Reliable durability assessment of welded yellow goods equipment.

Weld fatigue performance is a main design consideration with Yellow Goods vehicles and can determine the overall product durability. Accurate fatigue life prediction is critical but current durability assessment involves extensive testing. This design process lacks efficiency and presents scope for a finite element (FE) based weld fatigue assessment method. Used early in the design stage, this method will improve time-to-market of products and achieve robust 'right-first-time' designs. Research work has been carried out into applying the 'Master S-N Curve' approach to thick-plate construction and agricultural equipment. Weld fatigue data was generated on a range of simple welded coupons and converted for the fatigue life prediction of welded structures using the structural stress damage parameter. Overall, a single Master S-N curve was achievable for a range of different weld joint configurations. The method achieved good condensation of the geometry dependent load-life fatigue curves into a single structural stress against life curve. The structural stress method was further extended to fatigue lives of weld throat failures with good condensation of the data. Excellent correlations were achieved between solid and shell element models. The concept proved to be effective and largely insensitive to FE mesh type and size. However, limitations were found with shell element models when predicting weld throat failures. The structural stress measurement technique was employed and a master curve generated, derived from coupon strain-gauge recordings. The Master S-N curve approach was applied in the fatigue assessment of a laboratory test component and production component for the construction industry with limited success. Predictions were compared with recorded values from component fatigue tests. More accurate predictions and improved correlations were found when using separate failure mode master curves. Overall the work showed some potential for the use of the Master S-N Curve approach in the early design stage of construction and agricultural welded structures

Effects of duty cycles on diesel engine component life estimation

Engine manufactures have relied on over designed of engines and performance testing to ensure product reliability. The efforts to maximize efficiency and to predict performance characteristics have evoked an interest to study the in-cylinder pressure throughout the respective duty cycle. The duty cycle of an engine is defined as the history of speed and load conditions over which the engine operates in a specific application. Understanding the transient on-road diesel engine duty cycles has been one of major goals for the engine developers. To date there have not been any research performed to identify a wide variety of on-road diesel engine duty cycles. One of the world largest diesel engine manufactures, Cummins Inc., had interest in developing and understanding how the effective life of a diesel engine component is related to its duty cycle. West Virginia University Engine and Emissions Research Laboratory (EERL) was commissioned to conduct this study.;The objective of this study is to create a mathematical model that predicts the effective life of diesel engine components with respect to its operational duty cycle. In particular, power cylinder components were considered along with the variations of in-cylinder pressure. Four different duty cycles were evaluated in this study: a concrete mixer, heavy hauler, dump truck, and a transit bus. In-cylinder pressure data for all four duty cycles were statistically analyzed using the tools from non-parametric function and regression analysis. A mathematical model that predicts the power cylinder component lives was created. Mimicking the infield operation, heavy hauler displays the minimum power cylinder component life, while concrete mixer has the maximum life. Ultimately, this mathematical model will enable the engine manufactures to produce more cost effective components for different duty cycle applications, while fulfilling the customer requirements

Application of Surrogate Based Optimisation in the Design of Automotive Body Structures

