Tolerant Design Research Articles

Experimental study and fretting fatigue life prediction in dovetail assembly considering stress–temperature nonlinear coupling effect

AbstractAs a paramount failure form of dovetail assembly, high‐temperature fretting fatigue seriously restricts the actual service life. Aiming at the problem of fretting fatigue life prediction of dovetail assembly of the aero‐engine compressor under the coexistence of stress and high temperature, based on D‐M contact theory and continuum damage mechanics theory, a fretting fatigue life prediction model considering stress–temperature nonlinear coupling effect is proposed in this paper by, respectively, introducing the fretting fatigue stress σfretting and the high‐temperature influence factor λ. Meanwhile, the judgment criterion of fretting fatigue crack initiation and failure is raised based on the strain–displacement method, and the fretting fatigue test is designed and carried out for experimental verification. The results show that the proposed fretting fatigue life prediction model has high life prediction ability, whose life prediction results are within ±1.7 times the error band, which can provide a theoretical reference for the structural design optimization and damage tolerance design of dovetail assembly.

Wide-Angular Tolerance Optical Filter Design and Its Application to Green Pepper Segmentation.

The optical filter is critical in many applications requiring wide-angle imaging perception. However, the transmission curve of the typical optical filter will change at an oblique incident angle due to the optical path of the incident light change. In this study, we propose a wide-angular tolerance optical filter design method based on the transfer matrix method and automatic differentiation. A novel optical merit function is proposed for simultaneous optimization at normal and oblique incidents. The simulation results demonstrate that such a wide-angular tolerance design can realize a similar transmittance curve at an oblique incident angle compared to a normal incident angle. Furthermore, how much improvement in a wide-angular optical filter design for oblique incident contributes to image segmentation remains unclear. Therefore, we evaluate several transmittance curves along with the U-Net structure for green pepper segmentation. Although our proposed method is not perfectly equal to the target design, it can achieve an average 50% smaller mean absolute error (MAE) than the original design at 20∘ oblique incident angle. In addition, the green pepper segmentation results show that wide-angular tolerance optical filter design improves the segmentation of the near-color object about 0.3% at 20∘ oblique incident angle compared to the previous design.

OsBBX11 on qSTS4 links to salt tolerance at the seeding stage in Oryza sativa L. ssp. Japonica.

Rice has been reported to be highly sensitive to salt stress at the seedling stage. However, the lack of target genes that can be used for improving salt tolerance has resulted in several saline soils unsuitable for cultivation and planting. To characterize new salt-tolerant genes, we used 1,002 F2:3 populations derived from Teng-Xi144 and Long-Dao19 crosses as the phenotypic source to systematically characterize seedlings' survival days and ion concentration under salt stress. Utilizing QTL-seq resequencing technology and a high-density linkage map based on 4,326 SNP markers, we identified qSTS4 as a major QTL influencing seedling salt tolerance, which accounted for 33.14% of the phenotypic variation. Through functional annotation, variation detection and qRT-PCR analysis of genes within 46.9 Kb of qSTS4, it was revealed that there was one SNP in the promoter region of OsBBX11, which resulted in a significant response difference between the two parents to salt stress. Transgenic plants using knockout-based technology and demonstrated that Na+ and K+ in the roots of the functional-loss-type OsBBX11 were translocated largely to the leaves under 120 mmol/L NaCl compared with the wild-type, causing osbbx11 leaves to die after 12 days of salt stress due to an imbalance in osmotic pressure. In conclusion, this study identified OsBBX11 as a salt-tolerance gene, and one SNPs in the OsBBX11 promoter region can be used to identify its interacting transcription factors. This provides a theoretical basis for finding the molecular mechanism of OsBBX11 upstream and downstream regulation of salt tolerance and molecular design breeding in the future.

Retracted: Interval uncertain optimization of cased telescoped ammunition interior ballistics considering tolerance design

AbstractAn interval optimization method considering tolerance design is proposed to solve the uncertainty optimization problem of interior ballistics of cased telescoped ammunition. Firstly, the interval optimization model of the interior ballistics of the cased telescoped ammunition considering tolerance design is constructed. The interval optimization model of the interior ballistics of the cased telescoped ammunition considering tolerance design under uncertainty is presented. Then, considering the extremely low computational efficiency of the interval uncertain optimization, the back propagation neural network surrogate model is introduced. A series of pareto optimal solution is obtained by using non‐dominated sorting genetic algorithm II. Through the given design scheme, it provides a reference for the optimization of the interior ballistic performance of the cased telescoped ammunition under uncertain condition.

