Pin Probe Research Articles

Optimizing Micro Friction Stir Spot Welding (mFSSW) of Aluminum Alloy AA1100 Using Neural Network Model

This study explores the optimization of Micro Friction Stir Spot Welding (mFSSW) by investigating the influence of tool profiles on welding outcomes, using aluminum alloy AA1100 with a 0.42 mm thickness as the specimen material. Monitoring temperature and RPM during welding with thermocouples and tachometers, mechanical properties are assessed through tensile shear tests, microhardness measurements, and macrostructural observations. The findings serve as the basis for developing Neural Network models using Rapidminer software, marking a transformative development that positions Neural Networks as potent tools for optimizing welding processes, potentially leading to achieving optimal weld quality. The investigation also delves into three welding tool configurations – the two-stage pin, one-stage pin, and pinless mFSSW probes – highlighting their distinct impacts on tensile shear test values and overall welding quality. Notably, the two-stage pin configuration emphasizes the significance of larger pin diameters and controlled heat generation for enhanced weld strength, while the one-stage pin configuration underscores the pivotal role of pin diameter and elevated temperatures in improving weld quality. The pinless mFSSW probe configuration, on the other hand, emphasizes the importance of shoulder diameter and temperature control for superior tensile shear test results. Leveraging Neural Network modeling for optimization, this study advances our understanding of parameter interactions and underscores the efficacy of Neural Networks in achieving superior tensile shear test values and welding quality in mFSSW, offering valuable insights for future endeavors in the field..

Low-Loss Pogo Pin Probe Card with a Coupling Isolation Structure up to 50 GHz

A design for a millimeter wave RF probe card that removes resonance is proposed. The designed probe card optimizes the position of the ground surface and the signal pogo pins to resolve the resonance and signal loss issues that occur when connecting a dielectric socket and a PCB. At millimeter wave frequencies, the height of the dielectric socket and pogo pin matches the length of half a wavelength, allowing the socket to act as a resonator. When the leakage signal from the PCB line is coupled to the 2.9 mm high socket with pogo pins, resonance at a frequency of 28 GHz is generated. The probe card uses the ground plane as a shielding structure to minimize this resonance and radiation loss. The importance of the signal pin location is verified via measurements in order to address the discontinuity caused by field polarity switching. A probe card fabricated using the proposed technique exhibits an insertion loss performance of −8 dB up to 50 GHz and eliminates resonance. A signal with an insertion loss of −3.1 dB can be transmitted to a system-on-chip in a practical chip test.

Fluctuations of the plasma potential in atmospheric pressure micro-plasma jets

Fluctuations in plasma floating potential in an atmospheric pressure micro-plasma jet are investigated experimentally. The transport of charged particles toward the ambient air is often seen to be affected by plasma fluctuations. The dependence of fluctuations on operating parameters such as applied voltage, gas flow rate, and gas mixture ratio (He:Ar) is investigated so as to be able to control the fluctuations in the intended application. A single pin probe measures the fluctuations in the jet in a region where the plasma emerges out of the capillary. The fluctuations are characterized by fast Fourier transform and time-frequency analysis (TFA). It is found that with an increase in applied voltage at a fixed flow rate (1 l/min), the fluctuations increase and reach a peak value at ∼11 kV and thereafter decrease at higher voltages due to a high value of discharge current (∼4.77 mA) at 11 kV arising from the intense ionization taking place in the jet. When the gas flow rate is increased at a fixed voltage (14 kV), the fluctuations get enhanced for flow rates beyond 2 l/min due to transition to turbulent flow occurring at a buoyancy induced Reynolds number of ∼474. In the case of gas mixing, an increase in the concentration of Ar and a reduction in He at a fixed applied power (80.6 W) and flow rate (1 l/min) give rise to a higher level of fluctuations, which is considered to be due to lower thermal conductivity and ionization potential of Ar, leading to gas heating, and ponderomotive force, giving rise to filamentation. The TFA shows the time evolution of fluctuation frequencies, which can be tuned by varying the experimental parameters. Understanding the influence of experimental parameters is crucial in controlling the fluctuations in the micro-plasma jet.

