Practical Engineering Example Research Articles

Analysis of Stiffening Methods and Effects on Irregular Single-layer Lattice Shell Structures

Local stiffening is often a good solution to mechanical property problems of irregular single-layer lattice shell structures. The effects of three local stiffening methods, namely section enlargement stiffening, planar truss stiffening, and space truss stiffening, on their structural stiffness, strength, and overall stability were analyzed in this study. A practical engineering example showed that these three stiffening methods could effectively reduce the deformation of the lattice shell under vertical and lateral loads, reduce the comprehensive stress ratio, and increase the buckling eigenvalue and ultimate bearing capacity factor. The local space truss stiffening method had the best comprehensive effect. The same stiffening methods were applied to a regular lattice shell and the analysis showed that the stiffening effect on a regular shell is quite different from that on an irregular lattice shell. The three stiffening methods could not reduce its deformation under vertical loading but could reinforce the strength and overall stability of the structure effectively. Proper suggestions are proposed according to the preceding analysis in case a single-layer lattice shell structure cannot meet the demands of the design code.

Reliability analysis of motion mechanism under three types of hybrid uncertainties

Hybrid reliability analysis of motion mechanism, in which the inputs contain both random variables and interval variables, is investigated in this paper. Firstly, the hybrid uncertainty is divided into three categories. In the first category, the inputs that include both random variables and interval variables are considered. In the second category, the inputs that include random variables with interval distribution parameters are considered. In the third category, the inputs that include both random variables with interval distribution parameters, and interval variables are considered. The above three types of uncertainties outline the general situation of hybrid uncertainties. In order to achieve the reliability analysis of motion mechanism under the above three hybrid uncertainties, this paper presents a method of combining the Poisson's assumption-based first passage method and a double loop iterative algorithm. The specific calculation process is described in detail by a numerical example. Simultaneously, the accuracy and efficiency of the proposed is also shown and discussed by comparing the Monte Carlo simulation (MCS) results in this numerical example. Finally, the proposed method is applied to two practical engineering examples, a crank slider mechanism and a rack-and-pinion steering linkage.

A Kriging and Stochastic Collocation ensemble for uncertainty quantification in engineering applications

We propose a new surrogate modeling approach by combining two non-intrusive techniques: Kriging and Stochastic Collocation. The proposed method relies on building a sufficiently accurate Stochastic Collocation model which acts as a basis to construct a Kriging model on the residuals, to combine the accuracy and efficiency of Stochastic Collocation methods in describing stochastic quantities with the flexibility and modeling power of Kriging-based approaches. We investigate and compare performance of the proposed approach with state-of-art techniques over benchmark problems and practical engineering examples on various experimental designs.

A hybrid sequential approximate programming method for second-order reliability-based design optimization approach

The second-order reliability method (SORM) is an effective tool to evaluate the reliability, but its application for reliability-based design optimization faces unbearable computational cost. In this study, a new hybrid sequential approximate programming (HSAP) method is developed to calculate the optimum efficiently by developing a distance-checking criterion and a convex approximate method. Since the distance-checking criterion identifies the feasibility of the probabilistic constraint effectively, the proposed method combines the efficiency of the sequential approximate programming method and the accuracy of SORM. The convex approximate method is also constructed using the sensitivity and function value of the probabilistic constraint. So no additional computational cost is required in the optimization process. Five illustrative examples, including two mathematical examples and thee practical engineering examples, demonstrate the efficiency and accuracy of the proposed HSAP.

Engineering Fluid Mechanics Teaching with Practical Engineering Examples and CFD Technology

In this paper, the CFD technology and the analysis of a practical engineering example are combined in the teaching of engineering fluid mechanics. Through the numerical simulation of the practical engineering example, the flow field is visualized and the abstract theoretical knowledge becomes more vivid, which is beneficial to the students' understanding and learning. The flow analysis of the engineering example includes many theoretical knowledge points and improves the students' comprehensive ability and innovative thinking. A swirl mixer is taken as an example for numerical simulation and its internal flow field is analyzed. The analysis involves many theoretical points, such as Bernoulli equation, total pressure, static pressure, streamline and vortex etc. So these knowledge points are digested and the understanding is deepened. Therefore, the engineering fluid mechanics teaching with practical engineering examples and CFD technology is a good teaching method, which enhances the traditional teaching mode with multimedia and blackboard and improves the teaching effect compared with previous injection teaching, and is worthy of discussing and trying.

