Offset Strength Research Articles

Impact of standard and unexpected bolt-hole-washer tolerances on the performance of pinned and torqued joints in CFRP composites

This study aimed to investigate the impact of some practical assembly errors on the performance of composite joints with M6 bolts in quasi-isotropic CFRP laminates with stacking sequence of [±45/0/90]2S, which are increasingly used in aerospace and automotive industries. The detailed experimental explanations of the behaviors of the bolted joints in CFRP composites with standard and unexpected joining parameters, exhibited a vital impact on the bearing and ultimate joint strength, stiffness, energy absorption, and failure mechanisms. The joining parameters include tightening torque (0-16Nm), bolt-hole clearance (0–240 μm), and washer-to-bolt hole clearance (0–500 μm) with different offset arrangements. The bolt axial force is monitored during the testing of double-lap bolted composite joints. The maximum performance of the bolted joints was observed at tightening torque of 12Nm, bolt-hole clearance up to 60 μm, washer-to-bolt hole neat-fit or with negative clearance arrangement. The first peak, 2 % offset, and ultimate strengths are increased, respectively, by 55.9 %, 56.4 % and 52.4 % compared to those of the pinned joints. The 2 % offset strength and stiffness of bolted joints with negative washer-to-bolt hole clearance arrangements is improved by 26.8 % and 57 % respectively compared to those having positive arrangements. Energy absorption increase almost linearly with bearing load with correlation coefficient of 0.982.

Simultaneously improving tensile properties and stress corrosion cracking resistance of 7075-T6 aluminum alloy by USRP treatment

The effect of gradient nanostructure prepared by ultrasonic surface rolling on stress corrosion behavior of 7075-T6 aluminum alloy was studied. Results showed that gradient structure improved stress corrosion cracking (SCC) resistance-strength-ductility synergy. Grain refinement and dislocation proliferation offset strength reduction caused by the dissolution of precipitated phase. The superior SCC resistance was attributed to the reduction of surface roughness and the introduction of compressive residual stress. In addition, grain refinement, re-precipitation of coarse η phase at trigonal grain boundaries and the transformation of intracrystalline precipitated phase from GP zone to η' phase further enhanced SCC resistance.

Effets des solutions de lavage sur la polymérisation du ciment

IntroductionLittle is known about the impact irrigation solutions have on the material properties of cement used in hip and knee arthroplasty. We sought to compare the effect of three commonly used lavage solutions on cement polymerization. MethodsTen groups were used for cure and mechanical testing: two cement controls, and eight cement groups mixed with test solutions. Test solutions included a commercially available benzalkonium chloride/citric acid solution (BCS), chlorhexidine gluconate (0.05%) (CHG), povidone-iodine 0.35%, and normal saline added at cement mixing onset. Cement dough-time, set-time, and compression testing were performed following The American Society for Testing and Materials guidelines. ResultsPovidone-iodine had shorter dough-time (1min 34sec, sd 1min 5sec) versus controls (1min 56sec, sd 1min 35sec), p=0.0419. Cement exposed to all lavage samples had significantly reduced set-time. Compressive strength was reduced for all surgical lavages (p<0.001). Pairwise testing revealed that all lavage treatments reduced offset strength versus controls (p<0.001). ConclusionBone cement exposed to lavage solutions during the cement mixing-phase showed accelerated set-times and decreased compressive strength. If bone is not dry, and cement has not finished mixing at the time of application, cement curing time may be shortened. Additionally, bone cement should reach dough phase prior to pre-closure surgical lavage. Level of evidenceIII; case control study.

Modeling the Noticeability of User-Avatar Movement Inconsistency for Sense of Body Ownership Intervention

An avatar mirroring the user's movement is commonly adopted in Virtual Reality(VR). Maintaining the user-avatar movement consistency provides the user a sense of body ownership and thus an immersive experience. However, breaking this consistency can enable new interaction functionalities, such as pseudo haptic feedback [45] or input augmentation [37, 59], at the expense of immersion. We propose to quantify the probability of users noticing the movement inconsistency while the inconsistency amplitude is being enlarged, which aims to guide the intervention of the users' sense of body ownership in VR. We applied angular offsets to the avatar's shoulder and elbow joints and recorded whether the user identified the inconsistency through a series of three user studies and built a statistical model based on the results. Results show that the noticeability of movement inconsistency increases roughly quadratically with the enlargement of offsets and the offsets at two joints negatively affect the probability distributions of each other. Leveraging the model, we implemented a technique that amplifies the user's arm movements with unnoticeable offsets and then evaluated implementations with different parameters(offset strength, offset distribution). Results show that the technique with medium-level and balanced-distributed offsets achieves the best overall performance. Finally, we demonstrated our model's extendability in interventions in the sense of body ownership with three VR applications including stroke rehabilitation, action game and widget arrangement.

