic zone and the previously reported R-curve behavior of these joints. The micro-topography of the fracture surfaces, measured using an optical profilometer, showed that a ductile–brittle transition occurred in the fracture behavior of the joints as degradation progressed. The crack path in the (brittle) degraded specimens was normal to the first principal stress, but could not be predicted in the undegraded joints because of its highly three-dimensional nature. Based on the distribution of the maximum von Mises stress in the adhesive layer ahead of the crack tip, a crack growth mechanism was proposed that is consistent with these experimental observations and explains the highly three-dimensional nature of fracture in these highly constrained joints.
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Mixed-Mode fracture load prediction in lead-free solder joints
Engineering Fracture Mechanics, 2011Co-Authors: Siva P.v. Nadimpalli, Jan K. SpeltAbstract:Abstract Double cantilever beam (DCB) fracture specimens were made by joining copper bars with both continuous and discrete SAC305 solder layers of different lengths under standard surface mount (SMT) processing conditions. The specimens were then fractured under Mode-I and various mixed-Mode loading conditions. The loads corresponding to crack initiation in the continuous joints were used to calculate the critical strain energy release rate, J ci , at the various Mode Ratios using elastic–plastic finite element analysis (FEA). It was found that the J ci from the continuous joint DCBs provided a lower bound strength prediction for discrete 2 mm and 5 mm long joints at the various Mode Ratios. Additionally, these J ci values calculated from FEA using the measured fracture loads agreed reasonably with J ci estimated from measured crack opening displacements at crack initiation in both the continuous and discrete joints. Therefore, the critical strain energy release rate as a function of the Mode Ratio of loading is a promising fracture criterion that can be used to predict the strength of solder joints of arbitrary geometry subject to combined tensile and shear loads.
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R-curve behavior of Cu–Sn3.0Ag0.5Cu solder joints: Effect of Mode Ratio and microstructure
Materials Science and Engineering: A, 2010Co-Authors: Siva P.v. Nadimpalli, Jan K. SpeltAbstract:Abstract Double cantilever beam (DCB) specimens were prepared with three different time–temperature profiles to achieve distinct intermetallic microstructures and then tested under Mode I and various mixed-Mode loading conditions to obtain the R-curves. The time above solder liquidus and the cooling rate were selected to be representative of typical microelectronics production. Both the initiation strain energy release rate and the steady-state values were found to increase with the relative amount of Mode II loading and decrease with the thickness of the intermetallic compound layer between the solder and the copper. The effect of the local geometry of the end of the solder layer was found to have only a small effect on the initiation strain energy release rate.
Barry D. Davidson - One of the best experts on this subject based on the ideXlab platform.
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Influence of Mode Ratio and hygrothermal condition on the delamination toughness of a thermoplastic particulate interlayered carbon/epoxy composite
Composites Part A: Applied Science and Manufacturing, 2009Co-Authors: Barry D. Davidson, M. Kumar, M.a. SoffaAbstract:Abstract Double cantilever beam, end-notched flexure and single leg bending tests were used to determine the effects of temperature and moisture on the toughness of a thermoplastic particulate-toughened carbon/epoxy composite. Tests were performed on both dry and moisture-saturated specimens at temperatures of −43 °C, 21 °C and 98 °C, and on dry specimens only at 125 °C. In-situ observations and post-test scanning electron microscopy showed increasing matrix ductility with increasing temperature and moisture content. This correlated to an increase in the Mode I and a decrease in the Mode II toughness. The mixed-Mode toughness data and fracture surface morphologies displayed a blend of the Mode I and Mode II behaviors.
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influence of Mode Ratio and hygrothermal condition on the delamination toughness of a thermoplastic particulate interlayered carbon epoxy composite
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Barry D. Davidson, M. Kumar, M.a. SoffaAbstract:Abstract Double cantilever beam, end-notched flexure and single leg bending tests were used to determine the effects of temperature and moisture on the toughness of a thermoplastic particulate-toughened carbon/epoxy composite. Tests were performed on both dry and moisture-saturated specimens at temperatures of −43 °C, 21 °C and 98 °C, and on dry specimens only at 125 °C. In-situ observations and post-test scanning electron microscopy showed increasing matrix ductility with increasing temperature and moisture content. This correlated to an increase in the Mode I and a decrease in the Mode II toughness. The mixed-Mode toughness data and fracture surface morphologies displayed a blend of the Mode I and Mode II behaviors.
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Geometrically Nonlinear Determination of Energy Release Rate and Mode Ratio in Single Leg Bending Tests
Journal of Reinforced Plastics and Composites, 2008Co-Authors: Barry D. Davidson, Amitabh Bansal, Qida Bing, Xuekun SunAbstract:Geometrically linear and nonlinear finite element analyses are used to determine the energy release rate and Mode Ratio in simulated tests of unidirectional, symmetric, single leg bending (SLB) specimens. It is shown that the finite diameter loading rollers that are typically used in practical test set-ups cause this test to be inherently nonlinear. The differences between the linear and nonlinear results are presented parametrically as a function of material properties, specimen thickness, roller diameter, span length and crack length. These results are used, along with empirically derived equations, to develop an approach for designing SLB experiments where one will have a high degree of confidence in toughness values as obtained from conventional data reduction techniques, and for which relatively little specimen-to-specimen variation in Mode Ratio will be observed.
