Dissipation Devices Research Articles

A critical review on single-phase thermo-hydraulic enhancement in geometrically modified microchannel devices

The usage of liquid-cooled microchannel heat dissipation devices is gaining importance in thermal management of electronic components owing to miniaturization. The development of such devices requires a deeper knowledge of the flow characteristics within geometrically modified microchannels. This article critically examines the research on modifications in geometry of channels for thermo-hydraulic performance enhancement. The article aims to determine the best channel configuration with optimal parameters that can maximize the overall performance of the device. For this purpose, collected research have been scrutinized in ascending order of the complexity in channel design. This article explores various designs and their influencing parameters, starting with linear and non-linear microchannel shapes, followed by bifurcated and connected secondary channels and, in the end, configurations with structured roughness such as cavities, ribs and cavity-rib combinations in it. Finally, conclusions of the examined research are presented with an analysis of their implications as well as gaps and potential recommendations for future research.

Thermal enhancement of heat sinks with bio-inspired textured surfaces

The current requirements of the electronics industry for heat sink design are to increase heat dissipation and to reduce the occupied space and weight. Research to improve the thermal efficiency and reduce the size of heat sinks has mainly been conducted by modifying their geometry to increase the heat transfer area. In the field of tribology research, one way to modify a surface is to apply texture, which involves reducing the contact area but increasing the external area, which in turn could improve the performance of heat dissipation devices. In this paper, bio-textured surfaces are fabricated on straight fin heat sinks and numerically evaluated by thermal finite element analysis. The simulation results are validated by experimental measurements on a single-fin heat sink. The potential of surface texturing in heat sinks is demonstrated here through a numerical parametric analysis of a full-scale heat sink. The results show a reduction in operating temperatures of more than 26 %, reduction in thermal resistance around 34 % and increase between 21 % and 40 % of heat sink effectiveness for textured surface heat sinks compared to smooth fin heat sinks, depending on the convection coefficient. These results suggest that the design methodology proposed here is more relevant for heat sinks used in high power dissipation applications such as computer CPUs and GPUs.

Performance analysis of a novel flat lay-type synthetic jet pump with Y-shaped jet chamber.

Recently, synthetic jet pumps have been expected to be used in electronic heat dissipation devices due to the vortex suction phenomenon for transporting fluids. Aiming to improve the delivery ability of the jet pump to output fluid continuously, a novel flat lay-type synthetic jet pump (FLTSJP) with a Y-shaped jet chamber is proposed in this paper. Based on the synthetic jet effect, the pump chamber continuously outputs fluid in one cycle. The output performance of FLTSJP is theoretically analyzed to be affected by the outlet cone angle. The one-cycle flow mechanism of the fluid in the Y-shaped jet chamber is simulated. FLTSJP is manufactured, and a test system is built. Experiments show that the Y-shaped jet chamber effectively improves the output performance. The optimum flow rate and outlet pressure were both reached at 160V and 40Hz, which were 20.63 ml/min and 333.43Pa, respectively. This FLTSJP effectively improves the output performance of synthetic jet pumps and provides a new research concept of water-cooled devices for electronic heat dissipation.

Experimental investigation on a novel curved steel damper for the beam-column joints of steel structures

Researchers have developed many passive damping devices to dissipate seismic energy using steel’s yielding property. Some proposed thick curved steel plates, while others proposed complex-shaped steel dampers. For instance, some have developed Shear Yielding Panel Devices (SYPD) and Triangular-plate Added Damping and Stiffness (TADAS) dampers for moment-resisting frames. However, these devices require additional steel bracings to be fitted into the structure. The present work reports an experimental study on a new energy dissipation device. The proposed damper is made of a steel plate cut into a curved shape (diaphragm), welded to flanges, and stiffened to create sub-panels. The damper can be fitted to the beam-column joints of steel structures using a bolted connection and does not need bracings; hence, it can be easily replaced after a seismic event. Eight devices were fabricated and tested under quasi-static cyclic loading protocol as per ATC 24. The results showed that all specimens exhibited hysteresis behavior, dissipated between 10 and 20 kJ of input energy, and provided a damping ratio of up to 40 %, depending on the damper’s geometry. Thus making it an effective seismic-resistant design system for new constructions and an alternative retrofitting tool for existing structures.

