Search

In order to solve the optimization design problem of complex shape of underwater glider and improve the optimization efficiency of Kriging surrogate model while improving its lift drag ratio, an adaptive surrogate optimal algorithm is proposed. The proposed improved parallel expectation improvement（PEI） criterion and probability of improvement（PI） criterion are used for global exploration, and the minimizing surrogate prediction（MSP） criterion is used for local exploration. The switching between global exploration and local exploration is realized according to the relationship between new sample points and known sample points. The proposed algorithm, the maximum expected improvement（EI） criterion multiple expectation of improvement（q-EI） and the improved probability improvement（IPI） are combined through a mathematical example. The result shows that the proposed algorithm converges faster and has higher accuracy. Finally, the optimal algorithm is used to optimize the shape of the underwater glider, and the maximum lift drag ratio is increased by 19.37%.

Transportation and human protection industry constantly demands for lightweight and better energy absorption materials and structures. By designing customizable porous materials, the mechanical properties and energy absorption of hexagonal honeycomb-structured polydimethylsiloxane（PDMS） were investigated through experiments and numerical simulations. PDMS has adequate viscoelastic properties for 3D directing ink writing（DIW）, therefore the honeycomb structures with different line widths were fabricated through optimizations of the printing speed and air pressure. Quasi-static compression tests were performed on the fabricated samples to evaluate their mechanical properties and energy absorption. The results show that the average stress in the plateau stage of the honeycomb structure increase with the increase of the line width, but is anisotropy. The honeycomb structure with line width of 900 μm has highest energy absorption of 0.018 J/cm~3. The corresponding finite element analysis were in agreement with the experimental results.

In recent years, as a new type of anti-corrosion material, polyurea coatings have been widely applied to the protection of internal and external walls for pipes. In order to overcome the shortage of traditional ultrasonic testing with low efficiency, the imagine of detecting some cracks in polyurea anti-corrosive pipes was proposed, which based on ultrasonic guided wave detection technology, and it would be studied by numerical simulation. By analyzing the analytical model in the polyurea anti-corrosion pipes, established the three-dimensional cylindrical model of the viscoelastic-elastic composite material by finite element software Abaqus, and simulated the propagation state in which the L（0,2） modal guided wave with the different excited frequencies. Combined with the study of its dispersion and attenuation for selecting optimize frequency, and the analysis of defect detection for the model were accomplished the simulated. The results of research show that the results of numerical simulation are basically consistent with experimental verification, which show that it is effective to use the ultrasonic guided waves for detecting defects of polyurea anti-corrosion pipes and realizing the location of defects.

In order to solve the problem of bolt loosening and failure, based on self-developed aviation self-locking bolts, the influence of locking coating on locking performance of self-locking bolts was studied, and the locking effect of bolts with molybdenum disulfide（MoS2）, nylon 11（PA11） and polyvinyl chloride（PVC） coating materials was explored. Bolt connection locking mechanism are analyzed in this paper, by using the method of finite element simulation analysis and experimental verification, the air with the self-locking bolt lock the simulation and experimental research of the coating material selection, the mathematical model of the thread contour complete accurate set finite element meshing, boundary conditions, load simulation, experimental verification and test bench.The results show that the average locking torque of MoS2, PA11 and PVC is 1.06 N·m, 1.95 N·m and 2.18 N·m respectively in the finite element simulation. When PA11 is used as the coating, it is closer to the requirement that the maximum locking torque is less than or equal to 2.05 N·m in American standard IFI524. The bench test verifies that the average locking torque of the locking bolt with PA11 coating material is 1.82 N·m. Compared with the value of simulation analysis, it is within a reasonable fluctuation range, and PA11 as the coating material can meet the actual production requirements.

In order to improve the working reliability of the biomimetic robotic fish, put forward a gradient reliability robust optimization design method method which is applied to the biomimetic robotic fish.Taken the bionic killer whale as the research object, based on the flapping wing motion theory, the dynamic load of the bionic killer whale was obtained by using MATLAB.Based on the theory of reliability sensitivity design, robust design theory and the theory of performance degradation, established optimization evaluation function of bionic killer whale, obtained the influence of the bionic killer whale’s design variables to reliability sensitivity gradient.The improved quantum evolutionary algorithm was used to optimize the design, the optimal solution of caudal fin propulsion mechanism was obtained.The results show that the absolute value of sensitivity of the design variables is decreased, the reliability is improved and the structure is more robust. This paper combine the flapping wing movement theory, the reliability sensitivity design theory, the reliability-based robust design theory, the theory of performance degradation and improved quantum evolutionary algorithm were combined, put forward a gradient reliability robust optimization design method method which is applied to the biomimetic robotic fish, it provides theoretical method and data support for the reliability analysis and design of bionic robot fish.