Tests and Numerical Study of Single-Lap Thermoplastic Composite Joints Bolted by Countersunk.

Tensile tests were carried out to investigate the effect of stacking sequences on the bearing strength of single-lap thermoplastic composite countersunk bolted joints. A 3D elastoplastic model was built based on a plastic theory for numerical analysis. The damage initiation was judged based on LaRC05 criteria, and the damage propagation was described by using a nonlinear, gradual unloading method based on crack band theory. The accuracy of the present model was validated by comparing the numerical results to those from the tests. The test results showed that the effects of stacking sequences on the ultimate bearing strength and the 2% offset bearing strength are limited. Moreover, the numerical results depicted that the ultimate bearing strength and the 2% offset bearing strength reduce when the bolt-tightening torque or the bolt–hole clearance is increased.

Effect of commonly used lavage solutions on the polymerization of bone cement

IntroductionLittle is known about the impact irrigation solutions have on the material properties of cement used in hip and knee arthroplasty. We sought to compare the effect of three commonly used lavage solutions on cement polymerization. MethodsTen groups were used for cure and mechanical testing: two cement controls, and eight cement groups mixed with test solutions. Test solutions included a commercially available benzalkonium chloride/citric acid solution (BCS), chlorhexidine gluconate (0.05%) (CHG), povidone-iodine 0.35%, and normal saline added at cement mixing onset. Cement dough-time, set-time, and compression testing were performed following The American Society for Testing and Materials guidelines. ResultsPovidone-iodine had shorter dough-time (1min 34sec, sd 1min 5sec) versus controls (1min 56sec, sd 1min 35sec), p=0.0419. Cement exposed to all lavage samples had significantly reduced set-time. Compressive strength was reduced for all surgical lavages (p<0.001). Pairwise testing revealed that all lavage treatments reduced offset strength versus controls (p<0.001). ConclusionBone cement exposed to lavage solutions during the cement mixing-phase showed accelerated set-times and decreased compressive strength. If bone is not dry, and cement has not finished mixing at the time of application, cement curing time may be shortened. Additionally, bone cement should reach dough phase prior to pre-closure surgical lavage. Level of evidenceIII; case control study

Effect of Washer Size and Tightening Torque on Bearing Performance of Basalt Fiber Composite Bolted Joints

ABSTRACT The effect of tightening torque and washer size on the performance of basalt natural fiber composite joints was investigated experimentally. It was found that washer size is the main design driver in controlling the out-of-plane behavior of the joint. Specifically, there was a 36.5% increase in the 0.2% offset strength when the torque was increased for small washer configurations, whereas a 42% increase was observed when the torque was increased for large washer configurations. Moreover, the ultimate bearing strength also showed an improvement under the combined effect of washer size and tightening torque. Additionally, damage onset and failure mechanisms of the bolted joint were investigated using optical microscopy. The morphological observations indicated excessive crushing for large washer configurations. It is postulated that bearing performance could be improved by choosing appropriate washer size and tightening torque.

A contactless sensing system for indoor fall recognition based on channel state information

This paper introduces the designs and the implementation of a non-invasive indoor fall recognition system based on channel state information (CSI) in the Wi-Fi physical layer. We use a wireless router and a laptop computer equipped with an Intel Wi-Fi Link 5300 network card (802.11n) to setup a hardware platform. The platform receives and stores CSI data under various circumstances when a person in the Wi-Fi covered area stands up, sits down, walks, and falls. The CSI data are then processed and analysed using Matlab tools. Feature variables such as signal offset strength, period of motion, normalised standard deviation, median absolute deviation, interquartile range, and signal entropy are examined and best feature variables are chosen. Finally, cross validation algorithm and support vector machine (SVM) are used to establish the pattern recognition model. We tested the system in a laboratory environment and the experimental results showed that the fall incidents were effectively differentiated from other movements.

A contactless sensing system for indoor fall recognition based on channel state information

This paper introduces the designs and the implementation of a non-invasive indoor fall recognition system based on channel state information (CSI) in the Wi-Fi physical layer. We use a wireless router and a laptop computer equipped with an Intel Wi-Fi Link 5300 network card (802.11n) to setup a hardware platform. The platform receives and stores CSI data under various circumstances when a person in the Wi-Fi covered area stands up, sits down, walks, and falls. The CSI data are then processed and analysed using Matlab tools. Feature variables such as signal offset strength, period of motion, normalised standard deviation, median absolute deviation, interquartile range, and signal entropy are examined and best feature variables are chosen. Finally, cross validation algorithm and support vector machine (SVM) are used to establish the pattern recognition model. We tested the system in a laboratory environment and the experimental results showed that the fall incidents were effectively differentiated from other movements.