结合工程实例和CFD技术进行工程流体力学教学

本文提出将CFD技术和工程实例分析融合在工程流体力学教学中，通过CFD技术对工程实例进行数值模拟，将其流场进行直观形象的展示，使抽象的理论知识变得形象具体，有利于学生理解并激发学习兴趣。对工程实例的流动分析囊括多个理论知识点，提高学生对理论知识的综合运用能力和创新思维。本文以一个旋流混合器为例，对其进行数值模拟并分析其内部流场，分析过程中运用了伯努利方程、总压、静压、流线和旋涡等多个工程流体力学知识点，将这些知识点进行融会贯通，加深了对理论知识的理解。因此，结合工程实例和CFD技术为工程流体力学课程提供了有利的教学手段，提升了传统多媒体加板书的教学模式，改善了以往的注入式教学效果，是值得探讨和尝试的教学方式。 In this paper, the CFD technology and the analysis of a practical engineering example are combined in the teaching of engineering fluid mechanics. Through the numerical simulation of the practical engineering example, the flow field is visualized and the abstract theoretical knowledge becomes more vivid, which is beneficial to the students’ understanding and learning. The flow analysis of the engineering example includes many theoretical knowledge points and improves the students’ comprehensive ability and innovative thinking. A swirl mixer is taken as an example for numerical simulation and its internal flow field is analyzed. The analysis involves many theoretical points, such as Bernoulli equation, total pressure, static pressure, streamline and vortex, et al. So these knowledge points are digested and the understanding is deepened. Therefore, the engineering fluid mechanics teaching with practical engineering examples and CFD technology is a good teaching method, which enhances the traditional teaching mode with multimedia and black- board and improves the teaching effect compared with previous injection teaching, and is worthy of discussing and trying.

Parameter analysis of water flow during EPBS tunnelling and an evaluation method of spewing failure based on a simplified model

Spewing failure always occurs when a tunnel is constructed in water-rich sand stratum using an earth pressure balance shield, which could lead to considerable disturbance of the environment. However, few studies have investigated the mechanism of spewing. To understand the mechanism of screw conveyor spewing, a new simplified model was proposed to calculate the groundwater flow rate and water pressure gradient in the earth pressure balance shield. Ergun’s equation was used to consider the influence of turbulent flow, which is inevitable during spewing. The model was verified by tests, and a parameter analysis was conducted to investigate the effects of soil behaviour, fluid kinematic viscosity and shield geometry. Additionally, an evaluation method to predict spewing was proposed based on the simplified model, and the method was verified by investigating real-world engineering problems. The results indicate that the groundwater flow rate and velocity in the screw conveyor increase significantly with increasing soil hydraulic conductivity in the turbulent flow range. The influence of soil porosity on the groundwater flow rate and velocity is greater than that of the soil’s average particle diameter. In addition, increasing the screw conveyor length can be used to control spewing. Comparisons with practical engineering examples show that the proposed method is effective. The proposed method can be used to predict the risk of spewing such that appropriate measures can be taken.

An Anisotropic Sparse Grid Numerical Integration-Based Statistic Moment Estimation Method

Statistic moment estimation is a paramount task in design optimization under uncertainty. In the existing isotropic sparse grid-based statistic moment estimation method, each dimension is considered to be of equal importance and collocated with the same number of integration points. Therefore, “curse of dimensionality” is still very serious. To address this issue, a new statistic moment estimation approach is developed by employing the anisotropic sparse grid technique from the numerical integration point of view in this paper. A new rule allowing different accuracy levels to each dimension according to their varying importance is proposed to determine the eligible multi-index combinations. Integration points can be collocated more reasonably, and more points can be removed from unimportant dimensions to the important ones. The effectiveness of the proposed approach is demonstrated through comparative studies on several mathematical examples and a practical engineering example. It is observed that compared with the existing method, the proposed approach can further mitigate “curse of dimensionality” and significantly improve the accuracy of statistic moment estimation with even less computational cost.

Analysis on Line Differential Protection Based on Transient Saturation Characteristics of TPY-Type Current Transformer

Transient saturation characteristics of TPY-type current transformer have great impact on the right action of line differential protection. This paper proposes an analytical method of line differential protection under current transformer saturation by utilizing current transformer model and test methods. The true current value of primary side can be obtained by our proposed method and therefore it yields correct assessment of line operating status. This method has high reliability applying to practical engineering examples of differential protection.

