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弹性模量是表征与评定材料力学性能的基础,本文基于超声波斜入射至异质界面时的波型转换原理,提出了测量材料弹性模量的方法.当超声纵波以小于第一临界角的角度入射至材料时,可在材料的底面和水的界面产生反射纵波与反射横波.通过计算材料表面回波与反射纵波、反射横波之间的声时差,并结合材料的厚度值可计算得到材料的纵波声速与横波声速,进而获得弹性模量与泊松比的数值.本文对厚度约2 mm的轧制铝和镍试样进行了超声测量,结果表明:弹性模量、泊松比的测量值与理论值之间的相对误差分别小于2%,6%. 相似文献
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碳纤维复合材料孔隙率超声声阻抗法检测 总被引:3,自引:1,他引:2
基于复合材料孔隙率与材料密度、超声波纵波声速之间的内在联系,采用超声水浸底波反射回波法,利用5 MHz平探头测量碳纤维单向增强复合材料超声声阻抗。借助金相显微镜测试复合材料孔隙率,并利用实验进行参数标定后,建立了超声声阻抗与碳纤维增强环氧树脂复合材料孔隙率P的经验公式。对0.03 %≤P≤2.21%同批复合材料试样进行实验验证,发现声阻抗法测量结果与金相法测量结果相符。利用该方法测量孔隙率,无须测量材料声速和密度,且测量结果受孔隙形貌影响较小,易于实现,在复合材料孔隙率无损检测方面具有可行性。 相似文献
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激光超声是利用激光照射在媒质中产生的一种超声波,与传统的压电技术相比,它具有非接触,宽带,能定量检测以及时空分辨率高等特点,现已广泛用于材料的无损检测[1,2,3],然而,在对超薄材料的声速的测量中,需要精确测量直达波和回波的时间间隔,但由于受激光超声本身,声传播介质,传感器和测量系统等多种因素的影响,所采集的信号往往是比较复杂叠加波形,如何从中提取有用的波形信息,是测量超薄材料声速的关键. 相似文献
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为评定汽车安全碰撞实验模拟人的皮肤肌肉等效复合材料的力学特性,提出仿生皮肤等效材料的超声检测方法。通过测试仿生皮肤等效材料对超声波声速、衰减、散射和吸收率的变化,建立仿生皮肤等效材料力学性质与超声回波信号频率之间的关系模型,对仿生皮肤等效材料的弹性模量、组织特性、粘弹性和松弛模量进行等效性的分析与评定。对3种不同密度的仿生皮肤等效材料的声速、弹性模量和声衰减等参数进行了测算,结果表明:该测试方法正确可行,测试数据为仿生皮肤等效材料的设计合成、制备提供力学参数依据,对仿生材料的力学等效性能评定有着重要的参考价值。 相似文献
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According to thermoviscoelastic theory, the relations of laser-generated Rayleigh waves in viscoelastic plates with thermophysical and viscoelastic properties are investigated quantitatively. The displacement spectra are calculated in the frequency domain using the finite element method, and the temporal displacement waveforms are obtained by applying inverse fast Fourier transforms. And then, the effects of the laser parameters, including the laser spot radius, pulse rise time, and optical penetration depth, on the propagation of laser-generated Rayleigh waves are studied. In addition, the influence of the increase of each elastic modulus and viscous modulus of the viscoelastic plates on laser-generated Rayleigh waves is investigated in detail. 相似文献
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以掠入射纵波法研究了超声波在Ti6Al4V合金和Ti27Nb8Zr时效样品中的传播速度,推算其弹性模量,并与拉伸法获得的弹性模量进行比较.结果发现:两种方法测得的数值较为接近,相差仅为3.6%,表明掠入射纵波法实现低弹钛合金弹性模量的无损评价是可行的,这为小尺寸稀有合金样品弹性指标的评价提供了极有价值的测试方法.应用该方法进一步考察了时效温度对Ti18Nb7Zr弹性模量的影响,结果表明:随着时效温度的升高,弹性模量E,切变模量G,体弹模量K分别增加11%,10%和6%,泊松比σ仅下降了1.2%.分析认为:弹性模量的变化与合金的组织由层片状的β+α向弥散分布的α相和β相的转变密切相关. 相似文献
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M. Posarac M. Dimitrijevic J. Majstorovic B. Matovic 《Research in Nondestructive Evaluation》2013,24(1):48-59
Two different types cordierite/silicon carbide composite ceramic materials (KS 50 and KZ 50) were used for this investigation. Both materials were exposed to the water quench test from 950°C, applying various numbers of thermal cycles. When refractory samples are subjected to the rapid temperature changes crack nucleation and propagation occurs resulting in loss of strength and materials degradation. The formation of cracks decreases the density and elastic properties of material. Therefore, measuring these properties can directly monitor the development of thermal