Position Of Maximum Stress Research Articles

대진폭 전단유동장에서 잔탄검 농후계의 비선형 점탄성 거동 연구: 응력파형 및 Lissajous 패턴 해석

The objective of the present study is to phenomenologically characterize the nonlinear rheological behavior of concentrated xanthan gum systems in large amplitude oscillatory shear (LAOS) flow fields by means of stress waveform and Lissajous pattern analysis. Using an Advanced Rheometric Expansion System (ARES), the dynamic viscoelastic behavior of aqueous xanthan gum solutions with different concentrations has been experimentally investigated in LAOS flow conditions with a various combination of several fixed strain amplitudes and constant angular frequencies. The main findings obtained from this study are summarized as follows: (1) When a sinusoidal deformation with large strain amplitude is applied, a distorted and nonsinusoidal but symmetrical stress response waveform is observed with time. (2) A saw-tooth shaped stress signal detected at large strain amplitudes may arise from a unique microstructure of xanthan polymer chains. A small peak of stress wave appearing at the position of maximum and minimum stress represents a nonlinear viscous nature of concentrated xanthan gum systems in LAOS flow fields. (3) As an increase in polymer concentration, the shape of stress wave becomes sharper and more distorted. This trend may be explained by an increase in structural density. (4) As a decrease in angular frequency, the stress wave exhibits a more distorted shape and both of the maximum and minimum peaks of a saw-tooth shaped stress response becomes more dominant. (5) At relatively small strain amplitudes, the Lissajous patterns (stress versus strain rate loops) show an elliptical form and their normalized ones are coincident with each other. When larger strain amplitudes are applied, however, the Lissajous patterns are noticeably nonelliptical, and moreover, as the strain amplitude is further increased, the tips of loops become more pointed with exhibiting a characteristic "S" shape.

Microstructural Effect on Crack Propagation Behavior of Ceramic Tool Materials via Cohesive Zone Modeling

A systematic and parametric study of the effect of grain size and volume fraction of secondary phase on crack propagation behavior of Al2O3 based ceramic tool materials was carried out. Two-dimensional centroid V toughness oronoi tessellations were generated with random grain orientations. Cohesive Zone Method (CZM) was utilized to simulate crack propagation behavior. Zero-thickness cohesive elements were embedded on grain boundaries and inside grains. Crack initiation and propagation in ceramic tool materials microstructure were simulated without predefined crack. Simulation results revealed that crack initiated at the maximum stress position and propagated along the direction perpendicular to external load. Decreasing the grain size or increasing the volume fraction of secondary phase can improve the fracture stress of Al2O3 ceramic tool materials.

Influence of die-shift-distance of overhang dies on residual thermal shear stress in 5-chip SiP after EMC curing

This paper investigates the effects of the die-shift-distance (DSD) of overhang dies on residual thermal shear stress and warpage in a 5-chip stacked-die system-in-packaging (SDSiP) implementation. The proposed 5-chip SDSiP includes a single microprocessor (chip 1) and four pieces of dynamic random access memory (chips 2 to 5) with chip 4 stacked atop chip 2 and chip 5 stacked atop chip 3. Computer software based on finite element method (ANSYS) in conjunction with the measured material properties made it possible to obtain the shear stress, shear strain, warpage, and shear strain energy density (U0) within the chips in the 5-chip SDSiP. We also conducted experiments to obtain the interfacial shear stress as well as U0 between the EMC and die, which was compared with the numerical U0. When the DSD exceeded 0.4mm, the position of maximum shear stress at EMC/die interface in the 5-chip SDSiP changed from chip 4 to chip 1 due to a decrease in the rigidity of the stacked dies. Maximum warpage in the 5-chip SDSiP appeared in the top-left corner with movement in a downward direction. This effect can be attributed to mismatch in the CTE among the various materials in the 5-chip SDSiP.

