Prediction of stiffener buckling in press bend forming of integral panels

In order to predict the buckling of stiffeners in the press bend forming of the integral panel,a method for solving the critical buckling load of the stiffeners in press bend forming process was proposed based on energy method,elastic-plastic mechanics and numerical analysis.Bend to buckle experiments were carried out on the designed press bend dies.It is found that the predicted results based on the proposed method agree well with the experimental results.With the proposed method,the buckling of the stiffeners in press bend forming of the aluminum alloy integral panels with high-stiffener can be predicted reasonably.

Principal Face-based Recognition Approach for Machining Features of Aircraft Integral Panels

Feature recognition aims at extracting manufacturing features with geometrical information from solid model and is considered to be an efficient way of changing the interactive NC machining programming mode.Existing recognition methods have some disadvantages in practical applications.They can essentially handle prismatic components with regular shapes and are difficult to recognize the intersecting features and curved surfaces.Besides,the robustness of them is not strong enough.A new feature recognition approach is proposed based on the analysis of aircraft integral panels＇ geometry and machining characteristics.In this approach,the aircraft integral panel is divided into a number of local machining domains.The machining domains are extracted and recognized first by finding the principal face of machining domain and extracting the sides around the principal face.Then the machining domains are divided into various features in terms of the face type.The main sections of the proposed method are presented including the definition,classification and structure of machining domain,the relationship between machining domain and principal face loop,the rules of machining domains recognition,and the algorithm of machining feature recognition.In addition,a robotic feature recognition module is developed for aircraft integral panels and tested with several panels.Test results show that the strategy presented is robust and valid.Features extracted can be post processed and linked to various downstream applications.The approach is able to solve the difficulties in recognizing the aircraft integral panel＇s features and automatic obtaining the machining zone in NC programming,and can be used to further develop the automatic programming of NC machining.

Optimization of press bend forming path of aircraft integral panel

In order to design the press bend forming path of aircraft integral panels,a novel optimization method was proposed, which integrates FEM equivalent model based on previous study,the artificial neural network response surface,and the genetic algorithm.First,a multi-step press bend forming FEM equivalent model was established,with which the FEM experiments designed with Taguchi method were performed.Then,the BP neural network response surface was developed with the sample data from the FEM experiments.Furthermore,genetic algorithm was applied with the neural network response surface as the objective function. Finally,verification was carried out on a simple curvature grid-type stiffened panel.The forming error of the panel formed with the optimal path is only 0.098 39 and the calculating efficiency has been improved by 77%.Therefore,this novel optimization method is quite efficient and indispensable for the press bend forming path designing.

Blank Panel Design of Integral Wing Skin Panels Based on Feature Mapping Methods

A blank panel design algorithm based on feature mapping methods for integral wing skin panels with supercritical airfoil surface is presented.The model of a wing panel is decomposed into features,and features of the panel are decomposed into information of location,direction,dimension and Boolean types.Features are mapped into the plane through optimal surface development algorithm.The plane panel is modeled by rebuilding the mapped features.Blanks of shot-peen forming panels are designed to identify the effectiveness of the methods.

FEM equivalent model for press bend forming of aircraft integral panel

An original plastic equivalent model was proposed to solve the problem of excessive FEM simulation time when designing the press bend forming path and optimizing the process parameters of press bend forming of the integrally stiffened aircraft panels. Based on the in-depth analysis of the mechanics of the bending and springback of the detailed model and the equivalent model of the integral panels,the plastic equivalent model of the virtual material with special initial yield stress and hardening coefficients was constructed. FEM results indicate that the objective of getting the similar contour with the same press bend forming path is achieved with the error less than 6%,and the efficiency of FEM simulation is improved by more than 80%. The plastic equivalent model is valuable and essential for the further research on the press bend forming process of large scale complicated integral panels.

Dynamic modeling of spacecraft solar panels deployment with Lie group variational integrator

The spacecraft with multistage solar panels have nonlinear coupling between attitudes of central body and solar panels, especially the rotation of central body is considered in space. The dynamics model is based for dynamics analysis and control, and the multistage solar panels means the dynamics modeling will be very complex. In this research, the Lie group variational integrator method is introduced, and the dynamics model of spacecraft with solar panels that connects together by flexible joints is built. The most obvious character of this method is that the attitudes of central body and solar panels are all described by three-dimensional attitude matrix. The dynamics models of spacecraft with one and three solar panels are established and simulated. The study shows Lie group variational integrator method avoids parameters coupling and effectively reduces difficulty of modeling. The obtained continuous dynamics model based on Lie group is a set of ordinary differential equations and equivalent with traditional dynamics model that offers a basis for the geometry control.

