Joint Layout Research Articles

Joint layout, pipe size and hydraulic reliability optimization of water distribution systems

A multicriteria maximum-entropy approach to the joint layout, pipe size and reliability optimization of water distribution systems is presented. The capital cost of the system is taken as the principal criterion, and so the trade-offs between cost, entropy, reliability and redundancy are examined sequentially in a large population of optimal solutions. The novelty of the method stems from the use of the maximum-entropy value as a preliminary filter, which screens out a large proportion of the candidate layouts at an early stage of the process before the designs and their reliability values are actually obtained. This technique, which is based on the notion that the entropy is potentially a robust hydraulic reliability measure, contributes greatly to the efficiency of the proposed method. The use of head-dependent modelling for simulating pipe failure conditions in the reliability calculations also complements the method in locating the Pareto-optimal front. The computational efficiency, robustness, accuracy and other advantages of the proposed method are demonstrated by application to a sample network.

Topology optimization by penalty (TOP) method

In traditional structural topology optimization (TO), the material properties of continuum finite elements of fixed form and coupling are varied to find the optimal topology that satisfies the design problem. We develop an alternative, fundamental formulation where the design space search is dependent on the coupling, and the goal of the topology optimization by penalty (TOP) method is to determine the optimal finite element coupling constraints. By this approach, seemingly disparate topology design problems, e.g., the topology design of structural supports, topology optimization for fluid mechanics problems, topology optimization with convective heat transfer, topology optimization by the element connectivity parameterization method, and the optimal layout of structural joints, can be understood as related formulations under a common topology optimization umbrella, and more importantly, this general framework can be applied to new design problems. For example, in modern multibody dynamics synthesis, the geometric form of finite elements of fixed material properties and interconnectivity are varied to find the optimal topology that satisfies the mechanism design problem. The a priori selection of coupling, e.g., by revolute or translational joints, severely limits the design space search. The TOP method addresses this limitation in a novel way. We develop the methodology and apply the TOP method to the diverse design problems discussed above.

Enhancing the Reliability of Wafer Level Packaging by Using Solder Joints Layout Design

During the design and manufacturing processes of electronic packaging, solder joints are fabricated using a variety of methods to provide both mechanical and electrical connections for different applications. They include flip chip, wafer level chip scale packaging (WLCSP), fine pitch ball grid array (BGA), and chip scale packaging (CSP). The solder joint shape prediction methods have been incorporated as a design tool to enhance the reliability of the WLCSP. However, the reliability of solder joints for a large chip size such as 10mmtimes10mm without underfill remains questionable. In this research, a hybrid method combining an analytical algorithm with the energy-based approach is applied to predict standoff heights and geometry profiles of the solder joints. In addition, a hybrid-pad-shape system is proposed to design the solder ball layout, and to enhance the reliability of the solder joints. Next, a nonlinear and parametric finite element analysis is conducted to investigate the reliability issues that result from several design parameters. In addition, an experimental validation is completed to verify the correctness and feasibility of the solder joint shape prediction methods and finite element analysis procedures. The design parameters considered in this study include solder joint layout, solder volume, pad diameter, as well as the ratio and orientation of the elliptical pad. With regards to solder joint layout design, the solder joints located in the corner areas can be considered as structural dummy balls with no electrical signals passing through them. The results reveal that when the WLCSP has large round pads, or properly oriented elliptical solder joint pads at the corner areas underneath the chip, then the maximum equivalent plastic strain of the solder joints will be effectively reduced. As a result, the solder joint fatigue life under thermal loading will be greatly enhanced. Furthermore, the findings of this research can be used as a design guideline for electronic packaging with area array interconnections such as CSP, flip chip packaging, Super CSP, and fine pitch BGA

Application of a max–min ant system to joint layout and size optimization of pipe networks

