Shear Force Coefficient Research Articles

Research on the tool influence function characteristics of magnetorheological precession finishing (MRPF).

Magnetorheological finishing (MRF) technology is characterized by its high convergence rate and minimal subsurface damage as advantages. However, the non-Gaussian type tool influence function (TIF) it generates may cause mid-frequency errors and oriented surface texture issues. Magnetorheological precession finishing (MRPF) technology capable of generating Gaussian-like removal functions, lacks a clearly defined removal function model. This study acquired polishing spots in tilted polishing, discrete precession, and continuous precession modes via fixed-point polishing experiments. Using Multiphysics simulation software, stress and velocity distribution in the contact area were simulated. A TIF model, incorporating the synergistic effects of pressure and shear force and multiple influence coefficients, was proposed based on velocity characteristics across the three modes. To accurately predict the TIF, surface topographies with varying coefficients were constructed using this model, analyzing the coefficients' impact on the TIF profile. Optimal coefficients were identified using a least fit error algorithm. Further analysis of the TIF's internal textures revealed that the precession mode of MRPF yields superior surface quality, thereby elucidating the material removal mechanism of MRPF and laying a theoretical groundwork for advancing processing technologies.

Proposal for vertical distribution of seismic design load and equivalent isolation ratio for seismically isolated buildings with multiple types of dampers: Vertical distribution of seismic design load for seismically isolated buildings corresponding to diversity of seismic isolation devices, part 2

AbstractAs previously reported, we have proposed a vertical distribution of seismic design load for seismically isolated buildings (SIBs) corresponding to diversity of seismic isolation devices such as hysteretic dampers and velocity‐dependent dampers. This proposed seismic design load is obtained from the relationship between response amplification caused by higher mode responses and the isolation ratio which represents structural characteristics of SIBs. In this paper, we build a concept of the equivalent isolation ratio which has applicability to various dampers in order to simplify an evaluation formula of vertical distribution of seismic design load. Moreover, an effect of the combined application of various dampers on vertical distribution of shear force coefficient of SIBs is analyzed on the basis of the equivalent isolation ratio.

Determination of force coefficient based on instantaneous forces and linear mechanistic model in ball end milling

Due to the intricate geometry, force prediction in the ball end milling process (BMP) is a challenging task. Cutting forces generated during BMP have an impact on important aspects of machining characteristics such as form error, chatter and vibration, surface finish, tool wear, and dimensional accuracy. These machining problems might be resolved by foreknowledge of the cutting forces. In the present research, a new and quick mathematical model based on the linear mechanistic method is reported to determine the force coefficients. The cutter’s hemispherical part is discretized into five discs along the axis at 0.4 mm uniform spacing in the range of 0.2–1.8 mm. For one cutter revolution, forces in the tangential, radial, and axial directions are measured for each disc to prevent radial runout. The current disc makes use of the preceding disc’s cutting force. To derive the shear and edge force coefficients, these are further divided into edge and shear forces. Validation experiments have been conducted and compared with the simulated forces to assess the predictive power of the developed force coefficient model. The predicted results are found to be remarkably close to the experimental results with an error of 5.5%, −8.6%, and 8.9% at 6631 rpm and 2.8%, −4.4%, and 2.21% at 10,052 rpm in tangential, radial, and axial forces, respectively.

Dynamic Tangential Contact Stiffness and Damping Model of the Solid–Liquid Interface

In order to establish the tangential contact stiffness and damping model of the solid–liquid interface by tangential exciting vibration force under mixed lubrication, the finite difference method was firstly used to solve the average flow equation considering the effect of roughness on the lubrication effect, and the bearing capacity, shear force, and friction coefficient of the oil film were obtained, and thereby the dynamic tangential contact stiffness and damping of the oil film under tangential harmonic excitation were calculated. Then, according to the relationship between the normal deformation and the load of the solid contact microconvex body in the elastic/elastic–plastic/plastic deformation stage, integrating the tangential stick–slip theory, considering the effect of fluid lubrication on the solid contact friction coefficient, and tangential dynamic excitation, the tangential contact stiffness and damping of the microconvex body in three deformation stages were calculated. Furthermore, the dynamic tangential contact stiffness and damping of the solid–liquid interface were obtained by summing the solid surface contact part and the solid–liquid contact part in parallel according to the assumption of microconvex Gaussian distribution. Finally, through simulation analysis and experiments, the variation of the tangential dynamic contact stiffness and damping of the solid–liquid interface with normal load, tangential exciting frequency, and displacement amplitude was revealed and verified.

