Prediction of the cross-sectional capacity of cold-formed CHS using numerical modelling and machine learning

The use of circular hollow sections (CHS) have seen a large increase in usage in recent years mainly because of the distinctive mechanical properties and unique aesthetic appearance. The focus of this paper is the behaviour of cold-rolled CHS beam-columns made from normal and high strength steel, aiming to propose a design formula for predicting the ultimate cross-sectional load carrying capacity, employing machine learning. A finite element model is developed and validated to conduct an extensive parametric study with a total of 3410 numerical models covering a wide range of the most influential parameters. The ANN model is then trained and validated using the data obtained from the developed numerical models as well as 13 test results compiled from various research available in the literature, and accordingly a new design formula is proposed. A comprehensive comparison with the design rules given in EC3 is presented to assess the performance of the ANN model. According to the results and analysis presented in this study, the proposed ANN-based design formula is shown to be an efficient and powerful design tool to predict the cross-sectional resistance of the CHS beam-columns with a high level of accuracy and the least computational costs

Computer aided optimization of tube hydroforming processes

Tube hydroforming is a process of forming closed-section, hollow parts with different cross sections by applying combined internal hydraulic forming pressure and end axial compressive loads or feeds to force a tubular blank to conform to the shape of a given die cavity. It is one of the most advanced metal forming processes and is ideal for producing seamless, lightweight, near net shape components.. This innovative manufacturing process offers several advantages over conventional manufacturing processes such as part consolidation, weight reduction and lower tooling and process cost. To increase the implementation of this technology in different manufacturing industries, dramatic improvements for hydroformed part design and process development are imperative. The current design and development of tube hydroforming processes is plagued with long design and prototyping lead times of the component. The formability of hydroformed tubular parts is affected by various physical parameters such as material properties, tube and die geometry, boundary conditions and process loading paths. Finite element simulation is perceived by the industry to be a cost-effective process analysis tool and has the capability to provide a greater insight into the deformation mechanisms of the process and hence allow for greater product and process optimization. Recent advances in the non-linear metal forming simulation capabilities of finite element software have made simulation of many complex hydroforming processes much easier. Although finite element based simulation provides a better understanding of the process, trial-and-error based simulation and optimization becomes very costly for complex processes. Thus, powerful intelligent optimization methods are required for better design and understanding of the process. This work develops a better understanding of the forming process and its control parameters. An experimental study of ‘X ’ and ‘T’-branch type tube hydroforming was undertaken and finite element models of these forming processes were built and subsequently validated against the experimental results. Furthermore these forming processes were optimized using finite element simulations enhanced with numerical optimization algorithms and with an adaptive process control algorithm. These new tools enable fast and effective determination of loading paths optimized for successful hydroforming of complex tubular parts and replace trial-and-error approaches by a more efficient customized finite element analysis approach

Flexural Buckling of Steel Cold-Formed Hollow Profiles in the Framework of Eurocodes

The use of cold-formed hollow structural (CFHS) steel has been growing in the past decade due to several advantages such as superior behavior towards lateral-torsional buckling, aesthetic structures, and feasibility of using internal volume to increase load-carrying capacity. The cold-forming process can change drastically the shape of the stress-strain curve and strength parameters of the base material. There are several investigations on buckling tests of hollow section columns; however, studies on cold-formed hollow sections are still lacking. This shortcoming of experimental data becomes more pronounced when the corner behavior of CFHS is under consideration. Only a limited number of corner coupon tests can be found in international literature. This Ph.D. thesis is developed in line with the progress of the European project INNOvative 3D JOINTS for Robust and Economic Hybrid Tubular Construction (INNO3DJOINTS). The primary objective is to advance, through analytical and experimental research, knowledge on the flexural buckling behavior of CFHS columns. An extensive experimental program ( 21 flexural buckling tests) on SHS and RHS columns has been carried out varying the steel grade (i.e. S275 and S355) and the overall slenderness ratio. This database serves as the basis for the assessment and improvement of the flexural buckling curve for CFHS. The stress-strain behavior of the sections was investigated by performing tensile coupon tests (81 tests) from both flat and corner areas. special effort was made to obtain the static stress-strain data by pausing the test for 60 seconds during the test. We also employed an innovative method to perform the coupon test on the corner area of CFHS. This procedure will reduce the secondary effect results from methods such as welding a plate or flattening the end grip, and therefore reduce the bias in the results of the corner area. A comprehensive discussion on the definition of safety and the adopted safety levels in EN1990 and EN1993-1-1 has been presented. The results show some potential criticisms of the application of current rules for plastic design and analysis of such a column and a further investigation is required on the matter. In addition, it is shown that the current material test procedures in BSI and ATM standards may lead to misevaluate the static strengths of material which is required for the design of structures

