Shear-induced Damage Research Articles

The Effects of Loading Angles on the Failure of Cross-Ply Notched Bio-Basalt Composites

A cross-ply basalt V-notched butterfly specimens were subjected to pure tension, combined tension-shear, and shear stress-strain state using a modified Arcan test fixture with loading angles from 0° to 90° with 15° increment. Multiaxial stress and strain states were studied using the principal stress and strain ratio, from which the principal angle was determined and used to represent principal states in the gauge section. The quasi-elastic to non-linear transition stresses were determined for each loading angle. In biaxial stress-strain states and pure shear, the deformation and consequently the shear-induced damage start to accumulate significantly. Also, in biaxial stress-strain states between 15°-75°, the shift from tension-shear to pure shear was observed after the transition to the non-linear part of the stress-strain curve. The digital image correlation (DIC) images and microscopic evaluation show that a large extent of damage is the consequence of the shear deformation after the rotation of 0° clamped fibres, while the 90° fibres maintained their original straight form. In off-axis tests, the principal strain axis rotates towards the weakest material axis even at small off-axis angles. This causes a transition from a tension-shear biaxial state in the linear loading part to shear in the non-linear part, leading to irreversible damage beyond the transition point.

Bearing performance and progressive failure analysis of bolted joint in 3D printed pseudo-woven CFRP composite with fibre steering

This study investigates the bearing failure process of 3D printed pseudo-woven carbon fibre reinforced polymer (CFRP) composite joints, with a particular focus on the damage mechanisms influenced by steered fibres. A multiscale finite element model employing LaRC05 failure criteria is developed and validated against the experimental load–displacement curves and micro-computed microtomography (CT) images of four distinct cases. The model clearly demonstrates the critical importance of maintaining fibre continuity around the bolt hole, as this significantly influences the ability to reduce stress concentrations caused by the direct bearing loads from the bolt. Moreover, the model reveals that fibre steering can substantially improve the composite joint’s performance. This enhancement is achieved by adjusting the level of shear-induced damage propagation in individual filaments. The results demonstrate the potential and capability of the model to capture individual filament behaviour for the failure analysis of 3D printed composites, achieving good correlations with experimental measurements and observations, in terms of failure modes and load-bearing capacities.

Fiber-Reinforced Thermoplastic Sucker Rods Provide Artificial Lift Efficiencies

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 23949, “Fiber-Reinforced Thermoplastic Sucker Rods Providing High-Strength, Lightweight, Low-Cost, and Environmentally Responsible Artificial Lift Efficiencies,” by Jeff Saponja, SPE, Oilify, and Corbin Coyes, SPE, and Michael Conner, SPE, Q2 Artificial Lift Services. The paper has not been peer reviewed. Copyright 2024 International Petroleum Technology Conference. _ The complete paper focuses on the development of fiber-reinforced thermoplastic (FRTP) sucker rods, highlighting their potential advantages and challenges, for rod pumping (in general) and for offering an earlier transition from electrical submersible pump (ESP) pumping or gas lifting to reliable deep high-rate rod pumping. A unique feature of an FRTP composite rod is its remarkably high shear failure resistance compared with that of a thermoset composite rod. A high shear-failure resistance means the rods have compressional loading tolerance and that an entire sucker rod string could be comprised of FRTP sucker rods. Introduction Sucker rods made from steel are relatively heavy. Extensive well-specific designs require tapering of rod strings to optimize the overall sucker rod string weight relative to the strength and fatigue requirements and consideration of the dynamic loadings from accelerations and decelerations of the rods and fluids, frictional effects, and structural or power limitations of the pump jack or unit at surface. Steels suffer from corrosion risks. Corrosion, which rapidly can accelerate fatigue failure, often is the root cause of sucker rod failure. Fiber-reinforced composites (i.e., fibers surrounded by or wetted by a resin matrix) have gained considerable popularity because they can be tailored to have outstanding mechanical, thermal, and physical properties, and have superior material mechanical properties to metal. The fatigue behavior of composite materials and structures is complex because composites fail by a series of, or collection of, damage mechanisms, including fiber breakage, matrix cracking, fiber/matrix debonding, delamination, and the effect of shear-induced damage on cracks. Cracking can be slowed somewhat if the reinforced fibers are of high stiffness. Composite materials can offer a lower environmental footprint over their entire life cycle. They can require less energy to manufacture, thereby reducing CO2 emissions. A high strength/weight ratio offers less energy consumption during operational use, further reducing CO2 emissions. Composite materials can be recycled and reused. Composite sucker rods, in the form of thermoset fiberglass sucker rods, have offered a high strength/weight ratio with greater corrosion tolerance, but they are too stretchy from a low glass fiber tensile modulus of elasticity for deep high-rate rod pumping and when a high production-rate decline is likely. This limitation results in a large bottomhole pump-stroke variability as operating conditions change. Such rods have low tolerance to compressional and impact loads, forcing a larger proportion of a sucker string to remain as steel. They are also more costly than steel rods. For sucker rod pumping, an ideal composite rod should tolerate compressional loads and feature high impact resistance and high fatigue endurance with an ability to limit or control crack formation. A composite material that potentially offers these important sucker rod properties is FRTP.