The rapid development of automotive industry requires manufacturers to continuously reduce the development cost and time and to enhance the product quality. Thus, modern automotive design pays more attention to using CAE analysis based optimisation techniques to drive the entire design flow. This thesis focuses on the optimisation design to improve the automotive crashworthiness and fatigue performances, aiming to enhance the optimisation efficiency, accuracy, reliability, and robustness etc. The detailed contents are as follows: (1) To excavate the potential of crash energy absorbers, the concept of functionally graded structure was introduced and multiobjective designs were implemented to this novel type of structures. First, note that the severe deformation takes place in the tubal corners, multi-cell tubes with a lateral thickness gradient were proposed to better enhance the crashworthiness. The results of crashworthiness analyses and optimisation showed that these functionally graded multi-cell tubes are preferable to a uniform multi-cell tube. Then, functionally graded foam filled tubes with different gradient patterns were analyzed and optimized subject to lateral impact and the results demonstrated that these structures can still behave better than uniform foam filled structures under lateral loading, which will broaden the application scope of functionally graded structures. Finally, dual functionally graded structures, i.e. functionally graded foam filled tubes with functionally graded thickness walls, were proposed and different combinations of gradients were compared. The results indicated that placing more material to tubal corners and the maximum density to the outmost layer are beneficial to achieve the best performance. (2) To make full use of training data, multiple ensembles of surrogate models were proposed to maximize the fatigue life of a truck cab, while the panel thicknesses were taken as design variables and the structural mass the constraint. Meanwhile, particle swarm optimisation was integrated with sequential quadratic programming to avoid the premature convergence. The results illustrated that the hybrid particle swarm optimisation and ensembles of surrogates enable to attain a more competent solution for fatigue optimisation. (3) As the conventional surrogate based optimisation largely depends on the number of initial sample data, sequential surrogate modeling was proposed to practical applications in automotive industry. (a) To maximize the fatigue life of spot-welded joints, an expected improvement based sequential surrogate modeling method was utilized. The results showed that by using this method the performance can be significantly improved with only a relatively small number of finite element analyses. (c) A multiojective sequential surrogate modeling method was proposed to address a multiobjective optimisation of a foam-filled double cylindrical structure. By adding the sequential points and updating the Kriging model adaptively, more accurate Pareto solutions are generated. (4) While various uncertainties are inevitably present in real-life optimisations, conventional deterministic optimisations could probably lead to the violation of constraints and the instability of performances. Therefore, nondeterministic optimisation methods were introduced to solve the automotive design problems. (a) A multiobjective reliability-based optimisation for design of a door was investigated. Based on analysis and design responses surface models, the structural mass was minimized and the vertical sag stiffness was maximized subjected to the probabilistic constraint. The results revealed that the Pareto frontier is divided into the sensitive region and insensitive region with respect to uncertainties, and the decision maker is recommended to select a solution from the insensitive region. Furthermore, the reduction of uncertainties can help improve the reliability but will increase the manufacturing cost, and the tradeoff between the reliability target and performance should be made. (b) A multiobjective uncertain optimisation of the foam-filled double cylindrical structure was conducted by considering randomness in the foam density and wall thicknesses. Multiobjective particle swarm optimisation and Monte Carlo simulation were integrated into the optimisation. The results proved that while the performances of the objectives are sacrificed slightly, the nondeterministic optimisation can enhance the robustness of the objectives and maintain the reliability of the constraint. (c) A multiobjective robust optimisation of the truck cab was performed by considering the uncertainty in material properties. The general version of dual response surface model, namely dual surrogate model, was proposed to approximate the means and standard deviations of the performances. Then, the multiobjective particle optimisation was used to generate the well-distributed Pareto frontier. Finally, a hybrid multi-criteria decision making model was proposed to select the best compromise solution considering both the fatigue performance and its robustness. During this PhD study, the following ideas are considered innovative: (1) Surrogate modeling and multiobjective optimisation were integrated to address the design problems of novel functionally graded structures, aiming to develop more advanced automotive energy absorbers. (2) The ensembles of surrogates and hybrid particle swarm optimisation were proposed for the design of a truck cab, which could make full use of training points and has a strong searching capacity. (3) Sequential surrogate modeling methods were introduced to several optimisation problems in the automotive industry so that the optimisations are less dependent on the number of initial training points and both the efficiency and accuracy are improved. (4) The surrogate based optimisation method was implemented to address various uncertainties in real life applications. Furthermore, a hybrid multi-criteria decision making model was proposed to make the best compromise between the performance and robustness

Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives

Continuous earthmoving machines, such as bucket-wheel excavators (BWEs), are the largest mobile terrestrial machines exposed to the working loads of a periodic character. This paper aims to launch a new idea regarding the preservation of the load-carrying structures of these machines by the means of implementing a controllable frequency-controlled drive of the excavating device. Successful implementation of this idea requires a detailed analysis of the dynamic response of the load-carrying structure in order to determine the domains of frequency of revolutions of the bucket-wheel-drive electromotor (FREM) where the dynamic response of the structure is favorable. The main goal of the presented research was the development of a unique three-step method for the identification of the FREM ranges, where the vibroactivity of the load-carrying structure is within the allowed boundaries. A methodologically original study of the dynamic response was conducted on a unique dynamic model of the BWE slewing superstructure that allows for continuous variation of the FREM, i.e., of the frequency of excitation caused by the forces resisting the excavation. Validation of the spatial reduced dynamic model of the slewing superstructure and the corresponding mathematical model, as well as the overall approach to the determination of the dynamic response, were performed by the means of vibrodiagnostics under the real exploitation conditions. Application of the developed method has yielded: (1) the resonant-free FREM domains; (2) the FREM domains, where the structure is not exposed to the excessive dynamic impacts; and (3) the frequency ratio ranges defining the resonant areas. Additionally, the results of the research have pointed out that the resonant-free state represents a necessary but insufficient condition for the proper dynamic behavior of the BWE slewing superstructure

