Volumetric Damage Research Articles

A novel hydro-elastoplastic constitutive model incorporating hydrostatic damage for predicting high-pressure performance of concrete under blast loading

The evolution of damage and failure modes of concrete under blast or impact loads are the outcomes of stress wave propagation. The stress state at a point within the concrete changes instantaneously with time and space. Establishing a constitutive model that can cover the nonlinear behavior of materials under complex loading paths and histories is an extremely challenging task. The main difficulty lies in the construction of the damage model, which has not yet been fully resolved in commonly used concrete models. This paper, based on the mechanisms of damage and failure of concrete under hydrostatic pressure, constructs a state equation that includes the description of crushing and compaction damage due to the collapse and closure of pores, as well as their interactive model, negative pressure degradation caused by hydrostatic pressure, and nonlinear volumetric behavior under loading/unloading/reloading. By introducing independent shear and tensile deviatoric damage scaling functions and a damage scaling function under isotropic tension, the coupling relationship between deviatoric and volumetric damage is considered. Corresponding strength models and element erosion criteria are developed based on the new state equation and damage models. Then, single-element numerical experiments of unconstrained uniaxial compression and tension, triaxial compression under different confining pressures, monotonic and cyclic hydrostatic compression, and isotropic tension were conducted to verify the predictive accuracy of the proposed model under single loading paths. Finally, numerical experiments of contact explosion on plain concrete thick and thin targets were carried out using the proposed model, revealing the propagation laws and failure processes of the loading compression wave, unloading tensile wave, and reflected tensile wave within the concrete target. The predicted final failure modes are consistent with the experimental results.

Can Robotic-Arm Assistance Decrease Iatrogenic Soft-Tissue Damage During Direct Anterior Total Hip Arthroplasty?

Manual techniques for total hip arthroplasty (THA) have been widely utilized and proven to be clinically successful. However, the use of advanced computed tomography (CT) scan-based planning and haptically-bounded reamers in robotic-arm assisted total hip arthroplasty (RTHA) holds promise for potentially limiting surrounding soft-tissue damage. This cadaver-based study aimed to compare the extent of soft-tissue damage between a robotic-arm assisted, haptically-guided THA (RTHA) and a manual, fluoroscopic-guided THA (MTHA) direct anterior approach. There were six fresh-frozen torso-to-toe cadaver specimens included, with two surgeons each performing three RTHA and three MTHA procedures. One hip underwent an RTHA and the other hip received an MTHA in each cadaver. Postoperatively, one additional surgeon, blinded to the procedures, assessed and graded damage to nine key anatomical structures using a 1 to 4 grading scale: (1) complete soft-tissue preservation to <5% of damage; (2) 6 to 25% of damage; (3) 26 to 75% of damage; and (4) 76 to 100% of damage. Kruskal-Wallis hypothesis tests were used to compare soft-tissue damage between RTHA and MTHA cases and adjusted for ties. Pooled analysis of the gluteus minimus, sartorius, tensor fascia lata, and vastus lateralis muscle grades demonstrated that cadaver specimens who underwent RTHA underwent less damage to these structures than following MTHA (median, IQR: 1.0, 1.0 to 2.0 vs. 3.0, 2.0 to 3.0; p=0.003). Pooled analysis of the calculated volumetric damage (mm3) for the gluteus minimus, sartorius, tensor fascia lata, and vastus lateralis muscles demonstrated that the cadaver specimens that underwent RTHA underwent less damage to these structures than those that followed MTHA (median, IQR: 23, 2 to 586 vs. 216, 58 to 3,050; p=0.037). This cadaver-based study suggests that utilizing RTHA may lead to reduced soft-tissue damage compared with MTHA, likely due to enhanced preoperative planning with robotic-arm assisted software, real-time intraoperative feedback, haptically-bounded reamer usage, reduced surgical steps, as well as ease of use with reaming. These findings should be carefully considered when evaluating the utilization of robotic-arm assisted THA in practice.

Online and Ex Situ Damage Characterization Techniques for Fiber-Reinforced Composites under Ultrasonic Cyclic Three-Point Bending.

