An approach to identify the weak parts of stiffness for the machine tool cantilever structure

2021 ◽  
pp. 095440622199871
Author(s):  
Tieneng Guo ◽  
Lingjun Meng ◽  
Jinxuan Cao ◽  
Chunsheng Bai
Keyword(s):  
Machine Tool ◽  
Elastic Support ◽  
Structural Stiffness ◽  
Vibration Data ◽  
Stiffness Reduction ◽  
Fe Simulations ◽  
Cantilever Structure ◽  
Combined Structure ◽  
Space Method ◽  
Zero Frequency

Investigating weak parts of the structure is one of the most important issues for improving the stiffness of the machine tool. However, studies show that overcoming the static deformation is a challenging problem in practical structures. In the present study, the dynamic hammer testing approach is applied to analyze the cantilever structure of the machine tool with elastic support. Accordingly, a new weakness index (WI) is proposed to identify weak parts of the cantilever structure with an elastic support. Then the cantilever beam with the elastic support is numerically simulated and weak parts are modeled as stiffness reduction. In this regard, finite element (FE) simulations are carried out to evaluate the effectiveness of the WI method in several scenarios with single and multiple weaknesses, including the noise case. In the combined structure of the tailstock and the bed of the machine tool, sensors are utilized to collect vibration data. Furthermore, the dynamic characteristics are calculated through the modal state-space method to obtain the stiffness data at zero-frequency. Then, weak parts of the structural stiffness are identified based on the weakness index. It is found that the FE simulations are in an excellent agreement with the experiment. Therefore, it is proved that the WI can accurately identify the weak parts of the machine tool cantilever structure.

scholarly journals Study on the dynamic identification method of the weak part of the bar-shaped combined structure

2021 ◽  
Vol 13 (2) ◽  
pp. 168781402199652
Author(s):  
Tieneng Guo ◽  
Lingjun Meng ◽  
Jinxuan Cao ◽  
Chunsheng Bai ◽  
Xu Hua ◽  
...  
Keyword(s):  
Machine Tool ◽  
Test Method ◽  
Fe Method ◽  
Dynamic Identification ◽  
Vibration Data ◽  
Weak Part ◽  
Combined Structure ◽  
Type Machine ◽  
Value Decomposition ◽  
Space Method

The weak part of the stiffness of machine tool combined structure is the key to improve the stiffness of machine tool. To overcome the static deformation with difficulty acquisition, the paper chooses machine tool combined structure which can be equivalent to one-dimensional bar structure, and a weakness index (WI) is proposed to identify the weak part of the stiffness by means of the dynamic hammer test method. Based on the bar structure as a numerical example, the weak parts are modeled as EA reduction in stiffness while the mass is maintained at a constant value. Thorough finite element (FE) method simulations are performed to assess the robustness and limitations of the method in several scenarios with single and multiple weakness. On the crossbeam of gantry type machine tool, the sensors are used to collect vibration data, the structural modal parameters are obtained by singular value decomposition (SVD) technique, and the dynamic characteristics are systematically reconstructed by using modal state space method to obtain stiffness data at zero-frequency. Then, the weak part of the structural stiffness is identified by the weakness index. Finally, the comparison of FE simulations and experiment results are provided to illustrate the working of the method.

scholarly journals Research on the dynamic identification method of weak parts in cantilever structures

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110169
Author(s):  
Tieneng Guo ◽  
Lingjun Meng ◽  
Xu Hua ◽  
Cheng Zhou ◽  
Liwei Peng
Keyword(s):  
Machine Tool ◽  
Complex Problem ◽  
Static Deformation ◽  
Machining Accuracy ◽  
Test Machine ◽  
Dynamic Identification ◽  
Stiffness Reduction ◽  
Weak Part ◽  
Cantilever Structure ◽  
System Reconstruction

Determining the weak parts of a structure is one of the key issues in the field of machine tool stiffness improvement. However, studies show that overcoming the static deformation with acquisition difficulty is a complex problem in practical structures. This study considers the machine tool cantilever structure, as a cantilever beam and bar structure, where the objective is to propose a weakness index, to identify the weak part, using system reconstruction to extract the measured static deformation data and the fitting data. Stiffness reduction is used to simulate weak parts, while the effectiveness of the method is evaluated, in the case of various weakness values and of different noise levels, using the finite element simulation approach. The validity of the proposed method is illustrated through comparison of the theoretical results to the experimental ones, using the cantilever structure of a test machine tool. The research content provides some means of improving the machining accuracy of machine tools.

scholarly journals Numerical Study of the Seismic Response of an Instrumented Building with Underground Stories

