Fillet Formation Research Articles

Towards understanding subsurface integrity alteration of gear fillet formed by gear skiving method

The subsurface integrity of the fillet affects the gear service life during high-power-density transmission. To clarify the fillet formation in the gear skiving process, the internal subsurface integrity of gear fillets at the approach and recess sides were investigated by considering the surface texture. Metallurgical and mechanical investigations were conducted to advance the understanding of the fillet formation mechanism. The long-axis angle of the deformed grains and geometrically necessary dislocations (GNDs) of the subsurface revealed the dominant deformation mode and strain hardenability. As a result, the surface texture must be analyzed to elucidate the local cutting feature-induced plastic deformation owing to the high velocity gradient near the skived surface. The long-axis angle difference at the fillet of recess side increased approximately 5 to 10 times compared to that of the approach side, indicating that the refinement and slip-dominated deformation mode prevails at the formation of the leading and trailing fillets, respectively. Greater strain hardenability at the subsurface of the leading fillet was elucidated by the nanoindentation test and grain dislocation density. This work advances the understanding of microstructural alteration at the subsurface of the leading and trailing fillets, contributing to the gear functionality-based assessment of the gear skiving process.

Numerical Analysis of Fillet Shape and Molten Filler Flow during Brazing in the Al–Si Alloy of Automotive Radiator

In the brazing process of an automobile radiator, eutectic melting of the Al–Si filler alloy of the clad sheets, fillet formation in the brazed joints, and the flow of the molten filler metal on the solid core metal between joints occur continuously. With regard to designing heat exchangers, the optimum placement of the filler metal, considering the flow of the molten filler metal, is an important subject. In this study, a new numerical analysis was applied to predict the shape of the fillets and the molten filler flow. The molten filler flow was calculated using the difference method applied to a one-dimensional unsteady flow that is assumed to be a uniform flow of incompressible viscous fluid between two parallel plates. Among some numerical results, when the hydraulic mean depth of the flow path was reduced 0.3 times, the calculation results were consistent with the actual values. It was necessary to narrow the flow path because it was calculated assuming that the flow of brazing was between two parallel flat plates, whereas the actual flow path of the molten filler metal was not flat and a large flow resistance was produced.

Effect of electron irradiation and bayberry polyphenols on the quality change of yellowfin tuna fillets during refrigerated storage

This study evaluated the synergistic effect of bayberry polyphenols and electron irradiation in controlling the chemical, microbiological and sensory changes of raw yellowfin tuna fillets at 4°C for 7 days. The results indicated that the initial values of each index were dose-dependent. The dose of 5 kGy notably accelerated adenosine triphosphate degradation and lipid oxidation, while the doses of 1 and 3kGy had acceptable sensory quality and yielded a shelf-life of 5 days. The addition of bayberry polyphenols had evident effect in inhibiting freshness breakdown, bacteria growth, histamine formation, and discoloration of tuna fillets. Bayberry polyphenols, as an antioxidant, could inhibit lipid oxidation and sensory side-effects made by irradiation up to 3kGy. The dose of 1–3kGy coupled with bayberry polyphenols was optimum to preserve tuna fillets which prolonged the shelf-life to 7 days.

Multiphysics Modeling of Underfill Flow and Cure during Thermocompression Bonding

We present a model of fillet formation and cure during thermocompression bonding with a non-conductive film. Process variables in the model include the position and temperature profiles applied to the silicon die and substrate by the bonding tool. The chemorheology of the underfill is accounted for in order to track the degree of cure of the material and its impact on dynamic viscosity. Simulation predictions of how the underfill chemorheology impacts the fillet shape and level of cure advance during the processes are presented.

