In glass research, the effect and influence of pre-deformation by thermal or chemical treatment is of great importance when configuring different mechanical properties or scratch resistance on the surface of glasses. In particular, such pre-deformation affects dynamic fracture or damage evolution when glass structures are under impact or collision conditions. Peridynamics provides a seamless approach for the simulation of dynamic damage evolution of the system under aggressive environments. Revising the pair interaction of each material point, the effect of pre-deformation is implemented, and the corresponding damage evolution can be simulated conveniently. Our approach is composed of two steps: first, a static solution is found via energy minimization with thermal boundary conditions in the peridynamic platform. Second, comparing the initial and the pre-deformed structures from the energy minimization, the effect of residual deformation, strengthening and reactive behaviour of brittle structures are seamlessly simulated. The developed methods are applied to the Prince Rupert’s drop and Bologna vial, which are classic examples of strengthened glasses. This study reports the first complete and successful simulation of dynamic behaviour of strengthened glasses, and a significant contribution in simulating residual stress behaviour in any material.

The importance of power cycling as a mean of reliability assessment was revisited for flip chip plastic ball grid array (FC-PBGA) packages. Conventionally, reliability was addressed empirically through accelerated thermal cycling (ATC) because of its simplicity and conservative nature of life prediction. It was well accepted and served its role effectively for ceramic packages. In reality, an assembly is subjected to a power cycling, i.e., nonuniform temperature distribution with a chip as the only heat source and other components as heat dissipaters. This non-uniform temperature distribution and different coefficient of thermal expansion (CTE) of each component make the package deform differently than the case of uniform temperature in ATC. Higher substrate CTE in a plastic package generates double curvature in the package deformation and transfers higher stresses to the solder interconnects at the end of die. This mechanism makes the solder interconnects near the end of die edge fail earlier than those of the highest distance to neutral point. This phenomenon makes the interconnect fail earlier in power cycling than ATC. Apparently, we do not see this effect (the die shadow effect) in ceramic packages. In this work, a proper power cycling analysis procedure was proposed and conducted to predict solder fatigue life. An effort was made for FC-PBGA to show the possibility of shorter fatigue life in power cycling than the one of ATC. The procedure involves computational fluid dynamics (CFD) and finite element analyses (FEA). CFD analysis was used to extract transient heat transfer coefficients while subsequent FEA–thermal and FEA–structural analyses were used to calculate temperature distribution and strain energy density, respectively.

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Experimental and numerical techniques are employed to assess the thermomechanical behavior of ceramic and organic flip chip packages under power cycling (PC) and accelerated thermal cycling (ATC). In PC, nonuniform temperature distribution and different coefficients of thermal expansion of each component make the package deform differently compared to the case of ATC. Traditionally, reliability assessment is conducted by ATC because ATC is believed to have a more severe thermal loading condition compared to PC, which is similar to the actual field condition. In this work, the comparative study of PC and ATC was conducted for the reliability of board level interconnects. The comparison was made using both ceramic and organic flip chip ball grid array packages. Moiré interferometry was adopted for the experimental stress analysis. In PC simulation, computational fluid dynamics analysis and finite element analysis are performed. The assembly deformations in numerical simulation are compared with those obtained by Moiré images. It is confirmed that for a certain organic package PC can be a more severe condition that causes solder interconnects to fail earlier than in ATC while the ceramic package fails earlier in ATC always.

Properties of concrete depend up on properties of ingredients and their relative proportion. Due to addition of mineral as well as chemical admixture in concrete design of concrete mixes has become increasingly complex. BIS has rationalized concrete mix proportioning code in Dec 2009, which is used to design standard concrete mixes using both mineral as well as chemical admixtures. By considering the code, the present work deals with the development of fly ash based concrete mix proportion. This paper presents the results of an investigation dealing with Concrete cubes of 100 mm size, to replace 0%, 5%, 10% and 15% cement with fly ash. To cover a wide range of concrete mixes water cementitious material ratio (W/C) of 0.3, 0.4 and 0.5 were used for water content of 186 kg/m3, 191.58 kg/m3 and 197.16 kg/m3 each. The effect of various parameters such as replacement of cement by fly ash, water to cementitious material ratio and water content is studied on fresh and hardened properties of concrete. The study mainly consisted of establishing relation between these parameters in the form of Graphs to specify proportioning of required fly ash based concrete. Both workability and strength aspects are considered.