Soft Impact Research Articles

Earthquake‐induced impact of base‐isolated buildings: theory, numerical modeling, and design solutions

AbstractEarthquake shaking more intense than that used to size the horizontal clearance between a base‐isolated building and near‐rigid perimeter moat wall will result in hard impact, producing high‐frequency, high‐amplitude acceleration response in the structure and supported equipment. This paper provides a design solution for the damaging effects of hard impact by installing a compliant engineered element in the load path between the base‐isolated building and the moat wall, resulting in soft impact and a much smaller acceleration response. The engineered element assumed herein is a commercial‐off‐the‐shelf marine fender with mechanical properties determined by physical testing. The attachment of a flexible engineered element, with well‐defined stiffness and damping, to a near‐rigid moat wall, simplifies the numerical modeling of the building‐moat wall system and eliminates the need to bound the lateral stiffness of the wall for impact calculations. The simple model of the engineered element can be implemented in commercial finite element codes. Theory is developed for two‐sided impact of a single‐degree‐of‐freedom oscillator. Analytical solutions are derived for the shifted first‐mode frequency of the impacted oscillator and for its free‐vibration response. The shifted first‐mode frequency is a function of the composite lateral stiffness of the isolator‐engineered element assembly and its earthquake‐induced displacement. Local peaks in the spectral response of the impacted oscillator form at odd integer multiples of the shifted first‐mode frequency. The analytical solutions can be used to verify, in part, the numerical model used for impact analysis.

Methodology of Russian soft and hard power impact in Estonia.

ObjectivesSoft power elements can be the so-called persuasive means of political influence (culture, propaganda, diplomacy). The Russian Federation, with its historical legacy, by some historians referred to as the "siege complex", still seems to prefer changes in the distribution of power at the global level, while being aware of the benefits of cooperation with the wider West. Nevertheless, the position regarding some former USSR Republics, which it would most likely see directly in its sphere of influence, seems to remain the same, hence the actions taken and the methodology of conduct have their own characteristic features.MethodsIn accordance reference to the typology established by Nye - the methodology of the so-called hard influence generally implies the use of military means, compulsory diplomacy and economic sanctions to influence on the behavior or interests of other political bodies (Wilson, 2008, p. 114).ResultsRussia seems to use the hard combination in its own specific way and soft impact. However, the soft impact is primarily based on propaganda activities implementing the clear strategy of the Federation. As argued by Alexander et al. (2005, p. 31): "the theory of the image at the international level shows a clear relationship between the image of another nation and the choice of a strategic policy towards that nation."ConclusionsIn this sense, Russia will apply a shifting strategy in line with the old Latin principle: divide et impera. For this purpose, it will use a combination of soft and hard impact depending on Estonia's internal and international situation.

Soft impact behavior of composite I-beams

As the increasing requirement of high-strength and lightweight structure in engineering applications, thin-wall I-section beams made of composite materials have drawn much attention in recent years. This paper made an effort to reveal the dynamic behavior of composite I-beams under soft impact. I-beam specimens were manufactured through resin transfer molding and then struck by aluminum foam projectiles. Numerical models were subsequently built up and verified through comparison of deflection and failure types with test results. After modification of the models with more reasonable construction method, parametric study was carried out and structure with the optimal dimensions was chosen. The I-beam was further optimized through adding polyurethane foam in the web. It was proved that the introduction of foam core with proper thickness will prevent buckling of the web and reduce the damage occurred during soft impacts.

Armenia as Object of Influence of Turkish Policy of “Soft Power”: Difficulties, Successes and Prospects

Despite the fact that Turkey was among the first to recognize the independence of Armenia on December 24, 1991, diplomatic relations have not been established between the countries to this day. In the first decade of the 21 st century, there were attempts to normalize relations, but they were unsuccessful. After the Second Karabakh War, Turkey resumed efforts to normalize relations. The article discusses the importance of Armenia for Turkey, presents the tools of the Turkish policy of “soft power”, a separate emphasis is placed on the existing obstacles that impede its advancement in this country. One of the main objectives of this article is an attempt to evaluate the effectiveness and research the results of Turkey’s soft impact policy in Armenia. The authors studied public opinion polls, speeches and statements of politicians, opinions of labor migrants and representatives of the Armenian community in Turkey, publications in the media, scientific works of scientists from both sides on this topic. The authors found that the absence of diplomatic relations is not a barrier to the policy of “soft power”. To achieve its foreign policy goals, Turkey uses all kinds of tools not only of “hard” but also “soft power”, such as various funds, media, the Armenian diaspora in Turkey, etc. If in other South Caucasian states Ankara pursues a policy of “soft power” with the help of state and non-state organizations, then in Armenia, due to the lack of diplomatic relations, only with the help of non-state actors.

