Dynamic Testing Machine Research Articles

Poster 216: The Effects of Lateral Opening Wedge Distal Femoral Osteotomy on Meniscus Allograft Transplantation: A Biomechanical Evaluation

Objectives:Lateral meniscus deficiency with valgus malalignment increases the risk and rate of lateral compartment osteoarthritis. Lateral meniscus allograft transplantation (LMAT) with concomitant varus-producing lateral opening wedge distal femoral osteotomy (LOWDFO) is an available option to treat this pathology. No biomechanical data currently exists evaluating the effect on joint forces with these combined procedures. The purpose of this study is to evaluate the effects of LMAT with concomitant varus-producing LOWDFO on lateral and medial compartment biomechanics. We hypothesize that LMAT restores lateral compartment biomechanics back to native intact forces, varus-producing LOWDFO improves lateral compartment forces following LMAT, and medial compartment forces change to a lesser degree in response to mechanical varus.Methods:Ten human cadaveric knees underwent varus-producing LOWDFO and were placed in an external fixator. Anatomic alignment was standardized for each knee and utilized as a proxy for mechanical alignment. Thin film Tekscan pressure sensors were placed sub-meniscal and specimens were loaded on a biaxial dynamic testing machine to 800N within a custom designed apparatus, with loading angles between 9° valgus and 6° varus of mechanical alignment. Testing conditions included the intact meniscus, lateral meniscus deficiency, and LMAT. Statistical analysis was performed by creating two-factor random-intercepts linear mixed-effects models to compare peak pressure and contact area among the three experimental meniscus conditions.Results:Isolated varus-producing LOWDFO to 6° varus in the setting of meniscus deficiency was unable to restore joint forces to the level of the intact meniscus in neutral alignment (Mean Contact Pressure: 175%, Peak Pressure 135%, Contact Area -41%, P>0.05). LMAT restored mean contact and peak pressures, with no significant differences compared to the intact meniscus (P<0.05). LMAT resulted in significantly lower contact areas from 9° valgus to 0° (P>0.05), but this was restored to intact state at 3° and 6° varus (P<0.05). Within the lateral compartment following LMAT, every additional 1° of DFO correction contributes to a decreased in mean contact pressure of 5.6% (-0.0479 N/mm2)(Figure 1), a decrease in peak pressure of 5.9% (-0.154 N/mm2)(Figure 2), and a decrease in contact area of 1.4% (6.99 mm2)(Figure 3), as compared to forces in neutral alignment. Within the medial compartment following LMAT, every additional 1° of DFO correction contributes to an increase in mean contact pressure of 7.3% (+0.034 N/mm2), an increase in peak pressure of 12.6% (+0.160 N/mm2), and an increase in contact area of 4.3% (20.53 mm2), as compared to forces in neutral alignment. However, baseline forces in the medial compartment are significantly lower at baseline compared to lateral compartment forces (P>0.05).Conclusions:This is the first biomechanical study evaluating the effects of concomitant LMAT and varus-producing LOWDFO. Isolated varus-producing LOWDFO is inadequate to restore forces in the meniscus deficient knee. LMAT restores near normal forces, and concomitant LOWDFO improves the lateral compartment biomechanical profile. Although to a smaller magnitude, force changes in the medial compartment are significant with varus-producing LOWDFO. Unloading to 0° following LMAT may be ideal. Overall, this study provides tools to for the surgeon to individualize alignment correction for each patient to optimize outcomes.Figure 1.Mean Contact PressureFigure 2.Peak Contact PressureFigure 3.Contact Area

Influence of oligomer content on viscosity and dynamic mechanical properties of epoxy asphalt binders

The impact of oligomer content on the viscosity, dynamic mechanical properties and mechanical behaviors of hot-mix epoxy asphalt binders was investigated by Brookfield viscometer, dynamic mechanical analysis and universal testing machine. The viscosity of epoxy asphalt binders during curing decreased in the oligomer content. However, the allowable construction time increased with the oligomer content. The storage modulus of epoxy asphalt binders at the glassy stage decreased in the oligomer content, whereas an opposite trend appeared at the rubbery stage. Epoxy asphalt binders exhibited two glass transition temperatures (Tgs) for both epoxy resin and asphalt, and increased in the epoxy oligomer content. The Tg of epoxy of epoxy asphalt binder increased from 30.9 to 42.4 °C when the mass fraction of oligomer increased from 23.5 % to 25.5 %. The damping properties and tensile strength of epoxy asphalt binders increased in the oligomer content, while the elongation at break and toughness showed a contrary trend. The tensile strength of epoxy asphalt binder with 23.5 % oligomer was only 0.89 MPa, which was much lower than the specification required.

