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Chemical mechanical polishing plays a pivotal role in enhancing the topography of wafers during semiconductor fabrication. The hardness of polishing pads holds great significance as it determines the material removal rate during the planarization process. Hence, precise determination of polishing pad hardness at both micro and macro scales is essential for optimizing the semiconductor polishing process, ensuring the prevention of wafer erosion or dishing. In this study, an automated system was developed for determining Vickers hardness of microporous polishing pads employing a closed-loop control method. The system was calibrated based on the relationship between load-unloading force and displacement observed in Vickers indentation experiments. The designed apparatus is not only successfully verified with standard values for Vickers reference blocks with less than 2% error, but it also demonstrated a smaller average relative error percentage than the commercial system using traditional open-loop measurement method. The closed-loop Vickers hardness apparatus proves to be a promising alternative for measuring hardness accurately, particularly in samples with noisy surfaces, rough surfaces, and porous microstructures. [ABSTRACT FROM AUTHOR]

This work studies the mechanics of novel origami solar modules with tensegrity architecture for integration in the dynamic solar façades of energy-efficient buildings. The analyzed modules are deployed by adjusting the rest lengths of cables attached to given nodes, so as to form a tensegrity origami. Their stiffness is tuned by adjusting the pretension of the actuation cables, when the deployment motion is locked. The insertion of solar thermal or photovoltaic panels into the rigid elements of the module makes it possible to form positive-energy solar systems. The work studies the kinematics and the mechanics of the investigated structures through analytic and numerical methods. Two folding motions are examined: to open and close the modules and to track sun rays. The rapid prototyping of a physical mock-up permits an experimental validation of the force–displacement response in a given configuration of the sun-tracking motion. A procedure for the computation of the fundamental vibration modes and vibration frequencies of a quadrangular solar module is also given, and the expected response of the system under wind loading is outlined.

Rocking self-centering (RSC) bridge piers were proposed based on the bridge seismic resilience design theory, pushing the development of bridge sustainability. To develop a seismic design method for RSC bridge piers, a clear understanding of their behavior under earthquakes is essential. This study analyzed the whole lateral force–displacement response of RSC piers, taking into account both rotational and flexural deformation, which resulted in a clearer understanding of their behavior under seismic actions. In this study, the whole loading process was simplified into three statuses, and a calculation method was developed to determine the relationship between lateral force and displacement of both single-column and double-column RSC bridge piers. The accuracy of the proposed method was verified by comparing the calculated results with experimental data for six single-column and two double-column RSC bridge piers. The results show that the proposed calculation method predicts the initial stiffness, yield and peak loads, and yield and peak displacements well for RSC bridge piers. The method offers valuable insights into the seismic response of RSC bridge piers, which can serve as a reference for future research, promoting the safety and stability of these structures. [ABSTRACT FROM AUTHOR]

Approach for mechanical characteristic experimental analysis of honeycomb core manufactured by fused deposition modelling is suggested. Experimental analyses of shear and tension of the honeycombs specimens fabricated from PLA and ULTEM 9085 materials are performed. The experimental studies are accompanied by the finite element simulations of the shear and the tension experiments of honeycomb core. As follows from experimental and numerical studies, both the geometrical nonlinearity and plasticity behavior of the material must be accounted for the honeycomb tension analysis. The force-displacement response of honeycomb tension has nonlinear behavior. [ABSTRACT FROM AUTHOR]

Summary: Steel wire mesh held by a pattern of bolts can be used to stabilize a rock slope. Knowledge of the force‐displacement response of steel mesh is essential in the design of this support system. Laboratory tests have been used to test mesh that is held to rigid steel frames. These testing conditions differ from how steel mesh is held in the field by bolts. The existing laboratory test data may underestimate the deformation and overestimate the load‐bearing capacity of the steel mesh. This paper focuses on the response of the high tensile strength steel mesh held by commonly used bolt patterns. Discrete element models were used to study the force‐displacement response of the steel mesh pinned by bolts. The influences of different bolt patterns and varying ratios of bolt spacing on the effectiveness of steel wire mesh were analyzed. Relationships between the resistance force of steel mesh and bolt density at various mesh deformations were developed. These relationships can help engineers choose the bolt spacing and provide an estimate of the resistance force that a steel mesh can mobilize at a desired deformation limit for a given bolt pattern. [ABSTRACT FROM AUTHOR]

