Numerical Study on the Impact of Gap between Sheets on the Quality of Riveted Single-Strap Butt Joints

Some controllable process parameters in the riveting process such as the gap between sheets, have an important impact on the quality of a riveted butt joint. In this paper, the finite element model of a riveted single-strap butt joint is established with the help of ABAQUS analysis software, and the riveting process is simulated under five kinds of gaps between sheets. From the perspectives of rivet upsetting size, rivet interference, radial deformation of sheet, and analysis of residual stress around the hole of sheet, the influence of the gap between sheets on the connection quality of the riveted butt joint is summarized. The results show that the left and right sheets will contact each other and there is extrusion stress between the sheets when the gap is zero. When the applied tensile load continues to increase, due to the influence of the secondary bending, the strap sheet responsible for the connection produces warping deformation, and there will be no further contact between the sheets. When the gap between sheets increases from 0 to 2 mm, the maximum deformation of strap sheets increases from 0.876 to 0.927 mm, which proves that the gap between sheets have no significant effect on the deformation of the strap sheet.

New Indicators of Myocardial Work in Healthy Individuals

Aim. To study in healthy individuals the gender and age characteristics of left ventricular (LV) myocardial work indicators, their correlations with global LV deformity indicators and echocardiographic parameters characterizing LV systolic and diastolic functions.Materials and methods. 70 Healthy individuals (n=70; 34 men and 36 women; aged 39.3±8.9 years) were included in the study. The echocardiographic examination determined the standard parameters and indicators of myocardial work: global work efficiency (GWE), global constructive work (GCW), global wasted work (GWW), global myocardial work index (GWI); as well as the myocardium deformation characteristics: global longitudinal deformation (GLS), global radial deformation (GRS) and global circular deformation (GCS). Spearman's correlation coefficient was used to investigate the relationship between parameters. A correlation was considered weak at r≤0.3, moderate at 0.3<r<0.7, and strong at r≥0.7.Results. The average value of global work efficiency (GWE) in men was 97% (96; 98), in women – 98% (97; 98). Global constructive work (GCW) in men was 2343.8±350.4 mm Hg%, in women – 2362.2±343.8 mm Hg%. The average value of global wasted work (GWW) in men was 46 mm Hg% (27; 75), in women – 44 mm Hg% (33; 55.5). The global myocardial work index (GWI) in men was 2069.9±356.4 mm Hg%, in women – 2055.7±339.9 mm Hg%. No significant differences were found in the comparative analysis of performance indicators. The analysis of correlations found that the myocardial work indicators didn't have significant correlations with age. Ejection fraction was moderately correlated with GWI (r=0.45) and GCW (r=0.49). Global longitudinal strain was strongly correlated with GWI (r=0.77) and GCW (r=0.77). Global radial strain correlated moderately directly with GWI (r=0.4) and GCW (r=0.4). Global circular strain was moderately correlated with GCW (r=0.35). A strong negative correlation was found between the GWE indicator and the post systolic contraction index (PSI) (r=-0.85). At the same time, PSI and GWW had a strong positive correlation (r=0.85).Conclusion. Indicators of LV myocardial work in healthy individuals do not have gender differences. The efficiency of the work of the myocardium depends primarily on the deformation of the LV, while the constructive work is determined by the volume characteristics. The wasted work indicator depends on the number of segments that peak in the post-systolic period.

A Regression Model to Determine Pressure Ratings of Slotted Tubular Components With Imperfections

The objective of the present work is to develop a prediction model to predict the pressure rating accounting for the imperfections using Design of Experiments (DoE) approach. Each imperfection is modelled in terms of a design parameter and bounded by a certain realistic variation. The DoE approach aids in identifying the most influencing imperfections and in further developing an approximate model that relates the input design parameters to the maximum radial deformation. Furthermore, the regression model is built to obtain the pressure rating of the component accounting for the imperfections. The study identifies that ovality and its orientation are by far the most influential imperfections when compared to others and provides the designer the effects of imperfection parameters on the component. The prediction model developed, serves as a ready reckoner to obtain the pressure rating of the component within the design space without any exclusive analysis. This approach leads to effective design and saves computational time.

Research on coordination design method of main bearing assembly structure based on the maximum radial deformation of bearing bush

Aiming at the difficulty of control and evaluation of main bearing deformation in the coordination design of the main bearing assembly structure for a high-speed diesel engine, taking MRD (the MRD means the maximum radial deformation of the bearing bush) of the bearing bush as an index to evaluate the out-of-round deformation of the bearing bush was proposed in this paper. The numerical calculation method of the MRD was given and the correctness of the method was experimentally verified. And the influence rules of different design parameters on the MRD were analyzed. On this basis, the coordination multi-objective optimization research of the main bearing assembly structure was carried out, and the optimization results were analyzed based on the influence rules of different design parameters on the reliability indexes. The results show that, when the pre-tightening force of the vertical bolt and the bearing bush interference are 240 kN and 0.17 mm respectively, the MRD reaches the minimum value. If the two values continue to increase, redundant loads can be generated, leading to the increase of the MRD. After optimization, the engine block strength coordination and bearing cap strength coordination had increased by 2.47% and 10.48%, respectively, and the deformation coordination and contact coordination had increased by 46.15% and 14.84%, respectively.