Effect of Bed Roughness and Negative Step on Characteristics of Hydraulic Jump in Rectangular Stilling Basin

Water flow often releases excess energy after passing through gates and spillways. This energy should be reduced to avoid the destruction of downstream structures. The hydraulic jump, a natural phenomenon, inevitably reduces incoming flow energy. The experiments were carried out in this study to investigate the effect of bed roughness and abrupt negative drops on the characteristics of the hydraulic jump. Also, to investigate the effect of geometric and hydraulic parameters on energy dissipation and location of the hydraulic jump, there was a change in the height of the abrupt drop and roughness for different discharges between 30 and 50 L/s and the Froude numbers were ranging from 4.9 to 9.5. The results showed that increasing the bed roughness causes a reduction of the sequent depth ratio and the relative length of the jump by 16.6% and 20.7%, respectively, and increases the relative energy loss and the bed shear force coefficient by 10% and 31%, respectively. In contrast, increasing the step height causes an increase in the sequent depth ratio and the relative length of the jump by 6.5% and 7%, respectively, and increases the relative energy loss and the bed shear force coefficient by 11% and 3.2%, respectively.

Probability characteristics and extreme value analysis of base shear force of flat roof parabolic solar condenser (FRPSC)

The wind load is the main control load of the parabolic solar condenser (PSC) due to the special structure thereof. To ensure normal operation of the flat roof parabolic solar condenser (FRPSC), the probability characteristics of the FRPSC's upright post base shear force coefficient were explored in the present study, and the extreme values were analyzed. Multi-order moments were used to conduct Gaussian discrimination of the base shear force coefficient of the FRPSC's upright post. Subsequently, three methods were adopted to calculate the extremum of the base shear force coefficient. By analyzing the FRPSC's upright post base shear force coefficient extreme value, the data obtained by the Sadek-Simiu (SAD) extreme value calculation method were found to be the most accurate. Through the analysis of the base shear force coefficient under 250 working conditions, the change rule of the extreme value was obtained, and then compared with the mean base shear force coefficient. The identification standard of whether the base shear force coefficient of the FRPSC's upright post met the Gaussian distributive was determined, and the Gaussian distribution and non-Gaussian distribution areas were divided.

Evaluation of the Modal Coupling Effect in Midstory Isolation Systems Based on Random Vibration Analysis

At present, the midstory isolation (MSI) technology has great potential for application in historical buildings’ retrofitting and multifunction buildings. The coupling effect due to the variability of the location of the isolation layer may amplify the structural seismic response and is required for in-depth analysis. This paper aims to evaluate the magnitude of the coupling effect and delimitate the region of the coupling effect to be considered. Based on the complex mode superposition method, the explicit formulas for calculating the random response of the simplified model are deduced. The root-mean-square (RMS) ratio of the shear force coefficient of the upper isolation system is adopted as the performance indicator to evaluate the coupling amplification effect of the MSI system. Parameter analysis indicates that the coupling region is closely related to the mass ratio and frequency ratio of the upper and lower structures to the isolation layer. In general, the region of the coupling effect to be considered can be divided into two parts according to parameters of frequency ratios, depending on the thresholds of the performance indicator. As the mass ratio of the upper isolation system to the entire system increases, one of the coupling regions shrinks and eventually disappears, indicating that the coupling amplification effect in this region can be neglected under certain conditions. Finally, the time-domain analysis of three representative numerical cases of MSI buildings was performed to verify the reliability of the results obtained from the frequency-domain analysis. The research results can provide technical guidance for the preliminary design of the MSI buildings.

A development method of cutting force coefficients in face milling process using parallelogram insert

This paper presents a modeling method of cutting force and a combination approach of theory and experimental methods in the determination of cutting force coefficients in the face milling process using a parallelogram insert. By the theoretical method, the cutting forces were modeled by a mathematical function of cutting cutter geometry (Cutter diameter, the number of inserts, the insert nose radius, insert cutting edge helix angle, etc.), cutting conditions (depth of cut, feed per flute, spindle speed, etc.), and cutting force coefficients (shear force coefficients, edge force coefficients). By the theoretical method, the average cutting forces in three directions (feed – x, normal – y, and axial – z) were modeled as the linear functions of feed per flute. By the experimental method, the average cutting forces in these three directions were also regressed as the linear functions of feed per flute with quite large determination coefficients (R2 were larger than 92 %). Then, the relationship of average cutting forces and feed per flute was used to determine all six cutting force coefficient components. The validation experiments were performed to verify the linear function of average cutting forces, to determine the cutting force coefficients, and to verify the cutting force models in the face milling process using a cutter with one parallelogram insert. The cutting force models were successfully verified by comparison of the shape and the values of predicted cutting forces and measured cutting forces. These proposed methods and models can be applied to determine the cutting force coefficients and predict the cutting force in the face milling process using a parallelogram insert and can be extended with other cutting types or other insert types