With ultrasonic fatigue testing (UFT), it is possible to investigate the damage initiation and accumulation from the weakest link of the composite material in the very high cycle fatigue (VHCF) regime in a shorter time frame than conventional fatigue testing. However, the thermal influence on the mechanical fatigue of composites and the scatter in fatigue data for composites under ultrasonic cyclic three-point bending loading still need to be investigated. In this study, we conducted interrupted constant-amplitude fatigue experiments on a carbon-fiber satin-fabric reinforced in poly-ether-ketone-ketone (CF-PEKK) composite material. These experiments were carried out using a UFT system, which operates at a cyclic frequency of 20 kHz with a pulse-pause sequence. Various parameters, such as the CF-PEKK specimen's surface temperature, acoustic activity, and the ultrasonic generator's input resonance parameters, were measured during cyclic loading. During experiment interruption, stiffness measurement and volumetric damage characterization in the CF-PEKK specimens using 3D X-ray microscopy (XRM) were performed. The locations of damage initiation and accumulation and their influence on the changes in in situ parameters were characterized. Under fixed loading conditions, damage accumulation occurred at different locations, leading to scattering in fatigue life data. Further, the damage population decreased from the surface to the bulk of the composite material.

Crystallization Cycles in Masonry Walls: Experimental Technique to Develop Accelerated Aging on a Real Scale

Moisture in historic built heritage is one of the main degenerative agents, because it supports or manifests itself through multiple pathologies. Current knowledge allows for the diagnosis and assessment of the problem, but there are deficiencies in the evaluation of corrective systems due to the time it takes for moisture to become significant. In response, this study proposes an experimental methodology that aims to reproduce the accelerated aging of real scale specimens under laboratory conditions. Thereby improving the understanding of the impact of moisture related deterioration on masonry structures. To achive this, eight masonry walls were constructed and subjected to eight cycles of sulfate crystallization. They were saturated with different sulfate concentrations (5% or 10%) and exposed to different drying conditions (outdoor or solar dehydrator) in order to identify the factors favoring sulfate crystallization and the resulting deterioration. The progress of the experiments was monitored using a hygrometer, a thermographic camera and photogrammetry. The results indicate that it is possible to induce efflorescence in real scale specimens. Temperature and moisture monitoring helped identify the solar dehydrator as a more effective drying treatment. While digital photogrammetry was considered inefficient for quantifying volumetric damage, since this technique can present errors greater than 2%, a value exceeding the observed wear. Reason why the weight of material detached at the end of the experiment was recorded and a positive correlation between the increase in sulfate concentration and the use of the dehydrator was observed. Finally, pertinent considerations are made to improve the experimental conditions.

A material model for thick, rate‐dependent adhesives with delocalized softening

AbstractThis contribution is dedicated to the development and implementation of a material model to describe the deformation behaviour of assembly adhesives. These assembly adhesives are usually used with thicknesses of several millimetres up to centimetres in order to compensate for large relative displacements of joining parts. These large displacements can be resisted by assembly adhesives, since they have a low shear modulus and thus a high strain until failure above their glass transition temperature. As a basis, the isothermal and isotropic hyperelasticity theory is used to describe the elastic deformation behaviour up to the postcritical range by using an isochoric–volumetric decomposition of the deformation gradient. The Arruda–Boyce and Ogden models are employed here for the isochoric‐elastic and volumetric‐elastic description. The modelling of the rate‐dependence concerning shear and bulk viscosity succeeds by extending the hyperelasticity theory to the theory of finite viscoelasticity with the generalized Maxwell model in each case. In order to model the postcritical deformation behaviour, an isotropic damage model is developed based on the energy limiting method and used to define an isochoric and a volumetric damage variable, so that the mapping of softening due to change of shape, as well as cavitation, succeeds. Furthermore, the damage variables are delocalized to prevent pathological mesh dependence by using the integral regularization method. Finally, the material parameters are determined and validated by means of measurement data due to tests at the assembly adhesive Betaforce 2850L. The results demonstrate a high prediction quality.