Dynamic Behaviour of the Platform-vibrator with Soft Impact. Part 1. Dependence on Exciting Frequency

Dynamic Behaviour of the Platform-vibrator with Soft Impact. Part 1. Dependence on Exciting Frequency

Forecasting and diagnostics of critical states in platform-vibrator with shock.

A platform-vibrator with shock is a low-frequency machine used in the construction industry for compaction and molding of large concrete products. Its mathematical model is a two-degree-of-freedom two-body vibro-impact system with a soft impact. Some changes in its parameters can increase the machine performance and improve the product quality, but these same changes may lead to the emergence of critical states, such as coexisting regimes in hysteresis zone, chaotic motion, intermittency and crisis-induced intermittency, crises, and transient chaos. Some of them can be undesirable and dangerous. This article shows their diagnostics and recognition, the possibility of their prediction, as well as the criterion determining the set of parameter ranges where critical states can occur. Diagnostics is carried out both by traditional tools and by the less common ones, such as the construction of fractal structures and wavelet characteristics.

Experimental and numerical investigation on glass panel subjected to pendulum impact

Glass panels are widely used in modern architecture, such as in building envelopes and balustrades. However, there is a lack of clarity in terms of their structural safety under soft-body impact. Therefore, a pendulum impact testing system is developed in this study to simulate the soft body impact and investigate the impact resistance of the monolithic glass panel. Two-degrees-of-freedom model and finite element model were built to verify the experimental dynamic response and progressive damage behavior of the glass panel subjected to pendulum impact. All results are in agreement with each other. The flexural strength of the glass panel is slightly higher than that of the code provisions, and the vibration frequency and damping ratio of the glass panel are 30.2 Hz and 3.8%, respectively. The dynamic responses of the glass panel and impactor increase with release height; further, energy dissipation occurs during the impact process. The energy loss increases with an increasing release height until the fracture failure of the glass panel. This study can help improve the understanding of the dynamic behavior of glass panels under low-speed impact.

Smooth Planning for Manipulator with Multi-dimensional Actuator based on Quintic B-spline

In order to solve the impact problem of uneven velocity during continuous operation for manipulator with multi-dimensional actuator, a smooth planning scheme based on Quintic B-spline algorithm was proposed. Firstly, the physical model of multi-dimensional actuator and its working principle were introduced. At the same time, the motion of the output axis vertex in space was decomposed into three steps, which can make the position relationship between the points more intuitive and convenient for our study. Secondly, the characteristics of Quintic B-spline algorithm were analysed. In this step, the B-spline interpolation function was defined at first, and the basis function of polynomial of degree p was defined according to the relevant information and its characteristics were indicated. Then, we analysed the node sequence parameters. For Quintic B-spline algorithm, when the position sequence of the rotor running track was given, three conditions must be satisfied to uniquely determine the corresponding B-spline function, namely: node vector, control vertex and the degree p of the B-spline curve. On this basis, the boundary constraints and control vertices were solved, which was a very important step. By solving the control vertices of Quintic B-spline curve, a smooth and continuous angular displacement curve can be obtained. The addition of four boundary conditions greatly increases the controllability of the system, making the rotor can start and stop in any way within the constraint conditions, and the connection of each interpolation point is smooth and continuous. The Quintic B-spline algorithm interpolation curve was obtained by simulation based on the time-position sequence of the actuator interpolation points. The results of the interpolation curve verified the effectiveness of the Quintic B-spline algorithm. In addition, three continuous running planning conditions were designed for the same interpolation sequence of the rotor to verify the controllability of the algorithm to the angular velocity and angular acceleration of the rotor during operation. The simulation results show that the Quintic B-spline algorithm has strong controllability for the angular velocity of actuator, and can effectively alleviate the soft impact of the system. Finally, a smooth planning experimental platform with multi-dimensional actuator was built. By setting the same trajectory and different interpolation points, the proposed Quintic B-spline algorithm was compared with the existing S-shaped curve planning algorithm based on the improvement. The results show that the proposed scheme has high control accuracy and strong impact mitigation performance, which can provide a reference for other multi-dimensional actuator trajectory planning.