The application of a max–min ant algorithm to the layout and size optimization of pipe networks is described in this paper. The formulation conventionally used for the pipe size optimization of networks with fixed layout is extended to account for the layout determination of the networks. This is achieved by including new constraints regarding the reliability of the network and modifying some of the constraints of the optimization problem. A deterministic concept of reliability is used in which the number of independent paths from source nodes to each of the demand nodes is considered as a measure of reliability. The method starts with a predefined layout which includes all possible links. The method is capable of designing the layout and pipe sizes of water distribution networks of predefined reliability including tree-like and looped networks. It is also shown that a layout optimization of a network followed by size optimization does not lead to an optimal or a near-optimal solution. This emphasizes the need for simultaneous layout and size optimization of networks if an optimal or near-optimal solution is desired. The performance of the method for layout and pipe size optimization of pipe networks is tested against two benchmark examples in the literature and the results are presented. The first example is considered to show the necessity of joint layout and size optimization even for the simple tree networks while the second example is considered to illustrate the efficiency of the proposed method for layout and size optimization of real-world networks with different levels of reliability.

FORCE-UNCONSTRAINED POSES FOR PARALLEL MANIPULATORS WITH REDUNDANT ACTUATED BRANCHES

A study of the effect of including a redundant actuated branch on the existence of force-unconstrained configurations for a planar parallel layout of joints is presented1. Two methodologies for finding the force-unconstrained poses are described and discussed. The first method involves the differentiation of the nonlinear kinematic constraints of the input and output variables with respect to time. The second method makes use of the reciprocal screws associated with the actuated joints. The force-unconstrained poses of non-redundantly actuated planar parallel manipulators can be mathematically expressed by means of a polynomial in terms of the three variables that define the dimensional space of the planar manipulator, i.e., the location and orientation of the end-effector. The inclusion of redundant actuated branches leads to a system of polynomials, i.e., one additional polynomial for each redundant branch added. Elimination methods are employed to reduce the number of variables by one for every additional polynomial. This leads to a higher order polynomial with fewer variables. The roots of the resulting polynomial describe the force-unconstrained poses of the manipulator. For planar manipulators it is shown that one order of infinity of force-unconstrained configurations is eliminated for every actuated branch, beyond three, added. As an example, the four-branch revolute-prismatic-revolute mechanism (4-RPR), where the prismatic joints are actuated, is presented.

Force-unconstrained poses for a redundantly-actuated planar parallel manipulator

A study of the effect of including redundant actuators on the existence of force-unconstrained configurations for a planar parallel layout of joints is presented. The 3-branch, revolute-jointed, 8-bar configuration is considered in detail. This layout is referred to as a 3-RRR configuration to denote its three branches and the number of joints per branch. Concepts of reciprocal screw quantities and kinematic geometry are used to determine the feasibility of the existence of force-unconstrained positions. Redundant actuation is discussed from the perspective of eliminating families of degeneracies. For the 3-RRR it is shown that one order of infinity of unconstrained configurations is eliminated for each actuator, beyond three, added.

A maximum entropy based approach to the layout optimization of water distribution systems

This paper investigates the idea that minimum cost maximum entropy designs of water distribution systems can be used to identify good layouts of water distribution systems in the sense that designs based on these layouts could achieve a reasonable compromise between reliability and cost. The proposed approach presupposes that there is a sufficiently strong relationship between entropy and reliability to achieve this purpose. Evidence is provided to support this view. A fundamental issue relating to the invariance of the entropy function with respect to permutations of its arguments is also addressed. The proposed technique is assessed using an example, which shows that the method yields good solutions to the joint layout, reliability and pipe-size optimization problem. It is also shown that if two or more layouts of a water distribution system have the same maximum entropy value, then minimum cost maximum entropy designs based on these layouts can be expected to be similar in terms of their overall performance.

Reconfigurable main‐arm for assembly of all revolute‐only kinematically simple branches

Within previous work by Podhorodeski and Pittens,a class of kinematically simple (KS) joint layouts was defined for spatial serial joint-assemblies consisting of revolute joints only. The identified KS class of layouts was comprised of main-arms with three successively parallel and/or perpendicular revolute joints and end located spherical joint groups. Arguments of degeneracy and kinematic equivalency can be used to demonstrate that only five unique main-arm layouts belong to the KS class. Within the current work, the design of a reconfigurable main-arm (RMA) allowing the construction of all of the KS branches is examined. Sufficient joints are included within the RMA to allow, by the locking of certain joints and the freeing (actuation) of others, the kinematic attributes of each of the unique KS main-arm layouts to be acquired. It is concluded that five successively perpendicular revolute joints are required within the RMA to allow such reconfiguration. Inverse kinematic solutions are presented for each of the five layouts. Potential RMA applications, use of the RMA for kinematically redundant layouts, and an RMA prototype are discussed. ©2000 John Wiley & Sons, Inc.

