Pressure Angle Research Articles

Extension of transmission performance evaluation for planar higher pair mechanisms

Comprehensive and accurate evaluation of performance is essential for profile synthesis and profile analysis of higher pair mechanisms. Aiming at the transmission performance of planar higher pair mechanisms, the evaluation indices and methods are proposed from different perspectives. On the one hand, the kinematic performance indices in lower pair mechanisms are extended to higher pair mechanisms, including the mechanical advantage and the generalized pressure angle. On the other hand, novel indices specific to higher pair mechanisms are developed, including the contact closure index and the singularity distance index. Considering the performance of individual elements and that of the overall joint, the transmission performance of higher pairs is subdivided into element-based performance and joint-based performance, and the evaluation indices are classified accordingly. A graphical mapping method based on element-based performance is further proposed for intuitive analysis and qualitative evaluation. Practical examples validate the effectiveness of the proposed indices and methods for evaluating the performance of higher pair mechanisms, as well as their potential to enable optimal profile solution selection and design in the profile synthesis process.

Effectiveness of water spray in infrared signature suppression of engine plumes

In modern military aircraft, reducing the Infrared (IR) signature is critical for stealth. However, the IR signature from the engine plume is particularly challenging to address due to its link with engine operation and its unique, non-continuous characteristics. In this study, a novel approach using a water spray cloud to attenuate the IR signature from the engine plume was proposed, and it is experimentally verified by employing a micro-turbine engine. Six water nozzles generated the water spray cloud, and IR signature reduction was quantitatively measured using an IR spectrometer. Variations in water injection pressure and observation angles were used as experimental conditions. The results revealed that the IR signature was reduced with higher water injection pressure, attributed to the increased thickness of the water spray cloud. The IR signature from the engine plume was effectively attenuated by the water spray cloud in overall, with a more pronounced effect observed at lower observation angles due to the extended path within the cloud. The potential of water spray clouds for enhancing the IR stealth of military aircraft is underscored by this research.

Fully ceramic versus steel gears: Potential, feasibility and challenges

The most common gear strength calculations performed in accordance with ISO/TC 60/SC 2 include surface durability and root bending strength. Typical geared power transmissions are characterized by high Hertzian contact stresses (surface durability) on the flanks – frequently in the order of 103 MPa – versus almost half an order magnitude lower first principal stresses on the tooth root (tooth bending strength). Therefore, the use of high strength special steel alloys is almost mandatory, especially in high-end applications, mainly to withstand the high contact stress values. Ceramic materials are typically characterized by high compressive strength versus very low flexural strength that at first glance makes them inefficient for gear transmissions since they are unlikely to withstand the tensile root stresses. Nevertheless, ceramic materials possess a number of advantages that makes them potential candidates for geared transmissions, such as their exceptional thermal properties, their low density (weight), their excellent wear characteristics and limited lubrication demands. The present work investigates the main challenges of using high-end ceramic gears and attempts to provide an insight on defining the design envelope of such gears to counter the main disadvantages. The increase of the normal pressure angle beyond the 25° limit set by ISO 6336 is primarily investigated, since in minimizes the tensile tooth root stresses, while also increasing the curvature of the contact surfaces without greatly increasing Hertzian stresses. Comparative assessment of the performance of fully ceramic gear designs versus their conventional steel counterparts is performed through quasi-static FEA simulations to set the basic design requirements for such gears and to promote further investigation of the feasibility of their usage in high power density applications.

Bistable composites with intrinsic pneumatic actuation and non-cylindrical curved shapes

This study presents a novel mechanically-prestressed laminate with non-cylindrical shapes and pneumatic actuation. A third-order analytical model is proposed to determine the laminates’ quasi-static responses to different prestrains with arbitrary θ and pressures. Three laminates are fabricated to validate the model. Model-based sensitivity studies reveal the bistability response to multiple design factors, including the angle of non-orthogonal prestress, prestrains, and pneumatic pressure.

