Yangqing Dou

Analytical investigation and parametric study of lateral impact behavior of pressurized pipelines and influence of internal pressure

ABSTRACT This article provides a combined computational and analytical study to investigate the lateral impact behavior of pressurized pipelines and inspect all the parameters such as the outside diameter and internal pressure and evaluate how they affect such behavior. In this study, quartic polynomial functions are applied to formulate the maximum crushing force (Fmax), maximum permanent displacement (W), and absorbed energy (E) of the pressurized pipelines during the impact problem. The effects of the diameter and pressure on Fmax, W, and E are therefore illustrated through analyzing these functions. Response surfaces are also plotted based on the generated quartic polynomial functions and the quality (accuracy) of these functions are verified through several techniques.

Computational Investigation of Effects of Grain Size on Ballistic Performance of Copper

ABSTRACT Numerical simulations were conducted to compare ballistic performance and penetration mechanism of copper (Cu) with four representative grain sizes. Ballistic limit velocities for coarse-grained (CG) copper (grain size ≈ 90 µm), regular copper (grain size ≈ 30 µm), fine-grained (FG) copper (grain size ≈ 890 nm), and ultrafine-grained (UG) copper (grain size ≈ 200 nm) were determined for the first time through the simulations. It was found that the copper with reduced grain size would offer higher strength and better ductility, and therefore renders improved ballistic performance than the CG and regular copper. High speed impact and penetration behavior of the FG and UG copper was also compared with the CG coppers strengthened by nanotwinned (NT) regions. The comparison results showed the impact and penetration resistance of UG copper is comparable to the CG copper strengthened by NT regions with the minimum twin spacing. Therefore, besides the NT-strengthened copper, the single phase copper with nanoscale grain size could also be a strong candidate material for better ballistic protection. A computational modeling and simulation framework was proposed for this study, in which Johnson–Cook (JC) constitutive model is used to predict the plastic deformation of Cu; the JC damage model is to capture the penetration and fragmentation behavior of Cu; Bao–Wierzbicki (B-W) failure criterion defines the materials failure mechanisms; and temperature increase during this adiabatic penetration process is given by the Taylor–Quinney method.

Wave Energy Converters and Design Considerations for Gulf of Mexico

ABSTRACTThis article presents an investigational study on wave energy converters (WECs) and the design considerations for possible implementation in the Gulf of Mexico (GOM). The types of WEC available from the market are studied first. The design considerations for implementing a WEC in GOM are then evaluated. There are several different types of devices that can be used in the system design. Each device type has different attributes that may be helpful or hurtful for the area and wave activity in the GOM. From the evaluation there is a recommendation of the optimal device design conditions, and three device types are recommended for further pursuit as design candidates. Six different WEC projects that are currently being developed and most are ready for commercial testing are examined. Our study evaluates the usefulness of the WECs for the GOM, and provides design factors of both physical and economic scaling. The result of this investigation reveals that while none of the devices can be installed “as i...

Experimental Study of High Velocity Penetration of an Aluminum Target Plate by a Spherical Projectile

A high velocity penetration experimental between an aluminum sphere and a square aluminum plate is carried out to provide data for depicting the penetration process and behavior of both projectile and target at multi-length scales. Residual stress patterns of the plate’s surface before and after penetration are recorded and compared through X-ray diffraction (XRD). Effects of the penetration on microstructure of the Al plate and the material’s microstructural evolution are also illustrated through SEM. Important Physical features of the penetration phenomena are observed from the penetration tests. A good understanding of Al-Al penetration mechanism can therefore be achieved from the experimental study, along which a standard experimental procedure can be established for investigating plasticity mechanisms that govern engineering material penetration.Copyright

Computational Investigation of High Velocity Penetration of Copper Subjected to Impact From Nickel Projectiles

A computational simulation of penetration between nickel projectile and copper plate with high velocity in macro scale has been built. It is the first time a comprehensive investigation of penetration between these two materials. A threshold velocity between a nickel projectile and a copper plate is determined by mathematical equation in this paper. ABAQUS/Explicit is used to verify this threshold velocity by setting different velocities under the same condition and displaying visual animation of penetration results. John-cook model has been chosen to represent two material plastic behaviors. The shapes of penetrator and target are shown in order to expose penetration procedure and phenomena. Stress patterns and perforation features are adopted to make a good understanding of Ni-Cu penetration mechanism from computational study.Copyright

Analytical Investigation and Parametric Study of Lateral Impact Behavior of Pressurized Pipelines and Influence of Internal Pressure

This paper provides a combined computational and analytical study to investigate the lateral impact behavior of pressurized pipelines and inspect all the parameters such as the outside diameter and internal pressure affects such behavior. In this study, quartic polynomial functions are applied to formulate the maximum crushing force (F), maximum permanent displacement (W), and absorbed energy (E) of the pressurized pipelines during the impact problem. The effects of the diameter and pressure on F, W, and E are therefore illustrated through analyzing those functions. Response surfaces are also plotted based on the generated quartic polynomial functions and the quality (accuracy) of those functions are verified through several techniques.Copyright

Computational Study of Lateral Impact Behavior of Pressurized Pipelines

This paper presents a computational study to investigate the crash responses and collapse mechanisms of pipelines subjected to lateral impact. Influence of internal pressure of the pipelines on their lateral impact behavior is revealed through a serious of numerical crashworthiness analysis. FEA software package, LSDYNA, is used to model the pressurized pipelines and perform the crashworthiness analysis. The simulation results provide a substantial background for the future experimental study to completely investigate dynamic responses and failure modes of pipelines subjected to low-velocity lateral impact. The results presented in this paper also have potential benefits on research of safety and reliability of civil pipelines and development of advanced pipelines materials.

Application of a Microstructure-Based ISV Plasticity Damage Model to Study Penetration Mechanics of Metals and Validation through Penetration Study of Aluminum

A developed microstructure-based internal state variable (ISV) plasticity damage model is for the first time used for simulating penetration mechanics of aluminum to find out its penetration properties. The ISV damage model tries to explain the interplay between physics at different length scales that governs the failure and damage mechanisms of materials by linking the macroscopic failure and damage behavior of the materials with their micromechanical performance, such as void nucleation, growth, and coalescence. Within the continuum modeling framework, microstructural features of materials are represented using a set of ISVs, and rate equations are employed to depict damage history and evolution of the materials. For experimental calibration of this damage model, compression, tension, and torsion straining conditions are considered to distinguish damage evolutions under different stress states. To demonstrate the reliability of the presented ISV model, that model is applied for studying penetration mechanics of aluminum and the numerical results are validated by comparing with simulation results yielded from the Johnson-Cook model as well as analytical results calculated from an existing theoretical model.

COMPUTERIZED DATABASE DECISION MANAGEMENT SYSTEM IN PRODUCTION TRAVELER SHEET

A production traveler sheet is a document which is filled by people, records how a product is manufactured and how many steps need to be followed during the process period. Problems arise when manual work is negatively impacted because production traveler sheet are either deficient, incomplete and time consuming. In this paper a production traveler sheet shows how aircraft skin is assembled and traveled. A lean tool, value stream mapping and computerized database management system were used to analyze the production traveler sheet for automatic assembling of aircraft skin. Through the application of lean concept and computer database system, lead time saving and manufacturing efficiency are obtained by reducing or eliminating nonvalue activities and process time.