Tip Deformation Research Articles

Reorienting Lower Lateral Cartilages With Lateral Crural Struts: Aesthetic and Functional Benefits

Nasal tip shape and position play a major role in the aesthetic appearance of the nose. Cephalically oriented lower lateral cartilages (LLC) are associated with a broad boxy nasal tip. Reorienting cephalically positioned LLC with lateral crural strut grafts is a technique used to correct the nasal tip. An open approach surgical technique is described to evaluate the true orientation of the LLC and correct the boxy nasal tip. Five cases are shown with pre- and post-op pictures. The identical surgical technique is used in all cases with a variation in grafts necessary to create the desired esthetic result. All 5 described cases are on female patients. In all cases, reorientation of the lateral crura with lateral crural strut grafts were performed. In all, 4 of the 5 cases required a columellar strut graft, 3 cases required a shield graft to increase nasal tip projection and control the columellar-lobular angle, and 2 cases required spreader grafts for internal nasal valve support. All 5 cases required a variation of inter and intra-domal suture techniques to refine the nasal tip. A boxy nasal tip with supra-tip fullness is commonly associated with cephalically oriented LLC. Changing the orientation of the LLC to a more favorable angle and using lateral crural strut grafts can be used to not only correct the nasal tip deformity, but also facilitate projecting/de-projecting the nose, changing the rotation of the tip, and also supporting the external nasal valve. Reorienting cephalically oriented LLC is a versatile approach to reshaping the nasal tip. It is a technically demanding maneuver that when executed, allows complete control of the nasal tip complex. We have used this approach in many cases involving a boxy nasal tip with long ptotic tips and poorly supported external valves.

Numerical study of transient thermal profile and thermally deformed tip shape in Wire EDM of narrow angles

The geometrical error observed in the tip while machining sharp corners in thin workpieces with WEDM is studied numerically. A finite element model is developed to study the contribution of thermal effects in the tip deflection phenomenon. Initially a temperature distribution model is developed by considering formation of kerf gap and time dependent changes in material properties of different zones in the domain. The transient temperature data is fetched from the model and used in a sequentially coupled Thermo-Mechanical model to predict the deformation of tip. Numerically predicted tip deflection and the shape of the profile is validated and compared with experimental results.

Developing A Needle-Knife Surgical Device for Ultrasonic Assisted Surgery.

Introduction: A new era of orthopedic surgery is happening nowadays. Procedures like Video Surgery, Ultrasound Guided Interventions, Pain interventions invasive orthopedics procedures, hydrodissection, dry needling; thermography assisted pain procedures and acupuncture started to be widely performed [1]. Objective: The aim of the project is to assess Ultrasonic assisted surgery in pig foot from butchery using three differences needleknife devices. Method: All three needles were used for ultrasonic assisted surgery in pig feet from butchery. An ultrasonic assisted surgery was performed in 9 nine pig feet. The two well developed digits were assessed. The pig has two larger central toes. These larger central toes bear most of the weight, but the outer two are also being used in soft ground. Two toes each foot was assessed, one medial and one lateral. We numbered the pig foot from I to IX in roman figures. The first three I, II and III were used for needle A (control) for all medial and lateral toes. The samples IV, V and VI were used for needle B for all medial and lateral toes. The samples VII, VII and IX were used for needle C for all medial and lateral toes. The surgical technique consists in an ultrasonic assisted percutaneous tenotomy of the deep flexor tendon between distal and proximal phalanx near the sesamoid bone on the pig toe. Assessed for clinical release of the joint; gap in the plantar cushion pad and ecographic assessment. A final open dissection was performed [2]. Results: Model 3 presented similar features in rigidity to the baseline model 1 (3,6%). They have a similar performance. The tip of model 3 increased a tension of 15%; but does not mean fracture risk. In ultrasonic assisted surgery in pig feet from butchery the geometry; puncture capability, cutting capability, tip deformation and tip fracture. Geometry: Group A Control; group C and then group B Puncture capability: Group B; Group C and then Grupo A. Cutting ability: Group C; then A and then B. (tip of B deformation) Resistance: Group A; then group C and then group B. Deformation: needle B has a tip deformation in 50 % of the cases. Conclusion: Two different bisel tips needle shapes were modified from the original one metal guide of an intravenous catheter in order to improve the cutting ability as well as maintain the aspiration and infusion feature. One longer surface edge and another one not so long. The longest, although supposed to be the best performer is not strong enough and deformed. The second one is the most useful for needle knife instruments. More clinical study is recommended.

