Random errors caused by temperature in magnitude of principal strains evaluated ith 3-element strain gauge rosettes

The effects of the uncertainties associated ith the apparent strain and gauge factor data, given by the manufacturer, in the evaluation of principal strains are examined. Principal strains are obtained by a reduction of the strains measured ith electrical resistance strain gauge rectangular or delta rosettes. The theoretical analysis points out the relevance of the effects caused.     

Computer aided analysis of strain rosette data

In this paper a computer program has been developed for analysing the strain gauge rosettes by considering the transverse sensitivity of all gauges. The program is capable of calculating principal strains, maximum shear strain, principal stresses, maximum shear stress and principal directions from the data obtained by using strain gauge rosettes of various configurations. The gauge factor and transverse sensitivity of all gauges in the rosette must be the same.     

Observations of sol-gel deposited lead zirconium titanate films using transmission electron microscopy and X-ray diffraction

Abstract

The microstructure of sol-gel PbZr _x Ti_1-x O₃ (PZT) thin films has been reported to depend strongly-upon deposition and thermal processing conditions. In this paper we describe two systematic series in which the thermal treatment of PbZr_0.3Ti_0.7O₃ films on Pt/Ti/SiO₂/Si substrates is varied. The films are deposited by repeated spin depositions and anneals, and consist of eleven individual layers of PZT. We find that we can obtain single phase perovskite layers at processing temperatures above 500°C. At 500°C and a 150s anneal for each depositions only partial transformation of the layer occurs. Some regions have nucleated or transformed more readily than others, leading to the formation of ‘rosettes'. Small changes in the temperature ramp have a large effect on the degree of crystallographic texture of the films. This is correlated with changes in the structure of the Ti layer below the Pt, and is a result of changes in the nucleation rate of different crystallographic orientations of PZT on the Pt. Evidence for an interfacial phase, with lattice parameter approx 10 Å, is presented.     

An experimental investigation on a crack propagating from a geartrain housing in an asphalt milling machine

The present paper deals with the analysis of a crack that developed in a gearbox panel mounted on a cold planer machine. The crack was discovered after approximately 950 work hours, after that an oil leakage was detected: at that stage of propagation it was about 40 mm long. A research was therefore tackled to experimentally reproduce the history of load that had led to cracking and to estimate the local amount of stress and strain. For this purpose, a not cracked identical panel was instrumented by three-grid strain gauge rosettes. Then, an experimental campaign was arranged to reproduce loads during assembly and in operating conditions. In particular, the most critical and frequent task, obstacle overcoming, was simulated 16 times in about two hours time. The most interesting result was that stress has always an increasing trend during stepping up and stepping down. This event can be regarded as a mechanical hysteresis: the primary cause, standing in the self-loosening of two bolts connecting the panel to the machine frame, due to engine induced vibrations, was found out. The mechanism leading to failure was therefore identified, as testified also by the maximum principal stress direction being perpendicular to that of crack propagation. The crack criticality at the current propagation stage was finally discussed, estimating its stress intensity factor.     

A Comparison of Various Patterns of Three‐Dimensional Strain Rosettes

Abstract: The strain tensor, principal strains and precision of the estimates of these values are derived for a range of different layouts of three‐dimensional strain rosettes. These values are based on the Monte Carlo technique applied to experimental work which was carried out on transducers tested in different laboratories. The estimates of precision are determined theoretically and compared with results based on experimental findings. A new design of a miniature tri‐rectangular tetrahedral rosette was manufactured and tested. Results suggest that this transducer does not perform as well as the rectangular patterns.     

基于光纤光栅应变花的平面应变状态实验分析

提出并实现了直角与三角形两种光纤光栅(FBG)应变花方案,分别由在1根光纤上实现准分布的3个FBG制成。将之粘贴存等强度梁上,判断主应变方向及大小,研究其平面应变测量性能。试验结果显示,测量主应变方向同实际方向符合,两种应变花测量结果一致。     

Rosettes and Other Arrangements of Circles

The process of design in art and architecture generally involves the combination and manipulation of a relatively small number of geometric elements to create both the underlying structures as well as the overlaid decorative details. In this paper we concentrate on patterns created by copies of just a single geometric form—the circle. The circle is an extremely significant shape. By virtue of its simplicity and its topology it has been highly esteemed by many different cultures for millennia, symbolising God, unity, perfection, eternity, stability, etc.     

Experimental evaluation of a method for separating axial and bending stresses from strain gauge measurements taken on one surface by three-element rosettes

A method is described and results presented for the separation of axial and bending components of stress taken on one surface of a structure with a two-tier, three-element rosette assembly.