In endoscopic surgery, the surgical navigation needs to calculate the internal deformation of the soft tissue by biomechanical model which needs to determine the elastic properties and boundary conditions. However, these information cannot be obtained accurately in a real operation scenario. For example, only a limited portion of a liver surface can be observed in a hepatic surgery under endoscope while its elastic properties remain unknown. In addition, simple boundary conditions such as fixed constraints and free-force constraints are not physically adequate to simulate the elastic effect of ligaments attached to the liver. Biomechanical models of the soft tissue have been thoroughly studied in recent years. In these studies, boundary conditions play an important role in identification of elastic properties for mechanical model based methods. But they rarely combine these unknown conditions together to construct the model, and instead set boundary conditions or elastic properties as known for simplification. In this paper, we present a novel method to identify the Young’s modulus and equivalent spring constraint boundary conditions of a partially observed soft object with incomplete boundary conditions. The spring constraint boundary condition is applied to alternate the conventional displacement boundary conditions (e.g. free constraint and fixed constraint) and an inverse algorithm based on the standard finite element method (FEM) and Gauss-Newton (GN) method is developed, which takes external forces and displacements of observable nodes as inputs. A series of numerical simulation experiments are implemented and the analysis of simulation results show the feasibility of the proposed method.

Aluminum, known for its low density and its ability to resist corrosion through passivation, is vitally important to the aerospace industry, transportation, and building industries. The most common problem when machining titanium using traditional metal cutting processes is that tools rapidly wear out and need to be replaced since the variation of chip thickness, high heat stress, high-pressure loads, spring back, and residual stress result in higher tool wear and worse machined surface integrity. Thus, a technique that allows high precision machining of titanium that preserves the integrity of the machined material, reduces tool wear or even eliminates tooling entirely is an important advance. This study examines the ability to machine Al 6061-T6 and Ti-6Al-4V using a pulsed water jet by simulation using ABAQUS Smoothed Particle Hydrodynamics (SPH). The aluminum results showed that between the three diameters the 0.4572 mm orifice is a better choice based upon the percent increase from the orifice diameter; but based off of the kerf, the 0.3556 mm is the better choice. The results show that the 621 MPa has the highest MRR for Al 6061-T6, 232.1 mm 3 /s. For the four pressure simulations for the titanium, the 138 MPa pressure has the smoothest surface. Even though the volume removed decreased as the pressures increased for the titanium, the MRR increased due to the shorter machining times with 621 MPa pressure having the second highest MRR, 170.051 mm 3 /s. The results show that overall the 621 MPa is the best choice from the parameters chosen for machining Al 6061-T6 and Ti-6Al-4V.

Fibre metal laminates are new sorts of composite materials with superior fatigue and impact properties. Forming parts from FMLs is very attractive to reduce the process cycle and labor cost. Laser peen forming (LPF) is a promising method to form FMLs with its design flexibility and adaptability to produce complex shapes. To predict the deformed shape of FMLs after laser peen forming, eigenstrain-based modelling is a helpful method with advantage in spending less computational time, but it is difficult to precisely determine eigenstrain distribution regarding material with layered structure. In the present research, an efficient and effective experiment-based method is proposed to determine eigenstrain in the metal layer of FMLs, which can avoid the complicated numerical simulation. The determined eigenstrain is assumed to be uniformly distributed in each metal layer while no plastic deformation is generated in composite layer due to its high strength yield. An analytical model is developed to relate the bending deformation to eigenstrain field. Firstly, the equivalent external bending moment applied on the samples is deduced from eigenstrain, and then the relation of deformation and bending moment is provided by a beam bending model. Chemical etching is utilized to remove metal layer by layer to calculate eigenstrain in each layer. With removal of each metal layer, the bending profiles will spring back or bend further due to change of applied moment and bending stiffness. The eigenstrain in each layer can be inversely determined by matching the residual bending profile after each etching with the developed bending model. One scanning strategy of LPF with reciprocating line and 50% overlapping rate is performed in experiments to apply laser shocks on the entire top surface of strip samples, which are prepared from glass laminate aluminum reinforced epoxy with a unidirectional orientation. Eigenstrain in the top and bottom metal layer is successively determined by the proposed analytical model and chemical etching. Finite element analysis is utilized to verify the determined eigenstrain by comparing the simulated shape with experiments and good agreement is obtained.

