Strain-energy density and fracture-process zone. Report 1. Theoretical premises

A representation is proposed for the total strain-energy density (SED) in dimensionless form. The -distribution of the elastic and plastic parts of the total SED, and also the strain-energy-density factor S for the full range of mixed fracture modes under plane strain and a plane stress state are presented. Differences, as defined by the strain-energy-density factor, are established between fracture conditions under plane strain and a plane stress state. A general relationship between strain-energy density and a material parameter (the size of the fracture-process zone) is brought to light in dimensionless form. The relationship obtained predicts the pattern of continuous variation in the size of the fracture-process zone from static to cyclic material fracture. A material constant can be considered one of the consequences of fracture. Equations are proposed for calculation of the size of the fracture-process zone under a plane stress state and plane strain over the full range of mixed deformation modes with respect to standard mechanical properties of the materials.Translated from Problemy Prochnosti, No. 10, pp. 3–17, October, 1995.     

Strain-energy based homogenisation of two- and three-dimensional hyperelastic solid foams

A possible classification of cellular solids can be made based on the dimension into honeycombs and foams. In numerical simulations 2D models that are employed primarily to study honeycombs can also be used to model open-cell foams. Thereby, a loss of information regarding the 3D connectivity of the microstructure is involved. To answer the question how the missing third dimension in 2D models affects the overall properties, spatially periodic 2D and 3D model foams are adopted. From the point of homogenisation, a strain-energy based scheme is used for adequately determining the effective mechanical properties at large strains. The key idea behind this method is to use directly the equivalence condition between the meso-strain energy and the macro-strain energy. In a first step a representative volume element with the given microstructure and a corresponding volume element containing the effective medium are subjected to equivalent states of deformation. Subsequently, the macroscopic stress-strain relationships are determined by volume-averaging of the stored strain energy. The results of some fundamental loading cases indicate that both model foams represent the deformation characteristics of hyperelastic solid foams like localized bending and elastic buckling. In addition, the development of anisotropy due to microstructural changes at large strains can be traced with both model foams. Nevertheless, the different cell morphology affects the stress-strain curves in a quantitative manner.     

Experimental confirmation of the optical-trapping properties of cylindrical objects

A sophisticated modeling program was used recently to predict the trapping and the manipulation properties of elongated cylindrical objects in the focal region of a high-intensity laser beam. On the basis of the model, the cylinders should align their longest diagonal dimension with the propagation axis of the laser beam and follow the beam when it is displaced transverse to the cylinder's central axis. Experimental confirmation of the cylinder's behavior is presented and confirms the suitability of the enhanced ray-optics approach to modeling micrometer-scale objects in optical-trap environments.     

Experimental confirmation of the transversal symmetry breaking in laser profiles

The Snell phase effects on the propagation of optical beams through dielectric blocks have been matter of recent theoretical studies. The effects of this phase on the laser profiles have been tested in our experiment. The data show an excellent agreement with the theoretical predictions confirming the axial spreading modification and the transversal symmetry breaking. The possibility to set, by rotating the dielectric blocks, different configurations allows to recover the transversal symmetry. Based on this experimental evidence, dielectric blocks can be used as alternative optical tools to control the beam profile.     

低温加注阀关闭状态确认试验研究

为验证采用传感器监测加注阀入口容腔压力对加注阀关闭状态判断的可行性,建立了低温加注阀关闭状态确认试验系统。研究加注阀无泄漏和加注阀预制泄漏通道两种状态下通过孔板模拟加注连接器顶杆中心小孔排放后加注阀入口容腔压力变化及连接器脱落前后加注阀泄漏量的变化,开展了加注阀关闭状态确认方法原理性试验和数值仿真研究。研究结果表明:加注阀无泄漏和存在泄漏时从压力传感器能明显监测到压力变化,且连接器脱落前后泄漏量变化较大,数值仿真结果与试验结果吻合较好。     

Energy density zone model and fatigue life prediction considering microscopic effects

An energy density zone (EDZ) model is developed for the prediction of fatigue life. The microscopic effects can be involved in the EDZ model. Three scale transitional functions in the model are utilized to describe the trans‐scale behaviours of fatigue failure from micro‐scale to macro‐scale. Fatigue failure behaviours of a low‐alloy and ultra‐high‐strength steel material (i.e. 40CrNi2Si2MoVA steel) is investigated. Two fatigue parameters in the model are determined from the experimental S–N curves for the smooth cylinder specimens (the stress concentration factor, SCF, K_t = 1). Then, fatigue lives of notched specimens with SCFs K_t = 2 and K_t = 3 are predicted respectively by the proposed model. The predicted S–N curves are satisfactory in comparison with the experimental results. Scatter of the fatigue test data can be depicted when the microscopic effects are considered. Influences of microscopic effects on the fatigue behaviours are explored by means of numerical simulations.     

Experimental characterization of focusing by high-numerical-aperture zone plates

High-numerical-aperture zone plates have important applications in high-resolution optical maskless lithography as well as scanning confocal microscopy. We describe two methods to experimentally characterize the focusing properties, i.e., the point-spread function, of such diffractive lenses. The first method uses spot exposures in photoresist and the second uses a conventional knife-edge scan. The experimental results agree well with rigorous theoretical calculations.     

