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对层状复合材料矩形截面圆柱螺旋弹簧的自由振动特性进行了研究,方程中首次考虑了簧丝截面的翘曲变形对固有频率和振动模态的影响。在各向异性自然弯扭梁理论的基础上,导出了该弹簧在考虑翘曲效应时的运动微分方程,它们由14个一阶偏微分方程组成。弹簧的固有频率可以使用改进的Riccati传递矩阵法确定,单元传递矩阵则采用Scaling- Squaring方法以及Pad´e逼近表达式进行计算。计算结果表明:对于对称层压复合材料矩形截面的圆柱螺旋弹簧,翘曲变形对其固有频率有一定的影响,在自由振动分析中应该加以考虑。最后研究了各种设计参数对该弹簧固有频率的影响,并发现了一些与各向同性材料矩形截面圆柱螺旋弹簧不同的性质。 相似文献
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GH2871合金的研制及其组织与性能 总被引:4,自引:2,他引:2
介绍了一种含0.5%左右Nb和1%左右W的15Cr-25Ni-2Ti-1.5Mo铁基高温合金(GH2871合金)的研制及其组织与性能。结果表明:由于Nb、W、Mo等高熔点低自扩散系数的组分进入了该合金MC、γ′相,改善了组织、增加了γ′相的数量和提高其稳定性,起到了良好的强韧化作用,从而大幅度提高了持久寿命和疲劳强度。与国内外同类合金相比,该合金具有更好的综合性能。 相似文献
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目的 研究不同成分GH6159合金冷拉态和热处理态显微组织的变化情况,分析不同成分对合金室温和高温拉伸性能的影响规律,为GH6159合金成分优化与性能提升提供理论指导。方法 基于MP159合金成分,设计熔炼了4种不同成分的GH6159合金,经锻造开坯和热轧,进行了拉伸率为48%的冷拉变形和663 ℃/4 h的时效热处理,分别制成冷拉态和热处理态GH6159棒材,采用MTS 8810拉伸实验机进行室温和595 ℃的高温拉伸测试,获得了不同成分合金冷拉态和热处理态的室温和595 ℃高温拉伸性能,结合OLYMPUS−PM3光学显微镜和Tescan Mira 3 XMU扫描电子显微镜观察了显微组织的变化情况。结果 GH6159冷拉态棒材内存在大量的变形孪晶,热处理态组织内析出了弥散分布的强化相,合金拉伸性能主要受到基体元素和强化相元素的影响。结论 较高含量的Co、Cr、Ni基体元素有利于提高冷拉态GH6159合金的室温和高温拉伸强度,而Al、Ti、Nb强化相元素会提高热处理态GH6159合金的室温拉伸强度,但过高的Ti元素会降低合金强度,一定含量的Al、Ti、Nb元素有利于提高冷拉态和热处理态合金的高温塑性。 相似文献
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对国内生产的低磷GH169[s(P)<0.001%]及常规GH169[w(P)0.008%~0.013%]变形合金锻件的力学性能进行了对比研究。结果表明,室温拉伸和高温拉伸强度未显现很大差异,然而低磷GH169合金反而显示出高温塑性特别是650℃/686MPa持久塑性的明显降低,且低磷合金在蠕变和疲劳/蠕变交互作用下的裂纹扩展速率皆高于常规合金,低磷合金的595℃/895MPa缺口周期持久寿命亦有降低的趋势。俄歇能谱分析表明,磷在晶界发生偏聚,透射电镜观察,发现低磷合金中的σ相的片状形式沿晶界析出,而磷含量提高使σ相的胞状形式沿晶界析出。 相似文献
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采用悬臂梁弯曲应力松弛测试方法对CuNiSiCo合金的应力松弛性能进行了测试,利用TEM探究Co对CuNiSi合金应力松弛组织的影响,并建立了应力松弛模型。结果表明,应力松弛过程可动位错密度是降低的经验公式σ*=[K′ln(t+a0)+C]-n的模拟结果,与实验结果基本相符;合金松弛分为2个阶段,第一阶段应力松弛速率较大,由于在应力松弛的初期阶段,可动位错数量很多,位错移动的阻力比较小,位错移动的驱动力比较大;第二阶段,应力松弛速率较小,处于缓慢松弛阶段,这一阶段位错与杂质原子以及位错与第二相粒子发生交互作用,使位错增殖;Co在Cu中的固溶度较小且易于与空位结合,从而抑制了调幅分解形成所需的空位移动,致使含Co元素的CuNi-Co-Si铜合金空位大量减少,抑制了可动位错的滑移;另一方面,促进了基体中析出相的析出,析出相弥散均匀地分布在合金基体中,在发生应力松弛过程中,移动的可动位错在遇到弥散分布的第二相之后,会被第二相所钉扎,故Co替代部分Ni形成的CuNiSiCo合金的应力松弛性能要优于CuNiSi合金。 相似文献
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研究了壁厚0.15mmGH169合金端接接头的焊接缺陷产生机理,认为焊接缺陷是焊接过程中焊缝金属被氧化造成的,由于金属被氧化导致了焊缝熔合不良。采用端接接头反面成型及加强背面保护等工艺措施可以极大地降低焊缝熔合不良的敏感性。 相似文献
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本文介绍了一种适用于沉淀强化型高温合金的特殊DA处理工艺,结果表明,这种工艺能够大幅度地提高GH33A合金的屈服强度和拉伸强度,使中等强度的GH33A合金的强度基本达到GH169合金的强度水平,由于采用预先固溶处理,可使GH33A合金在较高的锻造温度下获得满意的强化效果,从而可以克服通常的DA处理工艺由于锻造温度低带来的某些缺点。 相似文献
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《Materials Science & Technology》2013,29(11):947-954