Damage evolution and destabilization precursors in granite under splitting load at different temperatures

Brazilian splitting acoustic emission (AE) tests were conducted on the granite specimens that were heated at the temperatures from 50 to 600 °C to investigate the mechanical and damage characteristics of granite under high temperatures and splitting load in deep drilling. The results indicate that temperature variations significantly alter the mechanical characteristics and AE properties of granite, thereby influencing the evolution of fractures. At the temperature above 500 °C, the tensile strength of granite decreases significantly and the proportion of shear-induced damage modes increases. Furthermore, the rate of fracturing also exhibits a noticeable increase. Damage parameter mutation points on the damage parameter evolution curves of hit counts and energy counts were defined to determine the rock damage precursor. Mutation points based on hit counts arrive earlier than rock instability signals. The greater the damage is, the earlier the mutation points arrive. This time difference can be used to identify rock destabilization signals.

Characterization and Simulation of Shear-Induced Damage in Selective-Laser-Sintered Polyamide 12.

This paper presents the characterisation of selective-laser-sintered (SLS) samples of polyamide 12 (PA12) under shear loading. PA12 is a semi-crystalline thermoplastic and is used in various industries. Its behaviour under shear stress, which is particularly important for product reliability, has not yet been sufficiently investigated. This research focuses on understanding the material and damage behaviour of PA12 under shear-induced stress conditions. The study included quasi-static experiments and numerical simulations. Samples were prepared via SLS and tested according to ASTM standards. Digital image correlation (DIC) was used for precise deformation measurements. The Chaboche material model was used for the viscoplastic behaviour in the numerical simulations. Due to existing material discontinuities in the form of voids, the material model was coupled with the Gurson-Tvergaard-Needleman (GTN) damage model. A modified approach of the GTN model was used to account for low stress triaxiality under shear loading. These models were implemented in MATLAB and integrated into Abaqus via a User Material (UMAT) subroutine. The results of the experiments and simulations showed a high degree of accuracy. An important finding was the significant influence of the shear factor kw on the damage behaviour, especially during failure. This factor proved to be essential for the accurate prediction of material behaviour under shear-induced stress conditions. The integration of the modified GTN model with the Chaboche material model in UMAT enables an accurate prediction of the material and damage behaviour and thus makes an important contribution to the understanding of the mechanical material behaviour of SLS PA12 specimens.

Role of Shear on Strength and Damage Evolution in Soda-Lime Glass Under High Dynamic Pressures

Abstract Silica glasses, such as soda-lime glass (SLG), have found wide ranging applications in engineering due to their excellent optical properties, high strength, and relatively low cost. In such applications, SLG may be subjected to intense dynamic loading due to high/hyper-velocity impact and therefore necessitates understanding of the dynamic shear strength and kinetics for the development of constitutive models. However, while several investigations have generated Hugoniots for silicate glasses, none appear to have measured shearing resistance at pressures above ∼ 20 GPa. In this study, the role of pressure and strain rate on the shearing resistance of soda-lime glass is explored using sandwich configuration high pressure-pressure shear plate impact (HP-PSPI) experiments. These experiments are conducted at pressures ranging from 14 to 42 GPa and strain rates of 105 − 106 s−1, and analyzed using finite element simulations incorporating a modified Johnson–Holmquist (JH-2) material model. The yield strength of SLG is observed to decrease as a function of pressure, which is reminiscent of the evolution of shear strength in granular media at high pressures. This observation suggests a probable shear-induced damage progression from intact material to granular matter in SLG at high pressures.

