Thermal Damage Research Articles

Non-contact Non-linear Impact Resonance Acoustic Spectroscopy for thermal damage characterization on mortar samples

Abstract The high sensitivity of the nonlinear terms of the elastic response of materials to the incipient appearance of damage has led to the appearance of the Non-linear Elastic Wave Spectroscopy methods (NEWS). Particularly, the Non-linear Impact Resonance Acoustic Spectroscopy (NIRAS) technique detects changes in the resonance of a material (frequency, damping factor, etc.) as a function of the intensity of the impact. Traditionally, mechanical waves have been monitored using an external sensor in contact with the material. Currently, alternative technologies are capable of capturing mechanical waves without direct contact or with embedded sensors in the material itself from its manufacture. This helps the automation process or the continuous monitoring of the material. Mortar is the most used composite material in construction. In this work, thermal damage on mortar samples is characterized by NIRAS tests using different sensing techniques. Accelerometers have been used as the reference technique, while laser interferometer and Fiber Bragg Grating (FBG) have been used as non-contact and embedded sensor techniques respectively. Two levels of damage are presented: sound samples and 400ºC damage. The different techniques offer similar results, showing the capability of the proposed techniques (FBG and laser interferometry) to be an accurate alternative to traditional contact techniques for NIRAS testing.

Meta-analysis of application of minimally-invasive ablation methods and classical surgical approach in osteoid osteoma and osteoblastoma

Abstract Osteoblastoma and osteoid osteoma are rare benign bone tumours, sometimes considered variations of the same pathologic process. However, they differ in location, incidence, age group, and size. The gold standard treatment is surgical excision for osteoblastoma and radiofrequency ablation for both. Minimally invasive techniques, including radiofrequency ablation, microwave ablations, cryoablation, ultrasound ablation, and laser ablation, are increasingly used. This meta-analysis aimed to review current treatments, focusing on minimally invasive methods versus traditional surgical excision. A data comparison of 17 original articles from the PubMed database (2014-2024) was conducted, examining treatment methods, patient numbers, success rates, pre/post-operative pain scores, and complication rates. New ablation methods achieve similar clinical results to traditional surgery for treating osteoid osteoma and osteoblastoma while minimizing invasiveness. Most procedures have technical success rates near 100%. Both invasive and non-invasive methods significantly reduce preoperative pain. Classical surgery has higher minor complication rates compared to minimally invasive treatments. Among ablation techniques, magnetic resonance guided focused ultrasound surgery is the least invasive, avoiding radiation and antibiotic-related complications. However, in ablation methods caution is needed to prevent thermal damage to nearby joints and nerves. Protective methods, such as skin protection, hydrodissection, gas dissection, and intraoperative neurostimulation, are recommended. New ablation methods provide less invasive alternatives to surgery, with high clinical and technical success rates and lower complication rates. Among these, magnetic resonance guided focused ultrasound surgery is the least invasive and most promising, though more clinical data is needed due to its recent development.

Tailoring mechanical and tribological properties of oscillatory pressure sintered binderless WC ceramics with expanded graphite addition

The fracture toughness and wear resistance of WC-based ceramics are crucial factors that determine their subsequent applications. In this study, the mechanical and tribological properties of expanded graphite (EG) reinforced WC ceramics consolidated by oscillatory pressure sintering (OPS) were investigated. The results demonstrated that the combination of dynamic pressure and EG had a synergistic effect, resulting in a much higher relative density of 0.2 wt% EG/WC ceramics reaching up to 99.78%. Simultaneously, 0.2 wt% EG/WC ceramics demonstrated a reduced grain size, with fracture toughness, flexural strength and wear rate reaching 7.54 MPa·m1/2, 1262 MPa and 2.16×10-7 mm3·N-1·m-1, respectively. EG was present in the form of graphene nanoplatelets (GNPs) within WC ceramics. The primary toughening mechanisms involved the bridging and pulling out of GNPs, as well as the generation of microcracks induced by GNPs. Additionally, the exceptional thermal conductivity of GNPs can facilitate heat dissipation and reduce thermal damage. The wear resistance of WC-EG ceramics was primarily enhanced through improving overall mechanical properties and decreasing the occurrence of oxidation and adhesive wear.

