Alan Slade

Issues concerning the measurement of transformation temperatures of NiTi alloys

The transformation between martensite and austenite in shape memory alloy is characterized by four transformation temperatures: martensite start temperature (Ms), martensite finish temperature (Mf), austenite start temperature (As) and austenite finish temperature (Af). In actuator designs that rely on the shape memory effect, it is important to obtain an accurate measure of these transformation temperatures, especially As and Af, because they determine the functional temperature range of the actuator. Several methods of determining these temperatures have been reported, but their accuracy and coherence are not clear. The transformation temperatures of NiTi wire under different heat treatment conditions were measured by the three commonly used methods: differential scanning calorimetry (DSC); an electrical resistance method, which uses a sudden change in resistance as an indication of transformation; and an applied loading method, where a macroscopic displacement indicates the transformation. The results show that the transformation temperatures measured by DSC do not correspond to those measured by the other two methods, which are similar. The applied loading method is most effective for providing practical information about the stress-dependent transformation temperatures. The electrical resistance method gives clearly determined points for Ms and Mf in the cooling resistance–temperature curve, but As and Af are not clearly identifiable in the heating process.

Robotic sorting of paper items from a random pile

Abstract A random stack of documents is physically sorted into ordered stacks according to type and condition. This is done by first locating the topmost item using a machine vision system with algorithms based upon the Hough Transform. The edges of the items are identified from the shadows created by illuminating the pile from different directions. Having located the position and orientation of the topmost item, a robot arm is programmed to pick the item from the pile using an end-effector with vacuum picking mechanisms. The robot arm offers the picked item “on-the-fly” to devices which ascertain its physical fitness and classification. Finally, the item is placed on the appropriate one of a number of piles of similar category.

Design of SMA Actuator Based Access Device for Transanal Endoscopic Microsurgery

An access device using a combination of a compression coil spring made of NiTi shape memory alloy (SMA) and NiTi superelastic strips has been developed. Particular consideration is given to the application of the concept in transanal endocopic microsurgery (TEM), but it could be used in other procedures where tissue expansion is required. In TEM, it could realize the gasless dilation of the rectum with safety and reliability, and facilitate surgeons to perform TEM. The theoretical design procedure to determine the specifications of the NiTi SMA spring and superelastic components is established. The feasibility and the possible problems associated with this application are discussed generally.

Optimization of Ultrasonic Tool Performance in Surgery

This paper investigates the tool/material interface boundary conditions in an actual operation environment. The aim is to establish a fundamental understanding of the tool/material interfacial mechanisms using finite element methods and to predict how the vibration parameters and material properties might influence the overall system performance. In the simulation, a 3D FE simulation is being developed using dynamic mechanical analysis to characterize the vibration parameters of the tool at its tuned frequency. A selection of the material and geometry required for the tool is examined in this analysis. An ultrasonic cutting system is then implemented to achieve maximize ultrasonic benefits. This knowledge is then used to maximize ultrasonic benefits, and to quantitatively identify a close approximate model of the interfacial boundary conditions for estimating the effects on the die termination in the analytical stages of design.

Soluble Gas Tight Capsules for use in Surgical Quality Testing

During many surgical procedures such as gastrointestinal or vascular surgery it is necessary to excise and reconnect bodily conduits. Failed connections can have extremely serious consequences and a method to help surgeons determine the integrity of connections has been proposed. This involves the detection of trace gas breaching an anastomosis. A key feature of this is establishing a method to place a controlled volume of gas into the conduit. A soluble capsule method is presented here. The requirements were that the capsule must be safe, a volume of 0.5 − 1.0ml of gas at 2 Bar pressure should be contained, that the filling gas can be varied to suit the clinical application and that the capsules have a shelf life of at least 5 days without showing loss of gas. A device and procedure were developed to meet these criteria. This consists of modified oral pharmaceutical capsules and a capsule filling mechanism contained in a vacuum chamber. Sealing the capsules has been achieved via an alcohol / water mix coupled to capilliary action. Results show performance which meets the design specification and the capsules have shown themselves effective in tests using phantom scenarios.

