Defect and Diffusion Forum Vol. 431

Abstract: The thermosonic bonding technique is a widely used method for Cu wire interconnections. However, issues arise due to volumetric changes in intermetallic compounds (IMCs) formed at the Cu-Al bonding interface, leading to voids in the Cu-Al IMC layer. This problem is exacerbated after annealing, such as in high-temperature Storage (HTS). In this study, a statistical modelling approach was employed to quantitatively analyse stress, studying the evolution and characteristics of the interfacial microstructure in the thermosonic Cu wire-Al bond pad system. Microstructural analysis focused on Cu-Al IMC crystallography and compositional classification. A stress model was proposed, considering both thermal misfit and diffusion-induced stresses. Results showed that interfacial stress generally increased with higher bonding temperatures. The influence of forming gas supply was relatively minor, with oxide layers minimally impeding Cu-Al interdiffusion during Cu-Al IMC formation. This stress modelling technique hold potential as a valuable failure analysis tool for implementing Cu wire in various industries.

Abstract: In recent years, surface defect detection methods based on deep learning have been widely applied to steel plate surface defect detection. By locating and classifying defects on the surface of steel plates, production efficiency can be improved. However, there is still a conflict between speed and accuracy in the defect detection process. To address this issue, we propose a high-precision, low-latency surface defect detection algorithm called the GhostConv-ECA-YOLOv5 Network (GEA-Net). The GEA-Net model can predict defect categories without compromising classification and detection accuracy. Experimental results show that our proposed improved model has higher performance compared to other comparative models, achieving a 75.6% mAP on the NEU-DET dataset.

Abstract: The compact tension (CT) and tensile specimens of the AISI 4140 steel in cold rolling condition (untreated steel) were austempered by immersing it into the salt bath at 362°C for 60 minutes. The tensile strength properties and the fatigue crack growth (FCG) resistance were performed to investigate the effect of the austempering process in AISI 4140 steel. A significant increase in the yield strength for austempered steel is about 8.7 % and the elastic strain energy increases by 55.7 %. Austempered steel's fatigue crack cycle is longer than that of untreated steel. Data of stress intensity factor range (ΔK, MPa.m^1/2) and FCG rate (da/dN, m/cycle) was constructed in double log plot x-y axes for determining the materials constants m and C according to Paris’s law equation using a linear regression method. From the curve of ΔK versus da/dN, the constant m value for austempered steel (m = 3.45) shows better resistance than untreated steel (m = 3.77). On the other hand, the constant C value of 1.409×10^-12 for austempered steel is one order magnitude higher than that of untreated steel (C = 4.151×10^-13). The resistance of austempered steel against fatigue crack growth can be attributed to the formation of a bainite structure.

Abstract: Seismic risk is a challenging problem in tall buildings due to the possibility of loss of human life and economic caused by seismic events. Peru is located at the interaction of the South American plate and the Nazca plate, which is why various seismic events of moderate to large magnitude occur. Today there are many ways to solve these problems and it is a very challenging case to reinforce tall buildings. In addition, technological advances in software facilitate and help through programmed models in tall buildings that analyze their structure characteristics such as drift, shear and others. This article proposes a comparative analysis of three types of dissipators: viscous fluid, friction, and metal creep through a Time-History analysis in a 15-story high-rise building located in Peru. The proposed methodology considers three stages: (i) definition of the characteristics and properties of the structure in accordance with Peruvian Standard E.030, in addition three accelerograms are used for the dynamic time-history analysis and maximum displacements and drifts are determined by ETABS software. (ii) calculate the design drift of the tall building and the properties of the viscous fluid, friction, and creep dissipator. In addition, calculations are made for the design parameters of each dissipator, and it is modeled as required for the case study. (iii) the new drifts and the damping values that the building presents for each dissipator are analyzed. According to the results obtained, the dissipator with the best results is of the flow type, since it has better performance in drifts and manages to produce an average damping of 96.87% for tall buildings. While the viscous dissipators obtain a 57.85% damping and the friction ones are estimated at 81.57%.

Abstract: In this paper, there is considered MHD boundary layer flow and heat transfer characteristics of Fe-Casson base nanofluid over an exponentially stretching/shrinking surface along the heat source/sink and Newtonian heating effects. In this regard, to develop the system of the governing equations, the one phase model named as Tiwari and Das model is considered with iron nanoparticles. The non-linear governing PDEs are first changed into the system of ODEs using suitable similarity transformations. Later on, the equations are solved numerically by using bvp4c in Matlab software. Effects of certain physical parameters on skin friction coefficient and the local Nusselt number are illustrated graphically. Moreover, the velocity and temperature profiles are examined to observe the influence of various physical parameters such as, Casson, magnetic, suction, radiation, Newtonian heating, heat source/sink and the nanoparticles volume fractions. It is seen that an increase in Casson, magnetic, suction and the nanoparticle volume fractions decrease the velocity profiles for both shrinking and shrinking cases of surface. The temperature profile recedes due to augmentation of Prandlt number and the suction parameter for both stretching/shrinking case while increases with increase in Magnetic, radiation and nanoparticles volume fractions.

Abstract: In various fields such as engineering, nanotechnology, and biomedical sciences, the study of non-Newtonian nanofluid flow with heat generation is becoming increasingly important. However, it is challenging to accurately model such flows due to their complex behavior and slip effects at the fluid-solid interface. This research investigates the impact of first and second-order slip conditions on the flow and heat transfer properties of a non-Newtonian nanofluid using a power law model to describe the fluid's non-Newtonian behavior and numerical methods to solve the resulting equations. To determine the influence of various parameters such as slip parameters, Brinkman number, power law index, and Eckert number on the velocity, temperature, and concentration profiles, which this study examines. The study shows that slip parameters significantly determine the flow and heat transfer properties of non-Newtonian nanofluids, the study also reveals that slip parameters are a crucial factor in understanding the flow and heat transfer characteristics of nanofluids, with the second-order slip condition having a greater impact on velocity and temperature profiles than the first-order slip condition. These findings are valuable for developing and optimizing heat transfer devices that involve non-Newtonian nanofluids with heat generation, which is essential for technological advancements in today's industry.

Abstract: This study analyses physical aspects of power-law fluid flow over a diamond shaped cylinder under the impact of a movable screen fixed in the middle of a channel keeping an aspect ratio as 0.5 with height of the channel. The perforated plate is a screen at the middle especially settled at orientation of π/6, π/4 or π/3 degrees. The Reynolds number (Re) has been kept in the range of 1000-10,000 with power-law index in the range 0.8-1.2. For the corresponding two-dimensional problem, the governing momentum equations coupled with energy equation have been solved numerically using non-isothermal laminar fluid flow interface in the software COMSOL Multiphysics 5.4. The dimensionless velocity magnitude and the non-dimensional temperature on the diamond shaped cylinder along the vertical non-dimensional length are expressed via fixing any two parameters from (Re), angle of screen θ and power-law index. The heat transfer coefficient, effective thermal conductivity and the Nusselt number are also expressed besides the dimonsionless length of the surface of the chosen cylinder. In conclusion, we will be going to suggest points to increase the dynamics and thermal variables with the use of selected parameters Re, θ, and power law index n.