Pin Height Research Articles

Gap Waveguide PMC Packaging for Two-Layer PEC Surfaces

This paper shows the investigation of gap waveguide (GW) packaging for an irregular perfect electric conductor (PEC) composed of two layers of metal surfaces. The stopband for a GW with two-layer PEC surfaces is carefully studied, considering the top-layer PEC width, pin size, pin height, columns of pins, as well as dielectric substrate thickness and permittivity. A strategy of the GW packaging for such an irregular PEC surface is presented. In addition to the unit cell-based stopband study, such GW packaging is also demonstrated for a substrate-integrated waveguide (SIW)–microstrip line structure, which is typical of the circuit with two-layer PEC surfaces. A Chebychev bandpass filter built on the SIW and microstrip line is finally designed and fabricated to provide experimental verifications. In particular, a dedicated defect of the side air gap existing in the SIW-based circuits using the GW PMC packaging is found, and an effective remedy is presented.

Heat removal capacity enhanced micropin array heatsink with optimised pin height and inlet–outlet positions

A micropin array heatsink with high heat removal capacity for its optimised pin height and inlet–outlet positions is presented. Computational fluid dynamics simulation indicates pin height has a big impact on the pressure difference and heat removal capacity. A decrease of 2.67°C of the maximum temperature was achieved when pin height increased from 200 to 500 µm. Meanwhile with the proper pin height, the different positions of inlet and outlet that the maximum temperature decreases 13.89°C, the best design compared with the worst design among 63 samples under the same working condition. The two typical samples were fabricated and tested through micromachining technology and an infrared imaging testing system. Experiment result preferably matches with the simulation result of the same variation trend of 5.8°C. The positions of inlet and outlet were proved to play an important role in enhancing the heat removal capacity of the micropin array heatsink.

Three-Dimensional Integrated Circuit With Embedded Microfluidic Cooling: Technology, Thermal Performance, and Electrical Implications

This paper reports on novel thermal testbeds with embedded micropin-fin heat sinks that were designed and microfabricated in silicon. Two micropin-fin arrays were presented, each with a nominal pin height of 200 μm and pin diameters of 90 μm and 30 μm. Single-phase and two-phase thermal testing of the micropin-fin array heat sinks were performed using de-ionized (DI) water as the coolant. The tested mass flow rate was 0.001 kg/s, and heat flux ranged from 30 W/cm2 to 470 W/cm2. The maximum heat transfer coefficient reached was 60 kW/m2 K. The results obtained from the two testbeds were compared and analyzed, showing that density of the micropin-fins has a significant impact on thermal performance. The convective thermal resistance in the single-phase region was calculated and fitted to an empirical model. The model was then used to explore the tradeoff between the electrical and thermal performance in heat sink design.

Gap Waveguide-Based PMC Packaging for via Holes-Caused Nonsmooth PEC Surface

We investigate the application of perfect magnetic conductor (PMC) packaging for a nonsmooth perfect electric conductor surface, caused by metalized via holes. The PMC shielding is artificially built by a metal lid of pins, based on the gap waveguide (GW) technology. As a foundation, the effects of via hole in a unit cell are studied first considering its diameter, substrate thickness, pin size, pin height, as well as relative position between the via hole and the pin. The via adjacent space and pin rows are also considered for a general grounded coplanar waveguide along with ground vias. The effectiveness of package for such a transmission line containing metalized via holes is then verified experimentally. It is shown that the measured performance agrees well with the simulation. This paper presents a guideline for the GW-based PMC packaging technology.

Effect of welding parameters (plunge depths of shoulder, pin geometry, and tool rotational speed) on the failure mode and stir zone characteristics of friction stir spot welded aluminum 2024-T3 sheets

The main purpose of this study was to investigate the effect of welding parameters on the failure mode and stir zone characteristics of aluminum alloy 2024-T3 joined by friction stir spot welding. The welding parameters in this work are tool rotational speed, plunge depths of shoulder, and pin geometry. In accordance with the methods of previous investigations, the rotational speeds were set to 630 rpm to 2000 rpm. Two pin geometries with concave shoulder were used: triangular and cylindrical. The plunge depths of the shoulder were 0.3, 0.5 and 0.7 mm. The shoulder diameter and pin height for both geometries were 14 and 2.4 mm, respectively. The diameter of the cylindrical and triangular pins was 5 mm. Results show that the parameters mentioned earlier influence fracture mode under tensionshear loading. Two different fracture modes were observed during the examinations. Low-penetration depths and low-rotational speeds lead to shear fracture, whereas high values of these factors cause the tension-shear fracture mode. Fracture of the lower sheet sometimes occurs at high rotational speeds.