One Step Chip Attach Materials (OSCA) for Conventional Mass Reflow Processing

One step chip attach (OSCA) materials are dispensable polymeric materials for flip chip assembly, which are designed to flux metallic interconnections and subsequently turn into an underfill upon curing. OSCA materials enable a drastic simplification of the assembly process by combining the reflow (fluxing/soldering), defluxing and capillary underfilling steps used in traditional processing into a single step. One key challenge for the design of OSCA materials is timing the cure kinetics with fluxing activity and solder reflow during processing. A second key challenge is to factor a process-friendly rheological design into the formulation. The OSCA material rheology must allow for high filler loading levels, seamless integration with standard dispensing equipment, flow control during and after dispense (avoid keep out zones), flow during die placement (elimination of voids), after placement (fillet formation) and during reflow. The final key requirements for a functional device are defect-free interconnections combined with optimal thermo-mechanical and water resistant properties of the final underfill to guarantee the long-term reliability of the assembly in various environmental conditions. This paper presents the properties of materials designed by Kester for use in mass reflow processing (OSCA-R). The rheological design principles behind a seamless integration into customer-friendly processes will be presented In addition results illustrating the timing of cure kinetics with fluxing and soldering events during processing will be discussed. Preliminary device reliability results will also be presented for several types of test vehicles including; Si-Si and Si-FR4.

Adhesive Pressing Veneer Performance Study of Compound Sheet of Straw

Using veneer and Straw shavings two kinds of raw materials to manufacture composite way veneer straw composite panels, Straw is discussed when the shop is the amount of glue, Adhesive proportion factor effect the performance of the veneer, and this kind of plank makes a simple analysis of economic benefit.The results show that: SEM test proves that the API surface diffusion performance is better than that of UF adhesive. Urea-formaldehyde resin adhesive on the surface of straw respectively formed by the uneven and thick, API adhesive fillet formation is relatively uniform and relatively thin.In the production of veneer straw composite board is best craft hot-pressing temperature is 160°C, hot pressing time is 1 min /㎜, sizing amount of straw content is 12%, API adhesive formulations: Ratio of main agent PVA: SBR for 7:3, Crosslinking agent amount (P - MDI) 30% , density of not less than0.85g/cm³. The board each performance index of the optimal, fully able to meet the requirements of national standard, adopt the process sheet belongs to no aldehyde board.

Influence of Roughness on the Mechanical Adhesion of Single Lap Joints

The single lap joints analysis has been developed from different perspectives, including overlap length, adhesive thickness, spew fillet formation, stress distribution, and manufacturing parameters. This paper describes recent results in the study of the roughness influence on the mechanical adhesion of single lap joints in composite test specimens made of glass fiber with a polymeric matrix. Analysis techniques were based on both finite element and experimental approaches. For the above-explained purpose, two cases were simulated: one with a surface roughness of the adherend in the joint overlap, and another one with a minimal roughness surface in the overlap zone. It was considered that the adhesive behaves like an isotropic material. As for the specimens used in the experimental tests, the surface roughness of the adherends was controlled by using an anti-adhering fabric, and the adherend specimen's surface without roughness was controlled using glass as a mould. The numerical results were validated experimentally by means of tensile tests. In the simulation where substrates with surface roughness were used, it was observed that the maximum shear stress at the joint ends decreases by 21% when compared with the model developed with adherends without roughness. Nevertheless, in the test specimen with roughness, a redistribution of the stresses exists that move from the adhesive to the substrates, which causes an increase of the single lap joint resistance. The same was observed in the experimental tests where an increase of four times in the load supported by the joint was obtained.

Evaluation of skin-core adhesion bond of out-of-autoclave honeycomb sandwich structures

