Introduction Integrins are a large family of adhesion molecules broadly expressed on the surface of a wide variety of cells as heterodimers. Binding of integrins to ligands provides not only mechanical anchorage for t...Introduction Integrins are a large family of adhesion molecules broadly expressed on the surface of a wide variety of cells as heterodimers. Binding of integrins to ligands provides not only mechanical anchorage for the cell to another cell or展开更多
Using the single crack solution and the regular solution of plane harmonic function, the problem of Saint_Venant bending of a cracked cylinder by a transverse force was reduced to solving two sets of integral equation...Using the single crack solution and the regular solution of plane harmonic function, the problem of Saint_Venant bending of a cracked cylinder by a transverse force was reduced to solving two sets of integral equations and its general solution was then obtained. Based on the obtained solution, a method to calculate the bending center and the stress intensity factors of the cracked cylinger whose cross_section is not thin_walled, but of small torsion rigidity is proposed. Some numerical examples are given.展开更多
The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test syste...The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test system,and the constitutive equations were established.It is found that fracture morphology of rock beams under no disturbance load is regular,cracking position of fractures is on part of loading concentration,the crack starts from a neutral plane.However,fracture morphology of rock beams under disturbance load is irregular,cracking position of fractures deviates from a neutral plane.Delayed instability of rock beam occurs for some time under constant disturbance load.When disturbance load is beyond a certain range,suddenly instability of occurs rock beam in a certain time.The results show that there is a guiding significance for creep stability in the geotechnical engineering fields.展开更多
The numerical control (NC) precision bending process of thin-walled tube is on e of advanced plastic forming processes with high efficiency, forming precision, strength/weight ratio and low cost, thus it is playing mo...The numerical control (NC) precision bending process of thin-walled tube is on e of advanced plastic forming processes with high efficiency, forming precision, strength/weight ratio and low cost, thus it is playing more and more important role in manufacturing parts in aerospace and automobile industries. However, the determination of parameters crucial to make sure tube parts qualified is heavil y experience-based and involves repeated trial-and-errors in practice, which makes the production efficiency reduce drastically and does not fulfill the deve lopment of high technology. With quick development of computer technology and gr adual perfect of plastic forming theory, computer numerical simulation based on finite element method (FEM) has become one of important tools of researching and developing plastic forming technology. Development trend of NC precision bendin g process of tube is simulating its forming process by FEM. Because NC tube bend ing is of 3D nature, it is of great importance to analyze the forming mechanism and find out the influence law of forming parameters on forming process in the N C precision bending process of thin-walled tube quantitatively by 3D FE simulat ion. Based on the rigid-plastic finite element method (FEM) principle, a 3-dimens ional (3D) rigid-plastic FE simulation system named TBS -3D (tube bending simu lation by 3D FEM) for the NC bending process of thin-walled tube has been devel oped, a reasonable FEM model has been established. By use of this FEM simulation system, a NC bending process of thin-walled has been simulated. And deformed m eshes under different bending stages, stress distribution along bending directio n, relationship between maximal wall thickness changing ratio and bending angle have been obtained. And then some forming laws of NC tube bending obtained are a s follows: (1) NC bending process make tube elongate to some extent; (2) Charact eristic of stress distribution is that the outer area is undergoing tensile stre ss, the inner area is undergoing compression stress, and stress neutral layer mo ves close to the inner area, which is in good accordance with the practice; (3) Maximal wall thinning ratio in the outer tensile area changes only a little with increase of bending angle, and maximal wall thickening ratio in the inner compr ession area increases linearly with bending angle. The above results show that 3 D FE simulation is an important and valid tool of analyzing NC bending process o f tube, this research is beneficial for the practical tube bending process, and it may serve as a significant guide to the practice of the relevant processes.展开更多
The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulat...The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulative fatigue criterion and the stress-life equation, the key meshing states of the gear pair were investigated for the contact fatigue and the bending fatigue. Then, the reliability of the proposed model was proved by comparing the calculation result with the simulation result. Further study was performed to analyze the variation of the contact fatigue stress and the bending fatigue stress under different loads. Furthermore, the roles of the driving pinion and the driven gear pair were evaluated in the fatigue life of the straight bevel gear pair and the main fatigue failure mode was determined for the significant gear. The results show that the fatigue failure of the driving pinion is the main fatigue failure for the straight bevel gear pair and the bending fatigue failure is the main fatigue failure for the driving pinion.展开更多