In mechanical systems, the gap between mechanical components causes nonlinear elastic collisions during their movement. Taking the two-degree of freedom vibro-impact system with gap as the research object, the mathematical model was established and the numerical simulation analysis was carried out in Matlab software. Based on this, the application of function generators, resistors, capacitors, operational amplifiers and oscilloscopes and other analog electronic components in Multisim software to establish the equivalent circuit model for simulation analysis. The results show that the simulation results of equivalent circuit are consistent with those of numerical simulation analysis.The difference is that the equivalent circuit simulation not only has faster and more efficient operation, but also can realize dynamic parameter adjustment and conversion analysis under different modes. The Equivalent circuit simulation provides a reference method for the dynamics research of nonlinear vibration system.

Improving the efficiency of tidal turbine is the key research of oceanenergy development. The focus of improving the efficiency of tidal turbine lies in the geometry of the turbine blades. Based on the hydrofoil of NACA4412,the method of Joukowski conformal transformation was used to build the parameterized model,the genetic algorithm was realized by MATLAB programming and an optimal solution was found on the basis of using high lift-drag ratio as the objective function under the design variables and constrains. After obtain the optimal solution,use the CFD software was used to simulate the initial hydrofoil and the optimized laminar hydrofoil. According to the results,we can find that the optimized hydrofoil hada great improvement in the liftdrag ratio and lift coefficient compared with the initial hydrofoil. The lift coefficient and the maximum lift-drag ratio of the hydrofoil are increased by 18. 72% and 46. 84% respectively,and the angle of attack is smaller when the hydrofoil reaches the maximum lift-drag ratio after being optimized. The results validate the rationality and validity of the proposed optimal solution and provide a theoretical basis for the subsequent optimization design of tidal turbine hydrofoils.

In order to study the ballistic resistance of TC4 titanium alloy under different impact angle,the experimental study on the high velocity impact of hemi-spherical projectile on TC4 titanium alloy target plate by light gas gun was carry out. The ballictic limit and failure mode was obtained. Based on experimental conditions,simulation model and material parameters had been validating through ABAQUS and the influence of impact angle on the ballistic resistance of TC4 titanium alloy had been further analyzing. The research result indicate that the main failure mode of TC4 titanium alloy against hemi-spherical projectile is petal-shaped failure caused by tensile shear and ductile holing; There exists an easiest penetration angle under which the projectile can penetrate the TC4 titanium alloy target most easily; The impact resistance of the target plate is closely related to the failure mode which is different under varying impact angel.

As a kind of bionic robot fish,bionic killer whale played an important role in ocean development and scientific investigation. Based on the flapping wing movement theory,the bionic killer whale’s mechanism was analyzed,its instantaneous load was simulated by MATLAB. Based on the stress-strength interference theory,the bionic killer’s load reliability state function was established,the reliability index and reliability of bionic killer whale was calculated,combined with the reliability sensitivity analysis theory,the dimensionless sensitivity was obtained,analyzed the influence of the bionic killer whale’s design variables to reliability sensitivity gradient. This paper provides the theoretical basis,accurate data support and an effective numerical calculation method for the design and optimization of the bionic underwater robot with flapping wing theory as the propeller,which has important practical engineering significance.

For pipeline transportation,it is very important to reduce the transportation resistance consumption. In order to reduce the transportation resistance consumption,the application of non-smooth surface drag reduction technology is particularly important. By using the fluid mechanics knowledge and the numerical simulation software,establishing a pit theoretical model.The smooth surface and the pit surface with matrix arrangement were simulated and calculated based on the RNG k-ε model. Two kinds of surface flow fields were simulated respectively,and different drag reduction effects were obtained. Through calculation and analysis,we can conclude that under different working conditions,the surface of the pit with h = 0. 05 mm is better in drag reduction; analyzing the pit surface under 12 m·s-1 conditions,the average shear force is smaller than the smooth surface. Under the pressure difference,the fluid inside the pit generates a low-speed swirling gas,promotes the flow in the main flow region,and further reduces the total resistance.

