基于UG_PDW的弯曲片级进模具设计

以一弯曲片零件为例,阐述了采用UG_PDW进行级进模具设计的过程。主要介绍了零件的成形工艺安排,对弯曲片的展开、坯料的排样、废料的分割、条料的排样做了较详细的分析和示例,表明了模具CAD技术在较复杂的级进模具设计中的重要作用。

双迭片弯曲压电陶瓷换能器及振动模态分析测量

介绍了双迭片弯曲压电陶瓷换能器的制作及边缘固定金属压电陶瓷双迭片弯曲振动 ,并利用有限元分析了换能器的谐振模式 ,采用激光多普勒干涉仪对换能器的谐振特性以及振动速度和位移分布进行了测量和分析。结果表明 :换能器空载性能良好 ;通过有限元分析与先进测量手段的结合 ,能够对换能器器件的制作与分析进行指导。

带有双弯曲肋片的细通道流动与传热的数值模拟

为了强化细通道的传热性能,设计了一种带有双弯曲肋片的细通道。采用数值模拟的方法研究双弯曲肋片对于细通道中流体的流动特性、传热特性以及综合特性的影响。分析了进口雷诺数、肋片的半径大小对于细通道热沉中的摩阻系数、努塞尔数以及综合传热因子的影响。结果表明:细通道的摩阻系数与努塞尔数随着肋片半径的增大而增大,热阻随其增大而减小;在设置的雷诺数范围内,综合性能最好的为MCDR-0.4。证明双弯曲肋片的添加可以有效地提升细通道的综合性能。

木板片弯曲结构与机械臂缝纫

随着数字技术的发展,数字计算与模拟技术被逐渐引入到设计之中,设计由形式驱动演变为性能驱动,性能成为设计过程中需要着重考虑的因素,无论是环境性能、材料性能还是行为性能,都成为了左右设计形式的要素。薄板片弯曲结构作为当今建构研究中的全新课题,具有较大的研究价值。文章通过对相关案例的研究,阐述了在机械臂技术的协助下,板片弯曲结构这种全新设计方法是如何实现的。

木质百叶窗木片弯曲分析

简要介绍了木质百叶窗加工工艺和生产过程,描述了木质百叶窗木片弯曲现象,分析了木质百叶窗木片产生弯曲变形的主要原因,提出了在生产过程中如何避免木片弯曲的建议以及消除木片弯曲的措施。

弯曲摆动无阀式压电泵理论分析与模拟

设计一种新型弯曲摆动无阀式压电泵,并对其进行理论分析,根据压电泵的尺寸、结构和动力学模型,对压电振子的位移响应进行分析;采用有限元分析的方法利用该公式函数对弯曲摆动式无阀压电泵进行仿真分析,得到该压电泵的内部流场特性,得到该压电泵出入口流速和内部压强的变化情况。对本文压电泵输出流量与频率的关系进行分析,结果表明:压电泵在工作频率在左右达到最大输出流量,具有较好的输出流量特性。

压电陶瓷驱动高频喷射阀的结构设计

为了提高喷气织机的引纬性能,降低能耗,课题组设计了一种基于压电陶瓷驱动的高频喷射阀。首先对喷射阀的核心部件压电弯曲片的刚度性能做了仿真分析和理论验证;然后对压电陶瓷驱动型高频喷射阀进行FLUENT模拟仿真;最后利用MATLAB软件对压电驱动系统进行动态仿真,确认了合理的工作间隙,进而对喷射阀的结构进行了优化。模拟得到最佳工作参数:喷射阀进气口直径为4 mm,压电喷射阀的工作间隙为1.5 mm。设计的这种喷射阀响应时间相比传统电磁式喷射阀缩短了60%,大大降低了气能损耗。

用激光干涉法分析薄膜应力

本文叙述了激光干涉弯曲晶片薄膜应力测定法的原理。依据这一原理建立了薄膜应力分析系统,并实际分析了作为X射线掩模基膜的Si_3N_4膜中的应力。用Stoney公式计算出Si_3N_4膜的内应力为6.4×10~8dyn/cm^2。

压电式摆动圆柱形偶极发射换能器优化研究

为了实现偶极信号有效辐射,获得足够高的信噪比,全面分析弯曲波频散,本文提出了一种新型的频带范围为0.5–5 k Hz的压电式摆动圆柱形偶极声波测井换能器,并采用有限元方法对其进行了模拟和优化设计。此外,论文还对换能器进行了实验样机制作和实验测量,将实验测量与数值模拟结果进行了对比。研究表明,提出的新型偶极声波换能器比传统换能器具有更高的发射灵敏度,尤其是在低频响应范围。本文为新型偶极声波测井换能器的研发工作奠定了基础。

多级环境风扇静叶优化

对某三级风扇静叶在全三级环境中进行了数值优化。原叶型的流场计算结果显示,第二级静叶根部通道涡的存在及其诱发的第三级静叶根部分离,制约了三级风扇性能的提高。运用弯叶片技术对第二级静叶进行优化,并借助NUMECA软件的Design3D软件包参数寻优。优化后所获得的根部正弯、顶部反弯叶型有效地抑制了第二级静叶根部通道涡的形成,消除了第三级静叶根部的分离区。优化后风扇的效率和稳定裕度有了大幅提高,而压比基本不变,优化前稳定边界线上的一个明显下陷点被抹平。

3D hydrodynamics involving multiple eccentric impellers in unbaffled cylindrical tank

In this paper, the numerical predictions of 3D hydrodynamics and power consumption in a vessel stirred by mul- tiple eccentrically located impellers are presented. The vessel is a fiat-bottomed cylindrical one equipped with six-curved bladed impellers. Aqueous solutions of xanthan gum are used, which have a shear thinning behavior with yield stress. The influence of several parameters on the mixing efficiency has been investigated, namely： the stirring rate, fluid theology, impeller number and impeller clearance from the tank bottom. Our predicted results are compared with other experimental data and a satisfactory agreement is found.