Experimental, mathematical model, and simulation of a dual-system self-centering energy dissipative brace equipped with SMA and variable friction device

The application of shape memory alloy (SMA) in seismic-resistant devices has received extensive attention due to its unique superelastic and shape memory effect. The poor energy dissipative capacity, insufficient reliability, and small bearing capacity are the main challenges that hinder the application of the developed SMA braces and dampers. The new system of self-centering energy dissipative (SCED) brace was proposed, fabricated, and tested, and the numerical model was defined and verified. The dates manifest that the load-displacement curve of the new dual-system SCED brace displays a typical flag shape. The new dual-system SCED brace exhibits the desirable energy dissipative ability and self-centering capacity and the theoretical and FE model established in this research can preferably express the hysteretic performance. The FE parametric analysis shows that the SMA screw preload has a small effect on the hysteretic curve of the new system brace, but it plays a decisive role in the shape of the hysteretic curve under small deformation. Furthermore, the bearing capacity and stiffness of the dual-system SCED brace can be adjusted by designing key parameters. The research shows that the new dual-system SCED device compensates for the shortcomings of the existing SMA braces and dampers, and it is a very promising and recommended self-centering energy dissipative device to use the wedge block system as the main energy dissipative system and SMA system as the main self-centering system.

Improving cable-stayed bridge longitudinal aseismic capability via fluid viscous damper parametric optimization and experimental investigation

The seismic vulnerability of Cable-stayed Bridges (CSBs) in high-earthquake intensity areas can be of significant concern to structural safety and resilience. A promising design practice for CSBs depends on decoupling the girder from the girder-pylon connection and involving energy dissipation devices such as fluid viscous damper (FVD) to mitigate the seismic responses. However, the parametric damper optimization algorithm and experimental validation on the FVD of a longitudinal aseismic system for CSB is still limited. In this study, three longitudinal aseismic systems (a semi-floating system with an elastic or damper connection, and a pylon girder consolidation system with a rigid connection) were investigated and compared based on the actual bridge Xigu Yellow River CSB erected in Lanzhou, China. The non-linear time history methodology was implemented to analyze the pylon and girder’s displacement and internal force responses, and the fluid viscous damper (FVD) aseismic system was the optimal choice considering the oval seismic performances. The optimal damping parameters were obtained by conducting parametrical analysis based on qualitative analysis and non-linear multi-function optimization in the pylon-girder and auxiliary pier-girder connections. A full-scale FVD model was designed and manufactured to conduct low velocity, constitutive law, and damping efficiency tests. The experimental results indicate that FVD achieved good energy dissipation capability and stability. FVD damping parameters were deduced according to the constitutive law test. The optimal analytical FVD damping parameter agreed well with the experimental results. Furthermore, the optimization was implemented in the final bridge design, referencing longitudinal aseismic systems for CSBs.

Optimization methods for the design of advanced 3d‐printed metal seismic dissipation devices

AbstractIn recent years, the topic of passive building protection became increasingly relevant due to the intense seismic activity in many parts of the world, often impacting densely populated areas. In the meantime, modern additive manufacturing technologies enabled the introduction of devices for structural applications that are innovative both in terms of final shape and design methods. The aim of the research project is to develop metal energy dissipation devices (dampers) from conventional geometric shapes and then direct the design towards specific performance in terms of strength, stiffness and dissipative capacity through optimization algorithms, with the aim of optimizing their function when employed as damper for the seismic protection of buildings. The subsequent removal of parts in excess of the real structural needs makes it possible to pursue important goals such as saving material, and reducing weight and costs. The proposed study illustrates the results of the first dampers designed through advanced topological and geometric optimization algorithms, implemented within the Abaqus software. The early models, designed from a spherical shape, are conceived to withstand axial stresses, simulating the load that can be transferred through a diagonal brace during an earthquake.

