Identification of a non-linear spring through the Fokker–Planck equation

Standard methods for the dynamic identification of civil engineering structures and mechanical systems generally rely on the determination of eigenfrequencies/eigenvectors and damping. A basic assumption for the use of these methods is the linear elastic behaviour of the tested structures. Nevertheless many structures exhibit a non-linear behaviour even at low levels of external excitation. For instance, reinforced concrete structures cracked by shrinkage or by the overcoming of the concrete tensile strength, exhibit different values of the flexural stiffness depending on the opening of the cracks. In the present paper a new methodology is presented to identify the characteristics of a non-linear mechanical system using the Fokker–Plank Equation (FPE) that allows evaluating the probability density function of the response of structural systems loaded with Gaussian white noise.     

Resilient metal spring network silicone-matrix composite for separable interconnections

Resilient metal spring silicone-matrix conducting composites for separable interconnections in electronics were fabricated by the impregnation of silicone into a preform comprising randomly oriented C-shaped Cu-Be springs and a small proportion of Sn-Pb solder, which served to connect the springs at some of their intersections. Composites containing 6.1-9.8 vol.% total filler exhibited volume electrical resistivity 0.5-1.0 mΩ.cm and contact resistivity (with copper) 11-17 mΩ.cm². A compressive stress of about 30 kPa was needed for the low contact resistivity to be reached. The volume 17-26% and the contact resistivity increased by 5% after heating in air at 130-150°C for seven days. Composites containing <9 vol.% total filler showed no stress relaxation for seven days at 6.0% strain.     

Investigating the benefits of using circular die springs instead of rectangular die springs

Die springs with rectangular cross section (rectangular die springs) are common in the industry. However, the production of rectangular die springs is difficult, and the cost of production is high. In this study, we examined the use of die springs with circular cross section (circular die springs), which are both easier to produce and less costly, in place of rectangular ones. To this aim, the fatigue life values of both die spring with equivalent specifications were compared experimentally. The results obtained were transferred to the finite element methods software to run the simulation of the fatigue test. From the experimental results obtained, it has been observed that using circular die springs in place of rectangular die springs is always possible, provided that the springs are guided with cast polyamide guides.     

下切式斜刃剪板机压紧装置的设计

剪板机是板材轧制生产工艺中重要的辅助设备之一,其工作状况好坏将直接影响到整个生产线的生产能力及工作效率。针对10 mm剪板机,介绍了其压紧装置的主要结构、工作过程以及压紧弹簧的设计计算。     

Collapsed spring observations in arson investigations: A critical metallurgical evaluation

Observation of collapsed coiled (steel) furniture springs has been utilized for several decades or more by arson investigators as an indicator of whether an accelerant or smoldering source (such as a cigarette) caused a fire. This paper cites the contradictory literature, synopsizes metallurgical phenomena operative when coiled steel springs are subjected to fires, and presents empirical data from U.S. Federal Bureau of Investigation (FBI) Laboratory testing. It is concluded that observation of the collapsed state of coiled furniture/bedding springs is not a reliable indicator of whether a fire was initiated by a smoldering cigarette or accelerated by the presence of a hydrocarbon.     

Spring stiffnesses of composite circular springs with extended flat contact surfaces under unidirectional line-loading and surface-loading configurations

Theoretical expressions based on the principle of minimum potential energy are presented which describe the stiffnesses of mid-surface symmetric, woven composite circular springs with extended flat contact surfaces subject to unidirectional line and surface-loading configurations. Three-dimensional finite element analysis has been employed to study the transverse shearing effects. Eighteen woven fibre/epoxy composite circular springs with extended flat contact surfaces in different radii and thicknesses were fabricated and tested. Comparison studies of the results obtained from both the analytical and numerical models are made with experimental data, and the results are found to be satisfactory. The semi-included angle of the flat contact surface is vital parameter to spring stiffnesses of the composite spring.     

Simple modelling of the effects of exploitation on hot springs, Geyser Valley, Wairakei, New Zealand

Many hot springs in Geyser Valley declined and ceased flowing during well testing (1950–1958) or the early stages of development (1958–1964) of the Wairakei field, North Island, New Zealand. A simple model that considers mixing, geothermal reservoir pressure, and Darcy flow is applied to analyse the changes in flow rate and chemistry of spring SP18. The model suggests that prior to the testing the observed flow rate of 3 l/s was comprised of about 2.1 l/s of water from the deep reservoir and about 0.9 l/s from shallow groundwater. As the pressure in the reservoir decreased as a result of exploitation, the reservoir component declined but the groundwater component remained near constant until the spring had nearly ceased flowing. The model reasonably predicts the flow cessation date for four other springs (Group A) but poorly predicts that for seven other springs (Group B). These two groups of springs do not appear to be clustered at the ground surface. The pressure–elevation relationship suggests that the Group A springs feed from within the shallower Waiora Formation and Group B springs from within the deeper Wairakei Ignimbrite Formation. The observation that declines of chloride concentrations in Group A springs occurred at least three years before those in springs of Group B is consistent with the finding that Group A springs have a shallower feeder depth.     

碟簧支承高速圆瓦推力轴承性能分析及标高误差影响研究

针对立式干气密封氦气压缩机轴系用高速圆瓦推力轴承承载性能问题,建立碟形弹簧支承推力轴承的润滑性能计算模型和搅拌功耗计算公式,分析圆形瓦推力轴承随转速、载荷的性能变化规律及标高误差对轴承润滑性能和支承碟形弹簧性能的影响。研究表明：轴承搅拌功耗与摩擦功耗的比值随转速和载荷的增大分别增大和减小,最高转速下搅拌功耗是摩擦功耗的两倍以上;弹性自适应调节技术可以有效改善瓦块标高误差对轴承承载平面度的影响,但各瓦标高误差越大,各瓦润滑性能及碟形弹簧积累的变形能差异也越大。因此,对于高速立式转子系统,推力轴承设计必须考虑搅拌功耗对轴承温升的影响,同时需要进一步研究标高误差对转子高速稳定性的影响。     

弹簧用高强钛合金的研究进展

β钛合金因综合性能优异（良好的冷热成形性、时效强化效应明显、耐蚀等）成为高强钛弹簧的理想选择。简述了2种弹簧用高强β钛合金Timetal LCB和Ti-B20的研发现状,并指出钛合金大量用作弹簧的关键在于合金性能的提高以及成本的降低。