一种新的金属压缩试验方法的有限元分析

对一种新的金属压缩试验方法进行了有限元数值分析，论证了这种方法的可行性和有性，并且对不同尺寸的试件进行了有限元计算．

三级金属氢化物氢压缩机设计及氢压缩材料的研究进展

随着氢能产业的发展,氢燃料电池汽车因无污染、零排放等优点逐渐进入公众的视野,引起了人们的强烈关注。在氢燃料电池汽车系统中,车载储氢罐发挥着至关重要的作用,为提高其体积储氢密度并确保其应用的安全性,国际标准组织氢技术委员会规定储氢罐最多可充入70 MPa的氢气。因此,实现氢气的安全、高效加注是氢燃料电池汽车市场化的关键,这也对加氢站中氢压缩机的研发提出了更高的要求。现阶段,大多数已建成的加氢站均使用机械式氢压缩机,其普遍存在安全性差、振动与噪音大以及维护成本高等缺点。金属氢化物氢压缩机是利用储氢合金(氢压缩材料)在不同温度下平台压的不同对氢气进行增压。相比传统的机械式氢压缩机,金属氢化物氢压缩机具有安全、环保、无振动和噪音、密封性好、无摩擦、能有效提纯氢气以及维护成本低等优点。为提升其加氢压力和压缩比,通常将几种不同的氢压缩材料串接设计为多级氢压缩机。而提升各级氢压缩材料的热力学与动力学性能则是优化整个金属氢化物氢压缩系统性能的关键。氢压缩材料的改性主要集中于合金化。例如:LaNi_(5)合金A侧常被混合稀土Mm和Ml取代,而B侧常被Co、Al、Mn、Sn等元素取代,改性后的AB_(5)型合金因具有较低的吸放氢平台、较强的抗毒化性能与循环稳定性,通常作为高密度储氢材料或初级氢压缩材料;而TiCr_(2)合金A侧常被同族的Zr取代,B侧常被同周期的V、Mn、Fe、Co、Ni等元素取代,改性后的AB_(2)型合金具有较高的吸放氢平台、较大的储氢量,一般可作为中级或末级氢压缩材料。除此之外,具有极高平台压的ZrFe_(2)基合金也是应用于氢压缩领域的潜在材料。本文首先介绍了金属氢化物氢压缩机的工作原理与特点,然后设计了三级氢压缩机系统并综述了各级氢压缩材料的研究进展,最后还对未来氢压缩材料的发展方向进行了展望。

金属材料拉伸压缩虚拟仿真实验平台建设与应用

虚拟仿真技术的应用是在网络信息背景下的实验教学改革的必要手段,基于此,我校开发了金属材料拉伸压缩虚拟仿真实验,使用虚实结合的实验教学模式,使学生能够较快地熟悉和掌握实验设备及操作流程,学生也可以根据需求进行自主学习,随时随地开展实验操作,提高学习的积极性和主动性。仿真实验中增加了多种金属材料的性能实验,以虚补实,拓展了实验内容的广度和深度。同时,实验老师可以通过系统后台的数据,及时了解学生对实验的掌握程度,对教学效果进行实时评估,有效提高了实验教学质量和水平。