Carbon nanotubes as base material for fabrication of gap waveguide components

Microfabrication with Si has its benefits but it is time consuming when etching high ratio structures. Previously a ridge gap resonator has been fabricated in Si, with a pin height of 278μm. In this paper carbon nanotubes, which can grow hundreds of micrometers within minutes are being used as a base material for a high frequency device. It has been implemented on a ridge gap resonator for 220–325GHz. Carbon nanotubes based structures offer a rapid and low-cost turnover for prototyping. Measurements comparing two carbon nanotubes-based structures to a previously made Si structure and simulations are presented. From these measurements the unloaded Q-value and the loss/mm have been calculated and shows a loss of 0.079dB/mm and 0.051dB/mm for the lower frequency range respectively the higher frequency range, indicating that carbon nanotubes can be used for fast and low-cost prototyping of high-frequency devices.

Multi-objective optimization of water-cooled pinfin heatsinks

This paper presents the multi-objective optimization of water-cooled pinfin heatsinks. The heat transfer rate and pressure drop were the objective functions, and four parameters (height, diameter, longitudinal pitch, and transverse pitch) of pinfin geometry were the design variables. The relationship between the objective functions and the design variables for pinfin heatsink was calculated by using our own semi-analytical equations. We applied two kinds of constraints. One is the clearance distance between the tip of the pins and the flow channel wall, and the other is the minimum gap between pins considering cost-effectiveness and manufacturability. The best trade-off curves between the pressure drop and the heat transfer rate were calculated using genetic algorithm. We found the similarity of the best trade-off curves under two different constraint conditions when the multiplication of the pin height and the minimum gap between pins were the same. We also showed that the small clearance causes the reduction of pressure drop while maintaining high heat transfer performance. Our calculated solutions were validated by comparing with experimental results. The pressure drops could be predicted within an error of 30%, and the effective heat transfer rates agreed within an error of 10%.

Using FEA in Assessing Backward Extrusion of Multiple Micro-Pins

FE analyses of backward extrusion of multiple micro-pins have been conducted to examine the effects of pin geometry, layout and spacing. The effect of friction on material flow and accuracy of pin geometry has been investigated. FE analysis was performed for a commercial grade Al1050 as well as its ultrafine grained version produced by severe plastic deformation allowing a comparison to be made. Pin layout plays a large role in achieving uniformity of pin height. Material starvation resulted in the central pins being shorter than the surrounding pins. Simulations without the centre pin were conducted, which resulted in increased pin height uniformity. Simulations with friction resulted in a greater uniformity of pin height but required a greater load. Using stronger ultrafine grained material increased the load and reduced the pin height uniformity.

Wind speed determines the transition from biocrust-stabilized to active dunes

Abstract We examine the hypothesis that above a certain height, crusted, stabilized dunes become non-crusted with a mobile crest. Toward this end, twelve plots, 10 × 10 m, were demarcated along a 1 km-long transect in the Nizzana research site (NRS), western Negev, Israel, extending along a ridge of a dune from the crusted interdune up to a height of 22 m above the interdune, characterized by a non-crusted mobile crest. Within each plot, a 4 × 4 m subplot was established where the upper 3 cm of all surfaces was removed. Surface stability was monitored using six erosion pins from March 2010 to February 2012. In addition, data from a nearby meteorological station were analyzed. The data indicated that drift potential (DP) was the highest during winter and spring. A good correlation (with r2 = 0.73) was found between the monthly DP and the absolute change in pin height. Also, a good correlation (with r2 = 0.85) was found between altitude and the absolute change in pin height. A monthly change in pin height of ∼0.3 cm marked the threshold between the crusted and the non crusted sections of the dune, which corresponds to 8 m above the interdune. The findings imply that as long as the absolute monthly change in pin height is

Effects of Process Parameters on Tensile Shear Strength of Friction Stir Spot Welded Aluminium Alloy (EN AW 5005)

Abstract Aluminium and its alloys have been used in automotive technology since the first model of the car. The need for aluminium material is getting increased for weight reduction, improved fuel economy and vehicle performance. The amount of the aluminium used in a car is mainly related with joining processes of aluminium alloy. This can be achieved by developing the welding techniques for aluminium alloys. The purpose of this study was to determine the effects of friction stir spot welding parameters on tensile shear strength of friction stir spot welded lap joint EN AW 5005 Aluminium alloy. The variable parameters were tool rotation (rpm), dwell time (s) and the tool pin height (mm). Tensile shear test results indicated that the weld performance was significantly affected by the tool rotation, dwell time and the tool pin height. The results of the study indicates that there are optimum process parameters which give the highest tensile shear strength.

