Greater Stiffness Research Articles

A Near-Infrared Mechanically Switchable Elastomeric Film as a Dynamic Cell Culture Substrate.

Commercial static cell culture substrates can usually not change their physical properties over time, resulting in a limited representation of the variation in biomechanical cues in vivo. To overcome this limitation, approaches incorporating gold nanoparticles to act as transducers to external stimuli have been employed. In this work, gold nanorods were embedded in an elastomeric matrix and used as photothermal transducers to fabricate biocompatible light-responsive substrates. The nanocomposite films analysed by lock-in thermography and nanoindentation show a homogeneous heat distribution and a greater stiffness when irradiated with NIR light. After irradiation, the initial stiffness values were recovered. In vitro experiments performed during NIR irradiation with NIH-3T3 fibroblasts demonstrated that these films were biocompatible and cells remained viable. Cells cultured on the light stiffened nanocomposite exhibited a greater proliferation rate and stronger focal adhesion clustering, indicating increased cell-surface binding strength.

Anatomic and Biomechanical Study of Thumb Carpometacarpal Dislocations: A Laboratory Study.

No previous study recreating an isolated thumb carpometacarpal (CMC) dislocation with or without suture augmentation has been performed in the laboratory. This investigation aimed to evaluate the mechanism and ligamentous complex of isolated thumb CMC dislocations. Biomechanical analysis was performed in 10 cadaveric specimens. A posteriorly directed force or axial loading with hyperflexion through the CMC joint was applied. Load was applied at a rate of 1 mm/s until posterior CMC dislocation was achieved. Maximum load, displacement under nominal loading, stiffness, and mode of failure were recorded. The native ligament was repaired, augmented with high-tensile suture, and testing was repeated. Posteriorly directed force produced posterior CMC dislocations, while axial loading and hyperflexion through the CMC joint caused fractures. Load-to-failure of the native CMC joint was 217.76 N (SD = 66.03). Stiffness of the ligamentous complex on average was 18.86 N/mm (SD = 8.83). Mean load-to-failure after repair with suture augmentation was 94.62 N (SD = 39.77), with average stiffness of 8.21 N/mm (SD = 3.06). The native ligament was noted to have greater stiffness (P = .002) and greater load-to-failure (P = .0001) than repair with suture augmentation. Maximum displacement-to-failure of the native ligament was 14.5 mm compared with repair with suture augmentation 11.9 mm (P = .068). Isolated CMC dislocation was achieved with a posteriorly directed force rather than hyperflexion of the joint. Ultimate failure load of the repaired ligaments with suture augmentation was about half of that of the native ligaments. Further research into this technique is warranted.

Two Versus Four Ilizarov Rings in All Schanz Screw Fixation for Fractures of the Tibia: Experimental Mechanical Testing.

The mechanical performance of the Ilizarov system is closely related to the biologic status of the fracture or osteotomy line. The aim of this study was to compare the mechanical performance of 2 different Ilizarov frame configurations. Two different frame models were applied to cow tibiae, 1 with 2 rings only, 1 proximal and another distal, vs the conventional 4 rings, 2 proximal and 2 distal. The 2 models were applied to both tibiae of the same animal to overcome variations between the animal's bones. The midpoint of the tibial bones was osteotomized, and the osteotomy was distracted for 2 cm. Six identical samples for each model were created, and each identical sample of each model was tested under axial compression. Mechanical testing was performed with a load cell of 20,000 N and a speed of 2 mm/min. Measurements were evaluated using load cell and goniometric grading; load deformation was calculated using load-deformation graphs. Our comparison showed that the 4-ring frame had 37.5% greater stiffness than the 2-ring frame under direct loading under larger loads (P<.01). A comparison between the 4- and 2-ring configurations demonstrated that the 4-ring frame had 7% greater stiffness than the 2-ring frame under direct loading under smaller loads (P>.05). An excellent outcome can be achieved by using a conventional 4-ring frame, but the use of the 2-ring frame remains an available option for fixation of fractures in low-weight patients. [Orthopedics. 2023;46(3):152-157.].

