Study on viscoelastic performance of asphalt mixture based on CAM model

In order to study the viscoelastic characteristics of asphalt mixtures in the whole-frequency range, a dynamic shearing rheometer is used to carry out dynamic frequency sweeps for asphalt mixtures, which obtains the three-dimensional relationships among G^＊, temperature and frequency. Then the time-temperature shift principle is used to translate the relationships from three dimensions to two dimensions, so master curves are obtained regarding dynamic modules changing along with the frequency over 15 amount levels. The Christensen- Anderson-Marasteanu （CAM） model, a kind of the rheological model, is used to analyze and compare rheological performances of several asphalt mixtures based on the obtained master curves. The results indicate that the dynamic theological test is an effective method for obtaining the master curve. Besides, the CAM model can describe well the viscoelastic deformation characteristics of asphalt mixtures.

基于Working Model 2D运动仿真的机构设计

介绍了基于Working Model 2D运动仿真的机构设计。该文利用该软件对四杆机构进行运动仿真和运动分析,结合Excel实现凸轮机构的凸轮轮廓线的设计并作运动仿真。此软件简单易学,仿真过程形象直观,为机构设计提供了一个极好的工具。

DEVELOPMENT AND APPLICATION OF COMPREHENSIVE OPTIMUM PROGRAM ON CYCLE MODELING AND VALVE SYSTEM FOR INTERNAL COMBUSTION ENGINES

A method of combining the valve system program with the engine cycle modeling software to form a full set of working process modeling is submitted,not only considering the system as an independent part,but also as a part of working process to evaluate comprehensively and indicate directly if the design is good or not.The designers can optimize the design by changing the engine structure,operation and the basic parameters of the cam on condition that the sysem should be stable so as to save large amounts of time and cost.Practical examples show that such a software package is an effective tool in optimizing the valve systems and performance of the machine.

A critical state based thermo-elasto-plastic constitutive model for structured clays

In this paper, a critical state based thermo-elasto-plastic constitutive model is developed for destructured, naturally structured and artificially structured saturated clays. The model is an extension of the previously developed thermo-mechanical model by the authors for saturated clays, considering the effects of structure on the mechanical behaviors of the soil. It is based on change in the position of normal consolidation line(NCL) in a compression plane(e-ln p′) due to the soil’s structure and variation of temperature. The present model is able to simulate the mechanical behavior of structured saturated clays in a triaxial plane at elevated temperatures lower than the boiling point of water. An attempt has been made to use the lowest possible number of parameters compared with that of Came Clay model and to ensure that these new parameters have clear physical interpretations. The sufficiency of the model was verified by the test results on artificially and naturally structured soils using thermal triaxial tests.

Multi Model Technology and Its Application in the Integration of CAD/CAM/CAE

The globalization and the intensive competition of th e automotive market require shortening the product development cycle, improving the quality and reducing the cost. Optimizing the product development process, b uilding product’s consistent defining model for life cycle, and realizing the in tegration of CAD/CAM/CAE and Concurrent Engineering (CE) become the means to acc ept the challenge. A new product modeling technology, Multi Model Technology (MM T), is provided in this paper to meet the needs of the challenge for automotive powertrain product development. First, the paper introduces the concept of Multi Model Technology. MMT introduce s Object-oriented Technology (OT) into product modeling process and combine OT with feature-based modeling technology. With the help of OT, MMT builds product object model to support system level management in product development. The obj ect model of the product is a Multi Model Structure. The MMS consists of finish part model level (assembly model level), rough part model level (part model leve l), function model level and basic model level. Every models in the MMS is creat ed by feature-based technology in design process. In this case, models in the M MS of product can be shared by casting mould, sand core and sand core mould. The refore, CAD engineers, CAE engineers and CAM engineers can work concurrently and the integration of CAD/CAM/CAE can be realized. Second, MMT is applied in cylinder head development. The multi model structures of cylinder head, its casting mould, sand core and sand core mould are built, an d the process-oriented feature models of every objects in the multi model struc tures are modeled, the application of different model objects in development pro cess is analyzed. The integrated modeling technology of cylinder head, its casti ng mould, sand core and sand core mould under MMT is studied. And the concurrent engineering oriented integration method of CAD/CAE and the method to realize th e integration of CAD/CAE under MMT are also discussed. Based on above, the integ ration of CAD/CAM/CAE of cylinder head is realized in automotive powertrain prod uct. The practice results shows that the modeling technology in this paper can optimi ze the development process, realize the data sharing and concurrent engineering in the product development process.