中国文化和旅游融合发展效率时空动态演化及其驱动机制

提高文旅融合发展效率是关乎效率变革和质量变革背景下文化和旅游深度融合及高质量发展的重要科学问题,有效把握其动态演化特征及驱动机制对推动区域文化产业与旅游产业转型升级和提质增效及其深度融合高质量发展具有重要的理论价值和现实意义。文章构建文化和旅游融合发展效率分析框架,运用耦合协调模型、基于松弛变量的超效率测度模型、空间马尔科夫链和面板空间杜宾模型等方法,剖析中国2011—2019年文化和旅游融合发展效率的时空动态特征及其驱动机制。研究发现:1)中国文化和旅游融合发展效率在9年间仅提升3.4%,距离最佳生产前沿面还存在至少17.3%的潜力空间,4大区域呈东部>中部>西部>东北格局,并且仅天津、上海、广东与云南4个省份常年达到最佳生产前沿面,其他省份还存在至少6.7%~33.9%的潜力空间;2)中国文化和旅游融合发展效率大致呈现“东南沿海高值集聚,西北内陆低值集聚”空间格局,存在显著的路径依赖与马太效应现象,短期内难以实现跨越式增长,但当与高效率的省份为邻时,本地省份文化和旅游融合发展效率向上转移概率有所提升;3)产业结构与交通水平是提高本地省份文化和旅游融合发展效率的主要因素,但对邻近省份产生了负向溢出效应,科技创新、消费需求和政府调控促进了邻近省份文化与旅游融合发展效率,但对本地省份的推动作用尚不显著,服务队伍抑制了本地省份文化与旅游融合发展效率,但对邻近省份的溢出效应并不显著。

产业链创新链融合对低碳转型的影响效应研究

加快实施创新驱动发展战略,促进产业链与创新链融合是实现低碳转型的重要举措。在梳理产业链创新链助推低碳转型相关文献的基础上,利用中国省级面板数据系统考察了产业链创新链融合对低碳转型的复杂影响效应。研究结果表明:(1)产业链创新链融合显著促进了低碳转型发展,这一结论在经过多重稳健性检验后依然成立,并且产业链创新链融合对低碳转型的影响在双重目标约束下存在一定的异质性。(2)机制分析表明产业链创新链融合可以通过产业结构升级、绿色技术进步和能源效率提升等路径推动低碳转型发展。(3)进一步分析发现在实现低碳转型的过程中,产业链创新链融合效果呈现出“先降后增”的“U”型阶段性特征。

结构-功能一体化异种复合材料壁板优化与验证

基于航空壁板结构承载-电气功能的一体化需求,对适用于智能蒙皮的异种复合材料壁板开展了优化设计与试验验证。通过在高模量碳纤维蒙皮的外侧增加玻璃纤维层,进行了以碳纤维-玻璃纤维-金属结构单元阵列-玻璃纤维复合顺序的壁板承载-电气功能一体化设计。针对异种复合材料结构的铺层优化需要考虑共胶接的分区域及铺层连续性的工艺要求,发展了基于丢层序列的优化方法,并对于加筋壁板的几何外形、筋条数量、筋条几何参数以及筋条与蒙皮的铺层角度进行了优化设计。通过压缩稳定性试验验证了该结构在承载能力和稳定性方面的收益,明晰了其压缩载荷下的屈曲模态及后屈曲失效机理。

冷弯薄壁型钢-结构防火一体板自攻螺钉连接性能试验研究

开展冷弯薄壁型钢-结构防火一体板自攻螺钉连接抗剪性能试验研究,完成35个典型试件单调拉伸及低周往复加载试验,分析结构防火一体板厚度、螺钉直径、螺钉端距及加载角度等因素对其抗剪性能的影响。结果表明:不同加载角度及螺钉端距的试件呈现不同的破坏模式,主要包括板材端部撕裂破坏、板材孔壁承压破坏、板材被拉断破坏等,且破坏时试件的自攻螺钉存在不同程度的倾斜。对于试验端分别采用直径为4.8、5.5 mm螺钉的试件,试件的峰值荷载及延性系数与螺钉直径无明显相关性,弹性刚度随着螺钉直径增大而显著提升;随着螺钉端距由15 mm增大至25 mm,试件的弹性刚度无明显变化,而峰值荷载和延性系数提高了约35%;随着板厚由12 mm增大到20 mm,试件的峰值荷载提高了约40%,弹性刚度提高了约90%,延性系数降低了约30%;与加载角度为0°的试件的特征参数相比,加载角度为45°时,试件弹性刚度提高了约100%,峰值荷载及延性系数无明显差别;加载角度为90°时,试件弹性刚度及峰值荷载无明显差别,延性系数降低了约40%。