Decellularized extracellular matrix as scaffold for cancer organoid cultures of colorectal peritoneal metastases.

Peritoneal metastases (PM) from colorectal cancer (CRC) are associated with poor survival. The extracellular matrix (ECM) plays a fundamental role in modulating the homing of CRC metastases to the peritoneum. The mechanisms underlying the interactions between metastatic cells and the ECM, however, remain poorly understood, and the number of in vitro models available for the study of the peritoneal metastatic process is limited. Here, we show that decellularized ECM of the peritoneal cavity allows the growth of organoids obtained from PM, favoring the development of three-dimensional (3D) nodules that maintain the characteristics of in vivo PM. Organoids preferentially grow on scaffolds obtained from neoplastic peritoneum, which are characterized by greater stiffness than normal scaffolds. A gene expression analysis of organoids grown on different substrates reflected faithfully the clinical and biological characteristics of the organoids. An impact of the ECM on the response to standard chemotherapy treatment for PM was also observed. The ex vivo 3D model, obtained by combining patient-derived decellularized ECM with organoids to mimic the metastatic niche, could be an innovative tool to develop new therapeutic strategies in a biologically relevant context to personalize treatments.

Novel multi-objective topology optimization method for stiffness and stress of continuum structures

In this paper, a topology optimization method combining Bi-directional Evolutionary Structural Optimization (BESO) and Fast Non-dominated Sorting Genetic Algorithm II (NSGA-II) is proposed, which is called BESO-NSGA-II. To effectively fuse the two algorithms, a semi-random double-penalized crossover and mutation operator is developed. The proposed algorithm extends the traditional single-objective optimization to a double objective optimization problem, and investigates the influence of the stress norm parameters on the optimization results. To verify the effectiveness of the new method, several examples of 2D structural stiffness and stress optimization are given. At the same time, the optimization design of each model was repeated six times to demonstrate the ability of the new method to converge to a solution. Compared with BESO, BESO-NSGA-II can effectively realize the double objective optimization of stiffness and stress, and eliminate the stress concentration phenomenon on the premise of ensuring that the structure has greater stiffness.

The effect of seatback deformation on out-of-position front-seat occupants in severe rear impacts

Objective This study assesses the effects of seat deflection in severe oblique rear impacts with laterally out-of-position ATDs where the head is not supported by the head restraint. Method Six high-speed rear sled tests were conducted at 48 km/h with a 195 degree PDOF. A lap-shoulder belted 50th percentile Hybrid III ATD was leaned inboard and seated in six different front passenger seats (A-F); five of the seats were selected from mid-sized sedans and one was a non-production rigidified Seat Integrated Restraint (SIR) seat. FRED-III pull tests resulted in seat stiffnesses that varied from 73 to 172 N/mm. Seat F had the greatest stiffness. The seat and ATD responses were assessed. The biomechanical responses were evaluated and compared to relevant IARVs. Results In all tests the ATD moved rearward and twisted the seat. There was limited differential motion of the torso relative to the seatback. The ATD position and PDOF prevented head restraint engagement allowing head and neck extension over the seatback. The seatback angle was measured on the inboard side. At maximum yield, it was greatest with Seat E, followed by Seat A and Seat D, at 71, 67 and 62 degrees, respectively. The duration of rearward deformation was also greatest with Seat A, Seat D and Seat E providing longer ride-down. The head, chest and upper neck responses were below IARVs. Lower-neck extension moments were above injury threshold with Seat B, C and F. Seat F had the highest lower-neck moment. Conclusion Seats with greater deformation provided the greatest ride-down durations and the lowest overall biomechanical responses. The combination of high impact severity and lack of head support resulted in high lower-neck responses, highlighting the potential benefit of energy management from deforming seat structures.

