Theoretical Model and Experimental Study of Dynamic Hot Rolling

At present, the commonly used hot rolling model is only applicable to the static rolling process. However, to study the dynamic rolling process, a dynamic rolling model with roll vertical movement velocity parameters is required. In this study, the influence of the vertical movement velocity of the rolls on the rolling process is considered, and a dynamic rolling process model is proposed when the roll gap is reduced during the hot rolling dynamic rolling process. Mathematically, the model is based on the upper limit method. The model considers the influence of the dynamic rolling process on the length of the deformation zone, establishes a dynamic velocity field model and an average deformation rate model, and then solves the total power of the rolling process. Finally, the dynamic rolling force equation is given. Compared with the experimental results, the dynamic rolling model in this paper has high accuracy with an average error of 4%. In addition, the influence of roll vertical velocity on rolling parameters is discussed, which provides a basis for the study of the dynamic rolling process.

Exploration of Support Structure Design for Additive Manufacturing at a Major OEM: a Case Study

The support structures required in many forms of additive manufacturing are often seen as waste that is tolerated as necessary. In metal additive processes, cost is frequently reduced by minimizing the amount of support structures needed to produce a part so that in turn, material use is decreased. However, there still exists the challenge of generating parts that are not deformed by the stresses created in the process. In this case study, support structures were leveraged to address deformation. A part was printed via direct metal laser melting with supports with a high grouping density in areas of high anticipated deformation in order to stiffen the part to prevent deformation. Then, they were printed again with a low grouping density to allow the part to relax and reduce stress. Combinations of support strategy and leaving supports on during post processing were used to investigate the effects of keeping or removing the supports in post-print operations such as surface treatment. The two optimized support strategies saw a lower deformation than the baseline approach to supports, and the releasing strategy was closest to the reference solid model with a 26% reduction in average deformation. The results suggest that the support structures in additively manufactured parts have a different impact on the part than the original intent of the supports to simply alleviate a process requirement. The support structures should be used to impact the final part geometry.

THE STUDY OF ORE BREAKAGE IN BALL MILL TO ASSESS THE ENERGY EFFICIENCY OF ITS GRINDING

The results of mathematical modelling of ore breakage by a ball mill based on mathematical models of loaded and unloaded elastic elements are presented. The property of the arrangement of balls in the drum due to segregation is used, under the influence of which they are distributed with increasing size from the loading to the unloading throat, and in the cross-sections from the lining to the axis. It is shown that it is advisable to use the balls in the cross-section of the drum, where their size is 50 mm. The more the volume of ore is destroyed, the more the ball's energy is spent on this, the less energy will be converted into deformation of the elastic element. Consequently, the value of the deformation of the elastic element corresponds to the volume of the destroyed ore, as well as the energy efficiency of its grinding. The approach of interaction of balls with an elastic element from the point of view of mass phenomena will be more effective. The average value of deformations by all balls that have passed through the elastic element, arbitrarily accurately characterizes the average value of the destroyed volume of ore, that is, the energy efficiency of its grinding. The controlled parameter is found in accordance with the proposed relationship with the measured average deformation value of the elastic element. The deviation of certain values from the reference values is within 1%, which meets the requirements of the technological process.

Microstructure of Vein Quartz Aggregates as an Indicator of Their Deformation History: An Example of Vein Systems from Western Transbaikalia (Russia)

We investigated the microstructural and crystallographic features of quartz from complex vein systems associated with the development of thrust and shear deformations in Western Transbaikalia using electron back scatter diffraction (EBSD) and optical microscopy. Vein quartz systems were studied to obtain insights on the mechanisms and localization of strains in quartz, in plastic and semibrittle conditions close to the brittle–ductile transition, and their relationship to the processes of regional deformations. Five types of microstructures of vein quartz were distinguished. We established that the preferred mechanisms of deformation of the studied quartz were dislocation glide and creep at average deformation rates and temperatures of 300–400 °C with subsequent heating and dynamic and static recrystallization. The formation of special boundaries of the Dauphiné twinning type and multiple boundaries with angles of misorientation of 30° and 90° were noted. The distribution of the selected types in the differently oriented veins was analyzed. The presence of three generations of vein quartz was established. Microstructural and crystallographic features of vein quartz aggregates allow us to mark the territory’s multi-stage development (with the formation of syntectonic and post-deformation quartz).

Physical Properties Characterization and Design Comparation of Knee Implant with Ti6Al4V Material

This study aims to describe the results of characterization of physical properties and design comparation of knee implant. the characterization of the material was intended to determine the morphology using SEM, crystal structure using XRD, and chemical composition using XRF. In both designs, the simulation was carried out to get the total deformation value. Simulation is carried out by loading humans walking, jumping, and downstairs in 0-1.1 seconds. While the comparation was focused on comparizing the total deformation value from the human activity of walking, jumping, and downstairs to determine the optimum design. The finding of this study were SEM showed that many parallel strokes on Ti6Al4V, then XRD test showed that the crystallinity peak was at position 40.5189˚ which were indicated by the crystal orientation index [200] reaching 29.35 counts (cts), and Full Width Half Maximum (FWHM) at an angle of 0.288˚ which had an atomic distance along the length of 2.2246 (Å ) with a relative intensity of 100%. And the XRF test showed the highest chemical content of Ti6Al4V was Ti, amounting to 85.12%. This was indicated by the total maximal deformation of the first design 0.23030 micormeter while the second design was 2.109600 micrometer, so the first design was more recommended for implant use. While comparation of total deformation showed that the first design had the lowest maximum average deformation value. The results showed that the first implant design was the optimum design.

