Stiffness Analysis Research Articles

Research on time-varying mesh stiffness analysis method of gears with local defective faults

Research on time-varying mesh stiffness analysis method of gears with local defective faults

Research on Stiffness Analysis and Technology of the Heavy Spidle Top

Background: The spindle top is an important component used to withstand the shaft workpiece on machine tools so that the spindle can meet high efficiency and high precision requirements. However, the selection principles under various load conditions are not stipulated in use. In addition, material selection, manufacturing, heat treatment technology, etc., are of practical significance for the production of high hardness, high wear resistance, and high precision spindle tops. Objectives: The spindle top type, material selection principles, heat treatment, cold working, and other manufacturing processes are given. Provide a reference for highperformance and top-notch design and manufacturing. Methods: The model of the spindle top will be created in UG software, then using ANSYS finite element analysis software to analyze stiffness of spindle top whose height-to-diameter ratios are 1:4 and 1:7 types in a variety of different load cases. The design and manufacturing process of the spindle top is analyzed and expounded from the selection and performance comparison of metal materials, heat treatment of different materials, cold manufacturing technology, and other aspects. Results: The deformation laws of different types of spindle tops are obtained. According to the deformation regular, find the selection principle of height to diameter ratio of spindle top. The defects that are easy to occur in the technology are obtained and the preventive and solution measures are put forward. Conclusion: According to the deformation regular, find the selection principle of height to diameter ratio of spindle top. The material selection, heat treatment technology, and other technical research on the spindle top provide the necessary basis for the production of the spindle top.

Numerical analysis of critical support stiffness in ring ribs of a sandwich composite pressure shell

ABSTRACT To study the hydro-static pressure carrying capability of a sandwich composite pressure shell with ring ribs, and explore a structure design method, we obtain an empirical formula of the ring rib segments critical support stiffness, which is defined as Dcr , via finite element simulation and theoretical analysis method. It was shown that, Dcr is of great significance in designing the sandwich composite pressure shell structure. On this basis, the parameters were dimensionless and the empirical formula was obtained by fitting serious independent simulated results. The fitting error of the empirical formula is within 2%. This fitting method has a certain theoretical value for the theoretical research of sandwich composite pressure shell structure. The obtained results are useful for desinging the bearing capacity of novel structure.

Asperity interaction induced vibration excitation of cylindrical roller bearings with localized defect

Asperity interaction induced vibration excitation of cylindrical roller bearings with localized defect

Reliability Analysis for Dynamic Behaviour, Stiffness, and Strength of Existing Steel Truss Bridge BH77

Railway bridges are old, especially on the Sumatra island and according to earthquake map on 2017 version show an increased risk, it is necessary to analyze the reliability of dynamic behaviour to extend the bridge life and damage can be detected early. The bridge reliability was assessed in terms of natural frequency, deflection, and internal force . The study was conducted on the BH77 Railway Bridge in Tegineneng-Lampung, a through truss type. Reliability analysis with a non-deterministic approach, using the probability concept, variability used is the dimensions of steel profiles based on fabrication drawings and field measurements. The research uses secondary data, one of which is measurement of the circumference of the steel cross section, that influenced by the paint layer, where the paint thickness sample to correct and obtain the actual dimensions. Dynamic behaviour analysis, consisting of modal analysis, Fast Fourier Transform, time history, and First Order Reliabilty Method. The analysis results showed the effect of steel dimension correction compared to the fabrication drawings did not have a significant effect on the changes in the values of natural frequencies, mode shapes, deflections, and internal forces. The reliability of the dynamic behaviour obtained was 99% at all reviews. Which indicates that the bridge is safe against potential resonance, the bridge stiffness is still high, and the axial+moment capacity is still sufficient against static & earthquake loads, as well as good bridge maintenance. The largest deflection point as a reference for placing strain and vibration gauges on structural health monitoring systems.

