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1
Bakshi, S., A. Sarkar, and S. Chakraborty. "Dynamic Response Control of Stiffened Plate with Hole in Stiffener: A Novel Concept of Additional Open Branched Stiffeners." Proceedings of the 12th Structural Engineering Convention, SEC 2022: Themes 1-2 1, no. 1 (December 19, 2022): 1033–39. http://dx.doi.org/10.38208/acp.v1.617.
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Modern day structures have found diverse applications of stiffened plates in civil, mechanical, aerospace, marine and offshore engineering. The stiffeners, mainly in the form of beams in these stiffened plates are often exposed to unfavourable environmental and service loads, inducing localized damage to the stiffeners. Sometimes, holes are deliberately made on the stiffeners for passing service pipes, cables etc. Both of the events cause localised loss of stiffness, finally affecting the global dynamic performances. One of the practised techniques to recover the lost stiffness and to safeguard the damaged site is to introduce enclosed prismatic stiffeners around the hole. However, this often fails to critically readjust the localised stiffness loss. A constructive alternate to alleviate such situation, is to provide open branched configurations of additional stiffeners within the near vicinity of the damage. The present research work deals with the demonstration of the suitability of the above solution through numerical modelling of dynamic behaviour of a rectangular isotropic stiffened plate with a central longitudinal stiffener using finite element software ANSYS. The damage, represented equivalently as a circular cut-out in the stiffener, is considered to be located arbitrarily. Free vibration characteristics viz. natural frequencies and mode shapes of the plate in undamaged and damaged conditions have been determined by solving eigenvalue problem employing Block Lanczos algorithm. Various configurations of open-branched stiffeners around the circular cut-out, placed at specified locations have been explored. The sensitivities of relevant geometric parameters, such as the distance of the branching from the damage site, orientations of the branching etc. indicate that it is possible to design a system of open branched stiffeners around a damaged site of a stiffener to keep the overall dynamic responses practically unchanged. Such idea of branched stiffener is novel and has potential practical applications towards damage mitigation of various engineering infrastructures.
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Yin, Xuewen, Wenwei Wu, Kuikui Zhong, and Hui Li. "Dynamic stiffness formulation for the vibrations of stiffened plate structures with consideration of in-plane deformation." Journal of Vibration and Control 24, no. 20 (October 19, 2017): 4825–38. http://dx.doi.org/10.1177/1077546317735969.
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A dynamic stiffness method is presented for the vibrations of plate structures that are reinforced by eccentric stiffeners. The model incorporates both out-of-plane and in-plane deformations of the plates and the stiffeners. Based on the relationship between the forces and displacements along the common edges of the plate or beam elements, the dynamic stiffness formulae for the plate and the beam elements are derived, respectively. The globally assembled dynamic stiffness matrix is then obtained using the finite element method so that the dynamics of built-up stiffened plates can be readily addressed by using the present method. Compared to the conventional finite element model, the dynamic stiffness model can provide very accurate solutions using only one element over each uniform plate and beam member, regardless of its geometry.
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SRIVASTAVA, A. K. L., P. K. DATTA, and A. H. SHEIKH. "VIBRATION AND DYNAMIC INSTABILITY OF STIFFENED PLATES SUBJECTED TO IN-PLANE HARMONIC EDGE LOADING." International Journal of Structural Stability and Dynamics 02, no. 02 (June 2002): 185–206. http://dx.doi.org/10.1142/s0219455402000518.
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The vibration and dynamic instability behavior of a stiffened plate subjected to uniform in-plane edge loading is studied using finite element analysis. The method of Hill's infinite determinants is applied to analyze the dynamic instability regions. Rectangular stiffened plates possessing different boundary conditions, aspect ratios, varying mass and stiffness properties and varying number of stiffeners have been analyzed for dynamic instability. The results are obtained considering the bending displacements of the plate and the stiffener. Eccentricity of the stiffeners give rise to axial and bending displacement in the middle plane of the plate. The results show that the principal instability regions have a significant effect considering and neglecting in-plane displacements. Comparison with published results indicates good agreement.
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Le, Nam Bich, Cuong Manh Nguyen, and Thinh Ich Tran. "CONTINUOUS ELEMENT FORMULATIONS FOR COMPOSITE RING-STIFFENED CYLINDRICAL SHELLS." Vietnam Journal of Science and Technology 56, no. 4 (August 6, 2018): 515. http://dx.doi.org/10.15625/2525-2518/56/4/10987.
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This research studies the free vibration of composite ring-stiffened cylindrical shells by the continuous element method (CEM). The dynamic stiffness matrix (DSM) of the investigated structure has been constructed based on the analytical solutions of the governing equations of motion for composite cylindrical shells and annular plates. By applying the powerful assembly procedure of continuous elements method, natural frequencies and harmonic responses of composite ring-stiffened cylindrical shells have been obtained. In addition, the proposed model allows extracting exactly ring-stiffener vibration modes by choosing appropriate points of response. Numerical examples have confirmed many advantages of the developed model.
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Gupta, Mohit, and Massimo Ruzzene. "Dynamics of Quasiperiodic Beams." Crystals 10, no. 12 (December 16, 2020): 1144. http://dx.doi.org/10.3390/cryst10121144.
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Quasiperiodic metastrucures are characterized by edge localized modes of topological nature, which can be of significant technological interest. We here investigate such topological modes for stiffened and sandwich beams, which can be employed as structural members with inherent vibration localization capabilities. Quasiperiodicity is achieved by altering the geometric properties and material properties of the beams. Specifically, in the stiffened beams, the geometric location of stiffeners is modulated to quasiperiodic patterns, while, in the sandwich beams, the core’s material properties are varied in a step-wise manner to generate such patterns. The families of periodic and quasiperiodic beams for both stiffened and sandwich-type are obtained by varying a projection parameter that governs the location of the center of the stiffener or the alternating core, respectively. The dynamics of stiffened quasiperiodic beams is investigated through 3-D finite element simulations, which leads to the observation of the fractal nature of the bulk spectrum and the illustration of topological edge modes that populate bulk spectral bandgaps. The frequency spectrum is further elucidated by employing polarization factors that distinguish multiple contributing modes. The frequency response of the finite stiffened cantilever beams confirms the presence of modes in the non-trivial bandgaps and further demonstrates that those modes are localized at the free edge. A similar analysis is conducted for the analysis of sandwich composite beams, for which computations rely on a dynamic stiffness matrix approach. This work motivates the use of quasiperiodic beams in the design of stiffened and sandwich structures as structural members in applications where vibration isolation is combined with load-carrying functions.
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Li, Xue-Qin, Guang-Chen Bai, Lu-Kai Song, and Wei Zhang. "Nonlinear Vibration Analysis for Stiffened Cylindrical Shells Subjected to Electromagnetic Environment." Shock and Vibration 2021 (July 19, 2021): 1–26. http://dx.doi.org/10.1155/2021/9983459.
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The nonlinear vibration behaviors of stiffened cylindrical shells under electromagnetic excitations, transverse excitations, and in-plane excitations are studied for the first time in this paper. Given the first-order shear deformation theory and Hamilton principle, the nonlinear partial differential governing equations of motion are derived with considering the von Karman geometric nonlinearity. By employing the Galerkin discretization procedure, the partial differential equations are diverted to a set of coupled nonlinear ordinary differential equations of motion. Based on the case of 1 : 2 internal resonance and principal resonance-1/2 subharmonic parametric resonance, the multiscale method of perturbation analysis is employed to precisely acquire the four-dimensional nonlinear averaged equations. From the resonant response analysis and nonlinear dynamic simulation, we discovered that the unstable regions of stiffened cylindrical shells can be narrowed by decreasing the external excitation or increasing the magnetic intensity, and their working frequency range can be expanded by reducing the in-plane excitation. Moreover, the different nonlinear dynamic responses of the stiffened cylindrical shell are acquired by controlling stiffener number, stiffener size, and aspect ratio. The presented approach in this paper can provide an efficient analytical framework for nonlinear dynamics theories of stiffened cylindrical shells and will shed light on complex structure design in vibration test engineering.
