Establishment and Growth of Potato Micro-Cuttings in Sand Trays

Two separate experiments were conducted to evaluate the success of the establishment and growth of micro-cuttings of potato (5 - 6 cm tall) in sand trays [38 cm (L) × 28 cm (W) × 7.5 cm (H) plastic trays] under controlled environment (22?C ± 2?C, 60 - 75 μmosm–1?s–1 light energy for 16 h daily). In the first experiment, micro-cuttings of potato cv. Diamant were planted at six populations (500, 600, 700, 800, 900 and 1000 cuttings per tray) in treated sand (sun dry, 1% formaldehyde, 0.2% Dithane M-45 and control). The mortality percentage of micro-cuttings was nil for sun dry sand while formaldehyde and dithane M-45 treated sand had 1% - 4% against 15% in the control with the highest population density. Mortality of micro-cuttings in formaldehyde and dithane M-45 treated sand trays were found not to be related to pathogenic organism rather toxic effect of these two chemicals. Micro-cuttings in Sun dry and control treatments showed better growth performance than these in chemically treated sand trays. In the second experiment, urea @ 1, 2 and 3 g per tray was applied as solid form after 15 days of planting the micro-cuttings and as liquid form @ 0.5, 1 and 2% solution sprayed in the micro-cuttings repeatedly after 15, 30, 45 and 60 days of planting. The micro-cuttings which received urea as solid state died within 2 - 3 days and 2% urea solution was also detrimental. Urea solution @ 0.5% found to be very effective for vegetative growth of micro-cuttings in sand trays. The control was also good for vegetative growth but at a slower rate.

Experimental and Finite Element Study of Steady State Micro-cutting Characteristics of Aluminum Alloy (2A12)

This paper studies the micro-cutting characteristics of aluminum alloy (2A12) based on a series of orthogonal experiments and finite element method (FEM) simulations. An energy-based ductile failure law was proposed in the FEM simulation. The simulated cutting forces and chip morphology were compared with experimental results. The simulation result indicates that there is a close relationship between the cutting force and cutting heat. The micro-cutting force decreases as the heat flux vector increases. Both the cutting heat and the micro-cutting force need a finite time to achieve a steady state. It is observed that with the cutting speed of 169.95 m/min and uncut chip thickness of 6 μm, the heat flux vector in the workpiece increases to a stable value after 0.06 ms; meanwhile, the principal cutting force decreases to a steady state correspondingly, i.e., the micro-cutting process achieves the steady state. It is concluded that the steady state micro-cutting simulation can reflect the cutting process accurately.

基于ABAQUS的YW1织构刀具切削仿真与试验研究

在硬质合金刀具表面植入微织构有利于提高刀具的切削性能。为深入探究织构化刀具对TC4钛合金加工性能的影响,设计一定几何参数的织构化刀具,通过调整刀具织构参数和加工参数对TC4钛合金进行切削仿真与试验分析,从切削力、切削温度、刀具磨损、切屑形貌、加工工件表面质量等方面评价刀具的切削性能。结果表明:带有微织构的硬质合金刀具对改善工件应力分布状态有积极作用,能降低切削力,缓解刀具瞬间的高温聚集,减小磨损面积,改善切屑的形貌,形成良好的工件表面质量;在不同形态织构刀具中,横向沟槽织构刀具(T3)改善切削力和降温效果最优,圆形织构刀具(T4)温度梯度分布最优;微织构的存在一定程度上提高了刀具的抗黏附性能,其中,横向沟槽织构刀具(T3)前刀面处磨损面积最小,减摩抗黏性能最好,能形成较好的工件表面质量。

