The existing investigations on piezoelectric materials containing an elliptic hole mainly focus on remote uniform tensile loads. In order to have a better understanding of the fracture behavior of piezoelectric materi...The existing investigations on piezoelectric materials containing an elliptic hole mainly focus on remote uniform tensile loads. In order to have a better understanding of the fracture behavior of piezoelectric materials under different loading conditions, theoretical and numerical solutions are presented for an elliptic hole in transversely isotropic piezoelectric materials subjected to uniform internal shearing forces based on the complex potential approach. By solving ten variable linear equations, the analytical solutions inside and outside the hole satisfying the permeable electric boundary conditions are obtained. Taking PZT-4 ceramic into consideration, numerical results of electro-elastic fields along the edge of the hole and axes, and the electric displacements in the hole are presented. Comparison with stresses in transverse isotropic elastic materials shows that the hoop stress at the ends of major axis in two kinds of material equals zero for the various ratios of major to minor axis lengths; If the ratio is greater than 1, the hoop stress in piezoelectric materials is smaller than that in elastic materials, and if the ratio is smaller than 1, the hoop stress in piezoelectric materials is greater than that in elastic materials; When it is a circle hole, the shearing stress in two materials along axes is the same. The distribution of electric displacement components shows that the vertical electric displacement in the hole and along axes in the material is always zero though under the permeable electric boundary condition; The horizontal and vertical electric displacement components along the edge of the hole are symmetrical and antisymmetrical about horizontal axis, respectively. The stress and electric displacement distribution tends to zero at distances far from the elliptical hole, which conforms to the conclusion usually made on the basis of Saint-Venant’s principle. Unlike the existing work, uniform shearing forces acting on the edge of the hole, and the distribution of electro-elastic fields inside and outside the elliptic hole are considered.展开更多
This paper introduces a kind of photoelectric hybridization measuring process.Owing to the characteristics of the compact form of shearing equipment to be analyzed and the connecting rod existing in two directional st...This paper introduces a kind of photoelectric hybridization measuring process.Owing to the characteristics of the compact form of shearing equipment to be analyzed and the connecting rod existing in two directional stress state during operation etc.,it is hard to obtain results by means of single electrical testing process.For this reason,this paper derives a group of calculation formulas of hybridization measuring process through comprehensive discussion of photoelectric analysis and electrical testing theories,thus providing an analytical method for actual measurement of complex engineering problems.展开更多
The purpose aims to improve the plate shearing section quality and metal yield by means of optimal blade clearance adjustment model of rolling-cut shear and accurate calculation of the maximum shearing force , as well...The purpose aims to improve the plate shearing section quality and metal yield by means of optimal blade clearance adjustment model of rolling-cut shear and accurate calculation of the maximum shearing force , as well as for the system optimization design , structure optimization design to provide important basis.A 3 500mm rolling shear of a large stainless steel factory was taken as the test object , and the blade clearance under different influence factors of the clearance value and the shearing section were tested.The optimized production accumulated data regression analysis and the rolling shear process of stainless steel shear test.The test results show that the optimal blade clearance adjustment module is a comprehensive function , which include steel plate thickness , material , temperature and shear plate volume.The shear stress at starting stage with the relative penetration depth increases affected by the above factors , and the fracture peak decreases rapidly after being cut into the roll phase constant.展开更多
The calculation results show that relative cut-in depth at the moment of maximum shearing force decreases with the increase of steel plate thickness; along with blade clearance increasing, shearing force would increas...The calculation results show that relative cut-in depth at the moment of maximum shearing force decreases with the increase of steel plate thickness; along with blade clearance increasing, shearing force would increase slightly compared with the slide pressure of blade carrier; shearing force increases significantly with the increasing blunt end radius; shearing force displays a bit decrement with the decreasing platen force, while the pressure on slide plate of blade carrier increases substantially; shearing force increases a bit with the increasing shear velocity and decreases when nip angle increases while the horizontal component force of shearing force along the direction of plate width increases rapidly. The above results have important reference and actual using value for studying calculation of mechanical parameters of rolling shear and its structural design.展开更多
As the“throat”of the drilling well control system,ram blowout preventers(BOPs)can effectively prevent blowout accidents.However,the ram shear mechanism under complex working conditions is unclear,and it is difficult...As the“throat”of the drilling well control system,ram blowout preventers(BOPs)can effectively prevent blowout accidents.However,the ram shear mechanism under complex working conditions is unclear,and it is difficult to evaluate the ram BOP shear force,leading to frequent shear failure accidents in oilfields.Aiming at the above problems,this paper takes the double-V ram BOP as the research object,and integrates the methods of theoretical analysis,simulation modeling,and test verification to analyze the shear force in the pipe shear process under both static and moving conditions.A ram BOP shear force evaluation method is proposed based on equivalent stress.Finally,by comparing with calculation data and experimental data,the error between them is less than 5%,demonstrating the applicability and effectiveness of the proposed method.The research results can provide a theoretical basis for oilfield operations of ram BOPs.展开更多
Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diamete...Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the ef/~cient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.展开更多
The nanoparticles suspended in a shear flow are subjected to a shear lift force,which is of great importance for the nanoparticle transport.In previous theoretical analysis on the shear lift,it is usually assumed that...The nanoparticles suspended in a shear flow are subjected to a shear lift force,which is of great importance for the nanoparticle transport.In previous theoretical analysis on the shear lift,it is usually assumed that the particle temperature is equal to the temperature of the surrounding gas media.However,in some particular applications,the particle temperature can significantly differ from the gas temperature.In the present study,the effect of particle temperature on the shear lift of nanoparticles is investigated and the corresponding formulas of shear lift force are derived based on the gas kinetic theory.For extremely small nanoparticles(with radius R<2 nm)or large nanoparticles(R>20 nm),the influence of the particle temperature can be neglected.For the intermediate particle size,the relative error induced by the equal gas–particle temperature can be significant.Our findings can bring an insight into accurate evaluation of the nanoparticle transport properties.展开更多
A modified Monte Carlo model of speckle tracking of shear wave propagation in scattering media is proposed. The established Monte Carlo model mainly concerns the variations of optical electric field and speckle. The t...A modified Monte Carlo model of speckle tracking of shear wave propagation in scattering media is proposed. The established Monte Carlo model mainly concerns the variations of optical electric field and speckle. The two- dimensional intensity distribution and the time evolution of speckles in different probe locations are obtained. The fluctuation of speckle intensity tracks the acoustic-radiation-force shear wave propagation, and especially the reduction of speckle intensity implies attenuation of shear wave. Then, the shear wave velocity is estimated quantitatively on the basis of the time-to-peak algorithm and linear regression processing. The results reveal that a smaller sampling interval yields higher estimation precision and the shear wave velocity is estimated more efficiently by using speckle intensity difference than by using speckle contrast difference according to the estimation error. Hence, the shear wave velocity is estimated to be 2.25 m/s with relatively high accuracy for the estimation error reaches the minimum (0.071).展开更多
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...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. Energybased 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.展开更多
This paper proposes a new technique which introduces the high-order single-step-β method(HSM)into the experimental study on the substructure pseudo-dynamic testing(SPDT).The technique is based on the proposed concept...This paper proposes a new technique which introduces the high-order single-step-β method(HSM)into the experimental study on the substructure pseudo-dynamic testing(SPDT).The technique is based on the proposed concept of equivalent shear stiffness which can meet the requirement of the HSM algorithm.A study is done to theoretically validate the technique by the numerical analysis of two-storey shear building structure,in comparison of the proposed substructure pseudo-dynamic testing algorithm with the central difference method(CDM).Then,a full-scale SPDT model,the three-storey frame-supported reinforced concrete short-limb masonry shear wall structure,is designed and tested to simulate the seismic response of the corresponding six-storey structure and verify the proposed force control HSM technique.Meanwhile,the techniques of both stiffness correction and force control are suggested to control algorithmic error,control error and measurement error.The results indicate that the force control HSM can be used in the full-scale multi-degree-of-freedom(MDOF)substructure pseudo-dynamic testing before descent segment of structure restoring force properties.展开更多
Experimental results of the temperature dependence of critical resolved. shear stresses (CRSS)of Mo, Fe, Al and Mg single crystals are shown. Associating reports in recent years, we point out that the approximate expo...Experimental results of the temperature dependence of critical resolved. shear stresses (CRSS)of Mo, Fe, Al and Mg single crystals are shown. Associating reports in recent years, we point out that the approximate exponential relationship between CRSS and the absolute temperatureat least in the region of the steep temperature dependence range of many materials is more common, even for bcc, fcc, and hcp single crystals. polycrystals and other covalent crystals,provided that the slip plane and slip direction are kept the same. Successful explanation with atomic force law shows that the interatomic forces (electronic structure) play a decisive role in determining the temperature dependence of yield stresses for a large number of materials.展开更多
Nanowires and nanotubes of diverse material compositions,properties and/or functions have been produced or fabricated through various bottom-up or top-down approaches.These nanowires or nanotubes have also been utiliz...Nanowires and nanotubes of diverse material compositions,properties and/or functions have been produced or fabricated through various bottom-up or top-down approaches.These nanowires or nanotubes have also been utilized as potential building blocks for functional nanodevices.The key for the integration of those nanowire or nanotube based devices is to assemble these one dimensional nanomaterials to specific locations using techniques that are highly controllable and scalable.Ideally such techniques should enable assembly of highly uniform nanowire/nanotube arrays with precise control of density,location,dimension or even material types of nanowires/nanotubes.Numerous assembly techniques are being developed that can quickly align and assemble large quantities of one type or multiple types of nanowires through parallel processes,including flow-assisted alignment,Langmuir-Blodgett assembly,bubble-blown technique,electric/magnetic-field directed assembly,contact/roll printing,knocking-down,etc..With these assembling techniques,applications of nanowire/nanotube based devices such as flexible electronics and sensors have been demonstrated.This paper delivers an overall review of directed nanowire/nanotube assembling approaches and analyzes advantages and limitations of each method.The future research directions have also been discussed.展开更多
