共查询到18条相似文献,搜索用时 102 毫秒
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首先分别在595℃、610℃、670℃下进行了P92钢的单轴蠕变拉伸实验。结果表明:当实验温度高于600℃时,应力和应变在双对数坐标下呈现非线性特征,蠕变过程无法通过Norton指数模型进行描述。为了进一步解决高温下蠕变寿命的计算和预测问题,本文提出了一种改进的蠕变本构模型;并在此基础上,引入损伤变量描述第三阶段蠕变。利用新的蠕变模型对P92钢在595℃、610℃温度条件下的蠕变过程进行了模拟,结果表明模型预测的蠕变寿命和实验值误差在5%之内,符合工程评估要求。 相似文献
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SUS304材料的小冲孔蠕变试验研究 总被引:5,自引:0,他引:5
小冲孔蠕变试验技术是一种采用微小试样、近乎无损地评定材料高温力学性能的新方法,本文应用小冲孔蠕变试验技术评定SUS304材料的高温力学性能。在不同温度下,对SUS304奥氏体不锈钢进行载荷范围为443N~513N的小冲孔蠕变试验,得到材料在不同试验条件下的蠕变曲线,通过中断试样的扫描电镜观察分析了试样的变形过程,讨论了影响小冲孔蠕变试验的主要因素。试验结果表明,从小冲孔实验获得的蠕变曲线与传统单轴拉伸蠕变实验的蠕变曲线具有一致性,都具有三个明显的蠕变阶段,利用小冲孔蠕变试验技术测试材料的高温性能是可行的。试验载荷越大,试样瞬时变形挠度越大,蠕变第二阶段速率越快,断裂时间越短。载荷、温度、试样厚度、环境是小冲孔试验的主要影响因素,对试验结果影响很大。 相似文献
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基于热力学相容的本构模型并合理地定义广义时间,得到了描述蠕变、塑性及其交互作用的统一型本构方程。进而通过对在蠕变—塑性交互作用过程中材料内部子结构及其变化的分析,将材料的强化分解为对应于非弹性应变范围的强化和由蠕变变形导致的附加强化。对高温环境二维应力路径下304不锈钢的蠕变—塑性交互作用过程进行了分析,取得了与Ohashi等的实验相吻合的结果。 相似文献
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1 引言文献[2]在S S Vyalov 的研究基础上,进一步改进和完善了Vyalov 的研究假设,分别提出了在纯剪和单轴压缩条件下的岩质材料非线性蠕变模型,但是,未曾进行复杂应力状态下的非线性蠕变性态的研究.因此,本文将在此基础上,对岩质材料非线性剪切蠕变性态进行深入的研究,进一步考虑最大剪应力面上的法向应力对岩质材料非线性粘塑性剪切蠕变的影响,提出了反映法向应力影响的岩质材料非线性粘塑性剪切蠕变的力学模型和蠕变方程,并给出了在一定的法向应力和剪切应力下,岩质材料发生衰减蠕变、线性蠕变和加速蠕变变形所需满足的条件. 相似文献
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本文介绍了作者研制的圆柱壳外压蠕变屈曲实验装置,用1Cr18N_i9Ti薄壁式筒在650℃下进行了外压失稳及蠕变屈曲实验,所得结果与理论分析有较好的一致性。 相似文献
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本文利用微观力学方法研究了金属基复合材料的常温蠕变和应力松弛,连续纤维在弹性粘塑性基体内单向铺设。本文的结果与实验结果符合较好。研究表明,纤维在轴向对基体的蠕变起到明显阻止作用,而在横向和剪切变形下的作用较小。在低应力水平下,复合材料的蠕变变形很小,在高应力水平时,蠕变变形明显甚至引起蠕变破坏。 相似文献
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An apparatus has been designed and built up to determine the shear creep compliance and viscosity with high accuracy in a wide range of temperature and time. The characteristic feature of this apparatus is the possibility to measure directly the recoverable compliance and to determine the steady state recoverable complianceJ
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. Disturbing instrumental forces are minimized by use of a magnetic bearing. The torque is applied inductively by a modified three phase asynchronous motor. The torsional angle is measured with a laser beam reflected from a mirror to an electro-optical measuring device. Sample thermostating is performed by radiation in a heating chamber, which allows observation of the specimen during measurement.First results of creep and creep recovery measurements are reported, which were carried out on a technical polystyrene above the glass rubbery transition.Dedicated to Prof. Dr. H. Janeschitz-Kriegl on the occasion of his 60th birthday. 相似文献
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采用自行设计加工的挂重型岩石材料直接拉伸装置,对重庆市某地红砂岩进行了短时分级加载单轴直接拉伸蠕变试验,并对该砂岩的蠕变特性进行了分析。结果表明,砂岩在该试验条件下具有明显的蠕变特性,其蠕变表现为衰减蠕变和稳态蠕变两个阶段,砂岩蠕变量与稳态蠕变速率随着荷载的增加而增加。应用三参量广义Kelvin模型与Burgers蠕变模型描述该砂岩的蠕变规律,结果表明,两个模型均可以准确描述该砂岩的蠕变特性,其中,Burgers蠕变模型效果更佳。本文所得结论可为从事相关研究的工作人员提供一定的借鉴。 相似文献
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Elastic properties of melts of a long-chain branched low density polyethylene (LDPE) with a broad molecular mass distribution
and a short-chain branched linear low-density polyethylene (LLDPE) with a more narrow molecular mass distribution were investigated
by creep recovery measurements in shear. The results obtained by means of a magnetic bearing torsional creep apparatus in
