Stress Testing Device Research Articles

Thermokinetics and reactive mechanism of lead azide (LA) in atmosphere/temperature mixed environment

To establish the influence of atmospheric and temperature factors on the stability of LA, a combined environmental stress testing device was designed to simulate reaction characteristics. Morphological characterization methods of SEM and FTIR were carried out to explore the changes of crystal structure, as the pyrolysis behavior of LA under the combined environmental stress was investigated by DSC with two isoconversional kinetic methods and thermal safety software (TSS). The research indicates that CO2 and H2O react with LA to generate basic lead carbonate in the air atmosphere, together with the stimulation of thermal stress, the synergistic effect formed microvoids to erode the crystal structure of LA. The microvoid effect reduced the apparent activation energy (Ea) from 156.47 to 29.52 kJ/mol as the order of degradation of thermal stability of LA was Air > N2 > CO2, which demonstrated that CO2 and N2 atmosphere have a particular protective effect for LA storage, transportation, and application. The pyrolysis reaction mechanism model of LA under the combined environment factors testing was the same as the original LA through the calculation of TSS, thereby the findings could contribute to a better understanding of available boundary conditions for LA.

Analysis and evaluation of temperature field and experiment for magnetorheological fluid testing devices

When a large amount of heat is produced during the operation of a MRF (magnetorheological fluid) testing device, the temperature of the device will increase, which will in turn affect the characteristics of the MRF. Exploring the temperature field characteristics of the MRF yield stress testing device is necessary to improve the accuracy of the device. In this study, first, the yield stress testing device is designed, and then its temperature field model, including enameled wire and assembly gap, is established. Second, simulation software is used to simulate the temperature field change. Finally, a test platform is developed to test the simulation results, especially for two factors, namely, thermal conductivity of the coil winding and assembly gap, which demonstrate considerable influence. Comprehensive thermal conductivity and assembly clearance are determined, and the optimum temperature field of the device for measuring yield stress is resulted.

Unilateral anterior knee pain is associated with increased patellar lateral position after stressed lateral translation.

To objectively compare side-to-side patellar position and mobility in patients with idiopathic unilateral anterior knee pain (AKP) using a stress-testing device concomitantly with magnetic resonance imaging. It is hypothesized that the painful knees present greater patellar mobility than the contralateral non-painful knees. From a total sample of 359 patients, 23 patients with idiopathic unilateral AKP (30.9years, 23.4kg/m2, 43% males) were included within the present study. Both knees of all the patients were examined by conventional imaging, including the measurement of trochlear sulcus angle, Caton-Deschamps index, tibial tuberosity to trochlear groove distance, patellar tilt angle and patellar subluxation (both at rest and upon quadriceps contraction). Additionally, the same patients underwent stress testing (Porto Patella Testing Device); these measurements were taken with the patella at rest, after lateral patellar translation and after lateral patellar tilt. Clinical and functional outcomes were obtained using physical examination and the Kujala and Lysholm scores. Painful knees showed statistically significant higher patellar lateral position after stressed lateral translation than non-painful knees (p = 0.028), 9.8 ± 3.6mm and 7.1 ± 6.3mm, respectively. The adjusted multivariate logistic model identified the patellar position after lateral displacement to be significantly associated with AKP (OR = 1.165) and the model (AUC = 0.807, p < 0.001) showed reasonable sensitivity (67%) and specificity (73%). Patients with idiopathic unilateral AKP with morphologically equivalent knees showed statistically significant increased patellar lateral position after stressed lateral displacement in their painful knee. The greater lateral patellar mobility quantified by the PPTD testing brings more objectivity to the diagnosis. II.

Characteristics of Magnetorheological Fluids under New Formulation

Abstract Magnetorheological fluid (MRF), an intelligent material with controllable properties, has been widely used because of its unique magnetorheological effect and excellent rheological properties. Therefore, studying the preparation and performance of the system is crucial. First, the related equipment and raw materials were prepared at four volume percentages of MRF specimens—20 %, 33.3 %, 45.9 %, and 58.9 %. Then, on the basis of the pull method principle, we built a stress-testing device for an MRF yield. Furthermore, the yield stress values of the four kinds of MRFs were tested by the yield stress test device. Finally, the effect of temperature on the yield stress of the MRF was investigated. The experimental results show that the yield stress of the MRF decreases with increase of the temperature.

A novel dynamic opto-thermo-mechanical stress testing device 2: In situ stretching process of polymeric fibers.

