Method For Evaluation Of Stress Research Articles

Prediction of axial compressive stresses in ultra-high-performance concrete blocks using non-destructive ultrasonic techniques

The application of ultra-high-performance concrete (UHPC) in civil engineering structures is growing rapidly. On the other hand, previous non-destructive testing (NDT) techniques mainly focused on determining the relationship between the acoustic characteristics and elastic modulus, Poisson's ratio, cracking resistance, and strength. This study presents an experimental approach utilizing ultrasonic techniques to predict the axial compressive stresses in UHPC structures. Both cubic and prismatic UHPC blocks were designed and tested under different compressive axial loading conditions, and their ultrasonic acoustic characteristics were evaluated in detail. Normal strength concrete (NSC) blocks were also included in the investigation for comparison purposes. A detailed account of the tests results is provided, including the relationships between the compressive stresses in UHPC blocks and the typical time- and frequency-domain acoustic parameters. Based on the experimental results, an analytical working stress evaluation method for UHPC components using the ultrasonic acoustic parameters is proposed. It is shown that there is close correlation and high prediction stability between the compressive stress in UHPC blocks and the ultrasonic velocity, which is suggested as the main acoustic parameter for stress detection. The correlation between the acoustic amplitude parameters and concrete compressive stress is also shown to be significant, yet is associated with relatively low prediction stability. Moreover, in comparison with conventional NSC blocks, greater correlation and regularity ratios are observed between the typical acoustic parameters and the axial compressive stress in UHPC specimens. Overall, the analytical models proposed in this study are shown to be in close agreement with the experimental results, and can be used, in conjunction with the ultrasonic NDT techniques, to provide a reliable prediction of the level of compressive stresses in UHPC members.

A new stress measurement strategy based on time-frequency characteristics of Lamb waves

Existing stress evaluation methods based on the Lamb waves mainly use the time of flight (TOF) or velocity as the means of stress measurement. However, these two features used for stress measurement are sometimes insensitive to stress changes. Therefore, it is essential to explore other features that are potentially more sensitive to stress changes. The time–frequency spectrums of signals containing stress information have not yet been fully studied for stress evaluation. This paper proposes a uniaxial stress measurement method based on two time–frequency characteristics of Lamb waves, i.e., the slope of time–frequency spectrum distribution (TFSD) and pulse width impact factor. Theoretical expressions of the slope of TFSD are derived. The impacts of excitation signal parameters (i.e., bandwidth and center frequency) and noise on two time–frequency characteristics were discussed. Then, the fitting results of the finite element simulation are consistent with the results predicted by theory. To experimentally validate the proposed theory, aluminum plate specimens with two different types of adhesives were used for the experiment. According to the experimental stress measurement expression, three uniaxial tensile tests in the range of 35–95 MPa were conducted on the identical batch of specimens. The maximum standard deviation of multiple measured stress based on pulse width impact factor is 3.76433 MPa, demonstrating excellent measurement stability. The maximum standard deviation of multiple measured stress based on the slope of TFSD is 9.12492 MPa. It shows that the proposed methodology is a promising alternative for stress measurement.

Non-exponential transients and the evaluation of stress in (disordered) organic thin film transistors

In this work, the transient techniques for disordered organic thin film transistors are analyzed. A special emphasis is made on stress. Stress in this work is the continuous increase of the threshold voltage upon applying a gate bias. In this work a new stress evaluation method is presented that allows for a rapid determination of stress. Moreover, a figure-of-merit is proposed that can be applied to non-exponential transients, including those of stressing. The transients are compared to the empirical transient functions reported in literature that range from power-law to stretched exponential and logarithmic.