Development of pinching‐free tension‐only CBFs based on the application of metal foam dampers

AbstractMetal foam is a relatively new and potentially revolutionary material due to its properties such as the low weight‐to‐stiffness ratio, high damping and energy dissipation capacity. Even if this material is widely used in mechanical, aerospace and automotive industries, it is still not frequently used in civil engineering applications. The large energy dissipation capacity that metal foams possess could be exploited to control the seismic performance of structures, but only few research investigations have been focused on this matter. Within this context, the present paper investigates a possible solution to realize dissipative aluminium foam dampers to be applied in X‐braced steel structures for concentrically braced steel frames (CBFs). The bracing system consists of a steel rod or tube linked to an aluminium foam damper. The damper device is constituted by aluminium foam that provides the structure with dissipation capacity when activated under compression. The permanent deformations of the aluminium foam are absorbed by a wedge device, avoiding a pinching behaviour in the global response. Analytical equations governing the global behaviour of the bracing system are herein presented. An X‐braced steel frame complying with Eurocode 8 provisions is designed and considered as case‐study. The structure is subsequently upgraded by introducing the dissipative device into the bracings. The results of preliminary experimental and numerical tests on the components of the device are herein presented, showing the potentiality of the solution.

Seismic assessment of the steel Moment Resisting Frame equipped with friction beam‐to‐column joints

AbstractSupplementary dissipative devices are viable solutions to enhance the seismic response of building structures. In particular, friction devices are low‐cost and easy‐to‐maintain systems that can be easily inserted into moment‐resisting beam‐to‐column joints of steel Moment Resisting Frames. The effectiveness of dissipative friction joints has been widely demonstrated in many research project. In Europe, the first building equipped with such devices will be fabricated in Italy within the framework of the ongoing RFCS DREAMERS project. The preliminary seismic assessment of this prototype building using the framework of performance‐based earthquake engineering method at different performance levels is summarized in the present paper. To this end, nonlinear dynamic analyses are carried out on three‐dimensional (3‐D) models of the prototype developed in “OpenSees”. The results show that this type of structure can be free of damage under earthquakes corresponding to significant damage and near collapse limit states.

Hysteretic energy distribution model of CFDST composite frame with metallic dampers using coupled shear-flexural beam model

Novel steel–concrete composite structures have drawn increasingly attention in recent years especially in high-rise buildings owing to its superior structural performance over conventional concrete and steel structures. Moreover, energy dissipation devices such as metallic dampers and buckling-restrained braces (BRB) were necessarily added in this type of structure to resist seismic loads. However, the existing research regarding to the dual system consisting of composite frame and energy dissipation was limited. In this paper, the dual system consisting of concrete-filled double skin steel tubular (CFDST) composite frame and metallic damper was set as the research subject, especially focusing on the analysis of hysteretic energy distribution along the height. The 10- and 20-story dual systems were designed with different parameters revealing the influence of semi-rigid connection and metallic damper. Nonlinear models of structures established by Opensees software were validated by the test results. Afterwards, the energy distributions of all stories were discussed. It demonstrated that the metallic damper could absorb considerable energy under seismic loads while a semi-rigid connection with relatively high moment strength had a detrimental effect on the column. Moreover, the semi-rigid connection in the span without metallic damper in high story exhibited significantly larger rotation than that in the span with metallic damper. Finally, the method to estimate the energy distribution estimation of the dual system was developed, in which the lateral displacement pattern was observed by the coupled shear-flexural beam model to fully consider the flexural deformation of the dual system. An equivalent distribution of the shear and bending stiffness was also proposed considering the effect of the semi-rigid in the span without metallic damper. The predicted results from the model were validated by the analysis results derived from the nonlinear model. The theoretical and analytical results of the paper could activate the application of the dual system and provide a reasonable method to estimate the hysteretic energy distribution of the dual system.

Evaluation of the Seismic Performance of Single-Plate Metallic Slit Dampers Using Experimental and Numerical Data