Development and validation of a mathematical model for evaluating shear-induced damage of von Willebrand factor

PurposeTo develop a mathematical model for predicting shear-induced von Willebrand factor (vWF) function modification which can be used to guide ventricular assist devices (VADs) design, and evaluate the damage of high molecular weight multimers (HMWM)-vWF in VAD patients for reducing clinical complications. MethodsMathematical models were constructed based on three morphological variations (globular vWF, unfolded vWF and degraded vWF) of vWF under shear stress conditions, in which parameters were obtained from previous studies or fitted by experimental data. Different clinical support modes (pediatric vs. adult mode), different VAD operating states (pulsation vs. constant mode) and different clinical VADs (HeartMate II, HeartWare and CentriMag) were utilized to analyze shear-induced damage of HMWM-vWF based on our vWF model. The accuracy and feasibility of the models were evaluated using various experimental and clinical cases, and the biomechanical mechanisms of HMWM-vWF degradation induced by VADs were further explained. ResultsThe mathematical model developed in this study predicted VAD-induced HMWM-vWF degradation with high accuracy (correlation with experimental data r2 > 0.99). The numerical results showed that VAD in the pediatric mode resulted in more HMWM-vWF degradation per unit time and per unit flow rate than in the adult mode. However, the total degradation of HMWM-vWF is less in the pediatric mode than in the adult mode because the pediatric mode has fewer times of blood circulation than the adult mode in the same amount of time. The ratio of HMWM-vWF degradation was lower in the pulsation mode than in the constant mode. This is due to the increased flushing of VADs in the pulsation mode, which avoids prolonged stagnation of blood in high shear regions. This study also found that the design feature, rotor size and volume of the VADs, and the superimposed regions of high shear stress and long residence time inside VADs affect the degradation of HMWM-vWF. The axial flow VADs (HeartMate II) showed higher degradation of HMWM-vWF compared to centrifugal VADs (HeartWare and CentriMag). Compared to fully magnetically suspended VADs (CentriMag), hydrodynamic suspended VADs (HeartWare) produced extremely high degradation of HWMW-vWF in its narrow hydrodynamic clearance. Finally, the study used a mathematical model of HMWM-vWF degradation to interpret the clinical statistics from a biomechanical perspective and found that minimizing the rotating speed of VADs within reasonable limits helps to reduce HWMW-vWF degradation. All predicted conclusions are supported by the experimental and clinical data. ConclusionThis study provides a validated mathematical model to assess the shear-induced degradation of HMWM-vWF, which can help to evaluate the damage of HMWM-vWF in patients implanted with VADs for reducing clinical complications, and to guide the optimization of VADs for improving hemocompatibility.

Effects of Microfluidic Shear on the Plasmid DNA Structure: Implications for Polymeric Gene Delivery Vectors.

Microfluidic manufacturing of advanced gene delivery vectors necessitates consideration of the effects of microfluidic shear forces on the structural integrity of plasmid DNA (pDNA). In this paper, we expose pDNA to variable shear forces in a two-phase, gas-liquid microfluidic reactor and apply gel electrophoresis to analyze the products of on-chip shear-induced degradation. The effects of shear rate, solvent environment, pDNA size, and copolymer complexation on shear-induced degradation are investigated. We find that small naked pDNA (pUC18, 2.7 kb) exhibits shear rate-dependent shear degradation in the microfluidic channels in a mixed organic solvent (dioxane/water/acetic acid; 90/10/<0.1 w/w/w), with the extents of both supercoil isoform relaxation and complete fragmentation increasing as the maximum shear rates increase from 4 × 105 to 2 × 106 s-1. However, over the same range of shear rates, the same pDNA sample shows no evidence of microfluidic shear-induced degradation in a pure aqueous environment. Quiescent control experiments in the same mixed organic solvent prove that a combination of solvent and shear forces is involved in the observed shear-induced degradation. Furthermore, we show that shear degradation effects in mixed organic solvents can be significantly attenuated by complexation of pDNA with the block copolymer polycaprolactone-block-poly(2-vinylpyridine) prior to exposure to microfluidic shear. Finally, we demonstrate that medium (pDSK519, 8.1 kb) and large (pRK290, 20 kb) naked pDNA are more sensitive to shear-induced microfluidic degradation in the mixed organic solvent environment than small pDNA, with both plasmids showing complete fragmentation even at the lowest shear rate, although we found no evidence of shear-induced damage in water for the largest investigated naked pDNA even at the highest flow rate. The resulting understanding of the interplay of the solvent and shear effects during microfluidic processing should inform microfluidic manufacturing routes to new gene therapy formulations.