Proceeding Of Mechanical Engineering Research Day 2016 (MERD’16)

This Open Access e-Proceeding contains a compilation of 105 selected papers from the Mechanical Engineering Research Day 2016 (MERD’16) event, which is held in Kampus Teknologi, Universiti Teknikal Malaysia Melaka (UTeM) - Melaka, Malaysia, on 31 March 2016. The theme chosen for this event is ‘IDEA. INSPIRE. INNOVATE’. It was gratifying to all of us when the response for MERD’16 is overwhelming as the technical committees received more than 200 submissions from various areas of mechanical engineering. After a peer-review process, the editors have accepted 105 papers for the e-proceeding that cover 7 main themes. This open access e-Proceeding can be viewed or downloaded at www3.utem.edu.my/care/proceedings. We hope that these proceeding will serve as a valuable reference for researchers. With the large number of submissions from the researchers in other faculties, the event has achieved its main objective which is to bring together educators, researchers and practitioners to share their findings and perhaps sustaining the research culture in the university. The topics of MERD’16 are based on a combination of fundamental researches, advanced research methodologies and application technologies. As the editor-in-chief, we would like to express our gratitude to the editorial board and fellow review members for their tireless effort in compiling and reviewing the selected papers for this proceeding. We would also like to extend our great appreciation to the members of the Publication Committee and Secretariat for their excellent cooperation in preparing the proceeding of MERD’16

Development of a Novel Linear Magnetostrictive Actuator

This dissertation presents the development of a novel linear magnetostrictive actuator. The magnetostrictive material used here is Terfenol-D, an alloy of the formula Tb0.3Dy0.7Fe1.92. In response to a traveling magnetic field inside the Terfenol-D element, it moves in the opposite direction with a peristaltic motion. The proposed design offers the flexibility to operate the actuator in various configurations including local and conventional three-phase excitation. The conceptual design of the linear magnetostrictive actuator was performed during which different configurations were analyzed. Finite Element Analysis (FEA) was extensively used for magnetic circuit design and analysis in conceptual design. Eventually one of these designs was chosen based on which detailed design of linear magnetostrictive actuator was carried out. A new force transmission assembly incorporates spring washers to avoid the wear due to the sudden collision of Terfenol-D element with the force transmission assembly. All mechanical parts were then fabricated at the mechanical engineering machine shop. The power electronics to operate the motor in a local three-phase mode was designed and implemented. It was demonstrated that the power consumption can be reduced significantly by operating the magnetostrictive linear actuator in the local excitation mode. A finite-element model of the actuator was developed using ATILA and an empirical model was presented using the data gathered from numerous tests performed on the actuator. The closed-loop control system was implemented using relay control which resulted in an optimal closed-loop performance. The magnetostrictive actuator has demonstrated 410-N load capacity with a travel range of 45 mm, and the maximum speed is 9 mm/min. The maximum power consumption by the motor is 95 W. The sensorless control of the linear magnetostrictive actuator was successfully conducted using two different approaches. First, using a linear-approximation method, we achieved a position estimation capability with ±1 mm error. Then, an adaptive neuro-fuzzy inference system was employed for estimating the position which resulted in a position estimation capability with only a ±0.5 mm error

Numerical Study of Concrete

Concrete is one of the most widely used construction material in the word today. The research in concrete follows the environment impact, economy, population and advanced technology. This special issue presents the recent numerical study for research in concrete. The research topic includes the finite element analysis, digital concrete, reinforcement technique without rebars and 3D printing

