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| 1 | Influence of loading path on formability of 304 stainless steel tubes显示文摘The loading path affects the metal formability remarkably in tube hydroforming, and it is also one of the research focuses. Recently, some scholars abroad proposed a new fluctuant hydraulic loading method, which can improve the formability of tubes in hydroforming. Related studies have shown that this new loading method can improve the tube formability, the distribution of deformation is more uniform and this is useful for avoiding excessive local thinning. In this paper, tube hydroforming experiments without axial feeding were carried out; the influences of the loading methods on formability of stainless steel tubes were studied. Through the comparison of the experimental results under the condition of monotonous increase loading and fluctuation hydraulic loading, the outside diameter distribution, the thickness distribution and the crack expansion forms of deformation zone all fully prove that the uniformity of the distribution of tube deformation and formability have been increased significantly under the condition of fluctuation loading without axial feeding, the reasons should be distinguished from the fluctuation hydroforming with axial feeding. In order to study the forming mechanism, uniaxial tensile test of tubes similar to fluctuation loading deformation is designed in this paper, namely intermittent tensile test. It is found that intermittent uniaxial stretch can improve the tube elongation at fracture by about 40% and the deformation distribution is more uniform than that through uniaxial tensile test of the stainless steel tube. In the process of intermittent tensile tests, changes of metal microstructures brought by the loading and unloading processes are the main reasons that improve the formability of the tubes. | ZHANG ShiHong YUAN AnYing WANG Bin ZHANG HaiQu WANG ZhongTang | 2009 | Science China(Technological Sciences)2009，52，8： | 3 |
| 2 | Application and prospects of 3D printing in physical experiments of rock mass mechanics and engineering:materials,methodologies and models显示文摘The existence of joints or other kinds of discontinuities has a dramatic efect on the stability of rock excavations and engineering.As a result,a great challenge in rock mass mechanics testing is to prepare rock or rock-like samples with defects.In recent years,3D printing technology has become a promising tool in the feld of rock mass mechanics and engineering.This study frst reviews and discusses the research status of traditional test methods in rock mass mechanics tests of making rock samples with defects.Then,based on the comprehensive analysis of previous research,the application of 3D printing technology in rock mass mechanics is expounded from the following three aspects.The frst is the printing material.Although there are many materials for 3D printing,it has been found that 3D printing materials that can be used for rock mass mechanics research are very limited.After research,we summarize and evaluate printing material that can be used for rock mass mechanics studies.The second is the printing methodology,which mainly introduces the current application forms of 3D printing technology in rock mass mechanics.This includes printed precise casting molds and one-time printed samples.The last one is the printing model,which includes small-scale samples for mechanical tests and large-scale physical models.Then,the benefts and drawbacks of using 3D printing samples in mechanical tests and the validity of their simulation of real rock are discussed.Compared with traditional rock samples collected in nature or synthetic rock-like samples,the samples made by 3D printing technology have unique advantages,such as higher test repeatability,visualization of rock internal structure and stress distribution.There is thus great potential for the use of 3D printing in the feld of rock mass mechanics.However,3D printing materials also have shortcomings,such as insufcient material strength and accuracy at this stage.Finally,the application prospect of 3D printing technology in rock mass mechanics research is proposed. | Qingjia Niu Lishuai Jiang Chunang Li Yang Zhao Qingbiao Wang Anying Yuan | 2023 | International Journal of Coal Science & Technology2023，10，1： | 2 |
| 3 | Orientational Chirality,Its Asymmetric Control,and Computational Study显示文摘Orientational chirality was discovered and characterized by a C(sp)-C(sp3)axis-anchored chiral center and a remotely anchored blocker.X-ray structural analysis proved that orientatiomers are stabilized by through-space functional groups,making it possible for 1 R-or S-chiral center to exhibit 3 orientational isomers simply by rotating operations.A new model system was proposed,fundamentally different from the traditional Felkin-Ahn-type or Cram-type models.In these traditional models,chiral C(sp^(3))center and blocking C(sp^(3))carbons are connected adjacently,and there exist 6 energy barriers during rotating along the C(sp^(2))-C(sp^(3))axis.In comparison,the present orientational chirality model shows that a chiral C(sp)-C(sp^(3))carbon is remotely located from a blocking group.Thus,it is focused on the steric dialog between a chiral C(sp^(3))center and a remotely anchored functional group.There exist 3 energy barriers for either(R)-or(S)-C(sp)-C(sp^(3))stereogenicity in the new model.Chiral amide auxiliary was proven to be an excellent chiral auxiliary in controlling rotations of orientatiomers to give complete stereoselectivity.The asymmetric synthesis of individual orientatiomers was conducted via multistep synthesis by taking advantage of the Suzuki-Miyaura cross-coupling and Sonogashira coupling reactions.Density functional theory computational study presented optimized conformers and relative energies for individual orientatiomers.This discovery would be anticipated to result in a new stereochemistry topic and have a broad impact on chemical,biomedical,and material sciences in the future. | Shengzhou Jin Yu Wang Yao Tang Jia-Yin Wang Ting Xu Junyi Pan Sai Zhang Qiankai Yuan Anis Ur Rahman James D.McDonald Guo-Qiang Wang Shuhua Li Guigen Li | 2023 | Research2023，，1： | 0 |
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