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Li, Xue-Qin, Wei Zhang, Xiao-Dong Yang, and Lu-Kai Song. "A Unified Approach of Free Vibration Analysis for Stiffened Cylindrical Shell with General Boundary Conditions." Mathematical Problems in Engineering 2019 (July 10, 2019): 1–14. http://dx.doi.org/10.1155/2019/4157930.
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A unified approach of free vibration analysis for stiffened cylindrical shell with general boundary conditions is presented in this paper. The vibration of stiffened cylindrical shell is modeled mathematically involving the first-order shear deformation shell theory. The improved Fourier series is selected as the admissible displacement function while the arbitrary boundary conditions are simulated by adjusting the equivalent spring stiffness. The natural frequencies and modal shapes of the stiffened shell are obtained by solving the dynamic model with the Rayleigh-Ritz procedure. Various numerical results of free vibration analysis for stiffened cylindrical shell are obtained, including natural frequencies and modes under simply supported, free, and clamped boundary conditions. Moreover, the effects of stiffener on natural frequencies are discussed. Compared with several state-of-the-art methods, the feasibility and validity of the proposed method are verified.
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Tounsi, D., J. B. Casimir, S. Abid, I. Tawfiq, and M. Haddar. "Dynamic stiffness formulation and response analysis of stiffened shells." Computers & Structures 132 (February 2014): 75–83. http://dx.doi.org/10.1016/j.compstruc.2013.11.003.
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Zhang, Jing, and Xing Hua Shi. "Dynamic Response of Stiffened Plate under Underwater Contact Explosions." Advanced Materials Research 255-260 (May 2011): 1665–70. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.1665.
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In order to study the dynamic responses of stiffened plate under underwater contact explosions, the FEM code LS-DYNA is used to discuss the problem, six different stiffened plates are included. The stiffened plate’s distortion, the size of crevasses in the numerical simulation are analyzed. The position where the maximum plastic strain appears, the effective stress and acceleration are also described. It is revealed that the deformation of stiffened plate is different with the position of the stiffener, but the stiffener can harmonize and reduce the deformation of plate, and the whole structure will be more safety when it is subjected to explosions. So the research of this paper can be help to the design of steel structure explode resistance.
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Hill, C. M., T. Kageyama, M. G. Conzemius, G. K. Smith, and F. M. Little. "Bending properties of stainless steel dynamic compression plates and limited contact dynamic compression plates." Veterinary and Comparative Orthopaedics and Traumatology 14, no. 02 (2001): 64–68. http://dx.doi.org/10.1055/s-0038-1632677.
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SummaryThe equivalent bending stiffness and bending strength of the stainless steel DCP and stainless steel LC-DCP were compared. Three plates, of each size, were tested destructively in ‘four point bending’. All of the LC-DCP were significantly less stiff and less strong than the comparable size DCP, with the exception of the 4.5 mm narrow LC-DCP which was significantly stronger and more stiff than the 4.5 mm narrow DCP (p <.01). The design advantages of the LC-DCP are ease and versatility of plate application and improved cortical blood flow which one assumes promotes fracture healing. Also, the lower recorded stiffness of the LC-DCP may be advantageous in that it decreases the stress protection of the plated bone. Since optimal strength and stiffness of bone plates are currently unknown, the clinical relevance of the decreased strength and stiffness of the LC-DCP has yet to be determined.Stainless steel LC-DCP and DCP of various sizes were tested in four point bending to ascertain equivalent bending stiffness and bending strength of each type of plate. The LC-DCP were consistently less stiff and strong than their DCP counterparts (p <.01) with the exception of the 4.5 mm Narrow LC-DCP which was stronger and more stiff than the 4.5 mm Narrow DCP. In general, as plate size increased. the difference between the two plate designs decreased. If it can be shown that there is not any detrimental effect on fracture healing, the design features of the LC-DCP make it a desirable choice for most fracture applications.
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Holmberg, D. L., and A. M. Fruchter. "Mechanical Analysis of the Veterinary Cuttable Plate." Veterinary and Comparative Orthopaedics and Traumatology 4, no. 04 (1991): 116–19. http://dx.doi.org/10.1055/s-0038-1633265.
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SummaryA laboratory model was chosen to compare the stiffness of various small bone plates during the application of a bending force. Forces were applied to and measured from the plate surface directly. Other compressible materials were not in contact with the supporting or measuring devices. Although we cannot recommend from this experimental model that the stiffest plate would be the best treatment option, we can conclude that: (1) the stiffness of two stacked veterinary cuttable plates was approximately equal to the sum of the stiffness for each plate, (2) screw size did not have an effect on the stiffness of the veterinary cuttable plate in three out of four comparisons, and (3) single and stacked veterinary cuttable plates were stiffer than mini bone plates accepting 1.5 mm and 2.0 mm cortical screws and less stiff than the 2.7 mm dynamic compression plate.
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Solaroli, G., Z. Gu, A. Baz, and M. Ruzzene. "Wave Propagation in Periodic Stiffened Shells: Spectral Finite Element Modeling and Experiments." Journal of Vibration and Control 9, no. 9 (September 2003): 1057–81. http://dx.doi.org/10.1177/107754603030677.
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The capability of periodic structures to act as filters for propagating waves is used to control the propagation of waves in thin shells. The shells are stiffened by periodically placed rings in order to generate periodic discontinuities in the stiffness and inertial spatial distribution along the longitudinal axes of these shells. Such discontinuities result in attenuation of the wave propagation over certain frequency bands called stop bands. A distributed-parameter approach is used to derive a spectral finite element model of the periodically stiffened shell. The model accurately describes the dynamic behavior of the shell using a small number of elements. The stiffening rings, modeled using the curved beam theory, are considered as lumped elements whose mass and stiffness matrices are combined with those of the shell. The resulting dynamic stiffness matrix of the ring-stiffened shell element is used to predict the wave propagation dynamics in the structure. In particular, the shell propagation constants are determined by solving a polynomial eigenvalue problem, as a numerically robust alternative to the traditional transfer matrix formulation. The study of the propagation constants shows that the discontinuity introduced by the stiffeners generates the typical stop/pass band pattern of periodic structures. The location and width of the stop bands depend on the spacing and geometrical parameters of the rings. The existence of the stop bands, as predicted from the analysis of the propagation constants, is verified experimentally. Excellent agreement between theoretical predictions and experimental results is achieved. The presented theoretical and experimental techniques provide viable means for designing periodically stiffened shells with desired attenuation and filtering characteristics.
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Dung, Dao Van, and Vu Hoai Nam. "An analytical approach to analyze nonlinear dynamic response of eccentrically stiffened functionally graded circular cylindrical shells subjected to time dependent axial compression and external pressure. Part 2: Numerical results and discussion." Vietnam Journal of Mechanics 36, no. 4 (December 2, 2014): 255–65. http://dx.doi.org/10.15625/0866-7136/36/4/3986.