Experimental study on the acoustic wave propagation characteristics of bedding shales under changes in temperature and pressure

To determine the acoustic wave propagation characteristics of bedded shales under different confining pressures and temperatures, shales from the Longmaxi Formation in the Sichuan Basin are taken as research objects. Based on ultrasonic experiments, the acoustic wave propagation properties of shales with different bedding angles are investigated. The effects of the confining pressure, temperature, and bedding angle on the acoustic velocity, attenuation coefficient, and acoustic anisotropy coefficient are analyzed. Based on the results, an acoustic velocity prediction model for bedded shales considering the confining pressure, temperature, and bedding angle is established. The experiments show that, for confining pressures from 0 to 50 MPa and temperatures from 20 to 100 °C, the acoustic velocity of the shales increases with increasing confining pressure and decreases with increasing temperature and bedding angle. The attenuation coefficient of the shales exhibits a decreasing trend with increasing confining pressure, but increases with increasing temperature and bedding angle. The acoustic anisotropy coefficient of shale gradually decreases with increasing confining pressure, but increases with increasing temperature and bedding angle. The acoustic velocity prediction model for in-situ bedded shales established in this study has a high level of accuracy. The relationship between the acoustic anisotropy coefficient and the bedding angle is satisfied by a binomial equation. The relationship between the acoustic anisotropy coefficient and the confining pressure and temperature follows a binary linear logarithmic equation.

Evaluating Tire Tread Wear and Its Dependence on Tire Working Conditions by Using the Finite Element Method and Archard’s Wear Theory

ABSTRACT The tire industry still spends a considerable amount of resources on indoor and outdoor tests during the product development stage. Virtual tests provide conditions to complete this step faster, saving both money and time. Considering that life span and mileage are important issues, especially for truck tire consumers, virtual wear analyses provide valuable information that helps engineers to improve their products. This study aims to exemplify a way to predict tread band wear using the finite element method approach and Archard’s wear theory. In addition, it shows the importance of following the vehicle maintenance program as it has an impact on how long the set of tires will last. Tread wear simulation is implemented through user subroutine and adaptive meshing technique, whereas friction energy is calculated using a steady-state analysis at selected working conditions. Data collected from outdoor experiments provide the necessary information to check and validate the analysis. The impact of the lack of appropriate vehicle maintenance on tire wear is evaluated by changing some boundary conditions of the model such as load, inner pressure, and camber and toe angles. The simulation results show good agreement with the information found in the literature.

MODELLING AND TESTING OF SYNCHRONOUS MOTORS WITH PERMANENT MAGNETS

Applying a layer of polymer material to the fabric gives new characteristics to the base fabric. The resulting coated material may have functional properties such as resistance to dirt, liquid penetration, etc., or the finished leather products may have a completely different aesthetic appeal. The choice of the coating method depends on several factors: the type of substrate, the polymer formula and its viscosity for coating, the desired final product and the accuracy of the coating, the economy of the process. In the conditions of modern enterprises, it is advisable to use the spray application method for the application of polymer coatings due to the fact that the roller and brush methods do not provide the opportunity to operate with different forms of parts, and volumetric application is not always economically feasible. Jet application of the material is similar to spraying, but for polymer coatings, the temperature value is important, which in this case is difficult to control. Therefore, it is advisable to use the spraying method for applying polymer coatings The paper presents the results of preliminary research on the breakdown of polymers into droplets. The shape of the flow coming out of the nozzle was determined, and based on this, a model describing this process was developed. It is shown that for a sheet of polymer flow, its thickness is inversely proportional to the distance from the nozzle and K=2sx, calculated knowing the thickness of the sheet at some distance x from the nozzle. For a “hollow cone” spray nozzle with taper angle, θ and orifice diameter, δ and sheet thickness h, at the nozzle exit, an equation for the flow length break was derived. The obtained results of the calculations of the dependence of the droplet diameter on the flow rate. A spray test was carried out in different modes. The ratio of the length of the jet to the length of the gap L serves as the beginning of the decay mode. It was determined that the ratio of the length of the jet to the length of the gap of the canvas when reaching 1 can be a reasonable criterion for evaluating the determination of the limits of the spraying mode. For a good spraying (for example, tearing of the web), small values of the ratio of the length of the jet to the length of the tearing of the web are necessary. This is achieved due to low surface tension, high gas density, high injection pressure (velocity) and large nozzle exit angles. The obtained results can be used for the design of sprayers and their modes of operation.

