Straight-line Profile Research Articles

Experimental and Theoretical Study on Forming Film Properties of Hollow Cylindrical Rollers

Bending deformation of a hollow cylindrical roller (HCR) was calculated by curve bending theory and slice technology. Furthermore, an elastohydrodynamic lubrication (EHL) model involving hollow rollers was established by coupling the finite line EHL model and bending deformation. Measurements of film thickness for hollow rollers were carried out by using a line-contact optical EHL test rig, and the experimental data and theoretical results agreed well with each other. For a roller with a straight-line profile, the hollow structure could reduce pressure peak at the roller ends, but the edge effect was still present. The film thickness at the ends unfortunately could not be improved by such hollow structures, unless a profile modification for the operating surface is designed.

Contact stresses and bending stresses analysis of curvilinear cylindrical gears generated by a face-milling cutter with parabolic profile

Curvilinear cylindrical gear drives are a type of parallel-axis gear set, and the longitudinal geometrical shape of the gear teeth is a part of the circular arc. The main purpose of this paper is to explore the influence of modification amount and assembly error on con-tact stress and bending stress. This study proposes a curvilinear cylindrical gear drive with a parabolic profile. The gear tooth surfaces are generated by a face-milling cutter with a straight-line profile, and the matching gear tooth surfaces are generated by a face-milling cutter with the parabolic profile. Initially, mathematical models of the gear set are described based on the theory of gearing. The finite element method and tooth contact analysis algorithms were applied to contact and bending stress analyses. Finally, four numerical examples are provided to illustrate the mechanical performance of the curvilinear cylindrical gear drive with the parabolic profile. The study results show that curvilinear cylindrical gear drives have superior mechanical performance compared to those with a straight-line profile.

Geometrical profile of cohesive-frictional soil slopes for optimal stability

: In this study, finite element method with strength reduction technique is employed to study the stability of slopes with non-straight line profiles comprises three segments. According to this method, the strength parameters are reduced until the slope becomes on the verge of failure. A software called (Optum G2) is used to analyze the geometrical and mechanical parameters. The effect of the geometrical shape of the slope with specific limitations on the factor of safety (FOS) has been investigated to find the corresponding profile configuration that provides maximum stability. The profile (slope face geometry) has been divided into three straight lines (segments) with different lengths. The study involved the soil cohesion (c), angel of internal friction (∅) and the angle of the imaginary straight line linking the slope toe with slope crest (β) called herein slope inclination. The main results showed that using the three segments facing profile can increase the factor of safety (FOS) by up to 15% in comparison with the corresponding slopes of straight line profile. Design charts has been introduced to be utilized by engineers and practitioners to obtain the geometrical parameters for the optimal profile as well as the expected improvement percentage in factor of safety.

Circular-Arc Radial Cams with One Connection Arc

This paper deals with the geometric and kinematic analysis of the circular-arc profile cams with one connection arc. If the maximum lift of the follower is required, it is shown that it is possible to connect two circular-arcs – that are defined by center of curvature and radius – through a single circular-arc, and the connection points result. But, if the connection points of two given circular-arcs of the cam profile are required, at least two circular-arcs are needed to connect them. The specific equations for the geometric analysis for one circular-arc profile are described. Also, for two mechanisms, one with straight-line profile and another with one circular-arc connection profile, the geometric and kinematic analysis and simulations of the movements using SolidWorks and ADAMS programs are presented