Original vs compatible stock abutment- implant connection: An in vitro analysis of the internal accuracy and mechanical fatigue behaviour.

To assess the internal accuracy and mechanical behaviour under cyclic loading after artificial aging of implant-supported crowns restored with original stock abutments and two compatible non-original stock abutments. Forty-eight original internal hexagon connection implants were connected to different stock abutments. The samples were divided into three groups depending on the manufacturer of the abutment components (one original, two non-originals).Firstly, samples were cross-sectioned and observed by using Scanning Electron Microscope (SEM) to evaluate the internal accuracy in three different implant-abutment interface locations (platform, internal and screw).Further, cyclic fatigue loading was carried out according to the ISO Norm 14801 using dynamic testing machine under sinusoidal loads for 2,000,000 cycles at test frequencies of 2 Hz in air after thermocycling with 10,000 cycles at 5 °C and 55 °C in artificial saliva for aging simulation. Original abutment components presented the highest percentage of surface with tight contact with the implant in the three implant-abutment interfaces studied. Additionally, original configuration showed highest fatigue limit value and fatigue strength exponent (280 N and -0.054) than non-original 1 (225 N and -0.109) and non-original 2 (200 N and -0.101). Original abutment components provide better fit and mechanical results under cyclic loading than non-original configurations. The results obtained in this study seem to suggest that the use of the original stock abutments to implants leads to a more homogeneous load distribution between the components that can influence the long-term success of the restorations.

Finite element analysis of MIG welded ERW steel pipe joint

To increase the life of a product/machine, it is vital for the companies to critically examine the product from various aspects. Strength of material and joints is an important aspect, considered by design engineers while working on existing or new design. Fatigue life is an important aspect while working on moving machinery. Bicycle is the machinery of daily use. Many efforts have been made by bicycle industries to check and increase the strength of various joint of bicycle. It has been revealed from literature that Finite Element Analysis (FEA) is less preferred by bicycle industries in India, for examine the fatigue life of various parts of bicycle. Various parts of bicycle are joined by means of welding, brazing and fastening, etc. It has also been revealed from literature that FEA is less used for evaluating the fatigue if of MIG welded pipe joints. An attempt has been made to examine the fatigue life of heat affected zone of MIG welded bicycle fork. FEA has been performed by using ANSYS software was used to performed dynamic fatigue testing machine at innovation Centre for Bicycle and Sewing Machines. Crack initiation of all three forks (F1, F2, F3), as analysed by ANSYS, occursat 25,835, 10,298 and 6182 cycles respectively. It has been revealed that FEA suits well for examining the fatigue life of bicycle fork.

Anterior-Inferior Tibiofibular Ligament Suture-Tape Augmentation for Isolated Syndesmotic Injuries

Category:Sports; AnkleIntroduction/Purpose:Aggressive surgical treatment of isolated syndesmotic injuries has recently gained some traction in the media and sports world. New developments in syndesmotic fixation aim to restore native syndesmotic stability and ankle motion with a goal of returning athletes to sport quickly. However, the best surgical technique is debated. Dynamic repair with a suture- button (SB) can provide an accurate reduction of the syndesmotic space but may alter the rotational kinematics of the fibula. Previous studies have suggested that repair or reconstruction of the anterior-inferior tibiofibular ligament (AITFL) may restore the dynamics of the syndesmosis better than other devices. The purpose of this study was to biomechanically compare SB fixation and augmented repair of the AITLF using suture and suture-tape (ST) in isolated syndesmotic injuries.Methods:Twelve unpaired lower leg specimens underwent biomechanical testing in 6 states: 1) intact, 2) AITFL suture repair alone, 3) AITFL suture repair + ST augmentation, 4) AITFL suture repair + ST augmentation + SB fixation, 5) AITFL suture repair + SB fixation, and 6) complete syndesmotic injury. The testing consisted of subjecting the ankle joint to 6 cycles of 5 Nm internal and external rotation torque under a constant 750 N axial compression load in a dynamic tensile testing machine. A lower level of torque was chosen than in previous studies in order to replicate physiologic motion of everyday activities instead of injury level forces. The spatial relationship between the tibia and fibula and tibia and talus was continuously recorded using a 5-camera motion capture system.Results:AITLF suture repair and suture repair + ST augmentation repair constructs showed no statistically significant change in fibula kinematics during testing compared to the intact state. The suture repair + SB construct showed increased external rotation of the fibula (p<0.001, mean 2.32 degrees) and medial translation (mean 0.72 mm, p= 0.007) or overtightening compared to the intact state. The suture repair + SB + ST augmentation state also showed increased external rotation of the fibula compared to the intact state (p<0.001). Sagittal plane motion of the fibula was not significantly different in the repair states compared to the intact state. None of the repair states restored talus rotation back to the intact state; however, the repairs that utilized suture tape reduced the talus external rotation laxity compared to the complete syndesmotic injury.Conclusion:For isolated syndesmotic injuries without significant fibular displacement, augmentation of the AITFL with suture- tape best restored the rotational profile of the fibula and ankle joint. Suture-button constructs had a tendency to over-tighten and externally rotate the fibula when compared to the intact state. Suture-tape AITFL augmentation may be a good surgical option and alternative to suture-button fixation for isolated syndesmotic disruptions. Further clinical trials are needed to determine the role for suture-tape augmentation of the AITLF in syndesmotic injuries.