This work introduces a new approach to targeting the dynamic response of thin-walled energy-absorbing structures through the decomposition of the force-displacement (FD) response and the use of topometry (thickness) optimization. The proposed method divides the nonlinear optimization problem into a series of analytical subproblems. In each iteration, an explicit dynamic analysis is carried out and the dynamic response of the structure is then used to define the subproblem. Numerical examples show that the algorithm can tailor the FD response of the structure to a target FD curve. Progressive collapse, which is a high-energy collapse mode and desired in design for crashworthy, is observed in the optimized thin-walled structures. The proposed algorithm is computationally efficient as it uses a fewer explicit simulations to reach the target response. [ABSTRACT FROM AUTHOR]

The paper is dedicated to enhance the industry practice in collision simulations of ship structures when only limited time and material data are available. The idea is to establish a simple, but effective procedure to determine the ‘critical failure strain’ as a function of coarse mesh sizes, so as to predict the critical energy to be absorbed during the impact. For this reason, more complicated effects, such as strain-state dependence, strain concentration on the lateral stiffening, welding, as well as accurate deformation mechanisms, are omitted. A new expression is introduced to estimate the failure strain of coarse meshed ship structures struck by an indenter with hemispherical shape where the ship side or bottom sustains local penetration during a bulbous bow collision or stranding. The expression is valid for mild and high strength steels, accounts for the size of the elements, and is derived from finite element simulations of coarse meshed plates punched until the onset of necking, which critical point is first determined by using fine meshed plates. This ‘simple’ criterion is validated against reported experiments of 3 stiffened plates and 6 double-hull structures quasi-statically punched by an indenter. For the 6 double-hull specimens evaluated here, the absorbed energy at the end of the impact event is predicted with sufficient accuracy when a coarse mesh of size 10 times the plate thickness is used (the difference is about 10%). [ABSTRACT FROM AUTHOR]

Experimental drop weight impact tests have been performed to examine the failure characteristics of small-scale clamped rectangular aluminium plates struck by a mass with cylindrical and spherical indenters. The laboratory results are compared with numerical simulations. Six plate specimens are impacted at the same kinetic energy in order to study the influence of the shape and the diameter of the indenter. The experiments are conducted using a fully instrumented impact testing machine. The obtained force–displacement responses show a good agreement with the simulations performed by the LS-DYNA finite element solver. The strain hardening of the material is defined using experimental data of quasi-static tensile tests and the critical failure strain is evaluated measuring the thickness and the width at fracture of the tensile test pieces. The results show that the impact response and the failure mode of the specimens are highly sensitive to the geometry of the indenters. The failure modes are described by the matrix of the infinitesimal strain tensors and the shape of the deformation of the first failing element. In addition, the process of initiation and propagation of the material fracture is presented. [ABSTRACT FROM PUBLISHER]

Quasi-static punching tests and dynamic drop weight impact tests have been performed to examine the plastic response and failure of clamped rectangular cross-section tubes struck transversely by a hemispherical indenter. The laboratory results are compared with numerical simulations. The span lengths of the tube specimens are 125 and 250 mm, and they are impacted at different locations along the span. The results show that the impact location strongly influences the impact response of the tubes. Since the tubes are fabricated with strain-rate-insensitive high strength steel, the experimental plastic response and failure are similar when the tubes are loaded statically or under low impact velocity. The experimental results are presented in terms of the force–displacement responses and the failure modes, showing a good agreement with the simulations performed by the LS-DYNA finite element solver. The numerical results manage to describe the process of initiation and propagation of the material fracture and provide detailed information to analyse the large inelastic deformation and failure of ship structural components subjected to impact loading. The deformation and failure characteristics of the tube specimens are well described on the basis of the failure modes of the beam and plate models. Moreover, the crack initiation in both upper and lower walls is well described by the matrix of the infinitesimal strain tensors and the deformed shape of the first failing element. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents finite element simulations of a small-scale stiffened plate specimen quasi-statically punched at the mid-span by a rigid indenter, in order to examine its energy absorbing mechanisms and fracture. The specimen, scaled from a tanker side panel, is limited by one span between the web frames and the stringers. The paper provides practical information to estimate the extent of structural damage within ship side panels during collision accidents. Moreover, the results of this investigation should have relevance to evaluate grounding scenarios in which the bottom sustains local penetration. This is possible since the structural arrangement of the double hull and the double bottom of tanker vessels is very similar. The experimentally obtained force–displacement response and shape of the deformation show good agreement with the simulations performed by the explicit LS-DYNA finite element solver. The numerical analysis includes aspects of particular relevance to the behaviour of ship structures subjected to accidental loads which could give rise to difficulties in interpreting finite element calculations. In particular, the paper comments on the material nonlinearities, the importance of specifying the precise boundary conditions and the joining details of the structure. The considerable practical importance of these aspects has been the focus of attention in previous publications of the authors which evaluate the experimental-numerical impact response of simple ship structural components, such as beams and plates. Therefore, this paper uses the definitions proposed in those references to evaluate its applicability in the scaled tanker side panel, as an example of a more complex ship structure. [Copyright &y& Elsevier]