The essence of crashworthiness is to study the protection of people（ crew and passengers）,and the head injury of the occupants accounted for a large proportion in the crash. In order to investigate the influences of different impact velocity on the occupant ’s head injury under horizontal impact conditions,a comprehensive evaluation method based on occupant ’s Abbreviated Injury Scale（ AIS） and occupant’s injury risk probability to evaluate occupant injury is proposed,and a dynamic simulation model which including seat,restraint system and dummy was constructed by LS-Dyna software. Take the typical civil aircraft double-tube triple-seat as research objects,the effects of different horizontal impact velocity（ 8. 0 m/s,10. 0 m/s,12. 0 m/s,14. 0 m/s,16. 0 m/s） on the head injury of occupants,the stages and characteristics of injuries were analyzed. The results of dummies‘ dynamic response analysis shows that occupants may be severely injured in the head and legs during the aircraft’s longitudinal impact,occupant’head injury increases rapidly with the increase of horizontal impact velocity,and occupant’fatality rate increases exponentially with increasing horizontal impact velocity,the substantial leg movement of the occupants greatly increase the risk of injuries caused by collisions with other facilities in the cabin. In addition,the dummies ’ head trajectory,the peak load of seat belt is proportional to the horizontal impact velocity. Therefore,when the crash occurs,the horizontal impact velocity should be controlled deliberately（ the fatality rate was less than 10% when the impact velocity was13. 0 m/s,and more than 80% when the impact velocity was 16. 0 m/s）.

The ultimate goal of aircraft crashworthiness design is to protecting safety for occupants. In order to more accurately simulate the dynamic response and injury of the occupants during crash event,a crash simulation model of the fuselage section which including dummy and seat restraint system was developed using LS-Dyna,and the dynamic response of the structure and occupants is analyzed in detail when the vertical impact velocity is 9. 14 m/s,the analysis includes the energy absorption characteristics and failure mode of the fuselage structure,the mooring condition of the cabin facilities,the movement and injury of the occupants,etc.,and the validity of the crash simulation model is verified by comparison simulation results with the test data.Finally,the research on the evaluation method of civil aircraft crashworthiness was carried out. Through understanding and identification of relevant airworthiness clauses,advisory circular and standards,the comprehensively evaluation method to evaluating the crashworthiness of civil aircraft was proposed based on the survival space,the strength of mooring,the injury of occupants,the evacuation channel and the post-crash environment. The crashworthiness analysis of the fuselage section shows that the injury modes of occupant in the vertical crash environment are mainly lumbar and tibia injuries,the occupant’s maximum compression lumbar load is 6. 78 k N,and the maximum axial tibia load is 7. 46 k N during the crash process. The crashworthiness of the constructed civil aircraft is systematically evaluated by the comprehensive crashworthiness evaluation method proposed in this paper,it shows that the crashworthiness of this civil aircraft is good,except for the occupant’s lumbar load slightly exceeding the airworthiness limit and requiring corresponding design improvements,the other evaluation indexes are all in accordance with the requirements.

Combined simulation and test to investigate the collapse failure mode and energy absorption characteristics of wingding carbon fiber reinforced composite（CFRP[± 45°/90°]）/Al hybrid thin-walled circular tube under quasi-static axial compression load. Failure mode,Load-displacement curves and energy absorption characteristics were obtained under quasi-static axial crushing tests. A finite element model of hybrid tube was established according to samples. The simulation results with good agreement with the test were obtained by ABAQUS/Explicit,and the crushing failure behavior of the hybrid tube under quasistatic load was reproduced. Based on the simulation results,it was found that the initial crushing load,average crushing load,specific energy absorption and load efficiency of the mixing tube were increased by 97. 6%,93. 3%,57. 8% and 5. 9%,respectively. compared with the aluminum tube. The staged peaks and valleys of the crushing load were selected to analyze the shape of hybrid tube and the failure state of the fiber damage. The results show that when the hybrid tube is complete the fiber plays the main bearing role. In the crushing failure stage,the fiber damage failure mode changes with fiber winding angle,the crushing morphology of aluminum tube and the bonding interface state of CFRP/Al. Subsequently,the energy absorption characteristics of CFRP/Al hybrid circular tubes with three different structure forms were compared. It was found that hybrid circular tube with CFRP[90°/± 45°] wrapped the outside of the aluminum has the best energy absorption.