Bond behaviour of ribbed steel bar and concrete at 24-h elevated temperatures: Experimental study and theoretical analysis

This study attempts to remedy the lack of understanding on the bond behaviour of steel bar in concrete at elevated temperatures in current research. Pull-out tests were conducted using a unique test setup, and the effects of temperature (120 °C – 350 °C), heating duration (3 h – 24 h), and anchorage length (105 mm – 175 mm) were given attention. In addition, calculation theories for bond behaviour at elevated temperatures were derived. All specimens eventually showed failure characterised by pull-out-splitting. The increase in temperature induces a continuous decrease in bond strength and a continuous increase in peak slip. Moreover, the bonding performance deteriorates gradually with the heating duration, but could be stabilised at 24 h. This can be interpreted as a sufficiently long heating duration allowing full development of concrete thermal damage. Under the same heating regime, the specimens with longer anchorage lengths show lower bond strength, however, the degree of change in bond strength with temperature is not significantly related to anchorage length. The specimens with anchorage lengths of 105 mm, 140 mm, and 175 mm respectively exhibit 15.4 %, 16.9 %, and 16.4 % reduction in bond strength, as the temperature increases from 120 °C to 350 °C. Increasing the temperature helps the bond stress to distribute more uniformly in the bonding zone. However, increasing the anchorage length intensifies the non-uniform distribution of bond stress and the stress peak becomes larger. The bond-slip constitutive model developed considering anchorage length is proved to accurately predict the bond behaviour of steel bar in concrete at elevated temperatures. For reinforced concrete structures working in thermal environments, 0.08 is suggested as ribbed steel bar shape factor.

Evaluation of the power loss in IGBT single transistor device under the condition of pulse duration of 100 ns

The improvement in the reliability and lifespan of insulated gate bipolar transistor (IGBT) devices and the enhancement of system efficiency under high-frequency pulse conditions are receiving increasingly wide attention, and all of these are closely related to the evaluation of the power loss of the IGBT. The traditional method for assessing the power loss of the IGBT is through curve fitting of the dual-pulse experimental results, without delving into the conduction process of the IGBT and without considering the IGBT model itself and the parasitic parameters present in the test circuit. In response to the condition of a pulse duration of 100 ns for IGBT single devices, a universal test circuit has been designed to measure the collector-emitter voltage waveform and the collector current waveform. A method based on Computer Simulation Technology for field-circuit co-simulation to evaluate the power loss of the IGBT has been proposed, which takes into account the parasitic parameters in the actual circuit. In this method, the 3D model of the IGBT device, as well as the circuit model of the test circuit, is established. The power loss curve of the IGBT was obtained from the evaluation model, and the results agree well with the power loss curve obtained from experiments. This method provides guidance for seeking lower power loss in order to improve the reliability and lifespan of the IGBT, as well as enhance system efficiency. It also provides theoretical guidance for further research on the thermal damage mechanism of the IGBT.

The crack initiation mechanism of steel disc when paired with Fe-PM pad for high-speed train braking

In this study, the Fe-based powder metallurgy (Fe-PM) brake pad was paired with a cast steel brake disc to conduct braking tests on a full-scale flywheel braking dynamometer. We systematically analyzed the morphologies of the worn surfaces and the disc temperatures during braking, uncovering the friction and wear characteristics of the friction pair. As well as highlighted the changes in contact status between the friction pair throughout the braking process, which further affected the pad wear rate and thermal fatigue damage to the brake disc. The wear rate of the pad was 0.16 cm3/MJ during the braking tests at an initial brake speed (IBS) of 250 km/h. However, it rapidly increased to 0.66 cm3/MJ as the IBS rose to 380 km/h, indicating a severe decline in wear resistance as the speed increased. The curves of the instantaneous coefficient of friction (COF) displayed significant fluctuations throughout the single braking process and got more pronounced with the increase in the IBS, similar phenomena also occurred on the measured temperature during each braking test. These were caused by the constant changing of the contact status arose by dynamic equilibrium of the formation, spalling, and regeneration for the third body layer (TBL) on the contact surfaces. Additionally, the changing of the contact status also resulted in an uneven distribution of temperature on the disc surface, which in turn generated a temperature gradient and thermal stress. Concurrently, as the braking continued, high frequency alternating thermal stress (HFATS) on the disc surface was induced by the continuously changing contact status, which was confirmed by finite element method (FEM) simulation. As a result, the brake disc would undergo thermal fatigue after fewer braking cycles, and thermal cracks would appear on the disc surface.