Numerical simulation of the influence factors for rotary kiln in temperature field and stress field and the structure optimization

With the development of metallurgical industry and the improvement of kiln technology, the processing properties of kiln equipment are being paid more attention. The rotary kiln is one of the most representatives of the furnace equipment; higher requirements of the rotary kiln are put forward in response to the call of the national energy saving and emission reduction. That is, the new designed equipment has the characteristics of the optimal energy consumption and stable performance. In order to analyze the energy consumption of the rotary kiln, it is necessary to study the heat transfer process of the rotary kilns. The three-dimensional numerical model of the rotary kiln is set up by using the finite element technology. After analyzing the data, it is found that different thicknesses of the kiln crust and different working conditions have certain influence on the rotary kiln’s temperature field and stress field. After analyzing the result of the simulation, the temperature of the rotary kiln’s outer wall has an approximate linear relationship with the thickness of the kiln crust. Changing the thickness of the kiln crust will not only alter the value of the maximum stress but also have influence on the position of maximum stress. The increase in the thickness of the kiln crust can reduce the extreme value of stress. When the wind speed of induce fan inside the kiln is larger, the temperature of each layer will be relatively high as well, and the temperature curve is softer, and the temperature variation is more stable. It has also been found that when the comprehensive coefficient of heat exchange outside the kiln surface is larger, the thermal stress created by the body of kiln is smaller. The phenomenon of excessive thermal stress can be improved by changing the outer surface ventilation conditions of the rotary kiln. In order to ensure that the high temperature of the kiln wall has no influence on working wheels, and make sure the temperature of the kiln wall is well-distributed along the length direction of the kiln, the thickness of the kiln crust along the length direction is changed, and the structure of the cylinder with wheels on it is altered. After further numerical simulation, the optimized thickness of the kiln crust and kiln structure is found, and the above problem is solved effectively. The results can reduce the inputs of rotary kiln design and the production costs. It can also reduce energy consumption, and some guidance is given on the production process of kilns.

Effect of elastic modulus and thickness of the interlayer on the bond strength for ceramic coating-substrate system

Finite element method (FEM) was used to investigate the effect of elastic modulus and thickness of the interlayer on the bond strength for ceramic coating-substrate system in contact load condition. The maximum shear stress was acted as the criterion of the bonded strength. Firstly, the FEM simulation results indicate that the sharply changed shear stress (SCSS) can be more obviously decreased by the introduction of a interlayer as compared to by increasing the thickness of coating. Secondly, with the increase in the elastic modulus of interlayer, the SCSS of substrate/interlayer increases, while the SCSS of interlayer/coating decreases. Thirdly, with the increase in the thickness of the interlayer, the SCSS of interlayer/substrate decreases by decreasing rate. The SCSS of coating/interlayer shows the similar trends. Furthermore when the thickness increases to 0.6mm or above, the SCSS of coating/interlayer achieve a platform value and the SCSS of interlayer/substrate do not further decreases. And then, the position of maximum shear stress is moved away from interlayer/substrate to coating/substrate and the maximum shear stress of the interlayer decreases with the increase of thickness. Finally, in present work, the optimal elastic modulus (1×1012Pa) and thickness (0.6mm) of interlayer is summarized.

Elastohydrodynamic Lubrication Analysis of Pure Squeeze Motion on an Elastic Coating/Elastic Substrate System

A rigid sphere approaching a lubricated flat surface with a layer of elastic coating on the elastic substrate is explored under constant load conditions. The transient pressure profiles, film shapes, elastic deformation, von Mises stress (σvon) during the pure squeeze process under various operating conditions in the elastohydrodynamic lubrication (EHL) regime are discussed. The simulation results reveal that the greater the Young's modulus of coating is, the greater the pressure distribution is, the smaller the contact area is, and the greater the maximum stress (σvon) value is. As the Young’s modulus of coating decreases, the central elastic deformation at the surface (Z = 0) increases and the deformation at the interface of coating/substrate (Z = −1) decreases. For hard coating cases, the maximum central pressure increases to an asymptotic value and minimum film thickness decreases to an asymptotic value as the coating thickness increases. For soft coating cases, this phenomenon reverses. A thicker and stiffer coating leads to a higher maximum stress. At the deformation recovery stage, the positions of the maximum stress would begin to offset downwards and closer to the coating/substrate interface. Moreover, the position of maximum stress varies from the coating to the subsurface as the Young’s modulus of coating increases. The EHL with stress analysis can prevent the chance of fracture in coating or substrate. These characteristics are important for the lubrication design of mechanical elements with coatings.