汽车用压缩天然气金属内胆纤维缠绕气瓶外测法水压试验数据分析

为了保证汽车天然气气瓶的安全使用，提高汽车行使的安全可靠性，在这里本文主要从以下方面针对汽车用压缩天然气金属内胆纤维缠绕气瓶外测法水压试验进行具体分析。

比较CS-SEMAC、HBW和Dixon三种去金属伪影技术在脊柱金属植入术后MRI的应用价值

目的探讨压缩感知结合层面编码金属伪影校正(compressed sensing-slice-encoding metal artifact correction,CS-SEMAC)技术用于脊柱金属植入物术后MRI的应用价值。材料与方法比较招募的35例脊柱金属植入物术后患者3.0 T MRI矢状位CS-SEMAC序列、高带宽(high bandwidth,HBW)序列和水脂分离(Dixon)三种序列在金属植入物伪影面积、椎体信噪比(signal-to-noise ratio,SNR)、图像质量、图像清晰度、脂肪抑制效果以及植入物周围解剖结构的可见性方面的差异。结果CS-SEMAC在T1、T2矢状位图像上金属伪影面积分别为(15.45±6.84)、(22.23±9.76)cm^(2),显著低于其他两种序列,差异具有统计学意义(P<0.001);三种序列在T2抑脂矢状面图像上的SNR两两比较显示:HBW序列椎体SNR显著高于其他两种序列,Dixon序列椎体SNR显著低于其他两种序列,CS-SEMAC序列椎体SNR低于HBW序列,高于Dixon序列,差异均有统计学意义(P<0.001);在图像清晰度上,T2WI-tirm-CS-SEMAC序列评分低于其他两种序列,差异具有统计学意义(P<0.001);T2WI-tirm-CS-SEMAC序列在图像质量和脂肪抑制效果方面评分显著优于其他两种序列,差异具有统计学意义(P<0.001);并且CS-SEMAC序列相较于其他两种序列更能清晰显示植入物周围椎体、椎弓根、椎间孔及神经根,差异具有统计学意义(P<0.001)。结论CS-SEMAC序列相比于HBW、Dixon序列能够有效减少植入物周围的金属伪影,并且能显著提高T2抑脂序列的图像质量和脂肪抑制效果,虽然在T2抑脂上金属植入物邻近椎体SNR相比HBW序列有所下降,图像比HBW和Dixon图像略模糊,但是椎体周围关键解剖结构的可见度明显提升,对脊柱术后解剖结构的显示有一定优势。

非机械氢气压缩机的技术与性能研究

非机械氢气压缩机己被证明是机械压缩机的有效替代品,具有无运动部件且紧凑度高等优点,是提高氢能利用水平的重要研究方向。介绍低温压缩、金属氢化物、电化学和吸附等非机械氢气压缩机,分析每种压缩技术的基本工作原理和可实现的性能,描述其目前在氢气应用中的用途以及技术极限,为进—步提高氢气压缩性能提供了有力技术支持。

自动灌装称量设备提升机构的新颖设计

随着药品﹑食品包装机械业的发展,行业对包装机械的结构设计提出了新的更高的要求。本文就自动灌装称量设备中的提升机构,提出了一种新颖的设计思路,使该设备机械运动平稳﹑经久耐用﹑免维护以及降低了运行成本。

Effect of strain rate and crystalline inclusions on mechanical properties of bulk glassy and partially crystallized Zr_(52.5)Cu_(17.9)Ni_(14.6)Al_(10)Ti_5 alloy

The mechanical properties of the Zr52.5Cu17.9Ni14.6Al10Ti5 alloy were presented, with an emphasis on the strain rate effect and presence of crystalline inclusions on the deformation and fracture mechanisms. X-ray diffraction studies indicated fully amorphous alloy structures with lower oxygen contents and partial crystalline structures at higher oxygen levels;however, completely different compressive deformation behaviour was observed. Uniaxial compression tests of the fully amorphous alloy showed elastic deformation, followed by yielding, distinct plastic deformation and serration flow behaviour. An increase in strain rate from 1×10-4 to 1×10-2 s-1 did not affect the yield strength;however, it decreased the compressive fracture strength and reduced the plastic strain. Scanning electron microscopy (SEM) observations with energy dispersive spectroscopy (EDS) analysis showed that the intermetallic CuZr2 phase was present even in the low oxygen content alloy, leading to lower fracture strength and ductility loss. For the high oxygen level samples, the presence of the dendritic Zr51Cu28Al21 phase was confirmed, leading to fracture strength impairment. The difference between ductile and brittle samples has been reflected on the fracture surfaces. The higher the plastic strain was, the higher the density of shear bands forming during deformation manifested by a serration flow behaviour on stress-strain curves.

