WO2020118507A1 - 一种复杂结构内部应力场透明显示及定量表征的系统 - Google Patents

一种复杂结构内部应力场透明显示及定量表征的系统 Download PDF

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WO2020118507A1
WO2020118507A1 PCT/CN2018/120219 CN2018120219W WO2020118507A1 WO 2020118507 A1 WO2020118507 A1 WO 2020118507A1 CN 2018120219 W CN2018120219 W CN 2018120219W WO 2020118507 A1 WO2020118507 A1 WO 2020118507A1
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plane strain
test model
model
plane
stress
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PCT/CN2018/120219
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English (en)
French (fr)
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鞠杨
万昌兵
刘鹏
王建强
毛灵涛
刘红彬
付国明
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中国矿业大学(北京)
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Priority to PCT/CN2018/120219 priority Critical patent/WO2020118507A1/zh
Publication of WO2020118507A1 publication Critical patent/WO2020118507A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M99/00—Subject matter not provided for in other groups of this subclass
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials

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  • the present application relates to the technical field of stress field measurement, in particular to a system for transparent display and quantitative characterization of stress fields in complex structures.
  • geological bodies such as underground chamber surrounding rock, dam foundation, reservoir bank slope, etc. can be simplified as plane strain problems, and their stability is closely related to the distribution and evolution law of rock mass structure and surrounding rock stress field.
  • the actual engineering geological body contains a lot of complex structures such as cracks, pores and solid inclusions. For most projects, these complex structures are "invisible and untouchable”. So far, there is no plane strain experimental method that transparently displays and quantitatively characterizes the stress field distribution characteristics and evolution law of complex structures.
  • the current mainstream method is to use CT imaging and digital reconstruction algorithms to establish a three-dimensional digital model of the real structure of the geological body, and then use numerical simulation to achieve .
  • CT imaging and digital reconstruction algorithms to establish a three-dimensional digital model of the real structure of the geological body, and then use numerical simulation to achieve .
  • a series of problems such as the deviation between the geometric features and the real structure caused by the simplified numerical calculation model, the mesh coverage mode, the contact and separation of the elements, the solution algorithm, the selection of material parameters, the determination of the constitutive relationship, the calculation scale and efficiency, etc. It has been satisfactorily resolved, especially because the calculation results are difficult to obtain experimental or on-site construction parameter verification, which has caused some controversy or doubts.
  • the present application provides a system for transparent display and quantitative characterization of the internal stress field of a complex structure, which can accurately, quickly, and intuitively characterize the law of stress field distribution of a complex structure under plane strain conditions.
  • This application provides a system for transparent display and quantitative characterization of the internal stress field of a complex structure, including: a plane strain test model, two plane strain baffles, a dual-axis synchronous plane loading test machine, a controller and a processor; among them:
  • the plane strain test model is embedded with a complex structure
  • the two plane strain baffles are used to fix the plane strain test model and are clamped in the biaxial synchronous plane loading test machine;
  • the controller controls the operation of the dual-axis synchronous plane loading test machine, applies the pressure at the end of the plane strain test model, and simultaneously obtains the pictures of the isotonic and isochromatic stripes of the plane strain test model in combination with the phase shift method;
  • the processor obtains the main field stress difference and shear stress distribution based on the fringe picture, and uses stress separation means to obtain the full field stress distribution of the plane strain test model.
  • the plane strain baffle is a baffle with low stress sensitivity or no temporary birefringence effect, high transparency, high rigidity, and smooth surface.
  • the plane strain baffle is a quartz baffle.
  • the plane strain test model includes: a test model embedded with a complex structure and a model frame with screw holes; wherein:
  • test model with embedded complex structure and the model frame with screw holes are printed by a multi-material high-precision layered three-dimensional molding 3D printer;
  • An oil stop ring is provided at the interface between the test model with embedded complex structure and the model frame with screw holes;
  • the model frame provided with screw holes is provided with at least four round hole structures.
  • the form of the embedded complex structure includes one or more combinations of natural cracks, pores and solid inclusions;
  • the digital model of the embedded complex structure is automatically generated by computer simulation, or generated by CT scanning and three-dimensional reconstruction of the real structural geological body.
  • the printing material of the matrix part of the test model embedded with a complex structure is a rigid transparent material
  • the model frame printing material of the screw hole is any one of RGD8630 or a mixed material of rigid transparent material and rubber material.
  • the two quartz baffles are connected to the plane strain test model by at least 4 bolts.
  • the processor has built-in software for automatically solving principal stress difference and shear stress.
  • the phase shifting method includes: a four-step phase shifting method for obtaining a plane strain test model isobaric phase based on white light.
  • the phase shifting method further includes: a six-step phase shifting method for obtaining an isochromatic phase diagram of a plane strain test model based on monochromatic light.
  • this application discloses a system for transparent display and quantitative characterization of the internal stress field of a complex structure, including: a plane strain test model, two plane strain baffles, a dual-axis synchronous plane loading test machine, a controller and processing Among them: the plane strain test model is embedded with complex structure; two plane strain baffles are used to fix the plane strain test model and are clamped in the dual-axis synchronous plane loading test machine; the controller controls the dual-axis synchronous plane loading test machine Work, apply the pressure at the end of the plane strain test model, and obtain the isotonic and isochromatic stripe pictures of the plane strain test model by combining with the phase shift method; the processor obtains the main field stress difference and shear stress distribution based on the stripe picture, and uses The stress separation method obtains the full-field stress distribution of the plane strain test model.
  • the system provided by this application can accurately, quickly, cheaply and intuitively quantitatively characterize the stress field distribution law of complex structures under plane strain conditions.
