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Background: A solid conceptual understanding is essential for students to succeed in all academic disciplines. Student misconceptions are correlated with their poor academic performance and high at...

This paper describes a relatively simple closed form formula for predicting the strength of glulam assemblies in bending about the major axis based on statistical engineering mechanics using the tension strength of finger jointed of bonded lamination pairs. It has been calibrated against the strengths of full-size glulam beams ranging in depths from 150 mm to 1200 mm over spans of 2.7 m up to 19.5 m. Comparisons are made at both the mean strength and 5th percentile strength levels with the latter drawing attention to the fact that all test series invariably involve observation of minimum values that means the statistical distributions are invariably truncated. For Weibull distributions, this has an impact on the shape factor and, therefore, the local coefficient of variation of the lower tail, which plays an important role in size effects in glulam and potentially has wider implications.

Strain engineering provides an effective way of tailoring the electronic and optoelectronic properties of semiconductor nanomaterials and nanodevices, giving rise to novel functionalities. Here, we present direct experimental evidence of strain-induced modifications of hole mobility in individual gallium arsenide (GaAs) nanowires, using in situ transmission electron microscopy (TEM). The conductivity of the nanowires varied with applied uniaxial tensile stress, showing an initial decrease of ∼5–20% up to a stress of 1–2 GPa, subsequently increasing up to the elastic limit of the nanowires. This is attributed to a hole mobility variation due to changes in the valence band structure caused by stress and strain. The corresponding lattice strain in the nanowires was quantified by in situ four dimensional scanning TEM and showed a complex spatial distribution at all stress levels. Meanwhile, a significant red shift of the band gap induced by the stress and strain was unveiled by monochromated electron energy loss spectroscopy.

To accurately and efficiently carry out numerical calculations for blasting demolition projects, based on the basic principles of engineering mechanics, a simplified concrete model is established. This model represents the postpeak behavior of concrete in compression and the peak behavior in traction. Based on the mechanical properties of steel and concrete materials, a new reinforced concrete model is proposed. The proposed reinforced concrete model has been implemented in the computer program LS-DYNA and used to simulate a real blasting demolition. The result shows that this model can accurately reflect the collapse and movement process of the chimney.

In an earlier paper by the author it was mooted that glulam assembly bending strengths could be derived from the data provided by testing of bonded lamination pairs. The test concept separates the ...

The force analogy method (FAM) is considered as one of the most time-saving and cost-efficient methods for analyzing frames. Through a set of assumptions and restoring forces, FAM analyzes nonlinear frames responses through Hooke�s law. This study evaluates the effect of element type on FAM through numerical and experimental tests. The conventional Euler Bernoulli (EB) element is replaced by the Timoshenko (TS) beam-column element and the results are interpreted and compared with experimental findings. Three experimental tests were conducted for benchmarking and comparison purposes via 2D aluminum frames. The results indicated that during the analysis, when the frame response is in the linear region, there is no difference between the element types in the response of the frames. When the frame entered the plastic region, the frames which were analyzed by the TS element revealed closer responses to the experimental outcomes. The gap between the results of the frame which was analyzed by EB and TS enlarged especially when the frame experienced a sharp or huge rotation of more than 0.2 rad. The final recorded deformations based on the TS element revealed an accuracy between 98.05 to 98.65, while the EB element showed 14.66 to 45.14 for rotations of more than 0.2 rad at plastic hinge locations (PHLs). © 2020, Institute of Engineering Mechanics, China Earthquake Administration.

The probability of an instant rail break, initiated at a single pre-existing rail foot crack due to a severe wheel impact loading, is predicted using statistical methods and a time-domain model for the simulation of dynamic vehicle–track interaction. A linear elastic fracture mechanics approach is employed to calculate the stress intensity at the crack in a continuously welded rail subjected to combined bending and temperature loading. Based on long-term field measurements in a wayside wheel load detector, a three-parameter probability distribution of the dynamic wheel load is determined. For a faster numerical assessment of the probability of failure, a thin plate spline regression is implemented to develop a meta-model of the performance function quantifying the stress intensity at the crack. The methodology is demonstrated by investigating the influence of initial crack length, fracture toughness and rail temperature difference on the risk for an instant rail break.

