Highlights • Major works in cutting simulations of soft tissues and bones are reviewed. • These simulations focus on cutting forces and chip formation. • Fracture is the dominant mechanism in soft ...tissue cutting. • Johnson–Cook model is mostly used for bone cutting finite element simulations. • Mesh-free methods have been used for bone cutting but are not yet mature.
This paper presents an experimental study on low-velocity impact response of bi-material structures (BMS). BMS is a structural composite consisting of a 3D-printed lattice structure filled with a ...reinforcement material. In this study, BMS is made of polylactide (PLA) lattice structure and polyurethane (PU) foam for an enhanced impact resistance. Three different PU foams, including one rigid foam and two flexible foams, are selected for BMS. The impact tests are conducted to compare the impact attenuation, stiffness, toughness, and strength using the measured rate of change of acceleration (known as “jerk”), displacement, energy absorption, and the maximum acceleration, respectively. The results show that flexible foams have more positive effects on the impact properties than the rigid foam. The maximum reduction of jerk is about 9% compared to the baseline structure without foam reinforcement. The maximum displacement is increased by 17%; the maximum energy absorption is increased by 23%. The maximum acceleration remains similar for all samples. In conclusion, a proper selection of foam filling can significantly improve the impact properties.
In this paper, the authors present a physical model developed to simulate accurate external ventricular drain (EVD) placement with realistic haptic and visual feedbacks to serve as a platform for ...complete procedural training. Insertion of an EVD via ventriculostomy is a common neurosurgical procedure used to monitor intracranial pressures and/or drain CSF. Currently, realistic training tools are scarce and mainly limited to virtual reality simulation systems. The use of 3D printing technology enables the development of realistic anatomical structures and customized design for physical simulators. In this study, the authors used the advantages of 3D printing to directly build the model geometry from stealth head CT scans and build a phantom brain mold based on 3D scans of a plastinated human brain. The resultant simulator provides realistic haptic feedback during a procedure, with visualization of catheter trajectory and fluid drainage. A multiinstitutional survey was also used to prove content validity of the simulator. With minor refinement, this simulator is expected to be a cost-effective tool for training neurosurgical residents in EVD placement.
In this paper, the authors present a physical model developed to teach surgeons the requisite drilling techniques when using an endoscopic endonasal approach (EEA) to the skull base. EEA is ...increasingly used for treating pathologies of the ventral and ventrolateral cranial base. Endonasal drilling is a unique skill in terms of the instruments used, the long reach required, and the restricted angulation, and gaining competency requires much practice. Based on the successful experience in creating custom simulators, the authors used 3D printing to build an EEA training model from post-processed thin-cut head CT scans, formulating the materials to provide realistic haptic feedback and endoscope handling. They performed a preliminary assessment at 2 institutions to evaluate content validity of the simulator as the first step of the validation process. Overall results were positive, particularly in terms of bony landmarks and haptic response, though minor refinements were suggested prior to use as a training device.
•A neural network-based framework was proposed to visualize 3D heat maps of the bone drilling process immediately.•Finite element analysis (FEA) model was used to generate the training and testing ...data, and also the ground truth of two drilling cases for testing the framework.•A testing correlation of 97% was achieved by training 1% of the total data points.•The proposed framework can properly surrogate the 3D FEA model, where the computation time is less than 1 second.•The proposed framework is beneficial for understanding how the heat is generated, which can improve the drilling techniques and prevent thermal injury.
Heat generation and associated temperature rise in surgical drilling can cause irreversible tissue damage. It is nearly impossible to provide immediate temperature prediction for a hand-held drilling process since both feed rate and motion vary with time. The objective of this study is to present and test a framework for immediate bone drilling temperature visualization based on a neural network (NN) model and a linear time-invariant (LTI) model.
In this study, the finite element analysis (FEA) model is used as the ground truth. The NN model is used to predict the location-dependent thermal responses of FEA, while LTI is used to superimpose these responses based on the location history of the heat source. The use of LTI can eliminate the uncertainty of the unlimited possibility in the time domain. To test the framework, two three-dimensional drilling cases are studied, one with a constant drilling feed and straight path and the other with a varying feed and a varying path.
The NN model using U-net architecture can achieve the predicted correlation of over 97% with only 1% of the total number of data points. Using the framework with U-net and LTI, both case studies show good agreement in temporal and spatial temperature distributions with the ground truth. The average error near the drilling path is less than 10%. Discrepancies are mainly found near the heat source and the regions near the removed material.
An FEA surrogate model for rapid and accurate prediction of 3D temperature during arbitrary bone drilling is successfully made. The overall error is less than 5% on average in the two case studies. Future improvements include strategies for training data selection and data formating.