Effect of Alkaline-Stabilised Sewage Sludge on Extractable Organic Carbon and Copper in Soils

An incubation experiment was conducted to evaluate the potential for water contamination with sludge-derived organic substances and copper following land application of alkaline-stabilised sewage sludge. Twocontrasting sludge-amended soils were studied. Both soils were previously treated with urban and ruralalkaline biosolids separately at sludge application rates of 0, 30 and 120 t ha-1 fresh product. The air-driedsoil/sludge mixtures were wetted with distilled water, maintained at 40 % of water-holding capacity andequilibrated for three weeks at 4 ℃ before extraction. Subsamples were extracted with either distilled wateror 0.5 mol L-1 K2SO4 solution. The concentrations of organic C in the aqueous and chemical extractswere determined directly with a total organic carbon (TOC) analyser. The concentrations of Cu in the twoextracts were also determined by atomic absorption spectrophotometry The relationship between the twoextractable organic C fractions was examined, together with that between extractable organic C concentrationand extractable Cu concentration. Application of alkaline biosolids increased the concentrations of soil mobileorganic substances and Cu. The results are discussed in terms of a possible increase in the potential forleaching of sludge-derived organics and Cu in the sludge-amended soils.

Analysis of semi-solid response under rapid compression tests using multi-scale modelling and experiments

Simulating semi-solid metal forming requires modelling semi-solid behaviour.However, such modelling is difficult because semi-solid behavior is thixotropic and depends on the liquid-solid spatial distribution within the material.In order to better understand and model relationships between microstructure and behavior, a model based on micromechanical approaches and homogenisation techniques is presented.This model is an extension of a previous model established in a pure viscoplastic framework to account for elasticity.Indeed, experimental load-displacement signals reveal the presence of an elastic-type response in the earlier stages of deformation when semi-solids are loaded under rapid compression.This elastic feature of the behaviour is attributed to the response of the porous solid skeleton saturated by incompressible liquid.A good quantitative agreement is found between the elastic-viscoplastic predicted response and the experimental data.More precisely, the strong initial rising part of the load-displacement curve, the peak load and the subsequent fall in load are well captured.The effect of solid fraction on mechanical response is in qualitative agreement with experiments.

Hot deformation behavior and related microstructure evolution in Au−Sn eutectic multilayers

Hot compression was performed on a multilayered Au−20Sn eutectic alloy to investigate the deformation behavior and microstructure evolution.During hot compression,microstructural spheroidization was initiated from plastic instability regions,and it was preferentially activated in vertical lamellae with a growth direction parallel to the compressive direction.Continuous dynamic recrystallization associated with lattice dislocations was the mechanism in both AuSn and Au5Sn multilayers.After spheroidization,strain accumulations were weakened in both of the equiaxed phases,and the deformation mechanism was substantially replaced by grain boundary sliding and migration.Based on these findings,hot rolling was conducted on an as-cast Au−20Sn alloy and a foil with a thickness of~50μm was successfully prepared.The present study can promote the development of Au−20Sn foils,and provide insights into the deformation behavior and microstructure evolution of multilayered eutectic alloys.

Fatigue damage evaluation by metal magnetic memory testing

Tension-compression fatigue test was performed on 0.45% C steel specimens.Normal and tangential components of magnetic memory testing signals,Hp(y) and Hp(x) signals,with their characteristics,K of Hp(y) and Hp(x)M of Hp(x),throughout the fatigue process were presented and analyzed.Abnormal peaks of Hp(y) and peak of Hp(x) reversed after loading; Hp(y) curves rotated clockwise and Hp(x) curves elevated significantly with the increase of fatigue cycle number at the first a few fatigue cycles,both Hp(y) and Hp(x) curves were stable after that,the amplitude of abnormal peaks of Hp(y) and peak value of Hp(x) increased more quickly after fatigue crack initiation.Abnormal peaks of Hp(y) and peak of Hp(x) at the notch reversed again after failure.The characteristics were found to exhibit consistent tendency in the whole fatigue life and behave differently in different stages of fatigue.In initial and crack developing stages,the characteristics increased significantly due to dislocations increase and crack propagation,respectively.In stable stage,the characteristics remained constant as a result of dislocation blocking,K value ranged from 20 to 30 A/(m·mm)-1,and Hp(x)M ranged from 270 to 300 A/m under the test parameters in this work.After failure,both abnormal peaks of Hp(y) and peak of Hp(x) reversed,K value was 133 A/(m·mm)-1 and Hp(x)M was-640 A/m.The results indicate that the characteristics of Hp(y) and Hp(x) signals were related to the accumulation of fatigue,so it is feasible and applicable to monitor fatigue damage of ferromagnetic components using metal magnetic memory testing(MMMT).