2021 ◽  
Vol 11 (7) ◽  
pp. 3190
Author(s):  
Edmundo Schanze ◽  
Gilberto Leiva ◽  
Miguel Gómez ◽  
Alvaro Lopez
Keyword(s):  
Seismic Response ◽  
Soil Structure ◽  
Numerical Study ◽  
Time History ◽  
Building Design ◽  
Average Height ◽  
The Real ◽  
Vibration Data ◽  
Finite Element Software ◽  
Stiffness Reduction

Engineering practitioners do not usually include soil–structure interactions in building design; rather, it is common to model and design foundations as embedded joints with joint–based reactions. In some cases, foundation structures are modeled as rigid bodies, embedding the first story into lower vertical elements. Given that the effects of underground floors on the seismic response are not generally included in current building design provisions, it has been little explored in the literature. This work compares and analyzes models to study the effects of different underground stories modeling approaches using earthquake vibration data recorded for the 16–story Alcazar building office in downtown Viña del Mar (Chile). The modeling expands beyond an embedded first story structure to soil with equivalent springs, representing soil–structure interaction (SSI), with varying rigid soil homogeneity. The building was modeled in a finite element software considering only dead load as a static load case because the structure remained in the framing stage when the monitoring system was operating. The instruments registered 72 aftershocks from the 2010 Maule Earthquake, and this study focused on 11 aftershocks of different hypocenters and magnitudes to collect representative information. The comparisons between empirical records and models in this study showed a better fit between the model and the real vibration data for the models that do consider the SSI using horizontal springs attached to the retaining walls of the underground stories. In addition, it was observed that applying a stiffness reduction factor of 0.7 to all elements in deformation verification models for average–height buildings was suitable to analyze the behavior under small earthquakes; better results are obtained embedding the structure in the foundation level than embedding in the street level; the use of horizontal springs with Kuesel’s model with traction for the analysis of the structure yields appropriate results; it is necessary to carefully select the spring constants to be used, paying special attention to the vertical springs. Even though the results presented herein indicate that the use of vertical springs to simulate the SSI of the base slab can result in major differences concerning the real response, it is necessary to obtain more data from instrumentation across a wider variety of structures to continue to evaluate better design and modeling practices. Similarly, further analyses, including nonlinear time–history and high–intensity events, are needed to best regulate building design.

L1 Regularized Model Updating for Structural Damage Detection

2018 ◽  
Vol 18 (12) ◽  
pp. 1850157 ◽  
Author(s):  
Yu-Han Wu ◽  
Xiao-Qing Zhou
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Model Updating ◽  
Regularization Parameter ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Modal Data ◽  
Vibration Data ◽  
Stiffness Reduction ◽  
Regularized Model

Model updating methods based on structural vibration data have been developed and applied to detecting structural damages in civil engineering. Compared with the large number of elements in the entire structure of interest, the number of damaged elements which are represented by the stiffness reduction is usually small. However, the widely used [Formula: see text] regularized model updating is unable to detect the sparse feature of the damage in a structure. In this paper, the [Formula: see text] regularized model updating based on the sparse recovery theory is developed to detect structural damage. Two different criteria are considered, namely, the frequencies and the combination of frequencies and mode shapes. In addition, a one-step model updating approach is used in which the measured modal data before and after the occurrence of damage will be compared directly and an accurate analytical model is not needed. A selection method for the [Formula: see text] regularization parameter is also developed. An experimental cantilever beam is used to demonstrate the effectiveness of the proposed method. The results show that the [Formula: see text] regularization approach can be successfully used to detect the sparse damaged elements using the first six modal data, whereas the [Formula: see text] counterpart cannot. The influence of the measurement quantity on the damage detection results is also studied.

scholarly journals An identification method of the weak link of stiffness for cantilever beam structure

2020 ◽  
Vol 103 (3) ◽  
pp. 003685042095267
Author(s):  
Tieneng Guo ◽  
Lingjun Meng ◽  
Jinxuan Cao ◽  
Chunsheng Bai
Keyword(s):  
Machine Tool ◽  
Cantilever Beam ◽  
Weak Link ◽  
Difficult Problem ◽  
Beam Structure ◽  
Identification Method ◽  
Acceleration Data ◽  
Cantilever Structure ◽  
Practical Engineering ◽  
Value Decomposition

To find the weak link of the structural stiffness is important to improve machine tool stiffness. However, how to overcome the static deformation with difficulty acquisition is a difficult problem in machine tool structure. The article takes the cantilever beam structure as a numerical example, the weak link is modeled as EA reduction in stiffness. Thorough finite element simulations are performed to assess the robustness and limitations of the method in several scenarios with single and multiple weaknesses. The sensors are used to acquire the acceleration data, the structural modal parameters are obtained by the singular value decomposition technique, and the dynamic characteristics are systematically reconstructed by using the modal state-space method to obtain static stiffness. Then, an identification method proposed by measured data and reconstructed data to identify the weak link of stiffness of the cantilever structure. Furthermore, the comparison of numerical and experimental results validate the correctness and effectiveness of this method. The research has certain practical engineering value and provides an accurate guidance for the optimization of machine tool stiffness.

