A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite ...A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite element analysis was employed to model the delamination process,incorporating a contact cohesive zone model.This model couples the traction⁃separation law,the contact law,and the Coulomb friction law simultaneously.The thermomechanical analysis in this study is performed using a sequentially coupled approach,implemented with the finite element software ABAQUS.The findings underscore the importance of this study.展开更多
An algorithm is presented for better legal solution in detailed placement of large scale mixed macros and standard cells IC design.Due to the limitation of computing complexity,an effective and efficient initial place...An algorithm is presented for better legal solution in detailed placement of large scale mixed macros and standard cells IC design.Due to the limitation of computing complexity,an effective and efficient initial placement is very important for detailed placement.Novelty of this algorithm lies in a better solution at initial stage by using network flow method to satisfy row capacity constraint and the thought of linear placement problem(LPP) to resolve overlaps.Moreover,divide and conquer strategy and other simplified methods are adopted to minimize complexity.Experimental results show that the algorithm can get an average of 16% wire length improvement on PAFLO in reasonable CPU time.展开更多
The reliability assessment for an automobile crankshaft provides an important understanding in dealing with the design life of the component in order to eliminate or reduce the likelihood of failure and safety risks.T...The reliability assessment for an automobile crankshaft provides an important understanding in dealing with the design life of the component in order to eliminate or reduce the likelihood of failure and safety risks.The failures of the crankshafts are considered as a catastrophic failure that leads towards a severe failure of the engine block and its other connecting subcomponents.The reliability of an automotive crankshaft under mixed mode loading using the Markov Chain Model is studied.The Markov Chain is modelled by using a two-state condition to represent the bending and torsion loads that would occur on the crankshaft.The automotive crankshaft represents a good case study of a component under mixed mode loading due to the rotating bending and torsion stresses.An estimation of the Weibull shape parameter is used to obtain the probability density function,cumulative distribution function,hazard and reliability rate functions,the bathtub curve and the mean time to failure.The various properties of the shape parameter is used to model the failure characteristic through the bathtub curve is shown.Likewise,an understanding of the patterns posed by the hazard rate onto the component can be used to improve the design and increase the life cycle based on the reliability and dependability of the component.The proposed reliability assessment provides an accurate,efficient,fast and cost effective reliability analysis in contrast to costly and lengthy experimental techniques.展开更多
A feedback control system is needed to restrain plasma vertical displacement in EAST （Experimental Advanced Superconducting Toknmak）. A fast control power supply excites active feedback coils, which produces a magne...A feedback control system is needed to restrain plasma vertical displacement in EAST （Experimental Advanced Superconducting Toknmak）. A fast control power supply excites active feedback coils, which produces a magnetic field to control the plasma＇s displacement. With the development of EAST, new demands on the new fast control power supply have led to an enhanced ability of fast response and output current, as well as a new control mode. The structure of cascaded and paralleled H-bridges can meet the demand of extended capacity, and digital control can reMize current and voltage mixed control mode. The validity of the proposed scheme is confirmed by experiments.展开更多
Mixed mode Ⅰ/Ⅱ fracture erperiments of LC4-CS aluminum alloy were conductedby using tension--shear specimens with thicknesses of 2, 4, 8 and 14mm. Fracturemechanisms of thickness effect on mixed mode Ⅰ/Ⅱ fracture ...Mixed mode Ⅰ/Ⅱ fracture erperiments of LC4-CS aluminum alloy were conductedby using tension--shear specimens with thicknesses of 2, 4, 8 and 14mm. Fracturemechanisms of thickness effect on mixed mode Ⅰ/Ⅱ fracture were first examined fromfracture surface morphology to correlate with the macroscopic fracture behavior andstress state. It is found that specimen thickness has a strong influence on mixed modefracture. As thickness varies from thin to thick the macroscopic fracture surfacesappear the characteristics of plane stress state (2mm, 4mm--thick specimen), three--dimensional stress state (8mm--thick specimens), and plane strain state (14mm--thickspecimens), respectively. The specimens of all kinds of thicknesses are typical of ten-sile type failure under mode Ⅰ loading condition and shear type failure under mode Ⅱloading condition. Two distinct features coexist on the fracture surfaces under mixedmode loading conditions, and the corresponding proportion varies with loading mix-ity. Void--growth processes are the failure mechanism in both predominately tensile-and shears--type fractures. The size and depth of dimples on the fracture surface varygreatly with thickness. Therefore, it is extraordinary necessary to take into accountthe thickness effect when a mixed mode fracture criterion is being established.展开更多
