沥青混凝土抗压强度与回弹模量的试验研究

通过对5种不同沥青含量的沥青混凝土进行单轴压缩试验,得到沥青混凝土抗压强度和沥青用量之间的关系;在测得抗压强度的基础上进行抗压回弹模量试验,得到抗压回弹模量和沥青用量之间的关系;同时根据动、静回弹模量的关系,将静态回弹模量换算为动态回弹模量,以促进路面设计理论由静态向动态的过渡.     

Some Physical Properties of High-Density Thorium Dioxide

The values for a number of physical properties are reported for a very high density form of thorium dioxide. When specimens of a mixture of 99½% ThO² and ½% CaO, by weight, were hydrostatically pressed at 30,000 lb. per sq. in. and heat-treated for 1 hour at 1800°C., they attained 99.0% of theoretical density. All the test specimens were extremely brittle. Physical-property values determined at room tempera- ture were the following: lattice constant; bulk and theoretical (X-ray) densities; compressive and impact strengths; Knoop hardness; modulus of rupture and Young's modulus, determined by a static method; Young's modulus and the shear modulus, determined by a dynamic method; Poisson's ratio and the bulk modulus, calculated from the dynamic-test data; and the velocity of sound through the material. The properties determined at elevated temperatures were the following : linear thermal expansion modulus of rupture and Young's modulus, determined by a static method; Young's modulus and the shear modulus, determined by a dynamic method; and Poisson's ratio, calculated from the elevated-temperature dynamic-test data. "Martin's diameter" grain counts were taken for the material both before and after heat-treatment.     

结构增强木塑板材的力学性能无损检测

以回收高密度聚乙烯和杨木纤维加工而成有、无加强筋的木塑板材试件,运用3种振动无损检测方法测试其动态弹性模量,并依据美国材料试验标准D790-03通过三点弯曲实验获得静态弹性模量.阐述了加强筋对3种振动无损检测弹性模量的影响,分析了3种木塑板材的动态弹性模量与其静态弹性模量的相关性.结果表明,加强筋能够增强木塑板材的强度...     

Effect of Temperature on Modulus of Elasticity of Porcelain Enameled Steel

The modulus of elasticity of porcelain enameled steel specimens was measured at different temperatures. A dynamic test (the sonic method) was used for the determination of the modulus of the metal and of the metal-enamel composites. Equations and constants are presented by which the elastic constant can be calculated for any enamel thickness in the temperature range from room temperature to 500° C. Graphs are also presented to show the relationship of the modulus of elasticity, temperature, and enamel-metal thickness ratio for ground-coated, white cover-coated, and direct white enameled steel specimens.     

熔融沉积PLA材料动态力学行为及本构模型研究

为分析低、高应变率下增材制造熔融沉积材料聚乳酸（PLA）的静、动态力学性能,利用万能材料试验机和分离式霍普金森压杆（SHPB）实验装置分别对3种打印速度（40、80、120 mm/s）的PLA材料进行加载应变率为0.000 5、1 000、1 500、2 000 s^-1的静、动态力学性能测试,并观测了试样表面微观形貌。结果表明,PLA材料的弹性模量、屈服应力随应变率的增加而显著增加;微观形貌分析发现,打印速度为80 mm/s的材料缺陷较少,相同应变率下,该打印速度材料的弹性模量和屈服应力明显高于40 mm/s和120 mm/s 2种打印速度材料;静态载荷下,PLA材料会出现明显的弹性和塑性阶段,且塑性段呈现出了应变软化现象;动态载荷下,PLA材料具有显著的黏弹性特征,选取朱-王-唐（ZWT）模型建立了材料的黏弹性本构,该本构模型拟合曲线与实验曲线吻合较好。     

The Ball-on-Three-Balls strength test for discs and plates: Extending and simplifying stress evaluation

The Ball-on-Three-Balls-test has proven to be an accurate and easy-to-use option for strength testing. However, the maximum stress must be calculated based on Finite-Element-Analysis results. For this purpose, a fitted function was already provided. This function is based on results which were generated under the assumption of punctiform load introduction. Deviations from these conditions occur through an increase in contact-area between the loading ball and the specimen, large specimen deformations, friction, or plastic deformation of the balls. These non-linear effects are investigated by Finite-Element-Analysis for a wide range of specimens. It is shown that the maximum stress is sensitive to the area of contact between the loading ball and the specimen. Furthermore, thin specimens are subject to large deformations, which significantly decrease the maximum stress. Therefore, a revised fitted function is derived. For specimens with exceptional geometries, non-linear effects are considered with correction factors added to the new fitted function.     