Impact cratering in and around the Orientale Basin: Results from recent high-resolution remote sensing datasets

Impact craters are the predominant geological features on the lunar surface. Data about the craters are crucial for inferring information about surface age, the generation processes of the geological units, and the sequences of geological events. The higher-resolution remote sensing datasets collected by recent lunar missions enable the investigation of impact craters of smaller size and provide more accurate information. This paper presents an investigation of the distribution and population characteristics of impact craters in and around the Orientale Basin based on high-resolution datasets. First, an update to the crater catalogue for the Orientale Basin and its surrounding area is provided, including craters as small as 1 km in diameter. Based on the updated crater catalogue, the crater densities and depth-to-diameter ratios in and around the Orientale Basin are investigated. The inclusion of small craters enables a crater density map with higher resolution, revealing a significantly higher crater density of the study area. Also, the surface age of Orientale Basin is estimated from the size–frequency distribution (SFD) using the new crater catalogue, showing an age of 3.75 Ga using the production function of Neukum et al. (2001), which is in good agreement with previous studies. Finally, distribution patterns of secondary craters around the Orientale Basin are investigated, indicating the Orientale Basin may be caused by an oblique impact with a downrange direction of about 235°–260° and an offset strength towards the direction of about 305°–350°.

Chaos Synchronization in Time‐Dependent Duplex Networks

Though the complete chaos synchronization on single‐layer networks has been well understood, it is still a challenge on multiplex networks. In this work, we study the complete chaos synchronization on time‐dependent duplex networks in which interaction pattern among oscillators alternates periodically between two single‐layer networks. The alternations between two layers are characterized by the offset strength A and the switching frequency ω. We find that there are two dynamical regimes depending on ω. For high ω, the critical A for the stable complete synchronization is independent of ω and the fast‐switching approximation suggests that the time‐dependent duplex networks can be approximated by the time‐independent duplex networks with effective coupling strength. For low ω, the critical A depends on ω nonmonotonically. At extremely low ω, the estimation of the critical A can be obtained by a single‐mode approximation taking one dominant transversal network mode to complete synchronization into considerations.

High-strength porous biomaterials for bone replacement: A strategy to assess the interplay between cell morphology, mechanical properties, bone ingrowth and manufacturing constraints

High-strength fully porous biomaterials built with additive manufacturing provide an exciting opportunity for load-bearing orthopedic applications. While factors controlling their mechanical and biological response have recently been the subject of intense research, the interplay between mechanical properties, bone ingrowth requirements, and manufacturing constraints, is still unclear. In this paper, we present two high-strength stretch-dominated topologies, the Tetrahedron and the Octet truss, as well as an intuitive visualization method to understand the relationship of cell topology, pore size, porosity with constraints imposed by bone ingrowth requirements and additive manufacturing. 40 samples of selected porosities are fabricated using Selective Laser Melting (SLM), and their morphological deviations resulting from SLM are assessed via micro-CT. Mechanical compression testing is used to obtain stiffness and strength properties, whereas bone ingrowth is assessed in a canine in vivo model at four and eight weeks. The results show that the maximum strength and stiffness ranged from 227.86±10.15 to 31.37±2.19MPa and 4.58±0.18 to 1.23±0.40GPa respectively, and the maximum 0.2% offset strength is almost 5 times stronger than that of tantalum foam. For Tetrahedron samples, bone ingrowth after four and eight weeks is 28.6%±11.6%, and 41.3%±4.3%, while for the Octet truss 35.5%±1.9% and 56.9%±4.0% respectively. This research is the first to demonstrate the occurrence of bone ingrowth into high-strength porous biomaterials which have higher structural efficiency than current porous biomaterials in the market. Statement of significanceWe present two stretch-dominated cell topologies for porous biomaterials that can be used for load-bearing orthopaedic applications, and prove that they encourage bone ingrowth in a canine model. We also introduce an intuitive method to visualize and understand the relationship of cell topology, pore size, porosity with constraints imposed by bone ingrowth requirements and additive manufacturing. We show this strategy helps to gain insight into the interaction of exogenous implant factors and endogenous system factors that can affect the success of load-bearing orthopaedic devices.