A combination of instrumented wheelset measurements and numerical simulations of axle bending stresses is used to investigate the consequences of evolving rolling contact fatigue (RCF) damage on a passenger train wheelset. In a field test campaign, stresses have been monitored using a wheelset with four strain gauges mounted on the axle, while the evolution of wheel tread damage (out-of-roundness) has been measured on regular occasions. The strain signals are post-processed in real time and stress variations are computed. Based on a convolution integral approach, the measured wheel out-of-roundness has been used as input to numerical simulations of vertical dynamic wheelset–track interaction and axle stresses. Simulated and measured axle stresses are compared for cases involving combinations of low or high levels of rail roughness and the measured levels of RCF damage. The study enhances the understanding of how wheel tread damage and track quality influence axle stress amplitudes.

Structural batteries consist of carbon fibres embedded in a porous structural battery electrolyte (SBE), which is composed of two continuous phases: a solid polymer skeleton and a liquid electrolyte containing Li-salt. In this paper we elaborate on a computational modelling framework to study the electro-chemo-mechanical properties of such structural batteries while accounting for the combined action from migration as well as stress-assisted diffusion and convection in the electrolyte. Further, we consider effects of lithium insertion in the carbon fibres, leading to insertion strains. The focus is placed on how the convective contribution to the mass transport within the SBE affects the general electro-chemo-mechanical properties. The numerical results indicate that the convective contribution has only minor influence on the multifunctional performance when the mechanical loading is caused by constrained deformation of constituents during electro-chemical cycling. However, in the case of externally applied mechanical loading that causes severe deformation of the SBE, or when large current pulses are applied, the convective contribution has noticeable influence on the electro-chemical performance. In addition, it is shown that the porosity of the SBE, which affects the effective stiffness as well as the mobility and permeability, has significant influence on the combined mechanical and electro-chemical performance.

There is a rapidly growing interest in using general-purpose CFD codes based on second-order finite volume methods for Large-Eddy Simulation (LES) in a wide range of applications, and in many cases...

In this paper, a methodology to capture the model-based haptic feedback control reference for closed-loop steering systems is demonstrated. The parameterisation is based on the measurements of open-loop driving manoeuvres for the inertia-spring-damper-friction reference model. The steady-state and transient manoeuvres are used to identify the model parameters. The reference model is limited to the haptic feedback of driver excitation in the linear vehicle handling range and intended to be used in closed-loop steering control strategies. The model parameters have an intuitive interpretation that allows to be used in both admittance and impedance control setting. The feasibility of the proposed model is demonstrated in a validated simulation environment for electric power assisted steering and on a real hardware for the steer-by-wire force-feedback case.

An innovative and affordable table-top experiential learning platform, that aims to redress the lack of ‘hands on’ experimentation opportunities in engineering mechanics courses, is present...

Measuring the bearing capacity is critical for assessing the safety and durability of civil engineering structures. However, the existing non-destructive testing (NDT) techniques cannot estimate the bending strengths of corroded reinforced concrete (RC) beams easily. Thus, the correlation between self-magnetic flux leakage (SMFL) and bending strength of corroded RC beams was investigated in this study to estimate the bending strength. First, a theoretical model was established based on the physical properties of ferromagnetic materials and engineering mechanics. Preliminary research found that the peak-to-valley differences of the SMFL curves of corroded RC beams were strongly correlated with the bending strength. The normalized peak-to-valley differences NBP(x) and normalized bending strength NBS were defined based on this correlation. NBS of corroded RC beams can be evaluated using NBP(x) of SMFL curves. The data from 18 corroded RC beams and the theoretical model were analyzed and employed to verify the correlation between NBP(x) and NBS. The experimental results were consistent with those predicted by theory and showed the semi-quantitative correlation that NBP(x) was related to NBS exponentially (without stirrups) or approximate linearly (with stirrups). Therefore, the bending strength can be estimated semi-quantitatively via the SMFL curves. In this work, a novel correlation between the SMFL and bending strengths of corroded RC beams was established. The SMFL technique can be regarded as a new effective NDT technique for estimating the bending strength of corroded RC beams.

