Temat: preload - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Optimizing static and dynamic stiffness of machine tools spindle shaft, for improving machining product quality
Autorzy:: Prakosa, T.
Wibowo, A.
Ilhamsyah, R.
Tematy:: static stiffness
dynamic stiffness
preload; Pokaż więcej
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Powiązania:: https://bibliotekanauki.pl/articles/244522.pdf Link otwiera się w nowym oknie
Opis:: Automotive industries in Indonesia have grown up fast, and in-line with it, machine tools population has also grown up. Nevertheless, most of these machines are imported, because there are only few machine tools industries in Indonesia. Based on this situation, Indonesia has started to build its own machine tools industry in order to support mostly, automotive industries. This paper deals with an activity in machine tools performance improvement researches in Indonesia, that is, improving spindle static and dynamic stiffness. Spindle shaft is the weakest point in machine tools structure, increasing its stiffness will further increase machine tools accuracy and machining product quality as well. Moreover, high productivity needs machine tools with high speed machining capability, which leads into unavoidable dynamic effects that occur in the machine tool spindle during production process such as regenerative chatter. A study has been conducted on developing mathematical model for calculating static and dynamic stiffness of machine tools spindle shaft and studying changes of spindle shaft static and dynamic stiffnesses, by varying bearings preload, number of bearings, bearings span and spindle length. The study was conducted theoretically and experimentally on a national-built CNC vertical milling machine. The study shows that the machine tools spindle shaft stiffness can be increased by optimizing the parameters aforementioned.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Effect of alignment errors on operation of machine tool spindle with active bearing preloading module
Autorzy:: Turek, Paweł
Stembalski, Marek
Tematy:: machine tool
preload
coaxiality
angular bearings; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/140187.pdf Link otwiera się w nowym oknie
Opis:: The article describes a test stand with a spindle equipped with an active bearing preload system using piezoelectric actuators. The proper functioning of the spindle and the active system was associated with the correct alignment of the spindle shaft and the drive motor. The article presents two methods of shaft alignment. The use of commonly known shaft alignment methods with dial indicators is insufficient from the viewpoint of being able to control this preload. This work aims at making the readers aware that, for systems with active bearing preload, the latest measuring devices should be used to align the shaft. The use of commonly known methods of equalization with dial gauges is insufficient from the point of view of controlling this preload. Increasing the accuracy of shaft alignment from 0.1 to 0.01 mm made it possible to obtain a 50% reduction in the displacement of the outer bearing ring during spindle operation.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Comparison of Methods for Adjusting and Controlling the Preload of Angular-Contact Bearings
Autorzy:: Turek, P.
Skoczyński, W.
Stembalski, M.
Tematy:: preload
angular-contact bearings
machine tool; Pokaż więcej
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Powiązania:: https://bibliotekanauki.pl/articles/99739.pdf Link otwiera się w nowym oknie
Opis:: The effect of preload on the operating conditions of angular-contact bearings is described. The interdependences occurring during mutual displacements of bearing rings at different bearing contact angles are discussed. The criteria of the classification into low-speed and high-speed angular-contact bearings are presented. Selected methods of preloading angular-contact bearings are compared and discussed. Their advantages and disadvantages with regard to the active control and adjustment of the bearing system during its operation are presented. The structure of a developed test stand with a spindle assembly is described. Preliminary measurements of the behaviour of the spindle assembly during operation are reported. Conclusions are drawn and the direction for further research is indicated.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Development of FEM model of an angular contact ball bearing with its experimental verification
Autorzy:: Turek, Pawel
Skoczynski, Waclaw
Stembalski, Marek
Tematy:: preload
angular-contact bearings
machine tool; Pokaż więcej
Wydawca:: Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Powiązania:: https://bibliotekanauki.pl/articles/100095.pdf Link otwiera się w nowym oknie
Opis:: The article presents FEM model of an angular contact ball bearing used in spindle systems with active preload control. A two-dimensional replacement model for a single rolling element was developed. Its elastic characteristics were determined and the stress distribution was presented for the FEM 2D model. Based on the elastic characteristics for a single rolling element, a complete 3D bearing was modelled. The substitute model of a bearing developed in this way was used to model the spindle system. The elasticity curve of this spindle was determined. The last stage of the work involved the experimental verification of the FEM model using a custom-built test bench, in which piezoelectric elements were used to preload the bearings.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Numerical analysis of the screw connection with preload tension used in the mounting of slewing bearings
Autorzy:: Reszka, P.
Kania, L.
