Bolted glass-fibre-reinforced plastic joints

1995 ◽  
Vol 22 (4) ◽  
pp. 736-744 ◽  
Author(s):  
M. A. Erki
Keyword(s):  
Glass Fibre ◽  
Carrying Capacity ◽  
Maximum Load ◽  
Load Carrying Capacity ◽  
Compression Tests ◽  
Reinforced Plastic ◽  
Load Carrying ◽  
Glass Fibre Reinforced Plastic ◽  
Glass Fibre Reinforced ◽  
Half Turn

Test results are presented for single fastener glass-fibre-reinforced plastic (GFRP) members connected with GFRP threaded rods, steel threaded rods, and steel bolts. Twenty-eight joints were tested in tension and thirty-five were tested in compression. For some of the tests, a GFRP pipe was used as a protective sleeve for the threads of the steel and GFRP threaded rods. The effect of fastener strength and stiffness on the load carrying capacity of the joints is reported. The major findings for both the tension and compression tests were that joints constructed with a GFRP threaded rod had approximately half the strength of joints constructed with a steel threaded rod. Also, joints constructed with a GFRP threaded rod and GFRP pipe sleeve were at least a third stronger than joints constructed with a GFRP threaded rod alone. The GFRP members used consisted of a pultruded glass fibre sheet, which was composed of symmetrically stacked, alternating layers of identically orientated unidirectional E-glass fibres and randomly orientated E-glass continuous strand mat. The maximum load carrying capacity decreased with increasing angle of loading with respect to the unidirectional fibres, but this was more pronounced for the tension tests than for the compression tests. For the tests performed, it was sufficient to finger tighten end nuts; indeed, tightening end nuts by a half turn-of-the-nut slightly decreased the strength of the joints. Key words: glass-fibre-reinforced plastic, connections, fibreglass bolts, experimental.

Maximum load carrying capacity of mobile manipulators: optimal control approach

Robotica ◽  
2009 ◽  
Vol 27 (1) ◽  
pp. 147-159 ◽  
Author(s):  
M. H. Korayem ◽  
A. Nikoobin ◽  
V. Azimirad
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Control Problem ◽  
Carrying Capacity ◽  
Nonholonomic Constraints ◽  
Maximum Load ◽  
Mobile Manipulators ◽  
Load Carrying Capacity ◽  
Maximum Payload ◽  
Load Carrying

SUMMARYIn this paper, finding the maximum load carrying capacity of mobile manipulators for a given two-end-point task is formulated as an optimal control problem. The solution methods of this problem are broadly classified as indirect and direct. This work is based on the indirect solution which solves the optimization problem explicitly. In fixed-base manipulators, the maximum allowable load is limited mainly by their joint actuator capacity constraints. But when the manipulators are mounted on the mobile bases, the redundancy resolution and nonholonomic constraints are added to the problem. The concept of holonomic and nonholonomic constraints is described, and the extended Jacobian matrix and additional kinematic constraints are used to solve the extra DOFs of the system. Using the Pontryagin's minimum principle, optimality conditions for carrying the maximum payload in point-to-point motion are obtained which leads to the bang-bang control. There are some difficulties in satisfying the obtained optimality conditions, so an approach is presented to improve the formulation which leads to the two-point boundary value problem (TPBVP) solvable with available commands in different softwares. Then, an algorithm is developed to find the maximum payload and corresponding optimal path on the basis of the solution of TPBVP. One advantage of the proposed method is obtaining the maximum payload trajectory for every considered objective function. It means that other objectives can be achieved in addition to maximize the payload. For the sake of comparison with previous results in the literature, simulation tests are performed for a two-link wheeled mobile manipulator. The reasonable agreement is observed between the results, and the superiority of the method is illustrated. Then, simulations are performed for a PUMA arm mounted on a linear tracked base and the results are discussed. Finally, the effect of final time on the maximum payload is investigated, and it is shown that the approach presented is also able to solve the time-optimal control problem successfully.

scholarly journals Seawater effects on static loads and interlayer cracking performance for polyvinyl chloride foam-cored sandwich composites

2018 ◽  
Vol 10 (11) ◽  
pp. 168781401880734
Author(s):  
Jian He ◽  
Dongyuan Xie ◽  
Qichao Xue ◽  
Yangyang Zhan
Keyword(s):  
Energy Release ◽  
Polyvinyl Chloride ◽  
Glass Fibre ◽  
Critical Energy ◽  
Bending Tests ◽  
Rate Dependent ◽  
Reinforced Plastic ◽  
Glass Fibre Reinforced Plastic ◽  
Glass Fibre Reinforced ◽  
Cantilever Bending