  • FIG. 1 is a schematic structural diagram of a system for transparent display and quantitative characterization of internal stress field of a complex structure disclosed in this application;
  • FIG. 2 is a schematic diagram of a plane strain test structure disclosed in this application.
  • FIG. 3 is a schematic diagram of a four-step phase shift method for white light disclosed in this application.
  • FIG. 4 is a schematic diagram of a six-step phase shift method for monochromatic light disclosed in this application.
  • the splint should not only ensure excellent light transmittance, but also have high rigidity, and also ensure that the maximum squeezing force on the splint due to the model loading Poisson effect will not cause the splint itself to produce stress fringe images, which interferes with the model The stripe information itself. Based on this, it is difficult to choose a reasonable splint material and structure, which requires a series of tests, screening and verification.
  • the present invention provides a system for transparent display and quantitative characterization of the internal stress field of complex structures, selecting colorless transparent materials as the printing materials for the matrix part of the test area of the embedded complex structure, and selecting low-strength SUP706 support materials to fill natural joints and cracks 1.
  • any one of RGD8630 or a mixture of colorless transparent material and rubber material is selected as the printing material for the screw hole installation area.
  • the plane strain test model was loaded with a dual-axis synchronous plane loading test machine, and the boundary conditions of the experiment were completely consistent with those of the real complex structure.
  • the angle of the polarizer is rotated, ten stripe pictures with different polarization angles are taken by the CCD camera, and the "Digital Photoelasticity V3.0" solution software is imported
  • the principal stress difference and shear stress distribution of the whole field are obtained, and then the automatic separation algorithm of the shear stress difference of the stress separation is used to obtain the full field stress distribution of the test model to realize the transparent display and quantitative characterization of the stress field of the complex structure under the plane strain condition.
  • a system for transparent display and quantitative characterization of the internal stress field of a complex structure includes a plane strain test model 101, two plane strain baffles 102, a biaxial synchronous plane loading test machine 103, and a control ⁇ 104 ⁇ processor105.
  • This application can make full use of CT scanning and three-dimensional reconstruction technology to generate a planar digital model of a complex fissure structure.
  • a transparent plane strain test model is prepared to test the model with embedded complex structure and a model frame with screw holes.
  • the processed constrained plane strain test model produces a plane-displaced quartz baffle.
  • the controller controls the loading of the dual-axis synchronous plane loading experiment machine, the rotation of the polarizer of the digital photoelastic instrument, the CCD camera shooting and the photoelastic stripes of the complex structure under the load.
  • the plane strain test model system includes a quartz plate A screw hole 1, a quartz plate A2, an inter-plate spacer 3, a model frame 4, an oil stop 5, a test model 6, and a model frame screw 7. , Quartz plate B screw hole 8, quartz plate B9, quartz plate B nut 10, quartz plate B gasket 11, flexible nest of screw holes 12, quartz plate A gasket 13, bolt 14, quartz plate A nut 15, ⁇ 16 ⁇ Flat press head 16.
  • the plane strain test model can be printed using a multi-material high-precision layered three-dimensional forming 3D printer, and the printing error does not exceed 14 ⁇ m.
  • the printed material of the matrix part of the embedded complex structure test model can be Vero Clear transparent photosensitive resin material.
  • the static stress fringe value f 0 is equal to 33.8N/mm, the elastic modulus E is equal to 3.1GPa, the Poisson's ratio ⁇ is equal to 0.38, and the parameters are relatively consistent with the rock Material parameters; the embedded complex cracks and pore structures can be filled with low-strength support material SUP706; the embedded complex solid particle inclusion structure can be selected from VeroWhitePlus, VeroBlackPlus, VeroCyan, VeroBlue and other Vero series based on the actual solid particle physical and mechanical parameters An opaque material or a mixed material of Vero series (opaque) transparent material and light yellow translucent rubber material TangoPlus according to a certain proportion; the model frame can be selected from transparent VeroClear and light yellow translucent rubber material Tango Plus according to a certain proportion
  • the prepared mixed material RGD8630 has an elastic modulus E of 1.3 GPa and a Poisson's ratio ⁇ equal to 0.43.
  • the printed test model and model frame are polished and polished as a whole, showing high transparency, surface smoothness
  • the size of the experimental model can be reduced based on the actual engineering geological parameters and based on the similarity theory to determine the geometric parameters of the test model and the model frame.
  • the selection of the contact method between the test model and the model frame is mainly based on the actual situation of the project site, which can be cemented contact with filled structure, cemented contact without filled structure, frictional contact with filled structure, and frictional contact without filled structure.
  • test model with embedded complex structure can choose any shape, such as: rectangle, trapezoid, circle, ellipse, semicircular arch, arc arch, etc.;
  • a 3D digital structure model is generated using 3D reconstruction technology, imported into AutoCAD, and the embedded complex structure model containing representative regions is intercepted according to the design size drawing as a 3D digital test model. And build a matching 3D digital frame model with screw holes model, and then enter the 3D printer control software for printing, set the test model material to VeroClear, the embedded complex structure filling material is SUP706, and the model frame material is RGD8630.
  • the plane strain experiment needs to use two quartz baffles shown in Figure 2 to clamp the test model to restrict the out-of-plane displacement of its two large surfaces.
  • the quartz baffle includes quartz plate A screw holes 1 , Quartz plate A2, British plate B screw hole 8, quartz plate B9.
  • the quartz baffle has a rectangular structure with a thickness greater than 20mm. Round holes with a diameter of 20mm can be provided at the four corners. Four M10 screws with higher strength can be used to fasten the two quartz baffles and tighten the nuts.
  • the pressure sensor on the inter-pad 3 shows the same small pressure, stop tightening and remove the rigid inter-pad.
