Long Wang

École Centrale de Lille | EC Lille · Département Mécanismes, Structures et Ouvrages

As one of the main structural materials widely used for the new generation of launch vehicles, the tensile properties and microstructural characterization of tungsten inert gas (TIG) welded 2219 aluminium alloy has been studied extensively. However, there are significant differences between fatigue fracture and tensile fracture modes. In this paper...

This study utilizes the genetic algorithm (GA) and Levenberg-Marquardt (L-M) algorithm to optimize the parameter acquisition process for two commonly used viscoelastic models: 2S2P1D and Havriliak-Negami (H-N). The effects of the various combinations of the optimization algorithms on the accuracy of the parameter acquisition in these two constituti...

Nitrate ester plasticized polyether (NEPE) solid propellant was widely used in carrier rocket and guided missiles, owing to its excellent mechanical properties, high specific impulse and good performance of low temperature storage. The material of NEPE suffered from thermal cycle, high pressure impulse and vibration during service life. Thus, the m...

Aiming at the issues of heavy weight and insufficient structural performance of optical instrument supporting structures in extremely large telescopes, the Wide-Field Optical Spectrograph (WFOS) of the Thirty Meter Telescope (TMT) was taken as a case to study. In order to develop lightweight structures which satisfies the design requirements for ma...

X-ray Computed Tomography allows the microstructures, defects and damages in the bulk of materials being imaged in three-dimension nondestructively, thus it has advantages to be applied to study the mechanical behaviors of materials. The principle of X-ray Computed Tomography and its applications to damage observations (experimental study), full-fi...

The AE (acoustic emission) technology widespread applications in the industry are importantly based on the key information from the analysis of damage signals produced in the materials and structures in great extent. The results from the analysis can be taken out, such as the source localization、damage modes and severity level of the material. The...

The composite structure shows different mechanical bearing properties under the special load, which will have a certain effect on its mechanical properties under the action of different velocity loads, and it is of practical significance to understand and study the mechanical properties of composite structures under different loading rate and the l...

An experimental protocol has been set up in order to study the low cycle fatigue (LCF) damage micromechanisms in a lost foam casting (LFC) A319 alloy at room temperature. The microstructure of the alloy was characterized by using X‐ray computed tomography (X‐ray CT) prior to the LCF tests performed with surface in situ observations using a long dis...

The synchrotron radiation–computed tomography (SR-CT) and digital volume correlation (DVC) methods were used to investigate the damage micromechanisms of lost foam casting (LFC) A319 alloy in low-cycle fatigue (LCF). LCF tests with SR-CT in-situ observations allow visualizing the damage evolution process in the bulk. DVC measures the mechanical fie...

The damage evolution and fracture behavior in the bulk of C/SiC material under monotonic tensile loading have been investigated with the 3D in-situ observations by using X-ray CT. Crack initiated inside the matrix within 0.02 mm below surface when the load was only 19% of the failure strength, and propagated to the surface of matrix and towards the...

The quartz lamp radiation heater is the most widely used for the aerothermal simulation in the thermal tests for structures. The determination of the radiation flux field of the quartz lamp heater is essential for improving the test accuracy, as well as evaluating the testing results and validating the structural design. The applicability of variou...

Pores and damages in the bulk of a two-dimensional plain woven C/SiC composite formed by chemical-vapor infiltration process are characterized in 3D by using X-ray Computed Tomography in order to validate the effectivity of X-ray Computed Tomography to establish the relations between pores and damage mechanisms in the following in-situ tests. An un...

A complex structure and/or joint may increase the strength of composite thin-walled structure, but may also increase the structural mass and complexity. Thus a good understanding of the influence of different structures and joints on the mechanical properties is necessary for the structural optimisations. The basic mechanical parameters of C/SiC co...

Considering the coupling interaction between oxidant system and fuel system in liquid-propellant rockets, the modeling and stability problem of Pogo vibration in liquid-propellant rockets with a two-propellant system are investigated. Firstly, the differential equations of the two-propellant equivalent system are derived through the physical charac...

An experimental protocol was developed in this thesis in order to study the influence of casting microstructure on the fatigue behavior in Lost Foam Casting Al-Si alloys in tension and in Low Cycle Fatigue at room temperature. First of all, the microstructures of studied alloys were thoroughly characterized both in 2D and in 3D. The most suitable a...

Aluminum alloy automotive parts produced by the Lost Foam Casting (LFC) process have coarser microstructure and porosity defects than parts produced with conventional casting processes at faster cooling rates. This coarse microstructure has a major influence on the fatigue properties and crack initiation. In order to study its influence upon the me...

In cast aluminum alloys used in the automotive industry the microstructure inherited from the foundry process has a strong influence upon the fatigue behavior. In the cylinder heads produced by the Lost Foam Casting process, the microstructure consists of hard intermetallic phases and large gas and microshrinkage pores. In order to study the influe...

An experimental protocol based on the coupling of kinematic field measurements on the surface and in volume at the microstructure scale has been set up in order to study the influence of the casting microstructure upon the initiation and propagation of cracks in low cycle fatigue. Preliminary applications of this protocol on tensile tests were succ...

A thermal-mechanical fatigue criterion is proposed to assess the lifetime of aluminium alloys produced by a lost foam casting process. It is based on the observed size distribution of pores sizes which are considered as critical zones for cracks initiation and gives reliable results when both pores sizes are identified from X-ray tomography and mea...

In cast aluminum alloys used in the automotive industry the microstructure inherited from the foundry process has a strong influence upon the fatigue behavior. In the cylinder heads produced by the Lost Foam Casting process, the microstructure consists of hard intermetallic phases and large gas and microshrinkage pores. In order to study the influe...

Aluminum alloy automotive parts produced by the Lost Foam Casting (LFC) process have coarser microstructure and porosity defects than parts produced with conventional casting processes at faster cooling rates. This coarse microstructure has a major influence on the fatigue properties and crack initiation. In order to study its influence upon the me...

The whole-rocket vibration isolation can improve dynamic environment during satellites launching, as well as reliability and security in satellite launching. In this study, analytic expression in multistage launch vehicles vibration isolation coupled dynamic system is firstly established. By using the analytic expression, the physical significance...

Starting from physical mechanism, the nonlinear equivalent dynamic model of a discrete vibration isolation system was built with the deformation of a cubic polynomial function and fractional derivative operator, and the vibration transmissibility from the bottom of the isolator to the satellite was obtained using harmonic balance method. The phenom...