Revealing the role of multi-scale fibers in the compressive behavior of a novel ultra-high performance concrete subjected to elevated temperatures

Ultra-high performance concrete has received widespread attention due to its excellent performance. However, the mechanical properties can seriously degrade at high temperatures. To improve the thermal resistance, cenospheres and multi-scale fibers such as polyethylene fiber, steel fiber, calcium sulfate whisker, carbon fiber, and carbon nanotubes, are added to develop a type of ultra-high performance (MSFUHPC) in this work. The effects of cenospheres and multi-scale fibers on peak strain, compressive strength, Young's modulus, specific toughness and stress-strain curve are studied at various temperatures (25 °C, 200 °C, 400 °C, 600 °C, and 800 °C) through uniaxial compression tests. Additionally, mercury intrusion porosimetry tests and scanning electron microscope tests are used to discuss the effect of cenospheres and multi-scale fibers on the microstructure. The results demonstrate that both CE and multi-scale fiber can reduce the thermal damage of MSFUHPC. The multi-scale fiber can significantly improve the mechanical strength of the material, while CE has the opposite effect. It is found that microscale and nanoscale fibers have negligible effect on the specific toughness, while the effect of CE on specific toughness depends on the temperature and its content. Results show that the incorporation of multi-scale fibers effectively decreases the fraction of large pores while simultaneously refining the pore structure and enhancing the proportion of gel pores. Furthermore, the stress-strain relationship of MSFUHPC is established by considering the influence of multi-scale fiber content and high temperature.

Effect of sequential delivery of 1- and 2-MHz bipolar microneedling radiofrequency energy on thermal tissue reactions in a minipig model.

Bipolar microneedling radiofrequency (RF) treatment generates different patterns of thermal reactions, depending on the skin impedance and RF treatment parameters, including the frequency, power, conduction time, settings of sub-pulse packs, and penetrating depth and type of microneedles used. We compared the effect of sequential delivery of 1- and 2-MHz bipolar RF energy to in vivo minipig skin on thermal tissue reaction. RF treatments at frequencies of 1 and 2MHz were sequentially delivered to minipigs' skin in vivo. A histological study was performed to analyze RF-induced skin reactions at 1-h and at 3-, 7-, and 14-days post-treatment. The skin specimens demonstrated that the two different frequencies of RF treatment generated mixed patterns of the peri-electrode coagulative necrosis (PECN) according to the experimental settings and tissue impedance. In the PECN zone, the tissue coagulation induced by the first RF treatment was surrounded by the effect of the later RF treatment at the other RF frequency. In the inter-electrode non-necrotic thermal reaction zone, the effect of the latter RF treatment was widespread and deep through the dermis, which had received RF treatment at the other frequency first. The delivery of pulsed-type RF energy at sub-pulse packs of 6 or 10 provided effective RF delivery over long conduction time without excessive thermal damage of the epidermis. Nonetheless, by sequential delivery of two different RF frequencies, RF-induced tissue reactions were found to be markedly enhanced. The sequential delivery of 1- and 2-MHz RF energy induces novel histological patterns of tissue reactions, which can synergistically enhance the thermostimulatory effects of each RF setting. Moreover, variations in patterns of tissue reactions can be generated by regulating the order of frequencies and the number of sub-pulse packs of RF used.