Stiffness increase and homogenization by coupled robots

This article presents the explanation of higher than expected increase of stiffness of coupled robots in some geometric configurations against its expected simple addition. This phenomenon was named the vault principle for robots. In order to achieve that and to explore fully the consequences it was necessary to develop a new method for robot stiffness analysis. Single serial robot is compared with two serial robots mutually connected. Connected (coupled) robots are analyzed in five various topological configurations. The end effector stiffness field is evaluated at particular points of intersections of workspaces of five topological configurations in order to preserve the objectivity of the comparison. The new method for robot stiffness analysis is based on the evaluation of minimum/maximum values of principal axes of stiffness distribution determined by the singular value decomposition. The manimum/maximum values across the workspace are processed by average/median and used for computing homogeneity factor. It is a new integral criterion for robot topology configuration judgment. The direct implications of these findings are relevant to high-precision milling applications in cooperative robotic setups.

Development of an elliptic vibration mechanism for wire electrochemical micromachining

A novel flexure-based mechanism driven by two piezoelectric actuators was developed to generate elliptic vibration at the tool cathode in the wire electrochemical micromachining, which presented higher machining quality. The flexure-based mechanism adopted lever type and half bridge-type amplification mechanisms to enlarge the output of the piezoelectric actuator, the cathode wire was installed on the vibration platform through a 3D-printed insulating clamp. In order to predict the output property of the elliptic vibration mechanism, the theoretical analysis including output stiffness, kinematic modelling, and finite element analysis were implemented. A semi-closed loop controller based on the strain measurement of piezoelectric actuators was established to improve the output precision. The experimental setup of the elliptic vibration mechanism was constructed to examine the correctness of the stiffness and kinematic models, the elliptic vibration trajectory was successfully generated on the cathode wire. Furthermore, the elliptic vibration mechanism was used in the wire electrochemical micromachining, the experimental results indicated that the elliptic vibration of the cathode wire effectively improved the machining quality.

Time varying torsional stiffness analysis of RV reducer

The rotary vector reducer (RV reducer) is a key reduction mechanism for industrial robots, and its torsional stiffness directly determines positioning accuracy and dynamic characteristics. Unlike traditional time-varying torsional stiffness analysis methods considering limited factors and statics solution method, a time-varying torsional stiffness analysis method considering output torque variability and dynamic nonlinearity is proposed to assess the time-varying torsional stiffness of the reducer. Firstly, the rigid-flexible coupling multi-body dynamic model was built employing software ADAMS, with crank shaft and cycloidal gears being treated as flexible bodies. Its correctness was verified under standard condition through grey correlation theory and the torsional stiffness under different conditions was obtained, respectively. Secondly, a contact finite element model of the reducer was established, taking contact relationships between different shaft-gear-bearings into account. As a comparison, a rotating-join finite element model was also constructed. And their torsional stiffness under experimental condition was calculated. Finally, the torsional stiffness test was conducted to verify the accuracy of the three models under this condition. The results show that the time-varying torsional stiffness obtained by the proposed method is only 8.83% different from the test results and exhibiting a certain periodic pattern under standard conditions.

Experimental and numerical analysis of rubber isolator dynamic stiffness under hydrostatic pressure

Due to their function in damping and attenuating vibrations, as well as their relatively low cost, rubber isolators have widespread applications in industries such as aerospace, automotive and maritime. As components with distinct nonlinear behavior, accurately predicting the dynamic characteristics of isolators is essential for overall structural design and vibration noise prediction. Although extensive research has been conducted on the static and dynamic performance of rubber isolators, there has been limited investigation into performance under certain specialized application scenarios, such as hydrostatic pressure environments. These environments are indeed real, for instance, isolators employed in the bow ballast tank of underwater vehicle to mitigate vibrations during weapon launch processes. In such instances, isolators are subjected not only to the influence of added mass due to the water medium during vibration but also to increasing hydrostatic pressure on the isolator surface with increasing depth. This study introduces an original experimental apparatus capable of measuring the dynamic stiffness of isolators while simulating hydrostatic pressure conditions. The constitutive model parameters governing the hyperelastic and viscoelastic properties of rubber were identified via nonlinear tests, serving as input parameters for numerically predicting the dynamic stiffness within a water medium environment. Furthermore, a comprehensive analysis was conducted to evaluate the impacts of preload, water medium, boundary conditions, and hydrostatic pressure on the dynamic stiffness of the isolator. Results indicate that preload tends to reduce peak dynamic stiffness in the shear directions, while the water medium significantly increases high-frequency dynamic stiffness in the shear directions. Within the range of 1 MPa, the impact of increasing hydrostatic pressure on dynamic stiffness can be largely disregarded. When calculating the dynamic stiffness of the isolator, it is crucial to consider the actual installation environment and set the acoustic boundary conditions of the surrounding water domain accordingly.