Material and structural behaviour of metal 3D printed elements

Wire arc additive manufacturing (WAAM) is a metal 3D printing method that enables large-scale structural elements with complex geometry to be built in a relatively efficient and cost-effective manner, offering revolutionary potential to the construction industry. Fundamental experimental data on the material and structural behaviour of WAAM elements are however lacking. Therefore, a comprehensive experimental study into the material properties, the cross-section and the member buckling behaviour of WAAM elements has been conducted and is reported herein. Tensile tests on 137 WAAM steel coupons, covering different steel grades, finishes, thicknesses, extraction directions and locations, and deposition strategies, have been conducted. Microstructural characterisation has also been performed by means of optical microscopy (OM) and electron backscatter diffraction (EBSD). At the cross-section and member levels, four-point bending tests on 14 WAAM stainless steel tubular beams and flexural buckling tests on 18 WAAM stainless steel tubular columns have been undertaken, respectively. Owing to the geometric undulations inherent to the WAAM process, 3D laser scanning and digital image correlation (DIC) were employed in the material, beam and column testing programme to capture the geometric properties and deformation responses of the specimens, respectively. The present research focuses on WAAM elements subjected to predominantly static loading (rather than fatigue loading), with an emphasis on structural stability. The examined WAAM steels exhibited consistent, almost isotropic mechanical properties, a Young’s modulus comparable to conventionally-produced steel plates, marginally lower strength, reflecting the slower cooling conditions than is customary, and good ductility. To describe the full stress-strain response of WAAM steels, material models were proposed and validated against the tensile test results and further experimental data collected from the literature. Following the beam and column tests, the applicability of the current cross-section and column design provisions in EN 1993-1-4 and AISC 370, as well as the continuous strength method (CSM), to WAAM stainless steel elements was assessed by comparing the test results with the strength predictions. The comparisons highlighted the need to allow for the weakening effect of the inherent geometric undulations of WAAM elements, in order to achieve safe-sided strength predictions.Open Acces

Advanced Theoretical and Computational Methods for Complex Materials and Structures

The broad use of composite materials and shell structural members with complex geometries in technologies related to various branches of engineering has gained increased attention from scientists and engineers for the development of even more refined approaches and investigation of their mechanical behavior. It is well known that composite materials are able to provide higher values of strength stiffness, and thermal properties, together with conferring reduced weight, which can affect the mechanical behavior of beams, plates, and shells, in terms of static response, vibrations, and buckling loads. At the same time, enhanced structures made of composite materials can feature internal length scales and non-local behaviors, with great sensitivity to different staking sequences, ply orientations, agglomeration of nanoparticles, volume fractions of constituents, and porosity levels, among others. In addition to fiber-reinforced composites and laminates, increased attention has been paid in literature to the study of innovative components such as functionally graded materials (FGMs), carbon nanotubes (CNTs), graphene nanoplatelets, and smart constituents. Some examples of smart applications involve large stroke smart actuators, piezoelectric sensors, shape memory alloys, magnetostrictive and electrostrictive materials, as well as auxetic components and angle-tow laminates. These constituents can be included in the lamination schemes of smart structures to control and monitor the vibrational behavior or the static deflection of several composites. The development of advanced theoretical and computational models for composite materials and structures is a subject of active research and this is explored here for different complex systems, including their static, dynamic, and buckling responses; fracture mechanics at different scales; the adhesion, cohesion, and delamination of materials and interfaces

Mastering Uncertainty in Mechanical Engineering

This open access book reports on innovative methods, technologies and strategies for mastering uncertainty in technical systems. Despite the fact that current research on uncertainty is mainly focusing on uncertainty quantification and analysis, this book gives emphasis to innovative ways to master uncertainty in engineering design, production and product usage alike. It gathers authoritative contributions by more than 30 scientists reporting on years of research in the areas of engineering, applied mathematics and law, thus offering a timely, comprehensive and multidisciplinary account of theories and methods for quantifying data, model and structural uncertainty, and of fundamental strategies for mastering uncertainty. It covers key concepts such as robustness, flexibility and resilience in detail. All the described methods, technologies and strategies have been validated with the help of three technical systems, i.e. the Modular Active Spring-Damper System, the Active Air Spring and the 3D Servo Press, which have been in turn developed and tested during more than ten years of cooperative research. Overall, this book offers a timely, practice-oriented reference guide to graduate students, researchers and professionals dealing with uncertainty in the broad field of mechanical engineering