  • the quartz glass plate used has high light transmittance, high compressive strength, and high hardness. After high temperature heat treatment, there is no initial residual stress. After many tests, it is found that when the thickness is greater than 20mm, the strain under the same load is small, and the birefringence effect caused by the material strain is negligible, which can effectively constrain the out-of-plane displacement of the two large surfaces of the plane strain model, and Accurately and transparently display the stress fringe image in the complex structure model, and realize the transparent display and quantitative characterization of the stress field of the test model under the plane strain loading condition.
  • the surface of the quartz baffle and the test model have been polished and polished with high precision, and the smoothness is very high; at the same time, a thin layer of lubricant is applied to the part in contact with the frame of the model to ensure the friction effect of the part in contact between the quartz plate and the test model It is greatly reduced and has little effect on the uniformity of model deformation during the experiment.
  • the quartz baffle structure that constrains the plane displacement of the two large surfaces of the plane strain model is due to its high stiffness, good agreement with the plane strain conditions, good light transmittance, small fringe interference and surface Friction can also be used in other plane strain photoelastic experiments.
  • the device has a wide range of uses, which solves the drawbacks of the current plane photoelastic experiment method that can only simulate the plane stress problem, but not the plane strain problem, making the simulation conditions closer to the real working conditions, and the simulation results are more realistic and reliable for guiding the project site. ,crucial.
  • the present invention provides a system and analysis method for transparent display and quantitative characterization of the stress field of a complex structure, and its working process includes the following steps:
  • the CT scanning method and the 3D reconstruction technology are used to obtain a true three-dimensional digital model of the sample block, intercepting the representative 10mm embedded complex structure
  • the thick block digital model is imported into AutoCAD as the test model structure. Then, design the frame structure of the model matching the test model structure and the experimental requirements in AutoCAD, and combine the model frame structure and the test model structure as the three-dimensional digital structure of the test model under plane strain conditions;
  • the ordinary indenter of the dual-axis synchronous loading test machine is replaced with a flat indenter.
  • the thickness of the flat indenter is slightly smaller than the thickness of the test model.
  • the main purpose is to avoid the colliding of the rigid indenter and the quartz plate to cause the quartz plate to crack.
  • the overall experimental model is accurately clamped in the dual-axis synchronous plane loading test machine, and then the controller controls the testing machine indenter to apply the preset axial uniform pre-load to the test model, and the loading is controlled by displacement, and the loading rate is 0.05 mm/min.
  • FIG 3 is a schematic diagram of the arrangement of the mirror group. Set the rotation angle ⁇ equal to 0, ⁇ /8, ⁇ /4, and 3 ⁇ /8 to obtain four groups of photoelastic fringe patterns with different polarization angles; after the shooting is completed, switch the monochromatic light source and add With two quarter wave plates on it, the arrangement of the mirror group is shown in Figure 4.
  • the system for transparent display and quantitative characterization of the internal stress field of a complex structure can make full use of CT scanning and three-dimensional reconstruction technology to generate a planar digital model of a complex fissure structure, and use 3D printing technology to prepare a transparent test
  • the model is embedded with a test model of complex structure and a model frame with screw holes.
  • the constrained test model designed and processed independently produces a quartz baffle with plane displacement.
  • the controller controls the biaxial synchronous plane loading experiment machine to load, digital photoelasticity meter Polaroid rotation, CCD camera shooting and exporting photoelastic stripe images of complex structures under load, import the images into the "Digital Photoelasticity V3.0" solution software to obtain the main field stress difference and shear stress distribution, and then use the stress separation
  • the automatic solution algorithm of shear stress difference obtains the stress distribution of the whole field of the test model, and realizes the transparent display and quantitative characterization of the stress field of complex structures under plane strain conditions.
  • the plane strain test model conforms to the actual engineering situation, the experimental method is designed reasonably, the operation is simple, the result is accurate, the quantitative analysis is intuitive, and the test cost is saved.
  • the digital test model of the present application is generated by CT scanning and three-dimensional reconstruction technology, and the generated complex structure is very different from the actual engineering geological body structure.
  • the plane strain test model of the present application is printed by a multi-material high-precision layered 3D printer. Compared with the existing embedded complex structure test model processing method, the printed model has extremely high dimensional accuracy control, convenient processing, and greatly reduces the model processing cycle And can print any complex structure.
  • the printing material of the matrix part of the embedded complex structure test model of this application uses VeroClear transparent photosensitive resin material, which has high light transmittance and pressure sensitivity; the interior of the pores and cracks is filled with a very low-strength supporting material SUP706, and can finally be passed through organic
  • the solution is cleaned; the solid inclusions are a mixed material prepared by Vero series materials and TangoPlus according to a certain proportion.
  • the physical and mechanical parameters have a wide range of changes, which can meet the adaptation of the solid inclusion structure of a large range of actual geological bodies.
  • the plane strain test model of the present application shows that the plane displacement constraint is made of a whole quartz plate, the processing technology is simple, the structure is closer to the true plane strain conditions, and there will be no strain inconsistency at the interface of the baffle of multiple material combinations Properties, causing baffle shear fracture.
  • the plane strain test model and the contact surface of the quartz plate of this application adopt a variety of methods to eliminate friction, including grinding and polishing the contact surface, applying lubricant to the contact portion of the quartz baffle and the model frame, and pasting a thin layer of oil stop ring Prevent oil from entering the test model area.
  • This application presents a physical test system for transparent display and quantitative characterization of the stress field of complex structures, which solves a series of problems that can be assumed to be transparent display and quantitative characterization of the structural stress field of the engineering geological body under the plane strain state. Stability analysis provides an important reference role.
