Establishment of a cutting force model and study of the stress–strain distribution in nano-scale copper material orthogonal cutting

This article focuses on the establishment of a cutting force calculation model in terms of nano-scale orthogonal cutting, and investigates the stress–strain distribution of single-crystal copper that occurs in terms of nano cutting. The cutting force that occurs during the nano-scale cutting of single-crystal copper, and also its changes under different situations, can be found in this study. The molecular dynamics (MD) model was proposed to evaluate the displacement components of the atom in any temporary situation on the nano-scale cutting. The atom and lattice were regarded as the node and element, respectively. The shape function concept of the finite element method (FEM) is used to calculate the equivalent strain of the nodal atom and element. The equivalent stress–strain relationship equation was acquired by nano-scale thin-film tensile simulation in this study, and was used to further calculate the equivalent stress that occurs under the equivalent strain. Subsequently, a stress–strain distribution during nano-scale orthogonal cutting can be acquired.     

304不锈热轧带钢表面质量工艺研究

就304不锈热轧带钢表面“侧翻”和划伤缺陷产生的原因进行了分析,并提出了相应的控制措施。     

针对2Cr25N管材内划道问题探讨与改进

主要针对以挤压方式生产小外径薄壁2cr25N管材规格Ф89MM×4MM时,极易出现的内划道等质量问题,采取了生产时进行观察、记录并就现场出现的问题进行了分析讨论等措施,在生产工艺上进行了相应的改进,并取得了较好的实际效果,为固化小外径薄壁管材生产工艺打下了一定的基础。     

Visual Object Tracking and Servoing Control of a Nano-Scale Quadrotor: System,Algorithms, and Experiments

There are two main trends in the development of unmanned aerial vehicle(UAV)technologies:miniaturization and intellectualization,in which realizing object tracking capabilities for a nano-scale UAV is one of the most challenging problems.In this paper,we present a visual object tracking and servoing control system utilizing a tailor-made 38 g nano-scale quadrotor.A lightweight visual module is integrated to enable object tracking capabilities,and a micro positioning deck is mounted to provide accurate pose estimation.In order to be robust against object appearance variations,a novel object tracking algorithm,denoted by RMCTer,is proposed,which integrates a powerful short-term tracking module and an efficient long-term processing module.In particular,the long-term processing module can provide additional object information and modify the short-term tracking model in a timely manner.Furthermore,a positionbased visual servoing control method is proposed for the quadrotor,where an adaptive tracking controller is designed by leveraging backstepping and adaptive techniques.Stable and accurate object tracking is achieved even under disturbances.Experimental results are presented to demonstrate the high accuracy and stability of the whole tracking system.     

New approaches to surface roughness evaluation of special surfaces

This work concerns itself with two approaches to the evaluation of surface roughness parameters. The first approach identifies vacancies in the surface and removes them from calculations. The second approach uses the parameters defined in German standard draft DIN 4776 E. The advantages and disadvantages of both methods are discussed and their potentials evaluated for different assignments.     

Development of fatigue cracks from mechanically machined scratches on 2024‐T351 aluminium alloy—part I: experimentation and fractographic analysis

Clad and unclad 2024‐T351 aluminium alloy sheets, weakened by mechanically machined scratches, were fatigued to investigate the effect of small surface damage, like scribe marks, on aircraft fuselage joints. The role of scratch cross section geometry on fatigue life of scribed components was analysed. Scratches between 25 and 185 µm deep, with 5, 25 and 50 µm root radii, were cut on sample surface by using diamond‐tipped tools. After testing, fracture surfaces were examined using a scanning electron microscope, and crack growth rates were measured by striation counting. Scratches reduced aluminium fatigue life under tensile and bending load up to 97.8% due to multiple crack nucleation at their roots. Short cracks nucleated from sharp scratches coalesced to form unique elongated cracks growing through sample thickness. Cracks initiated from scratches were typical short cracks, growing faster than conventional long cracks. Despite the different scribing process, fatigue data of regular diamond tool cut scribes can be used to conservatively predict life reduction owing to ploughed in‐service scribe marks on fuselage joints. Finite element analyses on scribed samples and the fatigue life prediction models are described in Part II of this paper.     

