正交各向异性材料电阻应变测量的横向效应修正

本文讨论了电阻应变片测量正交各向异性材料应变的横向效应修正。将测量各向同性测量的表观弹性模量、表观泊松比推广应用于正交各向异性材料，得出了一组与广义虎克定律形式上相同的计算式，并讨论了横向效应对应力测量精度的影响。     

Load and Boundary Condition Calibration Using Full-field Strain Measurement

For critical load bearing structures, it is often necessary to experimentally determine the load distribution on the structure so that accurate finite element models can be developed for stress and fatigue life predictions. An inverse problem approach is presented here for computing or calibrating the loads and boundary conditions acting on a structure. This enables the creation of more accurate finite element models, especially for structures that have complicated load distribution and compliant boundary conditions. The method presented here involves minimizing the least square error between the strains computed using the finite element model and the strains and displacements obtained experimentally. The nodal loads and the compliance at fixed boundaries are treated as the variables in the optimization problem. The compliance is modeled as springs attached at the nodes that are on the boundary where the structure is restrained. The method is verified by computing the loads and boundary conditions when displacements, maximum shear strain or both are available at large number of points on the surface of the structure. The experimental data set was generated using the luminescent photoelastic coating (LPC) technique.     

Bearing Load Measurement in a Hydropower Unit Using Strain Gauges Installed Inside Pivot Pin

To determine a machine’s mechanical condition it is of importance to know the radial bearing forces in the machine. Radial forces are caused by magnetic pull forces in the generator, clamped shafts, mass unbalance and flow properties around the turbine. Measuring the shaft displacement in the bearing or the bearing housing acceleration is not sufficient for status determination of a vertical hydropower unit. It is the magnitude and frequencies of the radial forces in combination with structure properties which give information as to whether a measured value is harmful or not. This paper presents an alternative method for measurement of radial bearing load in a hydropower unit. The method presented in this paper is based on strain measurements on pivot pins. The pivot pins are placed behind the bearing pad and the radial loads acting on the pad propagate through the pivot pin. New pivot pins were purchased and equipped with strain gauges. The new pivot pins were calibrated and a transfer function between applied load and measured output voltage was identified for each pivot pin. After calibration the pivot pins were installed in a vertical hydropower unit. Measurements were performed for several different operating modes of the hydropower unit. To verify that the measured load levels were of right order of magnitude, the radial bearing loads were calculated from numerical simulations of bearing properties and shaft eccentricity measurements. The two methods for determining bearing load showed almost the same results. This indicates that either method can be used to determine bearing load.     

测量高塑性变形用20%大应变应变计

本文主要介绍了国内最新研制成功，用于测量材料高塑性变形量的新型传感器件－２０％大应变应变计的产品性能和应用技术、为分析材料进入塑性变形区复杂的应力应变分布，提供了新型、准确、简便的测量手段。     

A Procedure for Accurate One-Dimensional Strain Measurement Using the Grid Method

This paper deals with the accurate calculation of strain using the grid method. The strain field is first directly deduced from the fringe pattern without calculating the displacement field. This procedure is validated with two numerical examples. Two types of experiment are then carried out: a translation and a tensile test. It is observed that some additional fictitious strains appear in both cases. They are due to two main reasons which interact with each other: the grid defects and the displacement of the grid lines during testing. A suitable procedure is proposed to cancel out these fictitious strains. This procedure is successfully applied in two cases of fringe patterns.