Submerged wall jets on corrugated beds

The present study was performed to investigate the effect of jet Froude number, submergence factor, and boundary roughness on the submerged wall jets. The jet Froude number ranged from 4 to 10, the submergence factor ranged from 0.375 to 3.5, and the relative roughness ranged from 0.25 to 0.50. The results showed that the rough boundary could effectively reduce the hydraulic characteristic parameters. Compared to the smooth bed, the depression in water surface elevation at the beginning of submerged wall jet and the length scales along and vertical the flow direction over the rough bed decreased. The maximum velocity u m of cross-section appeared farther away from the bed, and the decay of it along the distance was faster than that on the smooth bed. The decay of the ratio for the maximum velocity to the nozzle velocity u 1 had two stages along the distance x/L, where L was the longitudinal distance at which u m = 0.5u 1. The first decay stage was like that in a plane wall jet, and the second decay stage was more and more like a free jump with the decrease of Froude number and submergence factor. While the decay of maximum velocity has good similarity using the new length scale L*, where L* was the longitudinal distance at which u m = 0.2u 1. The shear force coefficients for submerged wall jets on corrugated beds were much smaller than those for free jumps on smooth beds, let alone for free jumps on corrugated beds.

Hydraulic jump on rough beds: conceptual modeling and experimental validation

Abstract The aim of this study was to assess and quantify the effect of channel bed roughness on hydraulic jumps based on sound physical theories. Assuming that integrated bed shear stress due to surface roughness changes linearly with supercritical velocity, a novel definition for the shear force coefficient and for roller length were obtained. Experimental findings and Pearson's correlation verify that the developed equations perform reasonably well and they prove that a linear correlation assumption between integrated bed shear stress and supercritical velocity is valid for a Froude number between 1.1 and 9.8. The shear force coefficient is defined in terms of the Reynolds coefficient and the supercritical flow velocity is directly related to the modified Reynolds number. A new analytical equation for roller length as a function of the modified Reynolds number was also developed and validated by using data from the experimental study.

Evaluation of the damage distribution of buildings considering the characteristics of far-fault long-period ground motions

In this study, the damage distribution of buildings was evaluated considering the characteristics of far-fault long-period ground motions. The results demonstrated that the damage distribution trend of the analytical model concentrated on the lower floors with an increase in the seismic wave predominant period and concentrated on the top floor with an increase in the fundamental natural period of the building. The regression line for the yield shear force coefficient distribution, according to the seismic wave predominant period and the fundamental natural period of the building, was calculated using the multiple regression analysis. The curvature of the yield shear force coefficient distribution and the top floor yield shear force coefficient was observed to increase as the fundamental natural period of the building increased and as the seismic wave predominant period decreased.

Optimum Strength Distribution for Structures with Metallic Dampers Subjected to Seismic Loading

A key aspect of the seismic design of structures is the distribution of the lateral strength, because it governs the distribution of the cumulative plastic strain energy (i.e., the damage) among the stories. The lateral shear strength of a story i is commonly normalized by the upward weight of the building and expressed by a shear force coefficient αi. The cumulative plastic strain energy in a given story i can be normalized by the product of its lateral strength and yield displacement, and expressed by a plastic deformation ratio ηi. The distribution αi/α1 that makes ηi equal in all stories is called the optimum yield-shear force distribution. It constitutes a major aim of design; a second aim is to achieve similar ductility demand in all stories. This paper proposes a new approach for deriving the optimum yield-shear force coefficient distribution of structures without underground stories and equipped with metallic dampers. It is shown, both numerically and experimentally, that structures designed with the proposed distribution fulfil the expected response in terms of both damage distribution and inter-story drift demand. Moreover, a comparison with other distributions described in the literature serves to underscore the advantages of the proposed approach.