基于ABAQUS的微织构刀具切削钛合金仿真研究

构建无织构刀具和呈微凹坑、平行槽、垂直槽、斜向槽形貌的微织构刀具模型,并利用有限元分析软件ABAQUS研究了微织构刀具对钛合金车削过程的影响。通过分析不同形貌微织构刀具在切削过程中的切削力、摩擦系数、切削温度和工件表面残余应力,确定了较优的微织构形貌;研究了切削速度对微织构刀具切削钛合金性能的影响。结果表明,微织构刀具能有效降低切削力、摩擦系数和切削温度,使工件表面残余应力由拉应力转变为压应力,其中垂直槽微织构刀具能最有效地改善切削质量;随着切削速度的提高,切削力和切削温度增大,摩擦系数减小,工件表面残余应力由压应力向拉应力转变并有增大的趋势。

多线切割保公差工艺对烧结钕铁硼永磁体表面质量的影响

采用多线切割保公差工艺切割烧结钕铁硼永磁体,利用SJ-410粗糙度仪、JMS-6010LA型扫描电子显微镜对微观形貌及表面粗糙度R_(a)进行表征。结果表明:随着进给速度增高和线速度的降低,金刚石磨粒压入深度减小,微观形貌由深犁沟、凹坑、破损变为浅犁沟、浅凹坑和破碎,材料去除机理由塑性去除变为塑性变形。粗糙度R_(a)随着进给速度和线速度的增高而减小;进给速度和线速度对法向载荷呈相反作用,在不同工艺参数下的材料去除方式中,塑性变形和塑性去除占据主导作用,进给速度10 mm/h和线速度1190 m/min的粗糙度最低,表面质量最优。切割时间只与进给速度有关,线弓随着进给速度增加,随线速度降低。

任豆组培再生研究

为完善任豆Zenia insignis组培快繁技术,研究采用微枝扦插的组培再生方式,探讨了基本培养基中NO-3、K+、Ca2+不同含量,以及不同植物生长调节剂种类与浓度对任豆组培芽增殖与生根效果的影响,结果表明:(1)任豆种子用75%酒精、0.1%升汞分别浸泡灭菌10,30 min,再用始温为85℃无菌水浸种24 h效果最好,种子萌芽快,种子发芽率可达92.16%;(2)RD基本培养基中NO^(-)_(3)、K^(+)、Ca^(2+)含量分别以600,360,330mg/L为最优配比,最佳继代培养基配比为RD+6-BA 0.2 mg/L+NAA 0.01 mg/L,20 d增殖系数可达3.32;(3)NAA对任豆组培芽生根以及生长有极显著的影响,最佳生根培养基配比为1/2 MS+NAA 0.5 mg/L+AC 1.0 g/L,生根率可达100%,且根系粗壮发达,组培苗生长健壮,叶片浓绿舒展。

微量润滑工况下纳米粒子协同微织构对刀具切削性能的影响

目的探究微量润滑工况下纳米粒子与织构协同作用对刀具切削性能的影响及其变化规律。方法通过有限元数值模拟软件ABAQUS对不同工况下刀具的等效塑性应变、等效应力以及切削力的变化进行仿真和预测评估。同时,通过切削试验进行验证分析,并结合刀具前刀面的磨损状态、前刀面磨损区主要元素含量、切屑形貌及其变化以及已加工表面质量对刀具的切削性能进行综合评价,以探究纳米粒子与织构刀具的协同作用对刀具切削性能的影响机制。结果仿真结果表明,N-O-M切屑的等效塑性应变较小,切屑层较薄,与N-O-T相比,最大等效应力值降低了26.4%,平均切削力为232N,刀具减摩效果最为明显;不同工况下平均切削力误差均控制在10%以内,试验值与仿真值高度一致;N-O-M磨损面积仅为1.95×10^(-2) mm^(2),刀具表面无明显的黏结物和崩刃现象,磨损面积仅为N-O-T的39.8%;N-O-M切屑卷曲半径最小,已加工工件表面脊线较长,工件表面质量较优。结论微量润滑工况下纳米粒子与表面织构的协同作用对提高刀具切削加工性能具有重要意义。微液滴在一定的压力下能渗入刀-屑界面接触区形成液膜,织构沟槽中的纳米粒子随着液膜中润滑介质的流动能够周期性释放到摩擦副的接触表面,持续作用于切削区域改变原有的摩擦接触状态和润滑方式,促进摩擦副间摩擦形式由滑动摩擦向滚动摩擦状态转变,实现减摩降磨的目标。