Fatigue crack growth mechanism in ferroelectric ceramics under alternating electric field: An investigation by digital image correlation technique

The deformation of crack tip in PZT ceramics under cyclic electric field loading was characterized by Digital Image Correlation (DIC) technique. Two other specimens without speckles were used to observe the physical processes during the crack propagation in-situ. The deformation of the region of interest is elucidated. Near the U-shaped notch, the DIC results directly reveal the existence of incompatible deformation. However, in the front of the newly formed crack, no incompatible deformation was observed. Additionally, in-situ observation reveals that, the crack growth occurs at the stage of crack closure when the crack propagates steadily. The observed pop-in behavior of the crack during the first cycle of electric field loading is rationalized by the interaction between the incompatible domain switching zones with and without U-shaped notch, which is consistent with the explanation of Westram et al. The subsequent crack propagation after the pop-in cannot be rationalized by the model exploited by Zhu and Yang, Westram et al., and Liu and Fang, which is thought to be related to three different factors – arcing, wedging and grain-to-grain interaction. The mechanism for the appearance and the disappearance of the incompatible domain switching zone near the U-shaped notch and around the tip of the newly formed crack is discussed based on the electrical boundary condition (EBC) of the crack surfaces we proposed recently.

High-cycle-fatigue properties of selective-laser-melted AlSi10Mg with multiple building directions

Axial loading fatigue tests with stress ratio of 0 were conducted in investigating the influence of building directions (0°, 45° and 90°) on high cycle fatigue property of a selective laser melted AlSi10Mg in combination with two-dimensional microscope observation and three-dimensional ultra-depth imaging. Results show that fatigue strength decreases with the increase of building angle due to larger defects and sparser melting pool boundaries. Two failure modes, i.e. surface and subsurface failures, are mainly induced by irregular lack of fusion whose size arises as building angle increases. Also, the roughness of crack nucleation region is mainly attributed to the plastic deformation of crack tip under tensile stress. Based on the stress intensity factor evaluation at crack tip, both long crack growth threshold value and transition size from small to long crack growth all drop as building angle increases. Based on these, the microstructure-based crack nucleation and propagation behavior is clarified, and an energy based fatigue life prediction model considering the stress concentration effect of defect is proposed. The agreement between experimental and predicted data is satisfied.

In-situ experimental study on the fatigue crack propagation behavior of 7075-T6 and 2024-T3 aluminium alloys under variable amplitude loading and retardation model modification

Fatigue crack propagation behavior of Al7075-T6 and Al2024-T3 under four typical variable amplitude loading (VAL) patterns are investigated by using in-situ testing. The near-tip strain fields and crack opening level are measured combining in-situ optical microscopy testing and digital image correlation (DIC) technique. The crack tip deformation process is directly observed by in-situ scanning electron microscope (SEM). The results show that both the crack propagation behaviors and the crack-tip strain distributions are greatly influenced by the VAL patterns. The shape effect of the overload-induced plastic zone may prolong the crack growth retardation. The crack-front plasticity plays a dominant role in controlling fatigue crack growth. The crack-front plasticity supplies a link between crack closure and crack growth. The crack tip resharpening caused by the underload applied immediately after the overload may reduce the retardation extent. Finally, a modified retardation model is proposed and gives reasonable prediction results of the crack growth rate under VAL.

Preservation Rhinoplasty: Open or Closed?

