Influences of modal shape and tool orientation on evolution of dynamic responses in 5-axis milling of thin-walled parts

2022 ◽  
Author(s):  
Dazhen Wang ◽  
Junxue Ren ◽  
Weijun Tian
Keyword(s):  
Dynamic Responses ◽  
Tool Orientation ◽  
Modal Shape ◽  
Thin Walled

Cutting Path Design to Minimize Workpiece Displacement at Cutting Point: Milling of Thin-Walled Parts

2012 ◽  
Vol 6 (5) ◽  
pp. 638-647 ◽  
Author(s):  
Yusuke Koike ◽  
◽  
Atsushi Matsubara ◽  
Shinji Nishiwaki ◽  
Kazuhiro Izui ◽  
...  
Keyword(s):  
Cutting Force ◽  
Material Removal ◽  
Tool Orientation ◽  
Numerical Example ◽  
Path Design ◽  
Minimum Displacement ◽  
Low Stiffness ◽  
Thin Walled ◽  
Cutting Path ◽  
Cutting Point

Vibrations of a tool or workpiece during cutting operations shorten tool life and causes unwanted surface roughness. In this report, we propose an algorithm for determining the sequence of material removal, tool orientation, and feed directions, an algorithm minimizes workpiece displacements by considering workpiece stiffness and cutting force. In this research, the cutting path consists of the material removal sequence, tool orientation and feed directions. The material removal sequence changes the workpiece compliancematrix at the cutting points, and the feed directions and tool orientation change the direction of the cutting force. In our algorithm, workpiece displacements are reduced by changing the material removal sequence and applying the cutting force in the direction of higher workpiece stiffness. A numerical example demonstrates how the algorithm obtains appropriate cutting paths to mill a cantilever form. In the numerical example, three optimized cutting paths are compared with an unoptimized cutting path, a path used by an expert and based on the expert’s personal experience, to machine a low-stiffness workpiece. The obtained material removal sequence of the minimax compliance path is almost the same as that of the unoptimized cutting path. Workpiece displacements at the cutting point of three optimized cutting paths are approximately 10% smaller than those of the unoptimized cutting path. The minimum displacement path is the best of these three optimized cutting paths because fluctuations in workpiece displacements at cutting point are the smallest. These optimized cutting paths show the cutting path strategy as a rough cutting path for machining the thin-walled cantilever.

Impact Crushing and Rebound of Thin-Walled Hollow Spheres

2013 ◽  
Vol 535-536 ◽  
pp. 40-43 ◽  
Author(s):  
Rong Hao Bao ◽  
T.X. Yu
Keyword(s):  
Impact Velocity ◽  
Analytical Modeling ◽  
Hollow Spheres ◽  
Rigid Wall ◽  
Coefficient Of Restitution ◽  
Dynamic Responses ◽  
Relative Thickness ◽  
Thin Walled ◽  
Impact Crushing ◽  
The Impact

The dynamic behavior of a thin-walled hollow sphere colliding onto a rigid wall has been studied by experiments, numerical simulation and analytical modeling, as reported in our previous papers. In the present paper, the impact crushing of metallic thin-walled hollow spheres onto rigid plates and the subsequent rebound are analyzed using finite element method. The effects of hollow sphere’s thickness-to-radius ratio, the material properties and the impact velocity on the dynamic responses are systematically investigated. The transition from axisymmetric dimpling to non-axisymmetric lobing is found to depend on the relative thickness of spheres and impact velocity; while the coefficient of restitution almost merely depends on impact velocity.