Thermophysical and thermodynamic properties of NaF-BeF2-UF4-ZrF4 fuel salt

Molten NaF-BeF2-UF4-ZrF4 salt is a fuel-salt candidate for molten salt reactors (MSRs). However, properties of the salt, which are key parameters for a MSR design, were not well-studied and reported. The present study measured and analyzed its phase transition, specific heat capacity, vapor pressure, and contact angle with nuclear grade graphite as a function of temperature. The methodologies used in the study were validated by measuring the properties of other salts or metals that have been well studied. Therefore, the present study not only provides important data about properties of molten NaF-BeF2-UF4-ZrF4 salt but also develops and/or validates the property measurement methods.

Combustion stability for early and late direct hydrogen injection in a dual fuel diesel engine

The paper presents an analysis of the experimental results of direct hydrogen injection in a dual-fuel diesel engine. The test object is a four-cylinder, four-stroke ADCR engine. An analysis of the following parameters was carried out: indicated mean effective pressure, peak pressure, angle of maximum pressure and released heat. Statistical analysis of the obtained results was carried out for each cylinder separately for four different hydrogen doses. Both early and late direct hydrogen injection were analyzed. The significance of the differences for each of the analyzed parameters and type of injection was determined. The stability of the combustion process was evaluated using the coefficient of variation CoV(IMEP).

Effect of Tire Inflation Pressure and Wheel Front Toe Angle on Fuel Consumption of a Light-Duty Vehicle

Effect of Tire Inflation Pressure and Wheel Front Toe Angle on Fuel Consumption of a Light-Duty Vehicle

Stress intensity factors of partially compressed centrally cracked disk with frictional crack surfaces

This work analytically calculates mixed-mode I/II stress intensity factors for an inclined central frictional crack in a Brazilian disc partially compressed with a uniform pressure. Wide-range controlling parameters are invoked. The analyzed parameters include the pressure angle, relative crack length, crack inclination, and friction coefficient between the two crack surfaces. For partially compressed discs, there exists a critical pressure angle at which a crack with any angle will experience pure II loading. This critical pressure angle is not affected by friction and decreases as the crack length increases. A crack of any angle becomes inactive once the pressure angle exceeds another critical value of pressure angle. This value decreases as the friction coefficient or/and crack length increases. The handling of frictional surfaces of short cracks is simplified. The analysis defines the conditions to have (1) the crack opened and (2) the two crack surfaces sticking. A close agreement is achieved with relevant findings in previous relevant investigations. The present results do not exist in relevant literature and are valuable in solving fracture mechanics problems of significance in relation to crack path in cracked brittle materials.

Determination of Transmission Error and Mesh Stiffness in Spur Gear Pair using CAD-FEM Integration Approach

Unwanted sound and sensations are key sources of excitations in gear drives. They developed because of Transmission Error (TE). TE is a consequence of geometric or engineering flaws like profile/pitch error etc. or distortions like spall, indentation, crack, rubs etc. arising due to the diverse load conditions. These distortions and various gear parameters like number of teeth, contact ratio, module, pressure angle etc. have huge effects on TE and produce changes in mesh stiffness. This demands to investigate the effects of these parameters on TE and mesh stiffness for the avoidance or early finding of causes of malfunctions in the transmission system using computer models using CAD-CAE (FEM) software. In this paper the TE and mesh stiffness is determined using CAD-FEM integration approach and the impact of some of the gear parameters, tooth tip radius and geometric flaw-pitch error is analyzed. The modeling of spur gears & assembly to form gear pair is done in CAD software SOLIDWORKS. The gear pair formed is then introduced into FEM software Ansys for simulation using transient structural analysis method to find angular deformations and then TE and mesh stiffness. Several charts are drawn amongst rotation angle of one of the gears (driver gear) and TE/mesh stiffness for different gear parameters. The work demonstrated the use of CAD-CAE integration approach and point out that all these parameters affect TE and mesh stiffness in a meaningful way.

