Computational dynamics and virtual dragline simulation for extended rope service life

The dragline machinery is one of the largest equipment for stripping overburden materials in surface mining operations. Its effectiveness requires rigorous kinematic and dynamic analyses. Current dragline research studies are limited in computational dynamic modeling because they eliminate important structural components from the front-end assembly. Thus, the derived kinematic, dynamic and stress intensity models fail to capture the true response of the dragline under full operating cycle conditions. This research study advances a new and robust computational dynamic model of the dragline front-end assembly using Kane\u27s method. The model is a 3-DOF dynamic model that describes the spatial kinematics and dynamics of the dragline front-end assembly during digging and swinging. A virtual simulator, for a Marion 7800 dragline, is built and used for analyzing the mass and inertia properties of the front-end components. The models accurately predict the kinematics, dynamics and stress intensity profiles of the front-end assembly. The results showed that the maximum drag force is 1.375 MN, which is within the maximum allowable load of the machine. The maximum cutting resistance of 412.31 KN occurs 5 seconds into digging and the maximum hoist torque of 917. 87 KN occurs 10 seconds into swinging. Stress analyses are carried out on wire ropes using ANSYS Workbench under static and dynamic loading. The FEA results showed that significant stresses develop in the contact areas between the wires, with a maximum von Mises stress equivalent to 7800 MPa. This research study is a pioneering effort toward developing a comprehensive multibody dynamic model of the dragline machinery. The main novelty is incorporating the boom point-sheave, drag-chain and sliding effect of the bucket, excluded from previous research studies, to obtain computationally dynamic efficient models for load predictions --Abstract, page iii

Investigation on the Mechanical Behavior of the Prestressing Strand by the Finite Element Method

Wire ropes that have a wide range of applications endure loads, stresses, strains, and moments while carrying out the duty of carrying loads. Wire ropes and strands are frequently used as load carrying elements due to their flexible structure and being reliable products. A prestressing steel strand is a form of the pattern of 1x6 helical wires which supply extra stiffness. Contact conditions between adjacent wires, helical geometry of wires at outer layers make it difficult to find the mechanic response of wire ropes or strands under axial load. A good way to overcome this difficulty is to perform a computer-aided simulation with finite element method. In this study, a prestressing strand having 11.11 mm diameter is computer-aided modeled by using SolidWorks, and then ANSYS Workbench is used to determine the mechanical response of the investigated rope strand. The findings indicate that results remained in the elastic region in all finite element simulations until the strain value of 0.00728

Dynamic analysis of an overhead crane carrying a canister by finite element method

A finite element model for an overhead crane carrying a nuclear waste canister is developed. This model is used to perform the static, dynamic and impact analysis using the finite element software COSMOS/M. Static results are compared with simplified model solutions to verify the accuracy of the finite element model. Frequency analysis is also performed to determine the first six natural frequencies of the system. Three of these six frequencies are compared with analytical results for verification. In the dynamic analysis, the crane is allowed to travel for a specified time. A computer program is written to connect static and dynamic modules because COSMOS/M software needs nodal displacements from static program as initial conditions for dynamic analysis. Displacement analysis is shown for nodes one each on the I beam, trolley, rope, and canister. The response studies of the system are obtained when the crane is stopped by using the nodal displacements and velocities from the dynamic analysis as input. Lastly, impact between two canisters is analyzed by taking impact velocity from dynamic analysis. Stresses in the canisters are compared with the dynamic yield strength of the canister material to determine whether yield point of the stainless steel is exceeded