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Based on the classical thin shell theory with the geometrical nonlinearity in von Karman-Donnell sense, the smeared stiffener technique, Galerkin method and an approximate three-term solution of deflection taking into account the nonlinear buckling shape is chosen, the governing nonlinear dynamic equations of eccentrically stiffened functionally graded circular cylindrical shells subjected to time dependent axial compression and external pressure is established in part 1. In this study, the nonlinear dynamic responses are obtained by fourth order Runge-Kutta method and the nonlinear dynamic buckling behavior of stiffened functionally graded shells under linear-time loading is determined by according to Budiansky-Roth criterion. Numerical results are investigated to reveal effects of stiffener, input factors on the vibration and nonlinear dynamic buckling loads of stiffened functionally graded circular cylindrical shells.
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Li, Jieli, Michael A. Mkrtschjan, Ying-Hsi Lin, and Brenda Russell. "Variation in stiffness regulates cardiac myocyte hypertrophy via signaling pathways." Canadian Journal of Physiology and Pharmacology 94, no. 11 (November 2016): 1178–86. http://dx.doi.org/10.1139/cjpp-2015-0578.
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Much diseased human myocardial tissue is fibrotic and stiff, which increases the work that the ventricular myocytes must perform to maintain cardiac output. The hypothesis tested is that the increased load due to greater stiffness of the substrata drives sarcomere assembly of cells, thus strengthening them. Neonatal rat ventricular myocytes (NRVM) were cultured on polyacrylamide or polydimethylsiloxane substrates with stiffness of 10 kPa, 100 kPa, or 400 kPa, or glass with stiffness of 61.9 GPa. Cell size increased with stiffness. Two signaling pathways were explored, phosphorylation of focal adhesion kinase (p-FAK) and lipids by phosphatidylinositol 4,5-bisphosphate (PIP2). Subcellular distributions of both were determined in the sarcomeric fraction by antibody localization, and total amounts were measured by Western or dot blotting, respectively. More p-FAK and PIP2 distributed to the sarcomeres of NRVM grown on stiffer substrates. Actin assembly involves the actin capping protein Z (CapZ). Both actin and CapZ dynamic exchange were significantly increased on stiffer substrates when assessed by fluorescence recovery after photobleaching (FRAP) of green fluorescent protein tags. Blunting of actin FRAP by FAK inhibition implicates linkage from mechano-signalling pathways to cell growth. Thus, increased stiffness of cardiac disease can be modeled with polymeric materials to understand how the microenvironment regulates cardiac hypertrophy.
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Pruyn, Elizabeth C., Mark Watsford, and Aron Murphy. "The relationship between lower-body stiffness and dynamic performance." Applied Physiology, Nutrition, and Metabolism 39, no. 10 (October 2014): 1144–50. http://dx.doi.org/10.1139/apnm-2014-0063.
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Greater levels of lower-body stiffness have been associated with improved outcomes for a number of physical performance variables involving rapid stretch-shorten cycles. The aim of this study was to investigate the relationship between several measures of lower-body stiffness and physical performance variables typically evident during team sports in female athletes. Eighteen female athletes were assessed for quasi-static stiffness (myometry) for several isolated muscles in lying and standing positions. The muscles included the medial gastrocnemius (MedGast), lateral gastrocnemius, soleus, and Achilles tendon. Dynamic stiffness during unilateral hopping was also assessed. Participants were separated into relatively stiff and compliant groups for each variable. A number of significant differences in performance were evident between stiff and compliant subjects. When considering the quasi-static stiffness of the MedGast in lying and standing positions, relatively stiff participants recorded significantly superior results during agility, bounding, sprinting, and jumping activities. Stiffness as assessed by hopping did not discriminate between performance ability in any test. Relationships highlighted by MedGast results were supported by further significant differences in eccentric utilisation ratio and drop jump results between stiff and compliant groups for the lateral gastrocnemius and soleus in lying and standing positions. Higher levels of lower-body stiffness appear to be advantageous for females when performing rapid and (or) repeated stretch-shorten cycle movements, including sprinting, bounding, and jumping. Further, the stiffness of the MedGast is of particular importance during the performance of these activities. It is important for practitioners working with athletes in sports that rely upon these activities for success to consider stiffness assessment and modification.
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Enferadi, Javad, and Mohammad Tavakolian. "Lagrangian Dynamics Analysis of a XY-Theta Parallel Robotic Machine Tool." Periodica Polytechnica Mechanical Engineering 61, no. 2 (March 30, 2017): 107. http://dx.doi.org/10.3311/ppme.9368.
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Dynamics of a highly stiff parallel machine tool is the subject of this paper. High stiffness, good accuracy, relatively large workspace and free of singularities on the whole workspace makes the manipulator suitable for machining applications as an XY-Theta precision table. First, obtaining kinematics constraints, inverse kinematics analysis and velocity analysis are performed. Next, using six redundant generalized coordinates, we obtain Lagrangian of the manipulator. Also, a Lagrangian approach is proposed to obtain dynamics equations of the machine tool using three Lagrangian multipliers. This method allows elimination of constraint forces and moments at the joints from the motion equations. Dynamic equations of the manipulator are formed as inverse dynamics and direct dynamics problems. Finally, two examples are presented that confirms the obtained dynamics equations.
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Ma, Ou, and Jiegao Wang. "Model order reduction for impact-contact dynamics simulations of flexible manipulators." Robotica 25, no. 4 (January 5, 2007): 397–407. http://dx.doi.org/10.1017/s026357470600316x.
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SUMMARYDynamic simulation of a flexible manipulator performing physical contact (including low-speed impact) tasks with stiff environment is very time consuming because very small integration step sizes have to be used for numerical stability. Existing model order reduction techniques cannot be readily applied due to the nonlinear nature of the contact dynamics. In this paper, a method is introduced to deal with this problem. The method first linearizes the contact force model on the right-hand side of the dynamics equations periodically. It then identifies the linear “stiffness” and “damping” terms from the linearized contact force model and combines them with the existing structural stiffness and damping matrices of the associated multibody system on the left-hand side of the equations. After such a process, the traditional modal analysis and reduction techniques for linear dynamic systems can be applied to reduce the order of the resulting dynamic system. Two numerical examples of flexible manipulators performing a contact task are presented to demonstrate the significant gain in computational efficiency and the improved output results.
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Wang, Rui, Hao Zhang, Xian Sheng Li, Xue Lian Zheng, and Yuan Yuan Ren. "Vehicle Dynamics Model Establishing and Dynamic Characteristic Simulation." Applied Mechanics and Materials 404 (September 2013): 244–49. http://dx.doi.org/10.4028/www.scientific.net/amm.404.244.
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By establishing bus simplify coordinate system model and equivalent mechanical model, inertial forces and external forces are analyzed through vehicle lateral movement and vehicle's yaw motion and roll motion. Three degrees of freedom linear motion equation of vehicle is established taking into account lateral motion, yawing movement and rolling motion of vehicle and it can be solved by using method of state space equation. Vehicle dynamic characteristics are analyzed by using this method and programming with Matlab. Vehicle in steering wheel angle step response is analyzed under the conditions of different tire wheel cornering stiffness, moment of inertia, height of center of mass. The results show that increasing rear wheel cornering stiffness, reducing front wheel cornering stiffness and center of mass height, which can effectively improve stability of vehicle. Simulation results provide a theoretical basis and reference for the selection and design of vehicle.
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Mo, Shuai, Ting Zhang, Guoguang Jin, Zhanyong Feng, Jiabei Gong, and Shengping Zhu. "Dynamic Characteristics and Load Sharing of Herringbone Wind Power Gearbox." Mathematical Problems in Engineering 2018 (October 31, 2018): 1–24. http://dx.doi.org/10.1155/2018/7251645.