Performance evaluation of a novel single-screw compressor and expander design

Single-screw machines have seen significant development and improvement over the last decades and they are currently employed as both compressors and expanders in several applications. The correct functioning of the machine heavily relies on the meshing between the gate rotors and the central rotor which is directly linked to the precision of the manufacturing process to avoid unexpected wear of the tooth profiles. It is well known that the wear of the gate rotor tooth profiles over time is one of the limiting factors with respect to twin-screw machines. To this end, a number of studies have been reported in the literature about improved tooth profiles. For instance, the conventional straight-line profile has been replaced by multi-column tooth flank designs to enlarge the contact surface. However, the manufacturing process is still based on CNC machines with associated challenges.In a previous study, the authors proposed and modeled a new tooth profile design to overcome the aforementioned limitations. In particular, 3D printing technique was utilized to manufacture the non-conventional tooth design. A geometry model has also been developed to calculate the sealing lines, groove volume curves, and surface areas of the new design.In this work, a detailed mechanistic model of the single-screw machine is exercised to compare the conventional straight-line profile with the newly proposed tooth profile. Particular emphasis is given to the effect of seal lines on the leakage flows. Furthermore, the design implications of the new tooth profile on internal volume ratio, porting, and displacement are also discussed.

Novel approach to single-screw compressors and expanders design**This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript,

Single-screw machines are currently employed as both compressors and expanders in vapor compression systems and organic Rankine cycles (ORCs), respectively. The working principle of single-screw machines is based on the simultaneous meshing of two starwheels with one central grooved rotor. The performance of the machine is heavily affected by the wear of the tooth meshing profile after several hours of running. In order to improve the wear resistance of the conventional straight-line profile, multi-column tooth flank designs have been introduced and investigated by several researchers. Cylindrical multi-column envelope profiles are able to distribute the local contact over a larger surface area reducing the wear of the tooth flank profile. Nevertheless, the manufacturability of such profiles is directly linked to the accuracy and limitations of CNC machines.In this work, an attempt is made to overcome the aforementioned limitations. To push the boundaries of possible tooth and rotor profile designs, 3D printing is utilized as manufacturing technique. Such approach allows the investigation of more complex designs that improves the sealing lines during the meshing process.A detailed geometry model based on polygon intersections is utilized to calculate the sealing lines, groove volume curves, and surface areas of the different designs. As a result of this study, a novel rotor design has been manufactured.

Spiral Sampling Method for Quantitative Estimates of Joint Roughness Coefficient of Rock Fractures

Abstract Representative sampling of surface roughness is essential for reliable and consistent estimates of joint roughness coefficients (JRCs) by quantitative formulations. The most commonly used sampling method is the straight-line profiling along a predetermined shear direction. Because of anisotropy and nonuniform distribution of roughness features on natural joint surfaces, this method may work well only when the potential shear direction is known or can be predicted. However, there are no guidelines for the density of parallel straight-line profiles and how these can be synthesized into a representative profile. This article presents a spiral sampling method that addresses the shortcomings of the straight-line method. The roughness parameters derived from the spiral scanlines are closely correlated with the JRC values back-calculated from direct shear tests.

Experimental investigation of EHD grease lubrication in finite line contacts

The objective of this study was to investigate the grease-lubricated film-forming mechanisms in the finite line contact and to improve the grease-lubricated finite line contact’s film-forming capacity. An elastohydrodynamic lubrication (EHL) test rig with two interferometry microscopes, which could simultaneously monitor two different contact locations in the finite line contact, was constructed in order to study the influences of the grease thickener formulation on the film thickness and lubrication condition. By using the relative light intensity method, the thickness maps of the grease-lubricated film were calculated from the interferometer images captured by the two microscopes. The test results revealed that the grease thickener’s formulation had remarkable effects on film formation and the perturbation of film thickness. For the lithium-based grease, the film’s thickness near the two ends of the roller was prone to severe perturbation caused by the conglomeration of clumps that were hard to shear. For the aluminum-complex-based grease, the fibers tended to accumulate in the middle of the roller rather than at the two ends. The urea-based grease could be easily sheared into smaller particles. In addition to the straight-line profile rollers, the logarithmic profile rollers were tested and found to effectively enhance the axial grease flow, increase the axial shear stress, and thus shear more fibers into particles within the contact area.