Modeling and compensation of twist error of helical gear with lead modification in continuous generating grinding

A compensating method based on continuously deflecting the dressing wheel is proposed to eliminate the twist error of the lead modification tooth flank. Combining the tooth flank contact trace and the lead modification curve, the mechanism of the twist error is first analyzed. Second, a tooth profile error model is developed at the upper and lower end faces. The flank twist amount is calculated by subtracting the tooth profile error at the upper and lower end faces. Then, the profile slope deviation of the twisted tooth flank is transformed into the pressure angle deviation of the tooth profile, and the method of compensating the pressure angle of the worm wheel is applied to eliminate the pressure angle deviation of the tooth flank caused by the twist error. The grinding partition of the worm wheel is performed according to the diagonal grinding process, and a worm wheel dressing method for continuously deflecting the dressing wheel is provided to compensate for the twist error. Finally, the continuous generating grinding experiment of the lead modification gear verifies the feasibility of the proposed method.

Asymmetric/Symmetric Glass-Fibre-Filled Polyamide 66 Gears—A Systematic Fatigue Life Study

This work aims to determine how the behaviour of symmetry and asymmetry can affect the bending fatigue performance of glass-fibre-filled PA66 gears. Gears with pressure angles ranging from 20° to 35° at increment steps of 5° on the driving side and 20° on the coast side are considered. Temperature in the gear contact region was recorded at various torque levels to examine the effects of increasing torque on different polymer test gears and gear profiles. According to the findings of the fatigue test, the PA66/40GF gear demonstrated a 23% increase in fatigue life when the pressure angle on the drive side was increased from 20° to 35° and a 38% increase when a torque of 0.8 Nm was applied. When put under bending stress levels ranging from 13.11 MPa to 32.76 MPa, the performance of the PA66/40GF gear with a 20–35° gear profile was exceptional. However, for a torque of 2 Nm, this test gear was unable to withstand and cross 106 stress cycles. Along with the inclusion of glass fibre, the increased driving-side pressure angle improved the fatigue performance of polymer test gears. This leads to the conclusion that PA66/40GF is a better material for gears.

Design and Optimization of a Novel Electronic Mechanical Brake Actuator Based on Cam

The electronic mechanical brake (EMB) is considered an ideal actuator for brake-by-wire systems. We applied the negative radius roller cam mechanism as the clamping mechanism of the EMB, solving the problem of large size, poor load-bearing capacity, and the inefficiency of the existing EMBs. When designing a cam as a clamping transmission mechanism, it is necessary to take the pressure angle, contact stress, motion law, etc., as goals and constraints. Existing design methods cannot easily solve this problem. Therefore, we propose a new analysis method from the cam profile and combine it with an improved particle swarm optimization (PSO) algorithm to design the cam profiles. This method can handle various complex goals and constraints of the EMB and obtain the required negative radius roller cam profile. Finally, the logical consistency of the profile-based analysis method was verified, and the EMB design objectives and accuracy were compared using ADAMS. Under the same conditions, the result showed that the optimized cam mechanism requires only 40.52% motor power and only 65.65% clearance elimination time compared to the EMB with the lead screw mechanism.