Magneto-plasticity in micro-cutting of single-crystal copper

The plasticity of metals can be significantly affected by the application of a magnetic field,otherwise known as the magneto-plastic effect.This paper investigates the magneto-plastic effect in the microcutting of a non-magnetic ductile material,single-crystal copper,under a weak magnetic field and reports the influence of the phenomenon on the cutting forces and machined surface quality.A softening effect was observed from the large reduction in cutting forces from 3.2 N to 1.5 N under the magnetic field.As compared to the magnetic field intensity and polarity,the variation in magnetic field orientations with respect to the cutting direction exhibited a stronger influence on the cutting force,chip morphology,machined surface texture,subsurface microstructure,surface roughness,and machined surface microhardness of the copper sample.An analytical model was developed based on the geometry of the cutting chips to correlate the orientation-dependent influence of the magnetic field on the cutting forces.On the surface quality,excessive folds with four different types of morphology produced under magnetic-free cutting were suppressed after applying the magnetic field with the most significant improvement achieved with the 90°magnetic field direction.The magnetic-assisted changes in machined surface morphology also led to the reduction in machined surface roughness and microhardness.The optimistic micro-cutting outcomes in this work establish a greater understanding of the magneto-plastic effect and demonstrate the applicability of magneto-plasticity in ultraprecision manufacturing.

Effect of a weak magnetic field on ductile-brittle transition in micro-cutting of single-crystal calcium fluoride

Magneto-plasticity occurs when a weak magnetic field alters material plasticity and offers a viable solution to enhance ductile-mode cutting of brittle materials.This study demonstrates the susceptibility of non-magnetic single-crystal calcium fluoride(CaF_(2))to the magneto-plastic effect.The influence of magneto-plasticity on CaF_(2) was confirmed in micro-deformation tests under a weak magnetic field of 20 mT.The surface pile-up effect was weakened by 10-15 nm along with an enlarged plastic zone and suppressed crack propagation under the influence of the magnetic field.Micro-cutting tests along different crystal orientations on the(111)plane of CaF_(2) revealed an increase in the ductile-brittle transition of the machined surface with the aid of magneto-plasticity where the largest increase in ductile-brittle transition occurred along the[112]orientation from 512 nm to a range of 664-806 nm.Meanwhile,the subsurface damage layer was concurrently thinner under magnetic influence.An anisotropic influence of the magnetic field relative to the single-crystal orientation and the cutting direction was also observed.An analytical model was derived to determine an orientation factor M that successfully describes the anisotropy while considering the single-crystal dislocation behaviour,material fracture toughness,and the orientation of the magnetic field.Previously suggested theoretical mechanism of magneto-plasticity via formation of non-singlet electronic states in defected configurations was confirmed with density functional theory calculations.The successful findings on the influence of a weak magnetic field on plasticity present an opportunity for the adoption of magnetic-assisted micro-cutting of non-magnetic materials.

微纳织构涂层刀具切削性能研究进展

刀具磨损严重、服役寿命短仍然是切削加工所面临的难题。随着现代制造业的发展,钛合金、高温合金等难加工材料在工业中广泛运用。但由于这些材料具有低导热系数、变形系数小等特点,在机械加工中存在切削力和切削温度高、刀具磨损严重等问题,严重缩短了刀具的服役寿命。通过表面织构技术和表面涂层技术在刀具切削表面置入微纳织构和涂层可以显著改善切削性能;特别是在减小刀具磨损、降低切削力、切削温度以及刀-屑接触界面摩擦因数等方面具有显著效果。系统概述微纳织构涂层刀具的作用机理、切削性能以及应用领域,对微纳织构涂层刀具后续发展有重要推动意义。首先,介绍微纳织构涂层刀具的制备方式。其次,分析总结微纳织构涂层刀具的作用机理,并从抗磨损性、抗粘结性和刀具寿命三个方面总结微纳织构涂层刀具的自身性能。随后,从切削力、切削温度、刀-屑接触处的摩擦因数三个方面总结微纳织构涂层刀具的切削性能。最后对微纳织构涂层刀具在现代制造业中的应用进行阐述。提出在刀具切削表面同时置入微纳织构和涂层的当前研究现状以及未来发展方向,可为进一步研究微纳织构涂层刀具在切削加工中改善切削性能以及加工表面质量与性能提供参考。

