共查询到20条相似文献,搜索用时 62 毫秒
1.
对原始态、步冷态、脱脆态和脱脆步冷态2.25Cr-1Mo-0.25V钢母材及焊缝冲击试验结果进行分析,得到了母材和焊缝在不同状态下的韧脆转变温度vTr54.2和FATT以及脆化度ΔvTr54.2和ΔFATT。试验结果表明,步冷试验之后,母材发生较低程度脆化或脱脆现象,但是脆化度或脱脆度较低,表明母材具有良好的抗回火脆化性能;经脱脆试验后,母材和焊缝都发生较高程度的脱脆,表明材料的脆化主要是由于回火脆化引起的,脱脆试验使得材料的韧脆转变温度降低;脱脆步冷试验后,焊缝发生较高程度的脆化,焊缝对脱脆步冷试验的敏感性较高,脱脆步冷试验有效促进了焊缝的脆化。在相同脆化条件下,母材的脆化敏感性低于焊缝,焊缝更易发生脆化。 相似文献
2.
16MnR钢通过三种热处理工艺获得细晶细碳化物、细晶粗碳化物和粗晶粗碳化物三种不同组织,对这三种不同组织的材料进行系列低温(–99~20℃)下的Charpy-V冲击试验。通过冲击韧度比较、断口形貌观察以及断裂微观参数的测量,研究晶粒尺寸和碳化物尺寸对16MnR钢冲击韧度的影响。结果发现,不同微观组织的材料其冲击韧度随温度降低而减小;细晶细碳化物组织比细晶粗碳化物组织和粗晶粗碳化物组织韧脆转变温度低,同一温度下的断裂韧度好,而且晶粒尺寸对韧脆转变温度和断裂韧度值的影响要比碳化物尺寸显著得多。通过断口微观参数的测量得知,韧脆转变温度区的断裂能量主要消耗在裂纹尖端的钝化与塑性裂纹扩展中。韧脆转变低温区,裂纹尖端在钝化过程中吸收大量能量从而韧性陡升。 相似文献
3.
4.
研究了V型缺口,预制裂纹试样及在含0.5%CH3COOH的H2S饱和溶液中浸泡后2组X52输送管母材和焊缝的系列温度冲击转变特性。结果表明,由于两组输送管母亲才成分和母材与焊缝组织的不同,导致母材和/或焊缝韧性有较大差异;母亲才在上述三种状态7的韧性变化不大,但焊缝预制裂纹试样大幅度降低焊缝韧性,提高韧脆转变温度。 相似文献
5.
6.
利用凯尔测控EUM-25K20型拉扭疲劳试验机,在110 K下对S30408母材试件、含焊缝试件、无预应变、预应变8%、12%的试件进行了单轴棘轮效应试验研究。实验发现,母材试件与焊材试件的棘轮行为与平均应力、幅值应力及其加载历史密切相关。由于焊缝金属中少量铁素体的软化作用,焊缝试件的初始棘轮应变及小循环应力下的棘轮应变大于母材。但随着塑性变形的增加,焊缝金属中更高含量合金元素存在更为明显的强化作用,使得焊缝试件在较大循环应力下一定循环圈数后的棘轮应变小于母材。无论母材试件还是焊缝试件,棘轮应变随预应变的增加而降低,在较小的循环应力水平下,预应变可以完全抑制棘轮应变的累积。S30408在110 K下为率相关材料,棘轮应变随加载率的升高而降低。 相似文献
7.
通过试验获得9Ni钢焊接接头、母材和焊缝在室温20℃和低温-158℃下的拉伸和断裂性能,对比分析了温度对性能的影响;建立了母材和焊缝的近似R6选择2失效评定曲线(FAC)以及9Ni钢焊接接头的FAC,并进行了对比。结果表明:低温下母材的拉伸和断裂性能以及接头和焊缝的拉伸性能均高于室温下,焊缝的断裂韧度几乎不随温度改变;不同温度下焊缝的屈服强度和断裂韧度均低于母材,焊缝是9Ni钢焊接接头的薄弱区域。由室温拉伸性能构建的近似选择2 FAC包络面积均略小于采用低温拉伸性能构建的FAC,故可用室温拉伸性能构建近似选择2 FAC对9Ni钢焊接接头进行安全评定;分段选取室温下母材和焊缝的近似选择2 FAC构建的焊接接头FAC能最保守地对低温9Ni钢含缺陷结构进行安全评定。 相似文献
8.
《机械工程材料》2017,(5)
对运行10a的3Cr1Mo1/4V钢制加氢反应器内试块取样进行了脱脆热处理,与未热处理(脆化态)试样在不同温度下进行了小冲杆试验和夏比冲击试验,提出了以断裂能与最大载荷的比值(E_(SP)/F_m)作为确定小冲杆试验韧脆转变温度的方法,得到韧脆转变温度及其增量,并与夏比冲击试验结果进行了对比。结果表明:小冲杆试验得到的E_(SP)/F_m-温度曲线与夏比冲击试验得到的冲击功-温度曲线具有相同的变化趋势;与断裂能相比,E_(SP)/F_m可以更好地表征材料的韧脆状态;以E_(SP)/F_m稳定值的60%对应的温度作为韧脆转变温度,得到的韧脆转变温度增量与由夏比冲击试验得到的近似相等,小冲杆试验可以用来评价3Cr1Mo1/4V钢的回火脆性。 相似文献
9.
10.
HQ785C钢示波冲击试验韧脆断裂转变特性研究 总被引:3,自引:0,他引:3
利用示波冲击试验及断口分析方法对HQ785C钢的韧脆断裂转变特性进行了研究。结果表明,动态断裂韧性KId与最大载荷吸收功Em具有随温度一致变化的规律,而与总的冲击能Et则无这种关系。试验还发现,屈服载荷与最大载荷相等的温度为材料的韧脆转变温度,该温度受控于材料的解理断裂应力σf,在此温度下有解理断裂发生。 相似文献
11.
Clarence W.DE SILVA 《Instrumentation》2019,(4):72-84
An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t... 相似文献
12.
INTEGRAL EQUATION METHOD'S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES 总被引:1,自引:0,他引:1
LI Cheng ZHENG Yanping 《机械工程学报(英文版)》2008,21(6):115-118
The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value. 相似文献
13.
30 keV Ga+ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z2, and shows a non-monotonic relationship between contrast and Z2. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z2, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory. 相似文献
14.
This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an... 相似文献
15.
分布动态载荷识别的抗噪处理 总被引:2,自引:2,他引:0
针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性. 相似文献
16.
针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。 相似文献
17.
J. A. Williams 《Lubrication Science》1997,3(3):267-306
Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface. 相似文献
18.
The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar... 相似文献
19.
The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods.... 相似文献
20.
M. Stedman 《Journal of microscopy》1988,152(3):611-618
Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space. 相似文献