A closed-form solution for predicting the tangential stress of an inclusion located in mixed mode Ⅰ and Ⅱ crack tip field was developed based on the Eshelby equivalent inclusion theory. Then a mixed mode fracture cr...A closed-form solution for predicting the tangential stress of an inclusion located in mixed mode Ⅰ and Ⅱ crack tip field was developed based on the Eshelby equivalent inclusion theory. Then a mixed mode fracture criterion, including the fracture direction and the critical load, was established based on the maximum tangential stress in the inclusion for brittle inclusioninduced fracture materials. The proposed fracture criterion is a function of the inclusion fracture stress, its size and volume fraction, as well as the elastic constants of the inclusion and the matrix material. The present criterion will reduce to the conventional one as the inclusion having the same elastic behavior as the matrix material. The proposed solutions are in good agreement with detailed finite element analysis and measurement.展开更多
Foam-cored sandwich materials have been widely used in the civil engineering due to their advantages such as lightweight,high strength,and excellent anti-corrosion ability. However,the interfacial bonding strength of ...Foam-cored sandwich materials have been widely used in the civil engineering due to their advantages such as lightweight,high strength,and excellent anti-corrosion ability. However,the interfacial bonding strength of foamcored sandwich materials is weakened at elevated temperatures. In practice,the effect of high temperature cannot be ignored,because the composites and foams are sensitive to the change of temperature in the environment. In this study,a series of single-leg bending beams were tested at different temperatures to evaluate the influences of high temperatures on Mode Ⅰ/Ⅱ mixed interfacial fracture of foam core sandwich materials. The temperature was from29 ℃ to 90 ℃,covered the glass transition temperature of composites and foam core,respectively. The Mode Ⅰ/Ⅱ mixed interfacial crack prorogation and its corresponding interfacial strain energy release rate were summarized.展开更多
Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve Mode I, Mode II and mixed mode I–II fracture, respectively. M...Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve Mode I, Mode II and mixed mode I–II fracture, respectively. Microscopic characteristics of the three fracture modes of brittle rock were studied by SEM technique in order to analyze fracture behaviors and better understand fracture mechanisms of different fracture modes of brittle rock. Test results show that the microscopic characteristics of different fracture modes correspond to different fracture mechanisms. The surface of Mode I fracture has a great number of sparse and steep slip-steps with few tearing ridges and shows strong brittleness. In the surface of Mode II fracture there exist many tearing ridges and densely distributed parallel slip-steps and it is attributed to the action of shear stress. The co-action of tensile and shear stresses results in brittle cleavage planes mixed with streamline patterns and tearing ridges in the surface of mixed mode I–II fracture. The measured Mode II fracture toughness K II C and mixed mode I–II fracture toughness K mC are larger than Mode I fracture toughness K I C · K II C is about 3.5 times K I C, and KmC is about 1.2 times K I C.展开更多
For a compression-shear mixed mode interface crack, it is difficult to solve the stress and strain fields considering the material viscosity, the crack-tip singularity, the frictional effect, and the mixed loading lev...For a compression-shear mixed mode interface crack, it is difficult to solve the stress and strain fields considering the material viscosity, the crack-tip singularity, the frictional effect, and the mixed loading level. In this paper, a mechanical model of the dynamic propagation interface crack for the compression-shear mixed mode is proposed using an elastic-viscoplastic constitutive model. The governing equations of propagation crack interface at the crack-tip are given. The numerical analysis is performed for the interface crack of the compression-shear mixed mode by introducing a displacement function and some boundary conditions. The distributed regularities of stress field of the interface crack-tip are discussed with several special parameters. The final results show that the viscosity effect and the frictional contact effect on the crack surface and the mixed-load parameter are important factors in studying the mixed mode interface crack- tip fields. These fields are controlled by the viscosity coefficient, the Mach number, and the singularity exponent.展开更多
