Complicated Parts Research Articles

Reduced-order modelling for real-time physics-based variation simulation enhanced with adaptive sampling and optimized interpolation

AbstractManufacturing industries require a right-first-time paradigm to remain competitive. Variation simulation (VS) is a key tool to predict variation of the final shape of flexible assemblies, allowing to reduce defects and waste. VS models involving compliant sheet-metal parts commonly integrate physics-based simulation with statistical approaches (usually Monte Carlo simulation). Although increasingly used as a backbone of synthesis techniques for (stochastic) optimization of assembly systems, the main roadblock of VS methods is the intense computational costs due to time-intensive simulations and high-dimensional design space. Driven by the need of time reduction, this paper presents an innovative real-time physics-based VS model of assembly systems with compliant sheet-metal parts. The proposed methodology involves a non-intrusive reduced-order model (niROM), empowered by a novel adaptive sampling procedure for dataset generation, and a cross-validation-based optimized radial basis function (RBF) formulation for interpolation. Demonstrated through two case studies—(i) a remote laser welding operation to predict mechanical distortions, with two input parameters, and (ii) the assembly of an aircraft vertical stabilizer with five input parameters—the methodology achieves accurate real-time results, with up to a 43% improvement in accuracy compared to traditional sampling techniques. Findings highlight the critical influence of the sampling strategy and the number of input parameters on ROM accuracy. Better results are reached by employing adaptive sampling in combination with optimum RBF, which additionally disengages the user from the choice of the interpolation settings. This study unlocks new avenues in the field of variation simulation and dimensional/quality monitoring by narrowing the gap between any advanced CAE solver and VS models with real-time physics-based simulations.

A six-axis force and torque sensor consisting of compliant mechanisms and full-bridge strain gauges

Compliant mechanisms offer the deformable structure that is required by a force and torque sensor (FTS). If strain gauges must be manually attached to a deformable structure’s side surface, considerable expense is incurred. By contrast, installation on bottom and top surfaces can be automated, thereby simplifying FTS fabrication. A six-axis FTS comprising H-bridge amplification mechanisms with 24 strain gauges (serving as strain sensors) appended to only the bottom and top surfaces, with the gauge connections creating six full Wheatstone bridges, was proposed. Analytical models of the functional relation among the applied strain, force and torque, and stress of the compliant parts were developed and validated using the finite-element method. A prototype was calibrated to acquire a cubic polynomial transformation matrix and achieved a mean error of 1.06 %. Moreover, thermal stability experiments revealed that the variation of the strain signal was under 0.07 % over a temperature range of 30 °C.

Fixturing Scheme Design in the Shipbuilding Industry: A Fixture Amount and Layout Optimization for Curved Compliant Parts

Fixturing Scheme Design in the Shipbuilding Industry: A Fixture Amount and Layout Optimization for Curved Compliant Parts

Optimization of Cargo Pump Treatment by Hydrochloric Acid (HCl) Loading at MT. Cipta Anyer

The research is motivated by the occurrence of mechanical seal leakage in cargo pumps, which hampers the efficiency of the loading and unloading process. A mechanical seal is a mechanical component used in various industrial applications, such as pumps, to prevent leakage from the rotating shaft and stationary wall.
 The research method used in this thesis is qualitative descriptive, employing the SWOT (Strengths, Weaknesses, Opportunities, and Threats) approach to facilitate data analysis. The data collection methods utilized by the author include observation, interviews, and documentary studies to strengthen the data analysis. The objectives of this research are to identify the causes of damage to the mechanical seal, the handling of mechanical seal damage, and the efforts/methods to prevent mechanical seal damage on MT. Cipta Anyer.
 The conclusion revolves around the causes of mechanical seal damage, the methods to handle such damage and preventive measures. The causes of damage include surface wear connected to the pump shaft, direct contact of hydrochloric acid (HCl) with the cargo pump, and incorrect installation of spare parts for the mechanical seal. Solutions to address the damage involve identifying the specific issues, replacing them with genuine and compliant spare parts, and ensuring proper and procedure-compliant installation. To prevent damage, it is advisable to utilize modern equipment, maintain supervision by engineers, and select experienced crew members.

