Stress analysis and applicability analysis of the elliptical head

As the main pressure components of pressure vessels, the mechanical performance of cylinders and heads affects the normal operation of pressure vessels. At present, no unified theoretical formula exists for the connection region between an elliptical head and the cylinder. Therefore, the authors consider the standard elliptical head as the research object. First, the theoretical stress calculation formula is deduced according to the deformation continuity equation. Second, the stress is experimentally measured using an internal-pressure thin-walled-vessel stress measurement device, and the theoretical and experimental stress values in the discontinuous region between the elliptical head and cylinder are analysed and compared to verify the accuracy and applicability of the theoretical stress calculation formula. The results show that the theoretical stress calculation formula in the discontinuous region between the elliptical head and cylinder is valid. By comparing and analysing the theoretical and experimental stress values, the accuracy and applicability of the theoretical stress calculation formula in the discontinuous region are verified. The findings can provide guidance for the stress measurement of internal-pressure vessels.

HYBRID EXPERIMENTAL AND NUMERICAL CHARACTERIZATION OF THE 3D RESPONSE OF WOVEN POLYMER MATRIX COMPOSITES

The need for advanced material models to simulate the deformation, damage, and failure of polymer matrix composites under impact conditions is becoming critical as these materials are gaining increased usage in the aerospace and automotive industries. The purpose of this work is to characterize carbon epoxy fabrics for composite material models that rely on a large number of input parameters to define their nonlinear and 3D response; e.g. elastic continuum damage mechanics models or plasticity damage models [1, 2]. It is challenging to obtain large sets of experimental stress-strain curves, therefore, careful selection of physical experiments that exhibit nonlinear behavior is done to significantly reduce the cost of generating threedimensional material databases. For this work, plain weave carbon fabrics with 3k and 12k tows are manufactured by VARTM. Testing is done using MTS hydraulic test frames and 2D digital image correlation (DIC) to obtain experimental stress-strain curves for in-plane tension and shear as well as transverse shear. For cases where actual experimental data is either not available or difficult to obtain, the required model input is virtually generated using the NASA Glenn developed Micromechanics Analysis Method/Generalized Method of Cells (MAC/GMC) code. A viscoplastic polymer model is calibrated and utilized to model the matrix constituent within a repeating unit cell (RUC) of a plain weave carbon fiber fabric. Verification and validation of this approach is done using MAT213, a tabulated orthotropic material model in the finite element code LS-DYNA, which relies on 12 input stress-strain curves in various coordinate directions [2]. Based on the model input generated by the micromechanics analyses in combination with available experimental data, a series of coupon level verification and validation analyses are carried out using the MAT 213 composite model.

Stress Responses, Competition, and Free-Throw Performance: The Predicting Role of Other-Approach Goals

Experimental stress paradigms have been little used in the sport psychology literature because they are unrelated to the specific sport task. The Trier Social Stress Test (TSST) was used in the present study to investigate its influence on the free-throw performance of skilled basketball players. We also investigated the influence of adopting other-approach goals (i.e., doing well relative to others) on free-throw performance when basketball players were placed in a competition immediately after the TSST, comparatively with a control condition without competition. The results showed that free-throw performance decreased in the control condition, while free-throw performance remained stable when the TSST was followed by a competition. They also highlighted that other-approach goals were significant positive predictors of post-TSST performance in the competition condition but not in the control condition. The TSST may now be used with skilled athletes as an experimental stress paradigm to induce acute stress in the sport domain.

Stress Analysis And Applicability Analysis of Elliptical Head

In view of the phenomenon that there is no uniform theoretical formula for the connection area between the elliptical head and the cylinder, the author takes the standard elliptical head as the research object. Firstly, the theoretical stress calculation formula of the elliptical head and the discontinuous area of the cylinder is derived according to the deformation continuity equation. Secondly, the experimental stress is measured by means of the internal pressure thin-walled vessel stress measuring apparatus, The theoretical stress and experimental stress in discontinuous region are analyzed and compared to verify the accuracy and applicability of the formula for calculating the theoretical stress of the elliptical head and the cylinder discontinuity region. The results show that the theoretical stress calculation formula of discontinuous region of elliptical head is obtained according to the equation of deformation continuity, edge force and edge moment, internal force and internal moment; The internal pressure load is kept unchanged, and for the theoretical longitudinal stress, the constant stress is greater than 0, which is the tensile stress, and decreases gradually from the vertex to the equator; For the theoretical circumferential stress, the change trend is more complex, which can be divided into three stages, and there is pressure stress. At the vertex, the magnitude of the meridional stress and the circumferential stress is approximately equal; The change of the change from point 8 to point 10 is affected by discontinuous stress, and the change trend is abrupt; The theoretical stress and experimental stress in discontinuous region of elliptical head are analyzed and compared, and the accuracy and applicability of the formula are verified. The results are of great significance for the stress measurement of internal pressure vessels.

MORPHOLOGICAL FEATURES OF SPERMATOZOA FROM MALE WHITE RATS UNDER EXPERIMENTAL STRESS

We present the effect of stressogenic factors on the morphological parameters of spermatozoa. Objective. We studied the morpho-physiological features of spermatozoa from male albino rats under experimental stress. Materials and methods. A experiment was carried out using sexually mature outbred white rats. Combined stress was performed to an experimental group: after three days of starvation, an emotional stress of “free swimming in a cage” technique was provided. Under a microscope, the spermatozoa were counted per volume of epididymal suspension, the activity was evaluated, and the morphology was studied. Results. A study of the epididymal suspension of male rats under starvation and “emotional” stress showed a decrease in the total number of spermatozoa and sperm motility indices, and an increase in the abnormal gamete forms compared to the control. Conclusion. The combined effect of even short-term stressogenic factors leads to significant changes in the spermogram, allowing the quantitative and qualitative seminal fluid parameters to be a convincing criterion of maladaptation processes in the body under the stress.