Concrete plates with externally bonded FRP under contact detonations

Local damage on concrete elements subjected to a contact detonation include spalling and cratering of the back and front face, respectively. This paper presents the results of a detailed experimental and numerical methodology aiming to analyse the influence of externally bonded fibre reinforced polymers (FRP) on the spalling phenomena of concrete when it is subjected to contact explosions. The influence of externally bonded reinforcement (EBR) on the diameter and depth of the spalling is experimentally investigated, as is also the total momentum transferred to the ejected fragments when their mass increases. The experimental observations enable the development of a computational framework, where a finite element (FE) model is validated and used to perform a through-thickness analysis focused on the stress wave propagation and associated damage mechanisms. It is found that the extent of concrete volumetric damage is highly influenced by the mass of the bonded material, as well as increased bonded areas leading to enlarged surface damage. Additionally, it was verified that the compressive strength of concrete plays a major role in the spall damage.

METHODS AND CRITERIA FOR ASSESSING THE CONDITION OF RIGID PAVEMENT CONTAINING CRACKS

Road agencies around the world note the aging of the national road network and the accelerated destruction of pavement during operation due to changes in the composition of the traffic. Many scientific studies have noted that cracks of various configurations, depths, origins are the most characteristic type of pavement damage, make up a significant part of the total area of destruction and are the main danger as the initial stage of more serious damage leading to loss of pavement distribution. Timely detection of hidden cracks in the coating layers and the base layers allows to prevent the destruction of pavement and significantly reduce the cost of road repairs. The purpose of the article is to analyze the methods and criteria for assessing the condition of non-rigid pavement, which contains hidden defects in its structural layers. The results of the analysis make it possible to take into account a particular type of defect when choosing a calculation scheme and the order of calculation of pavement. The analysis proved that the calculated schemes of pavement design do not allow to take into account such indicators of pavement condition as the number of cracks, their position, geometric parameters of hidden cracks, sizes of cracked base blocks, volumetric damage of the layer material. The assumptions and simplifications accepted in the normative documents actually make it impossible to assess the condition and predict the failure of the design of paved roads with cracks. Therefore, the assessment of the condition of non-rigid pavement should be based on probabilistic methods and criteria for assessing the condition of pavement, which allow to take into account the heterogeneity of pavement design, due, inter alia, the presence of cracks in layers of monolithic materials. The next stage of research is the analysis of existing probabilistic methods of designing and assessing the condition of pavement.

Methods for assessing the strength of the blades of soil-cutting parts of forestry machines

One way of increasing the wear resistance of working bodies of forestry machines is the use of strengthening technologies. Working tools of tillage machines used in forestry are dampened as a result of edge damage during multiple strike impacts of solid soil inclusions along blade edge. The purpose is to identify the pattern of damage of the blade edge of the of soil-cutting parts of forestry machines and theoretically justify the algorithm of strength evaluation in order to determine the rational thickness of the wear-resistant coating during strengthening. Instrumental and analytical studies were carried out on the damage of the reinforced blade edges as a result of multiple impacts on the pendulum copra. Mathematically described is the process of blade edge failure. In the course of multiple strike impacts of soil solid inclusions on the blade edge, there will be accumulation of volumetric damage because of plastic crumpling or chipping. The sharpness of the self-sealing reinforced blade is determined by the thickness of the reinforcing layer and its ability to resist collapse under strike impactsize.

The cross-disciplinary approach to analysis and forecast of operational damage tolerance of the oil pipeline system – part 2

The paper presents the cross-disciplinary approach to the analysis of the oil pipeline system based on the methodologies of tribo-fatigue and mechano-thermodynamics. The pipeline section is analyzed as a complex system pipe-soil- flow of liquid subject to the set of mechanical, thermal and friction loads. It is shown that theses loads are mainly repeatedlyalternated, and the pipe metal works in the multi-cycle fatigue conditions. The procedure of resonance accelerated fatigue tests is proposed, and their results are presented. Also, the unorthodox method of integrated wear-fatigue tests of the pipeline steel was proposed with the model of simultaneous pressure and wall friction actions. The presented field test results of pipes subject to the long-term operation showed that their fracture may occur not only in the near-weld zone, but also in the vicinity of internal corrosion damages. New models of three-dimensional stress-strain state and volumetric damage tolerance for the system pipe-soil-liquid flow were developed. These models were applied with regard to the pipe internal corrosion damages, defined using the inline inspection technique. A new efficient method to describe static and cyclic elastic-plastic fracture of the pipe steel with crack using the transverse strain is proposed and tested. Results of the computer-simulated propagation of the crack-like damage are based upon the model of deformed solid with dangerous volume. The new model is proposed for risk and safety assessment with regard to the ultrasonic inspection data. The algorithm of the ‘oil line pipe’ problem solution is presented for drafting a short-term plan of particular R&amp;D actions.