Dynamic Analysis of Gear and Rack Transmission System

This paper firstly established a three-dimensional modal of gear and rack transmission system. By using finite element analysis software the model is analyzed and the first six natural frequencies of the gear and rack transmission system are acquired. According to the natural frequencies, actual working speed can be adjusted to avoid resonance. In light of the modal analysis, the transient dynamic finite element model of the gear and rack transmission system is established for the transient dynamic analysis. According to the equivalent stress contour of the gear and rack in contact progress at various times and based on transient dynamic analysis, contact strength and bending strength of the gear are verified and the maximum equivalent stress position is found, providing a theoretical basis for the optimization of the gear and rack.

Analysis and Optimization of Elastic Expansion Sleeve Based on the Finite Element

The contact finite element method is proposed to analyze the stress and deformation distribution of elastic expansion sleeve in the paper. The maximum stress position of each component under the most dangerous working condition is obtained. The effect of structure dimension on stress and deformation of elastic expansion sleeve is found out. The structure dimension meeting the practical requirements is gotten. The analysis results provide the reliable theory basis for the design. The optimization for the structure and processing technology of elastic expansion sleeve is realized, based on simulating the design structure.

Low Cycle Fatigue Failure of a Sitka Spruce Tree in Hurricane Winds

Pine plantations are prone to stem breakage due to high cyclic stress levels associated with hurricane force winds. Stress analytical and finite element simulation models were constructed of a representative profile of a (Sitka) Picea sitchensis tree. The profile surface stress (S) was determined due to the combined load of tree self-weight and hurricane wind speed. The results were complemented by reference to two other studies by other researchers that investigated the impact of fatigue cycles on failure (N) of pine wood and tree sway cycles to present a stem fatigue life prediction. The position of maximum surface profile stress and trunk fracture initiation location was ascertained from a non-uniform stress response. No stress uniformity along the trunk profile was observed for any wind-load case examined. The analytical model and finite element analysis of the P. sitchensis tree trunk profile revealed a statically adequate strength reserve factor of 1.4, which suggested another mode of failure was responsible. Fatigue life failure prediction was examined under cyclic and same-stress amplitude related to the hurricane wind speed of 33 m s-1. Predicted trunk fracture occurred in 2.6 hours, which dramatically reduced to two minutes with an increase in wind speed of only 1 m s-1. The calculated exposure time was similar to that recorded during Hurricane Hugo’s transit in 1989. The time-to-failure prediction obtained by the method of analysis provided in this study seemed plausible, and that the profile associated with the P. sitchensis tree would suffer trunk breakage by low cycle fatigue failure.

Restriction Effect of Structural Steel to Ultra High Strength Concrete in the Joint Core Area

In this paper, ANSYS finite element analysis software is used to research the restriction effect of steel skeleton to the joint core regions of ultra high strength concrete. The position of concrete crack is given and the crack development trend is explained. The study found the maximum stress position appears at the beam-column joints, and reaches the maximum in the web of “I” shape structural steel.

Experimental parameter sensitivity analysis of residual stresses induced by deep rolling on 7075-T6 aluminium alloy

The residual stress distribution induced by deep rolling depends on several factors: the material elasto-plastic curve, roller shape, indentation force and rolling feed. Among these, the force and the feed are those parameters that can be easily handled without cost or layout modifications. This paper shows an experimental investigation about these two parameters and a comparative analysis on the obtained residual stress profiles. The deep rolling treatment was performed on aluminium alloy 7075-T6 samples and the used tool was a carbide roller with conical and rounded contact. The residual stresses were measured by combining the hole drilling method and the X-ray diffraction technique. A first evident result was the large difference between the two principal residual stress components. The feed direction residual stress was almost a factor of two larger than the rolling direction residual stress. Parameter trends on residual stress distributions were investigated. The depth of the compressive region increased with the rolling force and the maximum stress position also tended to be subsurface, while for lower loads the maxima were at the surface. On the other hand, the feed parameter did not produce any effect at large depth, and just the initial subsurface distribution was slightly influenced. However, the surface hardness was noticeably affected by the feed, while the rolling force had a less predominant role. Finite element simulations were also carried out and reported in the paper, mainly to obtain information on induced work hardening. The plasticity depth was only affected by the load, indeed it was very similar to the compressive residual stress depth, while the maximum accumulated plasticity was significantly increased by the feed.