组合微织构刀具切削钛合金仿真研究

为提升刀具切削钛合金过程中的切削性能,考虑微织构形貌之间的交互作用,设计了微坑-微槽组合微织构刀具,并利用DEFORM-3D有限元模拟软件模拟组合微织构刀具切削钛合金的过程。以微织构刀具的刀具前角、切削速度和背吃刀量为因素变量设计了三因素三水平的正交试验,分析各试验因素对切削过程中主切削力的影响。结果表明:在组合微织构刀具切削钛合金过程中背吃刀量对切削力的影响最大,刀具前角次之,切削速度对切削力的影响程度最小,其最优组合为刀具前角为10°,切削速度为60 m/min,背吃刀量为0.1 mm;同时,组合微织构刀具在切削钛合金过程中,背吃刀量越小,切屑的卷曲程度越好;在不同背吃刀量的条件下,刀具前角对切屑形态的影响较为明显。

SLM成形件切削比能模型建立及影响因素分析

选区激光熔融(SLM)成形件在通过后处理加工提升表面质量时会消耗大量能量,而通过优化切削比能可以提高材料去除率和降低切削力,进而减小加工过程中的能量消耗。因此以SLM Inconel 718成形件为研究对象,建立基于切削力的切削比能模型。结合微铣削正交实验,拟合得到SLM Inconel 718微铣削切削比能与铣削参数的经验公式,并研究不同铣削参数对切削比能的影响规律。结果表明,SLM Inconel 718切削比能经验公式拟合程度在95%以上,切削深度对切削比能影响很小,切削比能随主轴转速和每齿进给量的增加而增加。

巧设Δ用微元思想解决物理问题

微元法是分析、解决物理问题常用的方法,微元法可以把复杂的物理过程简化为学生熟知的简单的物理过程、物理规律.以3个问题为例,在分析和解决问题过程中通过微元法巧妙设置Δl、ΔT、Δθ,避开繁杂运算过程,旨在培养学生从局部到整体的科学思维和提高学生运用核心知识解决问题的能力.

Calculation of the intracellular elastic modulus based on an atomic force microscope micro-cutting system

Better understanding of variations in the mechanical properties of cancer cells could help to provide novel solutions for the diagnosis,prevention,and treatment of cancers.We therefore developed a calculation model of the intracellular elastic modulus based on the contact pressure between the silicon tip of an atomic force microscope and the target cells,and cutting depth.Ovarian cells(UACC-1598) and colon cancer cells(NCI-H716) were cut into sequential layers using an atomic force microscope silicon tip.The cutting area on the cells was 8μm×8μm,and the loading force acting on the cells was increased from 17.523 to 32.126μN.The elastic modulus distribution was measured after each cutting process.There were significant differences in contact pressure and cutting depth between different cells under the same loading force,which could be attributed to differences in their intrinsic structures and mechanical properties.The differences between the average elastic modulus and surface elastic modulus for UACC-1598 and NCI-H716 cells were 0.288±0.08 kPa and 0.376±0.16 kPa,respectively.These results demonstrate that this micro-cutting method can be used to measure intracellular mechanical properties,which could in turn provide a more accurate experimental basis for the development of novel methods for the diagnosis and treatment of various diseases.