Abstract: Experimental drop weight impact tests have been performed to examine the dynamic plastic response and failure of clamped pre-notched beams struck transversely by a mass with a spherical indenter. The laboratory results are compared with numerical simulations. The machined notches are 2.0 and 4.0mm in depth, and the beams are impacted at the mid-span and at one-quarter from the support. The experiments are conducted using a fully instrumented impact testing machine. The obtained force–displacement responses show a good agreement with the simulations performed by the LS-DYNA finite element solver. The simulations aim at proposing techniques for defining the material characteristics and the boundary conditions of numerical models that analyse the large inelastic deformation and failure of ship structural components subjected to impact loading. The finite element model includes the experimental boundary condition so as to simulate small axial displacements of the specimen at the supports. The strain hardening of the material is defined using experimental data of the quasi-static tension tests and the strain rate sensitivity is evaluated using standard coefficients of the Cowper–Symonds constitutive model. The Cowper–Symonds model is also selected to estimate the dynamic critical failure strain by the use of the quasi-static failure strain predicted by numerical simulations of the tensile tests. Although the dynamic properties of the material should determine the response of the impacted specimens, the results show that the plastic response until failure is highly sensitive to the amount of restraint provided at the supports. [Copyright &y& Elsevier]

Experimental and numerical results of drop weight impact test are presented on the plas-tic behavior and fracture of rectangular plates stuck laterally by a mass with a hemi-spherical indent er. Six specimens were tested in order to study the influence of the impact velocity and the diameter of the indenter. The impact scenarios could represent abnormal actions on marine structures, such as ship collision and grounding or dropped objects on deck structures. The tests are conducted on a fully instrumented impact tester machine. The obtained force-displacement response is compared with numerical simulations, performed by the LS-DYNA finite element solver. The simulations aim at proposing techniques for defining the material and restraints on finite element models which analyze the crashworthiness of marine structures. The mesh size and the critical failure strain are predicted by numerical simulations of the tensile tests used to obtain the mechanical properties of the material. The experimental boundary conditions are modeled in order to represent the reacting forces developed during the impact. The results show that the critical impact energy until failure is strongly sensitive to the diameter of the striker. The shape of the failure modes is well predicted by the finite element models when a relatively fine mesh is used. Comments on the process of initiation and propagation of fracture are presented. [ABSTRACT FROM AUTHOR]

The elasticity and damping of the soft tissues of the hand contribute to dexterity while grasping and also help to stabilise the objects in manipulation tasks. Although some previous works have studied the force-displacement response of the fingertips, the responses in all other regions of the hand that usually participate in grasping have not been analysed to date. In this work we performed experimental measurements in 20 subjects to obtain a stiffness map of the different grasping contact areas of the human hand. A force-displacement apparatus was used to simultaneously measure force and displacement at 39 different points on the hand at six levels of force ranging from 1 N to 6 N. A non-linear force-displacement response was found for all points, with stiffness increasing with the amount of force applied. Mean stiffness for the different points and force levels was within the range from 0.2 N/mm to 7.7 N/mm. However, the stiffness range and variation with level of force were found to be different from point to point. A total of 13 regions with similar stiffness behaviours were identified. The stiffness in the fingertips increased linearly with the amount of force applied, while in the palm it remained more constant for the range of forces considered. It is hypothesised that the differences in the stiffness behaviour from one region to another allow these regions to play different roles during grasping. [ABSTRACT FROM AUTHOR]

Abstract: Experimental drop weight impact tests have been performed to examine the dynamic response of small-scale stiffened plates struck laterally by a mass with a spherical indenter. The laboratory results are compared with numerical simulations. The plates stiffened with a flat bar or L profile are supported at two opposite edges and impacted at different velocities and locations along the span. The impact scenarios could represent incidents in marine structures, such as load actions due to dropped objects on decks. The experiments are conducted using a fully instrumented impact testing machine. The obtained force–displacement responses show a good agreement with the simulations performed by the LS-DYNA finite element solver. The finite element model includes defining the experimental boundary conditions so as to simulate small axial displacements of the specimen at the supports. This representation can be used to analyze the structural crashworthiness of similar marine structures under collision scenarios. The strain hardening of the material is defined using experimental data of quasi-static tension tests and the strain rate sensitivity is evaluated using standard coefficients of the Cowper–Symonds constitutive model. The results show that the plastic response of the specimens is highly sensitive to the amount of restraint provided at the supports. Furthermore, it is found that in most of the specimens the contribution of the stiffeners to the impact response is insignificant, since the ends of the stiffener are free at the unsupported edges and the specimens experience small axial displacements at the supports. [Copyright &y& Elsevier]

