Force Diagram Research Articles

Impact responses of steel–concrete–steel sandwich panels with interlocked angle connectors: Experimental and numerical studies

This study explored the impact responses of a steel–concrete–steel sandwich composite panel with novel interlocked angle connectors (SCSP-IACs). Impact tests on nine SCSP-IACs were performed via a hemispherical hammer. The failure modes of all specimens were determined as the local punching failure of the concrete core. Moreover, the impact force–time and displacement–time histories and the permanent deformation were discussed. The experiment results showed that increasing the steel faceplate thickness and concrete core height enhanced the impact performance of the SCSP-IACs. By contrast, increasing the IAC spacing weakened the impact performance. Moreover, the interlocking bolts slightly affected the impact responses of the SCSP-IACs. A finite element (FE) model was established and verified with test data. The model was used to analyze the internal forces and energy absorption of the SCSP-IACs under impact loads. The internal force diagrams of the panels at different impact stages were provided, and a significant hogging moment was observed from the bending moment distributions. The FE results also showed that the zones close to the center of the panel absorbed most of the impact energy.

Conceptual Design of Cable-Stayed Bridges Using Graphic Simulation

The paradigm for structural design has been shifted from traditional engineering-oriented to more comprehensive holistic designs that consider visual aspects. Such trends need an integrated strategy to design a structure that follows force flow resulting in a pleasing visual appearance. Graphic statics is perfect for designing structural forms while visualizing structural behavior. Despite the advantages of graphic statics, there are limitations to its use manually in conceptual design, where various design alternatives must be created and compared. The objective of this study is to present the conceptual design of cable-stayed bridges by exploiting the novelty of graphic statics. It also focuses on the rapid prototyping of computer-supported design to overcome the problem of tedious and iterative manual tasks. The generation of form and force diagrams for some representative cable-stayed bridges is first discussed. This is for parametric modeling to generate structural forms with genetic information and to develop into a family of design alternatives by varying the values for predefined input parameters. Then, the information and tasks involved in the development of the form and force diagrams are formalized by using the concept of entity-based model for the computer-supported graphic simulation. The formalized entities are further implemented into the generative algorithms of graphics software that link form and force diagrams through dynamic binding. It is expected that the implemented design tool support designers to perform conceptual design iteratively and interactively by considering structural behaviour and visual silhouette in a balanced way.

Design of an over-constraint based nearly-constant amplification ratio compliant mechanism

A constant displacement amplification ratio is less investigated in compliant mechanisms. This study addresses this need by presenting an over-constraint based nearly-constant amplification ratio compliant mechanism (OCARCM) that alleviates the change in displacement amplification ratio. The free-body diagram (FBD) combined with the generic beam constraint model (BCM) method is employed to obtain the closed-form solutions that accurately and insightfully elaborate the nonlinear kinetostatic characteristics of the OCARCM. Comparative analysis is provided between the proposed OCARCM and the widely-used bridge-type compliant amplifier in terms of the ability to remain a constant amplification ratio, with and without external payloads. The closed-form models are verified by the nonlinear finite element results (FEA) with a maximum difference of 1%. In our case studies, it shows that the amplification ratio of the OCARCM changes by 1% over the range, while that of the bridge-type amplifier changes by approximately 14% under the same conditions. The results also reveal that a higher amplification ratio results in a greater variation in the ratio. An experiment based on the CNC machined aluminium alloy prototype with distributed-compliance is conducted, and experimental results show a maximum error of 3.4% for the amplification ratio compared with the analytical or FEA results.