Electrical properties of PZT under high-pressure stress pulse: Effects of loading frequency and circuit load

The research on the discharge characteristics of PZT under conventional applications has made good progress. In theory, the piezoelectric equation can be used to describe the relationship between stress and electrical output. However, existing studies have shown that the relationship becomes nonlinear under high-pressure stress pulses. To study the effect of the loading frequency and the circuit load on the electrical output performance of PZT under high-pressure stress pulse, the experiments were carried out based on the split Hopkinson pressure bar and a dynamic & static universal test machine. The effects of different circuits on the output voltage under different frequency high-pressure stress pulses are analyzed. Both theory and experiments prove that the critical open-circuit measurement resistance ( R critial ) of PZT decreases with the stress frequency. The output voltage is positively correlated with the load resistance when that is less than R critial . It is confirmed by loading different circuits (diodes are added in different positions) that reverse positive charge appears at the negative pole of the material during the stress unloading stage. PZT has the maximum dischargeable strain ε E M under the high-pressure stress pulses, and it no longer generates induced charges when the strain is greater than ε E M . When constant strain rate loading makes PZT completely release energy, its open-circuit output voltage is proportional to the strain rate.

Thermomechanical properties of epoxy resin/basalt fiber/hydrotalcite composites and influence of hydrotalcite particle size on their properties

AbstractNatural fibers (NFs) and inorganic particles have been successfully grown in the polymer to enhance its properties. The basalt fiber (BF) and modified hydrotalcite (LDHs) reinforced epoxy resin matrix composites were prepared, and the effects of fiber and modified hydrotalcite (G‐LDHs) on the microstructural characteristics of composites were investigated. Fourier transform infrared spectroscopy and X‐ray diffraction were respectively used to analyze the structure of modified BF and G‐LDHs, and thermogravimetric analysis was performed to study thermal stability. The mechanical properties of composites, including dynamic thermomechanical and tensile and flexural properties, were respectively studied by dynamic mechanical analysis (DMA) and universal testing machine. Experimental results show the successful synthesis of high‐performance epoxy copolymers. The impact strength, tensile strength, and elastic modulus of EP/BF/G‐LDHs respectively reached 7.07 kJ/m2, 20.52 MPa, and 2595 MPa when the content ratio of BF to hydrotalcite in the additive was 3:3. The DMA test showed that the glass transition temperature (Tg) value increased by 18.3°C, and the thermal stability of composite materials was improved. The storage modulus E′ value increased by 268.04 MPa, and the stiffness of the epoxy material and the mechanical properties were also elevated. The TGA and DTG curves indicate that the cured composites also exhibit excellent thermal stability. The effect of g‐LDHS particle size on the properties of composites was also discussed. Overall, the synergistic and complementary enhancement effect of the two materials is the best when the diameter of hydrotalcite is similar to that of BF, and the performance of the composite material is considerably improved.

Research Method of Fatigue Performance of Surgically Implanted Heart Valve Stent

The aim of this study was to evaluate the fatigue property in vitro of a domestic surgically implanted heart valve stent (SIHVS). The domestic SIHVS was used as a testing sample, and a protocol was developed according to the standards GB 12279-2008 and ISO 5840-2:2015. A dynamic fatigue testing machine was used to apply for a 0.365 mm cyclic radial displacement at the end of the SIHVS. The SIHVS were observed after 400 million cycles by a scanning electron microscope. The observed results show that the structure of SIHVS is intact. There are no fracture, no obvious wear, and no loosening of the wire and casing. In the tested stents, no structural distortion, no cracks and obvious pits were observed. This study demonstrated that SIHVS structure meets the expected fatigue performance requirements.