The existing tie-force requirements for disproportionate collapse prevention, as prescribed in the current European codes and American guidelines, are unpractical for the design of Cross-laminated timber (CLT) buildings with platform-type construction. An approach towards meeting structural integrity for such buildings is presented in this paper, specifically an improved procedure to quantify the minimum longitudinal, transverse and vertical tie-force requirements. This indirect approach for disproportionate collapse prevention solely applies linear-elastic static principles of engineering mechanics to satisfy force and moment equilibriums and ensure that CLT platform-type buildings have sufficient strength, stiffness, and ductility to bridge over damaged walls. Cantilever action of the walls and catenary action of the floor panels are identified as the main collapse-resistance mechanisms. Case-study building analyses show that typical seismic design connection detailing can be used to trigger cantilever action, whereas novel connection detailing is required to meet the axial force and deformation demands required for catenary action. The procedure presented herein can aid in designing mid-rise CLT platform-type buildings for disproportionate collapse prevention.

Reliable prediction of damage and failure in structural parts is a major challenge posed in engineering mechanics. Damage criterion is one of the most useful pieces of information about the RC structures when subjected to extreme dynamic loads. The damage index is the numerical approach to quantify the damage following a blast or an earthquake. The damage index was used to identify the capacity degradation of the structural elements under high strain rate loads. The few investigations conducted on evaluation of damage criterion and mode of failure for RC structures when subjected to blast loads. Therefore, the overall aim of this research is to overview on the damage criterion and failure modes of RC structures when subjected to extreme dynamic loads. In this study different damage criterion are demonstrated for structural elements. The results indicate the damage criterion using residual axial load carrying capacity is the appropriate method to evaluate the damage degree in columns as well as three main damage modes are observed for RC columns when subjected to blast loads. Also the maximum support rotation is a suitable approach to determine the level of damage in RC panel and slabs. The data collected from this research are being used to improve the knowledge of how structures will respond to a blast event, and improve analytical models for predicting the level of damage in concrete structures.

This paper contains an assessment of the added value of multiscale material models for concrete in the context of macroscopic structural analysis of (steel-reinforced) concrete structures. Two examples are discussed. They are inspired by the possibility of car accidents inside the immersed tunnel of the Hong Kong-Zhuhai-Macao Bridge (HZMB). The first example deals with vehicles crashing into the tunnel wall. The high-dynamic strengthening effect of concrete is studied based on an engineering mechanics model. The structural nature of the dynamic strength increase factor (DIF) is demonstrated by means of high-dynamic strength values measured on mortar cylinders of different size. Furthermore, the evolution of the DIF as a function of hardening of concrete at material ages beyond 28 days is studied. A validated multiscale model for concrete renders a customized analysis for the specific concrete used for the aforementioned tunnel possible. It is found that the DIF decreases with progressive hardening of concrete at material ages beyond 28 days. The second example is inspired by tunnel fires as may happen after car accidents. The study refers to thermal stresses in steel-reinforced concrete beams subjected to sudden heating. The thermal expansion coefficient of the concrete of the tunnel is quantified by means of a multiscale model. It is used as input for linear thermo-mechanical Finite-Element simulations of steel-reinforced concrete beams. The essential macroscopic simulation results are temperature distributions and associated stress fields. They are employed for top-down quantification of microscopic stress states inside the cement paste and the aggregates. This allows for quantifying two sources of microstructural stress fluctuations: (i) the macro-to-micro stress concentration and (ii) the mismatch of microscopic thermal expansion coefficients. In both examples, the multiscale models for concrete have increased the informative content of the structural simulations. Keywords: Concrete linings, High-dynamic strength, Thermal stresses

In this paper, a hybrid model for teaching Engineering Mechanics courses is presented. The model was applied during the year 2020 in which all the courses in our university had to move to an online format. Some recommendations are given for future implementations of hybrid models that work both, for on campus teaching and for online teaching in the new normality The results show that overall, the implementation of the model was successful and some indicators like student satisfaction and the students’ performance are high.

Low student learning outcomes in Engineering Mechanics subjects require good learning media so that it is easier to understand the material and can be seen how it works repeatedly, namely with mobile learning media. Almost all students now have smartphones, so it is better if smartphones are used as learning media. The android application in this study contains material competencies, sample questions, learning videos and interactive evaluation questions. This study aims to analyze the increase in student learning outcomes by optimizing mobile learning media. The research method is a development research method. This research procedure uses a modified 4-D model development model. The study population was 62 students. The research sample was 31 students. The data collection method used is by giving a questionnaire. The instrument used was a questionnaire in the form of a Likert scale. The data analysis technique used is primary and secondary data. The results showed that the results of the validation carried out obtained an average percentage of 88% in the valid category, so it can be concluded that the mobile learning media application is valid for use in Engineering Mechanics learning