Viscoelastic dampers(VEDs) are one of the most common passive control devices used in new and retrofit building projects which reduce the structure responses and dissipate seismic energy during an earthquake.Various...Viscoelastic dampers(VEDs) are one of the most common passive control devices used in new and retrofit building projects which reduce the structure responses and dissipate seismic energy during an earthquake.Various methods to design this kind of dampers have been proposed based on the desired level of additional damping,eigenvalue assignment,modal strain energy,linear quadratic regulator control theories,and other approaches.In the current engineering practice,the popular method is the one based on the modal strain energy that uses the inter-story lateral stiffness as one of the main variables for damper design.However,depending on the configuration of the structure,in some cases the resulting interstory lateral stiffness can be very large.Consequently,the dampers size would also be large producing much more damping than that effectively necessary,resulting in an increase of the overall cost of the supplemental damping system and causing excessive stress on the structural elements connected to the dampers.In this paper an alternative practical design method for structures with VEDs is proposed.This method uses the inter-story shear forces as one of the main variables to accomplish the damper design compared to what was done in previous studies.Nonlinear time-history analyses were conducted on a 7-story reinforced concrete(RC) structure to check the reliability and effectiveness of the proposed method.Comparisons on the seismic performance between the structure without dampers and that equipped with VEDs were carried out.It is concluded that the proposed method results in a very suitable size of dampers,which are able to improve the performance of the structure at all levels of earthquake ground motions and satisfying the drift requirement prescribed in the codes.展开更多
In this paper, resistance spot welding were performed on lmm-thickness magnesium AZ31B plates. The effect of welding current on the microstructure and tensile shear force was investigated. It was found that the weldin...In this paper, resistance spot welding were performed on lmm-thickness magnesium AZ31B plates. The effect of welding current on the microstructure and tensile shear force was investigated. It was found that the welding current governed the nugget growth, and the nugget could not form if current levels were insufficient. The nugget revealed a homogeneous, equiaxed, fine-grained structure, which consisted of non-equilibrium microstructure of α-phase dendrites surrounded by eutectic mixtures of α and β( Mg17All2 ) in the grain boundaries. With increasing welding current, the size of grains in nugget would be more smaller and uniform, and the width of plastic rings would be larger. Tensile shear tests showed that tensile shear force of the joints increased with increasing welding current when the welding current was smaller than 17 000 A. The maximum tensile shear force was up to 1980 N.展开更多
The Building Standard Law of Japan and related Enforcement Order and Notifications have been substantially revised since the year 2000 to introduce a performance-based regulatory and deregulation system for building c...The Building Standard Law of Japan and related Enforcement Order and Notifications have been substantially revised since the year 2000 to introduce a performance-based regulatory and deregulation system for building control systems. Up to then,time-history analyses were mandatory for isolated buildings and had to be specially approved by the Minster of the Ministry of Construction (MOC).Simplified design procedures based on the equivalent linear method for seismically isolated buildings have been issued as'Notification 2009-Structnral calculation procedure for buildings with seismic isolation'from MOC,and are now integrated into the Ministry of Land,Infrastructure,and Transportation (MLIT).Along with Notification 2009,'Notification 1446 of year 2000-Standard for specifications and test methods for seismic isolation devices'was also issued.Buildings with heights equal to or less than 60m and that are designed according to these Notifications,including base isolated buildings,only need approval from local building officials,and no longer require the special approval of the Minister of MLIT.This paper summarizes:1) some statistics related to buildings with seismic isolation completed up to the end of 2001; 2) simplified design procedures required by Notification 2009 of year 2000;and 3) performance of seismic isolation devices required by Notification 1446 of year 2000.展开更多
Titanium alloy lap joints were performed by combined laser welding and resistance seam welding process. The welding characteristics of this combined process were investigated compared with that of laser welding. The e...Titanium alloy lap joints were performed by combined laser welding and resistance seam welding process. The welding characteristics of this combined process were investigated compared with that of laser welding. The experimental results indicate that the combined process welded joint has larger weld width at the lap surface. The joint tensile shear force of combined process is 2. 5 times that of laser welding. There are some pores around the lap surface in laser welded joint, and most pores can be eliminated by resistance seam welding process. Metallographic examinations of combined process welded joint reveal that the microstructure in heat-affected zone (HAZ) and weld zone has the acicular martensite morphology, which causes that the microhardness in HAZ and weld zone increases compared with the base metal, and the microhardness in weld zone is highest.展开更多