Composite sandwich structures offer several advantages over conventional structural materials such as lightweight, high bending and torsional stiffness, superior thermal insulation and excellent acoustic damping. One failure mechanism in a composite sandwich structure is the debonding of the composite facesheets from the core structure. A well-formed adhesive fillet at the interface of the honeycomb core cell walls and the laminate is a significant factor in preventing bond failure. In the present work, honeycomb composite sandwich panels are manufactured using a low-cost vacuum-bag-pressure-only out-of-autoclave manufacturing process. CYCOM®5320 out-of autoclave prepreg is used for the facesheet laminates and FM® 300-2U film adhesive is used for the facesheet-to-core bond. The manufactured composite sandwich panels are of aerospace quality with a facesheet laminate void content of around 1%. In this study, adhesive fillet formation and adhesive mechanical strength are evaluated as a function of several different sandwich construction design variables. Both aluminum and aramid Nomex® honeycomb core materials are considered to study the effect of core cell size and core material. The effect of film adhesive thickness is studied. A process for reticulation of the adhesive is applied and studied. A quantitative investigation of the adhesive fillet geometry is carried out for all the panels. Manufactured panels are evaluated for flatwise tensile strength in accordance with test method ASTM C297. Optimized combinations of core material, core density, cell size and adhesive thickness are identified. Results show that the reticulation process improves fillet formation and increases flatwise tensile properties.

Analysis of partial suspension in stirred mixing cells using both MRI and ERT

Abstract Magnetic resonance imaging (MRI) and electrical resistance tomography (ERT) are collectively used to examine partial suspension of various glass and nylon particles in the same stirred baffled mixing cell of inner diameter 50 mm. Virtually complete suspension is observed to occur at critical agitation rates considerably lower than expected. Radial and axial particle concentration profiles, as measured using MRI and ERT, compare reasonably well. The higher resolution of MRI is able to detect concentration variations adjacent to the vessel wall whilst fillet formation of unsuspended solids is imaged at the base of the cell. To the best of our knowledge, this study represents the first direct comparison of MRI against ERT.

Effects of Anisotropic Conductive Film Viscosity on ACF Fillet Formation and Chip-On-Board Packages

In this paper, the effects of anisotropic conductive film (ACF) viscosity on ACF fillet formation and, ultimately, on the pressure cooker test (PCT) reliability of ACF flip chip assemblies were investigated. The ACF viscosity was controlled by varying the molecular weight of the epoxy materials. It was found that the ACF viscosity increased as the increase of molecular weight of the epoxy materials. However, there was little variation of the thermomechanical properties among the evaluated ACFs with different viscosites. Also, the results showed that the ACFs have no differences in moisture absorption rate, die adhesion strength, and degree-of-cure. In scanning electron microscopy images, the lower ACF viscosity resulted in the smoother ACF fillet shape and the higher fillet height. From the results of PCT, the ACF flip chip assembly with the smoother fillet shape showed better reliability in terms of contact resistance changes. After 130 h of PCT, the flip chip assembly with lower ACF viscosity also showed a lesser degree of delamination at the ACF/chip interface.

Experimental Investigation on the Co-Cure Processing of Honeycomb Structure with Self-Adhesive Prepreg

To optimize the co-cure processing of honeycomb sandwich composites, three parameters, namely the ramp rate, pressure and application time of pressure were varied. Meanwhile, the inner pressure profile was on-line monitored to reveal the influence mechanism the final quality of the samples. Fillet size, resin content and porosity were used to characterize the bonding performance and panel quality. In addition, the climbing drum peeling strength was applied to characterize the interfacial bonding performance of the sandwich structure. It is found that product with the good fillet and little void content in the panels can be obtained by applying pressure of 0.4 MPa after holding 50 min at 100 °C; plus force induced by the surface tension partly contributes to the formation of fillets; ramp rate of temperature has a significant influence on the quality of the panel and gas permeation of the panels should be considered during the optimization of operating conditions.

Braze Pressure Welding (BPW) - A New Method for Joining Steel Pipes -

Braze Pressure Welding (BPW) with high frequency induction heating is a newly developed pressure welding technique using interlayer metals for welding the general steel pipes for pipe arrangement in buildings. BPW enables to make joints by solid-state welding in air using a flux sheet which is also developed for this technique. In this method, the interlayer metal is expected to play the primary role in making high performance joints. At a joining temperature, the melted interlayer removes contaminations from the joining surfaces of the base metals. Then the liquid filler is discharged from the joining interface by the joining pressure, and forms fillets at the gaps around the joint. In this stage, the joining pressure is relatively small, so the welding deformation can be restrained to a minimum. The fillets have the effects both on relaxing the stress concentration at the joint and on increasing the joining area, which contribute to the strengthening of the joint. Thus, the high quality pipe joining without the dispersion in joint properties due to welder’s skill can be performed. In this report, the concept and merits of BPW are explained, and the results of the investigation on the cleaning effect of the interlayer metal and the effects of fillet formation on strengthening the joint are discussed. The practical application of BPW in Japan is also introduced.

