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Asymmetric mandibular prognathism is a clinically common skeletal dentomaxillofacial deformity. Unilateral sagittal split ramus osteotomy (USSRO) is an effective alternative procedure to bilateral sagittal split ramus osteotomy (BSSRO) for some patients. However, the biomechanical effect of temporomandibular joint (TMJ) of USSRO has not been fully studied. This study aims to evaluate the stress distribution changes in the TMJ of asymmetric mandibular prognathism treated with BSSRO/USSRO, to validate the clinical feasibility of USSRO. Nineteen patients with mandibular prognathism patients who were treated with BSSRO (n = 12) and USSRO (n = 7) had preoperative and postoperative computed tomographic scanning. Preoperative and postoperative 3-dimensional finite element analysis (FEA) of functional TMJ movements were made on one BSSRO patient and one USSRO patient. In all patients, the ANB angle and mandibular deviation were significantly improved postoperatively. There was no significant difference in the postoperative ANB angle and mandibular deviation between the BSSRO group and the USSRO group. In two preoperative FEA models, the maximum stresses of non-deviation side TMJ structures were greater than the deviation side during functional movements. The unbalanced stress distribution was corrected postoperatively in both BSSRO/USSRO FE models. Both BSSRO/USSRO can improve the ANB angle and mandibular deviation. The bilateral TMJ structure in patients with asymmetric mandibular prognathism had unbalanced stress, which could be significantly improved with the USSRO as effectively as BSSRO. [ABSTRACT FROM AUTHOR]

Steel fibres were used to reinforce the layered targets with surface-to-surface combination. The two- and three-layer metal targets with a total thickness of 5 mm were fabricated by explosive welding. The damage mechanism and the anti-penetration performance of the targets were studied experimentally and numerically using the LS-DYNA 3D finite element code. The effects of layer number and fibre spacing density on the anti-penetration performance were discussed. The results show that the failure modes of the steel front plate were shearing and plugging, and that the failure mode of the aluminium rear plate was ductile prolonging deformation when the tied interface failed by tension (or shearing and plugging when the interface remained connected) for the two-layer target. For the three-layer target, the failure modes of the steel front plate and the aluminium middle plate were shearing and plugging, while the steel rear plate failed by ductile prolonging deformation. At the same time, the steel-fibres failed by bending and tensile deformation. The anti-penetration performance of the three-layer composite targets was better compared with the performance of the two-layer targets when the areal density and fibre spacing density were equal. The reinforced fibres will improve the anti-penetration performance of the targets, and the ballistic resistance decreased with an increase in the fibre spacing distance. [ABSTRACT FROM AUTHOR]

In order to analyze the influence of different thickness distributions on the antipenetration performance of layered plates with a good surface-to-surface combination, five types of two-layer steel/aluminum and three-layer steel/aluminum/steel plates with the same areal density were manufactured by the method of explosive welding. Ballistic experiments and numerical simulation were performed to study the antipenetration performance of the plates impacted by a spherical steel projectile of diameter 8 mm. A 14.5-mm riffled gun was used to launch the projectile, and the numerical simulation were carried out by using the LS-DYNA 3D explicit finite-element code. Effects of the number of layers, their thickness distribution, and total thickness on the antipenetration performance of the layered plates were investigated. Results showed that the antipenetration performance of the multilayer plates was better than that of a monolithic plate with the same areal density - the ballistic limit speed of the two-layer and three-layer plates, on the average, increased by 9.6 and 19.9% compared with that of the monolithic one. In addition, the antipenetration performance of the three-layer plates was better than that of the two-layer ones if the thickness of the steel and aluminum plates was same. The influence of layer thickness distribution on the antipenetration performance was more pronounced for the two-layer plates. [ABSTRACT FROM AUTHOR]

Shanxi Province is a major coal base for the rapid development in China, but heavy production of coal resources has left abundant water-filled voids, creating significant geologic hazards around coal mines. It is necessary to quickly investigate the position and distribution of voids with effective geophysical methods. The feasibility of transient electromagnetic (TEM) method in detecting and monitoring water-filled voids is analyzed using 3D finite-element numerical simulation results as well as a case study in this paper. The case study was mainly to analyze and monitor the conditions around the site of a power transfer station under construction in the west of Shanxi province where many water-filled, mined-out voids existed. Central-loop TEM sounding was carried out three times from January 2010 to April 2011 around the building footprint. The low resistivity abnormal area had been repeatedly located and the survey results showed that the area of voids increased with time, which indicated that the ground at the site was in an unstable and dangerous state. The surveys provided more detailed geological information to the government for further safety arrangement and building re-design. [ABSTRACT FROM AUTHOR]