Preservation rhinoplasty (PR) is an evolving philosophy. The open approach was initially utilized, but the author felt a closed approach might be of benefit in certain patients. A total 162 primary rhinoplasty cases were studied retrospectively between May and November 2020. One hundred cases had at least 1 year of follow-up. Patients had follow-up at 1 week, 1 month, 3 months, and 1 year after surgery. Technical details were recorded, including dissection planes, preservation of the dorsum (DP) vs component reductions, surface vs foundational DP techniques, and open vs closed approach. One hundred patients had at least 1 year of follow-up. Fifty-six patients underwent an open approach and 44 a closed approach. Eighty-three patients had preservation of the dorsal soft tissue envelope. All patients who underwent a closed approach had preservation of the dorsal soft tissue envelope. Sixty-seven patients underwent DP, with 38 receiving surface techniques and 29 undergoing impaction techniques. Thirty-three patients underwent structural rhinoplasty with piezoelectric osteotomies and mid-vault reconstruction. All structural cases were performed employing an open approach. Four revision surgeries were necessary. Open and closed approaches have indications depending on the tip and dorsal deformities. A closed PR is favored with thin skin, minimal dorsal modification, osseocartilaginous preservation (foundation techniques), less complex tip deformities, and overprojected noses. An open PR is favored for extensive dorsal modification, S-shaped nasal bones, complex tip deformities, and tip augmentation. Structural dorsal rhinoplasty is always conducted open and preferred for complex dorsal deformities and severe septal deviations.

Role of Initial Crack Tip Shape, Plastic Compressibility and Strain Softening on Near-Tip Stress-Strain State in Fatigue Cracks during Simulation of a Finite Deformation based Elastic-Viscoplastic Constitutive Model

This paper deals with the effect of initial crack tip shape, plastic compressibility, and strain softening on near-tip stress-strain fields for a mode I crack subjected to fatigue loading under plane strain and small scale yielding. A finite strain-based elastic-viscoplastic constitutive equation with bilinear hardening and hardening-softening-hardening hardness functions is taken up for simulation. It is observed that plastic compressibility and strain softening have a significant impact on crack tip opening displacement (CTOD) and tip propagation. Furthermore, it has been viewed that the initial shape of a crack tip can significantly influence both the CTOD and the crack tip extension for the bilinear hardening material; however, with identical conditions for the hardening-softening-hardening material, the initial crack tip shape affects the fatigue crack growth much lesser though the CTOD is influenced considerably. In comparison to the crack growth in the plastically incompressible hardening-softening-hardening solids, the variation of the crack growth (with respect to the tip curvature radius) is more and peculiar in the corresponding plastically compressible solid. To explain and to get a better insight of the crack tip deformation, the near-tip plastic strain and hydrostatic stress have been illustrated.

Effect of interatomic potential on modelling fracture behavior in hcp titanium: a molecular dynamics study

Molecular dynamics (MD) simulations have unique advantages in capturing the details of the crack tip deformation at the atomic scale. As the accuracy of simulation results is heavily dependent on the selected interatomic potential, a comprehensive study of the anisotropic crack tip behavior of hcp titanium under plane strain mode-I loading with the commonly utilized potentials is presented in this paper. The typical crystallographic planes in hcp materials including {0001}, {101¯0}, {112¯0}, {101¯1} and {112¯2} are considered as the pre-existing crack planes. The intrinsic brittleness and ductility of different crack systems are discussed from the perspective of linear elastic fracture criteria. Depending on the selected potential, the dominant crack tip deformation mechanism may be basal a slip, prismatic a, pyramidal c+a slip or twinning modes in different crack systems. Finally, in comparison with experimental results, the different potentials are evaluated in the light of their capability to reproduce the experimentally observed crack tip deformation. Overall, the recent developed Mendelev-II potential is recommended for MD simulation of fracture behavior under mode-I loading, as this potential gives a more realistic crack tip response than other studied potentials.

