CuZnAl形状记忆合金热机械循环滞回曲线与振动衰减特性研究

运用电子万能拉伸试验机、动态数据采集分析仪,测试了CuZnAl形状记忆合金的力-变形滞回曲线和安装有CuZnAl形状记忆合金耗能器框架结构的减振性能.借助透射电镜、X射线衍射仪,分析了CuZnAl形状记忆合金热机械循环过程中显微组织的变化.比较了不同热处理方式、不同相变点的CuZnAl形状记忆合金热机械循环后的滞回曲线面积及减振性能.试验结果表明:CuZnAl形状记忆合金用于框架结构的被动振动控制具有较好的减振性能,同时明显降低框架结构的振动频率.马氏体CuZnAl形状记忆合金耗能器具有较大的耗能能力,热机械循环数十次以后滞回面积亦大幅度减小,但相变点高的CuZnAl形状记忆合金的滞回面积减小幅度较小.     

不同相变温度CuZnAl形状记忆合金的框架结构振动控制试验研究

采用电子式万能实验机测出相变点Ms为120℃、50℃和．10℃的三种CuZnAl形状记忆合金，经不同热处理工艺试验后的试验力．变形曲线。结果表明，常温下为马氏体状态的CuZnAl合金，相变点低的比相变点高的滞回曲线所包围的面积稍大，常温下为马氏体状态的CuZnAl合金，比超弹性状态的CuZnAl合金的滞回曲线所包围的面积大的多。滞回曲线所包围的面积越大减振效果越好。油淬、水淬和分级淬的CuZnAl合金具有较稳定的形状记忆效应，具有较好的超塑性和伪弹性。热处理工艺从油淬、水淬、分级淬的顺序，时效时间无论是1h还是5h，无论是小应变还是大应变，也无论是激振频率高低，η值逐渐减小。用动态数据采集分析仪对安装在两层框架结构模型上的CuZnAl形状记忆合金耗能器进行了振动控制试验和分析。结果表明，使用CuZnAl形状记忆合金耗能器后，框架结构的振动衰减比未安装CuZnAl形状记忆合金耗能器时快得多，衰减时间仅为未安装CuZnAl形状记忆合金耗能器的十分之一。常温下，马氏体状态的耗能器需要快速加热和冷却，而超弹性状态的耗能器则不用，这是常温下超弹性状态的CuZnAl耗能器的一大优点。     

H13热作模具钢热-机械疲劳损伤和寿命的预测

采用MTS热-机械疲劳试验机测定了H13热作模具钢在200～600℃、机械应变为0. 7%和0. 9%的同相和反相热-机械疲劳寿命,并基于循环损伤理论采用Ostergren寿命预测模型预测了H13钢的疲劳损伤和疲劳寿命。结果表明:无论是同相还是反相热-机械疲劳,其应力-应变响应曲线均明显不对称;高温半周的应力-应变响应曲线出现明显的应力松弛,且其塑性应变高于低温半周;随着循环周次的增加,H13钢的滞回能逐渐增大,机械应变增加,损伤加剧;与反相热-机械疲劳相比,H13钢的同相热-机械疲劳寿命更高。采用Ostergren寿命预测模型获得的机械应变为0. 7%和0. 9%的H13钢同相和反相热-机械疲劳寿命分别为323和313周次及198和194周次,均与实测值较为吻合。     

超弹性TiNi形状记忆合金棒材力学行为

基于工程振动控制的角度,通过TiNi形状记忆合金棒材在室温条件下的力学性能试验,以相变应力、变形模量、残余应变、耗能能力等作为该合金棒材的力学特征参数,分析了这些特征参数随加载速率、应变幅值、载荷循环等加载工况的变化规律.结果表明:超弹性TiNi形状记忆合金棒材具有良好的耗能能力及阻尼性能,可满足工程结构振动控制的需要.但在工程应用时,应考虑加载速率、应变幅值、载荷循环等因素对TiNi形状记忆合金棒材力学行为的影响,根据具体工况合理设计.     