微切削切削力建模及切削参数仿真分析研究

针对当前微切削加工中存在的加工中参数选择问题,借鉴传统车削原理,基于剪切流动应力、后刀面拉伸流动应力和前刀面摩擦力3部分建立微切削切削力理论公式预测模型。借助AdvantEdge FEM仿真软件,分析切削用量对切削力和切削温度两个方面的影响,从而确定出合理的切削用量,为进行微切削加工参数选择和优化提供了理论依据。该理论模型方法已用于实际生产中,并取得了良好的应用效果。

刀具微织构对6061铝合金切削性能的影响

为探索刀具微织构对6061铝合金切削性能的影响规律,借助有限元软件对该合金进行两种刀具的切削仿真研究,得到工件温度场、应力场、主切削力和切削温度的变化规律。结果表明:刀具的微织构特征可减小切屑与刀具前刀面的摩擦,进而减少摩擦热,降低切削温度。在降低主切削力方面,微织构特征对切削速度较敏感,对进给量不敏感。通过对两种刀具实测验证,误差均在合理范围。

刀具表面椭圆开口偏置抛物线微织构参数优化

为充分发掘微织构刀具提高钛合金切削性能的潜力。以硬质合金刀具切削钛合金为研究对象,基于响应面试验方法研究了椭圆开口偏置类抛物线微织构(elliptic opening offset parabola micro texture, EOOPT)特征参数对刀具切削性能的影响规律;通过神经网络和遗传算法对其进行多目标参数优化;对相同切削条件下织构最优参数EOOPT刀具和原型刀具的相关切削性能进行了对比分析。结果表明:与原型刀具相比,最优参数EOOPT刀具的最高温度、最大应力和主切削力的平均值分别降低了11.24%、15.48%和10.81%,这对提高钛合金零件的加工质量、提高刀具寿命、降低生产成本具有积极作用。

煤矿井下处理高浊矿井水工艺技术的研究

以陕西小保当矿业有限公司一号井煤矿为例,针对井下进水仓生产污水的水质、水量及其波动情况,利用微砂重介速沉设备进行处理,具有处理效率高、占地面积小、自动化程度高等优势,在井下运用微砂重介速沉水处理工艺技术将煤泥岩粉等悬浮物先行去除,实现泥水的有效分离,清水入仓后可提升至地面或井下直接回用,煤泥也得到了有效回收并产生经济效益,排水系统更节能降耗。

基于多弧离子镀TiAlCN涂层的结构、力学及切削性能研究

为提高硬质合金刀具的切削加工性能,研究基于多弧离子镀技术在316L不锈钢及硬质合金(WC/Co)刀具表面制备了C掺杂TiAlCN涂层。首先采用扫描电子显微镜(SEM)、能量色散光谱仪(EDS)、X射线衍射仪(XRD)、拉曼光谱仪(Raman)、X射线光电子能谱仪(XPS)分析了TiAlCN涂层的表面形貌、元素成分、物相结构、碳峰位及化学态信息;然后通过二维触针轮廓仪、三维光学轮廓仪、纳米压痕仪及摩擦磨损试验机表征了TiAlCN涂层的表面粗糙度、三维形貌、纳米硬度、弹性模量及摩擦系数;最后利用高速切削测试验证了TiAlCN涂层的切削加工性能。结果表明:TiAlCN涂层表面致密光滑,无针孔、凹坑等缺陷,表面粗糙度Ra为0.066μm;TiAlCN涂层的物相组成复杂,主要为TiN、Ti(C,N)及Ti_(3)Al(C,N),且涂层中形成了以sp^(2)及sp^(3)形式杂化的非晶碳;TiAlCN涂层的纳米硬度(H)、弹性模量(E)及H/E、H^(3)/E^(2)分别为34.18 GPa、398.57 GPa及0.086、0.25,非晶碳(a-C)的形成有助于阻碍涂层位错的运动、为裂纹的萌生及扩展提供空间,使涂层表现出高的硬度、良好的韧性及低摩擦系数(约为0.1);相较于未涂层刀具,TiAlCN涂层刀具表现出较为理想的切削性能,其切削磨损寿命约为未涂层刀具的3倍,且工件的表面加工质量稳定。