A Cohesive Traction Embedded Constitutive Law Combined with Shear-Induced Damage and Kinematic Hardening Law

A Cohesive Traction Embedded Constitutive Law Combined with Shear-Induced Damage and Kinematic Hardening Law

In vitro study of red blood cell and VWF damage in mechanical circulatory support devices based on blood-shearing platform.

Blood damage induced by mechanical circulatory support devices (MCSDs) remains a significant challenge to optimal clinical care. Although researchers have been conducting in vitro studies, the major determinant of blood damage is still unclear. An optimized capillary tube blood-shearing platform with custom designed parts was constructed to investigate the influence of two flow-dependent parameters (shear stress and exposure time) on the shear-induced damage of red blood cells and von Willebrand factor (VWF). Blood samples under different high shear stress and instantaneous exposure time were obtained by changing the flow rate and the length of capillary tube. Plasma free hemoglobin assay and immunoblotting of VWF were then performed on the sheared blood samples. The quantitative correlation between the hemolysis index and the two flow-dependent parameters was found following the power law mathematical model under the flow condition with high shear stress and instantaneous exposure time. The degradation of high molecular weight VWF was not obvious under high shear stress factor. However, the degradation of high molecular weight VWF was found as the result of the accumulation over exposure time under non-physiological shear stress, which was consistent with the different mechanism of VWF damage comparing to red blood cell damage. Compared to peak shear stress, exposure time has a greater effect on both red blood cell and VWF damage. To improve the hemocompatibility of MCSDs, it is more important to avoid regions of slow blood flow with non-physiological shear stress under laminar flow conditions.

異なる混合モード下における延性破壊の変化を予測するための結合力埋込型弾塑性構成則

The contribution of this study is to propose a cohesive traction embedded constitutive law to predict the changes of ductile failure under different mixed mode. Flat and shear-lip fractures in ductile failure under different mixed mode are represented by the cohesive traction-separation law and shear-induced damage, respectively, reflecting that these mechanisms are different from each other. For the flat fracture, the stiffness reduction and strain softening due to void nucleation, growth, and coalescence under high stress state are realized by the cohesive traction-separation law that determines the process of stress releases along with ductile crack opening. To realize crack nucleation at an arbitrary location and propagation in an arbitrary direction, the cohesive separation law is combined with the Hencky-type hyperelastic-plastic model by the introduction of apparent deformation gradient due to crack opening and local balance equations between cohesive tractions and principal stresses. On the other hand, for the shear-lip fracture, the shrink of yield surface caused from the evolutions of micro voids in a shear band is represented by the shear-induced damage variable that is incorporated into the Tresca yield function. Moreover, the evolution of shear-induced damage is determined by the damage loading function corresponding to the plastic energy release based on thermodynamics. Simple numerical examples are presented to demonstrate that our proposed model enables us to predict the change of ductile fracture under different mixed mode.

Post-liquefaction deformation and strength characteristics of sand in torsional shear tests

The estimation of strength deterioration with the increase in the undrained cyclic shear-induced strain in liquefiable soils is an important topic in geotechnical earthquake engineering that is still poorly understood and needs to be properly addressed. In this paper, in an attempt to provide new insights into this topic, the post-liquefaction undrained strength and deformation of Toyoura sand were investigated through a series of laboratory tests performed by using a large-strain torsional shear apparatus. In the tests, simple shear conditions were reproduced on a medium-size hollow cylindrical specimen to apply stress conditions that soil experiences in the field during earthquakes. Specimens prepared by the air-pluviation method were first liquefied by applying a constant amplitude undrained cyclic shearing to induce a target cyclic shear-induced damage strain (γΔ). The tests were terminated at different amplitudes of γΔ and subsequently loaded monotonically in undrained conditions to obtain stress-strain and excess pore water generation responses. The test results indicate that the post-liquefaction monotonic loading (ML) stress-strain behavior of sand can be divided into three regions, namely Region 1, 2 and 3. The sand behavior changes to strain-hardening from essentially zero strength and stiffness from Region 1 to 2. While Region 3 marks the beginning of strain-softening state in the sand. It is found that the strain localization is associated with the transition of sand behavior from strain-hardening to strain-softening state. It is proposed that the sand undrained strength in monotonic shearing is the true representation of specimen response until the state of uniform deformation is maintained, based on the sudden drop of the differential stress (σd = σ v′ - σh′). The test results also revealed that there is a progressive degradation in the shear strength with the increase in the amplitude of γΔ. A correlation depicting the degradation ratio (τd) with the increase in the γΔ is proposed. This correlation can be used to estimate the degree of degradation with the increase in the applied γΔ, and it is valid for different density states, confining stresses and cyclic stress ratios.

