科创中国

Three dimensional(3D)displacements,which can be translated further into 3D strain,are key parameters for design,manufacturing and quality control.Using different optical setups,phase-shift methods,and algorithms,several different 3D electronic speckle pattern interferometry(ESPI)systems for displacement and strain measurements have been achieved and commercialized.This paper provides a review of the recent developments in ESPI systems for 3D displacement and strain measurement.After an overview of the fundamentals of ESPI theory,temporal phase-shift,and spatial phase-shift techniques,3D deformation measurements by the temporal phase-shift ESPI system,which is suited well for static measurement,and by the spatial phase-shift ESPI system,which is particularly useful for dynamic measurement,are discussed.For each method,the basic theory,a brief derivation and different optical layouts are presented.The state of art application,potential and limitation of the ESPI systems are shown and demonstrated.

Lightweight design requires an accurate life prediction for structures and components under service loading histories. However, predicted life with the existing methods seems too conservative in some cases, leading to a heavy structure. Because these methods are established on the basis that load cycles would only cause fatigue damage, ignore the strengthening effect of loads. Based on Palmgren-Miner Rule(PMR), this paper introduces a new method for fatigue life prediction under service loadings by taking into account the strengthening effect of loads below the fatigue limit. In this method, the service loadings are classified into three categories: damaging load, strengthening load and none-effect load, and the process for fatigue life prediction is divided into two stages: stage I and stage II, according to the best strengthening number of cycles. During stage I, fatigue damage is calculated considering both the strengthening and damaging effect of load cycles. While during stage II, only the damaging effect is considered. To validate this method, fatigue lives of automobile half shaft and torsion beam rear axle are calculated based on the new method and traditional methods, such as PMR and Modified Miner Rule(MMR), and fatigue tests of the two components are conducted under service loading histories. The tests results show that the percentage errors of the predicted life with the new method to mean life of tests for the two components are –3.78% and –1.76% separately, much lesser than that with PMR and MMR. By considering the strengthening effect of loads below the fatigue limit, the new method can significantly improve the accuracy for fatigue life prediction. Thus lightweight design can be fully realized in the design stage.

The 3D inverse design method,which methodology is far superior to the conventional design method that based on geometrical description,is gradually applied in pump blade design.However,no complete description about the method is outlined.Also,there are no general rules available to set the two important input parameters,blade loading distribution and stacking condition.In this sense,the basic theory and the mechanism why the design method can suppress the formation of secondary flow are summarized.And also,several typical pump design cases with different specific speeds ranging from centrifugal pump to axial pump are surveyed.The results indicates that,for centrifugal pump and mixed pump or turbine,the ratio of blade loading on the hub to that on the shroud is more than unit in the fore part of the blade,whereas in the aft part,the ratio is decreased to satisfy the same wrap angle for hub and shroud.And the choice of blade loading type depends on the balancing of efficiency and cavitation.If the cavitation is more weighted,the better choice is aft-loaded,otherwise,the fore-loaded or mid-loaded is preferable to improve the efficiency.The stacking condition,which is an auxiliary to suppress the secondary flow,can have great effect on the jet-wake outflow and the operation range for pump.Ultimately,how to link the design method to modern optimization techniques is illustrated.With the know-how design methodology and the know-how systematic optimization approach,the application of optimization design is promising for engineering.This paper summarizes the 3D inverse design method systematically.

车辆行驶引起的桥梁振动的动力响应数据是车桥耦合振动分析中重要参数.采用超声波测速仪、录像机及桥梁动态测试仪同人工记录相结合的方法,对高速公路交通荷载各要素进行24 h连续、全面调查,记录的数据包括车型、车速、行驶车道、车辆到达时间以及每辆过桥车辆引起的桥梁动力响应数据.本调查采集了8片梁的5 650单车过桥的动响应数据,研究了交通荷载调查样本中不同梁体的动力响应数据的统计规律,全面分析了高速公路交通荷载车辆过桥引起的桥梁动力响应的时空分布规律.研究结论能够给车桥耦合振动研究及相关研究提供有益的理论指导和数据支持.

The thin-walled tube flexure(TWTF) hinges have important potential application value in the deployment mechanisms of satellite and solar array, but the optimal design of the TWTF hinges haven't been completely solved, which restricts their applications. An optimal design method for the qusai-static folding and deploying of TWTF hinges with double slots is presented based on the response surface theory. Firstly, the full factorial method is employed to design of the experiments. Then, the finite element models of the TWTF hinges with double slots are constructed to simulate the qusai-static folding and deploying non-linear analysis. What's more, the mathematical model of the TWTF flexure hinge quasi-static folding and deploying properties are derived by the response surface method. Considering of small mass and high stability, the peak moment of quasi-static folding and deploying as well as the lightless are set as the objectives to get the optimal performances. The relative errors of the objectives between the optimal design results and the FE analysis results are less than 7%, which demonstrates the precision of the surrogate models. Lastly, the parameter study shows that both the slots length and the slots width both have significant effects to the peak moment of quasi-static folding and deploying of TWTF hinges with double slots. However, the maximum Mises stress of quasi-static folding is more sensitive to the slots length than the slots width. The proposed research can be applied to optimize other thin-walled flexure hinges under quasi-static folding and deploying, which is of great importance to design of flexure hinges with high stability and low stress.