Development of a three-directional stress cell and measurement of stress distribution on a backhoe bucket

In order to solve the problems between soil and construction machinery such as a hydraulic excavator, it is important to understand their mechanism. The purpose of this research is the development of a three-directional stress cell to measure stress distribution on a backhoe bucket to understand the mechanism of excavation. This three-directional stress cell can directly measure three-directional stresses simultaneously and has both strong structure and high sensitivity, which is not changed by the abrasion of the detecting plate. By using these cells, three-directional stress distribution on the bucket during excavation is measured. The results of the excavation experiments have given us the most fundamental theory of soil excavation, some hints to solve the problems between soil and construction machinery, and a future image of intelligent construction machinery with intelligent sensors.     

Residual stresses and warp generated by one-sided quench of an epoxy-resin beam

This paper discusses the warp and accompanying residual stress in a rectangular epoxy beam produced by water cooling its lower surface. First, the theoretical values of this warp and residual stress are obtained by the linear-viscoelastic theory. The specimen is then subjected to quenching. The variations in the warp are observed. After quenching, the residual stress is measured by a layer-removal method. The experimental and theoretical results are then compared and discussed.     

Electrochemical monitoring of aging embrittlement of steel for gas-cooled reactor pressure boundary components

The nondestructive testing technique is applied to evaluate the temper embrittlement of normalized and tempered steel; it is based on the anodic polarization behavior in calcium nitrate solution. The steel specimen is aged at a stress of 210 MPa at 450°C for up to 8800 h in order to examine the effect of applied stress on the enhancement of intergranular segregation of phosphorus. The secondary peak observed in the polarization curve for the material aged under stress was compared with that for the non-stressed. It can be quantified with the degree of intergranular segregation of phosphorus. The data suggest that the enhancement of phosphorus segregation due to the applied stress is only recognized after 3000 h of aging. This effect diminishes with increasing aging time.     

Some new techniques for scattered-light photoelasticity

This paper describes some new techniques for determining the directions of the secondary principal stresses and their difference in scattered-light photoelasticity. These new techniques do not employ the compensator and are capable of obtaining the same degree of accuracy as the compensator method.     

Radiation effects on creep rupture and fatigue strength of pure aluminum

Paper describes an experimental investigation on the effect of nuclear radiation on the creep rupture and fatigue strength of pure aluminum for the ratios of alternating stress to mean stress ranging from zero to infinity. It was found that not only was the strength of the material tested affected by radiation over a range of ratios of stresses, but also the brittle-ductile transition was influenced.Based upon the experimental results obtained, an analytical model was developed to correlate creep rupture, fatigue strength and radiation effect for various ratios of stresses. This information may prove to be valuable in dealing with the stress analysis of nuclear reactors.Paper was presented at 1966 SESA Annual Meeting held in Pittsburgh, Pa., on November 6–9.     

Experimental investigation of creep-crack-tip deformation using moiré interferometry

High-temperature moiré interferometry was applied to obtain full-field creep-crack-tip displacements of a three-point bend Al 2024-T4 specimen uner constant temperature of 200°C up to 720 hr.C ^* was evaluated by the moiré data obtained at discrete time intervals. Test results indicate that under steady-state creep condition, the creepcrack-tipv-displacement rate agrees with the asymptotic solution based on theC ^* integral. However, no creeping behavior was observed for the crack-tipu-displacement field aftert=276 hr. This discrepancy may be due to the initial large creep-crack-tip blunting and cavitation damage which alter the creep-crack-tip singular field such that theC ^* integral is no longer applicable to characterize the steady-state creep-crack-tip field. Postmortem studies of the tested specimen also revealed transgranular fracture path with the ordered grain boundaries perpendicular to the crack line, which may relate to the existence of the substantial crack-tip blunting and noncreeping behavior of theu-displacement field, i.e., the size and shape of material grain boundaries play an important role in the crack-tip-creeping behavior of the material.Paper was preseted at the 1991 SEM Spring Conference on Experimental Mechanics held in Milwaukee, WI on June 9–13.     

Large frequency bands viscoelastic properties of honey

Honey is a viscoelastic material which presents a crystallization phase transition at low temperatures. This phase transition limits the studies of dynamic behavior at high frequencies from the classical rheometry using time–temperature superposition (TTS). In order to characterize the viscoelastic properties of honey at high frequencies, we have developed a multiple ultrasonic reflection device (MUR). The viscoelastic properties of honey were measured by MUR and classical rheometry at high and low frequencies, respectively, between 13.1 and 31.3 °$°$C. Matching both results, we built the master curve over a frequency range covering nine decades, from which we determined the main rheological parameters of honey. Finally, from an inverse approach, we extracted from this master curve, the acoustical parameters for frequencies inaccessible by the ultrasonic methods.     

Determining stress intensity factors in orthotropic composites from far-field measured temperatures

We demonstrate the ability to determine stress intensity factors in orthotropic materials directly from measured temperatures away from the crack and using far-field expressions for the stresses. This is advantageous, recognizing that recorded thermoelastic data can be very unreliable near the tip of a crack. In addition to singular terms that govern in the immediate vicinity of the crack tip, the present series expressions for the stresses contain higher-order finite terms. Little measured input information is needed and data acquisition positions can be selected largely at the user's discretion.     

On convective stability of suspensions

Convective flow onset in a dilute suspension filling a horizontal layer heated from below is studied analytically. It is shown that at a certain concentration of the suspension, instead of Rayleigh cells, lower-scale eddies surrounding each of the dispersed-phase particles may appear in the system.Perm. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 44–47, May–June, 1996.