Finite Element Analysis of a Go-Kart Chassis Prototype for the OK-J Category Under Static and Dynamic Loading Conditions

To investigate the stress distributions on implant-bone interface and fatigue behaviors of biomimetic titanium implant under static and dynamic loading conditions to provide theoretical basis for a new implant which may effectively transfer the stress to surrounding bones. A 3-D finite element model of a posterior mandible segment with an implant bone was constructed by a CAD (Pro/E Widefire 2.0) software. Two different implant models (a dense implant No.1 and a biomimetic implant No.2) were designed. The stress distributions on bone-implant interface under dynamic and static loading conditions were analyzed by Ansys Workbench 10.0 software, as well as the fatigue behavior of the biomimetic implant. The cervical cortical bones in the 2 implants were all high stress region under the same loading condition. The maximum von Mises stress on the interface and high-stress region in the cancellous bone region, and the maximum stress in the root region of the biomimetic implant were lower than those of the dense implant. The stress on the implant-bone interface decreased from the top to the bottom. The stress in the cervical cortical bone under the dynamic loading was 17.15% higher than that of the static loading. There was no significant difference in maximum stress at the cortical bone region between the dynamic and static loading conditions. The maximum stress of the dense implant in the cancellous bone region was 75.97% higher and that in the root region was 22.46% higher than that of the biomimetic implant. The maximum stress on the implant-bone interface was far less than the yield strength of pure titanium. The stress distribution in the cortical region of the biomimetic implant was 7.85% higher than that of the dense implant, and the maximum stress in the cortical bone was smaller than the yield stress of cortical bone. Within the dynamic loading of 50-300 N, the safety coefficient was all higher than 10, and with the increase of loading pressure, interface stress in the cancellous region increased linearly. Under the loading of 300 N in the axial and 25 N in the lingual 45:, the maximum stress was 11.38 MPa. Biomimetic style implant can effectively transfer the implant-bone interface stress to surrounding bones in the cancellous bone and root region, and the structure with the improved design is safe under normal loading pressure.

The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition. Based on the in-site geological conditions of Longgu coal mine, this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition. Results showed that under the static loading condition, the maximum vertical stress, deformation and failure range are large, where the stress concentration coefficient is 1.64. The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm, respectively. Then, under the dynamic and static combined loading condition: (1) The influence of dynamic load frequency on the two-sides is more obvious; (2) The dynamic load amplitude has the greatest influence on the stress concentration degree, and the plastic failure tends to develop to the deeper; (3) With the dynamic load source distance increase, the response of surrounding rock is gradually attenuated. On this basis, empirical equations for each dynamic load conditions were obtained by using regression analysis method, and all correlation coefficients are greater than 0.99. This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.

Sliding wear of cast zinc-based alloy bearings under static and dynamic loading conditions

The constitutive modelling of geosynthetic–geosynthetic interfaces is essential to predict the performance of the engineering structures such as landfills, flood control dykes and geotextile encapsulated-sand systems for the protection of shore. This article presents a mathematical model to simulate the shear stress/force–displacement behaviour of the interfaces involving smooth geomembrane and nonwoven geotextile under static and dynamic loading conditions. The model is the extension of an existing technique developed for predicting the soil-structure interface shear behaviour under static loading conditions. The proposed model can predict the non-linear pre-peak and the post-peak strain softening/hardening behaviour of the interfaces observed during the laboratory testing. The shear stress/force–displacement response of the interfaces has been modelled by dividing it into three parts: pre-peak, peak and post-peak behaviour. Subsequently, the modelling parameters are obtained using the results from the laboratory direct shear tests and fixed–block type shake table tests conducted on these interfaces. Finally, the shear stress/force–displacement response of the interfaces is evaluated and compared with the experimental results. The predicted shear stress/force–displacement response of the interfaces is found to be in good agreement with the experimental data for both static and dynamic loading conditions.