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In this study, the dynamic model for the herringbone planetary gear transmission system is established by the lumped parameter method based on the system dynamics and the Lagrange equation, and the impact of the support stiffness and the torsional stiffness on dynamic characteristics is studied. The research results have a guiding significance for the design of the herringbone gear transmission system. In this model, the herringbone gear is treated as a special gear coupled by 2 opposite helical gears, where the stagger angle, comprehensive meshing error, support stiffness, support damping, and load inertia are considered in the analysis of dynamics. Moreover, the dynamic characteristic of the carrier is considered as well. By calculating the meshing force curve of the transmission system, the impact of the stagger angle, supporting stiffness, and the torsional stiffness on meshing force and load sharing coefficient is analyzed. The results show that the stagger angle has an obvious impact on load sharing coefficient while it has little impact on maximum meshing force. And the support stiffness has a more obvious impact on the dynamic characteristics of the system. The recommendary support stiffness of the system is that all of the support stiffness of the sun gear, planetary gear, ring gear, and carrier is 107 N/m. The torsional stiffness has little impact on the dynamic characteristics of transmission system, except the torsional stiffness of planetary gear, and carrier has an obvious impact on load sharing coefficient. The commercial software ADAMS carried out dynamics analysis of the transmission system to verify the necessity validity of the theoretical analysis.
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Soegihardjo, Oegik, Suhardjono, Bambang Pramujati, and Agus Sigit Pramono. "Modal and Harmonic Response Analysis: Linear-Approach Simulation to Predict the Influence of Granular Stiffeners on Dynamic Stiffness of Box-Shaped Workpiece for Increasing Stability Limit against Chatter." Applied Mechanics and Materials 493 (January 2014): 501–6. http://dx.doi.org/10.4028/www.scientific.net/amm.493.501.
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Chatter is a self-excited vibration that occurs during machining process. It becomes a limitation to productivity and reduces the surface quality of work piece. Increasing dynamic stiffness of the work piece will improve its stability limit against chatter occurrence.Initial linear-approach simulation performing finite element modal and harmonic response analysis of the work piece filled with granular stiffener (sand and gravel) is presented. Drucker-Prager granular frictional material model is chosen to represent sand and gravel used as stiffener. Drucker-Prager parameters are chosen based on the experiment setting condition.Effect of an addition of the granular stiffener on the dynamic stiffness of the work piece will be evaluated. The simulation results are verified by experiment results.
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He, Jian, Ben Yang Wang, Ming Wei Zhu, and Hui Zhao Sun. "Dynamic Response on Stiffened Plate Subjected to Air Explosive Loading." Key Engineering Materials 486 (July 2011): 183–86. http://dx.doi.org/10.4028/www.scientific.net/kem.486.183.
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Stiffened plate is a common structure form in plate and shell structure. There are important theoretical significance and project application value on studying dynamic response of stiffened plate subjected to air explosive loading. The motion equation of orthotropic plate which subjected to explosive loading is established adopting Lagrange’s equation of motion, and the stiffened plate where the stiffener is arranged uniformly is treated as textural orthotropic plate. Then the motion equation of the orthotropic plate is converted into motion equation of the stiffened plate. Therefore the maximum deformation of stiffened plate can be determined.
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Dulinska, Joanna M., and Katarzyna Nowakowska. "Influence of Structural Irregularities of Tserkov Building on its Dynamic Behavior under Induced Seismic Shock of Mining Origin." Key Engineering Materials 703 (August 2016): 365–70. http://dx.doi.org/10.4028/www.scientific.net/kem.703.365.
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In the paper the influence of structural irregularities of a building on its dynamic behavior under a mining tremor was examined. A building of tserkov was taken into consideration as an example of irregular building. The geometry and the material properties of the tserkov resulted in irregularities of the stiffness of structure: the massive concrete walls were much more stiffer than the floor slab and the structural columns. It turned out that the irregularities of structural stiffness strongly influenced the dynamic behaviour of the object. The stiff concrete walls repeated the ground motion and moved like a rigid body. The dynamic response of the softer parts of structure, i.e. the floor slab and the concrete columns, reflected the natural modes of vibration connected with low frequencies rather than the ground movements. The higher frequencies occurring in the kinematic excitation were filtered out. To evaluate the influence of the roofing on the dynamic characteristics of the structure two variants of a numerical model were analysed: a model of the building with and without roofing. It occurred that in case of an irregular building with large roof area the inclusion of non-structural roofing elements is essential and may be of crucial importance while assessing the dynamic response of structure to seismic excitation. The negligence of these elements may result in unrecognizing of the resonance phenomenon.
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Mukhopadhyay, M., and S. Goswami. "Transient finite element dynamic response of laminated composite stiffened shell." Aeronautical Journal 100, no. 996 (July 1996): 223–34. http://dx.doi.org/10.1017/s000192400006718x.
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AbstractThe paper uses the conventional nine-noded Lagrangian element for studying transient linear response analysis of composite stiffened shells. An improved version of the stiffener modelling has been used in which the stiffener can be placed anywhere inside the element. For the first time, concentric or eccentric stiffeners have been used for composite stiffened shells for solving the transient dynamic response of these structures. These are not available in existing commercial packages. Different types of time dependent loading such as short duration air-blast loading, suddenly applied uniformly distributed step loading and sinusoidally harmonic loading have been considered in this paper. The results of stiffened composite cylindrical shells and doubly curved shells with different boundary conditions and various laminate orientations have been presented for eccentric stiffeners. Parametric studies considering different variables have also been carried out.
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Wang, Feng Tao, Lu Tao Song, and Bin Zhang. "Analysis for Effect of Key Parts on Precision of High Precision Machine Center." Advanced Materials Research 189-193 (February 2011): 2107–11. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.2107.
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Increasing the machining precision of machine tools has imposed higher demands for dynamic characteristics of the key components. Taking the MDH50 precision machining center as a example, this paper established the flexible body of five key components, bed, column, spindle boxes, slipway and worktable, and built the rigid-flexible coupling systems of whole machine, based on the basic theory of multi-body system dynamics. Then the cutting force reference to the actual constraints was applied to the system and the dynamics simulation was carried out. The effect of every component on machining precision was effectively identified. Dynamic stiffness testing of the machine is based of principles of testing the transmission components dynamic stiffness, and further analysis of the each component dynamic stiffness is conducted, which can verify the accuracy of flexible body analysis.
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Lan, Bo, Lu Wang, Jenny Zhang, Chris D. Pascoe, Brandon A. Norris, Jeffrey C. Y. Liu, Dennis Solomon, Peter D. Paré, Linhong Deng, and Chun Y. Seow. "Rho-kinase mediated cytoskeletal stiffness in skinned smooth muscle." Journal of Applied Physiology 115, no. 10 (November 15, 2013): 1540–52. http://dx.doi.org/10.1152/japplphysiol.00654.2013.
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The structurally dynamic cytoskeleton is important in many cell functions. Large gaps still exist in our knowledge regarding what regulates cytoskeletal dynamics and what underlies the structural plasticity. Because Rho-kinase is an upstream regulator of signaling events leading to phosphorylation of many cytoskeletal proteins in many cell types, we have chosen this kinase as the focus of the present study. In detergent skinned tracheal smooth muscle preparations, we quantified the proteins eluted from the muscle cells over time and monitored the muscle's ability to respond to acetylcholine (ACh) stimulation to produce force and stiffness. In a partially skinned preparation not able to generate active force but could still stiffen upon ACh stimulation, we found that the ACh-induced stiffness was independent of calcium and myosin light chain phosphorylation. This indicates that the myosin light chain-dependent actively cycling crossbridges are not likely the source of the stiffness. The results also indicate that Rho-kinase is central to the ACh-induced stiffness, because inhibition of the kinase by H1152 (1 μM) abolished the stiffening. Furthermore, the rate of relaxation of calcium-induced stiffness in the skinned preparation was faster than that of ACh-induced stiffness, with or without calcium, suggesting that different signaling pathways lead to different means of maintenance of stiffness in the skinned preparation.