The diffusion influence of seawater on the static and interlayer cracking properties of a polyvinyl chloride foam sandwich structure is investigated in this study. After soaking specimens in seawater for various durations, various comparison tests are performed to investigate the effects of seawater. Compression tests for H60 and H200 polyvinyl chloride foam specimens are conducted to study strength and modulus degradation, and the results show that immerging time and temperature have significant effects on polyvinyl chloride foam properties. Tensile tests for glass-fibre-reinforced plastic panels, four-point bending tests and double cantilever bending tests for polyvinyl chloride foam sandwich specimens are also performed. The results show that seawater immerging treatment has a noticeable influence on glass-fibre-reinforced plastic tensile properties and interlayer critical energy release rate values, but has almost no effect on bending properties of foam sandwich specimen. Furthermore, a rate-dependent phenomenon is observed in double cantilever bending tests, in which higher loading rate will lead to larger critical energy release values. Numerical simulation is also performed to illustrate the cracking process of double cantilever bending tests and shows a certain accuracy. The simulation also demonstrates that the viscoelasticity of foam material after immerging treatment results in the rate-dependent characterization of double cantilever bending tests.

Development of Z-Factor for Circumferential Part-Through Surface Cracks in Dissimilar Metal Welds

2008 ◽  
Author(s):  
D.-J. Shim ◽  
G. M. Wilkowski ◽  
D. L. Rudland ◽  
F. W. Brust ◽  
Kazuo Ogawa
Keyword(s):  
Correction Factor ◽  
Carrying Capacity ◽  
Limit Load ◽  
Maximum Load ◽  
Load Carrying Capacity ◽  
Surface Cracks ◽  
Crack Driving Force ◽  
Dissimilar Metal ◽  
Load Carrying ◽  
J Estimation

Section XI of the ASME Code allows the users to conduct flaw evaluation analyses by using limit-load equations with a simple correction factor to account elastic-plastic fracture conditions. This correction factor is called a Z-factor, and is simply the ratio of the limit-load to elastic-plastic fracture mechanics (EPFM) maximum-load predictions for a flaw in a pipe. The past ASME Section XI Z-factors were based on a circumferential through-wall crack in a pipe rather than a surface crack. Past analyses and pipe tests with circumferential through-wall cracks in monolithic welds showed that the simplified EPFM analyses (called J-estimation schemes) could give good predictions by using the toughness, i.e., J-R curve, of the weld metal and the strength of the base metal. The determination of the Z-factor for a dissimilar metal weld (DMW) is more complicated because of the different strength base metals on either side of the weld. This strength difference can affect the maximum load-carrying capacity of the flawed pipe by more than the weld toughness. Recent work by the authors for circumferential through-wall cracks in DMWs has shown that an equivalent stress-strain curve is needed in order for the typical J-estimation schemes to correctly predict the load carrying capacity in a cracked DMW. In this paper, the Z-factors for circumferential surface cracks in DMW were determined. For this purpose, a material property correction factor was determined by comparing the crack driving force calculated from the J-estimation schemes to detailed finite element (FE) analyses. The effect of crack size and pipe geometry on the material correction factor was investigated. Using the determined crack-driving force and the appropriate toughness of the weld metal, the Z-factors were calculated for various crack sizes and pipe geometries. In these calculations, a ‘reference’ limit-load was determined by using the lower strength base metal flow stress. Furthermore, the effect of J-R curve on the Z-factor was investigated. Finally, the Z-factors developed in the present work were compared to those developed earlier for through-wall cracks in DMWs.

The Elastic-Softening Failure of Floating Beams

1988 ◽  
Vol 32 (01) ◽  
pp. 37-43
Author(s):  
Paul C. Xirouchakis
Keyword(s):  
Carrying Capacity ◽  
Maximum Load ◽  
Point Load ◽  
Negative Stiffness ◽  
Load Carrying Capacity ◽  
Perfectly Plastic ◽  
Load Carrying ◽  
Elastic Perfectly Plastic ◽  
The Moment ◽  
Elastic Softening

The solution is presented for an infinite elastic-softening floating beam under a point load. The response depends on two nondimensional parameters: the negative stiffness coefficient that characterizes the descending part of the moment-curvature curve, and the nondimensional softening region half-length. The solution exhibits two important features that the elastic-perfectly plastic solution does not show. First, in certain ranges of parameters, the elastic-softening beam has a clearly defined maximum load carrying capacity. Second, in some other ranges of parameters, the elastic-softening beam has a minimum load or residual strength. The beam stiffens up upon further deformation due to the reactions of the water foundation. Critical softening parameters are calculated that separate stable from unstable behavior.

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