This study investigates the effects of atmospheric pressure plasma treatment on the mechanical properties and durability of wool pile carpets. Wool yarns were subjected to plasma treatment using mixtures of argon and oxygen gases. The plasma treatment yielded a 31% enhancement in yarn tensile strength, increasing from 8.50 to 11.13 cN/Tex, and a 20% increase in Young’s modulus, rising from 55.03 to 66.08 cN/Tex. Additionally, surface wettability exhibited significant improvement, as evidenced by a reduction in water absorption time and a decrease in contact angle. Despite these enhancements at the fiber and yarn level, plasma treatment demonstrated a minimal impact on the thermal insulation properties of the wool carpets under the conditions tested. Importantly, durability tests on the carpets revealed that plasma-treated samples exhibited greater thickness loss and reduced recovery under both dynamic and static loading conditions when compared to untreated samples. Carpets woven with plasma-treated wool piles demonstrated a thickness reduction of 19.93% after 100 impacts, in contrast to a reduction of 4.03% observed in untreated samples. Furthermore, after 1000 impacts, the plasma-treated carpets exhibited a 27.13% loss in thickness, compared to a 22.74% loss in untreated carpets. Under static loading conditions, plasma-treated carpets exhibited an immediate thickness reduction of 29.66%, in contrast to a reduction of 21.69% observed in untreated carpets. Furthermore, the 24-h recovery rate for plasma-treated carpets was only 42.58%, compared to 63.11% for untreated carpets. The tuft withdrawal force remained statistically unchanged. These findings underscore the dual effect of plasma treatment. While surface modifications enhance yarn strength and surface properties, they simultaneously weaken carpet resilience by damaging fiber cuticle cells due to etching. The process generates micro-abrasions and increases surface roughness, resulting in altered inter-fiber friction and elasticity. Consequently, carpets with plasma-treated wool yarns exhibit greater susceptibility to deformation and thickness loss under static or repeated loading. This situation underscores the necessity for careful optimization of plasma treatment parameters, particularly in the context of carpet applications, where there is currently limited research. Achieving a balance between surface enhancement and the preservation of structural integrity is essential to ensure overall carpet performance.

This study aimed 1) to determine whether talar cartilage deformation measured via ultrasonography (US) after standing and hopping loading protocols differs between chronic ankle instability (CAI) patients and healthy controls and 2) to determine whether the US measurement of cartilage deformation reflects viscoelasticity between standing and hopping protocols. A total of 30 CAI and 30 controls participated. After a 60-min off-loading period, US images of the talar cartilage were acquired before and after static (2-min single-leg standing) and dynamic (60 single-leg forward hops) loading conditions. We calculated cartilage deformation by assessing the change in average thickness (mm) for overall, medial, and lateral talar cartilage. The independent variables include time (Pre60 and postloading), condition (standing and dynamic loading), and group (CAI and control). A three-way mixed-model repeated-measures ANCOVA and appropriate post hoc tests were used to compare cartilage deformation between the groups after static and dynamic loading. After the static loading condition, those with CAI had greater talar cartilage deformation compared with healthy individuals for overall (-10.87% vs -6.84%, P = 0.032) and medial (-12.98% vs -5.80%, P = 0.006) talar cartilage. Similarly, the CAI group had greater deformation relative to the control group for overall (-8.59% vs -3.46%, P = 0.038) and medial (-8.51% vs -3.31%, P = 0.043) talar cartilage after the dynamic loading condition. In the combined cohort, cartilage deformation was greater after static loading compared with dynamic in overall (-8.85% vs -6.03%, P = 0.003), medial (-9.38% vs -5.91%, P = 0.043), and lateral (-7.90% vs -5.65%, P = 0.009) cartilage. US is capable of detecting differences in cartilage deformation between those with CAI and uninjured controls after standardized physiologic loads. Across both groups, our results demonstrate that static loading results in greater cartilage deformation compared with dynamic loading.

