Boss Structure Research Articles

Strengthening flat-die friction self-pierce riveting joints via manipulating stir zone geometry by tailored rivet structures

Achieving high-strength joints with flat surfaces is of significant importance for reducing wind resistance and enhancing aesthetic appeal. In this study, a novel flat-die friction self-piercing riveting (flat-die F-SPR) process is proposed. The rivet flaring without die guidance was achieved through the sophisticated design of rivet structures. Three types of rivets with different internal structures were designed to manipulate the base material flow and microstructure evolution during the joining process. Based on the method of emergency stop, the load-stroke curves, evolutions of macroscopic morphology, and microstructure of the joints made with different rivets were investigated. A novel mechanism for solid-state bonding of joints was proposed to elucidate the generation and evolution of fine grain regions. The results indicate when downward pressure is applied to the material inside the rivet cavity, a central stirring zone appears. By using a rivet with an annular boss structure, the base material flows continuously into the stirring zone and piled up in the rivet cavity, forming a unique conical-shaped fine grain zone. Finally, a comprehensive assessment of the strength of different types of joints and the transition of the fracture modes were conducted based on different lower sheet thicknesses. The joints of Rivet_B and Rivet_C demonstrate 11.1% and 6.9% strength enhancement compared with the joint of Rivet_A, respectively. Two strategies for enhancing the strength of solid-state bonding are proposed by analyzing the joint strengthening mechanism, which offers insights for the optimizations of rivet structures.

Analysis of the Boss Structure of Type Ⅳ Composite Vessel for a High-Pressure Hydrogen Tube Trailer

Currently, large-volume type IV composite vessel tube trailers garner significant attention and development within the hydrogen energy storage and transportation industry due to their cost-effectiveness and practicality. This study aims to assess the static strength and sealing performance of the boss structure in order to optimize its design. Firstly, a model of the mouth structure of type IV vessels was constructed to analyze the stress distributions in the boss and liner. Subsequently, innovative boss and liner structures were developed based on the primary mouth structure to investigate the impact of geometric dimensions through finite element analysis. This study revealed that changes in geometrical dimensions led to significant alterations in the stresses of the plastic liner in comparison to metallic bosses. Building upon these findings, the structural safety and sealing performance of the boss and liner structure were further validated through finite element analysis. The outcomes of this research can serve as a reference for guiding the structural design of bosses and aiding in the development of hydrogen storage vessels.

Design and experiment of multidimensional and subnanometer stage driven by spatially distributed piezoelectric ceramics.

Multidimensional microdriving stage is one of the key components to realize precision driving and high-precision positioning. To meet nanometer displacement and positioning in the fields of micro-/nano-machining and precision testing, a new six-degree-of-freedom microdriving stage (6-DOF-MDS) of multilayer spatially distributed piezoelectric ceramic actuators (PZTs) is proposed and designed. The interior of the 6-DOF-MDS is a hollow design. The flexure hinge is used as the transmission mechanism, and the series-parallel hybrid driving of the corresponding PZTs achieves the microtranslation in the X, Y, and Z directions and the microrotation around the three axes of the microdriving stage, forming a microdisplacement mechanism with high rigidity and simple structure, which can realize the microfeed of 6-DOF. The force-displacement theory and lug boss structure optimization of the 6-DOF-MDS are analyzed, while the strength checking and natural frequency of the 6-DOF-MDS are also simulated by the finite element method. In addition, the real-time motion control system of the 6-DOF-MDS is designed based on Advanced RISC Machines. Through a series of verification experiments, the stroke and resolution results of the 6-DOF-MDS are obtained, where the displacements in the X, Y, and Z directions are 20.72, 20.02, and 37.60μm, respectively. The resolution is better than 0.68nm. The rotation angles around X, Y, and Z are 38.96″, 33.80″, and 27.87″, respectively, with an angular resolution of 0.063″. Relevant coupling experiments were also performed in this paper; in the full stroke linear running of X-axis, the maximum coupling displacements of the Y- and Z-axes are 1.04 and 0.17μm, respectively, with the corresponding coupling rates of ∼5.0% and 0.8%. The maximum coupling angles for the X-, Y-, and Z-axes are 0.33″, 0.14″, and 2.30″, respectively. Considering the coupling of the 6-DOF-MDS, decoupling measures and specific mathematical models have also been proposed. The proposed multidimensional microdriving stage achieves subnanometer resolution and can be used for the precise positioning and attitude control of precision instruments at the nano-/subnanometer level.