Micro-indentation of a Conical Rigid Wedge by Numerical Slip-line Field Theory: A Hybrid Approach

Slip-line field theory is generally applied for determination of plastic flow lines, stress, velocity of flow and plastic work. In this work, micro-indentation of a conical wedge into an infinitely long block has been analysed by numerical simulation of slip-line field equations. Though the previous works in this field considered straight line profile of the bulged material around the wedge, experimental results showed that the free surface of the material is not actually straight but curvilinear in shape. This work computes the slip line field considering the free surface separately as linear, or parabolic, or circular in nature. The combinations of linear and parabolic as well as linear and circular profiles are also studied. Results obtained in this work indicate suitability of the method showing good matching with the results reported in published literature.

Revisiting the definition of the electronic chemical potential, chemical hardness, and softness at finite temperatures

We extend the definition of the electronic chemical potential (μe) and chemical hardness (ηe) to finite temperatures by considering a reactive chemical species as a true open system to the exchange of electrons, working exclusively within the framework of the grand canonical ensemble. As in the zero temperature derivation of these descriptors, the response of a chemical reagent to electron-transfer is determined by the response of the (average) electronic energy of the system, and not by intrinsic thermodynamic properties like the chemical potential of the electron-reservoir which is, in general, different from the electronic chemical potential, μe. Although the dependence of the electronic energy on electron number qualitatively resembles the piecewise-continuous straight-line profile for low electronic temperatures (up to ca. 5000 K), the introduction of the temperature as a free variable smoothens this profile, so that derivatives (of all orders) of the average electronic energy with respect to the average electron number exist and can be evaluated analytically. Assuming a three-state ensemble, well-known results for the electronic chemical potential at negative (-I), positive (-A), and zero values of the fractional charge (-(I + A)/2) are recovered. Similarly, in the zero temperature limit, the chemical hardness is formally expressed as a Dirac delta function in the particle number and satisfies the well-known reciprocity relation with the global softness.

Design of the conjugated straight-line internal gear pairs for fluid power gear machines

The conjugated straight-line internal gear pair, including a pinion with straight-line profile and an internal gear with profile conjugated to the pinion profile, is the key components to the conjugated straight-line internal gear pumps. Truninger [ Truninger gear pump. Patent 3491698, USA, 1970] pointed that this kind of gear pairs leads to a very small trapped volume, which is 10 times smaller than that of the conventional involute internal gear pumps. Therefore, it can yield significant reduction in noise levels of the pumps. However, to the authors’ knowledge, there is no research on the design of these gear pairs until now. First, our study describes the straight-line profile of the pinion mathematically with definitions of some geometric parameters. Second, according to the theory of gearing, the mathematical models of the rack-cutter and the conjugated internal gear are derived. Then, the condition to avoid overcutting is obtained for the generation of the pinion by a rack-cutter. Finally, the condition to avoid interference in the internal gear pair is derived as a non-linear equation system and an algorithm is developed to find a numerical solution. Two examples are presented to demonstrate how to determine tooth numbers of the internal gears for avoiding interference. It is hoped that the study in this article should be helpful to the designers of the conjugated straight-line internal gear pairs. Moreover, it could provide a prepared knowledge for the researchers to investigate the performances of the fluid power gear machines, pumps, and motors, with the conjugated straight-line internal gear pumps.

A new performance based design approach for moment resisting frames

This paper proposes a simple, relatively new elastic–plastic design method for earthquake resisting frames that enables the engineer to directly control the essential aspects of the future behavior of certain structural forms, through basic statics and imposition of predetermined modes of behavior. The method is particularly applicable to the preliminary design of low to mid-rise buildings where the fundamental period of vibrations dominates the response of the system to seismic loading. The focus of this paper is directed towards simplified but accurate manual design rather than sophisticated structural analysis. The premise of the proposed solution is that the constituent elements of the system can be selected in such a way as to cause both the elastic as well as the plastic drift functions to follow linearly varying straight line profiles during all phases of loading. Frameworks designed by this method act not only as structures of uniform response (UR), i.e., uniform strength and stiffness, where the demand/capacity ratios of its members remain the same, both before and after formation of plastic hinges, but they also result in unique solutions, satisfying the prescribed yield criteria, the boundary support, as well as the of static equilibrium conditions.