热-机械循环训练对Fe-15Mn-4Si-8Cr-4Ni形状记忆合金耐腐蚀性能和低温应力松弛的影响

研究了热-机械循环训练对Fe-15Mn-4Si-8Cr-4Ni形状记忆合金耐腐蚀性能以及低温松弛的影响,结果表明,随着循环次数的增加,合金在5%NaOH溶液中的耐腐蚀性能呈下降的趋势,这是因为热-机械循环处理导致了碳化物的大量析出,从而降低合金的耐腐蚀性能;经过热-机械循环处理后合金的低温应力松弛率高于未经循环处理的合金,约提高3%左右.导致合金低温应力松弛率提高的原因是回复应力的提高为应力诱发ε马氏体相变提供了大的机械驱动力以及应力诱发ε马氏体的临界应力的降低.     

IN718镍基高温合金的热机械疲劳性能

对IN718镍基高温合金进行温度循环为350～650℃及不同应变幅条件下的同相(IP)和反相(OP)热机械疲劳试验;比较同相和反相的热机械疲劳循环应力响应行为、滞后回线以及疲劳寿命;运用金相显微镜、扫描电子显微镜对材料的微观结构以及断口特征进行分析。结果表明:IN718合金的热机械疲劳应力-应变滞后回线最大拉应力与压应力不对称,表明合金在350～650℃范围内高温时抵抗变形阻力较小;合金的循环应力响应行为在低应变幅的同相热机械疲劳的高温半周呈现循环硬化现象,其余情况均为循环软化现象;合金的同相热机械疲劳寿命明显低于反相热机械疲劳寿命,合金热机械疲劳寿命在应变幅超过0.6%的条件下符合Coffin-Manson方程,在应变幅0.4%的情况下实际疲劳寿命值偏高;IN718合金的同相热机械疲劳的疲劳源处断口为沿晶断裂,反相热机械疲劳的为穿晶断裂,裂纹扩展区和瞬断区均为韧窝断裂。     

热循环对不同相变温度CuZnAl形状记忆合金性能的影响

研究了预应变量、热处理工艺和循环介质对不同相变温度CuZnAl形状记忆合金形状记忆效应的影响.结果表明:尽管预应变量、热处理工艺及训练介质均不同,但回复率均随循环次数的增加先上升而后下降,相变温度(361 K以上)高的合金回复率偏低;随着冷热循环训练次数的增加,合金的马氏体转变开始温度(Ms)和奥氏体转变结束温度(Ar)均有所提高,其Mf和As均有所降低;经过热循环之后,相变温度(361 K以上)高的合金的相变温度的幅度提高较大,且具有较大的热滞.     

原始组织对FeMnSiCrNi记忆合金热机械循环训练效果的影响

研究了FeMnSiCrNi形状记忆合金母相原始微观组织对热机械循环训练效果的影响.结果表明:原始微观组织显著影响热机械循环训练对FeMnSiCrNi形状记忆合金的作用效果.对具有不利于形状记忆效应的原始微观组织的合金,热机械循环训练的作用效果更加显著.原因在于初始形状记忆效应优良的合金,退火以后大部分应力诱发ε马氏体逆转变为奥氏体,而不是分解成堆垛层错.     

S30408奥氏体不锈钢的应变疲劳与寿命预测模型

对S30408奥氏体不锈钢进行应变疲劳试验研究,通过循环应力-应变响应特征、应力-应变滞回曲线和疲劳寿命研究其疲劳性能,并获得应变疲劳参数.为了构建其疲劳寿命预测模型,对比了 Manson-Coffin方程、三参数幂函数、三参数幂函数能量法和基于塑性应变能的寿命方程的适用性.结果表明:4种疲劳寿命预测模型能有效表征应变...     