Analysis of the Dynamic Response as a Basis for the Efficient Protection of Large Structure Health Using Controllable Frequency-Controlled Drives

Continuous earthmoving machines, such as bucket-wheel excavators (BWEs), are the largest mobile terrestrial machines exposed to the working loads of a periodic character. This paper aims to launch a new idea regarding the preservation of the load-carrying structures of these machines by the means of implementing a controllable frequency-controlled drive of the excavating device. Successful implementation of this idea requires a detailed analysis of the dynamic response of the load-carrying structure in order to determine the domains of frequency of revolutions of the bucket-wheel-drive electromotor (FREM) where the dynamic response of the structure is favorable. The main goal of the presented research was the development of a unique three-step method for the identification of the FREM ranges, where the vibroactivity of the load-carrying structure is within the allowed boundaries. A methodologically original study of the dynamic response was conducted on a unique dynamic model of the BWE slewing superstructure that allows for continuous variation of the FREM, i.e., of the frequency of excitation caused by the forces resisting the excavation. Validation of the spatial reduced dynamic model of the slewing superstructure and the corresponding mathematical model, as well as the overall approach to the determination of the dynamic response, were performed by the means of vibrodiagnostics under the real exploitation conditions. Application of the developed method has yielded: (1) the resonant-free FREM domains; (2) the FREM domains, where the structure is not exposed to the excessive dynamic impacts; and (3) the frequency ratio ranges defining the resonant areas. Additionally, the results of the research have pointed out that the resonant-free state represents a necessary but insufficient condition for the proper dynamic behavior of the BWE slewing superstructure

Analysis of damage in precast concrete tunnel segments during the construction phase and the influence of FRC

The increase of the demand for tunnels is palpable. In big cities with urban density ever increasing, more and more infrastructure is competing for the limited available space, so the underground constructions have become a suitable solution. Therefore, there is a high demand for optimizing the construction processes, as well as the materials and machinery. The development of the tunnel boring machines (TBMs) had represented a significant step forward in terms of efficiency. When constructing tunnels with TBMs, the tunnel lining is built during the excavation. The precast concrete pieces that create the lining are used as a support for the TBM hydraulic jacks to push forward the machine. This interaction between the TBM and the lining can highly influence the occurring damage in the segments. The tunnel lining is one of the most important parts of the tunnel as it ensures the protection of the cavern and the stability of the tunnel, hence the quality is of paramount importance. As mentioned before, the construction phase of the tunnel is one of the most strenuous loading case for the segments. In the presented paper, two possible causes of segment damage are analysed: the uneven support of the segments when subjected to the hydraulic jack’s loading and the radial eccentricity of the hydraulic jacks. In both cases, the stress field developed is obtained through the so-called Strut-and-tie method. This method provides a simplified version of the occurring stress fields that is very useful in the calculation of D-regions where the common flexion theory is not applicable. In addition, the simplicity of the strut-and-tie models helps to provide a physical understanding of the stress fields. In Chapter 3 four cases of possible uneven supports of the segments are presented. Through the Strut-and-tie method, the stresses developed in the segment are analysed depending on the segment’s geometrical characteristics and the load applied. In Chapter 4 the effect of the radial eccentricity of the hydraulic jacks is considered. The stress field is calculated also by means of the strut-and-tie method. In both cases, the corresponding segment damages due to the two loading situations are described. Once the failure situations in Chapters 3 and 4 are described, the advantages of using fibres as a reinforcement for the segments are presented. Prior studies have shown that fibres have a positive influence in the behaviour of the hardened concrete and that they are suitable for the tunnel segments. Fibre reinforced concrete in tunnel segments may offer additional advantages over those of conventional reinforcement. In Chapter 5, the advantages of FRC segments and in particular to the type of failures described in the previous chapters are shown

Fatigue Analysis of Central Bridge Deduced from Strain Gage Data and Probability Analysis

This report presents evaluations of the load history of the Central Bridge from both strain gage data and probability analysis. Estimation of remaining service life is made through fatigue criteria. Also included is a comparison (from strain gage data) of live load stresses carried by parallel eye bars. An appendix provides a user\u27s manual for the computer program for probability-based analyses of load events and fatigue-life computations