Strand resistance distribution in an improved full size joint for the ITER conductors

An improved joint layout is proposed for the electrical connections of the large Nb/sub 3/Sn cable-in-conduit conductors for the central solenoid and toroidal field coils of ITER, International Thermonuclear Experimental Reactor. The driving design criteria are a reliable electrical performance and an easy manufacturing procedure, limiting the risk of failure and allowing generous assembly tolerances. The development results are reported, as well as the manufacture of a hairpin joint using sections of the ITER CS conductor. The joint sample has been used to investigate the resistance between strand pairs belonging to the two conductor sections. From the distribution of the strand-to-strand resistance, it is possible to infer the current distribution in the conductor under DC conditions, which is a crucial issue for the stability analyses.

Further improvement of optimisation method for mass transit signalling block-layout design using differential evolution

The paper describes the ongoing development of optimisation methods for the layout design of equi-block n-aspect mass transit signalling systems. The authors previously applied genetic algorithms (GAs) in place of conventional gradient search methods for solving the problem. Being theoretically and empirically sound for providing multiple-point search, the GA-based approach simplifies the gradient search approach, broadens the scope for dealing with changes of either the objective function or signalling scheme, and provides robust and global convergence in complex search spaces. The GA-based formulation divides an inter-station run into three sections: a constraint section, a stretchable section and a critical section. Since each of these sections was prescribed with a different design criterion, the GA optimises separately the layout of block joints in each section and their positions within each section. The solution time for optimal signalling design is further reduced with the use of differential evolution (DE) algorithms. The DE-based method combines the three subordinate objective functions in the original GA algorithm into one composite objective function for one single search. The performance improvements of the DE algorithms over the GA-based method are shown. The choice of variants for solving the DE-based signalling design problem is also discussed.

Single-bolt tension joint tests on pultruded GRP plate — effects of tension direction relative to pultrusion direction

The literature on single-bolt tension joints in structural grade pultruded GRP plate is reviewed and the differences between the main investigations are highlighted. Details are given of the test setup and the joint configurations used in a series 54 such tests on single-bolt joints in which the angle between the pultrusion and tension axes (the off-axis angle) and the joint geometry are varied. Ultimate strength, intial stiffness, initial bolt slip and bolt displacement at failure data are presented as functions of the joints' principal geometric ratios. The observed joint failure modes show that, for off-axis angles ≥ 30 °, bearing failure (a relatively benign failure mode) does not arise. Instead, tension mode failure predominates and cracks tend to propagate parallel to the rovings diagonally across the width of the joint. It is concluded that the rovings play a significant role in controlling the crack propagation and this has implications for joint layout and design in pultruded GRP plate.

Strategies for economic design of unbraced steel frames

In frame design for optimal economy, beam and column properties, as well as the properties of the joints, should be selected in such a way that economy can be achieved during fabrication. A method by which an impression of the possible layout of rigid joints can be obtained in a very early design stage is presented. The method is simple and straightforward, requiring only a limited amount of design information. It allows the effects of the increase of beam or column sections on the joint layout to be investigated. The joints normally will behave semirigid. The layout can be checked with a simple hand method based on the principle that the solution with semirigid joints should have the same performance as that with rigid joints.