Rheological fingerprinting and tribological assessment of high internal phase emulsions stabilized by whey protein isolate: Effects of protein concentration and pH

The effects of protein concentration and pH on the rheological and lubrication behavior of high internal phase emulsions (HIPEs), stabilized by whey protein isolate (WPI), were investigated by combining large amplitude oscillatory shear (LAOS) and tribology characterizations. All HIPEs showed predominantly solid-like behavior with greater stiffness at higher protein concentration. Emulsions at lower protein concentrations experienced extensive intracycle shear thinning with increased energy dissipation, indicating less resistance to large deformations and ready alignment in the shear flow. Increasing pH from 3 to 7 resulted in greater fragility with easier yielding to nonlinear behavior and faster transition to Newtonian fluid dissipation. This is likely due to the greater interfacial elasticity of oil droplets at neutral pH. In addition, tribological testing showed that increasing protein concentration resulted in a transition to the hydrodynamic regime. Emulsions at pH 3 had better mixed lubrication than those at pH 7, which can be attributed to easier entrainment of more deformable oil droplets. The findings of this study provide insights into the design potential of HIPEs with tunable textural properties and better prediction of structural transformations during food processing.

Numerical investigation of mechanical properties of foams modeled by regular Gibson–Ashby lattices with different internal structures

Using the methods of effective moduli and finite elements, the elastic properties of foam materials are investigated based on models of regular lattices composed of Gibson–Ashby cells. The dependencies of the effective moduli and the anisotropy coefficient on porosity are analyzed for different lattice sizes and for different thicknesses of the edges of the Gibson–Ashby cells. It is noted that with the same porosity lattices with thicker edges have greater stiffness than lattices with thin edges. In addition, the level of anisotropy increases with increasing porosity, and to a greater extent for lattices with thick edges.

A Biomechanical Comparison of Fixation Techniques in Metacarpal Shaft Fractures.

Background Typically, metacarpal shaft fractures are treated with closed reduction percutaneous pinning, intramedullary nails, or plate fixation. Recently some surgeons have begun using intramedullary headless compression screws. Questions/Purposes The purpose of this study was to compare intramedullary screw fixation to K-wire fixation, which is the standard of care in a transverse metacarpal midshaft fracture, using a cadaveric model. Our hypothesis was that intramedullary screw fixation would have a biomechanical advantage (higher stiffness and peak load to failure) when compared with dual Kirschner wire fixation of transverse metacarpal shaft fractures. Methods Four-point bend testing was performed to compare stiffness and failure load values of seven paired 2nd and 3rd metacarpals instrumented with headless intramedullary compression screw fixation or Kirschner wire fixation. Similar testing was performed on 14 unpaired 4th metacarpals. Results There was no significant difference in peak load ( p = 0.60) or stiffness ( p = 0.85) between fixation groups for the 2nd and 3rd instrumented metacarpals. For the instrumented 4th metacarpals, there was no significant difference in peak load ( p = 0.14), but the stiffness was significantly greater ( p = 0.01) for the compression screw group compared with the Kirschner wire fixation. Conclusions/Clinical Relevance In this study, the load to failure was not different between the two fixation methods and likely both techniques can sustain physiologic loads needed for rehabilitation. The greater stiffness in the 4th metacarpal compression screw group may be related to the smaller canal morphology than in the 2nd and 3rd metacarpals. Larger diameter screws may be needed to obtain a better fit particularly in the 2nd and 3rd metacarpals.

Mechanical Properties of the Developing Brain are Associated with Language Input and Vocabulary Outcome

ABSTRACT The quality of language that children hear in their environment is associated with the development of language-related brain regions, in turn promoting vocabulary knowledge. Although informative, it remains unknown how these environmental influences alter the structure of neural tissue and subsequent vocabulary outcomes. The current study uses magnetic resonance elastography (MRE) to examine how children’s language environments underlie brain tissue mechanical properties, characterized as brain tissue stiffness and damping ratio, and promote vocabulary knowledge. Twenty-five children, ages 5–7, had their audio and video recorded while engaging in a play session with their parents. Children also completed the Picture Vocabulary Task (from NIH Toolbox) and participated in an MRI, where MRE and anatomical images were acquired. Higher quality input was associated with greater stiffness in the bilateral inferior frontal gyrus and right superior temporal gyrus, whereas greater vocabulary knowledge was associated with lower damping ratio in the right inferior frontal gyrus. These findings suggest changes in neural tissue composition are sensitive to malleable aspects of the environment, whereas tissue organization is more strongly associated with vocabulary outcome. Notably, these associations were independent of maternal education, suggesting more proximal measures of a child’s environment may be the source of differences in neural tissue structure underlying variability in vocabulary outcomes.