High strength-ductility nano-structured high manganese steel produced by cryogenic asymmetry-rolling

A bulk nanostructured twinning-induced plasticity (TWIP) steel with high ductility and high strength was fabricated by cryogenic asymmetry-rolling (cryo-ASR) and subsequent recovery treatment. It was found that the cryo-ASRed TWIP steels exhibit simultaneous improvements in the ductility, strength and work hardening. Typical microstructures of the cryo-ASR TWIP steel were characterized by shear bands and intensive mechanical nano-sized twins induced by cryogenic deformation. These mechanical nano-scale twins remain thermally stable during the subsequent recovery treatment. It is believed that the ductility enhancement and high work-hardening ability for the cryo-ASR TWIP steels should be mainly attributed to the high-density pre-existing nano-scale twins.     

Experimental Study of the Influence of Scratches on the Performance of a Two-Lobe Journal Bearing

During maintenance operations of steam turbines, a common issue is the degradation of the supporting and guiding components for the rotating shafts due to the presence of scratches. To examine this issue, a numerical software program has been developed. In order to validate and complete the elaborated modeling, experimental tests have been carried out on the Pprime Institute test bench. A preloaded two-lobe journal bearing (diameter: 100 mm, length: 68.4 mm, preload: 0.524) lubricated with an ISO VG 46 mineral oil has been tested. Scratches were machined on the shaft at two axial locations and at different depths. Pressures and temperatures have been measured for several rotational speeds and applied loads. Seven configurations (one unscratched surface and six with a scratch) have been tested in order to evaluate the influence of a scratch on the performance of the bearing. It is found that the pressure profile is significantly affected by the presence of a scratch, whereas the temperature field is weakly modified.     

An accurate analytical I-V model for sub-90-nm MOSFETs and its application to read static noise margin modeling

We propose an accurate model to describe the I-V characteristics of a sub-90-nm metal-oxide-semiconductor field-effect transistor(MOSFET) in the linear and saturation regions for fast analytical calculation of the current.The model is based on the BSIM3v3 model.Instead of using constant threshold voltage and early voltage,as is assumed in the BSIM3v3 model,we define these voltages as functions of the gate-source voltage.The accuracy of the model is verified by comparison with HSPICE for the 90-,65-,45-,and 32-nm CMOS technologies.The model shows better accuracy than the nth-power and BSIM3v3 models.Then,we use the proposed I-V model to calculate the read static noise margin(SNM) of nano-scale conventional 6T static random-access memory(SRAM) cells with high accuracy.We calculate the read SNM by approximating the inverter transfer voltage characteristic of the cell in the regions where vertices of the maximum square of the butterfly curves are placed.The results for the SNM are also in excellent agreement with those of the HSPICE simulation for 90-,65-,45-,and 32-nm technologies.Verification in the presence of process variations and negative bias temperature instability(NBTI) shows that the model can accurately predict the minimum supply voltage required for a target yield.     

Nano-TiO2/HIPS母料流变性能的研究

采用Rosand Rheometer流变仪研究了nano-TiO2/HIPS母料及EVA蜡改性母料的流变性能。结果表明,nano-TiO2对母料的表观粘度影响较小。在nano-TiO2质量分数低于20％时，表观粘度仅略高于纯HIPS。在低剪切速率下。nano-TiO2可加速熔体偏离牛顿流体的速度。体系的粘弹性增强；而在较高剪切速率下则相反。EVA蜡可在较大范围内调整母料体系的流变性能。在低剪切速率下，EVA蜡质量分数超过5％就可明显改善体系的流动性，且体系流动行为接近牛顿流体，粘弹性很弱；在高剪切速率下，EVA蜡对体系的流动性影响不大，流变行为及牯弹行为与纯HIPS相当。原子力显微镜测试表明。采用EVA蜡改性的nano-TiO2/HIPS母料。可得到表观及分散性良好的制品。