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Kashani, H., and A. S. Nobari. "Structural Nonlinearity Identification Using Perturbed Eigen Problem and ITD Modal Analysis Method." Applied Mechanics and Materials 232 (November 2012): 949–54. http://dx.doi.org/10.4028/www.scientific.net/amm.232.949.
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Identification of nonlinear behavior in structural dynamics has been considered here, in this paper. Time domain output data of system are directly used to identify system through Ibrahim Time Domain (ITD) modal analysis method and perturbed eigen problem. Cubic stiffness and Jenkins element, as case studies, are employed to qualify the identification method. Results are compared with Harmonic Balance (HB) estimation of nonlinear dynamic stiffness. Results of ITD based identification are in good agreement with the HB estimation, for stiffness parts of nonlinear dynamic stiffness but for damping parts of nonlinear dynamic stiffness, method needs some additional improvements which are under investigation.
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Lanz, O., R. McLaughlin, S. Elder, S. Werre, and D. Filipowicz. "A biomechanical comparison of 3.5 locking compression plate fixation to 3.5 limited contact dynamic compression plate fixation in a canine cadaveric distal humeral metaphyseal gap model." Veterinary and Comparative Orthopaedics and Traumatology 22, no. 04 (2009): 1–8. http://dx.doi.org/10.3415/vcot-08-05-0042.
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Summary3.5 locking compression plate (LCP) fixation was compared to 3.5 limited contact dynamic compression plate (LC-DCP) fixation in a canine cadaveric, distal humeral metaphyseal gap model. Thirty paired humeri from adult, large breed dogs were separated into equal groups based on testing: static compression, cyclic compression, and cyclic torsion. Humeral constructs stabilized with LCP were significantly stiffer than those plated with LCDCP when loaded in static axial compression (P = 0.0004). When cyclically loaded in axial compression, the LCP constructs were significantly less stiff than the LC-DCP constructs (P = 0.0029). Constructs plated with LCP were significantly less resistant to torsion over 500 cycles than those plated with LC-DCP (P<0.0001). The increased stiffness of LCP constructs in monotonic loading compared to constructs stabilised with non-locking plates may be attributed to the stability afforded by the plate-screw interface of locking plates. The LCP constructs demonstrated less stiffness in dynamic testing in this model, likely due to plate-bone offset secondary to non-anatomic contouring and occasional incomplete seating of the locking screws when using the torque-limiting screw driver. Resolution of these aspects of LCP application may help improve the stiffness of fixation in fractures modeled by the experimental set-up of this investigation.
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Zeng, Zhi-Ping, Yan-Cai Xiao, Wei-Dong Wang, Xu-Dong Huang, Xiang-Gang Du, Lan-Li Liu, Joseph Eleojo Victor, Zhong-Lin Xie, Yu Yuan, and Jun-Dong Wang. "The Influence of Track Structure Parameters on the Dynamic Response Sensitivity of Heavy Haul Train-LVT System." Applied Sciences 11, no. 24 (December 13, 2021): 11830. http://dx.doi.org/10.3390/app112411830.
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Background: In order to study the applicability of Low Vibration Track (LVT) in heavy-haul railway tunnels, this paper carried out research on the dynamic effects of LVT heavy-haul railway wheels and rails and provided a technical reference for the structural design of heavy-haul railway track structures. Methods: Based on system dynamics response sensitivity and vehicle-track coupling dynamics, the stability of the upper heavy-haul train, the track deformation tendency, and the dynamic response sensitivity of the vehicle-track system under the influence of random track irregularity and different track structure parameters were calculated, compared and analyzed. Results: Larger under-rail lateral and vertical structural stiffness can reduce the dynamic response of the rail system. The vertical and lateral stiffness under the block should be set within a reasonable range to achieve the purpose of reducing the dynamic response of the system, and beyond a certain range, the dynamic response of the rail system will increase significantly, which will affect the safety and stability of train operation. Conclusions: Considering the changes of track vehicle body stability coefficients, the change of deformation control coefficients, and the sensitivity indexes of dynamic performance coefficients to track structure stiffness change, the recommended values of the vertical stiffness under rail, the lateral stiffness under rail, the vertical stiffness under block, and the lateral stiffness under block are, respectively 160 kN/mm, 200 kN/mm, 100 kN/mm, and 200 kN/mm.
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Yin, Xuewen, Wenwei Wu, Hui Li, and ，Kuikui Zhong. "Vibration Transmission within Beam-stiffened Plate Structures Using Dynamic Stiffness Method." Procedia Engineering 199 (2017): 411–16. http://dx.doi.org/10.1016/j.proeng.2017.09.133.
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Yuan, Zhe, Fei Fan, and Xiaotian Bai. "Nonlinear dynamics analysis of a gear system considering tooth contact temperature and dynamic wear." Advances in Mechanical Engineering 14, no. 9 (September 2022): 168781322211210. http://dx.doi.org/10.1177/16878132221121056.
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Increased temperature and surface wear of high-speed and heavy-load gears are inevitable. Thermal deformation and surface wear modify the position of the action line of the tooth surface and thus influence the dynamic characteristics of the gear mesh. In this study, the elastic modulus and tooth profile thermal deformation were calculated when the tooth contact temperature (TCT) increased. A dynamic wear calculation method was used to combine the dynamic mesh force and dynamic wear coefficient caused by the dynamic mesh force obtained in the nonlinear dynamics model with the quasi-static wear model to obtain the cumulative wear depth. The changed elastic modulus, the tooth profile thermal deformation and the wear depth are considered when calculating the mesh stiffness using the energy method. A nonlinear dynamics model was established by considering the effects of TCT and dynamic wear on the internal dynamic excitation of the gear transmission system. The effects of internal excitation variations such as mesh stiffness, STE and backlash on gear dynamics are analyzed, and the study showed their complex effects on gear dynamics. Comparing the bifurcation diagrams with or without considering TCT and dynamic wear reveals that the system enters chaos earlier after considering TCT and dynamic wear.
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Oyelade, Akintoye O. "Sound transmission through a stiff double-panel structure periodically stabilized by negative stiffness module: Theoretical modeling." Journal of Vibration and Control 26, no. 23-24 (April 13, 2020): 2286–96. http://dx.doi.org/10.1177/1077546320921049.
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Analytic expressions are derived for models predicting the influence of periodically spaced structural links on sound transmission through a double-panel structure. The double panel has been configured to have two sets of structural links: a rib stiffener and negative stiffness component. The stiffener is identical and is spaced periodically at a distance. However, the negative element component is shifted by an amount q from the other set. The dynamic equation of the vibroacoustic of the system is formulated in terms of the space harmonics and by the principle of virtual work. The model is validated by comparing the model predictions with the existing result from the literature. Then, influences of the negative element, engineering safety, offset, and elevation angle are investigated. A new antiresonance with a huge sound transmission loss value can be engineered at the low-frequency region when these parameters are varied. In addition, the application of the stiff model is implemented for a periodic acoustic metamaterial structure. The negative stiffness inclusion can prevent wave propagation at low frequency. The periodic structure can be designed to obtain more and wider frequency bandgaps.
