Dynamical Analysis and Design of Bearingless Rotor Flexbeam

Shi, Weixing,Wang, Jidong The Society for Aerospace System Engineering 2015 International Journal of Aerospace System Engineer Vol.2 No.1

In helicopter bearingless rotor design, the flexbeam is the key component of rotor system, which plays an importantrole in the blade flapping, lead-lag movement, torsion, and load transfer. Flexbeam must have the minimum torsion stiffness with enough tension strength. In this paper, we first investigated the torsion stiffness of different cross section configurations of the flexbeam through some simple experiments. Then we analyzed a rotor's dynamical characteristics with finite element method and got the rotor's fan plot. After that, we studied the relationship between the frequency changes with the spanwise distribution of mass and stiffness in bearingless rotor. Finally, we analyzed the influence of the flexbeam on dynamical characteristics of the bearingless rotor system, and completed the design of this type of rotor flexbeam.

Neoadjuvant Chemotherapy-Guided Bladder-Sparing Treatment for Muscle-Invasive Bladder Cancer: Results of a Pilot Phase II Study

Hongzhe Shi,Wen Zhang,Xingang Bi,Dong Wang,Zejun Xiao,Youyan Guan,Kaopeng Guan,Jun Tian,Hongsong Bai,Linjun Hu,Chuanzhen Cao,Weixing Jiang,Zhilong Hu,Jin Zhang,Yan Chen,Shan Zheng,Xiaoli Feng,Changlin 대한암학회 2021 Cancer Research and Treatment Vol.53 No.4

Purpose Reduced quality of life after cystectomy has made bladder preservation a popular research topic for muscle-invasive bladder cancer (MIBC). Previous research has indicated significant tumor downstaging after neoadjuvant chemotherapy (NAC). However, maximal transurethral resection of bladder tumor (TURBT) was performed before NAC to define the pathology, impacting the real evaluation of NAC. This research aimed to assess real NAC efficacy without interference from TURBT and apply combined modality therapies guided by NAC efficacy. Materials and Methods Patients with cT2-4aN0M0 MIBC were confirmed by cystoscopic biopsy and imaging. NAC efficacy was assessed by imaging, urine cytology, and cystoscopy with multidisciplinary team discussion. Definite responders (≤ T1) underwent TURBT plus concurrent chemoradiotherapy. Incomplete responders underwent radical cystectomy or partial cystectomy if feasible. The primary endpoint was the bladder preservation rate. Results Fifty-nine patients were enrolled, and the median age was 63 years. Patients with cT3-4 accounted for 75%. The median number of NAC cycles was three. Definite responders were 52.5%. The complete response (CR) was 10.2%, and 59.3% of patients received bladder-sparing treatments. With a median follow-up of 44.6 months, the 3-year overall survival (OS) was 72.8%. Three-year OS and relapse-free survival were 88.4% and 60.0% in the bladder-sparing group but only 74.3% and 37.5% in the cystectomy group. The evaluations of preserved bladder function were satisfactory. Conclusion After stratifying MIBC patients by NAC efficacy, definite responders achieved a satisfactory bladder-sparing rate, prognosis, and bladder function. The CR rate reflected the real NAC efficacy for MIBC. This therapy is worth verifying through multicenter research.

Tuned mass dampers for human-induced vibration control of the Expo Culture Centre at the World Expo 2010 in Shanghai, China

Xilin Lu,Kun Ding,Weixing Shi,Dagen Weng 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.5

The Expo Culture Centre is one of the permanent buildings at the World Expo 2010 in Shanghai, China. The main structure has an oval shape and consists of 36 radial cantilever steel trusses with different lengths and inner frames made of concrete-filled rectangular steel tube members. Tuned mass dampers are used to reduce the excessive vibrations of the sixth floor that are caused by humaninduced resonance. A three-dimensional analytical model of the system is developed, and its main characteristics are established. A series of field tests are performed on the structure, and the test results show that the vertical vibration frequencies of most structural cantilevers are between 2.5 Hz and 3.5 Hz, which falls in the range of human-induced vibration. Twelve pairs of tuned mass dampers weighing 115 tons total were installed in the structure to suppress the vibration response of the system. These mass dampers were tuned to the vertical vibration frequency of the structure, which had the highest possibility of excitation. Test data obtained after the installation of the tuned mass dampers are used to evaluate their effectiveness for the reduction of the vibration acceleration. An analytical model of the structure is calibrated according to the measured dynamic characteristics. An analysis of the modified model is performed and the results show that when people walk normally, the structural vibration was low and the tuned mass dampers have no effect, but when people run at the structural vibration frequency, the tuned mass dampers can reduce the floor vibration acceleration by approximately 15%.