Modal shape identification for short and medium span bridges using wavelet based vehicular sensing approach

2021 ◽  
Author(s):  
Xudong Jian ◽  
Limin Sun ◽  
Ye Xia
Keyword(s):  
Dynamic Responses ◽  
Modal Parameter ◽  
Roughness Effects ◽  
Modal Shape ◽  
Shape Identification ◽  
Modal Parameter Identification ◽  
Road Roughness ◽  
Moving Vehicles ◽  
Key Issues ◽  
Vehicular Sensing

<p>Modal parameter identification has been one of the key issues in the research of indirect bridge structural health monitoring. This paper presents a new indirect approach identifying modal parameters for short and medium span bridges, using dynamic responses of three connected vehicles. Accelerations of these vehicles are firstly subtracted to eliminate road roughness effects, so that the bridge frequency visibility in the frequency domain is improved. The wavelet analysis is performed to identify modal frequencies and shapes of bridges from the subtracted acceleration of moving vehicles. Systematic numerical experiments are performed to investigate the fidelity of the approach. Results show that the proposed approach can identify the bridge modal frequencies and shapes with promising accuracy and robustness.</p>

Inherent Characteristic Similarity Analysis on Short Thin-Walled Cylindrical Shell

2014 ◽  
Vol 607 ◽  
pp. 386-392
Author(s):  
Qing Bin Han ◽  
Jian Guo ◽  
Ning Sun ◽  
Zhong Luo
Keyword(s):  
Cylindrical Shell ◽  
Scaling Laws ◽  
Equations Of Motion ◽  
Excitation Frequency ◽  
Dynamic Responses ◽  
Scale Model ◽  
Similarity Analysis ◽  
Prototype System ◽  
Thin Walled ◽  
Elastically Supported

A method for predicting the vibration characteristics of the short thin-walled cylindrical shell was presented by dynamic similarity analysis. Firstly, the similarity conditions between the prototype system and its complete-similitude scale model were derived from their equations of motion. Then, the scaling factors, such as length, radius, thickness, force, and excitation frequency, spring constant and dynamic responses of the cylindrical shell were determined based on the last similarity conditions and the dimensional analysis theory. Free and forced vibration analyses of the elastically supported prototype cylindrical shell and those of its complete-similitude scale model were performed to validate the derived scaling laws, and satisfactory results were obtained.

Development of a New Model for the Varying Dynamics of Flexible Pocket-Structures During Machining

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Mouhab Meshreki ◽  
Helmi Attia ◽  
József Kövecses
Keyword(s):  
Dynamic Models ◽  
Ritz Method ◽  
Computation Time ◽  
Dynamic Effect ◽  
Dynamic Responses ◽  
Prediction Errors ◽  
Continuous Change ◽  
Thin Walled Structures ◽  
Aspect Ratios ◽  
Thin Walled

Many of the aerospace components are characterized by having pocket-shaped thin-walled structures. During milling, the varying dynamics of the workpiece due to the change of thickness affects the final part quality. Available dynamic models rely on computationally prohibitive techniques that limit their use in the aerospace industry. In this paper, a new dynamic model was developed to predict the vibrations of thin-walled pocket structures during milling while taking into account the continuous change of thickness. The model is based on representing the change of thickness of a pocket-structure with a two-directional multispan plate. For the model formulation, the Rayleigh–Ritz method is used together with multispan beam models for the trial functions in both the x- and y-directions. An extensive finite element (FE) validation of the developed model was performed for different aspect ratios of rectangular and nonrectangular pockets and various change of thickness schemes. It was shown that the proposed model can accurately capture the dynamic effect of the change of thickness with prediction errors of less than 5% and at least 20 times reduction in the computation time. Experimental validation of the models was performed through the machining of thin-walled components. The predictions of the developed models were found to be in excellent agreement with the measured dynamic responses.