Full thickness quadriceps tendon grafts with bone had similar material properties to bone-patellar tendon-bone and a four-strand semitendinosus grafts: a biomechanical study.

Despite increasing interest in utilizing quadriceps tendon (QT) grafts in anterior cruciate ligament reconstruction (ACLR), data on the optimal quadriceps graft thickness are limited. The purpose of this study was to characterize the mechanical properties for the quadriceps tendon, comparing full-thickness (FT) QT grafts with and without bone to a partial-thickness (PT) QT graft, and comparing the three QT grafts to four-stranded semitendinosus (4-SST) and bone-patellar tendon-bone (BTB) grafts and one experimental graft, the two-stranded rectus femoris (RF). Forty-eight (n = 48) young cadaveric grafts (mean age 32 ± 6years) were utilized for testing with N = 8 specimens in each of the following groups; (1) FT QT with bone, (2) FT QT without bone, (3) PT QT without bone, (4) BTB, (5) RF, and (6) 4-SST. Each specimen was harvested and rigidly fixed in custom clamps to a dynamic tensile testing machine for biomechanical evaluation. Graft ultimate load and stiffness were recorded. Independent groups one-factor ANOVAs and Tukey's pairwise comparisons were performed for statistical analyses. FT QT with bone and 4-SST grafts demonstrated similar ultimate loads to BTB grafts (both n.s), whereas PT QT demonstrate statistically significantly lower ultimate loads to BTB grafts (n.s) and 4-SST grafts (n.s). Furthermore, no statistically significant differences were observed between the ultimate loads of FT QT vs. PT QT grafts without bone (n.s) or between FT QT with vs. without bone (n.s). FT QT grafts with bone did not demonstrate statistically significantly greater ultimate loads than PT QT grafts without bone (n.s). The RF graft demonstrated statistically significantly lower ultimate loads to BTB grafts (p < 0.005) and 4-SST grafts (p < 0.014). Full thickness QT grafts with bone had similar material properties to BTB and a 4-SST grafts, while Partial thickness QT graft without bone had significantly lower material properties than BTB and 4-SST, in a biomechanical setting.

Biomechanical Analysis of Segmental Medial Meniscal Transplantation in a Human Cadaveric Model

Background: Meniscal deficiency has been reported to increase contact pressures in the affected tibiofemoral joint, possibly leading to degenerative changes. Current surgical options include meniscal allograft transplantation and insertion of segmental meniscal scaffolds. Little is known about segmental meniscal allograft transplantation. Purpose: To evaluate the effectiveness of segmental medial meniscal allograft transplantation in the setting of partial medial meniscectomy in restoring native knee loading characteristics. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen human cadaveric knees underwent central midbody medial meniscectomy and subsequent segmental medial meniscal allograft transplantation. Knees were loaded in a dynamic tensile testing machine to 1000 N for 20 seconds at 0°, 30°, 60°, and 90° of flexion. Four conditions were tested: (1) intact medial meniscus, (2) deficient medial meniscus, (3) segmental medial meniscal transplant fixed with 7 meniscocapsular sutures, and (4) segmental medial meniscal transplant fixed with 7 meniscocapsular sutures and 1 suture fixed through 2 bone tunnels. Submeniscal medial and lateral pressure-mapping sensors assessed mean contact pressure, peak contact pressure, mean contact area, and pressure mapping. Two-factor random-intercepts linear mixed effects models compared pressure and contact area measurements among experimental conditions. Results: The meniscal-deficient state demonstrated a significantly higher mean contact pressure than all other testing conditions (mean difference, ≥0.35 MPa; P < .001 for all comparisons) and a significantly smaller total contact area as compared with all other testing conditions (mean difference, ≤140 mm2; P < .001 for all comparisons). There were no significant differences in mean contact pressure or total contact area among the intact, transplant, or transplant-with-tunnel groups or in any outcome measure across all comparisons in the lateral compartment. No significant differences existed in center of pressure and relative pressure distribution across testing conditions. Conclusion: Segmental medial meniscal allograft transplantation restored the medial compartment mean contact pressure and mean contact area to values measured in the intact medial compartment. Clinical Relevance: Segmental medial meniscal transplantation may provide an alternative to full meniscal transplantation by addressing only the deficient portion of the meniscus with transplanted tissue. Additional work is required to validate long-term fixation strength and biologic integration.