Magnetic and structural properties of biogenic magnetic nanoparticles along their production process for use in magnetic hyperthermia

Iron-oxide nanoparticles synthesized by magnetotactic bacteria can be used in cancer treatment by means of magnetic hyperthermia. In order to study the structural properties of samples through the successive steps of their production from cultivated magnetotactic bacteria to coated magnetosomes, and their effect on magnetic properties, we performed a combination of (cryo-)Transmission Electron Microscopy observations and magnetic hysteresis as well as First-Order Reversal Curve diagrams at low temperature. The anisotropy of magnetic interactions was investigated by recording field-cooled FORC diagrams with a measuring field either parallel or perpendicular to the field-cooling direction. The results from the various techniques are in very good agreement. We found that magnetosomes in magnetotactic bacteria are arranged in chains and have magnetic properties typical of stable single-domain aligned particles. Extracted magnetosomes form clusters of interacting maghemite particles with some remaining chains, while purified magnetosomes are solely arranged in clusters. Finally, magnetosomes coated with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) are still organized in clusters but with less magnetostatic interactions than in purified magnetosomes, while magnetosomes coated with citric acid tend to recover a chained structure forming loops. The main features observed on the FORC diagrams are consistent with the various arrangement observed. Lastly, hyperthermia properties were measured for the two coated samples and we found that magnetosomes coated with citric acid display a higher Specific Absorption Rate and therefore hold a better potential for biomedical applications.

Elegant Computational Frameworks For the Analysis of Cantilevers and Beams

Abstract : In various fields like automobiles, construction, etc., the structural analysis of each component or sub-system must be done to ensure its safe operation. The structural analysis of these components entails the determination of parameters like shear force, bending moment at different locations. Usually, such computations are cumbersome, and hence a simplified approach is adopted, that involves drawing shear force diagram (SFD) and bending moment diagram (BMD) for the components. These diagrams can be effectively utilized to determine the dimensions of the components, select the appropriate material for the structure etc. Also, by utilizing the values of maximum shear force and bending moments, the maximum deflection in a beam or other structure can be ascertained. However, the process of drawing these diagrams is cumbrous and involves a lot of meticulous effort and time, which sometime poses a challenge in the effective teaching and learning of these concepts.The current paper reports the development of computational tools using the excel VBA platform and its implementation in the pedagogy of an undergraduate solid mechanics classroom. The developed tools can be easily employed to instantaneously draw the SFD and BMD diagrams for the beam under a variety of loading conditions, facilitating the inference-based learning of cantilevers and beams. Two distinct tools were developed, one for drawing the SFD and BMD of both cantilever and simply supported beams, and another one to determine the deflection and slope in the same two beams. The tools reported in the current manuscript can be effectively utilized for teaching by the demonstration of parametric variations under various loading conditions, for improved comprehension of the concepts and self-learning as well as in real world engineering to get preliminary design guidelines. Upon the development of these computational tools, these have been introduced to undergraduate mechanical engineering class of a sizable population and student responses regarding the efficacy of such tools in aiding the learning process has been recorded through an anonymous feedback. The subsequent hypothesis testing and obtained p-values strongly justify the extreme usefulness of the tools, both as a teaching and learning strategy. Keywords : SFD, BMD, cantilever beam, simply supported beam, computational tool, Excel VBA

Reversible Thermal Hysteresis in Heating‐Cooling Cycles of Magnetic Susceptibility: A Fine Particle Effect of Magnetite

AbstractThermomagnetic curves of magnetic susceptibility (κ) are key to characterizing magnetic properties. We report hump‐shaped κ‐T curves of magnetite‐bearing basalt during heating‐cooling cycles to ∼340°C, with a large thermal hysteresis and similar starting and ending values, even in multiple repeated cycles, ruling out changes in magnetic mineralogy. Based on FORC diagrams and published results of engineered materials, we propose that thermal hysteresis arises from configurations of magnetic moments in clusters of single‐domain particles due to dipolar coupling, with different collective behavior during heating and cooling. This effect modifies the hump‐shaped thermal relaxation behavior of the individual nanoparticles. FORC and κ‐T results indicate an increase in effective particle sizes after 700°C‐heating. Our results are a warning against premature interpretation of a decreasing trend in κ‐T curves by maghemite inversion. Instead, fine particle behavior should be considered when a hump‐shaped κ‐T behavior is detected.

Total knee arthroplasty coronal alignment and tibial base stress-a new numerical evaluation.

