共查询到20条相似文献,搜索用时 62 毫秒
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摘要:采用紧凑拉伸c(T)试样测试了某台国产反应堆压力容器用508-Ⅲ锻件的主曲线参考温度死。为了方便今后在热室中进行辐照材料的断裂韧性试验,专门修改了c(T)试样的前端面设计。有限元分析和采用修改、未经修改的C(T)试样的试验结果均表明,对试样的修改不会影响断裂韧性试验。发现C(T)试样测得的瓦值与前期采用三点弯曲SE(B)试样确定的%值仅相差约1℃。为此详细探讨了ASTME1921标准第1.3和5.7条款有关试样形式对%的影响,试验结果印证了这些条款的阐述,所测得的r,n试验值接近材料的%平均值。 相似文献
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对16Mn钢CharpyV型缺口试样进行了系列温度的示波冲击试验。揭示了出断裂载荷随温度的变化呈现反“S”型特性,且在断裂载荷谷值点对应的温度T^VC处发生断 韧脆转变行为。研究表明温度T^VC受控于材料的解理特征应力SCO。 相似文献
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Shin-Beom Choi Yoon-Suk Chang Young-Jin Kim Min-Chul Kim Bong-Sang Lee 《Journal of Mechanical Science and Technology》2010,24(3):687-692
The aim of this paper is to suggest an approach to generate master curves by using miniature specimens, especially pre-cracked
Charpy V-notched (PCVN) specimen, made of SA508 carbon steel. Firstly, fracture toughness diagram is derived from comparing
finite element analyses results with the fixed mesh size at crack tip between standard compact tension and PCVN specimens.
To compensate the constraint effects from different geometry, further examination based on the fracture toughness diagram
was performed. In this context, a scale factor to deal with specimen size effects is proposed by statistically manipulating
the numerical analysis data. Finally, the proposed scale factor is applied to calculate reference temperature which affects
on the master curve. We expect that the approach can be applicable to compensate the geometrical constraint effects on fracture
toughness of SA508 carbon steel when the PCVN specimen is used. 相似文献
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Shin-Beom Choi Sung Choi Jae-Boong Choi Yoon-Suk Chang Min-Chul Kim Bong-Sang Lee 《Journal of Mechanical Science and Technology》2012,26(9):2727-2734
Although the well-known master curve method has been widely used to estimate the ductile to brittle transition temperature and to prevent subsequent brittle fracture of reactor pressure vessels, it has a limitation to determine reference temperatures on heat affected zone and weld metals. The present paper is to propose an enhanced master curve method. Prior to this, several schemes to provide the master curve of inhomogeneous materials such as bimodal master curve estimation, randomly inhomogeneous master curve estimation and single point estimation were reviewed to confirm their applicability. As a result, the single point estimation scheme was chosen as the basic algorithm to calculate the reference temperature and modified by adopting three T 0sp parameters concept to enhance the accuracy. The proposed method can be used to inhomogeneous materials for more accurate reference temperature calculation of reactor pressure vessels even with dispersed fracture toughness test data. 相似文献
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Beizhi Li Dahu Zhu Jingzhu Pang Jianguo Yang 《The International Journal of Advanced Manufacturing Technology》2011,54(9-12):931-940
In order to estimate temperature distribution and the influence of grinding parameters on grinding temperature in the grinding zone, a theoretical model used for calculating and simulating the grinding process must be established. Many simplified heat source models developed previously have some errors compared with the actual heat flux to the workpiece. Therefore, based on the triangular heat flux distribution model and temperature distributions measured, an inverse method for the heat transfer mechanism in the grinding zone was investigated and a quadratic curve heat flux distribution model was developed to determine the heat flux distribution and predict the surface temperature of the workpiece. From the theoretical expression of heat flux to the workpiece, it has been found that the quadratic curve heat flux is the superposition of square law heat flux, triangular heat flux, and uniform heat flux in the grinding zone. By comparison of theoretical analysis with the experimental results, it has been demonstrated that the solution using a quadratic curve heat flux can improve the grinding model by decreasing the error, although the uniform and triangular heat fluxes can explain the condition of the heat flux to the workpiece along the grinding zone. 相似文献