Pullout Strength of All-Suture and Metallic Anchors in Repair of Lateral Collateral Ligament Injuries of the Elbow

To compare the biomechanical properties of metallic anchor (MA) and all-suture anchor (ASA) constructs in the anatomic reattachment of the lateral ulnar collateral ligament complex to its humeral insertion. Twenty paired male human cadaveric elbows with a mean age of 46.3 years (range: 33-58 years) were used in this study. Each pair was randomly allocated across 2 groups of either MA or ASA. A single 3.5-mm MA or 2.6-mm ASA was then inserted flush into the lateral epicondyle. A dynamic tensile testing machine was used to perform cyclic loading followed by a load to failure test. During the cyclic loading phase, the anchors were sinusoidally tensioned from 10 N to 100 N for 1,000 cycles at a frequency of 0.5 Hz. In the load to failure test, the anchors were pulled at a rate of 3 mm/s. Load at 1-mm and 2-mm displacement, as well as load to ultimate failure were assessed. Clinical failure was defined as displacement of more than 2 mm. Normality of data was assessed with the Shapiro-Wilk test. Continuous data are presented as medians and compared with the Mann-Whitney U test and categorical data was compared with the χ2 test or Fisher exact test. Displacement was significantly greater for the ASA group during cyclic loading starting from the tenth cycle (P < .05). Displacement of more than 5 mm within the first 100 cycles was observed in 2 anchors in the ASA group. No difference was observed in loads required to displace 1 mm (MA: 146 N [6-169] vs ASA: 144 N [2-153]; P= .53) and 2 mm (MA: 171 N [13-202] vs ASA: 161 N [9-191]; P= .97), but there was a statistically significant difference between ultimate loads in favor of ASA in the load to failure test (MA: 297 N [84-343] vs 463 N [176-620]; P < .01). In the cyclic test, no difference in clinical failure defined as pull-out of more than 2 mm was observed between 3.5 mm MAs and 2.6 mm ASAs. In the ultimate load to failure analysis, no difference was observed between groups in force causing 1 and 2 mm of displacement, but there was a significant difference in favor of ASA in the pull to ultimate failure test. Potential benefits of all-suture anchors include preservation of bone stock, reduced radiographic artifacts, and easier revisions. Although their use has been investigated thoroughly in the shoulder, there remains a paucity of literature regarding displacement and pull-out strength in the elbow.

Suture Tape Augmentation Improves the Biomechanical Performance of Bone-Patellar Tendon-Bone Grafts Used for Anterior Cruciate Ligament Reconstruction

The purpose of this study was to investigate the time-zero biomechanical properties (stiffness, displacement, and load at failure) of bone-patellar tendon-bone (BTB) grafts used for anterior cruciate ligament (ACL) reconstruction with and without suture tape augmentation as a means to determine the potential clinical benefit of this technique. Eight juvenile porcine knees underwent ACL reconstruction with a human cadaveric BTB graft (control). These were compared to 8 juvenile porcine knees that underwent ACL reconstruction with a BTB graft augmented with suture tape. All knees underwent biomechanical testing utilizing a dynamic tensile testing machine. Cyclic loading between 50-250N was performed for 500 cycles at 1 Hz to simulate invivo ACL loads during the early rehabilitation phase. The grafts were displaced during load-at-failure tensile testing at 20 mm/min. Differences in graft displacement, stiffness, and load at failure for the control and suture tape augmented groups were compared with the Student t-test with a significance level of P < .05. There was no difference in graft displacement between the 2 groups. A 104% higher postcyclic stiffness was noted in the augmented group compared to the controls (augmentation: 261 ± 76 N/mm versus control 128 ± 28 N/mm, P= .002). The mean ultimate load at failure was 57% higher in the augmented group compared to controls (744 ± 219 N vs postcyclic 473 ± 169 N, respectively [P= .015]). There was no difference in mode of failure between the control knees and those augmented with suture tape, with approximately half failing from pull off of the tendon from the bone plug and half with pull out of the bone plug from the tunnel. Independent suture tape augmentation of a BTB ACL reconstruction grafts was associated with a 104% increase in graft stiffness and a 57% increase in load at failure compared to nonaugmented BTB grafts. Invivo suture tape augmentation of a BTB ACL reconstruction increases graft construct strength and stiffness, which may reduce graft failure in the clinical setting.