Issues Concerning the Measurement of Transformation Temperatures in NiTi Alloys

The transformation between martensite and austenite is characterized by four transformation temperatures: martensite start temperature (Ms), martensite finish temperature (Mf), austenite start temperature (As) and austenite finish temperature (Af). In actuator design that relies on the shape memory effect, it is important to obtain an accurate measure of these transformation temperatures, especially As and Af. Several methods of determining these temperatures have been reported, but their accuracy and coherence are not clear. Three methods were used to measure the transition temperatures of NiTi wire under different heat treatment conditions: differential scanning calorimetry (DSC); an electrical resistance method, which uses a sudden change in resistance as an indication of transformation; and an applied loading method, where a macroscopic change in displacement indicates the transformation. The results show that the transition temperatures measured by DSC do not correspond to those measured by the other two methods, which are similar. The applied loading method is the most effective for providing practical information about the stress-dependent transformation temperatures. The electrical resistance test gives clearly determined points for Ms and Mf in the cooling resistance-temperature curve, but As and Af are not clearly identifiable in heating process.

Using an infra-red sensor to measure the dynamic behaviour of N2O gas escaping through different sized holes

An anastomosis is a surgical procedure that consists of the re-connection of two parts of an organ and is commonly required in cases of colorectal cancer. Approximately 80% of the patients diagnosed with this problem require surgery. The malignant tissue located on the gastrointestinal track must be resected and the most common procedure adopted is the anastomosis. Studies made with 2,980 patients that had this procedure, show that the leakage through the anastomosis was 5.1%. This paper discusses the dynamic behavior of N2O gas through different sized leakages as detected by an Infra-Red gas sensor and how the sensors response time changes depending on the leakage size. Different sized holes were made in the rigid tube to simulate an anastomostic leakage. N2O gas was injected into the tube through a pipe and the leakage rate measured by the infra-red gas sensor. Tests were also made experimentally also using a CFD (Computational Fluid Dynamics) package called FloWorks. The results will be compared and discussed in this paper.

The Study of Active Noise Control Method for Moving Target in Noisy Space

For the noise problem of moving target in noisy space, This work is dedicated to developing a novel and promising solution based on the moving target tracking technology and the active noise control (ANC) technology. The development process began with the simplified sound field interaction model, the “auto position tracking near head space ANC” strategy has been proposed from the modelling study. Furthermore, the primary experimental system that consists of the acoustic positioning and tracking subsystem for tracking the control point and the ANC subsystem for generating the anti-noise signal is presented, with the emphasis on the development of the improved TDC-FXLMS ANC algorithm. Finally, the performance of the auto-position tracking near head space ANC device is evaluated by carrying out the primary experiments on an experimental evaluation system.

A Smart Ultrasonic Cutting System for Surgery

Ultrasonic cutting is widely used in food processing applications to produce a clean and accurate cut. However, it is yet to be adopted in orthopedic applications, mainly due to the high temperatures that can be generated at the cut site. In this paper a single-blade ultrasonic cutting device is used to study ultrasonic cutting of different materials using materials of cheese, plastic and wood. A comparison between experimental and computed results is used for the relationship between the forming force and tool displacement and visualization which demonstrate close agreement. If deformation is performed under superimposed vibration, the mean stress necessary to maintain plastic now decreases appreciably in comparison with that for purely static deformation, and this decrease is accurately predicted by the finite element (FE) models. The future work aims to perform the experiments at temperatures close to that of the body in order to explore whether it is possible to maintain cutting temperatures within safety limits by controlling the cutting parameters.

Robotic System for Femoral & Tibial Osteotomies Assistance

Typical osteotomy procedures around the knee joint involve the removal of a wedged shaped section of bone from either the proximal tibia or distal femur in order to correct a deformity and alter the alignment of the lower extremities. Unfortunately, the subjective nature of the preoperative planning and free-hand surgical techniques currently employed can lead to significant outcome variability and high complication rates. A prototype computer-robotic system, KneeCAS-1 (Knee Computer-Assisted System), has been developed to assist such osteotomy procedures around the knee joint. It consists of a custom-built six degree-of-freedom “fail-hard” surgical robot, with an instrumented saw driver unit, and a computer based planning system. It is intended to perform automated cutting (sawing) of the osteotomy planes under surgeon supervision.