Total knee arthroplasty (TKA) is one of the most frequently performed orthopedic procedures. The correct positioning and alignment of the components significantly affects prosthesis survival. Considering the current controversy regarding the target of postoperative alignment of TKA, this study evaluated the tension at tibial component interface using two numerical methods. The stress of the prosthesis/bone interface of the proximal tibial component was evaluated using two numerical methods: the finite element method (FEM) and the new meshless method: natural neighbor radial point interpolation method (NNRPIM). The construction of the model was based on Zimmers NexGen LPS-Flex Mobile® prosthesis and simulated the forces by using a free-body diagram. Tibiofemoral mechanical axis (TFMA) for which a higher number of nodes are under optimal mechanical tension is between 1° valgus 2° varus. For values outside the interval, there are regions under the tibial plate at risk of bone absorption. At the extremities of the tibial plate of the prosthesis, both medial and lateral, independent of the alignment, are under a low stress. In all nodes evaluated for all TFMA, the values of the effective stresses were higher in the NNRPIM when compared with the FEM. Through this study, we can corroborate that the optimal postoperative alignment is within the values that are currently considered of 0 ± 3° varus. It was verified that the meshless methods obtain smoother and more conservative results, which may make them safer when transposed to the clinical practice.

Numerical modelling of fatigue crack closure and its implication on crack front curvature using ΔCTODp

One of the widely used approaches to characterize fatigue crack propagation is the use of the effective stress intensity factor range ΔKeff, which relies on determination of crack closure value Kcl. The used models of crack closure are most frequently-two-dimensional, however, for real cracks, the 3D effects should be taken into account. The paper presents 3D finite element analyses of the influences of crack front shape, inserted cycles (loading cycles between node releases) and crack closure on the crack driving force in terms of ΔKeff and ΔCTODp (plastic part of crack tip opening displacement range). Numerically obtained crack closure depended on the simulation strategy. In the case of inserted cycles, crack closure disappeared in the internal part of the specimen and remained only near the free edges. The use of ΔCTODp had the advantage of a well-defined parameter in situations where ΔKeff was problematic, namely at the corner points, which did not allow finding of equalized crack driving force along the whole crack front using ΔKeff. Equalized crack driving force in terms of ΔCTODp was found for crack front curvature with the edge angle 15.4° in simulation with crack closure, which was in good agreement with the experimentally measured value of 16°. Loops produced by loading and unloading branches of the force vs CTOD diagrams helped to describe the crack closure process and magnitude. Actual values of CTOD did not agree with the classical idea of 2D solutions under plane strain and plane stress. CTOD was larger in the internal part of the specimen than at the free edges, even in simulations with no crack face contact.

Application of mathematical modeling for calculation of dock structures of the spillway construction of the Krasnodar reservoir

The article deals with modern issues of the application of mathematical modeling taking into account the changing parameters of the reliability of the final resource of the dock structures of the spillway construction of the Krasnodar reservoir. Hydraulic structures of the pressure front of the Krasnodar reservoir are designed and built as structures of the II capital class. Analyzing the performed mathematical modeling, we see that the sections in the wall are “dangerous” at the place where it adjoins the bottom. To perform static calculations, we select a strip with a width of 1 linear meter in the longitudinal direction. Authors apply all types of loads acting on the structure of the strip of the cross-section of the structure and determine the forces in the dangerous sections of the wall and bottom. The main one is the calculation of the structure in the transverse direction. To construct diagrams of bending moments and transverse forces in the bottom plate, with the worst-case scenario of the structure, during mathematical modeling, a model of the dock structures of the spillway construction of the Krasnodar reservoir was built and later various emergency situations under the influence of seismic loads were calculated.