RSM applied to lattice patterns for stiffness optimization

PurposeIn this study, response surface methodology (RSM) is applied to a three-point bending stiffness analysis of low-cost material (PLA) specimens printed using FDM technology to analyze the performance of different internal lattice structures (Octet and IsoTruss principally). The purpose of this study is to extend the definition from a discrete (lattice) model to an analytical one for its use in subsequent design phases, capable of optimizing the type of cell to be used and its defining parameters to find the best stiffness-to-weight ratio.Design/methodology/approachThe representative function of their mechanical behavior is extrapolated through a two-variable polynomial model based on the cell size and the thickness of the beam elements characterizing it. The polynomial is obtained thanks to several tests performed according to the scheme of RSM. An analysis on the estimation errors due to discontinuities in the physical specimens is also conducted. Physical tests applied to the specimens showed some divergences from the virtual (ideal) behavior of the specimens.FindingsThe study allowed to validate the RSM models proposed to predict the behavior of the system as the size, thickness and type of cells vary. Changes in stiffness and weight of specimens follow linear and quadratic models, respectively. This generally allows to find optimal design points where the stiffness-to-weight ratio is at its highest.Originality/valueAlthough the literature provides numerous references to studies characterizing and parameterizing lattice structures, the industrial/practical applications concerning lattice structures are often still detached from theoretical research and limited to achieving functioning models rather than optimal ones. The approach here described is also aimed at overcoming this limitation. The software used for the design is nTop. Subsequent three-point bending tests have validated the reliability of the model derived from the method’s application.

No Difference in Systolic Dysfunction from Left Ventricular Pressure-Volume Loop’s Area and Stroke Work Between Chronic Late Load vs. Early Systolic LV Load in Porcine Model

<i>Background: </i>in increased LV afterload as in hypertension, early systolic LV dysfunction (SD) in late compares to early peak systolic LV load for P-V area, stroke work, potential energy with effective LV work (EW) is not being defined (aortic stenosis, arterial hypertension or coarctation of the aorta) in LVH remodeling. <i>Objectives:</i> to assess in porcine model how LV stroke work, PVA and EW are related to LVH remodeling in developing early SD with HF, between 4<sup>th</sup> vs 8<sup>th</sup> week in chronic LL compares to EL. It is suggested that reduced proximal thoracic or asc. aortic compliance results with myocardial ischemia. However, difference for LV O<sub>2</sub> demand and effective LV work in different LV afterload is not understood in early development systolic HF. <i>Methods:</i> in fourteen domestic male pigs (28±3 kg) with moderate descending aortic banding having chronic late LV load (LL=8) or ascending aortic stenosis with early systolic LV load (EL=6) SD was assessed, from PVA, in invasive LV pressure-volume loops’ measurements, at 4<sup>th</sup> vs. 8<sup>th</sup> week, to assess LV maximal ESPVR, with Millar 5Fr P-V pig-tailed conductance catheter. LV stroke work, and pressure-volume area PVA, reflecting the maximal LV O<sub>2</sub> demand were assessed in chronic LL compares to EL from nonlinear regression analysis of maximal LV end-systolic stiffness, in special software. For variance analysis, two-way repeated measures ANOVA was performed, with normality assessment. Results are means±(SEM) or medians for significant p<0.05. <i>Results: </i>LV PVA was not different, in LL compared to EL at 4<sup>th</sup> vs. 8<sup>th</sup> week. LV stroke work with effective works were not different and potential energy, neither were changed between 4<sup>th</sup> vs. 8<sup>th</sup> week. No difference was found in different LV afterload, in both indexed and absolute LVO<sub>2</sub> demand, in LL vs. EL at 4<sup>th</sup> or 8<sup>th</sup> week. Indexed PVA parameters with LV stroke work, effective work and potential energy were not different or changed in LL compares to EL between 4<sup>th</sup> vs. 8<sup>th</sup> weeks, normalized per body surface-area (in m<sup>2</sup>). <i>Conclusion:</i> Both absolute and indexed LV stroke work, potential LV energy, PVA with EW and maximum LV O<sub>2</sub> demand are not different in LL compares to EL at 4<sup>th</sup> vs. 8<sup>th</sup> week of LVH remodeling, indicating no difference in early SD development in increased late vs. early LV afterload.