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Yang, Xiaodong, Chaodong Zhang, Wennian Yu, Wenbin Huang, Zhiliang Xu, and Chunhui Nie. "A Refined Dynamic Model for the Planetary Gear Set Considering the Time-Varying Nonlinear Support Stiffness of Ball Bearing." Machines 11, no. 2 (February 1, 2023): 206. http://dx.doi.org/10.3390/machines11020206.
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Dynamics models of planetary gear sets (PGSs) are usually established to predict their dynamic behavior and load-sharing characteristics. The accurate modeling of bearing support stiffness is essential to study their dynamics. However, in most of the existing PGS dynamic models, the effect of characteristics coupling the rolling bearing time-varying nonlinear stiffness with the translational property of PGSs on the dynamic responses was completely neglected. To investigate this problem, a refined dynamic model for PGSs is proposed considering the coupled relationship between the radial translation of the rotating components and the time-varying nonlinear support stiffness of the ball bearing. The refined dynamic model simultaneously considers the coupled effect of the time-varying characteristic caused by the orbital motion of the rolling elements and the nonlinear characteristic caused by Hertzian contact between the rolling elements and raceways of the ball bearing. Comparisons between the simulations and experimental results are presented, which indicate that the PGS vibration spectrums yielded by the proposed time-varying nonlinear stiffness model are much closer to the actual scenarios than those of traditional models. The analysis results provide theoretical guidance for fault monitoring and diagnosis of the rolling bearings used in the PGS.
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Yang, Zemin, Xiaopeng Li, Jinchi Xu, Renzhen Chen, and Hexu Yang. "Study of Dynamic Performance and Control Strategy of Variable Stiffness Actuator System Based on Two-Inertial-System." Mathematics 11, no. 5 (February 27, 2023): 1166. http://dx.doi.org/10.3390/math11051166.
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The study of position control for variable stiffness actuators is important for improving their energy efficiency and robustness. In this paper, for the previously proposed nonlinear variable stiffness actuator, firstly, a dynamic model of the variable stiffness actuator system is established based on a two-inertia-system theory. Secondly, the effects of friction and gravity factors on the dynamic performance of the system are analyzed. The results of the study show that friction and gravity have obvious effects on the dynamic characteristics of the system in the constant stiffness state, and that these effects are more complex and obvious in the variable stiffness state, which proves the reasonableness and necessity of considering friction and gravity in the dynamics modeling process. Then, in order to improve the dynamic performance of the system and make its positioning performance meet the requirements, the control strategy of the variable stiffness actuator system is studied. The results show that the sliding mode control strategy based on nonlinear disturbance observer and dynamics model is a good solution to the effect of friction and gravity on the system, and can make its position-tracking performance meet the requirements. Finally, the correctness and effectiveness of the control strategy are verified experimentally.
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Du, Chao, Jun Zhang, Dun Lu, Huijie Zhang, and Wanhua Zhao. "A parametric modeling method for the pose-dependent dynamics of bi-rotary milling head." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 232, no. 5 (July 6, 2016): 797–815. http://dx.doi.org/10.1177/0954405416654599.
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Bi-rotary milling head is one of the core components of five-axis machining center, and its dynamic characteristics directly affect the machining stability and accuracy. During the sculptured surface machining, the bi-rotary milling head exhibits varying dynamics in various machining postures. To facilitate rapid evaluation of the dynamic behavior of the bi-rotary milling head within the whole workspace, this article presents a method for parametrically establishing dynamic equation at different postures. The rotating and swing shafts are treated as rigid bodies. The varying stiffness of the flexible joints (such as bearings and hirth coupling) affected by gravity and cutting force at different swing angles is analyzed and then a multi-rigid-body dynamic model of the bi-rotary milling head considering the pose-varying joint stiffness is established. The Lagrangian method is employed to deduce the parametric dynamic equation with posture parameters. The static stiffness, natural frequencies and frequency response functions at different postures are simulated using the parametric equation and verified by the impact testing experiments. The theoretical and experimental results show that the dynamics of the bi-rotary milling head vary with the machining postures, and the proposed method can be used for efficient and accurate evaluation of the pose-dependent dynamics at the design stage.
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Hu, Yong, and David B. Bogy. "Dynamic Stability and Spacing Modulation of Sub-25 nm Fly Height Sliders." Journal of Tribology 119, no. 4 (October 1, 1997): 646–52. http://dx.doi.org/10.1115/1.2833864.
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Designing a reliable sub-25 nm spacing head/disk interface for today’s magnetic hard disk drives demands a greater dynamic stability and a smaller spacing modulation. An air bearing dynamic simulator with multiple features is developed to investigate the dynamic characteristics of three shaped-rail negative pressure sub-25 nm fly height sliders. Various simulations including air bearing stiffness, impulse response, surface roughness induced spacing modulation, bump response, and track seeking dynamics are performed. The results indicate that the roughness induced spacing modulation decreases with the increase of the air bearing stiffness and the decrease of the slider size. The suspension dynamics is integrated into the air bearing dynamics simulation for the track accessing motion by modal analysis. It is concluded that the fly height modulation during a track accessing event is attributed to many factors such as the effective skew angle, the seeking velocity, and the roll motion caused by the inertia of the moving head. The extent of the roll motion effect depends on the air bearing roll stiffness and the level of the inertia force of the moving head. Larger roll stiffness and smaller inertia force produce a smoother track accessing performance.
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Shi, Zhenghong, and Sheng Li. "Nonlinear dynamics of hypoid gear with coupled dynamic mesh stiffness." Mechanism and Machine Theory 168 (February 2022): 104589. http://dx.doi.org/10.1016/j.mechmachtheory.2021.104589.
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Klamecki, B. E. "On the Effects of Turning Process Asymmetry on Process Dynamics." Journal of Engineering for Industry 111, no. 3 (August 1, 1989): 193–98. http://dx.doi.org/10.1115/1.3188749.
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The implications of a fundamental asymmetry in the lathe turning process are considered. The asymmetry is the directional dependence of system stiffness that exists at the cutting tool edge. Depending on tool edge displacement, the system stiffness is determined by the workpiece stiffness or the relatively much stiffer tool support structure. A one degree-of-freedom, lumped parameter model with nonlinear stiffness is constructed and subjected to a periodic forcing. Time and frequency domain analyses show that extremely complex dynamic behavior can occur in this simple system.
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Le, Lily Thao-Nhi, Oscar Cazares, Janna K. Mouw, Sharmila Chatterjee, Hector Macias, Angel Moran, Jillian Ramos, Patricia J. Keely, Valerie M. Weaver, and Lindsay Hinck. "Loss of miR-203 regulates cell shape and matrix adhesion through ROBO1/Rac/FAK in response to stiffness." Journal of Cell Biology 212, no. 6 (March 14, 2016): 707–19. http://dx.doi.org/10.1083/jcb.201507054.
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Breast tumor progression is accompanied by changes in the surrounding extracellular matrix (ECM) that increase stiffness of the microenvironment. Mammary epithelial cells engage regulatory pathways that permit dynamic responses to mechanical cues from the ECM. Here, we identify a SLIT2/ROBO1 signaling circuit as a key regulatory mechanism by which cells sense and respond to ECM stiffness to preserve tensional homeostasis. We observed that Robo1 ablation in the developing mammary gland compromised actin stress fiber assembly and inhibited cell contractility to perturb tissue morphogenesis, whereas SLIT2 treatment stimulated Rac and increased focal adhesion kinase activity to enhance cell tension by maintaining cell shape and matrix adhesion. Further investigation revealed that a stiff ECM increased Robo1 levels by down-regulating miR-203. Consistently, patients whose tumor expressed a low miR-203/high Robo1 expression pattern exhibited a better overall survival prognosis. These studies show that cells subjected to stiffened environments up-regulate Robo1 as a protective mechanism that maintains cell shape and facilitates ECM adherence.