Paper 02: ACL Reconstruction in Cutting and Pivoting Athletes: Soft Tissue Quadriceps Tendon Autograft vs. Bone-Patellar Tendon-Bone Autograft

Objectives:ACL reconstruction is one of the most common knee procedures performed annually in the United States. Athletes participating in cutting and pivoting sports are at high risk for ACL injury. In the general population, most graft choices including allograft, bone-patellar tendon-bone (BTB) autograft, hamstring autograft and quadriceps autograft have all been shown to excellent results following reconstruction. However, in the high-level cutting and pivoting athlete, the optimal graft for reconstruction remains controversial. Most consider BTB autograft to be the gold standard for such athletes. However, BTB autografts have drawbacks including anterior knee pain, difficulty kneeling and possible patellar fracture and patellar tendon rupture. Quadriceps autograft has increased in popularity since it offers a thicker graft with more favorable tensile properties compared to BTB and hamstring autografts. The quadriceps autograft has nearly twice the cross sectional area, higher load to failure and greater stiffness than the BTB autograft. Studies have shown equivalent outcomes when directly comparing BTB autograft vs. soft tissue quadriceps autograft in the general population. No studies have directly compared these two grafts in athletes participating in cutting and pivoting sports. We hypothesized that the quadriceps autograft would lead to similar patient outcomes, re-tear rates, return to sport and complications as BTB autografts in the cutting and pivoting athlete.Methods:A retrospective review of cutting and pivoting athletes with ACL tears treated with BTB autograft or soft tissue quadriceps autograft with at least 2 years of follow up was performed. Only athletes participating in cutting and pivoting sports were included in the study. Four sports were considered to be cutting and pivoting including soccer, football, lacrosse and basketball. The decision on which graft to use was based on the athlete’s choice after discussing the pros and cons of each graft. Exclusion criteria included those athletes with recurrent ACL tears, multiligamentous injuries, previous meniscal surgery and those requiring osteotomies. International Knee Documentation Committee Subjective Knee Evaluation (IKDC) and Lysholm knee scoring scale were used to evaluate patient reported outcomes. Through chart review, ability to return to sport, time to return to sport and complications were identified. The postoperative rehabilitation protocol for both grafts was identical.Results:There were 32 athletes in the soft tissue quadriceps autograft group and 36 in the BTB autograft group. The average age was 18.6 years for the quad group and 19.7 years for the BTB autograft group (p=0.63). Females made up 62.5% of the quadriceps group and 44.4% of the BTB group (p=0.14). The quad group was made up of 56.3% high school and 43.7% college athletes compared to 61.1% high school and 38.9% college athletes in the BTB autograft group (p=0.53). Soccer was the most common sport with 16 in the quad group and 14 in the BTB group. The rest of the quad group included 8 football players, 4 lacrosse and 4 basketball players. The remaining BTB group consisted of 12 football players, 8 lacrosse and 2 basketball players. Meniscal surgery was performed in combination with the ACL reconstruction in 17 (53.1%) of the quad group and 22 (61.1%) of the BTB autograft group (p=0.37). Average graft size was 9.5mm for the quad autograft group and 10 for the BTB autograft group. The 2-year IKDC score was 93.6 for the quad group and 95.1 for the BTB group (p=0.45). The 2 year Lysholm scores were 95.7 and 96.1 for the quad and BTB groups respectively. Return to play at the same or higher level was 90.6% in the quad group and 86.1% in the BTB autograft group (p=0.82). Time to return was also similar between the groups with 7.1 months for the quad group and 7.6 months for the BTB autograft group. There was 1 re-tear which required revision in the BTB group and no re-tears in the quad group (p=0.34). Arthrofibrosis requiring MUA and lysis of adhesions occurred in 2 quad autografts and 4 BTB autografts (p=0.49). One contralateral ACL rupture occurred in the quad autograft group and 4 in the BTB autograft group (p=0.21).Conclusions:The optimal ACL graft in high level athletes participating in cutting and pivoting sports remains in question. In our comparison of quadriceps autograft compared to BTB autograft in this athletic population, no difference in patient reported outcomes, return to sport or re-tear rates was identified. Based on these findings, quadriceps autograft is as effective as BTB autografts in cutting and pivoting athletes and should be part of the graft choice discussion with the athlete.