The experiments under the coupling of the multi-physics field don’t have the conditions to be carried out in the heat exchange tubes fouling test. And it’s very important to establish the accurate ultrasonic propagation model for achieving the numerical simulation of selecting the detection frequency. Based on the finite element method,the three-dimension model with different heat exchange tubes had been established under the COMSOL Multiphysics condition. The varied relationship of the ultrasonic wave propagation,the different heat exchange tubes and echo exciting frequency were discussed respectively. The characteristic frequency and echo vibration mode of multi-layer tubes were found. The results show that the relationship between different characteristics of the heat exchange tubes（ material and wall thickness） and pressure load is similar. The ultrasonic time-domain reflectometry technology to detect the thickness of the tube fouling needs to select 5 MHz echo exciting frequency at least for inhibiting the pseudo-Gibbs oscillation. The optimal detection frequency is 10 MHz,and the detection effect is the best when the thickness at 3 mm ～ 5 mm. The numerical simulation agrees with the test results,and ultrasonic detection produces an error around ±5% in examining tube fouling deposit. These results provide a basis for quantitative detecting basis to select the characteristic frequency under the different tubes.

Aiming at the problem of erosion in oil pipeline transportation system on solid particles in liquid-solid two-phase flow of tee pipes,the erosion area which is caused by solid particles what contain in oil can be simulated by using DPM erosion prediction model.Results show that the erosion location and the degree of solid particles are different from different types of tee pipe.The erosion of T pipe is mainly concentrated on the bottom of the horizontal pipe and the pipe wall near them.The erosion of tee pipe which has a sphere elbow is mainly concentrated on the horizontal pipe wall near the sphere,and the erosion degree is relatively small.

The simulation model of 2 mm thick 2 A12 aluminum alloy thin plate impacted by blade projectile was established by using the ABAQUS finite element software, including impact of yaw and oblique, and the yaw angle is 0-90° and the incidence angle is 0-60°. The effect of impact angle on the impact process, the ballistic limit of the target and the energy absorption of the target were investigated. The simulation results show that the target is mainly shear failure when the yaw angle is 0°, and a long plug and rectangular reaming are remained. When the yaw angle is 15°-60°, the failure mode of the target is ductile expansion and the hole area increases with the increase of the yaw angle. For the yaw angle ranges from 75° to 90°, the target is tore by tensile and the damage is serious. The failure mechanisms of target is both plug and petal damage when oblique impact. The ballistic limit of the target increases with the increase of the yaw angle, and the energy absorption of the target is related with the yaw angle and impact velocity of the projectile. The energy consumption of the target is not independent of the incidence angle.

Due to the fluctuations for high-pressure gas, the displacement of reciprocating air compressor needs to follow the change in requirements. At present, the regulating methods can be applied, including the refluxing regulation, the variable speed adjustment and the pressing-off inlet valve regulation. Among them the pressing-off inlet valve regulation has the best effect, but its control technique and structural modification are relatively difficult. In this paper, according to the demand of the air capacity regulation for reciprocating compressor, an improved operating cycle model of air compressor under the capacity regulation was established. The behaviors of the netted valves and the changes of the pressure in cylinder were analyzed. Additionally, different control parameters in the air capacity regulation system were numerically simulated, the different regulating effects are obtained. The influence of the above parameters was analyzed, which lays the foundation for the system optimization design.

In order to study the crushing process and its influencing factors of the coal rock ploughing and planing by the plough cutters,the planing process is analyzed by numerical simulation, in view of the fact that coal and rock are heterogeneous media, coal rock images are identified, the three-dimensional model of coal rock is established by image reconstruction method, the accuracy of simulation is increased, it provides a new theory and method for three-dimensional finite element modeling of heterogeneous materials, and obtains more accurate simulation data. Through the simulation of coal crushing process under different conditions of plow bit,get contact force plow bit and simulation of coal wall. The results show that:with the increase of planing depth, plow bit stress force increase, the stress gradually stabilized,but because of the change of the coal quality, the forces fluctuate up and down near a steady value;planing speed has little effect on the plane load;coal rock firmness coefficient is larger,the greater the load simulation tool.

Cellular metal materials structure is a new type of porous metal material, it is made up by lots of metal hollow spheres（MHS）, and mechanical behavior research of the single metallic hollow sphere is the foundation of the whole material mechanical performance. The individual MHS with 2 mm to 3 mm outside diameter,10 μm to 40 μm thick walls with porosity were studied, and nano-indentation test, quasi-static uniaxial compression experiment and elastic compression test were performed on the metallic hollow spheres to get the Young’s modulus and hardness of the MHS and the material which was made up of the sphere, also single MHS compression deformation process and characteristics could be observed, finally simulated elastic stage of metallic hollow sphere by finite element software ABAQUS, analyzed the influence of the Young’s modulus of the whole MHS by porosity on thin wall, and result shows that with the porosity increasing, the elastic modulus of MHS will decrease, and present nonlinear distribution, it can be described the same format of a power law function as the relation of porosity with the porous thin wall.