Homogeneous removal of heterogeneous CFRP composite via aluminum/polyimide laminate assisted femtosecond laser processing

Carbon fiber reinforced polymer (CFRP) composed of carbon fiber and polymer matrix has been used in extensive applications due to its light weight and superior strength. However, the distinct difference in physicochemical properties between two constituents poses a significant challenge for laser homogeneous processing of heterogeneous CFRP. Herein, an aluminum/polyimide laminate is introduced onto CFRP as an assisting layer during femtosecond laser processing, which prevents CFRP from direct energy deposition of low-energy edge of the Gaussian laser. Moreover, a synergetic mechanism of horizontal heat conduction of aluminum foil and vertical heat insulation of polyimide film is proposed and confirmed through temperature measurements and simulation calculations. The heat is dissipated through the aluminum foil and obstructed by the polyimide film, alleviating the detrimental heat transfer and accumulation on CFRP. Therefore, it significantly inhibits thermal damage and entrance size expansion. Compared with traditional femtosecond laser direct processing, the maximum reduction ratio of HAZ and taper are up to 98% and 83%, respectively. High-quality CFRP homogeneous processing with an ultra-low HAZ (0.7 μm), minimal taper (0.07°) and intact smooth sidewalls can be achieved. The method shows great potential to dramatically improve processing quality and broaden applications of heterogeneous composites.

Ultralow radiant exposure of a short-pulsed laser to disrupt melanosomes with localized thermal damage through a turbid medium

Short-pulsed lasers can treat dermal pigmented lesions through selective photothermolysis. The irradiated light experiences multiple scattering by the skin and is absorbed by abnormal melanosomes as well as by normal blood vessels above the target. Because the fluence is extremely high, the absorbed light can cause thermal damage to the adjacent tissue components, leading to complications. To minimize radiant exposure and reduce the risk of burns, a model of the melanosome-disruption threshold fluence (MDTF) has been developed that accounts for the light-propagation efficiency in the skin. However, the light-propagation efficiency is attenuated because of multiple scattering, which limits the extent to which the radiant exposure required for treatment can be reduced. Here, this study demonstrates the principle of melanosome disruption with localized thermal damage through a turbid medium by ultralow radiant exposure of a short-pulsed laser. The MDTF model was combined with a wavefront-shaping technique to design an irradiation condition that can increase the light-propagation efficiency to the target. Under this irradiation condition, melanosomes were disrupted at a radiant exposure 25 times lower than the minimal value used in conventional laser treatments. Furthermore, almost no thermal damage to the skin was confirmed through a numerical simulation. These experimental and numerical results show the potential for noninvasive melanosome disruption and may lead to the improvement of the safety of short-pulsed laser treatment.

Numerical Investigation on Improving The Effectiveness of Film Cooling Using Vortex Generators

Film cooling is an effective way for the blades to cool of an exceptionally powerful gas turbine. This process involves injecting a cooler fluid, typically air. The injected fluid forms a thin insulating layer or "film" that protecting the underlying material from thermal damage. However, due to the primary flow and film jet's interaction, a counter-rotating vortex pair is created, which causes severe jet-off and inadequate film coverage. Protrusion V-shaped and rectangular winglet vortex generators were employed In this research at the top place of the film hole to impede the counter-rotating vortex pair, in an effort to boost cooling's efficiency. Numerical simulations with Realizable k-ε were solved at a blowing ratio was between 0.5–2 and a 30° inclination angle. Results shows that vortex generators of both kinds can produce more anti-counter-rotating vortex pairs to be able to lessen the strength of the counter-rotating vortex pairs. The downwash vortices produced by the vortex generators lessen the detrimental effects of the counter-rotating vortex pair. Downwash vortices and counter-rotating vortex pair are engaged in a competitive mechanism, hence as the ratio of blowing rises, the vortex generators' favorable effects will diminish. So it was noted through this study that the best blowing ratio is (1.0). When the blowing ratio is 1.0, the results demonstrate improved film cooling performance for the flat plate. This was observed for both types of vortex generators. Specifically, the rectangular vortex generator showed this capability, with the average effectiveness of adiabatic film cooling surpassing the baseline case by 27.33%.

