Stress Measurement Test Research Articles

Research on non-contact dynamic stress calibration method of fan blade on simulation

In order to establish the non-contact measurement method of fan blade dynamic stress, the most important thing is to establish the method of fan blade dynamic stress calibration. In this paper, the static virtual loading and harmonious response analysis of fan blades in the simulation platform, and the calibration equation between the blade tip displacement and the blade dynamic stress is established. Finally, the calibration equation is verified and the error analysis is carried out by simultaneously carrying out contact and non-contact dynamic stress measurement tests on the rotor test bench.

Residual stress and microstructure control in welding of SA508 low alloy steel

Various types of solid-state phase transformation (SSPT) occur during the SA508 steel welding process, especially for multi-pass welding. The multiple thermal cycles lead to a more complex microstructure distribution and significantly influence the residual stress distribution. Therefore, to better control the microstructure and residual stress, it is necessary to optimize the process parameters which are closely related to the welding thermal cycles. This study established a thermo-mechanical-metallurgical multi-field coupling model and then validated it using X-ray and neutron diffraction residual stress measurement tests. Furthermore, the influence of welding heat input and preheating temperature on the formation of phase constituents and the ultimate residual stress field were analyzed in detail, concomitantly with a comprehensive discussion on their underlying mechanisms. The results showed that the increase of heat input expanded the domain occupied by the bainite phase, accompanied by the increase of compressive stress region. Moreover, the rise of preheating temperature promoted the bainite phase transformation, thus decreasing the longitudinal compressive stress and the stress gradient. The variation induced by welding parameters was closely related to the welding cooling rates. To obtain a full bainite and low residual stress condition of welded joint, it becomes imperative to exercise control over cooling rates, maintaining them at approximately 1.0 °C/s.

Methodology for Mapping the Residual Stress Field in Serviced Rails Using LCR Waves.

Non-destructive stress measurement by ultrasonic testing is based on calculating the acoustoelastic modulus obtained from the relationship between material stress and sound wave velocity. A critically refracted longitudinal (LCR) wave, which is a bulk longitudinal wave penetrating below and parallel to the surface below an effective depth, is most suitable for ultrasonic stress measurement tests because it exhibits a relatively large change in travel time in response to a change in stress. In particular, the residual stress distribution through the thickness of the subject can be calculated if transducers of different frequencies are applied because of the characteristic of propagation to different depths of penetration depending on the frequency. The main purpose of this study was to visualize the internal or residual stress distribution through the thickness of rails using LCR waves. To this end, LCR probes with different center frequencies were designed and manufactured, and the residual stress values ​​of an unused railroad rail and two used railroad rails operated under different conditions were calculated. This was done using the ultrasonic signals received from each probe, of which the distributions were mapped. Through these mapping results, different residual stress values could be calculated according to the depth. The differences in residual stress generation and distribution according to the conditions surrounding the contact between train wheels and rails, and their characteristics, were visualized and analyzed. As a result, it could be concluded that the non-destructive evaluation technique using LCR waves could detect differences in the residual stress of a rail, and thus can be used to measure the residual stress of the rail accurately.

Strength-based design of a fertilizer spreader chassis using computer aided engineering and experimental validation

In this research, stress measurement tests and advanced application algorithms based on computer-aided design and engineering (CAD and CAE) were developed and tested. The algorithm was put implemented through a case study on the strength-based structural design and fatigue analysis of a chassis. This algorithm consists of numerical and experimental methods and additionally includes material tests, three-dimensional CAD, a finite element method (FEM)-based analysis procedures, a structural optimization strategy, prototype production, stress tests, a fatigue analysis, and design verification procedures. In the optimization study targeting the optimum chassis weight/strength ratio, two chassis prototypes, with 8 mm and a 5 mm wall thicknesses, were manufactured to verify the structural analysis and experimental tests. As a result of the FEA analyses, for 20 kN, which is the target load value of the chassis, for chassis thicknesses t = 5 mm and t = 8 mm, the maximum tensile strength was obtained as 93 MPa and 83 MPa, respectively. Thus, the material gain of 35.85 kg mass was achieved, and chassis utilization efficiency was increased. This research provides a useful methodology for experimental and advanced CAE techniques, especially for further research on complex stress and deformation analysis of chassis that are desired to be of optimum weight/strength ratio.

Optimization of Hot Workability of Cu-Cr-Zr-Ti Alloy Through Development of a Processing Map

Abstract Owing to high thermal conductivity, copper-based alloys are used to fabricate heat transfer elements of rocket engines, such as combustion chambers, nozzle liners, and metal gaskets. One such alloy is the Copper-Chromium-Zirconium-Titanium (Cu-Cr-Zr-Ti) alloy, which possesses a good combination of thermal conductivity and strength at high temperatures. Thermomechanical processing is an important step in the realization of the various aforementioned heat transfer elements from this alloy. Hence, it is imperative to understand the hot deformation behavior of the alloy as a function of the process variables such as temperature and strain rate. An attempt is made to study the hot deformation behavior of the Cu-Cr-Zr-Ti alloy by subjecting it to uniaxial hot compression tests in the temperature range of 600°C–800°C and strain rate range of 0.001–10 s−1. The flow stress measurement tests were conducted up to a true strain of 0.5 using a Gleeble 3800 simulator. The nature of the flow curves obtained at the completion of the tests indicated the occurrence of dynamic recrystallization (DRX) at deformation temperatures greater than 700°C and with a strain rate below 1 s−1. The work hardening rate was plotted as a function of effective flow stress to assess the flow softening behavior due to DRX at different deformation conditions. A processing map delineating the stable and unstable regions during hot working is developed and validated by observing the microstructures in the corresponding domains. Optimum processing parameters (temperature of 750°C and strain rate of 0.1–10 s−1) for hot working of the alloy were proposed based on a contour map of efficiency of power dissipation. Two constitutive equations are also established: one using the Hyperbolic sine law as proposed by Sellars and McTegart and the other using Kocks Mecking analysis.