Prediction and diagnostics of crises and critical states in an unusual vibro-impact system with soft impact

In nonlinear dynamical systems, whenchanging control parameters, critical states may occur. To predict these undesirable events, it is necessary to study the system dynamic behavior with changing in different control parameters. Two-body 2-DOF vibro-impact system is under consideration. The huge mass of the upper body, which can break away from the lower one and be in “free flight” for a short time, may be attributed to its specific and is a cause to consider it unusual. Some changes in the parameters of both external loading and the system itself can increase the efficiency of the machine, the mathematical model of which is the considered vibro-impact system. But the same changes lead to appearance of unwanted nonlinear phenomena, such as permanent sustained chaos, transient chaos, crisis-induced intermittency, and coexisting regimes with larger oscillatory amplitudes. The article shows their occurrence, traces the precursors, carries out their diagnostics by both traditional and less common methods. The description of many numerical experiments is accompanied by numerous figures and tables that clearly and convincingly demonstrate the results obtained.

Double grazing bifurcations of the non-smooth railway wheelset systems

There are numerous non-smooth factors in railway vehicle systems, such as flange impact, dry friction, creep force, and so on. Such non-smooth factors heavily affect the dynamical behavior of the railway systems. In this paper, we investigate and mathematically analyze the double grazing bifurcations of the railway wheelset systems with flange contact. Two types of models of flange impact are considered, one is a rigid impact model and the other is a soft impact model. First, we derive Poincaré maps near the grazing trajectory by the Poincaré-section discontinuity mapping (PDM) approach for the two impact models. Then, we analyze and compare the near grazing dynamics of the two models. It is shown that in the rigid impact model the stable periodic motion of the railway wheelset system translates into a chaotic motion after the grazing bifurcation, while in the soft impact model a pitchfork bifurcation occurs and the system tends to the chaotic state through a period doubling bifurcation. Our results also extend the applicability of the PDM of one constraint surface to that of two constraint surfaces for autonomous systems.

Design Calculation for Concrete-Filled Steel Tube under Soft Lateral Impact

In recent decades, the rapid development of transportation construction has increased the possibility of concrete-filled steel tubes (CFSTs) subjected to soft lateral impact. Some kinds of deviation may still exist between the soft impact process and its design prediction due to frequent safety accidents. To improve the prediction accuracy, this paper contrasted the current soft impact design with the experimental impact processes of CFSTs. The current design is represented by the method and route in Eurocode-1 Actions on structures, which belongs to the one-step type. Extra parameters were added to the one-step method to describe the inertia effect of CFST. According to the experiments and predictions, the soft impact process contains two stages, which are the initial peak stage (IPS) and the stable stage (SS). The current one-step method is consistent with SS but incorrect in IPS and its accuracy is related to the proportion of IPS and SS. An empirical formula, based on the weight of IPS, is summarized to evaluate the overall error of the one-step method in the soft impact design of CFST. This error is due to the unreasonable assumption of the inertial effect in IPS. For the demands of an accurate design in IPS, a new technical route is proposed, consisting of two steps: qualitative analysis and two-stage calculation. The qualitative analysis achieved an approximate quantitative division of IPS and SS, and provided the design loads for the two-stage calculation. The two-stage calculation supplemented the prediction of the inertia effect in IPS and independently estimated the resistances and responses of CFST in the two stages. The above qualitative analysis and two-stage calculation constituted the two-step method and its accuracy and applicability are generally better than that of the one-step design.

Qualitative changes in bifurcation structure for soft vs hard impact models of a vibro-impact energy harvester.

Vibro-impact phenomena in engineering systems, considered an adverse effect in some settings, are an intrinsic part of the mechanism in others. In energy harvesting, a vibro-impact component is often intentionally introduced to increase the power output or the system's bandwidth. The impacts can be treated as "hard" for instantaneous impacts or "soft" for compliant materials. Since both types of models exhibit complex dynamics, a comparison is non-trivial. We develop a soft impact model for a vibro-impact energy harvester, calibrating it with the relevant hard impact model for large stiffness, and systematically compare the different phenomena and dynamics in various compliant regimes. Numerical results are used in two different parametric analyses, considering the bifurcation diagrams in terms of device size and external forcing parameters. Varying the natural frequency of the membranes that form the impact boundaries, we observe shifts in the bifurcation structure that promote period-1 orbits for increased softness parameters, often generating higher power output, but also introducing parameter sensitivities for increased softness. Complementary analytical results reveal unstable periodic orbits and co-existing behaviors, potentially missed by computational methods, that can influence the bifurcation structure and in turn the energy output. A non-dimensional formulation highlights the significance of ratios of external and natural frequencies in delineating soft and hard impact scenarios parametrically. The soft impact model exhibits new symmetry breaking bifurcations related to key quantities that characterize the soft impact dynamics, such as the effective restitution coefficients, the impact phase, and the contact time interval, not captured by hard impact models.

