Magnetorheological elastomers(MREs)hold significant promise in various fields such as automotive engineering,and civil engineering,where they serve as intelligent materials.Depending on the application of an external ...Magnetorheological elastomers(MREs)hold significant promise in various fields such as automotive engineering,and civil engineering,where they serve as intelligent materials.Depending on the application of an external magnetic field,these materials exhibit varying magnetorheological and viscoelastic properties,including shear stress,yield stress,dynamic moduli,and damping.In this work,a new type of MRE,termed self-healing MREs(SH-MREs),has been developed by adding a novel self-healing agent into existing MREs.The dynamic modulus and loss factor of SH-MREs with different compositions have been characterized under various conditions of frequency,temperature,and strain.The results show that as the strain value increases,the loss factor also increases.Moreover,the loss factor initially increases and then decreases with increasing magnetic field strength.Although higher concentrations of ferromagnetic particles increase the loss factor,they enhance the operational range due to their better responsiveness to magnetic fields.SH-MREs demonstrate improved damping capabilities,attributed to the formation of coordination bonds between ferromagnetic particles and the self-healing agent.The stable structure increases the viscosity of MREs.The results of the regression model suggest a direct proportionality between sensitivity to the magnetic field and the ferromagnetic particle concentration.展开更多
Comparison of the loss factor determination methods of the sandwich composite structure with polyethylene terephthalate core in the aspect of core material rheological parameters identification was the purpose of the ...Comparison of the loss factor determination methods of the sandwich composite structure with polyethylene terephthalate core in the aspect of core material rheological parameters identification was the purpose of the study. Three frequency bandwidths n dB: 1 dB, 2 dB, 3 dB methods, the resonant amplitude method and the fit method of the response of the one degree of freedom model system are taken into considerations. Identification procedure, according to ASTM E756-2005 [1] based on experimental studies of the forced vibrations of the composite structure was presented in the paper. To determine the function of the complex shear modulus of the core material, the Nelder-Mead method is applied. Shear modulus and loss factor identification results were presented on the plots in the frequency domain. The results in a quantitative manner set the applied methods and their practical utility in order.展开更多
Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress conce...Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress concentration factor (SCF). Seven shape factors of the elliptic hole and three levels of elasticity modulus of the soft filler were considered. The reduction coefficient and sensitivity index of SCF are the two indicators in evaluating the influence of soft filler. It was found that the reduction coefficient of SCF increases significantly as the shape factor and the elasticity modulus of the filler increase, indicating that soft filler can reduce the concentrated stress effectively, especially when the shape factor is great. Analysis for the sensitivity index of SCF indicates that SCF is more sensitive to materials with small elasticity modulus than to materials with large one.展开更多
The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its ...The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its topological structure. Then, according to the intrinsic relation of different cells, the axial moduli of internal, surface and corner cells are systematically deduced, and the influence of corner-cell periodic discontinuity on the moduli is also analyzed. Finally, considering the actual shape of axial yarns after consolidation, the longitudinal moduli of the different cells are modified based on energy theory. The technology factor λ is also proposed in this modification. The results show that the axial mechanical properties of this material can be strongly designable. The straightness of the axial yarns greatly affects the longitudinal modulus. Technology factor λ is between 1 to 2, corresponding to the minimum and the maximum modulus, respectively.展开更多
Thorn scrub vegetation in Mexico is distributed over 50 million ha, where native tree species are the source of forage, timber, firewood and charcoal. Research describing wood durability of species from this vegetatio...Thorn scrub vegetation in Mexico is distributed over 50 million ha, where native tree species are the source of forage, timber, firewood and charcoal. Research describing wood durability of species from this vegetation type has not been fully determined, nor classified according to international standards. Thus, the aim of this study was to determine and classify the natural durability of ten woody species. Their natural durability was determined according to the European Pre-Norm 807, the loss of dynamic modulus of elasticity (MOEdyo) (MPa) was determined and wood mass loss (g) after being exposed to Trametes versicolor and Coniophora puteana fungi. Wood durability was classified accord- ing to the European Norm 350-1. Highly significant differences (p 〈 0.001) were found between the durability of woody species. The more durable species with lower MOEdyn lost were Condalia hooked (57.5% ± 0.6%), Havardia pallens (58.2% ± 0.4%) and Acacia schaffneri (58.9% ±6.3%). Species with lower mass loss after exposed to Coniophora puteana were Ebenopsis ebano (6.3% ±1.9%), Condalia hooked (8.6% ±2.3%) and Cordia boissieri (11.8% ±2.3%). E. ebano (7.1% ±2.4%), Condalia hooked (8.2% ± 2.5%) and Cordia boissieri (11.5% ± 3.1%) showed the lower mass lost after exposed to T. versicolor. According to European Norm 350-1, three woody species were classified as very durable and durable species.展开更多