一种新型结构与保温一体化复合墙板节点试验

为解决复合墙板节点常见的保温板易燃、易脱落等棘手问题,并使其抗震性能良好。给出了一种新型的结构与保温一体化陶粒混凝土T型复合墙板节点。该复合墙板节点具有夹芯独特构造优势,主要表现在绿色节能,轻质高强,力学性能好,保温系统连接可靠,还能杜绝火灾的发生。通过对T型复合墙板节点进行抗震试验,分别研究了其滞回性能、破坏机理、承载及变形能力、延性、耗能、损伤等。结果表明:一体化复合墙板节点的破坏顺序为腹板-翼缘-节点核心区;薄弱位置主要发生在腹板脚部,混凝土被拉裂或压碎,钢筋被拉长或压弯等;节点核心区受力相对良好,安全储备充足;符合“强节点,弱构件”设计要求和墙板革新发展政策。延性系数大于3,墙板节点安全性能良好。通过损伤指标评估分析,了解了试件各阶段工作状态。

数字经济对湖北省城乡融合发展及其空间溢出效应研究

以2015—2022年湖北省面板数据为基础,运用空间面板模型,选择最优的杜宾模型,从技术创新、产业升级、资源配置3个方面分析数字经济对城乡融合发展及其邻近地区城乡融合发展的影响效果和空间溢出效应。结果表明,湖北省数字经济对本地区城乡融合发展有显著的促进作用,并且对邻近地区的城乡融合发展也有正向的影响。数字经济各方面的发展都能够提升城乡发展水平,并产生空间溢出效应。该效应反映了数字经济向中小城市扩散的趋势,以及数字经济在城乡融合发展过程中对资源配置和流通效率的中介作用。建议积极推进数字经济发展,优化资源配置,提高流通效率,促进城乡一体化发展。

新型轻质结构一体化复合墙板抗弯试验研究

以有无边框龙骨、面板厚度、加载方向、横龙骨数量、有无洞口、跨度和宽度为基本参数,对7组共11个复合墙板足尺试件进行抗弯试验研究并给出了优化建议,得到了各试件的破坏模式及其荷载-位移曲线、变形分布曲线和钢龙骨荷载-应变曲线。结果表明:有无边框龙骨、面板厚度、横龙骨数量、跨度和宽度对试件的极限抗弯承载力影响显著;加载方向不同,试件破坏模式区别较大;试件开洞对其极限承载力有一定影响但仍能满足使用要求;在正常使用极限荷载作用下,试件承载力及变形均可满足使用要求且有较大安全余量。

粮食平房仓“结构-隔热”一体化墙板热工性能研究

为了提高散装粮食平房仓墙体保温隔热性能,提出了一种新型“结构-隔热”一体化墙板(SIW墙板)。通过试验和数值模拟,分析了保温板厚度、连接件等对SIW墙板热工性能的影响,揭示了内、外叶墙板温度、热流密度随时间的变化规律,得到了SIW墙板的传热系数,基于传热系数指标开展了SIW墙板在不同储粮生态区的适用性评价。结果表明:相较于传统平房仓砖砌墙体,保温板厚度为50 mm和80 mm的SIW墙板传热系数分别降低了45.81%和56.13%;GFRP连接件在SIW墙板中的热桥效应不显著,对墙板温度场的影响较小;相较于保温板厚度为50 mm的SIW墙板,80 mm厚的SIW墙板能满足3个储粮生态区对粮食平房仓墙体传热性能的要求。

一体化双总线电源屏辅助电源板电路改造方案

一体化双总线电源屏采用配电、储能、变电、供电集成一体化设计,是信号专业设备供电的重要发展方向,而电源屏稳定的供电输出则是影响信号系统功能的关键因素。针对复杂故障条件下一体化双总线电源屏无法实现冗余供电的缺陷开展研究,分析具体故障原因,提出相应电路改造方案,并在实际运用中验证并推广了改造,完善了一体化电源屏的供电冗余功能,提升了电源屏供电稳定性。