A mathematical model of symmetry based on mathematical definition

Tolerance is imperative for seamless integration of CAD/CAM(Computer Aided Disign/Computer Aided Manufacture) which is just a text attribute and has no semantics in present CAD systems. There are many tolerance types, the relations between which are very complicated. In addition, the different principles of tolerance make study of tolerance difficult; and there may be various meanings or interpretation for the same type of tolerance because of the literal definition. In this work, latest unambiguous mathematical definition was applied to study, explain and clarify: (1) the formation and representation of tolerance zone, and (2) the formation and representation of variational elements; after which, the mathematical models of symmetry of different tolerance principles and different interpretations were derived. An example is given to illustrate the application of these models in tolerance analysis.

Thermo-mechanical constitutive modeling of unsaturated clays based on the critical state concepts

A thermo-mechanical constitutive model for unsaturated clays is constructed based on the existingmodel for saturated clays originally proposed by the authors. The saturated clays model was formulatedin the framework of critical state soil mechanics and modified Cam-clay model. The existing model hasbeen generalized to simulate the experimentally observed behavior of unsaturated clays by introducingBishop＇s stress and suction as independent stress parameters and modifying the hardening rule and yieldcriterion to take into account the role of suction. Also, according to previous studies, an increase intemperature causes a reduction in specific volume. A reduction in suction （wetting） for a given confiningstress may induce an irreversible volumetric compression （collapse）. Thus an increase in suction （drying）raises a specific volume i.e. the movement of normal consolidation line （NCL） to higher values of voidratio. However, some experimental data confirm the assumption that this reduction is dependent on thestress level of soil element. A generalized approach considering the effect of stress level on themagnitude of clays thermal dependency in compression plane is proposed in this study. The number ofmodeling parameters is kept to a minimum, and they all have clear physical interpretations, to facilitatethe usefulness of model for practical applications. A step-by-step procedure used for parameter calibrationis also described. The model is finally evaluated using a comprehensive set of experimental datafor the thermo-mechanical behavior of unsaturated soils.2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Mathematical Modeling of the Numerical Control Cam Grinder Wheel Center Displacement and Its Application

Considering grinding a cam with numerical control（NC）cam grinder,a mathematical model should be estab- lished with the unified parameter based on the original cam-lobe lift data to describe the movement of wheel and establish the relation between the wheel center coordinate,the measuring angle and workpiece’s spindle rotation angle.By analyzing,the grinding wheel can be regarded as different followers.To the planar and roller followers,different mathematical models are established, but they can be unified in Eqs.（17）of this paper with the different value of the roller radius r1.And also the model is suit for the edged follower when assuming the roller radius r1=0.Experimental verification was done with TKM120 CNC/CBN grinder with NC sets’ interpolation according to the model,which shows that high precision parts can be manufactured and this mathemat- ical model can be practically applied for NC cam grinder.

Mathematical Model on the Manufacture of Blade-root Precise Mill

The manufacturing course of blade-root precise mill for processing the blade installing notch on rotors and the corresponding mathematical model are introduced. The reliability of this mathematical model is illustrated by a practical example.

Study on the Digital Manufacturing System of Ship Model Surface

Because a ship model surface (SMS) is a large double-curved 3-D surface,the machining efficiency of the cur- rent handcraft manufacturing method are very low,and the precision is difficult to control also.In order to greatly improve the machining efficiency and precision of SMS,based on the CAD/CAM/CNC technology,this paper proposed a model of SMS digi- tal manufacturing system,which is composed of five functional modules (preprocess module,CAD module,CAM module,post- process module and CNC module),and a twin-skeg SMS as an example,the key technologies & design principle of the nodtules were investigated also Based on the above research works,the first set of 4-axis SMS Digital Manufacturing System in China has been successfully developed,which can reduce the machining time of the twin-skeg SMS from 30 working days needed for the cur- rent handcrafting manufacturing method to 8 hours now,and which can control more effectively the precision of SMS also.

GS-CAD98: A Windows-Based Product Modeling System

GS CAD98, a feature based parametric product modeling system that facilitates dexterous manipulation of mechanical design is presented. The system allows designer to make substantial changes to a part or assembly at any time during the design process. User can develop his/her own special CAD system with the help of GS CADS98s macro language PPL or kernel routines. Furthermore, it is flexible enough to exchange product data with other CAD/CAE/CAM systems according to neutral file. GS CAD98s product data is managed by an object oriented database management system called OSCAR, and the product model is built according to the standard STEP. As a result of the unified product model, all product data are globally associated in GS CAD98. GS CAD98 supports the integration with CAPP, CAM and PDM.