Studies of interactions between wind and saltating particles (i.e., the wind-saltation interaction) are usually conducted without consideration of the downwind air pressure gradient. However, in a wind tunnel with l...Studies of interactions between wind and saltating particles (i.e., the wind-saltation interaction) are usually conducted without consideration of the downwind air pressure gradient. However, in a wind tunnel with limited size, this gradient is required to maintain the movement of the saltation cloud. Attempts are made to investigate the effects of the downwind air pressure gradient on the wind-saltation interaction in a saltation boundary layer based on the experimental results from a wind tunnel with a relatively small cross-sectional area. The wind-saltation interaction is characterized by airborne stress, grain-borne stress, and the force exerted on the wind by the saltation cloud. Basic equations were developed for wind-saltation interactions without and with a downwind air pressure gradient. The results reveal that unacceptable values of negative grain-borne stress and negative force exerted on the wind by the saltation cloud are obtained if the downwind air pressure gradient is ignored. When this air pressure gradient is defined using the measured wind velocity profiles in the presence of saltation and the downwind air pressure gradient is taken into account, reasonable values for grain-borne stress and the force exerted on the wind by the saltation cloud are obtained. These results suggest that attention must be paid to the effects of downwind air pressure gradients when studying the wind-saltation interaction in a wind tunnel. Consideration of the downwind air pressure gradient, inertial forces, and other unidentified variables will provide a more thorough understanding of the interactions within a saltation boundary layer.展开更多
Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a maj...Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a major disadvantage as compared to environmental impact, that is, wildlife habitat disruption. In as much as it has become optimal for investment in hydropower dam construction, the scourge for dam failure is still eminent, which is as a result of excessive seepage compromising the integrity of the mechanical properties of the dam. The aim of the paper is to highlight successful application methods in joint bonding to avoid excessive seepage and reduce the autogenous healing to a few years of operation. In view of optimization, this paper presents a comprehensive study on the influences of interlayer joints bonding quality from RCC mix performances and how it consolidates the RCC layers to withstand the shear strength along the interface, especially on the high dams. The case study is the RCC dam at the 750 MW Kafue Gorge Lower Hydropower Station. The scope of the study reviews the joint type judged by Modified Maturity Factor (MMF) with joint surface long time exposed in regions with dry and high temperature, technical measures of layer bonding quality control under condition of long time joint surface exposure, effects of joints shear strength and impermeability of the RCC layers when under the conditions of plastic and elasticity. The subtle observations made during the dam construction phases were with respect to the optimal use of materials in relation to RCC mix designs and the basis for equipment calibration for monitoring important data that can be referenced during analysis of shear forces acting on the RCC dam over time.展开更多
Blade clearance is an important technical parameter of the shear, which determines the shear quality of plate. The finite element method was used to simulate shearing process which is in the different specifications a...Blade clearance is an important technical parameter of the shear, which determines the shear quality of plate. The finite element method was used to simulate shearing process which is in the different specifications and blade clearances, and the impact on blade section and shearing force of blade clearance was analyzed. Comparing with traditional experience formulas and measured values, the limitations of the experience formulas were proved. And by contrasting with the shearing force data collected from Linfen Iron and Steel Company, the reliability of the finite element method was further proved. The simulated results show that the simulated values controlled by ductile fracture criterion and measured values are very close, and the deviation value is in the range of 4.8%-20.8%. For the same steel, if the plate is thicker, the blade clearance will be greater, and thickness and blade clearance are approximately linear. The difference between numerical simulation of the maximum shearing force and the measured results is 7.7% to 12.0%, and the simulation results are close to facts. With the increase of blade clearance and the thickness, the shearing force was increased to some degree.展开更多
This paper reports the effects of shear force on anoxic granular sludge in sequencing batch reactors (SBR). The study was carried out in two SBRs (SBR1 and SBR2) in which sodium acetate (200mg COD·L^-1) was...This paper reports the effects of shear force on anoxic granular sludge in sequencing batch reactors (SBR). The study was carried out in two SBRs (SBR1 and SBR2) in which sodium acetate (200mg COD·L^-1) was used as the sole substrate and sodium nitrate (40 mgNO3-N·L^-1) was employed as the electron acceptor. The preliminary objective of this study was to cultivate anoxic granules in the SBR in order to investigate the effects of shear force on the formation of anoxic granular sludge and to compare the properties of anoxic sludge in the SBR. This study reports new results for the values of average velocity gradient, a measure of the applied shear force, which was varied in the two SBRs (3.79 s^-1 and 9.76 s^-1 for SBR1 and SBR2 respectively). The important findings of this research highlight the dual effects of shear force on anoxic granules. A low shear force can produce large anoxic granules with high activity and poor settling ability, whereas higher shear forces produce smaller granules with better settling ability and lower activity. The results of this study show that the anoxic granulation is closely related to the