Towards Long-Term Monitoring of the Structural Health of Deep Rock Tunnels with Remote Sensing Techniques

Due to the substantial need to continuously ensure safe excavations and sustainable operation of deep engineering structures, structural health monitoring based on remote sensing techniques has become a prominent research topic in this field. Indeed, throughout their lifetime, deep tunnels are usually exposed to many complex situations which inevitably affect their structural health. Therefore, appropriate and effective monitoring systems are required to provide real-time information that can be used as a true basis for efficient and timely decision-making. Since sensors are at the heart of any monitoring system, their selection and conception for deep rock tunnels necessitates special attention. This work identifies and describes relevant structural health problems of deep rock tunnels and the applicability of sensors employed in monitoring systems, based on in-depth searches performed on pertinent research. The outcomes and challenges of monitoring are discussed as well. Results show that over time, deep rock tunnels suffer several typical structural diseases namely degradation of the excavation damaged areas, corrosion of rock bolts and cable bolts, cracks, fractures and strains in secondary lining, groundwater leaks in secondary lining, convergence deformation and damage provoked by the triggering of fires. Various types of remote sensors are deployed to monitor such diseases. For deep rock tunnels, it is suggested to adopt comprehensive monitoring systems with adaptive and robust sensors for their reliable and long-lasting performance

Recycling Concrete for Sustainable Construction

The demolition of concrete structures has made concrete debris the largest portion of the waste stream in the U.S. With landfills becoming scarcer, the need to recycle demolition debris is becoming increasingly relevant. An effective way to recycle this material is to produce recycled concrete aggregate (RCA) and use this material in the reconstruction of buildings and roads. Producing and re-using RCA will reduce landfill waste and save energy by minimizing the production and transport of natural aggregates. The focus of this thesis is to quantify how much energy can be saved by producing and re-using RCA instead of landfilling demolition debris and using natural aggregates. However, in order to do this, a thorough understanding of RCA and the natural aggregates industry must first be addressed. Through literature review, the properties, uses, production, and criteria to use RCA was determined. The availability and energy required to produce and transport natural aggregates was also determined. Three case studies were conducted in order to perform analysis on energy savings associated with RCA. In each case, a building was demolished and RCA was produced and re-used from the demolition debris. All of the energy inputs from the production and transportation of the RCA to its re-use site was calculated. This data was compared to the energy inputs to landfill demolition debris and produce and transport virgin aggregates to those same sites. For each case, energy savings were seen by producing and re-using RCA. However, these savings varied greatly for each case. It was determined that variables such as re-use location, location of the quarry/distribution center and modes of transportation used in shipping were the main contributors for these differences. For this reason, it was determined that this model is effective, but that the difference in the variables can have huge impacts and are all project specific. Therefore, this analysis must be made on a case by case basis to determine if this is a sustain

Recycling Concrete for Sustainable Construction

The demolition of concrete structures has made concrete debris the largest portion of the waste stream in the U.S. With landfills becoming scarcer, the need to recycle demolition debris is becoming increasingly relevant. An effective way to recycle this material is to produce recycled concrete aggregate (RCA) and use this material in the reconstruction of buildings and roads. Producing and re-using RCA will reduce landfill waste and save energy by minimizing the production and transport of natural aggregates. The focus of this thesis is to quantify how much energy can be saved by producing and re-using RCA instead of landfilling demolition debris and using natural aggregates. However, in order to do this, a thorough understanding of RCA and the natural aggregates industry must first be addressed. Through literature review, the properties, uses, production, and criteria to use RCA was determined. The availability and energy required to produce and transport natural aggregates was also determined. Three case studies were conducted in order to perform analysis on energy savings associated with RCA. In each case, a building was demolished and RCA was produced and re-used from the demolition debris. All of the energy inputs from the production and transportation of the RCA to its re-use site was calculated. This data was compared to the energy inputs to landfill demolition debris and produce and transport virgin aggregates to those same sites. For each case, energy savings were seen by producing and re-using RCA. However, these savings varied greatly for each case. It was determined that variables such as re-use location, location of the quarry/distribution center and modes of transportation used in shipping were the main contributors for these differences. For this reason, it was determined that this model is effective, but that the difference in the variables can have huge impacts and are all project specific. Therefore, this analysis must be made on a case by case basis to determine if this is a sustain