Sinteraustempering Of Two Mo-(Cu)-(Cr)-(Ni)-(Mn)-C Steels In A Semi-Closed Container In Flowing Nitrogen

Abstract Three types of heat treatment, sinteraustempering in 500°C, 400°C and 350°C; sinterhardening and sintering with cooling at the rate 10K/min) as the final operation, on steels sintered semi-closed container were investigated. Results of mechanical properties, microstructure investigations and fracture and EDX analyses are reported. The study involved two PM steels: DH-1 (Fe-2%Cu-1.5%Mo-0.5%C) and 34HNM (Fe-0.2%Mo-0.8%Mn-1.5%Cr-1.5Ni-0.4%C). Prealloyed Höganäs DH (Direct Hardening) iron powder and graphite powder (grade C-UF) were used to produce DH-1 steel. Prealloyed Astaloy CrL iron powder, low carbon ferromanganese, elemental nickel and graphite grade C-UF powder were the starting powders of 34HNM steel. Pressing was in rigid dies at 660MPa according to PN-EN ISO 2740 standard. After compaction, green compacts were sintered in a specially designed semi-closed container at 1120°C for 60 minutes in a nitrogen atmosphere. The chemical composition of the sintering atmosphere was modified by adding ferromanganese and/or activator into the container. All specimens were tested for tensile strength (UTS), elongation (A), yield offset strength (R0,2), TRS, apparent surface and cross section hardness (HV 30). The best combination of strength and plasticity for both steels was achieved after sinteraustempering at 500°C. The results show that, using the specially designed semi-closed container, sinteraustempering in N2 atmosphere offers the same or even better mechanical properties in comparison with sinteraustempering in vacuum. It means that sinteraustempering in N2 atmosphere is a very interesting process in terms of cost in comparison with vacuum sinteraustempering.

Effect of preload stress on the dynamic response of 9%Cr heat-resistant steels with various microstructures

With a uniaxial oscillation load coupled to different preload stresses, the dynamic responses of 9%Cr heat-resistant steels with different microstructures (martensite and cell structure) were measured on a low-cycle fatigue machine at the elevated temperature of 823K. The experiment results show that the internal friction of 9%Cr heat-resistant steel is dependent on not only the microstructure, but also the preload stress. The internal friction of 9%Cr heat-resistant steel with martensite reaches the minimum when the preload stress is close to half of its 0.2% offset strength. Within the present range of preload stress, however, the internal friction of cell structure monotonically increases with the preload stress. Based on the analysis of obtained results, it indicates that for the 9%Cr heat-resistant steels with martensite and cell structure, the different behaviors of internal friction with the preload stress are mainly attributed to various dynamic configurations of internal defects.

AN EXPERIMENTAL STUDY ON EMBEDMENT STRENGTH FOR BOLTED CONNECTIONS LOADED PERPENDICULAR TO THE GRAIN

For bolted connections in timber structures, calculation method based on European yield theory is well known and widely used in the world. On this equation, we need some material properties, embedment strength of wood, yield strength of bolt and each size of specimens. Based on some test results, the strength on the latest standard in Japan announced in public. On the other hand, failure modes in wood aren't considered enough. On this study, we conducted bearing tests based on BS EN 383 and 3-point-bearing test, using end-distance, bolts diameter and wood species as tests parameter. We arranged the specimens with or without clearance between specimen and loaded-steelplate to observe crack behavior. Additionally tension-loaded bolted specimens were analyzed by failure modes and the bearing strengths were calculated according to EYT equation. As a result, 2%off-set strength was corresponding with the crack-starting-strength on bearing tests. The cracked-strength of bolted connection was almost the same with the calculation result with 2%off-set strength.

Size Effects on Tensile Strength of Lotus-Type Porous Copper

Effects of specimen thickness on the tensile strength of lotus-type porous copper were investigated. The ultimate tensile strength in the direction perpendicular to the longitudinal axis of pores hardly depends on the thickness of a specimen when the width of the specimen is large enough compared with the pore diameter, while the ultimate tensile strength increases with an increase in the thickness when the width is not large enough compared with the pore diameter. The 0.2% offset strength in the direction and strain at the peak stress depend on the thickness of specimens; the 0.2% offset strength decreases with an increase in the thickness, and the strain at peak stress increases with the increase in the thickness.