New avenues for residual stress analysis in ultrathin atomic layer deposited free-standing membranes through release of micro-cantilevers

The fabrication of thinnest, yet undeformed membrane structures with nanometer resolution is a prerequisite for a variety of Microelectromechanical systems (MEMS). However, functionally relevant thin films are susceptible to growth-generated stress. To tune the performance and reach large aspect ratios, knowledge of the intrinsic material properties is indispensable. Here, we present a new method for stress evaluation through releasing defined micro-cantilever segments by focused ion beam (FIB) milling from a predefined free-standing membrane structure. Thereby, the cantilever segment is allowed to equilibrate to a stress-released state through measurable strain in the form of a resulting radius of curvature. This radius can be back-calculated to the residual stress state. The method was tested on a 20 nm and 50 nm thick tunnel-like ALD ▪ membrane structure, revealing a significant amount of residual stress with 866 MPa and 6104 MPa, respectively. Complementary finite element analysis to estimate the stress distribution in the structure showed a 97% and 90% agreement in out-of-plane deflection for the 20 nm and 50 nm membranes, respectively. This work reveals the possibilities of releasing entire membrane segments from thin film membranes with a significant amount of residual stress and to use the resulting bending behavior for evaluating stress and strain by measuring their deformation.

Novel method for evaluation of stress assisted corrosion through compact tension specimens to assess material compatibility in latent heat thermal energy storage systems

The next generation Concentrated Solar Power (CSP) plants integrated with Thermal Energy Storage (TES) offer a promising solution for dispatchability, reliability, and economic concerns associated with renewable energy technologies. However, the expected operational life of up to 30 years proves to be a major challenge due to the impact of high temperatures and corrosive eutectic salts utilised in the latent heat TES systems. Additionally, the system is under varying degrees of stress that can accelerate corrosion mechanisms. Unfortunately, this stress corrosion relationship is often neglected during the material compatibility assessment. This study utilises a novel static immersion testing approach with three designs of modified Compact Tension (CT) specimens manufactured from AISI 316L to investigate the interaction of alloys under stress with various eutectic salts at up to 750 °C for up to 1000 Hours. The results indicate that oxidation is accelerated up to four times and Intergranular Corrosion (IGC) up to two times in the high-stress region of the test samples. Furthermore, the findings suggest that static immersion testing using CT specimens can be regarded as an effective approach to assess the influence of stress on corrosion and conduct a reliable material assessment for latent heat TES systems and CSP plants.

Stress evaluation method of reinforced wall-thinned Class 2/3 nuclear pipes for structural integrity assessment

When wall-thinning occurs in nuclear Class 2 and 3 pipes, reinforcement is typically applied rather than replacement. To analyze the structural integrity of reinforced wall-thinned pipe, stress analysis results using full 3-D FE analysis are not compatible to the design code equation, ASME BPVC Sec. III NC/ND-3650. Therefore, the efficient stress evaluation method for the reinforced wall-thinned pipe, compatible to the design code equation, needs to be developed. In this paper, stress evaluation methods for the reinforced wall-thinned pipe are proposed using the equivalent straight pipe concept. Furthermore, for fatigue analysis of the reinforced wall-thinned pipe, the stress intensification factor of reinforced wall-thinned pipe is presented using the structural stress method given in ASME BPVC Sec. VIII Div.2.

Stress Classification Lines for Non-Standard Y-Tee Design in Piping System

All processes fluids in the oil and gas industry are generally transferred from one point to another via complex piping networks. The process temperature and the pressure of the fluids may vary between -21 °C to 816 °C and from atmospheric, 1.013 barg to 431 barg, respectively. Under these conditions, the entire piping networks are exposed to thermal expansion and contraction resulting in mechanical bending, potentially causing mechanical failures. The most common pipe fitting used in piping networks to divide the fluid flow into two different directions would be a standard equal tee which was designed in accordance with ASME B16.9. The equal tee, however, has distinctive flexibility characteristics compared to the pipe, which is well defined in ASME B31.3. These flexibility characteristics generate a stress intensification factor (SIF) through bending moment equations for beam-type element analysis for standard equal tee components. However, due to the limitation of SIF and flexibility characteristics for the non-standard pipe fittings, the stress evaluation could not be done using beam-type element analysis. When using finite element method (FEM) analysis, generally equivalent stresses (Von Mises or Tresca) or principal stresses would be evaluated depending on the stress categorization as explained in ASME codes and standards. In this paper, a stress evaluation method for non-standard Y-tee was developed and demonstrated against ASME VIII Div. 2 Part 5 requirement. The developed SCLs line for the non-standard Y-tee fittings provides the guides for stress assessment against design stress allowable. An optimum design for non-standard Y-tee is proposed at 45° and 60° crotch radii which resulted in lower stress value at SCL lines, hence improving the structural integrity.