The cross-disciplinary approach to analysis and forecast of operational damage tolerance of the oil pipeline system – part 1

The paper presents the cross-disciplinary approach to the analysis of the oil pipeline system based on the methodologies of tribo-fatigue and mechanothermodynamics. The pipeline section is analyzed as a complex system pipe-soil- flow of liquid subject to the set of mechanical, thermal and friction loads. It is shown that theses loads are mainly repeatedly-alternated, and the pipe metal works in the multi-cycle fatigue conditions. The procedure of resonance accelerated fatigue tests is proposed, and their results are presented. Also, the unorthodox method of integrated wear-fatigue tests of the pipeline steel was proposed with the model of simultaneous pressure and wall friction actions. The presented field test results of pipes subject to the long-term operation showed that their fracture may occur not only in the near-weld zone, but also in the vicinity of internal corrosion damages. New models of three-dimensional stressstrain state and volumetric damage tolerance for the system pipe-soil-liquid flow were developed. These models were applied with regard to the pipe internal corrosion damages, defined using the inline inspection technique. A new efficient method to describe static and cyclic elastic-plastic fracture of the pipe steel with crack using the transverse strain is proposed and tested. Results of the computer-simulated propagation of the crack-like damage are based upon the model of deformed solid with dangerous volume. The new model is proposed for risk and safety assessment with regard to the ultrasonic inspection data. The algorithm of the ‘oil line pipe’ problem solution is presented for drafting a short-term plan of particular R&D actions.

An energy approach to Modified Cam-Clay plasticity and damage modeling of cohesive soils

An alternative approach to Modified Cam-Clay (MCC) critical state plasticity coupled with damage is proposed. The provided hyper-elastoplastic/damage framework is motivated by a desire to ensure thermodynamic consistency of model predictions, and is shown to satisfy the principle of maximum plastic dissipation, enabling enforcement of the plastic dissipation (and Clausius–Planck) inequality. A small strain Eshelby-like stress is derived as being energy-conjugate to the plastic strain rate, and relation to the damage-energy release rate is exploited to pose a coupled damage/yield MCC criteria (MCC-D). Relations between volumetric damage and porosity changes are examined, along with a method for estimating the damage state from bulk moduli measurements. The model is shown to simulate well existing high pressure compression measurements of Boulder clay, and connections between damage-related model parameters and behavior exemplifying different microstructural states is examined through numerical experiments.

Experimental study of material behavior of AP-HTPB base composite solid propellant

In the present study, to characterize material behavior of an ammonium perchlorate - hydroxyl terminated polybutadiene (AP-HTPB) base composite solid propellant, tension tests were performed with various temperatures and strain rates. Stress relaxation tests were also carried out at various temperatures to determine the tensile modulus of the material. In addition to these tests, three types of cyclic tests and dilatation test were carried out to identify the effect of internal damage evolution to the material response. From the results of three cyclic tests, Mullins effect was observed, and from the dilatation test, volumetric damage incurred by de-bonding between the filler and matrix material was observed as well. Based on such findings, a viscoelastic constitutive modeling with the Mullins effect and damage is proposed. Numerical simulations with the newly proposed damage model reproduced the experimental findings at various test conditions fairly well. It was found out that the proposed viscoelastic constitutive model could be used to efficiently characterize the material response of the solid propellant depending on various strain rates and temperatures according to the present study.

Prediction on damage evolution of recycled crumb rubber concrete using quantitative cloud imagine correlation

Abstract To account for the improvement of mechanical properties for recycled crumb rubber concrete (RCRC) under uniaxial compression and flexural toughness test in detail, three groups of RCRC specimen covering contents of rubber aggregate from 10 percent to 30 percent and one group of normal concrete (NC) specimen were prepared. Experimental results present distinguished influence of rubber particle content on uniaxial compressive strength and failure mode. Then, improvement in toughness properties was displayed inherently through change of the index named ratio of flexural strength to compressive one ( R f - c ). Simultaneously, a mesoscopic numerical model on random aggregate of RCRC was built up and validated by comparison of results from damage simulating to in-door testing. Furthermore, the mechanism of ductility enhancement for RCRC is unveiled visually and the prediction on damage evolution is revealed in quantitative way by a novel methodology of quantitative cloud imagine correlation (QCIC) based on 2D analysis. Subsequently, the similar law is established by a 3D Extended QCIC named volumetric damage accumulation method (VDAM). Therefore, it put forward a step further from state-of-the-art research about mechanical properties of RCRC, which may promote the utility of optimal design for this ecological material in civil engineering.