A Strong Correlation Between the Severity of Flatfoot and Symptoms of Knee Osteoarthritis in 95 Patients.

ObjectiveThe purpose of this study is to assess the association between the presence and severity of flatfoot and symptoms of knee OA.Methods95 participants with knee OA were recruited from a patient cohort at a regional hospital. Symptoms of knee OA, including knee degeneration, femorotibial alignment, pain, stiffness and dysfunction were assessed using the Kellgren-Lawrence (K-L) grading system, femoral-tibial angle (FTA), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Participants were divided into groups with flatfoot (mild, moderate and severe) and without flatfoot based on the Clarke's angle. Linear regression and ordinal logistic regression were used for statistical analysis, as appropriate.ResultsHaving flatfoot was associated with a significantly increased risk of having a higher K-L grade (OR: 20.03; 95% CI, 5.88, 68.27; p < 0.001), smaller FTA (Beta: −2.96; 95% CI, −4.41, −1.50; p < 0.001), higher pain score (Beta: 0.47; 95% CI, 0.24, 0.69; p < 0.001) and greater loss of function (Beta: 0.25; 95% CI, 0.02, 0.48; p = 0.03). Severe grades of flat feet were associated with a higher K-L grade (OR: 0.19; 95% CI, 0.08, 0.44; p < 0.001), smaller FTA (Beta: 1.51; 95% CI, 0.66, 2.35; p = 0.001), higher pain score (Beta: −0.25; 95% CI, −0.39, −0.11; p = 0.001), greater stiffness (Beta: −0.24; 95% CI, −0.38, −0.09; p = 0.002) and greater loss of function (Beta: −0.27; 95% CI, −0.41, −0.14; p < 0.001).ConclusionThe results indicated that the severity of flattening is significantly associated with symptoms of knee OA. For the conservative management of knee OA, both flatfoot and its severity should be carefully considered.

Innovative seismic and energy retrofitting of wall envelopes using prefabricated textile-reinforced concrete panels with an embedded capillary tube system

This paper investigates the experimental seismic performance of an innovative seismic-plus-energy retrofit solution for RC and URM structures. The intervention aims to simultaneously improve thermal efficiency and seismic safety of buildings with a light, cost-effective, and sustainable approach. The proposed hybrid retrofit system consists of prefabricated textile capillary-tube panels, mechanically connected through mortar or adhesives to existing building envelopes. This study assesses for the first time the seismic behaviour of such a system through quasi-static in-plane cyclic tests on three 3/5-scaled masonry-infilled RC frames. First, the response of a frame retrofitted with textile capillary-tube elements is compared with its two counterparts: a non-retrofitted frame and a frame retrofitted with textile-reinforced mortar and extruded polystyrene boards. Next, the paper demonstrates the application of the panels on three squat URM piers and presents preliminary but promising results from in-plane cyclic shear-compression tests. Overall, the retrofitted specimens exhibited considerably greater stiffness, strength, and displacement capacity than bare configurations. Furthermore, the panels proved to be equally effective in improving overall seismic response and controlling damage with established retrofit techniques based on textile-reinforced mortars. Finally, the thermal performance of the proposed integrated retrofitting system was assessed through in-situ experimentation on a real residential masonry building wall, exhibiting high efficiency.

