Fused deposition modelling(FDM), a widely used rapid prototyping process, is a promising technique in manufacturing engineering. In this work, a method for characterizing elastic constants of FDM-fabricated materials ...Fused deposition modelling(FDM), a widely used rapid prototyping process, is a promising technique in manufacturing engineering. In this work, a method for characterizing elastic constants of FDM-fabricated materials is proposed. First of all, according to the manufacturing process of FDM, orthotropic constitutive model is used to describe the mechanical behavior. Then the virtual fields method(VFM) is applied to characterize all the mechanical parameters(Q, Q, Q, Q) using the full-field strain,which is measured by digital image correlation(DIC). Since the principal axis of the FDM-fabricated structure is sometimes unknown due to the complexity of the manufacturing process, a disk in diametrical compression is used as the load configuration so that the loading angle can be changed conveniently. To verify the feasibility of the proposed method, finite element method(FEM) simulation is conducted to obtain the strain field of the disk. The simulation results show that higher accuracy can be achieved when the loading angle is close to 30?. Finally, a disk fabricated by FDM was used for the experiment. By rotating the disk, several tests with different loading angles were conducted. To determine the position of the principal axis in each test, two groups of parameters(Q, Q, Q, Q) are calculated by two different groups of virtual fields. Then the corresponding loading angle can be determined by minimizing the deviation between two groups of the parameters. After that, the four constants(Q, Q, Q, Q) were determined from the test with an angle of 27?.展开更多
The isotropic and anisotropic behaviors are considered as the important formats of the constitutive behaviors,and can also be called the global properties.To improve the identification ability of virtual fields method...The isotropic and anisotropic behaviors are considered as the important formats of the constitutive behaviors,and can also be called the global properties.To improve the identification ability of virtual fields method(VFM)when the global properties are unknown,this paper proposes the strain correlation method(SCM)to determine the global properties before the parameter identification using the VFM.Firstly,the basic principle of SCM is described in detail.Then,the feasibility and accuracy of SCM are verified through the numerical experiments based on the three-point bending configuration and the real experiment of polymethyl methacrylate(PMMA).The influence of the additive Gaussian white noise,local errors in the strain fields,and missing data at the specimen edges on the characterization results are evaluated.The results show that the SCM has good noise immunity and lower accuracy requirements for the strain fields.As an application,the mechanical properties of Ti-6A1-4V alloys fabricated by selective laser melting(SLM)are characterized by the SCM.The results show that the alloys are isotropic,and the isotropic VFM is utilized to determine the mechanical parameters.By using the SCM,the accuracy of identification results can be improved for the isotropic or bidirectional reinforced orthotropic materials when using VFM.展开更多
矿山微震事件震源位置和近震震级是矿震最基本的参数,其准确计算对矿震事件分析与信息挖掘具有重要作用。介绍了一种有别于传统定位思路的定位方法—虚拟场优化法(virtual field optimization method,VFOM),并给出了以台站计算震级偏差...矿山微震事件震源位置和近震震级是矿震最基本的参数,其准确计算对矿震事件分析与信息挖掘具有重要作用。介绍了一种有别于传统定位思路的定位方法—虚拟场优化法(virtual field optimization method,VFOM),并给出了以台站计算震级偏差最小为目标的近震震级公式回归方法。将VFOM和近震震级参数回归方法用于开阳磷矿用沙坝矿区401个微震事件的震源定位和近震震级公式的重新标定。结果表明,定位结果可靠,重新标定震级公式得到的震级台站偏差相比于现有公式有明显的减小。此外,采用标定震级公式计算的震级分布观察到了明显的双峰分布现象,表明用沙坝矿的微震数据可能由两种成因的事件构成。实例表明,不同地区的近震震级计算公式必须根据实测数据重新标定,否则将可能丢失一些重要的震级分布特征。展开更多
针对传统人工势场法在多障碍物复杂环境的全局路径规划中出现的目标不可达、易陷入陷阱区域以及局部极小点问题,提出一种简化障碍物预测碰撞人工势场法(simplified obstacles and predict collision of artificial potential field meth...针对传统人工势场法在多障碍物复杂环境的全局路径规划中出现的目标不可达、易陷入陷阱区域以及局部极小点问题,提出一种简化障碍物预测碰撞人工势场法(simplified obstacles and predict collision of artificial potential field method,SOPC-APF),算法引入预测碰撞思想,在机器人未进入陷阱区域或者极小点问题前做出决策;对于多障碍物的斥力与目标点的引力产生的合力使机器人陷入震荡,提出简化障碍物,即简化为影响范围内目标点一侧的受限障碍物;针对目标不可达问题,在碰撞预测基础上,设定虚拟目标点,经改进的斥力函数引导机器人快速生成一条平滑、平稳、无碰撞的路径。通过与传统算法、改进APF算法以及改进蚁群算法的仿真对比实验表明,SOPC-APF有效解决了人工势场法不适用于多障碍物复杂环境的问题,以及传统算法容易陷入陷阱区域和局部极小点问题。展开更多
