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This paper aims to describe the formulation of a displacement-based triangular membrane finite element with true drilling rotational degree of freedom (DOF).

The presented formulation incorporates the true drilling rotation provided by continuum mechanics into the displacement field by way of using the polynomial interpolation. Unlike the linked interpolation, that uses a geometric transformation between displacement and vertex rotations, in this work, the interpolation of the displacement field in terms of nodal drilling rotations is obtained following an unusual approach that does not imply any presumed geometric transformation.

New relationship linking the mid-side normal displacement to corner node drilling rotations is derived. The resulting new element with true drilling rotation is compatible and does not include any problem-dependent parameter that may influence the results. The spurious zero-energy mode is stabilized in a careful way that preserves the true drilling rotational degrees of freedom (DOFs).

Several works dealing with membrane elements with vertex rotational DOFs have been published with improved convergence rate, however, owing to the need for incorporating rotations in the finite element meshes involving solids, shells and beam elements, having finite elements with true drilling rotational DOFs is more appreciated.

During drilling in coal mines, sticking of drill rod (referred to as SDR in this work) is a potential threat to underground safety. However, no practical measures to deter SDR have been developed yet. The purpose of this study is to develop an anti-SDR strategy using proportional-integral-derivative (PID) and compliance control (PIDC). The proposed strategy is compatible with the drilling process currently used in underground coal mines using drill rigs. Therefore, this study aims to contribute to the PIDC strategy for solving SDR.

A hydraulic circuit to reduce SDR was built based on a load-independent flow distribution system, a PID controller was designed to control the inlet hydraulic pressure of the rotation motor and a typical compliance control approach was adopted to control the feed force and displacement. Moreover, the weight and optimal combination of the alternative admittance control parameters for the feed cylinder were obtained by adopting the orthogonal experiment approach. Furthermore, a fuzzy admittance control approach was proposed to control the feed displacement. Experiments were conducted to test the effectiveness of the proposed method.

The experimental results indicated that the PIDC strategy was appropriate and effective for controlling the rotation motor and feed cylinder; thus, the proposed method significantly reduces the SDR during drilling operations in underground coal mines.

As the PIDC strategy solves the SDR problem in underground coal mines, it greatly improves the safety of coal mine operation and decreases the power cost. Consequently, it brings the considerable benefits of coal mine production and vast application prospects in other corresponding fields. Actual drilling conditions are difficult to accurately simulate in a laboratory; thus, for future work, drilling experiments can be conducted in actual underground coal mines.

The PIDC-based anti-SDR strategy proposed in this study satisfactorily controls the rotation motor and feed cylinder and facilitates the feed and rotation movements. Furthermore, the tangible novelty of this study results is that it improves the frequency response of the entire drilling system. The drilling process with PIDC decreased the occurrence of SDR by 50%; therefore, the anti-SDR strategy can significantly improve the safety and efficiency of underground coal mining.

This paper aims to propose a simple but robust three-node triangular membrane element with rational drilling DOFs for efficiently analyzing plane problems.

This new element is developed within the general framework of unsymmetric FEM. The element test functions are determined by using a conforming displacement field which is slightly different with the classical Allman’s interpolations, while a self-equilibrated stress field formulated based on the analytical airy stress solutions is adopted as the trial functions. To ensure the correctness between the drilling DOFs and the true rotations in elasticity, reasonable constraints are introduced through the penalty function method. Moreover, the special quadrature strategy is used for operating related integrations for future enrichment of element behavior.

Numerical benchmark tests reveal that this new triangular membrane element has exceptional prediction capabilities. In particular, this element can correctly reproduce a rigid body rotation motion and correctly undertake the external in-plane twisting moments; thus, it is a reasonable choice for being used to formulate flat shell elements or to be connected with other kind of elements with physical rotational DOFs.

This work provides a new approach for developing high-performance lower-order elements with simple formulations and good numerical accuracies.

Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore aims to give the reader an encyclopaedic view on the subject. The bibliography at the end of the paper contains 2,025 references to papers, conference proceedings and theses/dissertations dealing with the analysis of beams, columns, rods, bars, cables, discs, blades, shafts, membranes, plates and shells that were published in 1992‐1995.

