Optimization of the Curved Metal Damper to Improve Structural Energy Dissipation Capacity

Structural curved metal dampers are implemented in various applications to mitigate the damages at a specific area efficiently. A stable and saturated hysteretic behavior for the in-plane direction is dependent on the shape of a curved-shaped damper. However, it has been experimentally shown that the hysteretic behavior in the conventional curved-shaped damper is unstable, mainly as a result of bi-directional deformations. Therefore, it is necessary to conduct shape optimization for curved dampers to enhance their hysteretic behavior and energy dissipation capability. In this study, the finite element (FE) model built in ABAQUS, is utilized to obtain optimal shape for the curved-shaped damper. The effectiveness of the model is checked by comparisons of the FE model and experimental results. The parameters for the optimization include the curved length and shape of the damper, and the improved approach is conducted by investigating the curved sections. In addition, the design parameters are represented by B-spline curves (to ensure enhanced system performance), regression analysis is implemented to derive optimization formulations considering energy dissipation, constitutive material model, and cumulative plastic strain. Results determine that the energy dissipation capacity of the curved steel damper could be improved by 32% using shape optimization techniques compared to the conventional dampers. Ultimately, the study proposes simple optimal shapes for further implementations in practical designs.

Cutting mechanism of straight-tooth milling process of titanium alloy TC21 based on simulation and experiment

Due to the characteristics of high strength, high chemical activity and low heat conduction, titanium alloy materials are generally difficult to machine. As a typical titanium alloy with higher strength and lower heat conductivity, the machinability of titanium alloy TC21 is very poor and its cutting process is companied with larger cutting force and rapid tool wear. Straight-tooth milling tool is often used to cut the groove and side surface in the titanium alloy parts. And the milling method can be used to investigate the cutting mechanism because the cutting force has only two components and the better chip morphology is obtained. To investigate the straight-tooth milling process of TC21 alloy, a series of milling force experiments have been done. In addition, a 3D finite element model (FEM) for the straight-tooth milling process of TC21 alloy is presented to simulate the milling process. In the model, the constitutive material model, the failure model, the friction model and the heat transfer model were adopted. Through the simulation, chip formation, stress distribution, cutting force and milling temperature were obtained. The cutting force reaches its maximum when the spindle speed reaches about 13000 rpm, and then decreases as the speed continues to increase. The results confirmed that the similar “Salomon” phenomenon existed in the cutting process of TC21 alloy.

Soil-Structure Interaction of Flexible Temporary Trench Box: Parametric Studies Using 3D FE Modelling

This paper presents the results of two parametric finite-element studies that were carried out using the PLAXIS-3D finite element (FE) computer code. The following objectives and corresponding parameters were considered: (i) to evaluate the soil pressure on the steel trench box shield; the parameters studied were related to soil type and material, and the study considered till, dry sand, wet sand, and sensitive clay soil; (ii) to assess the effect of trench box material and geometry on earth pressure; the parameters studied were related to trench box material (steel versus aluminum) as well as geometry (plate thickness and strut diameter). These studies included simulation of two steel (or aluminum) trench box shields stacked upon each other to cover the total 6 m (20 ft) deep trench. A Mohr-Coulomb (MC) constitutive material model was chosen for FE analysis (FEA). The FEA results were compared to empirical apparent earth pressure diagrams for a sensitive clay. Comparisons showed that the parameters related to the soil and the trench box have a significant influence on earth pressures.

CO2 injection and storage in porous rocks: coupled geomechanical yielding below failure threshold and permeability evolution

With the increasing demand for CO2 storage into the subsurface, it is important to recognize that candidate formations may present complex stress conditions and material characteristics. Consequently, modelling of CO2 injection requires the selection of the most appropriate constitutive material model for the best possible representation of the material response. The authors focus on modelling the geomechanical behaviour of the reservoir material, coupled with multi-phase flow solution of CO2 injection into a saline saturated medium. It is proposed to use the SR3 critical state material model which considers a direct link between strength-volume-permeability that evolves during the simulation; furthermore the material is considered to yield prior to reaching a peak strength in agreement with experimental observations. Verification of the material model against established laboratory tests is conducted, including multi-phase flow accounting for relative permeabilities and fluid densities. Multi-phase flow coupled to advanced geomechanics provides a holistic approach to modelling CO2 injection into sandstone reservoirs. The resulting injection pressures, CO2 migration extent and patterns, formation dilation and strength reduction are compared for a range of in-situ porosities and incremental material enhancements. This work aims to demonstrate a numerical modelling framework to aid in the understanding of geomechanical responses to CO2 injection for safe and efficient deployment and is particularly applicable to CO2 sequestration in less favourable aquifers with a relatively low permeability, receiving CO2 from a limited number of injection wells at high flow rates. The proposed framework can also enable additional features to be incorporated into the model such as faults and detailed overburden representation.Thematic collection: This article is part of the Geoscience for CO2 storage collection available at: https://www.lyellcollection.org/cc/geoscience-for-co2-storage

Biomechanical duality of fracture healing captured using virtual modeling and validated in ovine bones