Distribution of Optimum Yield-Strength and Plastic Strain Energy Prediction of Hysteretic Dampers in Coupled Shear Wall Buildings

The structural behavior of reinforced concrete coupled shear wall structures is greatly influenced by the behavior of their coupling beams. This paper presents a process of the seismic analysis of reinforced concrete coupled shear wall-frame system linked by hysteretic dampers at each floor. The hysteretic dampers are located at the middle portion of the linked beams which most of the inelastic damage would be concentrated. This study concerned particularly with wall-frame structures that do not twist. The proposed method, which is based on the energy equilibrium method, offers an important design method by the result of increasing energy dissipation capacity and reducing damage to the wall’s base. The optimum distribution of yield shear force coefficients is to evenly distribute the damage at dampers over the structural height based on the cumulative plastic deformation ratio of the dissipation device. Nonlinear dynamic analysis indicates that, with a proper set of damping parameters, the wall’s dynamic responses can be well controlled. Finally, based on the total plastic strain energy and its trend through the height of the buildings, a prediction equation is suggested.

Simplified Analysis Method for Parallel Composite Isolation System

The simplified analysis of the parallel composite isolation system (PCI) was carried out based on equivalent linearization method. Through the derivation, the restoring force model expressed in the form of basal shear force and displacement was converted to the basal shear force coefficient and displacement model. According to the new code for seismic design of buildings, the application of the simplified analysis method was illustrated by an example. The results showed that the simplified analysis method could be conveniently and effectively used for preliminary design of the PCI system, which laid a foundation for the popularization and application of the PCI system.

Seismic Design of Coupled Shear Wall Building Linked by Hysteretic Dampers using Energy Based Seismic Design

In coupled shear wall systems, the excessive shear forces are induced in the coupling beams. As a result, in such systems, the coupling beam and the joint of wall-coupling may yield first. The critical concern about the coupling beam is ductility demand. In order to have such ductility, the coupling beams are required to be properly detailed with significantly complicated reinforcement arrangement and insignificant strength degradation during ground motion. To solve these problems and to increase energy dissipating capacities, this study presents an investigation of the seismic behavior of coupled shear wall-frame system, in which energy dissipation devices are located at the middle portion of the linked beam. The proposed method, which is based on the energy equilibrium method, offers an important design method by the result of increasing energy dissipation capacity and reducing damage to the structure. The design procedure was prescribed and discussed in details. Nonlinear dynamic analysis indicates that, with a proper set of damping parameters, the wall’s dynamic responses can be well controlled. Thereafter, an optimized formula is proposed to calculate the distribution of the yield shear force coefficients of energy dissipation devices. Thereby, distributing equal damages through different heights of a building as well as considering the permissible damage at the wall’s base. Finally, numerical examples demonstrate the applicability of the proposed methods.

Derivation of energy-based base shear force coefficient considering hysteretic behavior and P-delta effects

A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom (MDOF) system is approximated by using the modal energy-decomposition. Energy-based base shear coefficients are verified by means of both pushover analysis and nonlinear time history (NLTH) analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation.

Optimization of compression formulation and load of food-grade tracers for grain traceability using central composite design

Food-grade tracers have been developed as an identification technology for grain traceability from original harvest to final destination for transportation. The characteristics of food-grade tracers must be able to satisfy the environmental demands for grain traceability. To optimize the food-grade tracer production process, the effects of direct compression formulation and load on the mechanical characteristics were studied using response surface methodology (RSM) with central composite design (CCD). Among the four tested formulations, Formulations #2 (consisting of 35.00% lactose 100 mesh, 64.50% microcrystalline cellulose 102 and 0.50% magnesium stearate) and #4 (consisting of 38.00% lactose 100 mesh, 50.00% microcrystalline cellulose 102, 11.00% pregelatinized starch and 1.00% magnesium stearate) were selected for tracer production based on their physical properties as powders. The value of Carr’s flowability index was 68 for both Formulations #2 and #4, which was the highest among all the formulations. Therefore, Formulations #2 and #4 also had the best powder flowability. The magnesium stearate ratio (1.00%-3.00%) and pressure (6.00-16.00 kgf) were used as independent variables to detect changes in the breaking rate, peak shear force and friction coefficient of tracers compressed by the selected formulations. The optimal production parameters could be achieved at a magnesium stearate ratio of 2.25% and pressure of 16.00 kgf for Formulation #2 and at a magnesium stearate ratio of 1.02% and pressure of 16.00 kgf for Formulation #4. Under these optimal conditions, the tracers had good impact characteristics (breaking rate), compression characteristics (peak shear force) and frictional characteristics (friction coefficient). Moreover, Formulation #2 was more suitable for production because compared to Formulation #4, its breaking rate and friction coefficient values were lower, and its peak shear force value was higher. Keywords: grain traceability, food-grade tracer, optimization, food safety, formulation, mechanical property, central composite design DOI: 10.25165/j.ijabe.20171006.3531 Citation: Liang K, Zhang L L, Lu W, Okinda C S, Shen M X. Optimization of compression formulation and load of food-grade tracers for grain traceability using central composite design. Int J Agric & Biol Eng, 2017; 10(6): 221–230.