Passive energy dissipation systems and devices are helpful in mitigating the danger of earthquake damage to structures. Metallic slit dampers (MSDs) are one of the most efficient and cost-effective solutions for decreasing seismic energy intake. The potential importance of MSDs in managing vibrations and limiting structural fatigue continues to grow as research advances and new materials and designs are introduced. This study evaluated the seismic performance of single-plate MSDs (SPMSDs) through a combination of numerical simulation and assessment of experimental results. ABAQUS software was used to create an assembly consisting of endplates, bolts, and SPMSDs. A real-world earthquake scenario was simulated using cyclic loads based on ASCE/SEI standards, and displacement-measuring devices such as strain gauges and LVDT were employed to record the behavior of the SPMSDs. The results of the experiment are used to assess the compliance of the SPMSDs and discuss their behavior as they undergo minimum and maximum displacements due to minimum and maximum applied forces. The energy dissipation capabilities of the dampers are presented by analyzing and comparing the area of their hysteresis loops, equivalent viscous damping, and their damping ratios. Actual failure modes are identified and shown to describe the limitations and potential vulnerability of the dampers. The relative error between the lowest and greatest recorded forces from experimental data and numerical simulation ranges from 4.4% to 5.7% for SPMSD 1 and from 1.6% to 2.1% for SPMSD 2, respectively. These deviation values represent a satisfactory level of precision, demonstrating that the numerical simulation accurately predicts the actual performance and behavior of the dampers when subjected to cyclic stress. The topology optimization performed in this study yielded an improved geometry of the SPMSD suited for a corresponding maximum considered earthquake (MCER) displacement of ±33 mm. This research also suggests practical implementations of the investigated and improved SPMSDs.

Theoretical and experimental research on the mechanical properties of magnetorheological elastomers based on PDMS

Magnetorheological Elastomers (MREs) are smart materials with the ability to modulate their mechanical properties by changing the external magnetic fields, offering extensive potential for applications requiring variable stiffness and damping devices. A comprehensive mechanical model that explains the influence of loading conditions on the performance of MRE is crucial for understanding their intrinsic mechanisms during operation, and for the design, analysis, and improvement of intelligent energy dissipation and vibration control devices based on MRE. In this study, a four-parameter mechanical model was established to reveal the intrinsic mechanisms about the effects of external magnetic fields, loading frequency, and strain amplitude on the storage modulus, loss modulus, equivalent stiffness, and equivalent damping of MRE materials. The dynamic mechanical properties of the MRE materials prepared from carbonyl iron powder and PDMS were tested, and parameter identification of the established model was performed. The comparison results between the theoretical model analysis and the testing results demonstrated that the proposed mechanical model effectively characterizes and predicts the mechanical behavior of MRE materials. Furthermore, based on the prepared MRE materials, a stiffness-controllable energy dissipator operating in shear mode was designed and fabricated, and the mechanical performance of the shear energy dissipator was experimentally evaluated. This research provides a basis and guidance for the design and mechanical performance analysis of devices based on MRE, confirming the feasibility of MRE materials as core components in intelligent energy dissipation devices.

Buckling-controlled braces for seismic resistance inspired by origami patterns

Equipping energy dissipation devices in the structures is one of the effective methods to resist earthquake disasters. Here, a novel buckling-controlled brace inspired by origami (O-BCB) was proposed as anti-seismic technology for protecting engineering structures. A hierarchical design and analysis strategy was adopted for various types of origami patterns. An O-BCB based on Tachi origami pattern was manufactured, tested, and analyzed to verify the hysteretic performance under cyclic reversed loading. Considering the non-uniform distribution of deformation and stress in the Tachi patterned brace, two gradient design schemes in the lengthwise direction were proposed. To balance the bearing capacity and energy-dissipating capabilities of O-BCBs, the implementation of non-rigid origami patterns including pyramid, crash-box, and triangular patterns were analyzed. Results show that O-BCBs could provide valuable options for the development of earthquake-resistant technologies in the field of civil engineering.

Experimental validation of a novel curved steel damper for steel frames with flexible beam-column joints

In this study, results of an experimental program are presented to validate the performance of a novel energy dissipation device (EDD) designed for use in moment-resisting steel frame structures with flexible beam-column connections. The EDD, composed of a curved steel plate, stiffeners, and flanges on both ends, was tested in laboratory conditions using a displacement control quasi-static loading protocol. Three half-scale steel frames were used, one serving as a control and the other two incorporating the device in both column-beam joints. The device was fabricated using two different materials, mild steel, and stainless steel, and the results were compared. The results of the experimental program revealed that the frames equipped with the energy dissipation device performed significantly better than the control frame. This was observed qualitatively, in terms of the amount of damage sustained by the frames, and quantitatively, through measurements of the frames' capacity and displacement ductility. Frames that were equipped with dampers showed an approximately 1.5-fold increase in displacement ductility and an 84–113% increase in cumulative energy dissipation compared to the control frame. Overall, this research highlights the potential of this novel energy dissipation device to enhance the seismic performance of moment-resistance steel frame structures.

