An experimental method to measure initiation events during unstable stress-induced martensitic transformation in a shape memory alloy wire

An experimental configuration is demonstrated that captures features of the initiation of unstable stress-induced transformation in a shape memory alloy (SMA). The apparatus uses circulating fluids through the grips and a heat sink and thermoelectric devices to control the temperature profile of a specimen within a mechanical testing machine. The configuration can be used to restrict the initiation of phase transformation to a small region of interest of the free length, while permitting full-field optical tracking, infrared imaging, use of laser extensometry, and monitoring of load and extension. In this way, some longstanding difficulties in the measurement of thermo-mechanical phenomena in SMA wire have been resolved. The size of initiation stress peaks can be accurately measured for both transformation directions without changing the wire geometry, the temperature of a region of interest can be selected over a wide range, and imaging can be performed for multiple loading cycles and for events that occur from static to near dynamic rates. The motivation for this work is to produce high quality data for use in calibrating numerical models that study thermo-mechanical coupling during unstable transformation behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58145/2/sms7_1_S16.pd

CT-GUIDED TRANSTHORACIC NEEDLE BIOPSY: ADVANTEGES IN HISTOPATHOLOGICAL AND MOLECULAR TESTS

Aim: The present study aimed to demonstrate that computed tomography-guided transthoracic needle biopsy (TTNB) is a safe procedure that gives a more accurate pre-operative tissue diagnosis for peripheral lung nodules than transthoracic needle aspiration, obtaining suitable samples for molecular test in lung adenocarcinomas. Patients and methods: Between December 2016 and March 2018 at Thoracic Surgery Department of the University of Palermo - Policlinico Paolo Giaccone Hospital, TTNB was performed in 42 patients with computed tomography-detected peripheral lung nodules > 10 mm, using 16-18 -Gauge tru-Cut needles. Results: With TTNB, we have estimated an accuracy for tissue diagnosis of 97,6%. At the molecular test, EGFR overexpression and ALK mutation resulted positive for 12/23 patients with lung adenocarcinoma. Conclusion: TTNB has showed a low rate of complications and it is adoptable as standard diagnostic procedure for peripheral lung nodules

Double traumatic diaphragmatic injury: A case report

Introduction: Traumatic diaphragmatic injuries are rare complications resulting from a thoracic-abdominal blunt or penetrating trauma. Left-sided diaphragmatic injuries are more commonly reported in literature. Bilateral injuries are extremely rare, occurring in about 3% of the patients and just few cases reported in literature. Traumatic diaphragmatic hernias are definitely a marker of a severe trauma, in fact diaphragmatic injuries are often related to thoracic and abdominal organs injuries. Sometimes the classic clinical signs and symptoms of diaphragmatic injuries may initially not be present so that definitive evaluation is delayed or even missed. Case report: A 62-years old woman was admitted in Emergency Department after a pedestrian accident. A whole-body CT scan showed multiple fractures (ribs, pelvic and vertebral) but no organ injury. The next CT detected a left-sided posterior diaphragmatic hernia involving transverse colon. Thus we performed an explorative laparoscopy and found a double diaphragmatic injury. A primary repair with non-absorbable sutures and a prosthetic titanized patch was performed

Plastic anisotropy evolution of SS316L and modeling for novel cruciform specimen

In this paper, the evolution of the plastic anisotropy of stainless steel 316L samples is investigated under proportional loading paths using a customized cruciform specimen. The determination of a novel cruciform specimen by a design of experiments approach integrated with finite element simulations is described. The mechanical properties of the material are characterized under uniaxial tension applied in every 15° from the rolling direction and equibiaxial tension from hydraulic bulge experiments. The results reveal that the plastic anisotropy shown in stress and strain significantly evolves with respect to the plastic work. Based on the experiments, the material behavior is modeled using a non-quadratic anisotropic yield function, Yld2004–18p, with parameters modeled as a function of the equivalent plastic strain, assuming plastic work equivalence, and with constant parameters for comparison. The Hockett-Sherby model is also used for the strain hardening behavior to extrapolate the results to higher strain values. The models are implemented into a user material subroutine for finite element simulations. To validate the model, in-plane biaxial tension experiments are performed, using a customized specimen, to achieve greater deformation than previous designs by introducing double-sided pockets for thickness reduction and notches in the corner areas. The results are compared with finite element simulations implemented with the plasticity models

Evaluation of biaxial flow stress based on elasto-viscoplastic self-consistent analysis of X-ray diffraction measurements

Biaxial flow behavior of an interstitial free steel sample was investigated with two experimental methods: (1) Marciniak punch test with in situ X-ray diffraction for stress analysis; (2) hydraulic bulge test. The stress analysis based on X-ray diffraction using (211) lattice planes was accompanied by the use of stress factors and intergranular (IG) strains. Stress factors and IG strains were experimentally obtained ex situ on samples after prescribed equi-biaxial deformations. An elasto-viscoplastic self-consistent (EVPSC) crystal plasticity model was used to predict the stress factors and the IG strains. The model predictions of the stress factors were in good agreement with the experiments. However, the predictions of IG strains were in poor agreement with their experimental counterparts. As a result, the flow stress solely based on the computationally predicted stress factors and IG strains was unrealistic. The input of the experimental stress factors and IG strains for stress analysis improved the agreement with a reference flow curve obtained by a hydraulic bulge tester. The resulting flow curves based on X-ray diffraction were in good agreement with that of the bulge test up to an effective strain of 0.3. However, an unrealistic softening was observed in larger deformations regardless of whether the stress factor used were experimentally measured or determined from EVPSC calculations. (C) 2014 Elsevier Ltd. All rights reserved.X11169Nsciescopu