In this article, we used the opto-mechanical stress testing-device to stretch a monofilament of isotactic Polypropylene, iPP, fibers. This device was used to obtain the mechanical behavior of these fibers by measuring the complete stress-strain curves at different stretching conditions. Using this device, the different regions of iPP fiber where the mechanical deformation takes place was characterized, including the necking region and fracture initiation process. The obtained mechanical behavior of iPP fibers was correlated to the variations of different optical parameters by attaching the device with the Pluta polarizing interference microscope. This microscope and the stress device allowed us to simultaneously measure the optical parameters and stress-strain data during stretching process at different stretching speeds. These data provide us with comprehensive information on the opto-mechanical behavior of polymeric fibers. Interferograms are included for illustration. The opto-mechanical stress testing-device was used to stretch a monofilament of, iPP, fibers. The mechanical deformation takes place was characterized, including the necking region and fracture initiation process at different stretching speeds.

Simulation and Experimental Research on Magnetic Circuit of MRF Yield Stress Testing Device

Yield stress is one of the main performance parameters of magnetorheological fluid (MRF). In order to satisfy the magnetic field requirement of yield stress test device, a magnetic circuit with current excitation is designed, and the finite element software is used to simulate the magnetic circuit. The test bench is built, and the magnetic field loading test is carried out. The magnetic induction intensity of the working gap of MRF is tested, and its B–I curve is obtained. Under the same current, there is a certain error between the magnetic induction intensity and the simulation result, and the maximum relative error is within 6%.

A novel dynamic opto‐thermo‐mechanical stress testing device 1: Design of the device

This article presents a dynamic opto-thermo-mechanical stress testing device to characterize fiber properties. The device has multi-modes and consists of many functions. These modes include stretching, bending, rotating, twisting, and heating processes. Every process can be controlled by micro-controller unit via software programs specially designed for this purpose. The micro-controller unit can execute two different processes at the same time. Such as, dynamic stretching process under the effect of thermal treatment, dynamic stretching process and relaxation, bending process under the effect of thermal treatment, and so forth. Software programs with their flow charts are designed for the application of these processes. The advantage of this device is that it can be done statically and dynamically to characterize all types of fibers (polymer and optical). The device is designed to be attached with two-beam polarizing interference microscope to investigate the dynamic opto-thermo-mechanical properties of the tested fiber under the effect of different applied stresses. Isotactic polypropylene, iPP, fiber is used for some applications of this device, as examples, in stretching, rotation, and twisting modes. Interferograms and graphs are given for illustration.

Measurement of temperature-dependent mechanical properties of magnetorheological fluids using a parallel disk shear stress testing device

Mechanical properties are critical to the working performance of magnetorheological fluids (MRFs), especially in high temperature situations. This paper presents an experimental investigation to analyze the effects of temperature on mechanical properties of MRFs. First, a parallel disk method was implemented for the shear stress measurement of MRFs and the measurement principle was theoretically illustrated. Then, a detailed introduction to the MRF sample preparation and the testing device development was performed as well. In the study, five kinds of MRF samples with different material parameters were prepared and a shear stress testing device which possesses the temperature control function was developed and evaluated. After these, a series of measurements were conducted on the viscosity–temperature characteristic, shear stress–temperature characteristic and thermal stability of MRF samples. Measuring results indicated that the mechanical properties of MRFs were obviously dependent on temperature. The phenomenon mainly embodied in the reduction of off-field viscosity and shear stress with increasing temperature, as well as the performance degradation after undergoing a low–high–low temperature cycle or a high temperature treatment of more than 150 ℃.

Validation of a non-radiographic ankle arthrometer

IntroductionCommonly used stress tests require radiography. The respective reliability and sensitivity is still under debate. We developed a non-radiographic ankle arthrometer to objectively assess mechanical ankle stability. The aim of...