Objective:To observe the application effect of“online+offline”mixed teaching mode in clinical nursing teaching.Methods:A total of 72 clinical nursing workers,who work in PLA General Hospital and participated in the ...Objective:To observe the application effect of“online+offline”mixed teaching mode in clinical nursing teaching.Methods:A total of 72 clinical nursing workers,who work in PLA General Hospital and participated in the experiment from March 2019 to March 2021,were selected as the subjects of this study.According to the odd numbers assigned to the participants’names,the participants were divided into two groups:the experimental group and the control group,with 36 cases in each group.The experimental group received“online+offline”hybrid teaching,whereas the control group received traditional offline teaching.In order to evaluate the efficacy and safety of the two groups of nursing workers,their assessment scores,teaching satisfaction scores,and teaching evaluation indicators were observed.Results:The experimental group was significantly better than the control group in terms of assessment scores,teaching satisfaction scores,and teaching evaluation indicators(P<0.05).Conclusion:In clinical nursing teaching,the“online+offline”mixed teaching mode plays a unique role in improving students’scores and teaching quality;thus,it should be promoted.展开更多
A series of mixed mode tests were carried out on 18-8 stainless steel in boiling 42% MgCl_2 solution.The results show that for any K_Ⅱ/K_Ⅰ ratio,the SCC direction coin- cides well with the crack tip maximum normal s...A series of mixed mode tests were carried out on 18-8 stainless steel in boiling 42% MgCl_2 solution.The results show that for any K_Ⅱ/K_Ⅰ ratio,the SCC direction coin- cides well with the crack tip maximum normal stress plane,while the SCC resistance of the material reduces as the ratio of K_Ⅱ/K_Ⅰ increases.The experimental results were discussed in the light of anode dissolving mechanism and the effect of mixed mode loading on crack tip stress and strain.It is concluded that for fracture analysis if mixed mode cracks were simply taken into account as mode Ⅰ cracks,and only mode Ⅰ testing results as mode Ⅰ fracture criter- ion were employed,it may not be safe.展开更多
Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture beha...Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.展开更多
Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution...Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution,the material behaved hydrogen embrittlement in all the cases studied.The threshold K_(ⅡH)/K_(ⅡX) of HIC under mode Ⅱ load- ing was 0.27,which was nearly the same as that K(ⅠH)/K_(ⅠX)=0.29 under mode Ⅰ loading. While the thresholds of-HIC under(Ⅰ+Ⅱ)mixed mode loading were 0.36,0.41 and 0.37 cor- responding to the K_Ⅱ/K_Ⅰ ratio of 0.27,0.4 and O.81.The results show that simple mode Ⅰ or mode Ⅱ loading is more susceptible to hydrogen embrittlement than(Ⅰ+Ⅱ)mixed mode. For explaining the experimental results,the effects of triaxial stress as well as plastic deformation ahead of crack tip has been discussed.展开更多
Under the premise of building an innovative country and cultivating innovative talents,teaching innovative learning,cultivating students’innovative thinking and improving the teaching mode and curriculum form have al...Under the premise of building an innovative country and cultivating innovative talents,teaching innovative learning,cultivating students’innovative thinking and improving the teaching mode and curriculum form have already become one of the main directions of deepening the reform of higher education.Data Structure is essential part in the undergraduate program.It is crucial for student to carry out research and project.In the actual teaching activities,the problems of content updating,practice ability for research projects of data structures are to be improved.Therefore,the course reform is imperative.This paper analyzed the main problems of the current data structures course,explored the solution of the problems,and proposed a new mixed teaching mode and evaluation method.展开更多
E-commerce is an important part of the teaching system in higher vocational colleges, and occupies an important position in higher vocational colleges. At present, the rapid development of information technology has p...E-commerce is an important part of the teaching system in higher vocational colleges, and occupies an important position in higher vocational colleges. At present, the rapid development of information technology has promoted the development of e-commerce in China. For this reason, the requirements of e-commerce talents in various industries are getting higher and higher. As the main position of training professional and skilled talents in China, higher vocational colleges bear the heavy responsibility of training high-quality e-commerce talents. The implementation of the mixed teaching mode of e-commerce major can effectively improve the quality of e-commerce teaching in higher vocational colleges. This paper will discuss the implementation countermeasures of the mixed teaching mode for e-commerce majors in higher vocational colleges, hoping that the discussion in this paper can provide some reference and help for the majority of e-commerce teachers in higher vocational colleges.展开更多