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Effects of Mode Ratio, Ply Orientation and Precracking on the Delamination Toughness of a Laminated Composite
Journal of Reinforced Plastics and Composites, 1996Co-Authors: Jonathan J. Polaha, Barry D. Davidson, Ryan C. Hudson, A. PieracciAbstract:Results are presented from an investigation of the effects of Mode Ratio, interfacial ply orientation and precracking on the delamination toughness of a graphite/ epoxy composite. Delamination toug...
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Effect of interlayer modulus on fracture Mode Ratio for interleaved composite laminates
Engineering Fracture Mechanics, 1995Co-Authors: Barry D. DavidsonAbstract:Results are presented from a study to assess the effect of the interlayer modulus on the energy release rate and fracture Mode Ratio in interleaved composite laminates. Two different geometries and material systems are studied. It is found that the fracture Mode Ratio is a very strong function of the interlayer modulus, and that varying the interlayer modulus can significantly change the percentage of opening Mode which occurs for a given remote loading. The significance of these results is addressed with respect to choice of an interleaving system, as well as with respect to methodologies to eliminate computational difficulties associated with the oscillatory stress singularity in non-interleaved composites.
M.a. Soffa - One of the best experts on this subject based on the ideXlab platform.
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Influence of Mode Ratio and hygrothermal condition on the delamination toughness of a thermoplastic particulate interlayered carbon/epoxy composite
Composites Part A: Applied Science and Manufacturing, 2009Co-Authors: Barry D. Davidson, M. Kumar, M.a. SoffaAbstract:Abstract Double cantilever beam, end-notched flexure and single leg bending tests were used to determine the effects of temperature and moisture on the toughness of a thermoplastic particulate-toughened carbon/epoxy composite. Tests were performed on both dry and moisture-saturated specimens at temperatures of −43 °C, 21 °C and 98 °C, and on dry specimens only at 125 °C. In-situ observations and post-test scanning electron microscopy showed increasing matrix ductility with increasing temperature and moisture content. This correlated to an increase in the Mode I and a decrease in the Mode II toughness. The mixed-Mode toughness data and fracture surface morphologies displayed a blend of the Mode I and Mode II behaviors.
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influence of Mode Ratio and hygrothermal condition on the delamination toughness of a thermoplastic particulate interlayered carbon epoxy composite
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Barry D. Davidson, M. Kumar, M.a. SoffaAbstract:Abstract Double cantilever beam, end-notched flexure and single leg bending tests were used to determine the effects of temperature and moisture on the toughness of a thermoplastic particulate-toughened carbon/epoxy composite. Tests were performed on both dry and moisture-saturated specimens at temperatures of −43 °C, 21 °C and 98 °C, and on dry specimens only at 125 °C. In-situ observations and post-test scanning electron microscopy showed increasing matrix ductility with increasing temperature and moisture content. This correlated to an increase in the Mode I and a decrease in the Mode II toughness. The mixed-Mode toughness data and fracture surface morphologies displayed a blend of the Mode I and Mode II behaviors.
Yuezhu Wang - One of the best experts on this subject based on the ideXlab platform.
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Optical bistability effects in a Tm,Ho:YLF laser at room temperature.
Optics letters, 2007Co-Authors: Xinlu Zhang, Yuezhu WangAbstract:We demonstrate strong optical bistability in a 2 μm continuous-wave Tm,Ho:YLF laser pumped by a 792 nm laser diode near room temperature. The bistable region is as much as 100 mW wide at 283 K and can be controlled by the temperature of the laser crystal. The influence of crystal temperature on the characteristics of optical bistability is obtained. The influence of the pump-to-Mode Ratio on the bistable characteristics of the laser is also discussed. To our knowledge this is the first report of optical bistability effects in Tm,Ho:YLF lasers.
M. Kumar - One of the best experts on this subject based on the ideXlab platform.
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Influence of Mode Ratio and hygrothermal condition on the delamination toughness of a thermoplastic particulate interlayered carbon/epoxy composite
Composites Part A: Applied Science and Manufacturing, 2009Co-Authors: Barry D. Davidson, M. Kumar, M.a. SoffaAbstract:Abstract Double cantilever beam, end-notched flexure and single leg bending tests were used to determine the effects of temperature and moisture on the toughness of a thermoplastic particulate-toughened carbon/epoxy composite. Tests were performed on both dry and moisture-saturated specimens at temperatures of −43 °C, 21 °C and 98 °C, and on dry specimens only at 125 °C. In-situ observations and post-test scanning electron microscopy showed increasing matrix ductility with increasing temperature and moisture content. This correlated to an increase in the Mode I and a decrease in the Mode II toughness. The mixed-Mode toughness data and fracture surface morphologies displayed a blend of the Mode I and Mode II behaviors.
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influence of Mode Ratio and hygrothermal condition on the delamination toughness of a thermoplastic particulate interlayered carbon epoxy composite
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: Barry D. Davidson, M. Kumar, M.a. SoffaAbstract:Abstract Double cantilever beam, end-notched flexure and single leg bending tests were used to determine the effects of temperature and moisture on the toughness of a thermoplastic particulate-toughened carbon/epoxy composite. Tests were performed on both dry and moisture-saturated specimens at temperatures of −43 °C, 21 °C and 98 °C, and on dry specimens only at 125 °C. In-situ observations and post-test scanning electron microscopy showed increasing matrix ductility with increasing temperature and moisture content. This correlated to an increase in the Mode I and a decrease in the Mode II toughness. The mixed-Mode toughness data and fracture surface morphologies displayed a blend of the Mode I and Mode II behaviors.