The effect of pin probe length on the characteristic of dissimilar metal Al-CuZn lap joint using friction stir welding (FSW)

Dissimilar lap joint between aluminum 6061 and brass is performed by using friction stir welding (FSW) method where universal milling machine is used to implement this method. The parameters that use in welding are probe design with a varied length of pin probe 11.0 mm, 11.5 mm and 12.0 mm at 2000 rpm rotation of machine and feedrate 10 mm min−1. The macrostructure result of pin probe length 11.0 mm better than of pin probe 11.5 mm and 12.0 mm. The mechanical properties results with a pin probe length 11.5 mm a higher mean hardness value of 104.26 VHN than a pin probe length 11.0 mm and 12.0 mm with hardness values of 98.93 VHN and 70.43 VHN. Shear stress result of 67.32 MPa with a pin probe length 12 mm, better than of pin probe length 11.0 mm and 11.5 mm shear values of 40.2 MPa and 42.14 MPa.

Experimental Examination of Weld Hardness Profile with Various Tool Pin Probes using Friction Stir Welding of AA 6082-T6 Aluminium Alloy

In the present research work, an attempt was made to evaluate the weld hardness profile on the weldments along the weld traverse direction fabricated using various tool pin probes (Concave triangular threaded probe, Inner rake angle probe, Flats on edges of probe and Scroll threaded flute probe) at three different rotational speeds 1000 rpm, 1200 rpm, 1400 rpm at single weld traverse speed 25 mm/min. Hardness profiles are useful for establishing interpretation on microstructure and weld mechanical properties, micro hardness was performed in order to outline the weld hardness profile in the vicinity of weld affected areas like Nugget zone, Thermo-mechanically affected zone, Heat affected zone and Boundary zone in the weldments. From the hardness profiles it was found that higher hardness value of 106 VHN1kg (Vicker’s Hardness Number at 1kg load) was obtained with the weldment fabricated using Scroll threaded flute probe at 1400 rpm and 25 mm/min i.e 15 mm distance away from the weld centreline on the advancing side of the weldment , besides lower hardness value of 49.8VHN1kg was obtained with weldment fabricated using concave triangular threaded probe at 1200 rpm and 25 mm/min at nugget zone i.e at the centerline of the weldment.

Design of a simple and low cost electrical property tester for graphene material : a preliminary study

A simple and low cost electrical property tester for material has been designed and built using cheap components. This instrument consists of simple adjustable current source circuit using LM317, gold coated pin probe and multimeters. The circuit arranged has produced sufficient current to do an electrical property measurement. Value of current could be adjusted to select suitable current in measurement. Resistance vs current graph shows a reciprocal function that generated by a constant voltage of 1.25 volts in output pin. An experiment to examine sheet resistance of ITO glass was carried out to make sure the instrument work properly.

Effect of Shoulder–Workpiece Interference Depth on the Quality of Friction Stir Welding of AA7075-T6 Aluminium Alloy

The joining of high strength aluminium alloy AA7075-T6 sheets of 3 mm thickness was an attempt utilizing friction stir welding process. The effect of interference depth between tool shoulder and surface workpiece on the welding quality and its effect on the mechanical and metallography properties of welded joints were studied. This process is carried out using a composite tool consists of a concave shoulder made of H13 tool steel and cylindrical left-hand thread with 1mm pitch pin (probe) made of cobalt-based alloy MP159. The dimensions of tools were 14mm shoulder diameter and the pin has 5mm diameter and 2.7mm length. The tool rotation speed and welding speed were 981 rpm 169 mm/min respectively, and the tilt angle was 2°. The range of interference depth between the shoulder and workpiece was selected (0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) mm. various tests were executed to evaluate the welding quality. The results show that lack of filling defect appeared on the welding surface at the interference depth 0.05 mm. An invisible tunnel and lack of penetration in the bottom of the stir zone appeared when the interference depths were 0.1 mm and 0.15 mm. Defect-free welds obtained when interference depths were (0.2, 0.25, and 0.3) mm. The welding efficiency of the defect-free welds was in the range (85.3-92.3%) depending on the ultimate tensile strength of the parent alloy.

