Calibration of anisotropic yield function by introducing plane strain test instead of equi-biaxial tensile test

The equi-biaxial tensile test is often required for parameter identification of anisotropic yield function and it demands thespecial testing technique or device. Instead of the equi-biaxial tensile test, the plane strain test carried out with the traditional uniaxialtesting machine is suggested to provide the experimental data for calibration of anisotropic yield function. This simplified method byusing plane strain test was adopted to identify the parameters of Yld2000-2d yield function for 5xxx aluminum alloy and AlMgSialloy sheets. The predicted results of yield stresses, anisotropic coefficients and yield loci by the proposed method were very similarwith the experimental data and those by the equi-biaxial tensile test. It is validated that the plane strain test is effective to provideexperimental data instead of equi-biaxial tensile test for calibration of Yld2000-2d yield function.

Early electrical field stimulation prevents the loss of spinal cord anterior horn motoneurons and muscle atrophy following spinal cord injury

Our previous study revealed that early application of electrical field stimulation（EFS） with the anode at the lesion and the cathode distal to the lesion reduced injury potential, inhibited secondary injury and was neuroprotective in the dorsal corticospinal tract after spinal cord injury（SCI）. The objective of this study was to further evaluate the effect of EFS on protection of anterior horn motoneurons and their target musculature after SCI and its mechanism. Rats were randomized into three equal groups. The EFS group received EFS for 30 minutes immediately after injury at T_（10）. SCI group rats were only subjected to SCI and sham group rats were only subjected to laminectomy. Luxol fast blue staining demonstrated that spinal cord tissue in the injury center was better protected; cross-sectional area and perimeter of injured tissue were significantly smaller in the EFS group than in the SCI group. Immunofluorescence and transmission electron microscopy showed that the number of spinal cord anterior horn motoneurons was greater and the number of abnormal neurons reduced in the EFS group compared with the SCI group. Wet weight and cross-sectional area of vastus lateralis muscles were smaller in the SCI group to in the sham group. However, EFS improved muscle atrophy and behavioral examination showed that EFS significantly increased the angle in the inclined plane test and Tarlov＇s motor grading score. The above results confirm that early EFS can effectively impede spinal cord anterior horn motoneuron loss, promote motor function recovery and reduce muscle atrophy in rats after SCI.

Sheet metal hardening curve determined by laminated sample and its adaptability to sheet forming processes

The hardening curve for sheet metal can be determined from the load-displacement curve of tensile specimen with rectangular cross-section. Therefore,uniaxial compression test on cylinder specimen made from laminated sample is put forward. Considering the influence of anisotropy on hardening properties and the stress state in popular forming process,plane strain compression test on cubic specimen made from laminated sample was advanced. Results show that the deformation range of hardening curves obtained from the presented methods is wide,which meets the need for the application in sheet metal forming processes. In view of the characteristics of methods presented in the paper and the stress strain state of various forming processes,the adaptability of the two methods presented in this paper is given.

Study and application of monitoring plane displacement of a similarity model based on time-series images

In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests,such as inadequate real-time monitoring and more manual intervention,an effective monitoring method was proposed in this study,and the major steps of the monitoring method include:firstly,time-series images of the similarity model in the test were obtained by a camera,and secondly,measuring points marked as artificial targets were automatically tracked and recognized from time-series images.Finally,the real-time plane displacement field was calculated by the fixed magnification between objects and images under the specific conditions.And then the application device of the method was designed and tested.At the same time,a sub-pixel location method and a distortion error model were used to improve the measuring accuracy.The results indicate that this method may record the entire test,especially the detailed non-uniform deformation and sudden deformation.Compared with traditional methods this method has a number of advantages,such as greater measurement accuracy and reliability,less manual intervention,higher automation,strong practical properties,much more measurement information and so on.

Physical,Thermal and Partial Discharge Evaluation of Nano Alumina Filled Silicone Rubber in an Inclined Plane Test

Silicone rubber(SiR)composite material is a modern-day insulator for high voltage outdoor applications.The imperfection attributed to SiR is its weak resistance to tracking and erosion when exposed to an outdoor polluted environment which reduces its operational lifetime.This paper investigates the performance of SiR with the addition of 0,1,2.5,5,10 and 20%by weight contents of nano alumina(Al_(2)O_(3)).Inclined plane tests are performed according to IEC 60587 using the step up tracking voltage method with an initial voltage of 3.0 kV and the contaminant solution flow rate is maintained at 0.3 ml/min using a peristaltic pump.The applied voltage level is increased at a rate of 0.25 kV/h.Results suggest that physical tracking,erosion,RMS leakage current and surface partial discharge(PD)performance of samples is improved with the addition of nano alumina.The tracking length,eroded mass,RMS leakage current and average PD magnitude are measured 22%,79%,30%and 52%lesser in 20 wt%relative to 0 wt%,respectively.A thermal distribution analysis is undertaken with infrared camera and it is discovered that heat is accumulated in the discharge area of the liquid flow.The maximum temperature on the insulating specimen is decreased with increasing nanofiller contents.The above promising findings can be due to better thermal stability with low chain mobility at the interaction zone of SiR and alumina.Moreover,less liquid evaporation due to better thermal conduction and improved physical bonding between SiR and nano alumina are possible reasons behind the excellent performance of nanocomposites.

Robot Plane Drops Bomb in Successful Test

[提示]从空中扔炸弹的飞机对飞行员来说是一件危险的差使,现在,美国人已经试验成功了遥控的"下弹"飞机。在描写试验情况时,文章用了以下一句:...adding that had the bomb contained explosives,the target would have been destroyed.典型的虚拟语气句也!