System-Level Fault Tolerance Design Process of Dual-Winding Motors for Overheat in Integrated Electric Braking System of Autonomous Vehicle

System-Level Fault Tolerance Design Process of Dual-Winding Motors for Overheat in Integrated Electric Braking System of Autonomous Vehicle

Fault tolerance designs of interconnection networks

Fault tolerance designs of interconnection networks

Observer-based fault tolerant control design for periodic piecewise time-varying systems: a fault estimation approach

ABSTRACT This study tackles the fault estimation issue for a continuous-time periodic piecewise time-varying systems (PPTVSs) with delays, fault signal and external disturbances. In particular, the PPTVSs are conjured up by segmenting the fundamental period of the periodic system into a finite number of subintervals. Moreover, fault estimator is designed in line with periodic piecewise observer systems to estimate the immeasurable states of the PPTVSs and the fault signal, simultaneously. Subsequently, in accordance with the estimated values of the fault signal and state dynamics, a fault-tolerant controller is devised. Moreover, by utilising Lyapunov stability theory and matrix polynomial lemma, sufficient criteria are procured in context of linear matrix inequalities to affirm the uniform boundedness of the undertaken system and error system. Further, relying on the acquired constraints, the precise configuration of the fault-tolerant control and observer gain matrices are proffered. Eventually, by offering two illustrative examples including mass-spring-damper system, the utility and potential of presented theoretical insights are validated.

A finite element-based continuum damage model for mechanical joints in fiber metal laminates under static and fatigue loading

In this study the theory and experimental validation of a novel continuum damage modeling framework for highly predictive strength and fatigue analyses of mechanical joints in fiber-reinforced polymer (FRP) composites with local metal hybridization is presented. In contrast to existing damage modeling approaches for mechanical joints in fiber metal laminates (FML), the herein presented framework is able to predict the joint’s failure mode both under static and fatigue loading, which is an indispensable feature for the identification of damage tolerant lightweight joint designs. For this purpose, the laminate’s constituent materials (i.e. the metallic inlays and the FRP plies) are simulated individually by physically motivated static-fatigue continuum damage models. Here, the elastic and plastic mechanical strain energy is utilized to compute the materials’ damage parameters. In this way, the models are (i) able to suppress any mesh-dependence during material softening, (ii) able to account for damage initiation and growth, and (iii) applicable both in the low- and high-cycle fatigue regime. The algorithms are implemented as user-material (UMAT) subroutine for the commercial finite element software ABAQUS. The damage modeling framework is validated for open hole tension and T-bolt joint setups both under static and fatigue loading.

Analysis and optimization of tolerance design for an internal thread grinder

Analysis and optimization of tolerance design for an internal thread grinder

Evaluation of the influences of the stress ratio, temperatures, and local microstructure on small fatigue crack propagation behavior of the FGH96 superalloy

Here, the influences of the stress ratios, temperatures, and local microstructure on the propagation behavior of small fatigue crack for FGH96 superalloy are quantitatively investigated. Following an increase in the stress ratio and temperature, the small fatigue crack growth rates increased. The influences of the local microstructure on the restrained ability for small fatigue crack propagation are analyzed, and the critical stress range of small fatigue crack propagation for the FGH96 superalloy at different stress ratios is proposed based on an amendatory-three-dimensional Kitagawa–Takahashi diagram. These results can aid in the fatigue damage tolerance design of FGH96 superalloy components.

Effect of adhesive de-bond and crack in adherent plate on single lap joint with bi-adhesive

PurposeThis paper aims to study the benefits of use of bi-adhesive (combination of two different adhesives) over conventional single adhesive in bonded lap joints. Characterise damage severity due to cohesive and adherent failure as feedback for operating load levels that assist in developing damage tolerance design of the adhesively bonded joints.Design/methodology/approachSingle lap joint where the adherent plate is made up of aluminium alloy joined together with bi-adhesives is analysed. The nature of adhesives ranges from brittle, elastic-plastic, moderately ductile to largely ductile. Numerical analysis is performed considering the material and geometric non-linear behaviour of the joint. The optimum bond ratio of bi-adhesives and the effect of the location of adhesive on the stress distribution are studied. The cohesive zone modelling (CZM) is adopted to account for the cohesive failure of the joint. The adherent plate failure is also addressed by modelling and studying the behaviour of the crack at different locations in the plate using modified virtual crack closure integral (MVCCI).FindingsThe results obtained from the stress analysis show some important characteristic behaviour of the bi-adhesive joint. Although bi-adhesive is expected to result in improved joint strength, the purpose gets defeated if a brittle adhesive is used at the corners and ductile adhesive at the middle. The joint strength based on CZM, evaluated for a single adhesive, is in good comparison with the experimental results from the literature. Also, the location of the crack in the adherent plate plays a significant role in the failure of the joint.Originality/valueEstimating joint strength for the bi-adhesive model using CZM and evaluating damage severity in the presence of de-bond and crack in the bi-adhesive lap joint model assists in developing robust damage tolerance design models of such joints.