Eye temperature measured after death in human bodies as an alternative method of time of death estimation in the early post mortem period. A successive study on new series of cases with exactly known time of death.

The paper presents a continuation of the studies on time of death (TOD) estimation based on post-mortem temperature measurements in the human eyeball. In the current study, single (in 20 patients) or double (within a 1-hour interval in 10 patients) eyeball and rectal temperature measurements were taken in patients who died in the University Hospital Intensive Therapy Unit. The actual TOD in each patient was exactly known and the body temperature was recorded shortly after (between 50 min and 3 h 30 min). The temperature was measured using pin probes connected to a high precision electronic thermometer. The measured eye temperatures ranged from 27.4 to 33.7°C. The ambient temperature in all cases was stable (22 °C), which corresponded to the usual room temperature. Post mortem interval (PMI) was calculated using a formula based on Newton's law of cooling, previously successfully applied in comprehensive studies on pigs and recent studies on human bodies. Thanks to knowledge of the exact TOD and the stable ambient temperature, the current study on 30 new cases allowed the method to be improved by adjusting the mean value of the cooling constant and the initial eye temperature in comparison to recent studies.

A Weldment characteristics on Friction stir welding process for shipbuilding materials

The Friction stir welding Process(FSW) is a solid state welding process that is used on metals where the original characteristics of metal remain as unchanged as possible.The technique has a energy efficient, environment friendly, decrease the fuel consumption and improve the metal performance. These study address the comparative performance of process parameters of Aluminium alloys 5052, 6061 using Friction stir welding. The tool pin probe plays a major role in processing and solidification of joints. The combination of low welding speed and high rotational speed respond the excessive flash generation and formation of grains. A Microstructure of the welded joint were observed by using scanning electron microscopy (SEM).The results exhibits a fine Coarsening and Dissolving of precipitates in weld nugget zone(WNZ).Tensile property shows that the heat treatable alloys undergoes increase in strength value. The Micro-Hardness value decreases gradually to the base metal of welded joints.The corrosion study suggested the no type of corrosion occurs in heat and non heat treatable alloys for 96 Hours.

A Compact Two-dimensional Power Divider for a Dielectric Rod Antenna Array Based on Multimode Interference

In this work, multimode interference is investigated for the design of a two-dimensional fully dielectric power divider, well suited for the usage of dielectric waveguides. Most important, power division is achieved in a single device without the need of cascading multiple dividers. This allows to design a very compact and lightweight power divider, well applicable for dielectric rod antenna arrays. As a proof of concept for the used technique, a 16-way power divider with 4 × 4 output ports, made out of Rexolite, is realized, working in a frequency range between 90 and 105 GHz. For the S-parameter measurements, a special measurement setup, including a modular pin probe technique as well as radiation taper for waveguide termination, is proposed. The measurements are in good agreement with the simulations with a power split of − 15 dB for all output ports within the desired frequency range. This is equal to an additional insertion loss of 3 dB. To demonstrate the usability for antenna arrays, a fully dielectric rod antenna array is realized based on the proposed power divider. With this array, a gain of 22.5 dBi at 97.5 GHz was achieved.

Perspective of Friction Stir Welding Tools

Friction Stir Welding is a solid state method of welding of materials like aluminum. It uses simple and special designed tool having shoulder and a pin (or probe) which causes thermomechanical action for joining the materials. Shoulder attached to machine with vertical tooling system transfers axial load on the surface of work piece necessary to produce friction and plunging into the work piece. The rotating pin (probe) carries and stirs the plasticized material over its length and traverses along the direction of weld. The shoulder size and pin (probe) geometry affects the mechanical properties of welds formed. Hence there is challenge of tool design to increase joint efficiency. In this paper, review and perspective of effect of different tool geometries on weld formation have been discussed in brief.

