Design of 3D-Printed Titanium Compliant Mechanisms

This paper describes 3D-printed titanium compliant mechanisms for aerospace applications. It is meant as a primer to help engineers design compliant, multi-axis, printed parts that exhibit high performance. Topics covered include brief introductions to both compliant mechanism design and 3D printing in titanium, material and geometry considerations for 3D printing, modeling techniques, and case studies of both successful and unsuccessful part geometries. Key findings include recommended flexure geometries, minimum thicknesses, and general design guidelines for compliant printed parts that may not be obvious to the first time designer

Deployment Methods for an Origami-Inspired Rigid-Foldable Array

The purpose of this work is to evaluate several deployment methods for an origami-inspired solar array at two size scales: 25-meter array and CubeSat array. The array enables rigid panel deployment and introduces new concepts for actuating CubeSat deployables. The design for the array was inspired by the origami flasher model (Lang, 1997; Shafer, 2001). Figure 1 shows the array prototyped from Garolite and Kapton film at the CubeSat scale. Prior work demonstrated that rigid panels like solar cells could successfully be folded into the final stowed configuration without requiring the panels to flex (Zirbel, Lang, Thomson, & al., 2013). The design of the array is novel and enables efficient use of space. The array can be wrapped around the central bus of the spacecraft in the case of the large array, or can accommodate storage of a small instrument payload in the case of the CubeSat array. The radial symmetry of this array around the spacecraft is ideally suited for spacecraft that need to spin. This work focuses on several actuation methods for a one-time deployment of the array. The array is launched in its stowed configuration and it will be deployed when it is in space. Concepts for both passive and active actuation were considered

The Compliant A-Arm Suspension

ABSTRACT The use of compliant mechanisms in a suspension system has been demonstrated with leaf spring mechanisms. In this research a novel compliant configuration called the Compliant A-Arm (C-A-Arm) suspension is selected for in-depth study. Closedform equations are derived for linear small-deflection stiffness equations. Large deflections are analyzed using finite element analysis. A pseudo-rigid-body model is developed to approximate mechanism deflections and stiffness for large deflections. The results suggest that the C-A-Arm configuration may be a viable suspension alternative for future commercial application. In addition, this configuration offers a number of performance variables that could be the basis for an active control system. This paper represents a necessary first step in modeling this new configuration

Microspine Gripping Mechanism for Asteroid Capture

This paper details the development and early testing of a compliant suspension for a microspine gripper device for asteroid capture or micro-gravity percussive drilling. The microspine gripper architecture is reviewed, and a proposed microspine suspension design is presented and discussed. Prototyping methods are discussed, as well as testing methods and results. A path forward is identified from the results of the testing completed thus far. Key findings include: the microspine concept has been established as a valid architecture and the compliant suspension exhibits the desired stiffness characteristics for good gripping behavior. These developments will aid in developing the capability to grasp irregularly shaped boulders in micro-gravity

A New Self-Adjusting CVT Configuration Using Compliant Mechanisms

ABSTRACT This paper introduces a new configuration of a Continuously Variable Transmission (CVT) that is self-adjusting and designed as a compliant mechanism. This new configuration is called the Pivot-Arm CVT. The criteria for classification as a Pivot-Arm CVT is discussed. An analytical model describing the performance of the Pivot-Arm CVT is developed. Special design considerations which may be useful in implementing Pivot-Arm CVTs are introduced and explained. The Pivot-Arm CVT model is validated through controlled testing of two Pivot-Arm CVT prototypes

Constraints on the Progenitor of SN 2016gkg From Its Shock-Cooling Light Curve

SN 2016gkg is a nearby Type IIb supernova discovered shortly after explosion. Like several other Type IIb events with early-time data, SN 2016gkg displays a double-peaked light curve, with the first peak associated with the cooling of a low-mass extended progenitor envelope. We present unprecedented intranight-cadence multi-band photometric coverage of the first light-curve peak of SN 2016gkg obtained from the Las Cumbres Observatory Global Telescope network, the Asteroid Terrestrial-impact Last Alert System, the Swift satellite and various amateur-operated telescopes. Fitting these data to analytical shock-cooling models gives a progenitor radius of ~25-140 solar radii with ~2-30 x 10^-2 solar masses of material in the extended envelope (depending on the model and the assumed host-galaxy extinction). Our radius estimates are broadly consistent with values derived independently (in other works) from HST imaging of the progenitor star. However, the shock-cooling model radii are on the lower end of the values indicated by pre-explosion imaging. Hydrodynamical simulations could refine the progenitor parameters deduced from the shock-cooling emission and test the analytical models.Comment: Accepted by ApJ

ACR Appropriateness Criteria® Non-Spine Bone Metastases

Abstract Bone is one of the most common sites of metastatic spread of malignancy, with possible deleterious effects including pain, hypercalcemia, and pathologic fracture. External beam radiotherapy (EBRT) remains the mainstay for treatment of painful bone metastases. EBRT may be combined with other local therapies like surgery or with systemic treatments like chemotherapy, hormonal therapy, osteoclast inhibitors, or radiopharmaceuticals. EBRT is not commonly recommended for patients with asymptomatic bone metastases unless they are associated with a risk of pathologic fracture. For those who do receive EBRT, appropriate fractionation schemes include 30?Gy in 10 fractions, 24?Gy in 6 fractions, 20?Gy in 5 fractions, or a single 8?Gy fraction. Single fraction treatment maximizes convenience, while fractionated treatment courses are associated with a lower incidence of retreatment. The appropriate postoperative dose fractionation following surgical stabilization is uncertain. Reirradiation with EBRT may be safe and provide pain relief, though retreatment might create side effect risks which warrant its use as part of a clinical trial. All patients with bone metastases should be considered for concurrent management by a palliative care team, with patients whose life expectancy is less than six months appropriate for hospice evaluation. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every two years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98458/1/jpm%2E2011%2E0512.pd

ACR Appropriateness Criteria® Spinal Bone Metastases

The spine is a common site of involvement in patients with bone metastases. Apart from pain, hypercalcemia, and pathologic fracture, progressive tumor can result in neurologic deterioration caused by spinal cord compression or cauda equina involvement. The treatment of spinal bone metastases depends on histology, site of disease, extent of epidural disease, extent of metastases elsewhere, and neurologic status. Treatment recommendations must weigh the risk-benefit profile of external beam radiation therapy (EBRT) for the particular individual's circumstance, including neurologic status, performance status, extent of spinal disease, stability of the spine, extra-spinal disease status, and life expectancy. Patients with spinal instability should be evaluated for surgical intervention. Research studies are needed that evaluate the combination or sequencing of localized therapies with systemic therapies including chemotherapy, hormonal therapy (HT), osteoclast inhibitors (OI), and radiopharmaceuticals. The roles of stereotactic body radiation therapy (SBRT) in the management of spinal oligometastasis, radioresistant spinal metastasis, and previously irradiated but progressive spinal metastasis are emerging, but more research is needed to validate the findings from retrospective studies. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140115/1/jpm.2012.0376.pd