Analytical solution for the axisymmetric plane strain electroelastic dynamics of a special non-homogeneous piezoelectric hollow cylinder

By virtue of the introduction of a dependent variable and the separation of variables technique, the axisymmetric plane strain electroelastic dynamic problem of a special non-homogeneous piezoelectric hollow cylinder is transformed to a Volterra integral equation of the second kind about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solutions of displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow cylinder with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are finally presented.     

Neutron Stress Measurement of W‐Fiber Reinforced Cu Composite

Stress measurement methods using neutron and X‐ray diffraction were examined by comparing the surface stresses with internal stresses in the continuous tungsten‐fiber reinforced copper‐matrix composite. Surface stresses were measured by X‐ray stress measurement with the sin²ψ method. Furthermore, the sin²ψ method and the most common triaxal measurement method using Hooke's equation were employed for internal stress measurement by neutron diffraction. On the other hand, microstress distributions developed by the difference in the thermal expansion coefficients between these two phases were calculated by FEM. The weighted average strains and stresses were compared with the experimental results. The FEM results agreed with the experimental results qualitatively and confirmed the importance of the triaxial stress analysis in the neutron stress measurement.     

Procedures for analysis of strain transfer in the acetabular region in vitro

The failure of acetabular cups via loosening, migration or fracture is partially related to the stress distribution existing in the acetabular region. The complexity of the investigation of these stresses demands the application of a variety of model testing techniques involving combined embedded strain gauging, finite element analysis, transmission and reflective photoelasticity and crack propagation studies. The application of these procedures are described and the difficulties of obtaining representative loadings and restraints are commented upon.     

Temperature–stress–strain trajectory modelling during thermo-mechanical fatigue

The isothermal strain‐life approach is the most commonly used approach for determining fatigue damage, particularly when yielding occurs. Computationally it is extremely fast and generally requires elastic finite element analyses only. Therefore, it has been adapted for variable temperatures. Local temperature—stress–strain behaviour is modelled with an operator of the Prandtl type. The hysteresis loops are supposed to be stabilized and no creep is considered. The consequences of reversal point filtering are analysed. The approach is finally compared to several thermo‐mechanical fatigue tests and the Skelton model.     

Strain waves in colliding bars having nonparallel faces

The paper reports the experimental investigation data for the effect that nonparallel faces of bars under impact exert on the parameters of longitudinal and bending strain waves generated in the bars. The changes in stress magnitudes in the bar under impact with growing angle of the impact faces offset are described. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 73–78, November–December, 2006.     

Spatiotemporal aspects of jerky flow in Al–Mg alloys, in relation with the Mg content

The spatiotemporal aspects of the Portevin–Le Chatelier effect in Al–Mg alloys are investigated using direct observations of the sample surface with a digital camera. Optical measurements of the surface profile using a white light interferometer allow the estimation of the local strain and strain rate associated with the bands. The effect of Mg content on instability characteristics is analyzed. The reloading time is shown to depend on the Mg content only at the strain and strain rates where type C bands are observed.     

糯扎渡心墙堆石坝心墙方案比较研究

糯扎渡工程在可行性研究阶段，比较了直心墙堆石坝和斜心墙堆石坝两种方案，分析表明，直心墙堆石坝在坝坡稳定性、坝体应力及抗震性方面均满足设计要求，且在地形地质条件、基础处理、抗震性能、施工方便性、工程造价等方面不同程度地优于斜心墙堆石坝，因此，设计最终选择直心墙堆石坝方案。     

An investigation of crack closure and the propagation of semi-elliptical fatigue cracks in Q1N (HY80) pressure vessel steel

The results of an experimental investigation of the effect of crack closure on the propagation of semi-elliptical fatigue cracks are presented. Load-shedding fatigue threshold tests were carried out at stress ratios of 0.2, 0.35, 0.5 and 0.7. Crack closure was measured at the surface and depth positions using backface strain gauges, near-tip gauges, and a clip gauge. Differences between the surface and depth growth behaviour are explained by considerations of the effects of the transition from plane stress conditions at the surface to plane strain conditions at the depth. The effects of stress ratios are attributed largely to differences in the crack opening displacement, which result in asperities coming into contact to induce roughness-induced crack closure.     

Flow stress of high density polyethylene and nylon 66 at high rates of strain

Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 10³ s^?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 10³s^?1.     

Optical analysis of crack tip stress fields: a comparative study

Four optical techniques for evaluating stress intensity factors in opaque specimens are described in outline, and compared for both an artificial crack and a fatigue crack. The results are compared to a standard solution for the geometry considered. All the techniques gave acceptable results over a range of stress levels and crack lengths. The methods of caustics and strain gauges were less good, whilst photoelasticity gave consistent results over a wide range of stress levels. Comments on the ease of application and the resource implications are also made in order to assist practitioners.