Flame Structure of Ammonia/Hydrogen/Oxygen/Argon Mixtures at High Pressure

The search of alternative fuels is one of the most important issues. Hydrogen is the most attractive one since its combustion products include only water. However, due to its specific properties wide implementation of hydrogen is not possible. There is an idea to use chemical carriers of hydrogen, for example, ammonia. The addition of hydrogen, which is the product of ammonia cracking, can improve the combustion characteristics of ammonia. The work presents experimental data on the structure of NH3/H2/O2/Ar flames at 4 atm. Equivalence ratio values were 0.8, 1.0 and 1.2, NH3/H2ratio – 1/1. Flame structure was measured with molecular beam mass spectrometry with soft electron impact ionization. In the experiments, flames were stabilized on the flat burner. Temperature profiles were measured with thin S-type thermocouples. Numerical simulations were performed with PREMIX code from CHEMKIN package. The comparison of the experimental and numerical data enabled to reveal the mechanism of NH3/H2oxidation showing the best predictive capability. Experimental and numerical data showed that the nitrogen-containing species which are present in the post-flame zone are N2and NO whereas concentration of N2O and NO2is negligible. It was revealed that in terms of NO reduction slightly rich conditions are more effective. In addition, the effect of equivalence ratio on the peak concentration of NO, N2O and NO2was analyzed. Rich conditions appeared to be more effective to reduce peak concentrations of NO, N2O and NO2.

Parametric analyses on the impact fracture of laminated glass using the combined finite-discrete element method

Laminated glass is composed of glass and interlayer, and it is sensitive to impact actions which usually lead to fracture and fragmentation with high nonlinearity and strong discontinuity. The combined finite-discrete element method (FDEM) has been employed to examine the impact fracture of laminated glass against comprehensive parameters. Following the introduction on the FDEM, verification examples and convergence study are presented. A parametric investigation follows, and the influences of a variety of parameters are addressed. Parameters include impact velocity, glass material properties, interlayer thickness and position, glazing construction, shape and Young’s modulus of projectiles, etc. It is concluded that increasing neither tensile strength nor surface energy of glass would reduce the deformation of laminated glass remarkably, however, strengthening the outer glass is beneficial and meaningful. An optimum thickness of interlayer is found in the range of 11–44% of the total thickness, and laminated glass with multiple interlayers improves its energy absorption and displacement reduction capacities. Projectiles with a larger contact surface would damage laminated glass more seriously. It is also found that soft impact transfers more kinetic energy to the laminated glass than hard impact, while its peak impact force is lower than that of hard impact.

The Performance of Vacuum Insulating Glazing Units Subjected to a Soft Body Impact

The Vacuum Insulated Glazing is a highly thermally insulating structure consisting of two (or more) glass sheets, separated by an evacuated gap, and sealed hermetically at the glass edges. An array of support pillars maintains the separation of the panes under the constant load of atmospheric pressure. The performance and durability of the VIG, in terms of thermal loads and atmospheric pressure, has been well studied and ISO Standards have recently been published (ISO 19916-1:2018 and 19916-3:2021). However, the mechanical performance of the VIG, especially when exposed to dynamic loads, has not been dealt with in the scientific literature. The goal of this work is to investigate the mechanical performance of VIG’s subjected to soft body impact and gain insight into the failure mechanisms of the VIG when exposed to dynamic loads. Measurements of the surface stress on the glass were performed, when the VIG is subjected to the twin-tire pendulum impact test, as outlined in the Standard DIN EN 12600:2002. Two VIG units and one laminated VIG unit were tested and the results were compared to numerical data of a monolithic glass pane. It was found that the VIG failed at drop heights much lower than that prescribed in the Standard. An examination of the glass fracture patterns highlighted an origin of fracture caused by the contact of pillar-to-glass.

Dynamic Response of Structurally Reinforced Wing Leading Edge against Soft Impact

In this current research, a commercial aircraft metallic leading edge structurally reinforced with a Y-shaped and V-shaped plate system is numerically examined to investigate the effectiveness of such reinforcements against soft impacts, more commonly known as bird strikes in the aviation industry. A non-linear finite element code Ansys Explicit is adopted to run the virtual test cases. The computational bird model is presented with the Lagrange algorithm and Mooney–Rivlin hyperelastic material parameters which are validated against the experimental data found in the literature. A second validation of the leading edge deformation pattern is also carried out to ensure the accuracy of the present work. Numerical outcomes suggest that due to the presence of the reinforcement, the leading edge skin is restrained from being drastically deformed and the bird model tears apart into two pieces requiring the leading edge model to absorb much less kinetic energy. Additionally, it is found that both the reinforcements have similar crashworthiness performance against bird impacts. The novelty of the research lies in founding the structural reinforcement as a primary preference to strengthen the vulnerable wing leading edge during bird impacts.