Storage modulus and loss modulus is the main performance index of visco-elastic properties.In this paper the storage modulus and loss modulus of a new diverting acid and their influencing factors were systematically i...Storage modulus and loss modulus is the main performance index of visco-elastic properties.In this paper the storage modulus and loss modulus of a new diverting acid and their influencing factors were systematically investigated.Besides,the constitutive equations of the diverting acid at different temperatures were elicited from shearing experiments,which show that the visco-elastic surfactant(VES)acid system is a non-Newtonian power law fluid at low temperature and a Newtonian fluid at high temperature.The storage modulus and loss modulus at different temperatures,pH,and VES content in the acid are critical for the design of acid stimulation for oil well,especially when the VES acid is used in this field only on trial and the basic data are in urgent needed for the design and construction of the acidification stimulation.展开更多
The present work includes the study of the dynamic properties of the nanocomposites specimens. The dynamic properties of A356/Al2O3 nanocomposites were investigated through different fabrication conditions. The A356/A...The present work includes the study of the dynamic properties of the nanocomposites specimens. The dynamic properties of A356/Al2O3 nanocomposites were investigated through different fabrication conditions. The A356/Al2O3 nanocomposites specimens were fabricated using a combination between the rheocasting and squeeze casting routes. The composites were reinforced with Al2O3 particulates of 60 and 200 nm and different volume fractions up to 5 vol.%. The dynamic properties of the A356/Al2O3 nanocomposites were investigated through measuring the dynamic properties of specimens. Free vibration method is used to measure frequency response (fn ), and damping factor (ξ). The viscoelastic properties such as loss factor η, storage modulus (E'), and loss modulus (E") were obtained. The results concluded that, the dynamic properties of nanocomposites were improved by increasing the volume fractions of nanoparticulates and decreasing the nanoparticulates size. The results indicated also that, the damping factor, and the related parameters (η, E' and E") was strongly affected by increasing both volume fraction and the particulates.展开更多
In this paper, numerical method is used to study the strain rate effect on masonry materials. A typical unit of masonry is selected to serve as a representative volume element (RVE). Numerical model of RVE is establis...In this paper, numerical method is used to study the strain rate effect on masonry materials. A typical unit of masonry is selected to serve as a representative volume element (RVE). Numerical model of RVE is established with detailed distinctive modeling of brick and mortar with their respective dynamic material properties obtained from laboratory tests. The behavior of brick and mortar are characterized by a dynamic damage model that accounts for rate-sensitive and pressuredependent properties of masonry materials. Dynamic loads of different loading rates are applied to RVE. The equivalent homogenized uniaxial compressive strength, threshold strain and elastic modulus in three directions of the masonry are derived from the simulated responses of the RVE. The strain rate effect on the masonry material with clay brick and mortar, such as the dynamic increase factor (DIF) of the ultimate strength and elastic modulus as a function of strain rate are derived from the numerical results.展开更多
In order to study the compressive property of corroded concrete, accelerated corrosion test were performed on concrete C30.6 corrosive solutions, including hydraulic acid solution (pH=2), hydraulic acid solution (p...In order to study the compressive property of corroded concrete, accelerated corrosion test were performed on concrete C30.6 corrosive solutions, including hydraulic acid solution (pH=2), hydraulic acid solution (pH=3) were applied as the corrosive medium. 6 series of corrosion tests, including 111 specimens, were carried out. Mechanical properties of all the corroded specimens were tested respectively. Compressive properties of the corroded specimens (e.g. compressive strength, stress-strain relation, elastic modulus etc.) were achieved. Taking the strength degradation ratio and strain energy loss as damage index, effects of the corrosion solution on the compressive property of corroded concrete were discussed in detail. Relationship between the damage index and corrosion state of specimens were achieved.展开更多
Due to a viscoelastic damping middle layer,sandwich structures have the capacity of energy consumption.In this paper,we describe the frequency-dependent property of viscoelastic materials using complex modulus model,a...Due to a viscoelastic damping middle layer,sandwich structures have the capacity of energy consumption.In this paper,we describe the frequency-dependent property of viscoelastic materials using complex modulus model,and iterative modal strain energy method and iterative complex eigenvalue method are presented to obtain frequency and loss factor of sandwich structures.The two methods are effective and exact for the large-scale complex composite sandwich structures.Then an optimum analysis method is suggested to apply to sandwich structures.Finally,as an example,an optimum analysis of a clamped-clamped sandwich beams is conducted,theoretical closed-form solution and numerical predictions are studied comparatively,and the results agree well.展开更多
基金the National Natural Science Foundation of China(No.52003142).