Demand for large vibrating screen is huge in the mineral processing industry. As bending and random vibration are not considered in a traditional design method for beam structures of a large vibrating screen, fatigue ...Demand for large vibrating screen is huge in the mineral processing industry. As bending and random vibration are not considered in a traditional design method for beam structures of a large vibrating screen, fatigue damage occurs frequently to affect the screening performance. This work aims to conduct a systematic mechanics analysis of the beam structures and improve the design method. Total motion of a beam structure in screening process can be decomposed into the traditional followed rigid translation(FRT), bending vibration(BV) and axial linear-distributed random rigid translation(ALRRT) excited by the side-plates. When treated as a generalized single-degree-of-freedom(SDOF) elastic system analytically, the BV can be solved by the Rayleigh's method. Stochastic analysis for random process is conducted for the detailed ALRRT calculation. Expressions for the mechanics property, namely, the shearing force and bending-moment with respect to BV and ALRRT, are derived, respectively. Experimental and numerical investigations demonstrate that the largest BV exists at the beam center and can be nearly ignored in comparison with the FRT during a simplified engineering design. With the BV and FRT considered, the mechanics property accords well with the practical situation with the maximum error of 6.33%, which is less than that obtained by traditional method.展开更多
The hydraulic roll-bending device was studied, which was widely used in modem cold rolling mills to regulate the strip flatness. The loaded roll gap crown mathematic model and the strip crown mathematic model of the r...The hydraulic roll-bending device was studied, which was widely used in modem cold rolling mills to regulate the strip flatness. The loaded roll gap crown mathematic model and the strip crown mathematic model of the reversing cold rolling process were established, and the deformation model of roll stack system of the 6-high 1 250 mm high crown （HC） reversing cold rolling mill was built by slit beam method. The simulation results show that, the quadratic component of strip crown decreases nearly linearly with the increase of the work roll bending force, when the shifting value of intermediate roll is determined by the rolling process. From the first pass to the fifth pass of reversing rolling process, the crown controllability of bending force is gradually weakened. Base on analyzing the relationship among the main factors associated with roll-bending force in reversing multi-pass rolling, such as strip width and rolling force, a preset mathematic model of bending force is developed by genetic algorithm. The simulation data demonstrate that the relative deviation of flatness criterions in each rolling pass is improved significantly and the mean relative deviation of all five passes is decreased from 25.1% to 1.7%. The model can keep good shape in multi-pass reversing cold rolling process with the high prediction accuracy and can be used to guide the production process.展开更多
Heat pipe is always bent in the typical application of electronic heat dissipation at high heat flux,which greatly affects its heat transfer performance. The capillary limit of heat transport in the bent micro-grooved...Heat pipe is always bent in the typical application of electronic heat dissipation at high heat flux,which greatly affects its heat transfer performance. The capillary limit of heat transport in the bent micro-grooved heat pipes was analyzed in the vapor pressure drop,the liquid pressure drop and the interaction of the vapor with wick fluid. The bent heat pipes were fabricated and tested from the bending angle,the bending position and the bending radius. The results show that temperature difference and thermal resistance increase while the heat transfer capacity of the heat pipe decreases,with the increase of the bending angles and the bending position closer to the vapor section. However,the effects of bending radius can be ignored. The result agrees well with the predicted equations.展开更多
The breakage mechanism of the polycrystalline diamond compact(PDC) cutters was analyzed by the energy theory of bending waves. The cutting tests of granite block were conducted on a multifunctional testing device by u...The breakage mechanism of the polycrystalline diamond compact(PDC) cutters was analyzed by the energy theory of bending waves. The cutting tests of granite block were conducted on a multifunctional testing device by using the cutter at three kinds of negative fore angles of 30°, 45° and 60°. The results show that, when the edge of the PDC layer is broken, the layer of tungsten cobalt is broken a little under the angle of 30°, while the layer of tungsten cobalt is broken continuously under the angle of 60°, their maximum depths are about 2 and 7 mm respectively in the two cases. The eccentric distance mainly depends on the negative fore angle of the cutter. When the cutter thrusts into the rock under an attack angle of 60°, the energy of bending waves reaches the maximum since the eccentric distance is the maximum. So the damage of cutter is the most serious. This test result is consistent with the conclusion of theoretical analysis well. The eccentric distance from the axial line of cutter to the point of action between the rock and cutter has great effect on the breakage of the cutter. Thus during the process of cutting, the eccentric distance should be reduced to improve the service life of PDC cutters.展开更多
Textile reinforced concrete(TRC)has good bearing capacity,crack resistance and corrosion resistance and it is suitable for repairing and reinforcing concrete structures in harsh marine environments.The four-point bend...Textile reinforced concrete(TRC)has good bearing capacity,crack resistance and corrosion resistance and it is suitable for repairing and reinforcing concrete structures in harsh marine environments.The four-point bending method was used to analyze the influence of the salt concentration,the damage degree and the coupled effect of the environment and load on the bending performance of TRC-strengthened beams with a secondary load.The results showed that as the salt concentration increased,the crack width and mid-span deflection of the beam quickly increased,and its bearing capacity decreased.As the damage degree increased,the early-stage crack development and mid-span deflection of the beam were less affected and the ultimate bearing capacity significantly decreased.In addition,the coupled effect of the environment and load on the beams with a secondary load was significant.As the sustained load increased,the ultimate bearing capacity of the strengthened beam decreased,and cracks developed faster in the later stage.In addition,the mid-span deflection of the beam decreased at the same load level because of the influence of the initial deflection due to the sustained load corrosion.展开更多