Failure Analysis of Novel BOSS Structures for Type IV Hydrogen Storage Vessels

This study focuses on the critical connection area between type IV hydrogen storage vessels and external valves, which is commonly referred to as the BOSS structure. The novel BOSS structures were proposed to further ensure the safety of pressure vessels. In order to identify optimal structure that meet industrial requirements, finite element models were performed to analyze and compare the effectiveness of the proposed models in terms of strength, fatigue, and sealing performance. Some influences were discussed, including the angle of inclination of the stop-rotation platform and the number of sealing grooves in the BOSS structures. The results showed that the fatigue life of the proposed BOSS structures can exceed the design life of 30,000 cycles using austenitic stainless steel S31603. The maximum contact stresses were higher than the operating pressure of 58 MPa. Additionally, The BOSS structure model designed with a stop-rotation platform featuring a 65° tilt angle and two sealing grooves had the lowest mean square deviation of contact stress, which was 13.47 MPa, indicating reliable sealing performance.

Numerical Simulation of the Effect of Annular Boss Structure on DC Arc Anode Attachment

Numerical Simulation of the Effect of Annular Boss Structure on DC Arc Anode Attachment

The Establishment and Verification of the Sensitivity Model of the Piezoresistive Pressure Sensor Based on the New Peninsula Structure

In this paper, a mechanical-electrical-process integrated model of the piezoresistive pressure sensor sensitivity is established for the first time, and the nonlinearity is analyzed from two aspects of bridge arm resistance and piezoresistive stress difference. Furthermore, a new peninsula structure diaphragm (NPSD) piezoresistive differential pressure sensor is proposed. By creating stress concentration areas and adding the cross beam-circular boss structure, within the pressure range of 0–5 kPa, the sensitivity of the sensor measured by the experiment reaches 22.7 mV/kPa, and the nonlinearity is only 0.11%FSO (full-scale output). In addition, it has been proved theoretically and experimentally that the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> passivation film seriously affects the zero output voltage of the sensor, and causes the nonlinearity of 1.22% FSO. At the same time, compared with several typical structures, the pressure sensor proposed has the advantages of high sensitivity, low nonlinearity and small diaphragm. [2021-0206]

Study on the effect of surface characteristics of short-pulse laser patterned titanium alloy on cell proliferation and osteogenic differentiation

Concise, low-cost preparation of titanium alloy implants with high cell proliferation and osteogenic differentiation is urgently needed. Nanosecond laser ablation of titanium alloy has the advantages of short processing time, less pollution, and non-contact. In this research, we adopt a nanosecond UV laser to process the closed groove and cross groove titanium alloys with length to width ratio of 1:1, 2.5:1, 4:1, and 6:1. The surface morphology, surface roughness, phase, element distribution, surface chemistry, and wettability were characterized. The effect of the patterned surface's properties on the adhesion, proliferation, and osteogenic differentiation of stem cells was studied. The results show the laser-ablated lattice structure's surface energy can increase rapidly in the natural environment. The cell adhesion of stem cells on a lattice structure with low roughness and high surface energy is optimal. The element concentration at the ablated edges is higher than at the bottom under Marangoni and surface tension. Stem cells preferentially adhere to the ablated edges with high roughness, element concentration, and hardness. Cell differentiation is chiefly affected by patterning structure. On the surface of the boss structure with a length to width ratio of 2.5:1, the proportion of cell length to diameter is about 2.5, and the cell area is greater. The osteogenic differentiation of cells is the highest on the surface.

A novel anode structure for diffuse arc anode attachment

A novel method for adjusting the direct current arc anode attachment mode by changing the anode surface structure is proposed. A transferred arc device is used to investigate the effect on the arc anode attachment state of the electrode separation and the presence and dimensions of an annular boss, or embossing, on the anode. The experimental results show the diffuse arc anode attachment mode is more likely to be formed in the presence of an annular boss structure on the anode, compared to the standard planar structure. In the case of argon working gas, as the distance between the cathode and the anode increases from 15 mm to 30 mm, the arc maintains the diffuse arc attachment on the anode with the annular boss, while for a planar anode, the arc anode attachment mode changes from diffuse to constricted. Comparison of the measured temperature distribution by the relative intensity method and the emission intensity of the arc attachment region verifies that the annular boss anode can indeed promote diffuse attachment. Analysis of the electric field strength distribution between the electrodes shows that the introduction of the annular boss doubles the electric field strength near the anode surface due to the boss edge effect, which drives the arc to be evenly dispersed on the boss, resulting in the formation of diffuse arc attachment. The enlarged attachment area reduces the current density and heat flux on the anode surface, which is important for the stabilization of diffuse arc attachment. No obvious ablation is found on the surface of the annular boss anode after 1 h operation, while there significant ablation is evident on the surface of the planar anode.

