Three characteristic points in the deformation history of a fractured tensile specimen are selected tocalculate two values of n( n1 and n2 ) to represent the hardening ability of material during the homogeneous plas-t...Three characteristic points in the deformation history of a fractured tensile specimen are selected tocalculate two values of n( n1 and n2 ) to represent the hardening ability of material during the homogeneous plas-tic deformation and the following large plastic deformation. Experimental results obtained with mild streel andred copper show that n determined using the three-point method proposed is better to describe the hardening a-bility of material. It is therefore concluded that three-point method can be used to describe the hardening prop-erty of material during both homogeneous deformation and large plastic deformation.展开更多
In nature,there are widely distributed bi-modulus materials with different deformation characteristics under compressive and tensile stress states,such as concrete,rock and ceramics.Due to the lack of constitutive mod...In nature,there are widely distributed bi-modulus materials with different deformation characteristics under compressive and tensile stress states,such as concrete,rock and ceramics.Due to the lack of constitutive model that could reasonably consider the bi-modulus property of materials,and the lack of simple and reliable measurement methods for the tensile elastic parameters of materials,scientists and engineers always neglect the effect of the bi-modulus property of materials in engineering design and numerical simulation.To solve this problem,this study utilizes the uncoupled strain-driven constitutive model proposed by Latorre and Montáns(2020)to systematically study the distributions and magnitudes of stresses and strains of bi-modulus materials in the three-point bending test through the numerical method.Furthermore,a new method to synchronously measure the tensile and compressive elastic moduli of materials through the four-point bending test is proposed.The numerical results show that the bi-modulus property of materials has a significant effect on the stress,strain and displacement in the specimen utilized in the three-point and four-point bending tests.Meanwhile,the results from the numerical tests,in which the elastic constitutive model proposed by Latorre and Montáns(2020)is utilized,also indicate that the newly proposed measurement method has a good reliability.Although the new measurement method proposed in this study can synchronously and effectively measure the tensile and compressive elastic moduli,it cannot measure the tensile and compressive Poisson’s ratios.展开更多
The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the typ...The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the type A and type B systems were carried out to investigate the pull-out capacities and the slope stability reinforcement efficiency in soil and rock slopes.The results of the pull-out tests show the mobilized shear force and load transfer characteristics with respect to soil depth.The load-displacement relationship was examined for both type A and type B systems.Slope stability analyses were carried out to study the relationships between soil and nail reinforcement and bending stiffness as well as combined axial tension and shear forces.Factors of safety were calculated in relation to the number of nails and their outside diameters.Both soil and rock slopes were included in this evaluation.展开更多
Light beam deflections caused by stress or strain gradients are inves- tigated analytically and experimentally in homogeneous beam specimens which are subjected to a particular case of flexure with shear. This study i...Light beam deflections caused by stress or strain gradients are inves- tigated analytically and experimentally in homogeneous beam specimens which are subjected to a particular case of flexure with shear. This study is a generalization of the prior an alytical-experimental examination of strain-gradient light deflections produced in stressed plates, which had concentrated on the simplest case where in- formation of interest is collected along a line of symmetry of the stress field. Main purpose of the present investigation is to document the efficacy of the strain-gradient method in analysis of the general case of stress state. The most interesting stress state is that in a beam subjected to the Saint-Venant bending, where the transversal and the longitudinal axes of the beam are in pure shear. The obtained results are compared with the predictions of the developed analytical models and with the pre- dictions of Filon's stress function. The procedures of evaluating the photoelastic and material coefficients using strain-gradient techniques were tested positively.展开更多
To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending ...To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending test and an improved planar shear test are used to evaluate the shear performance of the CLT.In this study,the load-displacement curve is recorded,the experimental part is synchronized with the video,the dynamic process of cracking of the vertical layer is observed and analyzed throughout the test.From the load-displacement curve,the image characteristics of the initial cracking and the sudden increase of the cracking of the specimen are summar-ized.The description results of the whole dynamic process of the CLT vertical layer cracking are analyzed by pla-nar shear strength value,cracking phenomenon,and azimuth angle of cracking surface.The main conclusions show that the three-point bending test and the improved plain shear test can be used to test the plain shear strength of the CLT,with a difference of only 5.7%.The original crack and the new crack expansion account for 18.9%and 81.1%of the main cracking surface,respectively.And the vertical layer of the CLT specimen under three-point bending has three cracking morphologies,such as radial shake,ring shake,neither along with the radial shake nor along with the ring shake.The azimuth angle of the cracking surface of the CLT vertical layer under planar shear is quite consistent with the first main plane azimuth of the vertical layer of the CLT specimens under the three-point bending test and the shearing test.The shape in the cracking direction of the left half-span or the right half-span of the vertical layer of the specimen is similar to the Chinese character eight.展开更多