The engineering applications of thermoplastic 3D printing filaments are currently limited by their inherent flammability, especially in fields such as automotive and aerospace, which require high ...standards for material safety. Polyamide‐6 (PA6) is of particular interest for additive manufacturing but is a very flammable thermoplastic known to spread fires due to its aggressive melt‐dripping. A flame retardant (FR) composite filament composed of PA6, ammonium polyphosphate, and aluminum phosphate is shown to be printable under identical conditions to commercially available PA6. Calorimetry measurements reveal that the composite filament generates a 7000% increase in char yield, along with 47% and 31% decreases in peak heat release rate and total heat release, respectively. Additionally, open flame testing demonstrates a significantly reduced capacity for this filament to spread fire to other nearby combustible materials. This unique FR additive system represents an important step toward improving the safety and utility of 3D printed parts.
A flame retardant composite filament, based on polyamide‐6, is developed for 3D printing. The filament can be printed under ordinary conditions and yields parts with significantly reduced flammability. Microscale combustion calorimetry and open flame testing reveal a significantly reduced capacity for this filament to spread flame or cause secondary ignition.
Machined surface temperature in hard turning Chen, Lei; Tai, Bruce L.; Chaudhari, Rahul G. ...
International journal of machine tools & manufacture,
October 2017, 2017-10-00, 20171001, Letnik:
121
Journal Article
Recenzirano
Machined surface temperature is critical in turning of hardened steels because high surface temperature can lead to the formation of the white layer, which may have negative impacts on the steel ...fatigue life. This paper presents two experimental methods to measure machined surface temperatures in hard turning. The first method, based on a tool-foil thermocouple, estimates the machined surface temperature using a metal foil embedded in the workpiece to measure the tool tip temperature. The second method uses a thermocouple embedded in the tool with its tip continuously sliding on the machined surface behind the cutting edge during hard turning. A three-dimensional thermal model is developed and the inverse heat transfer method is applied to find the machined surface temperature near the cutting edge. For validation, hard turning tests were conducted and the cutting forces, tool-foil voltages and embedded thermocouple voltages were measured simultaneously at three levels of feed rates. The peak machined surface temperature occurred along the intersection of cutting edge and the machined surface. Its magnitude was mainly determined by the shear plane heat source and further increased due to flank face frictional heat source. Measurement results showed comparable predictions between the two developed methods with an average deviation of 30°C over the 500–800°C range. These two methods, although based on very different approaches, have both proven feasible for the measurement of hard turning machined surface temperatures.
•Two methods are developed to measure machined surface temperature in hard turning.•Method 1 measures the temperature at tool tip with an embedded metal foil.•Method 2 measures the temperature behind tool tip with an embedded thermocouple.•Peak temperature occurs along intersection of cutting edge and machined surface.•Predictions of two methods show good correlation under multiple turning parameters.
Surgical bone grinding using high-speed, small spherical abrasive tools could cause thermal damage to the surrounding neurovascular structures. Our prior work developed a thermal model based on the ...two-dimensional grinding theory to calculate the temperature distribution. To verify the grinding-theory-based model, this study used experimental data incorporated with an inverse heat transfer method to mathematically estimate the heat flux distribution. This inverse method also considered a time-varying system to reflect a temporal change of the heat flux. Specifically, a coupled approach combining sequential function specification method (SFSM) and sequential quadratic programming (SQP) was employed to calculate the temporal and spatial variables simultaneously. Numerical tests were performed to determine the effectiveness and the limitations of this method. Then, the experimental data of prior work was applied to reconstruct the heat flux. The results verified a nearly time-invariant heat flux and demonstrated a consistent trend in the spatial distribution.
•An inverse method is developed to estimate the temporal and spatial distributions of bone grinding heat flux.•This method couples sequential function specification method (SFSM) and sequential quadratic programming (SQP).•Numerical study is performed to evaluate the robustness and identify the limitations.•The heat flux reconstructed by this method is similar to the prior work with grinding thermal model.
Mist cooling in neurosurgical bone grinding Zhang, Lihui; Tai, Bruce L.; Wang, Anthony C. ...
CIRP annals,
2013, 2013-00-00, 20130101, Letnik:
62, Številka:
1
Journal Article
Recenzirano
This research investigates using cryogenic saline mist, in comparison to the conventional saline irrigation, in neurosurgical bone grinding to prevent thermal injury to surrounding nerves and to ...increase the visibility of surgical area for endoscopic operations. Delivery of cryogenic mist directly towards the grinding zone along with a backward grinding motion was found important to maximize and localize the cooling effect, thus reducing bone temperature rise. Experimental results also showed a pre-cooling effect of the cryogenic mist that helps reduce the initial temperature of bone prior to the occurrence of grinding.
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