Root rotations and root displacements in bimaterial layers and thin films

An elasticity technique to derive compliance coefficients describing crack tip root rotations and displacements in end-loaded, bimaterial, isotropic and orthotropic layers has been recently proposed in Ustinov and Massabò (Int. J. Solids Struct., 2022). The coefficients define the boundary conditions which account for the near tip deformations when using beam (plate) theories to describe the detached layers. The coefficients, collected into 6x6 compliance matrices, relate crack tip kinematic variables describing relative displacements and rotations between the detached and intact parts, and six elementary crack tip loadings, which combine to describe general end loadings. The steps necessary to use the coefficients in the solution of statically determined problems, when the forces acting on the layer are known through equilibrium, is presented here with reference to classical fracture mechanics specimens.

On Machining behaviour of various cutting Inserts: A review on hardened steel

Cutting tool plays an important criterion for the overall performance of machining to achieve better tool-life, superior surface finish along with immense productivity. The evolution of cutting temperature along with increased cutting parameters accelerates the plastic deformation of insert tip, cutting edge breakage and thus affects the surface quality. Built-up-edge (BUE) formation also enhances rapid tool wear, fluctuations of cutting forces, and vibration. Therefore in modern manufacturing to enhance productivity considering good surface quality, there is striving for innovation and research in the area of novel cutting tool materials. Hard machining emerges as a newer process alternative to traditional grinding performance where popular cutting tool materials used as CBN (Cubic Boron Nitride), ceramics, and coated carbides etc. The benefits of hard machining serve as reduction of the manufacturing cycle, cost, and environmental friendly. Thermal softening and reduction of shear stress due to the rise of cutting temperature enable hard machining easier under dry environment compared to flood cooling. However, tool wear and surface roughness deteriorates and thus reduces tool life due to frequent failure of cutting edge. Thus in the current review, the performance of cutting tool materials during machining hardened steels is focused. Moreover, a proper selection of cooling and lubrication strategy can prolong the tool life and surface finish. Different hard thin layer coatings on carbide tools enhance the machining performance due to thermal barrier, abrasion, and diffusion resistance properties. Due to techno-economical feasibility, coated carbide cutting tools are extensively used during hard machining in recent years which has been developed by CVD/PVD method.

A study on J-integral and J-integral range ΔJ applicable to finite deformation elastic-plastic problems

This paper summarizes the formulations and some of the applications of the three-dimensional J-integral and J-integral range ΔJ that were proposed by the authors. The proposed crack parameters are evaluated by the domain integral method. Their values are guaranteed to be unconditionally independent of size and shape of integral domain by their formulation. The numerical examples demonstrate that the proposed crack parameters can characterize the severity of the crack tip deformation field. Hence, they can characterize the crack propagation behavior.

A Study of Nasal Septal Deviation, External Nasal Deformities, and their Correlation with the Severity of Sino-Nasal Symptoms Using Sino Nasal Symptoms Score Questionnaire

Background/Rationale: The human nose is structurally complex and this complexity results in nasal shape and shape variations. Midline deformities such as hump nose, saddle nose, tip deformities and lateral nasal deformities such as crooked nose, deviated nose, alar depression are common forms of deformity affecting the external nose. Internal nasal valve (INV) is a key anatomical landmark of nasal cavity. Any obstructions in this region have tremendous effects on inspiratory and expiratory currents. This study aims to assess the nasal septal deviation and external nasal deformities and correlate the severity of sino nasal symptoms.
 Methods: This Prospective observational study will include total 50 patients with nasal septal deviation. Patients will undertake Sino Nasal Test -22 questionnaire. Investigations like Diagnostic nasal endoscopy with 30 degree nasal endoscope, X-ray PNS Water’s view and complete blood count including absolute eosinophilic count will be carried out. Data will be analysed using appropriate statistical tests.
 Expected Results: A significant correlation is expected between Nasal Septal Deviation, External Nasal Deformities, and Severity of Sino-nasal Symptoms.
 Conclusion: This study will reflect on internal nasal valve and it’s correlation with etiopathological process of upper respiratory tract. It will also guide clinicians in choosing appropriate surgical approach.

Paediatric nasal dermoid: evaluation and management.