A Differential Hall Effect Based Pressure Sensor

This paper presents the design and simulation of a pressure sensor integrated with two identical hall effect sensors and permanent magnets arranged in a differential configuration for measuring pressure in the range of 0–20 bar. The sensor uses the deflection of a circular diaphragm with a simple rigid mechanical structure to convert the applied pressure to a differential hall voltage output. A complete analytical modelling was carried out by assuming the rigid mechanical structure as a central circular boss structure on the circular diaphragm. Numerical simulations were also carried out in COMSOL Multiphysics FEM tool to support the analytical results. Before going for actual fabrication, the optimum sensor dimensions were also fixed from both analytical modelling and numerical simulation analysis. The sensor was planned to be fabricated completely using different grades of stainless steel and hence can be used in high temperature and corrosive environments. The fabricated sensor can be of low cost, self-packaged and the differential arrangement helps in compensating for any ambient temperature variations.

Design and Simulation of Digital Output MEMS Pressure Sensor

This paper presents the design and simulation of a MEMS pressure sensor with a digital output for measuring pressure in the range of 0–1 bar. The sensor uses the diaphragm deflection and a simple mechanical structure to convert the applied pressure to a logic digital output. Three different designs of the sensor have been proposed with square and circular diaphragms. The first design uses ten different sized square diaphragms on the same substrate to get a resolution of 0.1 bar. The second design uses a single square diaphragm instead of ten to get the same resolution. The third design also uses a single circular diaphragm with a central boss structure, which reduces the deflection nonlinearity at low pressures. Analytical analysis was carried out for all the diaphragm deflections, and the results are supported by numerical simulations carried out in COMSOL Multiphysics tool. The proposed sensor can operate on 5 V which suits well with conventional CMOS logic. The direct digital output from the pressure sensor makes its useful in wide variety of applications.

Numerical Study on Supersonic Combustor with an Allotype Cavity

The three-dimensional coupled explicit Reynolds Averaged Navier–Stokes (RANS) equations and the two equation shear-stress transport k-w (SST k-w) model has been employed to numerically simulate the cold flow field in a special-shaped cavity-based supersonic combustor. In a cross-section shaped rectangular, hypersonic inlet with airflow at Mach 2.0 chamber, shock structures and flow characteristics of a herringbone-shaped boss and a herringbone-shaped cavity models were discussed, respectively. The results indicate: Firstly, according to the similarities of bevel-cutting shock characteristics between the boss case and the cavity case, the boss structure can serve as an ideal alternative model for shear-layer. Secondly, the eddies within cavity are composed of herringbone-spanwise vortexes, columnar vortices in the front and main-spanwise vortexes in the rear, featuring tilting, twisting and stretching. Thirdly, the simulated bottom-flow of cavity is in good agreement with experimental result, while the reverse flow-entrainment resulting from herringbone geometry and pressure gradient. However, the herringbone-shaped cavity has a better performance in fuel-mixing.

Model independent tests of cosmic growth versus expansion

We use Gaussian Processes to map the expansion history of the universe in a model independent manner from the Union2.1 supernovae data and then apply these reconstructed results to solve for the growth history. By comparing this to BOSS and WiggleZ large scale structure data we examine whether growth is determined wholly by expansion, with the measured gravitational growth index testing gravity without assuming a model for dark energy. A further model independent analysis looks for redshift dependent deviations of growth from the general relativity solution without assuming the growth index form. Both approaches give results consistent with general relativity.

Cell Manipulation System Based on a Self-Calibrating Silicon Micro Force Sensor Providing Capillary Status Monitoring

In this paper, a system for cell manipulation is presented. A two axis stage is arranged on an inverted microscope to place cells in focus. Cell manipulation can thereby be observed while the system automatically runs force controlled measurements. A high precision linear motor moves a force sensor, which has been equipped with a stimulation tool, e.g., a micro capillary for cell injection. The sensor is made up of silicon and consists of a membrane with a boss structure, which enables measurements as low as 120 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm N}$</tex></formula> . For the first tests, an injection capillary is mounted on the topside, while the backside is fixed to a printed circuit board with an integrated air pressure connection. Air pressure was applied under the membrane because the glass capillaries with outer diameters of at least 1 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> do not allow calibration via other force sensors. This setup provides a self-calibration of the mounted sensor system, before the measurements of the occurred forces on the cells during the penetration of the capillary. Using the 3-D force measurement capability of the sensor, the system features a unique end-effector status monitoring.