In this paper, numerical simulations of drop weight impact tests examining the plastic response and failure of clamped pre-notched beams struck transversely by a mass with a hemispherical indenter are presented. The simulations aim at proposing techniques for defining the material and restraints on finite element models which analyse the structural crashworthiness of ships in collision and grounding scenarios. The mesh size and the critical failure strain are predicted by numerical simulations of the tensile tests used to obtain the mechanical properties of the material. The experimental boundary conditions are modelled in order to represent the axial displacements at the supports and the reacting forces developed during the impact. The beams are studied in terms of their force–displacement response during the impact event, which gives good agreement between experimental and numerical results. The shape of the failure modes is well predicted by the finite element model when a finer mesh is used. Comments on the stress and strain distribution at the impact point and the energy partitioning during the impact are included. [ABSTRACT FROM PUBLISHER]

Abstract: Experimental drop weight impact tests have been performed to examine the dynamic response of small-scale stiffened plates struck laterally by a mass with a spherical indenter. The laboratory results are compared with numerical simulations. The specimens are supported at two opposite edges and impacted at different locations along the span. In the unsupported edges, the ends of the stiffeners are either connected to transverse stiffeners or remain free. The impact scenarios could represent incidents in marine structures, such as load actions due to dropped objects on decks. The experiments are conducted using a fully instrumented impact testing machine. The obtained force–displacement responses show a good agreement with the simulations performed by the LS-DYNA finite element solver. The finite element model includes defining the experimental boundary condition so as to simulate small axial displacements of the specimen at the supports. This representation can be used to analyse the structural impact response of similar small-scale engineering structures. The strain hardening of the material is defined using experimental data of quasi-static tension tests and the strain rate sensitivity is evaluated using standard coefficients of the Cowper–Symonds constitutive model. The results show that the plastic response of the specimens is highly sensitive to the amount of restraint provided at the supports, particularly for the specimens with ends of the stiffeners free since they experience larger lateral deflections and, consequently, larger axial displacements at the supports. Furthermore, the contribution of the stiffeners to the impact response of the specimens is assessed through numerical simulations of unstiffened plates. [Copyright &y& Elsevier]

The technical note investigates the tensile force-displacement response of the hysteretic steel yielding brace known as Crescent Shaped Brace and characterized by a boomerang-like geometrical shape. The force-displacement curve is governed by three key performance points which correspond to the transition points separating the initial elastic behaviour, the flexural plastic behaviour, the geometrical hardening behaviour and the final axial plastic behaviour. In particular, the influence of the main geometrical parameter of the device, the so-called "lever arm", on the strongly non-linear force-displacement behavior is analyzed by means of a simplified kinematic model. Based on this, analytical estimations of the key performance points are derived and compared with numerically simulated force-displacement curves. • The Crescent Shaped Braces allow to satisfy multiple seismic performance objectives through ad-hoc geometrical properties. • A strong coupling between geometrical and material non-linearities governs the behavior of the CSB in tension. • The full force-displacement curve is completely described through analytical estimation of three key performance points. • The analytical estimation is verified through non-linear numerical simulations. [ABSTRACT FROM AUTHOR]

The paper presents experimental, numerical and analytical analyses of a small-scale double-hull structure quasi-statically punched at the mid-span by a rigid flat edge indenter, to examine its energy-absorbing mechanism and fracture. The present study aims to further validate the numerical analysis procedure and the analytical method of individual stiffened panels and web girders against the experiment of the double-hull structure. The specimen, scaled from a tanker's double side structure, includes three spans between the web frames and two spans between the stringers. The paper provides practical information to estimate the extent of structural damage within ship sides during collision accidents. The experimentally obtained force-displacement response and deformation shape show a good agreement with the simulations performed by the explicit LS-DYNA finite element solver. The analysis of the double-hull structure demonstrates the accuracy of the procedure for identifying standard inputs used in numerical codes, in particular the definition of material plastic hardening and the calibration of the critical failure strain by tensile test simulation. The experimental and numerical results are used to validate the analytical method proposed in previous investigations at the plastic deformation stage and a revised semi-analytical method is proposed in the present study for the large penetration stage. • A double-hull model punched by a rigid flat edge indenter is studied experimentally, numerically and analytically. • The specimen, includes three spans between the web frames and two spans between the stringers. • Experimentally obtained force–displacement response shows a good agreement with the results of LS-DYNA FEM. • The experimental and numerical results are used to validate the analytical method proposed here. [ABSTRACT FROM AUTHOR]