Random field-based reliability analysis of prestressed concrete bridges

A method for reliability assessment of prestressed concrete bridges accounting for the spatial variability of structural parameters is presented in this paper. The spatial variability of these parameters is modeled by means of random fields and the reliability estimates were determined by a generalized first-order reliability algorithm. The main feature of the random field-based reliability method is to consider the spatial variability of structural parameters that is disregarded in the traditional reliability method for prestressed concrete bridges. The accuracy and efficiency of the random field-based reliability method is demonstrated through two numerical examples. A software strategy for interfacing the random field-based reliability method with ANSYS is developed via a freely available MATLAB software tool (FERUM). As a practical engineering example, the reliability of a prestressed concrete bridge is illustrated. The obtained results clearly show the applicability and merits of the random field-based reliability method and the associated software strategy.

A Satisfaction Differential Evolution Algorithm for Detailed Machine Layout in Assembly Plant

We herein present a satisfaction differential evolution algorithm to deal with machine layout in assembly plant. This paper firstly provide the assumption for detailed machine layout problem, build a mathematical model of detailed machine layout, and replace the optimal solution with satisfactory solution, combine satisfactory optimization theory with differential evolution algorithms, employ satisfaction function as the objective function of differential evolution algorithm. The experimental results verified our methods with practical engineering examples.

Solution of two key issues in arbitrary three-dimensional discrete fracture network flow models

Summary It is necessary to consider a great number of arbitrarily developed fractures in applications involving realistic 3-d fracture network flow models of rock masses. In order to model the fluid flow in a complicated arrangement of discrete fracture networks (DFNs), two core issues have to be solved. Firstly, how does one identify the connection relationships between fractures in the 3-d arbitrary fracture network? Secondly, how can one calculate numerically the fluid flow in arbitrarily-shaped 2-d domains? This paper first proposes that the boundaries of all enclosed blocks form flow pathways. All enclosed blocks can be identified using a 3-d block cutting method. The boundaries of the blocks are composed of loops which are formed by intersecting lines between all faces (fractures and other surfaces). Therefore, the connection relationships between fractures can be determined according to the linkages of the loops. Accordingly, the linkages of the finite element nodes between different faces can also be determined. On the other hand, the fluid flow occurring in the fractures can be treated as a 2-d continuous flow within the arbitrarily shaped loops in the fracture’s local coordinates. We propose that these loops can be meshed into triangles using a method of simplex triangulation of the arbitrarily shaped domain. Then, according to the linkages between nodes, the global conductivity matrix can be assembled and the solution of the equations governing flow can be derived. Three cases are used to validate the model. Finally, an analysis is made of a practical engineering example (with 8914 lines of intersection and 4188 loops) which shows that the proposed flow model is practicable and can deal with complicated DFNs.

The Improved Elastic Stiffness Method Based on Energy Dissipation System with Buckling Restrained Brace Design

This paper brings up the improved elastic stiffness method to the energy dissipation system with buckling restrained brace design in high-rise buildings and super high-rise buildings, Introducing amplification factor technology by improving the original elastic stiffness method can amplify seismic action regularly and the iteration was notably reduced by the seismic action which was calculated from the amplified coefficient so that solving the problem of relatively slow iterative speed. According to the demand of displacement limit value and the stiffness distribution in main structure, the demand of lateral stiffness in general structure can be directly worked out so that it can get the effective stiffness which should be added to the energy dissipation with buckling restrained brace. By the practical engineering example which height of frame-core tube is 144m, the design steps and user principles of the method are clearly illustrated. Meanwhile the application of response spectrum method on the basis of the elastic stiffness is expanded.

Compensation Heating Technique for Experimental Investigation of Thermal Contact Conductance across GH4169/K417 Interface

Abstract An experimental apparatus to measure the thermal contact conductance (TCC) between interfaces of two contact solid materials was introduced, and a new compensating heater was proposed to better achieve the one-dimensional axial heat transfer. A practical engineering example was used with pressed pairs of GH4169/K417 contacts in the range 160∼280 °C and 60∼180 MPa to demonstrate the applicability of the experimental apparatus. The measured values of TCC with and without compensation heater were studied and compared. The results show that the measured TCC with compensation heater is larger than that without compensation heater under the same condition and the compensation heater works better at high temperature.