MXene-coated piezoelectric poly-L-lactic acid membrane accelerates wound healing by biomimicking low-voltage electrical pulses

Electrical stimulation therapy is effective in promoting wound healing by rescuing the decreased endogenous electrical field, where self-powered and miniaturized devices such as nanogenerators become the emerging trends. While high-voltage and unidirectional electric field may pose thermal effect and damage to the skin, nanogenerators with lower voltages, pulsed or bidirectional currents, and less invasive electrodes are preferred. Herein, we construct a polydopamine (PDA)-modified poly-L-lactic acid (PLLA) /MXene (PDMP/MXene) nanofibrous composite membrane that generates piezoelectric voltages matching the transepithelial potential (TEP) to accelerate wound healing. PDA coating not only enhances the piezoelectricity of PLLA by dipole attraction and alignment, but also increases its hydrophilicity and facilitates subsequent MXene adhesion for electrical conductivity and stability in physiological environment. When applied as wound dressings in mice, the PDMP/MXene membranes act as a nanogenerators with reduced internal resistances and satisfactory piezoelectric performances that resemble bioelectric potentials (~10 mV) responding to physical activities. The membrane significantly accelerates wound closure by facilitating fibroblast migration, collagen deposition and angiogenesis, and suppressing the expression of inflammatory responses. This piezoelectric fibrous membrane therefore provides a convenient solution for speeding up wound healing by sustained low voltage mimicking bioelectricity, better cell affinity.

Numerical simulation of the thermo-mechanical coupling behavior of skin tissue exposed to repetitive pulse laser irradiation

A thorough understanding of the thermo-mechanical coupling behavior during the interaction between pulsed laser and skin tissue is a prerequisite for successful application of pulsed laser technology in the treatment of various skin diseases and injuries. Taking into account the complex physiological structure of skin tissue, a theoretical model is established to characterize the thermo-mechanical response of multi-layer skin tissue with variable physical properties, in which the non-linear governing equations of bio-thermo-mechanics with dual-phase lag mechanism and Henrique burn equation are involved. The finite difference method was employed to obtain the time-space distribution of skin temperature, displacement and stress under repeated pulse laser action, and the incidental thermal damage was further evaluated on this basis. The numerical results stated that: i) repeated pulse laser can significant reduce the peak temperature of skin tissue and further reduce or even eliminate thermal damage under the premise of required energy threshold, ii) the thermo-mechanical coupling response and potential thermal damage will be inhibited when the temperature dependence of physical parameter is considered, in which the thermal stress is more sensitive to the temperature dependence than others, iii) the thermal damage is more sensitive to the input parameters than that of thermo-mechanical response, and the burn time can be effectively delayed or even avoided for appropriate input options.

Numerical investigation of thermal soak within engine bay using lattice Boltzmann method

A large amount of heat accumulates in the engine bay for a short time after the engine runs at high load and shuts down, that will lead to thermal damage and thermal fatigue caused by the temperature rise of some heat sensitive components. This paper uses an aero-thermal coupling approach to study the heat transfer problem in the engine bay of an SUV model under thermal soak conditions. Due to the transient characteristics of the heat transfer process, the natural transient CFD software developed based on the LBM method is used to study the engine bay heat transfer during the 400 s key-off soak process. The analysis reveals that convection and radiation are the main heat transfer modes in the early stage of hot immersion (0–120 s), and conduction only makes a significant contribution in contact with high temperature sources. The radiation and convection are the key contributors to heat transfer processes of engine bay during soak, but the efficiency of radiation heat transfer decreases with the increase of time, whereas the efficiency of convection heat transfer is not always reduced, it will increase and then decrease with the increase of time. The coupling method established can predict the thermal state in the engine bay well, and is in good agreement with the experimental results. The results show that the error in the engine coolant temperature is less than 1 °C, and the error in the temperature of the heat-sensitive components is less than 5 °C. Finally, the potential risks of thermal damage and thermal fatigue states were assessed, providing an important reference for the control design of cooling fan running time after key-off.