Pytlarz, R.
Tematy:: slewing bearings
screw connection
preload tension
FEM; Pokaż więcej
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Powiązania:: https://bibliotekanauki.pl/articles/246678.pdf Link otwiera się w nowym oknie
Opis:: Slewing bearings are used as devices that connect two part working machine, usually with a rotating chassis body must meet safety criteria, manage to cope with extreme loads and environmental factors operation life. In this paper the distribution of pressure on surfaces of the screw's connections with preload tension is considered. A joining model which is used in rolling bearing is the subject of the analysis. The aim of the work is to introduce an auxiliary criterion of 'connection tightness' to the calculating methodology of bearings' fastening connections with building structure. Considered part of the three-row roller bearing, rings bearings and mounting elements are modelled solid type, and the bolts are modelled with beam-type element introduced preload tension value equivalent catalogue. Connected elements of the screw head rigid elements. The screws used in such a combined coronary bearings are not close fit, and established contact between the surfaces of the rings and the building is not homogeneous. Work is not only dedicated to the stress of contact between the contact surfaces A and B, but also considered is the effect of pitch spacing of the screws on the pitch rolling element bearing in the numerical solution ADINA system was used to prepare numerical models of junction. The results of the calculations of pressure distributions for changeable screw's span are shown graphically and the table of percentages of the load loss of contact between the surfaces A and B of slewing bearing screw connection.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Rozkład sił i ich wpływ na prawidłową pracę kulkowych łożysk skośnych
Distribution of forces and their impact on the proper work of angular contact ball bearings
Autorzy:: Turek, P.
Piórkowski, P.
Tematy:: preload of angular contact bearings
machine tool spindles; Pokaż więcej
Wydawca:: ADVSEO
Powiązania:: https://bibliotekanauki.pl/articles/134798.pdf Link otwiera się w nowym oknie
Opis:: The paper presents the dependence that exists between the bearing preload, and its maximum speed. It discusses the distribution of forces within the bearing and behavior of the rolling element (ball) with increasing spindle speed. The definitions of slow and fast speed bearings commonly used in the literature are presented. It explained the need for systems with variable preload of angular contact ball bearings especially in systems operating over a wide speed range. Further we described the influence of preload on the bearing life and the influence of centrifugal force on the rigidity and accuracy of the spindle.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Thermal strength analysis of a steel bolted connection under bolt loss conditions
Autorzy:: Grzejda, Rafał
Tematy:: bolted connection
thermal strength
non-linearity
finite element method
preload; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Powiązania:: https://bibliotekanauki.pl/articles/2087009.pdf Link otwiera się w nowym oknie
Opis:: The aim of the paper is to analyse an exemplary bolted connection under the conditions of loss of bearing capacity of some fasteners in the connection. The presented tests are numerical and concern an asymmetric bolted connection. The joined elements in the connection were modelled as 3D finite elements, and the fasteners were treated as hybrid models consisting of rigid heads and nuts, and flexible beams between them. The bolted connection was first preloaded according to six different tensioning orders using a standardised force. After all bolts were tensioned, the selected bolts were removed, simulating bolt damage. The connection was then tested for external loads with temperatures ranging from 20 to 600°C. The influence of loosening the connection on the load in the remaining bolts at the operational stage of the connection was investigated. The calculation results were compared with the test results for a healthy bolted connection. It was shown that the bearing capacity of the connection in the damaged state decreased by 13%.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Non-destructive detection of high-strength wind turbine bolt looseness using digital image correlation
Autorzy:: Xie, Wei-Guo
Zhou, Peng
Chen, Li-Yun
Gu, Guo-Qing
Wang, Yong-Qing
Chen, Yu-Tao
Tematy:: bolt looseness detection
digital image correlation
loosening angle
preload force loss; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/58973588.pdf Link otwiera się w nowym oknie