文摘Magnetorheological elastomers(MREs)hold significant promise in various fields such as automotive engineering,and civil engineering,where they serve as intelligent materials.Depending on the application of an external magnetic field,these materials exhibit varying magnetorheological and viscoelastic properties,including shear stress,yield stress,dynamic moduli,and damping.In this work,a new type of MRE,termed self-healing MREs(SH-MREs),has been developed by adding a novel self-healing agent into existing MREs.The dynamic modulus and loss factor of SH-MREs with different compositions have been characterized under various conditions of frequency,temperature,and strain.The results show that as the strain value increases,the loss factor also increases.Moreover,the loss factor initially increases and then decreases with increasing magnetic field strength.Although higher concentrations of ferromagnetic particles increase the loss factor,they enhance the operational range due to their better responsiveness to magnetic fields.SH-MREs demonstrate improved damping capabilities,attributed to the formation of coordination bonds between ferromagnetic particles and the self-healing agent.The stable structure increases the viscosity of MREs.The results of the regression model suggest a direct proportionality between sensitivity to the magnetic field and the ferromagnetic particle concentration.
文摘Comparison of the loss factor determination methods of the sandwich composite structure with polyethylene terephthalate core in the aspect of core material rheological parameters identification was the purpose of the study. Three frequency bandwidths n dB: 1 dB, 2 dB, 3 dB methods, the resonant amplitude method and the fit method of the response of the one degree of freedom model system are taken into considerations. Identification procedure, according to ASTM E756-2005 [1] based on experimental studies of the forced vibrations of the composite structure was presented in the paper. To determine the function of the complex shear modulus of the core material, the Nelder-Mead method is applied. Shear modulus and loss factor identification results were presented on the plots in the frequency domain. The results in a quantitative manner set the applied methods and their practical utility in order.
基金Supported by National Natural Science Foundation of China (No. 50878142)
文摘Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress concentration factor (SCF). Seven shape factors of the elliptic hole and three levels of elasticity modulus of the soft filler were considered. The reduction coefficient and sensitivity index of SCF are the two indicators in evaluating the influence of soft filler. It was found that the reduction coefficient of SCF increases significantly as the shape factor and the elasticity modulus of the filler increase, indicating that soft filler can reduce the concentrated stress effectively, especially when the shape factor is great. Analysis for the sensitivity index of SCF indicates that SCF is more sensitive to materials with small elasticity modulus than to materials with large one.
基金Supported by the National High Technology Research and Development Program of China(2012AA112201)
文摘The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its topological structure. Then, according to the intrinsic relation of different cells, the axial moduli of internal, surface and corner cells are systematically deduced, and the influence of corner-cell periodic discontinuity on the moduli is also analyzed. Finally, considering the actual shape of axial yarns after consolidation, the longitudinal moduli of the different cells are modified based on energy theory. The technology factor λ is also proposed in this modification. The results show that the axial mechanical properties of this material can be strongly designable. The straightness of the axial yarns greatly affects the longitudinal modulus. Technology factor λ is between 1 to 2, corresponding to the minimum and the maximum modulus, respectively.
基金supported by the Professors improvement Program (PROMEP) and the Science and Technology Support Research Program (Granted to the first author PAICyT)
文摘Thorn scrub vegetation in Mexico is distributed over 50 million ha, where native tree species are the source of forage, timber, firewood and charcoal. Research describing wood durability of species from this vegetation type has not been fully determined, nor classified according to international standards. Thus, the aim of this study was to determine and classify the natural durability of ten woody species. Their natural durability was determined according to the European Pre-Norm 807, the loss of dynamic modulus of elasticity (MOEdyo) (MPa) was determined and wood mass loss (g) after being exposed to Trametes versicolor and Coniophora puteana fungi. Wood durability was classified accord- ing to the European Norm 350-1. Highly significant differences (p 〈 0.001) were found between the durability of woody species. The more durable species with lower MOEdyn lost were Condalia hooked (57.5% ± 0.6%), Havardia pallens (58.2% ± 0.4%) and Acacia schaffneri (58.9% ±6.3%). Species with lower mass loss after exposed to Coniophora puteana were Ebenopsis ebano (6.3% ±1.9%), Condalia hooked (8.6% ±2.3%) and Cordia boissieri (11.8% ±2.3%). E. ebano (7.1% ±2.4%), Condalia hooked (8.2% ± 2.5%) and Cordia boissieri (11.5% ± 3.1%) showed the lower mass lost after exposed to T. versicolor. According to European Norm 350-1, three woody species were classified as very durable and durable species.