Anisotropic Yield Behavior of Lotus-Type Porous Iron: Measurements and Micromechanical Mean-Field Analysis

Anisotropic yield behavior of lotus-type porous iron fabricated using the continuous-zone-melting method in a pressurized nitrogen and hydrogen atmosphere has been investigated. The 0.2% offset strength (compressive yield stress) in the loading direction parallel to the longitudinal axis of pores decreases linearly with increasing porosity, while the perpendicular strength decreases steeply. The strength versus porosity curves can be expressed using a well-known power law formula. In addition, the 0.2% offset strength of lotus iron prepared in a nitrogen and hydrogen atmosphere is found to be larger than that of lotus iron prepared in a hydrogen and helium atmosphere, which is attributed to the solid solution hardening by the solute nitrogen. Furthermore, we compare the experimental results to calculations obtained by means of the extended Qiu-Weng’s mean-field method, and the comparison suggests that local stresses deviated from the average stress are dominant in the macroscopic yield behavior of lotus metals.

Restoration of femoral offset in total hip arthroplasty

To explore the factors effecting restoring femoral offset and the relation between femoral offset and hip abductor strength during total hip arthroplasty (THA). Ninety-nine THA for 81 patients were performed from March 1998 to January 2002. And follow-up was finished. There were 53 women and 28 men and the average age was 57 years (29 to 80). The right hip had been replaced in 28 cases, the left in 35 cases and the bilateral in 18 cases. The mean duration of clinical and roentgenographic follow-up was 36.8 months (range, 19 approximately 66 months). A posterolateral approach was used in all THA. The femoral offset and the abductor lever arm were measured from each radiograph. The measurement of the hip abduction strength was made for some THA by the Cybex machine. Statistical data analysis was performed by SPSS10.0 software. Femoral offset correlated positively with the length of the abductor lever arm (r = 0.613; P < 0.001). Simple regression analysis showed that femoral offset was significantly and positively related to the length of femoral neck and neck-shaft angle (r = 0.451, P = 0.001; r = 0.567, P < 0.001). There was a highly significant and positive correlation between femoral offset (and consequently abductor lever arm) and hip abductor strength (r = 0.500, P = 0.009; r = 0.477, P = 0.014). It is very important to template both sides of hip preoperatively for restoring femoral offset in THA. Femoral component with more anatomical neck-shaft angle will be used with the increase in the femoral neck length.

Strength Dependence of Intergranular Stress Corrosion Cracking Susceptibility on 3.5% NiCrMoV Steel at 403K

Rotors and discs used in low-pressure turbines must be made of a material possessing high strength and toughness and be capable of manufacturing extremely large components. For these reasons, 3.5% NiCrMoV steel is widely used. It has been previously reported that intergranular stress corrosion cracking in this material is initiated in wet deaerated steam when the temperature reaches approximately 400K. As no rotor and disc material with high strength and toughness that can serve as a substitute for 3.5 NiCrMoV steel has been found, efforts to resolve this problem have been conducted to reduce material strength and lower the susceptibility to stress corrosion cracking.The purpose of this study was to elucidate a relationship between material strength and intergranular stress corrosion cracking susceptibility. Slow strain rate tests (SSRT) were performed in a neutral atmospheric environment at a test temperature of 403K. The results were as follows:(1) The SSRT found that, as the 0.2% offset strength decreased, the area of the intergranular fracture was reduced. For the test specimen with an 0.2% offset strength of 777 MPa, only a tiny intergranular fracture was observed; at 0.2% offset strengths of 697 MPa and below, cracking disappeared completely. (2) From the precipitation status of the two carbides M3C and M7C3 precipitated at the grain boundaries, it was found that the disappearance of the M3C carbide coincided with the disappearance of the intergranular fracture. From this observation, it is thought that differences in composition of these carbides have an effect on the susceptibility of 3.5% NiCrMoV steel to stress corrosion cracking. (3) It was confirmed that the M3C carbide disappears when the 0.2% offset strength is approximately 700 MPa or below, and that these materials achieve the target value for increased resistance to intergranular stress corrosion cracking in neutral environments.

SCC Life Estimation Based on Cracks Initiated from the Corrosion Pits of Bolting Material SCM435 Used in Steam Turbine

Life estimation was performed for the stress corrosion cracking (SCC) that occurs in deaerated and wet hot pure steam at the bottoms of the threads of bolts made of SCM435 (equivalent to AISI 4137) used in steam turbine. SCC is believed to occur when corrosion pits are formed and grow to critical size, after which SCC is initiated and cracks propagate until the critical fracture toughness value is reached. Calculations were performed using laboratory and field data. The results showed that, for a 40 mm diameter bolt with 0.2% offset strength of 820 MPa, the critical crack depth for straight-front cracks was 5.4 mm. The SCC life depends on the lubricant used; the SCC life estimated from this value is approximately 70 000 hours when graphite is used as a lubricant.