Influence of uncertainty factors on the dynamic characteristics of magnetorheological damper

The magnetorheological damper (MRD) is a kind of energy dissipation device, which converts vibration mechanical energy into self-heat energy during operation. The dynamic performance of MRD is affected by uncertain factors such as temperature and external magnetic field. In this paper, basing on the temperature rise theory and external magnetic field interference theory of MRD, it analyses the influence of temperature effect and external magnetic field on the dynamic performance of MRD. Under sinusoidal excitation, the internal temperature field and magnetic field distribution of MRD are simulated by COMSOL, and it calculates the changes of temperature and magnetic field in MRD by the conditions of input current of 0.4A, 0.8A and 1.2A. The temperature rise and external magnetic field test are carried out. Under the same input current, the temperature rise of the outer wall of the cylinder is measured. The results show that the input current increases, the temperature rise of MRD increases, and the temperature of MRD increases, the output damping force decreases obviously. When the input current is 0.4A, the temperature of MRD rises to 40℃, the maximum output damping force decreases by 11.2%, and the current is 1.2A, the maximum output damping force decreases by 18.6%. When external magnetic field is applied, the output damping force of MRD increases. The magnetic induction intensity of the external magnetic field increases from 10mT to 30mT, when the incoming current is 0.4A, the maximum output damping force increases by 5.9%, and the current is 1.2A, the maximum output damping force increases by 5.1%. Therefore, applying external magnetic field to compensate the decreasing value of output damping force caused by temperature rise effect has a certain effect. The results show that the variation trend of theoretical analysis, simulation calculation and experimental verification is consistent.

On the Role of Seismic Damage Tolerance on Costs and Life Cycle of CLT Buildings

This paper presents a contribution to reviewing the most common seismic design procedures of CLT buildings and their implications on structural features and technological solutions. Attention is particularly focused on the overall seismic performance, damage tolerance, construction costs and environmental impact. It is intended as a baseline for a more comprehensive study, thus the assessment is made with reference to a real building, representative of a class of common buildings recently designed and erected in many Italian regions exposed to low and moderate seismic hazards. As usual, the analysis was carried out according to a two-dimensional model of the panels, assumed to be elastic, varying the type of connections at the base, the presence of pre-stressing steel bars for rocking control and dissipative devices. The main outcomes of the study can be summarized as follows: (i) the structural seismic behavior of CLT buildings is significantly influenced by the structural schemes adopted for walls and connections; (ii) construction costs and environmental impact decrease whenever damage tolerance is accounted for in design procedures.

Cyclic behavior of a slit damper proposed for precast concrete beam-column connections

Since the 2017 Puebla-Morelos Earthquake, interest in limiting damage to structural components has exponentially increased in Mexico. Consequently, the use of energy dissipation devices has received renewed attention. Following that line, this paper studies an attractive solution, which is a slit damper proposed as a passive energy dissipation device for, but not limited to, precast beam-column connections. Slit dampers have been studied for their cost-effectiveness and ease of application. They present stable hysteretic behavior and dissipate substantial amounts of energy under cyclic loading while maintaining less ductile elements essentially elastic. The structural behavior of the proposed device was evaluated theoretically, followed by experimental verification. Quasi-static incremental and constant-amplitude cyclic tests were conducted on eight specimens, with two of them having non-uniform struts. Test results are presented and discussed, emphasizing ductility and energy dissipation capacity. The proposed damper showed stable hysteretic behavior and adequate seismic performance. Using non-uniform struts significantly increased the damper's deformation capacity and fatigue performance, which is desirable for seismic zones where long-duration earthquakes are expected, such as in Mexico City. Numerical modeling techniques were also validated with finite element analyses. It was shown that the proposed damper's hysteretic response could be accurately predicted using the combined non-linear isotropic and kinematic hardening model.