  • the transparent display and quantitative characterization of the stress field of this application are mainly based on the “four-step phase shift method” of white light to obtain the isobline phase of the model, and the “six-step phase shift method” of monochromatic light to obtain the corresponding isochromatic phase diagram; Obtain the first (or second) principal stress direction phase diagram and isochromatic unwrapping phase diagram by means of the unwrapping processing method; finally, through the automatic solution software of principal stress difference and shear stress, the principal stress difference and shear stress distribution of the whole field are obtained ; Use the shear stress difference algorithm of stress separation to obtain the full-field stress distribution of the test model under plane strain conditions. Compared with the existing method for characterizing the stress field of complex structures under plane strain conditions, it has the advantages of high quantitative analysis accuracy, intuitive visual display, easy operation, good repeatability and low test cost.
  • module or unit may be implemented by a hardware circuit, which includes a special VLSI circuit or gate array, such as a logic chip, a transistor, or other components.
  • VLSI circuit or gate array such as a logic chip, a transistor, or other components.
  • Modules or units can also be implemented in programmable hard devices, such as field-effect programmable gate arrays, programmable array logic, programmable logic devices, and so on.
  • Modules or units can also be implemented in software executed by various forms of processors.
  • an executable code module may include one or more physical or logical blocks of computer instructions, which may be formed as, for example, objects, programs, or functions.
  • the executable part of the authentication module or unit need not be physically placed together, but can be composed of different instructions stored in different locations. When logically combined together, the module or unit is formed and meets the requirements of the module or unit the goal of.
  • the executable code module or unit may be a single instruction or multiple instructions, and may even be distributed in several different code sections located in different programs and across several storage devices.
  • operational data can be identified and displayed in this module or unit, and can be implemented in any suitable form and organized within any suitable data structure form. The operation data may be aggregated into a single data set, or may be distributed in different locations with different storage devices, and at least partially exist only in a system or network in the form of electronic signals.
