• Structural Engineering and Mechanics
• /
• v.57 no.1
• /
• pp.141-159
• /
• 2016

Bearing joint dynamic parameter identification is crucial in modeling the high speed spindles for machining centers used to predict the stability and natural frequencies of high speed spindles. In this paper, a hybrid method is proposed to identify the dynamic stiffness of bearing joint for the high speed spindles. The hybrid method refers to the analytical approach and experimental method. The support stiffness of spindle shaft can be obtained by adopting receptance coupling substructure analysis method, which consists of series connected bearing and joint stiffness. The bearing stiffness is calculated based on the Hertz contact theory. According to the proposed series stiffness equation, the stiffness of bearing joint can be separated from the composite stiffness. Then, one can obtain the bearing joint stiffness fitting formulas and its variation law under different preload. An experimental set-up with variable preload spindle is developed and the experiment is provided for the validation of presented bearing joint stiffness identification method. The results show that the bearing joint significantly cuts down the support stiffness of the spindles, which can seriously affects the dynamic characteristic of the high speed spindles.

• Steel and Composite Structures
• /
• v.42 no.2
• /
• pp.173-190
• /
• 2022

With the development of spatial structures, the joints are becoming more and more complex to connect tubular members of spatial structures. In this study, an approach is proposed to establish high-efficiency finite element model of multiplanar KTX-joint with the weld geometries accurately simulated. Ultimate bearing capacity the KTX-joint is determined by the criterion of deformation limit and failure mechanism of chord wall buckling is studied. Size effect of fillet weld on the joint ultimate bearing capacity is preliminarily investigated. Based on the validated finite element model, a parametric study is performed to investigate the effects of geometric and loading parameters of KT-plane brace members on ultimate bearing capacity of the KTX-joint. The effect mechanism is revealed and several design suggestions are proposed. Several simple reinforcement methods are adopted to constrain the chord wall buckling. It is concluded that the finite element model established by proposed approach is capable of simulating static behaviors of multiplanar KTX-joint; chord wall buckling with large indentation is the typical failure mode of multiplanar KTX-joint, which also increases chord wall displacements in the axis directions of brace members in orthogonal plane; ultimate bearing capacity of the KTX-joint increases approximately linearly with the increase of fillet weld size within the allowed range; the effect mechanism of geometric and loading parameters are revealed by the assumption of restraint region and interaction between adjacent KT-plane brace members; relatively large diameter ratio, small overlapping ratio and small included angle are suggested for the KTX-joint to achieve larger ultimate bearing capacity; the adopted simple reinforcement methods can effectively constrain the chord wall buckling with the design of KTX-joint converted into design of uniplanar KT-joint.

• Structural Engineering and Mechanics
• /
• v.56 no.1
• /
• pp.67-83
• /
• 2015

The load transfer mechanism and load-bearing capacity of cast steel joints for H-shaped beam to square tube column connection are studied based on the deformation compatibility theory. Then the monotonic tensile experiments are conducted for 12 specimens about the cast steel joints for H-shaped beam to square tube column connection. The findings are that the tensile bearing capacity of the cast steel joints for beam-column connection depends on the ring of cast steel stiffener. The tensile fracture happens at the ring of the cast steel stiffener when the joint fails. The thickness of square tube column has little influence on the bearing capacity of the joint. The square tube column buckles while the joint without concrete filled, but the strength failure happens for the joint with concrete filled column. And the length of welding connection between square tube column and cast steel stiffener has little influence on the load-bearing capacity of the cast steel joint. Finally it is shown that the load-bearing capacity of the joints for H-shaped beam to concrete filled square tube column connection is larger than that of the joints for H-shaped beam to square tube column connection by 10% to 15%.

• Steel and Composite Structures
• /
• v.47 no.1
• /
• pp.19-36
• /
• 2023

An experimental study of eleven PVC-FRP Confined Concrete (PFCC) column-Reinforced Concrete (RC) beam joints reinforced with Core Steel Tube (CST) under axial compression is carried out. All specimens are designed in accordance with the principle of "weak column and strong joint". The influences of FRP strips spacing, length and steel ratio of CST, height and stirrup ratio of joint on mechanical behavior are investigated. As the design anticipated, all specimens are destroyed by column failure. The failure mode of PFCC column-RC beam joint reinforced with CST is the yielding of longitudinal steel bars, CST and stirrups of column as well as the fracture of FRP strips and PVC tube. The ultimate bearing capacity decreases as FRP strips spacing or joint height increases. The effects of other three studied parameters on ultimate bearing capacity are not obvious. The strain development rules of longitudinal steel bars, PVC tube, FRP strips, column stirrups and CST are revealed. The effects of various studied parameters on stiffness are also examined. Additionally, an influence coefficient of joint height is introduced based on the regression analysis of test data, a theoretical formula for predicting bearing capacity is proposed and it agrees well with test data.

