Mechanical model and contact properties of double row slewing ball bearing for wind turbine

In this paper, the mechanical models of large-scale double row slewing ball bearing considering combined loading conditions were presented based on the rigid rings and flexible rings, respectively. And the contact properties between the ball and raceway were studied. These workflows for the calculation were described and programmed by MATLAB. The load distributions of slewing bearing for 2MW wind turbine were presented. The results indicated that the load distribution with the ideal stiff assumption differs from the load distribution determined by taking into account the flexibility of rings. With flexible rings, the magnitude of contact force is less than that of the rigid rings. The influences of the initial contact angle, the coefficient of groove curvature radius, the clearance on maximum contact force were analyzed and some suggestions have been discussed. These parameters have significant effects on the load distribution. The maximum contact force decreases with coefficient of groove curvature radius decrease. A three dimensional finite element model of the slewing bearing is established and analyzed. The simulated results are compared with that of mechanical models.

Predictions of the Apple Bruise Volume on the Basis of Impact Energy or Maximum Contact Force Using Adaptive Neuro-Fuzzy Inference System (ANFIS)

Fruit quality drops significantly due to physical impacts and contact forces. Stress on the fruit surface during harvesting, transportation and storage operations causes bruising in its tissue and eventually result in fruit failure. Therefore, prediction of the bruise volume caused by impacts can be very important. In this research, adaptive neuro fuzzy inference system (ANFIS) was used to predict the bruise volume caused by the impacts on apples. The input parameters were the maximum contact force or impact energy; curvature radius at the contact point; temperature; and fruit mass. Its response was the bruise volume. The results show that the ANFIS models operated better in the bruise volume prediction than regression models. Between different available ANFIS models, the model based on the grid partitioning showed the best results with a mean squared error of MSE = 0.00015941, which was less than value showed by the sub-clustering mode. However, its implementation time to reach a fixed error was longer. Eventually, impact energy-based models, in contrast to maximum contact force-based models, were more capable in terms of the apple bruising prediction.

An experimental study on low velocity impact behavior of thermoplastic composites repaired by composite patches

In this study, low velocity impact behavior of E-glass fiber-reinforced thermoplastic composites repaired by pressing external laminated composite patches was investigated by experimental methods. Thermoplastic composites were manufactured from polypropylene granules with two different fiber contents of 40 wt. % and 60 wt. %. Repaired specimens were prepared by using unidirectional E-glass reinforced polypropylene based thermoplastic prepregs. In order to compare the low velocity impact behavior of the repaired and unrepaired specimens, a number of single impact tests (ranging from energy levels of 10 J to 50 J) were carried out through a drop weight impact test machine with a hemispherical impactor. Low-velocity impact response of the specimens was investigated with cross-examining contact force-deformation curves and damaged specimens. Impact damages occurred in the upside and bottom surfaces of the composites were recorded from the visual inspection and compared for repaired and unrepaired specimens. According to experimental results, bending stiffness and maximum contact force of the specimens having fiber content of 60 wt.% are higher than those of 40 wt.%. Moreover, it was concluded that the patch repaired specimens have achieved a better performance in terms of maximum contact force and absorbed energy compared to the intact specimens.

Study on Stacking Sequence of Plies in Green Sandwiches for Low Velocity Impact Application

The present paper deals with optimizing the stacking sequence configuration of flexible green composite for cladding application under low velocity impact regime. Initially six configurations of green composite comprising of jute fiber and natural rubber matrix are considered and their energy absorption behaviour and resistance to impact are studied using finite element analysis. The configurations considered are optimized for energy absorption and maximum contact force under low velocity impact condition. From the results it can be concluded that the variation in energy absorbed and sp. energy absorbed among the configurations are negligible and hence the configurations are prioritized based on contact force. JRJRJ configuration provides maximum contact force followed by JRJ, JRRJ, RJRJR, RJRJ and RJR. The configurations with rank 1, 2 and 3 should be taken into consideration for further analysis. Also the damage study shows that the stacking sequence with jute on impact side is better compared to rubber on impact side as tearing type of damage can be observed in sequences with rubber on impact side and no damage is visible with jute on impact side.