Deformation Law of Cold Drawing Process of High Strength Bridge Cable Steel

High-strength cable-steel bridge is the “lifeline” of steel structure bridges, which requires high comprehensive mechanical properties, and cold-drawing is the most important process to produce high-strength cable-steel bridge. Therefore, through the ABAQUS platform, a bridge wire drawing model was established, and the simulation analysis on the process of stress strain law and strain path trends for high-strength bridge steel wire from Φ 12.65 mm by seven cold-drawing to Φ 6.90 mm was conducted. The simulation results show that the wire drawing the heart of the main axial deformation, surface and sub-surface of the main axial and radial deformation occurred, with the increase in the number of drawing the road, the overall deformation of the wire was also more obvious non-uniformity. In the single-pass drawing process, the change in the potential relationship of each layer of material was small, and multiple inflection points appeared in the strain path diagram; the change in the seven-pass potential relationship was more drastic, which can basically be regarded as a simple superposition of multiple single-pass pulls.

Electrical Conductivity of Multiwall Carbon Nanotube Bundles Contacting with Metal Electrodes by Nano Manipulators inside SEM

Determining the metallicity and semiconductivity of a multi-walled carbon nanotube (MWCNT) bundle plays a particularly vital role in its interconnection with the metal electrode of an integrated circuit. In this paper, an effective method is proposed to determine the electrical transport properties of an MWCNT bundle using a current–voltage characteristic curve during its electrical breakdown. We established the reliable electrical nanoscale contact between the MWCNT bundle and metal electrode using a robotic manipulation system under scanning electron microscope (SEM) vacuum conditions. The experimental results show that the current–voltage curve appears as saw-tooth-like current changes including up and down steps, which signify the conductance and breakdown of carbon shells in the MWCNT bundle, respectively. Additionally, the power law nonlinear behavior of the current–voltage curve indicates that the MWCNT bundle is semiconducting. The molecular dynamics simulation explains that the electron transport between the inner carbon shells, between the outermost carbon shells and gold metal electrode and between the outermost carbons shells of two adjacent individual three-walled carbon nanotubes (TWCNTs) is through their radial deformation. Density functional theory (DFT) calculations elucidate the electron transport mechanism between the gold surface and double-wall carbon nanotube (DWCNT) and between the inner and outermost carbon shells of DWCNT using the charge density difference, electrostatic potential and partial density of states.

Semi-Analytical Model to Predict the Elastic Post-buckling Response of Axially Compressed Cylindrical Shells with Tailored Distributed Stiffness

This study introduces an approximate analytical model to predict the post-buckling response of cylinders with tailored nonuniform distributed stiffness. The shell's wall thickness, and thus its stiffness, is tailored so as to obtain multiple controlled elastic local buckling events when the cylinder is subjected to uniform axial compression. The proposed model treats cylinder segments of different stiffness as individual panels and combines their response by considering them as connected linear or nonlinear springs. The governing equations for the panels are formulated using von Karman's theory and solved by Galerkin's approximate method for a predefined radial deformation. Radial deformation functions are used to improve the model's accuracy and results show that the model's accuracy increases significantly with the number of considered radial functions. The model's predicted axial response for different cylinders are compared to results from experiments on 3D printed samples. Results indicate that this model accurately predicts the order of the buckling events while the buckling forces from the model are higher than those measured experimentally.

Thermal behavior of a radially deformed black hole spacetime

In the present article, we study the Hawking effect and the bounds on greybody factor in a spacetime with radial deformation. This deformation is expected to carry the imprint of a non-Einsteinian theory of gravity, but shares some of the important characteristics of general relativity (GR). In particular, this radial deformation will restore the asymptotic behavior, and also allows for the separation of the scalar field equation in terms of the angular and radial coordinates – making it suitable to study the Hawking effect and greybody factors. However, the radial deformation would introduce a change in the locations of the horizon, and therefore, the temperature of the Hawking effect naturally alters. In fact, we observe that the deformation parameter has an enhancing effect on both temperature and bounds on the greybody factor, which introduces a useful distinction with the Kerr spacetime. We discuss these effects elaborately, and broadly study the thermal behavior of a radially deformed spacetime.

Freezing Pressurized Water into a Standard Cylindrical Ice Sample in a Triaxial Cell

The mechanical characteristics of high-pressure frozen ice are a basis for the design of deep underground frozen walls, the drilling of thick permafrost and ice sheets, and the probing of extraterrestrial ice. The continuous control of the sample stress state from freezing to testing is essential for the experimental study of in situ mechanical response of high-pressure frozen ice. In the context, we developed a preparation technique for freezing pressurized water into a standard cylindrical ice sample in a triaxial cell. Through theoretical analysis, a cylindrical water sample with precise dimensions and strong sealing was fabricated using heat shrinkable tubing, sectional end caps, and an assembly cylinder. A mounting device was designed to insert the water sample into the triaxial cell without deformation. In order to deal with the lateral surface irregular of the resulting ice sample caused by freezing expansion, we proposed a pressurization method in which the volume of the confining medium is controlled to restrict the radial deformation of the sample, and the axial pressure on the sample is kept constant; thus, the freezing expansion will develop along the height direction through releasing the expansion pressure. Based on the analysis of sample deformation and finite element numerical simulations, the control method of the temperature fields of the sample and the confining medium was obtained, and the standard cylindrical ice sample which satisfies the geometric accuracy requirements was produced. The comparison of ice samples frozen by different freezing methods showed that the control of the confining medium mean temperature and the sample unidirectional freezing is necessary to improve the dimensional precision of the ice sample.