基金the financial support from the National Natural Science Foundation of China (Grants 11672153, 11232008, and 11227801)
文摘Fused deposition modelling(FDM), a widely used rapid prototyping process, is a promising technique in manufacturing engineering. In this work, a method for characterizing elastic constants of FDM-fabricated materials is proposed. First of all, according to the manufacturing process of FDM, orthotropic constitutive model is used to describe the mechanical behavior. Then the virtual fields method(VFM) is applied to characterize all the mechanical parameters(Q, Q, Q, Q) using the full-field strain,which is measured by digital image correlation(DIC). Since the principal axis of the FDM-fabricated structure is sometimes unknown due to the complexity of the manufacturing process, a disk in diametrical compression is used as the load configuration so that the loading angle can be changed conveniently. To verify the feasibility of the proposed method, finite element method(FEM) simulation is conducted to obtain the strain field of the disk. The simulation results show that higher accuracy can be achieved when the loading angle is close to 30?. Finally, a disk fabricated by FDM was used for the experiment. By rotating the disk, several tests with different loading angles were conducted. To determine the position of the principal axis in each test, two groups of parameters(Q, Q, Q, Q) are calculated by two different groups of virtual fields. Then the corresponding loading angle can be determined by minimizing the deviation between two groups of the parameters. After that, the four constants(Q, Q, Q, Q) were determined from the test with an angle of 27?.
基金This research was financially supported by the National Key Research and Development Program of China(Grant 2017YFB1103900)the National Science and Technology Major Project(Grant 2017-VI-0003-0073)+1 种基金the National Natural Science Foundation of China(Grant 11672153)Hubei Provincial Major Program of Technological Innovation(Grant 2017AAA121).
文摘The isotropic and anisotropic behaviors are considered as the important formats of the constitutive behaviors,and can also be called the global properties.To improve the identification ability of virtual fields method(VFM)when the global properties are unknown,this paper proposes the strain correlation method(SCM)to determine the global properties before the parameter identification using the VFM.Firstly,the basic principle of SCM is described in detail.Then,the feasibility and accuracy of SCM are verified through the numerical experiments based on the three-point bending configuration and the real experiment of polymethyl methacrylate(PMMA).The influence of the additive Gaussian white noise,local errors in the strain fields,and missing data at the specimen edges on the characterization results are evaluated.The results show that the SCM has good noise immunity and lower accuracy requirements for the strain fields.As an application,the mechanical properties of Ti-6A1-4V alloys fabricated by selective laser melting(SLM)are characterized by the SCM.The results show that the alloys are isotropic,and the isotropic VFM is utilized to determine the mechanical parameters.By using the SCM,the accuracy of identification results can be improved for the isotropic or bidirectional reinforced orthotropic materials when using VFM.
文摘矿山微震事件震源位置和近震震级是矿震最基本的参数,其准确计算对矿震事件分析与信息挖掘具有重要作用。介绍了一种有别于传统定位思路的定位方法—虚拟场优化法(virtual field optimization method,VFOM),并给出了以台站计算震级偏差最小为目标的近震震级公式回归方法。将VFOM和近震震级参数回归方法用于开阳磷矿用沙坝矿区401个微震事件的震源定位和近震震级公式的重新标定。结果表明,定位结果可靠,重新标定震级公式得到的震级台站偏差相比于现有公式有明显的减小。此外,采用标定震级公式计算的震级分布观察到了明显的双峰分布现象,表明用沙坝矿的微震数据可能由两种成因的事件构成。实例表明,不同地区的近震震级计算公式必须根据实测数据重新标定,否则将可能丢失一些重要的震级分布特征。
文摘针对传统人工势场法在多障碍物复杂环境的全局路径规划中出现的目标不可达、易陷入陷阱区域以及局部极小点问题,提出一种简化障碍物预测碰撞人工势场法(simplified obstacles and predict collision of artificial potential field method,SOPC-APF),算法引入预测碰撞思想,在机器人未进入陷阱区域或者极小点问题前做出决策;对于多障碍物的斥力与目标点的引力产生的合力使机器人陷入震荡,提出简化障碍物,即简化为影响范围内目标点一侧的受限障碍物;针对目标不可达问题,在碰撞预测基础上,设定虚拟目标点,经改进的斥力函数引导机器人快速生成一条平滑、平稳、无碰撞的路径。通过与传统算法、改进APF算法以及改进蚁群算法的仿真对比实验表明,SOPC-APF有效解决了人工势场法不适用于多障碍物复杂环境的问题,以及传统算法容易陷入陷阱区域和局部极小点问题。