Fixture layout optimization of large compliant ship part assembly for reducing and straightening butt clearance

Fixture layout is an essential factor in intelligent manufacturing in the shipbuilding industry, affecting assembly quality and efficiency. Its optimization has become an urgent problem in the assembly process of compliant parts. Traditional fixture layout depends on workers’ experience, which leads to butt clearance along the assembly interface. Thus, this article proposes a butt clearance control-oriented fixture layout optimization (BCCFLO) methodology. First, a method for calculating the part dimensional variation under the influence of fixture layout and fixture locating error is developed. Then, a constrained multi-objective integer nonlinear programming (CMINP) model is innovatively formulated to optimize the fixture layout. Furthermore, the non-dominated sorting genetic algorithm-II based on Latin hypercube sampling is designed to address the CMINP model. The case study illustrates and validates that the fixture layout achieved by the proposed method could significantly control the butt clearance for large compliant part assembly in the shipbuilding industry.

High-precision deformation prediction for compliant parts in the ship sub-assembly process

In the ship sub-assembly process, large compliant parts are common and generally thin. These compliant parts are normally easy to deform under the influence of gravity, which will greatly affect the accuracy of the sub-assembly processes. Thus, it is important to predict the deformation of the compliant part under a given fixture layout in advance. In current practice, existing methods of post-compensation are usually used to correct the deformation of the compliant part, which are inefficient and costly. In this paper, a transformer-based surrogate model with two-stage Latin hypercube sampling (TSM-TSS) is established. This surrogate model considers each fixture position and its deviation to predict the deformation of the entire compliant part. Compared with BPNN and Kriging, a case study reveals that TSM-TSS can predict the deformation of compliant parts with an error of 0.061mm. With the application of TSM-TSS, the deformation of the compliant part under gravity can be predicted accurately and the efficiency of shipbuilding can be improved.

Modeling Variation in Multi-Station Compliant Assembly Using Parametric Space Envelope

Abstract Compliant parts have different characteristics from rigid parts and are used frequently in industries. One of the biggest challenges facing by industries is geometric variation management of these compliant parts which can directly impact product quality and functionality. Existing rigid body-based variation modeling approaches are not suitable for compliant assembly while finite element analysis-based methods have the disadvantages of requiring heavy computation efforts and detailed design information which is unavailable during preliminary design phase. Hence, this paper proposes a novel geometric variation propagation model of multi-station compliant assembly based on parametric space envelope. Three sources of variation: location-led positional variation, assembly deformation-induced variation, and station transition caused variation are analyzed. In this study, geometric variations are modeled indirectly through control points of constructed variation tool. Compared with existing methods where geometric variation is modeled by tracking key feature points on the manufacturing part, the proposed approach brings unique benefits. It can deal with arbitrary complex compliant part, and it provides a unified modeling framework for different types of variation. The method is illustrated and verified through a two-station three parts case study on a multi-station compliant panel assembly. The proposed method provides industries with a new way to manage geometric variation from compliant assembly.

Multi-objective trajectory optimization of the manipulator transferring compliant sheet metal parts

The deformation of the compliant part is the key factor that affects the production efficiency of the automobile press line. Considering multi-manipulator trajectories and part contours, this paper quantitatively analyzes the deformation of compliant parts when the manipulator transfers sheet metal parts. A multi-objective co-optimization method is proposed to generate smooth motion curves with smaller velocity, acceleration, and jerk. Based on the built-in module of rigid to flex in ADAMS software, some rigid parts such as the end effector and sheet metal part are transformed into compliant ones. And the redundant manipulator in the press line is taken as the representative case to check whether the trajectory performance is conducive to deformation suppression. Simulation result shows that the jerk curve without cusp points is more conducive to suppressing the part deformation than that with cusp points.

An Approach to Variation Simulation of Final Aircraft Assembly With Presence of Sealant

Abstract The article discusses the process of aeronautical structure assembly in the presence of a sealant between the parts to be joined. An attempt to estimate the influence of sealant on assembly quality in terms of variation analysis is presented. The sealant is considered a highly viscous liquid that is applied to the surfaces of the assembled parts before the start of the final assembly. The modeling approach is based on the simulation of two-way coupled fluid–structure interaction between fluid sealant and compliant structural parts. Reynolds lubrication approximation is used in the fluid dynamics problem and variational formulation of contact problem combined with static condensation is used in the structural one. The joining of two aircraft panels is used as a numerical test for demonstration of the developed approach. Various phenomena connected with the presence of sealant are demonstrated. In particular, the difference in the fastener loosening due to sealant flow between different types of fasteners is investigated. Results of variation simulation show that the presence of sealant should be considered among determining factors in the analysis of assembly quality.