Sustainable Epoxidized Guayule Natural Rubber, Blends and Composites with Improved Oil Resistance and Greater Stiffness.

Production of petroleum-based synthetic rubbers (SRs) causes an enormous carbon footprint for the rubber industry. Carbon footprint would be reduced if natural rubber (NR) could take a larger market share and replace significant quantities of SR. However, some SRs have higher oil resistance than NRs, and, in applications where these properties are needed, chemically modified NR will be required. Epoxidation is a chemical modification of NR which partially converts unsaturated bonds on the backbone of NR to epoxy groups. In this research, epoxidized guayule natural rubber (EGNR)/guayule natural rubber (GNR) blends and GNR were used to make carbon black (CB) filled composites. The processability, mechanical properties, swelling behaviors and dynamic mechanical properties were characterized at various epoxide fractions. Composites made with EGNR/GNR had higher oil resistance, wet traction and stiffness than GNR composites, although tensile strength and elongation at break were reduced by epoxidation. EGNR is expected to lead to the development of new NR products with similar properties to SR, eroding SR markets and increasing the sustainability of the rubber industry.

Long Term Pulmonary Effects of E‐cigarettes on in‐utero Exposed Mice

IntroductionThe in‐utero environment is delicate, as it fosters the proper health and growth of the fetus. Negative environmental effects during gestation increase the chances of long‐term developmental consequences. As e‐cigarettes gain popularity in pregnant mothers, the aim of this study is to observe the chronic pulmonary function of adult mice exposed to e‐cigarette vapor during gestation.MethodsPregnant mice underwent exposure for 4 hours a day, 5 days a week beginning from the first day of pairing for breeding and ending at birth. Mice were separated into three exposure groups each receiving one 70 mL e‐cig vapor puff per minute of (1) E‐cig vapor with nicotine Nic(+) (2% Nic 50:50 propylene glycol:vegetable glycerin), (2) E‐cig exposure without nicotine Nic(‐) (propylene glycol: vegetable glycerin), or (3) continuous filtered air exposure (FA)HEPA filter. Resulting pups from each group were examined at adulthood (4‐5 months). Data including baseline lung mechanic scan and a dose response to different concentrations of methacholine, a drug used to induce airway hyperreactivity, were obtained via the FlexiVent FX2 (SCIREQ Inc.)ResultsMale and female offspring of mice exposed to Nic(‐) and Nic(+) witnessed a significant decrease in overall lung function as compared to the FA group. Baseline compliance (Crs) was significantly decreased in the Nic(‐) female group and Nic(‐) and Nic(+) male groups (P &lt; 0.05 via ANOVA). Female and male mice in the Nic(‐) had greater stiffness (Ers) than the corresponding FA group (P &lt; 0.05). Upon addition of methacholine, female mice in the Nic(‐) and male mice in the Nic(+) had an increased amount of lung resistance (Rrs)upon inhalation (P &lt; 0.05). Female mice in the Nic(‐) had decreased forced expiratory volume (FEV0.1) in comparison with the FA group (P &lt; 0.05).ConclusionPreliminary data supports that in‐utero exposed mice to e‐cigarette vapor with or without nicotine causes long term alterations in lung function. Future directions aim to understand the mechanisms of change through observing changes in histology, altered gene expression, protein analysis, and epigenetic changes through DNA methylation. Results of this work demonstrate that vaping may not be a safe alternative to smoking during pregnancy as the health of the offspring have detrimental pulmonary effects in adulthood.

Individual Roles of Network and Sheet Solids in Architectured Porous Materials

To understand the different roles played by sheet solids and network solids in complex porous biomaterials/native tissues, we designed a new kind of nature-inspired structure comprising these two solids by using triply periodic minimal surfaces and Voronoi diagrams using the CAD method and compared them with the previously reported Poisson-Voronoi (PV) solids that only comprise network solids. Here, we show that the sheet solids contribute greater stiffness and solid/void interface than the network solids, and our TPMS-Voronoi solids can improve/tune both the elastic moduli and specific surfaces even at fixed solid volume fraction and can be stiffer than the Poisson-Voronoi solids. This can directly guide the porous materials design for use in tissue engineering and aerospace.

