The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article. It is concluded that the inner original defects, which derived from the manufacturing ...The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article. It is concluded that the inner original defects, which derived from the manufacturing process of composite laminates, are the common and major reason of causing the random distributions of the static strength and the fatigue life. And there is a correlative relation between the two distributions. With the study of statistical relationship between the fatigue loading and the fatigue life in the uniform confidence level and the same survival rate S-N curves of material, the relationship between the static strength distribution and the fatigue life distribution through a material S-N curve model has been obtained. And then the model which is used to describe the distributions of fatigue life of composites, based on their distributions of static strength, is set up. This model reasonably reflects the effects of the inner original defects on the static strength dispersion and on the fatigue life dispersion of composite laminates. The experimental data of three kinds of composite laminates are employed to verify this model, and the results show that this model can predict the random distributions of fatigue life for composites under any fatigue loads fairly well.展开更多
The hoist bracket links the rescue hoist with the helicopter cabin, and its structure design greatly affects the operation convenience and safety of the hoistman and lifeguard in the rescue process with a helicopter.T...The hoist bracket links the rescue hoist with the helicopter cabin, and its structure design greatly affects the operation convenience and safety of the hoistman and lifeguard in the rescue process with a helicopter.This paper firstly builds the force model of the hoist and bracket, and gives five kinds of typical working conditions as the design ones of the bracket. Then this paper puts forward a design process of the hoist bracket based on the topology optimization and strength analysis with the 3D modeling and finite element analysis. This design process can make the bracket's structure lightweight by achieving the optimal material layout under the conditions of maximizing the static stiffness or minimizing the compliance of the bracket. And this improves the dynamic performance of the helicopter, and reduces the fuel consumption and cost under the strength constraints. Finally,taking the design of the hoist bracket used in a rescue helicopter as an example, this paper illustrates the proposed model and method. The analysis results show that the mass of the hoist bracket decreases by 12.5% while the static stiffness of the hoist bracket is achieved. The optimization design results meet the strength requirements of the hoist.展开更多
-The formulation of ring analogy method for the prediction of static strength (ductile collapse) of tubular T, X joints under axial compression based on the limit analysis of the ring with some assumptions is presente...-The formulation of ring analogy method for the prediction of static strength (ductile collapse) of tubular T, X joints under axial compression based on the limit analysis of the ring with some assumptions is presented in this papaer. The regression formula for the effective length of the chord based on test results is established by means of the least square method. The results computed by the present semi-analytic formula are compared with previous results and test data. They are quite close to each other. The accuracy of the present formula depends on the reasonable selection of the effective length of the chord, which requires numerous test data.展开更多
It is common practice in the offshore industry to solve the punching shear problem due to compression by using doubler plate. The finite-element method is a useful tool for studying this problem. The aim of this paper...It is common practice in the offshore industry to solve the punching shear problem due to compression by using doubler plate. The finite-element method is a useful tool for studying this problem. The aim of this paper is to study the static strength of doubler plate reinforced Y-joints subjected to compression loading. The finite-element method is adopted in numerical parametric studies. The individual influences of the geometric parameters βand τd （doubler plate to chord wall thickness ratio） and ld/d1（dubler plate length to brace diameter ratio） on the ultimate strength are made clear. The results show the size of plate may have important effects on the strength of reinforced joints. It is found that the ultimate strength of Y-joints reinforced with appropriately proportioned doubler plates can be greatly improved nearly up tothree times to un-reinforced Y-joints.展开更多
This paper reports investigation conducted to study the fatigue performance of steel fibre reinforced concrete (SFRC) containing fibres of mixed aspect ratio. An extensive experimental program was conducted in which 9...This paper reports investigation conducted to study the fatigue performance of steel fibre reinforced concrete (SFRC) containing fibres of mixed aspect ratio. An extensive experimental program was conducted in which 90 flexural fatigue tests were carried out at different stress levels on size 500 mm×100 mm×100 mm SFRC specimens respectively containing 1.0%, 1.5% and 2.0% volume fraction of fibres. About 36 static flexural tests were also conducted to determine the static flexural strength prior to fatigue testing. Each volume fraction of fibres incorporated corrugated mixed steel fibres of size 0.6 mm×2.0 mm×25 mm and 0.6 mm×2.0 mm×50 mm in ratio 50:50 by weight. The results are presented both as S-N relationships, with the maximum fatigue stress expressed as a percentage of the strength under static loading, and as relationships between actually applied fatigue stress and number of loading cycles to failure. Two-million-cycle fatigue strengths of SFRC containing different volume fractions of mixed fibres were obtained and compared with plain concrete.展开更多
