Finite Element Investigations of the Effect of Residual Stress in Cold-Formed Sigma Beams

Press braking is a cold forming operation used to fold the angle along the flat sheet between the top punch and bottom die. The residual stress will be induced in this process as a result of plastic deformation. In the welding process, a dynamic thermal cycle is introduced to generate a non-uniformly temperature distribution on the heat affected zone (HAZ), and the residual stress also occurs in the process as a result of uneven cooling along the welding bead. The existence of residual stress can superimpose onto the external loadings to affect the stiffness and load resistance capacity of the structures. Therefore, a comprehensive understanding of the distribution and the impact of residual stress on the performance of cold-formed sections (CFS) is essential. The primary motivation of this paper is to provide a numerical solution for exploring the effect of press braking and welding residual stress on CFS sigma beams. Modelling methods were validated against the published experimental data and the influence of inputs to the model was discussed by parametrical studies. Based on the laboratory test results, the effect of residual stress on sigma beams was further investigated. It is found that the residual stress on the corner region will increase the failure load of sigma beams while the residual stress on the flat portion will decrease the failure load

OPTIMIZING UPWARD LOAD BALANCING FOR LOSSY AND LOW-POWER NETWORKS

Presented herein are techniques for better load balancing of uplink flows at an overloaded node. The techniques presented herein leverage the capacity of neighboring nodes in order to share the traffic from the overloaded node. As a result, after several rounds of sharing, the probability of congestion decreases exponentially

Numerical studies of residual stress in cold formed steel sigma sections

Residual stress is a self-balanced internal stress generated in the metal component when it is loaded beyond the elastic plateau and then unloaded. The existence of residual stress will be superimposed onto the external loadings to affect the stiffness and load resistance capacity of the structures. The most common sources of residual stress in CFS sections are cold working process and heat-treating operation. The primary motivation of this thesis is to provide a numerical solution for exploring the distribution and effect of cold working and welding residual stress on CFS sigma sections. Initially, the magnitude and distribution of coiling-uncoiling, press braking, roll forming and welding residual stress in sigma sections are presented. Parametrical studies are conducted to investigate the influences of input parameters on the numerical model. Numerical prediction validity is evaluated with analytical solutions and measured result from the X-ray diffraction measurement. Moreover, for investigating the influence of residual stress on structural beam in sigma sections, comparisons are performed based on the finite element (FE) analysis between the virgin model without cold work effects and modified model incorporated the effect of residual stress and strain hardening. Finally, some conclusions and the recommendations for future works are presented

FIRMWARE COMPRESSION MECHANISM FOR SPEEDING UP FIRMWARE UPDATING IN A RESOURCE RESTRICTED NETWORK

Techniques are described herein for adopting a substring list creation and extraction mechanism as well as a variable-length patch mechanism to generate an Over-The-Air (OTA) image path file having a small size. This saves network resources and reduces side effects on data transmission / network service when executing image / firmware upgrading. As a result, OTA updating can be sped up, and the peak network traffic during the firmware updating may be narrowed

RATE ADAPTION TECHNIQUES FOR LOW-POWER AND LOSSY NETWORKS (LLNS) BASED ON LOSS DIFFERENTIATION AND SAMPLE RATE

Proposed herein is a complete solution to choose the appropriate PHY mode for delivering packets between nodes based on loss differentiation and sample rate. With the proper PHY mode selection, the described techniques are capable of distinguishing between fading and collision as the source of poor network performance, which can greatly assist in decreasing the latency of frames in low-power and lossy networks (LLNs)

TIMELY DELIVERY OF POWER OUTAGE NOTIFICATIONS IN LOW-POWER AND LOSSY NETWORKS

Techniques are described herein to timely deliver Power Outage Notification (PON) messages when a power outage occurs in smart utilities. Irrelevant packets may be proactively prevented by broadcasting the PON alert to notify the surrounding nodes, and may also be filtered and discarded when a node is experiencing an outage. Multiple PON packets may be intelligently aggregated and compressed

INTER PERSONAL AREA NETWORK BACKUP

Techniques are described herein for realizing an intra Personal Area Network (PAN) backup. The data traffic interrupt duration may be significantly reduced after the Field Area Router (FAR) goes down. These techniques may also keep the intra-PAN logical group stable after a FAR power cycle

FRAME COUNTER IN LOW-POWER AND LOSSY NETWORK

Techniques are described herein for using parameters such as Group Temporal Key (GTK) rest lifetime, GTK whole lifetime, and frame counter length/max packets per second to acquire a safe, available, and non-repeated initial frame counter. A node may use this frame counter to communicate with its neighbor node after joining any Personal Area Network (PAN)

GENETIC SIMULATED ANNEALING BASED GROUP MANAGEMENT SOLUTION FOR MULTIPLE VENDORS IN LOW-POWER AND LOSSY NETWORKS

Techniques are described herein to transform logical group traffic into a combination of broadcast and unicast messages rather than flood of broadcast messages. These techniques limit redundant traffic to manage logical group traffic over Wireless Mesh Networks (WMNs)

HEARTBEAT MECHANISM FOR SYNCHRONIZATION IN LOW-POWER AND LOSSY NETWORKS

Described herein are techniques to enable nodes to determine whether the Border Router (BR) is alive. These techniques leverage existing traffic, thereby avoiding wasting bandwidth resources such as periodic asynchronous messages to maintain Wireless Mesh Network (WMN) connectivity