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Rincón-Morantes, Jhon Fredy, Allex E. Alvarez, and Oscar J. Reyes-Ortiz. "Estimación de la rigidez de materiales granulares marginales no ligados mediante ensayo CBR dinámico." Ingeniería y Desarrollo 40, no. 01 (August 3, 2022): 92–113. http://dx.doi.org/10.14482/inde.40.01.621.992.
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La evaluación en laboratorio de la respuesta de materiales granulares no ligados (e.g., subbases- y bases-granulares para pavimentación) bajo carga dinámica es limitada en Colombia. Este estado de la práctica se relaciona, entre otros aspectos, con que el equipo triaxial dinámico requerido para su determinación es costoso y los protocolos de ensayo complejos. Como alternativa, en la última década se han realizado desarrollos sobre el ensayo CBR dinámico (dCBR), que emplea el equipo, pero modifica el protocolo del ensayo de CBR convencional. Esta investigación propone las bases de un nuevo protocolo para el ensayo de dCBR, para determinar la rigidez de materiales granulares (i.e., módulo resiliente equivalente) mediante la aplicación de siete etapas de carga repetida, donde cada etapa está definida por una deformación objetivo. El estudio incluyó dos materiales granulares marginales (MGMs), con índices de plasticidad altos (IP>6). Los resultados sugieren que el protocolo propuesto para el ensayo de dCBR permite la estimación del módulo resiliente equivalente. Adicionalmente, este protocolo discrimina el efecto de la plasticidad de la fracción fina del MGM sobre su rigidez (i.e., reducción de módulo resiliente equivalente al incrementar el índice de plasticidad). Con base en los resultados obtenidos, se propone avanzar en la caracterización de un mayor número de materiales para validar los resultados preliminares presentados e indagar sobre una posible correlación entre valores de módulo resiliente y módulo resiliente equivalente.
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Gupta, Tikam Chand. "Parametric studies on dynamic stiffness of ball bearings supporting a flexible rotor." Journal of Vibration and Control 25, no. 15 (June 26, 2019): 2175–88. http://dx.doi.org/10.1177/1077546319856147.
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Most of the researchers in the field of dynamics of the rolling element bearing have considered bearing stiffness as time invariant and/or not related to dynamics of the bearing. In the present paper, the bearing stiffness has been taken as function of dynamic response at every time step of numerical simulation and a detailed parametric study is performed to investigate the effect of flexibility of the rotor shaft, rotational speed, and internal radial clearance on the instantaneous and average value of dynamic stiffness of the ball bearing. The mathematical formulation is based on the Timoshenko beam finite element theory. Gravity and bearing forces are considered as external forces acting on a free-free flexible shaft. A stable Newmark- β numerical integration scheme coupled with Newton–Raphson method is used for numerical integration and for convergence to an accurate value of bearing stiffness. The results showing the variation of different components of bearing stiffness as a function of time-invariant parameters has improved the understanding of the dynamic behavior of the bearing during motion. The variation pattern of bearing stiffness coefficients is observed to be sensitive to direction of rotation. The amplitude of periodic change of these coefficients increases with the increase of the stiffness ratio of shaft and the decrease of radial clearance.
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Wang, Peng, Yifeng Zhong, Zheng Shi, Dan Luo, and Qingshan Yi. "Estimating of the Static and Dynamic Behaviors of Orthogrid-Stiffened FRP Panel Using Reduced-Order Plate Model." Materials 14, no. 17 (August 28, 2021): 4908. http://dx.doi.org/10.3390/ma14174908.
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The orthogrid-stiffened FRP panel (OSFP) is a generic structural element in weight-sensitive structure applications. Based on the variational asymptotic method, a 2D reduced-order plate model (2D-RPM) of OSFP was constructed through matching the strain energy of the original panel for static and dynamic analyses. The local field distributions were recovered using the recovery relationship and global response. The relative influences of select parameters on the effective performance of the OSFP were revealed by parametric studies. The comparative results showed that the effective performance of the OSFP predicted by the 2D-RPM were consistent with those predicted by the 3D finite element model, but the computational efficiency was greatly improved. The stiffener height had the greatest influence on the natural frequency of the panel. The layup configurations of laminates had significant influences on the equivalent stiffness and buckling load of the OSFP but had little effect on the vibration modes, which could be varied by adjusting the stiffening forms.
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Xu, Liufeng. "Mathematical Modeling and Characteristic Analysis of the Vertical Stiffness for Railway Vehicle Air Spring System." Mathematical Problems in Engineering 2020 (June 8, 2020): 1–12. http://dx.doi.org/10.1155/2020/2036563.
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Establishing a correct and reliable vertical stiffness model has an important significance on reproducing the characteristics of an air spring system. In this paper, a dynamic vertical stiffness model is developed based on thermodynamics and fluid dynamics, and geometric parameters are identified by an approximate analytical method. Meanwhile, experimental tests are performed to verify the accuracy and reliability of the proposed model. Furthermore, the impact of geometric parameters on the vertical stiffness characteristics is discussed through a sensitivity analysis. The conclusions show that the dynamic vertical stiffness model can well characterize the dynamic characteristics of the air spring system, which provides a theoretical basis for the optimal design of air spring parameters and the study of mechanical properties.
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Langley, R. S. "A dynamic stiffness technique for the vibration analysis of stiffened shell structures." Journal of Sound and Vibration 156, no. 3 (August 1992): 521–40. http://dx.doi.org/10.1016/0022-460x(92)90742-g.
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BANERJEE, J. R. "DYNAMIC STIFFNESS FORMULATION AND FREE VIBRATION ANALYSIS OF CENTRIFUGALLY STIFFENED TIMOSHENKO BEAMS." Journal of Sound and Vibration 247, no. 1 (October 2001): 97–115. http://dx.doi.org/10.1006/jsvi.2001.3716.
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Li, Hui, Xuewen Yin, and Wenwei Wu. "Dynamic stiffness formulation for in-plane and bending vibrations of plates with two opposite edges simply supported." Journal of Vibration and Control 24, no. 9 (August 30, 2016): 1652–69. http://dx.doi.org/10.1177/1077546316667205.
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A dynamic stiffness formulation is developed for both in-plane and bending vibrations of plates with two opposite edges simply supported. The bending motions of plates are described in terms of Leissa’s displacement functions while the in-plane motions take the forms take the forms that were proposed by Bercin and Langley. Using Projection Method, the forces and their corresponding displacements along plate junctions are projected onto a set of orthogonal functions, by which means the well-known spatial dependence difficulties can be overcome, and, as a result, local dynamic stiffness matrix is obtained. Classical finite element technique is utilized to assemble local stiffness matrix into global coordinates. Finally, dynamics of an L-shaped plate is addressed, within which conversion of in-plane and bending motions occurs. Our numerical results are in good agreement with those obtained from finite element method, which demonstrates that this dynamic stiffness formulation has great potential in modeling the dynamics of built-up plate structures, especially in characterizing the in-plane waves, bending waves, and their mutual conversions along plate junctions.
