Wang Ziqiang

Wang Ziqiang

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Wang Ziqiang, born in November 1938 in Shanghai, native place: Dinghai, Zhejiang Province, is a researcher in the Institute of mechanics, Chinese Academy of Sciences.

He graduated from Modern Mechanics Department of the University of science and technology of China in 1963. He was elected academician of the Chinese Academy of Sciences in 2009.

Wang Ziqiang has been engaged in solid mechanics for a long time, including elastic stability theory, fracture mechanics, plastic strain gradient theory and micromechanics.

Character experience

Born in Shanghai in November 1938. He graduated from the Department of modern mechanics, University of science and technology of China in 1963. 1986, researcher, Institute of mechanics, Chinese Academy of Sciences. in 2009, he was elected academician of the Chinese Academy of Sciences. march 1981 - March 1983, senior visiting scholar, Sheffield University, UK. from August 1988 to December 1989, he was a visiting professor in the school of engineering, Brown University, USA. from January 1990 to July 1990, he was visiting professor of materials research and design center of ENCP University, France. from March 1996 to June 1996, visiting professor, Department of solid mechanics, Lulea University, Sweden. from March 2000 to September 2000, visiting professor, Institute of materials and engineering, National University of Singapore.

Main achievements

Main achievements

Wang Ziqiang has been engaged in solid mechanics for a long time, including elastic stability theory, fracture mechanics, plastic strain gradient theory and micromechanics. In the study of elastic-plastic field and fracture criterion at crack tip, the high-order elastic-plastic field and J-K fracture criterion at crack tip are established, the elastic-plastic singularity field at crack tip of heterogeneous interface is obtained, and the specimens with three-point bending deviator crack and four point shear mixed mode crack are designed, which provide theoretical basis for energy release criterion of piezoelectric materials; in the study of strain gradient theory, the high-order stress field is found In this paper, a new strain gradient theory without high-order stress is proposed, which successfully illustrates the scale effect of torsion of thin copper wire, bending of micro beam, micro indentation and crack tip field. A strict algorithm for theoretical strength of solid is established, and the theoretical strength of metal aluminum and diatomic material SiC under various loading modes is obtained The prediction of degree.

1. Create a new field of elastoplastic fracture mechanics

(1) Wang Ziqiang and his graduate student Li Yaochen were the first to establish the basic equation of high-order elastic-plastic field at the crack tip in the world, which opened up a new field of elastic-plastic fracture mechanics. The second-order field is obtained, and it is confirmed that the amplitude K2 is an independent parameter, which can represent the high or low triaxial stress in the far field. Thus, the important influence of the triaxial stress in the far field on the fracture toughness is clarified, which provides a theoretical basis for the two parameter fracture criterion. He and his doctoral student Xia Lin are the first to give the third to fifth results of high-order field at crack tip in the world. He and his postdoctoral fellow Wei Yueguang proposed the J-K fracture criterion on the basis of the high-order field at the crack tip, which has been verified by systematic experiments abroad.

(2) The elastic-plastic singularity field at the crack tip of bimaterial interface is obtained

in the late 1980s, the research on the elastic-plastic stress-strain field at the tip of bimaterial interface crack has become a hot topic in the international fracture mechanics. At that time, the prevailing view in the international academic circles was that there was no fully continuous singular field at the tip of interface crack. Wang Ziqiang was the first to find that for a certain mixing degree (the ratio of shear stress in front of the crack tip to normal stress), the singularity field in the form of fully continuous separated variables exists. The mixing degree depends on the mechanical properties of the bimaterials. This new view was quickly recognized by the international academic community. Wang Ziqiang first obtained the elastic-plastic singularity field at the tip of bimaterial interface crack, which provides a theoretical basis for the fracture criterion of bimaterial interface crack. the above research content as a result of "elastic plastic stress-strain field and fracture criterion at crack tip", won the "third prize of National Natural Science" in 1995, and was written into the monograph "advanced fracture mechanics".