Opis:: Looseness of high-strength wind turbine bolts is one of the main types of mechanical failure that threaten the quality and safety of wind turbines, and how to non-destructively detect bolt loosening is essential to accurate assessment of operational reliability of wind turbine structures. Therefore, to address the issue of looseness detection of high-strength wind turbine bolts, this paper proposes a non-destructive detection method based on digital image correlation (DIC). Firstly, the mathematical relationships between the in-plane displacement component of the bolt’s nut surface, the bolt’s preload force loss and the bolt loosening angle are both deduced theoretically. Then, experimental measurements are respectively conducted with DIC with different small bolt loosening angles. The results show that the bolt loosening angle detection method based on DIC has a detection accuracy of over 95%, and the bolt’s preload force loss evaluated by the deduced relationship has a good agreement with the empirical value. Therefore, the proposed DIC-based bolt loosening angle detection method can meet the requirements of engineering inspection, and can achieve quantitative assessment of preload forces loss of wind turbine bolt.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Impaired left ventricular circumferential midwall systolic performance appears linked to depressed preload, but not intrinsic contractile dysfunction or excessive afterload, in paradoxical low-flow/low-gradient severe aortic stenosis
Autorzy:: Bartuś, Stanisław
Zawiślak, Barbara
Chyrchel, Bernadeta
Surdacki, Andrzej
Długosz, Dorota
Opis:: Paradoxical low-flow/low-gradient aortic stenosis (P-LFLG-AS) occurs in about one-third of patients with severe AS and preserved left ventricular (LV) ejection fraction (EF). Our aim was to differentiate between altered LV loading conditions and contractility as determinants of subtle LV systolic dysfunction in P-LFLG-AS. We retrospectively analyzed medical records of patients with isolated severe degenerative AS and preserved EF (30 subjects with P-LFLG-AS and 30 patients with normal-flow/high-gradient severe AS (NFHG-AS)), without relevant coexistent diseases (e.g., diabetes, coronary artery disease and chronic kidney disease) or any abnormalities which could account for a low-flow state. Patients with P-LFLG-AS and NFHG-AS did not differ in aortic valve area index and most clinical characteristics. Compared to NFHG-AS, subjects with P-LFLG-AS exhibited smaller LV end-diastolic diameter (LVd) (44 ± 5 vs. 54 ± 5 mm, p < 0.001) (consistent with lower LV preload) with pronounced concentric remodeling, higher valvulo-arterial impedance (3.8 ± 1.1 vs. 2.2 ± 0.5 mmHg per mL/m2, p < 0.001) and diminished systemic arterial compliance (0.45 ± 0.11 vs. 0.76 ± 0.23 mL/m2 per mmHg, p < 0.001), while circumferential end-systolic LV midwall stress (cESS), an estimate of afterload at the LV level, was similar in P-LFLG-AS and NFHG-AS (175 ± 83 vs. 198 ± 69 hPa, p = 0.3). LV midwall fractional shortening (mwFS) was depressed in P-LFLG-AS vs. NFHG-AS (12.3 ± 3.5 vs. 14.7 ± 2.9%, p = 0.006) despite similar EF (61 ± 6 vs. 59 ± 8%, p = 0.4). By multiple regression, the presence of P-LFLG-AS remained a significant predictor of lower mwFS compared to NFHG-AS upon adjustment for cESS (β ± SEM: −2.35 ± 0.67, p < 0.001); however, the significance was lost after further correction for LVd (β = −1.10 ± 0.85, p = 0.21). In conclusion, the association of P-LFLG-AS with a lower cESS-adjusted mwFS, an index of afterload-corrected LV circumferential systolic function at the midwall level, appears secondary to a smaller LV end-diastolic cavity size according to the Frank–Starling law. Thus, low LV preload, not intrinsic contractile dysfunction or excessive afterload, may account for impaired LV circumferential midwall systolic performance in P-LFLG-AS.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 10.

Tytuł:: Sterowanie układem zasilania i pomiar właściwości układu wrzecionowego z łożyskami skośnymi przy użyciu środowiska LabVIEW
Control supply system and measurement properties of spindle with angular contact bearings using LabVIEW
Autorzy:: Turek, P.
Skoczyński, W.
Tematy:: preload
angular bearings
machine tool
LabVIEW environment
monitoring of spindle
speed control; Pokaż więcej
Wydawca:: ADVSEO
Powiązania:: https://bibliotekanauki.pl/articles/134728.pdf Link otwiera się w nowym oknie
Opis:: The paper presents a research position with the spindle-speed. It is used in the PhD thesis, the aim of which is to develop an active bearing case. This case is intended to provide the opportunity to actively change the preload of the spindle of ball angular contact bearings. The article describes the construction of the test and the parameters of both spindle and measurement systems. It shows the hardware configuration used for the initial measurements. These measurements will allow to determine the operating parameters of the spindle so that setting a real relationship changes the preload of the spindle for changing working conditions. For data acquisition and control software environment LabVIEW was used, its general philosophy is presented in the work. The authors also present the application created in this program which allows for simultaneous control of spindle speed and monitoring of selected parameters of its work.
Dostawca treści:: Biblioteka Nauki

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