Stress Evaluation Method by Neutron Diffraction for HCP-Structured Magnesium Alloy

Tensile deformation in situ neutron diffraction of an extruded AZ31 alloy was performed to validate conventional procedures and to develop new procedures for stress evaluation from lattice strains by diffraction measurements of HCP-structured magnesium alloys. Increases in the lattice strains with respect to the applied true stress after yielding largely vary among [hk.l] grains. Some [hk.l] grains have little or no increase in lattice strain, making it difficult to use the conventional procedures to determine the average phase strain by using lattice constants or by averaging several lattice strains. The newly proposed procedure of stress evaluation from the lattice strains shows very high accuracy and reliability by weighting the volume fraction of [hk.l] grains and evaluating them in many [hk.l] orientations in addition to multiplication by the diffraction elastic constant. When multiple hk.l peaks cannot be obtained simultaneously, we recommend to use the 12.1 peak for stress evaluation. The lattice strain value evaluated from the 12.1 peak shows a good linear relationship with the applied true stress for the whole deformation region.

Stress measurement based on magnetic Barkhausen noise for thin films

Non-destructive testing methods based on magnetic Barkhausen noise (MBN) are expected to be applied to thin films. Recently, MBN analysis using machine learning has been performed on bulk materials and used as an in-situ stress and material evaluation method. However, for thin films, it is difficult to measure due to the weak MBN signal intensity, and few examples of its use as a stress and material evaluation method have been reported. This study acquired and analyzed MBN of FeCo polycrystalline thin films under bending stress. After pre-processing the acquired MBNs, two representative machine learning algorithms were used to learn the relationship between MBN and stress. By quantitatively comparing the prediction accuracy of each machine learning method, the characteristics of the MBN-based stress evaluation method were discussed from two perspectives: the need for domain knowledge and its applicability to unknown data. This study provides insight into machine learning-assisted MBN analysis as a stress evaluation method for thin films. The extension of MBN-based stress evaluation methods to thin films could be applied to the non-destructive stress evaluation of micro- and nanostructures, where stress state is critical, and could improve process development efficiency.

A commentary on 'Does speed equal quality? Time pressure impairs minimally invasive surgical skills in a prospective crossover trial' (Int J Surg 104 (2022) 106813).

Dear Editor, Time pressure is an important influencing factor in clinical work. Even though less operation time reduces patient exposure to surgical stressors or anesthetic time, leading to less infection and bleeding, lots of research indicate management failure of time pressure may lead to operating error and nosocomial damage1. A better understanding of the effect of time pressure in the clinic, especially during surgery, is meaningful work. In the impressive study from the University Hospital Carl Gustav Carus, the author stated that time pressure during minimally invasive surgery might improve procedural time but impair the quality of surgical performance in terms of the incidence of errors and force exertion. Accumulation of experience seems to be the only solution. The study makes time pressure detectable and indicates the antipressure ability of surgeons mainly based on experience accumulation. However, some issues in this article may need further interpretation. First, before the test, the surgeon group did not get the same training or pretest as the novice group. Although surgeons have more experience in daily surgery, the same training is still needed to diminish the difference in skills in four tasks: PEG (percutaneous endoscopic gastrostomy) transfer, precision cutting, balloon resection, and surgical sutures and knots. For example, in this research, the novice group spend much less time than the surgeon group only in PEG transfer but much more time in the other three tasks. And actually, the surgeon group showed higher error occurrences than the novice group in all kinds of error statistics except balloon perforation. It is hard to believe surgeons are less skillful. Lack of training can be a proper explanation for such a paradox. And interestingly, no matter whether time stress is applied or not, the surgeon group showed a noteworthy lower stress level than the novice group even though they had more errors and spent a long time during testing. When compared with invoices, the self-cognition of the surgeon may have a role that cannot be ignored in stress management2. Second, the difference between novice surgeons and skillful surgeons is not only in experience but also differs greatly in standardization of operation and operational fluency. Indeed, excessive force can lead to a medical injury. But in this research, the force of both groups is all far from 10.3N3, which leads to human small intestine perforations. On the other side, weak or fluctuating forces may also be related to a lack of self-confidence or hesitation, which leads to a stumbling surgery process. The meaning of force diversity should be explained not only in static but also in dynamic. Adding action mode analysis to force recording may help us have better awareness of the effect of time pressure. Finally, before and after the application of pressure, the experience of operating under no pressure can be ignored for the novice who has been trained for a long time, but it can make a big difference for the surgeons who have not received pretest and only rely on surgical techniques. As surgeons themselves have good operational skills, only one time of test could help them get a better understanding and movement to achieve better performance in the pressure-applied task. In conclusion, dealing with time pressure is an important issue during minimally invasive surgery. Distler provides a measurable method for stress evaluation and reveals that accumulation of experience is important for time pressure management. It is crucial that not only static force measurement but also dynamic recording and analysis should be considered. And with a larger sample size, the differences between surgeons with different seniority may better illustrate the role of time pressure in surgery. Ethical approval This manuscript was based on the previously published study; thus, no ethical approval is required. Patient consent N/A Sources of funding Chongqing Medical Scientific Research Project (Joint project of Chongqing Health Commission and Science and Technology Bureau) (2020FYYX189). Author contribution Z.L.: drafted the article; Y.S.: reviewed the article. Conflicts of interest disclosure There are no conflicts of interest. Research registration unique identifying number (UIN) None. Guarantor Yan Shu, Department of Clinical Laboratory, Chongqing University FuLing Hospital, Chongqing 408000, People’s Republic of China, E-mail: [email protected] Data availability statement Data sharing is not applicable to this article as no new data were created or analyzed in this study. Provenance and peer review None.

