Effects of Lap Configuration on Mechanical Properties and Composition Distribution of Three-layer Overlapped Laser Weldments on Al/Cu Dissimilar Materials

Battery cells are connected via bus-bars to meet performance requirements, such as power and capacity, and multiple layers of dissimilar materials functioning as anodes, cathodes, or bus-bars are overlapped and welded together. In laser welding, the formation of brittle intermetallic phases in the weld joint is inevitable and, in turn, deteriorates the mechanical properties. To obtain the desirable joint performance, appropriate welding parameters to avoid intermetallic phase formations and joint designs to release stress concentrations must be obtained. This study investigates the effects of lap configurations and process parameters on the tensile-shear load, T-peel load, and composition distribution when multi-layered joints of dissimilar materials are produced by laser welding. Two layers of 0.4 mm Al sheets were welded with a single 0.2 mm Cu sheet, which was emulated using electric vehicle battery interconnects. The results show that the penetration depth varied in accordance with the lap configuration even under the same heat input condition. The lap configuration and welding parameters influenced the composition distribution of the welds, as they altered the solidification rate, number of Cu/Al contact interfaces, and location of the high-density material. The failure load of the T-peel specimens was always lower than that of the tensile-shear specimens except for the Cu−Al−Al lap configuration. The T-peel load of the Cu−Al−Al lap configuration was similar to that of the tensile-shear load. When the stress-concentrated joint was homogeneous, it was more robust.

Simulating Pitting Corrosion in AM 316L Microstructures Through Phase Field Methods and Computational Modeling

This work investigates how the crystallographic features of additive manufactured (AM) microstructures impact the pitting corrosion process through computational simulations of phase field models. Crystallographic influence is explored by introducing orientation dependencies into the corrosion potentials and elastic constants of the model through microstructural data provided from AM 316L samples. Comparisons of evolved pit morphologies and stress responses are made to a standard homogeneous, semi-circular model to better highlight how the complexity of AM microstructures affects pit evolution and stress concentrations. The results illustrate that AM-informed modeling cases produce larger, deeper pits with numerous locations of elevated stress concentrations along the pit front.

Open holes in composite laminates with finite dimensions: structural assessment by analytical methods

Open circular holes are an important design feature, for instance in bolted joint connections. However, stress concentrations arise whose magnitude depends on the material anisotropy and on the defect size relative to the outer finite plate dimensions. To design both safe and light-weight optimal structures, precise means for the assessment are crucial. These can be based on analytical methods providing efficient computation. For this purpose, the focus of the present paper is to provide a comprehensive stress and failure analysis framework based on analytical methods, which is also suitable for use in industry contexts. The stress field for the orthotropic finite-width open-hole problem under uniform tension is derived using the complex potential method. The results are eventually validated against Finite-Element analyses revealing excellent agreement. Then, a failure analysis to predict brittle crack initiation is conducted by means of the Theory of Critical Distances and Finite Fracture Mechanics. These failure concepts of different modelling complexity are compared to each other and validated against experimental data. The size effect is captured, and in this context, the influence of finite width on the effective failure load reduction is investigated.

Simulation of Stress Concentrations in Notches

The fatigue life curves of materials are very sensitive to the magnitude of the stress amplitude. A small change or inaccuracy in the determination of the stress value causes large changes or inaccuracies in the calculated fatigue life estimate. Therefore, the use of computer simulations for fatigue life estimation requires a proper model development methodology. The paper is devoted to the problem of the modeling of components in notches using FEM. The modeling parameters significantly influencing the obtained stress results have been defined. Exact analytical solutions served as a benchmark for comparing the accuracy of the stress values obtained using FEM models. For the selected 2D and 3D notched components, diagrams were created for sensitivity analysis of the influence of the mesh element density at the root of the notch in correlation with the exact analytical solution. The findings from model building were applied to model the stress concentration at the root of a V-weld joint in a gas pipeline.

RECONSTRUCTION ON THE VOLTAGE OF THE PRE-SLIDING STATE OF THE TRAGICHOUS MOUNTAIN SLOPE LANDSCAPE «AK KAIN»

The method of reconstruction and investigation of the pre-landslide condition of the tragic landslide «Ak-Kain» of the Northern Tien Shan is proposed. A model and a finite element algorithm for studying the stress-strain state (VAT) of soil sediments of an obliquely layered structure are briefly presented. The established zones and places of accumulation of dangerous stress concentrations along the inclined layer that led to the tragedy are shown. The plots show the found other areas of hazardous stress concentrations prone to destruction.