Corona anemometry using dual pin probe

In this paper, we present an experimental study on the anemometry characteristics of a bipolar corona discharge probe with symmetrically arranged parallel electrodes. The possibility of measuring a wide range of air flow rate/flow velocity has been demonstrated. The parallel pin probe simultaneously creates positive and negative corona discharge, decomposes air media at both electrodes while keeping them with charge balance ensured by the use of a single isolated power source. This feature is fundamentally different from other reported unipolar discharge configurations, where the decomposed gas and charge is created from single electrode. Under the existence of the air flow, the decomposed gas is redistributed towards the downstream electrode, and changes the current–voltage characteristics of the system. When the probe is in open space, the discharge current is reduced with increasing flow velocity. In constrained space the discharge current behaviour is similar at high flow rates above 25lmin−1, while at low flow rates this relation is reversed. In addition, the sensitivity of discharge current to change in air flow is much higher when the negative pin is placed downstream. Both open space and constrained space characteristics are explained in terms of the influence of external flow on the ozone distribution and its effect on the discharge current. This explanation is supported by ozone measurements, with the data showing good correlation between the discharge current and ozone concentration with respect to the external flow. The role of the electrode separation and discharge voltage is also investigated.

A practical comparison of surface resistance test electrodes

Four surface resistance test electrodes are compared using a selection of materials under similar test conditions. The results vary considerably with some materials due to variation in surface resistivity. Using a relatively uniform material two concentric ring electrodes compliant with the same standard differed in results by a factor of 1.8. Silver stripe and copper tape electrodes gave results a factor 0.4 and 0.7 compared to the reference electrode. A 2-pin electrode gave results a factor 4.7 greater. The 2 pin probe cannot be expected to give similar results to the other electrodes for materials that have variable resistivity.

Parametric study of a pin-plane probe in moderately magnetized plasma

The application of a planar Langmuir probe in magnetized plasma is found to be problematic due to significant perturbation of plasma along the magnetic field lines intercepting the probe surface. This causes the Ampere–Volts ‘Ie(U)’ characteristics of the probe to deviate from its usual exponential law; in conjunction the electron saturation current Ies is significantly reduced. Moreover estimating the electron temperature Te by considering the entire semi-log plot of Ie(U) gives ambiguous values of Te. To address this problem, Pitts and Stangeby developed a formula for the reduction factor for Ies. This formula depends on a number of uncertain parameters, namely; the ion temperature T+, electron cross-field diffusion coefficient and the local potential hill Vh estimated by applying a floating pin probe in the vicinity of the planar probe. Due to implicit dependence of these parameters on Te, the resulting analysis is not straightforward. This paper presents a parametric study of different parameters that influence the characteristics of a planar probe in magnetized plasma. For this purpose a pin-plane probe is constructed and applied in the magnetized plasma column. A comprehensive discussion is presented that highlights the practical methodology of using this technique for extracting useful information of plasma parameters in magnetized plasmas.

Ag filament and surface particle formation in Ag doped AsS2 thin film

A study of Ag filament formation in resistive switching was carried out by pin probe contact on the surface of Ag doped AsS2. New switching algorithm, consisting of two different voltage steps, in parallel with the classical cyclic voltammetry was explored. The resulting Ag deposition on the AsS2 surface was observed by optical microscopy and scanning electron microscopy. Finally, the experiment results were explained by a model of “concentration-polarization” phenomena.

Finite Element Analysis of Stress-Strain Response at the Tool Pin During Friction Stir Process

Friction stir welding (FSW) is a relatively new solid-state joining process which is considered energy efficient, eco-friendly and versatile. High stress and strain occur at the rotating tool, consisting of a pin (probe) and a shoulder, during the friction stir process. The geometrical design of the tool has some impact in terms of stress and strain once static load is applied against the tool. In this work, specific stress can be found on the tool due to the plunging and travel process that is analysed using finite element method. In the present work, a steady state finite element stress analysis of friction stir welding was carried out using CATIA V5 software. The critical points of the FSW tool are located mainly on the edge between the shoulder and the pin, where a large amount of stress is found and further leads to failure or tool defects. This critical stress and strain can be reduced by enlarging the diameter size of the pin and increasing tool life.