Numerical Approach for Detecting the Resonance Effects of Drilling during Assembly of Aircraft Structures

This paper is devoted to the development of a numerical approach that allows quick detection of the conditions favorable for the beginning of noticeable vibrations during drilling. The main novelty of the proposed approach lies in taking into account the deviations of the assembled compliant parts during non-stationary contact analysis by means of variation simulation. The approaches to stationary analysis of assembly quality are expanded and generalized for modeling such non-stationary effects as vibration and resonance. The numerical procedure is based on modeling the stress–strain state of the assembled structures by solving the corresponding transient contact problem. The use of Guyan reduction, the node-to-node contact model and the application of the generalized α method allow the reformulation of the contact problem in terms of a series of quadratic programming problems. The algorithm is thoroughly tested and validated with commercial software. The efficiency of the developed numerical procedure is illustrated by analysis of the test joints of two aircraft panels. The unsteady process of drilling the panels with periodic drilling force was simulated. The influence of deviations in the shape of the parts on the non-stationary interlayer gap was modeled by setting different initial gaps between parts. It is shown that the oscillation amplitudes of the interlayer gap depend on the initial gaps and do not correlate with the mean value of the stationary residual gap. Thus, non-stationary analysis provides new information about the quality of the assembly process, and it should be applied if the assembly process includes periodic impact on the assembled parts.

Glue modelling in variation management of compliant assemblies: critical issues and possible solutions

ABSTRACT Variation management aims to reduce the effects of geometric variations of parts to assemble. Industry is facing a digital revolution in being able to manage geometrical deviation data along the entire lifecycle of a product. This requires the development of new assembly simulation models and tools. New design trends are orienting towards more and more lighter products. They are constituted by thin metal sheets or in composite material. Lighter products in composite materials are always joined through structural adhesive. This work presents different ways to model the adhesive inside a simulation that allows to predict the geometrical variations of an assembly constituted by compliant parts. Three different ways to model adhesive, i.e. glue contact, beam and shell elements, were taken into account. Different thickness values, different component constraints and application points of part variations were also considered. Two lighter assemblies were considered: one constituted by two metal plane sheets that are partially overlapped; the second is formed by three thin sheets in composite material, one plane and two L-shaped. The critical issues connected with the three different solutions to model adhesives in a simulation to manage geometric variations from component to assembly were underlined to guide a possible choice.

Optimal Design of Fixture Layout for Compliant Part With Application in Ship Curved Panel Assembly

AbstractIn a ship assembly process, a large number of compliant parts are involved. The ratio of the part thickness to the length or the width is typically 0.001–0.012. Fixture design is a critical task in the ship assembly process due to its impact on the deformation and dimensional variation of the compliant parts. In current practice, fixtures are typically uniformly distributed under the part to be assembled, which is non-optimal, and large dimensional gaps may occur during assembly. This paper proposed a methodology for the optimal design of the fixture layout in the ship assembly process by systematically integrating direct stiffness method and simulated annealing algorithm, which aims to minimize dimensional gaps along the assembly interface to further improve the quality and efficiency of seam welding. The case study shows that the proposed method significantly reduced the dimensional gaps of the compliant curved panel parts in a ship assembly process.

Object Shape Error Response Using Bayesian 3-D Convolutional Neural Networks for Assembly Systems With Compliant Parts

This article proposes a novel object shape error response (OSER) approach to estimate the dimensional and geometric variation of assembled products and then, relate these to process parameters, which can be interpreted as root causes (RC) of the object shape defects. The OSER approach leverages Bayesian 3-D convolutional neural networks integrated with computer-aided engineering simulations for RC isolation. Compared with the existing methods, the proposed approach: 1) addresses a novel problem of applying deep learning for object shape error identification instead of object detection; 2) overcomes fundamental performance limitations of current linear approaches for RC analysis (RCA) of assembly systems that cannot be used on point cloud data; and 3) provides capabilities for unsolved challenges such as ill-conditioning, fault-multiplicity, RC prediction with uncertainty quantification, and learning at design phase when no measurement data are available. Comprehensive benchmarking with existing machine learning models demonstrates superior performance with R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.98 and MAE = 0.05 mm, thus improving RCA capabilities by 29%.

