【作者】 彭浩；

【导师】 黄明辉； 郝长千；

【作者基本信息】 中南大学 ， 工程（专业学位）， 2022， 硕士

【摘要】 随着轻质薄板的广泛使用,板材连接技术受到越来越多的关注。无铆连接技术在连接轻质薄板方面具有巨大的优势,已成为汽车轻量化,实现节能减排的重要工艺。但该技术在实际应用中常出现连接点缺陷和强度不稳定等问题,且目前对连接点质量的检测是毁坏性的,不能实时、无损地监控连接点的质量。为了解决上述问题,本论文通过对不同工艺参数下无铆连接点力学性能的研究,首次提出连接点的外部尺寸参数,并建立连接点外部尺寸参数与内部尺寸参数的数学关系。深入研究了连接点关键尺寸参数与强度和失效模式之间的数学关系,建立了连接点无损检测系统,实现了实时、无损、远程地监控连接点的质量。通过对不同成形力形成的连接点的力学性能进行研究,得出连接点强度与其内部尺寸参数之间的数学关系。研究了不同工艺参数下形成的无铆连接点,发现了连接点常见的两种表面缺陷。分析了连接点材料流动机理和各缺陷产生的机制。并根据使用扩展模具成形的连接点的不同扩展区域有明显分界线的特点,定义了连接点的外部尺寸参数。搭建了无铆连接点外观图像采集系统,并深入研究连接点的外观图像的视觉处理方法,探讨不同的滤波算法、边缘检测算法对连接点外观图像处理的可行性,提出了连接点外部尺寸参数识别和缺陷识别的视觉处理方案,得到了各连接点外部尺寸参数的实际值。通过研究无铆连接工艺中板材形变前后体积变化规律,提出了等体积思想,并利用此思想建立了连接点的外部尺寸参数与内部尺寸参数之间的数学模型,采用实验数据验证了此模型,得其计算底厚偏差在3.69%以内,计算颈厚偏差在6.43%以内。对负载下的连接点进行受力分析,依据连接点的外部和内部尺寸参数,建立各类失效模式下无铆连接点的强度计算模型。并用实验所得结果验证各强度计算模型,得其静强度预测准确度在85.46%以上,失效模式的预测准确度达到了100%。但由于强度计算模型的计算量较大,时间复杂度较高,为了减少计算时间,本论文依据不同工艺参数所形成的连接点的外部尺寸参数不同,其所对应的静强度也不一致的特性,建立外部尺寸参数与强度之间的映射关系,并通过线性插值的方式实现了连接点的内部尺寸参数与强度的快速预测。基于远程、实时地检测思想,建立了连接点检测系统(线上地址http://www.clinching.top)。服务端开发了三个模块:用户管理模块、连接点检测模块和后台管理模块。用户管理模块用于验证用户是否有权限进入检测系统,并能记录每个用户的检测结果。连接点检测模块负责连接点缺陷和强度的检测,并将检测结果保存到数据库中。后台管理模块能够查看用户的所有历史检测记录,并能以Excel的格式导出,便于用户进行数据处理。图107幅,表21个,参考文献55篇更多还原

【Abstract】 With the widespread use of lightweight sheets,sheet joining technology has received more and more attention.Clinching technology has huge advantages in joining lightweight sheets,and has become an important process for reducing vehicle weight and achieving energy conservation and emission reduction.However,in practical applications of clinching technology,there are often problems such as clinched joint defects and unstable strength.And the current detection of clinched joint quality is destructive,and the existing quality inspection means regarding the clinched joints can not be achieved in a real-time and non-destructive way.To solve these problems,this paper proposed the concept of the joint’s external dimension parameters for the first time,and established the mathematical relationship between the external and internal dimension parameters of joint.The mathematical relationship between the key dimension parameters of the clinched joint and the strength was deeply studied,and a non-destructive testing system that can monitor the quality of clinched joints in a real-time,non-destructive and remote way was established.By studying the mechanical properties of clinched joints under different forming forces,the mathematical relationship between the strength of clinched joint and its internal parameters was obtained.The clinched joints formed under different process parameters were studied,and two common surface defects of joints were found.The material flow mechanism of the clinched joint and generating mechanism of each defect is analyzed.The external dimension parameters of the clinched joint were defined according to the characteristics of obvious dividing line in different extension areas of the joint produced by extension die.The appearance image acquisition system of the clinched joint point was built,the visual processing method of the appearance image of the joint was deeply studied,and the feasibility of different filtering algorithms and edge detection algorithms for the appearance image processing of the joint was discussed.A vision processing solution for the identification of external dimensional parameters and defect recognition of clinched joint was proposed.The actual values of the external dimension parameters of each clinched joint are obtained.The idea of equal volume is proposed by studying the volume change law of the sheets before and after clinching process.And based on the idea of equal volume,a mathematical model between external and internal dimension parameters of the clinched joint was established.The model was verified by experimental data within the error of 3.69%(bottom thickness)and 6.43%(neck thickness).The strength calculation models of clinched joint under various failure modes were established based on load analysis and external dimension parameters of clinched joints.After verification using experimental data,the models proposed can predict the static strength and failure mode of clinched joint with the accuracy of 85.46% and 100%,respectively.Considering the large amount of calculation and high time complexity of the strength calculation model,in order to reduce the calculation time,this paper established the mapping relationship between the external dimension parameters and strength according to the characteristics that different external dimension parameters of the clinched joint produced by different process parameters are different and the corresponding static strengths are also inconsistent.By this way,the internal dimension parameters and strength of clinched joint can be predicted quickly by linear interpolation.Based on the idea of remote and real-time detection,a joint detection system(online address http://www.clinching.top)was established.The server has developed three modules: user management module,joint detection module and background management module.The user management module was used to verify whether the user has the right to enter the detection system and record the detection results of each user.The joint detection module was responsible for the detection of joint defects and strength,and saved the detection results in the database.The background management module could view all historical detection records of users,and export them in Excel format,which is convenient for users to process data.更多还原