Calibration of a microprobe array

Conventional coordinate measurement machines are not well adapted to the specific needs for the measurement of mechanical microstructures that are made in a highly parallel production process. In particular, the increase of the measurement speed is addressed by using an array of microprobes to measure a number of objects in parallel. It consists of multiple microprobes that are etched into the same silicon substrate. The styli are glued onto a boss structure in the middle of a silicon membrane. To facilitate the alignment of an array and the underlying wafer, the array is mounted on three stacked rotational stages. Due to the production tolerances, the positions of the touching balls of the probes relative to their pivot have to be calibrated. The probe sensitivity is another field of calibration. This paper describes an efficient calibration procedure of the probe array which is usable for arrays with a large number of probes and different array layouts. The validation method of this procedure is explained and calibration results are discussed

Experimental investigation of spray formation as affected by sprinkler geometry

A preliminary study at low water discharge pressures was conducted to investigate the fire sprinkler spray formation as affected by sprinkler geometry using a laser-based shadow imaging system. A sprinkler typically consists of the following components: a deflector with tines and slots, a boss above the deflector and sprinkler frame arms. Prototypes of these components were fabricated to evaluate their effects on the spray formation process. The water sheet thickness formed on non-slotted deflectors, slot spray discharge angle, sheet breakup distance from the deflector perimeter, water flux and drop size distributions were measured. It was found that deflector diameter and boss structure have little impact on drop size and sheet breakup distance. However, wider slots form larger drops. At constant operating pressure, the slot spray discharge angle is insensitive to the slot width, but sensitive to the boss that helps directing the slot spray toward the sprinkler centerline. The frame arm tends to produce a vertical spray sheet downstream of the frame arm, which increases the complexity of overall spray formation. An integral model was developed to calculate the development of water sheet thickness and speed on the deflector for different degrees of viscous effect exerted by the deflector. An empirical correlation was also established to estimate the spray flux fraction discharging from a deflector slot. The above measurements and observations are useful for the development of a spray formation model for fire sprinklers.

감도특성 향상을 위한 국부적 표면식각 다이아프램 구조 연구

In the pressure sensor, about below 20 kPa, the center boss diaphragm structure is generally used, but it is hard to obtain the high sensitivity because the center boss structure is limited at the thickness and size of diaphragm with chip size. Therefore, this paper suggests that the Center boss structure has surface etched diaphragm using a stress concentration to improve the sensitivity. We carried out the simulation and fabrication applied new diaphragm design. In the result, the sensitivity is improved to 60% without the change of non-linearity (0.14%FS). So, the Center boss of surface etched diaphragm can be applied for the high sensitivity in the low-pressure sensor.

A capacitive silicon pressure sensor with low TCO and high long-term stability

A capacitive pressure sensor optimized for low thermal zero shift and excellent long-term stability is presented. The element is a variable gap capacitor located between two single-crystal silicon chips, one of which contains a micromachined pressure sensitive diaphragm. The silicon chips as well as the pressure port tube are sealed together by anodic bonding. FEM (finite element method) analyses are presented which show a reduction in temperature-induced mechanical stresses by using a silicon support chip with a thin sputtered layer of Pyrex 7740 instead of a Pyrex 7740 support chip. The nonlinearity in deflection of the diaphragm caused by the center boss structure is also quantified by the FEM analyses. The experimental results are in agreement with the objectives: a thermal zero shift of less than 0.01% of full-scale output (FSO) per °C, and a long-term drift of less than 0.01% of FSO per week.

A study of injection molding (3rd report. Partial thermal shrinkage in the boss strucutres).

In the injection molding process, when the melted resin solidified by the cooling effect from the die, non-equivalence of the cooling history caused the Sink-mark growth in the resin, near boss structures. In this study, relations between Sink-Mark depth in the boss structure and some molding parameters are experimentally evaluated, and especially the effect of the forming pin is considered. Also, cooling simulation by thermal analysis is done. In considering the P-V-T characteristics and cooling history of the resin, the experimental results are quantitatively explained.