A method of forced angular displacement loading based on ABAQUS software is proposed. In order to improve the efficiency of pretreatment, the type of model elements is selected as C3 D8 R and C3 D10 M suitable for contact analysis according to the structural characteristics of the threaded joints. In this method, the mechanical constraint is treated by balanced penalty function. The boundary conditions are established at the bolt head according to the way of obtaining the pretightening force in engineering. The pretightening force is defined by imposing a forced angular displacement on the rigid element. This method is simpler and more practical than other methods. Finally, the relationship between pretightening force and torsion is obtained by analyzing the thread connection structure of skirt plate lock with this method. The error between the results and the experimental results is within 8%, which is within the range of theoretical calculation. The validity of this method is proved.

In order to study the scraper conveyor load distribution in the process of cutting,a mathematical model between plow performance parameters and scraper conveyor transport performance parameters was established. Using numerical simulation obtained scraper conveyor loading capacity curve in condition of different planing speed ratio,different scraper conveyor lay length and different plow initial position,and analyzing its fluctuation characteristics. The results showed that: the maximum loading capacity of scraper conveyor is related to conveyor lay length,cutting speed ratio,plow face height,plow planing thickness,entity density of coal and so on,is independent of plow initial position; after reaching the maximum loading capacity of scraper conveyor,when planing ratio is odd,the loading capacity maintain maximum and constant,planing speed ratio to another value,the loading capacity presents fluctuation periodically.

Free spanning submarine pipeline work in the harsh condition and has many failure modes. Vortex-induced vibration is a significant cause leading to its fatigue failure. In order to study the law about different spanning clearance ratio and flow rate impacting on VIV strength of free spanning pipeline,this paper applied the software FLUENT to simulate twodimensional flow around actual diameter pipeline at high reynolds number and obtained the data about vortex shedding shape,lift coefficient and drag coefficient curves. The result indicates that: the lift coefficient amplitude and drag coefficient mean value of free spanning submarine pipeline decrease with clearance ratio increasing and gradually stabilize at last. In the case of small clearance ratio,lift extreme value is inequality on both sides of the pipe caused by the pipe bottom flow rate increasing. The lift coefficient amplitude and drag coefficient mean value present a trend of increasing first then decreasing with flow rate increaing,which is consistent with the conventional flow around a cylinder. Lift coefficient frequency increases with flow rate increaing and less affected by the clearance ratio. In engineering practice,water areas of high current velocity and large submarine spans should be avoid as much as possible to lay submarine pipelines and vortex-induced suppression device should be provided in danger sections.

The flow behavior and wall wear of a ball seat in frac sleeve with cone shapes have been studied numerically.The gas flow fields were simulated by means of standard k-εmodel. The effect of instantaneous turbulence on particle tracking was taken into account with the stochastic tracking approach in discrete phase model（ DPM） using Lagrangian method. The flow behavior during the cone part in ball seat was presented,and the changes of flow field and wall wear in ball seat caused by different cone shapes also can be predicted by CFD simulation. The results indicate that The distribution of the flow field in the large column section and the small column section of the ball seat is relatively uniform. Due to the wall effect of the sand,the flow field in the near wall has certain fluctuation. Optimized double cone structure can control the mainstream velocity gradient and sand concentration,and based on that this new design can reduce ball seat wear. Results obtained from the computer modeling have demonstrated the CFD is suitable for modeling an effect of wearing in ball seat on its performance.

In the aerospace sector,foreign object damage（ FOD） is a serious threat to the normal operation of aircraft and aviation security and bird strike damage is the most common. Based on AUTODYN finite element software,a bird bullet SPH model and a Lagrange model of 2024 aerospace aluminum alloy target are built to study the dynamic response and damage characteristic of aircraft envelope when subjected by bird strike. By comparing the simulation result with the experimental data,the validity of bird bullet SPH model is verified. Exploring the influences of largest drum kits,stresses and energies of target impacted by bird strike at different target laminates and bird strike velocities,the best target stack mode would be selected.

