用压痕法测陶瓷材料K_(lc)的研究

本文从研究这种方法的准确性出发,指出在压痕处的残余应力在这里扮演了一个极重要的角色,它使理论分析变得极其困难,同时又会使压痕裂纹慢速扩展,影响测量的准确性。本文还从微观结构分析出发,指出完全用传统断裂力学的观点去评价压痕法测K_(1e)的准确性是不可取的。     

A study of indentation scaling relationships of elastic-perfectly plastic solids with an inclusion near the conical indenter tip

Indentation hardness is found to be related to indentation depth when indentation test is applied on homogeneous materials under small indentation depth, which shows strong size effect in the indentation. While in contrast, indentation hardness has a very limited relationship with indentation depth when it is large, showing distinct scaling relationships between hardness and material properties. Previous studies on scaling relationships under deep indentation condition of elastic-perfectly plastic homogeneous materials have been carried out systematically by finite element analysis. In this paper, a heterogeneous material, particlereinforced matrix composite is detailed studied to investigate its scaling relationships under deep indentation with different particle positions and material properties by finite element analysis.     

Compressional Deformation in Indentation Process for Microlens Array Mold

The structure of a microlens array (MLA) can be formed on copper by an indentation process which is a new manufacture approach we applied here instead of a traditional method to test the material property,thereby work time can be saved.Single-indentation and multi-indentation are both conducted to generate a single dimple and dimples array,namely micro lens and MLA.Based on finite element simulation method,factors affecting the form accuracy,such as springback at the compressed area of one single dimple and compressional deformation at the adjacent area of dimples arrays,are determined,and the results are verified by experiments under the same conditions.Meanwhile,indenter compensation method is proposed to improve form accuracy of single dimple,and the relationship between pitch and compressional deformation is investigated by modelling seven sets of multi-indentations at different pitches to identify the critical pitch for the MLA's indentation processing.Loads and cross-sectional profiles are measured and analyzed to reveal the compressional deformation mechanism.Finally,it is found that MLA at pitches higher than 1.47 times of its diameter can be manufactured precisely by indentation using a compensated indenter.     

Compressional Deformation in Indentation Process for Microlens Array Mold

The structure of a microlens array (MLA) can be formed on copper by an indentation process which is a new manufacture approach we applied here instead of a traditional method to test the material property,thereby work time can be saved.Single-indentation and multi-indentation are both conducted to generate a single dimple and dimples array,namely micro lens and MLA.Based on finite element simulation method,factors affecting the form accuracy,such as springback at the compressed area of one single dimple and compressional deformation at the adjacent area of dimples arrays,are determined,and the results are verified by experiments under the same conditions.Meanwhile,indenter compensation method is proposed to improve form accuracy of single dimple,and the relationship between pitch and compressional deformation is investigated by modelling seven sets of multi-indentations at different pitches to identify the critical pitch for the MLA's indentation processing.Loads and cross-sectional profiles are measured and analyzed to reveal the compressional deformation mechanism.Finally,it is found that MLA at pitches higher than 1.47 times of its diameter can be manufactured precisely by indentation using a compensated indenter.     

激光熔覆陶瓷热应力分析

针对在金属表面熔覆陶瓷材料时容易因热应力产生微裂纹的问题,建立了陶瓷激光熔覆时的非定常温度场模型和弹性热应力模型,并采用求相应泛函极值的方法进行求解。对这些模型在激光作用条件下的有限元法数值模拟,分析加工参数与热应力的关系,并与实验结果相比较,符合实际情况,可以用以指导在激光熔覆时避免或减少裂纹的产生。     

Determination of Young''''s modulus by nanoindentation

Loadanddepthsensingindentationtechniqueisveryusefulinprobingthemechanicalpropertiesofmaterialsonsmallscales[1—5].Youngsmodulusisoneofthemostcommonlyconcernedmaterialpropertiesmeasuredbythiskindoftechnique.Conventionally,itisachievedonthebasisofthemethodproposedbyOliverandPharr[4]usingthewell-knownrelationship:whereSuistheinitialslopeofunloadingcurve,EristhereducedmodulusandrelatedwiththeYoungsmodulusEandPoissonsratioνoftheindentedmaterialandthose(Ei,ni)oftheindenterbytheequation1/Er=(1-n2…     

