基于近场动力学的薄板弯曲大变形及断裂分析

薄板结构仅在较小的荷载下就能产生较大的位移、旋转,甚至引发结构产生裂纹并扩展,进而发生结构整体断裂,因此,建立薄板结构在大变形过程中的裂纹扩展及断裂仿真模型,具有重要的工程实际意义.文章建立了用于薄板结构几何大变形和断裂分析的近场动力学(PD)和连续介质力学(CCM)耦合模型.首先基于冯·卡门假设,采用更新的拉格朗日法得到薄板在几何大变形增量步下的虚应变能密度增量公式,并利用虚功原理和均质化假设求出几何大变形微梁键的本构模型参数;接着分别建立几何大变形薄板PD模型与CCM模型的虚应变能密度增量,并建立了薄板几何大变形PD-CCM耦合模型;最后模拟了薄板结构在横向变形作用下的渐进断裂过程,得到与实验结果高度一致的仿真结果,验证了所提出的几何非线性PD-CCM耦合模型的精度.结果表明:本文所提出的薄板PD-CCM耦合模型具有简单高效,无需考虑材料参数限制和边界效应的特点,可以很好地用于预测薄板结构在几何大变形过程中的局部损伤和结构断裂,有利于薄板结构的断裂安全评价和理论发展.

汽车发动机原理课程思政教学改革与探索

为贯彻思政教育进课堂的思想,推进大连理工大学课程思政长效机制建设,分析了汽车发动机原理课程开展实施课程思政建设的必要性,通过课程教学内容、方法和手段的改革,使专业课程与思政建设同向同行,充分发挥专业课程对人才培养的育人能力,构建新时代思政课程考核体系,为社会主义现代化建设输送思想政治过硬、能适应新时代需求的高质量行业创新人才。

基于数值模拟和回归正交设计的AA5754铝合金温成形回弹特性

以圆筒温拉深切环实验为基础,采用数值模拟与回归正交试验相结合的方法,建立铝合金温成形过程中板料成形初始温度、摩擦因数、压边力、凹模圆角半径和凸凹模间隙与回弹之间的回归模型,得出各工艺参数对制件回弹的影响规律,确定最优工艺参数组合。通过回归模型进行回弹预测,并与相同工艺条件下4种温度的实验结果和数值模拟结果进行比较。研究结果表明:回归模型显著性明显,拟合度高,预测结果具有较高的可信度。

改进的键基正交各向异性近场动力学模型

针对经典的键基近场动力学(bond-based peridynamic,BPD)模型受固定泊松比限制的问题,提出一种改进BPD模型。该模型可解除泊松比限制,并可用于分析正交各向异性单向板的变形和裂纹扩展问题。在改进BPD模型中,每根键受到轴向和横向成对力的作用,额外增加的节点转动可消除由横向力引起的附加弯矩,从而确保该模型满足角动量守恒条件。仿真结果验证所提出的改进BPD模型的精度,并展示其预测碳纤维复合材料变形和裂纹扩展的能力。

基于神经网络的裂纹扩展过程预测

提出基于神经网络的裂纹扩展过程实时预测方法,其计算效率比近场动力学(peridynamic,PD)模型提高。使用PD算法获取裂纹扩展过程中的损伤云图,构建裂纹扩展数据集。基于数据集构建生成对抗网络(generative adversarial networks,GAN)模型,根据不同加载条件实时生成损伤云图,从而快速预测裂纹的扩展过程。将PD模型计算得到的损伤云图中的RGB值与相应位置处的损伤值结合,构建多层前馈神经网络模型的数据库,并使用多层前馈神经网络模型分析GAN模型产生的损伤云图,得到相应的损伤值。通过数值算例证明该方法的效率和准确性。

Application of Hot Forming High Strength Steel Parts on Car Body in Side Impact

Lightweight structure is an important method to increase vehicle fuel efficiency. High strength steel is applied for replacing mild steel in automotive structures to decrease thickness of parts for lightweight. However, the lightweight structures must show the improved capability for structural rigidity and crash energy absorption. Advanced high strength steels are attractive materials to achieve higher strength for energy absorption and reduce weight of vehicles. Currently, many research works focus on component level axial crash testing and simulation of high strength steels. However, the effects of high strength steel parts to the impact of auto body are not considered. The goal of this research is to study the application of hot forming high strength steel（HFHSS） in order to evaluate the potential using in vehicle design for lightweight and passive safety. The performance of HFHSS is investigated by using both experimental and analytical techniques. In particular, the focus is on HFHSS which may have potential to enhance the passive safety for lightweight auto body. Automotive components made of HFHSS and general high strength steel（GHSS） are considered in this study. The material characterization of HFHSS is carried out through material experiments. The finite element method, in conjunction with the validated model is used to simulate the side impact of a car with GHSS and HFHSS parts according to China New Car Assessment Programme（C-NCAP） crash test. The deformation and acceleration characteristics of car body are analyzed and the injuries of an occupant are calculated. The results from the simulation analyses of HFHSS are compared with those of GHSS. The comparison indicates that the HFHSS parts on car body enhance the passive safety for the lightweight car body in side impact. Parts of HFHSS reduce weight of vehicle through thinner thickness offering higher strength of parts. Passive safety of lightweight car body is improved through reduction of crash deformation on car body by the application of HFHSS parts. The experiments and simulation are conducted to the HFHSS parts on auto body. The results demonstrate the feasibility of the application of HFHSS materials on automotive components for improved capability of passive safety and lightweight.