To explore the damage of water jet to coal wall,built up the finite element calculation model of water jet breaking coal,applying software ANSYS/ls-dyna is used to numerically simulate the process of water jet breaking coal,the results show that the coal wall impact damage is most serious,the center around the center of coal wall damage is small,water jet shock wave attenuation faster. To explore the influence of different velocity of water jet to coal wall injury,the different velocity of water jet coal process in numerical simulation,the results show that with the increase of flow velocity,the stress of the coal wall are also increase,but the impact damage range is not big,around the center shows that increasing the velocity of shock wave attenuation speed. To explore water jet,affect the performance of coal winning machine cutting coal shearer drum is established in the presence of water jet conditions they finite element calculation model of coal,the two conditions of numerical simulation for the process of cutting coal,the results show that: under the condition of water jet and cutting tooth stress decreases,and with the increase of water jet velocity,the cutter tooth stress decreases,when the water jet velocity of 300 m/s,water jet assisted cutting coal and has good effect.

The depth of the pipeline depression has different influence on the safety of X60 pipeline steel,combining Oyane ductile fracture criterion with numerical simulation method to study damage degree of the pipeline. Establishing three dimensional spherical concave defect pipeline model by finite element software and solving the model,discussing internal pressure influence of the pipeline and the indenter size on the relationship between the depth of sag and the damage degree of oil and gas pipelines.The results show that: when the depth of the pipeline depression is in a certain range the internal pressure is beneficial to resist ductile rupture. Once the depth of the pit exceeds 100 mm,the internal pressure will increase the extent of damage of the pipeline.In the case of the ratio of wall thickness to pipe diameter and the constant pressure in the pipe,the smaller the size of the indenter,the more serious the damage degree increases with the depth of the depression. Under certain conditions,when the pipe sag depth exceeds the standard 7% pipe diameter,the degree of pipe damage still meet the integral value I > 1. The Oyane ductile fracture criterion can be applied to the evaluation of sags in engineering projects because of the limitation of sag depth evaluation criteria.

Based on the of theory heat conduction and thermal-elasticity,simulated the braking process of mine hoist. The changing laws of the boundary condition on the brake disc’s surface during braking were analyzed and the computing method of the convective coefficient was discussed emphatically. According to variable material properties and the actual dimension of brake disk,a 3-dimensional cycle-symmetric model of brake disk in mine hoist was established and the temperature and thermal stress distribution was researched under the different braking conditions. The article discussed the calculation method considering thermal stress,and analyzed and compared each method’s advantage with disadvantage. The results indicate that the temperature and stress distribution of brake disk are closely related to the braking initial velocity and braking acceleration. The simulation provides an important reference for the optimization of lifting speed and braking acceleration,and the design and development of high-performance brake system.

Since solar radiation has a great impact on the thermal environment,three dimensional temperature field of the passenger compartment was simulated by using ray tracing method based on RANS methods. The influence of the insulation glass on the passenger compartment temperature was also quantitative analyzed. The result of calculation shows that solar radiation and body heat flux have a significant impact on the temperature field inside the cabin. The application of the insulation glass can reduce the maximum intensity of the solar transmitted radiation by 14. 4 percent,consequently make the maximum temperature of panel area decreased by 3. 5 centigrade. The research results can be applied to optimize the thermal environment of the passenger compartment.

This article presents an experiment and simulation study on the effect of Z-pin reinforced on the pull-off and sheat carrying capacity of fiber placement composite T-joints,we used CMT5504 to conduct the pull-off test meanwhile we used MTS to conduct the shear test. we studied Z-pin reinforced And non-reinforced test-pieces,drawing Load-displacement curves.The pull-off test results donate that Z-pin can effectively improved the pull-off carrying capacity of T-joints and slow the decrease of the load significantly after pick loading compared to the non-reinforced T-joints. The failure location is between stiffener and interlayer. The shear test results donate that Z-pin can effectively improve the shear carrying capacity of T-joints. The failure location of Z-pin reinforced test is between skin and interlayer and the failure location of non-reinforced test is bwtween stiffener and interlayer. On this basis,we created pull-off and shear model of T-joint specimens. The interface failure was simulated with cohesive zone model,and the effect of Z-pin was simulated with nonlinear springs inserted into the interface. The numerical results agree well with the test data and shows that the model is effective.

Based on the tailor-welded blanks with the radius of 180 mm arc-weld-line,and use Dynaform numerical simulation techniques to study TWBs with the transverse arc-weld-line a under the variable blank holder force changing with travel distance or position,The research shows that a certain range of blank-holder force can control the weld-line movement of TWBs and the springback angle of TWBs under the condition of VBHF changing with position.But beyond the change of the blank holder force,it is beneficial to sheet metal forming,not to the control of springback angle.Compared with other methods,V loading method benefits for the control of the weld-line movement and springback control,it has great effect on the forming of welding plate under the condition of VBHF changing with travel distance.Variable blank-holder force control methods,including changing with position and changing with travel distance,allow more thin side in sheet metal forming into the die,and reduce the welding plate deformation of the thin side material,due to easing the tailor-welded plate thickness caused by uneven deformation.Finally,the weld-line movement and the springback angle controlled to improve the forming quality of welding plate.