• The Journal of Korean Physical Therapy
• /
• v.28 no.6
• /
• pp.381-384
• /
• 2016

Purpose: Previous studies reported changes in the first metatarsophalangeal (MTP) joint angle in relation with and without weight bearing, but it is unclear whether sesamoid bone of the great toe changes in weight bearing conditions particularly in subjects with hallux valgus (HV). To investigate how weight bearing conditions can affect the position of the medial sesamoid bone (MSB), first MTP joint angle, and second intermetatarsal angle (IMA) in the recruited subjects. Methods: Subjects were recruited 24 with HV and 21 without HV in study. X-rays were taken in the weight bearing and non-weight bearing conditions. The distance of the MSB, first MTP joint angle, and second IMA were measured from the radiographs. Data were analyzed by paired and Independent t-test. The statistical significance level was p<0.05. Results: In both groups, the first MTP joint angles and the distance of the MSB were significantly smaller, while the second IMA was significantly greater in the weight bearing condition. The difference in the distance of the MSB between the two postures was significantly greater in the group with HV. Conclusion: Weight bearing can affect the first MTP joint angle, second IMA, and position of the MSB; the change in the position of the MSB in weight bearing was greater in the group with hallux valgus. The difference in these variables between weight bearing and non-weight bearing conditions may be considered when measuring HV.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.1 no.1
• /
• pp.111-121
• /
• 1997

An investigation was performed to study the predicting the joint strength of mechanical fasteners. Bearing failure is most important failure mode for designing joint. So in this study, the prediction method in consideration with bearing failure was chosen. In the proposed method, the characteristic length is combined with the Yamada-Sun failure criterion, Tsai-Hill failure criterion and characteristic length for Tension and Compression is determined from investigation. Especially the length of compression is determined from the "bearing failure test" that newly conceived to take bearing failure into consideration. The proposed prediction method was applied to quasi-isotropic carbon/epoxy joint showing net-tension and bearing failure experimentally. Good agreement was found between the predicted and experimental result for each joint geometry. geometry.

• Journal of the Korean Wood Science and Technology
• /
• v.41 no.2
• /
• pp.100-104
• /
• 2013

Bearing occurs by the rotations of members induced from horizontal or vertical load at traditional wooden joint in frame. The bearing between wooden members is not occurring at the whole surface of joint, but occurring only at the particular bearing area. In this study, partial bearing according to the different grain direction was evaluated. The partial compressive strength showed 3 times higher than pure compressive strength perpendicular to grain, 1.5 times higher than parallel to grain and 3.3 times higher than both of them. It is expected that this result can be very importantly applied when evaluating and analyzing the actual behavior of traditional wooden mortise and tenon joint.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.1043-1048
• /
• 2002

This paper considers the vibration problem of vehicle driveline which consists of two propeller shafts and the center bearing. The excessive vibration occurs at the center bearing when the vehicle starts to run. Using the kinematic constraints at the universal joint between two propeller shafts, we develop an one d.o.f model which describes the radial motion of the center bearing. We find out the vibration occurs at the specific vehicle speed corresponding to the natural frequency of the model. Comparing the simulation results with test results we also show that the vibration at low vehicle speed is caused primarily by the joint angle and secondarily by the mis-aligned yoke flange rather than by the unbalance.

• Physical Therapy Korea
• /
• v.28 no.2
• /
• pp.108-116
• /
• 2021

Background: Whole-body vibration (WBV) has been used to alleviate proprioceptive damage by musculoskeletal and neurological conditions. However, no study has determined whether wearing shoes while applying WBV can affect proprioception precision of the knee joint. Objects: This study aimed to determine the differences in the proprioceptive precision of the knee joint before and after WBV and to compare the proprioceptive precision of the knee joint between barefoot and shoe-wearing conditions. Methods: This study recruited 33 healthy participants. A passive-to-active angle reproduction test was used to measure the proprioception precision of the knee joint using an electrogoniometer, and the target angle was set to a knee flexion of 30°. Proprioception precision was calculated using the error angle (angular difference from 30°). Proprioceptive precision was measured in weight-bearing and non-weight-bearing positions before and after applying WBV for 20 minutes at 12 Hz in barefoot and shoe-wearing conditions. Mixed repeated analysis of variance was used to determine the differences in changes in the proprioceptive precision of the knee joint according to foot conditions. Results: There were significant improvements in the weight-bearing (p = 0.002) and non-weight-bearing (p < 0.001) proprioceptive precision of the knee joint after applying WBV. However, there was no significant difference in the change in proprioceptive precision of the knee joint after applying WBV between the barefoot and shoe-wearing conditions. Conclusion: WBV stimulation had an immediate effect on improving the proprioceptive precision of the knee joint. However, foot conditions (barefoot or shoe-wearing) during WBV application did not influence the proprioceptive precision of the knee joint.

• Tribology and Lubricants
• /
• v.16 no.1
• /
• pp.39-45
• /
• 2000

In this paper, the effects of shaft and bearing flexibilities are investigated for the accurate modeling of a shaft-bearing system supported by ball bearings. Generally, rolling bearings are modeled by simple rigid pin-joint in the mechanical design. However, they can no longer be modeled by ideal boundary conditions in the advanced applications because the rigid pin-joint model cannot satisfy the current trends of mechanical design decreasing mass and reducing volume. Consequently the flexible support model of ball bearing is investigated using the static analysis module developed by A .B. Jones and T. A. Harris. A simple two-bearing system, supported by two deep groove ball bearings and radially loaded on the shaft midway between the bearings, is utilized to validate the coupled model of shaft-bearing system. Numerical computations using the model indicate that the shaft span length, locating/floating bearing arrangements and applied bearing size are significant factors in determining the mechanical behaviors. The flexible support model of ball bearing can be escaped to over-estimate in the bearing fatigue life. The proposed simple design formulation obtained by numerical simulations can approximately predict a rate of bearing life reduction as a function of shaft span length/shaft diameter (L/d).