Objective: to study the effect of distance education in the mixed teaching model of medical clinical skills. Methods: fifty interns who worked in our hospital from January 2020 to December 2020 were selected and divid...Objective: to study the effect of distance education in the mixed teaching model of medical clinical skills. Methods: fifty interns who worked in our hospital from January 2020 to December 2020 were selected and divided into the experimental group (distance education model) and the control group (conventional education model) according to different teaching models. The assessment results of interns and the satisfaction of interns with the teachers were compared. Results: the scores of theoretical knowledge and practical operation ability in the experimental group were significantly higher than those in the control group (P < 0.05). The satisfaction of each item in the experimental group was significantly higher than that in the control group (p < 0.05). Discussion: distance education in the mixed teaching model of medical clinical skills can effectively improve the assessment results of practice, and the satisfaction of interns with teaching can be significantly improved. This model can be applied.展开更多
With the continuous integration of information technology and education, a new spark has emerged between online teaching and traditional teaching. The emergence of online and offline mixed teaching model has opened a ...With the continuous integration of information technology and education, a new spark has emerged between online teaching and traditional teaching. The emergence of online and offline mixed teaching model has opened a new chapter for education. The organizational forms of online and offline teaching have their own advantages and disadvantages, which complement each other and play a new positive role. Through an example of vocational education, this paper makes a simple analysis and research on the online and offline mixed teaching model, aiming at introducing these models into the vocational education classroom from various angles and promoting the development of vocational education.展开更多
This paper studies the reform of outdoor sports courses by Henan University of Technology in recent years, and actively explores the learning-oriented mixed teaching model and puts it into practice. Giving priority to...This paper studies the reform of outdoor sports courses by Henan University of Technology in recent years, and actively explores the learning-oriented mixed teaching model and puts it into practice. Giving priority to learning is to highlight students' initiative in learning, students' happiness in learning and students' effectiveness in learning. The mixed teaching mode is the combination of the current online teaching mode and the traditional teaching mode under the class. Teachers have changed their role from "teaching" to "learning" as a guide and helper, making full use of online teaching to solve the problem of difficult or ineffective explanation of knowledge points or technical actions in traditional teaching. The mixed teaching mode creates a platform for students to learn independently, and releases more practice time for offline teaching at the same time, which makes them complement each other well online and offline, thus comprehensively improving the quality of outdoor sports courses and students' learning effect.展开更多
https://www.sciencedirect.com/journal/energy-and-buildings/vol/342/suppl/C Volume 342,1 September 2025[OA](1)Experimental validation of neural network-based prediction of natural ventilation bulk airflow rate by Jo ao...https://www.sciencedirect.com/journal/energy-and-buildings/vol/342/suppl/C Volume 342,1 September 2025[OA](1)Experimental validation of neural network-based prediction of natural ventilation bulk airflow rate by Jo ao Carlos Sim oes,Guilherme Carrilho da Graca,Article115871Abstract:To fully exploit natural ventilation(NV)as an energysaving strategy in mixed-mode buildings,accurate real-time prediction of NV airflow rates is essential.Current approaches for NV airflow rates prediction often rely heavily on expertise knowledge and computationally demanding methods such as Computational Fluid Dynamics(CFD)as well as expensive and complex direct airflow measurements.展开更多