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基于分段曲线拟合的稳态检测方法 总被引:6,自引:0,他引:6
稳态检测对热工过程的建模、优化和控制具有重要的意义。通过对变量信号采样数据的分段拟合得到其一阶导数和二阶导数序列,利用重叠数据加权来保证边界的连续性和光滑性。并根据变量信号的一阶和二阶导数序列信息,与相应的阈值比较后得到其变化趋势,进而得到该变量的稳态指数。稳态指数值的范围是0到1,代表稳定程度从非稳态到稳态。对系统的各个关键变量的稳态指数加权并考虑系统的响应延迟得到整个系统的稳态指数,进而判断系统工况是否稳定。最后以某电厂600MW机组的给水流量系统等数据进行稳态检测,结果表明该方法具有一定的工程实用价值。 相似文献
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基于数字标工模型的飞机数字化协调方法 总被引:1,自引:0,他引:1
为实现大型飞机全数字化生产,通过深化与扩展数字标工模型的概念和内涵,提出了数字标工模型的组成元素和组织结构,分析了数字标工模型中各关键要素的建立过程和作用,阐述了数字标工协调法的思想和原理,以及在并行产品数字化设计、制造过程中的应用。同时,分析了作为唯一生产依据的实物标工模型与数字标工模型在协调过程中的区别,总结了数字标工协调方法的优势。用实例详细说明了数字标工协调方法实现协调的有效性。 相似文献
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通过模拟焊接热影响区粗晶区组织,对模拟后的试样进行不同温度下的消除应力退火处理,测得其相应的冲击韧性,确定了P460NL1钢的再热脆化的温度区间,并通过对断口的分析,找出了产生再热脆化的原因,从而确定了最佳的消除应力退火温度。 相似文献
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Hyunjo Jeong Seung-Hoon Nahm Kyung-Young Jhang Young-Hyun Nam 《Journal of Mechanical Science and Technology》2002,16(2):147-154
The objective of this paper is to develop a nondestructive method for estimating the fracture toughness (K IC) of CrMoV steels used as the rotor material of steam turbines in power plants. To achieve this objective, a number of CrMoV steel samples were heat-treated, and the fracture appearance transition temperature (FATT) was determined as a function of aging time. Nonlinear ultrasonics was employed as the theoretical basis to explain the harmonic generation in a damaged material, and the nonlinearity parameter of the second harmonic wave was the experimental measure used to be correlated to the fracture toughness of the rotor steel. The nondestructive procedure for estimating theK IC consists of two steps. First, the correlations between the nonlinearity parameter and the FATT are sought. The FATT values are then used to estimateK IC, using theK IC versus excess temperature (i.e.,T-FATT) correlation that is available in the literature for CrMoV rotor steel. 相似文献
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基于NURBS曲线拟合的刀具路径优化方法 总被引:1,自引:0,他引:1
为解决复杂曲面高速、高精度加工中由于微小直线段链逼近自由曲线产生的刀具路径不连续问题,提出一种基于非均匀有理B样条曲线拟合的刀具路径优化方法.在该方法中,通过分析刀具路径的几何特征鉴别需要平滑的连续直线段链,对其分段进行基于最小二乘法的非均匀有理B样条曲线拟合优化,并设置相邻段连接点处的边界平滑条件,还原刀具路径应有的连续性.拟合算法采用特征点搜索法设定曲线参数,通过误差控制的曲线节点向量和控制顶点调整保证拟合曲线精度.实验表明,经过该算法拟合优化后的刀具路径具有良好的平滑性,显著提高了曲面加工的精度和效率. 相似文献
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Heung-Shik Lee Sung-Ho Bang Tae-Won Kim 《Journal of Mechanical Science and Technology》2014,28(10):4037-4047
A corrosion fatigue crack propagation test for 430 stainless steel and its heat affected zone was conducted in pH buffer solutions, and the results were compared with model predictions. The bare corrosion effect on fatigue crack propagation, particularly in corrosive environments was evaluated by means of a modified Forman equation. As shown in the results, the average corrosion rate determined from the ratio of corrosion induced crack length to the entire crack length under a cycle load was 0.11 and 0.37 for the base metal and heat affected zone, respectively, with a load ratio of 0.5, frequency of 0.5, and a pH 10.0 environment. The modeling and experimental processes demonstrate a step towards a methodology enabling the corrosion effects on fatigue crack propagation behavior to be determined. 相似文献
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本文提出了一个用三次NURBS曲线插值凸轮轮廓的新方法,该方法首先推导出三次NURBS曲线的矩阵形式,然后根据积累弦长参数法确定节点矢量,最后运用MATLAB软件算出凸轮轮廓的控制点及其权因子. 相似文献