含原生缺陷的风力机叶片宏细观裂纹转捩机理及早期损伤定量识别研究

In order to explore the early damage conformation of wind turbine blade with native defects, thermal dissipation and acoustic dissipation can be analyzed through the acquisition of infrared thermography and AE signal during the plastic deformation process by combining the irreversible thermodynamic theory with meso damage mechanics. The quantitative relationship between plastic deformation, heat dissipation and acoustic energy dissipation is researched to define the plastic deformation process of the native defects and meso-cracks. The stress - heat - acoustic energy conversion physical model is established. The extent of irreversible distortion is described by the internal storage energy as the damage variable of the meso defects during plastic deformation process based on the model. The random distribution evolution regulation of the native defects is obtained under the alternating stress. Finally, the damage evolution is quantified through the AE signal characteristics, and the qualitative change of the macro and meso transition mechanism is interpreted using the internal storage energy variables. It is difficult to quantify the energy according to the conventional fatigue energy theory. Not only the puzzle is resolved by this research, but also the early fatigue damage condition monitoring of wind turbine blades can be realized. The cross-scale fatigue energy theory is explored in this study. The mesoscopic defects evolution is constructed in the unified model for the composite multilayer material which can improve the damage mechanics theory and provide support for the fatigue prediction technology. It is helpful to improve the safe operation time of the wind turbine blade, to reduce maintenance costs and to provide efficient solutions to meet the needs of major national energy development strategy if the technology can be completed.

为研究含有原生缺陷的风力机叶片早期疲劳损伤的成因，本申报项目拟结合不可逆热力学理论和细观损伤力学，通过采集红外热像图和AE信号量化塑性变形前后的热能耗散和声能耗散，明晰原生缺陷和细观裂纹的能量转化定量关系，建立应力-热-声能量转化物理模型；在此模型基础上，以内储能作为损伤变量来描述细观缺陷塑性变形过程中发生不可逆畸变的程度，从而获得随机分布原生缺陷在交变应力作用下的演化规律；最后，通过AE信号特征参数表征损伤演化的量变，以内储能变化解释宏细观裂纹转捩的质变，从而解决以往疲劳能量理论难以量化的难题，实现风力机叶片早期疲劳损伤的状态监测。这项研究探索跨尺度疲劳能量理论，将复合多层材料的早期损伤演化过程统一在物理模型中，可进一步丰富损伤力学理论体系，为完善疲劳预测技术提供支持。项目的完成将为提高风力机叶片安全运行时间降低维护成本提供高效解决方案，从而满足国家能源发展战略的重大需求。

研究宗旨是通过风力机叶片内部原生缺陷转捩为宏观裂纹的机理研究来定量识别叶片的早期损伤。研究内容主要包括：（1）构造应力函数代表原生缺陷在损伤累积过程的塑性应变能，通过红外热像仪测量含原生缺陷叶片疲劳过程中热耗散能的变化规律；（2）建立风力机叶片缺陷演变过程的温度场-应力场关联分析和声发射能量耗散模型，将声发射能量耗散变化趋势作为原生缺陷演化为损伤的前兆特征；（3）在不可逆热力学理论和细观损伤力学基础上，建立应力-热-声能量转化物理模型，以内储能作为损伤变量来识别疲劳试验中损伤发生的原始状态点，明晰叶片早期疲劳损伤的成因；（4）实施各类缺陷叶片的现场测试用来验证和完善早期损伤识别技术，设计和制作了基于红外检测技术的大型风力机叶片的健康监测装置。. 项目的实施可尽早地准确识别风力机叶片的早期损伤，研究成果既适合于新型叶片的开发和设计制造，也适合于老龄叶片的后期监测，通过快速、直观、有效地判断风力机叶片的损伤状态和可靠性，对于保证风力机的安全性和高效性、延长使用寿命、减少维护成本和停机损失具有十分重要的意义。取得的成果主要包括：（1）获得辽宁省科技进步三等奖1项，省部级人才称号2项；（2）发表相关学术论文17篇，其中SCI检索3篇，EI检索6篇；（3）授权发明专利1项，申请发明专利3项；（4）获得软件著作权4项，全部完成技术转让；（5）出版专著1部；（6）主持科研项目6项；（6）主办学术会议3次，大会报告2次；（7）指导4名博士生和3名硕士生参与本课题的研究。. 综上，本项目已完成了申报时预期的成果指标，项目组的研究成果具有自主知识产权，实现了含原生缺陷的风力机叶片的早期疲劳损伤识别技术，并将该技术应用在中广核锡林浩特宝力格风电场和赤峰亿合公风力发电厂的风场监测中，为制定叶片再生修复方案、判断是否需要报废提供诊断依据。已与沈阳吉地安风电科技有限公司签订合作协议，可以将本课题继续深入研究。