2. A new strain gradient theory without higher-order stress is proposed

Wang Ziqiang and his postdoctoral fellow Chen Shaohua put forward a strain gradient theory which contains neither couple stress nor higher-order stress. The basic framework of classical plastic theory is retained. The strain gradient effect (including rotation gradient and tensile strain gradient) is introduced as an internal variable to increase the instantaneous shear modulus of materials. On the basis of couple stress theory, they introduced the tensile strain gradient into the tangent hardening modulus to form a strain gradient theory without higher-order stress, which greatly simplifies the analysis and is very effective. The scale effect in a series of experiments, such as torsion of thin copper wire, bending of thin beam, micro indentation, crack tip field and particle reinforced composites, has been successfully explained. as an important part of the achievement "Research on micro scale plasticity and micro scale fracture of solids", the above research content won the "second prize of National Natural Science" in 2008 and was written into the monograph "micro scale plasticity mechanics".

3. A strict algorithm of solid theoretical strength is established

Wang Ziqiang and his doctoral student Li Weixue proposed a periodic structure supercell model based on the periodic structure of crystals. It is assumed that the supercell system undergoes various typical uniform deformations, that is, the ions corresponding to each atom in the supercell move relatively according to the mode of uniform deformation. The interaction between electrons is described by density functional theory, and the interaction between electrons and ions is described by pseudo potential theory. they combined the first principle energy calculation with the large deformation instability theory of ideal crystal, and established a strict algorithm for theoretical strength of solid by using density functional theory, pseudo potential plane wave basis method and periodic structure supercell model. Based on this, the theoretical strength prediction of metal aluminum and diatomic material β - SiC under various loading modes was obtained. as an important part of the achievement "Research on micro scale plasticity and micro scale fracture of solids", the above research content won the "second prize of National Natural Science" in 2008

Participate in solution work

Cheng

(1) stiffness calculation of rotor arm and stator frame of large motor in the 1970s, Wang Ziqiang participated in the research work of Gezhouba hydropower unit on the Yangtze River. The new mechanical model and corresponding calculation formula are established, and the stiffness calculation of rotor arm and stator frame of large motor is completed, which provides a scientific basis for the stiffness design of large rotor arm and stator frame. As an integral part of the achievement "the second and third river project of Gezhouba and its hydropower units on the Yangtze River", it won the special prize of national science and technology progress in 1987 (collective Award). (2) safety analysis on defects of high and medium pressure rotors of the first domestic 300000 kW steam turbine generator in China. Whether the unit can be put into trial operation has become a technical problem that has an important impact on the national economy. The research group led by Wang Ziqiang successfully completed the scheduled task, which provided a scientific basis for the short-term safe operation and long-term operation under supervision of the unit. The results, as an important part of the application of composite crack brittle fracture and fracture mechanics in engineering, have won the National Science Conference award. (3) experimental and theoretical research on the lateral pressure instability of aircraft fuel tank tank panel in the 1970s, Wang Ziqiang and his colleagues cooperated to undertake the experimental and theoretical research tasks of J-12 aircraft pre research proposed by Nanchang 320 factory and J-8 aircraft fuel tank panel lateral pressure instability proposed by Shenyang 112 factory. This is a typical large disturbance nonlinear instability problem. The successful completion of this military task provides a scientific basis for the preliminary research of J-12 aircraft in Nanchang 320 factory and the design of J-8 aircraft tank tank wall plate proposed by Shenyang 112 factory. This work, as an important part of the achievement "study on the stability of stiffened and sandwich plates and shells", won the National Science Conference award. he has won the second and third prizes of National Natural Science Award, National Science and Technology Progress Award and many other awards. Wang Ziqiang has published 191 academic works (volumes). SCI included 101 articles, EI included 90 articles, 79 of which were cited 735 times in SCI.

Representative works

Wang Ziqiang, Fundamentals of rational mechanics, 2000, science press 2. Wang Ziqiang, Chen Shaohua, advanced fracture mechanics, 2009, Science Press 3, Micro scale plasticity mechanics, 2009, China University of science and Technology Press, 10 representative papers 1. Li Yaochen and Wang Ziqiang, higher order asymptotic solutions of plane strain mode I nonlinear crack problems, science Sinica (Chinese Science), series a, 291986, pp. 941-955. 　2.Xia,L.Wang,T.C.,Shih,C.F.,Highorderanalysisofcrack-tipfieldsinpowerlawhardeningmaterials，J. Mech.Phys.inSolids , 411993665-687 3. Wang Ziqiang, bimaterial interface crack projectile

Chinese PinYin : Wang Zi Qiang