For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-p...For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.展开更多
A new structure design method of elastic composite cylindrical roller bearing is proposed, in which PTFE is embedded into a hollow cylindrical rolling element, according to the principle of creative combinations and t...A new structure design method of elastic composite cylindrical roller bearing is proposed, in which PTFE is embedded into a hollow cylindrical rolling element, according to the principle of creative combinations and through innovation research on cylindrical roller bearing structure. In order to systematically investigate the inner wall bending stress of the rolling element in elastic composite cylindrical roller bearing, finite element analysis on different elastic composite cylindrical rolling elements was conducted. The results show that, the bending stress of the elastic composite cylindrical rolling increases along with the increase of hollowness with the same filling material. The bending stress of the elastic composite cylindrical rolling element decreases along with the increase of the elasticity modulus of the material under the same physical dimension. Under the same load, on hollow cylindrical rolling element, the maximum bending tensile stress values of the elastic composite cylindrical rolling element after material filling at 0° and 180° are 8.2% and 9.5%, respectively, lower than those of the deep cavity hollow cylindrical rolling element. In addition, the maximum bending-compressive stress value at 90° is decreased by 6.1%.展开更多
A lightweight aggregate concrete-filled steel tube(LACFST) spatial truss beam was tested under bending load. The performance was studied by the analysis of the beam deflection and strains in its chords and webs. Accor...A lightweight aggregate concrete-filled steel tube(LACFST) spatial truss beam was tested under bending load. The performance was studied by the analysis of the beam deflection and strains in its chords and webs. According to the test results, several assumptions were made to deduce the bearing capacity calculation method based on the force balance of the whole section. An optimal dimension relationship for the truss beam chords was proposed and verified by finite element analysis. Results show that the LACFST spatial truss beam failed after excessive deflection. The strain distribution agreed with Bernoulli-Euler theoretical prediction. The truss beam flexural bearing capacity calculation results matched test evidence with only a 3% difference between the two. Finite element analyses with different chord dimensions show that the ultimate bearing capacity increases as the chord dimensions increase when the chords have a diameter smaller than optimal one; otherwise, it remains almost unchanged as the chord dimensions increase.展开更多
In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element(FE) models were established. Effects of different initial thicknesse...In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element(FE) models were established. Effects of different initial thicknesses, pass reductions, speed ratios and offset distances on the bending value of the plate were analyzed. ‘Quasi smooth plate' and optimum offset distance were defined and quasi smooth plate could be acquired by adjusting offset distance, and then bending control equation was fitted. The results show that bending value of the plate as well as the extent of the increase grows with the increase of pass reduction and decrease of initial thickness; the bending value firstly increases and then keeps steady with the ascending speed ratio; the bending value can be reduced by enlarging the offset distance. The optimum offset distance varies for different rolling parameters and it is augmented with the increase of pass reduction and speed ratio and the decrease of initial thickness. A proper offset distance for different rolling parameters can be calculated by the bending control equation and this equation can be a guidance to acquire a quasi smooth plate. The FEM results agree well with experimental results.展开更多
Transformation-induced plasticity(TRIP)steel possesses high strength and formability,enabling the use of a thinner gauge material and allowing for the fabrication of complex shapes.In this research,we measured the eff...Transformation-induced plasticity(TRIP)steel possesses high strength and formability,enabling the use of a thinner gauge material and allowing for the fabrication of complex shapes.In this research,we measured the effect of bending temperatures on the microstructure and air-bending springback angle of TRIP steel at temperatures from 25 to 600C.Real-time in situ X-ray diffraction and scanning electron microscopy were used for pre-and postbending analysis.As the prebending temperature increased from 25C to 600C,the retained austenite(RA)volume fraction decreased,and the RA transformed to bainite at temperatures above 400C.The springback angle was positively correlated with the prebending RA volume fraction,with the smallest springback angle achieved at 400C.Additionally,the springback angle was positively correlated with the bending angle,because the RA transformation ratio contributed to increased strain hardening.Further microstructure analysis revealed that the RA became elongated in the tension direction as the bending temperatures increased.展开更多
Accurate springback prediction of wide sheet metal air bending process is important to improve product quality and ensure the precision in dimension. The definition of elastic limit bend angle was proposed. Based on c...Accurate springback prediction of wide sheet metal air bending process is important to improve product quality and ensure the precision in dimension. The definition of elastic limit bend angle was proposed. Based on cantilever beam elastic deforming theory, the geometrical parameters of forming tools, sheet thickness and the material yielding strain were derived and validated by the finite element method (FEM). Employing the degree of elastic limit bend angle, the equation for springback prediction was constructed, the results calculated fit well with experimental data. Especially for the small bend angle, the predicted results by equation were applied to conduct the springback prediction and compensation in industries and give closer correlation to the experimental data than those calculated by engineering theory of plastic bending.展开更多