Crashworthiness of tapered thin-walled S-shaped structures

In this study, the effect of high strain rate on the stress triaxiality is examined. The commercial 6061-T6 aluminum alloy which has wide applications as structural materials in the transport machine and construction industries is selected for this study. The response of the material to varying degrees of stress triaxiality under static and dynamic loading conditions is measured for circumferentially round-notched tensile specimens. Tensile tests are performed at RT with an Instron and servo hydraulic testing machines at three kinds of strain rates (e=7.2×10−4, 1.0×102 and 1.0×103 s−1). Fracture surface observations and finite element method simulations also reveal the effect of stress triaxiality on the mechanical response under dynamic loading condition. The plastic constraint factors of the round-notched specimen under dynamic loading condition are lower than those under static loading condition. Stress triaxiality is decreased by the reflection of the stress wave near the notch root of the round-notched specimen under dynamic loading condition. The decrease of the stress triaxiality under the dynamic loading condition affects the relaxation of the plastic constraint in the round-notched specimens. The fracture surface of the round-notched specimen with the high stress triaxiality level shows the tensile fracture type under static loading condition. When the stress triaxiality decreases with increasing strain rate in the round-notched specimens, the fracture surface changes to the shear type. On the other hand, the temperature rise during impact tests hardly affects the relaxation of the plastic constraint in the round-notched specimens under high strain rates.

Concrete-to-concrete bedding planes (CCBP) are observed from time to time due to the multistep hardening process of the concrete materials. In this paper, a series of direct/cyclic shear tests are performed on CCBP under static and dynamic normal load conditions to study the frictional behavior effect by the shear velocities, normal impact frequencies, horizontal shear frequencies, normal impact force amplitudes, horizontal shear displacement amplitudes and normal load levels. According to the experimental results, apparent friction coefficient k (k = FShear/FNormal) shows different patterns under static and dynamic load conditions at the stable shear stage. k is nearly constant in direct shear tests under constant normal load conditions (DCNL), while it is cyclically changing with nearly constant peak value and valley value for the direct shear tests under dynamic normal load conditions (DDNL), where k increases with decreasing normal force and decreases with increasing normal force. Shear velocity has little influence on peak values of k for the DCNL tests, but increasing shear velocity leads to increasing valley values of k for DDNL tests. It is also found that, the valley values of k ascend with decreasing impact normal force amplitude in DDNL tests. The changing pattern of k for the cyclic shear tests under constant and dynamic normal load conditions (CCNL and CDNL tests) are similar, but the peak value of k is smaller in CDNL tests than that in CCNL tests. Normal load levels, shear displacement amplitudes, vertical impact frequencies, horizontal shear frequencies and normal impact force amplitudes have little influence on the changing pattern of k for the cyclic shear tests. The tests of this study provide useful data in understanding the frictional behavior of the CCBP under distinct loadings, and these findings are very important for analyzing the stability of the jointed geotechnical structures under complicated in situ stress conditions.

The properties and failure mechanisms of anisotropic polymer composite materials in configuration of a single bundle of filaments microcomposite reinforced with carbon and aramid fibers under impact and static loading conditions are investigated by impact break method. Various failure mechanisms of the CM affected on their properties under static and impact loading conditions. The destruction processes in dynamically loaded CM are multistage. Failure mechanism is based on the multifilament fiber stretching and stress‐wave propagation through the CM. The processes of multibreaking and crushing of the filaments are imposed on the process of multistage stretching deformation. It led to a sharp decrease of the CM properties on impact as compared with that CM tested under static loading conditions. It has been found out that specific absorbed‐in‐break energy of CFRP and OFRP under impact loading conditions is significantly reduced by a factor of 3.1 and 4.1, respectively, as compared with that under static ones. POLYM. ENG. SCI., 57:693–696, 2017. © 2017 Society of Plastics Engineers

Brittle failure of high toughness steel structures tends to occur after ductile crack initiation/propagation. Damages to steel structures were reported in the Hanshin Great Earthquake. Several brittle failures were observed in beam-to-column connection zones with geometrical discontinuity. It is widely known that triaxial stresses accelerate the ductile fracture of steels. The study examined the effects of geometrical heterogeneity and strength mismatches (both of which elevate plastic constraints due to heterogeneous plastic straining) and loading rate on critical conditions initiating ductile fracture. This involved applying the two-parameter criterion (involving equivalent plastic strain and stress triaxiality) to estimate ductile cracking for strength mismatched specimens under static and dynamic tensile loading conditions. Ductile crack initiation testing was conducted under static and dynamic loading conditions using circumferentially notched specimens (Charpy type) with/without strength mismatches. The results indicated that the condition for ductile crack initiation using the two parameter criterion was a transferable criterion to evaluate ductile crack initiation independent of the existence of strength mismatches and loading rates.