One of the major issues with forming sheet metal is the tendency for parts to spring back towards their original shape when the applied loading is released. Springback is a form of geometric inaccuracy and is the result of residual stresses, which are created as the part deforms. As a result, forming intricate parts require specialized equipment and calculations to compensate for springback. Transportation industries that rely on forming high strength parts currently use complicated machinery that takes up time and energy to meet specifications. This research investigates the effects of electrically assisted manufacturing (EAM), a process in which electrical current is applied while a material is being manufactured, on springback. Bending and flattening testing will be performed on 4 metals: stainless steel 304 and 316, ASM-T-9046 titanium, and AZ31B magnesium. Additional testing will be performed on stainless steel, observing the effect of changing thicknesses, pulse durations, and current densities on springback. It was observed that an increase in pulse durations results in decreased springback for all the materials. Applying electricity to decrease springback was more effective for bending than flattening procedures in stainless steel and titanium, though it was equally effective for magnesium. For the additional testing on stainless steel, a change in thickness affected results when comparing it to current density, but not when observing similar applied current.

Deformation machining is a combination of thin structure machining and single point incremental forming. It enables the creation of thin monolithic structures with complex geometries in one setup, employing conventional manufacturing techniques. Elastic spring back is a major contributor to dimensional inaccuracy of the thin formed structures. Correct prediction of elastic spring back and its compensation is of utmost importance for the overall quality of the formed components. In the present work, an experimental study on elastic spring back in deformation machining bending mode components has been performed. Effect of machining and forming parameters along with dimensional attributes on the elastic spring back has been studied. The components were fabricated using a 3 axis CNC vertical milling machine and inspected for elastic spring back on a coordinate measuring machining (CMM). Other factors contributing to the dimensional inaccuracy, such as curvature in the bent structure and inclination of structure along its length have also been explored.

This paper presents a new simulation model for flexible needle insertion into soft tissue using modified local constraint method. In this work, we assume deformation of the needle is relatively small, therefore, the soft tissue deformation in the radial direction is far less than it is in the axial direction. Under the assumptions above, the spring model in the radial direction of the needle is established and applied in the puncture procedure to obtain the equilibrium position of the needle-tissue system. The FEM model for the simulation includes three iterative steps: 1. Distribute the axial force on the needle into tissue nodes, and add radial constraint on tissue nodes that are connected with needle’s shaft, then calculate the whole displacement of the tissue nodes; 2. Based on the whole displacement of all nodal points and the effective stiffness matrix, we get the radial force on the tissue, then we use the spring model in the radial direction to get the equilibrium position; 3. Compound the radial and axial force on the tissue nodal points to obtain the actual displacement. Simulation results are presented and discussed.

Finite Element Analysis (FEA) is widely used to simulate machining processes. However, in general, it is time consuming, error-prone, and requires repeated efforts to establish a verified successful Finite Element (FE) model. To rapidly investigate the effects of parameters such as tool angle, feed rate, cutting speed, and temperatures generated during the machining process, an efficient approach is proposed in this paper. The technique has been used to achieve rapid FF simulation during turning and milling processes using Python language programming of Abaqus. Sub-model 1 is programmed to simulate the chip formation process in Abaqus/Explicit. Sub-model 2 is programmed to simulate the cooling spring-back process by importing the machined surface into Abaqus/Implicit. The proposed method is capable of simulating the chip morphology, stress, strain and temperature of the machining process with different parameters immediately. The established FE models are automatically solved in batch by programming script. Post-processing is programmed by Abaqus script to easily achieve and evaluate the simulation results. The Programmed FE models are validated in terms of the predicted chip morphology, cutting forces and residual stresses. This method is extraordinarily efficient saving more than 33% simulation time in comparison to existing FEA approach used for machining processes. Moreover, the script is concise, easy to debug, and effectively avoiding interactive mistakes. The rapid programming model provides a novel, efficiency and convenient approach to thoroughly investigate the effects of a large number of parameters on machining processes.