Involute-Based Screw Driver Profiles With High Load Capacity

In this paper, involute profiles are used for the design of screw driver and screw heads instead of traditional straight line profiles to increase their load capacity and durability. New screw driver profiles have lower contact stress than traditional screw drivers due to the surface contact between screw driver and screw head. This enables the involute screw drivers to sustain higher load capacity than traditional screw drivers and reduce the material failure at the tip portions for both screw drivers and screw heads. Four different designs of screw driver profiles are provided for illustration.

Determination of tool nose radii of cutting inserts using machine vision

PurposeThe nose radii of cutting inserts are normally measured using a profile projector or toolmaker's microscope. Since only a sector of a circle is available for the measurement using such instruments, the radii determined from these methods are inaccurate. The purpose of this paper is to present an alternative method of determining the nose radii more accurately using machine vision.Design/methodology/approachThe 2D images of the cutting inserts were captured using a CCD camera with the aid of back lighting. The tool nose center in each digitized image was located based on the tool geometry. The curved nose profile was transformed into a linear profile using polar‐radius transformation. The nose radius was then varied within ten pixels of the nominal radius and the average deviation from a straight line profile in the nose region in the polar‐radius plot was evaluated. The radius corresponding to the minimum average deviation is identified as the most accurate radius value.FindingsFor the 15 simulated images of cutting inserts tested, the error in radii determine by the proposed method varied from −4.9 to 3.7 percent. But, the radii were about 9 to 22 percent higher than those measured using the profile projector on commercially available inserts. The radii measured using the profile projector was closer to the nominal radii with an average deviation of −3.2 percent compared to those measured using the proposed method.Research limitations/implicationsThe cutting inserts must be clean and free from dust particles when capturing the images; and the insert must be aligned accurately so that the plane of the nose profile is perpendicular to the optical axis of the CCD camera.Practical implicationsThe proposed method can be used to determine the nose radii accurately. If the exact nose radius of an insert is known, the tool path can be programmed precisely to obtain high‐dimensional accuracy in the finished product.Originality/valueThe paper shows how a new method of determining the tool nose radii of cutting inserts more accurately compared to the conventional methods, based on a sector of the nose profile, has been developed.

Synthesis and analysis of coupler curves with combined planar cam follower mechanisms

Cam and follower mechanisms are widely used to convert a rotary input motion into a controlled reciprocating or oscillating motion as output in machines or robots. As this mechanism has an ability to provide unlimited variety of output motions. Many works are done on the synthesis of coupler curves or path generation using four bar mechanism. The present work investigates the alternative way of dealing with the path generation problems of industrial application by using cam mechanisms. Proposed a new mechanism which comprises four bar and cam follower mechanism, these mechanisms are combined together to obtain a single-input combined cam mechanism (CCM). Dimensional synthesis has been carried out by guiding the coupler point along predefined path (ellipse or straight line) of profile cutting machine. One of the objectives was to compare the path of coupler in four bar and CCM. Further, kinematic simulation of both mechanisms was performed to estimate the error and validate the proposed methodology. Results show that coupler point follows same path as ellipse or straight line profile in both mechanisms. Proposed CCM successfully applied to the complex path generation problems of profile cutting machine like square, circle and figure eight profiles. A method of kinematic analysis of proposed mechanism was also discussed. Finally, dynamic stability and separation of cam follower contact was simulated by using Matlab Simulink tool. Results show that proposed CCM was found stable from kinematic and dynamic point of view. International Journal of Engineering, Science and Technology, Vol. 2, No. 6, 2010, pp. 231-243

超音波によるパンチの連続打撃式穴抜き加工

In this study, a simple and effective piercing method using ultrasonic vibration is newly developed to produce small holes with a fine sheared surface. This method uses two independent units : a vibration unit and a piercing unit. In the piercing unit, a coil spring is placed between the punch and the guide-bush to support the punch in a floating state. The punch is pushed into the target material by an ultrasonic vibration horn at a constant speed. When the ultrasonic vibration is transferred to the punch by the horn, the punch extends out and hits the material, and then rebounds to collide with the horn. This back-and-forth shuttling motion of the punch is repeated until the material is penetrated. Commercial stainless steel thin sheets are used as the test material. By optimizing the experimental conditions in the shuttle piercing process, the fractured zone on the sheared surface is almost eliminated. It has been experimentally determined that the punch shuttling motion effectively suppresses crack initiation and produces microholes with an almost straight-line profile in an axial direction around the hole exit portion.