Open-pit slopes contain numerous nonpenetrating, intermittent joints which maintain stability under blasting operations. The tip dynamic response coefficient (DRC) of parallel cracks in a typical rock mass under combined dynamic and static loading conditions was calculated in this study based on the superposition principle. The dynamic response law of the intermittent joint in the slope under blasting was determined accordingly. The influence of many factors (the disturbance amplitude of dynamic load, the lateral confining pressure, the length of rock bridge, the length between cracks, the staggered distance between cracks, and the crack inclination angle) on the dynamic response was theoretically analyzed as well. The ABAQUS numerical assessments were conducted on simulation models with parallel cracks under combined dynamic and static loading conditions. The results show that a larger dynamic load amplitude and smaller crack inclination angle/confining pressure result in greater Type II dynamic strengthening effect on the crack tip. When the length of the rock bridge between cracks (s) is smaller than the half length of the crack (a), the dynamic strengthening effect at the crack tip weakens gradually with increase ins; whens/a≥1, the strengthening effect is almost unchanged. With the increase in the staggered distance between cracks (h), the dynamic strengthening effect of the crack tip weakens at first and then strengthens; the strengthening effect is weakest whenh/a=0.4; the crack propagation under combined dynamic and static loading is the most sensitive to the lateral confining pressure (σ3) and is the least sensitive to the inclination angle of the cracks (α). Theoretical results are validated by comparison with numerical simulation results. Such information regarding the dynamic response law of the parallel cracks in rock masses under dynamic and static loading conditions is conducive to further research on the mesofailure mechanism of open-pit mine jointed rock slopes under blasting operations.

An experimental study on shear behaviour of fully grouted rock bolt under static and dynamic loading conditions

Presence of gap at the implant-abutment interface, leads to microleakage and accumulation of bacteria which can affect the success of dental implants. To evaluate the sealing capability of different implant connections against microleakage. In January 2017 an electronic search of literature was performed, in Medline, EBSCO host and Pubmed data base. The search was focused on ability of different implant connections in preventing microleakage. The related titles and abstracts available in English were screened, and the articles that fulfilled the inclusion criteria were selected for full text reading. In this systematic review, literature search initially resulted in 78 articles among which 30 articles only fulfilled the criteria for inclusion and were finally included in the review. Almost all the studies showed that there was some amount of microleakage at abutment implant interface. Microleakage was very less in Morse taper implants in comparison to other implant connections. Majority of studies showed less microleakage in static loading conditions and microleakage increases in dynamic loading conditions. In this systematic review maximum studies showed that there was some amount of microleakage at abutment implant interface. External hexagon implants failed completely to prevent microleakage in both static and dynamic loading conditions of implants. Internal hexagon implants mainly internal conical (Morse taper) implants are very promising in case of static loading and also showed less microleakage in dynamic loading conditions. Torque recommended by manufacturer should be followed strictly to get a better seal at abutment implant interface. Zirconia abutments are more to microleakage than Titanium abutments and there use should be discouraged. Zirconia abutments should be only restricted to cases where there was very high demand of aesthetics.

In a car crash, the higher level of energy absorption in the frontal structures leads to less transferred energy to the passengers and hence a safer car. S-shaped front rails, also known as S-rails, are one of the main structural elements and energy absorbers in a car body. Energy absorption in the S-rails happens through local buckling. In order to improve the passenger safety in a frontal crash, S-rails design should be optimized to absorb higher level of energy while crushing. In this study, we investigate the crashworthiness impact of tapering S-rails. Two S-rails, one without internal diagonal reinforcement (type-A) and one with this reinforcement (type-B), both are tapered with 20 different tapering ratios ranging from 110 % to 300 % in 10 % increments. All S-rail models are subjected to static and also dynamic loading conditions. The effectiveness of tapering S-rails is assessed through investigating the energy absorption (EA) and specific energy absorption (SEA) variations using finite element method. An equation is developed to verify the numerical results. In this study, we showed the reinforcing and tapering S-rails both could improve the EA and SEA in both static and dynamic loading conditions. Combining reinforcing and tapering the S-rails showed a noticeable improvement in SEA of more than 300 % in static loading condition as well as 275 % SEA increase in dynamic loading condition.