The aim of the present work is to investigate the numerical modeling of interfacial cracks that may appear at the interface between two isotropic elastic materials. The extended finite element method is employed to an...The aim of the present work is to investigate the numerical modeling of interfacial cracks that may appear at the interface between two isotropic elastic materials. The extended finite element method is employed to analyze brittle and bi-material interfacial fatigue crack growth by computing the mixed mode stress intensity factors(SIF). Three different approaches are introduced to compute the SIFs. In the first one, mixed mode SIF is deduced from the computation of the contour integral as per the classical J-integral method,whereas a displacement method is used to evaluate the SIF by using either one or two displacement jumps located along the crack path in the second and third approaches. The displacement jump method is rather classical for mono-materials,but has to our knowledge not been used up to now for a bimaterial. Hence, use of displacement jump for characterizing bi-material cracks constitutes the main contribution of the present study. Several benchmark tests including parametric studies are performed to show the effectiveness of these computational methodologies for SIF considering static and fatigue problems of bi-material structures. It is found that results based on the displacement jump methods are in a very good agreement with those of exact solutions, such as for the J-integral method, but with a larger domain of applicability and a better numerical efficiency(less time consuming and less spurious boundary effect).展开更多
文摘A comprehensive numerical investigation into mixed⁃mode delamination is presented in this study.It aims to assess the impact of thermal and friction effects through mixed⁃mode flexure crack propagation testing.Finite element analysis was employed to model the delamination process,incorporating a contact cohesive zone model.This model couples the traction⁃separation law,the contact law,and the Coulomb friction law simultaneously.The thermomechanical analysis in this study is performed using a sequentially coupled approach,implemented with the finite element software ABAQUS.The findings underscore the importance of this study.
文摘An algorithm is presented for better legal solution in detailed placement of large scale mixed macros and standard cells IC design.Due to the limitation of computing complexity,an effective and efficient initial placement is very important for detailed placement.Novelty of this algorithm lies in a better solution at initial stage by using network flow method to satisfy row capacity constraint and the thought of linear placement problem(LPP) to resolve overlaps.Moreover,divide and conquer strategy and other simplified methods are adopted to minimize complexity.Experimental results show that the algorithm can get an average of 16% wire length improvement on PAFLO in reasonable CPU time.
基金Supported by the Ministry of Education Malaysia(HLP Program,Grant No.HLP-KPT.B.600-2/3-781226085655)
文摘The reliability assessment for an automobile crankshaft provides an important understanding in dealing with the design life of the component in order to eliminate or reduce the likelihood of failure and safety risks.The failures of the crankshafts are considered as a catastrophic failure that leads towards a severe failure of the engine block and its other connecting subcomponents.The reliability of an automotive crankshaft under mixed mode loading using the Markov Chain Model is studied.The Markov Chain is modelled by using a two-state condition to represent the bending and torsion loads that would occur on the crankshaft.The automotive crankshaft represents a good case study of a component under mixed mode loading due to the rotating bending and torsion stresses.An estimation of the Weibull shape parameter is used to obtain the probability density function,cumulative distribution function,hazard and reliability rate functions,the bathtub curve and the mean time to failure.The various properties of the shape parameter is used to model the failure characteristic through the bathtub curve is shown.Likewise,an understanding of the patterns posed by the hazard rate onto the component can be used to improve the design and increase the life cycle based on the reliability and dependability of the component.The proposed reliability assessment provides an accurate,efficient,fast and cost effective reliability analysis in contrast to costly and lengthy experimental techniques.
基金supported by ITER Program of China(973 Program)(No.2011GB109002)National Natural Science Foundation of China(No.11275056)Hefei University of Technology Doctor Research Foundation of China(No.2011HGBZ1292)
文摘A feedback control system is needed to restrain plasma vertical displacement in EAST （Experimental Advanced Superconducting Toknmak）. A fast control power supply excites active feedback coils, which produces a magnetic field to control the plasma＇s displacement. With the development of EAST, new demands on the new fast control power supply have led to an enhanced ability of fast response and output current, as well as a new control mode. The structure of cascaded and paralleled H-bridges can meet the demand of extended capacity, and digital control can reMize current and voltage mixed control mode. The validity of the proposed scheme is confirmed by experiments.