基于图象处理的布氏硬度测试系统研究

布氏硬度压痕直径传统的测量方法是用20倍的读数显微镜,效率较低,误差较大。为了提高布氏硬度测试的效率和精度,利用OpenCV软件强大的运算和图形图像处理功能开发了基于图象处理的布氏硬度测试系统。可实现布氏硬度的自动测试和结果的自动显示,而且界面友好简单,操作方便可靠。实验结果表明,基于图象处理的布氏硬度测试系统大大提高了测量结果的准确性,提高了效率,且结果可以保存。     

服役后16Mn管材应变时效的自动球压痕测试

针对在役和不可取样的设备应变时效价难问题,以服役后16Mn管材为研究对象,通过自动球压痕和常规力学试验,对比应变时效前后材料的屈服强度、抗拉强度、冲击吸收能和断裂韧度,并深入探讨自动球压痕试验在材料应变时效上的应用。试验结果表明,自动球压痕可以准确测定材料发生应变时效后的力学性能值,因此可以定期通过自动球压痕技术对在役设备进行力学性能测试,并根据实际测试力学性能来调整运行压力或更换设备,不但可以有利于设备的安全运行,同时可以延长设备的使用寿命。     

Determination of plastic equation of state by indentation method on 304 stainless steel

An indentation method for determining the plastic mechanical equation of state (PES) was studied. The constant loading rate and constant loading rate/load indentation tests were carried out. The method for determining the work-hardening coefficient and the strain rate sensitivity coefficient of PES were discussed in detail. 304 stainless steel hot-treated at 1100℃ was used to verify the method. The work-hardening coefficient and strain rate sensitivity coefficient of 304 stainless steel were respectively determined as 0.30 and 0.015. These values are very close to those achieved by tensile tests. From the establishment of the PES of 304 stainless steel it is shown that the PES obtained by the indentation method is easier than that by the tensile test.     

熔石英元件抛光加工表面残余应力的计算方法

为解决传统检测方法无法直接定量检测非晶体熔石英玻璃表面残余应力的问题,基于脆性固体断裂力学理论,推导残余应力的理论计算公式,提出光学元件抛光加工表面残余应力计算新方法.采用尖锐压头进行纳米印压实验,提取压痕过程中对残余应力敏感的参数,并对实验数据进行线性拟合,确定拟合线的斜率,通过测量残余应力引起其他物理参数的变化计算残余应力.对比分析结果表明,计算得到残余应力值与应力双折射仪检测得到的数据基本吻合,验证了提出残余应力计算方法的正确性.     

沁水盆地煤储层微裂隙发育的煤岩学控制机理

基于沁水盆地主要矿区实测煤样的分析资料,总结了煤岩显微组分、煤岩类型和煤相与微裂隙发育的关系,探讨了微裂隙的成因及煤岩学控制机理.结果表明:该区微裂隙多以长度小于300μm,宽度小于5μm的裂隙为主,裂隙密度一般都在10～50条/9cm2之间;微裂隙通常发育于均质镜质体为主的组分中,且常见于条带状亮煤或以微镜煤为主的亮煤中.潮湿、弱氧化和弱水动力的成煤环境有利于微裂隙的发育.微裂隙是煤化作用过程中烃类气体的瞬间积聚形成高压流体单元后突然破裂而形成的,其中条带状亮煤或以均质镜质体为主的流体微单元,不仅具有较好的生烃潜能,同时孔隙发育差不利于气体的扩散,这是造成这些组分中微裂隙发育的主要原因.     

Fracture behavior of CrN coatings under indentation and dynamic cycle impact

Fracture behavior of CrN coatings deposited on the surface of silicon and AISI52100 steel by different energy ion beam assisted magnetron sputtering technique (IBAMS) was studied using indentation and dynamic cycle impact. It is found that, for the coatings on silicon substrate, the cracks form in the indentation corners and then propagate outward under Vickers indentation. The coating prepared using ion assisted energy of 800 eV shows the highest fracture resistance due to its compact structure. Under Rockwell indentation, only finer radial cracks are found in the CrN coating on AISI 52100 steel without ion assisting while in the condition of ion assisting energy of 800 eV, radial, lateral cracks and spalling appear in the vicinity of indentation. The fracture of CrN coatings under dynamic cycle impact is similar to fatigue. The impact fracture resistance of CrN coatings increases with the increase of ion assisting energy.     

