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1、微纳米力学测试,力学性能,是评价材料质量的主要指标，也是进行设计与计算的主要依据，不同的应用领域对材料的力学性能要求也不一样 钢材塑料橡胶纤维胶黏剂涂层或镀层,模量、硬度、强度、结合力、摩擦性能,力学性能的评价,1、简单应力状态实验单轴拉伸、压缩和扭转获得：应力、应变数据由于制样的局限性只适合尺度在100m量级的样品2、复杂应力状态的接触试验硬度实验表征材料抵抗局部变形的能力，是衡量材料软硬程度的性能指标由于只在材料表面局部产生很小的压痕，使其比较适合微尺度材料,常规硬度测量方法,静态压入硬度通过球体、金刚石椎体或其他椎体经载荷施加到被测材料上，使材料发生塑性形变，再根据总施加载荷与所产生的压
2、入面积或深度之间的关系，给出其硬度值。宏观硬度；2NP30KN显微硬度：P2N，h0.2纳米硬度：h0.2动态或回弹压入硬度（载荷与回弹高度，主要用于金属材料）划入硬度（法向力、划痕，材料抗划入、摩擦、变形、附着力）,Comparative Load Ranges,纳米压入和划入的特点,操作方便 连续记录载荷和压入深度，从载荷-位移曲线中获得硬度、模量样品制备简单对样品的尺寸和形状无特殊要求，薄膜、涂层、表面改性样品测量和定位分辨率高100nN, 1nm测试内容丰富硬度、模量、断裂韧度、应力-应变曲线、高聚物的存储模量、蠕变特性、疲劳特性、粘附；薄膜的临界附着力、摩擦系数等适用范围广泛金属、陶
3、瓷、高聚物、复合材料、表面工程系统、微系统器件、生物材料,Techniques Available Today,Load, displacement & timeHardness and Modulus Continuous Stiffness MeasurementCreep and Stress ExponentFracture ToughnessStorage and Loss ModulusScratch and FrictionProfilometry(台阶仪功能）3D Imaging (原位成像),Conventional Microhardness,Apply a specifi
4、c load on a diamond indenterThe residual impression after load removal is a measure of hardness,Load,Conventional Microhardness,Diagonal, D, is measured optically after removal of loadVickers（维氏）: D = 7hKnoop（努氏）: D = 30.5h,What is Depth-Sensing Indentation?,Apply a specific, quasi-static or dynamic
5、, load-time history on a diamond indenterMeasure the displacement-time responseUse these data to extract certain mechanical properties based on analytical modelsHardness, Youngs Modulus, Stress-Exponent for Creep, Storage Modulus, Loss Modulus, etc.,Hardness & Youngs Modulus,Hardness is the mean pre
6、ssure the material will supportYoungs modulus is calculated from the composite response modulus, ErThough not shown explicitly here, both H and E require load, depth and stiffness for calculations,Load-Displacement Behavior,Aluminum（铝）, typical of soft metallic behavior, shows very little displaceme
7、nt recovery upon unloadingFused silica（熔融石英）, typical of ceramic behavior, shows large elastic recovery upon unloading,Aluminum,Fused silica,Elastic/Plastic Indentations,For an ideally plastic indentation（塑性压痕）, hc （接触深度） ht（穿透深度，最大位移）For an elastic/plastic indentation, hc ht,Stiffness From Unloadin
8、g,hn, Pn,Modeling the P-h behavior,The unloading curve（卸载曲线） follows a power lawContact stiffness（接触硬度） is the slope of the unloading curveContact depth（接触深度） is determined from the displacement, load, and contact stiffness,Contact Area (the tip function),The “tip function” for the ideal Berkovich（玻
9、氏） tipExperimental tip functionArbitrary formCoefficients determined experimentally,Polymer thin film,Problems with Time-Dependence(粘弹塑性材料),“Conventional” stiffness determination unreasonableLarge amounts of time-dependent deformationLarge time-dependent recovery,Continuous Stiffness Measurement Tec
10、hnique（连续刚度测量技术CSM）,Patented Method for the Continuous Determination of the Elastic Stiffness of Contact Between Two Bodies“Frequency-Specific（固定频率）, Depth-Sensing Indentation.”,CSM - Force Oscillation（固定频率的简谐力）,CSM - Elastic & Viscoelastic,Elastic,Viscoelastic,Dynamic Model,Stiffness Calculation by
11、 CSM Technique,Benefits of CSM,Properties vs. depth-avoiding substrate effect（基底效应）Controllable strain rateTip calibrationSurface contact determinationViscoelastic materials and properties,Thin Film Testing without CSM,Unloading data Unloads at 0.1, 0.5 and 1.0 times thicknessValues imply film hardn
12、ess varies linearly with depth,Al film on glass,Thin Film Testing with CSM,CSM dataContinuous data with thickness (i.e., depth) shows true character of film,Al film on glass,CSM - Aluminum Thin Films,Continuous measure of hardness with depthEach curve is an average of ten indentationsFrom 10 nm to 2
13、 m with each indentation“Plateaus” in hardness vary with film thickness,Al films on glass,Tip Calibration(压头校准) Standard Method,Results of 60 indentations shownLarge gaps in data,Tip Calibration CSM Method,Results of same 20 indentations shownMore points for more dense data,Tip Calibration Shallow D