Cover Picture: Contrib. Plasma Phys. 4/2014

Abstract14 pin probe head with free‐standing proud pins in three radially staggered planes. The pins are separated poloidally by 5.4 mm and radially by 4 mm. The operation regime of the tips is indicated. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Liquid film thickness behaviour within a large diameter vertical 180° return bend

Experimental results of liquid film thickness distribution of an air–water mixture flowing through a vertical 180° return bend are reported. Measurements of liquid film thickness were achieved using flush mounted pin and parallel wire probes. The bend has a diameter of 127mm and a curvature ratio (R/D) of 3. The superficial velocities of air ranged from 3.5 to 16.1m/s and those for water from 0.02 to 0.2m/s. At these superficial velocity ranges, the flow pattern investigated in this work focused on churn and annular flows. It was found that at liquid and gas superficial velocities of 0.02m/s and 6.2m/s, respectively, the averaged liquid film thickness peak at 90°. At gas superficial velocity of 16.1m/s, the relationship between them is linear due to the shear forces overcoming gravity. Additionally, it was found that deposition of entrained droplets keeps the liquid film on the outside of the bend. The results of polar plots of average liquid film thickness in the bend showed that the distribution of the liquid film is not symmetrical with thicker films on the inside of the bend due to the action of gravity. Experimental results on average liquid film thickness showed good agreement with the simulation data reported in the literature.

Studies on time of death estimation in the early post mortem period – Application of a method based on eyeball temperature measurement to human bodies

This paper presents a verification of the thermodynamic model allowing an estimation of the time of death (TOD) by calculating the post mortem interval (PMI) based on a single eyeball temperature measurement at the death scene. The study was performed on 30 cases with known PMI, ranging from 1h 35min to 5h 15min, using pin probes connected to a high precision electronic thermometer (Dostmann-electronic). The measured eye temperatures ranged from 20.2 to 33.1°C. Rectal temperature was measured at the same time and ranged from 32.8 to 37.4°C. Ambient temperatures which ranged from -1 to 24°C, environmental conditions (still air to light wind) and the amount of hair on the head were also recorded every time. PMI was calculated using a formula based on Newton's law of cooling, previously derived and successfully tested in comprehensive studies on pigs and a few human cases. Thanks to both the significantly faster post mortem decrease of eye temperature and a residual or nonexistent plateau effect in the eye, as well as practically no influence of body mass, TOD in the human death cases could be estimated with good accuracy. The highest TOD estimation error during the post mortem intervals up to around 5h was 1h 16min, 1h 14min and 1h 03min, respectively in three cases among 30, while for the remaining 27 cases it was not more than 47min. The mean error for all 30 cases was ±31min. All that indicates that the proposed method is of quite good precision in the early post mortem period, with an accuracy of ±1h for a 95% confidence interval. On the basis of the presented method, TOD can be also calculated at the death scene with the use of a proposed portable electronic device (TOD-meter).

Predicting the effects of tool geometries on friction stirred aluminium welds using artificial neural networks and fuzzy logic techniques

Effect of friction stir welding (FSW) tool geometries on aluminium welds were investigated using different tool shoulder and pin probe geometry profiles. A combination of 27 tool shoulder and pin profile geometries were used for the experimental purpose using a design matrix. The effect of these tool geometries on the friction stir welds like the weld strength, weld cross-section area and grain sizes were investigated. The effects of the tool geometries were predicted using artificial intelligence techniques such as artificial neural networks (ANN) and fuzzy logic modelling. It was observed that, for a combination of FSW tool geometries, the ANN model was not so effective in predicting the FSW weldment characteristics, while the fuzzy logic model was able to predict the same with much lower percentage of error for the test cases.