scholarly journals Perbandingan Eksperimental dan Simulasi Frekuensi Pribadi pada Struktur Spindel CNC

2020 ◽  
Vol 11 (3) ◽  
pp. 497-510
Author(s):  
Hendri Van Hoten ◽  
◽  
Nurbaiti Nurbaiti ◽  
Afdhal Kurniawan Mainil ◽  
Jhonson Van Silitonga
Keyword(s):  
Machine Tool ◽  
Natural Frequency ◽  
Test Results ◽  
Cnc Machine ◽  
Vibration Data ◽  
Spindle Shaft ◽  
Tool Performance ◽  
Total Data ◽  
The Time Domain ◽  
Spindle Structure

The Research was about the comparison between experiment and simulation of natural frequency in CNC spindle. CNC spindle vibration will reduce machine tool performance. It could lead to the damage of the machine tool. The spindle structure unbalances of machine tools will cause vibration when it is operated. In the CNC machine, the spindle shaft vibration should be minimum. Based on this point, the natural frequency testing on the spindle shaft structure was carried out. The experiments were conducted by employing oscilloscope which could provide the vibration data in the time domain. The data was converted into the frequency domain using FFT. Measurements were carried out on 7 times of testing. Every one time of testing, 10 data were taken at each testing points. The tests were conducted at 10 testing points. Therefore, the total data obtained were 700 test data. The test results were then compared with the results of simulation modeling in 10 vibrate modes using Solidwork software. After testing and simulations were compared, 4 personal frequency values were obtained in the test that uses a measuring instrument and 6 personal frequency values could not be read. These were because the accelerometer used could not read up to 0 Hz frequency. Natural frequency obtained from simulations and tests were expressed in the percentage of errors. The largest error value in the 9th vibration mode measurement with a natural frequency was 2117.96 Hz with an error of 0.32%. The smallest error value was 0.11% with a natural frequency of 2995.79 Hz.

Modeling and simulation of the interaction of manufacturing process and machine tool structure in flycutting machining

2014 ◽  
Vol 229 (15) ◽  
pp. 2730-2736 ◽  
Author(s):  
Wanqun Chen ◽  
Yazhou Sun ◽  
Chenhui An ◽  
Hao Su ◽  
Kai Yang ◽  
...  
Keyword(s):  
Machine Tool ◽  
Dynamic Performance ◽  
Great Influence ◽  
Machining Process ◽  
State Space Method ◽  
Machined Surface ◽  
Machine Tool Structure ◽  
Machining Speed ◽  
The Relationship ◽  
Space Method

The process machine interactions in the flycutting machining are presented by integrating the state-space method and finite element method. The prediction of the cutting force fluctuations in the machining process caused by the compliance of machine tool structure is achieved. Furthermore, the relationship between the dynamic performance of the machine tool structure and the machining speed is discussed, which has great influence on the root mean square of waviness and flatness on the machined surface. The simulation results are validated by experiments.

Real-Time Tracking of Structural Stiffness Reduction with Unknown Inputs, Using Self-Adaptive Recursive Least-Square and Curvature-Change Techniques

2019 ◽  
Vol 19 (10) ◽  
pp. 1950123 ◽  
Author(s):  
Mohsen Askari ◽  
Yang Yu ◽  
Chunwei Zhang ◽  
Bijan Samali ◽  
Xiaoyu Gu
Keyword(s):  
Real Time ◽  
Computational Efficiency ◽  
Least Square ◽  
Structural Stiffness ◽  
Recursive Least Square ◽  
Unknown Parameters ◽  
Unknown Inputs ◽  
Damage Indices ◽  
Stiffness Reduction ◽  
Self Adaptive

In this paper, a new computationally efficient algorithm is developed for online and real-time identification of time, location, and severity of abrupt changes in structural stiffness as well as the unknown inputs such as earthquake signal. The proposed algorithm consists of three stages and is based on self-adaptive recursive least-square (RLS) and curvature-change approaches. In stage 1 (intact structure), a simple compact RLS is hired to estimate the unknown parameters and input of the structure such as stiffness and earthquake. Once the damage has occurred, its time and location are identified in stage 2, using two robust damage indices which are based on the structural jerk response and the error between measured and estimated responses of structure from RLS. Finally, the damage severity as well as the unknown excitations are identified in the third stage (damaged structure), using a self-adaptive multiple-forgetting-factor RLS. The method is validated through numerical and experimental case studies including linear and nonlinear buildings, a truss structure, and a three-story steel frame with different excitations and damage scenarios. Results show that the proposed algorithm can effectively identify the time-varying structural stiffness as well as unknown excitations with high computational efficiency, even when the measured data is contaminated with different levels of noise. In addition, as no optimization method is used here, it can be applied to real-time applications with computational efficiency.

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