Application of Sonic Moduli of Elasticity and Rigidity to Testing of Heavy Refractories

The application of A.S.T.M. C 215-51 T (Tentative Method of Test for Fundamental Transverse Frequency of Concrete Specimens for Calculating Young's Modulus of Elasticity) to the nondestructive testing of 1- by 1- by 7-in. laboratory fire-clay specimens and standard 9-in. fire-clay and high-alumina refractory brick is reviewed. Both room-temperature measurements and hot sonic modulus of elasticity measurements to 1700°F. are analyzed. Sonic moduli of elasticity and rigidity are compared with modulus of rupture by a theory of measurements and statistical analysis. The limits of uncertainty of the average of modulus of rupture are shown to be a function of the degree of verification whereas in the case of both sonic moduli they are not. Limits of uncertainty of the average of sonic moduli data are usually of the same order as errors calculated from the precision of measurements. In the case of modulus of rupture of well-vitrified clays, the uncertainty of the average is much greater than calculated error limits. Sonic moduli differentiate statistically between two samples of 60% alumina brick whereas modulus of rupture does not. If Poisson's ratio is assumed to be zero rather than the conventional one-sixth, ratios of sonic modulus of elasticity to rigidity are shown to approximate the theoretical ratio more closely. Effects of nonuniform density to displace normal nodes are illustrated. Hot sonic modulus of elasticity is shown to reflect changes due to crystallographic inversions, deterioration of chemical bond in unfired brick, and development of sintered bond in unfired brick.     

MECHANICAL PROPERTIES OF SOME ROLLED AND POLISHED GLASS1

A comparative study was made of the mechanical properties of several different kinds of rolled and polished glass. Young's modulus of elasticity and the transverse modulus of rupture were measured by the usual cross-bending method. Impact modulus of rupture was measured by means of a special form of pendulum which gave results that were free from the effects of cumulative chipping. Wind resistance was measured with a special form of hydraulic loading machine designed to give uniform pressure of the test plate against the supporting frame. The apparatus is described in detail and the results of the measurements are given in a series of graphs and tables.     

Shear Strength of Pressure Sensitive Adhesives and its Correlation to Mechanical Properties

Correlations between shear resistance and the mechanical properties of pressure sensitive adhesives are studied by measuring the deformation behaviour in the static and the dynamic shear test and determining the dynamic shear modulus of the adhesive. For polymers with low or moderate viscosities, the shear strain vs. time characteristics in a static shear test and, accordingly, the static shear strength, can be evaluated from the master curves of the dynamic shear modulus or the dynamic viscosity. The dynamic shear strength also can be calculated. These exact calculations cannot be applied to highly viscous or slightly crosslinked polymers. On the basis of the model experiments, empirical correlations between shear strength and the dynamic shear modulus are established which seem to be generally valid.     

Mechanical properties of polypropylene fibers produced from the binary polymer blends of different molecular weights

The mechanical properties of multifilament yarns, spun from the blends of a plastic‐grade polymer with a fiber‐grade CR‐polymer in the composition range of 10–50 wt % added, were investigated. The predicted modulus of a two‐phase blend, calculated from several representative equations, was compared with the elastic modulus of drawn yarns, determined from the stress vs. strain curve and dynamic modulus obtained from the sound velocity measurements. The best fit was achived with the Kleiner's simplex equation. For both the static and dynamic elastic modulus, the largest negative deviation is seen at the 80/20 and 60/40 plastic/fiber‐grade polymer blend composition, while the largest positive deviation is seen at the 90/10 plastic/fiber‐grade polymer blend composition, suggesting good compatibility of both polymers, when only a small percent of the fiber‐grade CR‐polymer is added. Improved spinnability and drawability of blended samples led to the yarns with the tensile strength over 8 cN/dtex, elastic modulus over 11 GPa and dynamic modulus over 15.5 GPa. Structural investigations have shown that the improved mechanical behavior of blended samples, compared to the yarn spun from the pure plasic‐grade polymer, is the consequence of a higher degree of crystallinity, and above all, of a much higher orientation of macromolecules. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1211–1220, 2000     

Effect of temperature and age on the relationship between dynamic and static elastic modulus of concrete

This study investigates the effects of cement type, curing temperature, and age on the relationships between dynamic and static elastic moduli or compressive strength. Based on the investigation, new relationship equations are proposed. The impact-echo method is used to measure the resonant frequency of specimens from which the dynamic elastic modulus is calculated. Types I and V cement concrete specimens with water-cement ratios of 0.40 and 0.50 are cured isothermally at 10, 23, and 50 °C and tested at 1, 3, 7, and 28 days.Cement type and age do not have a significant influence on the relationship between dynamic and static elastic moduli, but the ratio of static to dynamic elastic modulus approaches 1 as temperature increases. The initial chord elastic modulus, which is measured at low strain level, is similar to the dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic moduli for various cement types, temperatures, and ages.     