The importance of sensory information in product purchasing decisions has gained increasing attention in recent years. Tactile properties of packaging are usually measured with the help of trained evaluators. An objective, fast and repeatable method that describes the mechanical interaction and does not rely on a panel would have many benefits. We propose and evaluate such a method for measuring the mechanical interaction between a deformable finger-like shaped sensor and a package. Evaluation of the method shows good repeatability, the variability in the measurement result is within a few percent in most cases. The method captures indentation differences at contact between sensor and package due to measurement position and package design., Funding Agencies:Gunnar Sundblad Research FoundationBillerud KorsnäsTetraPak

For critical component application, such as aerospace turbine rotors, it is imperative to be able to make accurate in-service material behaviour and component life predictions for both design and monitoring of component life. The development of such predictive capability is dependent on the quality of the experimental data from which the material parameters are derived. This paper shows the effect that scatter which may be present within experimental data, manifesting itself within the constitutive parameters derived from this data, has on the resulting fatigue crack initiation life of the nickel-based superalloy RR1000. Industrial relevance was added to this investigation by the use of flight representative thermomechanical fatigue loading cycles and state of the art material behaviour and fatigue crack initiation models used within the finite element simulations conducted. The effect of the scatter in to the modelling approach on the outcoming predictions is made via a Monte-Carlo analysis. This analysis consisted of running the same simulation several times, but with the experimentally determined and validated baseline constitutive parameters varied via correction factors built into the model, for each run via a singular value decomposition procedure. It was found that small scatter in has only a very localised scatter out effect on the crack initiation predictions under the flight representative loading. Funding Agencies|Clean Sky 2 Joint Under-taking under the European Unions Horizon 2020 research and innovation programme [686600]

Nonlinear finite element (FE) analysis of reinforced concrete (RC) structures is characterized by numerous modeling options and input parameters. To accurately model the nonlinear RC behavior involving concrete cracking in tension and crushing in compression, practitioners make different choices regarding the critical modeling issues, e.g., defining the concrete constitutive relations, assigning the bond between the concrete and the steel reinforcement, and solving problems related to convergence difficulties and mesh sensitivities. Thus, it is imperative to review the common modeling choices critically and develop a robust modeling strategy with consistency, reliability, and comparability. This paper proposes a modeling strategy and practical recommendations for the nonlinear FE analysis of RC structures based on parametric studies of critical modeling choices. The proposed modeling strategy aims at providing reliable predictions of flexural responses of RC members with a focus on concrete cracking behavior and crushing failure, which serve as the foundation for more complex modeling cases, e.g., RC beams bonded with fiber reinforced polymer (FRP) laminates. Additionally, herein, the implementation procedure for the proposed modeling strategy is comprehensively described with a focus on the critical modeling issues for RC structures. The proposed strategy is demonstrated through FE analyses of RC beams tested in four-point bending&mdash, one RC beam as reference and one beam externally bonded with a carbon-FRP (CFRP) laminate in its soffit. The simulated results agree well with experimental measurements regarding load-deformation relationship, cracking, flexural failure due to concrete crushing, and CFRP debonding initiated by intermediate cracks. The modeling strategy and recommendations presented herein are applicable to the nonlinear FE analysis of RC structures in general.

Introduction to engineering mechanics: statics, when acceleration is 0. Concepts include: particles and rigid body equilibrium equations, distributed loads, shear and moment diagrams, trusses, method of joints and sections, & inertia. This book is intended for those who love to learn.

In this paper, a novel design strategy to minimize the dynamic compliance of a vibrating infill structure with a solid outer coating and a periodic uniform infill lattice is presented. The vibration of the linearly elastic infill structure is excited by time-harmonic external mechanical loading. The design optimization of the infill lattice is performed simultaneously with the topology optimization of the macroscale structure, which also includes the coating. Multiscale topological designs of infill structures are presented in numerical examples for different excitation frequencies, different limits on static compliance, different damping properties, and different boundary conditions. The results are obtained by the finite element method and gradient-based optimization using analytical sensitivity analysis, which is derived and presented in the fully discrete setting. The influences of excitation frequencies, static constraints, damping properties, coating thicknesses, and boundary conditions on the optimized macrostructures and microstructures are discussed in the numerical examples. In general, the optimized microstructures reflect the shape characteristics of the macrostructure configuration, where Kagome-like microstructures have been obtained in some examples. Moreover, in the optimized results the microstructures include more but finer structural members for the design optimized for low excitation frequencies. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