strength of the shear force. For high shear force, this research demonstrated that: 1) granules with smaller diameters, high density and good settling ability were formed in the reactor, and 2) granular sludge formed faster than it did in the low shear force reactor (41days versus 76 days). Once a steady-state has been achieved, the nitrate and COD removal rates were found to be 98% and 80%, respectively. For low shear force, such as was applied in SBR1, this research demonstrated that: 1) the activity of anoxic granular sludge in low shear force was higher than that in high shear force, 2) higher amount of soluble microbial products (SMPs) were produced, and 3) large pores were observed inside the larger granules,which are beneficial for nitrogen gas diffusion. Electron microscopic examination of the anoxic granules in both reactors showed that the morphology of the granules was ellipsoidal with a clear outline. Coccus and rod-shaped bacteria were wrapped by filamentous bacteria on the surface of granule.展开更多
基金supported by Hebei Provincial Natural Science Foundation of China (Grant No. A2011210033)Foundation of Hebei Provincial Education Department of China (Grant No. ZH2011116)Hebei Provincial Research Program for Higher Education and Teaching Reform of China (Grant No. 103024)
文摘The existing investigations on piezoelectric materials containing an elliptic hole mainly focus on remote uniform tensile loads. In order to have a better understanding of the fracture behavior of piezoelectric materials under different loading conditions, theoretical and numerical solutions are presented for an elliptic hole in transversely isotropic piezoelectric materials subjected to uniform internal shearing forces based on the complex potential approach. By solving ten variable linear equations, the analytical solutions inside and outside the hole satisfying the permeable electric boundary conditions are obtained. Taking PZT-4 ceramic into consideration, numerical results of electro-elastic fields along the edge of the hole and axes, and the electric displacements in the hole are presented. Comparison with stresses in transverse isotropic elastic materials shows that the hoop stress at the ends of major axis in two kinds of material equals zero for the various ratios of major to minor axis lengths; If the ratio is greater than 1, the hoop stress in piezoelectric materials is smaller than that in elastic materials, and if the ratio is smaller than 1, the hoop stress in piezoelectric materials is greater than that in elastic materials; When it is a circle hole, the shearing stress in two materials along axes is the same. The distribution of electric displacement components shows that the vertical electric displacement in the hole and along axes in the material is always zero though under the permeable electric boundary condition; The horizontal and vertical electric displacement components along the edge of the hole are symmetrical and antisymmetrical about horizontal axis, respectively. The stress and electric displacement distribution tends to zero at distances far from the elliptical hole, which conforms to the conclusion usually made on the basis of Saint-Venant’s principle. Unlike the existing work, uniform shearing forces acting on the edge of the hole, and the distribution of electro-elastic fields inside and outside the elliptic hole are considered.
文摘This paper introduces a kind of photoelectric hybridization measuring process.Owing to the characteristics of the compact form of shearing equipment to be analyzed and the connecting rod existing in two directional stress state during operation etc.,it is hard to obtain results by means of single electrical testing process.For this reason,this paper derives a group of calculation formulas of hybridization measuring process through comprehensive discussion of photoelectric analysis and electrical testing theories,thus providing an analytical method for actual measurement of complex engineering problems.
基金Item Sponsored by National Basic Research Program of China ( 2011CB612204 )National Natural Science Foundation of China ( 51105264 )
文摘The purpose aims to improve the plate shearing section quality and metal yield by means of optimal blade clearance adjustment model of rolling-cut shear and accurate calculation of the maximum shearing force , as well as for the system optimization design , structure optimization design to provide important basis.A 3 500mm rolling shear of a large stainless steel factory was taken as the test object , and the blade clearance under different influence factors of the clearance value and the shearing section were tested.The optimized production accumulated data regression analysis and the rolling shear process of stainless steel shear test.The test results show that the optimal blade clearance adjustment module is a comprehensive function , which include steel plate thickness , material , temperature and shear plate volume.The shear stress at starting stage with the relative penetration depth increases affected by the above factors , and the fracture peak decreases rapidly after being cut into the roll phase constant.
基金Item Sponsored by National Natural Science Foundation of China(50954003)New-Century Talents Support Plan of China(NECT-05-0268)Provincial Natural Science Foundation of Shanxi Province of China(2010011036-2)
文摘The calculation results show that relative cut-in depth at the moment of maximum shearing force decreases with the increase of steel plate thickness; along with blade clearance increasing, shearing force would increase slightly compared with the slide pressure of blade carrier; shearing force increases significantly with the increasing blunt end radius; shearing force displays a bit decrement with the decreasing platen force, while the pressure on slide plate of blade carrier increases substantially; shearing force increases a bit with the increasing shear velocity and decreases when nip angle increases while the horizontal component force of shearing force along the direction of plate width increases rapidly. The above results have important reference and actual using value for studying calculation of mechanical parameters of rolling shear and its structural design.
基金This research acknowledges the financial support provided by the Key Program of National Natural Science Foundation of China(52234007).