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Capanni, Felix, Kirk Hansen, Daniel C. Fitzpatrick, Steven M. Madey, and Michael Bottlang. "Elastically Suspending the Screw Holes of a Locked Osteosynthesis Plate Can Dampen Impact Loads." Journal of Applied Biomechanics 31, no. 3 (June 2015): 164–69. http://dx.doi.org/10.1123/jab.2014-0193.
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Impact damping by elastic fixation is a principal engineering strategy to increase the durability of load-bearing structures exposed to prolonged dynamic loading. This biomechanical study evaluated axial impact damping provided by a novel dynamic locking plate. In this design, locking screw holes are elastically suspended within a silicone envelope inside the locking plate. Axial impact damping was assessed for 3 distinct fixation constructs applied to bridge a 10-mm fracture gap of a femoral diaphysis surrogate: a standard locking plate, a dynamic locking plate, and an Ilizarov ring fixator. First, the 3 fixation constructs were characterized by determining their axial stiffness. Subsequently, constructs were subjected to a range of axial impact loads to quantify damping of force transmission. Compared with standard locked plating constructs, dynamic plating constructs were 58% less stiff (P < .01) and Ilizarov constructs were 88% less stiff (P < .01). Impact damping correlated inversely with construct stiffness. Compared with standard plating, dynamic plating constructs and Ilizarov constructs dampened the transmission of impact loads by up to 48% (P < .01) and 74% (P < .01), respectively. In conclusion, lower construct stiffness correlated with superior damping of axial impact loads. Dynamic locking plates provide significantly greater impact damping compared with standard locking plates.
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Luo, Haitao, Jia Fu, Changshuai Yu, Guangming Liu, Wei Wang, and Peng Wang. "Numerical simulation and experimental testing of dynamic stiffness of angular contact ball bearing." Advances in Mechanical Engineering 10, no. 9 (September 2018): 168781401879897. http://dx.doi.org/10.1177/1687814018798973.
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Angular contact ball bearings are widely used in the multiple rotor system, such as gear box, machine tool spindle, and aero-engine rotors. The support stiffness is very important to the vibration of shafting. In order to obtain the dynamic stiffness, a numerical simulation method for dynamic stiffness of angular contact ball bearings is presented. By means of LS-DYNA software, the displacement and stress curves of the bearing’s different components are obtained successfully, and then, the dynamic stiffness of bearing under certain working conditions also can be calculated. The maximum envelope radius of the inner ring of the measured bearing can be taken as the relative displacement change value of the inner and outer rings of the bearing. To obtain the dynamic stiffness, the test strategy for dynamic stiffness of the angular contact ball bearings is introduced. The experimental results show that the equivalent dynamic stiffness increases with the increase in the preload of measured bearing under certain conditions. The simulation result coincides with the experiments well. The research work can provide the basis for the design and dynamics analysis of the bearing rotor system and have important engineering significance to improve the service performance of angular contact ball bearings.
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Webber, Christina M., and Kenton Kaufman. "Instantaneous stiffness and hysteresis of dynamic elastic response prosthetic feet." Prosthetics and Orthotics International 41, no. 5 (December 23, 2016): 463–68. http://dx.doi.org/10.1177/0309364616683980.
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Background:Dynamic elastic response prosthetic feet are designed to mimic the functional characteristics of the native foot/ankle joint. Numerous designs of dynamic elastic response feet exist which make the prescription process difficult, especially because of the lack of empirical evidence describing the objective performance characteristics of the feet.Objectives:To quantify the mechanical properties of available dynamic elastic response prosthetic feet, specifically the stiffness and hysteresis.Study design:Mechanical testing of dynamic elastic response prosthetic feet.Methods:Static Proof Testing in accordance with ISO 10328 was conducted on seven dynamic elastic response prosthetic feet. Load–displacement data were used to calculate the instantaneous stiffness in both the heel and forefoot regions, as well as hysteresis associated with each foot.Results:Heel stiffness was greater than forefoot stiffness for all feet. The heel of the glass composite prosthetic foot was stiffer than the carbon fiber feet and it exhibited less hysteresis. Two different carbon fiber feet had the stiffest forefoot regions.Conclusion:Mechanical testing is a reproducible method that can be used to provide objective evidence about dynamic elastic response prosthetic foot performance and aid in the prescription process.Clinical relevanceThe quantitative stiffness and hysteresis data from this study can be used by prosthetists to aid the prescription process and make it more objective.
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Weaver, Valerie M. "Abstract SY23-01: Targeting the reciprocal interplay between inflammation, fibrosis, and pro-tumor immunity." Cancer Research 82, no. 12_Supplement (June 15, 2022): SY23–01—SY23–01. http://dx.doi.org/10.1158/1538-7445.am2022-sy23-01.
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Abstract Tumors are characterized by increased levels of remodeled and crosslinked extracellular matrix (ECM) proteins that progressively stiffen the tissue stroma. Transformed cells exhibit a perturbed oncogene-stimulated and ECM-tuned mechanophenotype that further stimulates ECM remodeling and stiffening. We have been exploring how these aberrant cell and tissue level forces arise and by what means these forces contribute to malignancy and metastasis, and how they promote tumor recurrence and treatment resistance. We use two and three dimensional culture models with tuned ECM stiffness, as well as transgenic and syngeneic mouse models, human PDX models and human biospecimens, in which ECM crosslinking and stiffness and integrin mechanosignaling are manipulated and quantified. Our work has thus far revealed that the tumor ECM is progressively remodeled, and stiffened, primarily by stromal fibroblasts. We determined that infiltrating pro-tumorigenic myeloid cells secrete factors that stimulate stromal fibroblasts to remodel and crosslink the ECM and that this occurs quite early during tumor evolution. The stromal-fibroblast stiffened ECM thereafter disrupts tissue organization, promotes cell growth and survival and drives cell invasion. The stiffened tumor stroma additionally drives angiogenesis, and activates STAT3 to increase expression of cytokines and chemokines that further stimulate immune cell infiltration. The stiffened ECM thereafter reprograms the infiltrating myeloid cells by altering integrin adhesions and TGFβ SMAD signaling to induce an ECM synthetic metabolic phenotype in the myeloid cells. The metabolically reprogrammed myeloid cells ultimately compromise arginine tissue availability and increase tissue levels of ornithine that severely disrupt CD8 T cell tissue infiltration and perturb their anti-tumor function to accelerate tumor aggression and metastatic dissemination. I will discuss the dynamic and reciprocal interplay between tissue tension and innate and acquired immunity. I will then present data to show how ECM stiffness is able to promote tumor aggression and metastasis by dysregulating anti-tumor immunity. I will end with a short discussion regarding approaches to design therapies informed by these results to improve cancer treatment. Citation Format: Valerie M. Weaver. Targeting the reciprocal interplay between inflammation, fibrosis, and pro-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr SY23-01.
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Wu, Nan, Yuzhen Zhao, Qing Guo, and Yongshou Liu. "The effect of two-parameter of Pasternak foundations on the dynamics and stability of multi-span pipe conveying fluids." Advances in Mechanical Engineering 12, no. 11 (November 2020): 168781402097453. http://dx.doi.org/10.1177/1687814020974530.
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In this paper, the dynamics and stability of multi-span pipe conveying fluid embedded in Pasternak foundation is studied. Based on Euler-Bernoulli beam theory, the dynamics of multi-span pipe conveying fluid embedded in two parameters Pasternak foundation is analyzed. The dynamic stiffness method (DSM) is used to solve the control equation. A seven span pipe is calculated. The affection of two parameters of Pasternak foundation is mainly studied. Along with increasing the elastic stiffness K and shear stiffness G, the frequency is also increasing.