14、epths,CSM gives higher data densityCSM gives lower noiseThus CSM gives more reliable calibration of tip shape,Surface Contact Determination（表面探测）(Critically important for very thin films and soft materials)1、拟合函数，外推法确定零点2、载荷或接触刚度的首次增加为零点,Point of Contact ?,AccuTip Berkovich Diamond Tips,The sharper
15、the tip, the shallower an indent can be made to give reliable hardness values,AccuTip Berkovich Diamond Tips,Old diamond tipsFace angles（中心线与面的夹角） fairly consistent, but not known with any precisionTip radius typically 100 150 nmNew AccuTip Berkovich diamond tipsFace angles known to 0.025Tip radius
16、50 nm (typically 40 nm) before 2007Tip radius 20 nm since 2008,Old Berkovich Diamond Tip,Two different DLC films, both 20 nm thickNo significant difference between them measuredPlasticity does not begin at a shallow enough indent depth to see a significant effect of the film in the measurement,Tip S
17、harpness,A sharp tip is required for making hardness measurements at very shallow indentation depths,AccuTip Berkovich diamond Tip,Two different DLC films, both 20 nm thick same films shown in previous slideStatistically significant difference between the twoPlasticity begins at a shallower indent d
18、epth shallow enough to see a significant effect of the film in the measurement,Hard coating & surface modification,Ion Implantation of Hard Chrome Plating,TiC Coated Ball Bearings,Optical Coatings - Siloxane on PC,Micro Electronic Machines (MEMS),The Nano Indenter XP makes a great MEMS TesterLFM mic
19、ro tensileDouble dog bone micro-tensile,Raytheon RF MEMS Switch,Youngs modulus of membrane very important for switch performanceNeed to deflect membrane without complicated stress states,Published by H.D. Espinosa, M. Fischer, Northwestern University and E. Herbert, W.C. Oliver, MTS Nano Instruments
20、,Diamond Tip Geometry,More acute diamond wedge,Obtuse angle diamond wedge will limit amount of vertical displacement possible,Membrane Deflection（膜偏离） Experiments,With diamond wedge wider than membrane, line load is applied and relatively simple stresses and models result,Published by H.D. Espinosa,
21、 M. Fischer, Northwestern University and E. Herbert, W.C. Oliver, MTS Nano Instruments,Membrane Deflection,Stiffnesses as low as 2 - 3 N/m were measured quite reproducibly with the standard Nano Indenter XP head,Published by H.D. Espinosa, M. Fischer, Northwestern University and E. Herbert, W.C. Oli
22、ver, MTS Nano Instruments,AccuTip Diamond TipsScratch Testing划痕测试,Scratch Friction Coefficient,FN,FT,s,t,indenter,material,Motion of indenter,Scratch friction coefficient划痕摩擦系数Actual friction coefficient实际摩擦系数,(Indenter geometry dependent),(same with Berkovich and Cube Corner),Scratch testing with a
23、 Berkovich,Low angle of attack（小接触角）Plastic deformation（塑性变形）,Face forward面划入,Edge forward（棱划入）,-1200,-1000,-800,-600,-400,-200,0,200,400,600,800,20,30,40,50,60,70,80,profile distance (um),profile height (nm),a,hb,p,Fracture Initiation: Critical Load Measurement,Study of fracture damage mechanisms（破
24、裂损坏机理）,Cube Corner indenterChipping processImportant parameters:Indenter geometryLoad for fracture initiation,Berkovich with face forward,Visco-Plastic Recovery of ScratchesTime and Temperature Dependence,Automotive paint polymer clear coat,3D Profilometry & Nanopositioning,100 x 100 um travel Resol
25、ution: 2nm Reproducibility: 2nm Linearity error:500um Resolution : 0.1nm Closed Loop,TopoSurface 3D Profilometry,Acquisition of 3D Topographic data,Acquisition of 3D Topographic data,TestWorks Data,TopoSurf 3D,Acquisition of 3D Topographic data,Inputs in the TestWorks MethodLength of scanNumber of points per scanDistance between scansNumber of scansOrientation of the scansSet the start location with microscope just like an indent,Nanopositioning Capability,Nanopositioning Capability,Nanopositioning Capability,