Deep learning-based automatic volumetric damage quantification using depth camera

Abstract A depth camera or 3-dimensional scanner was used as a sensor for traditional methods to quantify the identified concrete spalling damage in terms of volume. However, to quantify the concrete spalling damage automatically, the first step is to detect (i.e., identify) the concrete spalling. The multiple spots of spalling can be possible within a single structural element or in multiple structural elements. However, there is, as of yet, no method to detect concrete spalling automatically using deep learning methods. Therefore, in this paper, a faster region-based convolutional neural network (Faster R-CNN)-based concrete spalling damage detection method is proposed with an inexpensive depth sensor to quantify multiple instances of spalling simultaneously in the same surface separately and consider multiple surfaces in structural elements. A database composed of 1091 images (with 853 × 1440 pixels) labeled for volumetric damage is developed, and the deep learning network is then modified, trained, and validated using the proposed database. The damage quantification is automatically performed by processing the depth data, identifying surfaces, and isolating the damage after merging the output from the Faster R-CNN with the depth stream of the sensor. The trained Faster R-CNN presented an average precision (AP) of 90.79%. Volume quantifications show a mean precision error (MPE) of 9.45% when considering distances from 100 cm to 250 cm between the element and the sensor. Also, an MPE of 3.24% was obtained for maximum damage depth measurements across the same distance range.

On cavitation in transparent structural silicone adhesive: TSSA

Cavitation in rubber-like materials describes sudden void growth of an initially voided material under hydrostatic tension until the material fails. To study the cavitation effect numerically, classical cavitation criteria are coupled with a continuum damage formulation of a Neo-Hookean material. A cavitation criterion defines a failure surface in three-dimensional stress or strain space, which represents the onset of excessive void growth and therefore the strong degradation of the bulk modulus. To account for this special case of material softening, a novel continuum damage formulation at finite strains is presented, where the initially constant bulk modulus of a hyperelastic material is reduced after satisfying a cavitation criterion. Since this formulation leads to an abrupt damage initiation, additionally a continuously volumetric damage formulation is proposed and compared with it. Therefore, novel void growth criteria are developed, which describe the cavitation effect even under smallest volumetric strains. For numerical validation, a single element test is simulated under hydrostatic tension. Furthermore, pancake tests are numerically analysed. The results with regard on the chosen cavitation criterion and the abrupt/continuously damage formulation are compared with each other analysing TSSA.

Hyper-elastoplastic/damage modeling of rock with application to porous limestone

Relations between porosity, damage, and bulk plasticity are examined in the context of continuum damage and hyper-elastoplasticity of porous rocks. Attention is given to a thermodynamically consistent derivation of the damage evolution equations and their role in the constitutive equations, for which the Eshelby stress is found to be important. The provided phenomenological framework allows for volumetric damage associated with pore growth to be distinguished from the isochoric damage associated with distributed microcracks, and a novel Drucker-Prager/cap type material model that includes damage evolution is presented. The model is shown to capture well the hardening/softening behavior and pressure dependence of the so-called brittle-ductile transition by comparison with confined triaxial compression measurements from the literature. Non-linear finite element simulations are also provided of the prediction of damage within porous limestone around a horizontal borehole wall.