A reciprocating pin-on-plate test-rig for studying friction materials for holding brakes

This paper refers to testing of friction materials for holding brakes. In contrast to the more typical case of high energy brakes, holding brakes operate usually in a reciprocating sense, at very low sliding speeds and allow significantly higher clamping pressures. The design of a reciprocating pin-on-plate test-rig for studying the evolution of wear by monitoring the pin height reduction using Eddy-current proximity sensors is presented. Moreover, a new mechanism for recording the friction force is suggested. Apart from the design of the test-rig, friction force and wear rate measurements for two different friction materials running against an unhardened steel surface are presented as a usage case.

Heat Transfer Characteristics of Square Micro Pin Fins under Natural Convection

In order to comply with the recent demand for downsizing of the electric equipment, the minia- turization and the improvement in heat transfer performance of a heat sink under natural air-cooling are increasingly required. This paper describes the experimental and numerical investigations of heat sinks with miniature/micro pins and the effect of the pin size, pin height and the number of pins on heat transfer characteristics of heat sinks. Five types of basic heat sink models are investigated in this study. The whole heat transfer area of heat sinks having the different pin size, pin height and the number of pins respectively is kept constant. From a series of experiments and numerical analyses, it has been clarified that the heat sink temperature rises with increase in the number of pins. That is, the heat sink with miniaturized fine pins showed almost no effect on the heat transfer enhancement. This is because of the choking phenomenon occurred in the air space among the pin fins. Reflecting these results, it is confirmed that the heat transfer coefficient reduces with miniaturization of pins. Concerning the effects of the heat transfer area on the heat sink performance, almost the same tendency has been observed in other three series of large surface area, that is, higher pin height. Furthermore as a result of studying non-dimensional convection heat transfer performance, it was found that the relation between the Nusselt number (Nu) and the Rayleight number (Ra) is given by Nu = 0.16 Ra0.52.

Uncertainty of pin height measurement for the determination of wear in pin-on-plate test

The paper concerns measurement of pin height for the determination of wear in a pin-on-plate (POP) or pin-on-disc (POD) test, where a pin is mounted on a holder that can be fixed on the test rig and removed for measurements. The amount of wear is assessed as difference of pin height before and after the test, using the distance between holder plane and pin friction plane as measurand. A series of measurements were performed in connection with POP testing of different friction material pins mounted on an aluminium holder. Pin height measurements were carried out on a coordinate measuring machine (CMM), achieving an expanded measurement uncertainty (k=2) better than 1μm. A simple dedicated fixture adaptable to workshop environment was developed and its metrological capability investigated, estimating an average uncertainty of measurement in the order of 5μm (k=2). Fixture measurements were compared with CMM measurements using the normalised En value. Acceptable En values (En<1) were obtained in 58% of the measurements, showing a discrepancy which was explained in terms of different probing patterns on CMM and fixture.

Demonstration of Helical Antenna Stability Beyond C-Band Frequency

The paper demonstrates design of helical antenna to achieve stable frequency response and impedance matching beyond C-band microwave frequency. An impedance matching cavity is developed for excitation of higher order modes along with the fundamental mode in the helical antenna. Triple frequency bands are resonated by loading the designed helical antenna inside the cavity and a dual band response is realized by introducing variation in feed pin height with an incremental offset of 0.1λ to the initial height which is taken as 0.2λ. The broadband gain for all the designs and a detail analysis of modes along the helical antenna loaded in rectangular cavity is reported. A highest measured bandwidth of 5.4 GHz and a peak gain of 10.65 dB is obtained. The antenna being compact and conformal in design may find its application for terrestrial, aerospace communication and personal wireless communication. DOI: http://dx.doi.org/10.11591/ij-ict.v2i3.4861

H142 微細ピンフィン群を有する固体表面の自然空冷特性(OS-3:電子機器・デバイスの熱課題(4))

In order to meet the recent demand for downsizing of the electronic equipment, the miniaturization and the improvement in heat transfer performance of heat sink in natural air-cooling are required strongly than ever. From previous studies using large sized heat sink, it has been revealed that the heat sink performance depends on the pin size and the population density of pin. However, there seems almost no report focusing on pin parameters alone. In this study, the effects of pin size and the population density of pin on the heat transfer characteristics of small sized heat sink, especially with the pin height and pitch from several hundred micro meters to a few millimeters, have been investigated experimentally.