  • RAM random access memory
  • ROM read-only memory
  • electrically programmable ROM electrically erasable and programmable ROM
  • registers hard disks, removable disks, CD-ROMs, or all fields of technology. Any other known storage medium.

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Abstract

一种复杂结构内部应力场透明显示及定量表征的系统，包括：平面应变试验模型（101）、两块平面应变挡板（102）、双轴同步平面加载试验机（103）、控制器（104）和处理器（105）；其中：平面应变试验模型（101）内嵌复杂结构，两块平面应变挡板（102）用于固定平面应变试验模型（101），并夹持于双轴同步平面加载试验机（103）中，控制器（104）控制双轴同步平面加载试验机（103）工作，施加平面应变试验模型（101）端部压力，同时结合相移法分别获取平面应变试验模型（101）等倾线和等色线条纹图片，处理器（105）基于条纹图片得到全场主应力差及剪应力分布，并使用应力分离手段获取平面应变试验模型（101）全场应力分布，能够准确、快速、经济、直观实现定量表征平面应变条件下的复杂结构应力场分布规律。

Description

一种复杂结构内部应力场透明显示及定量表征的系统 技术领域
本申请涉及应力场测量技术领域，尤其涉及一种复杂结构内部应力场透明显示及定量表征的系统。
背景技术
土木与水电工程领域中，地下硐室围岩、坝基、库岸边坡等地质体可简化为平面应变问题，其稳定性与岩体结构及围岩应力场的分布演化规律密切相关。实际工程地质体内部均含有大量裂隙、孔隙及固体夹杂等复杂结构，而对于绝大多数工程而言，这些复杂结构是“看不见、摸不着”的。迄今为止，尚未有一种透明显示及定量表征复杂结构应力场分布特征及演化规律的平面应变实验方法。
为实现对平面应变条件下复杂结构地质体内部应力场的透明显示及定量表征，目前主流的方法是利用CT成像及数字重构算法建立地质体真实结构三维数字模型，然后使用数值模拟手段去实现。然而，数值计算模型简化造成的几何特征与真实结构之间的偏差、网格覆盖模式、单元的接触与分离、求解算法、材料参数选取、本构关系确定、计算规模与效率等一系列问题未得到圆满解决，特别是计算结果很难得到实验或现场施工参数的验证引发了一些争议或质疑。
因此，针对上述平面应变条件下复杂结构应力场数值模拟表征方法存 在的不足，发展一种准确、快速、经济、直观实现复杂结构应力场透明显示与定量表征的平面应变实验系统显得尤为重要。
发明内容
有鉴于此，本申请提供了一种复杂结构内部应力场透明显示及定量表征的系统，能够准确、快速、直观的定量表征平面应变条件下的复杂结构应力场分布规律。
本申请提供了一种复杂结构内部应力场透明显示及定量表征的系统，包括：平面应变试验模型、两块平面应变挡板、双轴同步平面加载试验机、控制器和处理器；其中：
所述平面应变试验模型内嵌复杂结构；
所述两块平面应变挡板用于固定所述平面应变试验模型，并夹持于所述双轴同步平面加载试验机中；
所述控制器控制所述双轴同步平面加载试验机工作，施加所述平面应变试验模型端部压力，同时结合相移法分别获取平面应变试验模型等倾线和等色线条纹图片；
所述处理器基于所述条纹图片得到全场主应力差及剪应力分布，并使用应力分离手段获取所述平面应变试验模型全场应力分布。
优选地，所述平面应变挡板为：应力敏感度低或无暂时双折射效应、透明度高、刚度高、表面平整的挡板。
优选地，所述平面应变挡板为石英挡板。
优选地，所述平面应变试验模型包括：内嵌复杂结构的测试模型和设 置螺孔的模型边框；其中：
所述内嵌复杂结构的测试模型和设置螺孔的模型边框均由多材料高精度的分层立体成型3D打印机打印；
所述内嵌复杂结构的测试模型和设置螺孔的模型边框表面交界处设置有止油圈；
所述设置螺孔的模型边框至少设有4个圆孔结构。
优选地，所述内嵌复杂结构的形式包括天然裂隙、孔隙及固体夹杂中的一种或多种组合；
所述内嵌复杂结构的数字模型由计算机模拟自动生成，或对真实结构地质体进行CT扫描、三维重构而生成。
优选地，所述内嵌复杂结构的测试模型基质部分打印材料为刚性透明材料；
所述天然裂隙、孔隙内部采用材料SUP706填充；
所述螺孔的模型边框打印材料选择RGD8630或刚性透明材料与橡胶类材料的混合材料中的任意一种。
优选地，所述两块石英挡板与平面应变试验模型采用至少4个螺栓连接。
优选地，所述处理器内置主应力差和剪应力自动求解软件。
优选地，所述相移法包括：基于白光的获取平面应变试验模型等倾线相位的四步移相法。
优选地，所述相移法还包括：基于单色光的获取平面应变试验模型等色线相图的六步移相法。
综上所述，本申请公开了一种复杂结构内部应力场透明显示及定量表征的系统，包括：平面应变试验模型、两块平面应变挡板、双轴同步平面加载试验机、控制器和处理器；其中：平面应变试验模型内嵌复杂结构；两块平面应变挡板用于固定平面应变试验模型，并夹持于双轴同步平面加载试验机中；控制器控制双轴同步平面加载试验机工作，施加平面应变试验模型端部压力，同时结合相移法分别获取平面应变试验模型等倾线和等色线条纹图片；处理器基于条纹图片得到全场主应力差及剪应力分布，并使用应力分离手段获取平面应变试验模型全场应力分布。本申请提供的系统能够准确、快速、便宜、直观的定量表征平面应变条件下的复杂结构应力场分布规律。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本申请公开的一种复杂结构内部应力场透明显示及定量表征的系统的结构示意图；
图2为本申请公开的一种平面应变试验结构示意图；
图3为本申请公开的一种白光的四步相移法光路布置示意图；
图4为本申请公开的一种单色光的六步相移法光路布置示意图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
针对现有表征平面应变条件下复杂结构应力场分布方法存在的不足，发展一种准确、快速、经济、直观实现定量表征平面应变条件下复杂结构应力场分布规律的实验系统显得尤为重要，而过去人们很少考虑该方法，造成这种情况的原因主要有以下三点。