Experimental studies of longitudinal and perpendicular high density recording

Single layer and double layer Co-Cr disks of various coercivities were sputter-deposited on rigid substrates and magnetic parameters measured. Record and playback properties were studied using both ferrite and thin film heads under identical system environments. A well optimized Ni-Co plated longitudinal disk was used as a benchmark throughout this investigation for direct comparison. With the objective of using "off the shelf" ring heads to bring up the perpendicular recording technology on rigid substrates, it was found that the performance of both our preliminary single and double layer Co-Cr perpendicular disks were at least as good as the well optimized longitudinal disk. The double layer disks have an added advantage of lower write current. Signal processing via Hilbert transform using both rectangular and Hamming windows was also studied and applied to the output waveforms.     

Effects of work zone configurations and traffic density on performance variables and subjective workload

This paper investigates the effect of changing work zone configurations and traffic density on performance variables and subjective workload. Data regarding travel time, average speed, maximum percent braking force and location of lane changes were collected by using a full size driving simulator. The NASA-TLX was used to measure self-reported workload ratings during the driving task. Conventional lane merge (CLM) and joint lane merge (JLM) were modeled in a driving simulator, and thirty participants (seven female and 23 male), navigated through the two configurations with two levels of traffic density. The mean maximum braking forces was 34% lower in the JLM configuration, and drivers going through the JLM configuration remained in the closed lane longer. However, no significant differences in speed were found between the two merge configurations. The analysis of self-reported workload ratings show that participants reported 15.3% lower total workload when driving through the JLM. In conclusion, the implemented changes in the JLM make it a more favorable merge configuration in both high and low traffic densities in terms of optimizing traffic flow by increasing the time and distance cars use both lanes, and in terms of improving safety due to lower braking forces and lower reported workload.     

Photon-measurement density functions. Part 2: Finite-element-method calculations

This paper presents a method to calculate photon-measurement density functions (PMDF's), which were introduced in Part 1 [Appl. Opt. 34, 7395-7409 (1995), for near-infrared imaging and spectroscopy in complex and inhomogeneous objects through the use of a finite-element model. PMDF's map the sensitivity of a measurement on the surface of an object to the perturbations of the optical parameters within the object. Data are presented for homogeneous and layered circular objects and for a complex two-dimensional model of a head. In particular the influence of the optical parameters on the shape of the PMDF and the distortions caused by boundary layers and complex inhomogeneties are investigated.     

Experimental confirmation of the J integral as a thin section fracture criterion

Recent experimental results have indicated that the J integral may serve as a valid parameter for predicting elastic-plastic plane strain fracture. Similar confirmation for thin section or predominantly plane stress fracture does not exist. The purpose of this investigation was to examine experimentally the validity of a J integral fracture criterion by performing tests on thin section metals. Seven alloys and three specimen configurations were tested under conditions that caused elastic-plastic fracture. Results indicated that a critical value of J existed for each alloy that could be used as a fracture criterion.     

Experimental fundamentals of tribofatigue. Part 2

We present a general survey of the experimental results that can be regarded as fundamental for tribofatigue (the theory of wear-fatigue damage to power systems of machines). In Part 2, we describe and analyze basic regularities of the inverse effect under the conditions of friction-mechanical fatigue. “Tribofatigue” Scientific-Industrial Concern, Gomel, Belarus. Translated from Problemy Prochnosti, No. 4, pp. 17–20, July–August, 1997.     

Experimental study of density and viscosity of four-component liquid systems

Results are offered from an experimental study of the P-V-T functions and viscosity of multicomponent liquid systems, for which an equation of state is developed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 4, pp. 617–620, October, 1981.     

“需确认的过程”的识别与确认

长期以来,"生产和服务提供过程的确认"一直是贯标组织和审核员理解与实施ISO 9001标准的难点所在,为使标准关于过程确认的要求更易于理解和实施,ISO9001:2008标准7.5.2条款第一段,在语言描述方面较2000版标准发生     

Comparison of the results of interference and numerical determinations of stream density in a separation zone

Density fields in the separation zone are determined from interferograms of supersonic turbulent flow over a body. A comparison is made with the results of numerical calculations by a combined scheme.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 5, pp. 769–773, November, 1985.     

消除爆炸焊接中心不结合区的实验研究

从理论上分析了消除爆炸焊接中心起爆中心不结合区的可能性 ,并分别采用中心起爆和边缘起爆对SA2 6 6 - 30 4爆炸焊接复合板的结合界面及地基下应力进行了对比测试 .实验结果表明只要合理选择装药参数 ,采用中心起爆可获得最佳的焊接界面 .     

Experimental investigation of the transformation zone of tetragonal zirconia polycrystalline ceramics

Stress-induced martensitic transformation plastic zones of ceria-stabilized tetragonal zirconia polycrystalline ceramics, under some typical loading conditions, were studied by Moiré interferometry. The full-field fringe patterns, including u-fields and v-fields, were acquired. According to these patterns, the transformation zone shape and transformation plasticity distributions of the specimens were obtained. The experimental results show that the stress-induced transformation at room temperature is concentrated in some narrow bands and the transformation plasticity is not uniform within the transformation zone. Experiments also reveal that the transformation zone with a characteristic elongated shape ahead of the notch, in a single-edge notch bending specimen, is obviously different from that resulting from some constitutive relation of transformation. This work provides a significant experimental foundation for establishing the theoretical models of transformation toughening.