Structural design of flexible wheel of harmonic reducer based on efficiency improvement

With the rapid development of robot, the efficiency of harmonic reducer is more and more demanding. The transmission efficiency model of harmonic reducer under variable speed and load is established in this paper. The accuracy of the model is verified by experiments. The model can solve the friction coefficient of harmonic reducer, which provides a new method for calculating friction coefficient. In order to improve the efficiency of harmonic reducer, this paper analyzes the influence of flexible wheel structure size on transmission efficiency. The transmission efficiency of harmonic reducer can be improved by reducing the thickness, length and pressure angle of the flexible wheel. The efficiency decreases with the increase of speed and increases with the increase of load. In the case of the same dividing circle diameter, reasonable flexible wheel structure design can improve the transmission efficiency under variable speed and load. The maximum difference of transmission efficiency of different flexible wheel structure design can reach 17.88%. This work provides theoretical guidance for the structural design of harmonic reducer to improve efficiency.

Experimental characterization of shock-separation interaction over wavy-shaped geometries through feature analysis

A canonical wavy surface exposed to a Mach 2 flow is investigated through high-frequency Pressure Sensitive Paint, Kulite measurements, and shadowgraph imaging. The wavy surface features a compression and expansion region, two shock-boundary layer interactions, and two shock-separation regions. The unsteady characteristics of the wall pressure and shock angles are presented, demonstrating an increase in the amplitude of the instabilities when traveling through the shock systems. The pressure sensitive paint measurements confirm a two-dimensional flow pattern with small transversal unsteadiness. Higher-Order Dynamic Mode Decomposition and Spectral Proper Orthogonal Decomposition are implemented to dissect the different flow features, revealing several dominant low-frequency and medium-frequency phenomena. The separation region appears at frequencies with Strouhal numbers between 0.01 and 0.2, confirmed by the frequency content in the local pressure measurement using Kulites and the pressure sensitive paint.

Nonlinear Dynamic Modeling and Analysis for a Spur Gear System with Dynamic Meshing Parameters and Sliding Friction

The performance of gear systems is closely related to the meshing parameters and sliding friction. However, the time-varying characteristics of meshing parameters caused by transverse vibration are usually not regarded and the sliding friction has always been ignored in previous studies. Therefore, the influence of the transverse vibration on meshing parameters and sliding friction have not been considered. In view of this, a nonlinear dynamic model for a spur gear system is proposed. The dynamic meshing parameters (pressure angle, backlash, etc.) and the effects of the variations of these parameters on the dynamic mesh force (DMF) and sliding friction are emphasized. The differential equations of motion are derived by the Lagrange method and solved by the Runge–Kutta method. Then, the input speed and friction coefficient are used as control parameters to compare the dynamic responses of the new and previous models. The results show that the meshing parameters and sliding friction are affected by transverse vibration, leading to distinctive nonlinear dynamic responses. This paper can provide a basis for further research and give a better understanding of system vibration control.

Effect of Back Pressure and Divergence Angle on Location of Normal Shock Wave

Effect of Back Pressure and Divergence Angle on Location of Normal Shock Wave

Prediction of Fracture Initiation Pressure for Slotting-Directional Hydraulic Fracturing Based on the Anisotropy of Coal

Abstract The precise estimation of fracture initiation pressure is crucial for the effective implementation of slotting-directional hydraulic fracturing methods in coal seams. Nonetheless, current models fail to account for the impact of the morphology of the slotted borehole and the anisotropy of coal. To address this issue, a three-dimensional model was created in this study, which simplified the slotted borehole as an elliptical medium and the coal as an orthotropic medium. Laboratory experiments were conducted to validate the model, and the findings regarding the changes in fracture initiation pressure and deflection angle due to various factors were presented. The calculated outcomes of the proposed model align with the observed pattern of the experimental results, and the numerical discrepancy falls within the acceptable range of 7%, showcasing the precision of the proposed model. A rise in the horizontal stress difference and a decrease in the depth of the slots will result in an elevation of the fracture initiation pressure and deflection angle. In addition, the slotting angle will impact the distribution pattern of the fracture initiation pressure and deflection angle, underscoring the significance of these factors in the hydraulic fracturing of slotted boreholes.