The study presents a novel source location method based on EEMD （ensemble empirical mode decomposition） and optimized FastICA （independent component analysis） for determining the position of the AE （acoustic emis...The study presents a novel source location method based on EEMD （ensemble empirical mode decomposition） and optimized FastICA （independent component analysis） for determining the position of the AE （acoustic emission） sources in the damage structure of crane. Firstly, The AE signals are self-adaptive decomposed into a number of IMFs （intrinsic mode functions） by using EEMD algorithm. Then, the main feature IMFs signals are extracted as the effective AE source signal by optimized Fast-ICA method, the PSD （power spectral density） of each IMF and the real IMFs are obtained. According to the principle of spectrum similarity, time delay is computed at the different channels in combination with the Cross Correlation time delay estimation principle. Thirdly, a novel source location algorithm based on EEMD-FastICA is proposed and the results of AE source location are obtained. Finally, the three-point bending test for the crane is implemented in order to validate the efficiency of the proposed method. The experimental results indicate that the proposed method has the ability to determinate the position of the AE sources and reduce the interference noises. Moreover, compared with the traditional location algorithm, a considerable improvement is obtained.展开更多
Intervertebral disc flexibility is influenced by lifestyle, loading history, trauma, preexisting conditions, age and degeneration. With regard to degeneration, intervertebral discs become less flexible and stiffer. In...Intervertebral disc flexibility is influenced by lifestyle, loading history, trauma, preexisting conditions, age and degeneration. With regard to degeneration, intervertebral discs become less flexible and stiffer. In this study, a testing protocol using bending and torsion loading was developed to gain the flexibility curves and stiffness often cadaveric lumbar discs. Measurements of rotation in the sagittal plane （flexion-extension）, coronal plane （right-lefl lateral bending） and transverse plane （torsion） due to a 5 N-m load are reported. Results show that overall normal discs are more flexible and behave in a nonlinear fashion. The testing results were used in a develop t＇mite element model of an intervertebral disc to investigate the stresses and strains in the disc components： annulus fibrosus and nucleus pulposus with regard to degeneration. Simulation of bending and torsion loadings show large strains in the annulus and nucleus from a normal disc, in contrast higher stresses develop in the annulus from a degenerated disc. The proposed methodology is novel, versatile, functional and economic with implications in bioengineering, medical sciences and the clinical field.展开更多
The aim of this paper is to present finite element model of a filament-wound composite tube subjected to three-point bending and bending in accordance with standard EN?15807:2011?(railway applications-pneumatic half c...The aim of this paper is to present finite element model of a filament-wound composite tube subjected to three-point bending and bending in accordance with standard EN?15807:2011?(railway applications-pneumatic half couplings) along with its experimental verification. In the finite element model, composite reinforcement plies have been characterized by linear orthotropic material model, while rubber liners have been described by a two-parameter MooneyRivlin model. Force-displacement curves of three-point bending show fairly good agreement between simulation results and experimental data. Reaction forces of FE simulation and experiment of standard bending test are in good agreement.展开更多
文摘Three characteristic points in the deformation history of a fractured tensile specimen are selected tocalculate two values of n( n1 and n2 ) to represent the hardening ability of material during the homogeneous plas-tic deformation and the following large plastic deformation. Experimental results obtained with mild streel andred copper show that n determined using the three-point method proposed is better to describe the hardening a-bility of material. It is therefore concluded that three-point method can be used to describe the hardening prop-erty of material during both homogeneous deformation and large plastic deformation.
基金funding support from the National Key Research and Development Program of China(Grant No.2022YFC3102402)as well as from the National Natural Science Foundation of China(Grant No.51879257).
文摘In nature,there are widely distributed bi-modulus materials with different deformation characteristics under compressive and tensile stress states,such as concrete,rock and ceramics.Due to the lack of constitutive model that could reasonably consider the bi-modulus property of materials,and the lack of simple and reliable measurement methods for the tensile elastic parameters of materials,scientists and engineers always neglect the effect of the bi-modulus property of materials in engineering design and numerical simulation.To solve this problem,this study utilizes the uncoupled strain-driven constitutive model proposed by Latorre and Montáns(2020)to systematically study the distributions and magnitudes of stresses and strains of bi-modulus materials in the three-point bending test through the numerical method.Furthermore,a new method to synchronously measure the tensile and compressive elastic moduli of materials through the four-point bending test is proposed.The numerical results show that the bi-modulus property of materials has a significant effect on the stress,strain and displacement in the specimen utilized in the three-point and four-point bending tests.Meanwhile,the results from the numerical tests,in which the elastic constitutive model proposed by Latorre and Montáns(2020)is utilized,also indicate that the newly proposed measurement method has a good reliability.Although the new measurement method proposed in this study can synchronously and effectively measure the tensile and compressive elastic moduli,it cannot measure the tensile and compressive Poisson’s ratios.
文摘The pull-out capacities for soil nailing systems comprising of one single 29 mm diameter(type A) and four 16 mm diameter(type B) rebars with grouted cement were examined.A field test and numerical analysis for the type A and type B systems were carried out to investigate the pull-out capacities and the slope stability reinforcement efficiency in soil and rock slopes.The results of the pull-out tests show the mobilized shear force and load transfer characteristics with respect to soil depth.The load-displacement relationship was examined for both type A and type B systems.Slope stability analyses were carried out to study the relationships between soil and nail reinforcement and bending stiffness as well as combined axial tension and shear forces.Factors of safety were calculated in relation to the number of nails and their outside diameters.Both soil and rock slopes were included in this evaluation.