Nonlinear Response of Carbon-Carbon Composite Panels Subjected to Thermal-Acoustic Loadings

2011 ◽  
Vol 117-119 ◽  
pp. 876-881 ◽  
Author(s):  
Yun Dong Sha ◽  
Fei Xu ◽  
Zhi Jun Gao
Keyword(s):  
High Speed ◽  
Random Vibration ◽  
Nonlinear Response ◽  
Elevated Temperatures ◽  
Thermal Protection ◽  
Random Noise ◽  
Carbon Composite ◽  
Dynamic Responses ◽  
Composite Panels ◽  
Thin Walled

Carbon-Carbon composite materials are widely used as the surface thermal protection systems (TPS) of advanced high-speed air-craft and spacecraft. The thin-walled structures with this kind of materials would exhibit large displacement response under high-level acoustic loads and possibly display buckling at elevated temperatures. Reliable experimental data are difficult to acquire because of the high costs and difficulties with instrumentation at high acoustic intensity and elevated temperatures. Thus, in the design process greater emphasis will likely be placed on improved mathematical and computational prediction methods. Among these researches, the simulation methods for nonlinear response of thin-walled composite panels under thermo-acoustic loadings are being developed emphatically .This paper presents a nonlinear finite element model for analyzing nonlinear random dynamic behaviors of Carbon-Carbon composite panels under the combined effects of thermal and random acoustic loads. The acoustic excitation is assumed to be a band-limited Gaussian random noise and uniformly distributed over the structural surface and the thermal load is assumed to be a steady-state with different predefined temperature distribution. Three types of motion: 1) linear random vibration about one of the two buckled positions, 2) snap-through motion between the two buckled positions, and 3) nonlinear random vibration over the two thermally buckled positions can be predicted. And the dynamic response behaviors of the structures are discussed. Based on this, the influences of sound pressure level (SPL) and elevated temperatures on the dynamic responses are analyzed emphatically.

Dynamic Response of Pre/Post Buckled Thin-Walled Structure under Thermo-Acoustic Loading

2011 ◽  
Vol 80-81 ◽  
pp. 536-541 ◽  
Author(s):  
Yun Dong Sha ◽  
Ji Yong Li ◽  
Zhi Jun Gao
Keyword(s):  
Dynamic Response ◽  
Dynamic Responses ◽  
Transverse Displacement ◽  
Response Characteristics ◽  
Thin Walled Structures ◽  
Fem Method ◽  
Operating Environments ◽  
Thin Walled ◽  
Frequency Changes ◽  
High Level

Advanced aircraft and spacecraft structures are exposed to increasingly severe operating environments, including a combination of mechanical, aerodynamic, acoustic and thermal loads. Such loading conditions can cause thin-walled structures to respond in a nonlinear fashion and exhibit complex response characteristics. This paper investigates the dynamic response of pre/post buckled thin-walled structure under high level random acoustic loading. Firstly, different orders of critical buckling temperatures and modal frequencies under alternative temperatures are obtained using Finite Element Method (FEM), and the modal frequency changes in a disorder fashion are discussed in detail. Then with coupled BEM/FEM method, the dynamic responses including transverse displacement, strain and stress of a stiffened rectangular plate under thermo-acoustic loading are simulated. By comparing the response characteristics of the plate in pre/post buckled conditions, some valuable conclusions are derived, which can be used to explain the response behaviours of thin-walled structures.

Finite Element Analysis on the Vibration Mode of Composite Thin-Walled Box Beam with Double-Cell Sections

2012 ◽  
Vol 569 ◽  
pp. 495-499
Author(s):  
Shuang Shuang Sun ◽  
Fang Wu Jia ◽  
Yong Sheng Ren
Keyword(s):  
Finite Element ◽  
Width Ratio ◽  
Finite Element Models ◽  
Modal Shape ◽  
Element Analysis ◽  
Finite Element Software ◽  
Box Beam ◽  
Box Beams ◽  
Length Width ◽  
Thin Walled

The modal analysis of composite thin-walled box beams with double-cell sections is carried out by the finite element software ANSYS. The finite element models are established first for the double-cell composite thin-walled box beams, then the vibration modes of two box beams: Circumferentially Uniform Stiffness (CUS) and Circumferentially Antisymmetric Stiffness (CAS) are calculated and analyzed. The effects of length-width ratio and width-height ratio on the natural frequency and the modal shape of the double-cell composite thin-walled box beams are discussed.

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