Feature-based and objectoriented product information model for welding structure

Product information model for welding structure plays an important role for the integration of welding CAD/CAPP/CAM. However, existing CAD modeling systems are not capable of providing enough information for subsequent manufacturing activities such as CAPP and CAM. A new design approach using feature technique and object oriented programming method is put forward in this paper in order to create the product information model of welding structure. With this approach, the product information model is able to effectively support computer aided welding process planning, fixturing, assembling, path planning of welding robot and other manufacturing activities. The feature classification and representing scheme of welding structure are discussed. A prototype system is developed based on feature and object oriented programming. Its structure and functions are given in detail.

Mathematical model of slotting manufacture and simulation for cosine gears

A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by discrete points and the cutter figuration determined by analytic function was built for their geometrical relationship and conjugate motion during the machining process. Conjugate points in the cutter section corresponding to the discrete points on the cosine gear tooth surface and the conjugate movements were solved. By using the flexible control of the CNC procedure, the active control of the cutting trace of the slotting cutter was accomplished and the envelop forming of the cosine gear was obtained. Based on the software C++ and Matlab, the computer aided manufacturing(CAM) system of the cosine gear was developed, and the simulation of the slotting process was accomplished. Several examples were provided to illustrate the approach. The result of the simulation demonstrates that the proposed slotting method is feasible.

Modeling,Analysis and Simulation for High Voltage Vacuum Circuit Breaker with CAD/CAM System

How CAD design and simulation tools can assist in developing vacuum circuit breaker （VCB） in general is demonstrated. The electric field calculation has been widely utilized for electrical insulation design of VCB. ADAMS is applied in dynamic simulation to fulfill the complex calculation of mechanical characteristics. Satisfactory simulation results can be obtained by iteratively refining parameters of the model, and it is shown that this scheme can be used to provide a good basis for optimum design of VCB.

软黏土地区深大基坑工程桩-连续墙体系空间变形效应

土体开挖过程中深大基坑存在明显的空间变形效应,对其主体结构力学行为产生影响。以新建苏州南站枢纽深大基坑为工程背景,考虑地连墙厚度及工程桩的影响,基于ABAQUS建立三维空间有限元模型,采用修正剑桥模型考虑软黏土的应变硬化特征,从地连墙侧向位移、墙后地表沉降、工程桩和坑底土体隆起3个方面,研究软黏土地区深大基坑工程桩-连续墙体系的变形特征及空间效应。研究结果表明:深大基坑地连墙的侧向位移和地表沉降均呈现明显的角部效应,基坑A区(地连墙厚度1 m、桩径1 m)地连墙侧向位移角部效应的影响范围为1.05~1.71倍开挖深度,基坑B区(地连墙厚度0.8 m、桩径1.5 m)地连墙侧向位移角部效应的影响范围为0.91~1.48倍开挖深度;基坑A区、B区地表沉降角部效应的影响范围分别为1.24~2.10和1.77~2.47倍开挖深度;深大基坑空间变形角部效应与工程桩桩径及地连墙厚度有关,并且对基坑长边的影响效果大于短边。工程桩可有效增大基坑开挖面以下土体的刚度,减小地连墙的侧向位移;增大地连墙厚度可有效降低基坑的整体变形。基坑工程桩与坑底土体隆起总体呈现中间大、周边小的特征,工程桩周边土体受其约束,隆起较小;在一定范围内,工程桩对土体隆起抑制作用与其桩径呈正相关,与其桩间距呈负相关。软黏土地区深大基坑设计计算中需关注工程桩-连续墙结构体系的空间变形效应。

FEATURE SOLID MODELING TOOL SYSTEM:FSMTS

In conformity with the principle of Design for Manufacture,feature-based design strate- (?)es have been developed.As the“feature”is relevant to the“macro process plan”and“macro NC programs”,obviously,“feature”is beyond the power of conventional solid modellers.Neverthe- less,substantial breakthrough has not been made in the solid modeling field,except“feature at- taching”or“feature recognizing”methods have been taken on.In this paper,the theory, concepts,system architecture,and algorithm principles of solid modeling tool system have been represented.The practice of Feature Solid Modeling Tool System (FSMTS) developed at Huazhong University has proved that the tool may be a new foundation of Feature-Based Design.