Reliability plays an important role in the execution of the maintenance improvement and the understanding of its concepts is essential to predict the type of maintenance according to the equipment state. Thereby, a computational tool was developed and programming with VBA in Excel® for reliability and failure analysis in a mining context. The paper aims to discuss these issues.

The developed approach use the modeling of stochastic processes, such as the renewal process, the non-homogeneous Poisson process and less conventional method as the Bayesian approach, by considering Jeffreys non-informative prior. The resolution gives the best associated model, the parameters estimation, the mean time between failure and the reliability estimate. This approach is validated with the reliability analysis of inter-failure times from underground rock bolters subsystems, over a two-year period.

Results show that Weibull and lognormal probability distribution fit to the most subsystems inter-failure times. The study revealed that the bolting head, the rock drill, the screen handler, the electric/electronic system, the hydraulic system, the drilling feeder and the structural consume the most repair frequency. The hydraulic and electric/electronic subsystems represent the lowest reliability after 50 operation hours.

For the first time, this case study defines practical failures and reliability information for rock bolter subsystems based on real operation data. This paper is useful to the comparative evaluation of rock bolter by detecting the weakest elements and understanding failure patterns in the individual observation subsystems on the overall machine performance.

The purpose of this paper is to study the inter-element coupling effect of membrane and plate components between two adjacent shells occurring on the common boundary.

In this paper, three triangular flat shells developed by combining an excellent membrane element (OPT) with three outstanding plate bending elements (DKT, RDKTM and DST-BK), respectively, are used to study this phenomenon. Benchmark tests are implemented to evaluate the performance of three selected plate elements and the formulated flat shells.

The inter-element coupling effect of membrane and plate components belonging, respectively, to two adjacent shells deteriorate the performance of shells. Therefore, a shell’s performance cannot be guaranteed certainly by the superimposed membrane and plate behaviors.

The “order matching” criterion is proposed to explain this phenomenon and it is concluded that the flat shell that follows this criterion explicitly may alleviate or even overcome the inter-element coupling effect.

Previous studies mainly focus on formulation of high-performance membrane and plate elements. However, the inter-element coupling effect of membrane and plate components between two adjacent shells occurring on the common boundary, has attracted less attention. Thorough benchmark tests for three flat shells are implemented to investigate the phenomenon. The results shows that the inter-element coupling effect deteriorates the performance of shells. And the “order matching” criterion is proposed to explain this phenomenon and it is concluded that the flat shell that follows this criterion explicitly may alleviate or even overcome the inter-element coupling effect.

The objective of this work was to demonstrate a novel approach to human machine interaction that seamlessly uses teleoperation and automation in a complex environment.

This work leverages developments in the area of operational software Operational Software Components for Advanced Robotics (OSCAR), decision making, human‐machine interface, and motion planning. This demonstration uses a 17 degrees‐of‐freedom (DOF) dual arm robot that is equipped with modern tool changers, crash protectors, force‐torque sensors and electrical and pneumatic power at the tools. Four different end‐effector tools are also provided. These are electric grippers, electric rotary saw, electric drill, and a pneumatic spray gun. The system can be used both in teleoperation and automation mode. In teleoperation mode, the user has a choice of five different input devices. These are computer keyboard, spaceball and spacemouse, RSI manual controller and kraft force feedback controller. Automation is performed using a novel graphical user interface with 3D graphics used for previewing and verifying manipulator motion. Automation tasks that are demonstrated include automatic grasping, sawing, drilling, spray painting, point‐to‐point motion, and teaching. The controller for the dual arm system is developed using OSCAR and supports a variety of decision‐making algorithms and obstacle avoidance. The integration of this controller with the input devices and human machine interface is done using a novel protocol that is based on Extensible Markup Language (XML) for maximum reuse and distributed integration. This protocol is further based on a well‐defined and scalable XML schema that can be easily extended as controller functionality is changed and/or additional input devices are added.