Real-time Detection of Debonding between Honeycomb Core and Facesheet using a Small-diameter FBG Sensor Embedded in Adhesive Layer

The authors have developed a novel technique to detect debonding in honeycomb sandwich structures using small-diameter fiber Bragg grating (FBG) sensors. A small-diameter FBG sensor is embedded in the adhesive layer between the core and the facesheet during the curing process of the adhesive layer. After the curing process, the reflection spectrum from the small-diameter FBG sensor is distorted because the formation of fillets induces a non-uniform strain distribution in the adhesive layer. However, after debonding, the core with the fillets peels off the facesheet, and, as a result, the reflection spectrum recovers its original shape due to the release of the non-uniform strain. Debonding can thus be detected with high sensitivity in real time from the recovery in the shape of the reflection spectrum. In addition, a more reliable debonding detection technique using a small-diameter chirped FBG sensor is proposed, in which two indicators in the reflection spectrum have been successfully used for a more reliable judgment of debonding.

Solids suspension in stirred tanks with pitched blade turbines

In view of developing a universal correlation for critical speed of suspension, extensive suspension experiments were conducted with tank scales in the range of 15– 121 cm , D/ T from 0.083 to 0.625, using four different sizes of spherical glass beads and employing Pitched Blade Turbines with four and six blades as the impellers. The periphery of the tank bottom was modified to include a permanent fillet in order to eliminate the effect of induced recirculation loop, which account for the formation of peripheral fillets of unsuspended solids. The critical speed of suspension N c and power P c were observed to vary independently both with D and T to give two correlations for each of the variables, N c and P c ; one for the close proximity impeller operation where both N c and P c remained invariant with off-bottom impeller clearance and the second for the region where N c and P c were affected significantly by the impeller position. The effects of the physical characteristics of the solids were also included in the four correlations so proposed. It was clearly noticed that the correlations were valid up to a critical value of D/ T beyond which the trapped particles in the stagnant zone below the impeller needed extra energy to be raked out and suspended, thus breaking the log-linear relationship between N c (or P c ) and D/ T hitherto maintained. Comparisons of the suspension speed and power have been made with open literature. More importantly, the reasons why the earlier studies differed with each other in N c -predictions have been identified.

516 配管用鋼管の高周波ろう付圧接におけるフィレット形成効果の解析

516 配管用鋼管の高周波ろう付圧接におけるフィレット形成効果の解析

Characteristics extraction of Pb free solder fillet profile for external feature inspection

First, the light intensity (luminance) distributions reflected from quad flat package (QFP) gull wing lead solder fillets were calculated by a simple geometrical model, using a modified diffusion equation. The dependence of the microscope angle /spl theta/ (= incident angle of light) on the highlight distribution from specular surfaces was obtained. Luminance distributions from top to toe fillets were experimentally observed, using Sn-Pb eutectic solder and two kinds of Pb-free solder (Sn-Ag-Cu and Sn-Zn-Bi systems) and the characteristics were compared with the simulation results. As the Sn-Pb solder fillet has a specular (or smooth) surface, it is not so difficult to identify the profiles of Sn-Pb fillets by changing /spl theta/. On the other hand, the luminance distributions for Pb-free solder were strongly affected by the surface roughness. However, it is not impossible to extract the characteristics of the fillet profile if wetting properties of Pb-free solder are taken into consideration. It was found for Pb-free solder that the fillet formation characteristics extraction becomes easy if elements of Bi and In are doped because the wetting properties were improved. In addition, some problems with characteristics extraction of fillet formation for Pb free solder are discussed from the viewpoint of an external feature inspection system.

