A theoretical formulation of the buckling analysis of a composite sandwich structure with multiple holes

This article presents a theoretical formulation presented for conducting a buckling analysis of the composite sandwich plate with multiple holes via the homogenization method. The validity of the theoretical formulation was verified by comparing the results of the finite element analysis and experimental analysis. Finally, the theoretical formulation was used to optimize a composite sandwich plate with multiple holes for the design of an aircraft structure to minimize the mass. The optimization result allows a database to be obtained on the buckling characteristics of composite sandwich structures with multiple holes for applying aerospace applications. We then concluded that the theoretical formulation is well-suited to buckling analysis of a composite sandwich structure with multiple holes for aerospace applications due to their relative simplicity and computational efficiency.

Assembly Wirebond Process Solution for Mitigating Leadframe Bouncing on Multi-Die QFN Device

Modification and improvement of an existing tooling design in semiconductor packaging industry has been a usual practice, to enhance the current setup and to provide a solution to a specific assembly problem. This paper discusses the solution in eliminating the smashed ball defect occurrence observed after wirebond process. Smashed ball is usually encountered if the unit is unstable and creates a bouncing effect during wirebond process. It is therefore important to mitigate this micro-bouncing effect by analyzing the package design and the window clamp and top plate (WCTP). The objective is to increase the stability of the unit during wirebonding, especially for quad-flat no-leads (QFN) package with no tape. To achieve this, the solution is to alter the vacuum hole design of the top plate from single hole per unit to multiple holes of varied sizes per unit. Ultimately, after changing the design of the top plate, the micro-bouncing encountered during wirebond process was significantly reduced. This in turn created a consistent ball formation in all bonded wires. The comparative data presented in this paper confirmed the effectivity of the redesigned WCTP. For future works and studies, the improvement and learnings could be used on devices with comparable configuration.

Combined dural inversion with multiple burr holes for refractory chronic subdural hematoma: A case report.

Background: Chronic subdural hematoma（CSDH） is a common disease in neurosurgery department. Burr-hole drainage is the main surgical treatment. And the recurrence rate is as high as 25%.Case presentation: In this case, a male patient with CSDH in the left frontotemporal parietal region underwent two drilling and drainage operations in the local hospital, but the hematoma recurred after operations. Being unable to bearing the repeated and progressive aggravation of headache, he came to our hospital for treatment. After considering the comprehensive situation, we use a new surgical method, removal of hematoma by drilling multiple holes in the lateral skull, to cure the patient.Conclusions: we get inspirations from the therapy for moyamoya disease, combining dura mater inversion and hole burr, the scalp forms many "meat column" like structures which have powerful capability in absorption through the bone holes, so the scalp could deep into the hematoma, then the CSDH could be cured. This case Provide a new surgical method for the treatment of refractory CSDH. Key words: CSDH R ecur Bone hole Scalp Dural mater inversion

Performance Analysis of Multi-Spindle Drilling of Al2024 with TiN and TiCN Coated Drills Using Experimental and Artificial Neural Networks Technique

Multi-spindle drilling simultaneously produces multiple holes to save time and increase productivity. The assessment of hole quality is important in any drilling process and is influenced by characteristics of the cutting tool, drilling parameters and machine capacity. This study investigates the drilling performance of uncoated carbide, and coated carbide (TiN and TiCN) drills when machining Al2024 aluminium alloy. Thrust force and characteristics of hole quality, such as the presence of burrs and surface roughness, were evaluated. The results show that the uncoated carbide drills performed better than the TiN and TiCN coated tools at low spindle speeds, while TiCN coated drills produced better hole quality at higher spindle speeds. The TiN coated drills gave the highest thrust force and poorest hole quality when compared with the uncoated carbide and TiCN coated carbide drills. Additionally, a multi-layer perceptron neural network model was developed, which could be useful for industries and manufacturing engineers for predicting the surface roughness in multi-hole simultaneous drilling processes.

Automated Tool Path Generation for Roughing Using Flat Drill

A method to calculate tool path uniquely for roughing using a flat drill is proposed. A flat drill is a drill with a flat tip. Unlike a square end mill, it cannot feed a tool laterally, but it is suitable for machining to feed a tool longitudinally. The advantage offered by the flat drill is expected to reduce machining troubles, such as tool breakages and chatter vibration, owing to the axial sturdiness of the tool. Furthermore, it can be used to machine lapped holes that cannot be machined with a normal drill owing to its flat tip. Hence, roughing using a flat drill by drilling multiple holes at constant intervals is proposed herein. Furthermore, in this method, a tool path for semi-finishing is generated only on the remaining region. A cutting experiment is conducted to validate the effectiveness of the proposed method. The result of the cutting experiment confirmed the effectiveness of the proposed method based on the machining time and the productivity of machining multiple products simultaneously.

The Effects of Cooling Holes on SiC/SiC CMC Tensile Strength

Silicon Carbide fiber-reinforced Silicon Carbide (SiC/SiC) Ceramic Matrix Composites (CMCs) are currently operating in select high temperature components of turbine engines. Primary benefits of CMCs compared to metals are improved temperature capability, reduced cooling requirements and reduced component weight. High temperature materials require less cooling air to be diverted from the compressor, resulting in improved engine performance. However, some amount of film cooling may be necessary when CMCs are implemented in higher temperature applications. Film cooling requires holes to be fabricated at appropriate locations and orientations within these components. It is important to understand how such holes will affect the material properties. While previous studies have shown that CMCs are notch insensitive, the effect of multiple holes and different hole orientations on SiC/SiC CMCs is not well documented. This study examines the effect of cooling holes on SiC/SiC tensile properties. Several hole geometries fabricated in SiC/SiC samples are explored. Mechanical test data on specimens with multiple holes is reported for tensile loading at room temperature. Tools such as Digital Image Correlation (DIC) and Acoustic Emission (AE) are used to monitor strain and cracking in the CMC upon loading.