We study the strength and texture of tantalum （Ta） under uniaxiM compression up to 80 GPa using an angle-dispersive radial x-ray diffraction technique together with the lattice strain theory in a diamond anvil cell ...We study the strength and texture of tantalum （Ta） under uniaxiM compression up to 80 GPa using an angle-dispersive radial x-ray diffraction technique together with the lattice strain theory in a diamond anvil cell at ambient temperature. The ratio of differential stress to shear modulus （t/G） is found to remain constant above -60GPa, indicating that the Ta starts to experience macro yield with plastic deformation at this pressure.Combined with independent constraints on the high-pressure shear modulus, we find that the Ta sample could support a differential stress of -4.67 GPa when it starts to yield with plastic deformation at -60 CPa under unlaxial compression. The differential stress in Ta ranges from 0.216 GPa to 4.67CPa with pressure increasing from 1 GPa to 60GPa and can be expressed as t=0.199（33）＋0.075（1）P, where P is the pressure in GPa. A maximum differential stress as high as -5.37 GPa can be supported by Ta at the high pressure of -80 GPa. In addition, we investigate the texture of Ta under nonhydrostatic compression to 80 GPa using the software package material analysis using diffraction. It is proven that the plastic deformation due to stress under high pressures is responsible for the development of texture.展开更多
-'The effect of interaction of loads on the ultimate static strength of tubular joints of offshore fixed platforms, is a practical problem. But there is still absence of rigorous theory to explain available experi...-'The effect of interaction of loads on the ultimate static strength of tubular joints of offshore fixed platforms, is a practical problem. But there is still absence of rigorous theory to explain available experimental data and empirical criteria for the static strength of tubular joints. The idea of yield at hot spot of tubular joints is introduced in this paper. The interaction equations of plastic capacity for the tubular joints under combined loads (two and three different kinds) are derived. Thereafter the Yura's test data and empirical criteria of ultimate static strength for the tubular joints can be explained. The idea of classification of category of loads in accordance with experimental data and the present theory is suggested. Finally, the improved ultimate capacity equations for tubular joints are recommended. The physical significance of the coefficient of plastic reservation Qp is discussed.展开更多
The cowcatcher is one of the unique devices at the front end of the train, which can remove obstacles on the track by crashing before the vehicle body to ensure the safety of the train. When a collision accident happe...The cowcatcher is one of the unique devices at the front end of the train, which can remove obstacles on the track by crashing before the vehicle body to ensure the safety of the train. When a collision accident happens, the cowcatcher serves as the first energy-absorbing structure to dissipate and guide the collision energy. The design of the existing cowcatcher of multiple units generally focuses on the good ability to remove obstacles, while the secondary function, the crashworthiness of orderly deformation under collision, still needs further research. In this study, a finite element model of structural static load and collision analysis was established under standard EN 15227, with the cowcatcher for 160 km/h train as the prototype. Then the solution and simulation process was accomplished under the environment of ANSYS and LS-DYNA. The analysis results showed that the structural static strength of the current cowcatcher met the requirements of the standard EN 15227, and the longitudinal stiffness was evenly distributed. When removing the obstacles with low mass, the impact force was small and the structure would not produce obvious deformation;when removing the obstacles with large mass, the impact force was large and the shear fracture might occur at the connection of the cowcatcher.展开更多
Clinching can be used for effective joining of different metallic materials, e.g., different grades of carbon and alloy steels, aluminum and its alloys and others. This is an alternative joining method to traditional ...Clinching can be used for effective joining of different metallic materials, e.g., different grades of carbon and alloy steels, aluminum and its alloys and others. This is an alternative joining method to traditional methods involving screws, rivets or welding. Clinching is applied in many fields of manufacturing industry. Future applications of clinch joining require advances in quality and among others things, combination with other processes, e.g., hybrid joining by clinching and adhesive bonding. Although the static strength of clinched joints is lower than that of the others joints （e.g., pressure welded joints）, the fatigue strength is comparable. But there is a lack of information about fatigue strength of clinched joints. The static and low cyclic fatigue strengths of mechanically clinched joints were determined experimentally. The load-displacement curves of static strength were compared with low cyclic fatigue strength curves. It was observed the effect of strain hardening for clinched joint of low carbon steels （DC4） under cyclic loading.展开更多