Damage effects of adhesives in modern glass façades: a micro-mechanically motivated volumetric damage model for poro-hyperelastic materials

This paper presents a micro-mechanically motivated volumetric damage model accounting for cavitation effects in modern glass connections, e.g. laminated glass connections. The volumetric part of an arbitrary Helmholtz free energy function is equipped with an isotropic damage formulation. To develop a micro-mechanical damage model, the porous micro-structure of a transparent structural silicone adhesive is analyzed numerically applying hydrostatic loading conditions. Based on the structural responses of different types of cubic representative volume elements incorporating an initial void fraction, three damage parameters are fitted utilizing the Levenberg–Marquard algorithm. The present volumetric damage model is implemented into ANSYS FE Code using a UserMat subroutine, where the algorithmic setting is described in detail in the present paper. To compare the structural responses of cubic equivalent homogeneous materials with representative volume elements, benchmark tests under hydrostatic loading are performed. The results indicate that the novel damage model accounts adequately for volumetric damage due to the cavitation effect. A special form of the pancake test is described briefly. The test allows for visualizing the cavitation effect during experimental testing. The experimental results of the pancake test are compared with numerical results, where the pancake test is simulated incorporating the micro-mechanical damage model. The micro-mechanically motivated scalar, internal damage variable is equipped with the obtained damage parameters from the structural response of the representative volume elements. The results show an adequate approximation of the experiment through the simulation. However, to optimize the results of the simulation, an optimization study on the damage parameters is conducted utilizing the Downhill-Simplex algorithm. Using the optimized damage parameters, the simulation of the pancake tests is further improved. Hence, it is shown that the novel micro-mechanically motivated volumetric damage model is excellently suited to represent the cavitation effect in poro-hyperelastic materials.

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Modified GTN model for a broad range of stress states and application to ductile fracture

Abstract Based on two ductile fracture mechanisms, a new modification to the Gurson–Tvergaard–Needleman (GTN) model is proposed for the simulation of ductile fracture behaviors under high, low and negative stress triaxiality loadings. In the modified GTN model, two distinctive damage parameters, respectively related to void growth mechanism and void shear mechanism, are introduced into yield function as internal variables of degradation process. The void volume fraction, similar to the original GTN model, is still adopted to capture the volumetric damage due to the void nucleation, growth and subsequent inner-necking, which plays the main role in tension. The additional shear damage, due to void rotation, distortion as well as “void sheet” effects, can accumulate in different stress states, even under negative stress triaxiality with the auxiliary of a new stress–state dependent function. The development of numerical procedures into finite element platform ABAQUS/Explicit allows the analysis of damage evolution, crack initiation and growth. The validity of the new model is examined by comparing numerical results with the experimental data of specimens including axisymmetric tensile bar, flat grooved plate, torsion tube and compression cylinder. The results show that the modified GTN model performs well in predicting the overall load–displacement responses and fracture paths of various specimens under stress states covering a wide range of triaxiality and Lode parameter combinations.

Volumetric Damage to the Femoral Physis During Double-Bundle Posterior Cruciate Ligament Reconstruction: A Magnetic Resonance Imaging Computer Modeling Study

The purpose of this study was to use computer models to evaluate the volume of femoral physeal disruption in double-bundle posterior cruciate ligament (PCL) reconstruction in patients with open physes. Ten skeletally immature patients (6 girls and 4 boys) were selected for this study. The magnetic resonance imaging scans of each patient were converted into a 3-dimensional model using computer-aided design/computer-aided manufacturing software. The software allowed the users to differentiate the epiphyseal, physeal, and metaphyseal tissues. This allowed for quantification of volume removed of each tissue type. Furthermore, we used the 3-dimensional models to simulate an anatomic double-bundle technique using 6-, 7-, 8-, and 9-mm-diameter tunnels. The software method reflects an inside-out drilling technique. For drill holes of all diameters, the posteromedial tunnels exited the knee inferior to the physis, thus avoiding physeal damage. In contrast, all the anterolateral tunnels perforated the physis. The results for the percent of total physis removed are as follows: 6-mm tunnel, 1.79% ± 0.99%; 7-mm tunnel, 2.23% ± 1.19%; 8-mm tunnel, 3.00% ± 1.54%; and 9-mm tunnel, 3.84% ± 1.73%. This computer modeling simulation of double-bundle PCL reconstruction in skeletally immature knees found that the posteromedial tunnel avoided disruption of the distal femoral physis. In contrast, the anterolateral tunnel did disrupt the physis with all drill hole sizes (6 to 9mm), but all had a less than 4% volume of total physis removed. A clear understanding of the drill hole position may reduce the volume of physeal injury during double-bundle PCL reconstruction. This study shows that physeal disruption of less than the experimental 7% threshold that has been shown to cause physeal arrest may not cause arrest, but this is still speculative.