航天用隧道管轴向低压压形成形精度控制研究

针对运载火箭的高密度发射需求,进一步提升贮箱用隧道管整体制造质量可靠性和生产效率。以航天用Φ340mm的5A03铝合金隧道管为研究对象,通过开展轴向低压压形成形波纹有限元仿真分析,探究不同内压和补料量等工艺参数对隧道管波纹型面精度和壁厚分布影响规律。结果表明,波纹成形内压为4MPa,补料量为16.5mm时,波形精度和波高均达到设计要求,环向和轴向的波纹壁厚分布一致性较好,最大减薄率为7.09%。

大直径铝合金波纹管复合整体制造工艺研究

为了得到具有大直径、高膨胀率、低壁厚减薄率的铝合金波纹管,提出了一种复合整体制造工艺,其核心思想是利用搅拌摩擦焊接获得大直径铝合金初始管坯,随后采用轴向压形法成形出所需的连续波形。首先开展平板焊接试验,确定搅拌摩擦焊接最佳工艺参数。通过实验与数值模拟分析结合的方式,基于ABAQUS有限元分析软件,建立了波纹管轴向压形过程的有限元模型,并基于波纹管轴向低压压形过程中的形状精度及壁厚分布情况,分析了不同成形工艺参数对波纹管成形过程的影响,获得了成形内压与轴向进给间最佳的匹配关系。最后开展静力试验考核。结果表明,采用该复合整体制造工艺可以获得满足设计要求的大直径大膨胀率铝合金波纹管,并且具有低成本、高效率优势。

大型薄壁U形波纹管轴向低压压形的形状精度

为了克服大直径U形波纹管液压成形时成形内压过高、设备吨位要求大等缺点,提出了一种轴向低压压形工艺成形该类零件。通过实验与数值模拟分析相结合的方式,分析了初始内压、最终内压和轴向进给3种工艺参数对形状精度(圆角填充、回弹)的影响。对于圆角填充,初始内压和轴向进给的增大,会导致管坯在波峰圆角区贴模更紧密,在波谷圆角区脱模程度加重,而当最终内压较小时,波峰的填充不完全。对于回弹,初始内压和轴向进给的增大以及最终内压的减小均有利于抑制回弹。最终得出了最佳工艺参数组合,即初始内压为1.2 MPa、最终内压为4.0 MPa、轴向进给为31.5 mm。同时,对波纹管的应力状态进行分析,得出了回弹产生的原因,并通过模具修正对回弹进行补偿。最终,实验成形了尺寸精度在0.5 mm以内、内径为Φ340 mm、壁厚为1.5 mm的U形波纹管,验证了工艺的可行性。

铝合金Ω形波纹管轴向低压压形工艺

为了得到具有大直径大膨胀率且壁厚减薄小的铝合金Ω形波纹管,提出了一种轴向低压压形工艺,其核心思想是通过合理匹配成形内压与轴向进给间的关系来提高波纹管的成形质量。同时,通过实验与数值模拟分析结合的方式,基于ABAQUS有限元分析软件,建立了波纹管轴向低压压形过程的有限元模型,并基于波纹管轴向低压压形过程中的等效应力及壁厚分布情况,分析了3种不同加载路径对波纹管成形过程的影响,获得了成形内压与轴向进给间最佳的匹配关系。结果表明,由加载路径3阶梯形匹配关系所得波纹管的形状精度高,最大减薄率为12.1%,验证了工艺的可行性。

Experimental investigation of friction coefficient in tube hydroforming

The friction coefficient between tube and die in guide zone of tube hydroforming was obtained. In hydroforming, the tube is expanded by an internal pressure against the tool wall. By pushing the tube through tool, a friction force at the contact surface between the tube and the tool occurs. In guiding zone, the friction coefficients between tube and die can be estimated from the measured axial feeding forces. In expansion zone, the friction coefficients between tube and die can be evaluated from the measured geometries of expanded tubes and FE analysis.

Experimental study on dimension-form effect for compressive strength of coal

The uniaxial compression tests of cylinder standard specimens and different dimension cube specimens of No.13 coal seam of Jianxin Colliery were carried out using MTS, and the basic mechanics parameters of Jianxin Colliery 13 coal were studied. The dimension-form effect of uniaxial compression strength was analyzed. The exponent formula σc=6.928＋130.269 8 exp（-0.105 95D）of dimension effect was fitted. While the side length of specimen reaches 80 mm, its unaxial strength tends to a stable value which is called to be the strength of coal mass. Studies indicates that since the cube specimen suffered more shake than the cylinder one during machining and processing and the stress is centralized at four corners of cube during compressive experiment, the coal strength of standard cylinder specimen is higher than that of cube one.

Postbuckling behavior of 3D braided rectangular plates subjected to uniaxial compression and transverse loads in thermal environments

Postbuckling behavior of the 3D braided rectangular plates subjected to uniaxial compression combined with transverse loads in thermal environments is presented.Based on a micro-macro-mechanical model,a 3D braided composite may be treated as a cell system and the geometry of each cell is deeply dependent on its position in the cross-section of the plate.The material properties of the epoxy are expressed as a linear function of temperature.Uniform,linear and nonlinear temperature distributions through the thickness are involved.The lateral pressure(three types of transverse loads,i.e.transverse uniform load;transverse patch load over a central area;and transverse sinusoidal load)is first converted into an initial deflection and the initial geometric imperfection of the plate is taken into account.The governing equations are based on Reddy’s higher-order shear deformation plate theory with a von Kármán-type of kinematic nonlinearity.Two cases of the in-plane boundary conditions are also taken into account.A perturbation technique is employed to determine buckling loads and postbuckling equilibrium paths of simply supported 3D braided rectangular plates.The results reveal that the temperature rise,geometric parameter,fiber volume fraction,braiding angle,the character of the in-plane boundary conditions and different types of initial transverse loads have a significant effect on the buckling and postbuckling behavior of the braided composite plates.

Deformation analysis of an incompressible composite cylindrical tube subjected to end axial loads and internal constraint

In this paper,the problem of axially symmetric deformation is examined for a composite cylindrical tube under equal axial loads acting on its two ends,where the tube is composed of two different incompressible neo-Hookean materials.Significantly,the implicit analytical solutions describing the deformation of the tube are proposed.Numerical simulations are given to further illustrate the qualitative properties of the solutions and some meaningful conclusions are obtained.In the tension case,with the increasing axial loads or with the decreasing ratio of shear moduli of the outer and the inner materials,it is proved that the tube will shrink more along the radial direction and will extend more along the axial direction.Under either tension or compression,the deformation along the axial direction is obvious near the two ends of the tube,while in the rest,the change is relatively small.Similarly,for a large domain of the middle part,the axial elongation is almost constant;however,the variation is very fast near the two ends.In addition,the absolute value of the axial displacement increases gradually from the central cross-section of the tube and achieves the maximum at the two endpoints.