Mathematical models for shear-induced blood damage based on vortex platform.

Non-physiological shear stress in Ventricular Assist Device (VAD) is considered to be an important trigger of blood damage, which has become the biggest shackle for clinical application. The researches on blood damage in literature were limited to qualitative but did not make much quantitative analysis. The purpose of this study was to investigate the quantitative influence of two flow-dependent parameters: shear stress (rotational speed) and exposure time on the shear-induced damage of red blood cells and von Willebrand Factor (vWF). A vortex blood-shearing platform was constructed to conduct in vitro experiments. Free hemoglobin assay and vWF molecular weight analysis were then performed on the sheared blood samples. MATLAB was used for regression fitting of original experimental data. The quantitative correlations between the hemolysis index, the degradation of high molecular weight vWF and the two flow-dependent parameters were found both following the power law model. The mathematic models indicated that the sensitivity of blood damage on red blood cells and vWF to exposure time was both greater than that of shear stress. Besides, the damage of vWF was more serious than that of red blood cells at the same flow condition. The models could be used to predict blood damage in blood-contacting medical devices, especially for the slow even stagnant blood flow regions in VAD, thus may provide useful guidance for VAD development and improvement. It also indicated that the vortex platform can be used to study the law of blood damage for the simple structure and easy operation.

Fatigue damage of cohesive interfaces in fiber-reinforced polymer composite laminates

The weak interfaces in fiber-reinforced polymer (FRP) composite laminates often dictates the reliability of the composite structures. In this respect, a new cyclic cohesive zone model (CCZM) is introduced for accurate quantitative description of the interlaminar fatigue failure process. The model incorporates the interlaminar damage through the measured fatigue degradation of the strength, stiffness, and critical energy release rate properties. A combined experimental-finite element (FE) approach is employed to establish the residual interlaminar properties. The new CCZM is examined for the case study on the end-notched flexure (ENF) beam specimen of unidirectional carbon fiber-reinforced polymer (CFRP) composite laminate. The calculated applied resultant shear stress at the critical interface material point, adjacent to the pre-existing crack front, fluctuates at (τmax = 30 MPa, R = 0.1). The interlaminar shear-induced damage shows a sigmoidal form of the damage evolution curve. The pre-existing interface crack propagation begins at 301750 cycles, while maintaining an almost straight advancing crack front.

Elastic shear modulus variations during undrained cyclic loading and subsequent reconsolidation of saturated sandy soil

To evaluate the variations in the elastic shear modulus G0 of saturated sandy soil during consolidation, undrained cyclic loading and reconsolidation, we performed a series of multiple-phased triaxial tests with measurements of shear wave velocity on specimens having different dry densities. At the same isotropic effective stress, the G0 value during undrained cyclic loading became smaller than that during initial consolidation. For the same effective stress parameter that was found to be relevant to the isotropic and anisotropic stress states, the G0 value at an identical effective stress parameter at isotropic and anisotropic stress states during undrained cyclic loading decreases similarly with an increase in the previous strain amplitude. By reconsolidation to the original effective stress state, the G0 value increased partly due to recovery from the shear-induced damage and partly due to a decrease in the void ratio. The effects of the former factor decreased as the specimen became denser, while the effects of the latter factor increased as the specimen became looser. As a result, compared with the initial value at the end of initial consolidation, the G0 value after reconsolidation of the same specimen became significantly smaller with dense specimens while it became significantly larger with loose specimens.

Couette shearing device for the investigation of shear-induced damage of the primary hemostasis by left ventricular assist devices.

