Recent Patents on Mechanical Engineering - Volume 2, Issue 1, 2009

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. In the present paper, a modification of conventional axial fan blades with experimental investigation is presented. Patented hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. They enable the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the trailing edge slots at the tip of the blade. The influence of internal flow on the flow field of axial fan and the modifications of aerodynamic characteristics of the axial fan have been studied along with recent patents. An experimental investigation of the interaction of two flows with the flow around hollow airfoil NACA series in a low-speed wind tunnel was studied. The determination of flow structure on the hollow airfoil was performed with computer-aided visualization. With the introduction of the internal flow and interaction with the external flow, a reduction of circulation effects on the fan hollow blade was achieved. The introduction of self-induced blowing led to the preservation of the direction of external flow, defined by blade geometry, and enabled maximal local energy conversion. Aerodynamic characteristic of the axial fan reached higher degree of pressure difference and efficiency through the entire fan working conditions.

Fixtures are used to locate, hold and support workpieces in manufacturing operations such as machining, inspection, and assembly. Designing and fabricating fixtures can take up to 10-20% of the total cost of a manufacturing system. Fixture planning is a complex activity restricted by the extreme diversity of workpiece, product batch size, product geometry, part accessibility, and working force. Computer-Aided Fixture Planning (CAFP) has been used to improve the fixture design for over 20 years. CAFP contributes to the reduction of lead-time and human interaction in fixture planning. It helps verification of the fixture quality and integration of fixture design with CAD/CAM systems. This paper summarizes constraints of fixture planning and four phases of CAFP. Various approaches to CAFP are surveyed. Application systems of CAFP including some recent patents are reviewed. The paper concludes with the research trend of CAFP.

Fluid dispensing is a process to deliver fluid materials in a controlled manner. This method has been widely used in various processes/applications such as electronics assembly and microelectromechanical systems (MEMS) packaging. With an increasing demanding for smaller size and higher density of components on boards, numerous efforts have been made in industry to enhance the efficiency and accuracy of the dispensing process and some of the techniques resulted have been patented. This paper presents an overview of the recent patents in the dispensing approaches, and the dispensing process measurements and control in electronic packaging.

The need for improved lifetime of air-breathing proton exchange membrane (PEM) fuel cells for portable applications necessitates that the failure mechanisms be clearly understood and life prediction models be developed, so that new designs can be introduced to improve long-term performance. A three-dimensional, multi-phase, non-isothermal computational fluid dynamics (CFD) model of an ambient air-breathing proton exchange membrane fuel cell has been developed and used to investigate the displacement, deformation, and stresses inside the whole cell, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the fuel cell during operation has been studied and investigated under real cell operating conditions. A unique feature of the present model is to incorporate the effect of mechanical, hygro and thermal stresses into actual three-dimensional fuel cell model. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. The nonuniform distribution of stresses can also contribute to delaminating between the gas diffusion layers and the current collectors, especially in the cathode side. These stresses may explain the occurrence of cracks and pinholes in the fuel cells components under steady-state loading during regular cell operation, especially in the high loading conditions. The paper ends with some recent patents and developments in the field.

This work concentrates on the first order Sugeno model of the power spectral density (PSD) of a multi degree of freedom system. Two models are introduced, single and multi degree of freedom system. In both models, the relationship between the input-output power spectral densities is modeled using first order Sugeno model. Minimum error model with fewer numbers of rules for the power spectral density for each model is obtained through enumerative search of the clustering parameters. The resulting models with best clustering parameters are then tuned by using adaptive neurofuzzy inference system (ANFIS). This paper is a first attempt in introducing fuzzy systems and some patents in modeling a very important vibration characteristic such as the power spectral density to identify complex mechanical behaviours. We also demonstrate the ability of these models to sense the sudden jump in the vibration amplitude when the system vibrates under a frequency equal to its natural frequency (resonance). Furthermore, these fuzzy models could be used to monitor, on line, the power spectral density of any rotating or non-rotating structures subjected to dynamic loads. This will give the machine operator the ability to stop the process or change the process parameters to avoid the resonance, which could lead to a machine failure or a disaster.

Standard Test Methods (e.g. ASTM, DIN) for materials characterization in general, and for fatigue in particular, do not contemplate specimens with complex geometries, as well as the combination of axial and in-plane bending loads in their methodologies. The present study refers to some patents and the new configuration or configurations of specimens (non-standardized by the “status quo” of test methods) and a device developed to induce axial and bending combined forces resultants from axial loads applied by any one test equipment (dynamic or monotonic) which possesses such limitation, towards obtaining more realistic results on the fatigue behavior, or even basic mechanical properties, from geometrically complex structures. Motivated by a specific and geometrically complex aeronautic structure (“motor-cradle”), non-standardized welded tubular specimens made from AISI 4130 steel were fatigue-tested at room temperature, by using a constant amplitude sinusoidal load of 20 Hz frequency, load ratio R = 0.1 with and without the above referred auxiliary fatigue apparatus. The results showed the fatigue apparatus was efficient for introducing higher stress concentration factor at the welded specimen joints, consequently reducing the fatigue strength when compared to other conditions. From the obtained results it is possible to infer that with small modifications the proposed apparatus will be capable to test a great variety of specimen configurations such as: squared tubes and plates with welded or melted junctions, as well as other materials such as aluminum, titanium, composites, polymeric, plastics, etc.

The focus of this paper is to survey recent patents related to mechanical tolerances. First, a general overview of tolerances is provided, followed by issues related to research in mechanical tolerances. Various research aspects of mechanical tolerances that are introduced are tolerance specification, analysis, allocation, synthesis, transfer and evaluation. Patents related to mechanical tolerances, issued since the beginning of the millennium, are selected for the survey. A comparison of the claims in the patents is provided, followed by the discussion of future research issues in mechanical tolerancing.

Electrical Discharge Machining (EDM) is a non-conventional manufacturing process based on removing material from a part by electrical discharges between the tool called tool electrode and the part being machined in the dielectric fluid called workpiece. Recently, numerous developments in EDM have focused on the production of very high accuracy of workpiece. The problematic areas in EDM are in the area of handling, electrode and workpiece preparation, machining processes, and measurement. This paper presents the current research trend and describes patents on the development of EDM especially in the years of 2007 and 2008, and particularly the development of Powder Mixed Electrical Discharge Machining (PMEDM). The result of the study shows that by applying PMEDM, the material removal rate is increasing and the surface roughness is decreasing.

A coupled hydro-thermal model is developed to study the phase-change process within partially saturated porous media. During the heating process (up to 1100°C), the increase of temperature in the medium is characterized by a plateau at a boiling point (around 100°C) revealing the energy absorption due to phase-change (liquid-vapor). In order to analyze this phenomenon, a modeling was performed on relatively lightweight materials as thin mortar walls. This model can also take into account the effect of pore pressure on the position of plateau. The paper ends with recent patents and future developments.

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