Retracted: Psychological Stress Identification and Evaluation Method Based on Mobile Human-Computer Interaction Equipment.

[This retracts the article DOI: 10.1155/2022/6039789.].

Detection and quantitative evaluation of elastic stress state of reinforcements in RC beams based on magnetic signal characteristics

This study developed a method for detection and quantitative evaluation of the elastic stress of the reinforcement in reinforced concrete (RC) beams. By combining the minimum energy and magnetic dipole theories, a quantitative model of the magnetic signal gradient and magnetization angle was established. The spatial distribution of the magnetic signals and variation of the average gradient with stress in the pure bending section of the RC beams were obtained through four-point bending experiments. The results show that the law of the average gradient with the stress is consistent with that predicted by the theoretical model. Based on the Bayesian theory, a method to evaluate the elastic stress was established, which can be applied for grading the elastic stress of the reinforcement within a certain range of accuracy.

Stress Evaluation of Welded Joints with Metal Magnetic Memory Testing Based on Tension-Compression Fatigue Test.

Metal magnetic memory testing (MMMT) is an effective nondestructive technique for fatigue damage monitoring of weldments because of its capacity for stress evaluation. An experimental investigation of the effect of the applied fatigue stress on MMMT signals, including the tangential component Bx and the normal component Bz, during tension–compression fatigue tests in welded joints was carried out systematically. The Bx and Bz signals at different fatigue cycles and fatigue stresses were collected and analyzed, and the results showed that there was a peak of Bx and abnormal peaks of Bz that existed at the welded joint before loading. After loading, the peak of Bx and the abnormal peaks of Bz reversed, and the Bx signals moved upward and the Bz signals rotated anticlockwise dramatically in the first few fatigue cycles. After the fatigue cycle number was larger than 1000, Bx and Bz were stable, with very little fluctuation. In addition, the characteristics of Bx signals, the mean value, and the peak value of the average of Bx had an extremely significant linear relationship with the applied fatigue stress during the stable stage of the fatigue test, which indicates that MMMT is a feasible method for fatigue stress evaluation and even residual fatigue life estimation for weldments in service.

Psychological Stress Identification and Evaluation Method Based on Mobile Human-Computer Interaction Equipment.