선박 및 해양구조물의 공법 설계 검증을 위한 다물체 동역학 기반의 통합 시뮬레이션 방법

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 조선해양공학과, 2018. 8. 노명일.It is the most important to verify the safety of the production design before the real operation. However, the verification which depends on the experience of the production engineer or the rule and regulation cannot be clearly proven or results in overestimation. Therefore, the verification based on dynamic analysis is widely adopted. However, it is impossible for existing programs to support some mechanical equipment such as the equalizer and SPMT (Self-Propelled Modular Transporter). Therefore, this study analyzes the requirements that are essential to simulate the lifting and erection operation in ships and offshore structures and proposes the integrated simulation framework based on multibody dynamics. The proposed framework is composed of five layers such as simulation core layer for solving the equations of motion, interface layer for data communication, simulation components layer including constraints, forces and collision, equipment layer, and service layer. This study develops a dedicated and differentiated program for dynamic analysis in ships and offshore structures, named SyMAP (SyDLabs Multibody Analysis Program). The proposed simulation framework integrates several modules based on various theoretical backgrounds. First of all, the equations of motion are based on multibody dynamics. Among the several formulations, we adopt the DELE (Discrete Euler-Lagrange Equation) to achieve the robustness during numerical integration. Furthermore, we formulate the equations of motion of the 1D frame element and 2D shell element based on ANCF (Absolute Nodal Coordinate Formulation). Kinematic constraints including joints and constraint-based wire rope between the rigid bodies, and between the rigid and flexible bodies are also derived. Especially, an equalizer which distributes the tension of wire ropes between the load and equipment equally is modeled based on the real mechanism by using the constraint-based wire rope. Meanwhile, we also deal with special issues in collision detection and response. Because the shape exports from the ship CAD system contains unenclosed meshes, we propose the position difference method which checks an intersection using the line segment made by the two vertices or the trigonal prism consisting of the two triangular meshes at time t0 and t1. Furthermore, BVH (Bounding Volume Hierarchy) and exclusion boxes were adopted to increase the performance. For collision response, non-interpenetration constraint method between a vertex and a plane is derived. This method is applicable when two bodies collide at the multiple points, and it does not compulsively violate the kinematic constraint because the collision force was also solved together when the equations of motion were solved numerically. Moreover, the collision force could be determined automatically, reflecting material properties such as restitution and softness. This study proposes the modeling of the mechanical parts of the SPMT taking into consideration the axle compensation mechanism to maintain the level of the platform when the SPMT drives over an uneven roadway by lifting up and down the wheel. As external forces, hydrodynamic force, wind force, current force, and mooring force are also explained. For the verification, comparison of the benchmarking tests of multibody systems and the examples of commercial multibody software DAFUL is conducted. The analytic solutions and the simulation results are compared in case of the flexible multibody dynamics. To verify the characteristics of the motion due to the hydrodynamic forces, the motion of the floating barge is compared with RAO given by WADAM, OrcaFlex, and SIMA. For the validation, the simulation results are compared with the data collected in the real operations. Finally, we provide four representative applications such as block lifting using equalizers, LPG tank erection considering a collision, thin plate block lifting considering deformation, and block offloading using SPMT, which have not been solved before. We conclude that the problems issued in ships and offshore structures are solved by the proposed or adopted methods. We convince that the developed program based on the proposed integrated simulation framework is able to cover all of the operations in ships and offshore structures.Nomenclature 1 1. Introduction 2 1.1. Research necessities 2 1.2. Requirements for new design verification software 6 1.2.1. Block lifting by the gantry and floating cranes 6 1.2.2. Block lifting considering deformation 9 1.2.3. Collision detection and response 10 1.2.4. Block offloading by SPMTs 11 1.2.5. Summary of requirements 15 1.3. Related work 16 1.3.1. Related work for simulation framework 16 1.3.2. Related work for dynamic analysis including flexible bodies 17 1.3.1. Related work for collision detection and response 18 1.3.2. Related work for the equalizer 19 1.3.3. Related work for block offloading 22 1.4. Configuration of integrated simulation framework 24 1.4.1. Simulation core layer 24 1.4.2. Interface layer 28 1.4.3. Simulation component layer 28 1.4.4. Equipment layer 28 1.4.5. Service layer 29 1.4.6. Library diagram and relations 29 1.4.7. New production design verification program 31 1.5. Research objective and work