Measurement of In-situ Stress in Ningdong Mine Area and In-situ Stress Distribution Law

In order to acquire the in-situ stress state and its distribution law in Ningdong mine area, in-situ stress measurement tests were conducted respectively in the coal mine of Zao Quan mine, Yang Changwan mine and Mei Hua mine. 3D in-situ stress states of five test points in three levels were obtained by using 3D stress reliving measurement technology and hollow inclusion strain gages combined with experiments of the rock core confining pressure test. The general distribution state and characteristics of in-situ stress field in Ning Dong mine area can be concluded as follow: Horizontal stress field acts as the main part, the direction of principal stress is horizontal basically the direction of the maximum principal stress N50.3 E in average. In-situ stress value in mine area increases linearly with the mining depth, and establish the model of in-situ stress of mine area.

Vibration Traits and Mechanism Analysis of an Engine Blades Fracture Failure

For the failure of twice centrifugal wheel blade fracture of an engine, the paper obtained the vibration traits of the fracture failure by analyzing the gross trend, time domain wave type, axial trajectory map and frequency spectrum diagram of the vibration signals at the failure time. The failure mechanism was analysed systematically based on the failure analysis of the fracture vane, the vibration characteristic analysis and stress distributing research of the vane. Finally, the paper verified the failure mechanism through the vane dynamic stress measurement test.

Hydraulic fracturing stress measurement in underground salt rock mines at Upper Kama Deposit

The paper reports the experimental results on hydraulic fracturing in-situ stress measurements in potash mines of Uralkali. The selected HF procedure, as well as locations and designs of measuring points are substantiated. From the evidence of 78 HF stress measurement tests at eight measuring points, it has been found that the in-situ stress field is nonequicomponent, with the vertical stresses having value close to the estimates obtained with respect to the overlying rock weight while the horizontal stresses exceed the gravity stresses by 2–3 times.

Research of Remote Monitor System for Agriculture Equipment Based on Embedded System and Wireless Network

A remote monitor system was came up with in this paper aiming at dynamically monitor agriculture equipment working status. The system used Zigbee based portable data terminal as data collector, ARM11 based embedded system as wireless gateway, and laptop as remote monitor device. An embedded software based on WinCE6.0 was developed for data processing and transmitting, and a VC++ based software was developed for remote monitor, data store and alarm. In order to verify the performance of the system, a working subsoiler stress measurement test was made in soil-bin, the result indicated the system showed a high performance in data collection, transmission, processing and remote monitor, and could provide a support in agriculture equipment working status monitor.

Industrial experiences of bending fatigue strength in table liner for cement mill

ABSTRACTA table liner for the vertical roller mill has been used to grind natural limestone. Unexpected fatigue failure accidents have occurred during portland cement manufacturing process. The design life of a table liner is 4 × 107 cycles, but the actual fatigue life of a table liner is 2 × 106 to 8 × 106 cycles. The fatigue crack of a table liner initiates from the outside edge of the grinding path of the limestone. When such a crack occurs, the table liner has to be replaced, and this requires 30% of the total maintenance cost of the vertical roller mill. Therefore, this study examines the fatigue failure of a table liner by plane‐bending fatigue test, stress measurement test, finite element analysis and fatigue fracture analysis.

Measured wall shear stress distribution pattern upstream and downstream of a unilateral stenosis by an electrochemical method.

An electrochemical surface shear stress measurement was applied to a model of unilateral arterial stenosis. The unilateral stenosis model was made up of a removable stenosis plug, in an electrochemical shear stress measurement test section with 100 cathodes. Three dimensional wall shear stress distribution was measured under steady flow field. At a relatively low Reynolds number, Re = 270, there was a characteristic high and low wall shear distribution pattern downstream of the unilateral stenosis. There were also remarkable high shear stress areas on the opposite wall up- and downstream, and both side walls of the stenosis upstream. It was clearly shown that detailed three dimensional structure of the flow field must be studied in order to correlate it to pathological findings.

Fatigue Life of Welded and Bolted Repair Parts

Fatigue crack propagation and residual stress measurement tests were conducted by using deep‐notched wide plate specimens with repaired parts. The main purpose of this study was to evaluate numerically the effects of some weld repair methods and a mechanically patching method with high strength grip bolts on residual fatigue life. The test results proved that the conventional welded repair method with no special treatment reduced fatigue life due to high tensile residual stress induced by welding repairs. However, through application of adequate treatment to cracks, compressive residual stress was induced in repair welds to increase the fatigue life. The remaining fatigue life of welded repair parts was further investigated using Fracture Mechanics. The patching method with high strength bolts and welded splice plates, on the other hand, had a remarkable effect on retarding the fatigue crack growth rate by decreasing it after bolted repairs to about 1/100‐1/1,000.