平面压痕的极限开裂角与临界载荷

当矩形平端刚性压头作用在无摩擦弹性基体的表面时, 在基体表面生成一个平面压痕, 同时在压痕边界处的近表面诱生奇异应力场, 该奇异应力场的奇异性与裂纹尖端I -型应力场的奇异性同价, 使平面压痕的表面产生断裂型开裂。利用能量释放率原理, 分析压痕边界断裂开裂的极限开裂角、极限开裂载荷等相关问题。     

Nanoindentation tests on single crystal copper thin film with an AFM

0　INTRODUCTIONThinfilmmaterialshavebeenwidelyemployedinmanyfieldssuchasmicroelectronics ,micro electro me chanicalsystems ,opticaldevicesandmagneticstoragematerials[1～ 4 ] .Theirmechanicalproperties ,whichmightdifferfromthosebulkmaterialswiththesamecomposi tion ,haveavitaleffectonreliabilityandservicelifeofthefilm .Therefore ,quantitativelycharacterizingtheme chanicalpropertiesofthefilmisincreasinglydemandedfortheapplications .Generallyspeaking ,themechanicalpropertiesofmaterialsonmacro…     

平面压痕开裂极限临界载荷与开裂角

平面压痕的开裂在材料机械性能的研究、破岩机理的研究中有着广泛的应用。当刚性压头作用在半 平面弹性体的表面时,会产生一个平面压痕,该压痕的两端将出现I 型奇异压应力场,该奇异应力场的应力集中达到一定程度时,即达到临界条件时,该奇异应力场所在的边界将开裂。压痕边界的开裂问题是一个新型的断裂力学问题,通过边界移动的能量释放率的分析定量地给出了平面压痕边界开裂能量释放率数学表征,给出了边界开裂的极限临界载荷和临界开裂角。     

石材框架砂锯锯切力特性分析

本文从岩石的裂纹扩展特性、材料强度特性及压头点载荷侵入破岩特性等方面入手,对单颗粒的切削力进行了深入分析,得出单颗粒切削深度是影响锯切力的主要因素的结论.通过对单颗粒切削深度影响因素的讨论,得出锯切条件及工艺参数与锯切力的关系结论:锯切力将随落锯速度的增大而增大,随锯切速度的增大而减小.锯切力实验结果与理论分析结果相一致.研究结果可为锯切机理的进一步研究及设备与工艺的改进提供理论依据.     

J-积分在镀层基体平面压痕边界开裂中的应用

当二维平端刚性压头作用在镀层基体的表面时,在镀层材料的表面形成一个平面压痕,同时在压痕的边界处将诱生奇异应力场和K-控制区。与裂纹问题类似,该应力场的平面压痕应力强度因子是描述奇异应力场应力集中程度的唯一参量。本文将利用守恒积分,讨论镀层基体平面压痕守恒积分的主要特征,同时给出镀层基体平面压痕应力强度因子的远场积分计算方法。     

周期阵列压痕奇异应力场与开裂（PartⅡ：压痕开裂临界载荷）

周期阵列压痕方法是研究微观摩擦学的工具之一。由于周期阵列刚性压头压在半平面弹性体的表面时,会产生周期的Ⅰ型奇异压应力场,该奇异应力场的应力集中达到一定程度时,即达到临界条件时,该奇异应力场所在的边界将开裂。压痕边界的开裂问题是一个新型的断裂力学问题,通过边界移动的能量释放率的分析给出了压痕边界开裂能量释放率数学表征,并给出边界开裂的临界载荷和临界开裂角。     

Finite element and experimental analysis of Vickers indentation testing on Al2O3 with diamond-like carbon coating

Numerical simulation and experimental study of the Vickers indentation testing of the Al₂O₃ ceramic coated by diamond-like carbon (DLC) layer were conducted. The numerical analysis was implemented by a two-dimensional finite element (FE) axis symmetry model. FE analysis results gave insight into the fracture mechanism of DLC films coated on brittle ceramic (Al₂O₃) substrates. The maximum principal stress field was used to locate the most expected area for crack formation and propagation during the Vickers indentation testing. The results show that the median crack initiates in the interface under indenter, before ring crack occurs as the indenter presses down. Finally, the plastic deformation appears when the indenter penetrates into the substrate. The thicker DLC coating increases the Vickers hardness and fracture toughness.     

机器视觉技术对纸质包装切割压痕设备控制性能的改进设计

针对在用NRG-P型切割压痕设备存在的问题,提出用机器视觉这种新型的检测方法对其进行控制性能改进.改进的主要任务是原点位置识别和偏差角度校正,并通过图像采集、图像处理手段对这两个量求解.图像处理过程包括图像二值化、图像降噪、图像边缘检测和图像标定等,同时还设计了CAN总线驱动电路.最后通过坐标系旋转变换,修正了刀具的运动轨迹,提高了加工精度.