This paper serves to report the findings of an initial study on the holing of laminated stacks of electrical steels. Three different holing methods were considered: plunge milling, helical milling (orbit milling), and drilling. Stack delamination, axial thrust force, and burr formation were measured at various feed rates for each process and utilized as comparison metrics. Results from the initial experimental investigation indicate that drilling produces significant burr and plunge milling, whilst reducing burr formation compared to drilling, led to delamination of the stack. Helical milling minimized thrust forces, avoided delamination and minimized burr formation. An interesting spring back effect was also observed during the cutting of the laminated stacks. It is concluded that helical milling is a viable and effective processing method for making holes in laminated stack of hard electrical steels.

The efficiency of the milling process is limited due to excessive vibrations that negatively impact the tool and work-piece quality. This becomes even more of a concern in micro-milling where sudden tool breakage occurs before the operator can adjust cutting parameters. Due to different chip formation mechanisms in micro-milling, an increased tool-radius to feed-rate ratio, and higher spindle speeds, micro-milling is a highly non-linear process which can produce multiple and broadband frequencies which increase the probability of tool failure. This paper investigates micro-milling through the development and analysis of a 3-D nonlinear micro-milling dynamic model. A lumped mass, spring, damper system is assumed for modeling the dynamic properties of the tool. The force mechanism utilized is a slip-line field model that provides the advantages of being highly dynamic by accounting for the constantly changing effective rake angle and slip-line variables. Accurate prediction of the chip thickness is important in correctly predicting the dynamics of the system since the force mechanism and its variables are a function of the chip thickness. A novel approach for calculating the instantaneous chip thickness which accounts for the tool jumping out of the cut and elastic recovery of the work-piece is presented. The derivation for the effective rake angle is given and the helical angle is accounted for resulting in a 3-D micro-milling model. The results of simulating the model demonstrate its capability of producing the high frequency force components that are seen in experimental data available in literature. The advantages of using this approach over the constant empirical force coefficient approach when studying micro-milling dynamics is discussed and the instability of the system is investigated utilizing instantaneous frequency.

This paper describes the dynamic characteristics of a newly-designed force sensor comprised of carbon nanoparticles embedded in a polyphenylene sulfide matrix and operating on the principle of contact resistance change with pressure. Sensor performance was investigated for frequencies ranging from 1 to 1,000 Hz using two testing setups: a load frame for low frequency characterization and a piezo-electric stack for describing higher-frequency behavior. Bode magnitude and phase response plots were developed and it was determined that the sensor under study can be modeled as a first order system up to 600 Hz. The −3 dB bandwidth was found to be 90 Hz and the sensor’s time constant was determined to be 0.0018 seconds. A dynamic model of the sensor is constructed and compared against performance data. The sensor was found to have non-linear spring properties, allowing for two damping coefficients, one for each spring constant range, to be calculated. The damping coefficient was calculated to be 619 lb-s/in for loadings under 600 lbs and 1928 lb-s/in for loadings greater than 600 lbs. The sensor’s time response was also found to be more similar in shape to the input loading waveform when it was compared to piezoelectric load transducers.

In this paper the dynamical behavior of a part and an actuated fixture system is studied. The part is modeled using the finite element method. Subsequently, a reduced model is established using the Craig-Bampton reduction method in order to create a small-sized model, accurately describing the dynamic behavior of the part. The clampers and locators of the fixture are modeled as springs. The fixture frame is considered to be much stiffer than the locators such that it provides zero displacement boundary conditions to the locators. An electromechanical actuator is utilized to provide the adaptive clamping forces. After investigating proportional control, integral control, the three term classical PID controller and a lag filter for dynamic compensation, the analysis shows that position feedback can be used effectively in combination with integral control action to minimize unnecessary displacement of the workpiece and increase the bandwidth of the actuated fixture system.