scope 32 2. Theoretical backgrounds 33 2.1. Multibody dynamics for rigid bodies 33 2.1.1. Discretization of the Euler-Lagrange equation 33 2.1.2. Discrete Euler-Lagrange equation with constraints 38 2.1.3. Discrete Euler-Lagrange equation with constraints and non-conservative forces 42 2.1.4. Regularization 44 2.1.5. Stabilization 47 2.1.6. Final form of the Discrete Euler-Lagrange equation 48 2.1.7. Physical meanings of the parameters in DELE 50 2.2. Multibody dynamics for deformable bodies (1D frame element) 52 2.2.1. Overview of flexible multibody dynamics 52 2.2.2. Kinematic description of frame element 54 2.2.3. Strain energy 61 (1) Axial strain energy 61 (2) Bending strain energy 65 (3) Torsional strain energy 66 (4) Summary of strain energy 68 2.2.4. Equations of motion for 1D frame element 68 (1) Euler-Lagrange equation revisit 68 (2) Kinetic energy of frame element 69 (3) Strain energy of frame element 71 (4) External forces 76 (5) Summary of equations of motion for 1D frame element 81 2.2.5. Discrete Euler-Lagrange equation including Flexible body 82 2.3. Multibody dynamics for deformable bodies (2D shell element) 86 2.3.1. Kinematic description of shell element 86 2.3.2. Strain energy for shell element 90 2.3.3. Strain energy for membrane element 94 2.3.4. Equations of motion for 2D shell element 95 (1) Kinetic energy of shell element 95 (2) Longitudinal and shear strain energy of shell element 97 (3) Bending and twisting strain energy of shell element 104 (4) External forces 105 (5) Summary of equations of motion for 2D shell element 110 2.4. Kinematic constraints between rigid bodies 111 2.4.1. Ball joint 111 2.4.2. Universal joint 113 2.4.3. Hinge joint 114 2.4.4. Slider joint 116 2.4.5. Fixed joint 117 2.4.6. Slider-hinge joint 119 2.4.7. Wire rope constraint 119 2.5. Kinematic constraints between rigid and flexible bodies 123 2.5.1. Joints on 1D frame element 123 (1) Ball joint between rigid and 1D flexible bodies 123 (2) Fixed joint between rigid and 1D flexible bodies 125 2.5.2. Joints on 2D shell element 127 (1) Ball joint between rigid and 2D flexible bodies 127 (2) Fixed joint between rigid and 2D flexible bodies 129 2.6. Collision detection and response 132 2.6.1. Collision detection 132 (1) Position difference method 134 (2) Space partitioning 141 (3) Exclusion box 143 2.6.2. Collision response 144 (1) Classification of collision response 145 (2) Non-interpenetration constraint method 146 (3) Consideration of material properties 151 2.6.3. Dynamic analysis including collision detection and response 153 2.6.4. Case studies of collision detection and response 154 (1) Collision for multibody system 154 (2) Performance tests of collision detection 158 (3) Collision between complex shapes 163 (4) Collision according to material properties 165 (5) Comparison with open source program 167 2.6.5. Consideration of impulse and impulsive force 168 2.7. Modeling of Equalizer 173 2.7.1. Real mechanism of the equalizer 173 2.7.2. Modeling of pulleys and the equalizer 174 2.7.3. Case studies 176 (1) Pulleys 176 (2) Equalizer 178 2.8. Modeling of Self-propelled modular transporter (SPMT) 184 2.8.1. Modeling of SPMT and axle compensation mechanism 184 2.8.2. Replication of ballasting and de-ballasting for the floaters 187 2.8.3. Case studies of SPMT 189 (1) Pass through small bump 189 (2) Pass through inclined bump 192 2.9. External forces 196 2.9.1. Hydrodynamic force 196 2.9.2. Buoyant force 198 2.9.3. Wind force 199 2.9.4. Current force 201 2.9.5. Catenary mooring 202 2.9.6. Wire rope tension 203 3. Verification and validation 204 3.1. Verification of multibody dynamics for rigid bodies 204 3.1.1. Multibody benchmarking tests 204 (1) A01. Simple pendulum 204 (2) A02. N-four-bar mechanism 205 (3) A03. Andrews mechanism 207 (4) A04. Bricards mechanism 210 3.1.2. Verification by commercial software 213 (1) Three links connected by hinge joints (Open loop system) 214 (2) Three links connected by hinge joints (Closed loop) 216 3.2. Verification of multibody dynamics for deformable bodies 219 3.2.1. Verification of 1D frame element 219 3.2.2. Verification of 2D shell element 224 3.3. Verification of hydrodynamic force 228 3.3.1. Barge motion by a regular wave (I) 228 3.3.2. Barge motion by a regular wave (II) 230 3.3.3. Barge motion connected by 4 springs 232 3.4. Verification of catenary mooring 238 3.5. Validation by real operation (1) Module erection 239 3.5.1. Modeling 239 3.5.2. Scenario 243 3.5.3. Comparison of the posture by images 245 3.5.4. Comparison of tensions 247 3.6. Validation by real operation (2) LQ erection 250 3.6.1. Modeling 250 3.6.2. Operation sequence 252 3.6.3. Comparison of tensions 253 4. Applications 255 4.1. Block lifting using equalizers 255 4.1.1. Load lifting simulation using a gantry crane 255 4.1.2. Load lifting simulation using a floating crane 259 4.2. LPG tank erection considering collision 264 4.3. Thin plate block lifting considering deformation 270 4.3.1. Thin plate block turn-over by a gantry crane 270 4.3.2. Thin plate block lifting by a floating crane 273 4.4. Block offloading using SPMTs 276 5. Conclusion and future work 289 5.1. Summary 289 5.2. Contributions (Originality) 291 5.2.1. Theoretical contributions 291 5.2.2. Contributions for applications 291 5.2.3. Other contributions 292 5.3. Future works 292 Reference 293 국문 초록 298Docto