Microstructure and dynamic mechanical properties epoxy/asphaltene composites

Asphaltenes tend to aggregate to nanoparticles or clusters in crude oil and solvents over a wide concentration and temperature range. In the present paper, asphaltenes extracted from the base asphalt was used as a filler to introduce into epoxy resin. The microstructure and evolution of asphaltenes aggregation in the epoxy resin were observed using laser scanning confocal microscopy. Furthermore, the effect of asphaltenes on the viscosity, dynamic mechanical behavior, thermostability, mechanical properties of epoxy resin was evaluated by Brookfield rotational viscometer, dynamic mechanical analysis, thermogravimetric analysis and universal testing machine. The presence of asphaltenes increased the viscosity of the neat epoxy during all stages of cure reaction. The viscosity of epoxy/asphaltenes composites increased with the filler concentration. Fractal asphaltenes aggregation formed in the composites with 1 mass% asphaltenes. Network microstructures of asphaltenes aggregation appeared in the epoxy phase with a further increase of asphaltenes content. Moreover, the increase of asphaltenes loading resulted in denser network microstructures in the epoxy matrix. Aggregation evolution revealed that asphaltenes particles redispersed evenly in the epoxy resin in the form of some aggregates at the beginning of curing. During the cure reaction of epoxy, asphaltenes aggregates started to agglomerate and grow to network microstructures. The presence of asphaltenes led to the enhancement of the storage modulus of the neat epoxy at the rubbery stage. The glass transition temperature (Tg) of the epoxy composites slightly increased with the increase of asphaltenes loading. The epoxy composite with 5 mass% asphaltenes had higher Tg than the neat epoxy. The inclusion of asphaltenes had a negligible effect on the damping properties and thermal stability of the neat epoxy. The aggregation and heterogeneous dispersion of asphaltenes resulted in the decrease of the tensile strength and elongation at break of the neat epoxy. However, the inclusion of asphaltenes significantly enhanced Young’s modulus of the neat epoxy. Young’s modulus of the neat epoxy was increased by more than fourfold with the addition of 5 mass% asphaltenes.

Characterization of Material Parameter based on Reverse Engineering using with IMPETUS&lt;sup&gt;®&lt;/sup&gt; and VALIMAT&lt;sup&gt;®&lt;/sup&gt;

In this presentation, the method to characterize resin material properties using with dynamic pendulum testing machine, IMPETUS, and material characterization software, VALIMAT, is introduced. Recently the more resin material has been used for the parts of automotive, therefore the demands of accurate crash simulation for this material has been increased. In general, deformation behavior of resin material shows the dependence of hydrostatic pressure and strain rate, and failure behavior of the material shows the dependence of stress triaxiality. To simulate these plastic material behaviors, complex material model such as Semi-Analytical Model for Polymers (SAMP) and Generalized Incremental Stress State dependent damage Model (GISSMO) was proposed, and we need to identify parameters of these material model by conducting the tests in different cases of stress triaxiality and strain rate. Dynamic testing machine IMPETUS can be used for these material testing and the software VALIMAT can be used for identifying the material properties based on reverse engineering. This method is expected to contribute accurate and efficient material characterization for complex material model.

Development of gear dynamic performance testing machine

With the development of gears towards high temperature, high pressure, high speed and high stress, gear measurement, in which only the static geometric accuracy is considered, is unable to meet the current application requirements. While, the low precision and single function gear tester constrains the measurement of gear dynamic performance. For the resolution of this problem, based on the principle of gear system dynamics and several precision mechanical design techniques, a gear dynamic testing machine has been developed, providing new instruments for gear testing. On the basis of research of the principle of dynamic performance test, the primary measurement items of the testing machine have been determined. The measuring principles of each item and the driving and loading form of the testing machine have been examined. The measurement and control system of the testing machine and its corresponding software have been developed. The instrument can not only obtain the static precision index of the gear, but also obtain the dynamic performance index of the gear in variable working conditions. According to the actual test, the uncertainty of instrument is 3.8 μm and the external disturbance caused by the shaft vibration is less than 0.6 μm, which can meet the 5–6 grade precision gear testing requirement.

A mathematical modelling and experimental study of annular-radial type magnetorheological damper

An experimental study was undertaken to evaluate the mathematical modelling of the magnetorheological (MR) damper featuring annular radial gap on its valve. The experiment was conducted using a fatigue dynamic test machine under particular excitation frequency and amplitude to get force-velocity and force-displament characteristics. Meanwhile, the mathematical modelling was done using quasi-steady modelling approach. Simulation using adaptive neuro fuzzy inference (ANFIS) Algorithm (Gaussian and Generalized Bell) were also carried out to portray the damping force-displacement modelling that is used to compare with the experimental results. The experimental characteristics show that amplitudes excitation and current input affect the result damping force value. The comparison of the experimental and mathematical results presented in this paper shows a significant difference in damping force value and that the quasi-steady modelling could not significantly approach the damping force-velocity results. Moreover, the semi-active damper is compared to the passive damper. The results show that a semi-active damper performs better than a passive damper because it only requires a little power. Based on the damping force-displacement modelling, it can be seen that Gaussian has a higher accuracy rather than Generalized Bell. Discussion on the energy dissipation and equivalent damping coefficient were also accomodated in this paper. Having completed in mathematical modelling and simulation, the damper would be ready for further work in-vehicle application that is development of control system.