It is necessary to combine automation with teleoperation to reduce worker fatigue and also provide higher value robotic functions. This is possible as most remote tasks can be broken down into structured and unstructured components. On the integration front, we see XML‐based integration providing a loosely coupled system that can make interoperability between various robot systems possible. For end‐effector tooling, it is better to have special purpose tools that can be switched out versus the use of a general purpose tool such as a robotic hand.

This research was done in a laboratory environment, and as such, its application in the field will require partnering with a commercial entity. Force‐feedback on manual controllers during teleoperation was not very effective. In fact, providing visual queues to the operator about the forces were a better guide to the operator.

The software for this work provides obstacle avoidance capability. The obstacle avoidance is based on a known world model that is derived from a CAD environment. In reality, this model will have to be sensed in real‐time, and decoded into a geometric model. Significant work in this area needs to be done.

The software developed for this work was based on the OSCAR software framework. This is a unique framework that at its core uses performance criteria to control the behavior of the robot during teleoperation and automation. The value of this work is that it shows as completely feasible the control of a 17 DOF dual arm system using the latest integration technologies (such as XML), integrated simulation, multiple tools and multiple input devices. It also shows that all these choices can be provided to an operator through a single user interface.

For the drilling of polyimide multilayers with acrylic adhesives, more care must be taken than for epoxy glass material. Due to the different mechanical properties in the multilayer ‘sandwich’ of the polyimide and the acrylic adhesive layers, the drilling parameters require a higher level of control. To avoid defects in the hole, such as nail heading of the polyimide or an uncontrolled ‘rip‐out’ of the acrylic adhesive, the relation between the cutting speed of the drill and the feed needs to be adjusted for each drill diameter. The following guidelines are valid: Wider drill diameters require a lower rotational speed and a lower feed to avoid deformation of the polyimide in the hole. Smaller drill diameters need high rotational speeds and a higher feed to minimise smear. In general, the drilling performance of wider drills is better than that of smaller drills. In all cases, it was impossible to prevent smear of the acrylic adhesive in the multilayer holes. The only reliable method for removing acrylic smear is by plasma etching. The minimum etch‐back required for acrylic adhesive was found to be ≥6 µm, which would be equivalent to an etch‐back of only 2 µm of the polyimide film. To achieve the etch‐back rate, the time in the plasma chamber should be between 20 and 30 minutes at 90–110°C. After the etch‐back, a high pressure water rinse is needed to remove some residues in the hole prior to through‐plating.

The flexible printed circuit (FPC) board with the characteristic of light and thin strengthened confronted the growing miniaturization requirements of the electronic product and the popularity of wearable devices. The reliability of circuit could be influenced by the hole quality of FPC, such as burrs, which is one of the major problem in FPC.

In this paper, micro-drill with a diameter of 0.1 mm was used to drill the double-sided flexible copper clad laminate. The thrust force, the burr and tool wear were investigated. The influencing factors of the height of the burrs were studied. The relationship between the thrust force and the height of the burrs was also explored. Finally, the formation mechanism of burrs was analyzed.

The entrance burrs were usually less than the exit burrs. The burr height increased with the feed per rotation. The height of the burr increased with the increase of the thrust force for the plastic deformation of the copper foil was dominant. The abrasion of the drill gave rise to increase the height of burr. In micro-hole drilling, the growth of burrs can be suppressed effectively by reducing the clearance between the FPC and the backup plate. The thrust force would be controlled in a certain range to reduce the burr with specific drilling parameters. There existed a certain relationship of Gaussian distribution between the height of the burrs and the thrust force of FPC.

The reliability of the integrated circuit was directly affected by the burrs of the FPC. This research on the formation mechanism of FPC burrs and forecast of burr height provided a firm foundation for further work in the area of improvement of the micro-hole quality.

In this work we present interrelations between different finite rotation parametrizations for geometrically exact classical shell models (i.e. models without drilling rotation). In these kind of models the finite rotations are unrestricted in size but constrained in the 3‐d space. In the finite element approximation we use interpolation that restricts the treatment of rotations to the finite element nodes. Mutual relationships between different parametrizations are very clearly established and presented by informative commutative diagrams. The pluses and minuses of different parametrizations are discussed and the finite rotation terms arising in the linearization are given in their explicit forms.