Abstract: Series of ballistic experiments and numerical simulation were adopt to analyze the anti-penetration performance of explosively welded steel/aluminum, steel/aluminum/steel and aluminum/steel/aluminum plates impacted by spherical projectile vertically in this paper. A 14.5mm slip chamber gun was used to launch the spherical steel projectile with diameter of 6mm and the finite element code LS-DYNA 3D was used to simulate the penetration process. The effects of layer number, thickness, combination state of the interface and strength of the plates on the anti-penetration performance and damage mechanism were analyzed based on the results of experiment and numerical simulation. The results show that the damage mechanism of the front plate and middle plate is shearing and plugging, respectively, the steel rear plate is petalling deformation and the aluminum rear plate is ductile deformation impacted by projectile vertically. The anti-penetration performance of three-layered plates is better than that of two-layered plates with the same total thickness, especially the anti-penetration performance of three-layered steel/aluminum/steel welded plates is the best. As to two-layered steel/aluminum plates, the best anti-penetration performance can be attained when the thickness ratio is about 3:1. The good accordance of numerical and experimental results indicates that the finite element method (FEM) can predict the anti-penetration performance of multi-layered explosively welded plates well. [Copyright &y& Elsevier]

In this study, hybrid excitation doubly salient machines (HEDSMs) with parallel excitation structures are introduced. The three types of main poles in the HEDSMs are described and researched, respectively. A 30/20-pole HEDSM is analysed by the magnetic circuit means. Regulation performance of the air-gap fluxes of different main poles is presented. The expression of the total air-gap flux shows the ideal linear relationship between the total air-gap flux and the field excitation ampere-turns. The finite element analysis also verifies the perfect effect of the field control. And the flux line plots and no-load electromagnetic force (EMF) waveforms are presented. The experimental EMF waveforms and no-load characteristic curve are coincident with the simulation results. [ABSTRACT FROM AUTHOR]

• A Grain boundary (GB) plasticity model for the mesoscale is proposed. • The GB plasticity model is parameter-free, and requires no special numerical treatment for implementation within a crystal-plasticity, finite element framework. • Model predictions were compared against EBSD images from Magnesium and Titantium. • A near one-to-one correspondence between twin patterns predicted and imaged is shown. In this paper we propose a parameter-free grain boundary (GB) model for the meso-scale, employing it to effectively capture one-to-one twin pattern development across polycrystals (for the first time), by means of crystal plasticity finite element methods (CPFEM). Our model does not require higher-order mechanics, involve limiting length-scales, or demand special considerations for its FEM implementation. It derives all its data from that of its adjacent grains, which are modeled using single crystal plasticity. We apply our mesoscale GB model to experimentally imaged microstructures of Magnesium and Titanium. We demonstrate a clear ability to capture the prominent role of GBs in the nucleation and patterning of twins, with high spatiotemporal fidelity (approaching one-to-one), as compared to electron back-scattered diffraction (EBSD) maps. [Display omitted] [ABSTRACT FROM AUTHOR]

Liquid metal embrittlement (LME) is one of the severe problems of Zn-coated steel in resistance spot welding (RSW). Hence, proper welding schedules for Zn-coated steel are of practical interest. RSW involves a complex interaction between electrical, thermal, and mechanical phenomena. Identification and integration of all these governing physics are almost impossible by performing simple experiments. Hence, phenomenological modeling of RSW has gained a significant attention in the recent past. The complexity of the physical process introduced by the dynamic nature of contact resistance brings challenges for the model. A simplified but effective modeling approach of RSW is proposed where attention is focused on the evaluation of the thermal field using the finite element (FE) method. The interaction of the mechanical and electrical field is performed by the dynamic variation of the contact area, stress concentration, and non-uniform current density distribution in a semi-analytical model. These internal variables of the model are incorporated through the scaling of the governing parameters by the dependence of the transient and converged temperature field within a time step. The transient-dynamic contact resistance is detached from the measurement of total resistance and mapped adaptively by the implicit scheme within a time step of the numerical model. The transient development of the nugget is investigated for dual-phase steel (DP980) with an interrupted test of the dynamic resistance curve. The FE model is validated with experimentally measured results at different process conditions. The characterization of the thermal history from the model relatively identifies the LME phenomena and suggests corresponding modification of the welding schedule. [ABSTRACT FROM AUTHOR]