Bone fractures commonly repair by forming a bridging structure called callus, which begins as soft tissue and gradually ossifies to restore the rigidity of the bone. In large animals and humans, this process typically requires only a few months to complete. Occasionally bones can fail to heal, resulting in nonunions that are difficult to diagnose and treat, partly because early detection of poor healing remains challenging. We present a translational technique for measuring what really matters in fracture healing – the structural integrity of the bone – using image-based virtual mechanical testing. This work shows that physical mechanical tests of osteotomized ovine tibiae can be reliably recapitulated in a simulation environment only when the soft-hard mechanical duality of the healing zone is accurately captured by the constitutive material model. A large-scale optimization analysis was performed on thousands of 3D finite element models derived from computed tomography (CT) scans of 33 osteotomized sheep. This identified a piecewise material model that successfully replicated the postmortem torsion testing data by differentiating between soft and hard callus based on material density alone. The results suggest that most of the structural integrity of a healing bone is conferred by an internal architecture of mineralized hard callus that is supported by interstitial soft tissue. We conclude that with appropriate material modeling, virtual mechanical testing is a reliable surrogate for physical testing and that this technique has high translational potential for diagnostic testing of nonunion.

Qualitative Investigation of Damage Initiation at Meso-Scale in Spheroidized C45EC Steels by Using Crystal Plasticity-Based Numerical Simulations

This research uses EBSD data of two thermo-mechanically processed medium carbon (C45EC) steel samples to simulate micromechanical deformation and damage behavior. Two samples with 83% and 97% spheroidization degrees are subjected to virtual monotonic quasi-static tensile loading. The ferrite phase is assigned already reported elastic and plastic parameters, while the cementite particles are assigned elastic properties. A phenomenological constitutive material model with critical plastic strain-based ductile damage criterion is implemented in the DAMASK framework for the ferrite matrix. At the global level, the calibrated material model response matches well with experimental results, with up to ~97% accuracy. The simulation results provide essential insight into damage initiation and propagation based on the stress and strain localization due to cementite particle size, distribution, and ferrite grain orientations. In general, it is observed that the ferrite–cementite interface is prone to damage initiation at earlier stages triggered by the cementite particle clustering. Furthermore, it is observed that the crystallographic orientation strongly affects the stress and stress localization and consequently nucleating initial damage.

Identification of the LLDPE Constitutive Material Model for Energy Absorption in Impact Applications

Current industrial trends bring new challenges in energy absorbing systems. Polymer materials as the traditional packaging materials seem to be promising due to their low weight, structure, and production price. Based on the review, the linear low-density polyethylene (LLDPE) material was identified as the most promising material for absorbing impact energy. The current paper addresses the identification of the material parameters and the development of a constitutive material model to be used in future designs by virtual prototyping. The paper deals with the experimental measurement of the stress-strain relations of linear low-density polyethylene under static and dynamic loading. The quasi-static measurement was realized in two perpendicular principal directions and was supplemented by a test measurement in the 45° direction, i.e., exactly between the principal directions. The quasi-static stress-strain curves were analyzed as an initial step for dynamic strain rate-dependent material behavior. The dynamic response was tested in a drop tower using a spherical impactor hitting a flat material multi-layered specimen at two different energy levels. The strain rate-dependent material model was identified by optimizing the static material response obtained in the dynamic experiments. The material model was validated by the virtual reconstruction of the experiments and by comparing the numerical results to the experimental ones.

CONSTITUTIVE MATERIAL MODEL FOR BLOCK MASONRY AND ITS MECHANICAL PROPERTIES

This research work aims at the development of a material model for concrete block masonry used in the load-bearing wall as well as masonry infill. To accomplish this, various tests were performed on concrete block (solid) units and concrete block masonry assemblage. A concrete block having a size of 12 x 8 x 6 inches, were fabricated in a mortar ratio of 1:4, 1:2:2, 1:8 and 1:4:4. The compressive strength of concrete block prisms having size 24.36 x 8.04 x 18.72 inches, was also determined by conducting the compressive strength test. The shear strength of square prisms, having size 26.76 x 8.04 x 25.20 inches, was found by applying diagonal loading. To investigate the bond shear strength of concrete block masonry, triplet tests were carried out on block masonry prisms. Before conduct, a test on block assemblage specimens, the constituent materials of block assemblage i.e. block and mortar were also tested for different properties. The average compressive strength of concrete block (12”x8”x6”) was 302.25 psi and the average unit weight was 119.83 lb/ft3. The compressive strength of mortars of 1:4, 1:2:2, 1:8 and 1:4:4 was 2367, 1752,815 and 1332 psi respectively.

A Comprehensive Assessment of Commercial Process Simulation Software for Compression Moulding of Sheet Moulding Compound

With a growing interest in the application of carbon fibre Sheet Moulding Compound (SMC), a number of commercial software packages have been developed for the simulation of compression moulding of SMC. While these packages adopt different algorithms and meshing strategies, the constitutive material model and processing control are usually adapted from injection moulding process simulation. Little has been done in the literature for assessing the capabilities of these software as design tools, and more importantly, validating the process simulation results using experimental data. This paper aims to provide an independent and comprehensive assessment of existing well-known process simulation software for SMC compression moulding. The selected software will be compared in terms of material models, and available processing settings in order to determine their robustness as a compression moulding design tool. The predictive accuracy of the software will also be assessed by comparing the compression force and filling patterns against the experimental data.