The aim of this study was to present the evaluation and current management of congenital paediatric nasal dermoid. There has been a trend towards less invasive surgical excision techniques, including purely endoscopic excision, endoscopic-assisted approaches and midline excision with nasal bone osteotomies and bone flap. These approaches allow adequate access for both total resection and nasal contour and skull base reconstruction. Following resection, if nasal bone osteotomies are insufficient for restoring nasal appearance, free temporoparietal fascial graft and/or conchal cartilage can be considered. For nasal tip deformities, interdomal sutures and free fat grafting are a suitable option. Complete surgical excision remains the treatment of choice for nasal dermoid lesions. The surgical approach taken and reconstruction depends on the type of lesion (cyst versus sinus or fistula), location (intranasal versus extranasal), whether or not there is intracranial extension, and experience of the surgical team.

EFFECTS OF OVERLOAD AND SUPPLYING OIL ON CRACK GROWTH BEHAVIOR IN MG ALLOYS

A single overload was applied during the crack growth process under constant stress amplitude, and retardation of crack growth was observed in the case of magnesium alloys as well as carbon steel, aluminum alloys, etc. The retardation of crack growth was related to crack closure, the fracture surface roughness, and crack tip deformation. In addition, the effects of supplying oil into the crack on crack growth behavior of an overloaded specimen were investigated in this study. The crack growth rate in the case of supplying oil became lower than in the case without supplying oil. In the case of the magnesium alloy AZ31, powder of oxide magnesium appeared from the crack after overloading. It is one of the typical behaviors of AZ31. In the case of AZ31 and AZX912, the crack growth behavior after overloading was slightly different due to the deformation of the crack tip.

A CLINICAL STUDY ON AYURVEDIC APPROACH IN PRASAV KALEEN ABHIGHAT (BIRTH INJURY) WITH SPECIAL REFERANCE TO ERB’S PALSY

A 3 month old Female baby was brought to my clinic and was presented with complete paralysis of Rt. Upper limb with typical waiter tip deformity associated with Dislocation of Rt. Shoulder. The baby was treated with the integrated approach of Allopathy and Ayurveda with the intension of faster recovery of the Baby, So that the baby can live a normal life. Innitially, Dislocated Rt. Shoulder Joint was fixed with the Help of Orthopedic Surgeon and was immobilized for 6 weeks. Later, baby was clinically showing. Asymmetric Moro’s Reflex, the rt. arm is adducted and internal rotated at elbow and flexion of wrist and fingers i.e Waiter tip deformity of the same hand which was suggestive of Erb’s Palsy i.e Injury to the Brachial Plexus (C5, C6)[9]. As per Ayurveda Classics: the Condition can be co-rrelated with Ekangvat which is Apatarpan in nature ( Disease which hampers the growth of the body tissues).[17] The Choice of Treatment is Santarpan Chikitsa ( nourshing treatment of the body tissues). Santarpan Chiktisa was palnned for both Antarparimarjan and Bahirparimarjan Chikitsa which nourishes the body tissues both internally as well as Externally. Antarparimarjan Chikitsa included a combination of Bala Churna, Shatawari Churna, Ashwagandha Churna, Musta Churna , shunti churna [7]with mother’s Milk where as Bahirparimarjan Chiktisa included Abhyang (external oiling) with Bala Ashwagandh laksha Tailam along with Shigru Pareebhadradi Tailam ( considering Birth trauma i.e Aghataj Hetu) ,Shashtik Shali Anna Lepan ( Application of Medicated Rice paste in the form of Hot Fomentation) and Matra Basti (Medicated Oil Enema).[17],[2] Remarkable Results were Observed in the form of reduction of dispatrity in length and mid arm circumference of rt. Upper limb as compared to Lt. Upper limb. The Muscle Power improved from 0 to IV. Thus, Facilitating baby to near normal Movement.