AbstractThe thermal and thermomechanical behaviour of the relaxation of the residual stresses of a shot peened Astroloy superalloy under tensile cyclic loads has been evaluated by X-ray diffraction and investigated. The stress relaxation under purely thermal conditions (550 and 650°C) and thermomechanical conditions (pulsating tensile loading at 650°C) as afunction of the exposure time is presented. The purely thermal relaxation is interpreted by annihilation and reorganisation of the crystalline defects induced by shot peening, whereas the mechanical relaxation is linked to cyclic plasticity of materials. In consequence, the thermomechanical relaxation is essentially due to the complex mechanism of the concurrent thermal and mechanical effects. A model is used to predict the residual stresses induced by the specified shot peening conditions and their relaxation under the specified thermal/thermomechanical conditions.MST/1963 相似文献
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In the present work, the time-dependent mechanical behavior of three materials from the fluorocarbon family, including PTFE without filler, 15 vol.% regenerated graphite particles-filled PTFE, and 32 vol.% carbon and 3 vol.% graphite particles-filled PTFE, was investigated using cylindrical macroindentation. Indentation relaxation experiments with a cylindrical flat-tip indenter having a diameter of 1 mm were performed at three different strain levels. The generalized Maxwell model in terms of the Prony series and a time-dependent solution based on the power-law creep equation were used to model the viscoelastic response and to extract the time-dependent properties. The stress relaxation properties were found to improve with the addition of fillers. The unfilled PTFE exhibited the lowest stress–relaxation properties, whereas the 32 vol.% carbon and 3 vol.% graphite particles-filled PTFE composite showed the highest stress–relaxation properties. 相似文献
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弹簧组是线性压缩机的关键部件。为了优化线性压缩机的弹簧组,减小弹簧组的体积和重量,提高线性压缩机的工作效率,设计了一种易于加工的、大刚度的多线型圆柱臂盘簧。采用ANSYS有限元分析软件对圆柱臂盘簧进行刚度计算和模态分析,研究了圆柱臂盘簧中心线的基圆半径、盘簧线径、盘簧轴向高度等主要结构参数对其刚度和应力的影响。结果表明:随着基圆半径的增大,圆柱臂盘簧的轴向刚度、最大应力逐渐减小,径向刚度变化曲线近似为开口向上的二次函数曲线;随着线径的增大,圆柱臂盘簧的轴向刚度和径向刚度加速增大,最大应力基本呈线性增大。在设计圆柱臂盘簧时,将基圆半径设定在15~19 mm,有利于提高盘簧的性能;若线径为4~6 mm,应优先选择0 mm的轴向高度;若线径为6~8 mm,则优先选择10 mm的轴向高度。研究结果对提升线性压缩机的弹簧支撑技术具有重要的参考价值。 相似文献
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A finite element study of thermal relaxation of residual stress in laser shock peened IN718 superalloy 总被引:1,自引:0,他引:1
Zhong ZhouAmrinder S. Gill Dong Qian S.R. MannavaKristina Langer Youhai WenVijay K. Vasudevan 《International Journal of Impact Engineering》2011,38(7):590-596
The residual stresses in laser shock peened (LSP) Inconel 718 Ni-base superalloy and their thermal relaxation behavior were investigated based on three-dimensional nonlinear finite element analysis. To account for the nonlinear constitutive behavior, the Johnson-Cook model has been employed and the model parameters for high strain rate response of IN718 are calibrated by comparison with recent experimental results. Based on the LSP simulation, the thermal relaxation behavior was studied through coupled thermal-structure analysis in LS-DYNA. More specifically, the effects of test temperature, exposure time and degree of initial plastic deformation are analyzed and discussed. It is observed that stress relaxation mainly occurs during the initial period of exposure, and the relaxation amplitude increases with the increase of applied temperature and as-peened plastic deformation. Based on the simulation results, an analytical model based on Zener-Wert-Avrami function is proposed to model the thermal residual stress relaxation. 相似文献