NiTi形状记忆合金回复应力-温度模型改进与实验研究

针对NiTi形状记忆合金的马氏体不完全逆转变带来的回复应力模型预测误差,开展了NiTi形状记忆合金一维回复应力-温度模型研究。在Brinson的形状记忆合金(SMA)一维本构模型基础上,增加马氏体回复因子为内变量,给出了马氏体回复因子与预应变的关系,综合考虑温度和应力对马氏体体积分数的影响,构造NiTi形状记忆合金回复应力-温度改进模型,通过实验测试了不同预应变量的NiTi合金回复应力与温度关系曲线。研究表明:本研究提出的改进模型预测的NiTi形状记忆合金回复应力-温度曲线,与实验曲线吻合较好。     

CuZnAl形状记忆合金磨损性能试验研究

对CuZnAl形状记忆合金采用不同热处理工艺处理后,在不同载荷、不同磨损时间、不同摩擦副条件下进行了干磨损和油润滑动磨损试验。同时与锡青铜和铝铁青铜进行了对比试验,并用电子扫描显微镜对磨损表面和磨屑进行了观察。结果表明:CuZnAl形状记忆合金在干磨损条件下,两级时效处理的合金耐磨性能优于分级淬火处理的合金,而在油润滑动磨损条件下,分级淬火处理的合金耐磨性能优于两级时效处理的合金。CuZnAl形状记忆合金的耐磨性能优于锡青铜和铝铁青铜。用CuZnAl形状记忆合金组成的摩擦副,其耐磨性优于用45#钢与形状记忆合金组成的摩擦副。     

Numerical and Experimental Characterizations of Damping Properties of SMAs Composite for Vibration Control Systems

Shape memory alloys (SMAs) are very interesting smart materials not only for their shape memory and superelastic effects but also because of their significant intrinsic damping capacity. The latter is exhibited upon martensitic transformations and especially in martensitic state. The combination of these SMA properties with the mechanical and the lightweight of fiberglass-reinforced polymer (FGRP) is a promising solution for manufacturing of innovative composites for vibration suppression in structural applications. CuZnAl sheets, after laser patterning, were embedded in a laminated composite between a thick FGRP core and two thin outer layers with the aim of maximizing the damping capacity of the beam for passive vibration suppression. The selected SMA Cu₆₆Zn₂₄Al₁₀ at.% was prepared by vacuum induction melting; the ingot was subsequently hot-and-cold rolled down to 0.2 mm thickness tape. The choice of a copper alloy is related to some advantages in comparison with NiTiCu SMA alloys, which was tested for the similar presented application in a previous study: lower cost, higher storage modulus and consequently higher damping properties in martensitic state. The patterning of the SMA sheets was performed by means of a pulsed fiber laser. After the laser processing, the SMA sheets were heat treated to obtain the desired martensitic state at room temperature. The transformation temperatures were measured by differential scanning calorimetry (DSC). The damping properties were determined, at room temperature, on full-scale sheet, using a universal testing machine (MTS), with cyclic tensile tests at different deformation amplitudes. Damping properties were also determined as a function of the temperature on miniature samples with a dynamical mechanical analyzer (DMA). Numerical modeling of the laminated composite, done with finite element method analysis and modal strain energy approaches, was performed to estimate the corresponding total damping capacity and then compared to experimental results.     

Superelastic tension and bending characteristics of shape memory alloys

The objective of this study was to develop a numerical model of the superelastic behavior of shape memory alloys (SMA) on a macro-scale level. Results from a study on this behavior under tension and pure bending tests are presented and discussed. Two SMA samples were used in the experimental work and subjected to various loading paths in tension and pure bending: a single crystalline CuZnAl alloy and polycrystalline NiTi wire. Bending tests were performed under a pure bending loading condition on a new testing apparatus designed for the specific needs of this study. The experimental part of this study focused mainly on the response of the SMA to the loading paths in a quasi-plastic domain where the deformation mechanism is dominantly governed by the stress-induced martensitic transformation. Experimental results obtained from the NiTi polycrystals by tensile tests indicate that the superelastic SMA exhibits sufficient repeatability useful enough for a modeling task, while similar results obtained from the single crystalline CuZnAl indicate that the same modeling approach is not easily feasible. The facts have been qualitatively verified by the experimental data from pure bending tests, and a further area as study is suggested.     