The method is to combine dynaform numerical simulation techniques and orthogonal experimental design to analyze the influence factors of intensity ratio,clearance between punch and die,thin side blank holder rate,friction coefficient,blank-holder force and thickness ratio to improve the quality of TWBs,. The research show that Strength ratio, friction coefficient,blank-holder force and the thickness ratio on the forming results is relative bigger. As a whole,tailor-welded sheet forming improved with the increment of the strength of parent metal,because the deformation degree of thin side parent metal reduce the weld-line movement for enhancing its ability to resist deformation. Friction coefficient and blank-holder force is not very big on the influence of the formability of tailor-welded sheet,but the bigger friction coefficient and the bigger total blankholder force affect on both sides of the base material of liquidity,finally,it affects the quality of the forming of the sheet metal.Thickness ratio should be carefully considered in the design of welding plate. Generally,the thickness ratio between 1. 0-1. 0and 1. 0-1. 4 improved the forming of tailor-welded blanks with arc-weld-line,the small and large of thickness ratio are not beneficial to tailor-welded sheet forming.

The stiffness of unidirectional laminates will reduce due to damage under static tensile loads. By analyzing the failure process of unidirectional laminates,study on the effect of stiffness reduction caused by the longitudinal,transverse and shear stress components was conducted. A new model of stiffness progressive reduction considering loads and ply angles was established. The rationality of this model was verified by static tensile tests of series of T700/YPX3001 unidirectional laminates with different ply angles. A numerical simulation based on the proposed model of the failure process of unidirectional laminates under static tensile loads was implemented. The analysis results are in good agreement with experimental results.

Freeze fabrication process is a new modern green additive manufacturing technology. During the depositing process,the freezing time needed would change with the increase of the deposition layer. The paper established the temperature field model of deposition process and simulated the temperature change of deposition process using numerical simulation. The relationship of depositing time with initial temperature,the number of depositing layer,environment temperature during the ice part building process and waiting time between layer and layer was analyzed and the minimum waiting time was found with a better depositing efficiency. The experiment result is also agree with the model proposed.

Excessive deflection of the truck scale body is a primary cause leading to measurement error. The prestressedtreatment method of steel structure was applied to the welding procedure of the truck scale body and U-beam. The mathematical relationship model between the preload and the deflection and stress of the truck scale body was constructed. In addition,the prestressed-treatment process was carried out based on finite element method. The results show the deflection of the simulation results is consistent with the changing rule of the mathematical model. Therefore,the deflection of the truck scale body can be improved effectively with the prestressed-treatment method of steel structure,which can be able to improve its measuring accuracy.

Applying the differential geometry theory and principle of coordinate transformation,the spatial curve parametric equations were derived. An geometric entity model of the anti-twist braided wire rope was established using the three-dimension software. The finite element model of the anti-twist braided wire rope can be acquired by appropriate meshing operation. The boundary conditions are set after loading the constraints and the mass force. and the numerical simulation of the strand stresses deformation was conducted. Then the distribution laws of strand stress distribution and axial deformation in axis dire- ction in its cross section were obtained. Friction coefficients were set as different parameters to obtain the influence law of friction coefficients on strand stresses deformation. The calculation results of strand with five different pitch were analyzed and the influence law of pitch on the strand was obtained.

In order to evaluate the impact process induced by uncontained failure,numerical simulation for one-third HPT（ High Pressure Turbine） disk impact was carried out under different obliquity angles and residual fuel volumes in the wing structure. The study,which resulted in continuous dynamic response,focused on the interaction among debris,turbine cowl and integral fuel tank. The constitutive material mode and failure criteria proposed by Johnson-Cook were applied in solid element definition,while SPH（ Smooth Particle Hydrodynamics） model was used for fuel particles. The analysis involved the debris velocity history,fuel tank deformation along with the stress distribution changes during the whole process. It is shown from the results that with the increase of obliquity angle and residual fuel volume, the velocity loss and energy reduction rise correspondingly. The turbine cowl absorbs most of the debris energy while fuel also contributes to the absorption due to its viscidity. Hydrodynamic ram fails to cause lethal destruction of the tank structure under large debris impact. In the last part,fuel tank boundary design has been discussed qualitatively according to the simulation results.