Condensation heat transfer on pin-fin tubes: Effect of thermal conductivity and pin height

New experimental data are reported for condensation of ethylene glycol and R-113 at near atmospheric pressure and low velocity on three identical pairs of pin-fin tubes made of copper, brass and bronze. The only geometric parameter varied was pin height. For both fluids tested, copper pin-fin tubes showed the highest gain in heat-transfer enhancement ratio with increasing pin height. Vapour-side, heat-transfer enhancement ratio was relatively weakly dependent on tube thermal conductivity for R-113 and more strongly dependant in the case of ethylene glycol. Data showed a strong heat-transfer enhancement dependence on unflooded area enhancement.

Numerical simulation of the thermal hydraulic performance of a plate pin fin heat sink

The computational fluid dynamic software FLUENT is used in assessing the electronics cooling potential of a plate pin fin heat sink (PPFHS), including the conjugate effect. The simulation results are validated with reported experimental data. The simulation shows that pin height and air velocity have significant influences on the thermal hydraulic performances of PPFHS while the influences of in-line/staggered array and neighbor pin flow-directional center distance (NPFDCD) of the PPFHS are less notable. In applying the present design to the cooling of a desktop PC CPU at a heat flux of 2.20 W/cm2, the temperature can be kept at less than 358 K with an air velocity over 6.5 m/s.

New equation for estimation of radial gate discharge

The flow discharge under a radial gate is a function of the geometric and hydraulic parameters upstream water depth, downstream water depth, gate opening, gate radius and trunnion pin height. A new equation for estimating radial gate discharge for movable trunnion pin height radial gates was developed based on comprehensive experimental testing with three such gates in a large laboratory flume (60×1×1 m). Data from previous field studies of 29 radial gates in the Doroodzan dam irrigation network were also used to derive new equations as functions of the above-mentioned parameters under free and submerged flow conditions. Dimensional analysis and non-linear regression were used to derive the water flow discharge relationships. These equations were validated using data of radial gates in the Doroodzan network and were also compared with several previously suggested equations for radial gates. Statistical results show good agreement between the proposed equations and field and laboratory data and they are hence recommended for use in practical applications.

Modeling and prediction of weld shear strength in friction stir spot welding using design of experiments and neural network

AbstractFriction Stir Spot Welding (FSSW) is a kind of the friction stir welding (FSW) process, creates a spot, lap‐weld without bulk melting work materials. The tensile shear strength of the FSSW welded joints mainly depends on the pin height, tool rotation and welding time. In the present study, two of the techniques, namely factorial design and neural network (NN) were used for modeling and predicting the tensile shear strength of EN AW 5005 aluminum alloy. Tensile shear strength was taken as a response variable measured after welding pin height, tool rotation and welding speed were taken as input parameters. Relationships between tensile shear strength and welding parameters have been investigated. The level of importance of the FSSW parameters on the tensile shear strength was determined by using the analysis of variance method (ANOVA). The mathematical relation between the tensile shear strength and FSSW welding parameters were established by regression analysis method. This mathematical model may be used in estimating the tensile shear strength of FSSW joints without performing any experiments. Finally, predicted values of tensile shear strength by techniques, NN and regression analysis, were compared with the experimental results and their nearness with the experimental values assessed. Results show that, NN is a good alternative to empirical modeling based on full factorial design.

Importance of Outlier Detection in Spatial Analysis of Wind Erosion

Spatial outliers in wind erosion are associated with severe weather events so, high rate of erosion or sedimentation in relevance to their spatial vicinity is called outlier. The aim of this paper is to investigate the influence of outliers on variogram model and their parameters in east of Iran. For measuring of soil erosion and sedimentation, some pins were established in nested grids. Decreasing and increasing of pin height, show sedimentation and erosion, respectively. Spatial analysis illustrate that outliers locate in NW-SE direction roughly in the same direction of predominant wind. The maximum amount of outlier is 22cm soil sedimentation.