文摘Mixed mode Ⅰ/Ⅱ fracture erperiments of LC4-CS aluminum alloy were conductedby using tension--shear specimens with thicknesses of 2, 4, 8 and 14mm. Fracturemechanisms of thickness effect on mixed mode Ⅰ/Ⅱ fracture were first examined fromfracture surface morphology to correlate with the macroscopic fracture behavior andstress state. It is found that specimen thickness has a strong influence on mixed modefracture. As thickness varies from thin to thick the macroscopic fracture surfacesappear the characteristics of plane stress state (2mm, 4mm--thick specimen), three--dimensional stress state (8mm--thick specimens), and plane strain state (14mm--thickspecimens), respectively. The specimens of all kinds of thicknesses are typical of ten-sile type failure under mode Ⅰ loading condition and shear type failure under mode Ⅱloading condition. Two distinct features coexist on the fracture surfaces under mixedmode loading conditions, and the corresponding proportion varies with loading mix-ity. Void--growth processes are the failure mechanism in both predominately tensile-and shears--type fractures. The size and depth of dimples on the fracture surface varygreatly with thickness. Therefore, it is extraordinary necessary to take into accountthe thickness effect when a mixed mode fracture criterion is being established.
基金Project supported by the National Basic Research Program of China (No. 2004CB619303).
文摘A closed-form solution for predicting the tangential stress of an inclusion located in mixed mode Ⅰ and Ⅱ crack tip field was developed based on the Eshelby equivalent inclusion theory. Then a mixed mode fracture criterion, including the fracture direction and the critical load, was established based on the maximum tangential stress in the inclusion for brittle inclusioninduced fracture materials. The proposed fracture criterion is a function of the inclusion fracture stress, its size and volume fraction, as well as the elastic constants of the inclusion and the matrix material. The present criterion will reduce to the conventional one as the inclusion having the same elastic behavior as the matrix material. The proposed solutions are in good agreement with detailed finite element analysis and measurement.
基金supported in part by the National Key Research and Development Program of China(No.2017YFC0703001)the National Natural Science Foundation of China(No. 51678297).
文摘Foam-cored sandwich materials have been widely used in the civil engineering due to their advantages such as lightweight,high strength,and excellent anti-corrosion ability. However,the interfacial bonding strength of foamcored sandwich materials is weakened at elevated temperatures. In practice,the effect of high temperature cannot be ignored,because the composites and foams are sensitive to the change of temperature in the environment. In this study,a series of single-leg bending beams were tested at different temperatures to evaluate the influences of high temperatures on Mode Ⅰ/Ⅱ mixed interfacial fracture of foam core sandwich materials. The temperature was from29 ℃ to 90 ℃,covered the glass transition temperature of composites and foam core,respectively. The Mode Ⅰ/Ⅱ mixed interfacial crack prorogation and its corresponding interfacial strain energy release rate were summarized.
文摘Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve Mode I, Mode II and mixed mode I–II fracture, respectively. Microscopic characteristics of the three fracture modes of brittle rock were studied by SEM technique in order to analyze fracture behaviors and better understand fracture mechanisms of different fracture modes of brittle rock. Test results show that the microscopic characteristics of different fracture modes correspond to different fracture mechanisms. The surface of Mode I fracture has a great number of sparse and steep slip-steps with few tearing ridges and shows strong brittleness. In the surface of Mode II fracture there exist many tearing ridges and densely distributed parallel slip-steps and it is attributed to the action of shear stress. The co-action of tensile and shear stresses results in brittle cleavage planes mixed with streamline patterns and tearing ridges in the surface of mixed mode I–II fracture. The measured Mode II fracture toughness K II C and mixed mode I–II fracture toughness K mC are larger than Mode I fracture toughness K I C · K II C is about 3.5 times K I C, and KmC is about 1.2 times K I C.