基金the Natural SciencesEngineering Research Council of Canadathe NATO Scientific Affairs Division
文摘Light beam deflections caused by stress or strain gradients are inves- tigated analytically and experimentally in homogeneous beam specimens which are subjected to a particular case of flexure with shear. This study is a generalization of the prior an alytical-experimental examination of strain-gradient light deflections produced in stressed plates, which had concentrated on the simplest case where in- formation of interest is collected along a line of symmetry of the stress field. Main purpose of the present investigation is to document the efficacy of the strain-gradient method in analysis of the general case of stress state. The most interesting stress state is that in a beam subjected to the Saint-Venant bending, where the transversal and the longitudinal axes of the beam are in pure shear. The obtained results are compared with the predictions of the developed analytical models and with the pre- dictions of Filon's stress function. The procedures of evaluating the photoelastic and material coefficients using strain-gradient techniques were tested positively.
文摘To describe the dynamic cracking process of the CLT vertical layer,the correlation between a load-displacement curve,specimen cracking,and planar shear failure mechanism of the CLT were explored.A three-point bending test and an improved planar shear test are used to evaluate the shear performance of the CLT.In this study,the load-displacement curve is recorded,the experimental part is synchronized with the video,the dynamic process of cracking of the vertical layer is observed and analyzed throughout the test.From the load-displacement curve,the image characteristics of the initial cracking and the sudden increase of the cracking of the specimen are summar-ized.The description results of the whole dynamic process of the CLT vertical layer cracking are analyzed by pla-nar shear strength value,cracking phenomenon,and azimuth angle of cracking surface.The main conclusions show that the three-point bending test and the improved plain shear test can be used to test the plain shear strength of the CLT,with a difference of only 5.7%.The original crack and the new crack expansion account for 18.9%and 81.1%of the main cracking surface,respectively.And the vertical layer of the CLT specimen under three-point bending has three cracking morphologies,such as radial shake,ring shake,neither along with the radial shake nor along with the ring shake.The azimuth angle of the cracking surface of the CLT vertical layer under planar shear is quite consistent with the first main plane azimuth of the vertical layer of the CLT specimens under the three-point bending test and the shearing test.The shape in the cracking direction of the left half-span or the right half-span of the vertical layer of the specimen is similar to the Chinese character eight.
基金Acknowledgments This work is supported by the National Natural Science Foundation of China （51575101, 51305176）, the funds of High-level talents of JIT （JIT6201623, FHXM201608）.
文摘The study presents a novel source location method based on EEMD （ensemble empirical mode decomposition） and optimized FastICA （independent component analysis） for determining the position of the AE （acoustic emission） sources in the damage structure of crane. Firstly, The AE signals are self-adaptive decomposed into a number of IMFs （intrinsic mode functions） by using EEMD algorithm. Then, the main feature IMFs signals are extracted as the effective AE source signal by optimized Fast-ICA method, the PSD （power spectral density） of each IMF and the real IMFs are obtained. According to the principle of spectrum similarity, time delay is computed at the different channels in combination with the Cross Correlation time delay estimation principle. Thirdly, a novel source location algorithm based on EEMD-FastICA is proposed and the results of AE source location are obtained. Finally, the three-point bending test for the crane is implemented in order to validate the efficiency of the proposed method. The experimental results indicate that the proposed method has the ability to determinate the position of the AE sources and reduce the interference noises. Moreover, compared with the traditional location algorithm, a considerable improvement is obtained.
文摘Intervertebral disc flexibility is influenced by lifestyle, loading history, trauma, preexisting conditions, age and degeneration. With regard to degeneration, intervertebral discs become less flexible and stiffer. In this study, a testing protocol using bending and torsion loading was developed to gain the flexibility curves and stiffness often cadaveric lumbar discs. Measurements of rotation in the sagittal plane （flexion-extension）, coronal plane （right-lefl lateral bending） and transverse plane （torsion） due to a 5 N-m load are reported. Results show that overall normal discs are more flexible and behave in a nonlinear fashion. The testing results were used in a develop t＇mite element model of an intervertebral disc to investigate the stresses and strains in the disc components： annulus fibrosus and nucleus pulposus with regard to degeneration. Simulation of bending and torsion loadings show large strains in the annulus and nucleus from a normal disc, in contrast higher stresses develop in the annulus from a degenerated disc. The proposed methodology is novel, versatile, functional and economic with implications in bioengineering, medical sciences and the clinical field.
文摘The aim of this paper is to present finite element model of a filament-wound composite tube subjected to three-point bending and bending in accordance with standard EN?15807:2011?(railway applications-pneumatic half couplings) along with its experimental verification. In the finite element model, composite reinforcement plies have been characterized by linear orthotropic material model, while rubber liners have been described by a two-parameter MooneyRivlin model. Force-displacement curves of three-point bending show fairly good agreement between simulation results and experimental data. Reaction forces of FE simulation and experiment of standard bending test are in good agreement.