Two-dimensional air spring based semi-active TMD for vertical and lateral walking and wind-induced vibration control

Yang Wang,Liangkun Wang,Weixing Shi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.4

A slender steel pedestrian bridge suffers from excessive vibration under walking-induced excitations, which include vertical and lateral dynamic loads. Meanwhile, a slender footbridge may also be sensitive to the wind excitation. Excessive vibration will not only cause a serviceability problem, but also even a safety problem. Tuned mass dampers (TMDs) have been applied in slender steel bridges widely for vibration control. However, a passive TMD is sensitive to the frequency deviation. Though a semi-active TMD (STMD) can improve the control effect of a passive TMD to a great degree, there is no STMD and related research that can simultaneously control vertical and lateral walking and wind-induced vibrations of pedestrian bridges. To fill this blank, in this paper, a two-dimensional air spring based STMD (TDAS-STMD) is proposed. The TDAS-STMD is connected to the bridge through two vertical air springs and two lateral air springs, and the stiffness of each air spring can be retuned through adjusting its air pressure by an air pump. At the same time, the damping of TDAS-STMD can be adjusted in real time through changing the air gap between the conductor plate and permanent magnets by a step putter. The mechanical detail of TDAS-STMD and the combined variable stiffness and damping control algorithm are introduced firstly. Then, a simply supported steel footbridge which is sensitive to both vertical and lateral walking and wind-induced excitations is proposed as a case study. In the numerical simulation, the bridge is simplified as a Euler-Bernoulli beam with a constant section. A group of two optimized passive TMDs which implemented in vertical and lateral directions respectively are presented for comparison. Single pedestrian walking-induced vertical and lateral vibration, wind-induced lateral vibration, and a low-density random crowd-induced vertical and lateral vibration coupled with the wind-induced lateral vibration are both considered in the case study. Numerical results indicate that the TDAS-STMD can control vertical and lateral vibrations of the beam effectively and always has the best performance.

Semi-active eddy current pendulum tuned mass damper with variable frequency and damping

Ying Zhou,Liangkun Wang,Weixing Shi,Quanwu Zhang 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.1

In order to protect a structure over its full life cycle, a novel tuned mass damper (TMD), the so-called semi-active eddy current pendulum tuned mass damper (SAEC-PTMD), which can retune its frequency and damping ratio in real-time, is proposed in this study. The structural instantaneous frequency is identified through a Hilbert-Huang transformation (HHT), and the SAECPTMD pendulum is adjusted through an HHT-based control algorithm. The eddy current damping parameters are discussed, and the relationship between effective damping coefficients and air gaps is fitted through a polynomial function. The semi-active eddy current damping can be adjusted in real-time by adjusting the air gap based on the linear-quadratic-Gaussian (LQG)-based control algorithm. To verify the vibration control effect of the SAEC-PTMD, an idealized linear primary structure equipped with an SAECPTMD excited by harmonic excitations and near-fault pulse-like earthquake excitations is proposed as one of the two case studies. Under strong earthquakes, structures may go into the nonlinear state, while the Bouc-Wen model has a wild application in simulating the hysteretic characteristic. Therefore, in the other case study, a nonlinear primary structure based on the Bouc-Wen model is proposed. An optimal passive TMD is used for comparison and the detuning effect, which results from the cumulative damage to primary structures, is considered. The maximum and root-mean-square (RMS) values of structural acceleration and displacement time history response, structural acceleration, and displacement response spectra are used as evaluation indices. Power analyses for one earthquake excitation are presented as an example to further study the energy dissipation effect of an SAECPTMD. The results indicate that an SAEC-PTMD performs better than an optimized passive TMD, both before and after damage occurs to the primary structure.

Tuned mass dampers for human-induced vibration control of the Expo Culture Centre at the World Expo 2010 in Shanghai, China

Lu, Xilin,Ding, Kun,Shi, Weixing,Weng, Dagen Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.5

The Expo Culture Centre is one of the permanent buildings at the World Expo 2010 in Shanghai, China. The main structure has an oval shape and consists of 36 radial cantilever steel trusses with different lengths and inner frames made of concrete-filled rectangular steel tube members. Tuned mass dampers are used to reduce the excessive vibrations of the sixth floor that are caused by human-induced resonance. A three-dimensional analytical model of the system is developed, and its main characteristics are established. A series of field tests are performed on the structure, and the test results show that the vertical vibration frequencies of most structural cantilevers are between 2.5 Hz and 3.5 Hz, which falls in the range of human-induced vibration. Twelve pairs of tuned mass dampers weighing 115 tons total were installed in the structure to suppress the vibration response of the system. These mass dampers were tuned to the vertical vibration frequency of the structure, which had the highest possibility of excitation. Test data obtained after the installation of the tuned mass dampers are used to evaluate their effectiveness for the reduction of the vibration acceleration. An analytical model of the structure is calibrated according to the measured dynamic characteristics. An analysis of the modified model is performed and the results show that when people walk normally, the structural vibration was low and the tuned mass dampers have no effect, but when people run at the structural vibration frequency, the tuned mass dampers can reduce the floor vibration acceleration by approximately 15%.