Effect of masonry infill walls with openings on nonlinear response of reinforced concrete frames

Masonry infill walls are unavoidable parts of any building to create a separation between internal space and external environment. In general, there are some prevalent openings in the infill wall due to functional needs, architectural considerations or aesthetic concerns. In current design practice, the strength and stiffness contribution of infill walls is not considered. However, the presence of infill walls may decisively influence the seismic response of structures subjected to earthquake loads and cause a different behavior from that predicted for a bare frame. Furthermore, partial openings in the masonry infill wall are significant parameter affecting the seismic behavior of infilled frames thereby decreasing the lateral stiffness and strength. The possible effects of openings in the infill wall on seismic behavior of RC frames is analytically studied by means of pushover analysis of several bare, partially and fully infilled frames having different bay and story numbers. The stiffness loss due to partial opening is introduced by the stiffness reduction factors which are developed from finite element analysis of frames considering frame-infill interaction. Pushover curves of frames are plotted and the maximum base shear forces, the yield displacement, the yield base shear force coefficient, the displacement demand, interstory drift ratios and the distribution of story shear forces are determined. The comparison of parameters both in terms of seismic demand and capacity indicates that partial openings decisively influences the nonlinear behavior of RC frames and cause a different behavior from that predicted for a bare frame or fully infilled frame.

Optimization of compression formulation and load of food-grade tracers for grain traceability using central composite design

Food-grade tracers have been developed as an identification technology for grain traceability from original harvest to final destination for transportation. The characteristics of food-grade tracers must be able to satisfy the environmental demands for grain traceability. To optimize the food-grade tracer production process, the effects of direct compression formulation and load on the mechanical characteristics were studied using response surface methodology (RSM) with central composite design (CCD). Among the four tested formulations, Formulations #2 (consisting of 35.00% lactose 100 mesh, 64.50% microcrystalline cellulose 102 and 0.50% magnesium stearate) and #4 (consisting of 38.00% lactose 100 mesh, 50.00% microcrystalline cellulose 102, 11.00% pregelatinized starch and 1.00% magnesium stearate) were selected for tracer production based on their physical properties as powders. The value of Carr’s flowability index was 68 for both Formulations #2 and #4, which was the highest among all the formulations. Therefore, Formulations #2 and #4 also had the best powder flowability. The magnesium stearate ratio (1.00%-3.00%) and pressure (6.00-16.00 kgf) were used as independent variables to detect changes in the breaking rate, peak shear force and friction coefficient of tracers compressed by the selected formulations. The optimal production parameters could be achieved at a magnesium stearate ratio of 2.25% and pressure of 16.00 kgf for Formulation #2 and at a magnesium stearate ratio of 1.02% and pressure of 16.00 kgf for Formulation #4. Under these optimal conditions, the tracers had good impact characteristics (breaking rate), compression characteristics (peak shear force) and frictional characteristics (friction coefficient). Moreover, Formulation #2 was more suitable for production because compared to Formulation #4, its breaking rate and friction coefficient values were lower, and its peak shear force value was higher. Keywords: grain traceability, food-grade tracer, optimization, food safety, formulation, mechanical property, central composite design DOI: 10.25165/j.ijabe.20171006.3531 Citation: Liang K, Zhang L L, Lu W, Okinda C S, Shen M X. Optimization of compression formulation and load of food-grade tracers for grain traceability using central composite design. Int J Agric & Biol Eng, 2017; 10(6): 221–230.

Modeling and Simulation of Cutting Forces in Side Milling

In order to acquire high machining quality and minimum machining time, cutting forces are usually modeled to understand the milling process, simulate or predict cutting forces, and optimize the machining parameters. In this paper, side milling tests were conducted on superalloy Inconel 718 with a solid carbide end mill, and the cutting forces vs. cutting time were measured. The average cutting forces were extracted from the measured instantaneous cutting forces under different feed rates of experiments, and the components of the shear forces and edge forces were determined by using the linear regression of the experimental data. The cutting force coefficients, including shear force coefficients and edge force coefficients, were identified. In addition, the algorithms of the mathematical model were implemented in Matlab. The predicted cutting forces were in good agreement with the experimentally measured forces, and the validation of the cutting force model was demonstrated.