The application of fracture in three-point bending to blanking of bearing steel is studied in this paper. Several mechanical models of stress blanking are discussed at first. And then the experiments have been made in...The application of fracture in three-point bending to blanking of bearing steel is studied in this paper. Several mechanical models of stress blanking are discussed at first. And then the experiments have been made in special equipment of three-point bending designed by us. Several problems, such as the suitable span, the relations between bending and tension bending complex, the ratio of blanking length to the diameter, the relations of blank length to force, the feature of fracture, are studied through the experiments. The suitable parameters of three-point bending to blanking, depth and tip radius of notch and the ratio between blanking length and stick diameter have been proposed.展开更多
Experimental study was carried out on the in-plane bending behavior of glass plates without lateral supports, and the effects of the factors, such as height-to-span ratio, on the stability of glass panels were studied...Experimental study was carried out on the in-plane bending behavior of glass plates without lateral supports, and the effects of the factors, such as height-to-span ratio, on the stability of glass panels were studied. Results show that the in-plane bending glass plates with both ends simply supported and their upper edge free lose overall stability under loads, which belongs to the limit-point type of instability. It is found that the buckling load increases linearly with the increase of height-to-span ratio of the glass plates. The lateral stress of in-plane bending glass plates without lateral supports increases linearly under loads; while the large-area stress increases nonlinearly and the lateral stress is not the controlling factor of instability. In finite element analysis, the first buckling mode is regarded as the initial imperfection and imposed on the model as 1/1000 of the span of the components. The numerical buckling load according to the theory of large deflection is less than the experiment result, which is more conservative and can provide some reference for design. For the design method, when the in-plane load is imposed on the glass plate, its lateral strength and the deflection should be verified. Considering the stability of the in-plane bending glass plate without reliable lateral support, buckling is another possible failure mode and calls for verification.展开更多
The dynamic fracture behaviors of the extruded 2024-T4 and 7075-T6 aluminum alloys are investigated by using an instrumented drop tower machine.The specimens are made from a 25 mm diameter extruded circular rod.The dy...The dynamic fracture behaviors of the extruded 2024-T4 and 7075-T6 aluminum alloys are investigated by using an instrumented drop tower machine.The specimens are made from a 25 mm diameter extruded circular rod.The dynamic three-point bending tests of each alloy are carried out at different impact velocities.The initiation fracture toughness and average propagation fracture toughness of 2024-T4 and 7075-T6 are determined at different loading rates.The results show that both the initiation toughness and the propagation toughness increase with the loading rate.Further,the difference between the fracture toughness behaviors of 2024-T4 and 7075-T6 is found to be dependent on the variation of fracture mechanism.The comprehensive fractographic investigations of the fracture surfaces clearly demonstrate that the fracture mode of 2024-T4 is predominantly transgranular fracture with high density small-sized dimples,and the fracture mode of 7075-T6 is mainly intergranular fracture with many intermetallic particles in the bottom of voids located in the fracture surface.展开更多
In order to study the bearing capacity and stability behavior of cold-formed steel flexural members with complicated sections,a total of 12 specimens divided into 6 groups were tested,including 3 groups of pure bendin...In order to study the bearing capacity and stability behavior of cold-formed steel flexural members with complicated sections,a total of 12 specimens divided into 6 groups were tested,including 3 groups of pure bending tests and non-pure bending tests each.There were three types of sections considered in this investigation,including channels with complex edge stiffeners(called B1-section),Σsection with complex edge stiffeners(called B2-section),and channels with complex edge stiffeners and V-type web stiffeners(called B3-section).Local buckling,distortional buckling and interaction buckling between them were observed in tests.The experimental results indicate that the bending strengths of B2-section specimens were the largest of these three types of specimens under the same conditions.It is found that the bending strength of B2-section specimens was increased by 6.47%for pure bending state and 8.12%for non-pure bending state,compared with that of B1-section specimens.Bending strength of B3-section specimens was almost the same with that of B1-section specimens under pure bending,but a little smaller than that of B1-section under non-pure bending state.It is also shown that B2-section specimens have better plastic deformation behavior than the other two sections.In addition,a non-linear finite element model was presented and verified against tests.The finite element analysis results agree well with experimental bending strength and failure modes.展开更多
基金supported by US National Institutes of Health grant R01 AI44902 (to C Z )a Pre-doctoral Fellowship from the American Heart Association (to W C )
文摘Introduction Integrins are a large family of adhesion molecules broadly expressed on the surface of a wide variety of cells as heterodimers. Binding of integrins to ligands provides not only mechanical anchorage for the cell to another cell or
文摘Using the single crack solution and the regular solution of plane harmonic function, the problem of Saint_Venant bending of a cracked cylinder by a transverse force was reduced to solving two sets of integral equations and its general solution was then obtained. Based on the obtained solution, a method to calculate the bending center and the stress intensity factors of the cracked cylinger whose cross_section is not thin_walled, but of small torsion rigidity is proposed. Some numerical examples are given.