Evolution Characteristics of Aluminum Thermal Weld Irregularity and Damage in Heavy-Haul Railway under Different Service Conditions

Aluminum thermal welding joints are widely used in the maintenance welding of heavy-haul railways due to their easy handling and high efficiency. However, due to their inherent welding characteristics, welding results in certain differences in the material’s physical properties at the welding zone compared to adjacent base materials, leading to the occurrence of short-wave irregularity under long-term wheel–rail interactive forces. In order to explore the evolution characteristics of weld irregularity, dynamic characteristics, and plastic deformation under long-term wheel–rail impact, a detailed tracking test was conducted on a normal aluminum weld, and the process from being put on the track to being damaged and replaced was evaluated. At the same time, a rigid–flexible coupling model was established for subsequent analysis, and plastic damage was analyzed using the finite element model. The results show that the service life of the weld can be divided into three different stages: the initial stage, the intermediate stage, and the damage stage. In the damage stage, a temporary separation occurred between the wheel and rail, leading to a sudden change in the wheel–rail interaction. The weight of 250 MT at the weld reached the repairment control limit. The concentration effect of equivalent plastic deformation was most serious at 2~5 mm below the rail head.

Steady-state versus burst lasing techniques for thulium fiber laser

ObjectiveTo evaluate the stone ablation rate and direct thermal damage from thulium fiber laser (TFL) lithotripsy using continuous (C) and burst (B) lasing techniques on an in vitro ureteral model.MethodsThe TFL Drive (Coloplast, Humlebaek, Denmark) was used in an in vitro saline-submerged ureteral model. Ten participants, including five junior and five experienced urologists, conducted the experimental setup with 7 different settings comparing two lasing techniques: steady-state lasing (0.5 J/10 Hz = 5W for 300 s and 0.5 J/20 Hz = 10W for 150 s) and burst, intermittent 5 s on/off lasing (0.5 J/20 Hz, 0.5 J/30 Hz, 0.5 J/60 Hz, 0.1 J/200 Hz, and 0.05 J/400 Hz) with a target cumulative energy of 1500 J using cubic 125 mm3 phantom BegoStonesTM. Ureteral damage was graded 1–3 based on the severity of burns and holes observed on the surface of the ureteral model.ResultsThe were no significant differences in stone ablation mass neither between C and B lasing techniques, nor between expertise levels. At C lasing technique had only mild ureteral lesions with no significant differences between expertise levels (p: 0.97) or laser settings (p: 0.71). At B lasing technique, different types of thermal lesions were found with no expertise (p: 0.11) or setting (p: 0.83) differences. However, B laser setting had higher grade direct thermal lesions than C (p: 0.048).ConclusionRegarding efficacy, C and B lasing techniques achieve comparable stone ablation rates. Safety-wise, B lasing mode showed higher grade of direct thermal lesions. These results should be further investigated to verify which of the lasing mode is the safest in vivo. Until then and unless proven otherwise, a C mode with low frequency should be recommended to avoid ureteral wall lesions.

Unified modeling of photothermal and photochemical damage.

Correlating damage outcomes to a retinal laser exposure is critical for diagnosis and choosing appropriate treatment modalities. Therefore, it is important to understand the causal relationships between laser parameters, such as wavelength, power density, and length of exposure, and any resulting injury. Differentiating photothermal from photochemical processes in an in vitro retinal model using cultured retinal pigment epithelial cells would be a first step in achieving this goal. The first-order rate constant of Arrhenius has been used for decades to approximate cellular thermal damage. A modification of this equation, called the damage integral (Ω), has been used extensively to predict the accumulation of laser damage from photothermal inactivation of critical cellular proteins. Damage from photochemical processes is less well studied and most models have not been verified because they require quantification of one or more uncharacterized chemical species. Additionally, few reports on photochemical damage report temperature history, measured or simulated. We used simulated threshold temperatures from a previous in vitro study to distinguish between photothermal and photochemical processes. Assuming purely photochemical processes also inactivate critical cellular proteins, we report the use of a photothermal Ω and a photochemical Ω that work in tandem to indicate overall damage accumulation. The combined damage integral (ΩCDI) applies a mathematical switch designed to describe photochemical damage relative to wavelength and rate of photon delivery. Although only tested in an in vitro model, this approach may transition to predict damage at the mammalian retina.