Postcritical Behavior of Nonlocal Strain Gradient Arches: Formulation and Differential Quadrature Solution

Arches are important components in nanostructures and systems. Because of the remarkable strength of nanomaterials, nanoarches are slender, thus enhancing their vulnerability to geometric instability, such as buckling. Although molecular simulations are often employed to analyze nanostructures, their use in routine analysis/design is formidable due to prohibitively exhaustive computation. Equivalent continuum models were developed as alternatives. The buckling and postcritical phenomena of the classical arch also form an important benchmark problem in nonlinear mechanics. This study investigates the buckling and the postcritical behavior of nanoarch subjected to inward pressure using nonlocal (NL), strain gradient (SG) continuum theory. The governing equations are derived in the form of a sixth-order nonlinear integrodifferential equation, unlike the fourth-order for a classical arch. The equation is then solved numerically using a differential quadrature (DQ) with appropriate boundary conditions. An incremental-iterative arc-length continuation is employed for the solution of the resulting algebraic system of equations. The equilibrium paths are traced for the possible instability modes, such as symmetric/antisymmetric bifurcations, snap-through and limit point instability, ascertained with the internal-external force diagrams. A particular instability mode is triggered at a certain threshold/range of the slenderness ratio of the arch, which is significantly influenced by the NL and SG interactions. These interactions not only cause quantitative changes in the instability behavior but also lead to qualitative changes, such as cessation, shift, and conversion of modes, more prominently for SG arches. Similar to classical arches, the prebuckling nonlinearity is shown to be significant.

Study on hybrid fibre reinforced UHPC beams under single and repeated lateral impact loading

This paper investigates the dynamic response of hybrid fibre reinforced ultra-high performance concrete (UHPC) beams against single and repeated low-velocity impact loads. A brief description of the drop weight impact tests on the UHPC beams was presented first followed by the development of the material and structural model in finite element analysis. A plasticity-based concrete material model with validated compressive and tensile strength surface and damage algorithm was adopted for hybrid fibre reinforced UHPC material. Based on the test results, the bond-slip behaviour between steel rebar and UHPC matrix was developed in an empirical form and incorporated in the model. Compared to the model with the bond-slip definition, the model with perfect bonding was found to underestimate the maximum mid-span deflection, which highlighted the necessity of considering the bond-slip behaviour in dynamic analysis where large deflection occurs. The repeated impact tests were performed numerically, and the results were validated with experimental data. A parametric study was then performed to investigate the effect of key parameters, including different impact energy and the same impact energy but different impact numbers. The results indicated when the total energy increased, the repeated impact loads became more hazardous than the single impact load. With the validated model, the dynamic shear force and bending moment distribution diagrams were compared to study the failure mechanism in single and repeated impact loads.

How does student skill on interpreting circular motion situation change in an online physics classroom?

High-school physics has become challenging to many teachers after their classrooms were moved to an online platform. How to teach effectively is concerned when students struggled to grasp the concept learning in the online classroom. Circular motion is the topic that the students could not understand the content well while concentrating on the screen. This work aims to investigate the achievement of using peer instruction to teach the first three steps of circular motion problem solving strategy. These are (i) identify the path of motion and its radius, (ii) draw a free-body diagram, and (iii) find the force components acting on the object. The approach was implemented to an online physics classroom with 12 high-school students. The result was analyzed from pre- and post-test data, and student practices during the teaching. The finding showed that there were more students who could interpret the circular motion situation correctly than at the beginning of the class. The path of motion and the forces acting on the object could be identified, and some students could find the centripetal force correctly. Moreover, their interaction in the class related to the of their understanding of the topic.

Marketing Risk Path Identification of Small and Medium-sized Energy Enterprises Based on ISM-MIMAC

To explore the path identification of marketing risk factors in small and medium-sized energy enterprises, this study extracts 16 factors influencing marketing from 3 aspects of the external environment, internal management and information feedback through literature analysis and expert interviews. In this paper, the interpretative structural model (ISM) is used to construct the multi-level structural diagram of influencing factors and the influencing factors are divided into three layers: direct factors, intermediate factors and fundamental factors. Then the matrix impact of cross multiplication applied to classification (MICMAC) is used to analyze the factors affecting the risk of small and medium-sized energy enterprises, and then the driving force and dependency classification diagram of marketing risk factors is drawn. The results show that the dependence and driving force of financing risk, partners, marketing personnel and other factors are relatively weak, and risk treatment can be prioritized. The factors such as lack of policies, sudden factors and organizational structure have high driving forces, which are the key factors that constitute the marketing risks of energy enterprises, and should be focused on. This study takes the marketing risk factors of small and medium-sized energy enterprises as the research object, and the research results have certain universality, which can provide new solutions for small and medium-sized energy enterprises to face marketing risks.