Improved optimisation method using genetic algorithms for mass transit signalling block-layout design

The application of an improved optimisation technique to an existing block-layout design process is proposed for equi-block n-aspect (n ≥ 2) mass transit signalling systems. The approach is built upon previous published work by applying genetic algorithms (GA) in place of conventional gradient search methods. The genetic algorithms have been proven theoretically and empirically for providing multiple-point search, as well as robust and global convergence in complex search spaces. Such characteristics have enabled GAs to simplify the original approach and to broaden its scope for dealing with either changes of the objective function or changes of the signalling scheme. In the proposed formulation, a railway line between two stations is divided into three sections, namely: a constraint section, a stretchable section and a critical section. Since each of these sections is prescribed with a different headway design criterion, GA is applied separately to each section to optimise the layout of block joints and their positions within each section. Train performance simulation is then used to verify each optimised signalling design against the overall requirements of mass transit signalling systems operation. It is also used to calculate the objective function for each candidate solution as generated by GA. Comparative studies are presented to show improvements made by GAs over conventional optimisation techniques.

Investigation of composite materials selection and joint layout design to enhance EMI shielding of electronic equipment

AbstractElectromagnetic shielding is a critical issue in the design of electronic equipment. This is mostly due to the high receptivity of electronic components to unwanted electromagnetic emission and interference. To reduce this interference, a study is initiated to determine the effect of material and joint types on the shielding effectiveness of an electronic enclosure. Eight different but progressively more complex joints are designed and investigated in this study. Filled polymers and metallized filled polymers are selected and compared with the all metallic structures. An analytical approach utilizing conformal mapping to calculate the shielding effectiveness of joints is attempted. An experimental apparatus is designed and manufactured to aid in finding the best possible joint configurations. Economic factors in selecting optimum joint layout are also studied. A cost index relating the effective length, design factors, and the total length of the part is developed. Results are presented for the best joint configuration and material with the highest shielding effectiveness.

乾式部材を用いた住宅外壁面における施工者の割付設計の特性

The purpose of this paper is to make it clear how workers decide design of joint layout of siding board on the exterior wall of a detached house. Questionnaires in reference of materials, considerations in deciding joint layout and the setting of joint layout in elevation models have been sent to 867 exterior wall workers. Main conclusions are the followings : 1) The more experience the workers have, the more frequently they consider drawings, conditions of construction site, outcome after completion, efficient utilization of siding boards, constructability, etc. together. 2)Theories about design of joint layout don't seem to apply much to the setting of joint layout by workers. 3) The setting of joint layout that workers believe to be efficient in utilizing siding boards, may not increase the ratios of boards' utility necessarily, and the layout believed to decrease the work-time improving constructability in most of the case.

A Class of Parallel Manipulators Based on Kinematically Simple Branches

Parallel manipulators consisting of serial branches acting in parallel on a common end effector are examined. All nonredundant, six DOF manipulators corresponding to this in-parallel class of structures are enumerated. A specific in-parallel structure, three branches with two actuated joints per branch (3–2,2,2), is chosen as most promising based upon performance considerations. A class of kimematically simple (KS) serial-chain branch joint layouts suitable for the chosen in-parallel structure is defined. Arguments based upon kinematic equivalency of the branches and mobility of the assembled in-parallel manipulator chain are used to show that there exist only five unique branch joint-layouts belonging to the KS class. It is demonstrated that the solution to the inverse displacement problem for in-parallel manipulators based on the KS branches can be expressed in a closed form. Furthermore, the 3–2,2,2 in-parallel manipulators are shown to belong to a family of manipulators whose forward displacement solutions can be resolved through roots of a 16th order polynomial.

乾式外壁を用いた一戸建住宅における外壁面の割付寸法と外壁材寸法の検討 : 住宅の外壁構法計画に関する研究 その3

乾式外壁を用いた一戸建住宅における外壁面の割付寸法と外壁材寸法の検討 : 住宅の外壁構法計画に関する研究 その3

La construcción con bloque: orientaciones constructivas y de proyecto

Concrete blocks are materials that have hardly been used in Spain up until recently, and for this reason the handling peculiarities are not sufficiently known. This article explains and discusses the good practice standards admitted all over the world for this material. Emphasis is placed on the characteristics that the block should have, the choice of suitable mortars, links with the blocks factory and the rest of the work site, and the limited dimensions of the panels. Recommendations are also given for the layout of the control joints and correct fitting of the reinforcement frame. The work is divided into four parts, corresponding to general recommendations, respectively, for: partition work, enclosing walls and weight-bearing walls: The resistant calculation in also described for the latter, based on varios European standards. Finally, a bibliography is included on the matter.