Thermal and Conjugate Heat Transfer Analysis of Exhaust Manifold of Multi-cylinder IC Engine

The exhaust manifold of multi cylinder IC engine is kept in between the engine block and the catalytic converter. So the exhaust manifold is exposed to very high temperature and care should be taken at the critical zone during the design stage. At several critical zones of the exhaust manifold, large compressive deformations are generated at elevated temperatures and tensile stresses remain at cold conditions. The thermal analysis will help in estimating the deformations and stress concentrations due to thermal loads. Therefore, the main aim of this study is to perform thermal analysis and conjugate heat flow analysis of an exhaust manifold of a multi-cylinder engine. The 3D model is generated using SolidWorks and analysis is carried out using Ansys workbench. Materials like grey C.I., aluminium nitride, silicon nitride, and stainless steel are used in this analysis. The results of total heat flux, directional heat flux and temperature distribution were compared. Silicon nitride material is suggested to be the suitable material for engine exhaust manifolds based on the material mechanical properties and thermal distribution-related thermal stress developed on the exhaust manifold.

Influence of Bone Quality on the Use of Implant Prostheses with Intermediate Pontic: Three-dimensional Finite Element Method

Objective The present study aimed to observe the differences in the dissipation of the main minimum stresses with the use of a fixed pontic partial prosthesis supported by two regular length implants in cortical and medullary bone tissues of different qualities. Materials and Methods Experimental groups were as follows: QI (two regular length implants with fixed pontic partial prosthesis and bony qualities consistent with type I), QII (identical to QI, with bony qualities consistent with type II), and QIII (identical to QI, with bony qualities consistent with type III). All the groups were developed and analyzed in virtual simulation environment using AnsysWorkbench software. Results The results showed highest stress concentrations in the region of the turns of the implants, especially in the apical region surrounding the implants and most notably in those positioned in the posterior region, supporting the molars. In addition, comparing the cortical bone among the groups, the results revealed increasing levels of stress in the order of QI, QII, and QIII. Comparing the medullary bone among the groups, the results revealed increasing levels of stress in the order of QIII, QII, and QI. Conclusion It was concluded that greater stress disparity occurred in the comparison between groups QI and QIII. There was a higher TMiP in QI in the cortical bone, but considering the literature values, it would not pose risks to its physiological limits. The use of a pontic fixed partial prosthesis on two regular implants of type III bone quality may cause unfavorable physiological repercussions for the posterior implant apical medullary bone.

Assessment of a Rock Pillar Failure by Using Change Detection Analysis and FEM Modelling

In this paper, various methods have been used to control and evaluate engineering difficulties in mining accurately. Different unstable scenarios occurring at the surfaces of underground mine walls, have been identified by comparing 3D terrestrial laser scanning surveys and subsequent point cloud 3D analysis. These techniques, combined with a change detection analysis approach and the integration of rock mechanics’ modelling, represent an asset for the assessment and management of the risk in mining. The change detection analysis can be used as control of mining and industrial processes as well as to identify valid model scenarios for establishing possible failure causes. A pillar spalling failure has been identified in an Italian underground marble quarry and this topic represents the basis of the present paper. A Finite-Element Method was used to verify the occurrence of relatively high-stress concentrations in the pillar. The FEM modelling revealed that stresses in the proximity of the pillar may have sufficient magnitude to induce cracks growth and spalling failure.

Prospects for the development of underground ore mining geotechnologies at the Talnakh and Oktyabrskoye deep mines

Rich sulphide, cuprous and impregnated ores are currently mined in the underground mines of the Talnakh and Oktyabrskoye deposits at the depths from 250 to 1,700 m. The reserves of rich ores are depleted, and therefore the growth of cuprous and impregnated ores is gaining importance. Their share may reach 80% of the total production by 2030. A distinctive feature of such deposits is the occurrence of cuprous and impregnated ores above the rich sulphide ore, which reserves have been mined out using mining systems with curing backfill mixtures. In this context, mining of impregnated ores will be done in the undermined zones, which will lead to significant rock mass deformation, opening of existing natural and formation of new cracks, will affect the stability of mining structures and will require special measures to control rock pressure in the mines. The paper presents the results of assessing the stress-and-strain condition of the undermined mass of impregnated ores mined using the room-and-pillar cut-and-fill method at the depths of 500, 1000 and 2000 m. The assessment shows that no dangerous stress concentrations arise in the mining structures at great depths which creates preconditions for the safe development of such deposits. A significant increase in ore extraction will require upgrading of existing underground facilities. It is proposed to carry out pre-concentration of the mined ore in the underground conditions using modern crushing complexes, high-capacity mine separators to remove waste rock, which can subsequently be used as the backfill material. In this way, a closed-loop mining system is created that meets the efficiency requirements of mining production and integrated subsoil development.

Reinforcement Mechanism of Carbon Black-Filled Rubber Nanocomposite as Revealed by Atomic Force Microscopy Nanomechanics

In this study, atomic force microscopy (AFM) nanomechanics were used to visualize the nanoscale stress distribution in carbon black (CB)-reinforced isoprene rubber (IR) vulcanizates at different elongations and quantitatively evaluate their volume fractions for the first time. The stress concentrations in the protofibrous structure (stress chains) that formed around the CB filler in CB-reinforced IR vulcanizates were directly observed at the nanoscale. The relationship between the local nanoscale stress distribution and macroscopic tensile properties was revealed based on the microscopic stress distribution and microscopic spatial structure. This study can help us gain insight into the microscopic reinforcement mechanism of carbon black-containing rubber composites.