一、在出现3D打印技术之前，很难在实验室中精准制备含复杂结构的透明模型。传统的模型制作工艺过中，模型主要由模具浇筑，然后通过手工或者机械加工而成的，由于加工设备的局限，原型结构的一些细微子结构只能被省去，造成了结构受力与变形分析过程中的较大误差。
二、针对透射式光弹性实验，要求保证光路的透明性特征。要实现透明模型的平面应变光弹性实验，选择合理的约束复杂结构模型出平面位移夹板显得尤为重要。该夹板既要保证优良的透光性，又要具备较高的刚度，同时也要保证因模型加载泊松效应作用到夹板上的最大挤压力不至于使夹板自身产生应力条纹图像，干扰模型本身的条纹信息。基于此，选择一种合理的夹板材料及结构难度较大，需要进行一系列测试、筛选及验证。
三、由于一些尚未解决的问题，包括简化模型和真实非均质结构的偏 差、适当材料参数的选择、本构关系的确定等，尤其是在数值计算很难在实验中和现场测试中得到验证的场合，数值分析的推广应用受到了阻碍。
由上述情况可知，平面应变条件下复杂结构的应力场分布特征及演化规律不清晰，导致在判断可假设为平面应变状态的结构体的稳定性时出现诸多困难和误差。为解决此问题，迫切需要开发一种准确、快速、经济、直观的研究系统来透明显示和定量表征平面应变条件下复杂结构的应力场，为结构体稳定性判断提供依据。
以往实践证明，利用光弹性实验能够直观、有效地表征荷载作用下复杂结构的应力场，基于最近发展起来的三维重构及3D打印技术，并结合数字光弹性实验方法，能够制作高精度、高透明度的光弹性复杂结构实验模型并定量可视化地观测其在荷载作用下的应力场分布特征及演化规律。
鉴于此，本发明提供一种复杂结构内部应力场透明显示及定量表征的系统，选取无色透明材料作为内嵌复杂结构测试区域基质部分打印材料，选取低强度的SUP706支撑材料填充天然节理、裂隙、孔隙内部区域，选取RGD8630或无色透明材料与橡胶类材料的混合材料中的任意一种作为设置螺孔安装区域打印材料。
采用双轴同步平面加载实验机对平面应变试验模型进行加载，实验的边界条件与真实复杂结构边界条件完全一致。依据白光的“四步相移法”和单色光的“六步相移法”旋转偏振片角度，通过CCD相机拍摄十幅不同偏振角度的条纹图片，导入“Digital Photoelasticity V3.0”求解软件中，得到全场主应力差及剪应力分布，再使用应力分离的剪应力差自动求解算法，获取试验模型全场应力分布，实现平面应变条件下复杂结构应力场透明显 示及定量表征。
为了更加清楚的对本申请的技术方案进行说明，下面进行详细的描述：
如图1～图4所示，一种复杂结构内部应力场透明显示及定量表征的系统，包括：平面应变试验模型101、两块平面应变挡板102、双轴同步平面加载试验机103、控制器104和处理器105。
本申请能够充分利用CT扫描和三维重构技术生成复杂裂隙结构平面数字模型，借助3D打印技术制备透明的平面应变试验模型的内嵌复杂结构的测试模型和设置螺孔的模型边框，自主设计并加工的约束平面应变试验模型出平面位移的石英挡板，通过控制器控制双轴同步平面加载实验机加载、数字光弹性仪偏振片旋转、CCD相机拍摄和导出荷载作用下复杂结构的光弹性条纹图像，将图像导入“Digital Photoelasticity V3.0”求解软件中，得到全场主应力差及剪应力分布，再使用应力分离的剪应力差自动求解算法，获取平面应变试验模型全场应力分布，实现平面应变条件下复杂结构应力场透明显示及定量表征。
具体的，如图2所示，平面应变试验模型系统，包括石英板A螺孔1，石英板A2，板间垫块3，模型边框4、止油圈5、测试模型6、模型边框螺7、石英板B螺孔8、石英板B9、石英板B螺帽10、石英板B垫片11、螺孔柔性嵌套12、石英板A垫片13、螺栓14、石英板A螺帽15、压机扁平压头16。
具体的，平面应变试验模型可以采用多材料高精度的分层立体成型3D打印机进行打印，打印误差不超过14μm。内嵌复杂结构测试模型基质部分打印材料可以选用Vero Clear透明光敏树脂材料，静态应力条纹值f 0等于 33.8N/mm，弹性模量E等于3.1GPa，泊松比μ等于0.38，参数比较吻合岩石类材料参数；内嵌复杂裂隙及孔隙结构内部可以由低强度的支撑材料SUP706填充；内嵌复杂固体颗粒夹杂结构根据实际固体颗粒物理力学参数，可选择VeroWhitePlus、VeroBlackPlus、VeroCyan、VeroBlue等Vero系列的不透明材料或Vero系列的(不)透明材料与淡黄色半透明橡胶类材料TangoPlus按一定比例配制而成的混合材料；模型边框可以选取由透明VeroClear和淡黄色半透明橡胶类材料Tango Plus按一定比例配制而成的混合材料RGD8630，其弹性模量E为1.3GPa，泊松比μ等于0.43。打印完成的测试模型和模型边框经过整体打磨、抛光处理，呈现出很高的透明度、表面平整度以及较好的应力敏感性。
具体的，在制备平面应变试验模型时，可以根据实际工程地质参数，基于相似理论对实验模型尺寸进行缩小，确定测试模型与模型边框的几何参数。
具体的，测试模型与模型边框的接触方式选择主要依据工程现场实际情况，可以是含充填结构胶结接触、不含充填结构胶结接触、含充填结构摩擦接触、不含充填结构摩擦接触。
具体的，内嵌复杂结构的测试模型根据研究对象不同，可选择任意形状，例如：矩形、梯形、圆形、椭圆形、半圆拱形、圆弧拱形等；
具体的基于对真实工程地质体的内部CT扫描结果，利用三维重构技术生成三维数字结构模型，导入AutoCAD中，按照设计尺寸图截取含有代表性区域的内嵌复杂结构模型作为三维数字化测试模型，并建立与之匹配的三维数字化带螺孔模型边框模型，然后输入3D打印机控制软件中进 行打印，设置测试模型材料为VeroClear，内嵌复杂结构填充材料为SUP706，模型边框材料为RGD8630。
具体的，平面应变实验需采用两块图2所示的石英挡板夹住试验模型以约束其两个大面的出平面位移，如图2所示，石英挡板包括石英板A螺孔1，石英板A2，英板B螺孔8，石英板B9。石英挡板为矩形结构，厚度大于20mm，在四个边角分别设有直径可以为20mm的圆孔，两块石英挡板之间可以采用四颗强度等级较高的M10螺杆紧固，拧紧螺母至板间垫块3上的压力传感器显示相同的微小压力时，停止拧紧并撤掉刚性板间垫块。