Flexible bending of aluminum profiles with polyurethane pad

The high flexibility of profile bending with hyperelastic pad enables it to be a promising method for small lot or single part production, especially for space frame and roof-rail parts in automotive and aerospace industries. Bending of two aluminum profiles with different sections was carried out to investigate the effect of main process parameters on the bending process. Results show that the shape of the cross-section and its relative thickness and section modulus in bending are the main factors that determine the bending properties of the profiles. Roller stroke, properties of polyurethane pad and constraints on profiles are key factors that determine the bending radius and section deformation of bent profiles. Failures and quality problems met in experiments were also analyzed.

Simulation and prediction in laser bending of silicon sheet

The laser bending of single-crystal silicon sheet （0.2 mm in thickness） was investigated with JK701 Nd：YAG laser. The models were developed to describe the beam characteristics of pulsed laser. In order to simulate the process of laser bending, the FEM software ANSYS was used to predict the heat temperature and stress-strain fields. The periodic transformation of temperature field and stress-strain distribution was analyzed during pulsed laser scanning silicon sheet. The results indicate that the mechanism of pulsed laser bending silicon is a hybrid mechanism in silicon bending, rather than a simple mechanism of TGM or BM. This work also gets silicon sheet bent after scanning 6 times with pulsed laser, and its bending angle is up to 6.5°. The simulation and prediction results reach well agreement with the verifying experiments.

Mechanism of improving ductility of high strength concrete T-section beam confined by CFRP sheet subjected to flexural loading

For the purpose of inventing a new seismic retrofitting method for the reinforced high strength concrete （HSC） T-section beam using carbon fiber reinforced polymer （CFRP） sheet, three series, a total of twelve T-section beams with nine specimens confined by CFRP sheet in the plastic zone and three control beams were conducted up to failure under four-point bending test. The effectiveness of confining CFRP sheet on improving the flexural ductility of tmstrengthened T-section beams was studied. The parameters such as the width and the thickness of CFRP sheet and the type of T-section were analyzed. The experimental results show that ductility and rotation capacity of plastic hinge can be improved by the confinement of CFRP sheet, and the ductility indices increase with the increment of width and thickness of CFRP sheet. A plastic rotation model considering the width of CFRP sheet and the effect of flange of T-section beam is proposed on the basis of the model of BAKER, and the test results show a good agreement with the perdicted results. The relevant construction suggestions for seismic retrofitting design of beam-slabs system in cast-in-place framework structure are presented.

试样直径对Ni-Ni_3Si定向凝固共晶组织失稳的影响

采用Φ4 mm、Φ7 mm两种Ni-Ni_3Si共晶合金试样,研究试样直径对定向凝固共晶组织失稳的影响。实验结果表明:Ni-Ni_3Si共晶耦合生长的初生相为Ni_3Si相,定向生长的小直径试样更易发生zigzag失稳,形成弯曲的层片组织。分析认为小直径试样的液相温度梯度较大,合金凝固过程中过冷度较低,在生长速率为4μm/s时,即可发生zigzag失稳,这种失稳有利于减小共晶两相扩散生长速率的差异性,缩小两相的宽度差。此外,这种晶内失稳与晶粒的层片取向有关。

Prediction of Dynamic and Aerodynamic Characteristics of the Centrifugal Fan with Forward Curved Blades

The main aim of this paper is determine the centrifugal fan with forward curved blades aerodynamic characteristics based on numerical modeling. Three variants of geometry were investigated. The first, basic "A" variant contains 12 blades. The geometry of second "B" variant contains 12 blades and 12 semi-blades with optimal length[1]. The third, control variant "C" contains 24 blades without semi-blades. Numerical calculations were performed by CFD Ansys. Another aim of this paper is to compare results of the numerical simulation with results of approximate numerical procedure. Applied approximate numerical procedure [2] is designated to determine characteristics of the turbulent flow in the bladed space of a centrifugal-flow fan impeller. This numerical method is an extension of the hydro-dynamical cascade theory for incompressible and inviscid fluid flow. Paper also partially compares results from the numerical simulation and results from the experimental investigation. Acoustic phenomena observed during experiment, during numerical simulation manifested as deterioration of the calculation stability, residuals oscillation and thus also as a flow field oscillation. Pressure pulsations are evaluated by using frequency analysis for each variant and working condition.

Effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor with self-recirculation casing treatment

The effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor were studied by experiments and numerical simulation.The results showed that the negative bowing was capable of increasing the choke mass rate and the efficiency but decreased the surge mass flow rate,while the positive bowing had the opposite effects.When coupling with the self-recirculation casing treatment,the surge mass flow rate of the compressor with negative bowing blade was almost identical with that of the prototype,while the choke mass flow rate was still larger,and the total effect contributed to an increase of the stable flow range by 5.85%at design speed.Besides,the flow mechanism of the coupling effects of blade bowing and self-recirculation casing treatment was discussed.