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Wenwang Wu room
PhD student tel +41 44 823 4276
  fax +41 44 823 4035
  email wenwang.wu@empa.ch

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Wenwang received his M.Sc. from the Department of Engineering Mechanics, Tsinghua University, Beijing, China. During his master period, he designed an in-situ micro-tensile device, and used the machine to study the mechanical properties of bamboo fibril, the nano-gold film and polycrystalline aluminium film.
After finishing his M.Sc., Wenwang started his pre-doctor program at Catholic University of Leuven (K.U.Leuven, Belgium). He designed a micro-force sensor for testing the mechanical properties of trabecular bone. After finishing his pre-doctor program at K.U.Leuven, he joined EMPA, Dübendorf, Switzerland. At the same time, Wenwang is also a Ph.D student at the department of Architecture, ETH Zürich.


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PhD: 4D experimental investigation of hygro-mechanical behaviour of wood on cellular scale

X-ray micro-tomography is a non-invasive technique for 3D imaging the internal structure of opaque materials. Wood shows very weak absorption contrast, but produce significant phase shifts in an X-ray beam, thus phase-contrast tomographic microscopy (3D reconstruction of the refractive index from 2D phase images) can be used for investigating the swelling process of wood at cellular scale.
During the Ph. D research project, the changing process of the 3D wood swelling will be investigated respectively at cellular scale(Fig.1).

Fig. 1: Cellular Late-wood and Early-wood.

Aim of this Ph:D project:

(1) Providing the supporting geometrical parameters of cellular wood(earlywood and late-wood) for the FEA modelling of the hygro-mechanical behaviour of wood.
(2) Study the 4D swelling process(constrained and unconstrained) of wood and explain the swelling mechanism.

  • The swelling(absorption and desorption) process at different relative humidities (constrained and unconstrained wood).
  • Volumetric digital image correlation will be employed to obtain the swelling along different directions and the swelling strain field(local, global and non-uniform swell-ing distribution).
  • Investigate the swelling hysteresis mechanism and physical origin of swelling hys-teresis(the cellular shape change or the mass flow induced thickness change of cel-lular wall?).

(3) Nano-tomography will be employed for investigating the sub-cellular geometry fea-tures, such as the different kind of pits pair, the torus inside the pits pair. The swelling process of different lamellas inside the cell wall will be investigated.


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