the linear-viscoelastic region, showed that the steady state recoverable compliance of the LLDPE is greater by a factor of
two than that of the LDPE. In the short-time region up to 1000 s, however, the time-dependent recoverable compliance of the
LDPE is higher than that of the LLDPE. The retardation times for the LLDPE are considerably longer than for the LDPE. For
the LDPE the temperature dependence of the entanglement transition is consistent with that of the terminal zone of the creep
compliance. The activation energy of 58 kJ/mole lies in the typical range for long-chain branched polyethylenes. In the case
of the LLDPE the creep compliances can be shifted to give a mastercurve with an activation energy of 34 kJ/mole, whereas the
recoverable compliances do not follow the time-temperature superposition principle. The molecular characterization using TREF
showed that the LLDPE has a bimodal branching structure. In addition to a short-chain branched component, a low percentage
of a linear constituent with high molecular mass was found. It is postulated that this linear component forms a dispersed
phase in the matrix of the short-chain branched constituent. The resulting interfacial tension could be the reason for the
long retardation times, the high steady state recoverable compliance and the fact that the time-temperature superposition
principle is not fulfilled in the case of the LLDPE investigated.
Received: 1 July 1997 Accepted: 12 November 1997 相似文献
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作者研制了一台可测试润滑油在高压下的粘度和密度的落柱式高压粘度装置。本装置采用了新型高压粘性动密封和新型高压流变平垫静密封,经1200MPa试压、1000MPa压力下48小时保压和使用试验证明均无泄漏。用本装置所获得的压粘数据的重现性好、灵敏度高、可比性强。 相似文献
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We have investigated the dynamical properties of gelatin gels using creep measurements. A commercial apparatus (Carrimed CSL500) was modified in order to increase the deformation of the gel and to take advantage of the inertia of the system. When a step stress is applied, the very first response of these materials is an oscillating strain owing to a coupling of the high elasticity of the gelatin gels and the inertia of the apparatus. From these damped oscillations, we have extracted the elastic and loss moduli as a function of frequency, which allows us to widen the frequency range (toward high frequencies) of measurement. After subtraction of the oscillations, we have obtained the compliance funtion from which, using Ferry's formalism, we can calculate the relaxation time distribution function over a very large time range (10–3–104 s). We show that the dynamics of gelatin gels is governed by two very different characteristic times. We interpret the faster relaxation time as relaxation at the scale of the gel network mesh-size, while the slower time we assign to relaxations involving the lifetime of the gelatin gel cross-links. It is now possible to use creep measurements as an alternative to the forced oscillatory function determination, as the same data can be obtained but, more quickly, and over a large frequency range. This gives us more indication of the gel's structure (gel network behaviour, kinetics of ageing) than all the laborious methods previously necessary. 相似文献
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高温高压花岗岩钻孔实验表明,温度低于500℃,静水应力低于150MPa 状态下,岩体的钻孔变形均属于稳态蠕变变形阶段. 该文选取了广义开尔文模型来反映其特征,通过拉普拉斯变换及逆变换,详细推演出了钻孔径向位移解析解,并且考虑温度-应力的耦合效应,给出了模型参数随温度及应力变化的关系式. 利用该关系进行拟合计算,说明广义开尔文模型来表达高温高压环境中的花岗岩稳态蠕变变形特性,寻求蠕变参数是合理可靠的. 该文对于高温岩体地热资源开发中的钻孔施工与维护、钻孔变形量预测等方面,具有实际的指导意义. 相似文献