Analisis Rancangan Rangka Kompor Hemat Energi Berbahan Bakar Air

Analysis of the design of this energy-efficient stove for distributing the results from the HHO (Hydrogen Hydrogen Oxygen) generator and turning this HHO into a fire. The purpose of this analysis is to determine the strength of the stove frame with the maximum load it can accommodate. This stove is made with a design and structure that is larger in scale with new innovations that combine metal materials and concrete materials where the two materials are combined to create a sturdy and strong stove structure, the structure of this stove is innovated from the stove in general. The result of the force diagram shows that the bending stress of the weld seam is smaller than the allowable stress of the material, namely: wb = 8, 03×10-3 180 N/mm2. Therefore the stove is safe to use.

Experimental and numerical study on the impact resistance of ultra-high performance concrete strengthened RC beams

To enhance the impact resistance of built reinforced concrete (RC) members, the effectiveness of using ultra-high performance concrete (UHPC) for strengthening RC structures was investigated in this study. The mechanical properties of UHPC were evaluated by the uniaxial compression, tension and flexural bending tests. Drop weights with hemispherical and wedge-shaped indenter were adopted to impact the beam specimens with and without UHPC strengthening. A total of six beams, including three control RC beams and three UHPC jacketed RC (RC-UHPC) beams, were tested. The beams were prestressed in the axial direction with a 200 kN force. The test results revealed that the UHPC jackets improved the structural impact resistance. With an impact mass of 411 kg and an impact velocity of 4.95 m/s, the maximum and residual deflection of the RC-UHPC specimen decreased by 15.3 % and 21.1 % as compared to the RC control specimen, and the failure mode shifted from diagonal shear failure to flexural failure. To further investigate the dynamic responses of the beams, a detailed finite element model was established and validated with the test results in terms of the impact force, structural deflection and damage profile. The dynamic shear force and bending moment distribution diagrams were numerically derived to examine the failure mechanism of the test specimens. Finally, a parametric study was conducted to evaluate the effect of different impact locations and UHPC jacket length on the impact resistance of strengthened RC beams.

Pushover Analaysis of Irregular Tall RCC Structures

The paper is based on the study of the Response of Irregular Plan Tall RCC structures by Pushover Analysis in order to find the Base Shear, Pushover Curve, Performance limit, Shear force Diagrams, Bending Moment of the structure. Nonlinear Static Analysis, is also called as “pushover analysis”, and is also regarded as the most widely used analysis method for estimation of performance of Irregular tall RCC structures. Most of the significant Seismic Codes which proposes methods for seismic analysis of new or existing tall RCC Structures have been originally defined for simple regular structures. Therefore the analysis of the seismic response of irregular Tall RCC Structures is difficult due to nonlinear and inelastic response of the structures and more difficult than that of regular structures. Most of the codes (IS 1893 (Part 1) 2016[1], ATC-40 1996[2], EC8-1 2004[3]) uses the concept of “regularity”, taking into account distribution of mass, stiffness and strength in the structures, both in plan and in elevation. But real structures seldom act in accordance with these regularity requirements, resulting in a narrowly dependable application of the basic non-linear static analysis. For the study we are considering two G+19 storey T shaped and U shaped irregular tall framed RCC structures having height of 68 meters each and storey height of 3.3 meters. Pushover Analysis is carried out using shear walls at different locations in the structure. The objective of this study is to finds out which irregular plan tall structure is the most efficacious in resisting lateral loads. The software used for modelling and analysis is ETABS 2017.

