This paper introduces the innovative concept of SMA-based multi-ring (SBMR) self-centering damping devices and numerically evaluates their performance and effective design. The SBMR devices are passive metallic dampers consisting of two types of concentric circular rings with rectangular cross-section: (a) superelastic (SE) rings and (b) supplemental energy dissipating (ED) rings. The rings are tightly fitted into each other such that their diametric deformations are constrained. The SE rings are made of SE shape memory alloys (SMA) (e.g., Nitinol), thereby providing the SBMR devices with both self-centering and hysteretic damping. The ED rings are made of metals with higher hysteretic damping capacity to supplement the damping of the SE rings. The SBMR devices can resist both tension and compression (without buckling) in multiple directions, allowing their installation via cross-bracing systems. To evaluate the SBMR devices, they were simulated through 3D nonlinear finite element models. The general response/behavior of the proposed devices and the effects of brace design and orientation on their response were examined. The SBMR devices were found capable of producing more than 100% higher damping compared to single SE SMA rings, particularly under small deformations. Moreover, brace design and orientation were found to have little to no effect on the performance of the SBMR devices.

National accident statistics consistently show that the profession of Class VIII truck drivers is dangerous, and that their fatality rate is very high. One significant reason for this is the lack of rollover crashworthiness of many commercial truck designs. Analysis of numerous trucks that have been through rollovers shows that cab designs are typically designed to be durable, rather than strong, energy absorbing, and able to maintain shape under significant loading. In this current work, both destructive rollover testing and finite element analysis were performed with the objective being the determination of the effectiveness of conventional structural cab reinforcement for diminishing tractor cabin deformation. Intrusion into the tractor’s survival space can lead to mechanical injury (crush) and can also facilitate partial, or full, occupant ejection. The results of this testing show that the amount of structural deformation of the tractor cabin can be significantly reduced, and the amount of occupant survival space preserved using straightforward and cost effective techniques.

The small punch test, currently being used to empirically estimate the material fracture appearance transition temperature (FATT) of a range of components in fossil power plant service, has been further developed for direct estimation of KIc and JIc in a manner that is analytical, material-independent, and requires no prior knowledge of material mechanical properties. The procedure follows an approach that is based on the continuum material toughness concept wherein the criterion for fracture is defined and measured via the continuum stress-strain deformation properties of the material. The procedure specifically involves computing the “local” strain energy density accumulated at the location and time of crack initiation in the small punch test specimen using large-strain finite element (FE) analysis. Since the procedure also includes estimation of the material uniaxial tensile stress-strain behavior from the small punch load-displacement curve, both the fracture toughness and the uniaxial tensile behavior are determined from a single test. The procedure has been developed in order to take advantage of the miniature sample removal techniques that can be applied “nondestructively” to operating components. Results are presented on a range of steels.

This paper investigates the performance of SMA-based multi-ring (SBMR) damping devices through an extensive experimental program. SBMR devices were recently proposed for the seismic damage mitigation of building structures. These devices combine the shape recovery capability of austenitic NiTi rings with the high energy dissipation of a ring made of other metals, such as mild steel or maretensitic NiTi, to achieve a balanced performance in terms of energy dissipation and self-centering. The experimental program consisted of two phases: (I) material testing, and (II) device testing. Phase I aimed at selecting the optimal heat treatments of austenitic and martensitic NiTi alloys for potential application in SBMR devices. To this end, 24 NiTi rod samples with various heat treatments were tested under uniaxial cyclic loading. With an optimal heat treatment, the residual strain of austenitic NiTi rods could be limited to less than 0.1% after 6% of elongation. In phase II, three rings made of austenitic NiTi, martensitic NiTi, and A36 steel, as well as a double-ring device and a triple-ring device, were tested under various bidirectional loading protocols. The test results showed that the austenitic NiTi ring with an optimized heat treatment could provide more than 93% of self-centering, but only less than 5% of effective damping ratio. However, both the double- and triple ring devices provided at least 64% of self-centering and up to 16% of effective damping ratio. SBMR devices were also found capable of remaining usable after at least three strong seismic events with different durations.

A process upset at a chlorine production facility resulted in a release that forced the partial evacuation of a nearby town. Investigations revealed that the events commenced with the failure of a shell and tube heat exchanger (liquefier) used to condense chlorine gas. Post-incident inspections revealed a cloth at the liquefier coolant inlet that accelerated the flow in that region, causing certain tubes to be breached. As a result, the water-based brine liquefier coolant was entrained in the chlorine process stream, forming a highly acidic oxidizing mixture. This corrosive mixture then flowed to the chlorine storage tanks destroying an elbow in the tank inlet piping and rendering the tank shut-off tank valve ineffective, thus allowing chlorine to vent into the atmosphere. This paper discusses the multi-disciplinary approach used to investigate this incident. In particular, this paper discusses the detailed physical inspections performed, the finite element analyses used to determine the flow conditions, and the corrosion testing conducted to evaluate the failure.