基金Projects(50474029,50174035) supported by the National Natural Science Foundation of China
文摘The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test system,and the constitutive equations were established.It is found that fracture morphology of rock beams under no disturbance load is regular,cracking position of fractures is on part of loading concentration,the crack starts from a neutral plane.However,fracture morphology of rock beams under disturbance load is irregular,cracking position of fractures deviates from a neutral plane.Delayed instability of rock beam occurs for some time under constant disturbance load.When disturbance load is beyond a certain range,suddenly instability of occurs rock beam in a certain time.The results show that there is a guiding significance for creep stability in the geotechnical engineering fields.
文摘The numerical control (NC) precision bending process of thin-walled tube is on e of advanced plastic forming processes with high efficiency, forming precision, strength/weight ratio and low cost, thus it is playing more and more important role in manufacturing parts in aerospace and automobile industries. However, the determination of parameters crucial to make sure tube parts qualified is heavil y experience-based and involves repeated trial-and-errors in practice, which makes the production efficiency reduce drastically and does not fulfill the deve lopment of high technology. With quick development of computer technology and gr adual perfect of plastic forming theory, computer numerical simulation based on finite element method (FEM) has become one of important tools of researching and developing plastic forming technology. Development trend of NC precision bendin g process of tube is simulating its forming process by FEM. Because NC tube bend ing is of 3D nature, it is of great importance to analyze the forming mechanism and find out the influence law of forming parameters on forming process in the N C precision bending process of thin-walled tube quantitatively by 3D FE simulat ion. Based on the rigid-plastic finite element method (FEM) principle, a 3-dimens ional (3D) rigid-plastic FE simulation system named TBS -3D (tube bending simu lation by 3D FEM) for the NC bending process of thin-walled tube has been devel oped, a reasonable FEM model has been established. By use of this FEM simulation system, a NC bending process of thin-walled has been simulated. And deformed m eshes under different bending stages, stress distribution along bending directio n, relationship between maximal wall thickness changing ratio and bending angle have been obtained. And then some forming laws of NC tube bending obtained are a s follows: (1) NC bending process make tube elongate to some extent; (2) Charact eristic of stress distribution is that the outer area is undergoing tensile stre ss, the inner area is undergoing compression stress, and stress neutral layer mo ves close to the inner area, which is in good accordance with the practice; (3) Maximal wall thinning ratio in the outer tensile area changes only a little with increase of bending angle, and maximal wall thickening ratio in the inner compr ession area increases linearly with bending angle. The above results show that 3 D FE simulation is an important and valid tool of analyzing NC bending process o f tube, this research is beneficial for the practical tube bending process, and it may serve as a significant guide to the practice of the relevant processes.
基金Project(51105287) supported by the National Natural Science Foundation of ChinaProject(2012BAA08003) supported by the Key Research and Development Project of New Products and New Technologies of Hubei Province, ChinaProject(2011-P05) supported by the State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology,China
文摘The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulative fatigue criterion and the stress-life equation, the key meshing states of the gear pair were investigated for the contact fatigue and the bending fatigue. Then, the reliability of the proposed model was proved by comparing the calculation result with the simulation result. Further study was performed to analyze the variation of the contact fatigue stress and the bending fatigue stress under different loads. Furthermore, the roles of the driving pinion and the driven gear pair were evaluated in the fatigue life of the straight bevel gear pair and the main fatigue failure mode was determined for the significant gear. The results show that the fatigue failure of the driving pinion is the main fatigue failure for the straight bevel gear pair and the bending fatigue failure is the main fatigue failure for the driving pinion.
