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The study summarises the selection of dedicated techniques and procedures for measuring real stresses arising in shaft steelwork components due to car-shaft steelwork interactions as well as stresses at critical points of the car frame in the elevator installation in the Regis Shaft of the Wieliczka Salt Mine. The implemented solution and operational parameters of the hoisting installation in the Regis Shaft of the Wieliczka Salt Mine are summarised, the adopted measurement method and dedicated equipment are presented, focusing on the procedure for locating the critical points on the car frame and shaft steelwork. The purpose-built measurement set-up as well as the adopted stress measurement procedure and results are explained in detail. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Continuous, real-time and remote measurement of stress in underground coal mines plays a vital role in the safety of the mines. Vibrating wire-based geotechnical sensors are widely used for stress measurement of strata in underground coal mines. These types of sensors have several advantages over other geotechnical sensors. However, the measurements from these sensors are taken in-situ using conventional readout unit manually till date even in the case of deep underground coal mines where the depth of cover is more than 300 m. When sensor site moves to inaccessible places due to dynamic nature of mining, then the measurement is discontinued and instruments become abandoned. Also, sensors connected through wire get disconnected during movement of machinery, roof falls, and other associated hazards. Therefore, there is a need for wireless sensing platform for vibrating wire-based geotechnical sensors which can assess the stress on a real-time basis and obviate the impending mishap associated with the strata failure. Hence, in the present paper, authors have designed a prototype wireless real-time sensing platform for vibrating wire-based geotechnical sensors for continuous, real-time and remote monitoring of strata behavior. The laboratory trial and the field demonstration of the same have been carried out and compared with conventional readout. The results are in agreement. [ABSTRACT FROM AUTHOR]

Robot-assisted therapy can provide effective rehabilitation training for stroke patients. The interfacial stress between the manipulator and the grasped patient's body is very important for a rehabilitation therapy robot. This paper presents a measurement method, which is able to decouple the measurement of the three-dimensional (3-D) interfacial stress components. To implement the method, interfacial stress sensors were fabricated based on plate capacitance and a superelastic material, while a high-resolution microcapacitance measurement circuit was developed based on a minimal system microprocessor and a programmable controller, and experiments are carried out by using a 3-D stress simulation equipment. The results show that the measurement circuit is capable of measuring a range of 1 fF–30 pF capacitance with a resolution better than 1 fF, and the sensor is capable of measuring Z-direction normal compressive stress at a range of \text0-3.0 \textkgf/\textcm^2 with a sensitivity of \text101 \textfF/\textkgf/\textcm^2 and X - and Y-direction shear stress at a range of 0-1.0 \textkgf/\textcm^2 with a sensitivity of \text118 \textfF/\textkgf/\textcm^2. This method can be applied to rehabilitation therapy robots to decouple the measurement of the 3-D interfacial stress components. [ABSTRACT FROM PUBLISHER]

In this paper we investigate the drain stress behavior and charge trapping phenomena of GaN-based high electron mobility transistors (HEMTs). We fabricated GaN-on-Si MIS-HEMTs with different dielectric stacks in the gate and gate-drain access region and performed interface characterization and stress measurements for slow traps analysis. 2-dimensional TCAD simulations were used to compare the electrical field distributions of the devices in OFF-state stress condition. Our results show a high dependency of the on-resistance increase on interfaces in the gate-drain access region. The dielectric interfaces near the channel play a significant role for long term high voltage stress and regeneration of the device. [ABSTRACT FROM AUTHOR]

Degradation in planar high-k metal gate p- and n-channel MOSFETs, respectively, under negative bias temperature instability (NBTI) and positive bias temperature instability (PBTI) stress is studied using different characterization methods. Ultrafast measure stress measure (UF-MSM) method with a measurement delay of a few microseconds is used to characterize the threshold voltage shift ( \Delta VT ). Gated-diode or direct current IV is used to directly estimate the trap generation (TG) during BTI, after correcting for the measurement inconsistencies. BTI experiments are performed under DC stress at different stress bias ( V\mathrm {G-STR} ) and temperature ( T ) values also under AC stress at different pulse duty cycle (PDC) and frequency ( f ) values. Measured \Delta VT as well as TG show remarkable similarities between NBTI and PBTI stress, under both DC and AC stress. It is shown that TG dominates NBTI and PBTI degradation under both DC and AC stress. [ABSTRACT FROM PUBLISHER]

Stress is central to many aspects of rock mechanics, and in the analysis of in situ stress measurement data the calculation of the mean value and an assessment of dispersion are important for statistical characterisation. Currently, stress magnitude and orientation are processed separately in such analyses. This effectively decomposes the second-order stress tensor into scalar (principal stress magnitudes) and vector (principal stress orientations) components, and calculation of mean and dispersion of stress data on the basis of these decomposed components, which violates the tensorial nature of stress, may either yield biased results or be difficult to conduct. Here, by introducing tensorial techniques, we examine two calculation approaches for the mean and dispersion for stress tensors – based on Euclidean and Riemannian geometries – and discuss their similarities, differences and potential applicability in engineering practice. We compare the two approaches using stress tensor superposition and interpolation, and the analysis of actual in situ stress data. The results indicate that Euclidean and Riemannian mean tensors are in general not equal, with the disparity increasing as stress tensor dispersion increases. Both Euclidean and Riemannian approaches are shown to be capable of characterising stress dispersion, although Euclidean dispersion is scale dependent and has units of stress whereas Riemannian dispersion is a scale independent unitless number. Finally, a paradox is revealed in that despite stress tensors being Riemannian entities, it is Euclidean mean stress that is the more meaningful for engineering applications. [ABSTRACT FROM AUTHOR]