Early Stage Variation Simulation and Visualization of Compliant Part Based on Parametric Space Envelope

Compliant, nonrigid parts are widely used in many industries today. Existing variation simulation analysis on the manufacturing part focuses on orientation and position deviation with part shape errors being largely omitted. This is a valid approach for the rigid part, but it is unrealistic and can be problematic for the compliant part. In this study, a new methodology has been introduced to compliant assembly early phase design to generate various probable variated manufacturing parts that conform to predefined tolerance specification or meet the certain industrial requirement. The proposed method is based upon the novel idea of a parametric space envelope, a purpose-designed variation tool constructed from parametric curves. Variation of embedded manufacturing part is linked to and controlled by a compact set of envelope’s boundary control points. Part variation instances are generated by simulating the control points’ movement in a systematic and efficient way. Importantly, simulated variations can be visualized in 3-D virtual space to provide user insight into part variation. The proposed methodology can help identify assembly high-risk regions, select proper fixtures, guide assembly engineering changes, and optimize assembly operations. An industrial case study on a deformable vehicle door hinge plate is presented to illustrate the methodology. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This article is motivated by two acute problems encountered in geometric variation simulation analysis for compliant parts in the early design stage. First, form errors of the nonrigid part are not fully captured in existing methods. Second, variation visualization can significantly enhance understanding of the geometric variation effects, but it is difficult to achieve under existing approaches. Inspired by the idea of a parametric space envelope, this article proposes a new methodology by building a variation tool to aid the task. Under the proposal, the geometric variation of the compliant part is indirectly modeled through the constructed variation tool. This indirect modeling enables capturing intrapart interactions that are the major source of the inaccuracy of existing methods. The simulated geometric variation can be visualized through the variation tool. In addition, the developed method does not rely on historical manufacturing experience. This can be valuable for early stage designer when such production information is not available or expensive to get. Furthermore, the proposed method can be integrated into existing computer-aided design (CAD), computer-aided manufacturing (CAM), and computer-aided engineering (CAE) systems to improve overall design quality and reduce reliance on multiple physical prototyping.

Newton projection method as applied to assembly simulation

In this paper, we consider Newton projection method for solving the quadratic programming problem that emerges in simulation of joining process for assembly with compliant parts. This particular class of problems has specific features such as an ill-conditioned Hessian and a sparse matrix of constraints as well as a requirement for the large-scale computations. We use the projected Newton method with a quadratic rate of convergence and suggest some improvements to reduce the solving time: a method for solving the system of linear equations, so-called constraint recalculation method, and compare different approaches for step-size selection. We use the duality principle to formulate alternative forms of the minimization problem that, as a rule, can be solved faster. We describe how to solve the considered nonlinear minimization problem with the nonsmooth objective function by modifying Newton projection method and employing subgradients. In addition, we prove the convergence of the suggested algorithm. Finally, we compare Newton projection method with the other quadratic programming techniques on a number of assembly simulation problems.

Generating a skin-based meta-model for compliant parts in composite material: numerical and experimental results

PurposeThe purpose of this paper is to present a skin-based approach able to generate the variability model for a component in composite material due to its manufacturing process. It generates a skin-based model of the manufactured part. The skin model discretizes the part surfaces by points to take into account the geometric deviations, those points are the nodes of finite element analysis used for tolerance analysis of compliant assemblies.Design/methodology/approachThe paper presents a general and systematic simulation model for generating a variability meta-model for a component in composite material due to its manufacturing process. The model is constituted by three steps: definition and pre-processing of the nominal model, generation of the manufacturing process model and evaluation of the part variability.FindingsThe advantage of this approach is related to the fact that it is designed as a part of a digital process that establishes a continuous and unambiguous flow of variation information from the part design to manufacturing and assembly and that takes into account the manufacturing signature. This is its uniqueness compared to other simulation approaches focused only on manufacturing.Research limitations/implicationsConsidering the variability around the nominal value of all the process parameters and parts with more complex geometries are not taken into account now, which will be modelled in practical applications.Practical implicationsTo properly manage uncertainty since conceptual design of complex product, next generation geometry assurance requires simulation models to realistically consider process signatures due to the manufacturing process. This work focusses on this next generation tool for geometry assurance.Originality/valueThe literature is focused on metal sheets joined by welding or riveting. There are other materials widely used and typically compliant: the composite materials that typically used mechanical fixing elements (bolting, riveting) and structural adhesives to joint parts. No software tools exist in the literature to deal with uncertainty from manufacturing to assembly processes in products made by composite. This is the reason of the present work.