基金Project(51221462) supported by the National Natural Science Foundation of ChinaProject(20120095110001) supported by the Ph D Programs Foundation of Ministry of Education of China
文摘Demand for large vibrating screen is huge in the mineral processing industry. As bending and random vibration are not considered in a traditional design method for beam structures of a large vibrating screen, fatigue damage occurs frequently to affect the screening performance. This work aims to conduct a systematic mechanics analysis of the beam structures and improve the design method. Total motion of a beam structure in screening process can be decomposed into the traditional followed rigid translation(FRT), bending vibration(BV) and axial linear-distributed random rigid translation(ALRRT) excited by the side-plates. When treated as a generalized single-degree-of-freedom(SDOF) elastic system analytically, the BV can be solved by the Rayleigh's method. Stochastic analysis for random process is conducted for the detailed ALRRT calculation. Expressions for the mechanics property, namely, the shearing force and bending-moment with respect to BV and ALRRT, are derived, respectively. Experimental and numerical investigations demonstrate that the largest BV exists at the beam center and can be nearly ignored in comparison with the FRT during a simplified engineering design. With the BV and FRT considered, the mechanics property accords well with the practical situation with the maximum error of 6.33%, which is less than that obtained by traditional method.
基金Project(20050311890) supported by the Science and Technology Development Foundation of University of Science and Technology Beijing,China
文摘The hydraulic roll-bending device was studied, which was widely used in modem cold rolling mills to regulate the strip flatness. The loaded roll gap crown mathematic model and the strip crown mathematic model of the reversing cold rolling process were established, and the deformation model of roll stack system of the 6-high 1 250 mm high crown （HC） reversing cold rolling mill was built by slit beam method. The simulation results show that, the quadratic component of strip crown decreases nearly linearly with the increase of the work roll bending force, when the shifting value of intermediate roll is determined by the rolling process. From the first pass to the fifth pass of reversing rolling process, the crown controllability of bending force is gradually weakened. Base on analyzing the relationship among the main factors associated with roll-bending force in reversing multi-pass rolling, such as strip width and rolling force, a preset mathematic model of bending force is developed by genetic algorithm. The simulation data demonstrate that the relative deviation of flatness criterions in each rolling pass is improved significantly and the mean relative deviation of all five passes is decreased from 25.1% to 1.7%. The model can keep good shape in multi-pass reversing cold rolling process with the high prediction accuracy and can be used to guide the production process.
基金Project(U0834002) supported by the Joint Funds of the National Nature Science Foundation of China and Guangdong ProvinceProject (2009ZM0134) supported by the Foundational Research Funds for the Central Universities in China
文摘Heat pipe is always bent in the typical application of electronic heat dissipation at high heat flux,which greatly affects its heat transfer performance. The capillary limit of heat transport in the bent micro-grooved heat pipes was analyzed in the vapor pressure drop,the liquid pressure drop and the interaction of the vapor with wick fluid. The bent heat pipes were fabricated and tested from the bending angle,the bending position and the bending radius. The results show that temperature difference and thermal resistance increase while the heat transfer capacity of the heat pipe decreases,with the increase of the bending angles and the bending position closer to the vapor section. However,the effects of bending radius can be ignored. The result agrees well with the predicted equations.
基金Project(06JJ20094) supported by the Natural Science Foundation of Hunan Province, China
文摘The breakage mechanism of the polycrystalline diamond compact(PDC) cutters was analyzed by the energy theory of bending waves. The cutting tests of granite block were conducted on a multifunctional testing device by using the cutter at three kinds of negative fore angles of 30°, 45° and 60°. The results show that, when the edge of the PDC layer is broken, the layer of tungsten cobalt is broken a little under the angle of 30°, while the layer of tungsten cobalt is broken continuously under the angle of 60°, their maximum depths are about 2 and 7 mm respectively in the two cases. The eccentric distance mainly depends on the negative fore angle of the cutter. When the cutter thrusts into the rock under an attack angle of 60°, the energy of bending waves reaches the maximum since the eccentric distance is the maximum. So the damage of cutter is the most serious. This test result is consistent with the conclusion of theoretical analysis well. The eccentric distance from the axial line of cutter to the point of action between the rock and cutter has great effect on the breakage of the cutter. Thus during the process of cutting, the eccentric distance should be reduced to improve the service life of PDC cutters.
基金Project(2017XKZD09)supported by the Fundamental Research Funds for the Central Universities,China
文摘Textile reinforced concrete(TRC)has good bearing capacity,crack resistance and corrosion resistance and it is suitable for repairing and reinforcing concrete structures in harsh marine environments.The four-point bending method was used to analyze the influence of the salt concentration,the damage degree and the coupled effect of the environment and load on the bending performance of TRC-strengthened beams with a secondary load.The results showed that as the salt concentration increased,the crack width and mid-span deflection of the beam quickly increased,and its bearing capacity decreased.As the damage degree increased,the early-stage crack development and mid-span deflection of the beam were less affected and the ultimate bearing capacity significantly decreased.In addition,the coupled effect of the environment and load on the beams with a secondary load was significant.As the sustained load increased,the ultimate bearing capacity of the strengthened beam decreased,and cracks developed faster in the later stage.In addition,the mid-span deflection of the beam decreased at the same load level because of the influence of the initial deflection due to the sustained load corrosion.