具体的，所采用的石英玻璃板透光度高，抗压强度高，硬度大，经高温热处理后，无初始残余应力。经过多次测试，发现厚度大于20mm时，其受相同荷载作用时的应变较小，由材料应变产生的双折射效应可忽略不计，可有效约束平面应变模型两个大面的出平面位移，并准确透明显示复杂结构模型内的应力条纹图像，实现平面应变加载条件下试验模型应力场透明显示及定量表征。
石英档板表面与试验模型表面均经过高精度的打磨、抛光处理，光滑度很高；同时，在与模型边框接触部分涂抹薄层润滑剂，保证了石英板与测试模型接触部分的摩擦力效应极大降低，对实验过程中模型变形的均匀性影响较小。
由于石英玻璃板脆性较强，直接在其四个角上机械打孔会导致石英板在打孔处的强度大大降低，易造成石英板在该位置发生剪切破坏，因此可以采用电火花打孔、超声波打孔或激光打孔等打孔方式。同时，在石英板与螺杆接触部分内嵌柔性嵌套，与螺母接触部分插入较大表面积刚性垫片， 采取这些措施是为了保证石英板不会发生破坏。
需要说明的是，约束平面应变模型两个大面出平面位移的石英挡板结构因其较高的刚度、与平面应变条件的良好吻合度、良好的透光性、较小的条纹干扰和表面摩擦作用，还可将其用于其他平面应变光弹性实验。装置用途广泛，很好解决了当前平面光弹性实验方法只能模拟平面应力问题，而不可模拟平面应变问题的弊端，使得模拟条件更加接近真实工况，模拟结果用于指导工程现场也更加真实可靠，意义重大。
为了更加清楚的说明本申请的技术方案，下面进一步对本申请公开的复杂结构应力场透明显示及定量表征的系统的工作过程进行介绍。
具体的，本发明提出了一种复杂结构应力场透明显示及定量表征系统与分析方法，其工作过程包括以下步骤：
a)基于可以假设平面应变问题的实际工程地质体代表性样本块体，采用CT扫描方法和三维重构技术，获得样本块体的真实三维数字模型，截取内嵌复杂结构且具有代表性的10mm厚块体数字模型作为测试模型结构，导入AutoCAD中。然后，在AutoCAD中设计匹配测试模型结构和实验要求的模型边框结构，结合模型边框结构和测试模型结构作为平面应变条件下的试验模型三维数字化结构；
b)将创建的三维数字化模型导入3D打印机控制软件中，设置测试模型材料为VeroClear，内嵌复杂结构填充材料为SUP706，模型边框材料为RGD8630。将打印完成的试验模型表面进行打磨、抛光处理，连通的裂隙、孔隙内部支撑材料SUP706采用氢氧化钠与硅酸钠的混合溶液进行溶解，然后将管片模型置于干燥皿中养护3天以消除内部的残余应力；
c)实验前，在模型边框和测试模型接触部分粘上一圈薄层海绵止油圈，在试验模型四个边角垫上板间垫块，然后调整两块石英板螺孔与试验模型螺孔位置，使之对准并插入螺孔柔性嵌套和螺杆。在螺杆与螺母之间垫上垫片，分别拧紧螺母至板间垫块上压力传感器输入一较小的相同压力值时，停止拧动螺母；
d)实验时，将双轴同步加载试验机普通压头更换成扁平压头，扁平压头厚度略小于测试模型厚度，主要为避免刚性压头与石英板发生磕碰造成石英板碎裂。将整体实验模型准确夹持于双轴同步平面加载试验机中，然后通过控制器控制试验机压头对试验模型施加预设轴向均布预压力，加载采用位移控制的方式，加载速率为0.05mm/min。
e)对准透射性光弹测试光路，调整好光源、光弹性仪的各镜片、实验机和CCD相机的相互距离，如图3、图4所示。
f)打开白光光源和CCD相机，调整相机的角度、曝光时间和增益，保证拍摄的条纹图片不出现过曝和欠曝现象。图3为镜组布置示意图，分别设置旋转角度β等于0、π/8、π/4、3π/8，获得四组不同偏振角度的光弹条纹图；拍摄完毕后，切换单色光源，加上两个1/4波片，镜组布置如图4所示。设置1/4波片镜组中每个波片角度γ依次等于0、0、0、π/4、π/2、3π/4，对应的分析镜镜组中每个波片角度β依次等于π/4、3π/4、0、π/4、π/2、3π/4，拍摄六幅不同偏振角度的光弹条纹图片。
g)采用ImageJ图像处理软件截取需要求解的测试模型区域的十幅不同的条纹图像，然后将这十幅处理后的条纹图像导入后处理软件“Digital Photoelasticity V3.0”中进行计算分析，得到全场剪应力和主应力差分布， 最后使用应力分离的剪应力差算法，获取平面应变条件下试验模型的全场应力分布。
综上所述，本申请公开的一种复杂结构内部应力场透明显示及定量表征的系统，能够充分利用CT扫描和三维重构技术生成复杂裂隙结构平面数字模型，借助3D打印技术制备透明的试验模型的内嵌复杂结构的测试模型和设置螺孔的模型边框，自主设计并加工的约束试验模型出平面位移的石英挡板，通过控制器控制双轴同步平面加载实验机加载、数字光弹性仪偏振片旋转、CCD相机拍摄和导出荷载作用下复杂结构的光弹性条纹图像，将图像导入“Digital Photoelasticity V3.0”求解软件中，得到全场主应力差及剪应力分布，再使用应力分离的剪应力差自动求解算法，获取试验模型全场应力分布，实现平面应变条件下复杂结构应力场透明显示及定量表征。
平面应变试验模型符合实际工程情况、实验方法设计合理、操作简便、结果精确、量化分析直观、节约测试成本。
本申请的数字化测试模型，采用CT扫描和三维重构技术生成，生成的复杂结构与实际工程地质体结构差异极小。
本申请的平面应变试验模型由多材料高精度分层立体3D打印机打印，相比现有的内嵌复杂结构试验模型加工方式，打印模型尺寸精度控制极高，加工方便，大大缩减了模型加工周期且可打印任意复杂结构。
本申请的内嵌复杂结构测试模型基质部分打印材料采用VeroClear透明光敏树脂材料，透光度及压力敏感性均较高；孔隙、裂隙内部采用极低强度的支撑材料SUP706填充，且最终可通过有机溶液清洗干净；固体夹 杂采用Vero系列材料与TangoPlus按一定比例配制而成的混合材料，物理力学参数变化范围大，可符合较大范围实际地质体固体夹杂结构的适配。
本申请的平面应变试验模型出平面位移的约束采用整块石英板加工而成，加工工艺简单，结构更接近真实平面应变条件，且不会出现多种材料组合挡板交界面处的应变不协调性，造成挡板剪切破裂现象。
本申请的平面应变试验模型和石英板接触表面采取了多种消除摩擦的方法，包括对接触表面进行打磨、抛光，在石英挡板与模型边框接触部分涂抹润滑油，并粘贴薄层止油圈阻止油污进入测试模型区域。
本申请提出了一种复杂结构应力场透明显示及定量表征物理试验系统，解决了一系列可假设为平面应变状态下工程地质体结构应力场透明显示及定量表征问题，对此类工程地质体的稳定性分析提供重要参考作用。