The demands associated with the production of advanced parts made of nickel-base superalloys are continuously increasing to meet the requirements of current environmental laws. The use of lightweight components in load-carrying aero-engine structures has the potential to significantly reduce fuel consumption and greenhouse gas emissions. Furthermore, the competitiveness of the aero-engine industry can benefit from reduced production costs and shorter development times while minimizing costly try-outs and increasing the efficiency of engines. The manufacturing process of aero-engine parts in superalloys at temperatures close to 950 °C produces reduced stamping force, residual stresses, and springback compared to traditional forming procedures occurring at room temperature. In this work, a hot forming procedure of a double-curved component in alloy 718 is studied. The mechanical properties of the material are determined between 20 and 1000 °C. The presence and nature of serrations in the stress–strain curves are assessed. The novel version of the anisotropic Barlat Yld2000-2D material model, which allows the input of thermo-mechanical data, is used in LS-DYNA to model the behaviour of the material at high temperatures. The effect of considering the stress-relaxation data on the predicted shape distortions is evaluated. The results show the importance of considering the thermo-mechanical anisotropic properties and stress-relaxation behaviour of the material to predict the final geometry of the component with high accuracy. The implementation of advanced material models in the finite element (FE) analyses, along with precise process conditions, is vital to produce lightweight components in advanced materials of interest to the aerospace industry. Validerad;2022;Nivå 2;2022-03-03 (hanlid);Artikeln har tidigare förekommit som manuskript i avhandling Virtual process chain for superalloy sheet metal aero engine structures - Validation and demonstrator (NFFP6)

This chapter of the book is intended to validate the accuracy and effectiveness of the proposed methods for feature extraction and statistical decision-making by some well-known benchmark structures associated with the SHM problem. All these structures are related to experimental programs and their vibration time-domain responses (acceleration time histories) acquired from the forced or ambient vibration are utilized in the validation of the proposed methods. The experimental structures include a three-story laboratory frame belonging to the Los Alamos National Laboratory (LANL) in the USA (Figueiredo et al. in Structural health monitoring algorithm comparisons using standard data sets. Los Alamos National Laboratory: LA-14393, 2009), a wooden truss bridge (Kullaa in Mech Syst Sig Process 25:2976–2989, 2011), the second phase of the IASC-ASCE structure (Dyke in Proceedings of the 16th ASCE engineering mechanics conference, 2003), and a large-scale cable-stayed bridge belonging to Structural Monitoring and Control (SMC) group at the Harbin Institute of Technology in China (Li et al. in Struct Control Health Monit 21:156–172, 2014).

As downhole environments becomes harsher, especially for high-pressure/high-temperature (HPHT) conditions, product developments based on empirical knowledge and learning from trial-and-error testing has increasingly become inadequate, leading to long project delays, cost overruns, and information silos. A different development paradigm, which is first engineering principle based, engineering simulation aided, and materials science coupled, has emerged. Within this paradigm, knowledge-generation centric projects were initiated for specific product families. These projects have high degrees of uncertainty and are thus iterative in nature. Project management per gate-based product life cycle management, which is typically applied in the oil and gas industry, is not suitable for this type of project. A lean product development-based, event-driven project management methodology, featuring iterative learning cycles and information sharing, is tailored for execution of these projects. Our approach for management of knowledge centric projects is based on lean product development. It consists of four main components: proactive learning cycles, cloud-based visual management, visible knowledge, and integration events. In our pilot projects, proactive learning cycles involve three interrelated knowledge domains: mechanical design, engineering mechanics, and materials science. The starting points, end goal, and number of learning cycles are determined, but not the specific goals of intermediate learning cycles, which are subject to the findings of previous learning cycles. The findings of learning cycles yield visible or reusable knowledge that can be effectively shared, including causal diagrams, limit curves, boundaries in higher-dimension design space, etc. A cloud-based visual management process is established for participating global multidiscipline teams for a virtual weekly or biweekly "standup" project meeting. Integration events define convergences between disciplines, teams, and facilitate workflow. The impact of our project management approach is highlighted through a pilot project on sealing system design fundamentals. Cloud-based visual management enabled close collaboration between global teams and disciplines. Integration events helped to heighten urgency, prioritize issues and tasks, change course based on the previous learning cycle, and make fast technical and program decisions.