Since the 1980s, the research of artificial neural networks in the field of artificial intelligence has become more and more common. It accepts nonlinear parallel processing, has strong learning and flexibility, and can be used for influencing factor analysis. The ideal power values and triggers are obtained in the Hopfield network model using genetic algorithm, which best avoids the drawbacks of the Hopfield network model instillation learning method. Through the BP of mobile human-computer interaction equipment, hereditary, genetic algorithms, and Hi-PLS regression method in the artificial neural network, the psychological pressure of college students is identified, evaluated, and predicted from three dimensions such as learning, life, and personal events. This makes it possible to understand the current physical and mental conditions of the students in a timely manner, guide to relieve anxiety and fear, and reach a safe psychological level. The three test results are less than 1%, which has high research significance and value.

Fecal Glucocorticoid Metabolites as a Noninvasive Indicator of Stress in the Tsushima Leopard Cats (Prionailurus bengalensis euptilurus): Application to Health Care.

Simple SummaryThe Tsushima leopard cat (Prionailurus bengalensis euptilurus) and the Iriomote cat (P. b. iriomotensis) are the only two wild felids living in Japan. Both species are endangered. The Tsushima leopard cat is undergoing captive breeding (ex situ conservation) in zoos with the aim of returning it to the wild, in addition to conservation activities in the habitat (in situ conservation). In order to promote captive breeding, it is important to elucidate the reproductive physiology and to evaluate stress conditions. We investigated the possibility of measuring glucocorticoid metabolites (GCMs), which are stress hormones, using feces in Tsushima leopard cats. We examined changes in fecal GCM in individuals who underwent a health examination under anesthesia as an unavoidable stressful condition during normal health care. Fecal GCM concentrations increased 1–2 days after the health examination. Fecal GCM concentrations were higher in diseased individuals than in apparently healthy individuals. Individuals diagnosed with disk herniation also showed a decrease in fecal GCM concentrations after treatment with therapeutics. These results indicate that the measurement of fecal GCMs is useful for improving the husbandry and health management of the Tsushima leopard cat.This study investigates whether the measurement of glucocorticoid metabolites (GCMs) in feces is a useful method for the noninvasive evaluation of stress in the endangered Tsushima leopard cats (Prionailurus bengalensis euptilurus). Feces were collected from six seemingly healthy and five diseased (renal dysfunction, adrenal tumor, hernia, feline immunodeficiency virus (FIV), feline leukemia virus (FeLV)) Tsushima leopard cats in captivity. Fecal GCMs were measured by enzyme immunoassay (EIA) for cortisol. Individuals that experienced a physical examination under anesthesia showed increased fecal GCMs 1–2 days after the event. An individual diagnosed with disk herniation showed decreased fecal GCMs after medical administration. The mean fecal GCM concentrations for six healthy animals and five diseased animals were 0.66 ± 0.08 and 2.65 ± 0.76 μg/g, respectively, which was significantly different. Cortisol and corticosterone were not clearly detected in the feces examined by the use of the HPLC-EIA analysis. GCMs may be excreted in the feces; however, the exact identification of these substances is not achieved. The results suggest that the measurement of fecal GCMs is useful for the husbandry and health management of this species.

Effects of Nature-Based Intervention in Occupational Health Care on Stress - A Finnish Pilot Study Comparing Stress Evaluation Methods.

PurposeTo assess methodology and its limitations for measuring effects of nature-based intervention (NBI).Patients and MethodsParticipants were 11 middle-aged female health care workers with lowered capacity to work. NBI included six group appointments in six months study period. Heart rate variability (HRV) and self-reported pain and work exhaustion were measured pre-post study period. Salivary α-amylase samples were collected immediately before and after three individual interventions. Salivary cortisol samples were collected on the same three interventions, on three consecutive days starting from the day of intervention, to assess (a) month effect (pre-post study period) and (b) day effect (intervention day vs non-intervention day).ResultsIndividual interventions resulted in increase in α-amylase activity. However, the average fold increase decreased from the 3.05 ± 1.20 of the first intervention to 1.91 ± 1.00 and 1.46 ± 0.77 in the second and third intervention, respectively (p < 0.001). Cortisol concentrations were lower on intervention days vs non-intervention days, the difference being indicative (p = 0.050). Pain and work exhaustion decreased during the study period, as well as HRV, although any of these changes was not statistically significant.ConclusionFor a large-scale study, it would be ideal to select assays for both major pathways: hypothalamic-pituitary-adrenal axis can be measured by cortisol, whereas response via autonomic nervous system can be measured by HRV, when roles of sympathetic and parasympathetic nervous systems can be pinpointed separately. Salivary α-amylase can be used when continuous monitoring is not possible. Psychological well-being of participants should be surveyed, as well as their activities and moods on sampling days recorded.