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A method of numerical calculation for stability of imperfect cylindrical shells with spiral ribs under a nonuniform subcritical state is presented. The relative effectiveness of spiral, vis-a-vis frame, stiffening is estimated (with equal mass of ribs).Translated from Problemy Prochnosti, No. 3, pp. 110–113, March, 1990. 相似文献
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《材料与设计》2015
In the present paper, finite element method (FEM) simulation of linear friction welding (LFW) GH4169 superalloy was carried out using ABAQUS software. The friction coefficients of GH4169 superalloy under different parameters (friction load, friction velocity and specimen temperature) were obtained using the friction and wear experiments. A two-dimensional (2D) coupled thermo-mechanical model was established. Using this model, the temperature fields of GH4169 superalloy during LFW process was firstly investigated. Based on the shearing and extrusion deformations during LFW process, the mises stress and the equivalent plastic strain fields of LFW GH4169 superalloy at different welding times were studied. The actual LFW process of GH4169 superalloy was recorded using a high speed camera. The surface temperature fields of joint were experimentally observed using an infrared thermal imaging instrument. Axial shortening and macroscopic morphology of linear friction welded joint obtained from experiments validated the simulation results. Finally, by consideration of the temperature fields of the simulated welded joint, the authors experimentally investigated the microstructure of the actual welded joint. 相似文献
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Effects of thermal exposure (TE) on high cycle fatigue (HCF) behaviours in Ni-based superalloy GH4169 have been investigated in this study. GH4169 specimens were thermally exposed at 650°C for 1, 2, 7, 14 and 21 days before fatigue test. These TEs produced eruptions, bulge-like features and pits at surface due to oxidation of carbides/nitrides. Fatigue life was not reduced evidently by TE as compared to the specimens in virgin conditions, indicating the insignificant influence of TE on HCF life. Fracture morphology analysis showed fatigue crack mainly initiated from oxides, crystallographic facets and subsurface inclusions. Although long TE is not necessarily related to crack initiation from oxides, crack initiation from oxides is generally associated with a shorter fatigue life. 相似文献