The elastic moduli of particulate-filled polymers

The static and dynamic elastic moduli of particulate composites, consisting of two phases, one of which has isotropic–elastic and the other linear viscoelastic properties, were studied. For this purpose a model defining the approximate equations for determining the elastic modulus of a composite from the properties of the constituent materials was used. Classical theory of elasticity was applied to this simplified model of a composite-unit cell. The following assumptions are made: (i) filler particles are spherical; (ii) fillers are completely dispersed; and (iii) the volume fraction of fillers is sufficiently small, so that any interaction among fillers may be neglected. A class of iron-filled epoxy composites was subjected to tests in order to compare the theoretical values with the experimental results. The elastic modulus calculated by the expression derived in this study seems to corroborate with the experimental results fairly well. Finally, by applying the correspondence principle to this expression, theoretical relationships for the dynamic storage and loss moduli were also derived.     

Micromechanics Analysis of Porous and Filled Ceramic Composites

A finite element analysis was used to calculate the internal stresses and deformations everywhere within spherically filled or porous ceramic materials. This analysis accounts for interactions between inclusions and demonstrates the importance of these interactions on stress fields around the inclusions. Modulus of elasticity and Poisson's ratio were calculated for porous and filled ceramics. The predicted modulus is compared with experimental data for two glass composites; the agreement is excellent.     

Compression wood as a source of reinforcing filler for thermoplastic composites

Compression wood (CW) is a reaction wood formed in gymnosperms in response to various growth stresses. Many of the anatomical, chemical, physical, and mechanical properties of CW differ distinctly from those of normal wood. Because of different properties, the CW is much less desirable than normal wood. This study was conducted to investigate the suitability of CW flour obtained from black pine (Pinus nigra Arnold) in the manufacture of wood plastic composite (WPC). Polypropylene (PP) and CW flour were compounded into pellets by twin‐screw extrusion, and the test specimens were prepared by injection molding. WPCs were manufactured using various weight percentages of CW flour/PP and maleic anhydride‐grafted PP (MAPP). Water absorption (WA), modulus of rupture (MOR), and modulus of elasticity (MOE) values were measured. The results showed that increasing of the CW percentage in the WPC increased WA, MOR, and MOE values. Using MAPP in the mixture improved water resistance and flexural properties. CW flour of black pine can be used for the manufacturing of WPC as a reinforcing filler. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

轮胎用芳纶帘线的性能研究

研究了纶帘线的物化性能、动态力学性能及芳纶带束层（缓冲层）轮胎性能。试验表明，芳纶帘线具有高断裂强度、高模量、低断裂伸长率及独特的耐切割性能；其动态模量高、弹性好、滞后损失率小，耐疲劳性能较差；芳纶子午线轮胎高速性能好、质量小、滚动阻力低。     

Influence of Chemical Reactions in Magnesia-Graphite Refractories: I, Effects on Texture and High-Temperature Mechanical Properties

Four formulations of magnesia-graphite-aluminum metal (antioxidant) bricks were prepared from the same raw materials, using the standard commercial practices. Chemical analysis and determination of room-temperature modulus of rupture and Young's modulus, as well as a complete microstructural characterization of the as-received materials, were performed. For high-temperature modulus-of-rupture and Young's modulus data, test samples of the four brick compositions were heated to 1000°, 1200°, and 1450°C in flowing argon (<1000 ppm oxygen at 1000°C) and then loaded mechanically in flexure. Modulus-of-elasticity values ranged from 3.7 to 16.2 GPa and reflected strong effects of aluminum-metal concentration and treatment temperature. Young's modulus evolution with temperature was determined by the evolution of the microstructure in the bulk of the specimens. Modulus-of-rupture values ranged from 6 to 21 MPa, and their evolution with temperature was determined by the evolution of the microstructure in the bulk of the specimens at the lower testing temperatures ( T lessthan equal to 1200°C) and by phase assemblages in the surface regions of the specimens-essentially by the presence of the dense MgO zone-at 1450°C.     

