First results are presented for a uniaxial tensile stage designed to operate on a scanning micro X‐ray diffraction synchrotron beamline. The new tensile stage allows experiments at typical loading cycles used in standard engineering stress–strain tests. Several key features have been implemented to support in situ loading experiments at the intragranular length scale. The physical size and weight of the load cell were minimized to maintain the correct working distance for the X‐ray focusing optics and to avoid overloading the high‐resolution raster scan translation stages. A high‐magnification optical microscope and image correlation code were implemented to enable automated online tracking capabilities during macroscopic elongation of the sample. Preliminary in situ tensile loading experiments conducted on beamline 12.3.2 at the Advanced Light Source using a polycrystalline commercial‐purity Ti test piece showed that the elastic–plastic response of individual grains could be measured with submicrometre spatial resolution. The experiments highlight the unique instrumentation capabilities of the tensile stage for direct measurement of deviatoric strain and observation of dislocation patterning on an intragranular length scale as a function of applied load. 相似文献
The linearity domain for the viscoelastic properties of high-molecular organic fibers is determined. The linearity criteria are coincidence of experimental compliance curves and linearity of isochronic creep curves. Statistical criteria are used to establish linearity. The influence function in the constitutive equation of linear viscoelasticity is an Abel-type power kernel. The calculated and experimental creep strains are in good agreement both at the initial stage of deformation and after long-term loading__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 5, pp. 97–106, May 2005. 相似文献
In this contribution a viscoelastic elastomer is examined with respect to its thermo‐mechanical behaviour. Therefore uniaxial tension tests and relaxation tests are performed at different constant temperatures up to the glass transition region. Hence an experimental data pool is provided. On the theoretical side a finite viscoelastic and incompressible material model is used and enhanced by temperature dependency in order to model the experimentally observed effects. The material parameters are strategically identified by means of biologic evolution strategies. Thereby it turned out that the investigated material cannot be modelled as a thermo‐rheologically simple material. Quite the contrary, a new ansatz is chosen. 相似文献
The lyotropic mixture of potassium laurate/decanol/water presenting only the uniaxial nematic calamitic phase was doped with one strong (potassium chloride, KCl) and 11 weak electrolytes with phenyl-rings (DL-mandelic acid, benzoic acid, DL-phenyllactic acid, phenylacetic acid, phenol and phenylmethanol) and with cyclohexyl-ring (RS-hexahydromandelic acid, cyclohexanecarboxylic acid, cyclohexaneacetic acid, cyclohexanol and cyclohexylmethanol), separately. We also chose two nonpolar dopant molecules, benzene and cyclohexane, for the comparison of them with weak electrolytes, since they are located in the hydrocarbon core of the micelle. The nematic phase sequences, in particular the presence of the biaxial nematic phase, were investigated as a function of the dopant molar concentration and temperature. The laser conoscopy and small-angle X-ray scattering techniques were used to characterise the different nematic phases. Weak electrolytes having –COOH group as polar part were found to be very effective in stabilising the three nematic phases (two uniaxial and a biaxial). Guest molecules with only the –OH group did not show any effect on the stabilisation of other nematic phases. The experimental results are interpreted considering the screening effect of the hydrophilic parts of the dopants on the repulsion between the polar heads of the main amphiphilic molecules at micelle surfaces. This process favours the increase of the more flat micellar surfaces of micelles, which triggers the orientational fluctuations responsible for the biaxial and discotic nematic phases. 相似文献
A microstructure‐based model of rubber reinforcement is presented describing filler‐induced stress softening and hysteresis by the breakdown and re‐aggregation of strained filler clusters. An extension of the previously introduced dynamic flocculation model, it considers incomplete deformation cycles that occur in the simulation of arbitrary deformation histories. For these inner cycles additional elastic stress contributions of clusters are taken into account. A constitutive generalization of the model is introduced by referring to the engineering concept of representative directions. This allows for an implementation of the model into FE codes. Fair agreement between measurement and simulation is obtained for CB‐filled EPDM, loaded along various deformation histories.