To study frictional contact problem between rubber tube and the casing,The friction coefficient is measured with Vertical universal friction and wear testing machine that type is MMW- 1. Based on Mooney-Rivlin model of rubber material,using the principle of penalty function and coulomb friction and Combining with rubber nonlinear large deformation problems,the frictional contact problem of Rubber tube and casing is analyzed by the finite element with measured data. The results shown that the friction coefficient of contact is the maximum and 0. 514 in the absence of lubricant,the minimum and 0. 122 under oil lubrication,and others is 0. 122 0. 514. With the increase of friction coefficient,friction stress increase gradually,but the contact pressure decrease as a whole. Equivalent stress of rubber tube first increases then decreases. When friction coefficient is0. 3,contact pressure can be better. With the increase of axial loading,contact pressure,friction stress and the equivalent stress of packing element increases gradually. Keep axial loading,the width of rubber tube has greatly influenced on contact problem.Finally,the structure of rubber tube has been optimized to obtain a better structure which is entire circular arc.

According to the stochastic distribution of parameters,the reliability analysis of spring locking mechanism is carried out for helical spring by using probability theory and mathematical statistics. The optimization model of the locking mechanism spring parameters is established. Using Simulated Annealing Algorithm（ SAA）,the optimal parameters of spring are provided with the help of computer program compiled with Visual Basic language. The rationality of optimization result is verified by simulation results of the finite element model.

The sub-impact phenomenon of a simply supported beam struck by a steel sphere were studied by the Hertz impact theory and the three-dimensional dynamic finite element method,and tested by a set of sub-impact experimental device self-designed and its corresponding transient measurement system of the sub-impact. The sub-impact phenomenon was thoroughly discussed and studied through the experimental tests and numerical simulations. The results show that:（ 1） the impact duration of the first sub-impact is coinciding very well with the Hertz impact duration;（ 2） The subsequence sub-impacts have some different characteristics from the first sub-impact. And their impact durations vary randomly around the Hertz impact duration,but their variation in general are coincide with the Hertz impact duration;（ 3） It shows that the complicated sub-impacts that look like random and sensitive to structural transient response are dominated by local impact-contact deformation,and their mechanism can be explained by the Hertz impact theory;（ 4） The theoretical analysis has shown that the processes of the subsequence subimpacts are influenced greatly by the global structure vibrations,in turn affecting sphere motion and beam vibration response,and eventually leading to the next collision is difficult to predict.

Simulate and analyze the multi-pass welds in under-matched welded joint between CF62 and 316 L stainless steel with element birth and death technology by 3D finite element method. Design the under-matched welded joint based on equal-load theory. Found the multi-pass welds in under-matched welded joint whose shape is normal symmetrical X and the under-matched joint based on equal-load theory. The results show that the under-matched welded joint can reduce the residual stress compared with the normal well-matched welded joint. The under-matched joint based on equal-load theory has a smaller residual stress than the normal under-matched welded joint does so that it can improve the load capacity when it is used so the under-matched welded joint based on equal-load is more advantageous.

The semi-analytical finite element method is a method that use the finite element method to discrete the structure in the spatial domain,and then use the precise integration method in time domain to solve the problem. There are two ways of carrying out the method: one is processing time domain first,and then deal with spatial domain; the other is to deal with spatial domain first,and then time domain again. Because of its high precision and wide applicability,this method got a number of research and applications. In this paper,its application to the numerical simulation of propagation of ultrasonic,in a number of different angles to the calculation result is analyzed. The analysis results show that semi-analytical finite element method is suitable for the simulation of ultrasonic transmission,and it has high precision,high stability in the calculation.

In order to avoid creating or modifying the huge amount of finite element model of the rocket engine,application of the RBF（ radial basis function） neural network which was used to predict structural frequency of the liquid rocket engine was analyzed. A high pressure staged combustion LOX（ liquid oxygen） / kerosene rocket engine was taken as research object. By considering the material differences between the inner and outer wall of the nozzle,the precise nozzle finite element model was established using the stiffness and mass equivalence principle. Then the finite element model of staged combustion rocket engine was established using the method of distributed parameter and the finite element model was modified by modal experimental data.The difference structural parameters which were chosen according to the structural sensitivity analysis were considered as training samples. Then the RBF neural network was trained using these samples,and the structural frequency was predicted by the trained RBF neural network. The results show that the RBF neural network can predict structural frequency of the rocket engine accurately and the prediction error was less than 1. 0%. This method also has a fast convergence pace and it can be widely used in the field of the structural simulation of the rocket engine.