基金Project supported by the National Natural Science Foundation of China(No.11302054)the Fundamental Research Funds for the Central Universities(No.HEUCF130216)
文摘For a compression-shear mixed mode interface crack, it is difficult to solve the stress and strain fields considering the material viscosity, the crack-tip singularity, the frictional effect, and the mixed loading level. In this paper, a mechanical model of the dynamic propagation interface crack for the compression-shear mixed mode is proposed using an elastic-viscoplastic constitutive model. The governing equations of propagation crack interface at the crack-tip are given. The numerical analysis is performed for the interface crack of the compression-shear mixed mode by introducing a displacement function and some boundary conditions. The distributed regularities of stress field of the interface crack-tip are discussed with several special parameters. The final results show that the viscosity effect and the frictional contact effect on the crack surface and the mixed-load parameter are important factors in studying the mixed mode interface crack- tip fields. These fields are controlled by the viscosity coefficient, the Mach number, and the singularity exponent.
文摘Objective:To observe the application effect of“online+offline”mixed teaching mode in clinical nursing teaching.Methods:A total of 72 clinical nursing workers,who work in PLA General Hospital and participated in the experiment from March 2019 to March 2021,were selected as the subjects of this study.According to the odd numbers assigned to the participants’names,the participants were divided into two groups:the experimental group and the control group,with 36 cases in each group.The experimental group received“online+offline”hybrid teaching,whereas the control group received traditional offline teaching.In order to evaluate the efficacy and safety of the two groups of nursing workers,their assessment scores,teaching satisfaction scores,and teaching evaluation indicators were observed.Results:The experimental group was significantly better than the control group in terms of assessment scores,teaching satisfaction scores,and teaching evaluation indicators(P<0.05).Conclusion:In clinical nursing teaching,the“online+offline”mixed teaching mode plays a unique role in improving students’scores and teaching quality;thus,it should be promoted.
文摘A series of mixed mode tests were carried out on 18-8 stainless steel in boiling 42% MgCl_2 solution.The results show that for any K_Ⅱ/K_Ⅰ ratio,the SCC direction coin- cides well with the crack tip maximum normal stress plane,while the SCC resistance of the material reduces as the ratio of K_Ⅱ/K_Ⅰ increases.The experimental results were discussed in the light of anode dissolving mechanism and the effect of mixed mode loading on crack tip stress and strain.It is concluded that for fracture analysis if mixed mode cracks were simply taken into account as mode Ⅰ cracks,and only mode Ⅰ testing results as mode Ⅰ fracture criter- ion were employed,it may not be safe.
文摘Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.
文摘Hydrogen induced cracking(HIC)of 0.3% C,1% Cr,1% Mn,1% Si high strength steel has been studied under simple mode Ⅰ,mode Ⅱ and(Ⅰ+Ⅱ)mixed mode loading conditions.Af- ter being hydrogen-charged in IN H_2SO_4 solution,the material behaved hydrogen embrittlement in all the cases studied.The threshold K_(ⅡH)/K_(ⅡX) of HIC under mode Ⅱ load- ing was 0.27,which was nearly the same as that K(ⅠH)/K_(ⅠX)=0.29 under mode Ⅰ loading. While the thresholds of-HIC under(Ⅰ+Ⅱ)mixed mode loading were 0.36,0.41 and 0.37 cor- responding to the K_Ⅱ/K_Ⅰ ratio of 0.27,0.4 and O.81.The results show that simple mode Ⅰ or mode Ⅱ loading is more susceptible to hydrogen embrittlement than(Ⅰ+Ⅱ)mixed mode. For explaining the experimental results,the effects of triaxial stress as well as plastic deformation ahead of crack tip has been discussed.
文摘Under the premise of building an innovative country and cultivating innovative talents,teaching innovative learning,cultivating students’innovative thinking and improving the teaching mode and curriculum form have already become one of the main directions of deepening the reform of higher education.Data Structure is essential part in the undergraduate program.It is crucial for student to carry out research and project.In the actual teaching activities,the problems of content updating,practice ability for research projects of data structures are to be improved.Therefore,the course reform is imperative.This paper analyzed the main problems of the current data structures course,explored the solution of the problems,and proposed a new mixed teaching mode and evaluation method.