HYDROPHOBIZATION OF BASALT FIBER AND ITS INFLUENCE ON THE MECHANICAL CHARACTERISTICS OF SAND CONCRETE

Abstract. The materials of the proposed article are devoted to the study of mechanical properties of sand concrete with the addition of hydrophobized basalt fiber and polycarboxylate superplasticizer Relaxol-Super PC. Adding hydrophobic properties to the basalt fiber causes a decrease of water consumption of fine-grained concrete mixture, which leads to improved mechanical properties of concrete. The aim of the work was to increase the mechanical characteristics of sand concrete by introducing hydrophobized basalt fiber into its composition. The objective of the research is to study the effect of hydrophobized basalt fiber on the mechanical characteristics of sand concrete. The polycarboxylate superplasticizer Relaxol-Super PC (Budindustriya, Zaporozhye) was used to increase the mobility of the concrete mixture. Basalt fiber Bauson-basalt 12 mm long and 18 ± 2μm in diameter was used as a fibrous filler. Sand concrete mixture was prepared in a laboratory forced-action mixer. Dosing of Portland cement, quartz sand and basalt fiber was carried out by weight, water and water-reducing additive ‒ by volume, taking into account the density of the additive. The fiber was introduced into a dry cement-sand mixture. After mixing for 120 ... 150 seconds, water with a dosed amount of additive was introduced into the mixture. The hardening of samples concrete took place under normal conditions in a chamber with a temperature of 20 ± 20C and a relative humidity of at least 95%. The compressive strength of concrete was determined by testing the halves of the samples – beams 4×4×16 cm in size at 28 days of age. The abrasion of the investigated concrete was determined by testing cube specimens with an edge of 7.07 cm on an LKI-3 device in accordance with the procedure set forth in DSTU B.V.2.7-212: 2009 “Building materials. Concrete. Methods for determining abrasion “. The impact resistance of concrete was determined from the results of testing cubic specimens with an edge of 7.07 cm on a vertical dynamic laboratory test machine. Especially effective is manifested positive role hydrophobization basalt fiber in combination with the water-reducing additive Relaxol-Super PC. The introduction of hydrophobic fiber (2 kg/m3) and Relaxol – Super PC (1.2% by weight of cement) into the sand concrete mix provides an increase in the strength of sand concrete by 45 ... 48%, impact resistance by 45 ... 50%. The abrasion of concrete is reduced by 36 ... 48% compared to the control.

The effect of glenosphere lateralization and inferiorization on deltoid force in reverse total shoulder arthroplasty.

A medialized center of rotation (COR) in reverse total shoulder arthroplasty (RTSA) comes with limitations such as scapular notching and reduced range of motion. To mitigate these effects, lateralization and inferiorization of the COR are performed, but may adversely affect deltoid muscle force. The study purposes were to measure the effect of RTSA with varying glenosphere configurations on (1) the COR and (2) deltoid force compared with intact shoulders and shoulders with massive posterosuperior rotator cuff tears (PS-RCT). We hypothesized that the highest deltoid forces would occur in shoulders with PS-RCT, and that RTSA would lead to a decrease in required forces that is further minimized with lateralization and inferiorization of the COR but still higher compared with native shoulders with an intact rotator cuff. In this study, 8 cadaveric shoulders were dissected leaving only the rotator cuff muscles and capsule intact. A custom apparatus incorporating motion capture and a dynamic tensile testing machine to measure the changes in COR and deltoid forces while simultaneously recording glenohumeral abduction was designed. Five consecutive testing states were tested: (1) intact shoulder, (2) PS-RCT, (3) RTSA with standard glenosphere, (4) RTSA with 4 mm lateralized glenosphere, and (5) RTSA with 2.5 mm inferiorized glenosphere. Statistical Parametric Mapping was used to analyze the deltoid force as a function of the abduction angle. One-way repeated-measures within-specimens analysis of variance was conducted, followed by post hoc t-tests for pairwise comparisons between the states. All RTSA configurations shifted the COR medially and inferiorly with respect to native (standard: 4.2 ± 2.1 mm, 19.7 ± 3.6 mm; 4 mm lateralized: 3.9 ± 1.2 mm, 16.0 ± 1.8; 2.5 mm inferiorized: 6.9 ± 0.9 mm, 18.9 ± 1.7 mm). Analysis of variance showed a significant effect of specimen state on deltoid force across all abduction angles. Of the 10 paired t-test comparisons made between states, only 3 showed significant differences: (1) intact shoulders necessitated significantly lower deltoid force than specimens with PS-RCT below 42° abduction, (2) RTSAs with standard glenospheres required significantly lower deltoid force than RTSA with 4 mm lateralized glenospheres above 34° abduction, and (3) RTSAs with 2.5 mm inferiorized glenospheres had significantly lower deltoid force than RTSA with 4 mm of glenosphere lateralization at higher abduction angles. RTSA with a 2.5 mm inferiorized glenosphere and no additional lateralization resulted in less deltoid force to abduct the arm compared with 4 mm lateralized glenospheres. Therefore, when aiming to mitigate downsides of a medialized COR, an inferiorized glenosphere may be preferable in terms of its effect on deltoid force.