文摘As the“throat”of the drilling well control system,ram blowout preventers(BOPs)can effectively prevent blowout accidents.However,the ram shear mechanism under complex working conditions is unclear,and it is difficult to evaluate the ram BOP shear force,leading to frequent shear failure accidents in oilfields.Aiming at the above problems,this paper takes the double-V ram BOP as the research object,and integrates the methods of theoretical analysis,simulation modeling,and test verification to analyze the shear force in the pipe shear process under both static and moving conditions.A ram BOP shear force evaluation method is proposed based on equivalent stress.Finally,by comparing with calculation data and experimental data,the error between them is less than 5%,demonstrating the applicability and effectiveness of the proposed method.The research results can provide a theoretical basis for oilfield operations of ram BOPs.
文摘Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the ef/~cient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.
基金the National Natural Science Foundation of China(Grant No.51776007)Beijing Nova Program of Science and Technology(Grant No.Z191100001119033)the Youth Talent Support Program of Beijing Municipal Education Committee(Grant No.CIT&TCD201904015)。
文摘The nanoparticles suspended in a shear flow are subjected to a shear lift force,which is of great importance for the nanoparticle transport.In previous theoretical analysis on the shear lift,it is usually assumed that the particle temperature is equal to the temperature of the surrounding gas media.However,in some particular applications,the particle temperature can significantly differ from the gas temperature.In the present study,the effect of particle temperature on the shear lift of nanoparticles is investigated and the corresponding formulas of shear lift force are derived based on the gas kinetic theory.For extremely small nanoparticles(with radius R<2 nm)or large nanoparticles(R>20 nm),the influence of the particle temperature can be neglected.For the intermediate particle size,the relative error induced by the equal gas–particle temperature can be significant.Our findings can bring an insight into accurate evaluation of the nanoparticle transport properties.
基金Supported by the National Key Scientific Instrument and Equipment Development Projects of China under Grant No 81127901the National Natural Science Foundation of China under Grant Nos 61372017 and 30970828
文摘A modified Monte Carlo model of speckle tracking of shear wave propagation in scattering media is proposed. The established Monte Carlo model mainly concerns the variations of optical electric field and speckle. The two- dimensional intensity distribution and the time evolution of speckles in different probe locations are obtained. The fluctuation of speckle intensity tracks the acoustic-radiation-force shear wave propagation, and especially the reduction of speckle intensity implies attenuation of shear wave. Then, the shear wave velocity is estimated quantitatively on the basis of the time-to-peak algorithm and linear regression processing. The results reveal that a smaller sampling interval yields higher estimation precision and the shear wave velocity is estimated more efficiently by using speckle intensity difference than by using speckle contrast difference according to the estimation error. Hence, the shear wave velocity is estimated to be 2.25 m/s with relatively high accuracy for the estimation error reaches the minimum (0.071).
文摘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. Energybased 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.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50508012)
文摘This paper proposes a new technique which introduces the high-order single-step-β method(HSM)into the experimental study on the substructure pseudo-dynamic testing(SPDT).The technique is based on the proposed concept of equivalent shear stiffness which can meet the requirement of the HSM algorithm.A study is done to theoretically validate the technique by the numerical analysis of two-storey shear building structure,in comparison of the proposed substructure pseudo-dynamic testing algorithm with the central difference method(CDM).Then,a full-scale SPDT model,the three-storey frame-supported reinforced concrete short-limb masonry shear wall structure,is designed and tested to simulate the seismic response of the corresponding six-storey structure and verify the proposed force control HSM technique.Meanwhile,the techniques of both stiffness correction and force control are suggested to control algorithmic error,control error and measurement error.The results indicate that the force control HSM can be used in the full-scale multi-degree-of-freedom(MDOF)substructure pseudo-dynamic testing before descent segment of structure restoring force properties.
文摘Experimental results of the temperature dependence of critical resolved. shear stresses (CRSS)of Mo, Fe, Al and Mg single crystals are shown. Associating reports in recent years, we point out that the approximate exponential relationship between CRSS and the absolute temperatureat least in the region of the steep temperature dependence range of many materials is more common, even for bcc, fcc, and hcp single crystals. polycrystals and other covalent crystals,provided that the slip plane and slip direction are kept the same. Successful explanation with atomic force law shows that the interatomic forces (electronic structure) play a decisive role in determining the temperature dependence of yield stresses for a large number of materials.
基金the financial support from Natural Science and Engineering Research Council of Canada (NSERC)funding from Science and Technology Commission of Shanghai Municipality (No.11PJ1403500)+1 种基金the Open Project Program of State Key Laboratory of Industrial Control Technology (No.ICT1113)Innovation Program of Shanghai Municipal Education Commission (No.12YZ022)
文摘Nanowires and nanotubes of diverse material compositions,properties and/or functions have been produced or fabricated through various bottom-up or top-down approaches.These nanowires or nanotubes have also been utilized as potential building blocks for functional nanodevices.The key for the integration of those nanowire or nanotube based devices is to assemble these one dimensional nanomaterials to specific locations using techniques that are highly controllable and scalable.Ideally such techniques should enable assembly of highly uniform nanowire/nanotube arrays with precise control of density,location,dimension or even material types of nanowires/nanotubes.Numerous assembly techniques are being developed that can quickly align and assemble large quantities of one type or multiple types of nanowires through parallel processes,including flow-assisted alignment,Langmuir-Blodgett assembly,bubble-blown technique,electric/magnetic-field directed assembly,contact/roll printing,knocking-down,etc..With these assembling techniques,applications of nanowire/nanotube based devices such as flexible electronics and sensors have been demonstrated.This paper delivers an overall review of directed nanowire/nanotube assembling approaches and analyzes advantages and limitations of each method.The future research directions have also been discussed.