Friction stir spot welding with refilling by friction forming process （FSSW-FFP） was successfully modified using filler plate. Both of this new refilling technique and conventional friction stir spot welding （FSSW...Friction stir spot welding with refilling by friction forming process （FSSW-FFP） was successfully modified using filler plate. Both of this new refilling technique and conventional friction stir spot welding （FSSW） process were used to weld A1 6061-T6 lap shear specimens and the results were compared. Effects of tool rotational speeds on mechanical and metallurgical properties in both the cases were studied. Static shear strength of refilled weld samples was found to be better than those welded by conventional FSSW process at all tool rotational speeds. This is explained in terms of effective increase in cross-sectional area of weld nugget due to addition of more material from filler plate, thereby eliminating the probe hole. Failure mechanisms were discussed and fracture surfaces were analyzed through scanning electron microscopy （SEM）. The hardness profile of the welds exhibited a W-shaped appearance in both the processes and the minimum hardness was measured in the HAZ.展开更多
The present study focuses on the design and choice of materials(steels S355 and 45SCD6)of a chassis of stirred tank(with a variable filling rate)for use in the manufacturing of cosmetic products.This tank or trough wi...The present study focuses on the design and choice of materials(steels S355 and 45SCD6)of a chassis of stirred tank(with a variable filling rate)for use in the manufacturing of cosmetic products.This tank or trough will be submitted to important mechanical and thermal loads and pressure according to the various manufacturing processes.The authors propose a model of thermal and mechanical loads which takes into account the operating conditions of the tank.The analysis of the first 10 modes of vibration of the frame shows that the frequencies are much higher when the filling rate is high.They are higher for steel 45SCD6 than for the$355.The simulation results show that for a selected type of steel,the equivalent Von Mises stress increases along with increase in fill rates and thermal gradient.It appears that the influence of the thermal gradient is predominant.For both steels,the Von Mises equivalent stress is maximum in the beam 32 when the thermal gradient is at its lowest stage,and in the beam 40 for the greatest thermal gradient.展开更多
文摘The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article. It is concluded that the inner original defects, which derived from the manufacturing process of composite laminates, are the common and major reason of causing the random distributions of the static strength and the fatigue life. And there is a correlative relation between the two distributions. With the study of statistical relationship between the fatigue loading and the fatigue life in the uniform confidence level and the same survival rate S-N curves of material, the relationship between the static strength distribution and the fatigue life distribution through a material S-N curve model has been obtained. And then the model which is used to describe the distributions of fatigue life of composites, based on their distributions of static strength, is set up. This model reasonably reflects the effects of the inner original defects on the static strength dispersion and on the fatigue life dispersion of composite laminates. The experimental data of three kinds of composite laminates are employed to verify this model, and the results show that this model can predict the random distributions of fatigue life for composites under any fatigue loads fairly well.
基金the Science and Technology Project of Ministry of Transport of China(No.2013328225080)the Natural Science Foundation of Liaoning Province of China(No.2015020121)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20122125120013)the Fundamental Research Funds for the Central Universities of China(Nos.3132016069 and 3132016354)
文摘The hoist bracket links the rescue hoist with the helicopter cabin, and its structure design greatly affects the operation convenience and safety of the hoistman and lifeguard in the rescue process with a helicopter.This paper firstly builds the force model of the hoist and bracket, and gives five kinds of typical working conditions as the design ones of the bracket. Then this paper puts forward a design process of the hoist bracket based on the topology optimization and strength analysis with the 3D modeling and finite element analysis. This design process can make the bracket's structure lightweight by achieving the optimal material layout under the conditions of maximizing the static stiffness or minimizing the compliance of the bracket. And this improves the dynamic performance of the helicopter, and reduces the fuel consumption and cost under the strength constraints. Finally,taking the design of the hoist bracket used in a rescue helicopter as an example, this paper illustrates the proposed model and method. The analysis results show that the mass of the hoist bracket decreases by 12.5% while the static stiffness of the hoist bracket is achieved. The optimization design results meet the strength requirements of the hoist.