Finite Element Analysis of Structural Strength of Concrete Mixing Truck’s Frame

The finite element model of the concrete mixing truck’s frame is builded by using shell as basic element, and the process of building the finite element model of the balance suspension is introduced in detail. Based on this, frame’s stress on five types of typical operating conditions are calculated by using the finite element analysis software, NASTRAN, and results can show the dangerous position and the maximum stress position on the frame. The analysis result on structural strength can provide the basis for further improving the frame structure.

Optimization of the Rotor Chuck Structure Based on Finite Element Analysis

Chuck for rotor is prone to fracture when working under axial tensile force of pulsation cycle. The maximum stress position of the chuck calculated by finite element analysis coincides with the actual fracture location, which confirms that chuck slotted root is the weakest part of the rotor. The structure optimization of part is proposed based on the results of the original structural analysis. It is found that the maximum stress of the chunk of rotor reduced by 56.59% after optimization based on the calculation of the finite element analysis. The strength of the optimized slotted roots of the chuck rotor is improved greatly and the service life is extended, which solved a technical problem for the enterprise.

The Vermicelli Cutting Machine Control System Design and Structure of the Finite Element Analysis

Along with the social demands for the amount of food and constantly improve, the cutting way is not able to meet the user's requirements. So the automatic production line for automatic vermicelli cutting machine is designed. This paper mainly introduces the design of control circuit for cutting off machine. The parameters are optimized by programs. Static analysis for supporting structure of cutting machine is given by ANSYS software. The distribution of stress and strain is obtained. The maximum stress position is found. Determine whether or not to meet the use requirements and provide optimization proposal, and discuss the feasibility of the improvement scheme. The modal analysis for the cutting machine is done by ANSYS which provides theoretical basis for optimization design.

Contact stress and residual stress in the nose rail of a high manganese steel crossing due to wheel contact loading

ABSTRACTFatigue failure of a high manganese steel crossing is related to its internal crack initiation and growth, which is affected significantly by the magnitude and distribution pattern of contact stress and residual stress in the crossing. Considering the actual service conditions of a crossing and the accuracy requirement for numerical calculation, a whole model of wheel/crossing/ties and a partial model of wheel/crossing are established using elastic‐plastic finite element method. The distributions of contact stress fields and residual stress fields due to wheel contact loading are studied. The effect of train speed on the residual stress in the nose rail is discussed. The contact stress field shows regular contours in the cross‐section of nose rail and decreases remarkably with increasing distance of the wheel‐crossing contact position. The maximum contact stress is located at the contact surface between wheel and crossing. The maximum residual stress is located at a position of 1.5‐2.0 mm below the surface of the nose rail, rather than at the contact surface of wheel and crossing. In a failed high manganese steel crossing, the dense cracks mainly were observed neither at the position of maximum contact stress (the contact surface between the wheel and the crossing), nor at the position of maximum residual stress (1.5‐2.0 mm below the surface of the nose rail), but around the depth of 0.8‐1.0 mm from the worn surface, which is between the position of maximum contact stress and the position of maximum residual stress. It indicates that the combined effects of the maximum contact stress and the maximum residual stress play important roles in fatigue crack initiation in the nose rail. The size of high residual stress region increases with the increase of the train speed. The maximum residual stress in the nose rail increases remarkably with the increase of the train speed.

Parameter Optimization Design and Stress Analysis of ANSYS in Inclined Gear Transmission System of Wind-Turbine

ncreasing speed Gear-box is one of the most important components of wind-turbine. Gear design directly affect the operating life and reliability of gear-box. Based on the 1.5MW wind-turbine as the research object in this paper, we optimized the design parameters of Inclined gears, analysed its bending stress reliability, further verified the gear maximum stress and stress position, to provide a scientific reference for making Inclined gears later.