基金National Key Research and Development Program of China under Grant No.2016YFC0701101the National Nature Science Foundation of China under Grant No.51678449
文摘Viscoelastic dampers(VEDs) are one of the most common passive control devices used in new and retrofit building projects which reduce the structure responses and dissipate seismic energy during an earthquake.Various methods to design this kind of dampers have been proposed based on the desired level of additional damping,eigenvalue assignment,modal strain energy,linear quadratic regulator control theories,and other approaches.In the current engineering practice,the popular method is the one based on the modal strain energy that uses the inter-story lateral stiffness as one of the main variables for damper design.However,depending on the configuration of the structure,in some cases the resulting interstory lateral stiffness can be very large.Consequently,the dampers size would also be large producing much more damping than that effectively necessary,resulting in an increase of the overall cost of the supplemental damping system and causing excessive stress on the structural elements connected to the dampers.In this paper an alternative practical design method for structures with VEDs is proposed.This method uses the inter-story shear forces as one of the main variables to accomplish the damper design compared to what was done in previous studies.Nonlinear time-history analyses were conducted on a 7-story reinforced concrete(RC) structure to check the reliability and effectiveness of the proposed method.Comparisons on the seismic performance between the structure without dampers and that equipped with VEDs were carried out.It is concluded that the proposed method results in a very suitable size of dampers,which are able to improve the performance of the structure at all levels of earthquake ground motions and satisfying the drift requirement prescribed in the codes.
文摘In this paper, resistance spot welding were performed on lmm-thickness magnesium AZ31B plates. The effect of welding current on the microstructure and tensile shear force was investigated. It was found that the welding current governed the nugget growth, and the nugget could not form if current levels were insufficient. The nugget revealed a homogeneous, equiaxed, fine-grained structure, which consisted of non-equilibrium microstructure of α-phase dendrites surrounded by eutectic mixtures of α and β( Mg17All2 ) in the grain boundaries. With increasing welding current, the size of grains in nugget would be more smaller and uniform, and the width of plastic rings would be larger. Tensile shear tests showed that tensile shear force of the joints increased with increasing welding current when the welding current was smaller than 17 000 A. The maximum tensile shear force was up to 1980 N.
文摘The Building Standard Law of Japan and related Enforcement Order and Notifications have been substantially revised since the year 2000 to introduce a performance-based regulatory and deregulation system for building control systems. Up to then,time-history analyses were mandatory for isolated buildings and had to be specially approved by the Minster of the Ministry of Construction (MOC).Simplified design procedures based on the equivalent linear method for seismically isolated buildings have been issued as'Notification 2009-Structnral calculation procedure for buildings with seismic isolation'from MOC,and are now integrated into the Ministry of Land,Infrastructure,and Transportation (MLIT).Along with Notification 2009,'Notification 1446 of year 2000-Standard for specifications and test methods for seismic isolation devices'was also issued.Buildings with heights equal to or less than 60m and that are designed according to these Notifications,including base isolated buildings,only need approval from local building officials,and no longer require the special approval of the Minister of MLIT.This paper summarizes:1) some statistics related to buildings with seismic isolation completed up to the end of 2001; 2) simplified design procedures required by Notification 2009 of year 2000;and 3) performance of seismic isolation devices required by Notification 1446 of year 2000.
文摘Titanium alloy lap joints were performed by combined laser welding and resistance seam welding process. The welding characteristics of this combined process were investigated compared with that of laser welding. The experimental results indicate that the combined process welded joint has larger weld width at the lap surface. The joint tensile shear force of combined process is 2. 5 times that of laser welding. There are some pores around the lap surface in laser welded joint, and most pores can be eliminated by resistance seam welding process. Metallographic examinations of combined process welded joint reveal that the microstructure in heat-affected zone (HAZ) and weld zone has the acicular martensite morphology, which causes that the microhardness in HAZ and weld zone increases compared with the base metal, and the microhardness in weld zone is highest.