Continuous-flow left ventricular assist devices have evolved from short-time therapy into permanent or so-called destination therapy. One complication in long-term usage is bleeding, which is presumably attributed to shear-induced interference of left ventricular assist devices with the coagulation system. The influence of dynamic shear stresses on primary hemostasis by single or multiple passes through left ventricular assist devices was investigated. A novel Couette-type shearing device, especially fitted to simulate left ventricular assist devices with highly dynamic and repetitive stresses, was developed. To evaluate the clotting ability of the blood and thus the bleeding tendency, the closure time of the platelet function analyzer (PFA-100®, Dade Behring, Marburg, Germany) was used. The relationship of the PFA-100 closure time was fitted to measurement points with shear stress and exposure time as parameters. 76 samples of human blood collected from four different healthy donors in sodium-citrate anticoagulant solution were tested, including 20 control samples. A damage model according to the power law approach could be developed. A linear correlation of shear stress and exposure time to the PFA-100 closure time could be determined. In addition, a model was developed to calculate the increase in the PFA closure time on the basis of shear stress over time curves. With the shearing device, half-sine-wave-shaped shear stress patterns relevant to rotary blood pumps can be achieved with very good repeatability. The proposed damage model could be used to compare and optimize left ventricular assist devices under development. The tests showed a significant decrease in coagulability after only a few repetitions.

Visualization of erythrocyte deformation induced by supraphysiological shear stress.

To elucidate development of shear-induced damage in erythrocytes, it is necessary to visualize erythrocytes under high-shear flow. Therefore, we prototyped a special shear flow chamber with a counter-rotating mechanism consisting of a transparent acrylic cone and a glass plate. The flow chamber was mounted on an inverted microscope and illuminated by a 350-W metal halide lamp. This experimental system made it possible for a digital video camera to record through the microscopes' objective lens the rheological behavior in shear flow of erythrocytes diluted in highly viscous polyvinyl pyrrolidone. We successfully visualized the blood cells' ellipsoidal deformation response to an unphysiological, high shear stress of 288 Pa, their shift into abnormal rheological behavior, and final collapse. When abnormality first appeared, the membrane surface of some ellipsoidal erythrocytes started undulating and their shape became more asymmetric. Finally, the erythrocytes appeared to fragment, although the fragments continued tumbling together suggesting that they were all still connected. One such abnormal erythrocyte became segmented through collision with other cell. The undulation of the membrane surface when erythrocytes experienced trauma suggests possible detachment of the lipid bilayer from the membrane cytoskeleton. As the damage increased, the morphological abnormality of cells became greater with less tank-treading, and then, the erythrocytes started tumbling. This unstable behavior increases the volume of flow region occupied by the erythrocytes and increases the chance that neighboring cells will hit them and break them into segmented pieces. This study clearly showed that the beginning of erythrocytes' morphological abnormality was induced by shear stress.

Rapid Detection of Shear-Induced Damage in Tissue-Engineered Cartilage Using Ultrasound.

Previous investigations have shown that tissue-engineered articular cartilage can be damaged under a combination of compression and sliding shear. In these cases, damage was identified in histological sections after a test was completed. This approach is limited, in that it does not identify when damage occurred. This especially limits the utility of an assay for evaluating damage when comparing modifications to a tissue-engineering protocol. In this investigation, the feasibility of using ultrasound (US) to detect damage as it occurs was investigated. US signals were acquired before, during, and after sliding shear, as were stereomicroscope images of the cartilage surface. Histology was used as the standard for showing if a sample was damaged. We showed that US reflections from the surface of the cartilage were attenuated due to roughening following sliding shear. Furthermore, it was shown that by scanning the transducer across a sample, surface roughness and erosion following sliding shear could be identified. Internal delamination could be identified by the appearance of new echoes between those from the front and back of the sample. Thus, it is feasible to detect damage in engineered cartilage using US.

Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching.

The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures.

Pathology-targeted cell delivery via injectable micro-scaffold capsule mediated by endogenous TGase.

Targeted cell delivery to lesion sites via minimally invasive approach remains an unmet need in regenerative medicine to endow satisfactory therapeutic efficacy and minimized side-effects. Here, we rationally designed a pathology-targeted cell delivery strategy leveraging injectable micro-scaffolds as cell-loading capsule and endogenous tissue transglutaminase (TGase) at lesion site as adhesive. Up-regulated TGase post-liver injury catalyzed chemical bonding between the glutamine and lysine residues on liver surface and micro-scaffolds both exvivo and invivo, facilitating sufficient adhesion on the pathological liver. Upon intraperitoneal injection, Mesenchymal Stem Cell-loaded capsules, exhibiting cell protection from shear-induced damage and post-transplantation anoikis, adhered to the CCl4-treated liver with a hundred-fold improvement in targeting efficiency (70.72%) compared to free-cell injection, which dramatically improved mice survival (33.3% vs. 0% for free-cell therapy) even with low-dosage treatment. This unique and widely-applicable cell delivery mechanism and strategy hold great promise for transforming cell therapy for refractory diseases.