Impact strength of underground cement materials

The article presents the results of a study of impact strength of underground cement materials with different water content activated by mixing water with the addition of high range plasticizers, biocidal agents, pigments, ground quartz, silica fume and fine aggregate. Samples for testing are formed in plates of size 150×100×10 mm. Testing was conducted at impact drop-weight method ASTM D7136. The maximum contact force, contact duration and magnitude of the pulse of the drummer were considered as the test parameters. The good results of the studied parameters showed highly filled plasticized compositions of the new generation. The use of iron oxide with yellow and green glauconitic pigments allows obtaining good results. Activation of the mixing water led to a rise in the maximum contact force in the case of the processing mode of E+М (3–3) while reducing the duration of the contact and the magnitude of the impulse. During the test of the biocidal composites with different biocidal preparations, it was established that the best indicators of the impact strength correspond to materials with the addition of «Teflex Antiplesen».

A Comparison of the Effectiveness of Design Approaches for Human-Friendly Robots

In this paper, different measures for reducing the maximum contact force during blunt collisions between a robot and a human are evaluated using simulations. An existing collision model is adapted to include a nonlinear compliant covering, articular safety mechanisms (compliant joint and two types of torque limiters), and a collision detection system. Several scenarios are simulated in which the collision occurs at a low or high velocity, the head of the person (on which the collision occurs) is constrained by a wall or free to move and the reflected motor inertia is large or small compared to the link inertia. The results show that a torque limiter in series with each actuator has the potential to significantly improve safety without reducing the robot's performances.

Correlation of Dent Depth to Maximum Contact Force and Damage of Composite Laminates

A major concern affecting the efficient use of carbon fibre reinforced composite laminates in the aerospace industry is the low velocity impact damage which may be introduced accidentally during manufacture, operation or maintenance of the composite structures. It is widely reported that the contact behavior of composite laminates under low-velocity impact can be obtained under quasi-static loading conditions. This paper focuses on the study of the correlation of the dent depth to the maximum contact force and damage of composite laminates under quasi-static loading. Analytical and finite element simulation approaches were employed to investigate relations between the contact force and the dent depth. Experimental investigations on the correlation between dent depth, maximum contact force and damage include quasi-static indentation testing, optical and scanning electron microscopic examination of the damage under different loading levels. The effect of damage initiation and growth on the contact behaviour has been discussed. Results show that consistent correlations between the dent depth, maximum contact force and damage exist and can be predicted with the analytical and numerical approaches. Dent depth can be used as an engineering parameter in assessing the severity of damage for composite structures that are subjected to low-velocity impact. This may lead to the development of a cost-effective technique for the inspection and maintenance of composite structures in aerospace applications.

Experimental Study of Composite-Antenna-Structures with High Electrical and Mechanical Performances

Embedding of an antenna within a structural surface is an excellent way to improve structural efficiency and antenna performance. We study the impact characteristics of a Composite-Antenna-Structure (CAS) and the degradation in the performance of the antenna after impact testing. We used an annular ring patch antenna designed to operate in two bands: GPS (1.575GHz) and DMB (2.62GHz). When 20J of impact energy was applied to the CAS surface, the maximum contact force was 4kN, and the CAS proved resistant to impact. The antenna performance, measured by the return loss and radiation pattern, remained excellent after the impact tests.

Lifetime Determination of the Raceway of a Large Three-Row Roller Slewing Bearing

This paper deals with calculation procedure for lifetime determination of a large three-row roller slewing bearing. First, the contact force distribution between the rollers and the bearing raceway is determined both analytically and numerically. Then, the position and the magnitude of the maximum contact force are identified. In a separate numerical model finite element analyses are performed to determine the subsurface stress distribution as the result of contact between the raceway and different rollers. These stress fields serve as an input for the fatigue lifetime calculation, which is done in accordance with the stress-life approach (S-N). At the end the influence of roller geometry on the calculated fatigue life is presented.

Towards Whole-Arm Statics

In this paper, a novel approach is proposed to compute the maximum contact force that can be applied by a manipulator at any point on its external surface. The approach consists in the approximation of the robot’s external surface by simple primitives for which the position and normal direction can easily be expressed analytically for any point on the surface. This approach is also used to compute analytically the boundaries of the zones on the external surface where the achievable force exceeds a predetermined threshold. A method is developed for determining the limit joint torques which ensure that the achievable force cannot exceed a predetermined magnitude for any point on the primitives. Specific equations are developed for two types of primitives (parallelogram and cylinder) along with generic procedures applicable to any shape. An example is presented to illustrate how the proposed procedures can be applied for the solution of a typical problem. Finally, the applicability and limitations of this approach are discussed. A potential application for this work is to provide information on a robot’s dangerousness to its controller in order to improve safety.