Study on the influence of cortical bone heterogeneity on the spatio-temporal distribution of drilling temperature

The degree of thermal damage during cortical bone drilling is an important factor in determining the success rate of surgery and postoperative recovery time. In this study, high and low feed rate drilling experiments are carried out on bovine femoral cortical bone by chisel edge thinning drill. Combined with the characterization of cortical bone tissue structure and the measurement results of important thermal property parameters, the potential impact mechanisms of cortical bone heterogeneity on the spatio-temporal distribution of drilling temperature and thermal damage are analyzed. The temperature rise rate and overheating duration at different distances from the hole wall in cortical bone drilling under different feed rates are also compared. The experimental results show that the specific heat gradually increases and the thermal conductivity gradually decreases from the periosteum to the endosteum. The hole wall temperature and thermal diffusion of cortical bone with different tissue structures are different under high and low feed rates. The closer to the cortical bone endosteum, the lower the drilling temperature, thermal diffusion and thermal damage area. This is not only related to the contact time between the drill bit and the hole wall of cortical bone with different tissue structures, but also closely related to the heterogeneous structure of cortical bone. In addition, it is found that in high feed rate cortical bone drilling, the temperature rise rate at different positions from the hole wall is higher and the overheating duration is shorter.

Bio-thermal non-equilibrium dynamics and thermal damage in biological tissues induced by multiple time pulse-laser irradiations

BackgroundLaser therapy offers precise medical treatment by directing focused light beams to specific areas without harming surrounding tissue. This precision is particularly valuable in tissue treatment, including cancer therapy, where minimizing collateral damage is critical. The current study focuses on bio-thermal dynamics and thermal damage in biological tissues induced by multiple pulse-laser irradiations. ModelThe Local Thermal Non-Equilibrium (LTNE) bio-heat Transfer model with porosity and dual lag effects is developed to investigate the thermal behavior in tissues. The model contains partial differential equations that is solved through numerical method. ResultsObtained results show temperature variations and thermal damage in tissues, influenced by parameters such as laser intensity, incident duration, and tissue porosity. Higher intensity of laser and extended laser durations increase the temperature distribution and thermal damage. Porosity inversely affects temperature distribution, with large values of porosity leading to decreased distribution. NoveltyThis study introduces the application of multi-time lasers induced on tissue for the therapies, a novel approach that has not been previously explored in the literature.

Design and performance analysis of low damage anti-skid crescent drills for bone drilling

BackgroundWith orthopedic surgery increasing year on year, the main challenges in bone drilling are thermal damage, mechanical damage, and drill skid. The need for new orthopedic drills that improve the quality of surgery is becoming more and more urgent.MethodsHere, we report the skidding mechanism of drills at a wide range of inclination angle and propose two crescent drills (CDTI and CDTII). The anti-skid performance and drilling damage of the crescent drills were analyzed for the first time. Inclined bone drilling experiments were carried out with crescent drills and twist drills and real-time drilling forces and temperatures were collected.ResultsThe crescent drills are significantly better than the twist drill in terms of anti-skid, reducing skidding forces, thrust forces and temperature. The highest temperature is generated close to the upper surface of the workpiece rather than at the hole exit. Finally, the longer crescent edge with a small and negative polar angle increases the rake angle of the cutting edge and reduces thrust forces but increases skidding force and temperature. This study can promote the development of high-quality orthopedic surgery and the development of new bone drilling tools.ConclusionThe crescent drills did not skid and caused little drilling damage. In comparison, the CDTI performs better in reducing the skidding force, while the CDTII performs better in reducing the thrust force.