文摘-The formulation of ring analogy method for the prediction of static strength (ductile collapse) of tubular T, X joints under axial compression based on the limit analysis of the ring with some assumptions is presented in this papaer. The regression formula for the effective length of the chord based on test results is established by means of the least square method. The results computed by the present semi-analytic formula are compared with previous results and test data. They are quite close to each other. The accuracy of the present formula depends on the reasonable selection of the effective length of the chord, which requires numerous test data.
文摘It is common practice in the offshore industry to solve the punching shear problem due to compression by using doubler plate. The finite-element method is a useful tool for studying this problem. The aim of this paper is to study the static strength of doubler plate reinforced Y-joints subjected to compression loading. The finite-element method is adopted in numerical parametric studies. The individual influences of the geometric parameters βand τd （doubler plate to chord wall thickness ratio） and ld/d1（dubler plate length to brace diameter ratio） on the ultimate strength are made clear. The results show the size of plate may have important effects on the strength of reinforced joints. It is found that the ultimate strength of Y-joints reinforced with appropriately proportioned doubler plates can be greatly improved nearly up tothree times to un-reinforced Y-joints.
基金Project supported by the Indian Council for Cultural Relations,India
文摘This paper reports investigation conducted to study the fatigue performance of steel fibre reinforced concrete (SFRC) containing fibres of mixed aspect ratio. An extensive experimental program was conducted in which 90 flexural fatigue tests were carried out at different stress levels on size 500 mm×100 mm×100 mm SFRC specimens respectively containing 1.0%, 1.5% and 2.0% volume fraction of fibres. About 36 static flexural tests were also conducted to determine the static flexural strength prior to fatigue testing. Each volume fraction of fibres incorporated corrugated mixed steel fibres of size 0.6 mm×2.0 mm×25 mm and 0.6 mm×2.0 mm×50 mm in ratio 50:50 by weight. The results are presented both as S-N relationships, with the maximum fatigue stress expressed as a percentage of the strength under static loading, and as relationships between actually applied fatigue stress and number of loading cycles to failure. Two-million-cycle fatigue strengths of SFRC containing different volume fractions of mixed fibres were obtained and compared with plain concrete.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10875142 and 11079040the Chinese Academy of Sciences under Grant Nos KJCX2-SW-N03 and KJCX2-SW-N20
文摘We study the strength and texture of tantalum （Ta） under uniaxiM compression up to 80 GPa using an angle-dispersive radial x-ray diffraction technique together with the lattice strain theory in a diamond anvil cell at ambient temperature. The ratio of differential stress to shear modulus （t/G） is found to remain constant above -60GPa, indicating that the Ta starts to experience macro yield with plastic deformation at this pressure.Combined with independent constraints on the high-pressure shear modulus, we find that the Ta sample could support a differential stress of -4.67 GPa when it starts to yield with plastic deformation at -60 CPa under unlaxial compression. The differential stress in Ta ranges from 0.216 GPa to 4.67CPa with pressure increasing from 1 GPa to 60GPa and can be expressed as t=0.199（33）＋0.075（1）P, where P is the pressure in GPa. A maximum differential stress as high as -5.37 GPa can be supported by Ta at the high pressure of -80 GPa. In addition, we investigate the texture of Ta under nonhydrostatic compression to 80 GPa using the software package material analysis using diffraction. It is proven that the plastic deformation due to stress under high pressures is responsible for the development of texture.