A bibliography of the literature on process capability indices (PCIs): 2010–2021, Part I: Books, review/overview papers, and univariate PCI‐related papers

AbstractThis is the author's second bibliography on process capability indices (PCIs) and contains approximately 1080 journal papers and books for the period 2010–2021. The related literature is classified into six major categories, namely, books, review/overview papers, theory‐ and method‐related papers, special applications, software packages, and papers omitted in the author's previous bibliography. Theory‐ and method‐related papers are further classified into univariate, multivariate, and functional PCI‐related papers. Special applications include acceptance sampling, control charts, supplier selection, and tolerance design and other optimizations. The present bibliography consists of two parts. Part I contains books, review/overview papers, and univariate PCI‐related papers, while Part II includes multivariate and functional PCI‐related papers, special applications, software packages, and papers omitted in the author's previous bibliography.

Concurrent optimization of parameter and tolerance design based on the two-stage Bayesian sampling method

ABSTRACT Researchers usually expect to reduce costs while improving product robustness in product quality design. The concurrent optimization of parameter and tolerance design assumes that the output response follows a normal distribution. However, non-normal responses are also common in product quality design. As for the concurrent optimization of parameter and tolerance design with a non-normal response, a novel total cost function based on the two-stage Bayesian sampling method is proposed in this paper. First, the hierarchical Bayesian model constructs the functional relationship between output response, input factors, and tolerance variables. Secondly, a two-stage Bayesian sampling method is used to obtain the simulated values of the output responses. The simulated response values are used to build the rejection cost and quality loss functions. Then, the genetic algorithm is used to optimize the constructed total cost model, including the tolerance cost, rejection cost, and quality loss. Finally, the effectiveness of the proposed method is demonstrated by two examples. The research results show that the proposed method in this paper can effectively improve product quality and reduce manufacturing costs when considering the uncertainty of model parameters and the variation of the output response.

Crack growth path of high-strength steel with different toughness under monotonic and cyclic loadings

In this paper, the crack growth path of 4340 steel with different toughness was studied in quasi-in-situ testing by scanning electron microscopy and X-ray technology. The crack growth behavior under monotonic loading shows that the critical load and crack growth distance increase with the fracture toughness. The angles between the crack growth direction and loading direction are 43.07° for 180 °C tempered steel, 28.36° for 350 °C tempered steel and 34.69° for 500 °C tempered steel, respectively. The crack grows synchronously in high fracture toughness steel, demonstrating high crack resistance and large energy consumption. The severe deformation zone width of 4340 steel after first unloading increases from 7.5 μm to 28.1 μm with fracture toughness. On the other hand, the crack growth behavior under cyclic loading displays that the surface roughness in high fracture toughness steel is higher than those in low fracture toughness steel. The fatigue cycle of high fracture toughness steel is nearly twice higher than that of low fracture toughness steel. Macro/micro crack bifurcation, crack growth uniformity, crack surface roughness and plastic deformation complexity play significant roles in the crack resistance of materials. These findings would provide an in-depth understanding for the damage tolerance design of high-strength steel.

Study on the relationship between machining errors and transmission accuracy of planetary roller screw mechanism using analytical calculations and machine-learning model

AbstractCorrelation between machining errors and transmission accuracy of planetary roller screw mechanism (PRSM) plays an important role in tolerance design. In this study, analytical calculations, machine learning, and experimental verification are utilized for exploring the internal correlation between the machining errors and the transmission accuracy of the PRSM. A multi-roller meshing transmission error model is established, which comprehensively considers the eccentric error, nominal diameter error, flank angle error, and cumulative pitch error of the screw, roller, and nut. The importance coefficients of various machining errors on the transmission error are determined using the random forest algorithm. A genetic algorithm-back propagation neural network algorithm-based method is utilized for training the dataset generated via analytical calculations. The results show that the proposed analytical calculation model reflects the alternate meshing characteristics of rollers during the PRSM motion, providing a more accurate prediction of the transmission error than the existing prediction methods. For an actual mean travel deviation, the most significant machining error is the cumulative pitch error of the screw, whereas for the actual bandwidth of useful travel, the most significant machining errors are the eccentric errors of the screw and nut. The proposed prediction formulae for transmission error considering the essential machining errors illustrate reasonable prediction accuracy, with an average error of 10.63% for the actual mean travel deviation and 14.27% for the actual bandwidth of useful travel compared with the experiments, which can effectively support the direct design of PRSM tolerance in engineering practice.