Methods for reducing weight of structural elements are important for a sustainable society. Over the recent years ultra high strength steel (UHSS) has been a successful material for designing light and strong components. Sandwich panels are interesting structural components to further explore areas where the benefits of UHSS can be utilized. The specific properties of sandwich panels make them suitable for stiffness applications and various cores have been studied extensively. In the present work, bidirectionally corrugated UHSS cores are studied experimentally and numerically. A UHSS core is manufactured by cold rolling and bonded to the skins by welding. Stiffness is evaluated experimentally in three-point bending. The tests are virtually reproduced using the finite element method. Precise discretization of the core requires large amounts of computational power, prolonging lead times for sandwich component development, which in the present work is addressed by homogenization, using an equivalent material formulation. Input data for the equivalent models is obtained by characterizing representative volume elements of the periodic cores under periodic boundary conditions. The homogenized panel reduces the number of finite elements and thus the computational time while maintaining accuracy. Numerical results are validated and agree well with experimental testing. Important findings from experimental and simulation results show that the suggested panels provide superior specific bending stiffness as compared to solid panels. This work shows that lightweight UHSS sandwiches with excellent stiffness properties can be manufactured and modeled efficiently. The concept of manufacturing a UHSS sandwich panel expands the usability of UHSS to new areas. Validerad;2020;Nivå 2;2020-05-14 (alebob)

The computer aided design or CAD/CAE is an important tool for various fields of engineering design. Many design software packages are based on the finite element formulation with the element-joint concept and available in rather expensive commercial finite element software packages such as SAP2000. Unfortunately, the simple explanations and demonstrations of application of the aforementioned element-joint concept for undergraduate student are not easily available. This work intends to fill the learning gap existing between engineering mechanics and mathematics in the engineering education. It aims to develop an educational procedure for learning engineering mathematics and mechanics using a commercial finite element software and a cheaply available spreadsheet software such as Microsoft Excel.

The current paper presents work on identification and evaluation of a range of factors influencing accuracy and comparability of data generated by three laboratories carrying out stress-controlled thermo-mechanical fatigue crack growth tests. It addresses crack length measurements, heating methods and temperature measurement techniques. It also provides guidance for pre-cracking and use of different specimen geometries as well as Digital Image Correlation imaging for crack monitoring. The majority of the tests have been carried out on a coarse grain polycrystalline nickel-base superalloy using two phase angles, Out-of-Phase and In-Phase cycles with a triangular waveform and a temperature range of 400-750 degrees C. Funding Agencies|European UnionEuropean Union (EU) [686600]

This paper shows that deep learning can eliminate the superimposed twin-image noise in phase images of Gabor holographic setup. This is achieved by the conditional generative adversarial model (C-GAN), trained by input-output pairs of noisy phase images obtained from synthetic Gabor holography and the corresponding quantitative noise-free contrast-phase image obtained by the off-axis digital holography. To train the model, Gabor holograms are generated from digital off-axis holograms with spatial shifting of the real image and twin image in the frequency domain and then adding them with the DC term in the spatial domain. Finally, the digital propagation of the Gabor hologram with Fresnel approximation generates a super-imposed phase image for the C-GAN model input. Two models were trained: a human red blood cell model and an elliptical cancer cell model. Following the training, several quantitative analyses were conducted on the bio-chemical properties and similarity between actual noise-free phase images and the model output. Surprisingly, it is discovered that our model can recover other elliptical cell lines that were not observed during the training. Additionally, some misalignments can also be compensated with the trained model. Particularly, if the reconstruction distance is somewhat incorrect, this model can still retrieve in-focus images.

The Industrial Revolution forced scientists and practitioners to devise new analytical methods to design machines and devices for solutions of technical problems. New industrial time is manifested by an intensification of work of machinery in which rotating objects have demonstrated the action of intricate inertial forces and motions called gyroscopic effects. Later, this property will be used in numerous devices for aviation, space and other industries. Contemporary research in an area of the dynamics of rotating objects finally solved all gyroscope problems in engineering. This chapter represents a short history of gyroscopic effects, applications in engineering and the fundamental laws and principles of the engineering mechanics that used for mathematical modelling of acting forces on rotating objects and their motions.