Impact of arterial system alterations due to amputation on arterial stiffness and hemodynamics: a numerical study

Subjects with amputation of the lower limbs are at increased risk of cardiovascular mortality and morbidity. We hypothesize that amputation-induced alterations in the arterial tree negatively impact arterial biomechanics, blood pressure and flow behavior. These changes may interact with other biological factors, potentially increasing cardiovascular risk. To evaluate this hypothesis regarding the purely mechanical impact of amputation on the arterial tree, we used a simulation computer model including a detailed one-dimensional (1D) arterial network model (143 arterial segments) coupled with a zero-dimensional (0D) model of the left ventricle. Our simulations included five settings of the arterial network: (1) 4-limbs control, (2) unilateral amputee (right lower limb), (3) bilateral amputee (both lower limbs), (4) trilateral amputee (lower-limbs and right upper-limb), and (5) quadrilateral amputee (lower and upper limbs). Analysis of regional stiffness, as calculated by pulse wave velocity (PWV) for large-, medium- and small-sized arteries, showed that, while aortic stiffness did not change with increasing degree of amputation, stiffness of medium and smaller-sized arteries increased with greater amputation severity. Despite a staged decrease in cardiac output, the systolic and diastolic blood pressure values increased, resulting in an increase in both central and peripheral pulse pressures but with an attenuation of pulse pressure amplification. The most significant increase in peak systolic pressure and decrease in peak systolic blood flow was observed at the site of the abdominal aorta. Wave separation analysis indicated no changes in the shape of the forward and backward wave components. However, the results from wave intensity analysis showed that with extended amputation, there was an increase in peak forward wave intensity and a rise in the inverse peak of the backward wave intensity, suggesting potential alterations in cardiac hemodynamic load. In conclusion, this simulation study showed that biomechanical and hemodynamic changes in the arterial network geometry could interact with additional risk factors to increase the cardiovascular risk in patients with amputations.

Short-Term Proteasome Inhibition: Assessment of the Effects of Carfilzomib and Bortezomib on Cardiac Function, Arterial Stiffness, and Vascular Reactivity.

Proteasome inhibitors such as bortezomib and carfilzomib induce apoptosis and are a cornerstone in the treatment of relapsed or refractory multiple myeloma. However, concerns have emerged concerning their link to cancer therapy-related cardiovascular dysfunction (CTRCD). Bortezomib, a reversible first-generation inhibitor, and carfilzomib, a second-generation irreversible inhibitor, are associated with hypertension, heart failure, and cardiac arrhythmias. The current study investigated the effects of bortezomib and carfilzomib on cardiac (left ventricular ejection fraction, LVEF) and vascular (arterial stiffness, vascular reactivity) function. Cardiac function assessment aimed to build upon existing evidence of proteasome inhibitors CTRCD, while arterial stiffness served as an early indicator of potential vascular remodeling. Groups of 12-week-old C57BL/6J male mice (n = 8 per group) were randomly assigned to receive vehicle, carfilzomib (8 mg/kg I.P.), or bortezomib (0.5 mg/kg I.P.). Additionally, proteasome inhibition was assessed in mice treated with L-NAME (0.5 mg/kg) to induce hypertension. Cardiac and vascular parameters were evaluated via echocardiography on days 0 and 3. On day 6, mice were sacrificed for ex vivo analysis of arterial stiffness and vascular reactivity. Overall, no changes in arterial stiffness were detected either in vivo or ex vivo at basal pressures. However, a steeper pressure-stiffness curve was observed for carfilzomib in normotensive (p < 0.01) and hypertensive (p < 0.0001) mice ex vivo. Additionally, in hypertensive mice, carfilzomib decreased LVEF (p = 0.06), with bortezomib exhibiting similar trends. Vascular reactivity remained largely unchanged, but proteasome inhibition tended to enhance endothelial-independent relaxations in both control and hypertensive mice. In conclusion, short-term treatment with carfilzomib and bortezomib is considered relatively safe for the protocols assessed in the study.