Enhancing heat transfer performance in 3D-printed integrated vapor chamber using composite structures

The demand for lightweight heat dissipation devices in aerospace and various other fields has spurred the development of aluminum-based vapor chambers. However, the surface of the aluminum particles is covered by a dense alumina layer, which poses a challenge in preparing the aluminum-based porous wick structure by sintering aluminum powder. In this study, two aluminum-based vapor chambers (60 mm × 50 mm × 4 mm) with distinct wick structures were integrated with the container utilizing 3D technology. The wicks of the vapor chamber included an aluminum-based grooved wick structure (GVC) and an aluminum-based grooved-porous composite wick structure (GPVC). A comprehensive experiment was conducted to evaluate the heat transfer characteristics of the vapor chamber, including startup performance, temperature uniformity, and thermal resistance, under different filling ratios and wick structure parameters. The working fluid was acetone. The results indicated that the GPVC demonstrated excellent startup performance under both low and high heat loads. The startup time of the GPVC was found to be 230 s, 30.3% less than that of the GVC under a heat load of 80 W. Furthermore, at a 60% filling ratio, the GPVC demonstrated lower thermal resistance and better temperature uniformity compared to the GVC. The GPVC achieved a minimum thermal resistance of 0.033 K/W with a maximum temperature difference of only 4.51 °C. This resulted in a reduction of thermal resistance by 47.5% and an improvement in temperature uniformity by 69%. The findings of this study provide valuable insights to the application of 3D printing technology to the production of aluminum-based composite porous wick structures.

Effect of corrosion on self-centering energy dissipative devices

This study reveals the effect of corrosion on the performance of typical self-centering energy dissipation devices for seismic resilience enhancement. Two types of SC devices, namely, high-strength steel ring spring-based SC damper (HSSR damper) and SMA ring spring-based SC damper (SMAR damper), are examined. These specimens were subjected to 720 h’ accelerated corrosion, corresponding to roughly 20 years’ exposure to city out-door environment. Numerical studies are carried out in ABAQUS to further interpret the test results. Among other important findings, the tests showed that the HSSR damper is likely to lose its self-centering capability after corrosion. The high-strength steel (HSS) rings were severely corroded, and the restoring force provided by the rings was insufficient to overcome the friction action. The SMAR damper showed much reduced sensitivity to corrosion. For both dampers, there was no damage to either the SMA/HSS rings or the other components under repeated loading, implying a low risk of corrosion-related low-cycle fatigue failure. The numerical study implies that the friction condition over the entire contact surface is not identical once the damper experiences corrosion. A “two-region modelling strategy” with a smaller friction coefficient and a larger friction coefficient leads to satisfactory agreements with the test results for the corroded HSSR damper. For the SMAR damper, a constant friction coefficient for the surfaces between inner and outer rings has been found to be appropriate for both non-corroded and corroded cases. Based on the limited experimental and numerical data, it is recommended that anti-corrosion measurement should be mandatory for HSSR dampers. Overstrength due to the long-term effect should also be considered in the design of HSSR dampers from a life-cycle design point of view. If no special anti-corrosion measurement is applied, an overstrength factor of 1.3 may be considered. Overstrength may be ignored for SMAR dampers. By representing the key components of SC devices as a group of springs, the analytical description of considered SC devices can be obtained.

Modeling uncertainty of specimens employing spines and force‐limiting connections tested at E‐defense shake table

AbstractIn light of the significant damage observed after earthquakes in Japan and New Zealand, enhanced performing seismic force‐resisting systems and energy dissipation devices are increasingly being utilized in buildings. Numerical models are needed to estimate the seismic response of these systems for seismic design or assessment. While there have been studies on modeling uncertainty, selecting the model features most important to response can remain ambiguous, especially if the structure employs less well‐established lateral force‐resisting systems and components. Herein, a global sensitivity analysis was used to address modeling uncertainty in specimens with elastic spines and force‐limiting connections (FLCs) physically tested at full‐scale at the E‐Defense shake table in Japan. Modeling uncertainty was addressed for both model class and model parameter uncertainty by varying primary models to develop several secondary models according to pre‐established uncertainty groups. Numerical estimates of peak story drift ratio and floor acceleration were compared to the results from the experimental testing program using confidence intervals and root‐mean‐square error. Metrics such as the coefficient of variation, variance, linear Pearson correlation coefficient, and Sobol index were used to gain intuition about each model feature's contribution to the dispersion in estimates of the engineering demands. Peak floor acceleration was found to be more sensitive to modeling uncertainty compared to story drift ratio. Assumptions for the spine‐to‐frame connection significantly impacted estimates of peak floor accelerations, which could influence future design methods for spines and FLC in enhanced lateral‐force resisting systems.