Reliability Evaluation and Fault Tolerance Design for FPGA Implemented Reed Solomon (RS) Erasure Decoders

Reed–Solomon erasure codes (RS-ECs) are widely applied in storage and packet communication systems to recover erasures. When implemented on a field-programmable gate array (FPGA) in a space platform, the RS-EC decoder will suffer single event upsets (SEUs) that can cause failures. In this brief, the reliability of an RS-EC decoder implemented on an FPGA to errors on the configuration memory is first studied based on hardware SEU injection experiments. We found that the reliability is lower for larger number of erased symbols, but there are still about 85% SEUs can be tolerated by the decoder itself even for the maximum number of erased symbols within the recovery capability. In addition, around 10%–25% SEUs on critical bits can cause system exceptions. Based on these results, a duplication with comparison (DWC) scheme is proposed for the protection of the RS-EC decoder. In particular, a checksum parity-based approach is proposed to detect the faulty decoder to reduce the computation overhead. Experimental results show that the reliability of the DWC protected RS-EC decoder to SEUs on the configuration memory is almost the same of a traditional triple modular redundancy (TMR) protection, and the resource usage is only about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.15\times $ </tex-math></inline-formula> that of the unprotected decoder.

Statistical Analysis using Taguchi Method for Designing a Robust Wind Turbine

The current paper presents the tolerance and parameter design for robust wind turbine. By utilizing the traditional Taguchi method along with its extensions, there is a way of designing a robust wind turbine by considering multiple objectives, constraints and design variables. The concept of design of experiment (DOE) i.e.; Taguchi Method is used to evaluate the constrained and unconstrained problems for the optimization. The current work produces an inexpensive and simpler approach for robust vertical axis wind turbine. DOE (Taguchi Method) of L-9 Orthogonal Array having four parameters along with their three levels i.e; type of NACA aerofoil, Reynolds number, Mach number and Angle of attack are utilized for the optimization and to derive the corresponding optimal values of CL, CD and CP. The parameters like coefficient of lift, drag and power for the wind turbine was determined by Q-Blade software, which is use for designing of wind turbine blades. From the obtained results the inferences drawn were: for CL the major impact was due to Reynolds number and least was due to angle of attack, for CD the major and minor impacting factors were angle of attack and Mach number respectively and for CP the most and least influenced parameters were Reynolds number and Mach number respectively. Also, for obtaining the optimized parameters, the Grey based Taguchi method was utilized which has the combination of orthogonal arrays and grey relational analysis. The analysis showed that the NACA0021 has the maximum lift coefficient of 1.0361 and the minimum drag coefficient of 0.02190 in the case of NACA0021 aerofoil.

Design and dynamic transmission error analysis of a new type of cycloidal-pin reducer with a rotatable output-pin mechanism

A new type of one-stage precision cycloidal-pin reducer is designed and explored in this study. The design innovatively replaces the fixed output-pin mechanism of conventional cycloidal-pin reducers with a rotatable output-pin mechanism, thereby transforming the sliding contact between the output-pin and the output-hole into a rolling contact. This new structural design is found to significantly improve the transmission efficiency of the reducer. To evaluate the dynamic transmission error (DTE) characteristics of the proposed reducer, a general dynamic model of the cycloidal-pin transmission system considering the influences of multi-source error factors on the geometry of the main components is established. The geometric error of the component is determined by taking random values within a given design-tolerance zone. The geometric error distribution introduced using this method can well match the actual machining situation. Finally, the DTEs of the new reducers with three different tolerance designs are analyzed numerically and tested experimentally. The results show that the new reducer with a reasonable tolerance design can achieve high transmission accuracy and has the potential for application in the joints of industrial robots.

Reliability-based optimal tolerance design of mechanical systems including epistemic uncertainty

Reliability-based optimal tolerance design of mechanical systems including epistemic uncertainty

Experimental tolerance design of robot manipulators accounting for positioning accuracy reliability

AbstractA new tolerance design method based on experimental design and positioning accuracy reliability is presented to deal with uncertainties of robot manipulators resulting from manufacturing and assembly processes. Initially, the performance function of positioning accuracy is established according to the kinematic model and response surface technique. An analytical algorithm for positioning accuracy reliability calculation is developed based on eigen‐decomposition and saddlepoint approximation methodologies. Inner orthogonal arrays of kinematic parameter tolerances along with the outer uniform arrays of joint variables are then constructed to analyze significant tolerances that affect the positioning accuracy reliability within the entire workspace. Finally, the applicability and performance of the proposed method are verified by case studies of a two‐link planar manipulator and a six‐degree‐of‐freedom robot manipulator. The results confirmed that the proposed method can efficiently and accurately analyze the positioning accuracy reliability, and the method recognizes the impact of kinematic parameters on the motion performance which is able to guide the tolerance range selection of robot manipulators.