文摘-'The effect of interaction of loads on the ultimate static strength of tubular joints of offshore fixed platforms, is a practical problem. But there is still absence of rigorous theory to explain available experimental data and empirical criteria for the static strength of tubular joints. The idea of yield at hot spot of tubular joints is introduced in this paper. The interaction equations of plastic capacity for the tubular joints under combined loads (two and three different kinds) are derived. Thereafter the Yura's test data and empirical criteria of ultimate static strength for the tubular joints can be explained. The idea of classification of category of loads in accordance with experimental data and the present theory is suggested. Finally, the improved ultimate capacity equations for tubular joints are recommended. The physical significance of the coefficient of plastic reservation Qp is discussed.
基金supports by the National Natural Science Foundation of China(Grant No.52172353 and 52202431).
文摘The cowcatcher is one of the unique devices at the front end of the train, which can remove obstacles on the track by crashing before the vehicle body to ensure the safety of the train. When a collision accident happens, the cowcatcher serves as the first energy-absorbing structure to dissipate and guide the collision energy. The design of the existing cowcatcher of multiple units generally focuses on the good ability to remove obstacles, while the secondary function, the crashworthiness of orderly deformation under collision, still needs further research. In this study, a finite element model of structural static load and collision analysis was established under standard EN 15227, with the cowcatcher for 160 km/h train as the prototype. Then the solution and simulation process was accomplished under the environment of ANSYS and LS-DYNA. The analysis results showed that the structural static strength of the current cowcatcher met the requirements of the standard EN 15227, and the longitudinal stiffness was evenly distributed. When removing the obstacles with low mass, the impact force was small and the structure would not produce obvious deformation;when removing the obstacles with large mass, the impact force was large and the shear fracture might occur at the connection of the cowcatcher.
文摘Clinching can be used for effective joining of different metallic materials, e.g., different grades of carbon and alloy steels, aluminum and its alloys and others. This is an alternative joining method to traditional methods involving screws, rivets or welding. Clinching is applied in many fields of manufacturing industry. Future applications of clinch joining require advances in quality and among others things, combination with other processes, e.g., hybrid joining by clinching and adhesive bonding. Although the static strength of clinched joints is lower than that of the others joints （e.g., pressure welded joints）, the fatigue strength is comparable. But there is a lack of information about fatigue strength of clinched joints. The static and low cyclic fatigue strengths of mechanically clinched joints were determined experimentally. The load-displacement curves of static strength were compared with low cyclic fatigue strength curves. It was observed the effect of strain hardening for clinched joint of low carbon steels （DC4） under cyclic loading.
文摘Friction stir spot welding with refilling by friction forming process （FSSW-FFP） was successfully modified using filler plate. Both of this new refilling technique and conventional friction stir spot welding （FSSW） process were used to weld A1 6061-T6 lap shear specimens and the results were compared. Effects of tool rotational speeds on mechanical and metallurgical properties in both the cases were studied. Static shear strength of refilled weld samples was found to be better than those welded by conventional FSSW process at all tool rotational speeds. This is explained in terms of effective increase in cross-sectional area of weld nugget due to addition of more material from filler plate, thereby eliminating the probe hole. Failure mechanisms were discussed and fracture surfaces were analyzed through scanning electron microscopy （SEM）. The hardness profile of the welds exhibited a W-shaped appearance in both the processes and the minimum hardness was measured in the HAZ.
文摘The present study focuses on the design and choice of materials(steels S355 and 45SCD6)of a chassis of stirred tank(with a variable filling rate)for use in the manufacturing of cosmetic products.This tank or trough will be submitted to important mechanical and thermal loads and pressure according to the various manufacturing processes.The authors propose a model of thermal and mechanical loads which takes into account the operating conditions of the tank.The analysis of the first 10 modes of vibration of the frame shows that the frequencies are much higher when the filling rate is high.They are higher for steel 45SCD6 than for the$355.The simulation results show that for a selected type of steel,the equivalent Von Mises stress increases along with increase in fill rates and thermal gradient.It appears that the influence of the thermal gradient is predominant.For both steels,the Von Mises equivalent stress is maximum in the beam 32 when the thermal gradient is at its lowest stage,and in the beam 40 for the greatest thermal gradient.