基金Supported by the Acidification for Heterogeneous Carbonate Reservoirs Program of Petro China Company Limited
文摘Storage modulus and loss modulus is the main performance index of visco-elastic properties.In this paper the storage modulus and loss modulus of a new diverting acid and their influencing factors were systematically investigated.Besides,the constitutive equations of the diverting acid at different temperatures were elicited from shearing experiments,which show that the visco-elastic surfactant(VES)acid system is a non-Newtonian power law fluid at low temperature and a Newtonian fluid at high temperature.The storage modulus and loss modulus at different temperatures,pH,and VES content in the acid are critical for the design of acid stimulation for oil well,especially when the VES acid is used in this field only on trial and the basic data are in urgent needed for the design and construction of the acidification stimulation.
文摘The present work includes the study of the dynamic properties of the nanocomposites specimens. The dynamic properties of A356/Al2O3 nanocomposites were investigated through different fabrication conditions. The A356/Al2O3 nanocomposites specimens were fabricated using a combination between the rheocasting and squeeze casting routes. The composites were reinforced with Al2O3 particulates of 60 and 200 nm and different volume fractions up to 5 vol.%. The dynamic properties of the A356/Al2O3 nanocomposites were investigated through measuring the dynamic properties of specimens. Free vibration method is used to measure frequency response (fn ), and damping factor (ξ). The viscoelastic properties such as loss factor η, storage modulus (E'), and loss modulus (E") were obtained. The results concluded that, the dynamic properties of nanocomposites were improved by increasing the volume fractions of nanoparticulates and decreasing the nanoparticulates size. The results indicated also that, the damping factor, and the related parameters (η, E' and E") was strongly affected by increasing both volume fraction and the particulates.
基金Supported by Australia Research Council(No.DP0451966)
文摘In this paper, numerical method is used to study the strain rate effect on masonry materials. A typical unit of masonry is selected to serve as a representative volume element (RVE). Numerical model of RVE is established with detailed distinctive modeling of brick and mortar with their respective dynamic material properties obtained from laboratory tests. The behavior of brick and mortar are characterized by a dynamic damage model that accounts for rate-sensitive and pressuredependent properties of masonry materials. Dynamic loads of different loading rates are applied to RVE. The equivalent homogenized uniaxial compressive strength, threshold strain and elastic modulus in three directions of the masonry are derived from the simulated responses of the RVE. The strain rate effect on the masonry material with clay brick and mortar, such as the dynamic increase factor (DIF) of the ultimate strength and elastic modulus as a function of strain rate are derived from the numerical results.
基金the National Natural Science Foundation Emphasis Project of China(No.50439010)Liaoning Provincial Natural Science Foundation of China(No.1050259)Open Laboratory Foundation of State Key Laboratory of Coastal and Offshore Engineering(No.LP0605)
文摘In order to study the compressive property of corroded concrete, accelerated corrosion test were performed on concrete C30.6 corrosive solutions, including hydraulic acid solution (pH=2), hydraulic acid solution (pH=3) were applied as the corrosive medium. 6 series of corrosion tests, including 111 specimens, were carried out. Mechanical properties of all the corroded specimens were tested respectively. Compressive properties of the corroded specimens (e.g. compressive strength, stress-strain relation, elastic modulus etc.) were achieved. Taking the strength degradation ratio and strain energy loss as damage index, effects of the corrosion solution on the compressive property of corroded concrete were discussed in detail. Relationship between the damage index and corrosion state of specimens were achieved.
文摘Due to a viscoelastic damping middle layer,sandwich structures have the capacity of energy consumption.In this paper,we describe the frequency-dependent property of viscoelastic materials using complex modulus model,and iterative modal strain energy method and iterative complex eigenvalue method are presented to obtain frequency and loss factor of sandwich structures.The two methods are effective and exact for the large-scale complex composite sandwich structures.Then an optimum analysis method is suggested to apply to sandwich structures.Finally,as an example,an optimum analysis of a clamped-clamped sandwich beams is conducted,theoretical closed-form solution and numerical predictions are studied comparatively,and the results agree well.