Design and development of a novel autonomous moored underwater profiler

The ocean is a dynamic and complex system. Understanding it through observation is critical to predicting and adapting to it. This thesis details a new approach to making vertical profiles at a fixed geographic location. It describes the design of a novel autonomous moored underwater profiler to characterize the water column of the continental shelf. The theory supporting the design is detailed, and the results of laboratory and field tests are presented. The rationale for the system, sub-system, and component design and selection is supported through calculations, and/or validated through bench testing. The resulting prototype is a hybrid of a wire follower type profiler. The profiler is attached to a subsea mooring and it is capable of profiling the entire water column. Using a buoyancy engine and compound pulley system, the unique propulsion system only requires power for the ascent. Performance analysis of the prototype during open water field trials indicated a high potential for the profiler to operate as intended

Design optimisation of shape memory alloy linear actuator applications

Shape memory alloy (SMA) actuators have drawn much attention and interest in recent decades due to their unique properties; and, are expected to be increasingly integrated within commercial automotive applications. Key advantages of SMA actuators include: potentially simplified construction, whereby the SMA can act as both sensor and actuator simultaneously; compatibility with Joule heating and convective ambient cooling; and, potential mass advantages over competing actuation technologies. These attributes potentially allow for the development of simpler, more reliable and cost effective actuation systems with significant reduction in mechanical complexity and size. SMA is readily available in commercial quantities and exhibits high wear resistance and durability, which make it an ideal candidate for application in automotive grade applications. Despite these identified advantages, SMA actuators are subject to a series of technical challenges associated with:  - Relatively small strain (displacement or stroke)  - Achievable frequency (actuation speed)  - Controllability (and stability)  - Positional accuracy  - Energy efficiency These technical challenges contribute to a relatively low success rate of commercial SMA actuator applications; and, provide motivation for this program to generate relevant research outcomes that enhance the commercialisation of SMA actuators. An extensive literature review of over 500 journal and patent documents was conducted to provide a clear roadmap for the commercial imperatives for SMA design. The formulated research methodology identifies milestones required for achieving the research objectives, which were addressed as research themes. Based on this literature review, the following research themes were identified:  - Design methods to resolve SMA actuator limitations  - Development of simple and practical numerical models for SMA actuator response  - Data for SMA linear actuator design Specific research contributions within these themes are presented within the thesis, with the objective of enhancing the commercial application of shape memory alloy (SMA) linear actuators, and include:  - A comprehensive analysis of SMAs: history, commercial applications, strength and limitations, design challenges and         opportunities.  - A novel investigation of transient heat transfer scenarios for cylindrical systems associated with their crossover and critical radii.  - Development of novel latent heat models for analytical and numerical applications, and proposal of readily applied activation and deactivation charts compatible with the requirements of SMA actuator designers.  - A novel investigation of the morphological effects of SMA-pulley systems (i.e. pulley diameter, SMA and lagging diameter) on structural and functional fatigue

The 24th Aerospace Mechanisms Symposium

The proceedings of the symposium are reported. Technological areas covered include actuators, aerospace mechanism applications for ground support equipment, lubricants, latches, connectors, and other mechanisms for large space structures

Time Localization of Abrupt Changes in Cutting Process using Hilbert Huang Transform

Cutting process is extremely dynamical process influenced by different phenomena such as chip formation, dynamical responses and condition of machining system elements. Different phenomena in cutting zone have signatures in different frequency bands in signal acquired during process monitoring. The time localization of signal’s frequency content is very important. An emerging technique for simultaneous analysis of the signal in time and frequency domain that can be used for time localization of frequency is Hilbert Huang Transform (HHT). It is based on empirical mode decomposition (EMD) of the signal into intrinsic mode functions (IMFs) as simple oscillatory modes. IMFs obtained using EMD can be processed using Hilbert Transform and instantaneous frequency of the signal can be computed. This paper gives a methodology for time localization of cutting process stop during intermittent turning. Cutting process stop leads to abrupt changes in acquired signal correlated to certain frequency band. The frequency band related to abrupt changes is localized in time using HHT. The potentials and limitations of HHT application in machining process monitoring are shown

The Sloop Boscawen: Hull Construction and Design During the Mid-Eighteenth Century in the Champlain Valley

In 1983, the British sloop Boscawen and two other vessels were discovered in the shallow waters near Fort Ticonderoga, New York. The vessels located at the site are believed to be some of the oldest sailing vessels in Lake Champlain and among the handful of naval vessels from the mid-eighteenth century that have been excavated in North America. Using Boscawen as the focal point, this dissertation explores how colonial shipwrights designed, built, and rigged early sailing vessels for use on Lake Champlain and considers Boscawen's hull construction in context with other eighteenth-century watercraft. Some of these vessels include those built by the British and French for use on the lake during the same conflict, while others were built for use on different inland and coastal waterways in northeastern North America. These cross-vessel comparisons reveal how multiple factors contributed to ship design and construction of the period and identify certain shipbuilding trends among these northeastern North American-built vessels

Safety and Mission Assurance Acronyms, Abbreviations, and Definitions

This NASA Technical Handbook compiles into a single volume safety, reliability, maintainability, and quality assurance and risk management terms defined and used in NASA safety and mission assurance directives and standards. The purpose of this handbook is to support effective communication within NASA and with its contractors. The definitions in this handbook are updated when the definition of the acronym or term is updated in the originating document