Mechanical Joint Laxity Associated With Chronic Ankle Instability

Context:Lateral ankle sprains can manifest into chronic mechanical joint laxity when not treated effectively. Joint laxity is often measured through the use of manual stress tests, stress radiography, and instrumented ankle arthrometers.Purpose:To systematically review the literature to establish the influence of chronic ankle instability (CAI) on sagittal and frontal plane mechanical joint laxity.Data Sources:Articles were searched with MEDLINE (1966 to October 2008), CINAHL (1982 to October 2008), and the Cochrane Database of Systematic Reviews (to October 2008) using the key words chronic ankle instability and joint laxity, functional ankle instability and joint laxity, and lateral ankle sprains and joint laxity.Study Selection:To be included, studies had to employ a case control design; mechanical joint laxity had to be measured via a stress roentogram, an instrumented ankle arthrometer, or ankle/foot stress-testing device; anteroposterior inversion or eversion ankle-subtalar joint complex laxity had to be measured; and means and standard deviations of CAI and control groups had to be provided.Data Extraction:One investigator assessed each study based on the criteria to ensure its suitability for analysis. The initial search yielded 1378 potentially relevant articles, from which 8 were used in the final analysis. Once the study was accepted for inclusion, its quality was assessed with the PEDro scale.Data Synthesis:Twenty-one standardized effect sizes and their 95% confidence intervals were computed for each group and dependent variable. CAI produced the largest effect on inversion joint laxity; 45% of the effects ranged from 0.84 to 2.61. Anterior joint laxity measures were influenced second most by CAI (effects, 0.32 to 1.82). CAI had similar but less influence on posterior joint laxity (effects, −0.06 to 0.68) and eversion joint laxity (effects, 0.03 to 0.69).Conclusion:CAI has the largest effect with the most variability on anterior and inversion joint laxity measurements, consistent with the primary mechanism of initial injury.

Evaluation of Arthrometer for Ankle Instability: A Cadaveric Study

Stress tests are used to diagnose both acute and chronic lateral ankle instability. Commonly used stress tests require radiography and their reliability and sensitivity is still under debate. We developed a non radiographic ankle arthrometer to objectively assess mechanical ankle stability. This device was validated against stress radiographs in a cadaver investigation. Nine cadaver specimens were tested under: 0, 15, and 30 degrees ankle plantarflexion and 50 N, 100 N, 150 N, and 200 N anterior drawer load application. First, intact specimens were tested. Then the anterior talofibular ligament, calcaneofibular ligament and posterior talofibular ligament were sequentially cut. Anterior drawer displacement was analyzed simultaneously by a displacement transducer and by radiographic measurement. Stiffness was calculated as the linear increment of the load deformation curve. Results of a commercially available stress testing device served as a standard. Stable and unstable ankles were differentiated by ankle arthrometer displacement and stiffness analyses (p = 0.012 and 0.003) with the arthrometer adjusted to 0 degrees of plantarflexion and 50 N anterior drawer load application. Standardized stress testing device and ankle arthrometer stress radiographic measurements correlated significantly (p = 0.000 to 0.027). Transducer measured anterior drawer instability was highly sensitive (96.3%), while specificity was 44.4%. Setting a cut off value of 4.5 N/mm, the stiffness analyses discriminated stable and unstable ankles with a sensitivity of 91.7% while the specificity was 62.5%. The ankle arthrometer was able to measure anterior subluxation of the talus in relation to the tibia in a cadaver experiment. The procedure is non-radiographic and highly sensitive in differentiating unstable from stable ankles. Availablity of a nonradiographic device to measure ankle instability could improve diagnostic accuracy and facilitate decision making in patients with chronic ankle instability.

Isolated posterior cruciate ligament reconstruction: Is non-aggressive rehabilitation the right protocol?

Reconstruction Surgery of the posterior cruciate ligament (PCL) has not yet been fully standardized, and associated rehabilitation protocols have not been clearly defined. The aim of this study is to report the results of a consecutive series of patients who underwent the same surgical technique for isolated PCL reconstruction and were submitted to the same specific rehabilitation protocol. A non-aggressive rehabilitation protocol which protects the graft from excess mechanical stress produces satisfying and reproducible clinical and laxity results in the knee. Our series included 17 patients who underwent single bundle arthroscopic reconstruction of the PCL with an autologous quadriceps tendon graft and who followed the same non-aggressive rehabilitation protocol. All patients were followed up for an average of 30 months (range 12-60 months). The preoperative evaluation and the last follow-up included objective and subjective IKDC scores as well as the Tegner & Lysholm knee scales. The side to side laxity was measured radiologically with the Telos stress testing device. A statistical analysis was performed to compare preoperative and postoperative results. Preoperatively, no patients were classified as A or B on the IKDC objective score. At last follow-up visit, 88.2% of patients were classified as A or B. Average side to side anteroposterior laxity was 11.9 mm (range 8-18) in the preoperative evaluation and 3.8mm (range 1-7) in the final follow-up (p=0.01) The average subjective IKDC score was 37.7 before surgery and 74.7 at last follow-up (p< 0.01). The Tegner & Lysholm scores were significantly improved by surgery. Although the results are still less successful than ACL reconstruction, successful PCL reconstruction results were obtained with a standardized single bundle reconstruction technique and an adapted specific postoperative rehabilitation protocol. A non-aggressive rehabilitation protocol can limit postoperative mechanical stress on the graft. Retrospective Level IV.