The hot compressive deformation behavior of the metal matrix composites with the large whisker orientation

Finite element analysis was used to investigate the effects of whisker misalignment on the hot compressive deformation behavior of whisker-reinforced composites. The simulation provided the evolution of the stress field of the composites and the whisker rotation process. It is found that with increasing the angle of whisker misalignment the whisker rotation angle decreases. Meanwhile, the mechanical behaviors of the composites such as work hardening or strain softening are affected by the whisker orientation and rotation during the hot compressive deformation. The predicted results are in agreement with the experimental results.

Design of small-area multi-bit antifuse-type 1 kbit OTP memory

A multi-bit antifuse-type one-time programmable （OTP） memory is designed, which has a smaller area and a shorter programming time compared with the conventional single-bit antifuse-type OTP memory. While the conventional antifuse-type OTP memory can store a bit per cell, a proposed OTP memory can store two consecutive bits per cell through a data compression technique. The 1 kbit OTP memory designed with Magnachip 0.18 μm CMOS （complementary metal-oxide semiconductor） process is 34% smaller than the conventional single-bit antifuse-type OTP memory since the sizes of cell array and row decoder are reduced. And the programming time of the proposed OTP memory is nearly 50% smaller than that of the conventional counterpart since two consecutive bytes can be compressed and programmed into eight OTP cells at once. The layout area is 214 μm× 327 μ,, and the read current is simulated to be 30.4 μA.

Deformation characteristics and constitutive model of seafloor massive sulfides

Deformation characteristics and constitutive model of seafloor massive sulfide(SMS)were selected as the research object.Uniaxial/triaxial compression test were carried out on the mineral samples,and the deformation characteristics of specimens under various conditions were studied.According to characteristics of the mineral,a new three stages constitutive equation was proposed.The conclusions are as follows:The axial strain,peak strain and maximum strength of seafloor massive sulfide increase with the confining pressure.The elastic modulus of the metal sulfide samples is decreased sharply with the increase of confining pressure.According to characteristics of seafloor massive sulfide,the constitutive equation is divided into three parts,the comparison between theoretical curves and experimental data shows that both of them are in good agreement,which also proves the correctness of the constitutive equation for uniaxial compression.

Hot compressive deformation behavior of an in-situ TiB whisker reinforced Ti matrix composite

An in-situ TiB whisker reinforced Ti matrix (TiBw/Ti) composite is fabricated by powder metallurgy technique followed by hot extrusion. Hot compressive deformation behavior of the composite, in which the TiB whiskers were oriented along the extruded direction, is investigated. The results indicate that the hot compressive resistance of the TiBw/Ti composite is higher than that of the unreinforced Ti, and hot compressive resistance of the composite in the direction parallel to the whisker orientation is higher than that in the direction perpendicular to the whisker orientation. The hot compressive resistance of the composite increases with increasing strain rate and decreasing temperature. With increasing test temperature, the rate of the decrement of the compressive flow stress of the composite is higher than that of the unreinforced Ti. With increasing amount of compressive deformation, more and more TiB whiskers rotate and break during deformation. The rotation of the whiskers is easier at higher temperature, while, at lower temperature it becomes more difficult and whisker breakage becomes much more serious.