相变温度对CuZnAl形状记忆合金干磨损性能的影响

研究了相变温度对复合细化后的CuZnAl形状记忆合金干滑动摩损性能的影响,结果表明：同样的热处理工艺,在摩擦副温升不大时高温相变合金比低温相变合金耐磨,摩擦副温升较大时,低温相变合金耐磨性优于高温相变合金。合金的磨损失重机制为粘着磨损、剥离磨损和犁削磨损。     

A Numerical/Experimental Study of Nitinol Actuator Springs

This study deals with the numerical modeling, simulation and experimental analysis of shape-memory alloy (SMA) helicoidal springs. An experimental campaign is conducted on both SMA straight wires and helicoidal springs that experienced the same annealing process. Then, we use such experimental results to investigate three phenomenological constitutive models able to represent SMA macroscopic behavior. In particular, after the identification of all the material parameters from experimental results on SMA wires, we inspect the thermo-mechanical behavior of SMA helicoidal springs by comparing numerical predictions to experimental data. Finally, we discuss models capabilities and some aspects characterizing SMA material behavior.     

Model and Simulation of an SMA Enhanced Lip Seal

The feasibility of using SMA wires to improve the seal effectiveness has been studied experimentally and numerically. In this article, we present only the numerical study of simulating the thermo-mechanical behavior for an SMA enhanced lip seal, leaving the test setup and results in the experimental counterpart. A pseudo 3D SMA model, considering 1D SMA behavior in the major loading direction and elastic response in other directions, was used to capture the thermo-mechanical behavior of SMA wires. The model was then implemented into ABAQUS using the user-defined material subroutine to inherit most features of the commercial finite element package. Two-way shape memory effect was also considered since the SMA material exhibits strong two-way effects. An axisymmetric finite element model was constructed to simulate a seal mounting on a shaft and the sealing pressure was calculated for both the regular seal and the SMA enhanced seal. Finally, the result was qualitatively compared with the experimental observation.     

模拟海洋大气环境对XCS-lode钢与30CrNi3Mo钢腐蚀行为的影响

采用盐雾腐蚀试验方法，研究了模拟海洋大气环境下XCS-lode钢与30CrNi3Mo钢的腐蚀性能，通过极化曲线及电化学阻抗谱(EIS)试验研究了两种钢在腐蚀行为上的差异。结果表明：XCS-lode钢相比30CrNi3Mo钢具有更高的自腐蚀电位， XCS-lode钢腐蚀产物膜的阻抗明显大于30CrNi3Mo钢，XCS-lode钢的耐海洋大气腐蚀性能优于30CrNi3Mo钢。     

DAMPING PROPERTIES OF MARTENSITE AND MARTENSITIC TRANSFORMATION IN CuZnAl ALLOYS

The internal friction of alloys in martensite state is believed to be an M/M interface one,which can be explained by an expression deduced from the theory of dislocation internal fric-tion.The internal friction during martensitic transformation consists of two parts,includingthose of the M/M interface and of the phase transformation.The latter is further composedof two portions,the major one produced by reverse martensitic transformation and the otherfrom stress-induced martensite.It was also found that the degradation of damping propertiesof the CuZnAl alloys is related to the dislocation,which is introduced from the exciting pro-cess,and tends to be of stable value after certain excitements.     

CuZnAlSMA形状记忆处理新工艺—瞬时高温分级淬火

本文实验表明,采用瞬时高温分级淬火工艺能有效地抑制CuZnAlSMA的马氏体稳定化。用该工艺处理的试样具有长期、稳定、良好的SME和RSME,其A_s温度基本上不受室温时效时间之影响。用本工艺处理试样作元件开发的冷端温度补偿器和密封式定温控测器工作可靠、精度高。由此得出瞬时高温分级淬火工艺是很有前途的形状记忆处理工艺。