Ultrasonic Measurement of Bolt Axial Stress Using the Energy Ratio of Multiple Echoes

The reliability and stability of a mechanical system generally counts on the effective detection and control of the stress state of its bolted connections. In this paper, a novel bolt axial stress evaluation method based on the scattering attenuation of polycrystal using the energy ratio of multiple echoes is proposed. Above all, the longitudinal-incident attenuation coefficients for preload cubic crystalline materials in the Rayleigh regime are introduced. In view of the estimation of frequency-dependent attenuation coefficients are prone to suffer from the disturbance of the cylindrical guided waves, the energy ratios of the first two back-end echoes within the signals are applied instead. Subsequently, a stress measurement experiment is conducted to validate the proposed method, in which the accurate energies of the echoes are evaluated using the S transform. The results reveal that, as long as the probe is firmly bonded, the proposed method can achieve better sensitivity and reliability than that of the existing methods using TOF (Time of flight), especially for short or full-threaded bolts.

Analytical model of magnetic Barkhausen stress test of ferromagnetic plates

As one of the important non-destructive testing techniques for evaluating material performance degradation and stress state, magnetic Barkhausen noise (MBN) has broad application prospects. Clarifying the relationship between internal stress distribution and detection signal can provide important guidance for evaluating the stress state of material based on the MBN signal. In this work, by constructing the expression of Barkhausen noise excitation intensity related to stress value, combining with the signal attenuation effect during signal propagation, and using the layered model along the thickness direction, we establish the analytical model of MBN signal on the surface of the ferromagnetic plate with internal stress distribution. Based on the existing experimental results, it is confirmed that the proposed model can reflect the effects of the different uniform stresses in the ferromagnetic plate on the signal at different detection frequencies. For the ferromagnetic plate with internal stress distribution, the effects of its stress distribution, magnetic conductivity, electrical resistivity, and thickness on the surface MBN signal are discussed in detail based on the proposed model. The theoretical analysis in this work can be applied to the testing mechanism analysis of the MBN stress evaluation method.

Evaluation of Stress and Stress Concentration Degree Based on the Online Piezomagnetic Measurement

ABSTRACT The goal of this research is to correlate the piezomagnetic field with the stress and the stress concentration degree of ferromagnetic steels. Specimens of X80 steels were machined into smooth plates with circular holes in the center and tensile tests were carried out to detect the online piezomagnetic field on the surface of defective specimens. The relationship between the distribution of the stress and the distribution of the piezomagnetic field components was systematically investigated. Compared with the normal component and its gradient, the tangential component showed a better correlation with the distribution of the stress. A piezomagnetic parameter was defined to characterize the abnormal changes of the tangential component around the defect. Quantitative algorithms were established to evaluate the stress concentration degree on the basis of piezomagnetic parameters. This research will be a supplement of stress evaluation methods based on magnetic measurement technologies.

Fast stress evaluation of the top coat of thermal barrier coatings under CaO–MgO–Al2O3–SiO2 penetration based on image recognition and an artificial neural network

An image recognition and artificial neural network (ANN)-based method for fast stress evaluation of thermal barrier coatings (TBCs) is proposed. Random two-phase images of ceramic top coats (TCs) with penetrated CaO–MgO–Al2O3–SiO2 (CMAS) are established, and the TC–CMAS image boundaries are recognized. Image-restoration finite element models are constructed based on boundaries optimized using the average coordinate method. The isothermal thermal stress in the restoration models is calculated. The structural parameters and local maximum stress are extracted to establish sample databases on which the ANN is trained. The thermal stress states in a new group of samples are predicted by the trained ANN. The root-mean-square error between the stress calculated by the new stress evaluation method and those of results calculated using the finite element method is approximately 6%. The new method also has a higher calculation efficiency and its stress evaluation speed is accelerated by a factor of approximately 77 compared with that of the finite element method.