Effect of microstructure on the high cycle fatigue behaviour of DP 600 and SPFH 590 steels with and without a hole

The performance of ferrite-martensite (DP 600) and ferrite-pearlite (SPFH 590) steels with a similar tensile strength of ∼650 MPa under cyclic loading was investigated. This work presents the high cycle fatigue properties of DP 600 and SPFH 590 steel in the presence and absence of a hole. In presence of the hole, the fatigue strength for both the steels drops significantly, with drop being more for SPFH 590 steel. While the fatigue strength in absence of a hole is a strong function of yield strength of material, the behaviour in presence of the hole depends on the steel microstructure. The presence of martensite in case of DP 600 steel delayed the crack propagation by branching and crack tip blunting. Additionally, martensite also increases the local strain, low angle grain boundary and dislocation density ahead of the crack tip, resulting in an increased amount of plastic deformation and blunting of the crack tip.

Machine Learning-Based and Experimentally Validated Optimal Adhesive Fibril Designs.

Setae, fibrils located on a gecko's feet, have been an inspiration of synthetic dry microfibrillar adhesives in the last two decades for a wide range of applications due to unique properties: residue-free, repeatable, tunable, controllable and silent adhesion; self-cleaning; and breathability. However, designing dry fibrillar adhesives is limited by a template-based-design-approach using a pre-determined bioinspired T- or wedge-shaped mushroom tip. Here, a machine learning-based computational approach to optimize designs of adhesive fibrils is shown, exploring a much broader design space. A combination of Bayesian optimization and finite element methods creates novel optimal designs of adhesive fibrils, which are fabricated by two-photon-polymerization-based 3D microprinting and double-molding-based replication out of polydimethylsiloxane. Such optimal elastomeric fibril designs outperform previously proposed designs by maximum 77% in the experiments of dry adhesion performance on smooth surfaces. Furthermore, finite-element-analyses reveal that the adhesion of the fibrils is sensitive to the 3D fibril stem shape, tensile deformation, and fibril microfabrication limits, which contrast with the previous assumptions that mostly neglect the deformation of the fibril tip and stem, and focus only on the fibril tip geometry. The proposed computational fibril design could help design future optimal fibrils with less help from human intuition.

Fatigue crack propagation analysis in 2024-T351 aluminium alloy using nonlinear parameters

In this work, fatigue crack growth (FCG) in the 2024-T351 aluminium alloy is studied using the plastic CTOD range, Δδp. Experimental tests were performed on 12 mm thick CT specimens in order to obtain FCG rate and in cylindrical specimens to obtain stress–strain loops. A numerical analysis replicated the experimental work in terms of material, geometry and loading conditions, but assuming pure plane strain state, in order to obtain Δδp. The material parameters were fitted using the experimental stress–strain loops. The experimental work showed an increase of FCG rate with the increase of stress ratio from R = 0.1 to R = 0.7 mm, which indicated the existence of the crack closure phenomenon. However, the analysis of the position of the first node behind the crack tip showed that there is no crack closure under plane strain state, while a maximum value of 36% was found for plane stress state. Therefore, the surfaces influence FCG rate even in 12 mm thick specimens. A nearly linear relation was found between da/dN and Δδp. The comparison with other aluminium alloys showed that there is a significant influence of material on da/dN-Δδp relation. The change from plane strain to plane stress state decreased FCG rate due to crack closure. Under plane strain state there is a minor influence of stress ratio in the range R = 0.1–0.7, also because there is no crack closure. Finally, a comparison was made between plastic CTOD and cumulative plastic strain at the crack tip. Well defined relations were found, showing that both parameters can be used to quantify crack tip deformation.

Effect of creep-fatigue loading condition on crack tip fields of grade 91 steel at crack initiation and growth

In this paper, the effect of creep-fatigue loading condition on crack tip deformation and stress fields of Grade 91 steel at 600 °C at crack initiation and growth is studied. By using finite element debond analysis method, creep-fatigue crack growth tests using C(T) specimens under various load ratios and hold times are simulated, and the effect of creep-fatigue load ratio and hold time on the crack opening profile, equivalent stress, crack-opening stress and triaxiality at crack initiation and growth is presented. It is found that the crack tip deformation and stress fields under tension–compression creep-fatigue loading are overall different from those under tension-tension creep-fatigue and pure creep loading, due to re-sharpening of the crack tip.