Improved Bi-Criterion flexible registration for fixtureless inspection of compliant parts

Because of the effects of gravity and/or residual stress, some manufactured mechanical parts, such as sheet metals and skins, often have a significantly different shape in a free-state position as compared to their state-of-use position. These parts are described as compliant, flexible or nonrigid. Expensive specialized fixtures are currently used prior to performing geometrical inspection operations in order to maintain compliant parts in the state-of-use position. This paper introduces an automatic bi-criterion flexible registration method for the dimensional and geometric inspection of such parts. The proposed method deforms the data acquired via a non-contact scanner of a compliant part in a free-state position until it reaches the nominal CAD shape for inspection with conventional Computer-Aided Inspection (CAI) tools. In other words, the method neutralizes the deviations induced in a compliant part by the effects of gravity and residual stress, allowing the acquired data to be treated as if it were obtained from a rigid part, using already available conventional (rigid) CAI tools. A proposed algorithm based on the BOFR-2 (the 2nd version of a Bi-Objective Flexible Registration algorithm) method is validated against both virtual simulated and experimental real industrial case studies from the aerospace sector. The resulting cost reduction and agility increasing make this fixtureless method well adapted to the requirements of unit-batch production in the context of Industry 4.0.

Homogenization and numerical modelling of poroelastic materials with self-contact in the microstructure

We present a two-scale homogenization-based computational model of porous elastic materials subject to external loads inducing the self-contact interaction at the pore level. Microstructures under consideration are constituted as periodic lattices generated by a representative cell consisting of a solid skeleton and a pore. On its surface, the unilateral frictionless contact appears when the porous material is deformed. We focus on microstructures with rigid inclusions whereby the contact process involves opposing surfaces on the rigid and the compliant skeleton parts. A macroscopic model is derived using the periodic unfolding homogenization and the method of oscillating test functions. An efficient algorithm for the two-scale computational analysis is proposed for the numerical model obtained using the finite element discretization of the homogenized model. For this, a sequential linearization of the two-scale elasticity problem leads to the consistent effective elasticity tensor yielding consistent stiffness matrices of the macroscopic incremental formulation. The micro-level contact problem attains the form of a nonsmooth equation solved using the semi-smooth Newton method without any regularization, or problem relaxation. Numerical examples of two-dimensional deforming structures are presented as a proof of the concept. The proposed modelling approach can be extended to treat self-contact in structures subject to finite deformation.

Development of Visible Manipulator With Multi-Gear Array Mechanism for Laparoscopic Surgery

In recent years, robotic technology has been introduced to medical fields, and many surgical robots have been proposed for minimally invasive surgery (MIS). However, due to the limitations in dexterity imposed by surgical instruments and occlusion area, surgeons experience great difficulties during operations. In this paper, we propose a visible manipulator for laparoscopic surgery. Unlike other multiple degree-of-freedom (DOF) manipulators that utilize compliant parts or tendons and pulleys, our proposed manipulator adopts a multi-gear array mechanism to perform the yaw and pitch motions. The manipulator is integrated with a visualization unit to provide macroscopic images for observation in a constrained cavity. Moreover, flexible surgical tools with different functions can be inserted through the central channel of the manipulator to perform diagnostic or therapeutic procedures. A master-slave system is developed to control the bending motions. Bending characteristics experiments and load capacity experiments are performed. The experimental results demonstrate that the proposed manipulator can perform bending motions with a yaw angle range of −76.8°∼76.2° and a pitch angle range of −75.2°∼75.6°. The manipulator can lift a workload of 250 g during yaw motion and a workload of 150 g during pitch motion, demonstrating the potential clinical value of the visible manipulator for robot-assisted surgery.

Convex optimization techniques in compliant assembly simulation

A special class of quadratic programming (QP) problems is considered in this paper. This class emerges in simulation of assembly of large-scale compliant parts, which involves the formulation and solution of contact problems. The considered QP problems can have up to 20,000 unknowns, the Hessian matrix is fully populated and ill-conditioned, while the matrix of constraints is sparse. Variation analysis and optimization of assembly process usually require massive computations of QP problems with slightly different input data. The following optimization methods are adapted to account for the particular features of the assembly problem: an interior point method, an active-set method, a Newton projection method, and a pivotal algorithm for the linear complementarity problems. Equivalent formulations of the QP problem are proposed with the intent of them being more amenable to the considered methods. The methods are tested and results are compared for a number of aircraft assembly simulation problems.