Research on Angle Connector in Composite Beam

As a critical component for steel beam and concrete slab to work together, the strength of the shear connector affects the flexural load capacity and stiffness of the composite beam. Connectors were generally studied for longitudinal shear resistance. However, transverse shear needs to be considered when the main beam is far away and the transverse connection is weak. In this paper, an angle connector pre-embedded in the precast slab was proposed, and its pre-embedded position makes it exhibit better transverse shear resistance. To assess the strength, stiffness, and slip capacity of the angle connector, two groups of composite beam with precast slabs negative moment flexural were tested, then several finite element groups were simulated in push-out test. The test variable was the existence of angle connectors, and the variables simulated were the yield strength of the angle connector and its flange thickness. The results showed that the composite beam with angle connectors has greater stiffness than ordinary ones, with little difference in flexural strength capacity and less slippage. The results show that angle connectors can replace extending rebars in precast slabs, which will reduce construction costs. In addition, a new design equation was proposed, including the yield strength of the connector and the thickness of its flange which are not unified in the current equations. The simulations determined the strength of the angle connectors in relation to the yield strength of the angle connector and its web thickness.

Bridge Damage and Repair Detection Using an Instrumented Train

The static and dynamic effects of a railway bridge subjected to train loads have been investigated and analyzed to assess its condition. This paper investigates the potential of using repeated dynamic measurements taken on a passing train to determine the condition of a bridge. The results indicated that instrumented trains could be successfully used for ongoing monitoring of condition and, by implication, for identification of the need for repair or rehabilitation. This full-scale approach expands the potential for applications of bridge–vehicle dynamic interaction responses, along with their ability to be demonstrators of successful implementations of decisions on public infrastructure. The work also provided insights into the impact of a stiffer foundation at one pier and greater stiffness in two spans of a viaduct, for which experimental evidence is rarely available. The work also identified some of the challenges of such detection, such as accurate positioning and variability in the speeds of the passing trains.

Shaft Design for Electric Go-kart

This article presents the results of work related to the design, analysis, and manufacturing of the shaft for an electric go-kart. Works considered the stiffness of the shaft for various conditions affecting the vehicle while driving. In the previous stage of the project, the electric motor and gear transmission were selected. The main goal of this case study was to design the shaft for 10 kW electric go-kart. The rear driving axle of the go-kart is not equipped with a differential. The equal rotational speed of two rear wheels causes that occurs skidding and greater forces acting on the vehicle and driver when cornering. We were considering two types of the shaft – full and drilled. The first one provides greater stiffness, the second one is “softer”. The analysis allowed for the selection of a more appropriate shaft, and then for its manufacture and assembly in the vehicle.

Design, modeling, and testing of a soft actuator with variable stiffness using granular jamming

AbstractSoft robots combine the load-bearing capability of rigid material with the resilience, shape-shifting capabilities of soft materials. This paper presents a novel soft actuator with stiffness variation using particulate jamming technology. We design a hybrid composite structure consisting of driving layer and jamming layer. The driving layer with the arc air chamber aim to achieve large bending deformation. A membrane containing particles is integrated with driving layer to module its stiffness. The influence factors of stiffness variation were analyzed from energy of point of view. The dependence of granular attributes on the stiffness of the actuator was studied. Furthermore, we illustrated influence of stiffness changes on the kinematic and dynamic performance of the soft actuator. The experimental results showed these performance indexes are twofold. On the one hand, the structural parameters have significant effect on the bending angle, but on the other hand they have little effect on the end force. We found that flow resistance inside air chamber results in bending morphology variation. The dynamic response subjected to a square-wave air pressure was analyzed to exhibit the actuator’s transient and steady vibration behavior. The actuator with greater stiffness has faster responsiveness, but smaller range of motion. These conclusions are helpful to adjust the stiffness behavior and to improve motion performance.