This letter reports the first experimental demonstration of time-dependent breakdown in GaN-based light-emitting diodes (LEDs); based on a number of constant voltage stress tests, carried out below the breakdown limit of the devices, we show that: 1) when submitted to reverse-bias stress, the LEDs show a gradual increase in current, well correlated with an increase in the breakdown luminescence signal; 2) for sufficiently long stress times, the LEDs can reach a catastrophic (sudden) breakdown, which leads to the failure of the devices; 3) the breakdown process is time-dependent and the time to failure (TTF) has an exponential dependence on stress voltage; and 4) TTF is Weibull distributed. The results presented within this letter demonstrate that the GaN-based heterostructures can show a TDDB-like behavior, and can be useful for the interpretation of the degradation data of LEDs and HEMTs. [ABSTRACT FROM PUBLISHER]

In the majority of fatal snow avalanches, skiers and snowmobilers trigger the initial failure in a weak layer by applying load to the snow cover. Understanding how stresses from dynamic surface loads transmit through the snow cover can help people avoid situations where they can trigger avalanches. We build on previous studies that provided more qualitative statements to a quantitative analysis about how the snow cover affects stress transmission. We quantified the upper snow cover for the experiments according to a bridging index which is the uniform hand hardness index of a particular layer in the snow cover multiplied by the thickness of that layer. Capacitive sensors were used to measure peak stress below dynamic surface loads within the mountain snow cover. The sensors were used on 33 separate field days to collect over 1420 measurements of loading by skiers and snowmobiles. In order to visualize this measured stress, static stress calculations for an elastic homogeneous 2D snow cover were calibrated to show measured stress values of loading caused by the passage of a snowmobile. The change in 2D shape and magnitude of the induced stress was plotted for three “typical” snow cover structures. Relatively soft snow allowed the specific levels of dynamic stress to penetrate deeper into the snow cover, thus increasing the probability of initiating a failure in a weak layer. Whereas, supportive snow limited the depth that the dynamic stress penetrated by spreading it out laterally. The added stress was then related to localized slope stability using stability indices. Bridging index thresholds of 130 to 190 for skiers and 160 to 260 for snowmobiles yielded stability index values greater than 1.5. Due to the high variability in the stress measurements, bridging index values for 77 skier-triggered avalanche slopes were computed and compared to the values found from the stability index analysis. [ABSTRACT FROM AUTHOR]

An evaluation procedure for predicting the unbonded tendon stress in the continuous post-tensioned beams was performed and calibrated through analyzing experimental data from 16 two-span specimens under static loading up to failure. As the relationship between the increase of the tendon stresses and the change of the tensile nonprestressed reinforcement stresses in a same critical section of a post-tensioned beam, response is nearly linear at various levels of loading such as zero, elasticity, cracking, and before yield of nonprestressed tension reinforcement. The non-prestressing bonded steel satisfied strain compatibility. Thus, the increase of the tendon stresses at the service load may be determined through linearly reducing the change of the tensile steel stresses. A model for predicting the ultimate stress of unbonded tendons treats the prestressing reinforcement index and the global reinforcement index as the two independent variables. This and the other variables, including the ratio of the two global reinforcement indexes of support and midspan, and span-depth, affect the rotation capacity of plastic hinges. This prediction model was derived from the equilibrium of the ultimate flexural capacity, and was calibrated by current testing data. Compared with the ACI code and China specification, the proposed equation of the model was validated and was found to provide better accuracy for predicting the ultimate stress of the unbonded tendons in the continuous posttensioned beams. [ABSTRACT FROM AUTHOR]

An atomistic model to account for the impact of stress during solid phase epitaxial regrowth (SPER) is proposed. This model is based on the lattice kinetic Monte Carlo method. It has been compared with experimental data of regrowth velocity as a function of hydrostatic and non-hydrostatic stresses. In particular, it permits to provide a physical explanation of the observations upon in-plane uniaxial stress based on the assumption that {100} events occur through a dual-timescale atomistic mechanism. Our model also catches the fact that compressive normal uniaxial stress and hydrostatic pressure result in an enhancement of the regrowth velocity with a similar activation volume. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Copyright of Synthesis of Theoretical & Applied Mechanics / Sinteze de Mecanică Teoretică și Aplicată is the property of Matrix Rom and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: In the paper the method of experimental temperature and stress measurement of reinforced concrete foundation slab during construction of the National Supercomputing Centre in Ostrava, Czech Republic is described. Measured results are compared with numerical analysis and time dependent development of concrete strength. Decreasing the tensile stress in concrete by use of the sliding joint was verified. [Copyright &y& Elsevier]

For CMOS technology, the increase of interconnects metal density is responsible for heterogeneous mechanical stress fields in active regions of silicon. Coupled mechanical–electrical measurements are performed to evaluate the impact of stress at circuit and device levels. This mismatch originated by interconnects metal lines stress is measured through the use of piezoresistive test structures. Local mechanical stress can thus be monitored in a simple process control compatible approach. [ABSTRACT FROM AUTHOR]

We report on a thin-flim transistor (TFT) degradation encountered in short channel amorphous indium–gallium–zinc–oxide TFTs under high applied power condition leading to self-heating. Negative shift was observed in the initial stage of stress period followed by positive shift with severe degradation. To understand the causes of this phenomenon in depth, trap density-of-states were measured by photo-excited charge-collection spectroscopy and time-dependent recovery of stressed device samples was also studied. As a result, we found that the combination of hot carrier effect and self-heating in channel was responsible for the degradation. [ABSTRACT FROM AUTHOR]