In the field of scanning probe microscopes (SPMs), a precision positioning stage has become an important component as the requirement of the SPMs has been extended from high resolution to high accuracy. The stages used in SPMs plays a role of transferring a specimen or a probe in multiple directions. The stage should satisfy the requirements for small parasitic motion and compactness. Therefore a coupled flexure leaf spring is used as a guide mechanism at recently developed multi-directional nano positioning stage with piezo actuator. Using the coupled flexure leaf spring mechanism, a compact and symmetric stage can be embodied. However, in this case, there are some problems caused by assembly process of piezo actuators. The first is that piezo actuator can be broken because of bending force when another axis is working. Commercially stack type piezo actuators are composed some ceramic materials, so they are brittle. This problem causes the durability weakening of ultra precision positioning stage. The second is unnecessary parasitic tilt error. When an actuator of one axis is acting, the other non-acting actuator works as constraint force. As a consequence, the accuracy of each axis gets lower and the control to compensate parasitic motion becomes difficult. In this research, we will propose a precision positioning stage with coupled flexures and piezo actuator to withstand bending force and avoid a parasitic tilt error. This research includes performance analysis and parametric design of the stage. The stage is designed for motion of two degree of freedom using a flexure leaf spring. Design optimization based on a finite element method (FEM) is also covered in this study. Simulation results show that the optimally designed stage decreases a tilt error less than 25% compared to the stage without concerning the bending and constraint.

During the past two decades, bio-physicists have had an increasing interest in finding out what happens when two bio-material solutions are mixed under high pressure. Compared to temperature, pressure makes more contributions to our fundamental understanding of the structure-function relationship of biological systems, because pressure produces only volume changes under isothermal conditions, and pressure results can then be interpreted in a more straightforward manner. Window-type High Pressure Optical Cell (HPOC) such as the one designed by Paladini and Weber have provided biophysicists with a powerful tool to understanding the structure-function relationships of biological molecules. However, the conventional HPOC is only good for single solution testing and does not allow for quick mixing and stirring of additional components while the specimen is under pressure. This research is to thoroughly study the feasibility of Shape Memory Alloy (SMA) as an actuator to perform mixing and agitation functions; and five types of SMA actuators were designed, simulated and tested for unplugging and mixing purposes. To conduct this research, SMA helical springs were fabricated in house according to the design requirements. With different combinations of SMA tensile springs, SMA compressive spring and biasing spring, significant ranges of vibration were developed. To further improving mixing process, a unique hybrid design of SMA as an actuator to unplug the stopper and micromotor as a stir device to agitate the solutions was developed. Rapid mixing of 95% of total solution in 10 seconds was achieved under 300 bars. A new HPOC was designed according to the new cuvette with its new unplug and mixing mechanism. Our industrial partner, ISS, further modified our design for easy manufacturing reason and fabricated the HPOC which made SMA actuator mixing test under pressure possible. A complete testing of the new HPOC system to observe bio-reagent mixing and reaction under high pressure was conducted and the results were satisfactory.

Hybrid Micro-composite E-springs are an optimized trend of springs first introduced to vehicle suspension systems. At first, a comparison between E-shape and other spring shapes is held theoretically. This theoretical comparison is verified numerically. The E-shape has proved to be the best shape in this comparison striking a balance between spring vertical deflection and maximum induced stress. Next, shape optimization of a hybrid micro-composite E-spring is conducted. At last, a thermoplastic-based hybrid micro-composite structure of the optimized E-spring is modified at micro-scale with additives of micrometer-sized particles of mineral clay. The proposed spring is presented in new passive and semi-active suspension mechanisms, displacing and remedying drawbacks of both the hydraulic dampers and steel springs.