弹性支承下弧齿锥齿轮齿面接触特性的理论与实验研究

航空发动机采用弹性支承后,转子弹性变形会造成主传动弧齿锥齿轮相对位置的变化,从而影响齿面接触性能。针对某型涡喷发动机转子系统,分析求解了弹性支承下齿轮安装处的变形,并将其等效地转化为齿轮副间的安装距偏差,在此基础上,完成了弧齿锥齿轮齿面接触特性分析。在转子系统模拟试验台上,对发动机主传动锥齿轮接触性能进行了实验研究。分析与实验结果同时表明支承刚度对齿面接触区和传动误差皆有很大影响。     

Ti—15—3钛合金超塑性最佳变形模式的研究

介绍了Ｔｉ－１５－３钛合金在等速和应变速率循环两种变形模式下的超塑性能,进而探讨它的最佳变形模式计算机优化的原理和实验方法。实验结果表明,未经细化处理的Ｔｉ－１５－３钛合金在应变速率循环的变形模式下具有比常规变形模式更显著的超塑性,而通过计算机优化可以进一步挖掘材料的潜力,获得更为优良的超塑性。     

磨削丝锥尾方专用机床头架结构原理设计

对于丝锥尾方的加工可以采用磨削的方法，欲实现尾方加工过程的自动化，则磨削尾方专用机床的头架，因其动能是夹持工件，所以在加工过程中必须能自动分度。俗实现此目的，其头架结构可以采用差动轮系。行星轮上装有弹簧夹头以夹持工作，系杆H与行星轮C之间的传动比iCH=nc/nH=1／4，便可实现自动分度。     

关于应变率敏感系数的定义

应变率敏感系数是宏观塑性动力学和位错动力学的一个基本概念,本文试图对其进行了重新解释。由于强动载荷作用下一般固体要发生有限变形的动力响应,还将应变率敏感系数推广到塑性动力大变形情形。本文也指出了由于应变率敏感性所引起的内耗增量和过应力的类比性。     

民用飞机LRU划分的双步迭代层次分析法

合理的航线可更换单元(LRU)划分可以有效提高民用飞机维修效率,避免飞机停场现象,保障民用飞 机安全可靠运行。在综合考虑民用飞机设计阶段及运营过程中多种因素影响的前提下,提出一种 LRU 划分方 法———双步迭代层次分析法(TSI-AHP)。梳理民用飞机设计阶段及运营阶段相关因素对 LRU 划分的影响; 将产品按照功能分解至最底层结构,将其作为研究对象,运用 TSI-AHP 确定民用飞机 LRU 划分方案;并以 ARJ21-700飞机起落架系统为例,运 用 所 提 方 法 实 现 其 LRU 划 分。结 果 表 明:基 于 TSI-AHP 的 民 用 飞 机 LRU 划分方法可有效实现 ARJ21-700飞机起落架系统的 LRU 划分;本文 LRU 划分项目与实际 LRU 项目基 本一致,验证了该方法的可行性和有效性,可为国产民用飞机 LRU 划分工作提供一种新思路。     

Geometrically exact nonlinear analysis of pre-twisted composite rotor blades

Modeling of pre-twisted composite rotor blades is very complicated not only because of the geometric non-linearity, but also because of the cross-sectional warping and the transverse shear deformation caused by the anisotropic material properties. In this paper, the geometrically exact nonlinear modeling of a generalized Timoshenko beam with arbitrary cross-sectional shape, generally anisotropic material behavior and large deflections has been presented based on Hodges’ method. The concept of decomposition of rotation tensor was used to express the strain in the beam. The variational asymptotic method was used to determine the arbitrary warping of the beam cross section. The generalized Timoshenko strain energy was derived from the equilibrium equations and the second-order asymptotically correct strain energy. The geometrically exact nonlinear equations of motion were established by Hamilton’s principle. The established modeling was used for the static and dynamic analysis of pre-twisted composite rotor blades, and the analytical results were validated based on experimental data. The influences of the transverse shear deformation on the pre-twisted composite rotor blade were investigated. The results indicate that the influences of the transverse shear deformation on the static deformation and the natural frequencies of the pre-twisted composite rotor blade are related to the length to chord ratio of the blade.     

Research on Maintainability Evaluation Model Based on Fuzzy Theory

分析了产品维修性影响属性,给出了维修性属性值与权重的确定方法;提出了基于相对接近度的维修性模糊评价方法。以虚拟环境下产品维修过程为研究对象,在分析产品各可更换单元的维修作业的基础上,建立了产品维修性评价模型。最后结合民机主起落架系统给出了应用实例,结果表明该模型适用于产品维修性的定性评价并且能够支持维修性并行设计。     

Dynamic Response Analysis of Bird Strike on Aircraft Windshield Based on Damage-modified Nonlinear Viscoelastic Constitutive Relation

Damage-modified nonlinear viscoelastic constitutive equation and failure criterion are introduced and the three-dimensional incremental forms are deduced based on the updated Lagrangian approach. A simple tensile test model and a split Hopkinson pressure bar model are built to verify the accuracy of the subroutine implemented within the non-linear finite element program LS-DYNA. A numerical model of bird strike on windshield is established to study the responses of windshield under three different bird velocities at three sites. The bird is represented by a cylinder with a hemisphere at each end and the contact-impact coupling algorithm is used in this study. It is found that the implemented subroutine can properly describe the mechanical behavior of polymethyl methacrylate under low and high strain rates and large deformation, and can be used validly.     

棘轮和蠕变条件下材料的附加塑性变形行为研究

针对316L不锈钢进行大量单轴棘轮和蠕变试验研究,对材料在棘轮和蠕变作用下的塑性变形行为以及变形量进行比较和分析.分析发现,材料棘轮和蠕变变形行为之间存在一些相似规律,而且相同试验时间下蠕变变形高于棘轮变形.在持续应力作用下,材料的附加塑性变形与作用应力间体现出上凸的抛物线规律,附加塑性变形先随应力的增长而升高,达到峰值后又逐渐减小.最后,根据这种上凸的抛物线规律提出相应的本构描述方程.     

A critical evaluation of two Reissner–Mindlin type models for composite laminated plates

The purpose of this paper is to critically evaluate two Reissner–Mindlin type theories developed recently for composite laminated plates, namely, VAPAS (Variational Asymptotic Plate And Shell analysis) and EFSDT (Enhanced First-Order Shear-Deformation Theory). The fundamentals of both models are briefly summarized along with their unique features in comparison to most other existing models. The similarities and differences between VAPAS and EFSDT are also examined. Exact solutions of three-dimensional elasticity theory for the cylindrical bending problems are used as the arbiter to assess the accuracy of both models. Such a systematic assessment demonstrates that both models have achieved an excellent compromise between the layer-wise theories, which are accurate but computationally demanding, and the first-order shear deformation theories, which are computationally cheap but not accurate.