PROGRESS REPORT ON INVESTIGATION OF SAGGER CLAYS. V. Preparation of Experimental Sagger Bodies According to Fundamental Properties1

This is a Fifth Progress Report giving the results obtained in a preliminary study of sagger bodies, which is a continuation of an extensive investigation of sagger clays for the purpose of determining the properties of clays and bodies best suited for sagger purposes. The report contains data on the modulus of elasticity, transverse breaking strength, plastic flow, thermal expansion, and resistance to failure due to heat shock of 55 sagger mixes representing 39 different bodies fired at either 1230°C or 1270°C. The 16 bodies prepared in duplicate were tested both after firing at 1230°C and 1270°C. All of these bodies were compounded with two clays whose properties are given in earlier progress reports, and a mixture of graded grog. The grog was graded into sizes so as to result in two types of bodies, those having (1) a coarse and open-grained structure and (2) a dense and fine-grained structure. The data on the fired bodies show that those containing the fine sizes of grog have the higher modulus of elasticity, transverse strength, and in the majority of cases, thermal expansion. Very little difference in total porosity of the two types of bodies is indicated although the rate of absorption shows large differences. The data obtained in this preliminary study indicate that those bodies having (1) a porosity of less than 25% (2) a low modulus of elasticity, (3) as high transverse strength as is compatible with the low modulus of elasticity, and (4) low thermal expansion below 250°C are the most desirable for sagger purposes.     

Comparison of recent rubber-elasticity theories with biaxial stress-strain data: the slip-link theory of Edwards and Vilgis

The Edwards-Vilgis (EV) slip-link theory (1986) derives the elastic free energy of a rubber-like network model containing stable and sliding network junctions (crosslinks and slip-links) and predicts both low-strain softening and high-strain hardening. The four-parameter stress-strain relations calculated by the theory for geometrically different deformation modes up to high strains were tested experimentally using published biaxial stress-strain data on simple covalently crosslinked networks. For networks with low degrees of strain softening and low extensibilities, the experimental dependencies could be described rather well but, generally, a simultaneous satisfactory fit to uniaxial, pure shear and equibiaxial data was not obtained. Systematic experiment-theory deviations exceeding 10% were observed and some of the parameters had a tendency to assume values lying outside the reasonably expected range. The prediction of a pronounced maximum in the strain dependence of stress supported by slip-links seems to be a reason for the discrepancy. Also, modeling of the high-strain singularity in entropy is done in the EV theory using a rather simple approximation. As a result, the finite extensibility contribution to the stress of a slip-link-free network model becomes improbably high and significantly exceeds that following, at a given modulus and locking stretch, from the rigorously derived Langevin-statistics-based eight-chain-network elasticity theory of Arruda and Boyce.     

On Mooney and Mooney stress relaxation. II. A nonlinear viscoelastic description: Experimental and numerical results

It has been investigated whether the stress build‐up and the stress relaxation involved in a Mooney test, with subsequent Mooney stress relaxation, can be described by nonlinear viscoelastic theory, more particularly the Wagner constitutive model. For this purpose, the viscoelastic behavior of three nonvulcanized EPDM materials, with similar Mooney viscosity but varying elasticity, has been studied. Relaxation time spectra were obtained from dynamic mechanical experiments, from which the step‐strain stress‐relaxation modulus was calculated. Stress build‐up experiments were performed with a cone and plate system in order to obtain the so‐called damping function (a measure for the deformation sensitivity) of the materials. Using these material functions, the Mooney test was successfully described with the Wagner constitutive model. Experimental and theoretical Mooney stress‐relaxation rates are in close agreement. The predicted Mooney viscosity is up to 25% lower than the measured value. This may be due to nonideal conditions during the Mooney test, such as inhomogeneous heating and secondary flows, and to inaccuracy of the damping function. The model calculations confirm the strong experimental dependence of Mooney measurements on small variations in instrumental conditions such as geometry, rotation speed, and so forth. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1220–1233, 1999     

Strength of Synthetic Single Crystal Sapphire and Ruby as a Function of Temperature and Orientation

The modulus of rupture of sapphire single crystals was determined as a function of temperature for specimens with orientations favoring plastic deformation and for specimens with unfavorable orientations. From 600°C. to l000°C., the strength of both types increased with increasing temperature, but the increase was more pronounced for the former. Ruby specimens oriented favorably for plastic deformation also showed a large increase in strength. It is conjectured that the increase in strength results from stress relief by microscopic plastic deformation.