Understanding Land Subsidence Along the Coastal Areas of Guangdong, China, by Analyzing Multi-Track MTInSAR Data

Coastal areas are usually densely populated, economically developed, ecologically dense, and subject to a phenomenon that is becoming increasingly serious, land subsidence. Land subsidence can accelerate the increase in relative sea level, lead to a series of potential hazards, and threaten the stability of the ecological environment and human lives. In this paper, we adopted two commonly used multi-temporal interferometric synthetic aperture radar (MTInSAR) techniques, Small baseline subset (SBAS) and Temporarily coherent point (TCP) InSAR, to monitor the land subsidence along the entire coastline of Guangdong Province. The long-wavelength L-band ALOS/PALSAR-1 dataset collected from 2007 to 2011 is used to generate the average deformation velocity and deformation time series. Linear subsidence rates over 150 mm/yr are observed in the Chaoshan Plain. The spatiotemporal characteristics are analyzed and then compared with land use and geology to infer potential causes of the land subsidence. The results show that (1) subsidence with notable rates (>20 mm/yr) mainly occurs in areas of aquaculture, followed by urban, agricultural, and forest areas, with percentages of 40.8%, 37.1%, 21.5%, and 0.6%, respectively; (2) subsidence is mainly concentrated in the compressible Holocene deposits, and clearly associated with the thickness of the deposits; and (3) groundwater exploitation for aquaculture and agricultural use outside city areas is probably the main cause of subsidence along these coastal areas.

Influence of Vibrational Loading on Deformation Behavior of Metallic Glass: A Molecular Dynamics Study

The influence of vibrational loading on the deformation behavior of a Zr50Cu46Al4 metallic glass (MG) was characterized via molecular dynamics approaches. High-frequency (1 GHz) vibrational loading was imposed on the elastoplastic deformation stage during the uniaxial tension of the MG conducted at 50 K. It was found that imposing vibrational loading scarcely reduces the average deformation resistance. On the contrary, it results in a notable residual hardening effect after the vibrational loading is removed, which differs significantly from the previously reported acoustic softening mechanisms. Vibrational loading can increase the fraction of STZed atoms and enhance the shear localization degree, which is beneficial to the shear deformation of MGs. Meanwhile, the influence of vibrational loading on the local microstructure of MG is negligible. A plausible explanation of these phenomena is given by considering the accelerated aging of MG stemming from the β relaxation.

P4491Noninvasive evaluation of force distribution in mitral annuloplasty rings: do rigid annuloplasty rings increase stress?

Purpose To evaluate forces distribution, local stresses and deformation of mitral annuloplasty rings in response to annuloplasty. Methods Seguin (St. Jude Medical), Physio I (Edwards LifeScience), Memo 3D (Sorin) and Future SG (Medtronic) MAR of size 30 mm were included in the study. The study group included 4 males patients aged 52–68 years who underwent isolated mitral valve annuloplasty for ischemic mitral regurgitation. All surgeries were performed by the same experienced operator according to the standardized protocol. The mechanical properties of the similar set of MAR were evaluated under uniaxial compression by 15% in the longitudinal and transverse directions on the Testing Machines Z5.0 (Zwick/Roell). Biomechanics was assessed with MSCT. The MAR frame models at the initial state and at the ventricular ejection and atrial systole phases were obtained from DICOM-data using computer tomography Sensation Somatom 64 (Siemens). The models were compared using the innovative numerical algorithm in MatLab (Mathworks) by forming pairs for “systole – diastole”, “initial state – diastole” for all four types of MAR. We compared the mobility of the implanted devices and changes in the physiological saddle shape geometry of the mitral annulus in response to annuloplasty. We performed the quantitative analysis of the movement of each point of the reconstructed model between two states with the subsequent calculation of the required forces based on the finite element analysis. Results Future CG MAR has the greatest longitudinal and transverse stiffness (18.1N and 4.8N, respectively), whereas Memo 3D demonstrates the lowest values (2.3N and 1.5N). The rest two models show intermediate values of 4.2 - 11.3 N to 2.0 - 4.3N. The comparative analysis of MAR before and after implantation shows that Physio demonstrates the most pronounced deviations from normal physiological shape with significant annular compression along the intercommissural diameter by 1.36 mm resulted in a rounded annulus shape. None significant geometrical deformity among the other prosthetic rings. MEMO 3D demonstrates an average deformation by 0.18 mm across all zones, Seguin - 0.42 mm, Future CG - 0.34 mm. The force distribution analysis demonstrated the least forces of MEMO 3D, whereas the largest ones (up to 1.5N) are shown by Future SG, leading to the induction of locally elevated stress in surrounding tissues, potentially triggering the development of paravalvular fistulae. Conclusion Preliminary results demonstrate that the use of flexible rings with initially mobile structure allows preserving the native mitral annulus mobility after annuloplasty and reducing the stress (forces) acting on the surrounding tissues. The presented non-invasive method for estimating the stress of mitral annulus is crucial for advanced clinical practice as it allows further studying of the underlying pathologic mechanisms of developing paravalvular fistulae.