本申请的应力场透明显示及定量表征主要基于白光的“四步相移法”获取模型等倾线相位，和单色光的“六步相移法”，获取对应的等色线相图；借助去包裹处理方法分别获得第一(或第二)主应力方向相图和等色线去包裹相图；最后通过主应力差和剪应力自动求解软件，得到全场主应力差和剪应力分布；使用应力分离的剪应力差算法，获取平面应变条件下试验模型的全场应力分布。相比现有的平面应变条件下复杂结构应力场表征方法，具有定量分析精度高、结果显示形象直观、操作简便、可重复性好及测试成本低等优势。
为了更加特定地强调实施的独立性，本说明书涉及许多模块或单元。举例而言，模块或单元可由硬件电路实现，该硬件电路包括特制VLSI电路 或门阵列，比如逻辑芯片、晶体管，或其它组件。模块或单元也可在可编程的硬设备中实现，比如场效可编程门阵列、可编程阵列逻辑、可编程逻辑设备等等。
模块或单元也可在藉由各种形式的处理器所执行的软件中实现。比如说，一可执行码模块可包括一个或多个实体的或逻辑的计算机指令区块，该区块可能形成为，比如说，对象、程序或函数。然而，鉴别模块或单元的可执行部分不需要物理上放置在一起，但可由存于不同位置的不同指令所组成，当逻辑上组合在一起时，形成模块或单元且达到该模块或单元所要求的目的。
实际上，可执行码模块或单元可以是一单一指令或多个指令，甚至可以分布在位于不同的程序的数个不同的码区段，并且横跨数个存储设备。同样地，操作数据可被辨识及显示于此模块或单元中，并且可以以任何合适的形式实施且在任何合适的数据结构形式内组织。操作数据可以集合成单一数据集，或可分布在具有不同的存储设备的不同的位置，且至少部分地只以电子信号方式存在于一系统或网络。
本说明书所提及的“实施例”或类似用语表示与实施例有关的特性、结构或特征，包括在本发明的至少一实施例中。因此，本说明书所出现的用语“在一实施例中”、“在实施例中”以及类似用语可能但不必然都指向相同实施例。
再者，本发明所述特性、结构或特征可以以任何方式结合在一个或多个实施例中。以下说明将提供许多特定的细节，比如编程序、软件模块、用户选择、网络交易、数据库查询、数据库结构、硬件模块、硬件电路、 硬件芯片等例子，以提供对本发明实施例的了解。然而相关领域的普通技术人员将看出本发明，即使没有利用其中一个或多个特定细节，或利用其它方法、组件、材料等亦可实施。另一方面，为避免混淆本发明，公知的结构、材料或操作并没有详细描述。
本说明书中各个实施例采用递进的方式描述，每个实施例重点说明的都是与其他实施例的不同之处，各个实施例之间相同相似部分互相参见即可。对于实施例公开的装置而言，由于其与实施例公开的方法相对应，所以描述的比较简单，相关之处参见方法部分说明即可。
专业人员还可以进一步意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，能够以电子硬件、计算机软件或者二者的结合来实现，为了清楚地说明硬件和软件的可互换性，在上述说明中已经按照功能一般性地描述了各示例的组成及步骤。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本发明的范围。
结合本文中所公开的实施例描述的方法或算法的步骤可以直接用硬件、处理器执行的软件模块，或者二者的结合来实施。软件模块可以置于随机存储器(RAM)、内存、只读存储器(ROM)、电可编程ROM、电可擦除可编程ROM、寄存器、硬盘、可移动磁盘、CD-ROM、或技术领域内所公知的任意其它形式的存储介质中。
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本发明。对这些实施例的多种修改对本领域的专业技术人员来说将是显 而易见的，本文中所定义的一般原理可以在不脱离本发明的精神或范围的情况下，在其它实施例中实现。因此，本发明将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (9)

  1. 一种平面应变条件下复杂结构内部应力场透明显示及定量表征的系统，其特征在于，包括：平面应变试验模型、两块平面应变挡板、双轴同步平面加载试验机、控制器和处理器；其中：
    所述平面应变试验模型内嵌复杂结构；
    所述两块平面应变挡板用于固定所述平面应变试验模型，并夹持于所述双轴同步平面加载试验机中；
    所述控制器控制所述双轴同步平面加载试验机工作，施加所述平面应变试验模型端部压力，同时结合相移法分别获取平面应变试验模型等倾线和等色线条纹图片；
    所述处理器基于所述条纹图片得到全场主应力差及剪应力分布，并使用应力分离手段获取所述平面应变试验模型全场应力分布。
  2. 根据权利要求1所述的系统，其特征在于，所述平面应变挡板为：应力敏感度低或无暂时双折射效应、透明度高、刚度高、表面平整的挡板。
  3. 根据权利要求2所述的系统，其特征在于，所述平面应变挡板为石英挡板。
  4. 根据权利要求3所述的系统，其特征在于，所述平面应变试验模型包括：内嵌复杂结构的测试模型和设置螺孔的模型边框；其中：
    所述内嵌复杂结构的测试模型和设置螺孔的模型边框均由多材料高精度的分层立体成型3D打印机打印；
    所述内嵌复杂结构的测试模型和设置螺孔的模型边框表面交界处设置有止油圈；
    所述设置螺孔的模型边框至少设有4个圆孔结构。
  5. 根据权利要求4所述的系统，其特征在于，所述内嵌复杂结构的形式包括天然裂隙、孔隙及固体夹杂中的一种或多种组合；
    所述内嵌复杂结构的数字模型由计算机模拟自动生成，或对真实结构地质体进行CT扫描、三维重构而生成。
  6. 根据权利要求5所述的系统，其特征在于，所述内嵌复杂结构的测试模型基质部分打印材料为刚性透明材料；
    所述天然裂隙、孔隙内部采用材料SUP706填充；
    所述螺孔的模型边框打印材料选择RGD8630或刚性透明材料与橡胶类材料的混合材料中的任意一种。
  7. 根据权利要求6所述的系统，其特征在于，所述两块石英挡板与平面应变试验模型采用至少4个螺栓连接。
  8. 根据权利要求7所述的系统，其特征在于，所述处理器内置主应力差和剪应力自动求解软件。
  9. 根据权利要求1所述的系统，其特征在于，所述相移法包括：基于白光的获取平面应变试验模型等倾线相位的四步移相法和基于单色光的获取平面应变试验模型等色线相图的六步移相法。
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