基金Project(51164030)supported by the National Natural Science Foundation of China
文摘For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.
基金Project(51175168)supported by the National Natural Science Foundation of ChinaProjects(2011GK3148,2012GK3092)supported by Science and Technology Program of Hunan Province,China
文摘A new structure design method of elastic composite cylindrical roller bearing is proposed, in which PTFE is embedded into a hollow cylindrical rolling element, according to the principle of creative combinations and through innovation research on cylindrical roller bearing structure. In order to systematically investigate the inner wall bending stress of the rolling element in elastic composite cylindrical roller bearing, finite element analysis on different elastic composite cylindrical rolling elements was conducted. The results show that, the bending stress of the elastic composite cylindrical rolling increases along with the increase of hollowness with the same filling material. The bending stress of the elastic composite cylindrical rolling element decreases along with the increase of the elasticity modulus of the material under the same physical dimension. Under the same load, on hollow cylindrical rolling element, the maximum bending tensile stress values of the elastic composite cylindrical rolling element after material filling at 0° and 180° are 8.2% and 9.5%, respectively, lower than those of the deep cavity hollow cylindrical rolling element. In addition, the maximum bending-compressive stress value at 90° is decreased by 6.1%.
基金Project(51208176)supported by the National Natural Science Foundation of ChinaProjects(2012M511187,2013T60493)supported by the China Postdoctoral Science FoundationProject(2015B17414)supported by the Fundamental Research Funds for the Central Universities,China
文摘A lightweight aggregate concrete-filled steel tube(LACFST) spatial truss beam was tested under bending load. The performance was studied by the analysis of the beam deflection and strains in its chords and webs. According to the test results, several assumptions were made to deduce the bearing capacity calculation method based on the force balance of the whole section. An optimal dimension relationship for the truss beam chords was proposed and verified by finite element analysis. Results show that the LACFST spatial truss beam failed after excessive deflection. The strain distribution agreed with Bernoulli-Euler theoretical prediction. The truss beam flexural bearing capacity calculation results matched test evidence with only a 3% difference between the two. Finite element analyses with different chord dimensions show that the ultimate bearing capacity increases as the chord dimensions increase when the chords have a diameter smaller than optimal one; otherwise, it remains almost unchanged as the chord dimensions increase.
基金Projects(2012CB619505,2010CB731703)supported by the National Basic Research Program of ChinaProject(CX2013B065)supported by Hunan Provincial Innovation Foundation for Postgraduate,China+1 种基金Project(51405520)supported by the National Natural Science Foundation of ChinaProject(zzyjkt2013-06B)supported by the State Key Laboratory of High Performance Complex Manufacturing(Central South University),China
文摘In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element(FE) models were established. Effects of different initial thicknesses, pass reductions, speed ratios and offset distances on the bending value of the plate were analyzed. ‘Quasi smooth plate' and optimum offset distance were defined and quasi smooth plate could be acquired by adjusting offset distance, and then bending control equation was fitted. The results show that bending value of the plate as well as the extent of the increase grows with the increase of pass reduction and decrease of initial thickness; the bending value firstly increases and then keeps steady with the ascending speed ratio; the bending value can be reduced by enlarging the offset distance. The optimum offset distance varies for different rolling parameters and it is augmented with the increase of pass reduction and speed ratio and the decrease of initial thickness. A proper offset distance for different rolling parameters can be calculated by the bending control equation and this equation can be a guidance to acquire a quasi smooth plate. The FEM results agree well with experimental results.
基金This research was funded by Faculty of Engineering,King Mongkut’s Institute of Technology Ladkrabang.
文摘Transformation-induced plasticity(TRIP)steel possesses high strength and formability,enabling the use of a thinner gauge material and allowing for the fabrication of complex shapes.In this research,we measured the effect of bending temperatures on the microstructure and air-bending springback angle of TRIP steel at temperatures from 25 to 600C.Real-time in situ X-ray diffraction and scanning electron microscopy were used for pre-and postbending analysis.As the prebending temperature increased from 25C to 600C,the retained austenite(RA)volume fraction decreased,and the RA transformed to bainite at temperatures above 400C.The springback angle was positively correlated with the prebending RA volume fraction,with the smallest springback angle achieved at 400C.Additionally,the springback angle was positively correlated with the bending angle,because the RA transformation ratio contributed to increased strain hardening.Further microstructure analysis revealed that the RA became elongated in the tension direction as the bending temperatures increased.