Serviceability reliability analysis of prestressed concrete bridges

An effective method for serviceability reliability analysis of prestressed concrete bridges is presented in this paper. The method integrates the advantages of the Artificial Neural Network (ANN) method, First Order Reliability Method (FORM) and the importance sampling updating method. A distinctive feature of the present method is the introduction of an explicit approximate limit state function. The explicit formulation of the approximate limit state function is derived by using the parameters of the developed ANN model. Once the explicit limit state function is obtained, the failure probability can be easily estimated by using a hybrid reliability method consisting of the FORM and the importance sampling updating method. The accuracy and efficiency of the robust method is demonstrated through two numerical examples. As a practical engineering example, the serviceability reliability of a prestressed concrete bridge is illustrated. The obtained results clearly show the applicability and merits of the present method.

The Design Application of Steel Fiber Concrete on Bottom Frame Structure

The concrete frame with bottom frame structure bear the load from the upper floors, roofing and brick walls, internal force is quite large, so the designed section size of frame beams is big, sometimes even the clear height of the building can't meet the architectural requirements; And more reinforcement, construction of concrete are difficult to pound, even vibration bar are difficult to insert into the beam, seriously influence the construction quality of reinforced concrete and the frame structure quality can't t be assured. This article introduces the design and application of steel fiber reinforced concrete in the bottom frame through the practical engineering examples. Steel fiber concrete can enhance the tensile and shear strength, and make it has good resistance to crack and toughness. As a result of the steel fiber concrete, the bearing capacity of bottom frame is greatly improved, and the problem in the project is solved.

Weighting-Grey Relative Degree Assessment Model of Concrete Structure Durability and its Application

A grey relative degree assessment model for durability of concrete structure, based on the combinatorial weight, in which expert experience & information entropy are taken into account, is established after analyzing problems in existing durability assessment theory. Both the influence of subjective factors and the significance of objective factors are considered in this model, and to avoid assessment deviation for emphasizing one side or another. The model, which is testified by practical engineering example, provides a new approach to make durability assessment more scientifically and exactly.

Investigation on Thermal Contact Conductance Based on Data Analysis Method of Reliability

The method of reliability is proposed for the investigation of thermal contact conductance (TCC) in this study. A new definition is introduced, namely reliability thermal contact conductance (RTCC), which is defined as the TCC value that meets the reliability design requirement of the structural materials under consideration. An experimental apparatus with the compensation heater to test the TCC is introduced here. A practical engineering example is utilized to demonstrate the applicability of the proposed approach. By using a statistical regression model along with experimental data obtained from the interfaces of the structural materials GH4169 and K417 used in aero-engine, the estimate values and the confidence level of TCC and RTCC values are studied and compared. The results show that the testing values of TCC increase with interface pressure and the proposed RTCC model matches the test results better at high interface pressure.

Experimental Study of Thermal Contact Conductance Based on Heat-Transfer Theory with Variable Thermal Conductivity

Abstract To calculate the interface temperature drop ΔT during the thermal contact conductance (TCC) testing, an optimization computing method based on the one-dimensional steady heat-transfer theory with variable thermal conductance is proposed in this paper. This method takes into account the physical process of heat transfer adequately, which can calculate the temperature drop (ΔT) accurately. Besides, a practical engineering example is utilized to demonstrate the applicability of the proposed approach. By using the optimization computing method along with traditional linear fitting method, the testing values of TCC obtained from the interfaces of the structural materials GH4169 and K417 used in aero-engines are studied and compared. The results show that there are large errors and poor stability in the traditional linear fitting method, and the relative errors of these two methods vary from about 3 % to 17 %.

Study of Dependability Evaluation for Multi‐hierarchical Systems Based on Max–Min Composition

This article presents the model for calculating the performance of dependability for complex technical systems. According to ISO‐IEC 300, dependability is an overall indicator for the quality of service and considers simultaneously reliability, maintainability, and maintenance support. For a proper understanding of the quality of service for any technical system, it is important to define dependability performance at the level of single component as well as at the upper levels—levels of subsystems and entire system. As dependability indicators (reliability, maintainability, and maintenance support) have been defined as linguistic variables, the fuzzy max–min composition has been used for the dependability determination and integration of its indicators. A procedure for the synthesis of single components dependability performance to upper levels in complex technical system is proposed. Max–min composition is again used as a tool for fuzzy synthesis because it enables obtaining the comprehensive and synergetic effect in a process of dependability evaluation. A practical engineering example (mechanical systems at bucket wheel excavator) has been used to demonstrate the proposed dependability synthesis model. Copyright © 2012 John Wiley & Sons, Ltd.