Nanomechanical thermometry for probing sub-nW thermal transport

Accurate local temperature measurement at micro and nanoscales requires thermometry with high resolution because of ultra-low thermal transport. Among the various methods for measuring temperature, optical techniques have shown the most precise temperature detection, with resolutions reaching (~10−9 K). In this work, we present a nanomechanical device with nano-Kelvin resolution (~10−9 K) at room temperature and 1 atm. The device uses a 20 nm thick silicon nitride (SiN) membrane, forming an air chamber as the sensing area. The presented device has a temperature sensing area >1 mm2 for micro/nanoscale objects with reduced target placement constraints as the target can be placed anywhere on the >1 mm2 sensing area. The temperature resolution of the SiN membrane device is determined by deflection at the center of the membrane. The temperature resolution is inversely proportional to the membrane’s stiffness, as detailed through analysis and measurements of stiffness and noise equivalent temperature (NET) in the pre-stressed SiN membrane. The achievable heat flow resolution of the membrane device is 100 pW, making it suitable for examining thermal transport on micro and nanoscales.

Coagulation Profile and Clot Stiffness Analysis from COVID-19-Positive Patients Using a Contactless Viscoelasticity Testing Technology

Coagulation Profile and Clot Stiffness Analysis from COVID-19-Positive Patients Using a Contactless Viscoelasticity Testing Technology

Comparative Analysis of Heart Rate Variability and Arterial Stiffness in Elite Male Athletes after COVID-19.

This study investigated the long-term cardiovascular effects of coronavirus disease (COVID-19) in elite male athletes by comparing the heart rate variability (HRV), arterial stiffness, and other cardiovascular parameters between those with and without prior COVID-19 infection. Methods: This cross-sectional study evaluated 120 elite male athletes (60 post COVID-19, 60 controls) using anthropometric measurements, body composition analysis, pulmonary function tests, HRV analysis, arterial stiffness assessments, hemodynamic monitoring, and microcirculatory function tests. Results: Athletes post COVID-19 showed significantly higher lean mass (p = 0.007), forced vital capacity (p = 0.001), and forced expiratory volume in 1 s (p = 0.007) than controls. HRV parameters did not significantly differ between the groups. Post-COVID-19 athletes exhibited peripheral vascular resistance (p = 0.048) and reflection index (p = 0.038). No significant differences were observed in the blood pressure, cardiac output, oxygen saturation, or microcirculatory oxygen absorption. Conclusions: Elite male athletes showed notable cardiovascular resilience after COVID-19, with only minor differences in vascular function. The maintained cardiac autonomic function and improved lung parameters in post-COVID-19 athletes suggests an adaptive response. These findings support the cardiovascular health of elite athletes following COVID-19 but emphasize the importance of continued monitoring.

Floor impact sound insulation performance of Korean domestic cross-laminated timber floors and the influence of resilient materials' dynamic stiffness

In this study, the floor impact sound insulation performance of floors made of korean domestic cross-laminated timber panels and with a resilient layer under concrete topping was evaluated. The properties of resilient materials used in the floors were measured to evaluate their influence on floor impact sound insulation performance. The results indicate that the highest reduction levels were provided by glass fiber, expanded polystyrene and wood fiber, in diminishing order, for both heavy-weight and light-weight floor impact sounds. Through the evaluation of dynamic stiffness and single-number quantities, a high correlation was observed at 125 Hz and 500 Hz for heavy-weight floor impact sounds and across all octave bands for light-weight floor impact sounds. The analysis of dynamic stiffness and single number quantity revealed a high correlation in both heavy weight and light weight floor impact sound. Lower dynamic stiffness was confirmed to be advantageous for reducing floor impact noise.