La_(1-x)Y_xNi_(4.8)Mn_(0.2)合金的储氢性能

研究了元素Y(钇)对La_(1-x)Y_xNi_(4.8)Mn_(0.2)(x=0.6,0.7,0.8)合金储氢性能的影响,结果表明:La_(1-x)Y_xNi_(4.8)Mn_(0.2)合金为CaCu_5型六方结构;随着Y含量的增加,晶格参数a和晶胞体积V减小,而c几乎不变,c/a线性增大;随着Y含量的增加,合金的吸放氢平台压显著升高,吸氢量减少,吸放氢平台斜率S和滞后系数_f略有增加,滞后系数H_f与XRD(111)峰的半高宽(FWHM)值的变化有着很好的对应关系,抗粉化性能提高。当Y含量x=0.8时,合金的吸放氢动力学综合性能最好。

La_(1-x)Y_xNi_(4.8)Al_(0.2)合金的储氢性能研究

本文系统地研究了Y元素对La1-xYxNi4.8Al0.2(x=0.6,0.7,0.8)储氢合金的晶体结构、吸放氢热力学、动力学和抗粉化性能的影响。研究结果表明,合金为CaCu5型六方结构,随着Y含量的增加,晶格参数a和晶胞体积V减小,而c几乎不变,c/a线性增大。随着Y含量的增加,合金吸放氢平台压显著升高;吸氢量略有减少;吸放氢平台斜率变小;滞后系数先减小后略增大,并与XRD(111)峰的半高宽FWHM值的变化有着很好的对应关系;抗粉化性能略有提高。当Y含量x=0.7时,合金的吸放氢动力学综合性能最好。

Numerical simulation of shock wave interaction with a deformable particle based on the pseudo arc-length method

In this paper, we combine the pseudo arc-length numerical method with the mathematical model of multiphase compressible flow for simulating the shock wave interaction with a deformable particle. Firstly, an arc-length parameter is introduced to weaken the discontinuous singularity of governing equations, and an efficient pseudo arc-length numerical method of multiphase compressible flow is proposed. Then the accuracy and adaptive moving mesh property of this algorithm are tested. Finally, the multiphase pseudo arc-length numerical method is applied to the problem of interaction between shock wave and the deformable particle. Through the flow flied change and data analysis of key points, it can be found the complex wave structures are presented after the interactions between the planar incident shock wave and the metal particle, and all these wave interactions lead to the movement and deformation of metal particle, and then the deformed particle will affect the transmitted shock wave back. According to the discussion, the deformation of particle and shock wave propagation in the particle are determined by the shock wave impedance of each medium and shock speed, so the interaction between shock wave and the deformable particle can be studied on the basis of physical properties of explosive mediums.

Generalization of Hill's yield criterion to tension-compression asymmetry materials

This paper is devoted to developing a yield criterion that can model the asymmetry and anisotropy in yielding of pressure insensitive metals,in terms of accuracy and simplicity of formulation.First,a new isotropic yield criterion,which can model the asymmetry in yielding of pressure insensitive metals,is proposed.Further,using Cazacu's generalizations to anisotropic conditions of the invariants of the deviatoric stress,the proposed isotropic yield criterion is extended to orthotropy.The proposed anisotropic criterion has a quite simple form,and the number of material constants involved is only half of that of Cazacu's(2004) yield criterion.Compared to Hill's(1948) yield criterion,the proposed anisotropic yield criterion has three additional constants,which are used to model the tension-compression asymmetry of materials.All the material constants involved in the criterion can be determined by simple tests.The proposed criterion reduces to Hill's(1948) yield criterion if the tensile and compressive yield stresses are equal.In other words,the proposed anisotropic yield criterion can be considered as an extension of Hill's(1948) criterion to tension-compression asymmetry materials.The anisotropic yield criterion is used to describe the plastic response of Cu-Al-Be shape memory alloy(data after Laydi and Lexcellent) and Ni3Al based intermetallic alloy IC10 sheets.It is shown that the proposed yield criterion can describe very well the asymmetry and anisotropy observed in those materials.