Devulcanization of natural rubber industry waste in supercritical carbon dioxide combined with diphenyl disulfide

The elimination of rubber wastes without affecting the environment is one of the most important challenges of the 21st century waste management. Accordingly, the present work is focused on the recycling of natural rubber (NR) industry waste by means of devulcanization in supercritical carbon dioxide (scCO2) atmosphere. With that aim, a novel device allowing to perform rubber devulcanization was developed. It consists of a triaxial compression reactor integrated into a dynamic hydraulic universal testing machine with a heating chamber. NR industry waste was devulcanized in the mentioned device at different temperatures, in scCO2 by using diphenyl disulfide (DD) as devulcanizing reagent. The devulcanization degree and quality of the treated materials were evaluated by the swelling test combined with the Horikx theory. It was appeared that a successful devulcanization, with almost no degradation, was obtained, and the devulcanization degree reached maximum value of ~90%. Thermogravimetric tests and scanning electron microscopy (SEM) images strengthened these results. Finally, it was concluded that the developed device is appropriate to perform rubber recycling, which contributes to the progress in the environmental protection.

The Hip Suction Seal, Part II: The Effect of Rim Trimming, Chondrolabral Junction Separation, and Labral Repair/Refixation on Hip Distractive Stability

Background: The acetabular labrum contains free nerve endings, and an unstable labrum can result in increased femoral head movement during hip motion. This can be caused by chondrolabral junction (CLJ) separation, especially in association with pincer-type femoroacetabular impingement, and may contribute to hip pain. Hypothesis: Rim resection alone has no effect on suction seal biomechanics. Further, separation of the CLJ changes hip suction seal biomechanics when compared with those of the native state, whereas repair and refixation with suture anchors restore these biomechanical parameters. Study Design: Controlled laboratory study. Methods: A total of 12 fresh-frozen human cadaveric hips were used in this study. Hips were mounted in a saline bath on a dynamic tensile testing machine and were distracted at a rate of 0.5 mm/s from neutral position. A total of 3 parameters (force, displacement, and intra-articular pressure) were measured throughout testing. Before testing, hips were randomly allocated to 1 of 2 groups: 1 that included the CLJ separation (CLJ Cut group) and 1 that did not (CLJ Intact group). Hips were tested in the following states: (1) native, (2) rim trimming, (3) separated CLJ (CLJ Cut group only), and (4) labral repair/refixation. For each group a linear mixed-effects model was used to compare biomechanical parameters between states. Results: Rim trimming did not affect any suction seal parameters relative to those of the native state. In the CLJ Cut group, no significant difference in distance to break the suction seal was observed for any states compared with that of the native state. In the CLJ Intact group, the distance to break the suction seal was significantly shorter in the labral refixation state (1.8 mm) than the native state (5.6 mm; P = .002). The maximum distraction force (62.1 ± 54.1 N) and the peak negative pressure (−36.6 ± 24.2 kPa) of the labral repair/refixation state were significantly lower than those of the native state in both groups (93.4 ± 41.7 N, P = .01; –60.7 ± 20.4 kPa, P = .02). Conclusion: Rim trimming did not change the biomechanical properties of the labral suction seal. Labral refixation resulted in a shorter distance to break the labral suction seal. This indicates that labral mobility is reduced by the labral refixation procedure, which could be beneficial in postoperative pain relief and labral healing. Clinical Relevance: The labral refixation reduced labral mobility, which could be beneficial for both pain relief and labral healing to the acetabulum after pincer-type femoroacetabular impingement resection.