面向板式家具数字化制造的拆单软件现状与发展分析

设计制造一体化是家具企业向数字化制造方向转型升级过程中的一个重要环节,通过将设计和制造过程紧密结合,能够实现更高效、更精确的产品设计和生产制造。板式家具企业在转型升级的过程中,存在设计端和制造端两端融合不畅的问题。拆单软件是板式家具企业实现设计制造一体化的有效工具,拆单技术能够促进设计与制造的有效融合。因此,首先对拆单的内涵及意义进行了分析,其次对拆单软件应具备的4层9种关键技术体系展开具体的研究后,分别对imos、造易、DSC 3款常见的拆单软件的拆单原理、拆单方法及应用现状进行了分析,最终从智能拆单、智能检验、数据驱动的智能化管理以及与其他工业软件的衔接或集成方面对拆单软件的技术发展趋势进行了探讨,以期拆单技术能够在数字化制造的推动下实现进一步的创新与突破,从而为我国家具行业带来更加快速、高效和可持续的发展。

农村三产融合促进农民增收的理论逻辑与实证分析

从收入结构的角度分析农村三产融合促进农民增收的机理,基于2010—2019年30个省份的面板数据,检验农村三产融合促进农民收入增长的效应,以城乡融合为门槛变量,考察农村三产融合对农民收入支持的门槛效应。结果显示:(1)农村三产融合能够拉动农民可支配收入、经营性收入和转移性收入增长,但对农民工资性收入和财产性收入增长的带动作用仍需加强。(2)城乡融合发展水平较高时,农村三产融合促进农民增收的效应更强,反之,该效应将被抑制,且城乡融合是农村三产融合的单向格兰杰原因。对此,应完善农村三产融合发展体系、助力农民各收入协调增长,助推城乡融合发展、发挥城乡融合与产业融合的联动作用,培养引进新型治理人才、提升农村信息化发展水平。

RFI整体成型复合材料帽型加筋壁板工艺设计及验证

复合材料树脂膜熔渗(Resinfilm infusion,RFI)工艺是复合材料成型工艺中广泛使用的一种整体制造技术,非常适合制造大型、带加强筋且具有复杂型面的航空结构件。本文选取了一种典型的复合材料帽型加筋壁板,完成工装结构及工艺流程等整体成型工艺设计,同时对不同树脂膜位置和固化压力下树脂渗透过程进行模拟仿真,并根据模拟结果选择合理的树脂膜位置和固化压力,最终根据所选方案完成工艺试验验证,典型件表观质量和无损检测均合格,验证了帽型加筋壁板RFI整体成型工艺设计及模拟分析的有效性。

大型整体壁板加工变形控制技术研究

针对典型大型整体壁板数控加工后变形量高达40mm且无法喷丸校形的问题,采用有限元仿真研究毛坯初始残余应力与零件变形量的相关性,通过改变加工顺序,优化加工过程材料去除策略,有效控制整体壁板的加工变形。结合实际工艺方案,通过合理选择切削参数,即采用小直径刀具径向逐层走刀,切削轨迹由沿宽度方向调整为沿长度方向,减少零件加工变形量。通过实例加工验证了该方法能有效解决大型整体壁板加工变形的问题。

数字普惠金融对乡村振兴的影响:机制与路径

本文从理论上分析了数字普惠金融的发展对乡村振兴的影响机制与传导路径,并提出了研究假设;通过构建乡村振兴指标体系,在测度各省(区、市)乡村振兴水平的基础上,通过构建面板数据模型对这些假设进行了实证检验。研究发现,数字普惠金融显著促进了乡村振兴,这一结论在经过一系列稳健性检验后依然成立。但是,数字普惠金融对于乡村振兴的影响具有异质性,在农村信息化水平和传统金融发展水平较高的省(区、市)数字普惠金融对乡村振兴的促进作用更明显。进一步的机制检验表明,数字普惠金融通过推动农村产业融合、提升农村人力资本水平来助力乡村振兴。鉴于此,本文从加强农村地区的数字基础设施建设、办好乡村教育、提升农村居民的金融素养、做好农村产业发展规划等几方面给出了相应的政策建议。