文摘E-commerce is an important part of the teaching system in higher vocational colleges, and occupies an important position in higher vocational colleges. At present, the rapid development of information technology has promoted the development of e-commerce in China. For this reason, the requirements of e-commerce talents in various industries are getting higher and higher. As the main position of training professional and skilled talents in China, higher vocational colleges bear the heavy responsibility of training high-quality e-commerce talents. The implementation of the mixed teaching mode of e-commerce major can effectively improve the quality of e-commerce teaching in higher vocational colleges. This paper will discuss the implementation countermeasures of the mixed teaching mode for e-commerce majors in higher vocational colleges, hoping that the discussion in this paper can provide some reference and help for the majority of e-commerce teachers in higher vocational colleges.
文摘Objective: to study the effect of distance education in the mixed teaching model of medical clinical skills. Methods: fifty interns who worked in our hospital from January 2020 to December 2020 were selected and divided into the experimental group (distance education model) and the control group (conventional education model) according to different teaching models. The assessment results of interns and the satisfaction of interns with the teachers were compared. Results: the scores of theoretical knowledge and practical operation ability in the experimental group were significantly higher than those in the control group (P < 0.05). The satisfaction of each item in the experimental group was significantly higher than that in the control group (p < 0.05). Discussion: distance education in the mixed teaching model of medical clinical skills can effectively improve the assessment results of practice, and the satisfaction of interns with teaching can be significantly improved. This model can be applied.
文摘With the continuous integration of information technology and education, a new spark has emerged between online teaching and traditional teaching. The emergence of online and offline mixed teaching model has opened a new chapter for education. The organizational forms of online and offline teaching have their own advantages and disadvantages, which complement each other and play a new positive role. Through an example of vocational education, this paper makes a simple analysis and research on the online and offline mixed teaching model, aiming at introducing these models into the vocational education classroom from various angles and promoting the development of vocational education.
文摘This paper studies the reform of outdoor sports courses by Henan University of Technology in recent years, and actively explores the learning-oriented mixed teaching model and puts it into practice. Giving priority to learning is to highlight students' initiative in learning, students' happiness in learning and students' effectiveness in learning. The mixed teaching mode is the combination of the current online teaching mode and the traditional teaching mode under the class. Teachers have changed their role from "teaching" to "learning" as a guide and helper, making full use of online teaching to solve the problem of difficult or ineffective explanation of knowledge points or technical actions in traditional teaching. The mixed teaching mode creates a platform for students to learn independently, and releases more practice time for offline teaching at the same time, which makes them complement each other well online and offline, thus comprehensively improving the quality of outdoor sports courses and students' learning effect.
文摘https://www.sciencedirect.com/journal/energy-and-buildings/vol/342/suppl/C Volume 342,1 September 2025[OA](1)Experimental validation of neural network-based prediction of natural ventilation bulk airflow rate by Jo ao Carlos Sim oes,Guilherme Carrilho da Graca,Article115871Abstract:To fully exploit natural ventilation(NV)as an energysaving strategy in mixed-mode buildings,accurate real-time prediction of NV airflow rates is essential.Current approaches for NV airflow rates prediction often rely heavily on expertise knowledge and computationally demanding methods such as Computational Fluid Dynamics(CFD)as well as expensive and complex direct airflow measurements.
文摘The aim of the present work is to investigate the numerical modeling of interfacial cracks that may appear at the interface between two isotropic elastic materials. The extended finite element method is employed to analyze brittle and bi-material interfacial fatigue crack growth by computing the mixed mode stress intensity factors(SIF). Three different approaches are introduced to compute the SIFs. In the first one, mixed mode SIF is deduced from the computation of the contour integral as per the classical J-integral method,whereas a displacement method is used to evaluate the SIF by using either one or two displacement jumps located along the crack path in the second and third approaches. The displacement jump method is rather classical for mono-materials,but has to our knowledge not been used up to now for a bimaterial. Hence, use of displacement jump for characterizing bi-material cracks constitutes the main contribution of the present study. Several benchmark tests including parametric studies are performed to show the effectiveness of these computational methodologies for SIF considering static and fatigue problems of bi-material structures. It is found that results based on the displacement jump methods are in a very good agreement with those of exact solutions, such as for the J-integral method, but with a larger domain of applicability and a better numerical efficiency(less time consuming and less spurious boundary effect).