基金Project(20050216013) supported by the Research Fund for the Doctoral Program of Higher Education
文摘Accurate springback prediction of wide sheet metal air bending process is important to improve product quality and ensure the precision in dimension. The definition of elastic limit bend angle was proposed. Based on cantilever beam elastic deforming theory, the geometrical parameters of forming tools, sheet thickness and the material yielding strain were derived and validated by the finite element method (FEM). Employing the degree of elastic limit bend angle, the equation for springback prediction was constructed, the results calculated fit well with experimental data. Especially for the small bend angle, the predicted results by equation were applied to conduct the springback prediction and compensation in industries and give closer correlation to the experimental data than those calculated by engineering theory of plastic bending.
文摘The application of fracture in three-point bending to blanking of bearing steel is studied in this paper. Several mechanical models of stress blanking are discussed at first. And then the experiments have been made in special equipment of three-point bending designed by us. Several problems, such as the suitable span, the relations between bending and tension bending complex, the ratio of blanking length to the diameter, the relations of blank length to force, the feature of fracture, are studied through the experiments. The suitable parameters of three-point bending to blanking, depth and tip radius of notch and the ratio between blanking length and stick diameter have been proposed.
文摘Experimental study was carried out on the in-plane bending behavior of glass plates without lateral supports, and the effects of the factors, such as height-to-span ratio, on the stability of glass panels were studied. Results show that the in-plane bending glass plates with both ends simply supported and their upper edge free lose overall stability under loads, which belongs to the limit-point type of instability. It is found that the buckling load increases linearly with the increase of height-to-span ratio of the glass plates. The lateral stress of in-plane bending glass plates without lateral supports increases linearly under loads; while the large-area stress increases nonlinearly and the lateral stress is not the controlling factor of instability. In finite element analysis, the first buckling mode is regarded as the initial imperfection and imposed on the model as 1/1000 of the span of the components. The numerical buckling load according to the theory of large deflection is less than the experiment result, which is more conservative and can provide some reference for design. For the design method, when the in-plane load is imposed on the glass plate, its lateral strength and the deflection should be verified. Considering the stability of the in-plane bending glass plate without reliable lateral support, buckling is another possible failure mode and calls for verification.
基金supported by the NatiS100onal Science Foundation of China under Grant No.11072119the Defense Industrial Technology Development Program under Grant No.B1520110003+2 种基金the K.C.Wong Magna Foundation of Ningbo University,Chinaa grant from the Department of Education of Zhejiang Province through the Impact and Safety of Costal Engineering Initiativea COE Program at Ningbo University
文摘The dynamic fracture behaviors of the extruded 2024-T4 and 7075-T6 aluminum alloys are investigated by using an instrumented drop tower machine.The specimens are made from a 25 mm diameter extruded circular rod.The dynamic three-point bending tests of each alloy are carried out at different impact velocities.The initiation fracture toughness and average propagation fracture toughness of 2024-T4 and 7075-T6 are determined at different loading rates.The results show that both the initiation toughness and the propagation toughness increase with the loading rate.Further,the difference between the fracture toughness behaviors of 2024-T4 and 7075-T6 is found to be dependent on the variation of fracture mechanism.The comprehensive fractographic investigations of the fracture surfaces clearly demonstrate that the fracture mode of 2024-T4 is predominantly transgranular fracture with high density small-sized dimples,and the fracture mode of 7075-T6 is mainly intergranular fracture with many intermetallic particles in the bottom of voids located in the fracture surface.
基金Project(51008200)supported by the National Natural Science Foundation of ChinaProject(2015020575)supported by Natural Science Foundation of Liaoning Province,ChinaProject(F16-205-1-14)supported by Science and Technology Program of Shenyang City,China
文摘In order to study the bearing capacity and stability behavior of cold-formed steel flexural members with complicated sections,a total of 12 specimens divided into 6 groups were tested,including 3 groups of pure bending tests and non-pure bending tests each.There were three types of sections considered in this investigation,including channels with complex edge stiffeners(called B1-section),Σsection with complex edge stiffeners(called B2-section),and channels with complex edge stiffeners and V-type web stiffeners(called B3-section).Local buckling,distortional buckling and interaction buckling between them were observed in tests.The experimental results indicate that the bending strengths of B2-section specimens were the largest of these three types of specimens under the same conditions.It is found that the bending strength of B2-section specimens was increased by 6.47%for pure bending state and 8.12%for non-pure bending state,compared with that of B1-section specimens.Bending strength of B3-section specimens was almost the same with that of B1-section specimens under pure bending,but a little smaller than that of B1-section under non-pure bending state.It is also shown that B2-section specimens have better plastic deformation behavior than the other two sections.In addition,a non-linear finite element model was presented and verified against tests.The finite element analysis results agree well with experimental bending strength and failure modes.