基金the funding received from the Natural Science Foundation of China (40638038)
文摘Studies of interactions between wind and saltating particles (i.e., the wind-saltation interaction) are usually conducted without consideration of the downwind air pressure gradient. However, in a wind tunnel with limited size, this gradient is required to maintain the movement of the saltation cloud. Attempts are made to investigate the effects of the downwind air pressure gradient on the wind-saltation interaction in a saltation boundary layer based on the experimental results from a wind tunnel with a relatively small cross-sectional area. The wind-saltation interaction is characterized by airborne stress, grain-borne stress, and the force exerted on the wind by the saltation cloud. Basic equations were developed for wind-saltation interactions without and with a downwind air pressure gradient. The results reveal that unacceptable values of negative grain-borne stress and negative force exerted on the wind by the saltation cloud are obtained if the downwind air pressure gradient is ignored. When this air pressure gradient is defined using the measured wind velocity profiles in the presence of saltation and the downwind air pressure gradient is taken into account, reasonable values for grain-borne stress and the force exerted on the wind by the saltation cloud are obtained. These results suggest that attention must be paid to the effects of downwind air pressure gradients when studying the wind-saltation interaction in a wind tunnel. Consideration of the downwind air pressure gradient, inertial forces, and other unidentified variables will provide a more thorough understanding of the interactions within a saltation boundary layer.
文摘Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a major disadvantage as compared to environmental impact, that is, wildlife habitat disruption. In as much as it has become optimal for investment in hydropower dam construction, the scourge for dam failure is still eminent, which is as a result of excessive seepage compromising the integrity of the mechanical properties of the dam. The aim of the paper is to highlight successful application methods in joint bonding to avoid excessive seepage and reduce the autogenous healing to a few years of operation. In view of optimization, this paper presents a comprehensive study on the influences of interlayer joints bonding quality from RCC mix performances and how it consolidates the RCC layers to withstand the shear strength along the interface, especially on the high dams. The case study is the RCC dam at the 750 MW Kafue Gorge Lower Hydropower Station. The scope of the study reviews the joint type judged by Modified Maturity Factor (MMF) with joint surface long time exposed in regions with dry and high temperature, technical measures of layer bonding quality control under condition of long time joint surface exposure, effects of joints shear strength and impermeability of the RCC layers when under the conditions of plastic and elasticity. The subtle observations made during the dam construction phases were with respect to the optimal use of materials in relation to RCC mix designs and the basis for equipment calibration for monitoring important data that can be referenced during analysis of shear forces acting on the RCC dam over time.
基金Item Sponsored by National Key Basic Research Program of China (2012CB722801)
文摘Blade clearance is an important technical parameter of the shear, which determines the shear quality of plate. The finite element method was used to simulate shearing process which is in the different specifications and blade clearances, and the impact on blade section and shearing force of blade clearance was analyzed. Comparing with traditional experience formulas and measured values, the limitations of the experience formulas were proved. And by contrasting with the shearing force data collected from Linfen Iron and Steel Company, the reliability of the finite element method was further proved. The simulated results show that the simulated values controlled by ductile fracture criterion and measured values are very close, and the deviation value is in the range of 4.8%-20.8%. For the same steel, if the plate is thicker, the blade clearance will be greater, and thickness and blade clearance are approximately linear. The difference between numerical simulation of the maximum shearing force and the measured results is 7.7% to 12.0%, and the simulation results are close to facts. With the increase of blade clearance and the thickness, the shearing force was increased to some degree.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant No. 50838005) and National Water Pollution Control and Management Technology Major Projects of China (No. 2009ZX07317-009). The authors are grateful for much assistance with microsensor measurements from Xi'an University Architecture and Technol- ogy.
文摘This paper reports the effects of shear force on anoxic granular sludge in sequencing batch reactors (SBR). The study was carried out in two SBRs (SBR1 and SBR2) in which sodium acetate (200mg COD·L^-1) was used as the sole substrate and sodium nitrate (40 mgNO3-N·L^-1) was employed as the electron acceptor. The preliminary objective of this study was to cultivate anoxic granules in the SBR in order to investigate the effects of shear force on the formation of anoxic granular sludge and to compare the properties of anoxic sludge in the SBR. This study reports new results for the values of average velocity gradient, a measure of the applied shear force, which was varied in the two SBRs (3.79 s^-1 and 9.76 s^-1 for SBR1 and SBR2 respectively). The important findings of this research highlight the dual effects of shear force on anoxic granules. A low shear force can produce large anoxic granules with high activity and poor settling ability, whereas higher shear forces produce smaller granules with better settling ability and lower activity. The results of this study show that the anoxic granulation is closely related to the strength of the shear force. For high shear force, this research demonstrated that: 1) granules with smaller diameters, high density and good settling ability were formed in the reactor, and 2) granular sludge formed faster than it did in the low shear force reactor (41days versus 76 days). Once a steady-state has been achieved, the nitrate and COD removal rates were found to be 98% and 80%, respectively. For low shear force, such as was applied in SBR1, this research demonstrated that: 1) the activity of anoxic granular sludge in low shear force was higher than that in high shear force, 2) higher amount of soluble microbial products (SMPs) were produced, and 3) large pores were observed inside the larger granules,which are beneficial for nitrogen gas diffusion. Electron microscopic examination of the anoxic granules in both reactors showed that the morphology of the granules was ellipsoidal with a clear outline. Coccus and rod-shaped bacteria were wrapped by filamentous bacteria on the surface of granule.