The pulley-belt experiment for determining coefficient of friction (μ) between belt and pulley surface is a standard experiment in engineering mechanics laboratory of undergraduate engineering programs (freshman year). It is used as a measure to establish the relation between the loads applied, angle of lap (θ) and coefficient of friction between the contact surfaces of pulley and belt. The value of coefficient of friction is calculated from friction equation by using measured load ratios and angle of lap. However, the value of coefficient of friction shows significant variation as angle of lap varies from one extreme to another, as this variation leads to a deviation from the theoretical model of the experiment. This further compromises the quality of the output, i.e. coefficient of friction, in addition to its inability to be experimentally measured. Also, no quantitative measure is available to validate the results of the experiment on the basis of measurable variables, which if present could serve as an indirect measure to check the quality of the output (μ). In the present work, parameters are identified to validate the experimental results based on the measurable variables of the experiment, i.e. load ratios and angle of lap. These parameters, i.e. difference in standard deviation of μ, load ratios for forward and reverse loading, help to determine a range for angle of lap, for which this experimental setup shall yield results which are closest to the theoretical framework of the same, giving a quantitative measure to validate the results.

In the present work, the wake development behind small-scale wind turbines is studied when introducing local topography variations consisting of a series of sinusoidal hills. Additionally, wind-tun ...

The damping potential of multiple friction contacts in a bladed disk is investigated. Friction contacts at tip shrouds and strip dampers are considered. It is shown that friction damping effectiveness can be potentially increased by using multiple friction contact interfaces. Friction damping depends on many parameters such as rotational speed, engine excitation order and mode family and therefore it is not possible to damp all the critical resonances using a single kind of friction contact interface. For example, a strip damper is more effective for the low nodal diameters, where blade/disk coupling is strong. The equations of motion of the bladed disk with multiple friction contacts are derived in the frequency domain for a cyclic structure with rotating excitations. A highly accurate method is used to generate the frequency response function (FRF) matrix. Furthermore, a finite element contact analysis is performed to compute the normal contact load and the contact area of the shroud interface at operating rotational speed. The multiharmonic balance method is employed in combination with the alternate frequency time domain method to find the steady state periodic solution. A low-pressure turbine bladed disk is considered and the effect of the engine excitation level, strip mass, thickness and the accuracy of FRF matrix on the nonlinear response curve are investigated in detail.

Three-dimensional Digital Image Correlation (3D-DIC) is a non-contact optical-numerical technique for evaluating the dynamic mechanical behavior at the surface of structures and materials, including biological tissues. 3D-DIC can be used to extract shape and full-?eld displacements and strains with high resolution, at various length scales. While various commercial and academic 3D-DIC software exist, the field lacks 3D-DIC packages which offer straightforward calibration and data-merging solutions for multi-view analysis, which is particularly desirable in biomedical applications. To address these limitations, we present MultiDIC, an open-source MATLAB toolbox, featuring the first 3D-DIC software specifically dedicated to multi-view setups. MultiDIC integrates robust two-dimensional subset-based DIC software with specially tailored calibration procedures, to reconstruct the dynamic behavior of surfaces from multiple stereo-pairs. MultiDIC contains novel algorithms to automatically merge meshes from multiple stereopairs, and to compute and visualize 3D shape and full-?eld motion, deformation, and strain. User interfaces provide capabilities to perform 3D-DIC analyses without interacting with MATLAB syntax, while standalone functions also allow proficient MATLAB users to write custom scripts for specific experimental requirements. This paper discusses the challenges underlying multi-view 3D-DIC, details the proposed solutions, and describes the algorithms implemented in MultiDIC. The performance of MultiDIC is tested using a low-cost experimental system featuring a 360-deg 12-camera setup. The software and system are evaluated using measurement of a cylindrical object with known geometry subjected to rigid body motion and measurement of the lower limb of a human subject. The findings confirm that shape, motion, and full-field deformations and strains can be accurately measured, and demonstrate the feasibility of MultiDIC in multi-view in-vivo biomedical applications.