Applications of a new In vivo tumor spheroid based shell-less chorioallantoic membrane 3-D model in bioengineering research

The chicken chorioallantoic membrane (CAM) is a classical in vivo biological model in studies of angiogenesis. Combined with the right tumor system and experimental configuration this classical model can offer new approaches to investigating tumor processes. The increase in development of biotechnolo- gical devices for cancer diagnosis and treatment, calls for more sophisticated tumor models that can easily adapt to the technology, and provide a more accurate, stable and consistent platform for rapid quantitative and qualitative analysis. As we discuss a variety of applications of this novel in vivo tumor spheroid based shell-less CAM model in biomedical engineering research, we will show that it is extremely versatile and easily adaptable to an array of biomedical applications. The model is particularly useful in quantitative studies of the progression of avascular tumors into vascularized tumors in the CAM. Its environment is more stable, flat and has a large working area and wider field of view excellent for imaging and longitudinal studies. Finally, rapid data acquisition, screening and validation of biomedical devices and therapeutics are possible with the short experimental window.

考虑化学反应的高聚物压密劈裂注浆仿真研究

考虑浆液化学反应原理,综合运用扩展有限元理论、修正剑桥模型和高聚物浆液膨胀力计算模型,建立了模拟高聚物在土体中压密劈裂注浆动态过程的二维仿真分析方法。通过模型试验验证了所提出方法的适用性,进而分析了浆液膨胀力、浆脉形态、土体孔隙比随时间变化规律及注浆孔埋深、土体断裂韧度对浆脉扩展过程的影响。结果表明:受高聚物化学反应进程驱动,在浆液与土体耦合作用下,浆液膨胀力初期随时间近似呈线性增长,达到峰值后快速下降并趋于稳定;浆脉长度和宽度发展速度不同步,裂缝启裂至二次扩展阶段,浆脉长度基本保持不变,宽度线性增大,裂缝二次扩展后,浆脉长度近似线性增大,而宽度增长速率趋缓;受浆液挤密作用影响,裂缝两侧一定范围内土体孔隙比显著降低,沿垂直于裂缝面方向,距注浆孔中心越近,孔隙比越小;孔隙比随时间整体呈下降趋势,随着裂缝的扩展和后期膨胀压力的下降,紧邻裂缝面两侧土体孔隙比有一定恢复,随后趋于稳定;随着注浆孔埋深和土体断裂韧度的增加,浆脉长度逐渐减小,宽度不断增大,两者变化速率基本保持不变;浆脉扩展稳定时间随埋深的增大而提前,随断裂韧度的增大而延后。

基于坐标注意力机制增强的CenterNet模型在烟草甲检测中的应用

通过在CenterNet模型中引入坐标注意力机制,使CAM-CenterNet模型更多地关注对烟草甲(Lasioderma serricorne)(以下简称烟虫)表征能力好的通道和位置,降低烟丝、烟末等杂质的干扰,将精确率(Precision)、召回率(Recall)、平均精度(mAP)、每秒帧率(FPS)以及模型参数量(Params size)作为评价指标,对CAM-CenterNet模型、CenterNet模型、YOLOv3模型和Faster R-CNN模型的烟虫检测性能进行对比。结果表明,在召回率和平均精度方面,YOLOv3模型表现最好,CAM-CenterNet模型稍落后于YOLOv3模型,但高于其他模型;在帧率方面,CAM-CenterNet模型检测烟虫图像的速度较YOLOv3模型更快,且模型参数量更少,对设备配置要求更低。在检测个体较小的烟虫时,CAM-CenterNet模型的烟虫检出数量高于Faster R-CNN模型、YOLOv3模型。CAM-CenterNet模型不仅能更多地关注烟虫目标特征,而且能很好地抑制烟丝、烟末等杂质带来的干扰,实现烟虫的有效检测。CAM-CenterNet模型能满足卷烟厂对烟虫检测速度和精度的要求,可以为烟厂的烟虫整治提供技术支持。

基于修正剑桥模型三轴剪切实验数值模拟

为了进一步拓展三轴剪切实验课教学内容,丰富实验教学方法,基于修正剑桥模型,构建三轴固结不排水实验数值模型,采用应力场与渗流场耦合模拟分析CU实验过程;分析CU实验应力路径、塑性体积应变、孔隙水压力的变化规律,推导出破坏时孔压系数公式,以及罗斯柯线归一化方程式。数值模拟实验允许实验参数或土性参数的改变,可以设计更全面的实验工况,得到更丰富的实验数据,再进行实验结果分析,得出的结论更准确。实验教学过程中引入数值模拟实验,可让学生不仅学会实验原理相关理论知识,还能将理论知识应用于实验过程,激发学生的学习兴趣,引导学生从被动学习实验理论知识向主动设计实验方向转变。