Study on axial and bending stiffness characteristics of reinforced S-shaped bellows

PurposeReinforced S-shape bellows are novel metal bellows with high pressure resistance. Displacement compensation ability is a key index in the design of metal bellows. Axial-tension-compression deformation and bending deformation are two typical displacement compensation forms. Thus, analysis of axial and bending stiffness is important in structure design.Design/methodology/approachIn this study, theory analytics of axial tension and compression stiffness of reinforced S-shaped bellows structure is derived, and the load-displacement relationship during axial deformation is obtained by correcting the geometric parameters of waveform during axial tension and compression deformations. On the basis of them, the relationships of bending stiffness with axial tensile and compression stiffness under the action of bending loading are constructed, and thus, the theory analytics of bending stiffness is realized for S-shaped bellows.FindingsThis theory analytics is verified by comparing the results of theory analytics with those of numerical simulation for a few typical examples. An investigation on the axial and bending non-linear mechanical behaviors of multi-layer-reinforced S-shaped bellows was also carried out by numerical simulation and experiment, and the experimental results verified the reliability of the analysis method.Originality/valueIt is found that non-linearity behavior occurs greatly during the first loading course of reinforced S-shaped bellows, and the structure is strain-strengthened due to plastic deformation; however, stable stiffness characteristic is exhibited during the succeeding cyclic-loading course.

Stability Conditions and Stiffness Variability of General Tensegrity Systems with Kinematic Joints

Abstract Tensegrity systems represent promising candidate mechanisms with in-situ stiffness variability through changing the cables' prestress levels. However, prestress-based stiffness behaviors of tensegrity systems with arbitrary kinematic joints have not been analyzed systematically. This paper adopts the natural absolute coordinates for static modeling of tensegrity systems consisting of rigid members and tension elements. Then, a generic stiffness analysis method is developed to formulate the reduced-basis tangent stiffness matrix, which is found to include three parts: positive semi-definite material and geometric stiffness matrices, and an indefinite constraint stiffness matrix. Based on these findings, a systematic stability-checking procedure is derived to determine prestress and super stability, which are qualitative indicators of the softening and stiffening effects in different tensegrity systems. Then, we proceed to quantify the range of prestress-based stiffness variability by formulating semidefinite programming problems that numerically pinpoint the maximum and zero stiffness points. Furthermore, this paper reveals the composable nature of multiple self-stress states, enabling the composability of stiffness properties in mechanism designs. Several numerical examples verify the efficacy and versatility of the proposed method and demonstrate interesting stiffness behaviors of tensegrity systems with kinematic joints.

Design and Analysis of an Adaptive Pipeline Detection and Correction Mechanism

This paper presents a novel adaptive pipeline probe detection and correction mechanism designed to address the challenge of detection interference caused by the movement of wall-climbing robots, particularly in complex environments such as water-cooled walls. The mechanism ensures that the detection probe can accurately detect individual pipelines even when the robot deviates from its intended path. To achieve this, the system incorporates a self-adaptive deviation correction mechanism that maintains consistent detection performance without requiring adjustments to the robot&amp;apos;s spatial position. The design includes a variable stiffness analysis of the buffer spring within the correction mechanism, which is optimized to minimize the impact of the robot&amp;apos;s movement on the detection components. By carefully selecting the spring&amp;apos;s size and stiffness parameters, the mechanism reduces vibration and enhances the stability and reliability of pipeline detection under offset conditions. In addition to maintaining detection accuracy, the system also supports automatic marking of pipelines that exhibit quality issues, ensuring that any detected defects are easily traceable. This adaptive mechanism not only improves detection efficiency but also enhances the overall operational stability of wall-climbing robots in industrial inspection tasks. The results demonstrate the mechanism&amp;apos;s effectiveness in mitigating the challenges posed by uneven friction and time delays in the control system, making it a significant contribution to the field of robotic inspection systems.