On the incorporation of the non-steroidal anti-inflammatory naproxen into cationic O/W microemulsions

Microemulsions (ME) containing hexadecyltrimethylammonium bromide (HTAB)/ethanol as surfactant, isopropylmyristate (IM) or butylstearate (BS) as oil phase and aqueous buffer were studied. Pseudo-ternary phase diagrams of the investigated systems were obtained at constant surfactant/cosurfactant molar ratio (1:5) by titration in order to characterize the proportions between the components to obtain clear systems. Oil in water microemulsions were prepared in a wide range of phase volume ( ϕ). UV–vis absorption spectra of naproxen at pH 5.5 showed that the solubility of Np increases significantly in the presence of O/W ME in high phase volumes. For both, IM and BS microemulsions, the dynamic light scattering experiments showed that the size of the oil droplets remains constant in low values of ϕ, increasing abruptly in high ϕ values. Phase solubility study revealed that for both IM and BS microemulsions, the drug incorporation followed a straight-line profile in all range of ϕ. The data could be analyzed through the phase-separation model and the association constants ( K) calculated varied from 27 to 90 M −1, depending on the pH and on the microemulsion oil phase.

Time Dependent Operator-split and Unsplit Schemes for One Dimensional Premixed Flames

This paper is concerned with a study of an operator split scheme and unsplit scheme for the computation of adiabatic freely propagating one-dimensional premixed flames. The study uses unsteady method for both split and unsplit schemes employing implicit chemistry and explicit diffusion, a combination which is stable and convergent. Solution scheme is not sensitive to the initial starting estimate and provides steady state even with straight line profiles (far from steady state) in small number of time steps. Two systems H2-Air and H2-NO (involving complex nitrogen chemistry) are considered in presentinvestigation. Careful comparison shows that the operator split approach is slightly superior than the unsplit when chemistry becomes complex. Comparison of computational times with those of existing steady and unsteady methods seems to suggest that the method employing implicit-explicit algorithm is very efficient and robust.

Tooth Profile Analysis of Circular-Cut, Spiral-Bevel Gears

An analysis of tooth profile changes in the transverse plane of circular-cut, spiral-bevel crown gears is presented. The analysis assumes a straight-line profile in the midtransverse plane. The profile variation along the centerline is determined by using expressions for the variation of the spiral angle along the tooth centerline, together with the profile description at the midtransverse plane. It is shown that the tooth surface is a hyperboloid and that significant variations in the pressure angle are possible.

直線歯形内歯車に関する研究 (第1報)

The advantages of an internal gearing may be summarized briefly : 1. The gearing is compact. 2. The tooth surface is highly durable. With such advantages on one hand, the internal gearing has limitations on the other hand. The biggest difficulty is cutting and grinding the internal gear teeth accurately. Accordingly, it is the purpose of this study to produce a pair of tooth profiles which are easily and accurately machined and which engage with an allowable transmission error. In this gearing, the teeth of the internal gear are made with straight line profiles, and the teeth of the mating pinion are made with various kinds of profiles approximating theoretical ones. These tooth profiles can be machined by standard machine tools. In this report, six kinds of approximate tooth profiles of mating pinion are examined. The deviation between the approximate and theoretical profiles is calculated and compared with each other. By this comparison, it is made clear that in the six kinds of tooth profiles, the circular arc which is obtained by the least squares method, has the least deviation of all and holds a fairly good approkimation under various specifications of gearing. And it is recognized that a designer needs to choose the most suitable value of inclination angle of an internal gear, taking the effective tooth depth and the deviation of approximation into consideration.