shock damage level. Dynamic Young modulus of elasticity and strength degradation were calculated using measured values of ultrasonic velocities obtained by ultrasonic measurements. Level of degradation of the samples was monitored before and during testing using Image Pro Plus program for image analysis. The capability of ultrasonic velocity technique and image analysis for simple and reliable nondestructive methods of characterization was presented in this investigation. It was found that both composite materials exhibit good thermal shock resistance. 相似文献
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岩石单轴抗压强度是岩土工程中最基础、最重要的参数之一,建立其快速、方便、经济的预测方法一直是岩土界的研究热点。为了获取片岩单轴抗压强度的预测模型,基于超声波试验和单轴压缩试验数据,对福建某矿山的片岩岩样分别开展了单轴抗压强度与纵波波速、横波波速、纵波模量、横波模量、动弹性模量和静弹性模量的回归性分析,并各自建立了线性、对数、多项式、指数函数和幂函数5种回归模型。分析表明,除了动弹性模量以外,其他参量都易受空间变异性和各向异性影响,不适合用于片岩单轴抗压强度的预测。最终,通过拟合度、所包含参量、量纲平衡、测试方法以及显著性分析,确定基于动弹性模量建立的线性回归模型是最合理、可靠、方便的片岩单轴抗压强度预测模型。研究成果可为开展岩石单轴抗压强度预测的相关理论研究和工程应用提供参考和帮助。 相似文献
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Mechanical and physical properties of a laminated, continuous SiC-fibre-reinforced Ti-15V-3Cr-3Al-3Sn (Ti-15-3) composite were analysed. The dynamic elastic modulus and damping of specimens with both unidirectional and cross-ply laminates were measured with the PUCOT (piezoelectric ultrasonic composite oscillator technique). The values of density, elastic modulus, and damping were evaluated with respect to heat treatment of the specimens. Metallographic examination was also done on the specimens to assess any changes in the microstructure in terms of changes in the mechanical or physical properties. 相似文献
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Tao Fu 《Materials Letters》2007,61(2):330-333
The three-dimensional (3-D) carbon fiber fabric is used to reinforce a hydroxyapatite (HA)/epoxy biocomposite. The elastic modulus calculation of the 3-D fabric reinforced composite by the stiffness average method and the finite element method shows that the elastic modulus of the composite is designable, and can be adjusted to the range of a human cortical bone (7-30 GPa) by varying the micro-structural parameters of the woven fabric to fulfill the nonisotropic requirement of the composite implants. The calculated elastic modulus is comparable with the flexural modulus of the 3-D fabric reinforced composites prepared by resin transfer molding. The incorporation of HA has decreased the flexural modulus of the composites for the weakened fiber-matrix interface, but the flexural modulus (22-36 GPa) is still close to that of the human cortical bone, which favors the avoidance of ‘stress shielding’ and the sequent bone absorption caused by implant materials with a high elastic modulus. 相似文献
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提出低频多模式超声兰姆波定征方法来估计超薄层状单向纤维增强复合材料的密度、厚度、弹性常数等参数。这里"超薄"的概念是指材料厚度h远小于材料中的声波波长λ,导致在时域上材料前后界面的各次回波信号相互混迭。分析了沿平行和垂直于纤维两个方向上,在超薄层状单向纤维增强复合材料中传播的低频兰姆波色散特性,提出在最小二乘意义下以材料色散曲线为基础的反向算法对材料参数进行了估计。文中分析了影响估计准确性的各种因素,研究了该方法对材料参数的灵敏度及其在误差传递中的意义。结合超声漏兰姆波频域分析方法,并使用超声耦合剂耦合方式和一对中心频率为2MHz的宽带纵波换能器,实验结果证实,该方法能够准确估计h<0.05 λ的单向玻璃纤维增强双酚A型聚砜(PSF)复合材料的材料参数。 相似文献