Rigid-Flexible Coupling Dynamics Simulation of 3-RPS Parallel Robot Based on ADAMS and ANSYS

This paper mainly investigated the rigid-flexible dynamics simulation method of multi-body system. The 3-RPS parallel robot dynamics model is created by ADAMS (multi-body dynamics software) and ANSYS (finite element analysis software). In accordance with the flexible-body theory, we analyzed mechanical characteristics of parallel robot with no-load or full-load working condition, and got the deformation of end measuring point, maximum stress position and dynamics stress curve. The analysis method is more intuitional and accurate, and can increase the accuracy of dynamic response analysis of links under the dynamic loads. The simulation results create conditions for structure design and optimization of 3-RPS parallel robot.

Simulation on Stress Distribution of Drill Pipe’s Surface Initial Crack

Abstract: In drilling process, drill pipes’ out surface always have lots of pits and scratches due to the corrosive and erosion of mud or wear of well wall in work environment. Through establishing drill pipe’s working model and constitutive equations with Finite Element Analysis Software, the paper have simulated stress distribution on drill pipe body under two different condition that without mechanical damage and with initial crack. Analysis results show that the maximum stress increases with the increasing of initial crack depth, and the maximum stress position turns to crack circumferential root from the crack radial root with the increasing of initial crack’s depth. The analysis result is completely consistent with the actual morphology of crack propagation, as a result, the simulation analysis provides a effective new methods and reference for remaining life assessment and failure analysis of drill pipe.

박스 암거가 통과하는 콘크리트 포장의 줄눈 위치에 관한 연구

지중구조물 주위는 다짐이 잘 되지 않아 지반이 장기 침하하므로 콘크리트 포장 하부에 공동이 발생하기 쉬우며, 이로 인해 지지력이 저하되기 쉽다. 여기에 하중이 가해지면 설계 시 기대한 것보다 큰 응력이 도입되어 포장에 파손이 발생하고 수명이 감소하게 된다. 본 논문에서는 한국도로공사 시험도로의 박스형 암거 상부 콘크리트 포장 슬래브의 파손을 조사하였다. 토피고가 다른 상행선과 하행선의 암거 위치에 발생한 슬래브의 횡방향 균열을 비교하였다. 시험도로의 횡방향 균열을 검증하기 위해 토피고가 없는 박스형 암거와 콘크리트 포장을 유한요소 방법으로 모형화하고 해석하였다. 포장의 자중을 고려하고 시험도로가 위치한 경기도 여주 지역 콘크리트 슬래브의 온도구배를 적용한 후 윤하중을 재하하였다. 각 하중조합에 대해 최대인장 응력이 발생하는 위치와 이때의 윤하중 위치를 찾아냈다. 이를 통해 최대인장응력을 감소시킬 수 있는 줄눈 위치를 찾아내고 암거 크기 별로 상부에 위치하는 슬래브의 적정 길이를 제안하였다. Hollows are easily made and bearing capacity is lowered near underground structures of concrete pavement because of poor compaction and long term settlement of the ground. Distresses occur and lifespan is shortened because of larger stress induced by external loadings expected than that in the design. In this paper, the distresses of the concrete pavement slab over box culverts were investigated at the Korea Expressway Corporation(KEC) test road. The transverse cracking of the slabs over the culverts was compared between up and down lines with different soil cover depth. The box culvert without soil cover and concrete pavement were modeled and analyzed by the finite element method(FEM) to verify the transverse cracking at the test road. Wheel loading was applied after self weight of the pavement and temperature gradient of the concrete slab at Yeojoo, Gyeonggi where the test road is located were considered. Positions of maximum tensile stress and corresponding positions of the wheel loading were found for each loading combination. Joint position minimizing the maximum tensile stress was found and optimal slab length over the culverts with diverse size were suggested.

Effects of Rim and Web Thicknesses on Root Stresses of Thin-Rimmed Helical Gear

This paper presents a study on root stresses of thin-rimmed helical gears with web arrangement of various rim and web thickness. Thin-rimmed helical gears used in this study were meshed with solid helical gear. Root stresses were measured from the beginning of engagement to the end of engagement by using the strain gauge method. The changes of root stresses from the beginning of engagement to the end of engagement were examined and the meshing position where the maximum root stress occurred (worst loading position) was determined. Effects of rim and web thickness on the root stress, the maximum root stress and the position of maximum root stress were clarified.