Comparison of three different adhesive joints using static and dynamic impact tests : Development of a new drop weight impact test rig incorporating a modified Arcan fixture

The paper proposes to compare static and dynamic properties of three structural adhesives selected for the integration of optical space systems. These comparisons are based on an original methodology using static test and drop weight impact test to determine the best shock-strength candidate. In a first section, the design of the drop weight impact rig integrating a modified Arcan fixture is described. Then validity of the impact test rig is discussed on a simplified case thanks to an analytical model of “soft impact” available in literature. In a second section, static tests results are presented and the adhesive's critical stresses are identified with a point stress criterion. Finally, impact tests results are used to discuss the dynamic tensile and shear behaviour of each adhesive with different stress concentrations. Static critical stresses and impact strengths of the adhesives are reported. In conclusion a strategy of adhesive choice is discussed.

Dynamic Behaviour of the Platform-vibrator with Soft Impact. Part 2. Interior crisis. Crisis-induced intermittency

Dynamic Behaviour of the Platform-vibrator with Soft Impact. Part 2. Interior crisis. Crisis-induced intermittency

The role of intangible resources in shaping the financial potential of high technology enterprises on the example of CD Projekt SA

Motivation: As a result of economic changes over the last few decades, the structure of enterprise resources has changed significantly. Therefore, their development potential is concentrated on intangible resources. A reflection of these changes is the emergence of the Resource-Based View of the Firm (RBV) which has its roots in the works of scientists such as: J.A. Schumpeter, A. Marshall, or E.H. Chamberlin. The importance of the resource theory is mainly based on the technological potential, people’s knowledge or the improvement of management techniques.
 Aim: The aim of the article is to propose a method for assessing the strength and direction of the impact of intangible resources on the financial potential of high-tech enterprises. In the article, as a case study, the impact of intangible resources on the financial potential of CD Projekt SA was presented. from the high-technology industry (Section C, subclass 26.20.) in 2011–2019. The choice of the company as the research object was primarily determined by the type of business activity, the high position of the enterprise among the fastest growing companies and a significant share of intangible resources.
 Results: To achieve the aim of the article, the soft modeling method was used which allows to study the relationship between directly unobservable variables. In the constructed soft model, two unobservable (hidden) variables constituting the internal model were adopted: intangible resources (IR) and financial potential (FP). Hidden variables were defined based on the potential set of indicators (observable variables). Specification of the model of the soft impact of intangible resources on the financial result of high-tech enterprises based on the concept of the resource theory. Identification of the most important variables shaping the intangible resources of high technology enterprises, their impact on the financial potential of enterprises, together with the analysis of the dynamics of changes. Defining proposals for recommendations for high-tech companies based on the results of empirical research.

Deformation behavior of fluid-filled porous elastomers: Analytical estimates and validation

Fluid-filled elastomers are used in soft body wearable electronics devices, optics, soft pressure transducers, vibration damping and impact protection. Deformation behavior of these materials is complex and would depend on elastomer properties, fluid properties, loading rate, porosity, pore size, pore shape, and pore end conditions. In this work, closed form analytical estimates are derived for effective behavior of a special class of fluid-filled elastomers composed of incompressible, hyperelastic matrix with mono-disperse circular pores, distributed in a square grid, filled with an incompressible, Newtonian fluid. The analytical estimates are validated using three dimensional numerical simulations modeled in COMSOL multiphysics software. The analytical estimates for pressure and velocity fields in the fluid, deformation of the matrix, viscous dissipation in fluid, and stored energy in the solid are seen to match well with that from numerical simulations. For small deformations and small porosities, while storage modulus is seen to be linearly proportional to shear modulus of elastomer and inversely proportional to the porosity, the loss modulus is seen to be linearly proportional to the product of loading frequency and fluid viscosity and inversely proportional to the product of porosity and square of ratio of pore radius to pore length. The analytical estimates presented here can be used to design fluid-filled elastomers with desired stiffness and damping by selecting appropriate elastomer stiffness, fluid viscosity, porosity, pore size and pore aspect ratio.