Cost and time for die tryout are significant within the car industry, and elastic deflections of dies and presses are most commonly not considered during the virtual die design and forming simulation phase. Because of this, active surfaces of stamping dies are only cambered based on previous experiences of tool types and presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new materials. Partners within the Eureka SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. Important breakthroughs in recent years enabling the cambering methodology consists of efficient simulation strategies for full scale simulations with elastic dies and optimization techniques for creating substitutive press structures based on measurements. Furthermore, modern press deflection measurement methods are beneficial in applications such as Industry 4.0, predictive maintenance, product quality control, etc. through a more advanced understanding and live monitoring of the press system.

Axially loaded members might experience compressive forces above their static buckling capacity because of dynamic buckling under rapid shortening. Although the subject is studied in the context of engineering mechanics, it has not been thoroughly investigated in the field of earthquake engineering. Such dynamic overshoots in the compressive capacity can also be observed for braces of concentrically braced frames (CBFs) during earthquakes. Consequently, a comprehensive investigation is conducted in this study regarding the effects of dynamic buckling of braces on the seismic behavior of steel CBFs. After providing a theoretical background, recent dynamic experiments on braces and CBFs are simulated and discussed to investigate the occurrence of dynamic overshoot during these tests. Eight archetype CBFs are then designed, modeled, and subjected to a large set of ground motions to provide a quantified insight on the frequency and anticipated level of dynamic overshoot in the compressive capacity of braces during earthquakes. Results of a total of 1600 nonlinear time history analyses revealed that dynamic overshoots occur frequently in braces and affect the behavior of CBFs notably. Considerable increases are recorded in forces transmitted to other members of CBFs as a consequence of such dynamic overshoots. Importance of incorporating these dynamic overshoots in the capacity design procedure of columns, beams, and gusset plates is highlighted. Furthermore, results of a parametric study are presented and summarized in the form of a simple formula that can be used as a guide for estimating the level of dynamic overshoot.

The standard mixed-mode fracture propagation models, based on near-tip stress approximations, have limited application for fractures under far-field compressive loading. Most studies in engineering mechanics have focused on extending or modifying the standard models to solve mixed-mode fracture propagation under tensile loading. However, for geomechanics and geologic applications, the ambient stress is compressive, and internal fluid pressure or frictional stress can play an important role in the near-tip stress field altering the predicted propagation path. In this study, we modify the maximum tangential principal stress (MTPS) criterion to improve fracture propagation path predictions relative to published experimental results under both tensile and compressive external loadings. In addition, new experimental results on open cracks under compressive loading were consistent with our proposed model. Accurate propagation path predictions are independent on whether small scale yielding conditions are met in the experiments. Overall, the modified MTPS-criterion proved capable for predicting propagation paths for open cracks under compressive far-field loading.

In associated plasticity, systems subjected to cyclic loading are sometimes predicted to shake down, meaning that, after some dissipative cycles, the response goes back to a purely elastic state, where no plastic flow occurs. Frictional systems show a similar behaviour, in the sense that frictional slips due to the external loads may cease after some cycles. It has been proved that, for complete contacts with elastic behaviour and Coulomb friction, Melans theorem gives a sufficient condition for the system to shake down, if and only if there is no normal-tangential coupling at the interfaces. In this paper, the case of discrete systems combining elastic-plastic behaviour and Coulomb friction is considered. In particular, it is proved that Melans theorem still holds for contact-wise uncoupled systems, i.e., the existence of a residual state, comprised of frictional slips and plastic strains, is a sufficient condition for the system to shake down. (C) 2017 Elsevier Masson SAS. All rights reserved.

In this study, a size-dependent composite laminated skew Mindlin plate model is proposed based on a new modified couple stress theory. This plate model can be viewed as a simplified couple stress theory in engineering mechanics. Governing equations and related boundary conditions are derived based on the principle of minimum potential energy. The Rayleigh–Ritz method is employed to obtain the numerical solutions of the center deflections of simply supported plates with different ply orientations. Numerical results show that the normalized center deflections obtained by the proposed model are always smaller than those obtained by the classical one, i.e. the present model can capture the scale effects of microstructures. Moreover, a phenomenon reveals that the ply orientation would make a significant influence on the magnitude of scale effects of composite laminated plates at micro scale. Additionally, the present model of thick skew plate can be degenerated to the model of Kirchhoff plate based on the modified couple stress theory by adopting the assumptions in Bernoulli–Euler beam and material isotropy.

This article summarizes key discussions from an interview of a select group of International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE) leaders, conducted by a small group of students assembled by the G-I Student Leadership Council's GeoLegend Committee.