Solder wetting in a wafer-level flip chip assembly

Wafer-level flip chips provide an innovative solution in establishing flip chip as a standard surface mount process. In this paper, the wetting of solder bumps within confining underfill during the reflow of a wafer-level flip chip assembly is addressed. For real time monitoring of an assembly during the reflow process, a system using a high-speed camera is utilized. The collapse of solder bumps on the chip in the vertical direction is found to be a prerequisite of solder wetting. Underfill voids and outgassing are found to cause chip drift and tilt during the reflow process. In addition, symmetry of the underfill flow and fillet formation is identified as a critical factor in maintaining chip to substrate alignment. During solder wetting of the metallization pads on the substrate, the underfill needs to maintain a low viscosity. With the selection of a thermally stable underfill and corresponding process development, wafer-level flip chip assemblies with good solder interconnects are demonstrated.

アルミニウムろう付用ＣｓＦ‐ＡｌＦ３系非腐食性フラックスの特性

To investigate the brazing characteristics of three CsF-AlF3 non-corrosive fluxes for aluminum, fillet formation test has been performed using magnesium containing base metal and zinc containing filler metals. The brazeability was evaluated by the length of formed fillet on tee-type joint and penetration depth of flux into magnesium containing base metals. The increase in magnesium content of base metal deteriorated the brazeability in all fluxes. The CsF-AlF3 fluxes showed inferior brazeability to KAlF4-K2AlF6 flux, however, one of the CsF-AlF3 flux with mole fraction of CsF/AlF3=1.2 (CA flux) gave similar brazeability and narrower flux penetration depth for magnesium containing base metal. Brazeability and flux penetration depth were closely related to fluorine content per unit mole of flux, the increase of fluorine content enhanced fillet formation, however, it enhanced penetration simultaneously. The CA flux offered excellent brazeability for zinc containing filler metal, whereas KAlF4-K2AlF6 flux showed poor brazeability in filler metal more than 5%Zn. The use of CA flux is recommended for brazing of magnesium containing base metals and zinc containing filler metals.

アルミニウム合金粉末ろうの真空ろう付性

Vacuum brazability of aluminum was investigated using various Al-Si-Mg powder brazing filler metals made by atomization. The effects of atomizing atmosphere and powder size on brazability were studied. After brazing a part of used filler metals gave no contribution for the fillet formation and gathered on the base metal, showing non-wetting among filler metal powders. Brazability was evaluated by the percentage of the filler metal remaining as fillet by measuring the weight change before and after brazing. After brazing of the powder filler metal, voids were found in the formed fillet. Although the completely sound fillet was not obtained, the fine powders and air atomized powders gave better brazability than coarse powders and those atomized in argon gas atmosphere. The difference in vaporization characteristics of magnesium in the filler metals seemed to be responsible for the void formation and poor brazability of the powder filler metals. Mixing of the filler metals with the Al-Mg powder was found to be effective for the improvement of the fillet formation, however, completely sound fillet was not obtained. It is believed that both the control of magnesium vaporization rate and the improvement of quality of vacuum are important to obtain the sound fillet using powder filler metals.

レーザ照射型熱画像法によるマイクロ接合部欠陥検出に関する研究 （第３報） ガルウィング型リードのソルダリング接合部のヒール部でのフィレットの形成度合の検出プロセスの検討

Detection process on the degree of fillet formation at the micro soldered joints of QFP lead has been researched and developed. The shape of the joints is expressed by three parameters (fillet length, average thickness of solder, angle of flat part of lead). The fillet length can be detected by temperature of three part on the surface of lead (toe part, center part, bend part), furthermore both average thickness of solder, and angle of flat part of lead can be detected by them. This detection process is investigated by the computer simulation on thermal model of the joint of QFP between copper alloy lead with 150μm thickness and glass epoxy substrates (1.6 mm thickness).