Meclib: Dynamic and Interactive Figures in STACK Questions Made Easy

Abstract—Making and interpretation of drawings and schematics is an important skill to be developed in engineering education. The question type STACK in the Moodle learning management system combined with the interactive graphics library JSXGraph has a great potential for implementation of e-learning resources addressing these skills in formative and summative settings. The authoring process of such materials is complex due to multiple markup and programming languages like HTML, LaTeX, Maxima and JavaScript (JS) being involved. The Meclib concept mitigates this complexity and allows for efficient bulk production of material with consistent appearance and user experience. The core of Meclib is a set of pre-defined JSXGraph-based objects with an interface to Maxima, such that no problem specific JS code is required at all. The present paper outlines the basic ideas of the implementation and demonstrates the approach for some typical examples of different complexity. The focus is on applications in engineering mechanics, starting from static illustrations up to an editor for free body diagrams, with rich adaptive formative feedback.

A new approach for the computation of design shear force in reinforced concrete walls subjected to seismic loads

SummaryThis paper investigates the dynamic shear amplification in reinforced concrete shear walls designed according to the seismic provisions of the current Turkish Building Earthquake Code (TBEC‐2018). Shear walls with a high ductility level and different aspect ratios are examined to evaluate the design shear force calculated by using the dynamic amplification factor (βv) and overstrength factor (D) defined in TBEC‐2018. For this purpose, response spectrum analyses (RSAs) are first carried out on two‐dimensional cantilever shear walls with heights of 30, 45, and 60 m and with lengths of 1.5, 3, and 4.5 m in the plan. Then, a total of 198 nonlinear time history analyses (NLTHAs) are performed with real and simulated ground motions matched to the elastic design spectrum defined in TBEC‐2018. The comparison of the design shear forces obtained from RSA and the shear demands obtained from NLTHA along the heights of the walls reveals that the design shear forces calculated according to TBEC‐2018 may underestimate the actual shear demands from studied ground motions. Moreover, the applicability of the updates proposed to TBEC‐2018 for the design shear force and shear force diagram along the wall height in reinforced concrete shear wall‐frame systems to cantilever shear walls is also examined.

Design and Dynamic Analysis of a 2 Dual Axes Solar Tracking Mechanism

This paper describes the implementation of general multibody system dynamics on sun tracker mechanism. In this study, a dual axes solar tracking mechanism designed within the scope of a project to obtain an efficient electrical energy from solar rays is examined. Dynamic and kinematic calculations of the moving and joint places in the mechanism were made. This study is important as the use of an efficient solar tracker is very useful in military, industrial and residential areas. Free Body Diagrams of all the elements or limbs that make up the sun tracker mechanism have been drawn. Thus, dynamic and kinematic values at elements points were calculated. The proposed dynamics model of the mechanism offers an accurate and fast method to analyze the dynamics of the mechanism knowing that there is no suchwork available for sun tracker. Also, 3D tracker elements were drawn and planned in Solid Work program. The simulation gives a clear idea about energy parameters for different link lengths of the mechanism over a linear displacement.

Hydrodynamic modelling of a multi-body wave energy converter using the Moving Frame Method

Significant wave energy conversion may be achieved with multiple floats with several modes of motion combining constructively to generate power. With the M4 system, power take off is at hinges to absorb resulting pitch motions. Complexity increases with number of floats and conventional vectorial multi-body dynamics may be conveniently replaced by the recently formulated moving frame method based on the calculus of variations to avoid free-body diagrams and joint reaction forces. Furthermore by utilising group theory to gather spatial rotations and angular velocities in a common structure, the obtained notation is general and straight-forward to apply for single and multi-body systems. This paper lays the foundations for incorporating hydrodynamic forces into the moving frame method. The method is applied to 3, 6 and 8 float cases in regular and irregular waves with results compared to the vectorial method and experimental measurements, showing close agreement. It is suggested that this is a more natural and general approach for complex multi-body, multi-hinge hydrodynamics systems.